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  • 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
  • Distribution of copper and iron components with hydrogen reduction of copper slag
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Guorui Qu; Yonggang Wei; Bo Li; Hua Wang; Yindong Yang; Alexander McLean

    In this study, a 70% H2–30% N2 mixture was used to simulate waste cooking oil pyrolysis gas products for reduction of copper slag. The microstructure of slag before and after reduction was analyzed, and the distribution characteristics of copper and iron components during the reduction process were evaluated. The results show that there is always a sedimentation behavior of the matte in the slag during the cleaning process. The residual matte in the cleaned slag is mainly related to chemically dissolved copper. A clear layering was observed between slag and matte after the reduction process. These findings provide support for the recovery of matte from copper slag using waste cooking oil as a green reductant.

    更新日期:2020-01-23
  • Thermal stability and crystallization of a Zr-based metallic glass produced by suction casting and selective laser melting
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Victor Pacheco; Dennis Karlsson; Jithin James Marattukalam; Moritz Stolpe; Björgvin Hjörvarsson; Ulf Jansson; Martin Sahlberg

    The thermal stability and crystallization mechanism of the Zr59.3Cu28.8Al10.4Nb1.5 (at%) metallic glass produced through selective laser melting SLM (from industrial grade material) was studied and compared with the same alloy produced by suction casting (from laboratory grade material of high purity). Oxygen- and Al-rich particles of a cubic phase (Fd3¯m) with a size of up to 200 nm are detected in the as-built selective laser melted samples by transmission electron microscopy. The crystallization process of the cast and SLM samples is investigated by in-situ X-ray diffraction experiments. In the cast samples, the initial crystallization occurs via the formation of a metastable tetragonal phase (Al2Zr3), together with tetragonal CuZr2 and hexagonal Al3Zr4 type structures, while the SLM samples initially crystallize through the formation of the metastable, oxygen- and Al-rich, cubic phase already present before annealing. The main phases present at the end of the crystallization for both type of samples are the same, mainly CuZr2 and Al3Zr4. The differences in the crystallization paths are attributed to differences in the oxygen levels. In general, the higher oxygen content (∼1 at%) of the SLM samples results in a decrease of the thermal stability of the alloy and promotes the formation of an oxygen-rich, metastable cubic phase.

    更新日期:2020-01-23
  • Versatile fluorescent CaGdAlO4:Eu3+ red phosphor for latent fingerprints detection
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Jin Young Park; Jong Won Chung; Sung Jun Park; Hyun Kyoung Yang

    Latent fingerprint detection is one of the promising technique in forensic science. Here, an oxide based red-emitting phosphors, CaGdAlO4:Eu3+ (CGA:Eu3+), have been successfully synthesized by a solvothermal reaction method. The structural phase was characterized with the XRD Rietveld refinement and TEM analyses. The luminescence properties and dynamics of Eu3+ in CGA were studied in detail by room temperature emission, excitation and decay curve measurements. Intense red emission peaking at 620 nm due to 5D0→7F2 transitions of Eu3+ under the excitation at 283 nm was obtained and the optimal Eu3+ ion concentration was found to be about 7 mol%. The CIE chromaticity coordinate evaluated from the PL spectra and exhibited (0.6410, 0.3581) coordinates within the pure red region of the CIE 1931 diagram with a close proximity to the commercial red phosphor (Y2O2S:Eu3+). Furthermore, with the use of the CGA:7Eu3+ phosphors, the developed latent fingerprint fluorescent images were well visualized and identified their level 1, 2 and 3 details with high contrast, selectivity and sensitivity. These results indicate that CGA:7Eu3+ has great potential for practical applications in the latent fingerprint detection.

    更新日期:2020-01-23
  • The improved strength and toughness in the quinary Cr2Nb/Cr in-situ composite
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Yunlong Xue; Shuangming Li; Yuanting Wu; Hulin Liu; Kewei Li

    A quinary Cr–12Nb–5Ti–5Mo–5Si (at.%) alloy was prepared by arc melting in this study to improve the strength and toughness of Laves phase Cr2Nb alloy. The quinary alloy was solidified with full eutectic Cr2Nb/Cr, in which the Cr2Nb phase exceeded 55 vol % and existed as matrix. The eutectic was developed with an orientation relationship of {001}Cr2Nb//{001}Cr, leading to a low lattice mismatch of 15.57% at the eutectic interface. The yield strength and fracture toughness of the quinary alloy reached 1950–1980 MPa and 14.0–14.8 MPa⋅m1/2, respectively, much higher than most reported Cr2Nb alloys. The reason for the superior properties is the synergistic effects of solid solution strengthening, alloying toughening, and eutectic strengthening-toughening.

    更新日期:2020-01-23
  • A simple method to fabricate NiFe2O4/NiO@Fe2O3 core-shelled nanocubes based on Prussian blue analogues for lithium ion battery
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Zhao Xue; Linlin Li; Linjuan Cao; Wenzhi Zheng; Wei Yang; Xinwei Yu

    Core-shelled NiFe2O4/[email protected]2O3 nanocubes were synthesized based on Prussian blue analogues. The core-shelled structure was built through ion-exchange process in aqueous solution, and was remained after calcination. Different concentrations of ferrous affect the size and surface states of PBA precursors and its successor. Fabricated core-shelled NiFe2O4/[email protected]2O3 nanocubes produced with the PBA precursor that soaked in the solution of ferrous ion with the highest concentration in this work appears the most stable capacity during cycles, because of its more homogeneous Fe2O3 layer surface and more complete crystal. At the current density of 100 mA/g, it offers an initial capacity of 1587.96 mA h/g, and the second capacity of 967.91 mA h/g, that was remained as 806.1 mA h/g after 50 cyles. At 500 mA/g, it performs a capacity of 472.5 mA h/g after 500 cycles with a strong stability.

    更新日期:2020-01-23
  • Crystal structure, spectroscopic, magnetic and dielectric studies of new doped ceramic ZrTe3O8:7%CuO
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    M. Koubaa; R. Karray; L. Bessais; A. Kabadou

    In this study, calcined ZrTe3O8 powder mixed with 7%wt of CuO was sintered at 750 °C. The new doped ceramic ZrTe3O8:7%CuO was synthesized using solid state reaction method and was studied with X-ray diffraction (XRD). At room temperature, the title compound crystallizes in cubic space group Ia3¯, with lattice parameter a = 11.328(3) Å, and exhibits a complex network of interconnected closed chains built up of TeO4E (E = electronic lone pair of Te (IV) atoms). The Zr/CuO6 octahedra are inserted into these chains ensuring the stability of the structure by Zr/Cu –O–Te bonding contacts. IR and Raman spectroscopic study are employed as means to obtain preliminary structural information and confirms the presence of the ZrO6 and TeO4E groups. Optical properties of the ceramic were explored by using UV–Vis absorption. The magnetic results reveal the appearance of a weak ferromagnetic behavior at low temperature (TC = 46.172 K). In addition, dielectric data were analyzed using real and imaginary permittivity ε' and ε'' respectively, the tan (δ) and the electrical modulus (M' and M″) for the sample ZrTe3O8:7%CuO at various frequencies. The Z' and Z'' versus frequency plots are well fitted to an equivalent circuit model composed of a series combination of two parallel combinations of resistance Ri and constant phase element CPEi.

    更新日期:2020-01-23
  • Carbon nanofibers supported by FeCo nanocrystals as difunctional magnetic/dielectric composites with broadband microwave absorption performance
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Yajing Wang; Yong Sun; Yan Zong; Tongguang Zhu; Linxue Zhang; Xinghua Li; Hongna Xing; Xinliang Zheng
    更新日期:2020-01-23
  • Damage identification in fiber reinforced titanium matrix composites using acoustic emission
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-23
    Xu Kong; Yumin Wang; Qing Yang; Xu Zhang; Guoxing Zhang; Lina Yang; Ying Wu; Rui Yang
    更新日期:2020-01-23
  • 更新日期:2020-01-23
  • CNT/Co3S4@NiCo LDH ternary nanocomposites as battery-type electrode materials for hybrid supercapacitors
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Dandan Wei; Youliang Zhang; Xuezhen Zhu; Mingli Fan; Yinling Wang
    更新日期:2020-01-22
  • Formation of PbMnI2 alloys: Structural, photoluminescence and nuclear quadrupole resonance studies
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    A.P. Bukivskii; I.G. Vertegel; E.D. Chesnokov; P.M. Bukivskij; O.I. Ovcharenko; R.V. Gamernyk; Z.D. Kovalyuk; V.M. Tkach; Yu.P. Gnatenko

    The structural, optical and nuclear quadrupole resonance (NQR) measurements of PbMnI2 alloys were carried out. This allows us to study the peculiarities of the formation of such alloys. It was found that pure PbI2 and Pb1-XMnXI2 crystals with X = (0.03–0.05) have the phase of 2H-polytype. It was shown that the investigated alloys can be presented as the crystal regions of Pb1-XMnXI2 solid solutions, embedded in PbI2 crystal matrix. These formations can be considered as platelet-shaped nanoparticles with a surface of several microns and a thickness of several tens of nm. Thus, PbMnI2 alloys are heterogeneous PbI2–PbMnI2 nanocomposites. The results of NQR spectra measurements also show that Mn2+ ions preferably replace Pb2+ ions in the crystalline layers. Here, the local deformations occur because the radii of Pb2+ and Mn2+ ions differ significantly. The broadening of optical and NQR lines is due to the presence of both these deformations and the crystal field fluctuations, which are characteristic of semiconductor solid solutions.

    更新日期:2020-01-22
  • Improvement in oxidation behavior of Al0.2Co1.5CrFeNi1.5Ti0.3 high-entropy superalloys by minor Nb addition
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Jun-Jie Yang; Chia-Ming Kuo; Po-Ting Lin; Hung-Chih Liu; Cheng-Yao Huang; Hung-Wei Yen; Che-Wei Tsai

    High-entropy superalloys (HESAs) can replace commercial Ni-based superalloys. For high-temperature applications, the oxidation resistance of HESAs must be considered. Herein, the oxidation mechanism of HESA with sufficient minor Nb addition was conducted at 900 °C under atmosphere. With 0.9 at% Nb added in the base metal, oxidation resistance was significantly improved, which was confirmed by a furnace test and thermogravimetry. The isothermal oxidation resistance was enhanced by approximately 66%, owing to the presence of the Nb-rich layer. This improvement was observed and analyzed by backscattering electron images through scanning electron microscopy and wavelength dispersive spectroscopy with a field-emission electron probe microanalyzer. The mechanism of oxide formation was elucidated by X-ray diffraction for various exposure time durations. With Nb minor addition, the microstructures of the present alloy were found to be composed of γ matrix and γ′ precipitates and the mechanical properties were slightly higher than those without Nb.

    更新日期:2020-01-22
  • Development of high-performance Mg–Zn–Ca–Mn alloy via an extrusion process at relatively low temperature
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    L.B. Tong; J.H. Chu; W.T. Sun; Z.H. Jiang; D.N. Zou; K.S. Wang; S. Kamado; M.Y. Zheng
    更新日期:2020-01-22
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  • 更新日期:2020-01-22
  • Se-doped Bi2S3 nanoneedles grown on the three-dimensional carbon foam as a self-supported anode for high-performance sodium ion batteries
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiangju Chen; Yang Hong; Xiaoli Ge; Caixia Li; Xianguang Miao; Peng Wang; Zhiwei Zhang; Longwei Yin

    Taking advantage of nano-sized active materials, doping and self-supporting, Se-doped Bi2S3/3D carbon foam (Bi2S3-xSex/CF) is synthesized through a pyrolysing-hydrothermal-heating three-steps process. The as-synthesized Bi2S3-xSex/CF hybrid exhibits a significant improvement in electrochemical performance, showing a high specific capacity of 441.8 mAh g−1 after 100 cycles with the coulombic efficiency approximating to 100%. The special nanoneedle-like structure of Bi2S3 makes for shortening ion transmission distance, minishing the mechanical stress and thus improving the electrochemical performance. And the introduction of Se can enhance the specific capacity, cycling stability and rate performance by improving of electronic conductivity and forming Se-contained inactive phase during alloying process. Furthermore, the self-supporting electrode is beneficial to simplify preparation process and reduce the loss of volume energy density. The strategy presented in this paper to improve the electrochemical performance of secondary ions battery can be also applied to other novel electrodes materials.

    更新日期:2020-01-22
  • Effects of ageing on microstructure, martensitic transformation and shape memory performance of a Ni-rich Ti49.5Ni34.5Cu11.5Pd4.5 alloy
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Hang Li; Xianglong Meng; Wei Cai

    The ageing effects on the microstructure, martensitic transformation and shape memory performance of a Ni-rich Ti49.5Ni34.5Cu11.5Pd4.5 alloy as a function of temperature were investigated. The formation of (Ni,Cu)2Ti-type precipitated phases arises from the ageing treatment. When ageing at 500 °C, the fine precipitated phases are diffusely distributed, which improves the shape memory performance efficiently. With the tensile deformation of 5%, the 500 °C aged specimen shows a 25% larger strain recovery rate (a maximum value of 96.8%) than that of the specimen under solution treatment. And after 100 thermal cycles, the transformation temperature variation is lesser than 0.2 °C in the specimen aged at 500 °C. There presents excellent thermal cycling stability while keeping near-zero thermal hysteresis.

    更新日期:2020-01-22
  • Enhanced mid-infrared emissions of Ho3+/Er3+ co-doped Na5Y9F32 single crystal by introduction of Pr3+ ions
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Yang Qiao; Xiong Zhou; Jianli Zhang; Haiping Xia; Hongwei Song; Baojiu Chen

    The Na5Y9F32 fluoride single crystals tri-doped with ∼1 mol% Ho3+/∼1 mol% Er3+, and various concentrations of Pr3+ (0, 0.5, 0.8 and 1.0 mol%) were successfully grown by a modified Bridgman method. The absorption, Raman, emission spectra and fluorescence decay curves of Pr3+/Ho3+/Er3+ tri-doped Na5Y9F32 single crystals were studied systematically. The intensity parameters (Ω2 = 1.96 × 10−20 cm2, Ω4 = 1.66 × 10−20 cm2, Ω6 = 1.46 × 10−20 cm2) of Er3+ ions and emission cross-sections at ∼2.7 μm (1.76×10−20 cm2) and ∼2.9 μm (1.34×10−20 cm2) were calculated according to the measured absorption spectra. The emission intensities at ∼2.7 μm of Er3+: 4I11/2 → 4I13/2 and ∼2.9 μm of Ho3+: 5I6→5I7 were enhanced gradually as increase of Pr3+ concentrations from 0 to 1.0 mol% under excitation of 800 nm laser diode (LD). However, the ∼2.0 μm of Ho3+: 5I7→5I8 and ∼1.5 μm of Er3+: 4I13/2 → 4I15/2 were gradually reduced. The introduction of Pr3+ can greatly reduce the lifetimes of Er3+: 4I13/2 and Ho3+: 5I7. The energy transfer from Er3+: 4I13/2 to Ho3+: 5I7 level and depopulating Er3+: 4I13/2 and Ho3+: 5I7 levels under the action of Pr3+ ions are responsible for the enhancement of ∼2.7 and ∼2.9 μm emissions. The Pr3+/Ho3+/Er3+ tri-doped Na5Y9F32 single crystal may become a new choice for ∼3.0 μm mid-infrared solid-state laser.

    更新日期:2020-01-22
  • Microstructure and property evolution of Al-0.4Fe-0.15Zr-0.25Er alloy processed by high pressure torsion
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Yaping Kong; Qingqing Pu; Zhihong Jia; Manping Liu; Hans J. Roven; Jiaqi Jia; Qing Liu

    An Al-0.4Fe-0.15Zr-0.25Er alloy was processed by high pressure torsion (HPT) at room temperature in order to explore the evolution of property, microstructure and texture during HPT. The evolution of microstructure revealed by electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS). The microhardness increases with increasing strain up to 60 HV at a strain of about 12, and then decreases slightly to a steady stage. HPT processing leads to a significant increase (>100%) in microhardness at expense of a slight reduction (<3%) in electrical conductivity. The synchronous improvement in microhardness and electrical conductivity is obtained after aging. A significant decrease from 40 μm to 600 nm in grain size is observed after HPT deformation for 5 turns and beyond. HPT processing might accelerate the dissolution of the Al3(Zr,Er) precipitate. The A- {111} <110>and C- {001} <110> texture components are dominating after 0.25 turn. After 1 turn, the A and C components weaken, and the {112} <111> new component appears. The texture is weak and close to random due to recovery and recrystallization after 5 turns and beyond.

    更新日期:2020-01-22
  • A surface multiple effect on the ZnO anode induced by graphene for a high energy lithium-ion full battery
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiaofei Yang; Jingyi Qiu; Meng Liu; Hai Ming; Huimin Zhang; Meng Li; Songtong Zhang; Tingting Zhang
    更新日期:2020-01-22
  • Ultrafine Cu6Sn5 nanoalloys supported on nitrogen and sulfur-doped carbons as robust electrode materials for oxygen reduction and Li-ion battery
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiaoying Zhang; Luyao Liu; Jiaxin Liu; Tingting Cheng; Aiguo Kong; Yu Qiao; Yongkui Shan
    更新日期:2020-01-22
  • Enhanced ferromagnetic and electric properties of multiferroic BiFeO3 by doping with Ca
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    F. Sánchez-De Jesús; A.M. Bolarín-Miró; C.A. Cortés-Escobedo; A. Barba-Pingarrón; F. Pedro-García

    We report the dependence of magnetic and electric properties with the substitution of Bi3+ by Ca2+ into the crystal structure of multiferroic calcium doped BiFeO3 for obtaining Bi1-xCaxFeO3, 0 ≤ x ≤ 0.10 Stoichiometric mixtures of Bi2O3, Fe2O3 and CaO were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powder was pressed at 900 MPa to obtain cylindrical pellets and sintered at 800 °C for 2 h. X-ray diffraction and Rietveld refinement were used to evaluate the effect of Ca2+ on the crystal structure and to determinate the phase transition from rhombohedral α-BiFeO3 (R3c) to orthorhombic β-BiFeO3 (Pbnm). In addition, vibrating sample magnetometry (VSM) was used to have knowledge of magnetic order: antiferromagnetism and ferromagnetism were identified for α-BiFeO3 and β-BiFeO3, respectively. Dielectric tests determinate Debye-type relaxation for samples with the rhombohedral crystal structure and no Debye type relaxations for orthorhombic samples. Differences in AC conductivity of rhombohedral samples show different mechanism compared with the conductivity of orthorhombic samples. Ferromagnetic and electrical properties of synthesized materials show a strong correlation with the lattice distortions induced by the ionic ratio between Ca2+ and Bi3+. The effect of Ca2+ over leakage current has an interesting response, an increase of Ca2+ reduce one magnitude order the leakage current for α-BiFeO3 samples; though for β-BiFeO3 samples increase of Ca2+ raise the leakage current in one magnitude order.

    更新日期:2020-01-22
  • Synthesis, characterization and thermoelectric performance of Mg2(Si,Sn,Ge) materials using Si-kerf waste from photovoltaic technology
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    G. Mesaritis; E. Symeou; A. Delimitis; M. Constantinou; G. Constantinides; M. Jeagle; K. Tarantik; Th Kyratsi

    The recycling acquisition of silicon waste from photovoltaic industry has gained an increasing attention nowadays, since more than 50% of high purity material ends up as kerf during the wafer cutting process. Currently, different Si-based applications are being exploited in terms of using such Si kerf, in order to lower cost and significantly increase environmental impact. Thermoelectric devices can efficiently contribute towards this recycling approach, via the preparation of highly efficient silicides for power generation. In this work, Bi doped Mg2(Si,Sn,Ge) materials were prepared using Si-kerf originated from photovoltaic (PV) cutting wastes. Different Bi concentrations were studied in terms of thermoelectric properties and performance and a high figure-of-merit of 1.1. was achieved at 800K. In addition, a thorough structural and mechanical property characterization, such as morphology, phase identification, hardness and indentation modulus has been conducted. These results, which were evaluated and compared to materials prepared with pure Si (>99.9%), are presented for the first time for Mg2(Si,Sn,Ge) materials.

    更新日期:2020-01-22
  • Achieving high stability of MgO/carbon nanotube interface via the co-deposition technique
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Qiu-hong Yuan; Han-qing Huang; Wei-cheng Wang; Guo-hua Zhou; Lan Luo; Xiao-shu Zeng; Yong Liu

    In this work, high stability of MgO/carbon nanotube (CNT) interface has been achieved through coating MgO nanoparticles on the surface of CNT via the co-deposition technique. Experimental results indicate that two types of MgO nanoparticles, those are single-crystal and poly-crystal nanoparticles were uniformly coated on the surface of CNT. The oxygen groups on CNT introduced by purification are crucial to the nucleation and growth of MgO nanoparticles on the surface of CNT via the C–O–Mg bonds interaction, and resulting in the formation of MgO/CNT interface in the sample of [email protected] The survived stable interface of MgO/CNT in the long time (22 h) and high intensity ultrasonic vibration (1000 W) treatment, suggests that the MgO/CNT interface has an excellent stability in microstructure. The calculations of work of adhesion for the interface models gives the evidence that MgO nanoparticles can form a strong interfacial bonding with CNT, proving the high stability of the MgO/CNT interface. MgO-coated CNT with high stable interface is suited to act as the reinforcing additive for the matrix of Mg alloy.

    更新日期:2020-01-22
  • Cr doped-Co9S8 nanoarrays as high-efficiency electrocatalysts for water splitting
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiaoqiang Du; Hui Su; Xiaoshuang Zhang
    更新日期:2020-01-22
  • First-principles study of phase stability and temperature-dependent mechanical properties of (Cr, M)23C6 (M = Fe, Mo) phases
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiaoguo Gong; Can Cui; Qiang Yu; Wei Wang; Wei-Wei Xu; Lijie Chen
    更新日期:2020-01-22
  • Structural and visible-near infrared optical properties of (Fe, Mo)-co-doped TiO2 for colored cool pigments
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiaolong Qing; Le Yuan; Can Wang; Mei Bi; Yaqin Wang; Xiaolong Weng

    Fe and Mo co-doped TiO2 pigments were prepared via solid-phase synthesis, and the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible–near infrared (UV-VIS-NIR) spectrophotometer. The effects of coloring impurity Fe3+ and compensating impurity Mo6+ on the phase, morphology, chemical structure, and optical properties of TiO2 pigments were systematically studied—especially the mechanism of synergistic effects of visible light color and near-infrared reflectance of TiO2 pigment. The results showed that single doping of Fe3+ or Mo6+ could accelerate the transition of TiO2 pigment from anatase phase to rutile phase. In the (Fe, Mo) co-doped sample, the Mo impurity helped accelerate the A→R crystal phase transition of TiO2, but an excessive amount of Fe impurity could inhibit the phase transition process. The morphology and particle size of the samples were also affected by the type of impurity and the doping concentration. In addition, the doped impurities could form a strong characteristic absorption peak in the visible light spectrum to enhance the absorption of visible light. The sample then gradually changed from white to pink, white gray to orange, etc. In the near-infrared region, the impurity compensation effect between Mo6+ and Fe3+ could be utilized to reduce the free carrier concentration of the TiO2 pigment and weaken its near infrared absorption. By reasonably adjusting the relative contents of Fe and Mo impurities, the developed Ti0.92125Fe0.0075Mo0.00375O2 yellow pigment could finally yield a NIR reflectance of 96%.This is expected to meet the application requirements of colored energy-saving pigments.

    更新日期:2020-01-22
  • Comparison between the use of Co3O4 or CoO on microstructure and electrical properties in a varistor system based on SnO2
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Martin I. Miranda-López; E.A. Padilla-Zarate; M.B. Hernández; L.A. Falcón-Franco; S. García-Villarreal; L.V. García-Quiñonez; Patricia Zambrano-Robledo; A. Toxqui-Terán; J.A. Aguilar-Martínez

    This comparative study pursues to clarify the differences between the addition of CoO or Co3O4 as a dopant on the non-linear electrical behavior and microstructure characteristics of a varistor system based on SnO2. The samples were fabricated according to the conventional ceramic processing using the nominal composition: (99.99-X)%SnO2 – 0.05%Cr2O3 – 0.05%Sb2O5 – X%CoO/Co3O4 where X = 0, 1, 3 and 5 mol%. The TGA-DTA analysis revealed essential differences in the thermal stability of CoO and Co3O4 during the sintering process, being CoO the oxide that induced the most visible changes. SEM micrographs, supported by EDS and XRD, showed remarkable grain growth even with a slight addition of cobalt oxide in comparison with the reference sample. The use of CoO holds the average grain size (6.7 μm), composition (SnO2), and shape homogeneity. In the case of Co3O4, a decreasing tendency in the average grain size and an increase in the residual porosity due to the in-situ formation of Co2SnO4 phase is observed. The electrical analysis revealed similarities on the alpha value for all molar percentages of both cobalt oxides: ∼9.6 and ∼8.1 units for CoO and Co3O4, respectively. In contrast, the breakdown electrical field shows notable differences: 1.08–1.16 kV cm−1 for CoO and 1.08–2.46 kV cm−1 for Co3O4. The evidence of this study confirms previous findings and suggests the existence of an essential role for the phase transitions of cobalt oxide on the final performance of SnO2-based varistors.

    更新日期:2020-01-22
  • A facile method to synthesize two-dimensional CsPb2Br5 nano-/micro-sheets for high-performance solution-processed photodetectors
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Ruonan Zhi; Jinming Hu; Shengyi Yang; Chandrasekar Perumal Veeramalai; Zhenheng Zhang; Muhammad Imran Saleem; Muhammad Sulaman; Yi Tang; Bingsuo Zou

    In this paper, a facile method to synthesize two-dimensional (2D) all-inorganic CsPb2Br5 nano-/micro-sheets at room temperature and their application as the active layer in solution-processed high-performance photodetectors are presented. The obtained CsPb2Br5 nano-/micro-sheets showed a photoluminescence emission peak at 522 nm with a narrow full-width-at-half-maximum of ∼17 nm, showing its high color purity, and an absorption peak at 307 nm with a shoulder peak at 339 nm. Then, the obtained CsPb2Br5 nano-/micro-sheets were used as the active layer in photoconductive photodetector and a high specific detectivity of 1.0 × 1012 Jones with a photoresponsivity of 0.02 A/W and an ultra-low dark current of ∼10−12 An under 16 μW/cm2 405 nm illumination were obtained from photoconductive photodetector Au/CsPb2Br5(85 μm)/Au. Further, the physical mechanism for the enhanced performance is discussed. Therefore, it provides a new method to suppress dark current for high-performance CsPb2Br5 photodetectors.

    更新日期:2020-01-22
  • In situ study of flow accelerated corrosion and its mitigation at different locations of a gradual contraction of N80 steel
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Xiankang Zhong; Tan Shang; Chenfeng Zhang; Junying Hu; Zhi Zhang; Qiang Zhang; Xi Yuan; Duo Hou; Dezhi Zeng; Taihe Shi
    更新日期:2020-01-22
  • Li and Ti Co-doping to stabilize slabs of high-voltage P2-type Na0.560[Li0.041Mn0.642Ni0.221Ti0.095]O2
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Bin Zhang; Biao Zhang; Lve Wang; Xu Chen; Yanluo Lu; Bin Xu; Wensheng Yang
    更新日期:2020-01-22
  • Wetting and interfacial behavior of Cu–Al/SiC systems: Influences of Si ion implantation and Al concentration
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-22
    Yalong Zhu; Mingfen Zhang; Xiangzhao Zhang; Zhikun Huang; Guiwu Liu; Guanjun Qiao

    Three doses (5 × 1015, 1 × 1016 and 5 × 1016 ions/cm2) of Si ions implantation into Si-terminated 6H–SiC substrate were carried out at an energy of 20 keV at room temperature. The wetting of pristine and Si-implanted 6H–SiC (Si–SiC) substrates by molten pure Cu, Cu-(42.9, 48.7, 70.4)Al alloys and pure Al were performed by the sessile drop technique under vacuum of ∼4 × 10−4 Pa at 1373 K. The surface characteristics of SiC substrates and wetting and interfacial behavior of Cu–Al/(Si-)SiC systems were analyzed and discussed. The equilibrium or final contact angles (θ) of Cu–Al/Si–SiC systems were increased more or less with the increase of Si ion implantation dose, and the Si ion implantation can markedly enhance the wettability of Cu-(0, 42.9)Al/SiC systems but weaken that of Cu-(48.7, 70.4, 100)Al/SiC systems. Interestingly, the graphitization phenomenon disappeared at the drop/substrate interface when the Al concentration was over 42.9%, and the Cu-42.9Al alloy cannot wet both the pristine 6H–SiC and Si–SiC substrates. These phenomena further demonstrated that the wetting of metal/SiC systems can be mainly determined by the metal-substrate interactions derived from the metal composition under a vacuum of and surface characteristics of metal drop and ceramic substrate during wetting.

    更新日期:2020-01-22
  • The mechanism of microwave response in layer-cofired Zn3Nb2O8–TiO2–Zn3Nb2O8 ceramic architecture
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Weijia Luo; Lingxia Li; Bowen Zhang; Jianli Qiao

    Tri-layered Zn3Nb2O8–TiO2–Zn3Nb2O8 ceramic with high temperature stability are initially fabricated. On the basis of X-ray diffraction, Raman spectra and HFSS (High Frequency Structure Simulator) simulation, a reasonable parallel mode is put forward, then the transition layer at the heterogeneous interface is considered to be crucial to the microwave response in this system, and the theoretical feasibility of layer-cofired microwave dielectric ceramics is verified. Contrasting to the random distribution type Zn3Nb2O8–TiO2, this structure can substantially reduce the amount of TiO2 and achieve an eightfold increase in Qf value, which is conducive to produce the new generation microwave passive devices.

    更新日期:2020-01-22
  • Facile and fast synthesis of SnO2 quantum dots for high performance solid-state asymmetric supercapacitor
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Jiguo Geng; Chuantao Ma; Dong Zhang; Xuefeng Ning
    更新日期:2020-01-22
  • Morphology of Fe2Al5 particles and the interface to WC coating in the context of hot-dip galvanizing: An ab initio study
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Daniel Scheiber; Werner Eßl; Johann Strutzenberger; Frank Goodwin; Jürgen Spitaler; Georg Reiss
    更新日期:2020-01-22
  • A comparative study on theoretical and experimental methods using basic electrical parameters of Au/CNTs/lnP/Au–Ge diodes
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Y. Saraç; S.Ş. Şener; A. Baltakesmez; B. Güzeldir; M. Sağlam

    In this study, we have reported experiments on interlayer performance of single and multi walled carbon nanotubes (SWCNTs and MWCNTs) for fabrication of n-InP substrates based diode applications and characterized with various methods to obtain ideal parameters. Structural and morphological properties of the nanotubes have been investigated by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) measurements, respectively. The Au/SWCNTs/n-InP and Au/MWCNTs/n-InP diodes have been prepared at the same conditions and electrically analyzed in the temperature range of 80–320 K by steps of 20 K, using forward bias current-voltage (I–V) characteristics. In characterization stage, various methods such as standard, analytical, evolutionary algorithm and numerical methods have been used to determine the ideality factor, barrier height and series resistance values of the diodes. The performance of the methods was compared in their classes and it was tried to find solutions more easily than the others.

    更新日期:2020-01-22
  • Effect of Mg content on shear texture evolution at variable processing conditions in Al–Mg alloys
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Chang-Hee Cho; Hyeon-Woo Son; Soong-Keun Hyun

    The current study is based on employing the torsional test parameters to observe the texture evolution of Al–Mg alloy with the face-centered cubic structure. We considered the Mg content in the alloy, which is an alloying composition, as our prime test parameter and examined how its variations are related to the test variables, such as temperature and strain rate. To confirm the torsion texture evolution of Al–Mg alloy, it was tested using the electron backscattered diffraction method and represented using a pole figure and an orientation distribution function. In the Al–Mg alloy, the change of Mg content causes a transformation of the physical properties, such as the stacking fault energy. Therefore, the difference in the shear texture evolution is observed to be remarkable. Further, the test results were compared to examine the validity of the rate sensitive crystal model. As the Mg content and strain rate increase, a specific face-centered cubic texture has been pronounced. Furthermore, as the temperature rises, the intensity of A fiber weakens, and the overall orientation distribution becomes random. From the results, this shear texture is discovered to be well suited for the rate sensitive crystal model, which demonstrates that the orientation persistence increases with increasing Mg content, higher strain rate, and lower temperatures.

    更新日期:2020-01-22
  • 更新日期:2020-01-22
  • Water-soluble ZnO quantum dots modified by (3-aminopropyl)triethoxysilane: The promising fluorescent probe for the selective detection of Cu2+ ion in drinking water
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Zou Tong; Xinxin Xing; Yue Yang; Zhezhe Wang; Zidong Wang; Rongjun Zhao; Xu Zhang; Yude Wang
    更新日期:2020-01-22
  • Corrosion-wear behavior of AA1050/mischmetal oxides surface nanocomposite fabricated by friction stir processing
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Mahdi Alishavandi; Mohammad Amin Razmjoo Khollari; Mahnam Ebadi; Sajjad Alishavandi; Amir Hossein Kokabi
    更新日期:2020-01-22
  • Hydrothermal synthesis of flower-like MgCo2O4 porous microstructures as high-performance electrode material for asymmetric supercapacitors
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Ya Wang; Jiale Sun; Shanshan Li; Yanfei Zhang; Chunju Xu; Huiyu Chen
    更新日期:2020-01-22
  • Nanomagnetism variation with fluorine content in Co(OH)F
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Haobo Liu; Mingjie Sun; Y. Li; Z.X. Cheng; J.L. Wang; W.C. Hao; W.X. Li

    Magnetic behaviors of cobalt hydroxide fluoride, Co(OH)F2-x Fx (x = 1.09 and 1.26), which are consisted with nanorods of ∼5 μm length and diameter ∼100 nm, obtained by a facile hydrothermal method, have been researched with the variation of fluorine content as a result of the different amount of reactant NH4F addition. Magnetic coupling performance are characterized based on the observation and analysis of magnetic susceptibility, X-ray Absorption Fine Structure (XAFS) and specific heat. Co(OH)F2-x is found to undergo an antiferromagnetic transition at 40 K. The peak temperature (T) on the transition curves shifts to lower temperature according with the increased magnetic field (H) following the rule of H2/3∞ (-T) because of the surface spin-glass behavior. The paramagnetic susceptibility can be fitted with the modified Curie–Weiss law between 100 K and 320 K. The negative Curie-Weiss temperature indicates that the antiferromagnetic coupling becomes stronger with the fluorine content. In addition, at temperatures below 5 K, the magnetic reordering was observed as spin-glass. Exchange bias behavior in Co(OH)F2-x was found after field cooling process demonstrating an exotic surface magnetic behavior generated with high fluorine contents due to the deformation of CoO6 octahedral induced large spin-glass behavior.

    更新日期:2020-01-22
  • Entropy stabilized single-phase (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders obtained via carbo/boro-thermal reduction
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Frédéric Monteverde; Federico Saraga

    This report deals with the synthesis of entropy stabilized (ES) single-phase (Hf,Nb,Ta,Ti,Zr)B2 powders, with specific surface area of about 1.6 m2/g, in a AlB2-type structure using individual transition metal (TM) oxides and, for the first time, elemental boron and carbon as precursors to feed the carbo/boro-thermal (CBT) reduction. Elemental B and C were intimately mixed into a mixture of five TM oxide powders, TM = Hf, Nb, Ta, Ti and Zr through an high energy planetary milling. ES single-phase TM diboride solid solution powders were obtained by a synthesis process consisting of a CBT reduction followed by solid solution formation. A B:C molar ratio = 1.27 (per 1 M mass of metals) was adjusted leading the CBT reduction to completion (i.e., full conversion of TM oxides), applying the synthesis temperature of 2123 K under vacuum. The micro-strain intended as deviation of some inter-planar distances of the entropy stabilized AlB2-type solid solution lattice, was analyzed by x-ray diffraction: a strong anisotropic micro-strain was found, and was attributed to the compositional disorder due to the coexistence of differing TM with different atomic radius.

    更新日期:2020-01-22
  • Electroactive FeS2-modified MoS2 nanosheet for high-performance supercapacitor
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Yinrui Wang; Yibing Xie

    Electroactive FeS2-modified MoS2 (FeS2/MoS2) nanosheet grown on Mo foil is designed as supercapacitor electrode material. FeS2/MoS2 nanosheet is crosslinked to form nanoporous microstructure. Density functional theory calculation reveals FeS2/MoS2 exhibits much narrowed bandgap and high density of states at the Fermi level, suggesting highly improved conductivity. The charge transfers resistance decreases from 1.375 Ω of MoS2 to 0.4167 Ω of FeS2/MoS2. FeS2/MoS2 exhibits higher specific capacity (495 and 394 mF cm−2) than MoS2 (132 and 218.1 mF cm−2) and FeS2 (315 and 286.5 mF cm−2) at 1.0 mA cm−2 in 3.0 M KOH and 0.5 M Na2SO4. The rate capacity retention is enhanced from 57.8% of MoS2 and 73.3% of FeS2 to 76.14% of FeS2/MoS2 in 0.5 M Na2SO4 when current density increases from 1 to 10 mA cm−2, indicating its improved rate capability. The cycling capacity retention keeps 100.2% of MoS2 and 100.7% of FeS2/MoS2 for 5000 cycles at 5 mA cm−2 in 0.5 M Na2SO4, indicating the similar cycling stability. An asymmetric solid-state supercapacitor using FeS2/MoS2 anode, exfoliated graphite carbon paper cathode and NaMoO4–Na2SO4-PVA gel electrolyte achieves specific capacity of 1.88 F cm−3 (112.8 mF cm−2) at 1.0 mA cm−2, energy density of 0.936 mWh cm−3 (56.56 mWh cm−2), capacity retention of 97.8% after 5000 cycles at 5.0 mA cm−2 and 1.9 V output voltage.

    更新日期:2020-01-22
  • The growth mode and Raman scattering characterization of m-AlN crystals grown by PVT method
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    L. Jin; H.L. Wu; Y. Zhang; Z.Y. Qin; Y.Z. Shi; H.J. Cheng; R.S. Zheng; W.H. Chen

    The growth mode of m-plane AlN crystal grown by physical vapor transport method is studied. The m-plane AlN crystal fabricated by spontaneous nucleation was used as a seed to grow bulk crystal, and 3-mm thick AlN crystals with a maximum lateral dimension of 20 mm were obtained. The Raman tensor elements of A1(TO), E2(high) and E1(TO) Raman models from the m-plane AlN crystal are investigated by angle-dependent polarized Raman scattering. The Raman tensor comparing with our previous report indicates the possible enhancement of the Raman tensor in the directions vertical to [0002] direction at higher growth temperature.

    更新日期:2020-01-21
  • Microstructures and hardnesses of AlCoCr0.5FexNi2.5 high entropy alloys with equal valence electron concentration
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Min Liu; Wenyao Xu; Shidong Zhang; Zemin Wang; Zhanyong Wang; Binjun Wang; Duo Wang; Fangjie Li

    A group of high entropy alloys (HEAs) in equal valence electron concentration (VEC), AlCoCr0.5FexNi2.5 (x = 0.5, 1.5, 2.5, 3.5), were melted and prepared. The microstructures and hardnesses were analyzed after homogenizing treatment. The results indicated that all of the equal-VEC HEAs consisted of FCC phase and BCC phase, their orientations obey Kurdjumov–Sachs relationship. This work also implied that the atomic size difference (Δr), like VEC, is an important parameter influencing the phase selection and worth considering in the HEA design. Fe is an FCC phase stabilizer for AlCoCr0.5FexNi2.5 HEAs and the ordered FCC phase (L12) gradually disappear with the Fe addition increased. The increasing FCC phase and the decreasing BCC phase resulted in the decreased hardness of HEAs.

    更新日期:2020-01-21
  • Highly luminescent water-soluble AgInS2/ZnS quantum dots-hydrogel composites for warm white LEDs
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Danlu Su; Le Wang; Min Li; Shiliang Mei; Xian Wei; Hanqing Dai; Zhe Hu; Fengxian Xie; Ruiqian Guo

    Ternary Ⅰ-Ⅲ-Ⅵ quantum dots (QDs) have become promising color-conversion materials for warm white light-emitting diodes (WLEDs) because of their broad emission, large stokes shift, high luminescence and low-toxicity. In this work, AgInS2/ZnS (AIS/ZnS) core/shell QDs were synthesized via a facile microwave-assisted aqueous method. The PL emission can be tuned from 540 to 622 nm by varying the Ag/In ratio and the maximum quantum yield can reach 58.27%. Flexible luminescent films were obtained by embedding AIS/ZnS QDs in polyacrylamide hydrogel, which were combined with blue InGaN chips to fabricate remote-type warm WLEDs. The as-prepared LEDs exhibit a relatively high color rendering index (CRI) of 87.5 and a correlated color temperature (CCT) of 3669 K, indicating that water-soluble AIS/ZnS QDs are competitive color-conversion materials for warm WLEDs.

    更新日期:2020-01-21
  • 更新日期:2020-01-21
  • Structural variation in improving thermal stability of transition alumina with La dopant
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Wenqiang Huang; Guihua Liu; Xiaobin Li; Tiangui Qi; Qiusheng Zhou; Zhihong Peng

    Structural variation in alumina directly determines the thermal stability of transition alumina with La dopant at high temperature. In this work, the thermal stability and alumina structure from well-crystallized ultrafine boehmite doped with various La-bearing compounds were studied. La2O3, LaAlO3, and LaAl11O18 could not efficiently inhibit transition alumina changing into α-Al2O3, α-Al2O3 seed benefited α-Al2O3 formation in the presence of La dopant. La(NO3)3 doping into boehmite effectively improved the thermal stability of θ-Al2O3 above 1200 °C. The nano-diameter active spots with low melting point led to the formation of α-Al2O3 with a smooth edge and sintering neck from the blank boehmite, whereas La dopant contributed to rhombus θ-Al2O3 with considerable pores, jagged edge, and wedge at 1200 °C for 2 h. Moreover, the Al and La contents fluctuated asynchronously during calcination, and the atomic ratio of Al/O decreased with the addition of La dopant. These results are attributed to La migration, assembling in active spots and increasing their melting point. Furthermore, relative to nearly 100% AlO6 coordination in α-Al2O3, La dopant significantly increased the AlO4 content above 900 °C. Therefore, La dopant increased the melting point of the active spots, hindered AlO6 formation, and inhibited α-Al2O3 nucleation on the alumina surface, thereby improved the thermal stability of the transition alumina.

    更新日期:2020-01-21
  • Microwave sintering of porous Ti–Nb-HA composite with high strength and enhanced bioactivity for implant applications
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Chander Prakash; Sunpreet Singh; Seeram Ramakrishna; Grzegorz Królczyk; Chi H. Le
    更新日期:2020-01-21
  • Long-life ablation resistance ZrB2-SiC-TiSi2 ceramic coating for SiC coated C/C composites under oxidizing environments up to 2200 K
    J. Alloys Compd. (IF 4.175) Pub Date : 2020-01-21
    Jinhua Li; Yulei Zhang; Haohao Wang; Yanqin Fu; Guohui Chen; Zengzhe Xi

    To improve the ablation resistance of carbon/carbon (C/C) composites at temperature about 2200 K, a ZrB2-SiC-TiSi2 ultra-high temperature ceramic coating was prepared by supersonic atmosphere plasma spraying on SiC coated C/C composites. The ZrB2-SiC-TiSi2 coating could protect C/C composites for more than 240 s under heat flux of 2400 kW/m2. The maximum surface temperature of the sample can reach to 2230 K. In addition, the mass and linear ablation rates of the coated samples after ablation for 240 s are only (0.314 ± 0.065) × 10−3 g/s and (0.221 ± 0.026) × 10−3 mm/s, respectively. The ZrB2-SiC-TiSi2 coating was converted into three layers after ablation: an outer layer, a particle-stacking layer, and a molten filled layer. The production of ZrTiO4, acting as sintering additive, could promote the sintering of ZrO2 and fill the pores, which effectively improved the ablation resistance of ZrB2-SiC-TiSi2 coating.

    更新日期:2020-01-21
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