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Applied Surface Science (v.257, #17)

Effect of laser treatment on the surface of copper alloys by Halina Garbacz; Elzbieta Fortuna-Zalesna; Jan Marczak; Andrzej Koss; Anna Zatorska; Grazyna Z. Zukowska; Tomasz Onyszczuk; Krzysztof J. Kurzydlowski (pp. 7369-7374).

▶ The materials of the investigated archaeological objects (bow and ring) is bronze. ▶ The main components of the corrosion layers are C, O, Cu and P. ▶ The cleaning with ns and μs pulses resulted in the external deposit layer removal. ▶ The laser-deposit interaction resulted in melting and evaporation of the surface layer. ▶ After ns pulses the surface was relatively smooth and only slightly re-molten.The paper presents the results of laser cleaning of the archaeological metal objects using two time widths of pulsed laser radiation, which are around 150μs and around 120ns. Two archaeological objects made of copper alloys were studied: a bow and a ring. Both objects came from a cemetery which is located in the garden complex of Wilanow Palace in Warsaw and are dated from XII to XIII century. The bow and bronze ring had ornamental longitudinal grooving and were part of burial jewellery. The materials of which these artefacts were made of, as well as corrosion products on these objects, were studied by using a variety of analytical techniques. The phase composition of the corrosion layers was determined by using Raman spectroscopy. The surface topography as well as the chemical composition of the deposits and cleaned surfaces were investigated. The samples were examined using scanning electron microscopes equipped with EDS. The investigations included observations in SE and BSE modes and point analyses of the chemical composition by EDS.

Keywords: Copper; Brass; Laser cleaning; Metal artwork

Microstructure and antibacterial properties of microwave plasma nitrided layers on biomedical stainless steels by Li-Hsiang Lin; Shih-Chung Chen; Ching-Zong Wu; Jing-Ming Hung; Keng-Liang Ou (pp. 7375-7380).

► During nitriding treatment between 350°C and 550°C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ→(γ+γ_N)→(γ+α+CrN). ► The nitrogen penetrated deeper into the substrate as treated temperature increases. ► The surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ_N phase in nitriding process. ► The antibacterial metallic ions (Fe⁺ and Cr⁺) can be dissolution from the γ_N and CrN phases on the nitrided layers of the nitrided samples and thus come into the bacterial suspension to kill bacteria.Nitriding of AISI 303 austenitic stainless steel using microwave plasma system at various temperatures was conducted in the present study. The nitrided layers were characterized via scanning electron microscopy, glancing angle X-ray diffraction, transmission electron microscopy and Vickers microhardness tester. The antibacterial properties of this nitrided layer were evaluated. During nitriding treatment between 350°C and 550°C, the phase transformation sequence on the nitrided layers of the alloys was found to be γ→(γ+γ_N)→(γ+α+CrN). The analytical results revealed that the surface hardness of AISI 303 stainless steel could be enhanced with the formation of γ_N phase in nitriding process. Antibacterial test also demonstrated the nitrided layer processed the excellent antibacterial properties. The enhanced surface hardness and antibacterial properties make the nitrided AISI 303 austenitic stainless steel to be one of the essential materials in the biomedical applications.

Keywords: Antibacterial stainless steel; Microwave plasma; Nitridation; Microstructure; Antibacterial property

Study on highly visible light active Bi-doped TiO₂ composite hollow sphere by Jingjing Xu; Mindong Chen; Degang Fu (pp. 7381-7386).

► Bi-doped hollow titania spheres were prepared using carbon spheres as template. ► The effects of Bi content on the physical structure and photocatalytic activity of doped hollow titania sphere samples were investigated. ► There was an optimal Bi-doped content (4%) for the photocatalytic degradation of methylene blue.Bi-doped hollow titania spheres were prepared using carbon spheres as template and Bi-doped titania nanoparticles as building blocks. The Bi-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis diffuse reflectance spectrum (DRS) and X-ray photoelectron spectroscopy (XPS). The effects of Bi content on the physical structure and photocatalytic activity of doped hollow titania sphere samples were investigated. Results showed that there was an optimal Bi-doped content (4%) for the photocatalytic degradation of methylene blue (MB).

Keywords: Photocatalysis; Bi-doped; Titania; Hollow spheres; Methylene blue

Influence of crystalline diamond nanoparticles on diamond-like carbon friction behavior by P.A. Radi; F.R. Marciano; D.A. Lima-Oliveira; L.V. Santos; E.J. Corat; V.J. Trava-Airoldi (pp. 7387-7393).

► The sp³/ sp² ratio slightly increased with the presence of CD particles. ► CD particles reduce DLC average friction coefficient by the formation of low-shear microfilms on the coating or by the asperity tips of the coating. ► DLC films with particles of 4nm presented the most homogeneous friction map, with minor variation in friction coefficient with the increase/decrease of load and sliding speed, even when the nanoparticle concentration increase.Crystalline diamond (CD) particles have been incorporated in diamond-like carbon (DLC) film structure in order to improve DLC electrochemical corrosion resistance. This paper shows the investigation of CD-DLC friction behavior according to the CD average sizes and concentration. The films were growth over 304 stainless steel using plasma enhanced chemical vapor deposition. The response surface methodology was used to develop a mathematical modeling of friction for these films, using the experimental results, in order to identify parameters that control friction and construct tribological maps according to the CD average sizes. The presence of bigger CD particles (250 and 500nm) increased the film roughness. Films with CD particles of 4nm presented the most homogeneous friction map, with minor variation in friction coefficient with the increase/decrease of load and sliding speed even when the CD concentration increase. This result suggests that in CD-DLC films containing CD particles of 4nm average size, the nanoparticles are better incorporated in DLC structure due to its average size (4nm) that is near than DLC grain size and could occupy the nanospaces between DLC grains.

Keywords: Diamond-like carbon; Crystalline diamond particles; Friction behavior

Considerable improvement in the stability of solution processed small molecule OLED by annealing by GuiLin Mao; Zhaoxin Wu; Qiang He; Bo Jiao; Guojin Xu; Xun Hou; Zhijian Chen; Qihuang Gong (pp. 7394-7398).

► We studied the annealing effect on solution processed small molecule organic films. ► The densities of the spin-coated films increased as the annealing temperature rose. ► The surface roughness decreased as the annealing temperature rose. ► Corresponding wet OLEDs’ stabilities are equivalent to the vacuum counterparts. ► Annealing process plays a key role in prolonging the stability of spin-coated OLED.We investigated the annealing effect on solution processed small organic molecule organic films, which were annealed with various conditions. It was found that the densities of the spin-coated (SC) films increased and the surface roughness decreased as the annealing temperature rose. We fabricated corresponding organic light emitting diodes (OLEDs) by spin coating on the same annealing conditions. The solution processed OLEDs show the considerable efficiency and stability, which were prior or equivalent to the vacuum-deposited (VD) counterparts. Our research shows that annealing process plays a key role in prolonging the lifetime of solution processed small molecule OLEDs, and the mechanism for the improvement of the device performance upon annealing was also discussed.

Keywords: Organic light emitting diodes; Solution processed; Stability; Annealing

Ellipsometric studies on TiO₂ thin films synthesized by spray pyrolysis technique by S. Tripura Sundari; N.C. Raut; Tom Mathews; P.K. Ajikumar; S. Dash; A.K. Tyagi; Baldev Raj (pp. 7399-7404).

► While many research articles are available on the optical properties of TiO₂ thin films synthesized by rf magnetron sputtering, reactive deposition etc., little information is available on the optical properties of thin films deposited by spray pyrolysis technique which is more versatile and can be applied for large area applications. ► This article explores the effect of substrate temperature and roughness of very thin films (typically ∼20nm) on the refractive indices. A Bruggemen effective medium approximation was carried out to estimate the void fraction and surface roughness of the thin films. ► A dielectric modeling based on Forouhi Bloomer formulation has been carried out to benchmark spray pyrolysed thin TiO₂ films.TiO₂ thin films were synthesized on quartz substrates at substrate temperatures of 350°C and 450°C by thermal spray pyrolysis technique using titanium oxy-acetyl acetonate as a precursor. The optical properties of the thin films were characterized by a Spectroscopic Ellipsometer (SE). The surface morphology of the thin films was studied using Atomic Force Microscopy (AFM). The surface roughness values obtained using AFM and SE was compared. The refractive indices of the films were computed using a point by point ellipsometric data extraction procedure. The porosity of the films were modeled from the optical data by effective medium approximation and corroborated from empirical relations. Using Forouhi–Bloomer optical dispersion model, further treatment of SE data was carried out. The experimental investigations and modeling of the data were directed towards optical benchmarking of spray pyrolyzed titania thin films.

Keywords: PACS; Code 07.60.Fs; 78.20.CiSpray pyrolysis; Ellipsometry; Refractive index; Forouhi–Bloomer model

Novel microstructural growth in the surface of Inconel 625 by the addition of SiC under electron beam melting by M. Ahmad; G. Ali; Ejaz Ahmed; M.A. Haq; J.I. Akhter (pp. 7405-7410).

► Electron beam melting is successfully used to grow the novel structure during the reinforcement of SiC in Inconel 625 alloy. ► Novel structures like rod/wires, bamboo, pyramid, ribbon, terraces and tweezers are formed. ► The microhardness of the modified surface enhanced about two times as compared to the as-received alloy. ► Changes in the composition as well as the cooling rate affect the morphology of re-solidifying melts.Electron beam melting is being used to modify the microstructure of the surfaces of materials due to its ability to cause localized melting and supercooling of the melt. This article presents an experimental study on the surface modification of Ni-based superalloy (Inconel 625) reinforced with SiC ceramic particles under electron beam melting. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques have been applied to characterize the resulted microstructure. The results revealed growth of novel structures like wire, rod, tubular, pyramid, bamboo and tweezers type morphologies in the modified surface. In addition to that fibrous like structure was also observed. Formation of thin carbon sheet has been found at the regions of decomposed SiC. Electron beam modified surface of Inconel 625 alloy has been hardened twice as compared to the as-received samples. Surface hardening effect may be attributed to both the formation of the novel structures as well as the introduction of Si and C atom in the lattice of Inconel 625 alloy.

Keywords: Microstructure; Hardness; Electron beam method; Scanning electron microscopy (SEM); Energy dispersive X-ray spectroscopy (EDXS); X-ray diffraction (XRD)

Fabrication of silicon wafer with ultra low reflectance by chemical etching method by Yingli Cao; Aimin Liu; Honghao Li; Yiting Liu; Fen Qiao; Zengquan Hu; Yongcang Sang (pp. 7411-7414).

► A pyramid and nanowire binary structure of monocrystalline silicon wafer was fabricated by chemical etching. ► Much lower reflectance of silicon wafer with this structure was obtained compared with that of single pyramid or nanowaire arrays. ► An average reflectance of 0.9% was obtained under optimized condition. ► The formation mechanism of silicon nanowires was explained by experimental evidence.A pyramid and nanowire binary structure of monocrystalline silicon wafer was fabricated by chemical etching. Much lower reflectance of silicon wafer with this structure was obtained compared with that of single pyramid or nanowaire arrays. The morphology, reflectivity and etching thickness of this structure were studied, as well as the influence on them caused by etching time and thickness of silver film. An average reflectance of 0.9% was obtained under optimized condition. The formation mechanism of silicon nanowires was explained by experimental evidence.

Keywords: Pyramids; Nanowires; Reflectance; Etching

Protein photoimmobilizations on the surface of quartz glass simply mediated by benzophenone by Xin Wu; Qi Tang; Chuanli Liu; Qin Li; Yuanyuan Guo; Yanlian Yang; Xuefei Lv; Lina Geng; Yulin Deng (pp. 7415-7421).

► The main intention of this manuscript is to photoimmobilize protein on the surface of quartz glass through a simple and effective way. ► Protein photo-immobilizations on glass surface simply using BP as a photochemical linker were realized by three different methods in this paper. ► Three different photoinduced methods were compared in respect of immobilization density, coverage homogeneities and photo-localization. ► The appealing characters will be of interests for industrial applications in silicon-based fields, including chips, sensors, etc.In this paper, photoinduced protein immobilizations on quartz glass slides utilizing benzophenone as photoinitiator without any photoactive group derivatizations involved were developed. Three different methods mediated by benzophenone were investigated, including protein photo-attachment onto untreated glass surface, protein attachment onto glass surface by reacting with pre-photografted maleic anhydride, and protein photo-attachment onto alkylamino silane functionalized glass surface, respectively. Protein immobilizations were characterized by fluorescence microscopy and atomic force microscopy. The preservation of biological activity after protein photo-attachments was confirmed by immunoassays. Area-defined protein immobilization was also primarily investigated. Comparative studies demonstrated that in respect of immobilization density, coverage homogeneities and photo-localization, protein photocoupling to amino-terminated quartz glass surfaces remarkably outperformed other photoinduced methods, as well as one kind of 3-(triethoxysilyl) propyl isocyanate chemical protein immobilization. The feasibility of this protein photo-immobilization on silicon-based materials is promising for widespread application because of its simplicity and effectiveness.

Keywords: Protein photo-immobilization; Benzophenone; Glass

Epitaxial growth of uniform NiSi₂ layers with atomically flat silicide/Si interface by solid-phase reaction in Ni–P/Si(100) systems by H.F. Hsu; H.Y. Chan; T.H. Chen; H.Y. Wu; S.L. Cheng; F.B. Wu (pp. 7422-7426).

► P atoms as diffusion barriers led Ni–P film to form NiSi₂ film at low temperature. ► Stable capping layer was formed with P, O, Ni and Si. ► Epitaxial NiSi₂ layer with atomically flat interface was formed at 700°C.As metal-oxide-semiconductor field-effect transistor (MOSFET) devices are shrunk to the nanometer scale, flat shallow metal/Si electrical contacts must be formed in the source/drain region. This work demonstrates a method for the formation of epitaxial NiSi₂ layers by a solid-phase reaction in Ni–P(8nm)/Si(100) samples. The results show that the sheet resistance remained low when the samples were annealed at temperatures from 400 to 700°C. P atoms can be regarded as diffusion barriers against the supply of Ni to the Si substrate, which caused the formation of Si-rich silicide (NiSi₂) at low temperature. Furthermore, elemental P formed a stable capping layer with O, Ni and Si during the annealing process. A uniform NiSi₂ layer with an atomically flat interface was formed by annealing at 700°C because of the formation of a Si–Ni–P–O capping layer and a reduction in the total interface area.

Keywords: Nickel silicide; Phosphorous; Interface

Structural and magnetic properties of Pt in Co/Pt multilayers by Yukai An; Lingshen Duan; Tao Liu; Zhonghuan Wu; Jiwen Liu (pp. 7427-7431).

► Structural and magnetic properties of Pt are investigated. ► Pt–Co intermixing region increases with decreasing the Pt layer thickness. ► The interface atoms are polarized by direct Pt–Co hybridization. ► An induced magnetism for Pt layers was quantitatively studied.[Co(30Å)/Pt( xÅ)]₂₀ multilayers with the Pt layer thicknesses varying from 5Å to 20Å were characterized structurally by high angle X-ray diffraction, X-ray reflectivity, X-ray absorption spectroscopy and magnetically by X-ray magnetic circular dichroism. It is found that the structure and magnetic properties of Pt have a strong correlation with the Pt layer thickness. The 20Å thickness Pt layer is not almost influenced by the adjacent Co layer and the nearest neighbors are dominated by Pt–Pt shells. With decreasing Pt layer thickness, the nearest neighbors are gradually dominated by Pt–Co shells and the Pt–Co intermixing regions also remarkable increase at the interfaces, especially for the 5Å thickness Pt layer. The orbital and spin magnetic moments as well as the ratio m_orb/ m_spin all decrease systematically with increasing Pt layer thickness, indicating that the interface atoms are polarized by direct Pt–Co hybridization, but that the adjacent layers are polarized by Pt–Pt interactions.

Keywords: Co/Pt multilayers; Structural; Magnetic properties

Solution synthesis and optimization of ZnO nanowindmills by Lijie Yu; Fengyu Qu; Xiang Wu (pp. 7432-7435).

► We synthesized a novel windmill-like ZnO structure. ► The as-synthesized ZnO nanowindmill has a central trunk of nanorod and six symmetrical nanorods grown epitaxially on the surface of the ZnO trunk. ► The as-obtained ZnO nanowindmills have strong ultraviolet emission at room temperature.In this work, novel windmill-like ZnO structures were fabricated through a solution route at low reaction temperature. The as-synthesized ZnO nanowindmill has a central trunk of nanorod and six symmetrical nanorods grown epitaxially on the surface of the ZnO trunk along [0001] direction. Each nanorod forming the windmill with a smooth top is about 6μm in length and about 700nm in diameter. Several control experiments were conducted to study the formation of the nanowindmills of ZnO in detail. Cathodoluminescence (CL) property of the as-obtained product was investigated, which shows there are three emission peaks centered at 384, 616 and 753nm in CL spectrum.

Keywords: Hydrothermal synthesis; ZnO; Nanowindmills; Cathodoluminescence

Layer structure variations of ultra-thin HfO₂ films induced by post-deposition annealing by Wei-En Fu; Yong-Qing Chang (pp. 7436-7442).

Display Omitted► Thermal annealing induces sizeable layer structure variation on 3nm ALD HfO₂ films. ► Crystallizes are monoclinic and orthorhombic at low annealing temperatures. ► Annealing causes films to crystallize into monoclinic phase at higher temperatures. ► XPS results showed formation of Hf silicate with increasing annealing temperatures. ► The existence of Hf silicate increases interfacial layer thickness in GIXRR analysis.To meet challenges for a smaller transistor feature size, ultra-thin HfO₂ high- k dielectric has been used to replace SiO₂ for the gate dielectric. In order to accurately analyze the ultra-thin HfO₂ films by grazing incidence X-ray reflectivity (GIXRR), an appropriate material model with a proper layer structure is required. However, the accurate model is difficult to obtain, since the interfaces between layers of the ultra-thin HfO₂ films are not easily identified, especially when post-deposition annealing process is applied. In this paper, 3.0nm HfO₂ films were prepared by atomic layer deposition on p-type silicon wafer, and annealed in Ar environment with temperatures up to 1000°C. The layer structures and the role of the interfacial layer of the films in the post-deposition annealing processes were evaluated by X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The experimental results and analysis showed that layer thicknesses, crystal phases and chemical structures of the ultra-thin HfO₂ films were significantly dependent on annealing temperatures. The binding energy shifts of Hf 4 f, O 1 s, and Si 2 p elements revealed the formation of Hf silicate (Hf–O–Si bonding) with increasing annealing temperatures. Due to the silicate formation and increasing silicon oxide formation, the interface broadening is highly expected. The structure analysis of the GIXRR spectra using the modified material structure model from the XPS analysis confirmed the interfacial broadening induced by the post-deposition annealing.

Keywords: Hafnium oxide; Post-deposition annealing; Atomic layer deposition; Layer structure analysis

Density functional theory prediction for diffusion of lithium on boron-doped graphene surface by Shuanghong Gao; Zhaoyu Ren; Lijuan Wan; Jiming Zheng; Ping Guo; Yixuan Zhou (pp. 7443-7446).

► We studied the electronic structure of boron-doped graphene, and analyzed the potential barrier of lithium diffusion on the different number of boron-doped graphene in this article. ► The investigation shows that graphene has changed from semimetal to semiconductor with the increasing number of doped boron atoms. ► Graphene became an electron-deficient system and is conducive to lithium-ion adsorption. ► The potential barrier for lithium diffusion on boron-doped graphene is higher than that of intrinsic graphene.The density functional theory (DFT) investigation shows that graphene has changed from semimetal to semiconductor with the increasing number of doped boron atoms. Lithium and boron atoms acted as charge contributors and recipients, which attracted to each other. Further investigations show that, the potential barrier for lithium diffusion on boron-doped graphene is higher than that of intrinsic graphene. The potential barrier is up to 0.22eV when six boron atoms doped (B₆C₂₆), which is the lowest potential barrier in all the doped graphene. The potential barrier is dramatically affected by the surface structure of graphene.

Keywords: Graphene; Boron; Potential barrier

Microstructure and mechanical properties of selective laser melted magnesium by C.C. Ng; M.M. Savalani; M.L. Lau; H.C. Man (pp. 7447-7454).

► Microstructure characteristic of the laser-melted magnesium is dependent on the grain size. ► The grains in the molten zone coarsen as the laser energy density increases. ► The average hardness values of the molten zone decreased significantly with an increase of the laser energy densities and then decreased slowly at a relatively high laser energy density irrespective of mode of irradiation. ► The hardness value was obtained from 0.59 to 0.95GPa and corresponding elastic modulus ranging from 27 to 33GPa.The effects of laser processing parameters on the microstructure and mechanical properties of selective laser-melted magnesium were investigated. The results show that the microstructure characteristics of the laser-melted samples are dependent on the grain size of SLM magnesium. The grains in the molten zone coarsen as the laser energy density increases. In addition, the average hardness values of the molten zone decreases significantly with an increase of the laser energy densities and then decreased slowly at a relatively high laser energy density irrespective of mode of irradiation. The hardness value was obtained from 0.59 to 0.95GPa and corresponding elastic modulus ranging from 27 to 33GPa. The present selective laser-melted magnesium parts are promising for biomedical applications since the mechanical properties are more closely matched with human bone than other metallic biomaterials.

Keywords: Magnesium; Selective laser melting; Microstructure; Mechanical properties; Hardness

Surface modification of TA2 pure titanium by low energy high current pulsed electron beam treatments by Yu-kui Gao (pp. 7455-7460).

► The surface integrity changes induced by LEHCPEBTs were investigated. ► The hardness was determined by nanoindention method. ► The modification mechanism for LEHCPEBTs was proposed. ► There is no new phase but dislocation and fine grains in modified surface layer.Surface integrity changes of TA2 pure titanium including surface topography, microstructure and nanohardness distribution along surface layer were investigated by different techniques of low energy high current pulsed electron beam treatments (LEHCPEBTs). The surface topography was characterized by SEM. Moreover, the TEM observation and X-ray diffraction analysis were performed to reveal the surface modification mechanism of TA2 pure titanium by LEHCPEBTs. The surface roughness was modified by electron beam treatment and the polishing mechanism was analyzed by studying the cross section microstructure of electron beam treated specimens by SEM and TEM. The results show that the surface finish obtains good polishing quality and there is no phase transformation but the dislocations by LEHCPEBT. Furthermore, the nanohardness in the surface modified layer is improved. The remelt and fine-grain microstructure of surface layer caused by LEHCPEBTs are the main polishing mechanism and the reason of modification of surface topography and the increment in nanohardness is mainly due to the dislocations and fine grains in the modified layer induced by LEHCPEBT.

Keywords: Low energy high current pulsed electron beam treatment (LEHCPEBT); Surface topography; TA2 pure titanium

Composition depth profiles of Bi_3.15Nd_0.85Ti₃O₁₂ thin films studied by X-ray photoelectron spectroscopy by Z.H. Zhang; X.L. Zhong; H. Liao; F. Wang; J.B. Wang; Y.C. Zhou (pp. 7461-7465).

► Composition depth profiles of the BNT film are studied by XPS. ► Chemical compositions are divided into three regions along the film depth. ► Compositions are uniform in the bulk film. ► Ar⁺-ion sputtering changes lots of Bi³⁺ ions into Bi⁰.In the present work, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition depth profiles of Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) ferroelectric thin film, which was prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by chemical solution deposition (CSD). It is shown that there are three distinct regions formed in BNT film, which are surface layer, bulk film and interface layer. The surface of film is found to consist of one outermost Bi-rich region. High resolution spectra of the O 1 s peak in the surface can be decomposed into two components of metallic oxide oxygen and surface adsorbed oxygen. The distribution of component elements is nearly uniform within the bulk film. In the bulk film, high resolution XPS spectra of O 1 s, Bi 4 f, Nd 3 d, Ti 2 p are in agreement with the element chemical states of the BNT system. The interfacial layer is formed through the interdiffusion between the BNT film and Pt electrode. In addition, the Ar⁺-ion sputtering changes lots of Bi³⁺ ions into Bi⁰ due to weak Bi–O bond and high etching energy.

Keywords: X-ray photoelectron spectroscopy; Ferroelectric thin film; Composition depth profiles; Chemical solution deposition

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles by J.P. Deepa; V.G. Resmi; T.P.D. Rajan; C. Pavithran; B.C. Pai (pp. 7466-7474).

► Uniformity of electroless copper coating on boron carbide is affected by surface contaminants. ► Ultrasonic surface cleaning and heating reduced the free surface carbon to some extent. ► The acidic and alkali treatment improved the uniformity of copper coating. ► Alkali treatment provides better coating by easily removing many of the surface contaminants. ► Coating morphology is dependent on the pH of bath and surface treatment.Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal–ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B₄C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B₄C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.

Keywords: Copper; Boron carbide; Electroless coating; Surface pre-treatment

Deformation and fracture of TiN coating on a Si(111) substrate during nanoindentation by T. An; L.L. Wang; H.W. Tian; M. Wen; W.T. Zheng (pp. 7475-7480).

► Permanent trigonal impressions and radial plastic grooves are confined within the contact regions even though the peak displacement increases to 1500nm. ► When the peak displacement increases to 2500nm, an interfacial fracture is observed using both SEM micrograph and in situ AFM images. ► Interfacial fractures determined by SEM micrographs are more accurate than those determined by in situ AFM images. ► The interfacial fracture mechanism can be investigated by either nanoindentation experiment or nanoscratch test.The deformation mechanisms and fracture behavior of TiN coating on a Si(111) substrate, deposited using magnetron sputtering Ti target, is characterized by nanoindentation experiments. The morphologies of the indentations are revealed by scanning electron microscopy, coupled with in situ atomic force microscopy in nanoindentation experiments. The results show that permanent trigonal impressions and radial plastic grooves are confined within the contact regions even though the peak indenter displacement increases to 1500nm. Local cracks of TiN appear around the indent marks making the edges of the indentations irregular. The cracks increase with an increase of the indenter displacement until the indenter arrives at (or approaches) the Si(111) substrate at a critical displacement. As the peak indenter displacement increases to 2500nm, an interfacial fracture between the TiN coating and the Si(111) substrate is observed using both scanning electron microscopy micrograph and in situ atomic force microscopy images. The diameter of the interfacial fracture determined by scanning electron microscopy micrographs is more accurate than that determined by in situ atomic force microscopy images in nanoindentation experiments. The failure mechanism of the TiN coating is also investigated by means of a standard nanoscratch test.

Keywords: TiN coating; Nanoindentation; Nanoscratch; Cube corner indenter; Radial crack; Interfacial fracture

Electrical and material characterization of tantalum pentoxide (Ta₂O₅) charge trapping layer memory by Hsiang Chen (pp. 7481-7485).

► A metal/oxide/high k-Ta₂O₅/oxide/silicon novel nanocrystal memory as a trapping layer was fabricated. ► Post-annealing treatment, which can passivate defects and improve the material quality of the high-k dielectric, was applied to optimize device performance. ► Material and electrical characterization techniques including XRD, XPS, AFM, and electrical measurements were performed to analyze the device under different annealing conditions. ► Devices with the best performance and material quality can be fabricated at an annealing temperature of 900°C.In this experiment, tantalum pentoxide (Ta₂O₅) was used in a metal/oxide/high-k Ta₂O₅/oxide/silicon (MOHOS) novel nanocrystal memory as a trapping layer. Post-annealing treatment, which can passivate defects and improve the material quality of the high-k dielectric, was applied to optimize device performance for a better memory window and faster P/E (program/erase) cycle. Material and electrical characterization techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and electrical measurements were performed to analyze the device under different annealing conditions. The Ta₂O₅ charge trapping layer memory annealed at 900°C had a higher window of 3.3V in the current–voltage ( C– V) hysteresis loop, and a higher charge retention capability than the samples prepared under various annealing conditions. These higher levels were due to the higher probability of deep-level charge trapping and lower leakage current.

Keywords: Ta; ₂; O; ₅; High-k material; Post annealing; Deep-level; Charge trapping

Fabrication and wear protection performance of superhydrophobic surface on zinc by Yong Wan; Zhongqian Wang; Zhen Xu; Changsong Liu; Junyan Zhang (pp. 7486-7489).

► The hierarchical nonorod structure was exhibited on zinc surface after treatment in DMF. ► Superhydrophobic films were prepared by a simple immersion technique. ► Superhydrophobic films provide an low friction and long wear protection durability.A simple two-step process has been developed to render zinc surface superhydrophobic, resulting in low friction coefficient and long wear resistance performance. The ZnO film with uniform and packed nanorod structure was firstly created by immersing the zinc substrates into 4% N, N-dimethylformamide solution. The as-fabricated surface was then coated a layer of fluoroalkylsilane (FAS) by gas phase deposition. Scanning electron microscopy (SEM) and water contact angle (WCA) measurement have been performed to characterize the morphological feature, chemical composition and superhydrophobicity of the surface. The resulting surfaces have a WCA as high as 156° and provide effective friction-reducing and wear protection for zinc substrate.

Keywords: Key words; Superhydrophobicity; Zinc; FAS; Friction

Effects of hydrogen treatment on ohmic contacts to p-type GaN films by Bohr-Ran Huang; Chia-Hui Chou; Wen-Cheng Ke; Yi-Lun Chou; Chia-Lung Tsai; Meng-chyi Wu (pp. 7490-7493).

► The surface inversion of p-GaN films was successfully achieved by H₂ treatment at high temperatures. ► The shifts in the surface Fermi level due to the H₂ treatment were identified by XPS measurement. ► The linear I-V behavior of the H₂-treated p-GaN films is due to the high V_N density pinned the surface Fermi level close to the conduction-band edge. ► The surface inversion by means of H₂ treatment can play an important role in lowering the metal contact resistance to p-GaN films.This study investigated the effects of hydrogen (H₂) treatment on metal contacts to Mg-doped p-GaN films by Hall-effect measurement, current–voltage ( I– V) analyzer and X-ray photoemission spectra (XPS). The interfacial oxide layer on the p-GaN surface was found to be the main reason for causing the nonlinear I– V behavior of the untreated p-GaN films. The increased nitrogen vacancy (V_N) density due to increased GaN decomposition rate at high-temperature hydrogen treatment is believed to form high density surface states on the surface of p-GaN films. Compared to untreated p-GaN films, the surface Fermi level determined by the Ga 2p core-level peak on 1000°C H₂-treated p-GaN films lies about ∼2.1eV closer to the conduction band edge (i.e., the surface inverted to n-type behavior). The reduction in barrier height due to the high surface state density pinned the surface Fermi level close to the conduction band edge, and allowed the electrons to easily flow over the barrier from the metal into the p-GaN films. Thus, a good ohmic contact was achieved on the p-GaN films by the surface inversion method.

Keywords: Hydrogen; XPS; p-GaN film; Inversion; Ohmic contact

Facile shape control synthesis and optical properties of silver nanoparticles stabilized by Daxad 19 surfactant by Nurul Akmal Che Lah; Mohd Rafie Johan (pp. 7494-7500).

Display Omitted► Temperatures dependence (80, 100 and 120̊C) and the addition of chemical reagents (AgNO₃ and Daxad 19) control the size and shape stabilization condition of silver nanoparticles produced via simple and productive inverse michelle reduction synthesis.It is known that silver (Ag) nanoparticles are attractive due to their novel and mild chemical and physical properties. In this research, anisotropic mono-dispersed silver nanoparticles are synthesized via a simple chemical reduction method and assisted by Daxad 19 surfactant. The reactant temperatures and weight ratios of the chemical constituents play a key role in controlling the hybrid shaping mechanism. The results indicate that the reduction rate of Ag⁺ to Ag⁰ nanoparticles is enhanced significantly with increasing weight ratios of Daxad 19 and AgNO₃ under controlled reactant temperature. The results show that the as-prepared silver nanoparticles are well-dispersed and uniform in size and shape. The dimensions of the particles are easily controlled. A comparison between experimental absorbance UV–visible spectra and simulated spectra from Mie's Scattering Theory is carried out. It is observed that the simulated spectrum confirms well with the optical behaviour of the experimental spectra.

Keywords: Silver nanoparticles; Daxad 19; Computer simulation; Inverse micelle reduction synthesis

Observation of the mechanisms causing two kinds of undercut during laser hybrid arc welding by Jan Karlsson; Peter Norman; Alexander F.H. Kaplan; Per Rubin; Javier Lamas; Armando Yañez (pp. 7501-7506).

► Identification of two types of undercuts in two cases, remaining or removed mill scale (oxides). ► With remaining mill scale, the oxide caused lack of fusion defect. ► Formation mechanisms of the two kinds of undercut are observed by high speed imaging. ► In case of mill scale, imaging showed that the melt does not attach to the top but glides down. ► A base material layer is the interface for rounded undercut formation.Two different kinds of undercut were identified when laser hybrid welding hot rolled HSLA-steel in either the as-rolled condition or with the top surface mill scale removed. The presence of mill scale on the steel surface was found to give a sharp angled undercut combined with a sharp oxide inclusion at the edge of the weld which would have the same mechanical effect as a crack in this position. Removal of the surface oxides before welding resulted in the elimination of the oxide inclusions and a more rounded undercut geometry indicative of superior mechanical properties, particularly fatigue life. The mechanisms of the formation of both types of undercut have been analysed by high speed photography and SEM.

Keywords: Laser hybrid arc welding; Welding; Undercut; Melt flow; Mill scale; Oxide; High speed imaging

Ab initio calculation of diffusion barriers for Cu adatom hopping on Cu(100) surface and evolution of atomic configurations by Wei Zhang; Jie Gan; Qian Li; Kun Gao; Jian Sun; Ning Xu; Zhifeng Ying; Jiada Wu (pp. 7507-7515).

► We study the self-diffusion dynamics of Cu adatoms on Cu(100) surface. ► The hopping of an active adatom is dependent on its nearest atoms and next nearest atoms. ► Dimers can move and rotate as a result of multiple hopping events, more readily than to dissociate. ► A triangle trimer can rotate more readily as a whole than to move. ► Adatoms on Cu(100) surface are inclined to aggregate to form compact islands at temperatures above 300K.The self-diffusion dynamics of Cu adatoms on Cu(100) surface has been studied based on the calculation of the energy barriers for various hopping events using lattice-gas based approach and a modified model. To simplify the description of the interactions and the calculation of the energy barrier, a three-tier hierarchy of description of atomic configurations was conceived in which the active adatom and its nearest atoms were chosen to constitute basic configuration and taken as a whole to study many-body interactions of the atoms in various atomic configurations, whereas the impacts of the next nearest atoms on the diffusion of the active adatom were considered as multi-site interactions. Besides the simple hopping of single adatoms, the movements of dimers and trimers as the results of multiple hopping events have also been examined. Taking into account the hopping events of all adatoms, the stability of atomic configurations has been examined and the evolution of atomic configurations has also been analyzed.

Keywords: PACS; 68.35.Md; 68.55.A−; 07.05.Tp; 81.16.DnSelf-diffusion dynamics; Diffusion barrier; Adatom hopping; Atomic configuration evolution; Ab initio calculation

Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on p-Si (100) substrates by J.W. Shin; Y.S. No; J.Y. Lee; J.Y. Kim; W.K. Choi; T.W. Kim (pp. 7516-7520).

► Atomic force microscopy and transmission electron microscopy (TEM) images showed that the surfaces of the ZnO thin films annealed in a nitrogen atmosphere became very rough in contrast to those annealed in an oxygen atmosphere. ► High-resolution TEM images showed that many stacking faults and tilted grains could be observed in the ZnO thin films annealed in a nitrogen atmosphere in contrast to those annealed in an oxygen atmosphere.Effects of different annealing atmospheres on the surface and microstructural properties of ZnO thin films grown on Si (100) substrates were investigated. X-ray diffraction results showed that the crystallinity of the ZnO thin film annealed in an oxygen atmosphere was better than that annealed in a nitrogen atmosphere. Atomic force microscopy and transmission electron microscopy (TEM) images showed that the surfaces of the ZnO thin films annealed in a nitrogen atmosphere became very rough in contrast to those annealed in an oxygen atmosphere. High-resolution TEM images showed that many stacking faults and tilted grains could be observed in the ZnO thin films annealed in a nitrogen atmosphere in contrast to those annealed in an oxygen atmosphere. Surface morphology and microstructural property variations due to different annealing atmospheres in ZnO thin films are also described on the basis of the experimental results.

Keywords: ZnO thin film; Microstructural property; Different annealing

In vitro studies of PBT Nonwoven Fabrics adsorbent for the removal of low density lipoprotein from hyperlipemia plasma by Ye Cao; Hong Wang; Chao Yang; Rui Zhong; Yu Lei; Kang Sun; Jiaxin Liu (pp. 7521-7528).

► Heparin and polyacrylic acid were grafted on PBT Nonwoven Fabrics surface to study their effect on the adsorption of low density lipoprotein and blood compatibilities. ► The adsorption efficiency of LDL was greatly increased by immobilized of PAA. ► And the immobilization of heparin could improve PBTNF-PAA's blood compatibility and decrease the adsorption capability of useful high density lipoprotein significantly.Polyanion ligands such as acrylic acid (AA) and heparin were grafted on PBT Nonwoven Fabrics (PBTNF) to study their effect on the adsorption of low density lipoprotein (LDL). These modified PBTNFs were characterized by Horizontal Attenuated Total Reflectance Fourier Transform Infrared spectroscopy and X-ray Photoelectron spectroscopy. The blood compatibilities of the modified PBTNFs were examined using in vitro hemolysis rate (HR), platelet adhesion, total protein (TP) and activated partial thromboplastin time. The results showed that direct immobilized heparin could improve PBTNF-PAA's blood compatibility and decrease the adsorption capability of useful high density lipoprotein, but would possess so low bioactivity that could not further improve the absorption of LDL and TC. Since the PBTNF-PAA55-Heparin adsorbent had quite good adsorption selectivity for these proteins, it can be an excellent candidate for depletion of LDL with good blood compatibility.

Keywords: PBT Nonwoven Fabrics; Polyacrylic acid; LDL; Heparin; Blood compatibility

Chemical bath deposition of Bi₂S₃ films by a novel deposition system by Chao Gao; Honglie Shen; Lei Sun; Zhou Shen (pp. 7529-7533).

► Bi₂S₃ films were prepared by a novel chemical bath deposition system in which ammonium citrate was used as the chelating reagent. ► Two sulfur source (thioacetamide and sodium thiosulfate) were used to prepare Bi₂S₃ films for comparison. ► The structures, morphologies, optical properties and electrical properties of the Bi₂S₃ films were studied systematically.Bismuth sulfide (Bi₂S₃) films were chemically deposited by a novel deposition system in which ammonium citrate was used as the chelating reagent. Two sulfur source thioacetamide (TA) and sodium thiosulfate (Na₂S₂O₃) were used to prepare Bi₂S₃ films. Both the as-prepared films have amorphous structure. However, annealing can improve the crystallization of the films. The composition of the films prepared by TA and Na₂S₂O₃ are all deviate from the stoichiometric ratio of Bi₂S₃. The Bi₂S₃ films are all homogeneous and well adhered to the substrate. The optical properties of the Bi₂S₃ films are studied. The electrical resistivity of the as-prepared films are all around 7×10³Ωcm in dark, which decreases to around 1×10³Ωcm under 100mW/cm² tungsten–halogen illumination. After the annealing, the dark resistivity of the Bi₂S₃ film prepared by TA decreases by four magnitudes. In contrast, the dark resistivity of the Bi₂S₃ film prepared by Na₂S₂O₃ only decreases slightly.

Keywords: Bi; ₂; S; ₃; films; Chemical bath deposition; Novel deposition system; Optical and electrical properties

Tunable surface wettability of ZnO nanorods prepared by two-step method by Jianguo Lv; Jianbo Zhu; Kai Huang; Fanming Meng; Xueping Song; Zhaoqi Sun (pp. 7534-7538).

► The proportion of nonpolar planes decreases with the increase of the growth time. ► The WCA of ZnO nanorods for 4h and 10h growth are ∼136° and ∼43°, respectively. ► The magnitude of WCA modulation with growth time is ∼93°. ► Effect of the proportion of nonpolar planes on the WCA has been studied. ► Increase of WCA reduction rate may be attributed to decrease of nonpolar planes.Zinc oxide (ZnO) nanorods were deposited on silicon substrate by two-step method. The crystal structure, surface morphology and water contact angle (WCA) were measured by X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), and water contact angle apparatus. It is demonstrated that the WCA of the as-grown ZnO nanorods varies between 136° and 43° and the contact angle reduction rate of ZnO nanorods changes rapidly with increasing growth time. The variation of contact angle in the as-grown samples and contact angle reduction rate has been attributed to the combined effects of the proportion of nonpolar planes in the outermost surface, the area fraction of vapor on the surface and the increase of surface energy of ZnO nanorods.

Keywords: ZnO nanorods; Two-step method; Nonpolar planes; Wettability

A theoretical study of thiophenic compounds adsorption on cation-exchanged Y zeolites by Lingtao Wang; Zhaolin Sun; Yong Ding; Yongchang Chen; Qiang Li; Ming Xu; Huailei Li; Lijuan Song (pp. 7539-7544).

► The adsorption desulfurization mechanisms of fuel oils over Cu(I)Y, Ni(II)Y, and Ce(III)Y zeolites have been investigated by a DFT method. ► The η1S and η5 adsorption modes of adsorbate interacted with the cation-exchanged zeolites have been discussed for three different thiophenic compounds. ► The key role of the exchanged metal cations (Cu⁺, Ni²⁺, Ce³⁺) on the adsorption behavior was shown. ► The Cu(I)Y zeolite as a sorbent presents the highest adsorption capability compared with the Ni(II)Y and Ce(III)Y zeolites.A density functional theory (DFT) method has been applied to study the adsorption of thiophenic compounds such as thiophene (TP), benzothiophene (BT), dibenzothiophene (DBT) on cation-exchanged Cu(I)Y, Ni(II)Y, Ce(III)Y zeolites. All of calculations were carried out by the generalized gradient approximation (GGA) with the BLYP exchange-correlation functional and DNP basis set. The calculated results indicate that the stable adsorption configuration of TP molecule adsorbed on the Cu(I)Y is the η5 adsorption mode, whereas for BT and DBT, the η1S adsorption mode was found for the both molecules. Only the η1S adsorption mode can be obtained for the three thiophenic compounds adsorbed on the Ni(II)Y. The η5 adsorption mode can be ascribed to the adsorption of thiophene molecules on the Ce(III)Y, but the competition of different adsorption modes could possibly occur during the adsorption process of BT and DBT on the Ce(III)Y. Moreover, the selectivity of TP adsorbed on the adsorbents is in the order of Cu(I)Y>Ce(III)Y>Ni(II)Y, while for BT and DBT, the order is Cu(I)Y>Ni(II)Y>Ce(III)Y.

Keywords: Adsorption desulfurization; Cation-exchanged zeolites; Thiophenic compounds; Density functional theory (DFT)

Physical and electrochemical study of platinum thin films deposited by sputtering and electrochemical methods by C. Quiñones; W. Vallejo; F. Mesa (pp. 7545-7550).

► The topic of research involves a broad research topic. ► Two deposition methods were studied. ► A complete physical and electrochemical characterization were done. ► Pt thin films fabricated in this work have adequate properties to be used as counter-electrode in DSSC.In this work platinum thin films deposited by sputtering and electrochemical methods were characterized through physical and electrochemical analysis. The as-grown platinum thin films were characterized through X-ray diffraction (XRD), atomic force microscopy (AFM); scanning electronic microscopy (SEM) and through electrochemical impedance spectroscopy (EIS) measurements. Structural studies indicated that platinum thin films were polycrystalline. Morphological characteristics were significantly affected by the substrate type and synthesis method. Finally the EIS analysis indicated that platinum films were electrochemically stable and present both low resistance of charge transfer and low series resistance; the equivalent circuit of platinum interface has been proposed.

Keywords: Platinum; Thin film; Counter-electrode; DSSC

Highly active Ce1−_xCu_xO₂ nanocomposite catalysts for the low temperature oxidation of CO by Hailing Mai; Dengsong Zhang; Liyi Shi; Tingting Yan; Hongrui Li (pp. 7551-7559).

.Display Omitted► The Ce1−_xCu_xO₂ nanocomposite catalysts were synthesized by a simple hydrothermal method. ► The particle size of Ce_0.80Cu_0.20O₂ nanocomposites is about 5.0nm with a narrow distribution. ► The optimum catalytic activity and stability is achieved for the Ce_0.80Cu_0.20O₂ nanocomposites.A series of Ce1−_xCu_xO₂ nanocomposite catalysts with various copper contents were synthesized by a simple hydrothermal method at low temperature without any surfactants, using mixed solutions of Cu(II) and Ce(III) nitrates as metal sources. These bimetal oxide nanocomposites were characterized by means of XRD, TEM, HRTEM, EDS, N₂ adsorption, H₂-TPR and XPS. The influence of Cu loading (5–25mol%) and calcination temperature on the surface area, particle size and catalytic behavior of the nanocomposites have been discussed. The catalytic activity of Ce1−_xCu_xO₂ nanocomposites was investigated using the test of CO oxidation reaction. The optimized performance was achieved for the Ce_0.80Cu_0.20O₂ nanocomposite catalyst, which exhibited superior reaction rate of 11.2×10⁻⁴mmolg⁻¹s⁻¹ and high turnover frequency of 7.53×10⁻²s⁻¹ (1% CO balanced with air at a rate of 40mLmin⁻¹, at 90°C). No obvious deactivation was observed after six times of catalytic reactions for Ce_0.80Cu_0.20O₂ nanocomposite catalyst.

Keywords: Ce; 1−; _x; Cu; _x; O; ₂; catalyst; Nanocomposite; Rare earth; CO oxidation

Effect of substrate hardness on the deformation behavior of subsequently incident particles in cold spraying by Shuo Yin; Xiao-fang Wang; W.Y. Li; Hong-en Jie (pp. 7560-7565).

► Hard substrate contributes to the deformation of the subsequently incident particles. ► Soft substrate enables the subsequently incident particles to deform slightly. ► Substrate hardness plays its best role only when the formed coating is thin.A systematic finite element analysis (FEA) on the subsequently incident particles which refer to the particles depositing after the formation of the first layer coating is conducted in this study to clarify the bonding mechanism inside the cold sprayed coating. A simplified particle impact model is proposed and the simulated results based on this model demonstrate that substrate hardness exerts some effects on the deformation behavior of the subsequently incident particles. Hard substrate makes these particles deform intensively but using soft substrate enables them to achieve a slight deformation. At the same time, it is also found that substrate hardness plays its best role only when the formed coating is thin, as the development of the coating, the particle deformation behavior becomes more and more insensitive to the substrate hardness. The multi-particle impact simulation based on Eulerian method is also performed and reaches the same conclusion, confirming the accuracy of the simplified model. Besides, it is also found that when the velocity is increased to a hypervelocity, excessive deformation occurs in the formed coatings due to the impact of the subsequently incident particles.

Keywords: Cold spraying (CS); Numerical simulation; Substrate hardness; Eulerian method; Multi-particle; Subsequently incident particle

X-ray standing waves in a multi-trilayer system with linearly varying period by Sumalay Roy; B.N. Dev (pp. 7566-7572).

► A depth-graded multi-trilayer system with a linearly varying period is investigated. ► Theoretical formalism is developed to describe X-ray standing wave generation in such a multilayer. ► Microstructure is investigated using a combined X-ray reflectivity and X-ray standing wave study.Generation of X-ray standing waves in a multi-trilayer system with a varying periodicity along its depth is described. Microstructures of a synthetic 15-period Pt/Ni/C multilayer, which has such a varying periodicity, are investigated using X-ray reflectivity (XRR) and X-ray standing wave (XSW) analysis. Microstructural parameters, e.g., thicknesses and electron densities of individual layers, interface roughnesses, varying periodicity along the depth, etc. are precisely determined by the XRR technique. The variation of period is essentially introduced in multilayer fabrication by varying the thickness of the C-layer as a function of depth. The linear increase in C-layer thickness from the bottom of the multilayer towards the surface of the multilayer structure is found by simulating the XRR data with a depth-graded multilayer model. Intensity of the XSW field is computed as a function of depth over the first order Bragg peak. Integrated intensities over the Pt- and the Ni-layers are computed and compared with the measured fluorescence yield from Pt and Ni. Sensitivity for the detection of inter-atomic diffusion across the interfaces in comparison to multi-bilayer systems, such as Pt/C multilayer, is discussed.

Keywords: X-ray standing waves; X-ray reflectivity; Multilayers

Effect of H⁺ ion implantation on structural, morphological, optical and dielectric properties ofl-arginine monohydrochloride monohydrate single crystals by K. Sangeetha; R. Ramesh Babu; P. Kumar; G. Bhagvannarayana; K. Ramamurthi (pp. 7573-7578).

► H⁺ ions implanted LAHCl single crystals at different ion fluence were studied for property changes. ► Ion implantation induced defect clusters were analyzed using optical absorption. ► H⁺ ions implanted crystal shows property enhancement.l-arginine monohydrochloride monohydrate (LAHCl) single crystals have been implanted with 100keV H⁺ ions at different ion fluence ranging from 10¹² to 10¹⁵ions/cm². Implanted LAHCl single crystals have been investigated for property changes. Crystal surface and crystalline perfection of the pristine and implanted crystals were analyzed by atomic force microscope and high-resolution X-ray diffraction studies, respectively. Optical absorption bands induced by colour centers, refractive index and birefringence, mechanical stability and dielectric constant of implanted crystals were studied at different ion fluence and compared with that of pristine LAHCl single crystal.

Keywords: H; ⁺; ions implantation; Crystalline perfection; UV–vis spectroscopy; Refractive index; Birefringence; Dielectric property

Adsorption orientation of sodium of polyaspartic acid effect on anodic films formed on magnesium alloy by YuPing Liu; Dingfei Zhang; Changguo Chen; Jiangang Zhang; libo Cui (pp. 7579-7585).

► The PASP concentration affects the anodizing process greatly. ► Increasing the PASP concentration ranging from 19.2g/L to 28.8g/L results in enhancing the corrosion performance. ► The anodic film consists of MgO and Mg₂SiO₄. ► The anodizing process is regulated by two main plausible adsorption orientations of PASP including “end-on” and “flat-on”.We previously reported organic addition agent in improving the performance of anodic film formed on magnesium alloy. Here we report that the environment-friendly electrolyte with sodium of polyaspartic acid (PASP) affects the anodizing process including the microstructure, phase constituents and corrosion performance. We have used SEM, XRD, XPS and polarization curve to study in detail the electrolyte impact. Our results show that the anodic film in electrolyte with 19.2–28.8g/L PASP is compact, smooth and high corrosion resistant. And also, increasing the PASP concentration ranging from 9.6 to 28.8g/L results in enhancing the cell voltage, thickness and the content of compound including MgO and Mg₂SiO₄ in anodic film. Interestingly, the anodic film is non-stoichiometric oxide. Comparing with Tafel curves of the anodic film to the addition of PASP or not to, the corrosion current density is 1–2 magnitudes less than the later. Furthermore, a plausible model we propose that the anodizing process is regulated by two main plausible adsorption orientations of PASP at the surface anode. With the increasing of PASP content, the adsorption orientation may transit from “end-on” to “flat-on”. This research using organic addition agent PASP may further broaden applications of organic additive in the anti-corrosion engineering and electrochemical surface treatment of magnesium alloy.

Keywords: PASP; Magnesium alloy; Anodizing; Corrosion; Adsorption orientation

First principles study of small cobalt clusters encapsulated in C₆₀ and C₈₂ spherical nanocages by M. Bezi Javan; N. Tajabor; M. Rezaee-Roknabadi; M. Behdani (pp. 7586-7591).

► The encapsulated Co_n clusters inside C₆₀ (Ih) and C₈₂ (C2v) cages, except Co₇@C₆₀, are energetically favorable. ► The encapsulation does not change significantly the structure of the enclosed clusters. ► The magnetic moment of the encapsulated clusters reduces due to a stronger Co–C hybridization for the larger clusters. ► It is found that for all complexes, additional peaks contributed by the Co_n atomic orbitals appear in the HOMO-LUMO gap (Eg) of the host fullerene.Structural, electronic and magnetic properties of the small Co_n clusters ( n=2–7) endohedrally doped in C₆₀ (Ih) and C₈₂ (C2v) fullerenes were investigated using ab initio calculations based on the density functional theory. It is found that the encapsulated Co_n clusters inside C₆₀ and C₈₂ cages are energetically favorable except for Co₇@C₆₀. The encapsulation does not change significantly the structure of the enclosed clusters, but the magnetic moment of the clusters reduces due to a stronger Co–C hybridization for the larger clusters.

Keywords: Endohedral metallofullerenes; Encapsulation energy; Magnetic moment

Studies and correlation among the structural, electrical and gas response properties of aerosol spray deposited self assembled nanocrystalline CuO by Iqbal Singh; R.K. Bedi (pp. 7592-7599).

Display Omitted► Deposition of CuO films by ultrasonic spray pyrolysis technique. ► Comparison of results with literature. ► Effect of substrate temperature on structural, morphological, electrical properties. ► CuO films as room temperature ammonia sensor. ► The kinetics of the ammonia gas adsorption by Elovich Model.Nanostructured CuO films have been grown on to the glass substrate by varying the deposition time from 10 to 30min and substrate temperature from 300 to 400°C by a simple ultrasonic spray pyrolysis technique, using aqueous a cupric nitrate solution as precursor. The effect of the substrate temperature on the textural, structural, electrical, and gas sensing properties of CuO films was studied and correlated. Thermal analysis of the dried precursor shows the elimination of physisorbed and chemisorbed water. It suggests the formation of CuO phase on substrate at temperature of 300°C. X-ray diffractograms of the films indicate the formation of polycrystalline monoclinic CuO having monoclinic with crystallite size around 18nm. The texture coefficient finds the (002) plane as the preferred orientation in films. The microstrain and dislocation densities have been calculated and found to decreases with increase in substrate temperature. The scanning electron micrographs indicate the formation of trapezium like facet structures on the film surface. AFM analysis shows uniform deposition of the CuO film over the entire substrate surface. Observations reveal that the film deposited at 300°C show comparatively higher activation energy and appreciable response to ammonia at room temperature. The use of aqueous cupric nitrate as precursor results in the deposition of single phase copper oxide films.

Keywords: Spray pyrolysis; Ammonia sensor; Elovich equation; CuO

Surface modification of ultra high molecular weight polyethylene fibers via the sequential photoinduced graft polymerization by Zhi Li; Wei Zhang; Xinwei Wang; Yongyi Mai; Yumei Zhang (pp. 7600-7608).

Display Omitted► Sequential photoinduced graft polymerization. ► Polymerization was initiated by dormant semipinacol groups and carried out in a thin liquid layer. ► The structure of grafted chains was analyzed. ► An extensively improved interfacial bonding property.In this study, a sequential photoinduced graft polymerization process was proposed to improve the poor interfacial bonding property of ultra high molecular weight polyethylene (UHMWPE) fibers. The polymerization was initiated by dormant semipinacol (SP) groups and carried out in a thin liquid layer. Methacrylic acid (MAA) and acryl amide (AM) were grafted stepwise onto the surface of UHMWPE fibers. Attenuated total reflectance infrared spectroscopy (ATR-IR) and thermo gravimetric analysis (TGA) confirmed the grafting. The analysis result of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) indicated the structure of grafted chains. Scanning electron microscopy (SEM) images and atomic force microscopy (AFM) images revealed the apparent morphology changing, and the grafted layers were observed. Interfacial shear stress (IFSS) test of the modified fibers showed an extensively improved interfacial bonding property. The active groups grafted onto the fibers would supply enough anchor points for the chemical bonding with various resins or further reactions.

Keywords: Photoinduced graft polymerization; UHMWPE fibers; Interfacial bonding property

Preparation and microstructure characteristics of low-temperature bainite in surface layer of low carbon gear steel by P. Zhang; F.C. Zhang; T.S. Wang (pp. 7609-7614).

► An approach is proposed for the development of ultrafine low-temperature bainitic microstructure in the surface layer of a low-carbon gear steel. ► Phase transformation within different depth of the carburized layer, which has different carbon content, is investigated. ► This type of material which has low-temperature bainite in the surface layer and low-carbon martensite in the center is potentially of use in the manufacture of heavy-duty gears if the process is further optimized.A kind of technology was proposed for the development of low-temperature bainitic microstructure in the surface layer of low-carbon gear steel 20CrMnMo, which is based on carburization and succedent low-temperature austempering. The carbon content in the surface carburization layer increases to 0.81wt.%, making the martensite starting point depressed. Low-temperature bainite formed in the carburization layer and lath martensite with low carbon content in the center by austempering at a low temperature slightly higher than the martensite starting point of the surface layer. Aluminum is added as alloying elements with the purpose of enhancing the driving force of bainitic transformation and retarding the precipitation of cementite during austempering. With the excellent toughness of low-temperature bainite, this low-temperature austempering technology could be a potential substitute of the traditional quenching and tempering heat treatment in the manufacture of gear.

Keywords: Low-temperature bainite; Carbonization; Austempering; Gear steel

Electrodeposition and characterization of Ni–Y₂O₃ composite by Liangliang Tian; Jincheng Xu (pp. 7615-7620).

► In this paper, mechanical properties of the Ni–Y₂O₃ were first reported. ► The incorporated Y₂O₃ slicks the surface of the coatings. ► Ni–Y₂O₃ coating reaches its highest microhardness 3566MPa at 4.4wt.%. ► The incorporated Y₂O₃ improves the frictional wear properties.Nano-sized Y₂O₃ particles were codeposited with nickel by electrolytic plating from a nickel sulfate bath. The effects of the incorporated Y₂O₃ on the structure, morphology and mechanical properties (including microhardness, friction coefficient and wear resistant) of Ni–Y₂O₃ composite coatings were studied. It is observed that the addition of nano-sized Y₂O₃ particles shows apparent influence on the reduction potential and pH of the electrolyte. The incorporated Y₂O₃ increases from 1.56wt.% to 4.4wt.% by increasing the Y₂O₃ concentration in the plating bath from 20 to 80g/l. XRD results reveal that the incorporated Y₂O₃ particles favour the crystal faces (200) and (220). SEM and AFM images demonstrate that the addition of Y₂O₃ particles causes a smooth and compact surface. The present study also shows that the codeposited Y₂O₃ particles in deposits decrease the friction coefficient and simultaneously reduce the wear weight loss. Ni–Y₂O₃ composite coatings reach their best microhardness and tribological properties at Y₂O₃ content 4.4wt.% under the experiment conditions.

Keywords: Y; ₂; O; ₃; Electrodeposition; Composite coating; Microhardness; Wear resistance

Electrophoretic deposition of BaTiO₃/CoFe₂O₄ multiferroic composite films by Dongxiang Zhou; Gang Jian; Yanan Zheng; Shuping Gong; Fei Shi (pp. 7621-7626).

► Electrophoretic deposition (EPD) method was introduced to fabricate bilayer BTO/CFO composite films. ► The percolation threshold of composite films was improved through dispersing ferromagnetic phase into ferroelectric phase. ► The ferroelectric properties of composite thick films were maintained when the ferromagnetic properties were enhanced significantly with increasing CFO content. ► The fabricated films showed evident multiferroic properties.Electrophoretic deposition was utilized for preparation of BaTiO₃/CoFe₂O₄ multiferroic composite thick films on indium–tin oxide substrates. The suspensions for electrophoretic experiments were prepared by dispersing BaTiO₃ and CoFe₂O₄ nanoparticles with different molar ratios into solvents composed of ethanol and acetylacetone. Polyvinyl butyral was added to the suspensions in order to enhance the adhesion and strength of deposit and prevent cracking. The zeta potential values of BaTiO₃/CoFe₂O₄ suspensions were measured to be 26.4–36.9mV. The experiment results showed that deposited films were obtained only when the applied electric field was larger than a certain critical value. XRD and SEM analysis depicted the presence of constituent phases in composite films. The percolation threshold of composite films was improved through dispersing ferromagnetic phase into ferroelectric phase. Therefore, the ferroelectric properties of composite thick films were maintained when the ferromagnetic properties were enhanced significantly with increasing CFO content.

Keywords: Multiferroic composite thick films; Electrophoretic deposition; Ferroelectric; Ferromagnetic

The thermal stability of Pt/Ir coated AFM tips for resistive switching measurements by M. Wojtyniak; K. Szot; R. Waser (pp. 7627-7632).

► We investigate most popular Pt covered silicon AFM tips by LC-AFM, XPS, SEM and TEM. ► The thermal stability under oxidizing and reducing condition was investigated. ► The platinum coating of the tips tends to agglomerate in high temperatures. ► The tip electrical conductivity decreases with the temperature.► Maximum applicable temperature is around 500° C in air and around 600° C in vacuum.In this paper, we focus on the thermally treated atomic force microscope tips used in the investigation of the resistive switching phenomenon. Since the resistive switching phenomenon is often connected with the red-ox process, it is crucial to investigate the influence of oxidizing and reducing conditions at elevated temperatures on typical AFM tips. To fully characterize the influence of different conditions on the tip properties we used several techniques such as: X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and local-conductivity atomic force microscopy. The chemical composition as well as the topography and morphology of the most popular Pt/Ir coated silicon tips were investigated. The influence of thermal treatment on the tip apex was also imaged and the changes in the electrical behavior of the tip coating were observed. Applied temperatures ranges were: 500–700° C for oxidizing conditions (air) and 300–700° C for reducing conditions (vacuum 10⁻⁶Torr), the annealing time was set to 0.5h. Results yielded the formation of Pt₂Si and SiO₂ on the tip surface. The Pt tends to agglomerate into particles over time, depending on the temperature and conditions. The tip apex radius increases while the electrical conductivity decreases with the temperature. In conclusion, even the lowest applied temperature leads to changes in the tip properties, while these changes are much more pronounced under oxidizing conditions.

Keywords: Atomic force microscopy; Tip temperature stability; Pt coating; Resistive switching

Quantification of oxygenated species on a diamond-like carbon (DLC) surface by Min Yang; Matthew J. Marino; Vincent J. Bojan; Osman L. Eryilmaz; Ali Erdemir; Seong H. Kim (pp. 7633-7638).

Display Omitted► The thickness of the oxidized surface layer of diamond-like carbon (DLC) films was estimated to be about 2–3nm thick. ► The use of chemical derivatization method in conjunction with XPS was demonstrated to determine the relative composition of hydroxyl, ether, carbonyl, and carboxyl groups in the oxidized surface region of the DLC film. ► In the oxidized surface region, the hydroxyl group content seems to be lower than other oxygenated groups.This paper discusses the use of chemical derivatization methods for surface chemical composition analysis of diamond-like carbon (DLC) films synthesized through plasma-enhanced chemical vapor deposition with X-ray photoelectron spectroscopy (XPS). The main challenge in applying chemical derivatization reactions for titration of organic functional groups on the DLC surface is that sub-surface oxygenated species are not accessible to the derivatizing agent. As a simple approximation, a functional group that can be quantified unambiguously with XPS can be used as an internal reference to estimate the accessible-to-inaccessible ratio, and this information can be used to estimate the total amount of other functional groups from the chemical-derivatization-assisted XPS analysis. The use of this principle to obtain the surface composition of hydroxyl, ether, carbonyl, and carboxyl groups in the oxidized surface region of the DLC film was demonstrated.

Keywords: Diamond-like carbon; DLC; Surface layer; Composition

Morphology transition in cluster growth at different temperature by Xiaojun Xu; Fengfei Wang (pp. 7639-7642).

► The cluster growth on 2D square lattice is investigated by Monte Carlo simulation. ► The binding energy of substrate, coupling energy of particles and a strain field are considered. ► Morphology transition, the branch width and the coordination number distribution are studied.The cluster growth on two-dimensional square lattice at different temperature is investigated by Monte Carlo simulation, considering the binding energy of substrate, the coupling energy of nearest neighbor particles and a strain field. The simulation shows that, for 400K≤ T≤480K, the average branch width of the fractal cluster is independent to the temperature T, which is almost equal to the diameter of single particle. For 500K≤ T≤680K, however, the branch width increases gradually to 4 with temperature. With T further increases, clusters consist of large number of particles disappear, due to the strong activity of each particle. The coordination number distributions of clusters at different temperature are also studied.

Keywords: Fractal; Computer simulation; Monte Carlo; Growth

Improvement of anti-oxidation capability and tribological property of arc ion plated Ag film by alloying with Cu by Xiaoming Gao; Jiayi Sun; Ming Hu; Lijun Weng; Feng Zhou; Weimin Liu (pp. 7643-7648).

► Ag–Cu alloy film was deposited by arc ion plating (AIP) and show considerable resistance to atomic oxygen (AO) irradiation. ► The affected thickness of Ag–Cu alloy film by atomic oxygen was greatly reduced and the oxidation product was mainly Ag₂O, but AgO and Ag₂O in case of pure Ag film. ► As a result, the Ag–Cu alloy film exhibited a stable friction and low wear after the AO irradiation compared with pure Ag film.Ag–Cu alloy film was deposited by arc ion plating (AIP). Atomic oxygen (AO) irradiation experiments were conducted using a ground AO simulation facility. The structure, morphology, composition and tribological property of the Ag–Cu alloy film before and after AO irradiation were investigated and compared with Ag film using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscope (XPS) and ball-on-disk tribometer, respectively. In depth XPS analysis clearly shows that the affected thickness of Ag–Cu alloy film was greatly reduced and the oxidation product was mainly Ag₂O, but AgO and Ag₂O in case of pure Ag film. As a result, the Ag–Cu alloy film exhibited better AO resistant behaviors, and showed a stable friction and low wear after the AO irradiation. The AO resistant behaviors of the Ag–Cu alloy film were discussed in terms of the film microstructure.

Keywords: Atomic oxygen; Ag–Cu alloy film; Microstructure

Features of island nanostructures formed by melting Sn, Bi and Sn–Bi thin films on C substrates by A.P. Kryshtal; N.T. Gladkikh; R.V. Sukhov (pp. 7649-7652).

► Melting of Sn, Bi and eutectic Sn–Bi solid films 2–70nm thick on a-C substrates. ► Morphology of molten films is determined by the formation of initial condensates. ► Non-uniform size dependence of the coverage after film melting. ► Spontaneous formation of island structures possessing a unimodal size distribution.We report the results of studying the morphological structure of island systems formed by melting Sn, Bi and eutectic Sn–Bi polycrystalline films 2–70nm thick deposited on carbon substrates. Substrate coverage with a film is found to be non-uniform against film mass thickness after its melting and crystallization. The interval of film thickness is determined where the island systems with narrow enough particle size distribution are formed under melting.

Keywords: Melting; Island films; Bi; Sn; Sn–Bi; Size distribution; Coverage

Deposition of tungsten nitride thin films by plasma focus device at different axial and angular positions by M.T. Hosseinnejad; M. Ghoranneviss; G.R. Etaati; M. Shirazi; Z. Ghorannevis (pp. 7653-7658).

► Tungsten nitride thin films deposited on the stainless steel–304 substrates, using a low energy plasma focus device. ► Effects of distance from anode tip investigated at three different angular positions with respect to anode axis (0°, 10° and 30°). ► Structural properties of deposited films analyzed using XRD spectra. ► Micro-structure, surface morphology and hardness of the films analyzed using SEM and AFM images and micro-hardness measurements.Tungsten nitride thin films were deposited on stainless steel–304 substrates by using a low energy (2kJ) Mather type plasma focus device. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and microhardness are used to study the surface of treated samples. The XRD analysis shows that the degree of crystallinity of deposited thin films strongly depends on axial and angular positions of samples. The SEM micrographs of the deposited films at different angular positions (0°, 10° and 30°) and axial position of 8cm show that the content of WN sub-micro crystalline structures on the surface of deposited films decreased with increasing the angle with respect to anode axis. From AFM results we observe that for the sample deposited at 8cm and 0° axial and angular positions, respectively, the most uniform surface and the most homogenous distribution of grains are obtained. Also the hardness results show that the highest mechanical hardness is obtained when the film is deposited at 8cm and 0° axial and angular positions, respectively.

Keywords: Plasma focus; Tungsten nitride; Thin film; XRD; SEM; AFM

Surface potential driven dissolution phenomena of [0001]-oriented ZnO nanorods grown from ZnO and Pt seed layers by Youngmi Seo; Jung Hyeun Kim (pp. 7659-7664).

► ZnO nanorods were hydrothermally synthesized on ZnO and Pt seed layers. ► ZnO nanorods showed the same crystalline structure for both cases. ► Dissolution of ZnO nanorods revealed big differences for both cases. ► Dissolution uniformly on ZnO seed layer, but rod-selectively on Pt seed layer. ► Rod-selective dissolution occurred by the surface potential difference.Highly oriented ZnO nanorods are synthesized hydrothermally on ZnO and Pt seed layers, and they are dissolved in KOH solution. The rods grown on ZnO seed layer show uniform dissolution, but those grown on Pt seed layer are rod-selectively dissolved. The ZnO nanorods from both seed layers show the same crystalline structure through XRD and Raman spectrometer data. However, the surface potential analysis reveals big difference for ZnO and Pt seed cases. The surface potential distribution is very uniform for the ZnO seed case, but it is much fluctuated on the Pt seed case. It suggests that the rod-selective dissolution phenomena on Pt seed case are likely due to the surface energy difference.

Keywords: ZnO nanorods; Nanotubes; Seed layers; Surface potential

Effect of substrate temperature and oxygen partial pressure on microstructure and optical properties of pulsed laser deposited yttrium oxide thin films by Maneesha Mishra; P. Kuppusami; T.N. Sairam; Akash Singh; E. Mohandas (pp. 7665-7670).

► The microstructural and optical properties of yttria films as a function of wide substrate temperature and oxygen partial pressure range have been reported for the first time for the films prepared by pulsed laser deposition. ► The X-ray diffraction results indicated that the films were polycrystalline yttria films with (222) preferred orientation. ► Yttria thin films have good transparency of ∼90% in the wavelength range of 400–800nm for the films deposited at 873K and 0.2Pa oxygen partial pressure. ► The band gap increases with increase in substrate temperature and decrease with increase in oxygen partial pressure as a consequence of increasing crystallite size.Yttrium oxide thin films were deposited on Si (111) and quartz substrates by pulsed laser deposition technique at different substrate temperature and oxygen partial pressure. XRD analysis shows that crystallite size of the yttrium oxide thin films increases as the substrate temperature increases from 300 to 873K. However the films deposited at constant substrate temperature with variable oxygen partial pressure show opposite effect on the crystallite size. Band gap energies determined from UV–visible spectroscopy indicated higher values than that of the reported bulk value.

Keywords: Yttria; Laser deposition; Microstructure; Optical properties

Preparation and characterization of TiO₂ photocatalysts co-doped with iron (III) and lanthanum for the degradation of organic pollutants by Qiangqiang Wang; Shihua Xu; Fenglei Shen (pp. 7671-7677).

The synergistic effect of doped Fe³⁺ and La³⁺ for enhancement photocatalytic performance under visible light irradiation and UV light irradiation is different.Display Omitted► Few reports dealt with TiO₂ codoped with Fe³⁺ and La³⁺. ► Fe³⁺ counteracts the effect of La³⁺ on the A–R transformation property of TiO₂. ► Fe-TiO₂ has a long tail in the absorption edges. ► La-TiO₂ results in a red shift of the absorption. ► Fe³⁺ and La³⁺ dopants have synergistic effect for improve the photocatalytic activity.Titanium dioxide photocatalysts co-doped with iron (III) and lanthanum were prepared by a facile sol–gel method. The structure of catalysts was characterized by X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were evaluated by the degradation of methylene blue in aqueous solutions under visible light ( λ>420nm) and UV light irradiation. Doping with Fe³⁺ results in a lower anatase to rutile (A–R) phase transformation temperature for TiO₂ particles, while doping with La³⁺ inhibits the A–R phase transformation, and co-doping samples indicate that Fe³⁺ partly counteracts the effect of La³⁺ on the A–R transformation property of TiO₂. Fe-TiO₂ has a long tail extending up the absorption edges to 600nm, whereas La-TiO₂ results in a red shift of the absorption. However, Fe and La have synergistic effect in the absorption of TiO₂. Compared with Fe³⁺ and La³⁺ singly doped TiO₂, the co-doped simple exhibits excellent visible light and UV light activity and the synergistic effect of Fe³⁺ and La³⁺ is responsible for improving the photocatalytic activity.

Keywords: Titania; Fe; ³⁺; doped; La; ³⁺; doped; Co-doped; Photocatalysts; Synergistic effect

Preparation and properties of cobalt oxides coated carbon fibers as microwave-absorbing materials by Ying Liu; Zhongquan Zhang; Songtao Xiao; Chengwen Qiang; Liangliang Tian; Jincheng Xu (pp. 7678-7683).

► Carbon fibers (CFs) are suitable substrates for electromagnetic absorption materials. ► Some carbon fiber-based composite materials have been developed for microwave absorption materials. ► Cobalt-oxides (CoO and Co₃O₄) are commonly used magnetic materials with good electromagnetic properties. ► Little work have been done to use cobalt-oxides as microwave absorption materials. ► We coupled cobalt oxides with carbon fibers to synthesis a new microwave absorption material.Cobalt oxides/carbon fibers (CoO_x/CFs) composites were synthesized by thermal oxidation of cobalt coated carbon fibers (Co/CFs). The scanning electron microscopy images and X-ray diffraction pattern indicate that the layers are about 0.7μm and composed of Co₃O₄ and CoO (CoO_x), the preferred condition for preparation of CoO_x/CFs composites is to anneal Co/CFs precursors at 350°C for 3h in air. The coercivity, saturation magnetization and residual magnetization of the CoO_x/CFs composites are 464.8Oe, 10.62emu/g and 2.21emu/g, respectively. The reflectivity of cobalt oxides coated carbon fibers (1.11–5.12mm in thickness) is less than −10dB over the working frequency range of 4.04–18.00GHz and less than −20dB over 11.54–14.77GHz. The lowest reflectivity is −45.16dB at 13.41GHz when the thickness is 1.50mm.

Keywords: Carbon fibers; Cobalt oxides; Thermal oxidation; Magnetic properties; Microwave absorbing materials

One-step synthesis of CdTe branched nanowires and nanorod arrays by Junwei Hou; Xiuchun Yang; Xiaoyi Lv; Dengfeng Peng; Min Huang; Qingyao Wang (pp. 7684-7688).

Display Omitted► We report the fabrication of single crystalline CdTe branched nanowires and well-aligned nanorod arrays via a facile chemical vapor deposition synthetic method. ► Morphology, composition, microstructure and optical property of CdTe branched nanowires and nanorod arrays were researched. ► The formation mechanisms of the CdTe branched nanowires and nanorod arrays were proposed.Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor–liquid–solid (VLS) and vapor–solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620nm, which can be well fitted by two Gaussian curves centered at 610nm and 635nm, respectively.

Keywords: Crystal morphology; Chemical vapor deposition; CdTe; Nanorod arrays

Tailoring the wettability of patterned silicon surfaces with dual-scale pillars: From hydrophilicity to superhydrophobicity by Yang He; Chengyu Jiang; Hengxu Yin; Weizheng Yuan (pp. 7689-7692).

► A convenient yet effective method of combining reactive ion etching and catalyzed etching to prepare silicon surface with micro–nano dual-scale pillars is presented. ► The hydrophilic surface transformed to a superhydrophobic surface when micro–nano dual-scale pillars were formed. ► The surface preserved superhydrophobicity even when the geometric parameters of the micropillars were changed. ► Overhangs of water drops on steep micro–nano dual-scale pillars result in superhydrophobicity.Wettability tailoring of patterned silicon surface has great potential in fields producing integrated circuits, solar cells, sensors, detectors, and micro/nano electromechanical systems. The present paper presents a convenient yet effective method of combining reactive ion etching and catalyzed etching to prepare silicon surface with micro–nano dual-scale pillars. The experimental results indicate that the hydrophilic surface transformed to a superhydrophobic surface when micro–nano dual-scale pillars were formed. The surface preserved superhydrophobicity even when the geometric parameters of the micropillars were changed. Overhangs of water drops on steep micro–nano dual-scale pillars result in superhydrophobicity. This method offers a new way for tailoring the wettability of patterned silicon surfaces.

Keywords: Wettability; Superhydrophobicity; Hydrophilicity; Patterned silicon surface

Effects of homogenous loading on silicon direct bonding by Li-Yang Huang; Kuan-Lin Ho; Chen-Ti Hu (pp. 7693-7698).

► Applying a homogenous plane-stress using the Nano-Imprint System on the SDB process. ► Highly consistent interface energy of SDB pairs when applying a homogenous plane-stress. ► Improves bonding quality of point-stress bonded wafers by re-applying a plane-stress with Nano-Imprint System.The effect of a homogenous loaded stress on the bonding quality of silicon wafer pairs was investigated by employing a Nano-Imprint System and a homogenous plane-stress applied over the entire surface area of pre-cleaned wafers. In addition, the effects of variations in the applied homogenous stress (1, 10, 100, 500psi) on the interface energy of the bonded pairs were examined using a dynamic blade insertion (DBI) method. Infrared imaging was used to evaluate the quality of the bonded interface of each bonded pair immediately after the bonding process and after allowing the bonded pairs to rest at room temperature for 80h after bonding. The results indicated that the homogenous loading with the Nano-Imprint System further improved the bonding condition of wafer pairs that had been pre-bonded using an anodic bonder. Furthermore, the bonded pairs exhibited almost identical interfacial energies of about 0.2Jm⁻² when the homogenous stress was varied from 1psi to 500psi, which clearly indicates that the interfacial energy of bonded wafers is independent of the amount of stress applied by the homogenous loading process.

Keywords: Silicon direct Bonding; Homogenous load; Bonding quality; Anodic Bonder; Nano-Imprint System

Organic molecules passivated Mn doped Zinc Selenide quantum dots and its properties by J. Archana; M. Navaneethan; S. Ponnusamy; Y. Hayakawa; C. Muthamizhchelvan (pp. 7699-7703).

► Mn doped ZnSe quantum dots have been synthesized by chemical route using N-Methylaniline as an organic ligand. ► Incorporation of Mn into ZnSe quantum dots and its influence on the optical properties of ZnSe have been studied. ► Thermal stability of the ZnSe quantum dots is really excellent and it is highly suitable for opto-electronics applications.Quantum dots of Mn doped Zinc Selenide with N-Methylaniline as the capping agent was prepared by simple and inexpensive wet chemical method. Size of the particles observed by TEM was of the order of 2–4nm which was well consistent with the size measured by UV analysis. The presence of paramagnetic substance Mn²⁺ in the ZnSe quantum dots was confirmed by EPR measurement. Mn doped ZnSe nanoparticles exhibited a strong blue emission that was strongly dependent upon the Mn dopant level and the surface passivation produced by N-Methylaniline. The stability of the product was studied by thermal analysis which shows that this product is highly suitable for opto-electronic applications.

Keywords: Mn doped Zinc Selenide; Nanoparticles; Wet chemical method; Optical properties; Structural properties

The effects of catalyst treatment on fast growth of millimeter-long multi-walled carbon nanotube arrays by Zhao-Yao Zhan; Ya-Ni Zhang; Geng-Zhi Sun; Lian-Xi Zheng; Kin Liao (pp. 7704-7708).

Display Omitted► We have achieved fast growth of 1.5mm CNT arrays in 10min by using an optimized catalyst treatment. ► Insufficient treatment cannot reduce iron oxide while excessive treatment will cause large particles. ► Ideal treatment should be that catalyst is fully reduced but undergoes limited ripening.An optimized strategy was developed for fast growth of millimeter-long CNT arrays using chemical vapor deposition (CVD). Growth temperature of 800°C was firstly determined, and catalyst heat treatment conditions were then optimized to probe the full potential of growth rate. 1.5mm long CNT arrays were obtained in 10min under optimized growth and catalyst heat treatment conditions. The growth rate of CNT arrays strongly depends on the growth temperature and catalyst heat treatment. Insufficient reduction could not reduce iron oxide into metallic state or/and crack down catalyst film into particles, but excessive treatment may result in large particles due to Ostwald ripening process. This method would offer more freedoms in designing the fast growth of high-purity, long CNT arrays.

Keywords: Fast growth; Millimeter-long; Heat treatment; Carbon nanotubes

Effects of substrate temperature on the structure and mechanical properties of (TiVCrZrHf)N coatings by Shih-Chang Liang; Zue-Chin Chang; Du-Cheng Tsai; Yi-Chen Lin; Huan-Shin Sung; Min-Jen Deng; Fuh-Sheng Shieu (pp. 7709-7713).

► The decrease of N content of (TiVCrZrHf)N obtained at elevated substrate temperature may be due to its higher desorption rate from the film surface at higher substrate temperature ► The TiVCr coatings have a two layer structure with amorphous and face-centered cubic (fcc) crystal phases, which resulted from lattice distortion of multiprincipal elements and mismatch in the lattice between (TiVCrZrHf)N and substrate. ► The maximum hardness of 48.13GPa in the as-deposited state of the present films is the highest among all the high entropy alloy coatings. This demonstrates that the present alloy design is effective in achieving even high hardness and could be a new route to develop nanocomposite or multilayer design.The present paper reports the influence of growth conditions on the characteristics of (TiVCrZrHf)N films prepared by rf reactive magnetron sputtering at various substrate temperatures. The nitrogen content is observed to decrease with increasing substrate temperature. The X-ray diffraction results indicate that all (TiVCrZrHf)N films are simple face centered cubic (FCC) structures. Initially, there is an obvious decrease followed by an increase in grain size with the increase in substrate temperature. The lower part of the microstructure has an amorphous structure. A nano grain structure (size ∼1nm) with a random orientation is also observed above the amorphous structure. The fully dense columnar structure with an fcc crystal phase then starts to develop. Extreme hardness of around 48GPa is obtained in the present alloy design.

Keywords: Coating materials; Nitride materials; Thin films; Vapor deposition; Crystal structure; Microstructure

Graphene/silicon photoelectrode with high and stable photoelectrochemical response in aqueous solution by Kedi Wu; Wenying Quan; Hongtao Yu; Huimin Zhao; Shuo Chen (pp. 7714-7718).

► A simple method to fabricate graphene/silicon electrodes has been developed. ► The adhesion of graphene/silicon interface can be improved via an annealing process. ► The electrodes display the good photoelectrochemical behaviors in aqueous solution.The graphene (Gr)/Si electrodes were fabricated by electrophoresis method and then following an annealing process. The p-Si surface was found to be covered completely with successive and transparent Gr sheets, and thus the impairment of aqueous solution on the photoelectrochemical capability of silicon could be avoided. This annealing process was a key process for improving the adhesion of Gr/Si interface. After annealing at 400°C, the Gr/Si electrodes displayed high photoresponse ability and high stability in aqueous solution. The carriers transfer between Gr and Si is discussed on the basis of the semiconductor energy band theory. The results demonstrated that the Gr/Si electrodes would be a promising candidate as solar energy materials using in aqueous solution.

Keywords: Graphene; Silicon; Interface; Anneal; Photoelectrochemical Stability

In situ atomic force microscopy studies of reversible light-induced switching of surface roughness and adhesion in azobenzene-containing PMMA films by M. Müller; Y. Gonzalez-Garcia; C. Pakula; V. Zaporojtchenko; T. Strunskus; F. Faupel; R. Herges; D. Zargarani; O.M. Magnussen (pp. 7719-7726).

► Morphology and adhesion of azobenzene-containing polymer films studied by AFM. ► Direct observation of highly reversible photoinduced changes. ► In situ measurements of transition kinetics reveal several processes with different time scales. ► A model for these reversible morphological transitions is presented.Thin films in the range 40–80nm of a blend of PMMA with an azobenzene derivative have been studied directly during UV and blue light irradiation by atomic force microscopy (AFM), revealing highly reversible changes in the surface roughness and the film adhesion. UV light induces an ≈80% increase in surface roughness, whereas illumination by blue light completely reverses these changes. Based on the observed surface topography and transition kinetics a reversible mass flow mechanisms is suggested, where the polarity changes upon switching trigger a wetting-dewetting transition in a surface segregation layer of the chromophore. Similar AFM measurements of the pull-off force indicate a decrease upon UV and an increase after blue light illumination with a complex kinetic behavior: a rapid initial change, attributed to the change in the cis isomer fraction of the azobenzene derivative, and a more gradual change, indicative of slow structural reorganization.

Keywords: Azobenzene; PMMA; Photoswitching; Atomic force microscopy

Al₂O₃ supported Ru catalysts prepared by thermolysis of Ru₃(CO)₁₂ for catalytic wet air oxidation by Chaoying Yu; Peiqing Zhao; Gexin Chen; Bin Hu (pp. 7727-7731).

Low loading catalysts (Ru 0.3wt.%) were prepared by thermolysis of Ru₃(CO)₁₂ on γ-Al₂O₃. These catalysts show high activities in the CWAO of different organic compounds with high concentration such as isopropyl alcohol, phenol, acetic acids and N,N-dimethylformamide.Display Omitted► Two kinds of new Ru species were detected in the decomposition process of Ru₃(CO)₁₂ on γ-Al₂O₃. ► The Ru catalysts show high activities in the CWAO of different organic compounds. ► Pollutants can be efficiently removed at much milder conditions with Ru and Ru-Ce catalysts.Low loading catalysts Ru/γ-Al₂O₃ and Ru-Ce/γ-Al₂O₃ were prepared by thermolysis of Ru₃(CO)₁₂ on γ-Al₂O_3. The catalysts were characterized by XPS, XRD and SEM. Two new Ru species (Ru_A and Ru_B) were detected during the Ru₃(CO)₁₂ decomposition process due to chemical interaction with the active OH groups on the surface of Al₂O₃ support, and the reduction of them can lead to more dispersed metallic phases. The sample was completely decomposed at 673K in H₂, and RuO₂ was formed with minor amounts of Ru⁰. When the temperature was increased to 773K to heat the sample, the ratio of Ru⁰ to RuO₂ increased. However, after the addition of CeO₂, only RuO₂ was detected on surface. The catalysts exhibited high activities in Catalytic Wet Air Oxidation (CWAO) of different organic compounds at high concentration such as isopropyl alcohol, phenol, acetic acids and N,N-dimethylformamide, which is attributed to the better dispersion of Ru particles and the addition of CeO₂ further enhanced number of effectively active sites on the cluster-derived catalyst surface.

Keywords: Catalytic wet air oxidation; Ruthenium carbonyl; Isopropyl alcohol; Phenol; Acetic acids; N,N-dimethylformamide

Study of the corrosion products formed on a multiphase CuAlBe alloy in a sodium chloride solution by micro-Raman and in situ AFM measurements by S. Montecinos; S.N. Simison (pp. 7732-7738).

► The use of AFM and micro-Raman is a great complement for the corrosion studies. ► The aluminium content of each phase affects the formation of the corrosion products. ► γ₂ phase suffers dealuminization, while α′ exhibit a high corrosion stability. ► CuCl₂ and a Cu₂O/CuO surface film are the stable products formed after long times.The corrosion products formed on a multiphase Cu–11.40Al–0.55Be (wt.%) alloy in 3.5% NaCl at open circuit potential, and their evolution with immersion time were studied mainly by micro-Raman and in situ AFM measurements. The aluminium content of each phase affects the formation of the corrosion products on them. After 1 day of immersion, γ₂ precipitates were more susceptible to dealuminization, while α′ phase exhibited a high corrosion stability. The corrosion products evolved with immersion time, and CuCl₂ and a Cu₂O/CuO double layer film were the stable products formed on all the phases after long times.

Keywords: In situ AFM; Micro-Raman spectroscopy; Copper-based alloys; Corrosion; Microstructure

Surface tension of liquid Cu–Ti binary alloys measured by electromagnetic levitation and thermodynamic modelling by S. Amore; J. Brillo; I. Egry; R. Novakovic (pp. 7739-7745).

Surface tension of Cu–Ti liquid alloys at 1473K, vs. Ti mole fraction. The experimental results behaviour (■) is well described by the Compound Formation Model (CFM) in the Cu-rich region.Display Omitted► Cu–Ti liquid alloys samples levitated and melted in the EML set-up. ► Surface tension of the Cu–Ti is measured for the entire composition range. ► Surface tension vs. temperature described by linear function with negative slope. ► Surface segregation calculated by the QCA and CFM thermodynamic models. ► Experimental results on Cu–Ti melts in agreement with modelling.The surface tension of liquid Cu–Ti alloys has been measured by using the containerless technique of electromagnetic levitation and theoretically calculated in the framework of the compound formation model. Measurements have been carried out on alloys covering the entire range of composition and over the temperature range 1275–2050K. For all investigated alloys the surface tension can be described by a linear function of the temperature with negative slope.Due to the presence of different intermetallic compounds in the solid state the surface properties of liquid Cu–Ti alloys are satisfactory described by the compound formation model.

Keywords: Cu–Ti liquid binary alloys; Surface tension; Surface segregation; Thermodynamic model

The influence of treatment temperature on the acidity of MWCNT oxidized by HNO₃ or a mixture of HNO₃/H₂SO₄ by Tawfik A. Saleh (pp. 7746-7751).

► Acidity of MWCNTs is a function of the type of oxidizing agent used and the treatment temperatures. ► The acidity increases by increasing the treatment temperature. ► The increase in oxygen content by increasing the treatment temperature was informed by EDX measurements.The nature of multi-walled carbon nanotubes (MWCNTs) varies with the change in oxidation conditions. In this work, the effect of treatment temperatures on the acidity of MWCNTs was studied. Oxidation was performed by refluxing the MWCNTs in nitric acid or mixtures of sulfuric acid and nitric acid at different temperatures. After oxidative treatment, a quantitative characterization of o-MWCNTs has been performed using acid–base titrations which show that the number of surface acidic functional groups increased by increasing the treatment temperatures. Energy dispersive X-ray (EDX) measurements show that the oxygen content increased with increasing treatment temperatures. Fourier transform infrared absorption spectroscopy (FTIR) was used for qualitative characterization. It has been demonstrated that the acidity is a function of the type of oxidizing agent used and the treatment temperatures. Due to the importance in attachment strategies and functionalization, this study adds to the global discussion of the possibility of controlling the MWCNTs’ surface chemistry which plays a crucial role in determining its reactivity.

Keywords: Multiwall carbon nanotubes; Oxidation; Treatment temperature

Preparation and characterization of boron nitride coatings on carbon fibers from borazine by chemical vapor deposition by Jun-Sheng Li; Chang-Rui Zhang; Bin Li (pp. 7752-7757).

► Turbostratic or hexagonal BN coatings were successfully deposited by CVD using borazine. ► The coating uniformly and perfectly surrounds the individual fibers within the bundles. ► The coatings are smooth and compact. ► A diffusion of carbon from the fiber to the coatings occurred at the fiber/coating interfacial zone.Boron nitride (BN) coatings were deposited on carbon fibers by chemical vapor deposition (CVD) using borazine as single source precursor. The deposited coatings were characterized by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The effect of temperatures on growth kinetics, morphology, composition and structure of the coatings was investigated. In the low temperature range of 900°C–1000°C, the growth rate increased with increasing temperature complying with Arrhenius law, and an apparent active energy of 72kJ/mol was calculated. The coating surface was smooth and compact, and the coatings uniformly deposited on individual fibers of carbon fiber bundles. The growth was controlled by surface reaction. At 1000°C, the deposition rate reached a maximum (2.5μm/h). At the same time, the limiting step of the growth translated to be mass-transportation. Above 1100°C, the growth rate decreased drastically due to the occurrence of gas-phase nucleation. Moreover, the coating surface became loose and rough. Composition and structure examinations revealed that stoichiometric BN coatings with turbostratic structure were obtained below 1000°C, while hexagonal BN coatings were deposited above 1100°C. A penetration of carbon element from the fibers to the coatings was observed.

Keywords: Borazine; Chemical vapor deposition; Boron nitride; Coatings; Interphase; Kinetics

Hydrothermal synthesis and photoelectric properties of BiVO₄ with different morphologies: An efficient visible-light photocatalyst by Haimei Fan; Dejun Wang; Lingling Wang; Haiyan Li; Ping Wang; Tengfei Jiang; Tengfeng Xie (pp. 7758-7762).

BiVO₄ with smaller size were synthesized by adjusting the amount of PVP, the relationship between the separation of photo-induced carriers and vis-photocatalytic activity was studied using the surface photovoltage technology.Display Omitted► A method simply adjusting the amount of PVP added. ► The synthesized BiVO₄ has a smaller size and a larger specific surface area. ► The relationship between the separation of photo-induced carriers and photocatalytic activity was studied using the surface photovoltage technical and corresponding phase spectra.Different morphologies of monoclinic BiVO₄ with smaller size were hydrothermal synthesized by simply adjusting the amount of surfactant (polyvinyl pyrrolidone PVP K30) added. The detailed field emission scanning electron microscope (FESEM) analysis revealed that the amount of PVP added could significantly affect the morphology and size of BiVO₄. Their photocatalytic activities were evaluated by the decolorization of methylene blue (MB) aqueous solution under visible-light irradiation ( λ>400nm), and the as-prepared sample with well-assembled flower-like morphology showed a much higher photocatalytic activity due to larger specific surface area and higher separation efficiency of photo-induced carriers. The relationship between the behavior of photo-induced carriers and photocatalytic activity was studied using the surface photovoltage spectroscopy (SPS) and corresponding phase spectra.

Keywords: BiVO; ₄; Monoclinic; Photocatalysis; Photovoltage

Largely improved photocatalytic properties of Ag/tetrapod-like ZnO nanocompounds prepared with different PEG contents by J. Wang; X.M. Fan; K. Tian; Z.W. Zhou; Y. Wang (pp. 7763-7770).

► Largely enhanced photocatalytic properties. ► Ag nanoparticles deposit at the surface of T-ZnOw. ► Content of PEG plays an important role in the photocatalytic property of the compound.Ag/tetrapod-like ZnO whisker (T-ZnOw) nanocompounds were successfully synthesized using photodeposition method. Remarkable improvements in photocatalytic property for all the nanocompounds are observed, while the extents of the improvements increase with increasing polyethylene glycol (PEG) contents. Various tests were carried out to determine the mechanism for the greatly improved photocatalytic property. And it is found that PEG can reduce Ag⁺ into Ag under UV irradiation, which can be subsequently deposited on the surface of T-ZnOw as nanoparticles. The conclusion that the heterostructure of Ag/T-ZnOw nanocompound contributes to its greatly enhanced photocatalytic property is proposed and later validated by carefully discussing the photocatalytic mechanism.

Keywords: Photocatalytic property; Ag/T-ZnO; _w; nanocompound; Photodeposition

Colorizing stainless steel surface by femtosecond laser induced micro/nano-structures by Md. Shamim Ahsan; Farid Ahmed; Yeong Gyu Kim; Man Seop Lee; Martin B.G. Jun (pp. 7771-7777).

Display Omitted► We demonstrate colorizing of stainless steel by laser induced periodic microholes. ► We also colorized stainless steel by femtosecond laser induced micro/nano-gratings. ► Variety of colors (single/multi-color) is produced on stainless steel surfaces. ► Color of the multi-color metals depends on incident/azimuthal angle of light. ► We explain the mechanism that facilitates color changes on stainless steel surfaces.We demonstrate colorizing of stainless steel surfaces by femtosecond laser induced periodic microholes and micro/nano-gratings on sample surfaces. Suitable adjustment of laser induced features on stainless steel surfaces offer a variety of colors, including multi-color, gold, and black. We also report that multi-color metal surfaces exhibit diverse colors when they are exposed to the incident light of different incident and azimuthal angles. Finally, we briefly explain how the femtosecond laser induced micro/nano scale features introduce different colors on stainless steel surfaces.

Keywords: Femtosecond laser; Self-organized nanograting; Microhole; Micrograting; Nanostructure; Incident angle; Azimuthal angle

Graphene oxide thin film coated quartz crystal microbalance for humidity detection by Yao Yao; Xiangdong Chen; Huihui Guo; Zuquan Wu (pp. 7778-7782).

► Graphene oxide thin film as a humidity sensing coating. ► An excellent humidity sensitivity properties (the maximum sensitivity reaches 22.1Hz/% RH). ► A linear frequency response versus relative humidity in the wide detection range of 6.4–93.5% RH. ► Humidity sensing mechanism of graphene oxide thin film.In this paper, we demonstrated that chemically derived graphene oxide (GO) thin film as a humidity sensitive coating deposited on quartz crystal microbalances (QCMs) for humidity detection. By exposing GO thin film coated QCMs to various relative humidity (RH) environments at room temperature, the humidity sensing characteristics of the QCMs such as sensitivity and linearity, response and recovery, humidity hysteresis were investigated. The experiment results show that GO thin film coated QCMs exhibit an excellent humidity sensing performance. Moreover, the possible humidity sensing mechanism of GO thin film coated QCMs was also investigated by monitoring the crystal's motional resistance change. It is suggested that the frequency response of the QCMs is dependent on water molecules adsorbed/desorbed masses on GO thin film in the low RH range, and on both water molecules adsorbed/desorbed masses on GO thin film and variations in interlayer expansion stress of GO thin film derived from swelling effect in the high RH range.

Keywords: Graphene oxide; Quartz crystal microbalance; Humidity sensor; Swelling effect

Influence of CrN surface compound on the initial stages of high temperature oxidation of ferritic stainless steel by H. Ali-Löytty; P. Jussila; M. Hirsimäki; M. Valden (pp. 7783-7791).

► Evolution of surface compounds on Fe–17Cr was studied upon annealing and oxidation. ► CrN surface compound promotes the selective oxidation of Cr at elevated temperatures. ► Nitrogen is buried below the oxide layer as the oxidation proceeds. ► High-resolution photoelectron spectroscopy was used to identify different N species.Segregation phenomena and formation of surface compounds on Fe–17Cr (ferritic stainless steel) were studied at temperatures up to 800°C upon annealing and kinetically controlled oxidation by photoelectron spectroscopy and inelastic electron background analysis. The results revealed the formation of a chromium nitride surface compound during annealing in ultrahigh vacuum at temperatures exceeding 527°C. Surface enrichment of P, As, and other trace elements became more prominent at higher temperatures approaching 800°C. It was found that nitrogen was buried below the surface oxide layer during oxygen exposure, yet it had little effect on the rate of oxidation. However, the formation of CrN surface compound promoted the selective oxidation of Cr initially, which is of great importance in processing and application environments involving high temperature and controlled atmosphere conditions.

Keywords: Stainless steels; Oxidation; Surface segregation; Photoelectron spectroscopy

Preparation and in vitro characterization of aerosol-deposited hydroxyapatite coatings with different surface roughnesses by Byung-Dong Hahn; Dong-Soo Park; Jong-Jin Choi; Jungho Ryu; Woon-Ha Yoon; Joon-Hwan Choi; Jong-Woo Kim; Young-Lae Cho; Chan Park; Hyoun-Ee Kim; Seong-Gon Kim (pp. 7792-7799).

► Hydroxyapatite (HA) coatings with different surface roughnesses are deposited on a Ti substrate via aerosol deposition. ► The surface microstructures of the HA coatings are remarkably altered by use of powders with different particle size distributions. ► There exists an optimum surface roughness of the aerosol-deposited HA coating for excellent cellular response.Hydroxyapatite (HA) coatings with different surface roughnesses were deposited on a Ti substrate via aerosol deposition (AD). The effect of the surface roughness on the cellular response to the coating was investigated. The surface roughness was controlled by manipulating the particle size distribution of the raw powder used for deposition and by varying the coating thickness. The coatings obtained from the 1100°C-heated powder exhibited relatively smooth surfaces, whereas those fabricated using the 1050°C-heated powder had network-structured rough surfaces with large surface areas and were superior in terms of their adhesion strengths and in vitro cell responses. The surface roughness (R_a) values of the coatings fabricated using the 1050°C-heated powder increased from approximately 0.65 to 1.03μm as the coating thickness increased to 10μm. The coatings with a rough surface had good adhesion to the Ti substrate, exhibiting high adhesion strengths ranging from 37.6 to 29.5MPa, depending on the coating thickness. The optimum biological performance was observed for the 5μm-thick HA coating with an intermediate surface roughness value of 0.82μm.

Keywords: Hydroxyapatite; Coating; Surface roughness; Aerosol deposition; Adhesion strength; Biological performance

Effects of magnesium film thickness and annealing temperature on formation of Mg₂Si films on silicon (111) substrate deposited by magnetron sputtering by Qingquan Xiao; Quan Xie; Xiangqian Shen; Jinmin Zhang; Zhiqiang Yu; Kejie Zhao (pp. 7800-7804).

► We report preparation of Mg₂Si films by magnetron sputtering method. ► We report effect of deposited Mg film thickness on formation. ► We report effect of annealing temperature on formation. ► High quality Mg₂Si films are prepared directly by annealing at 400°C for 5h. ► The texture of Mg₂Si films becomes dense as deposited Mg film thickness increases.Magnesium films of various thicknesses were first deposited on silicon (111) substrates by magnetron sputtering method and then annealed in annealing furnace filled with argon gas. The effects of the magnesium film thickness and the annealing temperature on the formation of Mg₂Si films were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Mg₂Si thin films thus obtained were found to be polycrystalline and the Mg₂Si (220) orientation is preferred regardless of the magnesium film thickness and annealing temperature. XRD results indicate that high quality magnesium silicide films are produced if the magnesium/silicon samples are annealed at 400°C for 5h. Otherwise, the synthesized films annealed at annealing temperatures lower than 350°C or higher than 450°C contain magnesium crystallites or magnesium oxide. SEM images have revealed that microstructure grains in the polycrystalline films are about 1–5μm in dimensions, and the texture of the Mg₂Si films becomes denser and more homogeneous as the thickness of the magnesium film increases.

Keywords: Magnesium silicide; Thin film; Annealing; Diffusion; X-ray diffraction; Scanning electron microscopy

Localized grafting through chemical lift-off by Alice Mesnage; Guy Deniau; Lorraine Tessier; Vincent Mévellec; Serge Palacin (pp. 7805-7812).

. The GraftFast© and SEEP processes are two complementary and versatile grafting methods which provide covalently grafted polymer films on any type of surfaces by radical polymerization in aqueous media. They rely on redox activation which creates radical species able to start a radical polymerization and chains grafting to the substrate as termination reaction. The use of a sacrificial physisorbed layer, easily removed, allows to obtain localized grafting.Display Omitted► Preliminary work obtains with very simple techniques. ► Two original chemical processes able to locally graft polymers onto the surface of materials. ► Localization is brought by chemical lift-off. ► Both grafting processes works thanks to redox activation of diazonium salts.In this work we present two techniques that provide localized functionalization of the surface of materials. Both lead to localized grafted thin organic films (10–200nm). The localization is brought by a chemical lift-off process, which relies on patterned weakly bonded films as sacrificial layers, combined with electrochemical (SEEP) or chemical (GraftFast©) processes which provides the final robust pattern on the surface. Both grafting processes, which were recently described, take advantage of the redox activation of diazonium salts associated with vinylic monomers in aqueous solution, and lead to similar grafted polymer films. Thanks to the high difference in adhesion between the grafted polymer and the patterned sacrificial layer (either an ink or weakly bound self-assembled monolayers), the latter may be easily removed, which unveils uncovered areas of the substrate.

Keywords: Patterned surfaces; Thin films; Grafting; Polymers; Diazonium salts; Redox

Comparison of tribological properties of CrN, TiCN and TiAlN coatings sliding against SiC balls in water by Qianzhi Wang; Fei Zhou; Xiaonan Wang; Kangmin Chen; Meiling Wang; Tao Qian; Yanxia Li (pp. 7813-7820).

► Deposition of CrN, TiCN and TiAlN coatings on WC cemented carbide disks using enhanced cathodic arc magnetron sputtering. ► Investigation of tribological properties of CrN, TiCN and TiAlN coatings sliding SiC balls in water. ► The lowest friction coefficient of 0.076 was obtained for the CrN/SiC tribopairs. ► The CrN coatings and the SiC balls against TiCN coatings showed the lowest specific wear rates.CrN, TiCN and TiAlN coatings were deposited on WC cemented carbide disks using enhanced cathodic arc magnetron sputtering and their topographies and structures were observed and analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The friction and wear properties of CrN, TiCN and TiAlN coatings sliding against SiC balls in water were investigated and compared synthetically using ball-on-disk tribometer. The results showed that the CrN/SiC tribopairs showed the lowest friction coefficient of 0.076, while the TiCN/SiC tribopairs displayed the highest friction coefficient of 0.264. For the CrN/SiC tribopairs the specific wear rate of CrN coatings was lowest while that of SiC balls became highest. But for the TiAlN(TiCN)/SiC tribopairs, the specific wear rate of TiAlN coatings was highest while that of SiC balls for the TiCN/SiC tribopairs became lowest. This indicated that the friction and wear behaviors of nitride coatings/SiC balls tribo-systems in water were more strongly influenced by the anti-oxidative ability of tribomaterials in water than by their mechanical properties.

Keywords: Friction; Wear; Water lubrication; CrN; TiCN; TiAlN

Polymetallic citric complexes as precursors for spray-pyrolysis deposition of thin ferrite films by M. Milanova; I. Koleva; R. Todorovska; J. Zaharieva; M. Кostadinov; D. Todorovsky (pp. 7821-7826).

► Spray-pyrolysis is a suitable method for ferrite thin films (40–800nm) deposition. ► Mixed-metal citric complexes (ethylene glycol solution) are promising starting material. ► Uniform stoichiometric single phase MFe₂O₄ films (M=Cu, Mg, Zn) are produced. ► Film morphological grains are in the intervals 30–100nm (Cu, Mg) and 0.15–1μm (Zn).Thin films of ferrites of the type M^IIFe₂O₄ (M=Cu, Mg, Zn) are prepared by spray-pyrolysis using ethylene glycol solutions of mixed-metal citric complexes of the respective metals at substrate temperature between 350°C and 450°C and post-deposition annealing at 480–750°C in air. Phase composition, crystal structure, morphology and adhesion of the obtained films (40–400nm in thickness) are studied by X-ray diffraction, SEM, energy dispersive X-ray microanalysis and AFM. Single phase dense uniform films with grains from 30–100nm (M=Cu, Mg) to 0.15–2μm (M=Zn) are obtained.

Keywords: Thin films; Ferrites; Spray pyrolysis; XRD; SEM; AFM

Properties of AlN grown by plasma enhanced atomic layer deposition by Markus Bosund; Timo Sajavaara; Mikko Laitinen; Teppo Huhtio; Matti Putkonen; Veli-Matti Airaksinen; Harri Lipsanen (pp. 7827-7830).

► We study the properties of the aluminum nitride films grown by plasma ALD. ► The effect of plasma pulse time and temperature on the film properties was studied. ► We found that the hydrogen level of AlN films is high. ► The growth temperature had a significant effect on the film properties. ► Hydrogen concentration correlated with the mass density and refractive index.The influence of growth parameters on the properties of AlN films fabricated by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia precursors was investigated. The atomic concentrations, refractive index, mass density, crystallinity and surface roughness were studied from the films grown in the temperature range of 100–300°C with plasma discharge times between 2.5 and 30s. The AlN films were shown to be hydrogen rich having H concentrations in the range of 13–27at.% with inverse dependence on the growth temperature. The carbon and oxygen concentrations in the films were less than 2.6% and 0.2%, respectively. The refractive index and mass density of the films correlated with the hydrogen concentration so that higher concentrations (lower growth temperatures) resulted in smaller refractive index and mass density. The film grown at 300°C was found to be crystalline whereas lower growth temperature produced amorphous films.

Keywords: Atomic layer deposition; Plasma; Aluminum nitride

First-principles calculations on Al/AlB₂ interfaces by Y.F. Han; Y.B. Dai; J. Wang; D. Shu; B.D. Sun (pp. 7831-7836).

► We calculated Al/AlB₂ system to clarify heterogeneous nucleation potential of AlB₂. ► The outmost layer of AlB₂ particles prefers metal to metalloid atom termination. ► Al atoms continue the natural stacking sequence of bulk AlB₂ across interface. ► The interfacial energy of Al/AlB₂ is much larger than that of Al(s)/Al(l). ► Poor nucleation potency of AlB₂ is elucidated from thermodynamic considerations.The AlB₂ (111) surfaces and Al (111)/AlB₂ (0001) interface were studied by first-principles calculations to clarify the heterogeneous nucleation potential of α-Al grains on AlB₂ particles in purity aluminium and hypoeutectic Al–Si alloys. It is demonstrated that the AlB₂ (0001) surface models with more than nine atomic layers exhibit bulk-like interior, wherein the interlayer relaxations localized within the top three layers are well converged. The outmost layer of AlB₂ free surface having a preference of metal atom termination is evidenced by surface energy calculations. With Al atoms continuing the natural stacking sequence of bulk AlB₂, Al–Al metallic bonds are formed across interface during the combination of Al atoms with Al-terminated AlB₂ surface. The calculated interfacial energy of the Al/AlB₂ interface is much larger than that between the α-Al and aluminium melts, elucidating the poor nucleation potency of α-Al grains on AlB₂ particles from thermodynamic considerations.

Keywords: First-principles calculation; Interface; AlB; ₂; Aluminium alloys; Grain refining

Nitrogen-doped carbon nanotubes with tunable structure and high yield produced by ultrasonic spray pyrolysis by Jian Liu; Yong Zhang; Mihnea Ioan Ionescu; Ruying Li; Xueliang Sun (pp. 7837-7844).

► Ultrasonic spray pyrolysis is developed to synthesize CN_x. ► CN_x prepared by this method have high yield. ► Imidazole as an additive in acetonitrile to control N doping and structure in CN_x. ► Imidazole decreases nanotube diameter while increases nanotube length and yield.Nitrogen-doped carbon nanotubes (CN_x) were prepared by ultrasonic spray pyrolysis from mixtures of imidazole and acetonitrile. Imidazole, as an additive, was used to control the structure and nitrogen doping in CN_x by adjusting its concentration in the mixtures. Scanning electron microscopy observation showed that the addition of imidazole increased the nanotube growth rate and yield, while decreased the nanotube diameter. Transmission electron microscopy study indicated that the addition of imidazole promoted the formation of a dense bamboo-like structure in CN_x. X-ray photoelectron spectroscopy analysis demonstrated that the nitrogen content varied from 3.2 to 5.2at.% in CN_x obtained with different imidazole concentrations. Raman spectra study showed that the intensity ratio of D to G bands gradually increased, while that of 2D to G bands decreased, due to increasing imidazole concentration. The yield of CN_x made from mixtures of imidazole and acetonitrile can reach 192mg in 24min, which is 15 times that of CN_x prepared from only acetonitrile. The aligned CN_x, with controlled nitrogen doping, tunable structure and high yield, may find applications in developing non-noble catalysts and novel catalyst supports for fuel cells.

Keywords: Carbon nanotubes; Spray pyrolysis; Nitrogen doping; Chemical vapor deposition

Magnetic properties of the semifluorinated and semihydrogenated 2D sheets of group-IV and III-V binary compounds by Yandong Ma; Ying Dai; Meng Guo; Chengwang Niu; Lin Yu; Baibiao Huang (pp. 7845-7850).

► H– ab ( ab=SiC, GeC, SnC, BN, AlN, and GaN) and F–GaN sheets are ferromagnets. ► F– ab sheets (except for F–GaN sheet) are predicated to be antiferromagnets. ► Surface decoration can tune the magnetic properties of the 2D sheet. ► Magnetism arises from combined effects of through-bond and p– p direct interactions.By performing first-principles calculations, the intriguing electronic and magnetic properties of the semidecorated sheets of group-IV and III-V binary compounds are investigated. Our results indicate that the semifluorinated and semihydrogenated ab ( ab=SiC, GeC, SnC, BN, AlN, and GaN) sheets exhibit diverse electronic and magnetic properties. Accordingly, the electronic and magnetic properties of the semidecorated sheets can be precisely modulated by controlling the adsorbed atoms on the a sites. Further, the preference of ferromagnetic or antiferromagnetic coupling can be attributed to the combined effects of both through-bond spin polarization and p– p direct interaction for the semidecorated ab sheets.

Keywords: Graphene-like; Magnetic; Density functional theory; Nanoelectronics; Semidecoration

Spontaneous evolution of nanotips on silicon surface below the laser ablation threshold by S. Lugomer; A. Maksimović; A. Karacs; G. Peto (pp. 7851-7855).

► Spontaneous evolution of 2D array of Si nanotips under laser irradiation of silicon surface. ► The equidistant nanotips are organized into a square, and the “ V”-shaped patterns. ► The nanotips evolve from the nonlinear flow instability of molten Si layer. ► These localized structures may be identified as the lump solitons.A low power density single-pulse laser irradiation of the Si surface has been used for the study of formation and self-organization of silicon nanotips. A two dimensional regular array of hillock-like nanotips has been created in the central region, a disturbed array comprising crossed lines of hillocks in the near-central region, and the “ V”-shaped array in the peripheral region. Therefore, the long-range organization of hillocks changes from the center toward the periphery, following the Gaussian-like laser power profile. The evolution of hillocks due to the flow instability of molten silicon is equivalent to the instability of a liquid layer falling down a vertical plate. The novel result is that the hillock-like soliton structures can be identified with the lump solitons resulting from the nonlinear hydrodynamic instability evolution.

Keywords: Silicon; Surface structure; Surface nanopatterning; Nonlinear dynamics; Solitons; Laser interaction

Surface structures and osteoblast response of hydrothermally produced CaTiO₃ thin film on Ti–13Nb–13Zr alloy by Jin-Woo Park; Yusuke Tustusmi; Chong Soo Lee; Chan Hee Park; Youn-Jeong Kim; Je-Hee Jang; Dongwoo Khang; Yeon-Min Im; Hisashi Doi; Naoyuki Nomura; Takao Hanawa (pp. 7856-7863).

► Submicro-structured CaTiO₃ thin film on Ti–13Nb–13Zr alloy was produced by hydrothermal treatment. ► Simple post heat-treatment significantly increased surface hydrophilicity of CaTiO₃ film without altering surface morphology and thickness. ► CaTiO₃ coating notably upregulated various integrin gene expressions in osteoblastic cells at an early incubation time-point. ► CaTiO₃ layer enhanced viability and ALP activity of osteoblastic cells. ► Post heat-treatment further increased initial cell attachment and ALP activity in CaTiO₃-coated Ti–13Nb–13Zr surface.This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti–13Nb–13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO₃ layer. Post heat-treatment at 400°C for 2h in air significantly decreased water contact angles in the CaTiO₃ layer ( p<0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces ( p<0.001), and also an upregulated expression of various integrin genes (α1, α2, α5, αv, β1 and β3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti–13Nb–13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti–13Nb–13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.

Keywords: Ti–13Nb–13Zr alloy; Calcium ion; Surface hydrophilicity; Osteoblast; Hydrothermal treatment

Parametric study of Al and Al₂O₃ ceramic coatings deposited by air plasma spray onto polymer substrate by Sun Guanhong; He Xiaodong; Jiang Jiuxing; Sun Yue (pp. 7864-7870).

► Al and Al₂O₃ ceramic were deposited onto the polymer substrate by plasma spray technology. ► Spray parameters have no effect on the phase composition of the coatings. ► The highest shear adhesion strength of the bond coating was 5.21MPa sprayed with the current of 180A and 190mm. ► Very thin Al₂O₃ top coatings have the composition of α-Al₂O_3, γ-Al₂O₃ and aluminum was sprayed onto the polymer substrate.Aluminum and ceramic (Al₂O₃) coatings were deposited onto the polymer substrate by air plasma spray (APS) to improve the mechanical properties of the polymer surface. The effect of spray parameters (current and spray distance in this paper) on the phase composition, microstructure and mechanical properties was investigated. Shear adhesion strength between the coatings and the substrates was also examined. The results indicate that the deposition parameters have a significant effect on the phase composition, microstructure and mechanical properties of as-spayed coatings. The maximum shear adhesion strength of the bond coats was 5.21MPa with the current of 180A and 190mm spray distance.

Keywords: Bond coat; Polymer matrix composite; Alumina; Plasma spray coatings

Nanostructure and conductivity study of yttria doped zirconia films deposited on samaria doped ceria by Ming-Hsiu Wu; Jow-Lay Huang; Kuan-Zong Fung; Hao-Chih Liu; Ding-Fwu Lii (pp. 7871-7875).

► Zirconia and ceria are co-used as solid electrolyte at high temperature. ► Inter-diffusion happens between the co-used electrolyte at temperature over 1000°C. ► Conductivity of zirconia becomes lower when it contains some cerium ions in lattice. ► On both of zirconia and ceria substrate, zirconia film becomes columnar structure.Yttrium doped zirconia (YSZ) film was deposited on poly-crystalline 10at.% samaria doped ceria (SDC) and YSZ plate (doped with 8at.% yttria) by electron beam evaporation deposition. For electrolyte application in solid oxide fuel cells, YSZ can be used with SDC and act as an electron barrier. The conductivity of YSZ and SDC was measured after sintering at 1000°C. Results indicated that YSZ film became columnar structure, and a new layer formed between the YSZ film and SDC, due to the inter-diffusion between zirconium ions and cerium ions.

Keywords: Yttria-doped zirconia; Samaria doped ceria; Electron beam evaporation; Solid electrolyte

Structural and dielectric properties of Ru-based gate/Hf-doped Ta₂O₅ stacks by A. Paskaleva; M. Ťapajna; E. Dobročka; K. Hušeková; E. Atanassova; K. Fröhlich (pp. 7876-7880).

► Homogeneous Hf-doped Ta₂O₅ high- k dielectric layers deposited. ► Ru-based gate deposition modifies more significantly interfacial layer parameters. ► Ru is thermally stable in contact with Hf-doped Ta₂O₅. ► O₂ annealing of RuO₂ metal electrode causes substantial structural modifications.Hf-doped Ta₂O₅ thin films are studied with respect to their composition, dielectric and electrical properties. The incorporation of Hf is performed by sputtering of a 0.7nm thick Hf layer on top of Ta₂O₅ and subsequent annealing to stimulate diffusion of Hf into Ta₂O₅ and their intermixing. The elemental in-depth distribution of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS), which has revealed that Hf and Ta₂O₅ are intermixed throughout the whole thickness. Two sub-layers exist in all the samples – an upper homogeneous Hf-doped Ta₂O₅ sub-layer and a near interfacial region which is a mixture of Ta- and Si-oxides. The X-ray reflectivity (XRR) analysis shows existence of interfacial layer with a thickness of about 1.9–2nm, irrespectively of the total thickness of the stacks. Metal–oxide–Si structures with Ru and RuO₂ metal electrodes have been prepared and investigated in terms of dielectric constant, effective work function (EWF) and interfacial layer parameters. The influence of post-metallization annealing steps on these parameters was also studied.

Keywords: Hf-doped Ta; ₂; O; ₅; high-; k; dielectrics; Ru-based metal gate; High-; k; /metal gate stacks

Effects of pulsed bias duty ratio on microstructure and mechanical properties of TiN/TiAlN multilayer coatings by Yongqiang Wei; Chunzhi Gong (pp. 7881-7886).

► TiN/TiAlN multilayer coatings with excellent mechanical and tribological properties were deposited by arc ion plating method. ► The phase of TiN/TiAlN multilayer coatings exhibited preferred orientation along (111) plane with the increase duty ratio of pulsed bias. ► The surface morphologies were strongly influenced by duty ratio and the multilayer structure was clearer and denser with the increase duty ratio of pulsed bias. ► The TiN/TiAlN multilayer coatings showed higher hardness at 20% duty ratio of pulsed bias and excellent tribological properties at 50% duty ratio of pulsed bias.TiN/TiAlN multilayer coatings were deposited on M2 high speed steel by a pulsed bias arc ion plating system. The effect of pulsed bias duty ratio on the microstructure, mechanical and wear properties was investigated. The amount of macroparticles reduced with the increase of the duty ratio. The surface roughness was 0.0858μm at duty ratio of 50%. TiN/TiAlN multilayer coatings were crystallized with orientations in the (111), (200) (222) and (311) crystallographic planes and the microstructure strengthened at (111) preferred orientation. At duty ratio of 20%, the hardness of TiN/TiAlN multilayer coatings reached a maximum of 3004HV, which was 3.2 times that of the substrate. The adhesion strength reached a maximum of 77N at 50% duty ratio. Friction and wear analyses were carried out by pin-on-disc tester at room temperature. Compared with the substrate, all the specimens coated with TiN/TiAlN multilayer coatings exhibited better tribological properties.

Keywords: Arc ion plating; Surface hardness; TiN/TiAlN; Multilayer coatings; Duty ratio

Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration by Jie Wei; Jiecheng Wang; Xiaochen Liu; Jian Ma; Changsheng Liu; Jing Fang; Shicheng Wei (pp. 7887-7892).

A fluorapatite cement was prepared and could be filled into the enamel carious cavities to repair the damaged enamel. The cement could be combined with the enamel because of the chemical reaction between the cement and enamel. The cement had good biocompatibility that satisfied the relevant criterion on dental biomaterials.Display Omitted► A fluorapatite cement was prepared and could be filled into the enamel carious cavities to repair the damaged enamel. ► The cement could be tightly combined with the enamel because of the chemical reaction between the cement and enamel. ► The cement had good biocompatibility that satisfied the relevant criterion on dental biomaterials.Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H₃PO₄) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3wt% after self-hardening for 2 days. The solubility of fs-AC in Tris–HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.

Keywords: Dental enamel; Carious cavities; Fluorapatite cement; Restoration; Cytocompatibility

Effect of crystallinity of ZnO buffer layer on the properties of epitaxial (ZnO:Al)/(ZnO:Ga) bi-layer films deposited on c-sapphire substrate by Zhiyun Zhang; Chonggao Bao; Shengqiang Ma; Shuzeng Hou (pp. 7893-7899).

► The lowest resistivity of 8.4×10⁻⁵Ωcm was obtained at annealed buffered substrate. ► The characteristic of c-axis oriented texture grows up at different substrates. ► Two kinds of stacking faults were observed at Fourier filtered images. ► Origin and consequences of stacking faults were discussed. ► Lower defect density of film has a benefit effect on the resistivity.Bi-layer ZnO films with 2wt.% Al (AZO; ZnO:Al) and 4wt.% Ga-doped (GZO; ZnO:Ga) were deposited on the ZnO buffered and annealed ZnO buffered c(0001)-sapphire(Al₂O₃) substrates respectively by Pulsed Laser Deposition (PLD). The effect of crystallinity of ZnO buffer layer on the crystallinity and electrical properties of the AZO/GZO bi-layer thin films was investigated. It was seen that the crystallinity of ZnO buffer layer had a great influence on the orientation and defect density of AZO/GZO bi-layer thin films from X-ray Diffraction (XRD) peaks and High Resolution Transmission Electron Microscopy (HRTEM) images. In a word, it was found in the films that more preferred c-axis orientation texture and reduction of the defects such as stacking faults and dislocations, with increasing of the crystallinity of ZnO buffer layer.

Keywords: HRTEM; AZO; GZO; Bi-layer film; Stacking faults; Defect density

Influence of annealing temperature on the structural, optical and mechanical properties of ALD-derived ZnO thin films by C.-Y. Yen; S.-R. Jian; G.-J. Chen; C.-M. Lin; H.-Y. Lee; W.-C. Ke; Y.-Y. Liao; P.-F. Yang; C.-T. Wang; Y.-S. Lai; Jason S.-C. Jang; J.-Y. Juang (pp. 7900-7905).

► ZnO thin films grown on Si(111) substrates by ALD and followed by RTA. ► XRD shows that the annealed ZnO films had a predominant (002) orientation. ► PL show manifest enhanced in intrinsic band edge UV emission of annealed ZnO films. ► Hardness of annealed ZnO films follows satisfactorily with the Hall–Petch equation.ZnO thin films grown on Si(111) substrates by using atomic layer deposition (ALD) were annealed at the temperatures ranging from 300 to 500°C. The X-ray diffraction (XRD) results show that the annealed ZnO thin films are highly (002)-oriented, indicating a well ordered microstructure. The film surface examined by the atomic force microscopy (AFM), however, indicated that the roughness increases with increasing annealing temperature. The photoluminescence (PL) spectrum showed that the intensity of UV emission was strongest for films annealed at 500°C. The mechanical properties of the resultant ZnO thin films investigated by nanoindentation reveal that the hardness decreases from 9.2GPa to 7.2GPa for films annealed at 300°C and 500°C, respectively. On the other hand, the Young's modulus for the former is 168.6GPa as compared to a value of 139.5GPa for the latter. Moreover, the relationship between the hardness and film grain size appear to follow closely with the Hall–Petch equation.

Keywords: ZnO thin films; Atomic layer deposition; XRD; AFM; Nanoindentation; Hardness

Corrigendum to “The properties of plasma-enhanced atomic layer deposition (ALD) ZnO thin films and comparison with thermal ALD” [Appl. Surf. Sci. 257 (2011) 3776–3779] by Doyoung Kim; Hyemin Kang; Jae-Min Kim; Hyungjun Kim (pp. 7906-7906).

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Applied Surface Science (v.257, #17)