Materials Letters (v.63, #12)

Selective nanoshaving of self-assembled monolayers of 2-(4-pyridylethyl)triethoxysilane by Luis G. Rosa; Jinyue Jiang; Ocelio V. Lima; Jie Xiao; Emmanuel Utreras; P.A. Dowben; Li Tan (961-964).
Single molecular layers of 2-(4-pyridylethyl)triethoxysilane have been deposited on native oxide surfaces of silicon, with the triethoxysilylethyl groups towards the silicon oxide interface and pyridine at the surface. It is possible to “shave” or mechanically break the molecular bonds at the alkoxy-silane (Si–C) bond using scanning atomic force microscope, leaving large swaths of surface area cut to a depth of 0.64 ± 0.06 nm, exposing the silicon of the alkoxy-silane ligand. Mechanical cleavage of the pyridine ligand alone is also possible, but more difficult to control selectively.
Keywords: Nanoshaving; Self-assembled monolayers; 2-(4-Pyridylethyl)triethoxysilane; Atomic force microscope; Electronic structure of organic layers;

In this paper, the phase transformation behaviors and structures of Ni50Mn28+ x Ga22 x (x  = 0, 1, 2, 3) alloys and ribbons as well as the magnetic properties of ribbons are discussed. Rapidly quenching process decreases the degree of order and introduces some internal stress, which influences the martensitic transformation temperatures of the ribbons. The structures of the ribbons become 7 M modulated, which is different from the 5 M modulated martensite of the corresponding bulk materials. Higher annealing temperature and annealing under magnetic field are all in favor of the magnetization of the ribbons, and this is related to the enhancement of orientation perpendicular to the surface of the ribbons.
Keywords: Magnetic materials; Rapidly quenched ribbons; Martensitic transformation behaviors; Magnetic properties; Crystal structure;

An easy route to prepare carbon black–silver hybrid catalysts for electro-catalytic oxidation of hydrazine by Chang Tan; Feng Wang; Jingjun Liu; Yongbin Zhao; Jianjun Wang; Lianghu Zhang; Ki Chul Park; Morinobu Endo (969-971).
Carbon black–silver hybrid catalysts were easily synthesized by a mixing method of acid-oxidized carbon black and the colloidal dispersion of silver nanoparticles. The silver colloidal dispersion was pre-synthesized by a chemical reduction of silver nitrate by dimethyl sulfoxide in the presence of trisodium citrate dihydrate as capping agents. In the mixing method, approx. 6.0 nm diameters of silver nanoparticles with face-centered cubic crystal structures are highly dispersed on the acid-oxidized carbon blacks due to the surface reactivity resulting from the enhancement of oxygen-containing functional groups. The hybrid catalysts were examined for electro-catalytic activity towards oxidation of hydrazine. The results clearly show that the carbon black–silver hybrid catalysts are highly active for electro-catalytic oxidation of hydrazine.
Keywords: Nanocomposites; Deposition; Catalysts;

p-type doping of ZnO by means of high-density inductively coupled plasmas by S.Y. Huang; S. Xu; J.W. Chai; Q.J. Cheng; J.D. Long; K. Ostrikov (972-974).
A custom-designed inductively coupled plasma assisted radio-frequency magnetron sputtering deposition system has been used to fabricate N-doped p-type ZnO (ZnO:N) thin films on glass substrates from a sintered ZnO target in a reactive Ar + N2 gas mixture. X-ray diffraction and scanning electron microscopy analyses show that the ZnO:N films feature a hexagonal crystal structure with a preferential (002) crystallographic orientation and grow as vertical columnar structures. Hall effect and X-ray photoelectron spectroscopy analyses show that N-doped ZnO thin films are p-type with a hole concentration of 3.32 × 1018 cm− 3 and mobility of 1.31 cm2 V− 1 s− 1. The current–voltage measurement of the two-layer structured ZnO pn homojunction clearly reveals the rectifying ability of the pn junction. The achievement of p-type ZnO:N thin films is attributed to the high dissociation ability of the high-density inductively coupled plasma source and effective plasma-surface interactions during the growth process.
Keywords: Semiconductors; Chemical vapor deposition; Microstructure; Nanomaterials;

Formation of Ag nanoparticles within the thermosensitive hairy hybrid particles by Zhongli Lei; Na Li; Lin Lin; Yongming Jia; Xiaolong Pang; Na Ren (975-977).
Herein we report on the production of composite core–shell particles, which are actually self-assembly of poly (N-isopropylacrylamide)-based amphiphilic block copolymers as a template for metal-block copolymer nanocomposites formation. Organic–inorganic composites were prepared with Ag nanoparticles embedded within colloidal particles of an amphiphilic, thermally responsive polymer. To promote the incorporation of unaggregated Ag nanoparticles, temperature responsive microspheres of poly (N-isopropylacrylamide) (NIPAM) block with polystyrene were synthesized. Polyethyleneimine (PEI) could act as the linker between Ag ions (Ag nanoparticles) and poly (styrene-b-N-isopropylacrylamide) (PS-b-PNIPAM) colloids and the reducing agent in the formation of Ag nanoparticles. Transmission electron microscopy (TEM) measurements confirmed the nanostructures, 1HNMR and FTIR characterized the components of the resulting nanoobjects. These stimuli-responsive hybrid microspheres will have potential applications in biomedical areas, such as tissue engineering and drug delivery.
Keywords: Composite materials; Ag nanoparticles; Polymers; Polyethleneimine;

Gallium nitride nanowires doped with magnesium by Dongdong Zhang; Chengshan Xue; Huizhao Zhuang; Haibo Sun; Yuping Cao; Yinglong Huang; Zouping Wang; Ying Wang; Yongfu Guo (978-981).
GaN nanowires doped with Mg have been synthesized on Si (111) substrate through ammoniating Ga2O3 films doped with Mg under flowing ammonia atmosphere. The Mg-doped GaN nanowires were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The results demonstrate that the nanowires were single crystalline with hexagonal wurzite structure. The diameters of the nanowires ranged 20–30 nm and the lengths were about hundreds of micrometers. The intense PL peak at 359 nm showed a blueshift from the bulk band gap emission, attributed to Burstein–Moss effect. The growth mechanism of the crystalline GaN nanowires is discussed briefly.
Keywords: Crystal growth; Nanomaterials; Nanowires; Mg-doped;

A simple approach is proposed to realize the three dimensional (3D) hierarchical Cu2S architectures at room temperature in this letter. The 3D Cu2S architectures are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectrum (XPS). The effects of synthetic conditions, such as reaction time and the amount of reagents, on the morphology of the product are investigated. The growth mechanism of the product is proposed, based on the evolution of the morphologies with the increasing of reaction time. Our work provides a facile and easy method on designing for the fabrication of 3D hierarchical architecture materials.
Keywords: Cu2S; Three-dimensional; Microstructure; Crystal growth;

Basic magnesium carbonate (Mg5(CO3)4(OH)2·4H2O) microrods with a surface of “house of cards” structure have been synthesized in an aqueous solution system without using any surfactants or templates during the precipitation process. By tuning the reaction temperature, the morphology evolved from microrod to microrod with a surface of “house of cards” structure. The products were characterized by field-emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), thermogravimetric analysis (TG) and X-ray powder diffraction (XRD). It was found out that with the morphological transformation, their corresponding compositions also change from MgCO3·3H2O to Mg5(CO3)4(OH)2·4H2O.
Keywords: Basic magnesium carbonate; Microstructure; Microrods; Electron microscopy;

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates by Jibin Miao; Jiasheng Qian; Xuhua Wang; Yuchuan Zhang; Haiyang Yang; Pingsheng He (989-990).
A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol–gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N2 adsorption–desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m2/g, large pore volume with more than 0.8 cm3/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.
Keywords: Nanomaterials; Sol–gel preparation; Polystyrene microemulsion; Mesoporous silica; Template;

In this study, we propose a new abacus based on a synthetic parameter: the Amlouk–Boubaker expansivity ψ AB . This abacus gathers the band gap energy E g., Vickers microhardness and ψ AB . This abacus is presented as a guide to evaluate and optimize photovoltaic–thermal semiconductor thin films thermal and optical performance. The definition of this parameter ψ AB takes into account the thermal diffusivity and the optical effective absorptivity of the material. As a first approximation, this parameter, could be considered as a 3D velocity of the transmitted heat inside the material.New functional semiconductor materials have been significantly classified using this abacus.
Keywords: Semiconductor thin films; Optothermal expansivity; Effective absorbance; BPES;

Hydrothermal process has been successfully applied to synthesize CdS hierarchical spindles. The compositions and morphologies of the as-produced CdS were investigated through X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. It is found that the hexagonal wurtzite-structured CdS spindles are endowed with hierarchical morphologies with the branches nearly perpendicular to the trunks. Some of the structural defects are also detected by TEM. Furthermore, the absorption and emission spectral properties were studied using UV–Vis spectrometer and photoluminescence spectrometer, respectively. It is speculated that the red shift of absorption edge and the enhanced deep-level (DL) emission are all related to the structural defects of the as-prepared CdS hierarchical spindles.
Keywords: Defects; Microstructure; Semiconductors;

Cu nanowires (NWs) with controlled crystalline orientation were obtained via electrodeposition inside the nanochannels of anodic aluminum oxide templates. By adjusting electrolyte composition, the orientation of Cu NWs was manipulated between [100] and [110]. [100]- and [110]-oriented single-crystal Cu NWs were also achieved under lower electrodeposition voltages in sulfate electrolyte and citrite electrolyte, respectively. Optical absorption spectrum measurements reveal that the surface plasma resonance peak of the Cu NW arrays has an obvious blue-shift of 11 nm when the orientation of Cu NWs is turned from [100] to [110].
Keywords: Nanomaterials; Crystal growth; Optical materials and properties; Surfaces;

Electrochemical reduction of CO2 by Cu2O-catalyzed carbon clothes by Tin-Yu Chang; Ru-Meng Liang; Pu-Wei Wu; Jing-Yu Chen; Yu-Chi Hsieh (1001-1003).
Cu2O cubes with average edge lengths of 640 nm were prepared by a chemical reduction approach. The as-synthesized Cu2O particles were deposited on carbon clothes for electrochemical characterizations in cyclic voltammetry (CV) and potentiostatic measurements. In 0.5 M NaOH electrolytes saturated with N2 or CO2, both the Cu2O and carbon clothes were stable at the potential range of 0 to − 1.7 V. Comparisons in the current responses from the CV and potentiostatic measurements suggested the Cu2O with notable catalytic abilities for the CO2 reduction. The mass activity was estimated at 0.94 mA/mg. Chemical analysis from gas chromatography confirmed the methanol to be the predominant product.
Keywords: CO2 sequestration; Cu2O; Electrochemical reduction; Alkaline electrolyte;

Hydrothermal synthesis of ultrafine A5Nb4O15 (A = Ba, Sr) powders by Chao Zhou; Gang Chen; Hongjie Zhang; Yingxuan Li; Jian Pei (1004-1006).
A5Nb4O15 (A = Ba, Sr) powders with hexagonal perovskite structures have been firstly synthesized by a two-step hydrothermal process. These oxides were crystallized directly from niobium oxide in the presence of potassium basic solutions at 240 °C for 48 h. The products were characterized by powder X-ray diffraction and scanning electron microscopy. It was found that the pretreatment of the niobium oxide through the hydrothermal technique firstly was the critical factor to prepare these niobates. Moreover, the alkaline concentration also played an important role in the formation of these niobates. On basis of the experimental data, a possible reaction process for the formation of A5Nb4O15 (A = Ba, Sr) was proposed.
Keywords: Ceramics; Perovskites; Dielectrics; Hydrothermal;

Oxygen permeation and electrical transport of Gd1−xPrxBaCo2O5 + δ dense membranes by Chunli Yang; Xiusheng Wu; Shumin Fang; Chusheng Chen; Wei Liu (1007-1009).
Double-perovskite Gd1−x Pr x BaCo2O5 +  δ membranes showed appreciable oxygen permeability at moderate temperatures. The overall oxygen permeation process of GdBaCo2O5 +  δ was found to be controlled mainly by the bulk diffusion step with the membrane thickness larger than 0.8 mm, and the limitation by oxygen surface exchange came into play at reduced thickness of 0.8 mm. The electrical conductivity measurement showed Gd1 –  x Pr x BaCo2O5 +  δ samples possessed a semiconducting behavior at a wide temperature range below 300 °C and a metallic behavior at 300–850 °C with a high conductivity of nearly 103 S cm− 1.
Keywords: Perovskites; Oxygen permeation; Electrical properties; Bulk diffusion; Oxygen surface exchange;

Thermoelectric power properties of Zn substituted Cu–Ga spinel ferrites by M.K. Fayek; S.S. Ata-Allah; Kh. Roumaih; S. Ismail (1010-1012).
Composition and temperature dependence of dc conductivity and Seebeck coefficient for Cu1−xZnxGa0.5Fe1.5O4 (0.0 ≤ × ≤ 0.5) are discussed. Thermoelectric power studies of this ferrite series are investigated from room temperature to well beyond the Curie temperature by the differential method. The Seebeck coefficient φ is found to be positive for compositions with x  ≤ 0.2 indicating that these ferrites behave as p-type semiconductors, while compositions with x  ≥ 0.3 show n-type semiconductors with φ negative. Results of the dc conductivity display semiconducting behavior of these materials. Transition temperatures obtained from both studies are in good agreement and was found to be decreased linearly with Zn content. Some physical properties of the samples such as density and porosity are also discussed. The obtained results are discussed in the light of the interactions over the metal sites in the spinel unit cell.
Keywords: Thermoelectric power; Cu–Zn–Ga ferrites; Dc conductivity;

Synthesis and characterization of ZrO2 hollow spheres by Chenyi Guo; Peng Hu; Lingjie Yu; Fangli Yuan (1013-1015).
ZrO2 hollow microspheres with the average diameter of about 500 nm and the shell thickness of about 50 nm were synthesized by a facile technique using carbon spheres as templates. The corresponding ZrO2 hollow microspheres were obtained by calcining the precursors of C–Zr(OH)4 core-shell heterostructures, which were synthesized with the precipitation of ZrCl4 solution with aqueous ammonia on the surface of colloid carbons. SEM, XRD, TGA and BET were used to characterize the composition, morphology, size and crystal structure of synthesized products. The effects of ultrasonic dispersion and separation process on the hollow spheres were studied, and the surfactant PEG-1000 was added to tune the shell structure of synthesized ZrO2 hollow spheres.
Keywords: ZrO2 hollow spheres; Sol–gel preparation; Microstructure;

Controlled synthesis and characterization of 10 nm thick Al2O3 nanowires by Chunlei Li; Hongbo Huang; Shaoguang Yang; Rongkun Zheng; Wenrong Yang; Zongwen Liu; Simon Ringer (1016-1018).
α-Al2O3 nanowires, with diameter around 10 nm, were synthesized in bulk quantity by heating the mixture of pure aluminum and graphite powders at 900 °C. Scarcity of oxygen is regarded as the reason for the growth of the small diameter α-Al2O3 nanowires at relatively low temperature. The product was characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy and photoluminescence. The Oxygen vacancies in the nanowires lead to the strong photoluminescence in the wavelength range of 400–700 nm with its peak at 527 nm.
Keywords: Nanomaterials; Sintering; Optical materials and properties;

One-dimensional (1D) ZnO nanorod (NR) arrays were grown on (101) and (002) single- and poly-crystalline Zn substrates via direct surface-oxidation in solution, i.e. solvothermal method. The surface-oxidation was done in a solvent mixture of water and 1-propanol with the optimum pH adjusted by adding ammonia. X-ray diffraction patterns revealed that the ZnO NRs grown on the Zn substrates were of single-crystalline with wurtzite structure. The ZnO NRs grown on the (002) single- and poly-crystalline substrates grew in the <001> direction, in contrast to the NRs grown on the (101) single-crystal substrate which were oriented predominantly in the <101> direction. The texture coefficient of the grown ZnO NRs was calculated from the XRD data. Well-aligned NRs that had tips of various shapes were examined by scanning electron microscopy and transmission electron microscopy techniques. The optical properties of the ZnO NRs grown on the Zn substrates were characterized by photoluminescence (PL) spectroscopy.
Keywords: Luminescence; Single-crystal Zn substrate; Solvothermal process; 1D ZnO nanorod; Nanomaterials;

Microwave hydrothermal synthesis and upconversion properties of NaYF4:Yb3+, Tm3+ with microtube morphology by Xun Chen; Wanjun Wang; Xueyuan Chen; Jinhong Bi; Ling Wu; Zhaohui Li; Xianzhi Fu (1023-1026).
Efficient upconversion Yb3+ and Tm3+ codoped β-NaYF4 is firstly synthesized via a novel and rapid microwave hydrothermal process. The as-prepared sample is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The sample shows a microtube morphology, which may be formed by the curliness of flakes. It is found that NaYF4:Yb3+, Tm3+ microtubes can be synthesized using microwave hydrothermal method in a much shorter reaction time compared with conventional hydrothermal method, and the upconversion fluorescent intensity is also greatly enhanced under 976 nm laser excitation. The energy transfer upconversion mechanisms and the possible reason for the enhancement of the fluorescent intensity are also proposed.
Keywords: Luminescence; Optical materials and properties; Microwave; Upconversion;

Nanocrystallization of ferroelectric lithium niobate in LiNbO3-SiO2 glasses by P. Prapitpongwanich; R. Harizanova; K. Pengpat; C. Rüssel (1027-1029).
Transparent glasses in the (100-x)LiNbO3-xSiO2 system where 20 ≤ × ≤ 35, were produced by conventional melt-quenching technique. The quenched samples were amorphous as proved by X-ray diffraction (XRD) technique. Annealing of the quenched samples at temperatures ranging from 580 to 975 °C resulted in the precipitation of lithium niobate nano-crystals. Scanning electron microscopy (SEM) showed the presence of randomly oriented LiNbO3 nano-crystals dispersed in a continuous glass matrix. The relative dielectric constant (ε r) was in the range of 80 to 180 and increased with increasing LiNbO3 concentration. The glass ceramic samples annealed at temperatures up to 600 °C are fully transparent.
Keywords: Crystallization; Nano-crystals; Ferroelectric; Lithium niobate; Glass-ceramics;

Synthesis of Sb2S3 peanut-shaped superstructures by Qiaofeng Han; Liang Chen; Wenchao Zhu; Meijuan Wang; Xin Wang; Xujie Yang; Lude Lu (1030-1032).
Peanut-shaped Sb2S3 superstructures have been synthesized via a hydrothermal process at 120 °C for 8 h using hydrochloric acid and antimony O-benzyl dithiocarbonate (benzylxanthate, Sb(S2COC7H7)3) as starting materials. The powder X-ray diffraction (XRD) pattern shows the product corresponds to the pure orthorhombic phase of Sb2S3, the purity and composition of which are further confirmed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies reveal that the peanut-shaped Sb2S3 superstructures are aggregated by nanorods. The possible mechanistic pathways in the formation of the structures are discussed.
Keywords: Antimony sulfide; Nanomaterials; Semiconductors; Microstructures;

Zeolite framework stabilized copper(I) oxide nanoparticles (4.8 ± 2.6 nm) were prepared for the first time by using a four step procedure: the ion exchange of Cu2+ ions with the extra framework Na+ ions in Zeolite-Y, the reduction of the Cu2+ ions within the cavities of zeolite with sodium borohydride in aqueous solution, the dehydration of Zeolite-Y with the copper(0) nanoclusters, and the oxidation of intrazeolite copper(0) nanoclusters by O2 at room temperature. Zeolite stabilized copper(I) oxide nanoparticles were thoroughly characterized by ICP-OES, XRD, HR-TEM, Raman, XPS, UV–vis spectroscopy and N2 adsorption–desorption technique.
Keywords: Copper(0) nanoparticles; Copper(I) oxide nanoparticles; Cuprous oxide nanoparticles; Copper(II) oxide; Nanomaterials; Surfaces;

Mesoporous metallosilicate zeolites by desilication: On the generic pore-inducing role of framework trivalent heteroatoms by Johan C. Groen; Rosario Caicedo-Realpe; Sònia Abelló; Javier Pérez-Ramírez (1037-1040).
Desilication in alkaline medium is demonstrated as a general route to synthesize hierarchical metallosilicate zeolite crystals with preserved crystallinity. The lattice trivalent cation (not only Al3+ but also Ga3+, Fe3+, and B3+) regulates the alkaline-assisted hydrolysis of silicon towards controlled mesoporosity development. This finding widens the family of modified zeolite compositions that integrate in a single crystalline material micropores and mesopores and enables better accessibility in catalytic applications compared to the purely microporous counterparts.
Keywords: Alkaline treatment; Desilication; Hierarchical zeolites; Mesopore formation; Trivalent cation;

Spark plasma sintering of Co–WC cubic boron nitride composites by Bilge Yaman; Hasan Mandal (1041-1043).
25 vol.% cubic boron nitride (cBN) added tungsten carbide (WC) powders containing 6 wt.% Co (WC–6Co) were densified by spark plasma sintering (SPS) technique under different experimental conditions and the effect of cBN addition on the microstructure, mechanical properties and thermal conductivity were investigated. Over 99.5% theoretical density was achieved for WC–6Co–cBN composites sintered at 1300 °C, under 75 MPa pressure for 7.5 min. Under these conditions, cBN → hBN phase transformation was not observed.
Keywords: Tungsten carbide; WC–6Co–cBN composites; Spark plasma sintering;

Indium oxide nanorods and nanowires on porous anodic alumina by R. Zhang; K.M. Jiang; D.L. Chen; G.Q. Ding (1044-1046).
We report indium oxide nanorods and nanowires with controllable microstructure deposited on porous anodic alumina membranes (PAAs). At the beginning of the deposition, indium oxide tends to nucleate on the top of PAAs, not at the bottom of PAAs' nanopores, and grows into nanorods. It is interesting that the indium oxide nanorods on the top of PAA just copy the topography of PAA, and form a new porous layer with the thickness of 40–50 nm. As the deposition goes on, the nanorods cannot maintain the ordered nanopore structure, and evolve into nanowire net. And the nanowires can stand upwards separately, and then fall down as the length goes up, forming an indium oxide entangled nanowires. The structure evolvement is discussed according to the field emission scanning electric microscope images.
Keywords: Nanomaterials; Deposition; Semiconductor;

Preparation and characterization of α-Fe2O3 polyhedral nanocrystals via annealing technique by Rajesh Kumar; S. Gautam; In-Chul Hwang; Jae Rhung Lee; K.H. Chae; Nagesh Thakur (1047-1050).
Polyhedral nanocrystals of α-Fe2O3 are successfully synthesized by annealing FeCl3 on silicon substrate at 1000 °C in the presence of H2 gas diluted with argon (Ar). Uniformly shaped polyhedral nanoparticles (diameter ~ 50–100 nm) are observed at 1000 °C and gases flow rate such as; Ar = 200 ml/min and H2  = 150 ml/min. Non-uniform shaped nanoparticles (diameter ~ 20–70 nm) are also observed at an annealing temperature of 950 °C with lower gases flow rate (Ar = 100 ml/min and H2  = 75 ml/min). Nanoparticles are characterized in detail by field-emission electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and high resolution transmission electron microscopy (HRTEM) techniques. HRTEM study shows well resolved (110) fringes corresponding to α-Fe2O3, and selected area diffraction pattern (SADP) confirms the crystalline nature of α-Fe2O3 polyhedral nanoparticles. It is observed that polyhedral formation of α-Fe2O3 nanocrystals depends upon annealing temperature and the surface morphology highly rely on the gas flow rate inside the reaction chamber.
Keywords: Nanomaterials; Crystal structure; Annealing temperature; Polyhedral; Gas flow;

Synthesis of nano-TiC powder using titanium gel precursor and carbon particles by Navin Chandra; Meenakshi Sharma; Deepesh Kumar Singh; S.S. Amritphale (1051-1053).
The paper presents a novel process for synthesis of nano-size titanium carbide by reaction between titanium bearing precursor gel and nano carbon particles derived from soot at different temperatures in the range of 1300–1580 °C for 2 h under argon cover. The HRTEM studies of TiC powder synthesized by heating at 1580 °C show the presence of cube shaped particles (~ 60–140 nm) and hollow rods (diameter ~ 30–185 nm). The average particle size of crystallites, calculated by Scherer equation is observed to be ~ 35 nm while the surface area–density measurements indicate it to be ~ 113 nm. The surface area decreases with increase in reaction temperature.
Keywords: Titanium carbide; TiO2; Sol–gel preparation; Nanomaterials; Carbon soot;

Anomalous behaviour of the magnetic hysteresis loop in the α-Fe2O3/SiO2 nanocomposite by Marin Tadic; Vladan Kusigerski; Dragana Markovic; Irena Milosevic; Vojislav Spasojevic (1054-1056).
The α-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol–gel method and characterized by using X-ray diffractometer (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) magnetometer. TEM microscopy showed spherical particles with average size about 10 nm, whereas XRD diffraction confirmed the formation of the hematite phase. The magnetic measurements showed anomalous behavior of the hysteresis loops including decrease of high field isothermal magnetization and overlap of initial, remagnetization and magnetization curves. This anomalous behavior represents a novel effect for α-Fe2O3/SiO2 nanocomposites. We conjecture that a field-induced antiferromagnetic coupling between nanoparticles may produce this effect.
Keywords: Sol–gel preparation; Hematite; Nanocomposites; Magnetic materials;

Temperature induced hierarchical growth of ZnO microcrystal by Dapeng Wu; Zhengyu Bai; Kai Jiang (1057-1060).
Unique ZnO microcrystal composed of hierarchical nanorod arrays was successfully prepared by a surfactant-free process in aqueous solution under moderate temperature. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The as-prepared ZnO microstructures are of hexagonal phase and high purity. On the basis of SEM images and parallel experiments, a possible formation mechanism for this ZnO microcrystal with hierarchical nanorod arrays is proposed and the reaction temperatures are found to have great influence on inducing secondary nucleation and the hierarchical growth. In addition, the optical properties of the ZnO samples were also investigated by the photoluminescence (PL) spectrometer.
Keywords: Zinc oxide; Crystal growth; Hierarchical growth; Luminescence;

Synthesis of high surface area mesoporous carbonates in novel ionic liquid by Yawei Hou; Aiguo Kong; Xinhua Zhao; Haiyan Zhu; Yongkui Shan (1061-1064).
High surface area mesoporous SrCO3, CaCO3 and MnCO3 with straw-like bundles morphology were synthesized in a novel imidazolium pyruvate ionic liquid. These carbonates were characterized by X-ray diffraction, Fourier transform infrared spectra and transmission electron microscopy. The results revealed that these carbonates have pure orthorhombic and rhombohedral structures, respectively, and the prepared products all show the unique straw-like morphology. Mesoporous properties and high surface areas of SrCO3(118 m2/g), CaCO3(43 m2/g) and MnCO3 (122 m2/g) were also confirmed by the corresponding N2 sorption analyses.
Keywords: Nanomaterials; Straw-like; Porosity; Carbonate; Ionic liquid;

Aluminum-doped ZnO nanorod array by thermal diffusion process by Yongseon Kim; Shinhoo Kang (1065-1067).
Aluminum doped ZnO nanorod array was prepared: ZnO nanorod was grown firstly by hydrothermal process and then aluminum was doped by spincoating and thermal treatment. This doping process neither disturbs growth condition of ZnO, nor imposes severe damages. Thus, it is possible to examine the doping effect of aluminum. Changes in the electrical and optical properties were measured as a function of aluminum content. It was found that aluminum doping enhances UV emission and electrical conductivity. This result confirms that N-type doping of aluminum can be accomplished effectively by this process. The doping amount can be controlled just by changing the number of spincoats.
Keywords: Nanomaterials; Zinc oxide; Al-doping; Electrical properties; Optical properties;

Synthesis of ZnS nanoparticles into the pore of mesoporous silica spheres by Yaoxia Li; Yihua Zhu; Cuiyan Li; Xiaoling Yang; Chunzhong Li (1068-1070).
The ZnS nanoparticles were exclusively synthesized in the pores of the mesoporous silica (MS) particles which had been coated with two bilayers of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) via the layer-by-layer (LbL) self-assembly technique. Measurements and analysis of XRD and TEM showed that the ZnS nanocrystals were inserted into the pores of the MS spheres. This approach can be used to prepare composite materials involving functional inorganic nanoparticles which have potential application in biological immunoassay and photoelectronic fields.
Keywords: Nanomaterials; Porosity; Semiconductors; Mesoporous silica; Layer-by-layer;

Novel and simple synthesis of ZnO nanospheres through decomposing zinc borate nanoplatelets by Yumei Tian; Huiming Ma; Lianchun Shen; Zichen Wang; Yuning Qu; Shengli Li (1071-1073).
Spherical zinc oxide (ZnO) nanoparticles had been successfully synthesized through decomposing zinc borate nanoplatelets at high temperature. The resulted ZnO nanospheres were characterized by X-ray diffraction (XRD), which indicated that ZnO had the hexagonal structure. Field-emission-scanning electron micrographs (SEM) revealed that ZnO nanoparticles had perfect spherical shape with narrow size distribution (average diameters 50 nm). These nanoparticles showed a broad emission band centered at 438 nm using an excitation wave of 325 nm at room temperature. Moreover, the sample was characterized by N2 adsorption–desorption and the pore size distribution showed a sharp peak at 3.1 nm.
Keywords: Zinc oxide; Luminescence; Composite materials; Nanospheres; Nanomaterials;

Nanocrystalline nickel as a material with high hydrogen storage capacity by D. Vojtěch; A. Michalcová; M. Klementová; J. Šerák; M. Morťaniková (1074-1076).
In the present work a nano-crystalline nickel powder is prepared by selective leaching of a rapidly solidified Al–20Ni ribbon in aqueous sodium hydroxide. Almost spherical powder particles of 50–150 nm in size consist of grains having diameters in a range of 2–5 nm. Elemental analysis shows a very high gravimetric density of hydrogen in the powder of 2.6 wt.%. Mass spectrometry reveals that hydrogen desorbs from the powder at 80–150 °C.
Keywords: Electron microscopy; Nanomaterials; Nano-crystalline nickel; Hydrogen storage; Rapid solidification;

Synchrotron based reciprocal space mapping and dislocation substructure analysis by F. Hofmann; X. Song; S. Eve; S.P. Collins; A.M. Korsunsky (1077-1081).
During plastic deformation of FCC materials, dislocation density does not evolve uniformly but a dislocation cell/wall structure is formed. X-ray diffraction reciprocal space mapping is used to investigate this substructure within a single grain in a large grained aluminium polycrystal. A simple dislocation cell/wall model capable of computing numerical reciprocal space maps is presented. The model qualitatively captures the experimentally observed features.
Keywords: Characterisation methods; Crystal structure; Defects; X-ray techniques; Reciprocal space map; Dislocation substructure;

Mechanical properties of sputter-deposited nanocrystalline Cr3Si film by Jiang Xu; Jian Sun; Shuyun Jiang (1082-1084).
The sputter-deposited Cr–Si film prepared by glow discharge was comprised of equiaxed nanocrystalline Cr3Si with a grain size of less than 5 nm. The hardness of the nanocrystalline Cr3Si film was 2.37 times higher than that of coarse-grained Cr3Si, whereas the elastic modulus of nanocrystalline Cr3Si was equal to that of coarse-grained Cr3Si. Compared with the coarse grain of Cr3Si, the sputter-deposited nanocrystalline Cr3Si film exhibited higher ductility or toughness due to the GB-mediated deformation.
Keywords: Thin films; Mechanical properties; Nanomaterials; Intermetallic alloys and compounds;

A precursor nanowire templated route to CdS nanowires by Xiao-Lin Liu; Ying-Jie Zhu (1085-1088).
We report the synthesis of the Cd-cysteine precursor nanowires using CdCl2·2.5H2O, L-cysteine and ethanolamine in the solvent of water at room temperature. The average diameter and lengths of Cd-cysteine precursor nanowires are 200 nm and several hundred microns, respectively. The precursor nanowires are used as the source materials for cadmium and sulfur and the template for the subsequent preparation of CdS nanowires using ethylene glycol as the solvent by a solvothermal method at 200 °C. The formation process of CdS nanowires is discussed. The samples are characterized using X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy.
Keywords: Nanomaterials; Crystal growth; CdS; Nanowire; L-cysteine; Solvothermal;

Microstructure and fundamental properties of nanostructured gadolinium (Gd) by Nianduan Lu; Xiaoyan Song; Jiuxing Zhang (1089-1092).
The nanoparticles and nanocrystalline bulk of pure gadolinium (Gd) were prepared by a novel route. The nanostructures of the single particle and the bulk of Gd were investigated, and the crystal structure was characterized. The fundamental properties, namely the physical, thermal, and mechanical characteristics, were studied for the prepared Gd bulk with an ultrafine nanograin structure. As compared with the conventional polycrystalline metal, the ultrafine nanocrystalline Gd has greatly enhanced functional and structural properties. The physical background for the changes of the fundamental properties with the reduction of the grain size to the nanoscale was analyzed.
Keywords: Gadolinium; Nanomaterials; Sintering; Physical properties;

ZnO–Au hybrid nanocrystals via a high temperature reflux route by Xue Han; Win-Jing Qin; Jing Sun; Jing Yang; Kai-Yang Niu; Hong-Li Wang; Xi-Wen Du (1093-1095).
ZnO–Au hybrid nanocrystals with good dispersibility and uniform size are prepared via a high temperature reflux route. The structure, morphology, interface structure and optical properties were characterized by X-ray diffraction high resolution transmission electron microscope and UV–vis absorption spectrophotometer. The formation of hybrid nanocrystals was believed to arise from the heterogeneous nucleation and epitaxial growth, high temperature and surfactant are proposed as the key factors for producing fine and uniform hybrid nanocrystals.
Keywords: Hybrid nanocrystals; Epitaxial growth; High temperature reflux; Electron microscopy;

A new yellowish green luminescent material SrMoO4:Tb3+ by Xu Li; Zhiping Yang; Li Guan; Qinglin Guo (1096-1098).
A novel yellowish green phosphor tervalent terbium (Tb3+) doped strontium molybdate (SrMoO4) was synthesized by conventional solid-state reaction method and its crystal structure and luminescent properties are investigated in this paper. The X-ray diffraction patterns (XRD) showed that the phosphor sintered at 750 °C for 3 h was a pure SrMoO4 phase. The excitation spectrum consisted of two bands and the two excitation peaks located at 375 nm and 488 nm respectively. The emission spectrum was composed of four narrow bands, in which the strongest emission was located at 548 nm. The particle size analysis indicated that the median particle size D 50  = 2.89 μm and range of particle size distribution was narrow. These results showed that the SrMoO4:Tb3+ phosphor was a promising yellowish green phosphor for ultraviolet light emitting diode (UVLED) and blue LED based white LED. The appropriate concentration of Tb3+ was 5 mol% for the highest emission intensity at 548 nm. Natrium ion (Na+) was found to be a promising charge compensator for SrMoO4:Tb3+ phosphor.
Keywords: Luminescence; SrMoO4:Tb3+; Phosphor;

A series of uniform spinel ferrite MFe2O4 (M = Ni, Co, Mn, and Zn) nanoparticles (NPs) were successfully synthesized on a large scale by direct hydrothermal decomposition of the trinuclear heterometallic oxo-centered acetate cluster of [MFe2O(CH3CO2)6(H2O)3]nH2O in solution. The crystal structure, composition and size of the synthesized NPs were characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometer (ICP-AES), transmission electron microscope (TEM) and high-resolution (HRTEM). Magnetic investigation revealed that all the synthesized MFe2O4 NPs showed superparamagnetic properties at room temperature. The possible formation mechanism was also proposed.
Keywords: Spinel ferrite; Nanoparticle; Hydrothermal; Acetate cluster; Magnetic materials;

The oriented ZnO nanowire-covered TiO2 nanoparticle composite film electrodes were fabricated by screen-printed TiO2 nanoparticle layer on conducting glass and low-temperature hydrothermal growth of ZnO nanowires. The film morphology, composition and crystalline structure were confirmed by field-emission scanning electron microscopy, energy dispersive X-ray spectra and X-ray diffraction patterns respectively. Dye-sensitized solar cells based on the composite electrode gained short-circuit current density of 8.04 mA/cm2, open-circuit photovoltage of 0.67 V, fill factor of 0.40, and overall conversion efficiency of 2.15%.
Keywords: Nanowire; Composite electrode; Solar cells; Hydrothermal method;