Journal of Alloys and Compounds (v.574, #C)

Full title (iii).

Keywords (I-II).

Removal of metallic impurities from Ti binary alloy scraps using hydrogen plasma arc melting by Jung-Min Oh; Back-Kyu Lee; Chang-Youl Suh; Jae-Won Lim (1-5).
In the present study, we produced button ingots using hydrogen plasma arc melting (HPAM), which enabled refining while suppressing the loss of alloy components as much as possible, in order to recycle Ti–Ni, Ti–Mo, and Ti–Al alloy scraps. When 20% hydrogen was added and the scraps were melted for 20 min, the weight losses were <1%, which is nearly no loss of components. The removal degrees (RD) of impurities for the Ti–Ni, Ti–Mo, and Ti–Al alloys were 82.6%, 86.2%, and 49.1%, respectively. The Ti–Ni and Ti–Mo alloys showed a refining effect nearly identical to the level of RD for pure titanium obtained in the same way. In contrast, the refining effect for the Ti–Al alloy was not as good as those for the other alloys because of the properties of the alloy component, Al.
Keywords: Titanium alloy; Recycling; Hydrogen plasma; Refining; Metallic impurity; GDMS;

Supercritical fluid chemical deposition of Pd nanoparticles on magnesium–scandium alloy for hydrogen storage by Samuel Couillaud; Marina Kirikova; Warda Zaïdi; Jean-Pierre Bonnet; Samuel Marre; Cyril Aymonier; Junxian Zhang; Fermin Cuevas; Michel Latroche; Luc Aymard; Jean-Louis Bobet (6-12).
The deposition of Pd nanoparticles on the binary compound Mg0.65Sc0.35 using the Supercritical Fluid Chemical Deposition (SFCD) method was performed. There, the SFCD operating parameters (co-solvent, temperature, CO2 and hydrogen pressure, reaction time) have been optimized to obtain homogeneous deposition of Pd nanoparticles (around 10 nm). The hydrogenation properties of the optimized Pd@Mg0.65Sc0.35 material were determined and compared to those of Mg0.65Sc0.35Pd0.024. The latter compound forms at 300 °C and 1 MPa of H2 a hydride that crystallizes in the fluorite structure, absorbs reversibly 1.5 wt.% hydrogen and exhibits fast kinetics. In contrast, Pd@Mg0.65Sc0.35 compound decomposes into ScH2 and MgH2 during hydrogen absorption under the same conditions. However, reversible sorption reaches 3.3 wt.% of hydrogen while keeping good kinetics. The possible roles of Pd on the hydrogen-induced alloy decomposition are discussed.
Keywords: Nanoparticles; Supercritical fluid chemical deposition method; Hydrogen storage;

Dual-metal nanoparticles were simultaneously embedded into amorphous carbon (a-C) matrix at room temperature. As-deposited Au/a-C/Fe sandwich composite multilayer films were fabricated by alternating multitarget pulsed laser deposition. More sp2 carbon content, narrower Tauc optical gap and stronger photoluminescence intensity of the amorphous carbon films were observed after metal-embedding. Especially for Au/a-C/Fe sandwich films, the fullerene-like microstructure demonstrated that the dual-metal embedding modulated greatly the intrinsic structure and properties of the a-C films. These results were attributed primarily to the extended state around the metal deep level in the band gap and the narrowing of the π and π band edge states. The metal deep level defects contributed chiefly to non-radiative recombination.
Keywords: Amorphous carbon; Pulsed laser deposition; Photoluminescence;

A thermodynamic parameter θ, defined as the multiplication of the mixing entropy and mismatch entropy, is proposed to evaluate the glass-forming ability of Al-based amorphous alloys, and then it is refined into θ/M by the kinetic parameter M, which exhibits a better proportional correlation with GFA than θ for Al-based amorphous alloys in the same alloy system.
Keywords: Thermodynamics; Kinetics; Glass-forming ability;

CaSnSiO5:Dy3+ exhibits white-light long persistent and photo-stimulated luminescence properties, originated from both the emission band of the host extending from UV to blue and the characteristic transitions 4F9/2  →  6HJ of Dy3+. Shallow and deep traps are evidenced by the thermoluminescence (TL) and positron annihilation (PA) techniques. TL glow curve of the material with low Dy3+ content exhibits a single band located around 300 K, which is quite favorable for room temperature persistent luminescence. The low-temperature TL band is suppressed with increasing Dy3+ concentration, while the intensity of the high temperature TL band (520 K) increases and finally becomes the dominant band. It is worth noting that the presence of deep traps being able to immobilize the carriers permanently at room temperature. Under 980 nm-light stimulation, a small part of the stored energy could be released and contribute to the observation of the weak white-light emitting. PA results demonstrate that it is attributed to the creation of the cluster defects 2 Dy Ca • · V Ca ″ with increasing Dy3+ concentration, which make it more difficult for trapped carriers to be released at room temperature.
Keywords: Persistent luminescence; Photo-stimulated luminescence; Thermoluminescence; Traps;

This paper reports the preparation of Cu2ZnSnSe4 (CZTSe) nanocrystals via a method under nitrogen atmosphere at a temperature of 235 °C using elemental copper, zinc, tin, and Se powders as precursors, and isophorondiamine (IPDA) as a coordinating solvent. We investigated the influence of reaction time on the crystal structure, shape, particle size, optical properties, and composition of the nanocrystals. We also carried out a systematic study of the growth and evolution pathways of quaternary CZTSe nanocrystals in the IPDA solution. The reaction began with the formation of binary and ternary crystals, which subsequently transformed into Cu2ZnSnSe4 nanocrystals. These binary and ternary compounds dissolved during the course of the reaction to produce the molecular precursor used in the formation of monophasic Cu2ZnSnSe4 nanocrystals. Experimental results indicate that the phase changes in CZTSe nanocrystals are time-dependent. Spherical CZTSe nanocrystals with diameters in the range of 20–30 nm were obtained at 20 h. Characterization using X-ray diffraction (XRD) confirmed the as-synthesized CZTSe as single-phase quaternary nanocrystals with a stannite structure. The band gap energy of the as-synthesized CZTSe nanocrystals is 1.6 eV. The proposed process of synthesizing CZTSe nanocrystals is applicable to the production of inexpensive thin film solar cells using a relatively simple, low cost, and convenient coordinating solvent route.
Keywords: Cu2ZnSnSe4; Nanocrystals; Synthesis; Isophorondiamine; Stannite structure; Band gap;

Experimental investigation of phase equilibria in the Co–Si–Zr ternary system by C.P. Wang; G.M. Tao; W.W. Xu; S.Y. Yang; C.C. Zhao; H.P. Xiong; X.J. Liu (33-40).
The phase equilibria in the Co–Si–Zr ternary system were investigated by means of back-scattered electron (BSE), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Two isothermal sections of the Co–Si–Zr ternary system at 1273 and 1373 K were experimentally established, and the compositions of the two ternary compounds (Zr5Co8Si9 and Zr4Co4Si7) were confirmed. The isothermal sections of the system at 1273 and 1373 K respectively consist of 29 and 30 three-phase regions, and also six ternary compounds was found in both two isothermal sections. The solubility of Zr in the intermediate and solution phases (i.e. αCo2Si, αCoSi, CoSi2, αCo and εCo) at the Co–Si side is extremely small, whereas the situation of Si in the Co-rich corner (especially for Co23Zr6 and Co2Zr phases) is reverse.
Keywords: Ternary alloy systems; Phase diagrams; Electron microprobe; Microstructure;

Pressure rate controlled unified constitutive equations based on microstructure evolution for warm hydroforming by Lihui Lang; Pingmei Du; Baosheng Liu; Gaocan Cai; Kangning Liu (41-48).
A viscoplastic model considering the influence of microscopic evolution and macroscopic deformation has been developed to represent the deformation behavior of material in warm sheet hydroforming process. Based on a hydroforming environment, a set of rate dependent constitutive equations, which is constructed by using the pressure rate, the evolution of dislocation density and kinematic isotropic hardening, has been proposed to predict stress–strain response of material. The non-linear Chaboche’s isotropic hardening criterion is also modified to characterize the instantaneous state of hardening considering microstructure evolution. Different from traditional sheet plastic forming process, the rate of fluid pressure variation is a significant factor that can determine the forming speed. Therefore, the pressure rate is applied to be one factor that can influence the deformation of material in warm hydroforming. The hydraulic bulge experiments on aluminum alloy at warm temperature indicated that the deformation behavior of material is sensitive to pressure rate. The genetic algorithm optimization technique was used to determine the optimum values of a set of free material constants associated with the proposed constitutive model. The computed data has been in a good agreement with the test data on the basis of the optimized material constants.
Keywords: Constitutive equations; Pressure rate; Warm hydroforming; Dislocation density; Non-linear isotropic hardening;

Self-assembled synthesis of TiO2/TiB2 nanowall and its photocatalytic properties by Fei Huang; Aihua Yan; Zhengyi Fu; Shibin Yin; Fan Zhang; Yinghuai Qiang (49-53).
The products are dominated by a kind of core/shell samples with nanowall structure when ethylenediamine (EDA) was added to the solution. The high-density nanosheets with about 10 nm in thickness stand on the cores. After annealing at 400 °C for 3 h, the nanosheets evolve to numerous nanoparticles. One possible explanation is that EDA takes part in the reaction and induces the growth of nanowall. Photocatalytic activity experiment indicates that nanowall samples have better decolorization rate than commercial P-25 TiO2.Display OmittedTiO2/TiB2 nanowall has been successfully synthesized by a facile hydrothermal approach in the hydrogen peroxide (H2O2) solution with ethylenediamine (EDA). The microstructure and morphology can be easily controlled by EDA. The formation mechanism has been discussed in detailed. Photocatalytic activity experiment indicates that nanowall has better decolorization rate than commercial P-25 TiO2. UV–vis spectra show that both broadening absorption peak and the absorption edge for such system shift to a lower energy state, which result in higher photocatalytic activity compared to commercial P-25 TiO2 catalyst. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX) spectrum indicate that the shift of absorption peak and absorption edge may result from N-doping in TiO2/TiB2 nanowall system.
Keywords: TiO2/TiB2 nanowall; Hydrothermal approach; Hydrogen peroxide; Photocatalytic activity;

Preparation and photoluminescence of some europium (III) ternary complexes with β-diketone and nitrogen heterocyclic ligands by Dunjia Wang; Yan Pi; Chunyang Zheng; Ling Fan; Yanjun Hu; Xianhong Wei (54-58).
Display OmittedPreparation and photoluminescence behavior of four new europium (III) ternary complexes with β-diketones (1-(6-methoxy-naphthalen-2-yl)-3-phenyl-propane-1,3-dione (MNPPD) and 1-(4-tert-butyl-phenyl)-3-(6-methoxy-naphthalen-2-yl)-propane-1,3-dione (BPMPD)) and 2,2-dipyridine (Bipy) or 1,10-phenanthroline (Phen) were reported, in the solid state. Complexes Eu(MPPD)3·Bipy, Eu(BMPD)3·Bipy, Eu(MPPD)3·Phen and Eu(BMPD)3·Phen were characterized by elemental analysis, FT-IR, 1H NMR, UV–vis absorption. The emission spectra show narrow emission bands that arise from the 5D0  →  7F J (J  = 0–4) transitions of the europium ion. Based on the emission spectra and luminescence decay curves in solid state, the intensity parameters (Ωt ), lifetime (τ) and emission quantum efficiency (η) were determined. The Ω 2 values indicate that the Eu(III) ion in these complexes is in a highly polarizable chemical environment. Complexes Eu(MPPD)3·Bipy and Eu(MPPD)3·Phen showed a longer lifetime (τ) and a higher luminescence quantum efficiency (η), which indicated that the energy transfer to the europium ion from MNPPD ligand is more efficient than that from BPMPD ligand.
Keywords: Europium (III) ternary complex; Photoluminescence behavior; Luminescent lifetime; Quantum efficiency; Judd–Ofelt intensity parameters;

The effect of the temperature on the electrochemical properties of the hydrogen storage alloy for nickel–metal hydride accumulators by C. Khaldi; S. Boussami; M. Tliha; S. Azizi; N. Fenineche; O. El-Kedim; H. Mathlouthi; J. Lamloumi (59-66).
The electrochemical properties of The LaNi3.55Mn0.4Al0.3Co0.75 alloy as a negative electrode material of a nickel–metal hydride accumulator have been investigated at different temperatures. The Activation of the alloy becomes faster with an increasing temperature. The enthalpy, the entropy and the apparent activation energy of the LaNi3.55Mn0.4Al0.3Co0.75H x hydride formation are evaluated. The calculated results show that the enthalpy change, the entropy change and the activation energy are (−29 kJ mol−1), (26.5 JK−1  mol−1) and (24.6 kJ mol−1), respectively. The corrosion current density increases with increasing the temperature and the corrosion potential becomes more positive and increases linearly with the temperature. This result is confirmed by the values of corrosion film resistance and the corrosion film capacitance determined through the electrochemical spectroscopy impedance modeling.
Keywords: Nickel metal–hydride accumulator; Electrochemical methods; Enthalpy change; Activation energy; Corrosion parameters;

Effects of oxygen vacancy on the electrical and magnetic properties of anatase Fe0.05Ti0.95O2− δ films by Q.H. Li; L. Wei; Y.R. Xie; F. Jiang; T. Zhou; G.X. Hu; J. Jiao; Y.X. Chen; G.L. Liu; S.S. Yan; L.M. Mei (67-70).
Epitaxial anatase Fe0.05Ti0.95O2− δ (δ: oxygen vacancy) thin films were grown on LaAlO3 substrates by pulsed laser deposition. Structural characterizations by X-ray diffraction confirmed the incorporation of substituting Fe atoms into anatase TiO2 lattice, no impurity phases or clusters formation were detected. The influence of growth oxygen pressure on the crystal structure and properties of Fe0.05Ti0.95O2− δ semiconductor films has been investigated systematically. As the oxygen pressure decreases, more oxygen vacancies are generated in the thin film. At the same time, the optical band gap narrows down and the electrical properties improve correspondingly. Room temperature ferromagnetism was observed in all samples and saturation magnetization increased from 0.8 emu/cm3 to 8.3 emu/cm3 with the increase of oxygen vacancy concentration. Strong correlation between ferromagnetism and oxygen vacancy density was established. This is explained by a modified bounded magnetic polaron model.
Keywords: Semiconductors; Magnetic materials; Anatase; Epitaxial films;

FeNi-based alloys commonly called Permalloys are interesting in their applications as soft magnetic materials with low coercivity and high permeability. In this study, nanocrystalline Fe–50 wt.% Ni alloy powders were prepared using a planetary ball mill at different milling times. The evolution of the microstructure and magnetic properties during the milling process were studied by the X-ray diffraction technique, the scanning electron microscope, the transmission electron microscope and the vibrating sample magnetometer. The results indicate that in the course of ball milling the Fe and Ni mixture, nanocrystalline FCC γ-(Fe, Ni) phase with the average crystallite size of 15 nm, particle size of 39 μm, nonuniform lattice strain of 0.45% and lattice parameter of 0.36062 nm formed after 24 h milling time. Although the crystallite size of the as-synthesized Permalloy powder is smaller than the magnetic exchange length, a low coercivity as expected from Herzer’s random anisotropy model is not observed. Among the different reasons, residual stress, γ-(Fe, Ni) phase formation and contamination are suggested as possible causes, which affect both coercivity and saturation magnetization.
Keywords: 50 Permalloy; Mechanical alloying; Curie temperature; Nanocrystalline; High angle grain boundary structure;

The titanium dioxide (TiO2) material has attracted great attentions because of its wide application in photocatalyst and optoelectronics devices. The microstructure and photoluminescence behavior of TiO2 thin films are related to the fabrication and annealing methods. In this article, the amorphous titanium oxide thin films were prepared by sol gel process with a mixture of tetraisopropyl orthotitanate, acetonylacetone, distilled water and alcohol at various molar ratios and then spin-coated on the p-Si(1 0 0) substrate. Subsequently, the CO2 laser irradiation at a power of 1.5 W was utilized for annealing treatment to form crystalline rutile TiO2 instead of conventional furnace annealing. The evolution of microstructure, bonding and photoluminescence (PL) of TiO2 films were characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy, Fourier transform infrared spectrometer and PL spectrometer. GIXRD showed that the crystalline phase of TiO2 after 1.5 W laser annealing was rutile. The PL spectra of annealed films covered broad wavelengths of 350–800 nm which extends conventional ultraviolet range. They can be deconvoluted into three peaks at about 411, 441 and 534 nm which were attributed to the lattice emission, deep-level emissions from oxygen vacancies and defect states from bonding of extra impurities of Ti, O and C in rutile TiO2 together with residual organics. The relationship between the process parameters, microstructure, bonding and PL behavior were further discussed and established.
Keywords: Titanium dioxide; Sol–gel; Laser annealing; CO2 laser;

Effects of Mn-doping on the properties of (Ba0.92Ca0.08)(Ti0.95Zr0.05)O3 lead-free ceramics by Xiang-Ping Jiang; Lu Li; Chao Chen; Xin-Jia Wang; Xiao-Hong Li (88-91).
Display OmittedLead-free piezoelectric ceramics (Ba0.92Ca0.08)(Ti0.95Zr0.05)O3xmol%Mn (BCTZ–xMn) were synthesized by a traditional solid-state reaction. Effects of Mn addition on the microstructure and electrical properties of ceramics were investigated in the composition range of 0 ⩽  x  ⩽ 2.2. High mechanical quality factor of Q m  = 921 and low dielectric loss of tan  δ  = 0.3% have been obtained at x  = 2.0. With the increase of Mn content, the piezoelectric constant d 33 and planar electromechanical coupling coefficient k p decrease with deviation from the polymorphic phase transition (PPT) region, and the Curie temperature T C gradually decreases. The relative high d 33, k p and T C still maintain about 224 pC/N, 33.6% and 102 °C at x  = 2.0, respectively. These results indicate that the BCTZ–xMn ceramics are promising candidate for the lead-free piezoelectric applications.
Keywords: Ceramics; (Ba0.92Ca0.08)(Ti0.95Zr0.05)O3; Mechanical quality factor; Piezoelectricity;

Precipitation evolution in Al–Er–Zr alloys during aging at elevated temperature by S.P. Wen; K.Y. Gao; H. Huang; W. Wang; Z.R. Nie (92-97).
The temporal evolution of the Al3(ErZr) precipitates is investigated in Al–0.04Er–0.04Zr and Al–0.04Er–0.08Zr alloys during aging at elevated temperature of 450 and 500 °C. The results show that the coarsening behavior of the precipitates in both alloys is similar, due to the core–shell structure with Zr segregated in the shell of the Al3(ErZr) precipitates. With the increase of the amount of Zr addition, the misfit between the precipitate and the Al matrix decreases, consequently the coherency transition size of the precipitates in Al–0.04Er–0.08Zr is larger than that of Al–0.04Er–0.04Zr. After aging at 500 °C for 100 h, some of the precipitates in Al–0.04Er–0.08Zr transform to D023 structure due to the high Zr/Er ratio, while the precipitates in Al–0.04Er–0.04Zr keep the L12 structure.
Keywords: Aluminum alloy; Precipitation; Erbium; Zirconium;

Creep behaviour of eutectic tin–bismuth (SnBi) and its constituent phase materials was studied using constant strain rate (CSR) nanoindentation. Eight strain rates from 5 × 10−4 to 0.1 s−1 were used to assess their strain rate–stress relationship. The stress exponents of 12.25 and 10.09 were found for Sn–3%Bi and pure Bi, respectively, suggesting power-law breakdown (PLB) as the rate controlling mechanism for the two constituent single-phase materials. Strain bursts that appear at the initial stage of loading of the single-phase materials were found to be a prerequisite to cause dislocation creep at the later stage of deformation. Grain boundary sliding (GBS) was found as the complementary mechanism to accommodate grain shape change in Sn–3%Bi and pure Bi as proven by post-indent microstructural examination. Eutectic SnBi showed bi-linear strain rate dependent creep behaviour with the transition at around 2 × 10−3  s−1. Stress exponent of 2.35 was found at low strain rate region suggesting that GBS dominates the creep deformation. At the high strain rate region, stress exponent of 5.20 suggests that dislocation climb in the crystal lattice is the creep mechanism.
Keywords: Nanoindentation; Creep; Tin–bismuth; Constant strain rate; Strain burst;

Preparation and characterization of electrodeposited ZnO and ZnO:Co nanorod films for heterojunction diode applications by Yasemin Caglar; Andaç Arslan; Saliha Ilican; Evrim Hür; Seval Aksoy; Mujdat Caglar (104-111).
Well-aligned undoped and Co-doped nanorod ZnO films were grown by electrochemical deposition onto p-Si substrates from an aqueous route. Aqueous solution of Zn(NO3)2⋅6H2O and hexamethylenetetramine (HMT) were prepared using triple distilled water. Two different atomic ratios of Co(NO3)2⋅6H2O were used as a dopant element. Electrodepositions were carried out in a conventional three electrode cell for the working electrode (p-Si), reference electrode (Ag/AgCl, sat.) and counter electrode (platin wire). The effects of Co doping on the structural, morphological and electrical properties of ZnO films were investigated. X-ray diffraction (XRD) measurement showed that the undoped ZnO nanorod film was crystallized in the hexagonal wurtzite phase and presented a preferential orientation along the c-axis. Only one peak, corresponding to the (0 0 2) phase, appeared on the diffractograms. The lattice parameters and texture coefficient values were calculated. The nanorods were confirmed by the field emission scanning electron microscopy (FE-SEM) measurements. The FE-SEM image showed that the ZnO nanorods grow uniformly on the substrates, providing a surface with fairly homogeneous roughness. The surface morphology was transformed into uniform multi-oriented rods with incorporation of Co. Co-doped ZnO nanorod films showed a multi-oriented spear-like structure. The diffuse reflectance spectra of the films were measured and the optical band gap values were determined using Kubelka–Munk theory. The van der Pauw method was used to measure the sheet resistance of the films. The sheet resistance was affected significantly by Co content. The pn heterojunction diodes were fabricated and the diode parameters were determined from the analysis of the measured dark current–voltage curves. Rectifying behavior was observed from the IV characteristics of these heterojunction diodes.
Keywords: Co-doped ZnO; Nanorod; Electrodeposition method; Kubelka–Munk; Sheet resistance; Heterojunction diode;

Structure, thermodynamic behavior and static magnetic properties of Al addition FeCoNbCuB alloy ribbons by Xin Wang; Li Zhang; Longjiang Deng; Jianliang Xie; Difei Liang (112-118).
The effect of Al addition on the crystallization process and thermodynamic behavior of FeCoNbCuB melt-spinning quenched ribbon alloy is reported. There was no boride phases formed during differential scanning calorimetry observation in Al addition alloy. The section morphology of Al addition as-quenched ribbon showed a vertical variation structure. There were totally different crystalline structures observed on the both sides of Al addition ribbon, with highly crystallized AlCo phase on the upper side and amorphous phase on the wheel side. Al was found to be precipitated from the upper side, and Cu precipitated from the wheel side after vacuum annealing. We also demonstrated that 7.5% aluminum addition would embrittle the alloy ribbon, but without decreasing saturation magnetization and increasing coercivity in terms of static magnetic properties. Only a strong magnetic perpendicular anisotropy was induced in alloy with Al addition after heat treatment.
Keywords: Nanostructured materials; Crystal structure; Thermal analysis; Magnetic measurements;

Display OmittedShape setting (stress relaxation) process which is generally defined by heating an elastically constrained material is used as an industrial technique for fixing accuracy of shape, and sometimes deformation of some materials specially those which have high spring back property. The present study attempts to explore stress relaxation process during heating an elastically constrained material using basic concepts of continuum mechanics, and lumped element modeling. Hence, Ni rich-NiTi wires were deformed elastically and their fixed strain during heat treatment (ε) was measured gradually by increasing the stress relaxation time (t). The εt curve was found to be a possible answer for a differential equation between discreet elements of the continuum specimen (NiTi wire). Ultimately, a white box model was expanded for predicting this phenomenon using general concepts of diffusion in solids. Results of the investigation illustrate that stress relaxation process depends on the temperature of shape setting process, chemical composition of the material, the amount of strain fixed in the material and also activation energy of diffusion.
Keywords: Metals and alloys; Diffusion; Shape memory;

Structural parameters, band-gap bowings and phase diagrams of zinc-blende Sc1−x In x P ternary alloys: A FP-LAPW study by William López-Pérez; Nicolás Simon-Olivera; Javier Molina-Coronell; Alvaro González-García; Rafael González-Hernández (124-130).
Using first-principles total-energy calculations, we investigate the structural, electronic and thermodynamic properties of the cubic Sc1−x In x P semiconducting alloys. The calculations are based on the full-potential linearized-augmented plane wave (FP-LAPW) method within density functional theory (DFT). The exchange–correlation effect is treated by both local-density approximation (LDA) and generalized-gradient approximation (GGA). In the latter approach, both Perdew-Burke-Ernzerhof (PBE) and EngelVosko (EV) functional of the exchange–correlation energy were used. The effect of atomic composition on structural parameters, band-gap energy, mixing enthalpy and phase diagram was analyzed for x  = 0, 0.25, 0.5, 0.75, 1. Lattice constant, bulk modulus, and band-gap energy for zinc-blende Sc1−x In x P alloys show nonlinear dependence on the aluminium composition x. Deviations of the lattice constant from Vegard’s law, and deviations of the bulk modulus and band-gap energy from linear concentration dependence (LCD) were found. The variation of the calculated equilibrium lattice constant versus indium concentration shows a small deviation from Vegard’s law with upward bowing parameter of −0.043 Å and −0.058 Å for PBE and LDA, respectively. The bulk modulus as a function of indium composition shows a small deviation from the linear concentration dependence (LCD) with upward bowing equal to −0.790 GPa using PBE, and with net downward bowing of 0.847 GPa using LDA. The results show that the band gap undergoes a direct (X  →  X)-to-direct (Γ  →  Γ) transition at a given indium composition x. The physical origin of the band-gap bowing in zinc-blende Sc1−x In x P semiconducting alloys was investigated. The calculated excess mixing enthalpy is positive over the entire indium composition range.
Keywords: Density functional calculations; Structural properties; Electronic properties; Thermodynamic properties;

Synthesis and size dependent exchange bias effect in CoCr2O4/Cr2O3 nanogranular systems by Zhaoming Tian; Shuai Huang; Songliu Yuan; Junfeng Wang (131-135).
Structure and magnetic properties have been investigated on the nanogranular systems of ferrimagnetic (Ferri) CoCr2O4 nanoparticles embedded in antiferromagnetic (AFM) Cr2O3 matrix, synthesized by a phase segregation route from diluted Cr2(1− x )Co2 x O3 (x  = 0.1) oxides. The CoCr2O4 nanoparticles with average particle size (D CCO) from 8 to 60 nm can be produced by varying synthesis temperatures. Magnetization measurement show that, both exchange bias fields (H EB) and vertical magnetization shift (M Shift) can be found at 10 K after field-cooled from 350 K. With increasing particle size (D CCO), both H EB and M Shift decrease monotonically and finally disappear as particle size is above 60 nm. The linear relationship between H EB and M Shift indicates that the interfacial frozen uncompensated spins play a critical role in inducing exchange bias effect.
Keywords: Exchange bias; Antiferromagnetic;

Sustainable preparation of Li(FeM)PO4/C from converter sludge and its electrochemical performance as a cathode material for lithium ion batteries by Zhong-Fang Zhang; Zhao-Jin Wu; Shi-Huai Su; Zhi-Fang Gao; Liao-Sha Li; Xing-Rong Wu (136-141).
Li(FeM)PO4/C (M  = Mg, Al, Zn and Mn) cathode material for lithium ion batteries is prepared by using converter sludge as a raw material through a sustainable wet chemistry method. The valuable elements (Fe, Mg, Al, Zn and Mn) are recovered from converter sludge through acidolysis process, and used as source materials of Fe and dopants for preparing Li(FeM)PO4/C. XRD and SEM analyses show that the obtained Li(FeM)PO4/C delivers single olivine-type phase with higher crystallinity, and presents a fine particle size less than 100 nm and a homogeneous elemental distribution in its contexture. Especially, Li(FeM)PO4/C prepared from the sludge gives outstanding capacity of 157, 154, 143, 127 and 118 mA h g−1 at a current density of 15, 75, 150, 300 and 750 mA g−1, respectively, and exhibits excellent cycling performance. The results demonstrate that a novel route to synthesize Li(FeM)PO4/C cathode material for lithium ion batteries by utilizing converter sludge as a abundant and inexpensive source of iron and dopants has been proposed.
Keywords: Cathode material; Converter sludge; LiFePO4/C; Multi-doping; Recycling;

With increasing sintering temperature, the emission intensities around 593, 612 and 626 nm (in the visible light range) first increase from 260 to 1300 °C, and then decrease due to the temperature quenching effect. However, the emission around 700 nm monotonously decreases with increasing the sintering temperature, originating from the variation of the outside surroundings of Eu3+ instead of the temperature quenching effect, which is useful in PDP application.Display OmittedYBO3:Eu3+ phosphors with different morphologies such as flower-like, spherical-like and cake-like have been hydrothermally synthesized without any additives by simply adjusting the B3+ sources, stirring speeds and initial solution pH values. During the hydrothermal reaction, stirring with suitable speed can reduce particle size and obtain more uniform size distribution. The emission intensity can be distinctly enhanced by stirring and post-annealing due to the micro-structural improvement and better crystallization. Interestingly, the weak acidity (pH = 6) in the initial solution or post-annealing enhances the emission in the wavelength range of visible light, and weakens the emission around 700 nm due to weakened distortion of the outside surroundings of Eu3+, which is useful in Plasma Display Panel (PDP) application.
Keywords: Nanostructures; Chemical synthesis; Luminescence;

Fe–doped ZnO (ZnO:Fe) thin films were successfully prepared by radio frequency magnetron sputtering under different substrate temperatures. The properties of ZnO:Fe films were systematically studied via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), ultraviolet visible spectrophotometer and fluorescence spectrophotometer with the emphasis on orientation, element composition, surface morphology and optical properties. The results indicated that the properties ZnO:Fe films were significantly affected by substrate temperature. XRD demonstrated that highly c-axis preferential orientation of ZnO:Fe film with wurtzite phase was fabricated exceed 300 °C. The optical absorption properties and the shift of the optical band gaps were also investigated. The analysis reveals that the increasing of the band gaps was caused due to the improvement of the quality of film and the decreasing of the band gaps was likely due to the raising the concentration of carriers caused by increasing substrate temperature. Urbach energy decreased with increasing the substrate temperature from RT to 150 °C while increased from 150 °C to 450 °C. The photoluminescence measurements of ZnO:Fe films at room temperature revealed a violet, a blue and a green emission and the origin of these emissions was discussed in detail.
Keywords: ZnO:Fe films; RF magnetron sputtering; Substrate temperature; Orientation; Optical properties;

Display OmittedNanosized LiFePO4 particles, each covered with a complete but thin carbon shell, are synthesized via a sol–gel process using citric acid (CA) as both chelating agent and organic carbon source in this study. Several precursors are prepared with various mole ratio of CA to total metal ions (n CA/n m) first. Then the prepared precursors are investigated by thermogravimetry and derivate thermal analysis. The LiFePO4/C samples obtained via calcining the precursors at different temperatures are characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscope and galvanostatic charge/discharge test. The systematic study shows that the LiFePO4/C nanocomposite, calcined from the precursor with a composition of n CA/n m equal to 1:3 at 650 °C, delivers discharge capacities of 166 and 153 mA h g−1 at 0.1 and 1C, respectively, and exhibits almost no capacity fade up to 50 cycles.
Keywords: Nanosized LiFePO4/C; Carbon shell; Sol–gel process;

A large scale of PbS tipped ZnS nanorods heterostructures (PbS/ZnS heterostructures) was successfully synthesized by laser ablation of Zn/Pb binary metal target immersed in dodecyl mercaptan (DDM) using long-pulse-width millisecond laser at room temperature and atmospheric pressure. The PbS/ZnS heterostructures were observed both on the surface of Zn/Pb target and in the ablated products after laser ablation. SEM and TEM results showed that the length and diameter of ZnS nanorods was in the range of 200–300 nm and 50–60 nm, the diameter of PbS tips in the one end of the ZnS nanorods was in the range of 70–80 nm, respectively. The pulse-width of laser, liquid media and weight ratio of Pb/Zn was critical for the synthesis of PbS/ZnS heterostructures. In addition, we proposed the growth mechanism of PbS/ZnS under laser ablation. This method is a simple but effective method for simultaneously fabricating of heterostructures directly onto a substrate and formation of heterostructures in the liquid from the ablated products, which implied a prospective application for the selective surface area chemical modification.
Keywords: Laser ablation; Metal target; Heterostructure; Dodecyl mercaptan;

The effects of minor Ca addition on the as-cast microstructure and mechanical properties of the Mg–4Y–1.2Mn–1Zn (wt.%) alloy were investigated by using optical and electron microscopies, differential scanning calorimetry (DSC) analysis, and tensile and creep tests. The results indicate that adding 0.3–0.9 wt.%Ca to the Mg–4Y–1.2Mn–1Zn alloy does not cause an obvious change in the morphology and distribution for the Mg12YZn phase in the alloy. However, the grains of the Ca-containing alloys are effectively refined, and an increase in Ca amount from 0.3 wt.% to 0.9 wt.% causes the grain size to gradually decrease. In addition, adding 0.3–0.9 wt.%Ca to the Mg–4Y–1.2Mn–1Zn alloy can effectively improve the tensile and creep properties. Among the Ca-containing alloys, the alloys with the additions of 0.6 and 0.9 wt.%Ca exhibit the relatively optimum tensile and creep properties. The improvement in the tensile and creep properties for the Ca-containing alloys is possibly related to the grain refinement and higher thermal stability of the Ca-containing Mg12YZn phases in the alloys, respectively.
Keywords: Magnesium alloys; Mg–Y–Mn–Zn alloys; Ca addition; Grain refinement; Mg12YZn phase;

Characterisation of precipitates in a Mg–7Gd–5Y–1Nd–0.5Zr alloy aged to peak-ageing plateau by Ting Li; Zhiwei Du; Kui Zhang; Xinggang Li; Jiawei Yuan; Yongjun Li; Minglong Ma; Guoliang Shi; Xin Fu; Xiaolei Han (174-180).
The precipitates in a Mg–7Gd–5Y–1Nd–0.5Zr alloy aged to peak-ageing plateau (aged at 210 °C from 18 h to 180 h) were studied using transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). Precipitation at the peak-ageing plateau involves the formation of the β ′ phase and a new type of plate-shaped phase precipitated along the ( 0 0 0 1 ) α habit plane. The ellipsoid morphology of β ′ was illustrated according to [ 0 0 0 1 ] α and [ 1 0 1 ¯ 0 ] α zone axes observations. The orientation relationship between the β ′ precipitates and matrix satisfies [ 0 0 1 ] β ′ / / [ 0 0 0 1 ] α and ( 1 0 0 ) β ′ / / ( 1 1 2 ¯ 0 ) α , respectively. The TEM and HRTEM results indicate that the β ′ precipitates have a base-centred orthorhombic structure with lattice parameters a  = 0.64 nm, b  = 2.22 nm and c  = 0.52 nm. Further, atomic-scaled HAADF-STEM observations suggest a Mg7RE-type and not a Mg15RE-type structure for the β ′ phase. The positive thermal stability of the alloy at 210 °C ageing is attributed to the coherent relationship with the matrix and the formation of an interlaced network of the β ′ precipitates. Aside from the β ′ phase, a large amount of precipitate particles were observed to form on the ( 0 0 0 1 ) α habit plane in the peak-aged samples. The new type of precipitates have a plate shape, of approximately 5 nm wide along the [ 1 0 1 ¯ 0 ] α direction of the matrix and approximately 5 nm long along the [ 2 ¯ 1 1 0 ] α direction. A completely coherent relationship with the matrix can also be observed.
Keywords: Mg–7Gd–5Y–1Nd–0.5Zr alloy; Precipitation; Crystal structure; HAADF-STEM technique;

Series of Ni–Co bimetal hydroxides nanosheets have been obtained by tuning the molar ratio of cobalt and nickel in an oleylamine assisted synthetic system. Porous Ni–Co bimetal oxide nanosheets with tunable compositions have been obtained by directly thermal decomposition of corresponding hydroxides at 400 °C. The physicochemical properties of these Ni–Co bimetal oxides have been fully characterized and analyzed. Compared with pure NiO and Co3O4, the bimetal oxides show better catalytic performance for CO oxidation. By increasing Co content in the reaction system, the as-prepared Ni–Co bimetal oxides system can be classified into three different crystal structure types. When Co percentage is less than 20%, the samples display identical cubic crystal structure with pure NiO and possess higher surface area and better catalytic performance than others. As Co percentage in the system is between 40% and 60%, the samples tend to form a stable lamellar structure of NiCo2O4. Co3O4 based crystal structure type of Ni–Co bimetal oxides is observed when Co percentage is more than 80%.
Keywords: Bimetal oxides; Crystal structure; CO oxidation;

The structural, magnetic and transport properties of the newly synthesized Ni35Mn50In15 alloy have been presented. It was observed to form in single phase Hg2CuTi-type structure. The Curie temperature (T C) of the sample is found to be 333 K. The magnetization versus field (MH) curve at 5 K and 300 K shows existence of ferromagnetic order in the alloy. The resistivity of the alloy varies as T 2 at low temperature and as T at high temperature. Above T C, sharp flattening in resistivity is observed. The negative MR of −1.7% is observed at 300 K and is found to increase linearly with the magnetic field.
Keywords: Heusler alloy; Magnetization; Resistivity; Magnetoresistance;

Annealing induced compositional changes in SmCo5/Fe/SmCo5 exchange spring trilayers and its impact on magnetic properties by P. Saravanan; Jen-Hwa Hsu; G.L.N. Reddy; Sanjiv Kumar; S.V. Kamat (191-195).
SmCo5/Fe/SmCo5 sandwich configurations have gained renewed interest when compared to the conventional SmCo5/Fe bilayers, as they exhibit enormous scope to impart high energy product values with strong magnetization reversal behavior. The compositional changes that occur in the intermediate soft layer upon annealing play a critical role in determining the phase chemistry, as well as magnetic performance of the trilayers and herein we address such a study. SmCo5/Fe/SmCo5 sandwich films with fixed layer thicknesses of SmCo5 (25 nm) and Fe (8 nm) were grown by sputtering on Cr buffered Si (1 0 0) substrates and subsequently, annealed at different temperatures: 673, 773 and 873 K. The effect of post-deposition annealing on the structure, composition and magnetic properties of the trilayer architecture was investigated by X-ray diffraction (XRD), Rutherford back-scattering (RBS) and super-conducting quantum interference device (SQUID), respectively. The XRD studies showed significant decrease in the lattice parameter values with increasing annealing temperature, which suggests an increase in the diffused Co-content in the Fe-intermediate layer. The XRD results were further validated by RBS measurements, which confirmed that both composition and thickness of the Fe-intermediate layer were strongly affected by the annealing temperature. The SQUID measurements demonstrated the existence of in-plane anisotropy and strong exchange coupling between the hard and soft layers for all the annealed sandwich films. The trilayer stack annealed at 773 K showed the best magnetic performance such as high coercivity (814 kA/m), remanence (944 kA/m) and energy product (243 kJ/m3).
Keywords: Nanocomposite magnets; Exchange coupling; SmCo5/Fe/SmCo5; Trilayers; Sputtering; Magnetic thin films;

In this study, a series of Nickel (Ni)–Tungsten (W) alloys were electrodeposited onto copper (Cu) substrates using electroplating baths and tri-sodium citrate (Na3C6H5O7) as the complex agent. The electro co-deposition of Ni–W alloys was carried out by varying several important experimental parameters: the tungstate ion [ WO 4 ] 2 - concentration, the bath temperature and the speed of stirring. Potentio-dynamic polarization and in-situ electrochemical impedance spectroscopy (EIS) techniques were used as electroplating methods to study the processes. The phases present in the films were identified using powder X-ray diffraction (XRD) and electron diffraction (ED). The films were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and their elemental compositions determined using X-ray energy dispersive spectrometry (XEDS). The electrodeposited films were found to be a mixture of amorphous and nanocrystalline Ni–W. This study has allowed us to reach a better understanding of the complex mechanisms and effective parameters of co-deposition of Ni and W using citrate ions complex baths.
Keywords: Electrodeposition; Nanocrystalline; Amorphous; Microscopy; Electrochemical impedance spectroscopy;

Performance enhancement of Sn–Co alloys for lithium-ion battery by electrochemical dissolution treatment by Chunhui Tan; Gongwei Qi; Yeping Li; Jing Guo; Xin Wang; Delong Kong; Hongjun Wang; Shuyong Zhang (206-211).
Three sets of Sn–Co alloy materials with improved porous structure are designed and facilely prepared via a two-step strategy comprising of electrodeposition followed by electrochemical dissolution treatment. The structure, composition and morphology of the Sn–Co alloy materials are investigated by scanning electron microscopy, X-ray diffraction and atomic absorption spectrophotometer. The electrochemical performance of the Sn–Co alloy materials as negative electrode materials for lithium-ion battery was tested by cyclic voltammetry, galvanostatic charge–discharge cycling and rate capability test. It is found that the resultant Sn–Co alloy materials after electrochemical dissolution treatment have porous structure and higher specific capacity than those of the as-deposited Sn–Co alloy materials. The initial capacity of a porous Sn–Co alloy sample attains 1109 mA h g−1, and remains 580 mA h g−1 after 70 cycles. This performance improvement can be mainly attributed to the formation of optimized porous structure during electrochemical dissolution treatment, which can buffer the great volume fluctuation of Sn phase during cycling and therefore reduce cracking and shelling of the materials.
Keywords: Lithium-ion battery; Anode materials; Sn–Co alloy; Porous structure; Electrochemical dissolution treatment;

Preparation and electric-field response of novel tetragonal barium titanate by Rui-jie Li; Wen-xin Wei; Jin-ling Hai; Ling-xiang Gao; Zi-wei Gao; Yan-yu Fan (212-216).
Display OmittedThe tetragonal barium titanate (BaTiO3) particles with novel shapes were synthesized by a surfactant-free hydrothermal method and fully characterized by Raman, XRD, SEM and contact angle analysis. The shape of particles are dependent on reaction temperature, pH value and mineralization time. The tetragonal BaTiO3 particles with different morphology possess different tetragonality, surface hydrophilicity and dielectric property, and so they exhibit distinct electric-field response. The high tetragonality and good dielectric property of the particles are proposed as a main power of enhancing the electric response of tetragonal BaTiO3 dispersed in hydrous elastomer.
Keywords: Barium titanate; Tetragonal phase; Hydrothermal method; Electric-field response;

Hydrothermal fabrication of Ni3S2/TiO2 nanotube composite films on Ni anode and application in photoassisted water electrolysis by Hongbo He; Aiping Chen; Hui Lv; Haijun Dong; Ming Chang; Chunzhong Li (217-220).
Display OmittedNanostructured films of rhombohedral Ni3S2 were hydrothermally synthesized on Ni and TiO2 nanotube layer, as substrates. A possible mechanism is proposed to explain the formation of rhombohedral Ni3S2 nanostructures. The results of UV–vis spectrophotometric studies indicate that optical absorption spectrum of Ni3S2/TiO2 nanotube composites could be extended to the visible region. As-synthesized Ni3S2/TiO2 nanotube composite films on Ni substrate had better (by about 40%) hydrogen production performance under the visible light irradiation, in comparison with the Ni anode modified by TiO2 nanotubes.
Keywords: Ni3S2/TiO2 nanotube; Water electrolysis; Photocatalysis; Hydrogen evolution;

One-pot synthesis of a composite of monodispersed CuO nanospheres on carbon nanotubes as anode material for lithium-ion batteries by Syed Mustansar Abbas; Syed Tajammul Hussain; Saqib Ali; Faisal Abbas; Nisar Ahmad; Nisar Ali; Yaqoob Khan (221-226).
Nanospheres of CuO are synthesized by a facile solution reaction of CuCl2 in the presence of carbon nanotubes (CNTs), yielding a composite material. Transmission electron microscopy (TEM) confirms the uniform dispersion of CuO nanospheres on the CNTs surface. The functional groups are determined by Fourier transform infrared spectroscopy (FTIR) and elemental composition is confirmed by Rutherford backscattering spectroscopy (RBS), while the structure and morphology of the deposited electrodes are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Electrochemical characterization by cyclic voltammetry (CV) and galvanostatic charge/discharge tests demonstrate high rate capability and superior cycling stability for CuO/CNT composite with a high specific capacity of 638 mAh/g for up to 50 cycles. It is anticipated that this high efficiency is due to the high dispersion of CuO nanospheres and excellent conductivity of CNTs mesh.
Keywords: Lithium-ion batteries; Anode; Carbon nanotubes; Composite; Electrochemical properties;

Facile synthesis of TiO2 hierarchical microspheres assembled by ultrathin nanosheets for dye-sensitized solar cells by Fang Xu; Xuyan Zhang; Yao Wu; Dapeng Wu; Zhiyong Gao; Kai Jiang (227-232).
TiO2 hierarchical microspheres assembled by ultrathin nanosheets were prepared via solvothermal route for dye-sensitized solar cells (DSSCs). The performance of cells was investigated by diffuse and reflectance spectra, photocurrent–voltage measurement, incident-photon-to-current conversion efficiency and electrochemical impedance spectra. Photoanodes with different thickness of TiO2 hierarchical spheres were studied, which proves that the photoanode with thickness of 15.9 μm exhibits higher performance (short-circuit current density of 12.36 mA cm−2, open-circuit voltage of 0.73 mV, fill factor of 61.95, and conversion efficiency of 5.56%) than that of P25-based DSSC due to the excellent particle interconnections, low electron recombination and high specific surface area (78 m2  g−1).
Keywords: TiO2; Hierarchical spheres; Solvothermal method; DSSC;

Structure, magnetic and transport properties in Ca3Co4− x Sb x O9 ceramics by Yanan Huang; Bangchuan Zhao; Ran Ang; Shuai Lin; Wenhai Song; Yuping Sun (233-239).
The structure, magnetic, electrical and thermal transport properties of Ca3Co4− x Sb x O9 (0 ⩽  x  ⩽ 0.2) have been investigated systematically. Base on the analysis of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), the valence state of the doped Sb ions is suggested to be +3 in the x  = 0.05 sample, and its content increases monotonously along with the gradual introduction of Sb5+ ions as x further increases. The resistivity and the metal–insulator-transition temperature increase with increasing x, indicating the more stable spin-density-wave state in the Sb-doped samples. The thermopower decreases first as x  = 0.05, and then increases monotonously with increasing x till to 0.15. The thermal conductivity decreases obviously due to Sb-doping. As a result, the Ca3Co3.90Sb0.10O9 sample has the largest thermoelectric figure-of-merit ZT value of 0.012 at room temperature, which is about two times larger than that of Ca3Co4O9. The results are suggested to originate from the variations of carrier concentration and electronic correlation via Sb-doping with the different valence states.
Keywords: Thermoelectric performance; Doping effect; Spin-density-wave; Electron correlation;

Controllable photoluminescent–magnetic dual-encoded wurtzite ZnS:Cu2+Mn2+ nanowires modulated by Cu2+ and Mn2+ ions by Jinghai Yang; Bingji Wang; Jian Cao; Donglai Han; Bo Feng; Maobin Wei; Lin Fan; Chunlei Kou; Qianyu Liu; Tingting Wang (240-245).
The wurtzite-type ZnS:Cu2+Mn2+ nanowires (NWs) were prepared by a simple hydrothermal method at 180 °C without any surface-active agent. The results of XRD, EDAX and XPS showed that both the Cu2+ and Mn2+ ions were incorporated into the ZnS lattice. The maximum concentration of the Cu2+ ions in the ZnS and Zn0.99Mn0.01S NWs was 7% and 1%, respectively. The maximum concentration of the Mn2+ ions in the Zn0.99Cu0.01S NWs can reach to 10%. The ZnS:Cu2+ NWs exhibited the Cu2+-related emission peak centered at 540 nm coming from sulfur vacancy to t 2 level of Cu2+, while the ZnS:Cu2+Mn2+ NWs exhibited the Mn2+ (4T16A1) and Cu2+ (interstitial S to t 2 level of Cu2+) related transition centered at 577 nm and 501 nm, respectively. Moreover, the ZnS:Cu2+Mn2+ NWs showed the room temperature ferromagnetism property, and the saturation magnetization was increased as the Mn2+ doped ratio increased.
Keywords: Hydrothermal; ZnS:Cu2+Mn2+; Photoluminescence; Ferromagnetism;

Laser-induced metal organic decomposition for Ce0.9Zr0.1O2− y epitaxial thin film growth by Albert Queraltó; Ángel Pérez del Pino; Susagna Ricart; Xavier Obradors; Teresa Puig (246-254).
Cerium–zirconium propionates precursor layers were decomposed by pulsed laser radiation for the development of epitaxial Ce0.9Zr0.1O2− y (CZO) thin-films on yttria-stabilized zirconia (YSZ) (0 0 1) single crystal substrates. The laser treatments were performed by means of a Nd:YAG laser system (λ  = 266 nm, τ  = 3 ns, ν  = 10 Hz). The influence of processing parameters such as the laser fluence, number of pulses and substrate temperature on the morphology, surface roughness and composition of the irradiated material was studied and correlated with the optical properties and thermochemical characteristics of the propionate precursors. We conclude that the metal organic decomposition proceeds both from direct optical absorption of the precursor film and from the heating effect associated to the optical absorption of the YSZ substrate. FTIR spectra allow us to define the laser irradiation conditions where a full elimination of the organic precursors is achieved. After the metal organic precursor decomposition, we investigated the thin films crystallization process through furnace annealing. Our analyses demonstrate that through an optimized laser treatment and a furnace heating process it is possible to create epitaxial 20 nm-thick CZO films, with similar nanostructure and surface flatness than in conventional thermal treatments but with an important saving of processing time and an enhanced versatility to define micrometric patterns.
Keywords: Chemical synthesis; Laser processing; Oxide materials; Crystal growth;

Optical properties correlated with morphology and structure of TEAH modified ZnO nanoparticles via precipitation method by M. Popa; A. Mesaros; R.A. Mereu; R. Suciu; B.S. Vasile; M.S. Gabor; L. Ciontea; T. Petrisor (255-259).
ZnO nanoparticles were synthesized by the precipitation method, with and without tetraethylammonium hydroxide (TEAH) addition. FTIR analysis was performed for the characterization of ZnO precursors. The as-obtained ZnO nanoparticles were analyzed by X-ray diffraction (XRD) and scanning and transmission electron microscopies (SEM/TEMs) in order to observe the structural and morphological properties of the samples. The ZnO sample, obtained from the precursor containing TEAH, thermally treated at 700 °C for 2 h, shows a compact structure with polygonal particles, having crystallites size around 42 nm. The correlation between morpho-structural characteristics and the optical properties of the as-obtained samples was mainly investigated.
Keywords: ZnO bulk; TEAH; Optical properties;

The effect of ball milling on the mechanical properties of TiN consolidated by pulsed current activated sintering by Wonbaek Kim; Ki-Min Roh; Jae-Won Lim; Hyun-Su Oh; In-Jin Shon (260-265).
Commercial TiN powders were high-energy ball milled for various durations and consolidated without a binder using the pulsed current activated sintering method (PCAS). The effect of milling on the sintering behavior, crystallite size and mechanical properties of TiN compacts were evaluated. A dense TiN compact with a relative density of up to 99% could be readily obtained within 4 min. The ball milling effectively refined the crystallite structure of TiN powders and facilitated the subsequent densification. The sinter-onset temperature was reduced appreciably by the prior milling for 40 h from 1200 °C to 800 °C. Accordingly, the relative density of TiN compact increased as the milling time increases. The microhardness of sintered TiN was linearly proportional to the density. It is clearly demonstrated that a quick densification of TiN bulk materials to near the theoretical density could be obtained by the combination of PCAS and the preparatory high-energy ball milling process.
Keywords: Sintering; Nanopowder; Hardness; TiN;

Phase diagram of CdO–V2O5–In2O3 system by Monika Bosacka (266-271).
The subsolidus phase equilibria of the ternary system CdO–V2O5–In2O3 were investigated by differential thermal analysis (DTA) and X-ray diffraction technique (XRD). It has been shown that the system consists of ten subsidiary systems in which three solid phases coexist in equilibrium in each subsystem. CdV2O6 and In2O3-were proved to react in the solid phase and at the molar ratio of 3:2 and the formation of a new compound Cd3In4V6O24 was observed. This new compound undergoes incongruent melting at 920 °C with deposition of solid In2O3. Cd3In4V6O24 crystallises in the monoclinic system with elementary cell parameters of a  = 0.8793(1) nm, b  = 1.578(1) nm, c  = 0.7506(7) nm, γ  = 96.6°, Z  = 2.
Keywords: Inorganic materials; Solid state reactions; Phase diagrams; Thermal analysis; X-ray diffraction; Scanning electron microscopy; SEM;

Colloidal CZTS nanoparticles and films: Preparation and characterization by Min Zhou; Yanmei Gong; Jian Xu; Gang Fang; Qingbo Xu; Jianfeng Dong (272-277).
Cu2ZnSnS4 (CZTS) compound semiconductor has the advantage of good matching with solar radiation in optical band-gap, large absorption coefficient, non-toxic and especially large abundance ratios of elements, so that CZTS has been considered as a good absorber layer used for the thin-film solar cells with most industrialization promising and environment friendly. In the present work, colloidal CZTS nanocrystals (average size ∼8–16 nm) with the band gap of ∼1.5 eV were synthesized via wet-chemical processing, using oleylamine (OLA) as solvent and capping molecules. The colloids were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–Vis–NIR spectroscopy. The structure and morphology of nanocrystals were influenced with the reaction temperature. The resulting nanocrystals were kesterite-phase CZTS when the reaction temperature was lower, but were wurtzite-phase CZTS when the reaction temperature above 275 °C. The CZTS films on glass substrates were prepared by drop-casting, from the colloidal 10 wt% CZTS–toluene solution where the CZTS colloids were synthesized at 260 °C with three different recipes. The resulting films with different heat-treatments were investigated by XRD, SEM and energy dispersive spectroscopy (EDS). Densified CZTS films (∼5 μm in thickness) could be obtained by drying and sintering in vacuum. The CZTS films have the band-gap around 1.6–2.0 eV, due to Zn rich and S poor in the films. The dark conductivity and photoconductivity under AM 1.5 irradiation of the CZTS films on ITO glass substrates with different heat-treatments were measured by the AC impedance method.
Keywords: Semiconductors; Chemical synthesis; X-ray diffraction; Thin films; Nanoparticles;

Optimal parameters for synthesizing single phase spinel-type Co2SnO4 by sol–gel technique: Structure determination and microstructure evolution by J.A. Aguilar-Martínez; M.A. Esneider-Alcala; M.B. Hernández; M.I. Pech Canul; S. Shaji (278-282).
Powder samples of spinel Co2SnO4 were successfully synthesized by the sol–gel technique at three different temperatures: 900, 1300 and 1400 °C for 1, 5 and 8 h. XRD patterns and SEM images provided evidence of the structural and morphological evolution during the formation of the spinel phase. Thermal analysis confirmed the reaction pathway in which the spinel is formed by the reaction between SnO2 (formed from SnCl4) and CoO which in its turn is produced during the decomposition reaction of Co3O4 [formed from Co(NO3)2] into CoO and O2. Determination of the quantitative phase at each combination of temperature and time as well as the lattice parameters was possible by the Rietveld refinement. The optimal parameters for the complete formation of Co2SnO4 are 1400 °C for 5 h. It is worth mentioning that at 1300 °C for 1 h, the percentage of the spinel obtained is considerably high (94.7%).
Keywords: Spinels; Sol–gel; X-ray techniques; Thermal analysis;

Precipitates formed in an Mg–0.5at%Ce alloy during age-hardening at certain temperatures ranging between 180 °C and 250 °C have been thoroughly investigated by a combined technique of TEM and HAADF-STEM. The precipitation sequence can be presented as Mg-solid solution → GP-zone →  β 1 (Mg3Ce; BiF3-type) →  β (Mg12Ce; Mn12Th-type). At an early stage of aging (180 °C for 2 h), fine precipitates of planar GP-zone with an ordered structure appear in parallel to (1 0 0) m planes of the Mg-matrix, having a thickness of sub-nm and an extension of 5–15 nm. With an advance of aging, the GP-zones increasingly grow larger and combine with the neighbors. When the GP-zones have reached as large as approximately 20 nm in diameter, the age-hardening effect is maximized (180 °C for 70 h). After the top-aging, the GP-zones begin to decompose and disappear, and instead precipitates of two other phases, i.e. the β 1- and the β-phase come into sight in the matrix with definite crystallographic orientation relations of [0 0 1] m //[1 1 0] β 1//[1 0 0] β and (1 1 0) m //(1 1 1) β 1//(0 1 0) β , finally completing the aging effect with full of coarse β-precipitates.
Keywords: Magnesium alloys; Precipitation; Atomic scale structure; Microstructure; TEM; HAADF-STEM;

Structural and impedance spectroscopy properties of Pr0.6Sr0.4Mn1− x Ti x O δ perovskites by S. Khadhraoui; A. Triki; S. Hcini; S. Zemni; M. Oumezzine (290-298).
An exhaustive study of structural, dielectric and impedance analysis on Pr0.6Sr0.4Mn1− x Ti x O δ (0 ⩽  x  ⩽ 0.4) perovskites were performed. Polycrystalline samples were prepared using solid state reaction method. The crystallographic structure was studied by X-ray diffraction experiments and Rietveld refinement revealed that all samples crystallize in an orthorhombic structure with Pnma space group. The approximate grain size was found from experiments’ scanning electron microscopy. The electrical response was studied using the impedance spectroscopy technique over a broad frequency range (0.1 Hz–1 MHz). The values of total conductivity for all samples were well fitted by the Jonscher law σ tot(ω) =  σ dc+n . For 0 ⩽  x  ⩽ 0.3 samples, the hopping process occurs through long distance, whereas for x  = 0.4 compound the hopping occurs between neighboring sites. The Pr0.6Sr0.4Mn0.6Ti0.4O δ sample presents the lowest real part Z′ and the highest dc-conductivity σ dc among these samples. For x  = 0.3 and 0.4 compounds, the variation of the imaginary part Z′′ shows a peak at a relaxation frequency related to the relaxation time (τ) by τ=1/2πfr . Nyquist plots of impedance show semicircle arcs for samples beyond 20% Ti content and an electrical equivalent circuit has been proposed to explain the impedance results.
Keywords: Perovskites; Rietveld refinement; Dielectric properties;

Display OmittedThe precipitation behavior of κ-carbide during isothermal aging was investigated in the Fe–9Mn–6Al–0.15C (wt.%) lightweight steel through thermodynamic calculations and microstructural analyses using various microscopes and an X-ray diffractometer. No precipitates of κ-carbide were observed in both hot-rolled and annealed specimens. The κ-carbide started to precipitate at the grain boundaries of δ-ferrite and at interphase boundaries between δ-ferrite and γ-austenite and between δ-ferrite and α′-martensite after isothermal aging at 550 °C for 1 h. While the precipitation and growth of κ-carbide at the boundaries continued, new κ-carbide precipitated alongside α-ferrite by the eutectoid reaction to form a lamellar structure in austenite during 6-h aging. This result confirmed that the precipitation of κ-carbide at the boundaries preceded the precipitation of the lamellar κ-carbide due to the pre-segregation of solute atoms to the boundaries. The α′-martensite was not transformed to γ-austenite and just tempered during isothermal aging at 550 °C.
Keywords: Precipitation; Lightweight steel; κ-Carbide; Multiphase microstructure; Isothermal aging;

New self-activated eulytite-type compounds of M7Zr(PO4)6 (M = Ca, Sr, Ba) by Lin Qin; Donglei Wei; Yanlin Huang; Sun Il Kim; Young Moon Yu; Hyo Jin Seo (305-309).
Eulytite-type orthophosphates M7Zr(PO4)6 (M = Ca, Sr, Ba) were prepared by conventional high temperature solid-state reaction. Sr7Zr(PO4)6 and Ba7Zr(PO4)6 crystallize in the pure eulytite-type phase with cubic space group ( I 4 ¯ 3 d ). The impurity phase β-Ca3(PO4)2 was inevitably coexisted with the Ca7Zr(PO4)6 phase. The luminescence properties are investigated by UV–VUV excitation and emission spectroscopy and X-ray-excited luminescence (XEL) spectroscopy. The broad excitation and emission bands are observed due to the charge transfer transition from Zr4+ to O2− in M7Zr(PO4)6 (M = Ca, Sr, Ba) eulytite. The characteristics of the phosphors including the luminescence mechanism are explained by Stokes shift, decay curves, and CIE color coordinates. The Sr7Zr(PO4)3 and Ba7Zr(PO4)3 phosphors exhibit unusual spectral features with the emission bands at 470 and 480 nm, respectively. The weak luminescence centered at 495 nm is observed in the Ca7Zr(PO4)6 eulytite with lifetime of 4.67 μs. The unusual self-activated luminescence is discussed on the base of the crystal structure of eulytite.
Keywords: Eulytite type structure; Inorganic compounds; Optical materials and properties; Ceramics; Luminescence; Zirconium;

Surfactant-assisted synthesis and luminescent properties of Gd2O3:Eu3+ core–shell microspheres by Jing Huang; Yanhua Song; Guowei Wang; Ye Sheng; Keyan Zheng; Hongbo Li; Hongguang Zhang; Qisheng Huo; Xuechun Xu; Haifeng Zou (310-315).
Homogeneous and monodisperse Gd2O3:Eu3+ core–shell mirospheres have been successfully synthesized via a solvothermal method with polyvinylpyrrolidone (PVP) as surfactant, followed by a subsequent calcination process. The as-prepared products were characterized by various methods, including X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), trans-mission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and photoluminescence spectra (PL). The results show that the obtained Gd2O3:Eu3+ mirospheres with a core–shell structure are uniform in size and distribution, and they have diameters of ∼350 nm, the core diameters of ∼150 nm, and the shell thicknesses of ∼45 nm. Under ultraviolet (UV) excitation, the corresponding Gd2O3:Eu3+ products exhibit strong red emission corresponding to the 5D07F2 transition of the Eu3+ ions, which might find potential applications in the fields such as light-emitting phosphors, advanced flat panel displays, or biological labeling.
Keywords: Gadolinium oxide; Core–shell microspheres; Luminescence; Rare earth;

Disorder controlled electrical transport properties of NdCo1− x NiO3 by Vinod Kumar; Rajesh Kumar; D.K. Shukla; Ravi Kumar (316-319).
The effect of Ni substitution on structural and electrical transport has been investigated in NdCo1− x Ni x O3 system for 0 ⩽  x  ⩽ 0.5. The Rietveld refinement of XRD data confirms orthorhombic, Pbnm symmetry for all the samples. The lattice parameters and hence unit cell volume is found to increase linearly with increase in Ni concentration. Substitution of Ni leads to the increase in conductivity and samples have been found to display semiconducting behavior in measured range of temperature. The explanation for the variation of resistivity with substitution and temperature has been provided on the basis of substitutional disorder and spin state related effects. Arrhenius and variable range hopping conduction approaches have been used to explain the temperature variation of resistivity. These results suggest that disorder-induced localization of charge carriers dominate the electrical transport in the substituted samples.
Keywords: Oxide materials; Solid state reactions; XRD; NEXAFS; Electrical transport; Disorder effects;

Display OmittedThe effect of Nb-substitution on the dielectric, electromechanical and piezoelectric properties of Pb-free 0.99[Bi1/2(Na0.82K0.18)1/2Ti1− x Nb x O3]–0.01LiSbO3 (x  = 0–0.05) piezoelectric ceramics has been investigated. X-ray diffraction analysis reveals the formation of single-phase perovskite structure with tetragonal symmetry for the compositions with x  ⩽ 0.025. Both the dielectric constant and depolarization temperature decreased with an increase in Nb-content. Analysis of the electric-field-induced polarization and strain hysteresis loops indicated that Nb substitution disrupted the long range ferroelectric order of BNKT-LS ceramics. This degraded the remnant polarization, coercive field and piezoelectric coefficient d 33 while the electric-field-induced strain increased (peaked at x  = 0.015) to 0.43% corresponding to a normalized strain ( d 33 ∗ ) of 614 pm/V at a deriving field of 7 kV/mm. This abnormal strain enhancement may be attributed to the coexistence of ferroelectric (FE) and relaxor ferroelectric (RFE) phases.
Keywords: Ceramics; Solid state reaction; Piezoelectricity electrostriction; X-ray Diffraction;

Co–Sn alloy embedded carbon nanofiber (Co–Sn/CNF) composites functioning as anode materials were prepared by using electrospinning technique followed with stabilization and carbonization with heat treatments. Co–Sn/CNF carbonized at 800 °C (Co–Sn/CNF-800) was composed of large amounts of CoSn alloy compared to CoSn2 alloy and Sn crystalline phases both embedded in carbon nanofibers (CNF). The 80th discharge capacity of Co–Sn/CNFs were ranked by their preparation temperature: 800 °C (560 mA h g−1) > 900 °C (504 mA h g−1) > 700 °C (501 mA h g−1). The excellent specific discharge capacity and cycle retention of the sample prepared at 800 °C were attributed to the abundant formation of CoSn facilitating the reversible reaction, the presence of Sn, the buffering role of CNF, and the excellent distribution of nanoparticles by electrospinning. The electrochemical performance for Co–Sn/CNF-900 is lower than that of Co–Sn/CNF-800 because of the formation of CoSn2 showing a two-step mechanism involving irreversible reaction.
Keywords: Co–Sn alloy; Anode; Carbon nanofibers; Electrospinning; Lithium battery;

The effect of Ti co-doping in BaAl2O4:Eu2+ phosphor material on crystalline quality, morphology and photoluminescence (PL) characteristics was investigated. The co-doped green phosphor compositions (BaAl2O4:Eu2+, Ti3+) with varying concentrations of Ti were prepared by solid-state synthesis method. These compositions were characterized for their phase, morphology and crystallinity by powder X-ray diffraction, SEM and TEM techniques. The photoluminescence properties were investigated measuring PL and decay time. Broad band UV excited luminescence was observed for BaAl2O4:Eu2+, Ti3+ in the green region (λ max  = 500 nm) due to transitions from 4f6 5d1 to the 4f7 configuration of the Eu2+ ion.
Keywords: Phosphors; X-ray diffraction; Electron microscopy; Photoluminescence;

Enhanced low field magnetoresistance in Sr2Fe1− x Ag x MoO6 double perovskite system by R.P. Aloysius; Meena Dhankhar; R.K. Kotnala (335-339).
Polycrystalline samples of Sr2Fe1− x Ag x MoO6 (x  = 0, 0.05, 0.10 and 0.20) have been prepared by solid state sintering. Single phase nature of the samples has been confirmed by the XRD analysis for the samples up to an Ag content of 0.10. SEM analysis shows that Ag enhances the grain growth and coarsening of the system. Though the saturation magnetisation and Curie temperature decreases, the Fe–Mo ordering as well as spin polarization enhances with respect to Ag substitution. All the samples except for the x  = 0.20, shows the LFMR hysteresis nature at 20 K indicative of the tunnelling magneto-resistance behaviour. The magneto-resistance values were found to increase with respect to Ag content up to a limit of x  = 0.10. The enhancement of LFMR behaviour and the tunnelling magnet-resistance is explained in terms of the formation of the non magnetic patches like Mo–O–Ag–O–Mo–O within the grain which acts as insulating tunnel barrier between the ferromagnetic regions of Fe–O–Mo–O–Fe–O due to the substitution of Ag in place of Fe. The striking feature of our finding is that the LFMR nature of the double perovskite increases with respect to the enhancement in the grain size which is contrary to the reported results wherein LFMR is found to increase with respect to a decrease in the grain size. So it is proposed that the LFMR nature and magnetoresistance of double perovskite systems in general and Sr2FeMoO6 in particular depend on intra-grain properties also.
Keywords: Spintronics; Low field magnetoresistance; Ag substitution; Double perovskites;

PEG-200-assisted hydrothermal method for the controlled-synthesis of highly dispersed hollow Fe3O4 nanoparticles by Guo Gao; Peiyu Qiu; Qirong Qian; Na Zhou; Kan Wang; Hua Song; Hualin Fu; Daxiang Cui (340-344).
Herein, we have developed a facile one-pot PEG-200-assited hydrothermal method for the controlled-synthesis of highly dispersed hollow Fe3O4 nanoparticles (∼150 nm in diameter, ∼25 nm in wall-thickness). Magnetic domains of hollow Fe3O4 nanoparticles are relatively regular with domain width of ∼150 nm. The capacity of hollow Fe3O4 nanoparticles retained 599 mA h g−1 after 50 cycles at 85 mA h g−1. When returning to the initial rate of 100 mA h g−1, the hollow Fe3O4 nanoparticles electrode returns a lower capacity (315 mA h g−1) than the original capacity (433 mA h g−1).
Keywords: Hydrothermal; Synthesis; Hollow; Fe3O4; LIBs;

Thin films of Ge15Se60Bi25 are prepared by thermal evaporation technique on to well cleaned glass substrates. The film thicknesses are measured by quartz crystal monitor method. Thin film capacitors of the type (Al–Ge15Se60Bi25–Al) have been fabricated. The films were well characterized by X-ray diffraction, differential thermal analysis and energy dispersive X-ray spectroscopy. AC conduction and dielectric studies performed on a stabilized samples of thickness range (89.3–214.3 nm) at various frequencies (102–105  Hz) and temperatures (303–413 K). From the AC conduction studies, it is confirmed that the mechanism responsible for the conduction process is hopping. The variations of the dielectric constant and loss as function of frequency and temperature are observed and the results are discussed. Finally, the maximum barrier height W m and the density of states N(EF) were determined.
Keywords: AC conductivity; Chalcoginied glass; Dielectric properties;

Preparation and crystallization of glass–ceramics derived from iron-rich copper slag by Zhihong Yang; Qiao lin; Jixiang Xia; Yong He; Guangdong Liao; Yi Ke (354-360).
Display OmittedIn this paper, the glass–ceramics were prepared and the iron was recovered from the iron-rich copper slag in the same process, which includes slag-melting, iron-glass separation and glass-crystallization. The results show that the iron was separated from copper slag and the residual slag was transformed into light-color glass–ceramics successfully. The crystallization kinetics, crystal phase and microstructure of glass–ceramics heated at different crystallization temperatures between 900 °C and 1100 °C were estimated by DSC, FTIR, XRD and SEM. It is found that the crystallization of the glass samples takes place via surface crystallization mechanism. The major crystalline phase is anorthite and the minor phases are quartz and diopside, the size of which increases with the rise in crystallization temperature. The optimal physical–chemical properties are achieved at 950 °C, with bulk density of 2.69 g/cm3, water absorption of 0.05% and porosity of 0.06%.
Keywords: Copper slag; Glass–ceramics; Crystallization; Iron recovery;

Microstructures and textures of a Cu–Ni–Si alloy processed by high-pressure torsion by Abdel Yazid Khereddine; Fayçal Hadj Larbi; Hiba Azzeddine; Thierry Baudin; François Brisset; Anne-Laure Helbert; Marie-Hélène Mathon; Megumi Kawasaki; Djamel Bradai; Terence G. Langdon (361-367).
Experiments were conducted to evaluate the evolution of microstructure and texture in a commercial Cu–2.5%Ni–0.6%Si (wt.%) alloy during processing by high-pressure torsion (HPT) at room temperature up to a maximum of 10 turns. It is shown that HPT leads to grain refinement to a mean equiaxed grain size of ∼200 nm, the evolution occurs rapidly at the edges of the disks but progresses more slowly in the center of each disk and ultimately, after 10 turns, the grain structure is reasonably homogeneous. There is an evolution also in the grain boundary misorientations and after 5 or more revolutions the fraction of high-angle grain boundaries is about 68%. The texture after HPT is characterized by typical shear components of face-centered cubic metals and mainly by the reinforcement of the {1 1 1}〈2  1 ¯ 1 ¯ 〉 orientation of the A* texture component.
Keywords: Cu–Ni–Si alloy; High-pressure torsion; Microstructure; Texture; Ultrafine-grained metals;

We report here a screening study using first-principles method in an attempt to identify ternary elements that can extend the CuPd B2 phase field at reduced Pd contents and thus lower cost. A total of 37 alloying elements are included for unbiased screening. The results show that addition of Mg, Al, Sc, Ti, Y, Hf, Zr, Ga, La, and Zn lowers the enthalpy of formation of the B2 phase noticeably. The atomic size, electronic density of states, charge transfer, and electronegativity are analyzed to interpret the results. Compromise between enthalpy and solubility suggests additional potential alloying elements: V, Fe, Cr, Nb, Ta, and Mn. To assess the effects of alloying on mechanical properties, we calculated the equation of states and elastic constants of 10 example alloys at 6.25 at% solute contents.
Keywords: First-principles calculations; B2 CuPd; Hydrogen separation membranes; Hume-Rothery rules; Charge transfer; Electronegativity;

Study of effects on LiNi0.8Co0.15Al0.05O2 cathode by LiNi1/3Co1/3Mn1/3O2 coating for lithium ion batteries by Ke Du; Jinlong Huang; Yanbing Cao; Zhongdong Peng; Guorong Hu (377-382).
Electrochemically active material, LiNi1/3Co1/3Mn1/3O2, was chosen to coat LiNi0.8Co0.15Al0.05O2 particle by a co-precipitation method with a weight ratio of 3:97. The thickness of coating layer is about 300 nm observed clearly by cross-section SEM photos. The coated material showed better electrochemical performance than that of the un-coated sample. At room temperature, the initial discharge capacity of the coated material was 188.2 mA h g−1 at 0.2C between 2.8 and 4.3 V and retained 96.2% after 100 cycles. Moreover, the discharge capacities of the coated cathode material at 50 °C could retain 163.2 mA h g−1 after 100 cycles. The composite also had a good rate performance with a capacity of about 146.3 mA h g−1 at 2C rate. Electrochemical impedance spectroscopy measurements showed that the coated material had a lower charge-transfer resistance.
Keywords: Lithium ion battery; Cathode material; LiNi0.8Co0.15Al0.05O2; LiNi1/3Co1/3Mn1/3O2; Coating;

In this work, AgCl/iron oxide composites were synthesized by a simple chemical precipitation method and calcining process. The composition of the material and magnetic and optical properties of the composites were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating specimen magnetometer (VSM) techniques, which confirms the high crystalline and magnetic behavior of the composites. UV-vis diffuse reflectance spectral (DRS) studies showed that the AgCl/iron oxide composites were of much higher absorption in longer wavelength region compared to bare iron oxide. The AgCl/iron oxide composites showed better performance in the photodegradation of organic dyes Rhodamin B (RhB) under the fluorescent lamp irradiation, which is remarkably superior to the N-TiO2. The degradation of microcystin-LR (MC-LR) and phenol was also found to be good owing to its effective electron-hole separation at AgCl/iron oxide interface. The separation of AgCl/iron oxide composites from the treated water was achieved by an external magnetic field as γ-Fe2O3 exhibits enough magnetic power to facilitate the separation.
Keywords: AgCl/iron oxide composites; Photocatalyst; Visible light; Magnetic properties; Recycle;

Borate oxide glass system of composition 10 KM–64.7 B2O3–25 Na2O–0.3 Cr2O3 (M = Cl, Br and I) was prepared by conventional melt quenching technique. The amorphous nature of the investigated glasses was checked by the X-ray diffraction (XRD) technique. The optical basicity of the system has been calculated, and was found to increase by going from KCl to KBr and to KI. Optical absorption spectra were recorded in the UV–visible range. Through a careful analysis of the data, the ligand field parameters (crystal field strength Dq, Racah parameters B and nephelauxetic functions h) and the optical parameters (optical band gap, Urbach tail band width, and refractive index) have been estimated. The obtained results reveal a strong correlation between that ligand field parameters and the type of halogen atom; the crystal-field strength of KCl or KBr samples are very pronounced but it is rather weak in the KI sample. Electron spin resonance (ESR) has been used to probe the valency of the Chromium ions. The resulting ESR parameters revealed that chromium ions are predominantly in the trivalent state with traces of hexavalent state. Using Infrared spectroscopy (IR) information on the boron structural units has been obtained. The N4 ratio increases by replacing the KCl by KBr or KI, and it was found that the tetrahedral coordination of Cr+ ions becomes preferential in the host glasses with increasing the optical basicity.
Keywords: Borate glasses; Transition metal; Halides; Optical basicity; Ligand field theory; Optical band gap and tails energies;

Optical absorption properties of Na x Si136 clathrate studied by diffuse reflection spectroscopy by Roto Himeno; Tetsuji Kume; Fumitaka Ohashi; Takayuki Ban; Shuichi Nonomura (398-401).
The optical absorption spectra of Na x Si136 clathrates (x  = 0.6–14.7) were experimentally clarified with the diffuse reflection spectroscopy. Strong free carrier absorption which becomes intensive with increasing Na concentration in Na x Si136 was found in infrared region, in addition to the absorption due to the interband transition. The origin of the free carries was interpreted with the ionization of Na. The position of the interband absorption edge was almost independent of Na content, and was estimated to be 1.6–1.8 eV if Na x Si136 has the direct gap.
Keywords: Clathrate compounds;

Photovoltaic property of sputtered BiFeO3 thin films by H.W. Chang; F.T. Yuan; Y.C. Yu; P.C. Chen; C.R. Wang; C.S. Tu; S.U. Jen (402-406).
Photovoltaic (PV) property of sputter-deposited BiFeO3 (BFO) polycrystalline films on Pt/Ti/SiO2/Si(1 0 0) substrates has been studied. Isotropic single phase perovskite BFO is obtained in the growth temperature (T g) range of 350–450 °C. The increase of T g and film thickness promote grain growth resulting in roughened surface. Significant PV effect under laser illumination with wavelength of 405 nm is obtained. Short-circuit photocurrent density (J sc) increases with the increase of laser intensity (I). The J sc at I  = 220 mW/cm2 (J max) are increased with the increase of the growth temperature and BFO thickness. The correlation between J max and the size of coherent scattering domain indicates that PV property is highly related to the structural defects. Furthermore, PV effect is reduced at higher T g  = 500 °C or for larger t  = 400 nm due to the appearance of the impurity phase and rougher surface.
Keywords: Photovoltaic effect; Multiferroic BiFeO3 films; Sputtering method;

Hot deformation behaviour of Ti–6Al–4V alloy with different hydrogen contents (0, 0.35 and 0.6 wt.%) was investigated over the temperature range from 1050 to 1100 °C and strain rate range from 0.005 to 5 s−1. The effects of hydrogen on the microstructural evolution, flow stress, work hardening, strain energy density and strain rate sensitivity were systematically analysed. Constitutive models for Ti–6Al–4V alloy with different hydrogen contents were established by using a stepwise multiple-linear regression method. The results show that δ hydride with an FCC crystal structure exists in the deformed matrix of the hydrogenated specimens. The size of δ hydride is refined when the deformation temperature is raised from 1050 to 1100 °C. The work hardening rate increases with hydrogen when the strain is lower than 0.01. When the strain is higher than 0.01, however, hydrogen does not show significant effect on the work hardening rate. Both the flow stress and the strain rate sensitivity show an increasing trend with hydrogen, and the strain rate sensitivity increases gradually with strain and temperature. The selected optimum variables for the constitutive equations after stepwise multiple-linear regression are different for the Ti–6Al–4V alloy with different hydrogen contents. The calculated flow stress is in good agreement with the tested value.
Keywords: Ti–6Al–4V alloy; Hydrogen; Hot deformation; Microstructure; Constitutive model;

Platinum silicide formation on Si1− y C y epitaxial layers by Kan-Rong Lee; I-Ping Lin; Hung-Tai Chang; Sheng-Wei Lee (415-420).
This study first investigates the formation of Pt silicides on Si1− y C y (y  = 0.024) epilayers in the presence of an interfacial oxide layer. The presence of C atoms is found to retard the growth kinetic of PtSi but significantly improve the thermal stability of PtSi thin films. Experimental results also indicate that an interfacial oxide layer present at the initial Pt/Si1− y C y interface should have no negative impact on the subsequent Pt silicidation in terms of process integration. We also propose a mechanism to discuss the relationship between microstructures, electrical property, and thermal stability of Pt silicides in terms of C solubility in PtSi. In this mechanism, C atoms accumulated at the PtSi grain boundaries may act as diffusion barriers, which effectively inhibit the grain growth and agglomeration of PtSi and thus widen the low-resistivity process window of PtSi. More importantly, it is possible to gain the benefits of excellent thermal stability of PtSi silicides and enhanced tensile strain in Si1− y C y epilayers simultaneously if the thermal budget is well controlled during the silicidation process.
Keywords: Platinum silicide; Epitaxy; Sheet resistance; Phase transformation; Transmission electron microscopy;

Electrodeposition of Sn-doped hollow α-Fe2O3 nanostructures for photoelectrochemical water splitting by Jiajia Cai; Song Li; Zhe Li; Jiansheng Wang; Yuping Ren; Gaowu Qin (421-426).
The hollow nanostructured hematite photoanodes were prepared by using template-assisted electrodeposition and heat-treatment process. The morphologies of the films were regulated through the synthesis parameters such as potential sweep rate, annealing temperature and Sn concentration in electrolyte, and confirmed by scanning electron microscopy and transmission electron microscopy. Sn-doping of hematite was achieved by using electrolyte containing tin salt. The photocurrent of Sn-doped hematite film reaches 0.25 mA/cm2 in 1 M NaOH at 1.23 V vs. RHE by optimizing the synthesis parameters. It is noted that both Sn doping and hollow nanostructure can affect and improve the PEC performance of hematite film.
Keywords: Hematite doping; Hollow structure; Photoelectrochemistry;

Tailoring of textured transparent conductive SnO2:F thin films by Qian Gao; Hong Jiang; Changjiu Li; Yanping Ma; Xiang Li; Zhaohui Ren; Yong Liu; Chenlu Song; Gaorong Han (427-431).
In order to optimize the light trapping, textured SnO2:F (FTO) films have been successfully deposited and optimized on glass in large scale using atmospheric pressure chemical vapor deposition (APCVD) method on an industrial production line. The microstructures, optical and electrical properties of the films were investigated as a function of the total flow rate and fluorine doping concentration. The as-deposited FTO polycrystalline films possessed the tetragonal rutile structure of SnO2. Enhanced light trapping has been achieved with the increased surface roughness of the films by manipulating the total flow rate of monobutyltin trichloride (MBTC) and trifluoro acetic acid (TFA), while the corresponding high transmittance and conductivity remained stable. The optimized film with haze value of 10.9%, a figure of merit at the level of ∼10−3 and sheet resistance of ∼11 Ω sq−1, showed good potential to improve the efficiency of silicon thin film solar cells.
Keywords: Fluorine-doped tin oxide; Flow rate; Texture surface; Optical and electrical properties; Thin film solar cells;

Synthesis and densification of W–Cu, W–Cu–Ag and W–Ag composite powders via a chemical precipitation method by G. Taghavi Pourian Azar; H.R. Rezaie; B. Gohari; H. Razavizadeh (432-436).
This research was undertaken with an aim of making a comparison between W–Cu, W–Cu–Ag and W–Ag composites. In this way, nanostructured W–20wt%Cu, W–10wt%Cu–10wt%Ag and W–20wt%Ag composite powders were prepared by calcination of chemically precipitated initial powders and a subsequent reduction treatment. The powders were characterized using XRD and SEM analysis. The sintering behavior and hardness of samples were also investigated as a function of temperature. The sintered samples were evaluated by SEM. The results showed that at all sintering temperatures, W–10wt%Cu–10wt%Ag and W–20wt%Ag composite powders showed the most and the least sinterability, respectively. Furthermore, the maximum hardness after sintering at 1200 °C was belonged to W–20wt%Cu sample.
Keywords: Metal matrix composites; Chemical synthesis; Sintering; Microstructure; Scanning electron microscopy; X-ray diffraction;

Oxidation mechanism of Fe–16Cr alloy as SOFC interconnect in dry/wet air by Zhi-Yuan Chen; Li-Jun Wang; Fu-Shen Li; Kuo-Chih Chou (437-442).
Experimental study on the oxidation corrosions of Fe–16Cr alloy was carried out at 800–1100 °C under dry/wet air conditions. Faster oxidation rate was observed at higher temperature and water vapor content. The degradation time t d between two stages in oxidation process showed an exponential relationship with elevating corrosion temperature in dry air, and a linear relationship with the water content in the case of water vapor introduced to the system.The mechanism of oxidation corrosions of Fe–16Cr alloy was suggested by the Real Physical Picture (RPP) model. It was found that the break-away oxidation in stage II was controlled by diffusion at initial both in dry and wet air, then became linear with the exposure time, which implied that the oxidation rate was then controlled by chemical reaction of the interface between the metal and the oxidized scale. Moreover, the effect of water in the oxidation process is not only to supply more oxygen into system, but also to modify the structures of oxide scale due to the existence of hydrogen atom, which results in the accelerated corrosions.
Keywords: Break-away oxidation; Real physical picture model; Oxidization; SOFC interconnector;

Hydrogen isotherms for annealed, un-activated LaNi5 (273–333 K) by S. Luo; Ted B. Flanagan; Robert C. Bowman (443-450).
Hydrogen absorption isotherms (273–333 K) have been measured for closely stoichiometric, annealed, un-activated LaNi5, i.e., a virgin un-activated LaNi5 sample was employed at each temperature. This is the first time that such isotherms have been measured for annealed, un-activated LaNi5 at such low temperatures ⩽298 K. After measurement of the initial absorption isotherms, the second absorption and desorption isotherms have been measured at each temperature. Van’t Hoff plots have been made from these absorption and desorption plateau pressure data and, from these, Δ H plat values have been obtained for the initial and subsequent absorption and desorption reactions. The ∣ΔHplat∣ determined from the van’t Hoff plot is smaller for the initial isotherm for the annealed, un-activated form of LaNi5 than it is for activated LaNi5.
Keywords: LaNi5; Isotherms; Un-activated;

The morphology and growth mechanism of intermetallic compound (IMC) layer at Sn–3Ag–0.5Cu/Cu interface during isothermal aging, thermal cycling and thermal shock were investigated in this study by microstructural observations and phase analysis. The results showed that the IMC layer flattened with aging duration because the grooves in scallop-like IMC provide a more convenient access for Cu atoms to dissolve and react with solders and previous IMCs. When isothermal aging was subjected, the growth rate of Cu6Sn5 was lower than that of Cu3Sn. While for thermal cycling, it was Cu6Sn5 that contributed much to the growth of IMC layer. This had much to do with abundant supply of Sn and Cu atoms at the interface of solder/Cu6Sn5 caused by recrystallization of solder and compression stress during thermal cycling. Growth mechanisms of total IMC layer both during isothermal and non-isothermal aging are stated as empirical power-law relationship by using an equivalent aging time parameter. And the growth time exponent depended on the evolution of grain structures of solder matrix, thermal stress and propagation of cracks during non-isothermal conditions.
Keywords: Morphology of intermetallic compound layer; Growth mechanisms; Isothermal aging; Non-isothermal aging; Equivalent aging time;

Influence of symmetry on Sm magnetism studied on SmIr2Si2 polymorphs by Michal Vališka; Jiří Pospíšil; Jan Prokleška; Martin Diviš; Alexandra Rudajevová; Ilja Turek; Vladimír Sechovský (459-466).
Polycrystalline samples of SmIr2Si2 formed at room temperature both the low temperature phase (LTP) and the metastable high temperature phase (HTP), respectively, depending on the heat treatment. The samples were studied by X-ray powder diffraction, DTA, specific-heat and magnetization measurements with respect to temperature and magnetic field. The first order LTP ↔ HTP polymorphic phase transition has been determined showing the huge temperature hysteresis of 264 °C caused by the high energy barrier due to the change of stacking of the Sm, Ir and Si basal plane sheets within the transition. Both polymorphs show indications of antiferromagnetic order at low temperatures. The considerably different magnetic phase transitions determined for the LTP and HTP confirm the strong influence of crystal structure symmetry on magnetism in the two polymorphs. The magnetism in SmIr2Si2 exhibits typical features caused by the specific behavior of Sm3+ ion characterized by energy nearness of the ground state and first excited state and crystal field influence. The interpretation of experimental results is corroborated by results of ab initio electronic structure calculations.
Keywords: SmIr2Si2; Polymorphism; DTA; Hysteresis; Crystal field; DFT;

High magnetostriction of the polycrystalline alloy (Fe0.8Al0.2)97B3 by Cristina Bormio-Nunes; Mateus Botani Dias; Luis Ghivelder (467-471).
In the present work we investigate the alloys (Fe0.8Al0.2)100− x B x , for x  > 2.0 up to x  = 5.0. A maximum of the total magnetostriction was found for the alloy (Fe0.80Al0.20)97B3. In this sample we measured the boron contents using WDS and we did not find boron in the matrix, while the precipitates formed after annealing of as cast samples are essentially the phase Fe2B. By a detailed XRD study of this sample using Mo Kα radiation, the presence of the phases Fe3Al (D03) and α (A2) was determined. The coexistence of both phases was determined to be the origin of the increase of the magnetostriction of this material. The value of λ long  = 80 × 10−6 achieved in the as cast sample with x  = 3 indicates that the introduction of texturing to the material should provide even higher enhancement of the magnetostriction. In addition to high magnetostriction values, the alloy can be machined, welded and is also a low cost material, therefore the alloy (Fe0.80Al0.20)97B3 reveals a great promise as a material to be used on sensors and actuators assembly.
Keywords: Magnetostriction; Fe–Al; Boron doping;

Display OmittedPolydispersed single crystal particles of the Nd2Fe14B and (Nd0.75Dy0.25)2Fe14B compounds with a short axes in the 60–140 nm range were prepared by high-energy ball milling and subsequent annealing of rare-earth oxides, iron oxide and boron oxide in the presence of a calcium reducing agent and a calcium oxide dispersant. The particles embedded in the CaO/Ca matrix in the presence of excess rare earth exhibit coercivity H c of 14.7 and 18.9 kOe. Removal of the matrix and excess rare earth is accompanied by interstitial modification of the 2:14:1 compounds with hydrogen; the H c of the Dy-free and Dy-containing particles declines with the washing to 1.4 and 3.2 kOe, respectively. After desorption of the hydrogen through vacuum annealing, the H c increases, but only to 4.6 and 6.2 kOe. This incomplete recovery is tentatively attributed to local anisotropy defects caused by loss of the rare earth atoms from the particle surfaces. If correct, this model implies that a much higher H c can be expected if the 2:14:1 particles are coated with or sintered in the presence of a rare-earth-rich phase.
Keywords: Permanent magnets; Mechanochemical processing; Metal hydrides; Rare earth alloys and compounds;

Synthesis and characterization of Fe–Pt based multishell magnetic nanoparticles by O. Pana; C. Leostean; M.L. Soran; M. Stefan; S. Macavei; S. Gutoiu; V. Pop; O. Chauvet (477-485).
Iron/platinum based core–shell nanoparticles were obtained by the inverse micelles method in two stages. Due to its specificity, this method produces an intermediate amorphous iron oxide layer. In this way the nanoparticles architecture is Fe@Fe-oxide@Pt. By thermal treatment in inert atmosphere, the amorphous shell crystallize and an additional magnetically ordered FePt alloy shell is formed at the interface between the Fe oxide and the outer Pt shell (Fe@Fe3O4/Fe2O3@FePt@Pt). The properties of these composites nanoparticles are investigated by TEM, HRTEM, X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID) magnetization measurements. The thermally treated nanoparticles show one order of magnitude higher coercivities than the initial Fe@Fe-oxide@Pt nanoparticles while preserving almost the same saturation magnetization. The complex magnetic behavior of these both multilayer coupled magnetic materials as a function of temperature and applied magnetic field is also discussed.
Keywords: Core–shell; Nanoparticles; Inverse micelles; Iron/platinum; Magnetization;

Newly found phase transition and mechanical stability of AuAl2: A first-principles study by Shouxin Cui; Dong-Qing Wei; Qingming Zhang; Zizheng Gong; Haiquan Hu (486-489).
Investigations of the structural stabilities and mechanical stability of AuAl2 were conducted by using first-principles pseudopotential method. A structural phase transition was predicted at 17.2 GPa, and the high-pressure phase is identified to be PbCl2-type structure, which was not classified by experimental studies. The stress–strain relationships under tensile deformations of AuAl2 are presented and compared with Au and Al metals, respectively. Moreover, the low tensile deformation resistance is interpreted by the electronic structure analysis.
Keywords: Intermetallics; High pressure phase; Electrical resistance; Tensile strength; Bond population;

Aging and Cu concentration effects on Sn–9Zn–xCu/Au couples by Yee-wen Yen; Wei-kai Liou; Wan-ching Chen; Chao-wei Chiu (490-494).
Aging and Cu concentration effects on the interfacial reactions between Sn–9 wt%Zn–x  wt%Cu (SZ–xCu) alloys and the Au substrate were investigated in this study. The Au3Zn7/AuZn2/AuZn and Au3Zn7/AuZn phases were formed in the SZ/Au and SZ–1Cu/Au couples aged at 160 °C for 24 h. Only the AuSn phase was found in the SZ–4Cu/Au couple aged at 160 °C for 24 h. When the aging time was extended to 800 h the Sn atoms became the dominant diffusion element. Binary Au–Sn phases and the metastable Au–Zn–Sn ternary phase were formed at the interface in the SZ–xCu couples when the Cu content was 1–4 wt%. When the Cu content was increased to 7–10 wt% AuSn and (Cu, Au)Sn phases were observed at the alloy/Au interface aged at 160 °C for 24 h. After 800-h heat treatment the SZ–xCu systems were transformed completely into the Cu–Sn/Au systems. The (Cu, Au)SnAuSn and Cu6Sn5/AuSn were formed in the SZ–7Cu/Au and SZ–10Cu/Au couples. The results indicate that the evolution of intermetallic compounds (IMCs) was very sensitive to the Cu concentration in the SZ solders and the heat treatment period.
Keywords: Aging and Cu concentration effects; Interfacial reactions; Sn–9 wt%Zn–x  wt%Cu alloys; Dominant diffusion element; Metastable Au–Zn–Sn ternary phase;

The impact of three new quaternary sulfides on the current predictive tools for structure and composition of diamond-like materials by Carl D. Brunetta; Jacilynn A. Brant; Kimberly A. Rosmus; Kylie M. Henline; Emma Karey; Joseph H. MacNeil; Jennifer A. Aitken (495-503).
Display OmittedIron-containing diamond-like materials Ag2FeSiS4, Li2FeSnS4, and Li2FeGeS4 were synthesized for the first time via high-temperature, solid-state synthesis and found to adopt the wurtz–kesterite structure, crystallizing in the noncentrosymmetric space group Pn. These materials are considered in the broader context of design principles for new cubic- and hexagonal-derived diamond-like materials. All three of these new compounds violate Pauling’s radius ratio rule and Pfitzner’s tetrahedral volume theory. An evaluation of the adherence of over 40 published quaternary diamond-like structures to Pauling’s radius ratio rule and Pfitzner’s tetrahedral volume theory reveals that tetrahedral structures can often be generated even though these ideals are violated. To assess the radius ratios in diamond-like structures, an appropriate radii set must be selected. Accordingly, five radii sets have been investigated for accuracy in predicting metal–sulfur bond distances in diamond-like materials. Furthermore, a crystal radius of 1.63 Å for four-coordinate S2− has been calculated using the metal–sulfur bond lengths of quaternary diamond-like materials and is proposed as an addition to the popular Shannon radii set.
Keywords: Radius; Diamond-like; Semiconductor; Kesterite; Stannite; Sulfide;

Response surface methodology (RSM) was successfully applied to process of preparation calcia partially stabilized zirconia (CaO-PSZ). Besides that, natural baddeleyite was used as starting materials instead of chemical pure zirconia. The pressureless sintering process was optimized by the application of RSM. The independent variables, which had been found as the most effective variables on the relative density and bending strength by screening experiments, were determined as holding time, sintering temperature and heating rate. Two quadratic models were developed through RSM in terms of related independent variables to describe the relative density and bending strength as the responses. Based on contour plots and variance analysis, optimum operational conditions for maximizing relative density and bending strength, at cooling rate of 3 °C/min, were 1540 °C of sintering temperature, 5 h of holding time and heating rate of 3 °C/min to obtain 98.57% for relative density and 165.72 MPa for bending strength.
Keywords: Stabilizer; Response surface methodology; Sintering; Natural baddeleyite;

Influence of mean grain size with ultrasonic velocity on microhardness of B4C–Fe–Ni composite by Vildan Özkan; İsmail H. Sarpün; Ayhan Erol; Ahmet Yönetken (512-519).
Composite samples were produced from boron carbide, iron and nickel matrix powders by using a powder metallurgy and electroless plating technique. Prepared samples were sintered at the temperature of ranging from 800 °C–1200 °C under Ar shroud. Ultrasonic velocity, ultrasonic attenuation and rate of screen heights of peaks were determined according to the pulse-echo method by using 2 MHz and 4 MHz probes. SEM (Scanning Electron Microscope), compressive testing and hardness measurements were employed to characterize the properties of the samples. Ultrasonic velocity, ultrasonic attenuation and rate of screen heights of successive peaks have showed a linear relation with mean grain size of samples. The ultrasonic velocity has been correlated with the hardness and the compressive strength and sintering temperature. We see that the sharp decrease in the hardness and a rapid increase in the ultrasonic velocities versus sintering temperature are attributed to the increase in the amount of grain size.
Keywords: Ultrasonic velocity; Attenuation; Mean grain size; Microhardness; Compressive strength; Composite materials;

We present a study of the structural, electronic, elastic and vibrational properties of the rhombohedral BiAlO3 structure within the local density approximation of density functional theory using norm-conserving pseudopotentials. The calculated equilibrium lattice constant, angle and atomic position are in reasonable agreement with the available experimental and theoretical dates. Based on the elastic constants and their related parameters, the crystal mechanical stability have been discussed. The elastic constants for BiAlO3 are also needed to completely determine its elastic properties including polycrystalline bulk, shear and Young’s moduli, Poisson’s ratio and the elastic anisotropy. Energy band structure shows that the rhombohedral BiAlO3 has an indirect band gap between D and Г-D symmetry points. We compute Born effective charge tensor, which is found to be quite anisotropic of Bi and O atoms. BiAlO3 have been studied by applying the direct method and deriving the phonon dispersion relations which include the longitudinal/transverse optical phonon mode splitting. In the rhombohedral phase the phonon dispersion curves show a soft mode between X and Г-point. This soft mode leads to the observed rhombohedral-cubic phase transition. The results are compared with the previous calculations and available experimental data.
Keywords: BiAlO3; Density functional theory; Elastic constants; Phonon dispersion curve; Electronic structure;

Effects of Cu interlayer on the wettability of aluminum on carbon by Young Jin Ko; Juil Yoon; Joonho Lee; Jun Hyun Han (526-531).
Wettability of Al on Cu coated graphites and the interfacial reactions between Al and the Cu coating were analyzed to examine in depth the effect of the Cu coating layer used to enhance the wettability of Al on carbon. The wetting behaviors of Al according to Cu coating method and Cu thickness were also investigated. The Cu/Cu double layer coated by sputtering the Cu single layer coated by electroless plating because it improved the stability of the Cu layer coated on graphite at high temperature. In order to suppress the dewetting of Al on graphite and improve the wettability of Al on graphite, a thick Cu coating layer to supply sufficient Cu atoms for saturation in an Al droplet is needed.
Keywords: Wettability; Aluminum; Composite; Carbon; Cu coating;

Effect of vanadium addition on the creep resistance of 18Cr9Ni3CuNbN austenitic stainless heat resistant steel by Dae-Bum Park; Moo-Young Huh; Woo-Sang Jung; Jin-Yoo Suh; Jae-Hyeok Shim; Seung-Cheol Lee (532-538).
The effect of vanadium addition on the creep property of niobium-containing 18Cr–9Ni austenitic heat-resistant steel was studied. After solution treatment, the MX precipitates of vanadium-free steel contained Nb only. On the contrary, high Nb and low V contents were detected from the MX precipitates in the steel with 0.3 wt% of vanadium. Vanadium-rich MX carbo-nitride was not observed in the matrix and at the grain boundaries after solution treatment. The vanadium precipitated as a form of Z-phase during early-stage creep deformation was attributed to the improvement in creep strength at 700 °C with applied stress higher than 150 MPa. And metallic Cu precipitates were confirmed in the nanometer scale using TEM and EDS technique. The Cu precipitates are believed to contribute to the strengthening of austenitic heat resistant steel independently. The precipitation behavior is discussed using transmission electron microscopy and thermo-kinetics simulation technique.
Keywords: Austenitic stainless steel; Z-phase; Creep strength;

Polycrystalline Ti1− x Mn x N films with different Mn atomic fractions (x) were grown by reactive facing-target sputtering. The preferred lattice orientation changes from (2 0 0) to (1 1 1) with the increase of x, which makes the surface morphology evolve from spherical to triangular-pyramid-like islands. Weak grain-boundary ferromagnetism with a Curie temperature of higher than 305 K has been observed. The saturation magnetization (Ms ) and coercivity do not show a monotonous change with x. Asymmetric MH curves can be observed at low temperatures, and the shift of MH curves decreases with the increase of temperature because of the relaxation of the low-temperature pinned moments. All of the films show semiconducting-like behavior with a mechanism of thermal fluctuation-induced tunneling. Magnetoresistance (MR) is negative, but is very small. The small Ms and MR can be ascribed to the weakly ferromagnetic interaction of moments at grain boundaries and low spin polarization.
Keywords: Metal nitride; Microstructure; Magnetic properties; Magnetoresistance;

Heterogeneous duplex structured Ti–Sn–Mo alloys with high strength and large plastic deformability by E.M. Park; C.H. Lee; J.M. Park; J.H. Han; G.A. Song; J.T. Kim; S.H. Hong; J.Y. Park; Y. Seo; N.S. Lee; K.B. Kim (546-551).
We report that the formation of the heterogeneous duplex structure and its influence on the mechanical properties in Ti–Sn–Mo alloys by optimization of the Mo concentration ratio. With the addition of Mo up to 5 at.%, the colony size and the alternating lamellar phase thickness are significantly decreased and the solid state phase transformation of supersaturated β-Ti to α-Ti phases is strongly suppressed. The unique heterogeneous duplex structure, which is micrometer-scale supersaturated β-Ti solid solution phase are encapsulated by ultrafine-scale α-Ti/Ti3Sn lamellar phases along the β-Ti phase boundary areas, effectively releases the stress concentration and hampers the excessive strain localization during deformation, leading to a high strength of ∼1 GPa and a large plastic strain of ∼30%.
Keywords: Metals and alloys; Microstructure; Mechanical properties; Ultrafine eutectic structure;

Crystal structure and magnetic properties of Ce2Fe14− x Co x B alloys by Eric J. Skoug; M.S. Meyer; F.E. Pinkerton; Misle M. Tessema; Daad Haddad; J.F. Herbst (552-555).
Permanent magnet materials based on the R2Fe14B phase (R = rare earth element) are essential to a wide variety of applications, among them automotive traction motors. Current state-of-the-art materials rely on R = Nd and Dy, for both of which there are supply uncertainties and rapidly rising costs. A possible alternative is R = Ce, the most abundant rare earth, but Ce2Fe14B has several disadvantages, including a low Curie temperature (T c) that limits its maximum operating point to well below that required for some automotive uses. Here we systematically investigate the Ce2Fe14− x Co x B system by exploring Co substitution for Fe in melt-spun ribbons as a means of increasing T c. In addition to T c we report the solubility of Co in Ce2Fe14B and its effect on the crystal structure and hard magnetic properties.
Keywords: Permanent magnets; Magnetically ordered materials; Rare earth alloys and compounds;

The nanocrystallization kinetics of the (Fe0.8Ni0.15M0.05)78Si8B14 (M = Nb, Ta, W) amorphous alloy was investigated by differential scanning calorimetry (DSC). Kissinger method, Ozawa method and the expended Friedman method were used to calculate and compare the kinetic parameters of the crystallization processes. The nanocrystallization mechanism for the non-isothermal primary crystallization of the amorphous alloys were discussed using Avrami exponent n. Transmission electron microscopy (TEM) studies verified the influence of nanocrystallization mechanism on the microstructure.
Keywords: Amorphous alloys; DSC; Crystallization kinetics; Activation energy; Avrami exponent n;

Novel three-dimensional (3D) flower-like Strontium sulfate (SrSO4) microstructures with hierarchical architecture were successfully fabricated by using Sr(NO3)2 react with Na2SO4 aqueous solution under ambient conditions at room temperature. The SrSO4 flower-like microcrystals have a uniform diameter of about 10 μm, which are composed of numerous well-aligned single tablet-like SrSO4 crystals oriented radially to their center. The growth mechanism of the flower-like hierarchical celestine particles is discussed to obtain a better understanding on their formation process. XRD patterns confirm the single crystal phase of SrSO4. In the photoluminescence property investigations of SrSO4:Sm3+, narrow bands observed are well identified with the electronic transition configurations of Sm3+. The temperature-dependent photoluminescence spectra show that the temperature of maximum emission intensity is 25 °C. The thermal stability and electron trapping luminescence properties were also characterized.
Keywords: Chemical synthesis; Crystal growth; Microstructure; Optical properties; Rare-earth ions; Phosphors;

Engineering stress-strain diagrams of monolithic AZ41, AZ51 alloys and their nano-Al2O3 and Ca added nanocomposites.Display OmittedIn the present study, new magnesium based AZ41/Al2O3–Ca and AZ51/Al2O3–Ca nanocomposites were successfully synthesized incorporating varying amount of elemental Al (1 and 2% by wt.), Ca (1 and 2% by wt.) and 1.5 vol.% nano-sized (50 nm) Al2O3 particulates into AZ31 alloy using disintegrated melt deposition technique. AZ41 and AZ51 alloys were also developed following the same processing route by adding 1 and 2 wt.% Al, respectively. All alloy and composite samples were then subsequently hot extruded at 400 C and characterized. Microstructural characterization studies revealed equiaxed grain morphology, reasonably uniform distribution of nanoparticulate and intermetallics in the matrix, good interfacial integrity and minimal porosity. Addition of nano-sized Al2O3 particulates and Ca into AZ41 and AZ51 samples helped to reduce the average grain size and diameter of Mg17Al12 second phase and introduced (Mg, Al)2Ca phase in the matrix. Microhardness test results revealed that AZ51/Al2O3–2Ca samples exhibited around 47% and 90% higher microhardness value when compared to monolithic AZ51 and AZ31 samples, respectively. Room temperature tensile test results also revealed that newly developed nanocomposites exhibited superior combination of tensile properties in terms of 0.2% yield strength, ultimate tensile strength and ductility when compared to their respective alloys and some commercially available Mg alloys.
Keywords: Magnesium alloy; Calcium; AZ41; AZ51; Nanocomposite;

First-principle investigations on the structural dynamics of Ti2GaN by Z.J. Yang; J. Li; R.F. Linghu; X.L. Cheng; X.D. Yang (573-579).
We report a first-principle study on the elastic and electronic properties of the nanolaminate Ti2GaN. Our calculated lattice parameter shows that c axis is always stiffer than a axis. The elastic constants investigations demonstrated that Ti2GaN is stable over a wide pressure range of 0–1000 GPa with the only exception of 350–600 GPa owing to the elastic softening. The softening behaviors of the Young’s and shear moduli are also found in the same pressure range of 350–600 GPa, indicating a structural metastability. Investigation on the axial compressibility we observed an abnormal c-axis expansion behavior within a pressure range of 350–600 GPa, resulting from the expansion of the Ti–Ti bond length and the increase of the Ti–Ti bond population. Study on the density of states (DOSs) we found that the Ti s and Ti p electrons shift towards higher energies with pressure.
Keywords: Ti2GaN; Elastic properties; First-principle;

Energy band structure calculations of Ga x In1− x P alloys under the influence of temperature and pressure by Abdel Razik Degheidy; Sayed Abdel Aty Elwakil; Elkenany Brens Elkenany (580-590).
Display OmittedThis work is concerned with the dependence of the electronic energy band structures for Ga x In1− x P alloys on temperature and pressure. The calculations are based on local empirical pseudo-potential method (EPM) coupled with the virtual crystal approximation (VCA) which incorporates compositional disorder as an effective potential. The direct and indirect energy band gaps of the considered alloys have been determined over entire composition parameter, x from 0 to 1, temperature from T  = 0 K to 500 K and pressure from P = 0 Kbar to 120 Kbar. In addition, the refractive index and dielectric constant of the considered alloys under the effect of composition, temperature and pressure have also been studied. The ternary alloys Ga x In1− x P is bordered by two binary compounds GaP and InP which have been studied recently by our group. Comparison of the calculated results with the experimental and published data showed good agreement.
Keywords: Nanostructures; Alloys; Electronic structure; Temperature; Pressure;

Dielectric properties of PZT–epoxy composite thick films by Vasilica Pascariu; Leontin Padurariu; Ovidiu Avadanei; Liliana Mitoseriu (591-599).
Composites with 0–3 connectivity patterns were prepared by gravity casting by using different amounts of Pb(Zr,Ti)O3 powder with concentrations (x  = 0%, 2.5%, 5%, 7.5%, 10% and 15%) embedded into a polymer matrix of epoxy resin. The role of the filling factor and of the gradient composition on the effective dielectric properties was theoretically investigated by Finite Element Method. The frequency dependencies of the real and imaginary parts of the dielectric permittivity at various temperatures showed a few relaxation mechanisms that were discussed. The composites exhibit a permittivity gradient and act as a natural impedance match system in the frequency range of 2–6 GHz, resulting in very low reflections. The compositionally graded PZT–epoxy resin composite thick films are suitable as adapting impedance materials for microwave applications.
Keywords: PZT; Dielectric properties; Coefficient reflection; Epoxy resin;

Near-infrared luminescence enhancing by co-doping Bi3+ in YVO4:Nd3+ by Quan-Lan Xiao; Jian-Xin Meng; Jian-Rong Qiu (600-603).
NIR luminescence phosphors Nd3+, Bi3+ co-doped YVO4 were prepared by conventional solid-state reaction and the optical properties are investigated by photoluminescence, photoluminescence excitation spectra and fluorescence decay measurements. Introduction of Bi3+ in YVO4:Nd3+ led to significantly enhancing of the NIR emission of Nd3+ ions, the peak excitation wavelength also red-shifted from 335 to 352 nm and match better with the solar spectrum. Energy transfer from VO 4 3 - , Bi3+ charge transfer states to the excitation states of Nd3+ accounts for this fluorescence enhancement and the possible energy transfer mechanism was briefly discussed. The peculiar optical properties of YVO4:Bi3+, Nd3+ help us to forecast the feasibility of potential application in enhancing the efficiency of Si-based solar cells.
Keywords: Near-infrared luminescence; Energy transfer; Solid-state reaction; YVO4:Nd3+, Bi3+; Sensitization;

CaCu3Ti4O12 thin films with non-linear resistivity deposited by RF-sputtering by C.R. Foschini; R. Tararam; A.Z. Simões; M. Cilense; E. Longo; J.A. Varela (604-608).
Display OmittedCalcium copper titanate, CaCu3Ti4O12, CCTO, thin films with polycrystalline nature have been deposited by RF sputtering on Pt/Ti/SiO2/Si (1 0 0) substrates at a room temperature followed by annealing at 600 °C for 2 h in a conventional furnace. The CCTO thin film present a cubic structure with lattice parameter a  = 7.379 ± 0.001 Å free of secondary phases. The observed electrical features of CCTO thin films are highly dependent on the [CaO12], [CaO4], [CuO11], [ CuO 11 V o x ] and [ TiO 5 · V O • ] clusters. The CCTO film capacitor showed a dielectric loss of 0.40 and a dielectric permittivity of 70 at 1 kHz. The JV behavior is completely symmetrical, regardless of whether the conduction is limited by interfacial barriers or by bulk-like mechanisms.
Keywords: Thin films; Chemical synthesis; X-ray diffraction; Electron microscopy;

Development of lead free pulse electrodeposited tin based composite solder coating reinforced with ex situ cerium oxide nanoparticles by Ashutosh Sharma; Sumit Bhattacharya; Siddhartha Das; H.-J. Fecht; Karabi Das (609-616).
Display OmittedPure Sn and Sn–CeO2 nanocomposite films have been pulse electrodeposited from an aqueous electrolyte containing stannous chloride (SnCl2⋅2H2O) and triammonium citrate (C6H17N3O7). The codeposition is achieved by adding different amounts of ball milled CeO2 nanopowders (1–30 g/L) with a mean particle size of ∼30 nm to the electrolyte. Microstructural characterizations have been carried out by X-ray diffraction analysis, scanning electron microscopy coupled with an energy dispersive spectroscopy, and transmission electron microscopy. The microstructural observations show that a uniform microstructure is obtained at a concentration of ∼6 wt% CeO2 in the deposits corresponding to 15 g/L CeO2 in electrolyte. Thus, incorporation of an optimum amount of CeO2 in a composite provides better mechanical, and wear and friction properties, without sacrificing the electrical resistivity significantly.
Keywords: Composites; Chemical synthesis; Electrochemical reactions; Microstructure;