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  • Surface microstructural characteristics and hardness of Cr-coated Zr702 sheet processed by pulsed laser
    Intermetallics (IF 3.353) Pub Date : 2020-01-25
    Jiahong Dai; Ke Chen; Linjiang Chai; Yufan Zhu; Haotian Guan; Ning Guo

    Microstructural characteristics and hardness of Cr-coated Zr702 sheet after the laser surface treatment (LST) were characterized and investigated by combined use of electron backscatter diffraction, electron channeling contrast imaging, energy dispersive spectrometry and hardness measurement. Results show that after the LST processing at 100 W, three zones with different microstructural characteristics are presented from the surface to the matrix: melted zone (MZ), solid-state phase transformation zone (SSPTZ) and matrix. Surface alloying with Cr occurs in the MZ, leading to the formation of a large number of discontinuous netlike ZrCr2 Laves phases. The SSPTZ is comprised of untransformed bulk α grains with internal substructures and fine martensitic plates. The appearance of such substructures can be attributed to dislocation movements induced by thermal stresses while the martensitic plates result from rapid β→α transformation induced by the pulsed laser. Hardness measurements show that the LST can remarkably increase surface hardness (by ~110%) of the Cr-coated Zr702 sheet, which can be ascribed to strengthening/hardening effects by solid solution of Cr, the formation of dense second phases and significant grain refinement.

    更新日期:2020-01-26
  • Recrystallization and Grain Growth Simulations for Multiple-Pass Rolling and Annealing of U-10Mo
    Metall. Mater. Trans. A. (IF 1.985) Pub Date : 2019-12-06
    William Frazier, Chao Wang, Zhijie Xu, Nicole Overman, Shenyang Hu, Vineet V. Joshi

    Abstract A simulation model of recrystallization and grain growth has been developed to investigate grain structure evolution during deformation and heat treatment in polycrystalline U-10 wt pct Mo (U-10Mo) fuel. Experimentally obtained U-10Mo post-homogenization microstructures were used as input for closed-loop simulations of multiple rolling passes, intermediate heating, and final annealing. Finite element model calculations of deformation and Potts model simulations of recrystallization and grain growth were used to iteratively inform each subsequent stage of simulation. The model was then applied to predict the grain structure evolution during multiple-pass hot rolling and annealing of U-10Mo and benchmarked against experimentally observed U-10Mo recrystallization behavior. The results showed that our model was able to capture the coupling between deformation and recrystallization as a function of microstructure, including particle stimulated nucleation and recrystallization nucleation on grain boundaries. Additionally, we have achieved reasonable quantitative agreement with U-10Mo recrystallization and grain growth behavior.

    更新日期:2020-01-26
  • Structural, magnetic and dielectric properties of nano-crystalline spinel NixCu1-xFe2O4
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    Adil Saleem; Yujun Zhang; Hongyu Gong; Muhammad K. Majeed; Jie Jing; Xiao Lin; Junjie Mao; M. Zeeshan Ashfaq
    更新日期:2020-01-26
  • Capturing dual behavior of the parallel coercivity in FeNi/Cu nanowire arrays by fine-tuning of segment thicknesses
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    M.H. Abbas; A. Ramazani; A.H. Montazer; M. Almasi Kashi
    更新日期:2020-01-26
  • Elastic moduli of high-density, sintered monoliths of yttrium dihydride
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    A.P. Shivprasad; D.M. Frazer; V.K. Mehta; M.W.D. Cooper; T.A. Saleh; J.T. White; J.R. Wermer; E.P. Luther; D.V. Rao
    更新日期:2020-01-26
  • Spectral converters for CdS–CdTe solar cell
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    P.K. Tawalare; P.D. Belsare; S.V. Moharil
    更新日期:2020-01-26
  • Effects of L-cysteine on the photoluminescence, electronic and cytotoxicity properties of ZnS:O quantum dots
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    Xiaoxuan Wang; Wen Dai; Xiaoxia Li; Zhenyu Chen; Zichuan Zheng; Zhong Chen; Guangzhi Zhang; Lina Xiong; Shuwang Duo
    更新日期:2020-01-26
  • Ru-impregnated needle-like NiCo2O4 embedded in carbon textiles as O2 electrode for a flexible Li–O2 battery
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-26
    Siqi Zhang; Ying Wang; Dan Li; Ziye Kang; Feilong Dong; Haiming Xie; Jia Liu
    更新日期:2020-01-26
  • Highly thermally conductive nanocomposites synthesized by PVD for thermal management applications
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Xiaopeng Han; Ying Huang; Jin Yan; Yade Zhu; Xiaogang Gao

    Uniform Ag and Si layers were successfully prepared on the surface of graphite films (GF) to improve thermal conductivity (TC) by physical vapor deposition method (PVD). The results demonstrate that the unique cubic crystal structure of Ag layer with different deposition time show good interface bonding and no carbide product of Ag/GF composites. Meanwhile, the dense Si coating contribute to the enhancement of the thermal diffusion ability. The Ag/GF composites with the deposition time of 2 h possess the best comprehensive property with the TC of 9.93 (W/m·K), which is approximately 73.30% higher than untreated GF. The TC of Si/GF composites reach the maximum TC of 11.12 W/(m·K) and increase about 101.81% due to the nano-Si layer comparing with untreated GF. Those composites with high performance make them promising thermal management laminated materials.

    更新日期:2020-01-26
  • 更新日期:2020-01-26
  • Laser processing as a high-throughput method to investigate microstructure-processing-property relationships in multiprincipal element alloys
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Mu Li; Katharine M. Flores

    A direct laser deposition processing method was applied to construct compositional and microstructural libraries of AlxCoCrFeNi in an efficient and high-throughput manner. Among the compositions (x = 0.51–1.25) and quench rates (26–6400 K/s) studied, most of the laser deposited alloys exhibit a cellular microstructure, similar to the cast materials. The microstructural feature sizes were found to follow a power law relationship with the quench rate. The dependence of the microhardness on microstructural length scale was also investigated and observed to follow a Hall-Petch relationship. This study indicates that laser processing is an effective method for rapidly and efficiently evaluating multiprincipal element alloys and their microstructures.

    更新日期:2020-01-26
  • Al–Al2O3 powder composites obtained by hydrothermal oxidation method: Powders and sintered samples characterization
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    A. Yu Nalivaiko; A.N. Arnautov; S.V. Zmanovsky; D. Yu Ozherelkov; P.K. Shurkin; A.A. Gromov
    更新日期:2020-01-26
  • A novel cobalt-free FeMnCrNi medium-entropy alloy with exceptional yield strength and ductility at cryogenic temperature
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    B.B. Bian; N. Guo; H.J. Yang; R.P. Guo; L. Yang; Y.C. Wu; J.W. Qiao

    In this study, a novel cobalt-free Fe40Mn20Cr20Ni20 medium-entropy alloy (MEA) with low cost is purposively designed. The partially recrystallized microstructure was introduced into the single-phase FeMnCrNi MEA via thermo-mechanical processing. Surprisingly, the present MEA displays ultrahigh yield and ultimate tensile strengths of 1.2 and 1.34 GPa, respectively, and large ductility with a uniform elongation of 22% at 77 K. This is mainly due to the accumulation and entanglement of a large number of dislocations and the activation of deformation twins at 77 K.

    更新日期:2020-01-26
  • 更新日期:2020-01-26
  • Study of the kinetics and products of the devitrification process of mechanically amorphized Fe70Zr30 alloy
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    A.F. Manchón-Gordón; J.J. Ipus; J.S. Blázquez; C.F. Conde; A. Conde; P. Svec

    DEVITRIFICATION of mechanically alloyed amorphous Fe70Zr30 at. % compound consists on a two-step process: amorphous → amorphous + bcc Fe + Fe2Zr → Fe2Zr + Fe23Zr6. This sequence is inferred from the evolution of the Mössbauer spectra, the thermomagnetic experiments and the X-ray diffraction (XRD) patterns. Hyperfine parameters for both intermetallics have been obtained from Mössbauer spectroscopy in correlation with the phase identification from XRD results. The broadening of the stable compositional range of Fe2Zr intermetallic above 1000 K is responsible for a strong dependence of the phase fractions on heating and cooling rates. Despite the overlapping of the two processes involved in the devitrification, the individual Avrami exponents of each one have been estimated.

    更新日期:2020-01-26
  • A comparative study of cell growth on a cold sprayed Ti–Ta composite
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Guang Zeng; Saden Zahiri; Stefan Gulizia; Yaping Chen; Xiao-Bo Chen; Ivan Cole
    更新日期:2020-01-26
  • Investigation on the tensile deformation mechanisms in a new Ni–Fe-base superalloy HT700T at 750 °C
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    P. Zhang; Y. Yuan; Y.F. Gu; J.B. Yan; Y.Y. Dang; J.T. Lu; J.C. Wang

    After a standard heat treatment and subsequent isothermal aging at 750 °C for 8,220 h, the tensile deformation behavior of a novel precipitation-hardened Ni–Fe-base superalloy HT700T containing around 23 vol% of γ′ precipitates is studied at 750 °C. It is found that the work-hardening rate decreases monotonously with plastic strain. Transmission electron microscopy observations on the specimens stretched to various magnitudes of plastic strain reveal that Orowan looping prevails at the very beginning of plastic deformation. Whereas, as plastic deformation proceeds, more and more isolated superlattice stacking faults are produced within the γ′ precipitates although numerous dislocation loops have surrounded the same γ′ precipitates, suggesting shearing of γ′ precipitates by {111} <112> slip systems plays a more and more important role in the plastic deformation with strain. Based on the experimental observations, the relationship between the operative deformation mechanisms and the work-hardening rate of HT700T is discussed.

    更新日期:2020-01-26
  • Critically assessing alloy design criteria of metallic glasses
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Sarika Kumari; R.K. Mandal

    Several criteria are available in literature for designing the alloy compositions for metallic glasses. We have analyzed characteristics of glass-forming compositions numbering around 1000 in terms of parameters, electron to atom ratio (e/a), volume ratio (VR) and radius ratio (RR). Venn-Diagrams created based on these parameters for Fe-, Cu-, Zr-, Ti-, La-, Mg-, Co-, Al-, Ni- and Pd-based alloy systems will be presented. Relative importance of e/a, VR, and RR will be indicated. Having done this, we would like to understand the process of stabilization of Bulk Metallic Glasses (BMGs) in terms of Fermi surface (FS) and Pseudo Brillioun zone (PBZ) interaction.

    更新日期:2020-01-26
  • 更新日期:2020-01-26
  • Single-phase ZnCo2O4 derived ZnO–CoO mesoporous microspheres encapsulated by nitrogen-doped carbon shell as anode for high-performance lithium-ion batteries
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Jinzhe Liu; Jing Wu; Chencheng Zhou; Peilin Zhang; Guo Shouzhi; Shuo Li; Yun Yang; Kuang Li; Luyang Chen; Mingyi Wang
    更新日期:2020-01-26
  • Performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ/Ce0.85Sm0.15O2−δ–CuO as a cathode for intermediate temperature solid oxide fuel cells
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Shuang Zhao; Ning Tian; Ji Yu

    Herein, we report enhancement of the electrochemical performance of the Ba0.5Sr0.5Co0.8Fe0.2O3−δ/Ce0.85Sm0.15O2−δ (BSCF/SDC) composite cathode for intermediate temperature solid oxide fuel cells by improving the ionic conductivity of SDC through addition of CuO. Furthermore, the effect of the sintering temperature on the crystal structures, surface morphology, and electrochemical properties of the BSCF/SDC–CuO cathode was investigated. Three sintering temperatures were investigated (900, 950, and 1000 °C). The findings showed that raising the SDC ionic conductivity and a sintering temperature of 950 °C were the optimal conditions for improving the performance of the composite cathode.

    更新日期:2020-01-26
  • Effects of powder size distribution on the microstructural and mechanical properties of a Co–Cr–W–Si alloy fabricated by selective laser melting
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-25
    Kefeng Li; Xinhua Mao; Khashayar Khanlari; Kaikai Song; Qi Shi; Xin Liu

    Co–Cr based alloys are recognized as one of the most widely used category of alloys amongst the biomedical materials. This is because these alloys show a high strength, corrosion resistance and good biocompatibility suitable for biomedical applications. Many researchers have been focused on the processing of these alloys using a selective laser melting process. The effects of different processing parameters on the obtained microstructural and mechanical properties of the processed parts have been investigated in these studies. However, the effect of powder distribution size (powder granulometry), as a primary processing parameter, on the microstructural and mechanical properties of Co–Cr alloys is not well investigated and studied so far. This study investigated the influence of this parameter, by using powders with the same composition and morphology but a different particle size of coarse and fine, on the microstructural and mechanical properties of as-built, homogenizing heat treated and homogenizing heat treated followed by subsequent aging treatment SLM fabricated Co28Cr9W1.5Si (wt.%) samples. X-ray diffraction, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy were used to characterize and identify the microstructure, phase composition and crystallographic information of the manufactured samples. Besides, the mechanical properties of samples, processed using powders having different size distributions, were measured using a tensile test machine and results were correlated to the microstructure of the samples. It was concluded that the powder granulometry has a negligible effect on the microstructural and mechanical properties of the as-built SLM Co–Cr–W–Si parts but a remarkable influence on those of the heat-treated ones.

    更新日期:2020-01-26
  • 更新日期:2020-01-26
  • The effects of SeO2 additive on Mn electrodeposition on Al substrate in MnSO4-(NH4)2SO4-H2O solution
    Hydrometallurgy (IF 3.465) Pub Date : 2020-01-25
    Fan Yang; Liangxing Jiang; Xiaoying Yu; Yanqing Lai; Jie Li
    更新日期:2020-01-26
  • Molecularly imprinted PEDOT on carbon fiber paper electrode for the electrochemical determination of 2,4-dichlorophenol
    Synth. Met. (IF 2.87) Pub Date : 2020-01-25
    Ann Maria C G; Akshaya K B; Sherin Rison; Anitha Varghese; Louis George

    A highly selective electrochemical sensor has been developed for the determination of the pesticide molecule, 2,4-dichlorophenol (2,4-DCP) using molecularly imprinted conducting polymer. 2,4-dichlorophenol imprinted polymer films were prepared by electropolymerising 3,4-ethylenedioxythiophene (EDOT) on surface of carbon fiber paper electrode (CFP) in presence of 2,4-dichlorophenol. Electrochemical over-oxidation was carried out for the controlled release of 2,4-DCP templates and to generate definite imprinting sites. Surface morphology of the imprinted electrode was analysed by Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometry, Fourier Transform Infrared and Raman spectroscopy. In optimized conditions, the voltammetric sensor gave a linear response in the range of 0.21 nM – 300 nM. The significantly low detection limit (0.07 nM) demonstrates the ultra-low sensitivity of the method. The imprinted sensor displayed higher affinity and selectivity towards the target 2,4-DCP over similar structural analogical interference than the non-imprinted sensor. MIP sensor was efficaciously employed for the selective determination of 2,4-DCP in real samples of water.

    更新日期:2020-01-26
  • Mechanical and thermoelectric properties of environment friendly higher manganese silicide fabricated using water atomization and spark plasma sintering
    Intermetallics (IF 3.353) Pub Date : 2020-01-24
    Peyala Dharmaiah; Chul-hee Lee; Gian Song; Soon-Jik Hong

    Here, we report on an economical, viable, one-step method for fabrication of Higher Manganese Silicide MnSi1.75 (HMS). Fabrication of the HMS was followed by spark plasma sintering (SPS) at different temperatures (850, 900, 950 and 1000 °C), after which the thermoelectric and mechanical properties were investigated. It was found that the electrical conductivity significantly increased with increasing SPS temperature. This was attributed to the simultaneous increase of carrier concentration and mobility, while a reduction in the Seebeck coefficient was attributed to the formation of secondary phase in the HMS samples. A low thermal conductivity of 1.86 W/mK at 723 K was obtained for the sample sintered at 850 °C, which was attributed to increased scattering of heat-carrying phonons due to pores or voids, and grain boundaries. In addition, a maximum ZT of 0.27 was obtained at 723 K for the HMS-1000 sample, which is comparable with other previously reported data for undoped HMS material. Nevertheless, the HMS-1000 sample exhibited compressive strength of 1208 MPa and fracture toughness of 1.99 MPa m1/2, which is significantly higher than other state-of-the-art thermoelectric materials. The proposed fabrication method could be adopted for mass market applications requiring superior mechanical and thermoelectric properties.

    更新日期:2020-01-24
  • A Review on Silicide-Based Materials: Thermoelectric and Mechanical Properties
    Met. Mater. Int. (IF 1.647) Pub Date : 2020-01-24
    Gwansik Kim, Hyunjun Shin, Jihyun Lee, Wooyoung Lee

    Abstract Silicide-based thermoelectric (TE) materials are promising candidates for automotive TE generators, which can collect wasted heat and convert it into electricity. Adequate strategies should be used to manufacture highly efficient silicide-based TE devices. This review summarizes novel strategies for obtaining materials that feature excellent TE properties and mechanical reliability. Controlling the carrier concentration and band structure could increase their electronic transport properties, while nanostructure engineering could effectively reduce their lattice thermal conductivity. Moreover, well designed microstructures are required to obtain mechanically reliable TE materials, which indicates that precisely controlling their nanostructure is essential for the improved trade-off relationship between TE and mechanical properties. While many challenges should still be overcome, the development of highly efficient TE materials and devices could represent new solutions for the global energy crisis. Graphic Abstract

    更新日期:2020-01-24
  • Preparation and characterizations of flexible photothermal Ti2O3-PVA nanocomposites
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Daoguang Bi; Yangyang Li; Yingbang Yao; Tao Tao; Bo Liang; Shengguo Lu

    Flexible photothermal devices have been extensively explored in a wide range of fields in recent years. In this work, a flexible photothermal nanocomposite film based on Ti2O3-PVA has been demonstrated for converting sunlight into thermal energy. Ti2O3 nanoparticles were surfaced-modified by four kinds of different surfactants (γ–aminopropyltriethoxy Silane, Hexadecyl Trimethyl Ammonium Bromide, Stearic Acid, Polysorbate-80), respectively, and then the nanocomposites were prepared by a simple solution casting method. The flexible composite shows strong sunlight absorption in a wide spectrum range (300 nm–2000 nm). Under illumination of 5 kW/m2 simulated sunlight, the nanocomposite can be quickly heated up to 64.1 °C. The nanocomposite presented stable performances after tens of bending tests, indicating good flexibility. Our results show that the nanocomposite with Ti2O3 nanoparticles modified with Stearic Acid exhibits the strongest light absorption capability and thus the best photothermal effect. This flexible composite material may have promising potentials in the applications of photothermal energy harvesting devices for wearable electronics, solar-driven steam generators, or seawater desalinators etc.

    更新日期:2020-01-24
  • Magnetic behavior and conductive wall switching in TiO2 and TiO2:Co self-organized nanotube arrays
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Heiddy P. Quiroz; J.E. Serrano; A. Dussan
    更新日期:2020-01-24
  • Blue laser-induced photochemical synthesis of CuAg nanoalloys on h-BN supports with enhanced SERS activity for trace-detection of residual pesticides on tomatoes
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Hua Zhang; Qingqiang Cui; Linlin Xu; Anxin Jiao; Yue Tian; Xiangdong Liu; Shuang Li; Hengshuai Li; Ming Chen; Feng Chen
    更新日期:2020-01-24
  • Effect of NASICON-type LiSnZr(PO4)3 ceramic filler on the ionic conductivity and electrochemical behavior of PVDF based composite electrolyte
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Tanvi Pareek; Sushmita Dwivedi; Shadab Ali Ahmad; Manish Badole; Sunil Kumar
    更新日期:2020-01-24
  • Optical properties and theoretical study of Mn doped ZnAl2O4 nanoparticles with spinel structure
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Shangpan Huang; Zhiqiang Wei; Xiaojuan Wu; Jiwen Shi

    Zn1-xMnxAl2O4 (x = 0, 0.10, 0.20, 0.30 and 0.40) nanoparticles were synthesized by hydrothermal method, and the effects of Mn doping on the microstructure, morphology, binding energy and optical property of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), x-ray photoemission spectroscopy (XPS), ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence spectra (PL) and fourier transform infrared spectroscopy (FT-IR). And the energy band structure of various defects in ZnAl2O4 structure were calculated by means of the first-principles calculations. The experimental results show that Zn1-xMnxAl2O4 nanoparticles possess cubic spinel structure without other impurity phases. The morphology of the samples exhibits irregular spherical or ellipsoid particles with uniform particle size. EDX Mapping display that Zn, Al, O and Mn elements are uniformly distributed without any enrichment phenomenon throughout the sample. Mn ions successfully used as doping agent replaced Zn2+ and entered ZnAl2O4 matrix. Combined with the calculated results of the first principle calculations, the substitution of Mn introduced new energy levels, which level make the intensity of PL spectra decrease and occur quenching phenomenon. XPS spectra demonstrate that the doped Mn ions mainly occupy the tetrahedral sites. UV-vis spectra indicate with the increase of Mn ion concentration, the band gap of the doped sample decrease with the increase of Mn content and exhibit red shift. FT-IR show that all Mn2+ ions substituted for Zn2+ ions without changing ZnAl2O4 spinel structure.

    更新日期:2020-01-24
  • Probing energy transfer mechanism via the upconversion spectra of Tm3+/Yb3+:LiNbO3 by tri-doping with Ba2+ in different site occupations
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Zhihua Liu; Yunzhong Zhu; Wenjia Wang; Decai Ma; Biao Wang

    Metal doping has been an efficient method to enhance upconversion (UC) luminescence, however, the relationship between fluorescence kinetics and site occupation of luminescence center has barely been revealed. To solve this issue, we have designed a tri-doping system of various Ba2+ doped Tm3+/Yb3+:LiNbO3 to investigate the energy transfer (ET) rate and the site occupation quantitatively, where 4.8 and 7.9 folds enhancement of blue and red emission has been achieved, respectively. Owing to the sensitive 4f-4f transition between lanthanide ions, the ion environment could be presented vividly by the zigzag-shaped UC intensity variation for different Ba2+ doping concentrations. Then, the corresponding ET rate equations are established by steady-state rate equations which draw the site occupation process of lanthanide ions simultaneously. The calculated results for Föster ET rate, local optical power density, and pump power absorption illustrate that Ba2+ could adjust the ET rate by transforming the site of lanthanide ions in crystal lattice. More importantly, this method could shed light on the mechanism of UC enhancement by modulating ET rate via ion doping.

    更新日期:2020-01-24
  • Dual Z-scheme MoS2/g-C3N4/Bi24O31Cl10 ternary heterojunction photocatalysts for enhanced visible-light photodegradation of antibiotic
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Jin Kang; Chongyue Jin; Zhilin Li; Min Wang; Zhiquan Chen; Youzhao Wang
    更新日期:2020-01-24
  • Influence of crystallinity of CuCo2S4 on its supercapacitive behavior
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    J.P. Cheng; S.Q. Gao; P.P. Zhang; B.Q. Wang; X.C. Wang; F. Liu

    The crystallinity of electrode materials affects the electrochemical performances of supercapacitors, typically for some transition metal oxides. The influence of crystallinity on the capacitive behavior of metal sulfides has not been well investigated so far. In this work, amorphous and crystalline CuCo2S4 materials are prepared by anion−exchange and post−annealing. The annealing treatment under reasonable temperatures does not change the morphology and structure of CuCo2S4 significantly. But, the degree of crystallinity of CuCo2S4 can be easily changed by adjusting the annealing temperature. A high temperature results in a highly crystalline material. The electrochemical performances of CuCo2S4 is investigated and it is obviously influenced by the crystallinity. The material annealed at 200 °C exhibits a higher specific capacitance compared to the amorphous and those treated at higher temperatures. The optimal material has the highest specific capacitance of 424 F g−1 at 1 A g−1 and good stability. When it is assembled a hybrid capacitor with activated carbon as a negative electrode, the hybrid capacitor shows a high energy density of 22 Wh kg−1 at a power density of 405 W kg−1 in a potential window of 1.62 V.

    更新日期:2020-01-24
  • Superhydrophobic surface containing cerium salt and organosilane for corrosion protection of galvanized steel
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Chongchong Li; Tingting Liang; Ruina Ma; An Du; Yongzhe Fan; Xue Zhao; Xiaoming Cao
    更新日期:2020-01-24
  • Precipitation behavior and mechanical properties of Al–Zn–Mg alloy with high Zn concentration
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Y. Chen; C.Y. Liu; B. Zhang; F.C. Qin; Y.F. Hou

    The effect of Mg content on the precipitation behavior and resultant mechanical properties of high Zn-content Al–Zn alloy was studied by adding Mg to Al–20Zn alloy. The dynamic precipitation of Zn and η phases occurred in the Al–Zn–Mg alloys during hot rolling. The Zn phase promoted the precipitation of the η phase, which increased in size with increasing Mg content. Mg addition led to the decomposition of Al–Zn supersaturated solid solution and the precipitation of the η′ phase during natural aging at room temperature. In addition to the η′ phase, the nano-sized Zn phase precipitated in high Zn-content Al–Zn–Mg alloy during artificial aging at 120 °C. The analysis of mechanical properties showed that 0.5 wt% Mg addition can enhance the strength of Al–20Zn alloy after rolling and heat treatments due to the presence of nano-sized η and η′ precipitates. However, when Mg content was increased to 1 wt%, the mechanical properties of the rolled and heat-treated Al–20Zn alloy deteriorated due to the complete decomposition of Al–Zn solid solution and extremely large amount of solute atoms.

    更新日期:2020-01-24
  • Study on microstructure and fracture characteristics of 5083 aluminum alloy thick plate
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Xinwei She; Xianquan Jiang; Ruihao Zhang; Puquan Wang; Binbin Tang; Weichang Du

    The microstructure and fracture characteristics of 105 mm thick 5083 aluminum alloy hot rolled plate are investigated by X-ray diffractometer, metallurgical microscope, scanning electron microscope, transmission electron microscope, energy dispersive spectrometer and tensile testing machine in this paper. The results show that the plate is mainly composed of α-Al, Al21(Fe, Mn)4Si, Al6(Fe, Mn) and Mg2Si. The second phase distribution is inhomogeneous along the thickness direction, resulting in an U shape change of elongation. The minimum elongation in Layer 5 is related to the dependence of Mg2Si on Fe-containing intermetallic compounds, state of dislocations and grooves. Al6(Fe, Mn) presents acicular in the surface layer and fragmented in the center, and its fracture mode can be used to roughly judge the stress. Under SEM, the common black phases in high Mg-containing aluminum alloys may be not Mg2Si, but holes formed by their shedding. Mg2Si tends to adhere to the surface of Fe-containing intermetallic compounds and it is more easily separated from Al matrix. This indicates that Mg2Si may be the source of stress concentration initially causing materials fracture. A comprehensive summary has been made to clarify the influence of structures on fracture characteristics of thick plate.

    更新日期:2020-01-24
  • Mechanical, corrosion and biological properties of advanced biodegradable Mg–MgF2 and WE43-MgF2 composite materials prepared by spark plasma sintering
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Drahomir Dvorsky; Jiri Kubasek; Eva Jablonska; Jiřina Kaufmanová; Dalibor Vojtech

    Newly developed magnesium composite materials with a continuous network of MgF2 prepared by powder metallurgy exerted enhanced corrosion resistance and seems to be suitable for application in medicine as biodegradable implants. In this work, the influence of conditions of preparation of Mg and WE43 composite materials on final mechanical and corrosion properties of spark plasma sintered samples is revealed. Immersion in HF leads to the significant improvement of corrosion properties of Mg and WE43, while mechanical properties of WE43 alloy are reduced due to the specific interface. Moreover, cytocompatibility tests revealed the nontoxic behavior of magnesium fluoride coating on both Mg and WE43 alloy. The better proliferation of cells was observed on the WE43 composite material.

    更新日期:2020-01-24
  • Femtosecond-laser induced two-photon absorption of GaN and AlxGa1-xN thin films: Tuning the nonlinear optical response by alloying and doping
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    M.G. Vivas; D.S. Manoel; J. Dipold; R.J. Martins; R.D. Fonseca; I. Manglano-Clavero; C. Margenfeld; A. Waag; T. Voss; C.R. Mendonça
    更新日期:2020-01-24
  • Functionalised graphene as flexible electrodes for polymer photovoltaics
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Sourabh Tiwari; Anushka Purabgola; Balasubramanian Kandasubramanian
    更新日期:2020-01-24
  • Spark plasma sintering (SPS) densified U3Si2 pellets: Microstructure control and enhanced mechanical and oxidation properties
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Bowen Gong; Tiankai Yao; Penghui Lei; Jason Harp; Andrew T. Nelson; Jie Lian

    Dense U3Si2 pellets with controlled grain structure and enhanced thermal-mechanical and oxidation properties are synthesized with spark plasma sintering (SPS). Microstructure and phase composition of the SPS densified pellets are characterized systematically using SEM, EDS, and XRD. Thermal-mechanical properties and oxidation behavior of the sintered silicide fuel pellets are analyzed by laser flash, indentation and dynamic thermogravimetric analysis. Dense U3Si2 pellets are consolidated by combining high energy ball milling and rapid sintering by SPS, and the microstructure structures are controlled from micron-sized (∼5.7 μm grain size) for conventional silicide to nanocrystalline matrix with average grain size of ∼280 nm. A dominant phase of distorted U3Si2 was identified with lattice expansion due to residual thermal stress upon SPS consolidation and rapid cooling processes. Both micron-sized and nano-sized pellets show exceptional thermal transport properties, consistent with monolithic silicides reported in literatures. The SPS-densified pellets possess simultaneously high hardness and fracture toughness. The SPS-densified silicide pellets also demonstrate exceptional oxidation performance with extended onset oxidation temperature above 500 °C and reduced oxidation kinetics particularly for nano-sized pellets. A strong strain effect was proposed in which compressive stress in nano-sized pellets enhances the oxidation resistance of silicide fuels, as evidenced by the degradation of oxidation performance upon strain relaxation by isothermal annealing. The correlation among the sintering process – microstructure control – physical properties and fuel behavior is established. A new concept of strain engineering is proposed further properties optimization, enabling the development of potentially oxidation and corrosion-resistant silicides with extended performance, the key technological challenge of U3Si2 as the leading concept of accident tolerant fuels.

    更新日期:2020-01-24
  • Impact of post annealing and hydrogen implantation on functional properties of Cu2O thin films for photovoltaic applications
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-24
    Raj Kumar; Kristin Bergum; Heine Nygard Riise; Eduard Monakhov; Augustinas Galeckas; Bengt Gunnar Svensson

    Polycrystalline cuprous oxide (Cu2O) thin films were sputtered, annealed (900 °C rapid thermal annealing) and subsequently implanted with various hydrogen ion (H+) doses from 5E13 to 2E15 cm−2 with a low acceleration energy of 36 keV at room temperature to tailor the functional properties of the thin films for solar cell application. The annealed and H+ implanted Cu2O thin films were post annealed at low temperatures from 100 °C to 600 °C in an inert atmosphere to promote hydrogen passivation of prevalent intrinsic acceptors and tune the carrier concentration for optimum performance as an absorption layer in a heterojunction solar cell. The H+ incorporation and post annealing tuned the structural, optical and electrical properties of annealed polycrystalline Cu2O thin films. The results show an enhancement of the excitonic feature around ∼2.0 eV with H+ dose. The normalized photoluminescence (PL) area around ∼1.7 eV was drastically enhanced with increasing H+ doses compared to excitonic and copper vacancy related area. The normalized total PL quantum efficiency shows an enhancement in yield with elevated H+ doses by two orders of magnitude. The hole concentration decreases down to ∼1013 cm−3, while hole mobility and resistivity increase to ∼27 cm2/V and ∼2.4 kΩcm, respectively, as the H+ implantation goes from lower to higher doses. In addition, the post annealing and H+ incorporation lead to a change in the energy level of the major acceptor from 0.21 eV to 0.27 eV above the valence band maximum. By following the qualitative (PL analysis) and quantitative (Hall data) outcomes, we can conclude that H+ implantation and post annealing likely indicates the passivation of both acceptor defects and compensating donor defects.

    更新日期:2020-01-24
  • Investigating local corrosion behavior and mechanism of MAO coated 7075 aluminum alloy
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Shengnan Wang; Yanhong Gu; Yinliang Geng; Jian Liang; Jie Zhao; Ju Kang

    In order to study the effect of defects on the corrosion behavior of MAO coatings, global electrochemical method including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) was used to measure the corrosion resistance of MAO coatings. Local electrochemical measurements including local impedance spectroscopy (LEIS) and scanning vibrating electrode technique (SVET) were used to study the local corrosion mechanism. The confocal microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the microstructure and phases of the samples. Results of global electrochemical measurement demonstrate that the scratches cause the reduction of the impedance and the increase of the corrosion current density. LEIS results show the impedance value distribution of the coating with the scratch. With the changes over time, the minimum impedance value of the scratch decreases first and then increases from the third hour. SVET results show the corrosion current density distribution of the scratched coating. The maximum corrosion current density at the scratch increases first and then decreases. The results of local electrochemical measurements show that the corrosion rate at the scratch decreases when the reaction lasted 3 h. Confocal microscopy found that the scratch is expanding with increasing time, and the depth and cross-sectional area of the coating is 5 times deeper and 10 times larger than that of 7075Al with scratch at the first 6 h. The 6-day immersion test proved that the scratch coating still has the protective effect on the substrate. The main corrosion product is Al(OH)3. A physical model reflecting the mechanism of the scratch propagation and the formation of the corrosion product film is proposed.

    更新日期:2020-01-24
  • 更新日期:2020-01-24
  • Enhanced energy storage properties of fine-crystalline Ba0.4Sr0.6TiO3 ceramics by coating powders with B2O3–Al2O3–SiO2
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Hongye Wang; Minghe Cao; Miao Liu; Hua Hao; Zhonghua Yao; Hanxing Liu

    A core–shell mixing technique was utilized to modify the Ba0.4Sr0.6TiO3 (BST)particles in order to obtain the fine-crystalline Ba0.4Sr0.6TiO3 ceramics and improve ceramics energy storage capability. Coating layers of (9B2O3–13Al2O3–78SiO2, mol%) (BAS)were deposited onto Ba0.4Sr0.6TiO3 nanoparticles by a sol-precipitation method. The microstructures, phase composition and dielectric properties were investigated. And fine-crystalline BST ceramics with an average grain size below 150 nm by coating BAS has been prepared. The dielectric breakdown strength and energy storage density significantly improved due to the addition of BAS. The maximum energy storage density obtained from coating 3 wt% BAS was 1.8 J/cm3 at 410 kV/cm, which was higher than pure BST ceramics. Thus, the core-shell architecture is an effective strategy to improve the energy storage performance.

    更新日期:2020-01-24
  • Cobalt ion intercalated MnO2/C as air cathode catalyst for rechargeable aluminum–air battery
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Zijie Xia; Yunfeng Zhu; Wenfeng Zhang; Tongrui Hu; Tao Chen; Jiguang Zhang; Yana Liu; Huaxiong Ma; Huizheng Fang; Liquan Li
    更新日期:2020-01-24
  • Band gap bowings of ternary REN (RE = Sc, Y, La, and Lu) alloys
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Maciej J. Winiarski; Dorota A. Kowalska

    Structural and electronic properties of ternary alloys of ScN, YN, LaN, and LuN semiconductors have been investigated within the density functional theory. Fully relativistic band structures were obtained with the modified Becke-Johnson approach. Although the lattice parameters of solid solutions of rare-earth elements nitrides exhibit a linear Vegard's law behavior, the dependences of band gaps on alloys compositions are strongly nonlinear, i.e., substantial band gap bowings are predicted for systems studied. Such strong band gap bowings were not found in any group III nitrides. The Sc/Y/Lu-based materials are indirect band gap (Γ–X) semiconductors. The ternary REN alloys containing La exhibit mainly direct type of band gaps (X–X), which may be completely closed in some Sc1−xLaxN systems. The findings presented in this work suggest that strong band gap bowings in ternary solid solutions of REN semiconductors may enable obtaining band gaps lower than 0.6 eV being characteristic for LaN, which are unavailable in group III nitride materials.

    更新日期:2020-01-24
  • Composite sulfur cathode for Li-S batteries comprising hierarchical carbon obtained from waste PET bottles
    Synth. Met. (IF 2.87) Pub Date : 2020-01-24
    Paulina Półrolniczak; Dawid Kasprzak; Justyna Kaźmierczak-Raźna; Mariusz Walkowiak; Piotr Nowicki; Robert Pietrzak

    Waste PET bottles have been processed towards carbonaceous material through pyrolysis at 500 °C in nitrogen atmosphere followed by chemical activation with K2CO3. The obtained carbon was found to feature hierarchical pore structure, as evidenced by nitrogen sorption isotherm analysis. Composite sulfur-carbon electrode has been prepared using this carbon by means of simple dry-mixing technique and subjected to electrochemical testing in model Li-S cells with electrolyte being 0.5 M lithium trifluoromethanesulfonate (LiTf) and 0.5 M lithium nitrate (LiNO3) in mixture of 1,2dimethoxyethane (DME) and 1,3-dioxolane (DOL). The Li-S cells assembled with obtained composite sulfur-carbon cathode demonstrated a large initial specific discharge capacity of about 829 mA h g−1 at 0.05 C current rate and delivered ca. 712 mA h g−1 after subsequent 50 charge and discharge cycles, which corresponds to 86% capacity retention. Generally, the investigated Li-S cells have exhibited good cycling stability and excellent reversibility. Thus, the obtained waste-derived activated porous carbon can be considered as a promising component for the composite cathode material of Li–S batteries.

    更新日期:2020-01-24
  • Structure and magnetic properties of Alnico8 alloy thermo-magnetically treated under a 10 T magnetic field
    Intermetallics (IF 3.353) Pub Date : 2020-01-23
    X.Y. Sun; C.L. Chen; M.Y. Ma; L. Yang; L.X. Lv; S. Atroshenko; W.Z. Shao; L. Zhen

    The structure and compositions of spinodal phases in Alnico8 alloy isothermally treated at 830 °C under external magnetic field (Hext) up to 10 T were investigated by transmission electron microscopy (TEM). Under ultra-high magnetic field (10 T), the spinodal structure of Alnico8 alloy presents interesting diversity for the shapes of α1 phase particles, namely, Π-shape, H-shape and Ш-shape apart from regular rod-shape. Composition analysis shows that the Fe was mainly distributed in the α1 phase. The Co content in the α1 phase was lower than that in the α2 phase as evidenced by the point analysis results, and Co content inα1 phase of the alloy treated without magnetic field was higher than that of the alloy treated with a magnetic field. In contrast, the Ni, Al, Cu and Ti were concentrated in the α2 phase. The average hyperfine field of the alloy treated without magnetic field was about 301.3 kOe. While the alloy treated under magnetic field, it was slightly decreased, which was about 292.0 and 296.1 kOe under 0.7 and 10 T, respectively. Magnetic properties of the alloy treated under a 10 T magnetic field were the best, which were about 1.09T, 396Oe and 9.5 kJ/m3 for Br, Hc and (BH)max respectively. Especially for the coercivity, which was mainly contributed by the anisotropy of the α1 phase induced by the high magnetic field.

    更新日期:2020-01-23
  • Burst-like shape recovery and caloric effects in Ni–Fe–Ga–Co single crystalline shape memory alloys
    Intermetallics (IF 3.353) Pub Date : 2020-01-23
    V.I. Nikolaev; S.I. Stepanov; P.N. Yakushev; V.M. Krymov; S.B. Kustov

    Shape recovery in conventional shape memory alloys is typically a relatively slow process showing low heating rate sensitivity. In contrast to that, some shape memory alloys such as Ni–Fe–Ga–Co, Cu–Al–Ni, Cu–Al–Fe–Mn can exhibit the effect of burst-like shape recovery when the original shape is restored almost instantaneously in a very narrow temperature range. Here we report on an abnormal stress-strain behavior of Ni49Fe18Ga27Co6 single crystals upon uniaxial compression along the [110] axis and caloric effects during burst-like recovery of shape memory strain in the samples. Differential scanning calorimetry (DSC) study revealed that DSC peak shifts to lower temperatures with increasing heating rate.

    更新日期:2020-01-23
  • Microstructure and cyclic deformation behavior of a 3D-printed Ti–6Al–4V alloy
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Y.L. Zhang; Z. Chen; S.J. Qu; A.H. Feng; G.B. Mi; J. Shen; X. Huang; D.L. Chen
    更新日期:2020-01-23
  • Facile synthesis of small MgH2 nanoparticles confined in different carbon materials for hydrogen storage
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Qiuyu Zhang; Yike Huang; Tiancai Ma; Ke Li; Fei Ye; Xuechao Wang; Lifang Jiao; Huatang Yuan; Yijing Wang

    We introduce a facile chemical solid state method to in situ grow MgH2 nanoparticles in various carbon materials. Commercial carbon materials, containing coconut shell charcoal (CSC), multi-walled carbon nanotube (CNT), graphite (G) and activated carbon (AC) are employed as the templates. The MgH2@X (X = CSC, CNT, G and AC) composites were successfully obtained by the simple solid state method. The hydrogen storage properties of MgH2@X (X = CSC, CNT, G and AC) composites are systematically studied by temperature-programmed desorption system, isothermal de/hydrogenation apparatus and differential scanning calorimetry measurements. Experimental results reveal that the MgH2@CSC composites have the most fascinating hydrogen absorption and desorption performance, followed by MgH2@CNT, MgH2@G and MgH2@AC composites. The dehydrogenation of MgH2@CSC composites begins at 245 °C. Moreover, the MgH2@CSC composites exhibit superior de/hydrogenation kinetic performance. The composites could desorb 5.4 wt% hydrogen within 10 min at 325 °C, and the dehydrogenated composites take up 5.0 wt% hydrogen within 5 min at 250 °C under 2 MPa H2 pressure. Among the carbon materials, CSC with layered structure composed of interconnected wrinkles is most beneficial to maintain the high dispersity and nano size of MgH2 nanoparticles, resulting in the superior de/hydrogenation performance.

    更新日期:2020-01-23
  • The partitioning behavior of dual solutes at the antiphase domain boundary in the B2 intermetallic: A microscopic phase-field study
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Kun Wang; Yongxin Wang

    The partitioning behavior of dual solutes at the antiphase domain boundary (APDB) in B2 intermetallic is studied by establishing a ternary BCC phase-field model of atomic-resolution. The influence factors doping concentration of the third alloying solute, temperature and lattice misfit strain are considered. The elemental co-distribution caused by the partitioning behavior is characterized by the topographic map of solute and micro deviation of concentration. Theoretical results reveal that the co-distribution is Ni segregation coupled with Al depletion and Fe segregation. At the microscopic level, the micro deviation level is confirmed to be strongly dependent on the magnitudes of Ni concentration, temperature and lattice misfit. At the atomic level, the micro deviation is heterogeneous. The mechanism, regular dependence, and heterogeneity of the elemental partitioning under three factors are revealed from the viewpoint of energy. This work provides a new perspective on understanding the origin of the partitioning behavior of constituent elements at the APDB in B2 intermetallics and will be beneficial to evaluate elemental distribution-APDB-properties in future FeAl-base superalloys design with multi alloying additions and the interface engineering.

    更新日期:2020-01-23
  • Crystal structure and cation ordering in novel perovskite type oxides PrBaCoTa(Nb)O6–δ
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    B.V. Politov; S.N. Marshenya; M.O. Kalinkin; M. Yu Mychinko; A. Yu Suntsov; S.A. Petrova; V.P. Zhukov; E.V. Chulkov; V.L. Kozhevnikov

    Novel complex oxides PrBaCoNbO6–δ (PBCN) and PrBaCoTaO6–δ (PBCT) are obtained via solid state reactions. X-ray and electron diffraction data for PBCN and PBCT demonstrate cubic space symmetry (S.G. Fm–3m) of the double perovskite crystalline lattice characterized by the rock salt type ordered arrangement of Co/Nb and Co/Ta and random distribution of Pr/Ba atoms. The ab initio electronic structure calculations reveal that the disordered elementary cell is distinguished with the minimum energy. The optical measurements show that PBCN and PBCT compounds are semiconducting materials having maximum light absorption in ultraviolet (UV) region which is consistent with the computer simulations of electronic structure. The thermodynamic modeling results suggest that the structural robustness of PBCN and PBCT phases at heating may be related with large absolute values of oxygen partial enthalpies.

    更新日期:2020-01-23
  • Cr doping effect on the structural, optoelectrical and photocatalytic properties of RF sputtered TiO2 thin films from a powder target
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    I. Ben Jemaa; F. Chaabouni; A. Ranguis

    In this study, thin films of pure and chromium doped TiO2 were deposited by RF magnetron sputtering technique with recourse to a low cost powder target. The dopant concentration was varied from 0 to 6 wt%. The structural, optical, electrical and photocatalytic properties of the sputtered deposited films were systematically investigated on the basis of the incorporated Cr content. XRD analysis revealed that the elaborated films are polycrystalline and have a preferential orientation along the (110) plane, characteristic of the rutile phase. The optical measurements showed a good homogeneity of the films and a high transmission that reached 85% in the visible range. The high transparency of these films allows their use as an optical window in thin film solar cells. Optical band gap decreased from 3.44 eV to 3.32 eV with the increase of the Cr content. In addition, the impedance spectroscopy analysis showed that the conductivity increases along with increasing frequency and temperature, and that the conduction mechanism follows the correlated barrier hopping model. The test of the catalytic efficiency of the chromium-doped TiO2 thin films at different concentrations demonstrated a degradation of the methylene blue (MB) and an improvement of the photocatalytic activity and that the 6 wt% doped thin films have the best photocatalytic activity.

    更新日期:2020-01-23
  • Preparation and electrochemical properties of an La-doped Pr2Ni0.85Cu0.1Al0.05O4+δ cathode material for an IT-SOFC
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Qingjun Zhou; Liangwu Qu; Ting Zhang; Yong He; Chen Zhao; Mingchao Wang; Tong Wei; Yuhang Zhang

    The cathode material Pr2-xLaxNi0.85Cu0.1Al0.05O4+δ (PLNCA, x = 0, 0.2, 0.5 and 1.0) was synthesized by an EDTA-citrate process for use in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The phase structure and compatibility of the PLNCA with a La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte was characterized by X-ray diffraction analysis. A test of thermodynamic stability shows that only PrLaNi0.85Cu0.1Al0.05O4+δ can work for 72 h at 700 °C without decomposition. The average thermal expansion coefficient of the PLNCA material matches well with that of the LSGM electrolyte. The electrical conductivity of the PLNCA material varies in the range of 40–80 S cm−1 at 400 °C. The area specific resistance of the PLNCA cathode on LSGM electrolyte was determined to be 0.029, 0.035, 0.036 and 0.037 Ω cm2 for x = 0, 0.2, 0.5, 1.0 at 800 °C, respectively. Moreover, the power density of the electrolyte supported single cell for x = 0, 0.2, 0.5, 1.0 was determined to be 392, 357, 350 and 341 mW cm−2 at 700 °C, respectively. Among PLNCA materials, PrLaNi0.85Cu0.1Al0.05O4+δ shows the best compromise between electrochemical properties and thermodynamic stability and could serve as a potential cathode material for application in IT-SOFCs.

    更新日期:2020-01-23
  • Determination of dislocation density in GaN/sapphire layers using XRD measurements carried out from the edge of the sample
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    J. Serafinczuk; K. Moszak; L. Pawlaczyk; W. Olszewski; D. Pucicki; R. Kudrawiec; D. Hommel

    In this paper, we show a novel measurement approach for determination of the threading dislocations density in GaN/sapphire structures using X-ray diffractometry at edge scans geometry. The presented method is based on measurements carried out both: classically from the surface and from the edge of the sample. Edge scans allow measurements of planes parallel to the growth direction, which permit the unambiguous determination of the number of edge dislocations. This is a new measurement approach that facilitates the characterization of structures. In addition, obtained results have been confirmed by using the wet etching method and on the basis of the obtained results, it can be concluded that both methods give the same results within the experimental uncertainty.

    更新日期:2020-01-23
  • Preparation of high-purity Ti–Si alloys by vacuum directional solidification
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Yakun Zhang; Yun Lei; Wenhui Ma; Hao Wang; Yuqiu Hu; Kuixian Wei; Shaoyuan Li

    To prepare high-purity Ti–Si alloys, we newly used vacuum directional solidification technology to purify and separate Ti–Si alloys, which have different compositions (Ti-8.45 wt%Si, Ti-63.7 wt%Si, Ti-71.6 wt%Si, and Ti-84.1%wt%Si). The pulling-down rates in the directional solidification were to be 3 μm/s, 5 μm/s, and 7 μm/s, respectively, to investigate their effects on the purification. The results showed that vacuum directional solidification can purify Ti–Si alloys efficiently without discharging waste acid, slag and gas, and the slower pulling-down rate could result in better purification results. The impurities, Fe, Al, V, and Ni, could be removed due to their segregation behavior on the boundary of the solid and liquid phases. However, the impurities Ca and Mg could be removed using the vacuum technology because their vapor pressures were significantly higher than those of Si and Ti. TiSi2 could be precipitated and separated from the Ti-63.7 wt%Si and Ti-71.6 wt%Si alloys. The precipitated TiSi2 could be agglomerated at the bottom of the Ti–Si alloys, under the effect of gravity. The phases in the Ti–Si alloys, after vacuum directional solidification, were observed and determined using an electron probe micro-analyzer (EPMA). The results showed that the eutectic Ti-8.45 wt%Si alloy consisted of Ti5Si3 and Ti, the Ti-63.7 wt%Si and Ti-71.6 wt%Si alloys consisted of TiSi2 and eutectic Si–Ti alloy at the Si-rich side, and the Ti-84.1 wt%Si alloy consisted of Si particles and eutectic Si–Ti alloy at the Si-rich side. The study shows that vacuum directional solidification is an efficient and clean technology for the purification of Ti–Si alloys, and for the preparation of TiSi2 through the separation of Ti–Si alloys.

    更新日期:2020-01-23
  • Microstructural analysis of SHI irradiated CdS nanocrystals- utilizing first principles method
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Debojyoti Nath; Simi Debnath; Pijush Ch Dey; Fouran Singh; Ratan Das
    更新日期:2020-01-23
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