Applied Surface Science (v.258, #22)
Controlled synthesis of ZnO hollow microspheres via precursor-template method and its gas sensing property
by Yu Tian; Jinchai Li; Hui Xiong; Jiangnan Dai (pp. 8431-8438).
Display Omitted► Zn powder as precursor template for synthesis ZnO hollow spheres. ► Different precursor templates result in different ZnO nanostructures. ► Different experimental conditions enable growth of different surface morphologies of ZnO sphere. ► ZnO hollow sphere materials have good gas sensing performance for detecting ethanol gas.Using Zn powder as precursor templates, ZnO hollow microspheres were successfully prepared by thermal evaporation method and characterized by X-ray diffraction analysis, scanning electron microscope and transmission electron microscope. It was found that different size and shape of precursor resulted in different ZnO nanostructures. When varying experimental conditions, such as air flow rate and working pressure, ZnO hollow spheres with different surface morphologies could be obtained. The advantages of the present synthetic technology are simple, relatively low cost, and high reproducibility. A gas sensor was fabricated from the as-prepared ZnO hollow microspheres and tested to the ethanol gas at different operating temperatures.
Keywords: Gas sensor; ZnO; Thermal evaporation; Precursor template; Ethanol sensing
Occurrence of two-photon absorption saturation in Ag nanocolloids, prepared by chemical reduction method
by K. Mani Rahulan; S. Ganesan; P. Aruna (pp. 8439-8443).
► Ag nanocolloids were synthesized via chemical reduction method. ► The molecules of PVP play an important role in growth and agglomeration of silver nanocolloids. ► Saturation behaviour followed by two photon absorption was responsible for good optical limiting characteristics in these nanocolloids. ► The nonlinear optical parameters calculated from the data showed that these materials could be used as efficient optical limiters.Silver nanocolloids stabilized with polyvinyl pyrrolidone (PVP) have been prepared from (AgNO3) by a chemical reduction method, involving the intermediate preparation of (Ag2O) colloidal dispersions in the presence of sodium dodecycle sulfate as a surfactant and formaldehyde as reducing agent. The molecules of PVP play an important role in growth and agglomeration of silver nanocolloids. The formation of Ag nanocolloids was studied from the UV–vis absorption characteristics. An energy dispersive X-ray (EDX) spectrum and X-ray diffraction peak of the nanoparticles showed the highly crystalline nature of silver structure. The particle size was found to be 40nm as analyzed from Field emission scanning electron microscopy (FESEM). The nonlinear optical and optical limiting properties of these nanoparticle dispersions were studied by using the Z-scan technique at 532nm. Experimental results show that the Ag nanocolloids possess strong optical limiting effect, originated from absorption saturation followed by two-photon mechanism. The data show that Ag nanocolloids have great potential for nonlinear optical devices.
Keywords: Silver nanocolloids; Optical limiting; X-ray diffraction; Surface plasmon resonance
In vitro study of cell differentiation by two type mouse embryo stem cells on mono- and multilayer nanocarbon tubes
by Koichi Imai; Tsukasa Akasaka; Fumio Watari; Akito Tanoue; Kazuaki Nakamura; Kazuhiko Suese; Hiromasa Takashima; Tetsunari Nishikawa; Akio Tanaka; Shoji Takeda (pp. 8444-8447).
► We previously investigated the myocardial cell differentiation of ES-D3 cells using monolayer (SWCNTs) and multilayer (MWCNTs) nanocarbon tubes. As a result, in spite of having the same carbon composition, the effects on the cell differentiation levels differed between the tubes. ► We investigated their cell differentiation and cytotoxic effects on EL M3 and ES-R1-EGFP B2/EGFP cells, which require feeder cells. ► The different surface structures of SWCNTs and MWCNTs may have influenced ES cell differentiation.The effects of nanomaterials on human reproduction and development remain unknown. The risks of nanomaterials for future generations should be elucidated. Thus, it is important to establish an experimental method to accurately examine embryotoxicity. We previously investigated the myocardial cell differentiation of ES-D3 cells using monolayer (SWCNTs) and multilayer (MWCNTs) nanocarbon tubes. As a result, in spite of having the same carbon composition, the effects on the cell differentiation levels differed between the tubes. We investigated their cell differentiation and cytotoxic effects on EL M3 and ES-R1-EGFP B2/EGFP cells, which require feeder cells. As a result, myocardial pulse rates differed between the presence of SWCNTs and MWCNTs even when feeder cells existed between the samples and cells. The different surface structures of SWCNTs and MWCNTs may have influenced ES cell differentiation.
Keywords: SWCNTs; MWCNTs; Embryotoxicity; ES cell; Cell differentiation; In vitro
Surface functionalization of graphite and carbon nanotubes by vacuum-ultraviolet photochemical reactions
by Pierre-Luc Girard-Lauriault; René Illgen; Juan-Carlos Ruiz; Michael R. Wertheimer; Wolfgang E.S. Unger (pp. 8448-8454).
► Graphite and CNT surfaces were functionalized by VUV photochemistry in NH3 or O2. ► Significant amounts of N and O were incorporated at the materials surface. ► Primary amine and hydroxyl groups were successfully incorporated at the surface. ► NEXAFS permitted to assess the conservation of the aromatic structure.Graphite and multiwall carbon nanotube surfaces were functionalized by vacuum-ultraviolet induced photochemistry in NH3 or O2, in order to introduce amino- (NH2) or hydroxyl (OH) functionalities, respectively. Modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), which showed significant incorporation of nitrogen (N) and oxygen (O) at the materials’ surface. While high-resolution XP spectra did not yield much specific information about the incorporated functional groups, chemical derivatization with 4-trifluoromethyl benzaldehyde and trifluoroacetic anhydride accompanied by XPS enabled quantification of NH2 and OH groups, respectively. Using near edge X-ray absorption fine structure spectroscopy, we assessed the conservation of the aromatic structure following functionalization treatments.
Keywords: Carbon nanotubes; Graphite; Vacuum ultraviolet photochemistry; Surface functionalization; Amino groups; Hydroxyl; Derivatization
Preparation and study on microwave absorbing materials of boron nitride coated pyrolytic carbon particles
by Wei Zhou; Peng Xiao; Yang Li (pp. 8455-8459).
Boron nitride coatings were synthesized on pyrolytic carbon (BN-coated PyC) particles via chemical reaction of boric acid and urea in nitrogen. The results of Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FI-IR) and X-ray photoelectron spectroscopy (XPS) show the formation of boron nitride coating. The TGA curves indicate that the oxidation resistance of the PyC particles is improved by incorporating BN coating on the surface. The mass of the BN-coated PyC particles remains over 60% at 1200°C whereas the PyC particles are oxidized completely at 920°C. The investigation of microwave absorbing property reveals that compared with the PyC particles, the BN-coated PyC particles have lower permittivity ( ɛ′, ɛ″) and better absorbing property. The BN-coated PyC particles show a strong absorbing peak at 10.64GHz, where the lowest reflectivity −21.72dB is reached. And the reflectivity less than −10dB is over the range of 9.6–12GHz.
Keywords: Pyrolytic carbon; Boron nitride; Oxidation resistance; Microwave absorbing properties
Wear behavior of gas tunnel type plasma sprayed Zr-based metallic glass composite coatings
by S. Yugeswaran; A. Kobayashi; K. Suresh; K.P. Rao; B. Subramanian (pp. 8460-8468).
► Zr-based metallic glass composite coatings are prepared by gas tunnel plasma torch. ► Increasing plasma current increases crystallinity amount and hardness of coatings. ► Coating produced at 300A plasma current gives minimum sliding wear rate. ► Coating produced at higher plasma current gives lower erosive wear rate.Gas tunnel type plasma spraying is a prospective method to produce metallic glass composite coatings with high quality due to its noteworthy feature of process controllability. In this study, Zr55Cu30Al10Ni5 metallic glass composite coatings were produced by gas tunnel type plasma spraying torch under optimum spraying conditions with selected plasma currents. The formation mechanism, sliding, and erosive wear behaviors of the coatings with respect to plasma current was examined. The phase and thermal analyses as well as microstructure of the plasma sprayed coatings produced at different plasma currents were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) techniques. The sliding and erosive wear behaviors of the coatings were studied using a pin-on-disc and a specially designed erosive wear tester, respectively. The results showed that an increase in plasma current increased the crystalline content in the metallic glass composite coatings, which enhanced the hardness and wear resistance of the coatings.
Keywords: Bulk metallic glass; Gas tunnel type plasma torch; Spray coatings; Sliding wear; Erosive wear
Modeling the effects of particle deformation in chemical mechanical polishing
by Xiaochun Chen; Yongwu Zhao; Yongguang Wang (pp. 8469-8474).
► The deformation of abrasive particles in CMP is quantitatively analyzed for the first time in this paper. ► The effect of particle deformation on the material removal rate of CMP is formulated into a novel model. ► The MRR model has been verified to be in good agreement with the experimental data. ► Further research on abrasive particles, material and its deformation, will help on obtaining better polished surface quality.In a chemical mechanical polishing (CMP) process, an active abrasive particle participating in the wear process will contact the pad and the wafer at the same time. The applied polishing load causes the deformation of the pad in the contact interface of the particle and the pad, and the deformation of the wafer in the contact interface of the particle and the wafer. Besides, this force causes the deformation of the abrasive particle. Based on the elastic–plastic micro-contact mechanics and abrasive wear theory, a novel model for material removal rate (MRR) with consideration of the abrasive particle deformation is presented in this paper. The deformation of the abrasive particle, affecting the indentation depth of the particle into the wafer, is quantitatively incorporated into the model. The results and analyses show that the present model is in good agreement with the experimental data.
Keywords: Chemical mechanical polishing; Pad; Wafer; Abrasive particle; Modeling
Time-resolved shadowgraph imaging of femtosecond laser-induced forward transfer of solid materials
by M. Feinaeugle; A.P. Alloncle; Ph. Delaporte; C.L. Sones; R.W. Eason (pp. 8475-8483).
► Femtosecond laser-induced forward transfer has been imaged by shadowgraphy. ► Transfer regimes identified for solid layers in molten, fragmented and solid state. ► Intact material was transferred without the creation of an observable shock wave. ► The transfer velocity of intact 1.8μm thick flyers was as low as 34m/s. ► The transfer velocity was the lowest ever observed via a shadowgram for LIFT.The transfer of solid phase material by femtosecond laser-induced forward transfer (LIFT) at atmospheric pressure by a time-resolved shadowgraph technique is studied. The influence of laser fluence on transfer of material in solid, fragmented and molten state is investigated during femtosecond LIFT of initially solid layers of thermoelectric bismuth selenide (Bi2Se3), piezoelectric lead zirconate titanate (PZT) and magnetostrictive Terfenol-D. We report ejection velocities of ∼48m/s and ∼34m/s for intact transfer of ∼1.1μm thick Bi2Se3 and ∼1.8μm thick PZT respectively, and of ∼140m/s for ∼0.5μm thick Terfenol-D. During intact transfer, contrary to what has been reported so far, no shock wave above the substrate surface was observed.
Keywords: Laser-induced forward transfer; Shadowgraphy; Time-resolved studies; Femtosecond; Shock wave; Laser material processing
First-principles study of oxygen adsorption on Fe(110) surface
by Xiaochao Tan; Jicheng Zhou; Yinqiao Peng (pp. 8484-8491).
► We model three O adsorption superstructures on Fe(110) surface. ► The atomic geometry and electronic properties have been calculated. ► Oxygen adsorption induces the surface spin density to be positive at Fermi level, unlike the clean Fe(110) surface. ► The surface Fe–O magnetic interaction causes the adsorbate O spin splitting. ► The adsorbate O exchange splitting band calculations need improve.We investigate three superstructures c(2×2), c(3×1) and c(1×1) of oxygen atom adsorption on Fe(110) surface by using first-principles density functional theory. The former two superstructures have been found by experiments at low oxygen exposures. The oxygen adsorption results in some electron transfer from surface Fe atom to O atom due to the strong electronegativity of oxygen atom, which also causes a positive work function change. For all three superstructures, the calculated surface spin density at Fermi level is positive, unlike that on a clean Fe(110) surface. The adsorbate–substrate hybridization is mainly from the interaction between O 2p and Fe 3d orbitals, and O 2p state exhibits obvious exchange spin–split induced by the Fe–O magnetic interaction. The adsorbate O 2p bands of c(2×2) and c(3×1) superstructures exhibit a weaker dispersion, whereas those bands of c(1×1) structure show larger dispersion due to the O–O interaction. Through the band structure calculation, we also calculate the exchange splitting energy of O 2p x orbital for c(3×1) structure in k space and compare them with experimental results.
Keywords: Density functional calculation; Oxygen adsorption; Atomic structure; Electronic properties
Effect of percolation on the electrical conductivity of amino molecules non-covalently coated multi-walled carbon nanotubes/epoxy composites
by Aibo Zhang; Jingfan Luan; Yaping Zheng; Li Sun; Meng Tang (pp. 8492-8497).
The scheme of preparation amino groups coated MWNTs/epoxy nanocomposites.Display Omitted► The amino groups were built on the surface of multi-walled carbon nanotubes (MWNTs) using tetrazine by non-covalent modification. ► The building of amino groups on the surface of MWNTs can greatly improve the dispersion of MWNTs in EP matrices, which is more important for MWNTs to form an electrically conductive network to enhance the electrical conductivity. ► The percolation threshold of the amino coated MWNTs/EP composites was 0.13wt%, while the pristine MWNTs/EP composites were 0.51wt%.The organic amino molecules of tetrazine compound were attached on the surface of multi-walled carbon nanotubes (MWNTs) by non-covalent method, in which amino groups can generate chemical bonding with the epoxide groups in epoxy (EP) matrices. The morphology investigation results showed that the introduction of amino groups on the surface of MWNTs can help MWNTs to disperse homogeneously in EP matrices. The electrical conductivity of the amino-coated MWNTs/EP composites is investigated and its dependence on the content of the MWNT is used to evaluate the percolation threshold of the MWNTs/EP composites. The results showed that the conductivity of the amino coated MWNTs/EP composites was significant higher than that of pristine MWNTs/EP composites at the same MWNT content. The percolation threshold of the amino coated MWNTs/EP composites was 0.13wt%, while the pristine MWNTs/EP composites were 0.51wt%. The lower percolation threshold indicates that the introduction of amino groups on the surface of MWNTs can greatly improve the dispersion of MWNTs in EP matrices, which is more important for MWNTs to form an electrically conductive network to enhance the electrical conductivity.
Keywords: Multi-walled carbon nanotubes; Tetrazine; Non-covalent modification; Dispersability; Percolation threshold
Effect of nitrogen flow rate on the properties of TiN film deposited by e beam evaporation technique
by Nishat Arshi; Junqing Lu; Bon Heun Koo; Chan Gyu Lee; Faheem Ahmed (pp. 8498-8505).
► Titanium nitride films with different nitrogen flow rates have been deposited at room temperature. ► The XRD results revealed the presence of strong FCC Ti (111) and TiN (200) phases. ► The XPS results shows presence of three groups of Ti 2p doublet. ► FESEM results showed a smooth morphology of the film with columnar grain structure. ► The electrical resistivity was found to decrease with the increase in nitrogen flow.In this work, titanium nitride (TiN) films have been deposited by e beam evaporation technique on Si/SiO2 (100) substrates at room temperature. The influence of nitrogen flow rate (N2=0, 4, 6, 8 and 10sccm (standard cubic centimeter per minute)) on the structural, morphological and electrical properties of the TiN films has been studied. The deposited TiN films have been characterized using X-ray diffraction (XRD), XPS (X-ray photoelectron spectroscopy), FESEM (Field emission scanning electron microscopy) and four-point probe resistivity measurement techniques. XRD patterns reveal FCC symmetry of the film with (111) preferred orientations for Ti film (N2=0sccm) and (200) preferred orientations for TiN film (N2=4, 6, 8 and 10sccm), respectively. The lattice parameters for TiN films are found to increase from 4.237Å to 4.239Å with the increase in nitrogen flow rate. The presence of different phases such as TiN, TiON and TiO2 were confirmed by XPS analysis. The FESEM images of the TiN films showed a smooth morphology with columnar grain structures. The grain size of the TiN films was found to increase as the nitrogen flow rate was increased from 4 to 10sccm. The electrical resistivity measurement showed that the resistivity of the film decreased from 333μΩcm to 111μΩcm on increasing nitrogen flow rate from 4 to10sccm.
Keywords: Titanium nitride; e beam evaporation; XRD; XPS; Resistivity; FESEM
Gold nano-particles fixed on glass
by Christian Worsch; Wolfgang Wisniewski; Michael Kracker; Christian Rüssel (pp. 8506-8513).
► We produced wear resistant gold–ruby coatings on amorphous substrates. ► Thin sputtered gold layers were covered by or embedded in silica coatings. ► Annealing above Tg of the substrate glass led to the formation of gold nano particles. ► A 111-texture of the gold particles is observed via XRD and EBSD. ► EBSD-patterns can be acquired from crystals covered by a thin layer of glass.A simple process for producing wear resistant gold nano-particle coatings on transparent substrates is proposed. Soda-lime-silica glasses were sputtered with gold and subsequently coated with SiO2 using a combustion chemical vapor deposition technique. Some samples were first coated with silica, sputtered with gold and then coated with a second layer of silica. The samples were annealed for 20min at either 550 or 600°C. This resulted in the formation of round, well separated gold nano-particles with sizes from 15 to 200nm. The color of the coated glass was equivalent to that of gold–ruby glasses. Silica/gold/silica coatings annealed at 600°C for 20min were strongly adherent and scratch resistant. X-ray diffraction and electron backscatter diffraction (EBSD) were used to describe the crystal orientations of the embedded particles. The gold particles are preferably oriented with their (111) planes perpendicular to the surface.
Keywords: Gold–ruby coatings; Sputtering; CCVD; Wear resistant; EBSD
Atomic layer deposition and characterization of stoichiometric erbium oxide thin dielectrics on Si(100) using (CpMe)3Er precursor and ozone
by Runshen Xu; Qian Tao; Yi Yang; Christos G. Takoudis (pp. 8514-8520).
► Atomic layer deposition of erbium oxide from (CpMe)3Er and ozone. ► Stoichiometric erbium oxide atomic layer deposition. ► Carbon-free atomic layer deposited erbium oxide. ► Interfacial erbium silicate formation at 800°C or higher temperatures. ► Hysteresis of 50mV and leakage current density of 10−7Acm−2 at 1MVcm−1.Thin stoichiometric erbium oxide films were atomic layer deposited on p-type Si(100) substrates using tris(methylcyclopentadienyl)erbium and ozone. The film growth rate was found to be 0.12±0.01nm/cycle with an atomic layer deposition temperature window of 170–330°C. X-ray photoelectron spectral (XPS) analysis of the resulting Er2O3 films indicated the as-deposited films to be stoichiometric with no evidence of carbon contamination. Studies of post deposition annealing effects on resulting films structures, interfaces, surface morphologies, and electrical properties were done using Fourier transform infrared spectroscopy, XPS, glancing incidence X-ray diffraction, optical surface profilometry, and C– V/ I– V measurements. As-deposited Er2O3 films were found to start crystallizing in the cubic structure with dominant (222) orientation; no erbium silicate was found at the interface. After annealing at 800°C in N2, a new XPS feature was found and it was assigned to the formation of erbium silicate. As the annealing temperature was increased, the interfacial erbium silicate content was found to increase in the temperature range studied. Electrical characterization of Er2O3 thin gate dielectrics annealed at 600°C exhibited higher dielectric constant ( κ=11.8) than that of as-deposited films (9.8), and a remarkably low hysteresis voltage of less than 50mV along with a leakage current density of 10−7Acm−2 at 1MVcm−1.
Keywords: Atomic layer deposition; Erbium oxide; Gate dielectric; Tris(methylcyclopentadienyl)erbium; Ozone
Facile methods for synthesis of core–shell structured and heterostructured Fe3O4@Au nanocomposites
by Lei Lou; Ke Yu; Zhengli Zhang; Rong Huang; Yiting Wang; Ziqiang Zhu (pp. 8521-8526).
Display Omitted► Core–shell structured and heterostructured Fe3O4@Au nanocomposites are synthesized. ► Both structures are aiming at diverse applications. ► The polyethylenimine coated Fe3O4 nanoparticles were used as seeds. ► Both structures combined the merits of both gold and Fe3O4 nanoparticles. ► The methods suggested new ways for synthesizing multifunctional nanostructures.Two different reaction strategies designed for core–shell structured and heterostructured Fe3O4@Au nanocomposites utilizing 50nm polyethyleneimine coated magnetite as seeds are presented aiming at diverse applications. The polyethylenimine (PEI) coated Fe3O4 nanoparticles were firstly used as seeds to carry out the synthesis of both core–shell structured and heterostructured Fe3O4@Au nanocomposites. Results show that these two structures combined the merits of both gold and Fe3O4 nanoparticles. What is more, the distinct morphology offers diverse applications: the shell of dense gold nanoparticles coating in the core–shell structure dominates the further surface functionalization while the heterostructure offers the particles with two distinct surfaces and functionalities due to different surfactant molecules on the surface of Fe3O4 and Au nanoparticles. Furthermore, the synthesis methods presented in this paper also suggested new ways to the synthesis of multifunctional nanostructures.
Keywords: JEL classification; 62.23.Pq; 75.50.Gg; 81.05.Bx; 61.41.+e; 74.25.HaNanocomposites; Fe; 3; O; 4; Gold; Polyethyleneimine; Magnetic properties
Effect of annealing temperature on properties of RF sputtered Cu(In,Ga)Se2 thin films
by Zhou Yu; Chuanpeng Yan; Yong Yan; Yanxia Zhang; Tao Huang; Wen Huang; Shasha Li; Lian Liu; Yong Zhang; Yong Zhao (pp. 8527-8532).
► Significantly loss of Se occur when films annealed under 300°C. ► Film composition remains constant as annealing temperature went beyond 350°C. ► Phase transformation from amorphous to chalcopyrite polycrystalline structure occurred at 300°C. ► Surface morphology has strong dependence on the annealing temperature.Cu(In,Ga)Se2 (CIGSe) thin films were prepared by radio frequency (RF) magnetron sputtering at room temperature, following vacuum annealing at different temperatures. We have investigated the effect of annealing temperature (150–550°C) on the phase transformation process of the CIGSe films. The as-deposited precursor films show a near stoichiometry composition and amorphous structure. Composition loss of the films mainly occur in the annealing temperature range of 150–300°C. Comparing with samples annealed at 300°C, films annealed at 350°C or higher temperatures exhibit almost similar composition and polycrystalline chalcopyrite structure. Crystal quality of the films improves with increasing annealing temperature. Reflectance spectra of the annealed films show interference fringe pattern. The calculated refractive indexes of the films are in the range of 2.4–2.5.
Keywords: Sputtering; Crystal structure; Selenide; Cu(In,Ga)Se; 2
Investigation on growth process and tribological behavior of mixed alkylsilane self-assembled molecular films in aqueous solution
by Yuhong Liu; Pengxiao Liu; Yuqi Xiao; Jianbin Luo (pp. 8533-8537).
► The water-based lubrication properties of mixed and single component self-assembled molecular films were investigated. ► The adsorption equilibrium of the molecular films is relative to the intermolecular interaction forces and the hydrolysis of C8F. ► The mixing of C8F with C12 and C16 increase the surface tension and reduce the electrical affinity, resulting in the weak hydrophobicity.In this paper, we investigated the frictional behaviors of the mixed self-assembled molecular films of the fluoroalkylsilane (FAS) molecules and non-fluoroalkylsilane (n-FAS) molecules with different chain length covalently absorbed on silicon surfaces, characterized by the universal ball-disk UMT-2 experimental tester under aqueous solution conditions. The surfaces of the substrate modified by mixed self-assembled molecular films were examined by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The formation processes of the molecular films were characterized by quartz crystal microbalance (QCM). The results indicated that it would take a longer time to reach the adsorption equilibrium of the molecular films with the increment of carbon chain length. The measured tribological results showed that the mixing of the fluoroalkylsilane and non-fluoroalkylsilane enhance the lubrication and decrease the friction and wear compared to the one-component thin films. This may be caused by the reduced excitation of the energy dissipation channels.
Keywords: Self-assembled molecular films; Growth mechanisms; Tribological properties
Controlled growth and photoluminescence of one-dimensional and platelike ZnS nanostructures
by Junfeng Lu; Xianghua Zeng; Hongfei Liu; Wei Zhang; Yong Zhang (pp. 8538-8541).
Display Omitted► We can confirm that the violet emission band centered at about 395nm has been attributed to the sulfur vacancies (VSE). ► The morphology of the ZnS nanostructures changing from nanowires to nanoribbons or nanobelts was observed with the increase in temperature. ► The morphology of the sample #D produced without an Au catalyst was plate-like shape with length and width of ∼1μm.Syntheses of the one-dimensional and platelike wurtzite ZnS nanostructures have been achieved by the thermal evaporation of ZnS powder. The role of the substrate temperature and Au catalyst in defining the morphology of the ZnS nanostructures has been found. The nanowires and nanoribbons were synthesized onto the Si substrate in the presence of the Au catalyst, and the platelike ZnS nanostructures were produced onto Au-uncoated Si substrate. The morphological change of the nanostructures was studied through scanning electron microscope. Room temperature photoluminescence measurements with 325nm excitation showed three emission bands located at 345nm, 395nm and 460nm, respectively.
Keywords: Thermal evaporation; ZnS nanostructures; Photoluminescence
The effects of magnetic field on pulsed laser deposition of Mg-doped ZnO thin films
by Jin Jae Park; Jae Kyu Song; Jeong Sook Ha; Seung Min Park (pp. 8542-8547).
► The magnetic field makes room-temperature pulsed laser deposition (PLD) possible. ► The crystallinity was improved by transverse magnetic field (tMF)-PLD. ► The photoluminescence was enhanced by tMF-PLD.Mg-doped ZnO thin films were deposited on Si surfaces by laser ablation of a Zn:Mg target to shed light on the effects of magnetic field in pulsed laser deposition. Both crystalline and photoluminescence properties of the Mg-doped ZnO film were dramatically enhanced by performing laser ablation under transverse magnetic field at room temperature. The ablation wavelength turned out to be crucial to bring about optimum effects of the magnetic field on the laser-induced plasma plume. Besides, cylindrically phase-separated polystyrene- b-poly(methylmethacrylate) employed as a template facilitated fabrication of bandgap-engineered ZnO nanodot arrays.
Keywords: Laser ablation; Pulsed laser deposition; Mg-doped ZnO; Magnetic field
Mechanisms in photoluminescence enhancement of ZnO nanorod arrays by the localized surface plasmons of Ag nanoparticles
by Jun-Cao Bian; Fei Yang; Zhe Li; Jie-Liang Zeng; Xi-Wen Zhang; Zhong-Dong Chen; Jeannie Ziang Yie Tan; Rui-Qun Peng; Hai-Yan He; Juan Wang (pp. 8548-8551).
Photoluminescence properties of ZnO nanorod arrays decorated by Ag nanoparticles have been studied. It was found the enhancement of near-band-edge emission of ZnO was attributed to the giant local electronic fields (EF) of Ag nanoparticles, which was confirmed by annealing treatment and surface-enhanced Raman scattering spectra. The enhancement of visible emission band was due to the exciton-localized surface plasmons coupling effect.Display Omitted► Surface plasmons enhancement mechanisms for different photoluminescence bands of ZnO are confirmed to be different. ► The enhancement of near-band-edge emission of ZnO was attributed to the giant local electronic fields of Ag nanoparticles. ► The enhancement of visible emission band was due to the exciton-localized surface plasmons coupling effect.Photoluminescence properties of ZnO nanorod arrays decorated by Ag nanoparticles have been studied. It was found the enhancement of near-band-edge emission of ZnO was attributed to the giant local electronic fields of Ag nanoparticles, which was confirmed by annealing treatment and surface-enhanced Raman scattering spectra. The enhancement of visible emission band was due to the exciton-localized surface plasmons coupling effect.
Keywords: ZnO; Ag nanoparticles; Localized surface plasmons; Electronic fields; Enhancement
A polishing process for nonlinear optical crystal flats based on an annular polyurethane pad
by Defeng Liao; Ruiqing Xie; Jing Hou; Xianhua Chen; Bo Zhong (pp. 8552-8557).
► Annulus Chemical Mechanical Polishing process is developed based on the conventional CMP process for polishing crystals. ► A septum & holder system suitable for the crystal is employed to replace the carrier & driving spindle. ► A turning system and ring conditioner are developed for planarization of the base plate and the pad respectivley.A process based on chemical mechanical polishing has been proposed to polishing ultra-precision nonlinear optical crystal flats with high surface quality. An annular polyurethane pad was employed in the process. An excellent flatness of the annular polishing pad can be obtained using a special conditioner. The newly developed septum and holder system in the process has significantly reduced the rigid punch effect and workpiece/pad deflection brought by the spindle and carrier system in the common chemical mechanical polishing (CMP) process. In addition, the pre-strain of the pad by the septum can effectively eliminate the elastic response of the pad on the exterior of the workpiece and hence greatly reduce the stress concentration on the edge. The ACMP process is especially suitable for the final polishing of fragile crystals that have anisotropic properties and demand strict requirements on surface figure and defects.
Keywords: Chemical mechanical polishing; Nonlinear optical crystal flats; Annular polyurethane pad; Conditioner; Septum and holder system
130MeV Au ion irradiation induced dewetting on In2Te3 thin film
by P. Matheswaran; K.M. Abhirami; B. Gokul; R. Sathyamoorthy; Jai Prakash; K. Asokan; D. Kanjilal (pp. 8558-8563).
► In2Te3 phase formed from In/Te bilayer by 130MeV Au ion irradiation. ► Lower fluence results mixed phases with initial state of dewetting. ► At higher fluence, In2Te3 phase with complete dewetting pattern is formed. ► Thermal spike model is used to explain the inter face mixing phenomena. ► SHI irradiation may be used to functionalize the structural and surface properties of thin films.In/Te bilayer thin films were prepared by sequential thermal evaporation and subsequently irradiated by 130MeV Au ions. The pristine and irradiated samples were characterized by X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. RBS spectra reveal the sputtering of Te film and interface mixing, with increasing fluence. The surface morphology showed the beginning of dewetting of Te thin film and formation of the partially connected with the mixed zones at the fluence of 1×1013ions/cm2. At the higher fluence of 3×1013ions/cm2, dewetted structures were isolated at the surface. Above results are explained based on the formation of craters, sputtering and dewetting followed by inter-diffusion at the interface of molten zones due to thermal spike induced by Au ions.
Keywords: SHI irradiation; Bilayer mixing; Dewetting; Indium chalcogenide
A simple two-step method to fabricate highly transparent ITO/polymer nanocomposite films
by Haitao Liu; Xiaofei Zeng; Xiangrong Kong; Shuguang Bian; Jianfeng Chen (pp. 8564-8569).
► A simple two-step method without further surface modification step was employed. ► ITO nanoparticles were easily to be uniformly dispersed in polymer matrix. ► ITO/polymer nanocomposite film had high transparency and UV/IR blocking properties.Transparent functional indium tin oxide (ITO)/polymer nanocomposite films were fabricated via a simple approach with two steps. Firstly, the functional monodisperse ITO nanoparticles were synthesized via a facile nonaqueous solvothermal method using bifunctional chemical agent (N-methyl-pyrrolidone, NMP) as the reaction solvent and surface modifier. Secondly, the ITO/acrylics polyurethane (PUA) nanocomposite films were fabricated by a simple sol-solution mixing method without any further surface modification step as often employed traditionally. Flower-like ITO nanoclusters with about 45nm in diameter were mono-dispersed in ethyl acetate and each nanocluster was assembled by nearly spherical nanoparticles with primary size of 7–9nm in diameter. The ITO nanoclusters exhibited an excellent dispersibility in polymer matrix of PUA, remaining their original size without any further agglomeration. When the loading content of ITO nanoclusters reached to 5wt%, the transparent functional nanocomposite film featured a high transparency more than 85% in the visible light region (at 550nm), meanwhile cutting off near-infrared radiation about 50% at 1500nm and blocking UV ray about 45% at 350nm. It could be potential for transparent functional coating materials applications.
Keywords: Indium tin oxide (ITO); Solvothermal; N-methyl-pyrrolidone (NMP); Transparent; Nanocomposite
Preparation and tribological properties of self-lubricating TiO2/graphite composite coating on Ti6Al4V alloy
by Ming Mu; Xinjian Zhou; Qian Xiao; Jun Liang; Xiaodi Huo (pp. 8570-8576).
► A TiO2/graphite composite coating is produced on Ti alloy by one-step PEO process. ► The TiO2/graphite composite coating exhibits excellent self-lubricating behavior. ► The self-lubricating composite coating improves the wear resistance by comparison to the conventional PEO coating.One-step plasma electrolytic oxidation (PEO) process in a graphite-dispersed phosphate electrolyte was used to prepare a graphite-containing oxide composite coating on Ti6Al4V alloy. The composition and microstructure of the oxide coatings produced in the phosphate electrolytes with and without addition of graphite were analyzed by X-ray diffractometer (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The tribological properties of the uncoated Ti6Al4V alloy and oxide coatings were evaluated using a reciprocating ball-on-disk tribometer. Results showed that the graphite-containing oxide composite coating can be successfully produced on Ti6Al4V alloy in the graphite-dispersed phosphate electrolyte using PEO process. The graphite-containing oxide composite coating registered much lower friction coefficient and wear rate than the uncoated Ti6Al4V alloy and the oxide coating without graphite under dry sliding condition, exhibiting excellent self-lubricating property.
Keywords: Plasma electrolytic oxidation; Ti6Al4V; Oxide coating; Graphite; Friction and wear
Calcium–phosphate coatings obtained biomimetically on magnesium substrates under low magnetic field
by A. Yanovska; V. Kuznetsov; A. Stanislavov; S. Danilchenko; L. Sukhodub (pp. 8577-8584).
► Hydroxyapatite coatings used for medical implants. ► Magnesium is a promising implant material. ► Hydroxyapatite coatings was obtained on magnesium substrates at 37°C and pH=6.65. ► Coatings were obtained under the permanent magnetic field 0.3T. ► The difference in texture of brushite under magnetic field is observed.A simple method of hydroxyapatite (HA) coating deposition on Mg substrates at 37°C is proposed. It was established that variation of ionic composition of the initial solution leads to the deposition of coatings with various phase composition, i.e. DCPD, DCPD+HA, HA which decreased corrosion rate of Mg. The paper also discusses the crystallization of dicalcium phosphate dehydrate (DCPD) and HA coatings on Mg substrates obtained by dipping method under the permanent magnetic field (0.3T) in the neighborhood of the north and the south pole. A difference in particle morphology and crystal texture of precipitates in the north pole and the south pole proximity was observed. Lattice parameters of DCPD coatings obtained near opposite magnet poles were calculated using XRD results. It was found that the proximity to the south pole of magnet increases the crystallinity of calcium–phosphates. Increase of crystallite sizes in (020) and (040) plane was observed for DCPD in the presence of magnetic field.
Keywords: Brushite (DCPD); North and south pole of magnet; Magnesium; Hydroxyapatite (HA); Coating
Facile fabrication of superhydrophobic ZnO nanoparticle surfaces with erasable and rewritable wettability
by Jian Li; Hongqi Wan; Xiaohong Liu; Yinping Ye; Huidi Zhou; Jianmin Chen (pp. 8585-8589).
► Superhydrophobic ZnO surfaces were fabricated by a simple spray-coating method. ► The superhydrophobic ZnO surfaces show a high water contact angle of 162±1° and a low water sliding angle of 3±1°. ► The superhydrophobicity could be erased and rewritten with full reproducibility more than eight times.In this article, ZnO nanoparticle surfaces have been fabricated successfully by a simple spray-coating method without limitations the shape and size of substrates. After being chemically modified with stearic acid, the wettability of ZnO surfaces changed from superhydrophilicity to superhydrophobicity. Furthermore, the superhydrophobicity could be erased and rewrote by the alternation of plasma or heat treatment and stearic acid coating. The process has been repeated with full reproducibility more than eight times, demonstrating that the ZnO surfaces exhibit good erasable and rewritable superhydrophobicity.
Keywords: Superhydrophobic; Contact angle; ZnO; Rewritable
Performance improvement mechanisms of i-ZnO/(NH4)2S x-treated AlGaN MOS diodes
by Ching-Ting Lee; Ya-Lan Chiou; Hsin-Ying Lee; Kuo-Jen Chang; Jia-Ching Lin; Hao-Wei Chuang (pp. 8590-8594).
► The high quality of i-ZnO film could be deposited by a vapor cooling condensation system. ► The i-ZnO/(NH4)2S x-treated AlGaN MOS diodes shows low interface density of 2.95×1011cm−2eV−1. ► The band alignment of the i-ZnO/AlGaN interface was analyzed by XPS and CNL model. ► The band offset of the i-ZnO/AlGaN interface was increased by the (NH4)2S x surface treatment.The intrinsic ZnO ( i-ZnO) film was deposited by a vapor cooling condensation system and used as the dielectric layer of the AlGaN metal–oxide–semiconductor (MOS) diodes. Before the deposition of the i-ZnO dielectric layer, the AlGaN surface was treated using (NH4)2S x solution. In view of the lattice match of the i-ZnO film and the reduced surface state density of the (NH4)2S x-treated surface, the quality of the i-ZnO/AlGaN interface was improved. According to the experimental results, the i-ZnO/(NH4)2S x-treated MOS diodes revealed the lower leakage current, the lower interface state density, and the high electrical performances compared with the i-ZnO/untreated ones. Furthermore, the X-ray photoelectron spectroscopy and the charge neutrality level model were used to analyze the conduction band offset and the valence band offset of the i-ZnO/AlGaN interface. The valence band offset of the i-ZnO film contacted with the untreated and the (NH4)2S x-treated AlGaN layer was 1.53eV and 1.96eV, respectively. The conduction band offset of the i-ZnO film contacted with untreated and (NH4)2S x-treated AlGaN layers was 0.77eV and 1.20eV, respectively. The mechanisms of the enhanced conduction band offset were attributed to the effective reduce of interface states by using the (NH4)2S x surface treatment.
Keywords: Band offset; Charge neutrality level model; Interface state density; (NH; 4; ); 2; S; x; surface treatment; Vapor cooling condensation system; X-ray photoelectron spectroscopy
Microstructure, optical and electrical properties of Al-doped ZnO films grown by MOCVD
by Jianfeng Su; Chunjuan Tang; Qiang Niu; Chunhe Zang; Yongsheng Zhang; Zhuxi Fu (pp. 8595-8598).
► Al-doped ZnO films were grown on quartz substrates by MOCVD. ► The preferred orientation of ZnO films decreased with the increase of Al content. ► Decomposition products of TMA bringing down the surface activity of ZnO grains. ► UV emission peak initially red-shifted and then blue-shifted as increasing Al content. ► Low electrical resistivity of Al-doped ZnO films was obtained.Al-doped ZnO films were grown on quartz substrates by MOCVD. A systematical and detailed study about the effect of Al content on structural, optical and electrical properties were discussed. XRD measurements revealed that the preferred orientation of ZnO films decreased with the increase of Al content. AFM images indicated that the TMA molecules or their decomposition products bringing down the surface activity of ZnO grains, and so grain growth is inhibited. By the band tail states and the quantum confinement effect, the UV emission peak initially red-shifted and then blue-shifted. All Al-doped samples demonstrated more than 80% of the optical transparency in the visible region. Low electrical resistivity of Al-doped ZnO films was obtained. However, due to defects and grain boundary scattering which caused by Al doping, the hall mobility is increased initially and then decreased.
Keywords: ZnO; MOCVD; Al doped
Preparation and electrochemical characterization of NiO nanostructure-carbon nanowall composites grown on carbon cloth
by Hsuan-Chen Chang; Hsin-Yueh Chang; Wei-Jhih Su; Kuei-Yi Lee; Wen-Ching Shih (pp. 8599-8602).
► The CNWs were synthesized on carbon cloth by rf magnetron sputtering without any catalyst. ► Ni film was deposited on the synthesized CNWs by e-beam evaporator. Subsequently, the vacuum annealing process and oxygen plasma treatment were used to form the NiO nanostructures. ► NiO has several oxidation numbers that have quickly reversible redox reaction at the electrode surface. ► The electronic transmission in NiO could be more efficient to enhance the capacitive current response.This study provided a simple method to form NiO nanostructures onto the carbon nanowalls (CNWs) surface to enhance the performance of electric double layer capacitor (EDLC) characteristics. The CNWs were synthesized on carbon cloth by rf magnetron sputtering without any catalyst. Ni film was then deposited on the synthesized CNWs by e-beam evaporator. Subsequently, the vacuum annealing process and oxygen plasma treatment were used to form the NiO nanostructures. The crystallize structures of NiO nanostructures and CNWs were examined by Raman scattering spectroscopy. To realize the electrochemical properties of NiO/CNWs/carbon cloth composite, cyclic voltammetry (CV) and galvanostatic charge–discharge tests were investigated. Due to the relatively larger surface area of CNWs and the quickly reversible redox reaction and pseudo-capacitive properties of NiO nanostructures, the measured results demonstrated that the NiO/CNWs/carbon cloth is a suitable electrode material for EDLC applications.
Keywords: NiO; Carbon nanowall; Thermal chemical vapor deposition; Plasma enhance chemical vapor deposition; Electric double layer capacitor; Scanning electron microscopy
Preparation of Ni-reduced graphene oxide nanocomposites by Pd-activated electroless deposition and their magnetic properties
by Yan Wang; Yan Zhao; Tianjiao Bao; Xiang Li; Yuqin Su; Yuexin Duan (pp. 8603-8608).
► A novel multi-step electroless deposition was employed to fabricate Ni/graphene hybrid materials. ► Nickel nanoparticles with a diameter around 20nm were distributed uniformly on graphene sheets. ► Graphene oxide was reduced during electroless deposition. ► As-prepared Ni-RGO nanocomposites exhibit ferromagnetic properties with saturation magnetization of 11.05emu/g and coercivity of 200Oe, which hold a broad prospect of applications.Nickel nanoparticles (NiNPs) with a diameter of around 20nm were decorated on reduced graphene oxide (RGO) sheets by multi-step electroless deposition, to fabricate Ni-RGO nanocomposites. A uniform dispersion of NiNPs was achieved easily with numerous Pd nanoparticles as active centers, and graphene oxide sheets, the substrates, were reduced at the same time. The magnetic hysteresis loop of as-synthesized sample indicates Ni-RGO nanocomposites exhibit ferromagnetic properties with saturation magnetization of 11.05emu/g and coercivity of 200Oe, which hold a broad prospect of applications.
Keywords: Graphene; Nanocomposite; Nickel; Electroless deposition; Magnetic properties
Effect of polymer binder on surface texturing by photoembossing
by N.F. Hughes-Brittain; O.T. Picot; M. Dai; T. Peijs; C.W.M. Bastiaansen (pp. 8609-8612).
► Relief height in PMMA–DPPHA films of high aspect ratio are created by photoembossing. ► New mixtures for photoembossing are presented, containing greater monomer content. ► At high monomer contents, mixtures are solid at room temperature allowing mask exposure. ► Greater material flux during photo-polymerisation. ► This results in an increase in relief height by 50%.Photoembossing is a simple and versatile technique to create relief structures in polymers using a patterned contact mask exposure and a thermal development step. Typically, the photo-resist consists of a polymeric binder such as poly(benzyl methacrylate) (PBMA) and a multifunctional monomer in a 50/50 weight ratio and the mixture is a solid and non-tacky material at room temperature. Here, new mixtures for photoembossing are presented, which contain higher monomer content and therefore show greater material flux during photopolymerisation. These mixtures are solid at room temperature even at high monomer contents (60wt.%), which is achieved by using a polymer binder with a higher glass-transition temperature ( T g) such as poly(methyl methacrylate) (PMMA). DSC experiments also indicated that the interactions between monomer and PMMA are less strong compared to PBMA. The combined effect of increased monomer content and weakened interactions with PMMA led to a greater mobility of the monomer and an increase in height of the relief structures by a 50%.
Keywords: Abbreviations; PBMA; poly(benzyl methacrylate); PMMA; poly(methyl methacrylate); DPPHA; dipentaerythritol penta-/hexa-acrylate; PGMEA; propylene glycol mono methyl ether acetateSurface texturing; Polymer; Photoembossing; Contact mask exposure
Oxidation and diffusion processes at the Mn-doped Fe(001) and Fe(110) surfaces from first-principles
by S. Chen; M.-L. Giorgi; J.-B. Guillot; G. Geneste (pp. 8613-8618).
► The presence of Mn in the Fe surface layer does not favour the O adsorption. ► The energy barriers for O, Fe or Mn diffusion are lower on Fe(110) than on Fe(100). ► On the Fe(001) termination, the Mn and O adatoms are more mobile than Fe. ► On the Fe(110) termination, the Mn adatom is much more mobile than O and Fe. ► The formation of MnO (resp. FeO) from adatoms is exothermic (resp. endothermic).Using density-functional calculations, we have studied the adsorption of atomic oxygen on the Fe(001) and Fe(110) surfaces with and without Mn substitution at the top layer, as well as the diffusion mechanisms of oxygen and metal adatoms (Fe, Mn) on these two surfaces. The elementary processes studied give microscopic insight into the first stages of selective oxidation of Fe–Mn steels, a phenomenon that leads, in suitable thermodynamic conditions, to the growth of MnO particles at the iron surface. Our calculations provide significant differences between the two terminations, especially in the diffusion barriers of the different atomic chemical species involved in these complex growth processes.
Keywords: Selective oxidation; Density functional calculations; Bcc iron surfaces; O; 2; adsorption; Surface diffusion barriers
Preparation of hydrogenated-TiO2/Ti double layered thin films by water vapor plasma treatment
by L.L. Pranevicius; D. Milcius; S. Tuckute; K. Gedvilas (pp. 8619-8622).
► We investigated reaction of water plasma with nanocrystalline TiO2 films. ► Simultaneous oxidation and hydrogenation of Ti was observed during plasma treatment. ► Water plasma treatment forms hydrogenated nanocrystalline TiO2 in the shallow surface.We have investigated the structural and compositional variations in 200–500nm thick Ti films deposited by magnetron sputter-deposition technique and treated in water vapor plasma at different processing powers. It was found that the upper layer of treated film with the thickness of 110nm was changed into the black hydrogenated-TiO2 with around 16nm sized nanocystals during 10min for dissipated power 200W at room temperature. Analysis of the experimental results is used to obtain insights into the effects of water layer adsorbed on hydrophilic oxidized titanium surfaces exposed to plasma radiation.
Keywords: Titanium; Thin film; Water vapor plasma; Oxidation; Hydrogenation
Controllable synthesis of functional nanocomposites: Covalently functionalize graphene sheets with biocompatible L-lysine
by Zunli Mo; Hao Gou; Jingxian He; Peipei Yang; Chao Feng; Ruibin Guo (pp. 8623-8628).
Display Omitted► The biocompatible L-lysine functionalized graphene sheets (Gs/Lys) were synthesized controllably using a novel method. ► The Gs/Lys nanocomposites are water-soluble, biocompatible and chiral. ► A chiral graphene derivative was proposed.In this paper a novel method to synthesize functionalize graphene sheets (Gs) by biocompatible L-lysine (Gs/Lys) is reported. The method was composed of two steps: (1) we controllably synthesized self-assembly Gs/Lys-Cu-Lys through the terminal amino of copper L-lysine (Lys-Cu-Lys) attaching to graphite oxide (GO) and then reducing. (2) Obtained the Gs/Lys by eliminating the copper ion. This method could also be used to functionalize other nanomaterials by L-lysine. The Gs/Lys nanocomposites are water-soluble, biocompatible, and above all, it is a chiral material of graphene, which is proposed by us. This novel material will be promising for more applications of graphene. The formation of Gs/Lys nanocomposites were confirmed by scanning electron microscopy (SEM), Fourier-transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermal gravimetric (TG) analysis.
Keywords: Graphene; L-lysine; Nanocomposites; Water-soluble
Structure and mechanical properties of TiC films deposited using combination of pulsed DC and normal DC magnetron co-sputtering
by K.H.T. Raman; M.S.R.N. Kiran; U. Ramamurty; G. Mohan Rao (pp. 8629-8635).
► Variation of preferred orientation with carbon content in the film. ► Variation of surface microstructure with Ti and C ratio. ► Coefficient of friction varies between 0.15 and 0.04 for all Ti and C ratio. ► Synthesis of TiC thin films using pulsed balanced magnetron sputtering. ► Better mechanical properties with reduced ion bombardment effect.Titanium–carbon (TiC) thin films of different compositions were prepared by a combination of pulsed DC (for Ti target) and normal DC (for graphite target) magnetron co-sputtering on oxidized silicon and fused quartz substrates. At 33.7at.% of C content, pure hcp Ti transforms into fcc-TiC with a preferential orientation of (220) along with (111) and (200). A clear transformation in the preferential orientation from (220) to (111) has been observed when the C content was increased to 56at.%. At 62.5at.% of C, TiC precipitates in an amorphous carbon matrix whereas further increase in C leads to X-ray amorphous films. The cross-sectional scanning electron microscope images reveal that the films with low carbon content consists of columnar grains, whereas, randomly oriented grains are in an amorphous carbon matrix at higher carbon content. A dramatic variation was observed in the mechanical properties such as hardness, H, from 30 to 1GPa and in modulus, E, from 255 to 25GPa with varying carbon content in the films. Resistance to plastic deformation parameter was observed as 0.417 for films containing 62.5at.% of C. Nanoscratch test reveals that the films are highly scratch resistant with a coefficient of friction ranging from 0.15 to 0.04.
Keywords: Titanium carbide; Pulsed balanced magnetron; Preferred orientation; Nanocomposite; Nanoindentation
Ga-grading profiles formed by incorporation of gallium into Cu(In1− xGa x)Se2 absorber thin films
by J. Wang; Y.F. Zhang; F. Dong; J. Zhu (pp. 8636-8640).
► CIGS thin films with Ga-grading profile were prepared by evaporation of Ga xSe for incorporation of gallium. ► The process was found to have little effect on the film structure. ► No new impurity phases were detected. ► The proposed process was feasible for forming a ‘notch’ Ga-graded structure in CIGS thin films.Cu(In1− xGa x)Se2 (CIGS) polycrystalline thin films were prepared by the two-stage method for two different precursors corresponding to the sequences CuGa/CuIn/CuGa and CuGa/In/Cu/CuGa, respectively. In order to obtain the required Ga-grading profile, co-evaporation of Ga xSe for incorporation of gallium into CIGS was used. Experimental results show that CIGS films were prepared by the proposed process with a ‘notch’ Ga-graded distribution, and the surface morphologies of the films after gallium incorporation were significantly changed compared with that of the as-selenized films, and the process was found to have little effect on the film structure. No new impurity phases have been found. The main XRD peaks shows a slight shift to higher diffraction angles with increasing Ga content, which could be attributed to Ga atoms substituting for In atoms in the chalcopyrite structure. The result of the present work implied that the proposed process was feasible for forming a ‘notch’ Ga-graded structure in CIGS thin films.
Keywords: Cu(In; 1−; x; Ga; x; )Se; 2; (CIGS); Ga-grading; Gallium incorporation; Chalcopyrite
Evolvement of cell–substrate interaction over time for cells cultivated on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface
by Chung-Ping Hsu; Po-Yen Hsu; You-Lin Wu; Wan-Yun Hsu; Jing-Jenn Lin (pp. 8641-8648).
► Cell–substrate interaction of single cells was observed directly from the post-cell-removal imprint left on γ-APTES soft substrate surface. ► The time evolvement of the cell–substrate interaction can be obtained by cultivating cells on the γ-APTES surface for different periods of time. ► The cell–substrate interaction property can be found from the post-cell-removal surface morphology profiles determined by AFM. ► It was found that the cancer cells tend to form deeper trenches along the circumference of the imprints, while the normal cells do not.Since cell–substrate interaction is directly related to the traction force of the cell, the cell property can be judged from the imprint it leaves on the soft substrate surface onto which the cell is cultured. In this letter, the evolvement of the cell–substrate interaction over time was observed by cultivating cells on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface for different periods of time. The cell–substrate interaction property as a function of time can then be found from the post-cell-removal surface morphology profiles determined by atomic force microscopy (AFM). Different surface morphology profiles were found between normal cells and cancer cells. It was found that the cancer cells tend to form deeper trenches along the circumference of the imprints, while the normal cells do not. In addition, our results indicated that normal cells involve cell–substrate interaction mechanisms that are different from those for cancer cells.
Keywords: Cell–substrate interaction; Atomic-force microscopy; Normal cells; Cancer cells; Cell imprints
Wafer-scale fabrication of silicon nanowire arrays with controllable dimensions
by Wei Wang; Dan Li; Miao Tian; Yung-Cheng Lee; Ronggui Yang (pp. 8649-8655).
Display Omitted► Wafer scale Si nanowire arrays can be fabricated through a simple route. ► The sizes of Si nanowires can be well controlled. ► Micro/nano hybrid structure can be obtained using same process.A novel and facile method was successfully developed to fabricate wafer-scale Si nanowire arrays with well-controlled sizes through the in-situ porous anodic alumina (PAA) template-assisted wet-etching process. The diameter and filling ratio (inter-wire spacing) of the as-prepared Si nanowires are determined by the size and density of pores in the in-situ PAA templates, which can be tailored independently by adjusting the anodization voltages and the immersion time of PAA templates in phosphoric acid. The length of Si nanowires can be more than one hundred micrometers long, which is controlled by adjusting the wet-etching time. Moreover, this method is compatible with complex Si surface topology for creating desirable 3-dimensional hybrid micro/nano-structures. Such Si nanowire arrays exhibit ultralow reflectance and interesting wettability that are of great importance to photovoltaics and thermal management applications.
Keywords: PACS; 81.05.Cy; 81.07.Gf; 81.10.Dn; 81.16.Be; 81.20.KaSilicon nanowires; PAA template; Dimension controllability
A new strategy to grow polymer brush on graphene oxide surface through microwave assisted polymer synthesis
by Min Su Park; B. Ramaraj; Kuk Ro Yoon (pp. 8656-8661).
► A new method for growing polymers directly from GPO surface was demonstrated. ► The IR peak characteristic of C–Cl stretching confirms the attachment of polymer layer on the GPO surface. ► TGA analysis indicate enhance thermal stability for polymer grafted GPO. ► EDX and XPS analysis show signal corresponding to chloride with proportionate reduction in oxygen percentage. ► SEM and TEM images show a fine layer of polymer coating on the surface of GPO.Herein, we report a method for growing polymers directly from the surface of graphene oxide (GPO). In this method, surface-initiated, microwave irradiation supported polymerization of benzyl chloride carrying vinylates was carried out from the surface of graphene oxide (GPO) for tailoring surface properties of GPO. This synthetic method consists of two important steps: first, the graphene was converted into GPO, then vinylbenzyl chloride (VBC) was polymerized on the surface of GPO by microwave induced irradiation polymerization. The structure and properties of the resultant polymeric conjugates were characterized by a range of characterization techniques viz.: Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The FT-IR analysis of polymeric conjugates shows infrared (IR) peaks characteristic of VBC on the surface of GPO. TGA reveals enhanced thermal stability for GPO surface polymerized with VBC. EDX and XPS analysis shows signal corresponding to the chloride with reduction in oxygen percentage and increase in carbon percentage. SEM and TEM images visually show the presence of PVBC polymer layer on GPO surface.
Keywords: Graphene oxide; Vinylbenzyl chloride; Surface polymerization; Microwave irradiation; Graphene
Self assembled surface adjoined mesoscopic spheres of SnO2 quantum dots and their optical properties
by Shweta Sharma; A.K. Srivastava; Santa Chawla (pp. 8662-8666).
► One pot solution synthesis of well crystalline SnO2 quantum dots. ► Self assembly of quantum dots into mesoscopic spheres by surface adjoinment without template. ► Quantum confinement effect observed for SnO2 quantum dots. ► Luminescence and decay time indicate the recombination mechanism. ► Large area meso spheres with quantum confined properties of SnO2 quantum dots achieved.A simple one pot acidic solution single precursor synthesis method has lead to highly crystalline SnO2 quantum dots (QD) that self assemble to form mesoscopic spheres. The precursor solvent and pH conditions were changed to optimise the crystalline quality, particle size and luminescence properties of SnO2 QDS. X-ray diffraction and high resolution transmission electron microscopy clearly reveal the crystalline nature of SnO2 particles of size about 2.5nm with well defined lattice fringes and the surface adjoining to form mesoscopic spheres. Band gap enhancement due to quantum confinement effect has been observed. Blue luminescence and fast decay (1.2ns) indicate creation of exciton and recombination with an oxygen vacancy centre. The results suggest that the optical properties follow the quantum size effect whereas the mesoscopic spheres of self assembled QDs lower the surface energy and provide large surface area for applications such as photovoltaic and gas sensing.
Keywords: Quantum dot; Optical band gap; Photoluminescence; Mesoscopic sphere
Thermal behavior of Ni- and Cu-containing plasma electrolytic oxide coatings on titanium
by V.S. Rudnev; S. Wybornov; I.V. Lukiyanchuk; T. Staedler; X. Jiang; A.Yu. Ustinov; M.S. Vasilyeva (pp. 8667-8672).
.Display Omitted► Plasma electrolytic oxidation of titanium. ► NiO and CuO inclusions into PEO coatings result in CO oxidation above 200°C. ► Annealing leads to Cu content decrease and whiskers formation. ► Oxide surfaces coated by whiskers.In this work the effect of thermal annealing on the surface composition, structure and catalytic activity in CO oxidation of NiO+CuO/TiO2/Ti composites is studied. The composites have been obtained by a plasma electrolytic oxidation (PEO) technique, followed by impregnation in a solution of nickel (II) and copper (II) salts and air annealing. The structures contain ∼20at% Ni and ∼12at% Cu. It has been shown that the additional air annealing of such structures at temperature above 750°C results in phosphate crystallization in the coatings and decreasing of Cu concentration in the surface layers. A growth of filiform nanocrystals containing mainly oxygen compounds of nickel and titanium on the coating surface takes place at the temperatures above 700°C. The nanocrystals have a diameter of 50–200nm and lengths below 10μm. Such changes result in decreasing of catalytic activity of the composites in CO oxidation. At the same time the ascertained regularities may be of interest for obtaining the Ni-containing oxide catalysts with an extended surface, perspective for usage in organic catalysis or for preparing oxide nanofibers.
Keywords: Oxide composites; Titanium; Plasma electrolytic oxidation; Thermal annealing; Surface morphology; CO oxidation; Filiform nanocrystals
Oxygen-induced physical property variation of deposited ZnO films by metal–organic chemical vapor deposition
by Zhifeng Shi; Shikai Zhang; Bin Wu; Xupu Cai; Jinxiang Zhang; Wei Yin; Hui Wang; Jin Wang; Xiaochuan Xia; Xin Dong; Baolin Zhang; Guotong Du (pp. 8673-8677).
► The microstructure of the film changes from nanorods form to continuous dense form as oxygen flow rate increases. ► With increase of oxygen discharge, the position of DLE in PL spectra demonstrates a significant shift, with transformation from VO to VZn. ► Qualitative percentage of surface VO from XPS data demonstrates an evident decrease trend from 43.7% (180sccm) to 34.4% (250sccm). ► The results indicate that higher O2-flow rate is able to promote OZn bond formation and reduce the number of VO.High-quality ZnO thin films were deposited on 6HSiC substrates using metal–organic chemical vapor deposition system. The physical properties of as-prepared ZnO layers under various oxygen flow rate were thoroughly studied. An increase in the O/Zn ratio yielded a decrease in growth rate. The experimental results also indicated that the size of ZnO nanoparticles, lattice constant and compressive stress inside the films displayed a regular variety as a function of O2-flow rate. In addition, with increase of oxygen discharge, the position of deep-level emission in photoluminescence spectra demonstrated a significant shift, with transformation from oxygen vacancy to zinc vacancy. The qualitative calculation from X-ray photoelectron spectroscopy data showed that higher O2-flow rate was able to promote OZn bond formation and reduce the number of oxygen vacancies.
Keywords: ZnO; Oxygen flow rate; Deep-level emission; Oxygen vacancy
Study on adsorption of O2 on LaFe1− xMg xO3 (010) surface by density function theory calculation
by Xing Liu; Bin Cheng; Jifan Hu; Hongwei Qin (pp. 8678-8682).
► Mg-doping can change the electronic properties of LaFeO3 (010) surface by decreasing the band gap. ► The position and content of Mg-doping can both affect the ability to adsorb O2. ► The strong hybridization between O2 p and Fe d orbital is the origin of binding mechanism.The adsorption of O2 on the clean and Mg doped LaFeO3 (010) surface has been investigated using the density functional theory (DFT) method. Calculation results show that Mg-doping can change the electronic properties of LaFeO3 (010) surface by decreasing the band gap. When Mg ions were not on the first layer of the surface, with increasing Mg content the adsorption of O2 was enhanced. When Mg ions were on the first layer, the adsorption of O2 was weakened with the increase of Mg content. The analysis results of the DOS indicated that the Mg ion and adsorbed O2 had no strong hybridization, and the bonding mechanism was originated from the strong hybridization between the O p and Fe d orbital. Referring to all the calculation results, it was found that except for the increase of stability of oxygen adsorption, the Mg doping could not improve the sensitivity to O2.
Keywords: Perovskites; Doping; Oxygen adsorption; Density functional theory (DFT)
Structural and morphological modifications of the Co-thin films caused by magnetic field and pH variation
by Agnieszka Franczak; Alexandra Levesque; Frederic Bohr; Jacques Douglade; Jean-Paul Chopart (pp. 8683-8688).
► Co electrodeposits were obtained at high electrolyte temperature under applied magnetic field. ► The temperature is commonly used in the industrial process. ► The effects of magnetic field up to 1T and pH on structure and morphology were investigated. ► The high process temperature enhances HER which is diminishing by the magnetic field application.Cobalt films were deposited by use of the electrochemical process from a cobalt (II) sulfate solution on a titanium electrode and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The experiments at electrolyte temperature of 50°C were performed which is commonly used in the industrial process. The effects of pH and low uniform magnetic field up to 1T on structure and morphology changes were investigated. The detected phase composition indicates the presence of both phases: hexagonal centered packed and face centered cubic independent on the pH value and the applied magnetic field amplitude. Calculation of the orientation index of Co phase shows the preferential orientation in the films obtained at higher pH. SEM micro-imagines have shown the nucleus shape transition from coarse-grained to needle-shaped dependent on the application of B-field as well as on the pH variation in the case of higher pH level. Co-films obtained from the electrolyte of low pH were characterized by the fine-grained morphology which was not modified by the influence of magnetic field. AFM images proved the effect on roughness of the Co-films which is closely related with the obtained morphology.
Keywords: Cobalt deposition; Structure and morphology modifications; Magnetic field effect; pH effect; Electrolyte temperature
Atomic force microscopy based repeatable surface nanomachining for nanochannels on silicon substrates
by Zhuxin Dong; Uchechukwu C. Wejinya (pp. 8689-8695).
► A diamond tip is employed for AFM based surface nanomachining on silicon. ► Nanochannels are produced at different user-control parameter settings. ► Scratching number up to 5 is conducted to investigate the correlation. ► The dimensions of nanochannels are analyzed using linear and logarithmic fits. ► Current results can be used for reliable predicting the fabrication of nanochannels.The atomic force microscopy (AFM)-based repeatable nanomachining for nanochannels on bare silicon surfaces is investigated experimentally for automated nano manufacturing applications. The relationship between the normal force applied on the AFM cantilever and the channel depth is established and analyzed using both linear and logarithmic fits. Thus, current results can be regarded as the calibration reference in order to accurately predict the nanochannel depth for additional nanotechnology related applications. An accurate prediction of the depth is not only for accuracy and efficiency, but also to prevent a costly diamond tip from unnecessary wear and tear. Furthermore, the experimental results also reveal that the fabrication procedure is repeatable.
Keywords: AFM; Surface nanomachining; Diamond tip; Si substrate; Linear and logarithmic fit
Preparation and characterization of visible-light-driven N–F–Ta tri-doped TiO2 photocatalysts
by Wei Wang; Chunhua Lu; Yaru Ni; Mingxing Su; Wenjuan Huang; Zhongzi Xu (pp. 8696-8703).
.Display Omitted► N–F–Ta tri-doping can further improve the visible-light photoactivity of N single doped TiO2. ► There are N 2p–Ta 5d hybridized states which narrow the band gap and reduce the photogenerated electrons and holes recombination rate located in the gap region of TiO2. ► The introduced F atoms enhance the N incorporation which further promote the N 2p–Ta 5d hybridized states. ► Charge compensation during the doping process is a very important factor.A new strategy to synthesize visible-light-driven N doped and N–F–Ta tri-doped TiO2 nanocatalysts via a hydrothermal combined with heat treatment method applied in Rhodamine B (RhB) and phenol decomposition was reported. The tri-doped sample gave the highest visible-light photocatalytic activity when the molar ratio of Ta to Ti was 1%. At a low tri-doping level, physicochemical analysis indicated that the synergistic effects of N, F and Ta could effectively increase not only the crystallite surface area but also the light absorption andOH generation ability, which contributed to the enhancement of visible-light photocatalytic activities. EPR and XPS analysis demonstrated that N–Ta interaction induced the charge compensation to form N 2p–Ta 5d hybridized states which improved the separation ability of the photoexcited electron–hole pairs. Still, F incorporation facilitated the incorporation of N which further promoted the N 2p–Ta 5d hybridized states. The N 2p, π*N–O, oxygen vacancy, Ti3+ and Ta 5d states were also responsible for the band gap narrowing. However, a high tri-doping level would affect the crystal growth and introduce too many defects into the lattice, reducing the visible-light photoactivity.
Keywords: Titanium dioxide; Hybridized state; Synergistic effect; Band gap narrowing; Visible-light photoactivity
Preparation and characterization of SnO2/ZnO/TiO2 composite semiconductor with enhanced photocatalytic activity
by Guidong Yang; Zifeng Yan; Tiancun Xiao (pp. 8704-8712).
Display Omitted► Synthesis of SnO2/ZnO/TiO2 composite photocatalyst using sol–gel and solid-state methods. ► The structure of composites is investigated by XRD, Raman, XPS and SEM. ► Composite semiconductors show the enhanced catalytic activity under UV and visible light. ► High activity is attributed to the increased separation of the charge carriers.In this study, SnO2/ZnO/TiO2 composite photocatalysts were successfully synthesized using sol–gel and solid-state methods. The as-prepared samples were characterized for the phase structure, optical absorption, thermal stability and surface property using X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The photocatalytic activity was tested with photodecomposition of Methyl Orange under both visible and UV light irradiations. The results indicated that the SnO2/ZnO/TiO2 composite materials have an apparent visible light absorption, combining TiO2 with SnO2 and ZnO could promote the TiO2 phase transition from anatase to rutile. The SnO2/ZnO/TiO2 heterojunctions with the highest performance was the one prepared using Sn(Zn)/Ti molar ratio of 0.05. It was found that the enhanced photocatalytic activity could be attributed to the increased separation of the charge carriers, which therefore depress the charge pair recombination and prolonged the electron lifetime in the composite structure, and a large number of electrons could take part in the photoreaction. Based on the results of the present study, a tentative mechanism for the enhanced photocatalysis of the SnO2/ZnO/TiO2 composite catalyst has been proposed.
Keywords: Composite semiconductor; Heterojunction; Visible light; SnO; 2; ZnO; TiO; 2; Photocatalyst
Phase formation and thermal stability of periodic Ni-silicide nanocontact arrays on epitaxial Si1− xC x layers on Si(100)
by S.L. Cheng; Y.C. Tseng; S.W. Lee; H. Chen (pp. 8713-8718).
► The interfacial reactions of nanoscale Ni metal dots on single-crystal Si1− xC x/Si(100) substrates were investigated. ► The incorporation of C to Si substrates exhibited significant beneficial effects on improving the thermal stability of low-resistivity NiSi nanocontacts. ► The process window of low-resistivity NiSi in the Ni nanodots/Si1− xC x(100) sample was greatly extended by 200–250°C as compared to that in the Ni nanodots/Si(100) sample. ► Highly curled and tangled amorphous SiO x nanowires with diameters of 8–20nm were found to form on the 900°C annealed Ni nanodots/Si1− xC x(100) samples.We report here on the first study of the interfacial reactions of nanoscale Ni metal dots on single-crystal Si1− xC x(100) substrates at various heat treatments. The formation of high-resistivity NiSi2 phase was found to be more favorable for the miniature size Ni nanodots. The incorporation of C to Si substrates exhibited significant beneficial effects on improving the thermal stability of low-resistivity NiSi nanocontacts. The process window of low-resistivity NiSi in the Ni nanodots/Si1− xC x(100) sample was greatly extended by 200–250°C as compared to that in the Ni nanodots/Si(100) sample. The presence of C atoms is thought to lower the NiSi nanocontact/Si1− xC x interface energy and/or to block the Ni diffusion paths during high temperature annealing. For the Ni nanodots/Si1− xC x(100) sample annealed at 900°C, highly curled and tangled amorphous SiO x nanowires with diameters of 8–20nm were found to form. The growth process of these amorphous SiO x nanowires could be explained by the solid–liquid–solid (SLS) mechanism.
Keywords: Si; 1−; x; C; x; Nanosphere lithography; Ni silicide; Nanocontact; Phase formation
Y thin films by ultrashort pulsed laser deposition for photocathode application
by A. Lorusso; M.L. De Giorgi; C. Fotakis; B. Maiolo; P. Miglietta; E.L. Papadopoulou; A. Perrone (pp. 8719-8723).
► We deposit Y thin films by pulsed laser ablation with 0.5 and 5ps pulse durations. ► Y thin films deposition is interesting for photocathode application. ► Y thin films are well adherent to the substrate with a high abundance of nano-particles on the film surface. ► Nano-particles abundance decreases as a function of the laser fluence.In this work, the deposition of Y thin films by laser beams with 0.5ps and 5ps pulse durations at different laser fluences (1.2–6.4J/cm2) is reported. The morphology of the deposited films and of the ablated target surface is investigated by scanning electron microscopy analyses. The present results show that the films, well adherent to the substrates, are characterized by a high abundance of sub-micrometric particulates with average size less than 0.3μm, whose density decreases with increasing laser fluence. The formation of columnar structures observed on the target surface seems to be responsible of the poor film homogeneity. Acceptable deposition rate in the range of 0.08–0.16Å/pulse with 5ps pulse duration is found; on the contrary with 0.5ps pulse duration, it is not possible to get information on deposition rate as a function of the laser fluence due to the high non-uniformity of the films. A comparison with the results previously obtained in ns regime is presented and discussed. The achievements of our investigation will be useful to optimize the synthesis of photocathodes based on Y films for the production of bright electron beams in radio-frequency photoinjectors.
Keywords: Pulsed laser ablation; Scanning electron microscopy; Y thin films; Photocathodes
Micro/nanostructure evolution of zircaloy surface using anodization technique: Application to nuclear fuel cladding modification
by Chan Lee; Hyungmo Kim; Ho Seon Ahn; Moo Hwan Kim; Joonwon Kim (pp. 8724-8731).
► We studied morphological evolution of surface structure on zircaloy anodization. ► The surface evolves from nanotubes to the superhydrophilic dual-scaled structure. ► Easy control of surface structure and corresponding wettability are reported. ► Our fabrication can greatly improve critical heat flux (CHF) of the zircaloy surface. ► This discovery would greatly contribute safety of nuclear power plant.Zircaloy with nano-scale and micro/nano-scale (dual-scale) surface structures was fabricated using an anodic oxidation fabrication technique. The surface structure evolved as a function of duration of anodization. The resulting nanotubes and dual-scale surface structure were characterized by scanning electron microscopy (SEM) to analyze the evolution of the structures. The current density curve during the anodization was closely related to morphology of surface structure. Thus, surface structures can be selectively fabricated by watching the current density and controlling the duration of anodization. Control of surface structure formation resulted in change of wettabilities in the range of 0°–50° contact angle. The modified surfaces significantly enhanced critical heat flux, meaning this simple yet effective surface modification method can enhance the thermodynamic performance of the surface, especially in the case of the nuclear fuel cladding application. This technique would greatly contribute to the safety of nuclear reactors.
Keywords: Dual-scale structures; Superhydrophilic; Anodic oxidation; Nanotubes; Nuclear materials
Tensile property of a hot work tool steel prepared by biomimetic coupled laser remelting process with different laser input energies
by Chuanwei Wang; Hong Zhou; Zhihui Zhang; Yu Zhao; Peng Zhang; Dalong Cong; Chao Meng; Fuxing Tan (pp. 8732-8738).
► Biomimetic coupled laser remelting (BCLR) process. ► Good combination of strength and ductility in the BCLR-processed hot work tool steel. ► Explanation of tensile property improvement on basis of microstructural changes and stress transfer reinforcement. ► Laser input energy was selected through surface morphology of biomimetic units and tensile test of BCLR samples.Coupled with the biomimetic principle, a hot work tool steel (4Cr5MoSiV1) was manufactured using a laser with different input energies. Results of tensile tests confirmed that the biomimetic coupled laser remelting (BCLR) process had an advance effect on improving the strength and ductility of 4Cr5MoSiV1 steel simultaneously. Microstructure examinations demonstrated that a fine microstructure along with nano scale carbide was acquired in the BCLR units, which produced an accumulative contribution of grain refinement, precipitation strengthening and a mixed microstructure. Based on the well distribution of the BCLR units, the beneficial effect of stress transfer from the matrix to the units on tensile property was also analyzed.
Keywords: Hot work tool steel; Biomimetic unit; Laser remelting; Tensile property
Sticky superhydrophobic filter paper developed by dip-coating of fluorinated waterborne epoxy emulsion
by Xiangxuan Huang; Xiufang Wen; Jiang Cheng; Zhuoru Yang (pp. 8739-8746).
► Fluorinated waterborne epoxy emulsion was synthesized for oil filter paper. ► Performances of fluorinated waterborne epoxy resin co-polymer were investigated. ► TEM was performed to observe the morphology of the emulsions particles. ► Superhydrophobic and superoleophilic filter paper was fabricated for O/W separation.A superhydrophobic and superoleophilic coating for oil filter paper was synthesized based on waterborne bisphenol-A novolac epoxy emulsion. The benzoic acid (BA) and maleic anhydride (MA) were used as modification agents to give the epoxy resin hydrophilic groups (carboxyl) and CC double bonds. And the fluorinated waterborne epoxy emulsion was prepared by free radical solution polymerization of dodecafluoroheptyl methacrylate (DFMA) monomer. The covalent bound low free energy fluorinated chains in the monomer reduce the surface energy of solidification polymers sufficiently to give rise to superhydrophobic behavior while conserving superoleophilicity. Surfaces prepared show a sticky property, which exhibits a static water contact angle of 152° for a 5μL droplet that does not slid off even when the sample is held upside down. This synthetic emulsion is simple and convenient as impregnating agent for filter paper, which can be considered as a suitable candidate for various substrates such as cotton textiles, E-glass and artificial fiber, and so on.
Keywords: Epoxy resin; Superhydrophobic; Superoleophilic; Sticky; Cellulose; Impregnating agent
Nanoporous metallic surface: Facile fabrication and enhancement of boiling heat transfer
by Yong Tang; Biao Tang; Jianbo Qing; Qing Li; Longsheng Lu (pp. 8747-8751).
► A facile approach for fabricating nanoporous metallic surface is proposed. ► The formation mechanism of the nanoporous structure is investigated. ► The morphology and wettability of the nanoporous surface are characterized. ► The nanoporous surface shows significant enhancement of boiling heat transfer.The paper reports a flexible and low-cost approach, hot-dip galvanizing and dealloying, for the fabrication of enhanced nanoporous metallic surfaces. A Cu–Zn alloy layer mainly composed of γ-Cu5Zn8 and β′-CuZn was formed during the hot-dipping process. The multiple oxidation peaks recorded in the anodic liner sweep voltammetry measurements indicate different dezincification preferences of the alloy phases. A nanoporous copper surface with approximately 50–200nm in pore size was obtained after a free corrosion process. The nanoporous structure improves the surface wettability and shows dramatic reduction of wall superheat compared to that of the plain surface in the pool-boiling experiments.
Keywords: Nanoporous metallic surface; Hot-dip galvanizing; Dealloying; Boiling enhancement
Crack propagation behavior of TiN coatings by laser thermal shock experiments
by Youngkue Choi; Seol Jeon; Min-seok Jeon; Hyun-Gyoo Shin; Ho Hwan Chun; Youn-seoung Lee; Heesoo Lee (pp. 8752-8757).
► The crack propagation behavior of TiN coating after laser thermal shock experiment was observed by using FIB and TEM. ► Intercolumnar cracks between TiN columnar grains were predominant cracking mode after laser thermal shock. ► Cracks were propagated from the coating surface to the substrate at low laser pulse energy and cracks were originated at coating-substrate interface at high laser pulse energy. ► The cracks from the interface spread out transversely through the weak region of the columnar grains by repetitive laser shock.The crack propagation behavior of TiN coatings, deposited onto 304 stainless steel substrates by arc ion plating technique, related to a laser thermal shock experiment has been investigated using focused ion beam (FIB) and transmission electron microscopy (TEM). The ablated regions of TiN coatings by laser ablation system have been investigated under various conditions of pulse energies and number of laser pulses. The intercolumnar cracks were predominant cracking mode following laser thermal shock tests and the cracks initiated at coating surface and propagated in a direction perpendicular to the substrate under low loads conditions. Over and above those cracks, the cracks originated from coating-substrate interface began to appear with increasing laser pulse energy. The cracks from the interface also spread out transversely through the weak region of the columnar grains by repetitive laser shock.
Keywords: Crack propagation; Laser ablation; Focused ion beam; Transmission electron microscopy
Visible laser induced positive ion emissions from NaCl nanoparticles prepared by droplet rapid drying
by Mao-Xu Sun; Deng-Zhu Guo; Ying-Jie Xing; Geng-Min Zhang (pp. 8758-8763).
► NaCl nanoparticles were firstly prepared by heat induced explosion on silicon wafer. ► We found that laser induced ion emissions from NaCl nanoparticles are more prominent. ► We found that water adsorption can efficiently enhance laser induced ion emissions. ► The ultra-photothermal effect in NaCl nanoparticles was observed and explained.A novel convenient way for the formation of sodium chloride (NaCl) nanoparticles on silicon wafer is proposed by using a droplet rapid drying method. The laser induced positive ion emissions from NaCl nanoparticles with and without water treatment is demonstrated by using a laser desorption/ionization time-of-flight mass spectrometer, with laser intensity well below the plasma formation threshold. It is found that the positive ion emissions from NaCl nanoparticles are obviously higher than that from microsize NaCl particles under soft 532nm laser irradiations, and water adsorption can efficiently enhance the ion emissions from NaCl nanoparticles. The initial kinetic energies of the emitted ions are estimated as 16–17eV. The synergy of the ultra-thermal effect in nanomaterials, the defect-mediated multiphoton processes, and the existence of intermediate states in NaCl-water interfaces are suggested as the mechanisms.
Keywords: Sodium chloride; Nanoparticle; Pulsed laser; Ion emission; Mass spectrometer
The Influence of Ta underlayers on the structure of TiO2 thin films deposited on an unheated glass substrate
by Masao Kamiko; Kazuaki Aotani; Ryo Suenaga; Jung-Woo Koo; Kenji Nose; Kentaro Kyuno; Jae-Geun Ha (pp. 8764-8768).
► Anatase TiO2 films were successfully obtained on unheated glass substrates. ► Crystallization of TiO2 thin films using Ta underlayers. ► Ti seed layer effect on the Ta underlayer crystallization. ► Anatase TiO2 films were also obtained on Ta/Ti underlayers without annealing.The influence of Ta underlayers on the structures of TiO2 thin films grown onto unheated glass substrates by radio frequency magnetron sputtering has been studied and compared. The crystal, electronic, and surface structures of fabricated TiO2 films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy, respectively. The X-ray diffraction results and valence band spectra by X-ray photoelectron spectroscopy revealed that the fabricated TiO2 films on the unheated glass substrate with a highly crystallized β-Ta underlayer showed an anatase structure, whereas the TiO2 film grown directly onto glass or onto a poorly crystallized Ta film showed an amorphous one. The results showed that the crystallized anatase TiO2 films were successfully obtained on glass substrates using the Ta underlayers without substrate heating and additional annealing.
Keywords: Crystallization; Thin film structure; Sputtering processes; Titanium dioxides; Tantalum
Electrical resistivity and dielectric properties of helical microorganism cells coated with silver by electroless plating
by Jun Cai; Mingming Lan; Deyuan Zhang; Wenqiang Zhang (pp. 8769-8774).
► We use the microorganism cells as forming templates to fabricate the bio-based conductive particles. ► The microorganism cells selected as forming templates are Spirulina platens, which are of natural helical shape and high aspect ratio. ► The sliver-coated Spirulina cells are a kind of lightweight conductive particles. ► The composites containing sliver-coated Spirulina cells exhibit a lower percolation value.In this paper, microorganism cells ( Spirulina platens) were used as forming templates for the fabrication of the helical functional particles by electroless silver plating process. The morphologies and ingredients of the coated Spirulina cells were analyzed with scanning electron microscopy and energy dispersive spectrometer. The crystal structures were characterized by employing the X-ray diffraction. The electrical resistivity and dielectric properties of samples containing different volume faction of sliver-coated Spirulina cells were measured and investigated by four-probe meter and vector network analyzer. The results showed that the Spirulina cells were successfully coated with a uniform silver coating and their initial helical shapes were perfectly kept. The electrical resistivity and dielectric properties of the samples had a strong dependence on the volume content of sliver-coated Spirulina cells and the samples could achieve a low percolation value owing to high aspect ratio and preferable helical shape of Spirulina cells. Furthermore, the conductive mechanism was analyzed with the classic percolation theory, and the values ofϕc and t were obtained.
Keywords: Bio-limited forming; Helical microorganism cells; Electroless silver plating; Electrical resistivity; Dielectric properties; Percolation theory
Characterization of delafossite-CuCrO2 thin films prepared by post-annealing using an atmospheric pressure plasma torch
by Hong-Ying Chen; Wei-Jung Yang; Kuei-Ping Chang (pp. 8775-8779).
► Dealfossite-CuCrO2 thin film was prepared using sol–gel processing and post-annealing with an atmospheric pressure plasma torch. ► X-ray diffraction pattern shows pure delafossite-CuCrO2 thin films can be obtained. ► The average transmittance of the film was 66% in the visible region and the direct optical bandgap was 3.08eV. ► The electrical conductivity of the film was 2.7×10−2Scm−1 with the carrier concentration of 2.8×1013cm−3.This study reports the preparation of delafossite-CuCrO2 thin films were prepared on quartz substrates using sol–gel processing and post-annealing with an atmospheric pressure plasma torch. The films were first deposited on a quartz substrate by spin coating. The specimens were then annealed at 500°C in air and post-annealed with an atmospheric pressure plasma torch with N2–5% O2 at 650°C for 20min. The specimens annealed in air exhibited CuO and CuCr2O4 phases. Post-annealing using an atmospheric pressure plasma torch obtained the pure CuCrO2 (delafossite,R3¯m) phase. The binding energies of the Cu-2p3/2 and Cr-2p3/2 peaks of the CuCrO2 thin films were centered at 932.1±0.2eV and 576.1±0.2eV, which revealed the valence state of Cu+ and Cr3+ in the films. The chemical composition of CuCrO2 thin films was close to the stoichiometry. As the CuCrO2 phase formed, the film surface began to exhibit agglomerate features and the cross-sectional morphology showed an equiaxed grain feature. The average transmittance of CuCrO2 thin films was approximately 66% in the visible region. The direct optical bandgap of CuCrO2 thin films was 3.08eV, which is consistent with reported data in the literature. The positive Seebeck coefficients of the CuCrO2 thin film prepared by post-annealing using an atmospheric pressure plasma torch confirmed the p-type characteristics of the film. The electrical conductivity of CuCrO2 thin films was 2.7×10−2Scm−1 with a carrier concentration of 2.8×1013cm−3. Hence, post-annealing using an atmospheric pressure plasma torch is an effective tool and a feasible method for preparing transparent conductive delafossite thin films.
Keywords: Transparent conductive oxides; Delafossite; CuCrO; 2; Thin films; Atmospheric pressure plasma; Annealing
A comparative study on surface morphological investigations of ferric oxide for LPG and opto-electronic humidity sensors
by Satyendra Singh; Nidhi Verma; B.C. Yadav; Rajiv Prakash (pp. 8780-8789).
► Flower-like, elliptical and spherical shaped surface morphologies of Fe2O3. ► The structural and surface morphological investigations. ► The relationship between the surface morphology and sensing property. ► Advancement in sensitivity of LPG sensor in comparison to prior work.In the present work nanostructured ferric oxides were synthesized via hydroxide precipitation method without using any surfactant and size selection medium. The surface morphologies and structure of samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The structural analysis confirmed the formation of Fe2O3 with α-phase and rhombohedral structure. Optical and thermal properties were investigated by using UV–visible absorption spectroscopy and differential scanning calorimetry (DSC) techniques. Pelletizations of materials were done using hydraulic press and these pellets were investigated with the exposition of liquefied petroleum gas. Variations in resistance of the pellet with time for different concentrations of LPG were recorded at room temperature (27°C). The maximum value of average sensitivity was found ∼5 for 5vol.% of LPG. Our results show that the LPG sensing behavior was inspired by the different kinds of surface morphologies of Fe2O3 and inferred that the spherical porous nanoparticles synthesized via hydroxide precipitation process (S-3) had best response to LPG.
Keywords: Surface morphologies; Nano-structural analysis; Solid state LPG sensor; Nano-sized ferric oxide
A new approach to study local corrosion processes on steel surfaces by combining different microscopic techniques
by A. Heyer; F. D'Souza; A. Bruin; G. Ferrari; J.M.C. Mol; J.H.W. de Wit (pp. 8790-8796).
► Corrosion studies of materials are cumbersome due to instrumental limitations. ► A new sample holder was implemented to switch among EFM, AFM and SEM. ► The method itself is elegant and easy to handle important in materials research.Corrosion studies of materials on the micro or even nano-scale level are cumbersome due to instrumental limitations and handling procedures. If biological processes are involved the spatial resolution is even more important and sample preparation is usually the limitation. Attachment of bacteria on stainless steel surface is a complex interfacial process including interactions of bacterial cells and bacterial extracellular polymeric substances with the surface. To overcome the limitations in sample preparations and resolution we present a new stainless steel sample holder to switch among epifluorescent microscope (EFM), AFM and SEM at exactly the same position. Exemplary bacterial accumulation was studied by staining the bacterial DNA with a fluorescent dye over time. It was possible to distinguish among bacteria and other surface characteristic such as deformations or grain structures. Also surface topographic features such as roughness at the grain boundaries and deposits were quantified. All three techniques complement one another in the way that AFM is a high-resolution technique that does not allow to distinguish directly bacterial cell structures, whereas EFM offers excellent bacterial identification based on staining at a low resolution that can complement AFM images. Application of SEM in the last step will reveal inclusions and grain structure and combined with EDX gives the composition of the substrate, inclusions and corrosion deposit. The combination of the three high-resolution techniques enables a more detailed understanding of surface phenomena. The method itself is quite elegant and easy to handle which is an important aspect in materials research, especially when a high sample throughput is needed.
Keywords: Bacteria; EFM; AFM; SEM
Improvement of electrical and optical properties of molybdenum doped zinc oxide films by introducing hydrogen
by Yanfeng Wang; Qian Huang; Changchun Wei; Dekun Zhang; Ying Zhao; Xiaodan Zhang (pp. 8797-8801).
► Hydrogen and molybdenum co-doped ZnO TCO films were deposited. ► The HMZO films with low resistivity and high transmittance from 400 to 1100nm. ► Crater-like surface morphology was obtained after etching by diluted HCl. ► The etched HMZO film with root-mean-square roughness of 46.5nm.Doped ZnO films are promising candidates as a front electrode in silicon film solar cells. In present work, we report on efforts to obtain highly conductive and transparent hydrogen and molybdenum co-doped ZnO (HMZO) films prepared by pulsed direct current (DC) magnetron sputtering. Investigations were made to see the effect of hydrogen (H2) flow rate on structural, electrical and optical properties. The results indicate that H2 flow rate has a considerable influence on the transparent conductive properties of molybdenum doped ZnO (MZO) films. A reduced resistivity of 69.2% and a broadening optical band gap of 5.7% were obtained with the optimal H2 flow rate of 5sccm. The average transmittance of more than 86% in the range of 400–1100nm was obtained with the optimal H2 flow rate. Crater-like surface morphology with root-mean-square (RMS) roughness of 46.5nm was also obtained after etching by diluted hydrochloric acid (HCl). Such a co-doping growing method present here may be useful for wide spectra absorption thin film solar cells.
Keywords: Transparent conductive oxide; Molybdenum doped ZnO; Hydrogen; Magnetron sputtering; Solar cell
The corrosion behavior of electroless Ni–P coating in Cl−/H2S environment
by Xu Xiu-qing; Miao Jian; Bai Zhen-quan; Feng Yao-rong; Ma Qiu-rong; Zhao Wen-zhen (pp. 8802-8806).
► An amorphous state Ni–P coating was prepared by electroless plating method. ► The electroless Ni–P coating surface has little microporous. ► The corrosion resistance of Ni–P coating in Cl−/H2S environment is superior to that of 316L stainless.At present, the Cl−/H2S corrosion of refinery heat exchanger at low temperature has a great impact on safety production. Aimed at this problem, an amorphous state Ni–P coating was prepared by electroless plating method in this paper. The electrochemical behavior and corrosion resistance of Ni–P coating in Cl−/H2S environment were investigated by means of electrochemical equipment and autoclave, respectively. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) analysis suggest that the Ni–P coating is amorphous state and little microporous appears on its surface. The electrochemical measurement and autoclave test results show that the corrosion resistance of Ni–P coating is superior to that of 316L stainless due to its amorphous state structure and low porosity. The corrosion rate of Ni–P coating in this Cl−/H2S environment is only 0.0011mm/a.
Keywords: Electroless Ni–P coating; Cl; −; /H; 2; S environment; Electrochemical test; Corrosion rate
XPS study of silver, nickel and bimetallic silver–nickel nanoparticles prepared by seed-mediated growth
by Pilar Prieto; Valentin Nistor; Khalid Nouneh; Munetaka Oyama; Mohammed Abd-Lefdil; Raquel Díaz (pp. 8807-8813).
► We have prepared Ag, Ni and AgNi NPs by derived seed-mediated growth method. ► The combined use of optical, structural and chemical characterization techniques allows to determine the presence of core–shell structures. ► The oxidation states of Ag and Ni at the outer layers of the NPs have been studied by XPS. ► Ag NPs are purely metallic with a fcc structure. ► Ni NPs are formed by Ni core@NiO+Ni(OH)2 shell structure. ► Ag core@NiO+Ni(OH)2 shell structure is determined for AgNi NPs, with oxidized silver atoms at the interface.The chemical structure of silver, nickel and bimetallic silver–nickel nanoparticles, i.e. Ag, Ni and AgNi NPs, with sizes ≤35nm, obtained by derived seed-mediated growth method on transparent and conductive indium tin oxide (ITO) substrates, has been studied by a comparative X-ray photoelectron spectroscopy (XPS) analysis of Ag 3d, Ni 2p and O1s core levels in combination with X-ray diffraction and optical absorption spectroscopy in the visible range. XPS indicates that the surface of Ag NPs is not oxidized, while Ni NPs are clearly oxidized to nickel oxide and hydroxide. Absorptions at 384 and 600nm in Ni optical spectrum are consistent with the presence of nickel in oxidized state; however the presence of metallic Ni 2p signal in Ni XPS spectrum indicates that a metallic nickel core is still present. In the case of bimetallic AgNi NPs, the XPS results are consistent with the presence of metallic silver core surrounded by NiO+Ni(OH)2 shell. XPS spectra also show the presence of Ag2O at the interface between the Ag metallic core and the oxidized nickel shell. XRD patterns of AgNi and Ag NPs show the typical fcc structure of metallic silver, confirming the presence of Ag metallic core in AgNi NPs. The surface plasmon resonance peak (SPR) of AgNi NPs shows a blue shift to 375nm with respect to the SPR of Ag NPs, located at 405nm, reflecting the character of the oxidized nickel shell.
Keywords: Nanoparticles; Ag, Ni, AgNi; Bimetallic nanoparticles; Core–shell structure; X-ray photoelectron spectroscopy
Influence of PEG molecular weight on morphology, structure and wettability of electroless deposited Cu–Ni–P films
by Wenjing Zhang; Xue Feng; Haiyong Cao; Anmin Hu; Ming Li (pp. 8814-8818).
► Cu–Ni–P coatings with unique architectures were fabricated by electroless deposition. ► The influence of PEG on morphology and structure were investigated. ► Cu–Ni–P coating is hydrophobic with maximum contact angle of 123.8°.Cu–Ni–P films with different morphologies were fabricated via electroless deposition route, due to the crystalline modification of polyethylene glycol (PEG). Effect of PEG molecular weight on morphology and structure of Cu–Ni–P films were investigated by field emission scanning electron microscopy and X-ray diffractometer. SEM observation reveals that electrolytes containing PEG 2000, 10000 and 20000, respectively can result in the formation of three kinds of unique architectures: pyramid with star-shaped cross section, cone and column. As PEG molecular weight increases, volume of the as-prepared microstructures increases but density decreases. The XRD pattern indicates the Cu–Ni–P coating is well-crystallized and preferred orientation formed in electrolyte without PEG, with PEG 2000, PEG 10000 and PEG 20000 are (111), (220), (111) and (111), respectively. Based on the proposition that properties of materials were affected by their size and morphology, wettability of the as-prepared Cu–Ni–P films were investigated. The hydrophobicity of coating deposited with PEG 2000 reached a climax exhibiting a contact angle of 123.8°.
Keywords: Electroless deposition; Microstructure; Cu–Ni–P coating; Hydrophobicity
Double layer structure of ZnO thin films deposited by RF-magnetron sputtering on glass substrate
by C. Besleaga; G.E. Stan; A.C. Galca; L. Ion; S. Antohe (pp. 8819-8824).
► ZnO films were deposited on glass by rf-sputtering under varying growth conditions. ► Structural, optical and electrical characterizations of the films were performed. ► We observed a tendency of ZnO thin films to form a double-layer structure. ► Heating the substrate makes the layer formed in the initial growth stages thinner.Transparent ZnO films are synthesized by RF-magnetron sputtering (1.78MHz) onto glass substrates, using a mild-pressed ZnO powder target. The depositions were carried at three inert argon pressures (0.25Pa, 0.30Pa, and 0.45Pa) at two substrate temperatures (100°C and 400°C). The role of the sputtering conditions on ZnO thin films nanostructuring, optical properties and morphology is investigated by X-ray diffraction (XRD), X-ray reflectometry (XRR) and Spectroscopic ellipsometry (SE). XRD investigations revealed that ZnO films show a (00 l) texture with nanosized crystallites. Right-angle asymmetry of the (002) diffraction peak is observed. The peak profile analysis using pseudo-Voigt functions unveils a double overlapped peak structure with different coherent zone size values. A double layer structure is evidenced by analyzing the XRR data. Samples prepared at 0.3Pa at a temperature of 400°C have a ∼4nm bottom layer consisting of highly depleted in oxygen ZnO1− x structure, continued by a 53nm top layer of textured ZnO. Electrical measurements show that the temperature dependence of the conductivity is well described by the Mott variable range hopping (VRH) law. The samples obtained at 400°C have a significantly lower resistivity.
Keywords: ZnO thin films; Magnetron sputtering; Interface; VRH mechanism; XRR
Fabrication and reflection properties of silicon nanopillars by cesium chloride self-assembly and dry etching
by Jing Liu; Marina Ashmkhan; Bo Wang; Futing Yi (pp. 8825-8830).
Display Omitted► We have fabricated CsCl nanoislands with average diameter ranging from 50nm to 1μm. ► Different nanopillars have been fabricated by CsCl self-assembly and dry etching. ► We can make nanopillars with different height, average diameter and morphology. ► The nanopillars with 180nm diameter and 1μm height reduce reflectivity to below 5%.Cesium chloride (CsCl) self-assembly has been successfully used to fabricate different average diameter CsCl nanoislands ranging from 50nm to 1μm through controlling CsCl film thickness, relative humidity and developing time. By process control of inductively coupled plasma (ICP) etching, the silicon nanopillars with different high aspect ratio (2–6), morphologies from column to cone, and diameters from 150 to 800nm have been made by dry etching with the structure mask of CsCl nano hemispheres. The reflectivity of the silicon nanopillars has also been measured for wavelength from 400 to 1000nm and shows the best antireflection under 5% by native silicon nanopillars with 200nm average diameter after 40min ICP etching. With a layer of SiO2 on silicon nanopillars by thermal oxidation process, the reflectivity reaches to below 2.5% at a large range of wavelength from 400 to 1000nm.
Keywords: Nanoislands; Nanopillars; Etching time; Reflectance
Effects of interactions between NiM (M=Mn, Fe, Co and Cu) bimetals with MgO (100) on the adsorption of CO2
by Baojun Wang; Ruixia Yan; Hongyan Liu (pp. 8831-8836).
Display Omitted► The existence of oxygen vacancy decreases the adsorption of CO2 on NiM/MgO. ► NiCo shows the strongest interaction with MgO. ► NiCo substrates show the highest CO2 chemisorptions.A density-functional theory method has been conducted to investigate the interactions of NiM (M=Mn, Fe, Co and Cu) with MgO (100) as well as the effects of interactions on the adsorption of CO2. The binding energies of NiM on MgO and the adsorption energies of CO2 on NiM/MgO have been calculated, and the results show that the defective NiM/MgO catalysts exhibit stronger metal–support interaction (MSI) than the perfect NiM/MgO catalysts do, leading to weaker adsorption ability to CO2, except NiMn/MgO system. However, for the catalysts with the same MgO surface and different bimetals, the stronger the MSI is, the stronger adsorption ability of the substrate to CO2 is, except NiCu/MgO system.
Keywords: Metal–support interaction; CO; 2; adsorption; Density functional theory
Fabrication of oxide-free graphene suspension and transparent thin films using amide solvent and thermal treatment
by Se Young Oh; Sung Hwan Kim; Yong Seung Chi; Tae Jin Kang (pp. 8837-8844).
New methodology for suspended graphene sheets of high-quality (oxide-free), high-yield (high concentration) using amide solvent exfoliation and thermal treatment at 800°C. We confirmed that the van der Waals force between the graphene layers decreases as increasing thermal treatment temperatures as shown XRD data (b).Display Omitted► Propose of new methodology to prepare oxide-free graphene sheets suspension. ► The graphene suspension concentration is enhanced by thermal treatment. ► Decrease of van der Waals force between the graphene layers by high temperature and pressure. ► This method has the potential as technology for mass production. ► It could be applied in transparent and flexible electronic devices.High quality graphene sheets were produced from graphite by liquid phase exfoliation using N-methyl-2-pyrrolidone (NMP) and a subsequent thermal treatment to enhance the exfoliation. The exfoliation was enhanced by treatment with organic solvent and high thermal expansion producing high yields of the high-quality and defect-free graphene sheets. The graphene was successfully deposited on a flexible and transparent polymer film using the vacuum filtration method. SEM images of thin films of graphene treated at 800°C showed uniform structure with no defects commonly found in films made of graphene produced by other techniques. Thin films of graphene prepared at higher temperatures showed superior transmittance and conductivity. The sheet-resistance of the graphene film treated at 800°C was 2.8×103kΩ/□ with 80% transmittance.
Keywords: Graphene sheets; Amide solvent; Thermal treatment; Transparent conductive film
Formation of corrugated and porous steel surfaces by femtosecond laser irradiation
by Kęstutis Kuršelis; Roman Kiyan; Boris N. Chichkov (pp. 8845-8852).
Display Omitted► Intense femtosecond laser pulses lead to microscale self-assembly processes. ► Various structures on porous and corrugated steel surfaces are demonstrated. ► Process-controlling parameters are identified and examined. ► Technique for a defined surface pattern is developed.Novel interaction regime of femtosecond laser pulses with steel surface at high peak irradiation fluences (0.82–10J/cm2) has been observed and thoroughly investigated. This interaction regime allows the generation of well defined microrough surfaces. To investigate the mechanisms involved in the formation of sub-focus microscale cavities and protrusions, the influence of key structuring parameters has been analyzed using a multi-pulse/multi-point layout. Threshold-like appearance of large amplitude sub-focus corrugations and micropores with the variation of laser fluence, hatch spacing, and radiation exposure has been observed. The dependencies of these threshold values on ambient gas pressure and focal spot size have been verified. The established experimental background has been applied for the fabrication of ordered rough-porous patterns with the feature sizes in the range of 1–25μm.
Keywords: Porous surface; Micropatterns; Microstructure formation; Self-assembled features; Femtosecond laser
Effect of SO3 on elemental mercury adsorption on a carbonaceous surface
by Ping He; Jiang Wu; Xiumin Jiang; Weiguo Pan; Jianxing Ren (pp. 8853-8860).
► SO3 competes for the active sites on the carbonaceous surface and inhibits Hg adsorption. ► SO3 suppresses the activity of its next-nearest-neighbor carbon atom. ► SO3 cannot directly provide the active sites. ► SO3 decreases the unoccupied frontier molecular orbitals of the carbonaceous surface. ► SO3 increases the LUMO–HOMO energy gap of the carbonaceous surface.The effect of SO3 on elemental mercury adsorption on a carbonaceous surface is investigated by the density-functional theory calculations. A nine-fused benzene ring model is employed to represent the carbonaceous surface. The edge atoms on the upper side of the model remain unsaturated to simulate the active sites for reaction. All of the possible approaches in which SO3 is adsorbed on the carbonaceous surface are conducted to evaluate their effects on Hg adsorption. The results indicate that the carbonaceous surface is energetically favorable for SO3 adsorption, which causes that SO3 competes for the active sites on the carbonaceous surface. But adsorption of SO3 decreases the adsorption capacity of the carbonaceous surface for Hg0 since SO3 suppresses the activity of its next-nearest-neighbor carbon atom and negatively affects on the frontier molecular orbitals and LUMO–HOMO energy gap of the carbonaceous surface.
Keywords: Mercury; SO; 3; Adsorption; Carbonaceous surface
Antistatic modification of polypropylene by incorporating Tween/modified Tween
by Anna Zheng; Xiang Xu; Huining Xiao; Na Li; Yong Guan; Shuzhao Li (pp. 8861-8866).
Display Omitted► Tween 40 is proved to be an effective inner antistatic agent for PP. ► A combination of T40 and cationic PP has improved the washing durability of antistatic PP. ► The modified T40 accumulated on PP surface is immobilized by UV crosslinking. ► Antistatic PP with washing durability is prepared by blending 1% MT40.Tween, one type of non-ionic surfactants, was used as inner antistatic agent of polypropylene (PP) and the antistatic performance of PP/Tween sheets were evaluated by surface resistivities ( ρs) and water contact angles. The influence factors including hydrophile–lipophile balance (HLB) of Tween, addition amount, process conditions and atmospheric humidity were investigated in detail and the results showed Tween 40 with HLB at 15.7 provided PP an optimum antistatic effect with surface resistivity of 1010Ω/sq, water contact angle of 57°, and surface energy of 49.5mN/m. The ρs of PP/Tween sheets declined approximately 1 order of magnitude with 10% increasing of relative humidity. In order to improve the washing endurance of antistatic PP, a combination of T40 and cationic PP (CPP) were blended with PP and PP/CPP/T40 sheets revealed improved washing durability, with ρs below 1011Ω/sq after ultrasound washing. In addition, T40 with double bonds was synthesized and UV crosslinking of modified T40 on PP surface also presented definite effects on water resistance.
Keywords: Tween; Polypropylene; Antistatic; Crosslinking; Surface treatment
A facile method for electrospinning of Ag nanoparticles/poly (vinyl alcohol)/carboxymethyl-chitosan nanofibers
by Yinghui Zhao; Ying Zhou; Xiaomian Wu; Lu Wang; Ling Xu; Shicheng Wei (pp. 8867-8873).
Display Omitted► AgNPs/PVA/CM-chitosan nanofibers were prepared via electrospinning method. ► AgNPs were in situ synthesized in electrospinning solution via a facile method. ► AgNPs distributed homogeneously on the surface of nanofibers. ► The prepared nanofibers possessed certain antibacterial ability against Escherichia coli. ► The AgNPs containing nanofibers had potential as antibacterial biomaterial.A facile method to prepare silver nanoparticles (AgNPs) containing nanofibers via electrospinning has been demonstrated. AgNPs were in situ synthesized in poly (vinyl alcohol) (PVA)/carboxymethyl-chitosan (CM-chitosan) blend aqueous solution before electrospinning. UV–vis spectra, viscosity and conductivity of the electrospinning solution were measured to investigate their effects on the electrospinning procedure. The morphology of AgNPs/PVA/CM-chitosan nanofibers was observed by Field Emission Scanning Electron Microscopy. The formation and morphology of AgNPs were investigated by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. The resulted nanofibers have smooth surface and uniform diameters ranging from 295 to 343nm. The diameters of AgNPs mainly distributed in the range of 4–14nm, and the electrostatic interaction between AgNPs and fibers was observed. Finally, in vitro Ag release from the nanofibers was measured and the antibacterial behavior of the nanofibers against Escherichia coli was studied by bacterial growth inhibition halos and bactericidal kinetic testing. The AgNPs/PVA/CM-chitosan nanofibers possessed certain antibacterial ability, which makes them capable for antibacterial biomaterials.
Keywords: Keyword; Silver nanoparticles; Poly (vinyl alcohol); Carboxymethyl-chitosan; Electrospinning; Antibacterial
Theoretical prediction of hydrogen storage on Li decorated planar boron sheets
by Yu Sheng Wang; Fei Wang; Meng Li; Bin Xu; Qiang Sun; Yu Jia (pp. 8874-8879).
Display Omitted► Li decorated boron sheets as hydrogen storage media. ► The gravimetric density of H2 is 9.22wt%. ► The average adsorption energy of hydrogen molecule is 0.35eV/H2. ► It can operate under ambient thermodynamic conditions.First-principles calculations based on density functional theory are carried out to study the effect of Li decorated boron sheets (BST) on hydrogen storage. The results show that physisorption of H2 molecules on a pristine BST gives a binding energy of ∼0.10eV/H2, which is too lower for hydrogen storage application. With Li atoms decorated on the both sides of each hexagonal ring, the average binding energy of H2 can reach ∼0.35eV/H2, acceptable for reversible H2 adsorption/desorption near the room temperature. The maximal hydrogen storage capacity is 9.22wt%. The enhanced binding energy of H2 molecules on the Li decorated BST can be attributed to the orbital hybridizations and polarization mechanisms.
Keywords: PACS; 68.43.Bc; 73.20.AtHydrogen storage; Boron sheets; Binding energy
The surface and electrochemical analysis of permanganate based conversion coating on alclad and unclad 2024 alloy
by G. Yoganandan; J.N. Balaraju; V.K. William Grips (pp. 8880-8888).
► Permanganate based conversion coatings were developed on 2024 alloy surface with and without alclad layer. ► To identify the compounds formed and the chemical state on the coated surfaces the Raman spectra and XPS analysis have been utilized. ► Electrochemical behaviour of all the coated surfaces was evaluated by standard methods for longer immersion durations. ► Developed alternate to chromate conversion coating on alclad specimen showed uniform and compact with higher corrosion resistance. ► A plausible pictorial representation of the corrosion reaction mechanism for the unclad coating surface had been given.In the present investigation permanganate based conversion coating (PCC) was developed on AA 2024 alloy using alkaline bath containing Mn/Mo oxyanions. Conversion coating was formed on alclad (APCC) and unclad (UPCC) aluminium alloys by simple immersion method. Surface morphology of the APCC and UPCC specimens exhibited smooth and mud-crack patterns respectively. Elemental analysis showed the presence of higher amounts of Mn (5–6wt.%) and Mo (0.3wt.%) on UPCC. Raman and XPS analysis showed the presence of compounds such as MnOx (Mn3O4 and Mn2O3), MnO2, KMnO4, MoOx, MoO2, MoO3/polymolybdate on both coating surfaces. The corrosion current density ( icorr) values obtained for both coated surfaces were less than 1μA/cm2. However, APCC specimen showed the lowest icorr value of about 0.05μA/cm2 after 168h of immersion in 3.5% NaCl. EIS studies revealed the higher charge transfer resistance ( Rct) values for APCC specimen after 1 and 168h immersion compared to UPCC. Coated specimens were also tested by continuous salt spray exposure (ASTM B117) with and without cross-hatch mark (‘X’) for about 750h. Coating discoloration along with the presence of few corrosion products had been noticed on UPCC specimen after continuous salt spray exposure.
Keywords: Permanganate conversion coating; EIS; Raman spectroscopy; Corrosion; Alclad unclad AA2024 alloy
Implications of alkaline solutions-induced etching on optical and minority carrier lifetime features of monocrystalline silicon
by N. Bachtouli; S. Aouida; R. Hadj Laajimi; M.F. Boujmil; B. Bessais (pp. 8889-8894).
► Three alkaline solutions: NaOH, KOH and TMAH are used to form pyramidal structure on silicon surface wafer. ► The apex angle of the formed pyramids varies between 75° and 82°. ► The heights and bases range from 230nm to 30μm. ► The photoconductivity enhancement is related to pyramidal sizes and reflectivity behavior ► The QSSPC measurement reveals an apparent increase in the minority carrier lifetime.In this work, we search to optimize the surface textures of monocrystalline silicon (c-Si) intended to be used in silicon solar cells. For this purpose, we studied the morphology of formed etch hillocks during anisotropic etching of silicon using alkaline solutions based on sodium hydroxide (NaOH), potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH). Such treatments lead to the formation of various pyramids-like textures that can be well optimized to improve the photocurrent of c-Si-based solar cells. The produced textures were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–visible optical reflectivity and minority carrier lifetime measurements. These investigations allow evaluating the size and density of the formed pyramidal textures; the apex angles vary between 75° and 82°, while the heights and bases of the pyramids range from a few hundred nanometers to several micrometers. A minimum reflectivity value of about 6% was obtained at specific conditions using NaOH, whereas it was found that the apparent effective minority carrier lifetime ( τeff) is sensitive to the injection level (Δ n), which shows an apparent increase from 1.2μs to 2.4μs for a minority carrier density of about Δ n=21014cm−3.
Keywords: Silicon; Surface texturization; QSSPC lifetime spectroscopy
Characterization and investigation mechanism of hydrothermal stability for micropore-free ordered mesoporous molecular sieves
by Hongping Pu; Caiyun Han; Hua Wang; Siwei Xu; Liuyi Zhang; Yanyan Zhang; Yongming Luo (pp. 8895-8901).
► Hydrothermal stability of mesoporous materials has attracted a lot of attention owing to many practical applications. ► Micropore-free SBA-15 can be used as a model host to investigate the behavior of matter in confined space and fabricating nanowires and related areas of nanotechnology. ► Characterization of micropore-free as well as investigation of the structure and location for five-membered ring subunits. ► Discussed the mechanism of highly hydrothermal stability.SBA-15-type mesoporous aluminosilicates molecular sieves (MSAMS-2 and MSAMS-4) were synthesized and characterized by N2 adsorption–desorption, XRD, FT-IR, TG/DTA, FE-SEM, TEM and HR-TEM. N2 adsorption–desorption and t-plots of N2 adsorptions show the two sieves are free of micropores within their mesoporous framework wall. MSAMS-2 and MSAMS-4 exhibit extraordinary stability both in boiling water (over 360h) and in high temperature steam (800°C for 6h). FT-IR together with XRD, TG/DTA, HR-TEM and FE-SEM characterizations demonstrate that five-membered ring subunits with small size rather than zeolite crystals were only formed within the framework pores of MSAMS-2 and MSAMS-4. These five-membered ring subunits are extraordinarily stable and can effectively keep them from water molecule attack, which should play a crucial role in improving the hydrothermal stability for MSAMS-2 and MSAMS-4.
Keywords: SBA-15; Mesoporous molecular sieves; Micropore-free; Hydrothermal stability; Synthesis and characterization
Pulsed direct current magnetron sputtered nanocrystalline tin oxide films
by A. Sivasankar Reddy; N.M. Figueiredo; A. Cavaleiro (pp. 8902-8907).
► The nanocrystalline SnO2 films were prepared by pulsed direct current magnetron sputtering. ► The crystallinity of the films was progressively improved by the annealing temperature. ► At the annealing temperature of 500°C, the RMS roughness of the films was 1.1nm. ► The red shift and improvement of the photoluminescence peaks intensity was found after annealed the films. ► The low electrical resistivity of 0.015Ωcm with high optical transmittance of 90% were obtained at annealing temperature of 500°C.The nanocrystalline tin oxide (SnO2) films were deposited on glass substrates by pulsed magnetron sputtering technique and subsequently annealed from 200 to 500°C. The structural, microstructural, electrical, and optical properties of as deposited and annealed SnO2 films were studied. The crystallinity degree of the films increased with annealing temperature. Photoluminescence (PL) measurements showed that the emission peaks have low intensity and are positioned at 535nm (2.31eV) and 605nm (2.05eV) in as deposited SnO2 films. The intensity of PL peak increases sharply with the increasing of annealing temperature. The as deposited films exhibited high electrical resistivity and low optical transmittance. After annealing at 500°C, the electrical resistivity of the films decreased to the lowest value of 0.015Ωcm, being the optical transmittance 90%.
Keywords: Oxides; Thin films; Sputtering; Electrical; Optical
Surface modification of copper using high intensity, 1015W/cm2, femtosecond laser in vacuum
by M. Momcilovic; J. Limpouch; V. Kmetik; R. Redaelli; J. Savovic; D. Batani; J. Stasic; P. Panjan; M. Trtica (pp. 8908-8914).
► Bulk copper surface modification with femtosecond laser in vacuum was studied. ► High (1015) and reduced laser intensity (1013W/cm2) modified the copper surface. ► Crater and periodic surface structure features were recorded at these intensities. ► Nearly complete oxygen removal from the damage area. ► Plasma emission contains soft and hard X-ray radiation.A study of copper target surface modification with high intensity (1015W/cm2, fluence of ∼300J/cm2) Ti:sapphire laser, operating at 800nm wavelength and pulse duration of 60fs is presented. The Cu surface variations were studied in vacuum ambience. The copper target specific surface changes and phenomena observed are: (i) creation of craters (with extra-low diameters); (ii) formation of periodic surface structures especially expressed at the reduced intensity; (iii) presence of the “clean” surface in the irradiated zone (mainly absence of the oxide(s)), and (iv) occurrence of plasma in front the surface, emitting predominantly X-ray radiation (soft and hard). It can be concluded from this study that the reported laser intensities can effectively be applied for copper surface modification. The appearance of plasma in front of the target, irradiating in the X-ray/UV region, offers additional effect of surface purification facilitating contaminant-free conditions which is highly important for specific applications, e.g. in microelectronics. Generally, femtosecond laser surface modification of copper is non-contact and very rapid compared to traditional modification methods.
Keywords: Copper bulk surface modification; High intensity femtosecond Ti:sapphire laser; Crater and periodic surface structure features
Urea as a long-term stable alternative to guanidium thiocyanate additive in dye-sensitized solar cell
by Mi-Jeong Kim; Nam-Gyu Park (pp. 8915-8918).
► GSCN additive shows poor stability with time. ► Dye analogue crystals form in the presence of GSCN. ► GSCN leads to dye desorption. ► Urea is found to be an additive alternative to GSCN. ► Urea shows almost the same performance after 40 days.Photovoltaic performance of 0.05M urea-contained redox electrolyte is compared to that of 0.05M guanidinium thiocyanate (GSCN)-contained one in dye-sensitized solar cell. No significant difference in the initial photovoltaic performance is observed, which means that the role of urea additive is similar to that of GSCN. Initial solar-to-electrical conversion efficiency of the device containing GSCN shows 7% that is diminished to 5.8% after 40 days, whereas the device containing urea exhibits stable photovoltaic performance showing that initial efficiency of 7.2% is almost remained unchanged after 40 days (7.1%). The lowered efficiency of the GSCN-contained device is mainly due to the decreased photocurrent density, which is ascribed to the formation of needle-shaped crystals on TiO2 layer. Infrared spectroscopic study confirms that the crystals are dye analogue, which is indicative of dye desorption in the presence of GSCN. On the other hand, no crystals are formed in the urea-contained electrolyte, which implies that dye desorption is negligible. Urea additive is thus found to be less reactive in dye desorption than GSCN, leading to long-term stability.
Keywords: Dye-sensitized solar cell; Additive; Urea; Guanidinium thiocyanate; Long-term stability
Fabrication of porous biopolymer substrates for cell growth by UV laser: The role of pulse duration
by Marta Castillejo; Esther Rebollar; Mohamed Oujja; Mikel Sanz; Alexandros Selimis; Maria Sigletou; Stelios Psycharakis; Anthi Ranella; Costas Fotakis (pp. 8919-8927).
Display Omitted► UV laser-induced superficial foaming in biopolymer films with fs, ps and ns pulses. ► Reduction of photochemical and structural modifications by ultrashort fs irradiation. ► Successful cell culture on laser-induced foam structure generated in chitosan.Ultraviolet laser irradiation using pulses with duration from the nanosecond to the femtosecond range was investigated aiming at the generation of a foam layer on films of the biopolymers chitosan, starch and their blend. We report on the morphological characteristics of the foams obtained upon irradiation and on the accompanying laser induced photochemistry, assessed by on line monitoring of the laser induced fluorescence. We identify the laser conditions (pulse duration) at which foaming is produced and discuss the obtained results in reference to the material properties, particularly extinction coefficient and thermal parameters. This article also reports on successful cell culture on the laser induced foam structure generated in chitosan, as an illustrative example of the possibility of broader use of laser induced biopolymer foaming structures in biology.
Keywords: Laser foaming; Biopolymers; Chitosan; Starch; Cell growth
Facile fabrication of non-sticking superhydrophobic boehmite film on Al foil
by Lijun Liu; Feiyan Xu; Zhenlin Yu; Ping Dong (pp. 8928-8933).
► A boehmite film was fabricated on Al foil via a facile solution-phase method. ► The film possesses dual scale roughness (nanoplatelets on the microprotrusions). ► The surface exhibits robust superhydrophobic and non-sticking behaviors. ► The surface shows an excellent anticorrosion in electrolyte solution.A superhydrophobic boehmite film composed of dual scale microprotrusions has been fabricated on an Al foil via a facile solution-phase approach. The hierarchical microprotrusions are built up of leaf-like nanoplatelets and follow a heterogeneous nucleation, growth and aggregation mechanism. Steric acid molecules chemisorb onto the boehmite film in order to effect hydrophobization. The resulting superhydrophobic surface exhibits a water contact angle of 168° and a sliding angle of ∼2.1° for a 5μL droplet. The combination of the dual scale roughness and the low surface energy coating accounts for the superhydrophobicity. The superhydrophobic surface has an excellent non-sticking behavior and exhibits anticorrosion in an electrolyte solution, which should be critical to the applications of Al materials in engineering.
Keywords: Boehmite; Superhydrophobicity; Dual scale roughness; Anticorrosion
Preparation of the NiFe2O4 electrochemical film for the solid-state reference electrode based on EB-PVD
by Yi Hong; Guofu Qiao; Guangping Song (pp. 8934-8939).
► The novel preparation technique, i.e., EB-PVD, has been successfully applied to prepare the Ni–Fe binary alloy film. ► The optimal heat-treatment and post-oxidation processes have been established to obtain the key material, i.e., NiFe2O4 film, for the solid-state reference electrode. ► The investigation has laid a solid way to realize the mass, large-scale, integrated, and low-cost production of the NiFe2O4 electrochemical functional films.As the key material of the solid-state reference electrode, NiFe2O4 electrochemical film, was prepared by the electron beam-physical vapor deposition technique for the corrosion monitoring sensors of the reinforced concrete structures. The Ni–Fe binary alloy film was obtained by two-source evaporation based on the evaporation currents control. After the heat treatment and the post-oxidation processes, NiFe2O4 spinel film was achieved successfully. Furthermore, the microstructure, phase composition, component and texture of the prepared state, heat treatment state and oxidized state films were investigated in detail, respectively. The results indicate that the NiFe2O4 electrochemical film was very suitable for mass production by using the optimized preparation processes.
Keywords: Corrosion monitoring; Solid-state reference electrode; NiFe; 2; O; 4; film; EB-PVD
Multifractal analysis of tensile toughness and filler dispersion for polypropylene–CaCO3 composites
by E. Pérez; C. Bernal; M. Piacquadio (pp. 8940-8945).
► Dispersion of CaCO3 microparticles into PP was studied by multifractal theory. ► Fracture surfaces morphology were described by multifractal theory. ► Multifractal spectra parameters were related to mechanical behavior of composites. ► Composites with MAPP displayed reduced Δ α values related to a brittle fracture.Multifractal analyses were performed to elucidate the effect of incorporating maleic anhydride grafted polypropylene (MAPP) into a Polypropylene matrix: (i) on the dispersion of CaCO3 particles and (ii) on the fracture morphology of tensile samples. The box-counting method was applied considering the number of particles and the mean gray value distribution as measured properties of composites. The dispersion analysis exhibited, for the composite with MAPP, a reduction of larger agglomerates sizes without variation of the most frequent size. Similar results were achieved by a typical particle size distribution. Moreover, the morphology of fractured surfaces showed an irregular topography for composites without MAPP suggesting a complex fracture process. Composites with MAPP, on the contrary, displayed a regular surface morphology suggesting a more regular fracture process with an important reduction of ductile mechanisms. This fracture behavior was related to the variation of the singularity width Δ α. The results obtained suggest that multifractal theory can be applied to elucidate the relationship between structure and mechanical behavior of PP–CaCO3 composite materials.
Keywords: Multifractal spectrum; Filler dispersion; Mechanical properties; Fracture surface
Preparation and high temperature oxidation resistance of microarc oxidation ceramic coatings formed on Ti2AlNb alloy
by Yuan-Hong Wang; Zhan-Guo Liu; Jia-Hu Ouyang; Ya-Ming Wang; Yu Zhou (pp. 8946-8952).
► MAO coatings on Ti2AlNb alloy consist of Al2TiO5, R-TiO2, Al2O3 and Nb2O5. ► NaF additive increases the thickness of coating and the content of Al2TiO5. ► MAO coatings protect Ti2AlNb substrate from the high temperature oxidation. ► The oxidized layer of MAO coating exhibits a multi-layer alternative structure.Microarc oxidation (MAO) was used to produce oxide ceramic coatings on Ti2AlNb alloy. The influences of NaOH and NaF additives in the electrolyte on microstructure and high-temperature oxidation resistance of MAO ceramic coatings were investigated. MAO ceramic coatings formed on Ti2AlNb alloy exhibit a volcanic-like porous structure, and consist of Al2TiO5, R-TiO2, γ-Al2O3 and small amounts of α-Al2O3, Nb2O5. NaOH additive in the electrolyte enhances the densification of ceramic coatings and the relative content of Al2TiO5. NaF additive in the electrolyte not only increases the thickness of coatings, but also promotes the formation of Al2TiO5. In the case of static oxidation at 800°C for 100h, MAO coatings improve high temperature oxidation resistance of Ti2AlNb alloy. The oxidized products after thermal exposure to 800°C for 100h in air exhibit a multiple-layered oxide structure, and are main composed of R-TiO2, γ-Al2O3 and Al2TiO5.
Keywords: Ti; 2; AlNb alloy; Microarc oxidation; High temperature oxidation
A new protocol for the carboxylic acid sidewall functionalization of single-walled carbon nanotubes
by Hossein Reza Darabi; Mohammad Jafar Tehrani; Kioumars Aghapoor; Farshid Mohsenzadeh; Rasoul Malekfar (pp. 8953-8958).
Display Omitted► Two approaches for covalent attachment of COOH groups to the side-walls of SWNTs. ► A simple one-pot entry into the formation of benzoic acid moieties. ► Formation of benzothiomorpholides grafted to SWNTs via Willgerodt–Kindler reaction. ► Thioamides as useful link for covalent bonding between SWNTs and biological systems. ► Characterization of SWNTs by FT-IR, UV/vis, TGA, SEM, XPS and Raman techniques.The carboxylic acid termination of the single-walled carbon nanotubes (SWNTs) provides a convenient link for covalent bonding between the SWNTs and polymer or biological systems. In this work, two approaches for covalent attachment of carboxylic acid groups to the side-walls of single walled carbon nanotubes are presented. Both protocols are based on chemical manipulation of benzonitrile residues, easily introduced onto the SWNTs by in situ diazonium salt formation of 4-aminobenzonitrile. In the first approach, benzonitrile groups on SWNTs were treated with aq. NaOH solution to form benzoic acid moieties. The second approach on benzonitrile groups is leaded to the formation of benzothiomorpholides via Willgerodt–Kindler reaction which is then converted to benzoic acid moieties on SWNTs. Moreover, a simple one-pot entry into the formation of benzoic acid moieties is presented. SWNTs were characterized by a set of methods including FT-IR, UV/vis, TGA, SEM and Raman techniques. The presence of thioamide groups on SWNT is also proved directly by XPS spectroscopy.
Keywords: Single walled carbon nanotubes; Functionalization; Carboxylic acid; Thioamide
Facile electrochemical synthesis of ZnO/PbSe heterostructure nanorod arrays and PbSe nanotube arrays
by Haohua Li; Juan Yang; Chaolun Liang; Wei Zhang; Ming Zhou (pp. 8959-8964).
Display Omitted► The ZnO/PbSe core-shell nanorod arrays were fabricated by a two-step electrodeposition method from aqueous solution for the first time. ► The absorption spectrum of ZnO/PbSe shows visible light absorption from 500nm to 650nm due to the PbSe coating. ► PbSe nanotube arrays were obtained by immersing the ZnO/PbSe core-shell nanorods arrays in hydrochloric acid for 10min.The ZnO/PbSe core-shell nanorod arrays were fabricated by a two-step electrodeposition method from aqueous solution for the first time. The synthesized core-shell nanorod arrays were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained samples share the characters of both ZnO and PbSe in XRD patterns. The SEM images show that the average diameter and length of ZnO nanorods are 120–200nm and 2.5μm, respectively. The TEM images show that these heterostructured nanorods are made up of two parts, a single crystalline ZnO nanorod with a  growth direction as the core and crystalline PbSe layer as the shell. The absorption spectrum of ZnO/PbSe shows visible light absorption from 500nm to 650nm due to the PbSe coating. In addition, the PbSe nanotube arrays were fabricated by immersing the heterostructures in hydrochloric acid, which were characterized by SEM and TEM. SEM images show that the average diameter of these nanotubes is 250nm and the average thickness of their walls is about 75nm. TEM images show that the PbSe nanotubes exhibit polycrystalline structure.
Keywords: ZnO; PbSe; Nanotube; Nanorod; Heterostructure; Electrodeposition
Single crystalline Cr2O3 nanowires/nanobelts: CrCl3 assistant synthesis and novel magnetic properties
by Shuhu Yang; Shijiang Liu; Changyong Lan; Shaoguang Yang (pp. 8965-8969).
► Single crystalline Cr2O3 nanobelts/nanowires were synthesized in a short time. ► The growth started from Cr foil in the assistance of CrCl3. ► The corrosion of Cr foil in Cl2 was found to be crucial to the growth. ► The Néel temperature of the Cr2O3 nanobelts/nanowires decreases to 150K.Large amounts of single crystalline Cr2O3 nanowires/nanobelts were obtained using CrCl3 assistant synthesis method. Scanning electron microscopy and transmission electron microscopy results showed the nanowire/nanobelt morphology of the product. X-ray diffraction and high resolution transmission electron microscopy illustrated the formation of the alumina phase Cr2O3 nanowires/nanobelts. A new growth mechanism of the nanowires/nanobelts is proposed and discussed. Zero field and field cooled temperature dependence of magnetization measurements of the nanowires/nanobelts showed clear decrease of the Néel temperature compared to their bulk forms, which is attributed to size and surface effect of the Cr2O3 nanowires/nanobelts.
Keywords: Cr; 2; O; 3; Nanowire/nanobelt; Chloride assistant growth; Néel temperature
A non-aqueous electrodeposition process for fabrication of superhydrophobic surface with hierarchical micro/nano structure
by Limei Hao; Zhi Chen; Ruiping Wang; Changli Guo; Pengli Zhang; Shaofang Pang (pp. 8970-8973).
► Micro/nano structure on anodic copper plate is created with electrodeposition method. ► An alkali ethanol electrolyte solution is first applied to electrodeposition process. ► Surface has a high contact angle, and no gas near an anode is released.In this work, we present a novel facile electrodeposition approach to create micro/nano structure on an anodic copper plate with an alkali ethanol electrolyte solution. The electrolyte solution is composed of potassium hydroxide, potassium persulfate and ethanol. Hierarchical structures were formed on an anodic copper surface by an alkali assistant oxidation process, water immersion and fluorination, the as-prepared surface exhibits superhydrophobic property. The creation of morphological structures and chemical compositions on the treated surface was revealed by scanning electron microscopy (SEM) and X-ray diffraction techniques. The resulting surfaces composing of Cu(OH)2 arrays demonstrates that water contact angle is as high as 165° and the rolling angle is less than 3°. The study is expected to create a new avenue for the basic research as well as real application.
Keywords: Superhydrophobicity; Electrodeposition; Contact angle; Non-aqueous; Alkali solution
Reliability assessment of ultra-thin HfO2 films deposited on silicon wafer
by Wei-En Fu; Chia-Wei Chang; Yong-Qing Chang; Chih-Kai Yao; Jiunn-Der Liao (pp. 8974-8979).
► Nano-mechanical properties on annealed ultra-thin HfO2 film are studied. ► By AFM analysis, hardness of the crystallized HfO2 film significantly increases. ► By nano-indention, the film hardness increases with less contact stiffness. ► Quality assessment on the annealed ultra-thin films can thus be achieved.Ultra-thin hafnium dioxide (HfO2) is used to replace silicon dioxide to meet the required transistor feature size in advanced semiconductor industry. The process integration compatibility and long-term reliability for the transistors depend on the mechanical performance of ultra-thin HfO2 films. The criteria of reliability including wear resistance, thermal fatigue, and stress-driven failure rely on film adhesion significantly. The adhesion and variations in mechanical properties induced by thermal annealing of the ultra-thin HfO2 films deposited on silicon wafers (HfO2/SiO2/Si) are not fully understood. In this work, the mechanical properties of an atomic layer deposited HfO2 (nominal thickness ≈10nm) on a silicon wafer were characterized by the diamond-coated tip of an atomic force microscope and compared with those of annealed samples. The results indicate that the annealing process leads to the formation of crystallized HfO2 phases for the atomic layer deposited HfO2. The HfSi xO y complex formed at the interface between HfO2 and SiO2/Si, where the thermal diffusion of Hf, Si, and O atoms occurred. The annealing process increases the surface hardness of crystallized HfO2 film and therefore the resistance to nano-scratches. In addition, the annealing process significantly decreases the harmonic contact stiffness (or thereafter eliminate the stress at the interface) and increases the nano-hardness, as measured by vertically sensitive nano-indentation. Quality assessments on as-deposited and annealed HfO2 films can be thereafter used to estimate the mechanical properties and adhesion of ultra-thin HfO2 films on SiO2/Si substrates.
Keywords: Ultra-thin HfO; 2; film; Atomic layer deposition; Annealing process; Atomic force microscope; Nano-indentation
Functionalization of  fullerene with butadienes: A DFT study
by Javad Beheshtian; Ali Ahmadi Peyghan; Zargham Bagheri (pp. 8980-8984).
► Reaction of C60 with 2,3-dimethylbutadiene (DMB) is theoretically investigated. ► The HOMO of DMB interacts with the LUMO of C60 via a Diels Alder reaction. ► Work function of C60 is decreased by increasing the number of DMB molecules. ► The reaction may facilitate the field electron emission from C60 surface.We have performed a density functional study on the reaction of C60 fullerene with one to six 2,3-dimethylbutadiene (DMB) molecule(s) which has previously been investigated by experimental researchers. Based on the obtained results, it has been found that (1) the reaction is regioselective, so that the DMB molecule prefers to be adsorbed atop a CC bond which is shared between two hexagonal rings of C60 (in good agreement with the experimental results) with reaction energy of −0.98eV; (2) the HOMO of DMB interacts with the LUMO of C60 via a Diels Alder reaction; (3) the energy of reaction and work function of C60 are decreased by increasing the number of adsorbed DMB molecules; (4) the HOMO–LUMO energy gap of C60 is slightly changed upon the reaction; (5) the reaction reduces the potential barrier of the field electron emission of C60 surface.
Keywords: 2,3-Dimethylbutadiene; C; 60; Cycloaddition; Functionalization; Density functional theory
Preparation and characterization of anodic films on AZ31B Mg alloy formed in the silicate electrolytes with ethylene glycol oligomers as additives
by Feng Zhu; Jinwei Wang; Shanghua Li; Jin Zhang (pp. 8985-8990).
Display Omitted► Anodic films formed on AZ31B Mg alloy in the silicate electrolyte. ► Compact and smooth film obtained by using PEGs as additives in the electrolyte. ► Anti-corrosion and Anti-friction enhanced by adding PEG1000 in the electrolyte. ► The growth rate and amount of the anodic oxides related to the length of PEG chains.Oxide coatings are prepared on AZ31B Mg alloy in an environment-friendly electrolyte with additives by plasma electrolytic anodization, and the effect of ethylene glycol oligmers on the performances of the anodized film is investigated. Under a constant current density of 10mAcm−2, the reaction overpotential of the silicate electrolytes with additives are found higher than that of the original electrolyte as measured by potential–time test. The EIS and DC polarization results reveal that the addition of PEG increases the impedance of the film and reduces its corrosion current density ( Icorr) at least by one order of magnitude. The surface morphologies are more and more compact and homogeneous with the increase in EG numbers, while a rougher surface appeared again if the PEG4000 is used as observed by SEM. As detected by XRD, the anodic films are found mainly consist of MgO, MgSiO3 and Mg2SiO4, and their relative amounts are related to the lengths of EGs, resulting in the differences in morphology and anticorrosion variations. Furthermore, the improvement in abrasive resistance of the anodic film formed in the electrolyte with PEG1000 may be attributed to its much more compact surface and the incorporation of ductile PEG chains among those oxides.
Keywords: Mg alloy; Anodic film; PEG; Corrosion protection
Gold nanoparticles grafting on glass surface
by Ondřej Kvítek; Marek Bot; Václav Švorčík (pp. 8991-8995).
New method as was used to bind Au nanoparticles (AuNPs) to the glass surface. This method is a combination of physical (plasma treatment) and chemical (binding of ethanedithiol) procedure.Display Omitted► Argon plasma treatment used to increase reactivity of glass surface. ► Gold nanoparticles bound to glass surface via ethanedithiol. ► X-ray photoelectron spectroscopy shows increasing dithiol concentration. ► Atomic force microscopy images of gold nanoparticles bound to glass surface.New method of grafting of gold nanoparticles (AuNPs) to glass surface was developed and investigated. The method based on glass activation by plasma discharge use dithiols for AuNP binding as an alternative to silane chemistry currently used for binding AuNPs onto glass surface. XPS measurements confirmed the presence of sulfur and gold on the modified glass surface. The presence of AuNPs on modified glass surface was then directly proven with AFM method. UV–vis spectra of samples with grafted AuNPs show a peak of SPR absorbance. With increasing modification time, more AuNPs are bound to the glass surface, which can aggregate.
Keywords: Glass; Plasma; Gold nanoparticle; Grafting; Atomic force microscopy; X-ray photoelectron spectroscopy
Coalescence driven size-controlled synthesis of ITO nanospheres
by J.H. Kang; P. Uthirakumar; Y.S. Katharria; J.H. Ryu; H.K. Kim; H.Y. Kim; N. Han; Y.J. Park; Y.S. Beak; S.M. Kim; C.-H. Hong (pp. 8996-9004).
► A simplistic size-controlled synthesis of ITO nanospheres using selective wet-chemical etching. ► Growth of multi-layers of ITO nanospheres stacked one on top of another. ► Application of the ITO nanospheres in the current-spreading p-electrode of a blue InGaN/GaN LED revealing improved light extraction.A well-controlled yet simple process to synthesize indium tin oxide (ITO) nanospheres of various sizes has been proposed and described. The process was also extended to grow multi-layers of ITO nanospheres stacked one on top of another. To obtain nanospheres, e-beam evaporated ITO films wee selectively wet-etched using a dilute HCl acid solution. Size of the ITO nanospheres was controlled by varying the thickness of the ITO film. This simple process is accomplished in only a few seconds during which ITO nanosphere formation takes place via coalescence. To understand the mechanism of nanospheres formation, variation of etching time, etchant concentration and ITO film thickness were employed. A model based on etching-reaction and coalescence is suggested to reproduce the evolution of the size of nanospheres with etching time and etchant concentration. A possible application of ITO nanospheres to enhance light output from a blue GaN based light-emitting diode is also demonstrated.
Keywords: ITO nanospheres; Wet chemical etching; Scanning electron microscopy; X-ray photoelectron spectroscopy; X-ray diffraction; Light-emitting diode
Development of natively textured surface hydrogenated Ga-doped ZnO-TCO thin films for solar cells via magnetron sputtering
by Fei Wang; Xin-liang Chen; Xin-hua Geng; De-kun Zhang; Chang-chun Wei; Qian Huang; Xiao-dan Zhang; Ying Zhao (pp. 9005-9010).
► Natively textured surface hydrogenated gallium-doped zinc oxide (HGZO) thin films have been deposited via magnetron sputtering on glass substrates. ► The directly deposited HGZO thin films present rough crater-type surface morphology. ► Typical HGZO thin film exhibits a high electron mobility of 41.3cm2/Vs and a relative low sheet resistance of ∼7.0Ω. ► These HGZO thin films have high optical transmittances in the visible and near infrared region (∼380–1100nm). ► A gradient H2 growth method for fabricating HGZO thin films has been proposed in magnetron sputtering process.The main purposes are to obtain high quality transparent conductive oxide (TCO) based on zinc oxide (ZnO) thin films with high optical transparency in the visible and near infrared spectral range, high electrical conductivity and good light-scattering capability to enhance the path of the light inside the Si-based thin film solar cells. Natively textured surface hydrogenated gallium-doped ZnO (HGZO) thin films have been deposited via pulsed direct current (DC) magnetron sputtering on glass substrates at a substrate temperature of 553K. These natively textured HGZO thin films exhibit high optical transmittance (over 80%) in the visible and near infrared region ( λ=380–1100nm) and excellent electrical properties. The optimized HGZO thin film with crater-type textured surface obtained at the hydrogen flow rate of ∼2.0sccm exhibits a high electron mobility of 41.3cm2/Vs and a relatively low sheet resistance of ∼7.0Ω. The influences of hydrogen flow rates on the surface morphology, electrical and optical properties of HGZO thin films were investigated in detail. In addition, we put forward a method of gradient H2 growth technique for fabricating HGZO thin films so as to obtain rough surface structure with good light-scattering capability and high electrical conductivity. “Crater-like” surface feature size and optical transmittance can be improved through gradient H2 growth technique.
Keywords: Hydrogenated zinc oxide thin films; Magnetron sputtering; Textured surface; Gradient H; 2; growth; Thin film solar cells
Determination of adhesion forces between smooth and structured solids
by Hartmut R. Fischer; Edwin R.M. Gelinck (pp. 9011-9017).
► Extension of know data with respect to decency of adhesion from probe radius to 8 decades. ► Use of large interaction surface areas for precision measurement of adhesion forces. ► Deliberated increase of roughness as tool to tune adhesion forces and to suppress spontaneous adhesion.Surfaces tend to be made smoother in order to gain flatness or in order to fulfill the need for more precise and reproducible positioning of parts. Adhesion or even sticking of the surfaces is a major showstopper for these applications. There are several measures that can be taken in order to reduce spontaneous adhesion. Quantification of the effectiveness of the chosen solution is most often done using an atomic force microscope (AFM) with probes varying from 1nm to 8μm of contact diameter. A serious disadvantage in measuring adhesion by sharp tips is the wear of the tips. Sharp tips wear easily, resulting in undefined contact areas. When the real area of contact is not well defined, the quantification of the adhesion force is not significant.In the current study results of AFM measurements from literature with different tip diameters of colloidal probes are compared with AFM cantilevers with a plateau tip and using probes from large spheres using an alternative setup in combination with a Universal Nano-mechanical Analyzer (UNAT). Test results are shown. Another part of the study deals with a deliberately roughening of smooth surfaces to minimize (spontaneous) adhesion. Good agreement has been found with existing results.
Keywords: Adhesion; Structured surfaces; Roughness
Hydrothermal synthesis and photoelectrochemical properties of In2S3 thin films with a wedgelike structure
by Lina Zhang; Wei Zhang; Haibin Yang; Wuyou Fu; Minghui Li; Hui Zhao; Jinwen Ma (pp. 9018-9024).
Display Omitted► Wedgelike In2S3 films are synthesized on FTO substrate via a hydrothermal method. ► Facile control the morphology and thickness of the films. ► Tartaric acid play key role in the formation of In2S3 films. ► The wedgelike In2S3 thin films exhibit higher photocurrent than previous reports.Indium sulfide (In2S3) thin films with a wedgelike structure were prepared on fluorine-doped tin oxide (FTO) substrate by a facile hydrothermal method. By properly monitoring the experimental conditions, including the reaction time, concentrations of tartaric acid, precursor concentration ratio and the reaction temperature, the In2S3 films with different morphologies and thickness could be obtained, and the growth mechanism of β-In2S3 films was also proposed in this work. Furthermore, UV–vis absorption study revealed that the absorption range broadened with the growth of the In2S3 crystals. In addition, a photocurrent of 0.48mAcm−2 was obtained under 100mWcm−2 UV–visible illuminations of the wedgelike In2S3 thin films.
Keywords: In; 2; S; 3; Wedgelike; Thin films; Hydrothermal synthesis
Correlation between temperature distribution and in situ formed microstructure of Fe–TiC deposited on carbon steel using laser cladding
by Ali Emamian; Masoud Alimardani; Amir Khajepour (pp. 9025-9031).
► Deposition process of Fe–TiC on steel is simulated in a 3D layer-by-layer fashion. ► Fe–TiC was developed based on its low weight, low cost and high hardness value. ► Temperature distribution of the melt pool plays a crucial role in particles distribution. ► Temperature distribution affects the surface hardness.In this paper, laser cladding of Fe–TiC composite coating on AISI 1030 carbon steel is investigated using a numerical and experimental method. Correlation between temperature distributions and formed microstructures of the deposited material are studied. Numerical and experimental results show that the distribution of the TiC particles within the deposited tracks varies according to the local temporal cooling rates. By increasing the substrate average temperature and thus decreasing the cooling rates, the TiC particles distribution becomes less uniform and larger dendrites are formed. Due to the lower cooling rates at the end segment of the deposition, clusters of TiC particles are detected at the top of the clad. It is shown that although higher cooling rates result in relatively more uniform TiC particles distribution, they are the potential source of micro-crack formation across the deposited layers.
Keywords: Laser cladding; Hardfacing alloys; Fe–TiC composite coating; Microstructure; Crack formation; Numerical analysis
Effect of an “in situ” hydrous strain on the ionic exchange process of dioctahedral smectite: Case of solution containing (Cu2+, Co2+) cations
by Ramzi Chalghaf; Walid Oueslati; Marwa Ammar; Hafsia Ben Rhaiem; Abdesslem Ben Haj Amara (pp. 9032-9040).
Display Omitted► The applied hydrous strain affects the interlamellar space configuration. ► Stressed Swy-Na sample, lose her homogeneous hydration character for %RH<60. ► The selective exchange process is started for both stressed and unstressed materials. ► For 10−2N solution, CEC of SWy-2N-S exhibit a partial saturation due to Co2+ cations.This work aims at determining the effect of hydrous strain produced by a continuous, in situ, hydration–dehydration cycles, using a variation of relative humidity (%RH) rate here, variable (%RH), on the cation exchange process in the case of Na rich-montmorillonite. This goal is accomplished in two steps. First, the starting material (Na rich-montmorillonite) is reported “in situ” at variable RH values in order to prepare and characterize a final stressed product that will be used later in the selective exchange study, in the case of solution containing (Cu2+, Co2+). An XRD profile modeling approach is used to describe all structural changes caused by the environmental evolution of the RH rate. The quantitative analysis of XRD patterns is achieved through an indirect method, which is based on the comparison of experimental XRD patterns with calculated ones. This investigation allows us to determine several structural parameters related to the nature, abundance, size, position and organization of exchangeable cation and water molecule in the interlamellar space along the c* axis.
Keywords: Wyoming montmorillonite; Disordered systems; In situ hydrous strain; Quantitative XRD analysis
Grain morphology and size disorder effect on the transport and magnetotransport in Sol–Gel grown nanostructured manganites
by D.G. Kuberkar; R.R. Doshi; P.S. Solanki; Uma Khachar; Megha Vagadia; Ashish Ravalia; V. Ganesan (pp. 9041-9046).
Display Omitted► Single phasic nanostructured manganites can be synthesized at low temperatures. ► Sol–Gel technique is low cost, simple and easy to handle. ► Grain morphology modifies the transport and magnetotransport properties. ► Surface contribution to the modifications in the transport and MR behavior. ► Interplay between low temperature extrinsic and room temperature intrinsic MR.Nanostructured polycrystalline La0.7Ca0.3MnO3 (LCMO) and Nd0.7Sr0.3MnO3 (NSMO) manganites have been successfully synthesized at various temperatures ranging between 700 and 1100°C using Sol–Gel method. Crystalline nature and morphology of the samples have been studied using XRD (Rietveld analysis) and TEM measurements. SEM studies reveal nanostructured grain morphology of LCMO and NSMO samples. It is observed that, with increase in sintering temperature, crystallinity and grain morphology get improved resulting in better transport. A strong dependence of transport on size variance has been observed in the systems studied. The modified transport and better magnetotransport properties of the manganites have been observed due to the large surface to volume ratio (surface contribution) in the nanostructured manganites. The observation of large low temperature MR in both the manganite systems and the interplay between the intrinsic and extrinsic MR components has been explained in the light of spin polarized tunneling effect, grain morphology, grain boundary nature and size disorder effect.
Keywords: Sol–Gel; Manganites; Grain morphology; Size disorder
Preparation and performance of novel thermally stable polyamide/PPENK composite nanofiltration membranes
by Lijie Hu; Shouhai Zhang; Runlin Han; Xigao Jian (pp. 9047-9053).
► Composite nanofiltration membranes based on PPENK UF membranes were prepared. ► Preparation parameters of polyamide/PPENK nanofiltration membranes were studied. ► Polyamide/PPENK nanofitration membrane shows excellent thermal resistance.Novel thermally stable composite nanofiltration (NF) membranes were prepared from piperazine (PIP) and trimesoyl chloride (TMC) on poly (phthalazione ether nitrile ketone) (PPENK) ultrafiltration (UF) membranes by interfacial polymerization. The effects of monomers concentration, reaction time and organic solvents on the performance of composite membranes were investigated. The effects of operating pressure and the salt solution concentration on the performance of composite membranes were also discussed. The different salts rejection of PPENK composite membranes decreased in the order of Na2SO4>MgSO4>Al2(SO4)3>NaCl>MgCl2, which indicated a negative charge at the membrane surface. The flux and Na2SO4 rejection of PPENK composite membranes reached 57.9L/m2h and 98.4% under the optimized conditions and operating pressure of 1.0MPa. Furthermore, the morphology and chemical structure of membranes were examined by scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. Moreover, the thermal stability of PPENK NF membranes was also investigated. When temperature of the feed solution raised from 20°C to 80°C, the permeation flux increased about four times without significant change of rejection. The flux increased first then reached a plateau and the rejection kept constant when PPENK NF membranes in boiling de-ionized water were boiled to 3h.
Keywords: Poly (phthalazione ether nitrile ketone); Interfacial polymerization; Nanofiltration membrane; Thermal stability; Composite membrane
rf Power dependence on the chemical and structural properties of copper oxide thin films obtained at various oxygen fractions
by Kyounga Lim; Juyun Park; Do-Geun Kim; Jong-Kuk Kim; Jae-Wook Kang; Yong-Cheol Kang (pp. 9054-9057).
► We deposit cupric/cuprous oxide thin films on a flexible substrate varying rf power. ► Preferential growth and the ratio of cupric and cuprous copper oxide was controlled by rf power. ► Different oxidation states and crystalline phase of Cu species were confirmed by X-ray induced Auger electron spectroscopy and XRD, respectively.Copper oxide (CuO x) thin films were deposited on flexible polyethyleneterephthalate (PET) substrates by rf magnetron sputtering and the effects of the rf power and the O2 fraction on the physical and chemical properties of the films were examined. The obtained films were characterized with a surface profiler, X-ray diffraction (XRD), scanning electron microscopy (SEM), four points probe, and X-ray photoelectron spectroscopy (XPS). The trend of surface resistance of CuO x films was almost identical as rf power varied from 200 to 300W. The surface resistance of the films increased as the O2 fraction increased up to 14.3%. After this point it decreased. The propensity of surface resistance of the films, however, monotonically increased as a function of O2 fraction at 400W of rf power. XRD study revealed that the preferential phase of CuO x changed from metallic cubic Cu(111) through cubic Cu2O(111) to monoclinic CuO(1¯11) as the O2 fraction increased. The compositional ratio of Cu species with different oxidation state in CuO x films was investigated by X-ray induced Auger electron spectroscopy (XAES). XAES study revealed that the compositional ratio of Cu was dependent with the rf power. The higher rf power applied, the more Cu+ species and less Cu2+ species formed in CuO x films.
Keywords: Copper oxide; X-ray induced Auger electron spectroscopy; rf Magnetron sputtering
Fabrication of novel thermal barrier coating on polymer composites via the combined sol–gel/sealing treatment process
by Wenzhi Huang; Binglin Zou; Yu Zhao; Xiangsheng Meng; Chunjie Wang; Xueqiang Cao; Zhen Wang (pp. 9058-9066).
► Thermal barrier coating was fabricated on polyimide composites at 400°C via a simple process. ► The strengthening mechanisms of coating were adhesive binding of phosphate and chemical bonding. ► Dual coating exhibited excellent bond strength and average bonding strength was 5.83MPa. ► Dual coating could hold at 905±15°C for 6min and resins of PMCs were improved against decomposition.Thermal barrier coating on the polyimide matrix composites was successfully fabricated at 400°C via the combined sol–gel/sealing treatment process. In this approach, zirconia coating was firstly deposited onto substrate by sol–gel process, followed by penetration of aluminum phosphate into the final coating. Sealing mechanisms of phosphate sealant were based on the adhesive binding of phosphates and the chemical bonding. After thermal cycling at 400°C for 135 cycles, no apparent delaminations and spallations appeared in the ZrO2/phosphates dual coating, and the average bonding strength was 5.83MPa. Thermal oxidation of substrate coated with the ZrO2/phosphates dual coating could be retarded at about 900°C.
Keywords: X-ray diffraction; Ceramics; Failure; Phase transformation
Texturization of Si(100) substrates using tensioactive compounds
by Irena Zubel; Filip Granek; Krzysztof Rola; Katarzyna Banaszczyk (pp. 9067-9072).
► Difficulties of alcohols application for Si solar cells texturization are considered. ► The novel KOH solution containing 1,2-pentanediol for Si texturization is proposed. ► Due to the high boiling point (206°C), 1,2-pentanediol may be an alternative to IPA. ► The obtained reflection coefficient is comparable with the one for KOH+IPA solution.Random pyramid texturization of Si(100) substrates in alkaline solutions with addition of surface active compounds is considered. Technological difficulties connected with the application of alcohol additives are analyzed and a new solution for the wet-chemical texturization is proposed. The commonly applied alcohols in the texturization process, such as isopropanol and tertbutanol have been replaced in this work by diols (the alcohols with multiple hydroxyl groups). The results of texturization in KOH solution with 1,2-pentanediol are presented. Optimization of the solution composition and process conditions is performed. Measurements of the coefficient of light reflection carried out in the spectral range from 300nm to 1200nm, for the textured substrates with and without an additional anti-reflection layer are presented. The reflection coefficient for the substrates obtained in the optimal etching conditions (1M KOH+2% 1,2-pentanediol, 90°C, 20min) is close to 10%, which is comparable with the coefficient of light reflection obtained in KOH solutions with isopropyl alcohol addition. Unquestioned advantages of the solutions with diol addition (higher process temperature, shorter etching time, technological improvements) show that they can successfully replace the currently applied solutions.
Keywords: Solar cells; Texturization; Silicon; Diols
Dealloying of single-phase Al2Au to nanoporous gold ribbon/film with tunable morphology in inorganic and organic acidic media
by Xiaoguang Wang; Zhonghua Zhang; Hong Ji; Junling Xu; Xiaobo Huang; Yong Ma (pp. 9073-9079).
► NPG with distinct morphologies can be obtained in different acids. ► Nature of acid anions significantly influences the dealloying process. ► Passivation is prone to occur when dealloying in organic acids.In this paper, the dealloying of single-phase Al2Au ribbons and morphological evolution of nanoporosity have been investigated in different inorganic and organic acid solutions. The results demonstrate that the acid strength coupled with the nature of acid anions can significantly influence the dealloying velocity, adatom diffusion and morphological evolution of the resultant nanoporous Au. Compared with those in inorganic acids, the dealloying velocities can be greatly reduced in organic carboxylic acids and severe passivation is prone to occur. The underlying mechanism of passivation occurring at the dealloying front in the organic acids has also been discussed.
Keywords: Nanoporous gold; De-alloying; Acid corrosion; SEM; Passivity
Effects of vanadium ion implantation on microstructure, mechanical and tribological properties of TiN coatings
by Bin Deng; Ye Tao; Deliang Guo (pp. 9080-9086).
► TiN coatings deposited by MFAIP are implanted with V ion by metal vapor vacuum arc. ► The V-implanted coatings have an improvement in hardness and plastic deformation resistance. ► The coatings with implantation have an improvement in wear behavior in terms of friction coefficient and wear rate. ► The wear mechanism for both un-implanted and V-implanted TiN coatings against GCr15 steel ball is adhesive wear. ► The improvement of the wear behavior is due to the existence of the VN new phase and vanadium oxide.TiN coatings were deposited on the substrates of cemented carbide (WC–TiC–Co) by Magnetic Filter Arc Ion Plating (MFAIP) and then implanted with vanadium through Metal Vacuum Vapor Arc (MEVVA) ion source with the doses of 1×1017 and 5×1017 ions/cm2 at 40kV. The microstructures and chemical compositions of the V-implanted TiN coatings were investigated using Glancing Incidence X-ray Diffraction (GIXRD) and X-ray Photoelectron Spectroscopy (XPS), together with the mechanical and tribological properties of coatings were characterized using nano-indentation and ball-on-disk tribometer. It was found that the diffraction peaks of the V-implanted TiN coatings at the doses of 5×1017 ions/cm2 shifted to higher angles and became broader. The hardness and elastic modulus of TiN coatings increased after V ion implantation. The wear mechanism for both un-implanted and V-implanted TiN coatings against GCr15 steel ball was adhesive wear, and the V-implanted TiN coatings had a lower friction coefficient as well as a better wear resistance
Keywords: Vanadium ion implantation; TiN; Tribological properties; Magnetic filter arc ion plating
Water adsorption behavior on metal surfaces and its influence on surface potential studied by in situ SPM
by L.Q. Guo; X.M. Zhao; Y. Bai; L.J. Qiao (pp. 9087-9091).
► Force–distance curves were established to characterize the thickness of water layer. ► The thickness of water layer on metal surfaces increased with the rise of humidity. ► The thickness of water layer and its variation are different for different metal. ► The corrosion potential decreases with the water adsorption on the metal surfaces. ► The corrosion potential of gold is the highest and that of chromium is the lowest.The water adsorption behavior on the surfaces of chromium, copper and gold and its effect on the surface potential at various relative humidity were studied by in situ scanning Kelvin probe force microscopy (SKPFM) combined with force calibration. The thickness of water layer on different surfaces was obtained from the force–distance curve. It increases with the rise of humidity. The Volta potential map was measured using SKPFM within a wide humidity range of 20–100% as a function of the thickness of water layers. The surface potential decreases with the increasing thickness of water layers on the metal surfaces. The difference in the water adsorption behavior and its effect on surface potential originates from the different surface properties of three metals, such as the roughness and contact angle.
Keywords: Metal coatings; SKPFM; Force–distance curve; Humid air; Water film
Production of few-layer graphene through liquid-phase pulsed laser exfoliation of highly ordered pyrolytic graphite
by Min Qian; Yun Shen Zhou; Yang Gao; Tao Feng; Zhuo Sun; Lan Jiang; Yong Feng Lu (pp. 9092-9095).
► Graphene was produced through liquid-phase pulsed laser exfoliation of HOPG. ► Compression and expansion of HOPG surface were found to lead to the exfoliation of graphene sheets. ► An electrical conductivity of ∼1000S/m and an optical transparency of ∼75% at 550nm were observed.Graphene suspension was obtained through liquid-phase pulsed laser exfoliation of highly ordered pyrolytic graphite (HOPG). The liquid-phase pulsed laser process leaded to the compression and expansion of HOPG surface, resulting in the exfoliation of graphene sheets. Graphene sheets of ∼1nm in thickness and micrometers in size were obtained. Transparent conductive graphene films were fabricated by vacuum filtration, showing an electrical conductivity of ∼1000S/m and an optical transparency of ∼75% at 550nm. This study demonstrated the growth of few-layer graphene by pulsed laser exfoliation of HOPG in liquid and explored its applications in transparent conductive films.
Keywords: PACS; 81.05.ue; 79.20.EbGraphene, Highly ordered pyrolytic graphite, Liquid-phase pulsed laser exfoliation
Comparative study of supported CuO x and MnO x catalysts for the catalytic wet air oxidation of β-naphthol
by Jie Liu; Chaoying Yu; Peiqing Zhao; Gexin Chen (pp. 9096-9102).
► Degradation of β-naphthol was carried out by CWAO and the COD removal was 93.7%. ► Comparative study of supported CuO x and MnO x catalysts was implemented. ► Destruction of β-naphthol was catalyzed by metal oxides supported on nano-TiO2.MnO x/nano-TiO2, MnO x/Al2O3–TiO2 (Al-Ti), CuO x/nano-TiO2 and CuO x/Al-Ti were prepared and their application in catalytic wet air oxidation (CWAO) of β-naphthol were investigated. The catalysts had been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. Phases of CuO, Cu2O, CuAl2O4, MnO2 and Mn2O3 could be found on the surface of the aforementioned catalysts. Significant differences in activities were observed among the prepared catalysts. Compared to CuO x/nano-TiO2, the combined action of highly dispersed CuO as well as CuAl2O4 of CuO x/Al-Ti helped to achieve higher activity for the CWAO of β-naphthol, while the Cu2O component lead to lower efficiency of CuO x/nano-TiO2. On the surface of MnO x/nano-TiO2, both the larger amount of highly dispersed MnO2 and the stronger electron transfer between MnO2 and Mn2O3 were helpful to promote the activity for the degradation of β-naphthol. However, the higher amount of bulk MnO2 and the weaker electron transfer for MnO x/Al-Ti were unfavorable to increase its efficiency. Among the four catalysts as-prepared, MnO x/nano-TiO2 was identified the highest activity with 93.7% COD removal.
Keywords: Mn; Cu; Nano-TiO; 2; Al; 2; O; 3; –TiO; 2; Catalytic wet air oxidation; β-Naphthol