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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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    Stability of metallic glasses under simulated space conditions

    Song J.Yao W.Zhao S.Bai H....
    7页
    查看更多>>摘要：Metallic glasses (MGs), due to their exceptional properties resulting from the amorphous structures, may be potential candidates for space applications. However, the effect of space conditions on the stability of MGs is not clear, which should be taken into account for practical use. The present work assessed the thermal stabilities of MGs in the simulated space thermal fields under vacuum condition, with a specific focus on the cryogenic thermal cycling with a high ratio of the non-isothermal to isothermal durations and the cryogenic treatment for a long-duration. The dynamics and thermal properties of MGs under the simulated space conditions were found to be different than those in laboratory-based conditions. MGs with lower fragility values were also determined to show greater thermal stability. On this basis, rules for the selection of MGs to ensure thermal stability during future space applications were proposed.
      原文链接:
    • NSTL
    • Elsevier

    Fabrication of N, S co-doped carbon nanofiber matrix with cobalt sulfide nanoparticles enhancing lithium/sodium storage performance

    Wang J.Cao K.Tian F.Zhang Y....
    11页
    查看更多>>摘要：In this work, N and S co-doped carbon nanofibers coated with cobalt sulfide nanoparticles (CoSx/N-SCFs) were synthesized by a simple method as anode materials for Li+/Na+ storage. The cobalt sulfide nanoparticles are uniformly embedded in carbon nanofibers in this composite, which effectively shortens the Li+/Na+ diffusion distance and buffers the volume expansion caused by discharge/charge. Besides, the doped N and S improve the conductivity of the carbon nanofibers and expand the carbon interplanar spacing, which facilitates the diffusion of Li+/Na+. The obtained CoSx/N-SCFs electrode shows an excellent reversible capacity of 761.3 mAh g?1 after 1000 cycles at 2 A g?1 for lithium storage and a reversible capacity of 505.1 mAh g?1 after 100 cycles at 100 mA g?1 for sodium storage. Density functional theory calculations further demonstrate that the N, S co-doping increases the electronic conductivity of carbon matrix and reduces Li+/Na+ diffusion barrier, thus effectively enhancing the adsorption of Li+/Na+. This work provides an effective method for synthesizing metal sulfide/carbon nanocomposites as high-performance anode materials.
      原文链接:
    • NSTL
    • Elsevier

    A novel Co-free Al0.75CrFeNi eutectic high entropy alloy with superior mechanical properties

    Jiao W.Li T.Lu Y.Yin G....
    9页
    查看更多>>摘要：Eutectic high entropy alloys (EHEAs) with superior mechanical properties and good castability are one of the most promising candidates among high entropy alloys (HEAs) for engineering applications. In this study, a new Co-free Al0.75CrFeNi EHEA with a low density of ~ 6.56 g/cm3 was designed and prepared, the solidification process and ambient deformation behavior of the alloy were investigated in detail. Al0.75CrFeNi was composed of a disordered body-centered cubic (BCC) phase and an ordered body-centered cubic (B2) phase, which grew alternately to form a beautiful sunflower-like eutectic morphology. The alloy exhibited excellent mechanical properties with a high yield strength (σ0.2) of 1482 ± 56 MPa, fracture strength (σbc) of 3639 ± 190 MPa, and elongation to fracture of ~37.8% ± 1.5%. The high strength and low density of the alloy lead to a superior specific yield strength of ~ 226 KPa?m3/kg. During deformation, dislocation gliding in the BCC phase dominated the plastic deformation in the early stage. Subsequently, the dislocation activated in the B2 phase when the strain was further increased. Dislocation interactions and microstructural features, such as grain boundaries and substructures, in different stages generated the good balance between the strength and the ductility of the alloy.
      原文链接:
    • NSTL

    Effects of Y addition on the microstructure, properties and softening resistance of Cu-Cr alloy

    Wang X.Jie J.Li T.Wang Y....
    12页
    查看更多>>摘要：The effects of Y content on the microstructure and properties of Cu-0.9Cr and Cu-1.45Cr alloys were investigated systematically in present manuscript. Cu-Cr-(Y) alloys were prepared by vacuum melting and casting, solid solution treatment at 960 °C, (90% cold rolling) and aging treatment at 460 °C. The results indicate that the addition of 0.1 wt% Y refines the eutectic structure of as-cast Cu-0.9Cr and Cu-1.45Cr alloys. Besides, the hardness of Cu-Cr-(Y) alloys after solid solution treatment increases with the increase of the Y content. CRA (cold-rolling and aging) process can enhance the hardness of peak-aged alloys compared with SSA (solid solution and aging), the peak-aged hardness and corresponding conductivity of cold-rolled alloys slightly increase by addition of Y. Especially, when CRA for 300 min, the ultimate tensile strength, hardness of Cu-0.95Cr-0.1Y alloy (433 MPa, 146.8 HV) are superior to those of Cu-0.9Cr alloy (333 MPa, 102 HV), indicating that addition of Y significantly inhibits the over-aging during CRA. The TEM results reveal that Cr precipitates of FCC and BCC structures exist in the Cu-Cr-Y alloy aged for 300 min, and Y element suppresses the coarsening of Cr precipitates and the reduction of dislocation density. Moreover, the softening temperature of peak-aged Cu-Cr-Y alloys is ~70 °C higher than that of Cu-Cr alloys since the addition of Y inhibits the coarsening of Cr precipitates.
      原文链接:
    • NSTL
    • Elsevier

    The effects of dual-doping and fabrication route on the thermoelectric response of calcium cobaltite ceramics

    Yu J.Liu X.Wang B.Freer R....
    13页
    查看更多>>摘要：Calcium cobaltite (Ca3Co4O9) is an attractive p-type thermoelectric oxide for energy harvesting. Our work provides insights into the way microstructure-property relationships in calcium cobaltite based ceramics can be controlled by dopants and fabrication routes. Ca2.63Bi0.3M0.07Co3.92O9+δ (M = Sr and Ba) ceramics were prepared by solid state reaction (SSR) and spark plasma sintering (SPS) routes. The roles of dopants were clearly identified; Bi and Sr entered the crystal lattice, whilst Ba mainly participated in forming Ba-rich secondary phases. Successful Bi/Sr dual-doping gave rise to pronounced lattice expansion, which could induce strain fields and atomic mass variations, thereby leading to enhanced carrier mobility and phonon scattering. In spite of an increase in porosity, the annealed SPS-processed Ca2.63Bi0.3Sr0.07Co3.92O9+δ ceramic showed enhanced electrical conductivity with minor changes to Seebeck coefficients, due to reduction of secondary phases, increased grain size and improved texture. By contrast, the thermal conductivity of SSR-processed Ca2.63Bi0.3Ba0.07Co3.92O9+δ ceramic was significantly reduced although the electrical conductivity was limited by the high porosity. As a result, a maximum ZT value (//ab) of 0.14 was achieved in both the solid state synthesized Bi/Ba dual-doped samples and annealed SPS-processed Bi/Sr dual-doped samples at 800 K.
      原文链接:
    • NSTL
    • Elsevier

    Flow behavior and forming characteristics of 2A14 aluminum alloy at cryogenic temperatures

    Huang K.Huang S.Yi Y.Dong F....
    13页
    查看更多>>摘要：Cryogenic forming is a promising new method for aluminum alloy manufacturing due to its improved formability, but the mechanical properties and microstructure evolution of alloys deformed at cryogenic temperatures require further study. In this work, the flow behavior and detailed deformation mechanism of 2A14 alloy at cryogenic temperatures were systematically studied. Uniaxial tensile tests at 113–298 K with a strain rate from 0.00025 to 0.01 s?1 were carried out, and a constitutive model was established and modified. Then, the Erichsen cupping index (IE) values were tested at different temperatures (298 K, 203 K, and 113 K). Finally, the microstructure of cryogenically-deformed samples was studied by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), X-ray diffractometry (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The stress-strain curves were serrated from 203 K to 298 K, but at temperatures below 203 K, a smooth curve was obtained due to the suppression of dynamic strain aging. The elongation and IE value of the alloy at 113 K were almost 51% and 21% higher than those obtained at 298 K, respectively. This was caused by the uniform deformation and the increased critical local dislocation density at cryogenic temperatures. The tensile strength increased by 27% at 113 K, and the improved strength was attributed to the high dislocation density deformation at cryogenic temperatures.
      原文链接:
    • NSTL
    • Elsevier

    Structural and magnetic alteration of Cu2GaBO5 forced by Mn3+ doping

    Moshkina E.Eremin E.Velikanov D.Bovina A....
    12页
    查看更多>>摘要：To study the gradual change of the structure and the magnetic state of the ludwigite Cu2GaBO5 upon Mn3+ doping, single crystals of Cu2Ga1?xMnxBO5 (x = 0.55, 0.7, 0.8) with the size up to 3 × 3 × 10 mm3 were grown using the flux technique. The phase homogeneity and crystal structure of the obtained compounds were investigated by the powder and single crystal X-ray diffraction. All the samples possessed the monoclinic-distorted ludwigite structure with the P21/c space group. The study of the actual Cu/Ga/Mn composition by the EDX (energy-dispersive X-ray spectroscopy) technique revealed the lower Mn content in all the samples and the refined formulas were Cu2Ga0.47Mn0.53BO5, Cu1.92Ga0.5Mn0.58BO5 and Cu2Ga0.32Mn0.68BO5, respectively. Despite the high manganese content, the concentration transition (from Cu2GaBO5 to Cu2MnBO5) and change of the monoclinic angle did not occur, but strong Me-O octahedra distortions exceeding those both in the parent ludwigites Cu2GaBO5 and Cu2MnBO5 were found. The study of the thermodynamic and magnetic properties revealed the low-temperature magnetic phase transition inherited from the parent Cu2GaBO5 in all the samples. However, the nature and ordering type for the compounds with different Mn content were different: there was a complex transformation of the magnetic state from the partially ordered AFM (antiferromagnetically) in Cu2Ga0.47Mn0.53BO5, through the spin glass state, to the combined spin glass/ordered state in Cu2Ga0.32Mn0.68BO5 with the appearance of magnetic anisotropy. The evident dependence of Tc (phase transition temperature) on the magnetic field was found as well as its decrease at the nonzero magnetic field in the samples with x = 0.53 and 0.68.
      原文链接:
    • NSTL
    • Elsevier

    Single-component white emitting phosphor Mg2Y2Al2Si2O12:Tb3+, Eu3+, Tm3+ for white LEDs

    Huo X.Wang Z.Yang Z.Wang D....
    13页
    查看更多>>摘要：A series of Tb3+, Eu3+, Tm3+ doped Mg2Y2Al2Si2O12(MYAS) phosphors were synthesized by high temperature solid-state method. The emission spectra and energy transfer between lanthanide ions in the materials were studied in detail. Under the excitation of near ultraviolet light, the emission spectra of Mg2Y2Al2Si2O12:Tb3+, Eu3+, Tm3+ phosphors show visible emission peaks of Tb3+, Eu3+, Tm3+, mainly including 1D2→3F4 electron transition (blue light) of Tm3+, 5D3→7FJ (J=4, 5, 6) and 5D4→7FJ (J=3, 4, 5, 6) electron transition (green light) of Tb3+ and 5D0-7F1, 5D0-7F2 and 5D0-7F3 electron transition (red light) of Eu3+. By measuring the emission spectrum, excitation spectrum and fluorescence lifetime of Mg2Y2Al2Si2O12:Tb3+, Eu3+ and Mg2Y2Al2Si2O12:Tm3+, Eu3+ phosphors, it is proved that the energy transfer mechanisms between Tb3+-Eu3+ and Tm3+-Eu3+ in the matrix Mg2Y2Al2Si2O12 are dipole-quadrupole interaction and dipole-dipole interaction, respectively. By changing the concentration of Tb3+, Eu3+, Tm3+ in the matrix, phosphors with adjustable colors from green to red and from blue to red can be obtained, importantly, Mg2Y2Al2Si2O12:0.03Tb3+, yEu3+, 0.05Tm3+ can emit white light with good temperature stability by the energy transfer.
      原文链接:
    • NSTL
    • Elsevier

    Light keys open locks of plant photoresponses: A review of phosphors for plant cultivation LEDs

    Fang S.Lang T.Han T.Cai M....
    15页
    查看更多>>摘要：Light is an indispensable energy source for agricultural production. But due to the limitation of season, changeable weather and different latitude, solely relying on natural light is absolutely not enough. In order to upgrade plant photosynthesis efficiency, light emitting diode (LED) as a new generation lighting source, has become an inevitable choice to improve agricultural production efficiency. Thus a range of different phosphors for plant lighting LED (phyto-LED) are widely studied and becoming a hot topic in recent years. However, how to design acceptable plant lighting phosphors, how to evaluate suitability of synthesized phosphors and how to achieve targeted irradiation to specific plant photoreceptors are urgently clarified. The answers of these issues will be given in this review. Proceeding from relationship between light quality and photoreceptor response, we thoroughly overview recent processes on plant lighting phosphors, including their structure, frequently-used activators, characteristic excitation and emission wavelengths and photoluminescence efficiency. Importantly, we propose a quantitative method to calculate similarity between emission spectra of phosphor and plant photoreceptor absorption spectra. Finally, we address remaining challenges in this exciting field and present our perspectives for further investigations and hope that this review can be a reference for those who want to design and study phosphors for plant lighting.
      原文链接:
    • NSTL
    • Elsevier

    One-pot synthesis of nanosized MnO incorporated into N-doped carbon nanosheets for high performance lithium storage

    Sun Z.Liu C.Shi J.Huang M....
    9页
    查看更多>>摘要：As potential anode materials for lithium-ion batteries, transition metal oxides have been extensively investigated due to their high theoretical capacity. Nevertheless, how to address rapid capacity degradation and improve rate capability is still a big challenge. Herein, nanosized MnO incorporated into N-doped carbon nanosheets (MnO/NCN) was rationally designed by a facile one-pot salt-templated synthesis method. The nanosized MnO particles (around 20 nm) were powerfully anchored on the ultrathin N-doped carbon nanosheets to build a high-efficiency electrons/ions hybrid conductive framework. In addition, based on the stable interfacial interaction between MnO and N-doped carbon nanosheets, the MnO/NCN hybrid exhibits great structural stability, thus delivering high reversible lithium storage capacity (719 mA h g?1 at 0.1 A g?1) and superior stability (497 mA h g?1 at 1 A g?1 over 1000 cycles). Besides, the assembled lithium-ion capacitor with MnO/NCN anode exhibits excellent energy-power characteristics (142 W h kg?1 at 412 W kg?1). Such impressive lithium storage performance demonstrates that the MnO/NCN electrode is promising for large-scale energy storage devices.
      原文链接:
    • NSTL
    • Elsevier