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Journal of Alloys and Compounds
Elsevier Science S.A.
Journal of Alloys and Compounds

Elsevier Science S.A.

0925-8388

Journal of Alloys and Compounds/Journal Journal of Alloys and CompoundsSCIISTPEI
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    ZnO-NWs/Cu-based metallic glass nanotube array (ZNWs/Cu-MeNTA) for field emission properties

    Ye J.-S.Huang B.-R.Chu J.P.
    8页
    查看更多>>摘要：The field emission properties of a novel ZnO-NWs/Cu-based metallic glass nanotube array (ZNWs/Cu-MeNTA) heterostructure are studied. A sample is annealed at 300 °C for 1 h at atmospheric pressure in a tube furnace as post-treatment. The turn-on electric field Eon (at a current density of 0.1 μA/cm2) and corresponding field enhancement factors β for the as deposited and 300 °C annealed ZNWs/Cu-MeNTA are respectively 1.47 V/μm, 13,042 and 1.77 V/μm, 10,954. The increase on the turn on field might be due to oxidation of the as-deposited ZNWs/Cu-MeNTA after the thermal post-treatment. Crystallization is enhanced after the field emission measurements, but parts of the ZnO-NWs break down. The Eon increases (1.29–1.47 V/μm) in the successive field emission measurements for the as-deposited ZNWs/Cu-MeNTA. In addition, the Eon decreases (2.26–1.77 V/μm) for the 300 °C annealed thermal post treatment ZNWs/Cu-MeNTA. This phenomenon might be due to the trade-off between the enhanced crystallization and the amounts of the ZnO-NWs break down, respectively causing a decrease and increase in the turn on field. This novel nanostructure for field emission studies might be useful for use in future mini-display device, optoelectronics, sensors, piezoelectric-nanogenerator, solar cells and battery applications.
      原文链接:
    • NSTL
    • Elsevier

    Large magnetocaloric effect in EuGd2O4 and EuDy2O4

    Palacios E.Evangelisti M.Saez-Puche R.Romero J....
    13页
    查看更多>>摘要：Magnetization, heat capacity and direct measurements of the magnetocaloric effect show that EuGd2O4 and EuDy2O4 have a remarkably large magnetocaloric effect at cryogenic temperatures, owing to their high magnetic density and low ordering temperatures. The Gd derivative orders antiferromagnetically at TN = 4.6 K, while its magnetocaloric effect largely exceeds that of the reference refrigerant Gadolinium Gallium Garnet (GGG) above 5 K. The Dy derivative undergoes two phase transitions at TC1 = 3.65 K and TC2 = 4.7 K, respectively, which are the result of a peculiar magnetic arrangement: the first Dy sublattice is parallel to the crystallographic c-axis, while the Eu sublattice makes a variable angle from 0o to 45o with the direction of the second Dy sublattice that lies in the ab-plane. EuDy2O4 has a lower magnetocaloric effect than EuGd2O4, yet larger than GGG. Both ordering mechanisms are semi-quantitatively explained within the frame of a mean-field simulation, which takes into account the magnetic anisotropy strength of the participating magnetic ions.
      原文链接:
    • NSTL
    • Elsevier

    Photovoltaic performance and physical characterization of Cu doped ZnO nanopowders as photoanode for DSSC

    Caglar M.Esgin H.Caglar Y.
    11页
    查看更多>>摘要：In this study, the effects of two fabrication factors, the Cu doping and the dye adsorption time on the ZnO-DSSC, were systematically investigated. ZnO nanostructures were obtained by hydrothermal synthesis method at different Cu doping ratio (0%, 0.1%, 1%, 3%) and used as photoanode in DSSC. The effects of Cu incorporation to ZnO on the morphological, structural, and optical properties were examined. As a result of XRD analysis, it was determined that all samples have highly crystallized hexagonal wurtzite structure. The doping process has caused the formation of protruding surfaces in the ZnO nanostructure and increased the surface area, which has been observed using SEM images. X-ray photoelectron spectroscopy (XPS) study demonstrated Cu-O and Zn-O bonding in the synthesized flake-shaped Cu doped ZnO nanostructures, which confirmed the Zn substitution by the Cu-ions. The maximum cell efficiency of 2.03% was achieved in DSSC when photoanode was fabricated by using %0.1 Cu doped ZnO nanopowder dipped in N719 solution for only one hour. The efficiency of DSSC with Cu doped ZnO photoanode has improved by 20%, and the dye adsorption time has been decreased by three times, obviously.
      原文链接:
    • NSTL
    • Elsevier

    Construction of LaFeO3/g-C3N4 nanosheet-graphene heterojunction with built-in electric field for efficient visible-light photocatalytic hydrogen production

    Tian Z.Yang X.Chen Y.Jiao T....
    13页
    查看更多>>摘要：Photocatalytic hydrogen desorption from water has been considered to be a more effective way to solve energy shortages. However, the relatively high charge recombination rate and poor recyclability are the principal factors restricting the realistic utilization of photocatalysts. Herein, in order to improve the utilization of photogenerated carriers and the response range of visible light, a ternary composite material LaFeO3/g-C3N4 nanosheets-graphene had been successfully prepared. A series of systematic studies on the structure, microscopic morphology, magnetic properties and photocatalytic hydrogen evolution activity have been carried out. The combination of CNNS, LaFeO3 and graphene in the composites was confirmed by XRD and XPS. SEM and TEM results show that LaFeO3 micro-particles grow uniformly on the CNNS flaps and the graphene is observed to cover the surface of the LaFeO3/CNNS. The optical properties indicate that the absorption edge of the composite material extends to the visible light region. The excellent photocatalytic performance of LFO/CNNS-0.25G composite (1326.5 μmol h?1 g?1) is mainly result in the improved redox capacity and carrier separation due to the tight C–O–Fe bond of Z-scheme heterojunction, meanwhile, the introduction of graphene also broadens the visible light response and accelerates the carrier transport. This research can provide a novel strategy for designing artificial photocatalytic systems with high charge transfer efficiency.
      原文链接:
    • NSTL
    • Elsevier

    Oxygen atmosphere-independent resistive switching effect at the CoCr2O4 (001) surface

    Lai X.Liu B.Zhang L.Wang Y....
    6页
    查看更多>>摘要：The resistive switching behavior of the spinel multiferroic CoCr2O4 film was investigated by in-situ scanning probe microscope in different atmosphere. The CoCr2O4 film on SrNbxTi1?xO3 substrate has an epitaxial structure and flat surface. Obvious local resistive switching along with reversible Fermi level shift were achieved by applying driving voltage with different polarity on the film surface, which suggests that the RS effect occurs uniformly near the top surface of the film. Unlike the oxygen ion migration related interface type RS effect, the CoCr2O4 film shows nearly identical RS behavior in both vacuum and oxygen rich atmosphere. Such oxygen atmosphere independent RS behavior was attributed to the charge trapping/detrapping process near the film surface. Furthermore, the stable RS effect with the same behavior was also found in macroscopic devices. These results demonstrate that the CoCr2O4 based RS devices have a robust switching performance and may have important applications in complex environment.
      原文链接:
    • NSTL
    • Elsevier

    Investigation of the microstructural evolution and detachment of Co in contact with Cu–Sn electroplated silicon chips during solid-liquid interdiffusion bonding

    Emadi F.Vuorinen V.Dong H.Ross G....
    10页
    查看更多>>摘要：Solid-liquid interdiffusion (SLID) bonding is one of the most promising novel methods for micro-(opto)-electromechanical system (MEMS/MOEMS) wafer-level packaging. However, the current SLID bonding solutions require the use of an electrochemical deposition method for MEMS/MOEMS wafers as well, which significantly complicates the process integration options. Hence, this work proposes Co as a potential option for compatible contact metallization on MEMS/MOEMS wafers to utilize mature Cu–Sn SLID bonding. The focus of this study is on gaining a fundamental understanding of the microstructural formation and evolution of Co substrates in contact with Cu–Sn electroplated silicon wafers and identifying possible failures of joints during bonding, which are prerequisites for guaranteeing devices’ manufacturability, functionality, and long-term reliability. The effect of bonding time and temperature on the microstructural evolution and phase formation of Co substrates in contact with Cu–Sn electroplated silicon chips was investigated. Moreover, a phase diagram of the Co–Cu–Sn ternary system was thermodynamically evaluated based on experimental data. Samples were successfully bonded at 250 °C for 1500 and 2000 s and at 280 °C for 1000 s. The main interfacial intermetallic compounds were identified as (Cu,Co)6Sn5, Cu3Sn, and (Co,Cu)Sn3. Co stabilized the high-temperature hexagonal (η) Cu6Sn5 phase down to room temperature. Bond detachment was observed when applying either a higher bonding temperature or a longer bonding time. Two critical factors that cause detachment during bonding were recognized: first, a change in thermodynamic equilibrium when exceeding the maximum allowed Co content in Cu6Sn5 formed adjacent to the CoSn3 phase and a discontinuous change in the Co content in the Cu6Sn5 grown on the Cu and Co sides; second, stress exerted due to the rapid growth of (Co,Cu)Sn3 between the Co substrate and (Cu,Co)6Sn5. Therefore, achieving successful bonding in the Co–Sn–Cu SLID system requires governing the amount of dissolved Co atoms in liquid Sn and the CoSn3 formation, both of which can be achieved by manipulating the relative thickness of the Co, Cu, and Sn layers. The observations and calculations in this work show that a prerequisite for obtaining successful bonding in the Co–Sn–Cu SLID system at 250 °C is a Co–to–Sn thickness ratio of 0.04 or less.
      原文链接:
    • NSTL
    • Elsevier

    Novel Nb26Mo4O77 rod-like nanoparticles anode with enhanced electrochemical performances for lithium-ion batteries

    Yu C.Cao X.Hu J.Cheng N....
    7页
    查看更多>>摘要：As a branch of intercalation type niobium-based anodes for lithium-ion batteries, Nb26Mo4O77 samples are synthesized by hydrothermal and solid-state method, respectively, while the structure and lithium-ion storage characteristics are studied in depth. Nb26Mo4O77 belongs to a monoclinic phase with ordered intergrowth ReO3 structure, which is constructed by a mixture of (Nb/Mo)O6 octahedra blocks of 3 × 4 × ∞ and 4 × 4 × ∞ occurring in alternate sequence and linked by MoO4 tetrahedra, favoring to the structural stability during the rapid lithium-ion deintercalation. Compared to agglomerated Nb26Mo4O77 microparticles synthesized via solid-state process, rod-like nanoparticles synthesized by hydrothermal method with the high specific surface area and reaction reactivity exhibit an improved initial coulombic efficiency (89.3%), notable cyclability (203 mAh g?1 after 503 cycles at 0.5 C), significant intercalation pseudocapacitive contribution (82.2% at 0.9 mV s?1) and increased rate capability (107 mAh g?1 at 10 C). These results provide some new supplements for the improvement of niobium-based anodes.
      原文链接:
    • NSTL
    • Elsevier

    Preparation and properties of situ-sintered SiC ceramics aided by ZnO-Al2O3-CaO

    Ye M.Teng Y.Zhao X.Wang S....
    9页
    查看更多>>摘要：The safe treatment and disposal of radioactive graphite waste is becoming an important issue worldwide. The objective of this paper is to prepare the SiC-ZAC (ZAC: ZnO-Al2O3-CaO) composite ceramic for immobilizing radioactive graphite, where ZAC is as sintering additives. The effects of the sintering system and ZAC content on the phase compositions, microstructure, and properties of SiC-ZAC composite ceramic are studied by XRD, SEM-EDS, TEM-EDS, linear shrinkage, Vickers hardness, and thermal conductivity. By vacuum hot pressing sintering at 1600 °C for 1 h, the results show that the S-35-1600 (65 wt% SiC, 10.5 wt% ZnO, 15.72 wt% Al2O3, 8.78 wt% CaO) sample is the potentially applicable formula composition due to its better performance, in which the Vickers hardness and the thermal conductivity are 165.2 HV10, 14.6 W m?1 k?1 respectively, and the normalized elemental mass loss of Si, Al and Ca are 0.0064–0.0108 g/m2, 21.4784–24.7837 g/m2, 56.9108–67.5637 g/m2 after 42 days at pH = 5/7/9 solution, respectively. Importantly, ZAC sintering additives can form the bond phases of CaAl4O7, CaAl2O4, Ca3Al2(OH)12, and Ca2Al2SiO7 under relatively low temperatures to reduce the sintering temperature for SiC ceramics. Meanwhile, the existing form of the Zn element is revealed: one part of the Zn forms glass phase, and the other part volatilized by carbothermic reduction.
      原文链接:
    • NSTL
    • Elsevier

    Microstructure, tribological and oxidation behaviour of spark plasma sintered Ti-Ni-xTiCN composites

    Rominiyi A.L.Shongwe M.B.Jeje S.O.Olubambi P.A....
    13页
    查看更多>>摘要：The dearth of information on the tribological and oxidation behaviour of Ti-Ni-TiCN composites has been identified in the literature. Therefore, in this work the tribological and oxidation behaviour of spark plasma sintered Ti-6Ni-xTiCN composites were reported. Microstructural and phase analyses showed the evolution of hard phases of Ti2Ni intermetallic, in-situ formed TiN and unreacted TiCN within matrix of the composites which enhanced the hardness. The dry sliding wear across all tested loads and oxidation behaviour up to 800 °C of the composites were better than that of CP-Ti. Ti-6Ni-10TiCN composite exhibited the highest wear and oxidation resistance across the tested loads and oxidation condition, respectively. This was attributed to the uniform distribution of the reinforcing phases and the formation of the protective oxide layer on the surface of the sintered composites.
      原文链接:
    • NSTL
    • Elsevier

    Effect of crystal orientations and precipitates on the corrosion behavior of the Al-Cu alloy using single crystals

    Wen F.Chen J.Zhong S.Zhou Z....
    10页
    查看更多>>摘要：Al-Cu single crystals with different typical orientations (i.e., (001), (101), and (111)) were prepared to investigate the corrosion behavior of the Al-Cu alloy with and without precipitates by scanning electron microscopy (SEM), transmission electron microscopy (TEM), immersion testing in EXCO solution, and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion rates of the alloy with different orientations increased in the order of (111)< (001)< (101) in the solid solution state (without precipitates), while those of the alloy increased in the order of (101)< (001)< (111) in the aged state (with precipitates). The corrosion resistance of the alloy without precipitates was mainly determined by the atomic density of the crystal plane, and that of the alloy with precipitates was mainly provided by the corrosion product film. After aging, the precipitation of the θ' phase led to anodic dissolution of the nearby matrix and further accelerated the corrosion rates of the alloy. Furthermore, the corrosion pits of the alloy without precipitates showed geometric shapes corresponding to the crystal orientations. The corrosion of the alloy with precipitates propagated in the form of corroded bands, which were parallel to the {001}Al plane.
      原文链接:
    • NSTL
    • Elsevier