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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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    (162619)Designing elastic modulus of Al_3X precipitates in Al alloys by identifying effective atomic bonds and stabilizing coherent structures

    Chengpeng XueYu WangJunsheng Wang
    11页
    查看更多>>摘要:In Al alloys, many experiments have shown the effectiveness of Al_3X precipitates in promoting the primary grain nucleation such as Al_3Ti, Al_3Er and Al_3Sc, preventing the α-Al grain recrystallization such as Al_3Cr and Al_3Zr, and strengthening the matrix such as Al_3Li and Al_3Ni. Almost all of those experiments have been measuring the stable structures, and none of them have been focusing on the intrinsic properties of Al_3X and their stabilities as a function of crystal structure and lattice constants due to the experimental limitations. In this study, the first-principle calculation is used to predict the metastablity of different Al_3X structures including L1_2, DO_(22), DO_(23), DO_(19), DO_(18), DO_(24), R3m and P6_3/mmc. The varitions of lattice constant have been achieved by changing external pressure from 0 to 50 GPa. It was found that the L1_2 structure not only had a smaller lattice mismatch with α-Al, but also had a higher symmetry than the other structures, and the stability of the L1_2 structure was enhanced when external pressure was applied, and some other structures may undergo a transition to the L1_2 structure, while the elastic modulus of the L1_2 structure was improved. In addition, the elastic modulus of the Al_3X precipitation phases of different structures was found to increase with decreasing distance between atomic pairs, and the distance between Al-X and X-X pairs had a much greater effect on the elastic modulus than the Al-Al pairs.

    (163062)Synthesis of porous Ag-Ag_2S@Ag-Au hybrid nanostructures with broadband absorption properties and their photothermal conversion application

    Huong Thi HoangKwon Taek LimAstrini Pradyasti
    10页
    查看更多>>摘要:Hybrid nanostructures composed of a plasmonic noble metal and a semiconductor have been studied intensively because of their unusual properties and wide range of potential applications. However, preparing these hybrid nanostructures with a precisely controlled shape, composition, heterostructure, and internal structure remains a challenge. Here, we describe a method for synthesizing new metal-semiconductor? bimetal hybrid nanostructures. Specifically, Ag-Ag_2S nanoplates were first prepared by site-controlled sulfidation, and these nanoplates were then used as seeds to synthesize Ag-Ag_2S@Ag-Au hybrid nanostructures with unique porous architectures through seed-mediated growth and a galvanic replacement reaction. The composition of the ternary alloy combined with the unique porous structure of the hybrid nanostructures resulted in excellent broadband absorption in the UV-Vis-NIR region (300-1100 nm), and hence a black color, without an additional post-treatment process. When used as photothermal conversion materials, the hybrid nanostructures showed good photothermal conversion activity, with a maximum efficiency of 76.1% under irradiation with an 808 nm near-infrared laser. A mechanism for the high photothermal conversion activity is proposed on the basis of experimental and simulation results.

    (163109)Structure and luminescent properties of Dy~(3+) activated NaLa9(SiO_4)_6O_2 yellow-emitting phosphors for application in white LEDs

    Sami SlimiPavel LoikoKirill Bogdanov
    13页
    查看更多>>摘要:A series of Dy~(3+)-doped sodium lanthanum orthosilicate oxyapatites, NaLa_(9-x)Dy_x(SiO_4)_6O_2 (NLSO:xDy, x = 0-0.3), were synthesized by the solid-state reaction method at 1100 °C, with the aim of developing yellow emitting phosphors for applications in w-LEDs. Their crystal structure, morphology and particle size distribution, electronic structure, Raman spectra, concentration- and temperature-dependent luminescent properties were investigated for the first time. The crystal structure was refined by the Rietveld method. Undoped NLSO is hexagonal (space group P6_3/m - C_(6h)~2) with lattice constants a = b = 9.6917(3) A and c = 7.1836(4) A. It is shown that Dy~(3+) ions substitute for the La~(3+) ones in two types of sites with C_3 and C_s point symmetries. The first-principle calculations for undoped NLSO revealed an indirect bandgap of 5.06 eV. The NLSO:0.2Dy phosphor exhibited intense yellow emission with CIE 1931 chromaticity coordinates of (0.469, 0.495) and a correlated color temperature of 3150 K owing to the hypersensitive electric-dipole transition ~4F_(9/2)→~6H_(13/2) (571 nm) dominating in the luminescence spectrum. Excellent thermal stability was found for this apatite phosphor (the activation energy is 0.23 ± 0.02 eV).

    (163048)Systematic fabrication and electromagnetic performance of porous biomass carbon/ferrite nanocomposites

    Manqing AiShuang-Shuang LyuHao Du
    8页
    查看更多>>摘要:Biomass carbon is a potential alternate for commercially expensive graphene and carbon nanotubes to fabricate nanocomposites as electromagnetic (EM) wave absorbers. Here, we systematically prepared porous biomass carbon/ferrite nanocomposites with different chemical compositions, particle sizes, and structures using rice husk ash, carbonized luffa sponge, carbonized kapok and cotton fibers. All the prepared nanocomposites show limited dielectric losses, indicating the permittivity is less affected by the micro-morphologies, chemical compositions, and structures of biomass carbon. The magnetic loss of microwaves by most samples is caused by eddy current effect. Both smaller and wider range sized particles would contribute additional natural resonance for the magnetic loss of ferrite nanoparticles. The EM wave absorption performance of the nanocomposites are controlled by both the impedance matching between the absorber and air and their magnetic/dielectric losses for incident EM waves. The maximum bandwidth of RL < -10 dB of the as-prepared nanocomposites is about 4.8 GHz, covering most of the K_u-band. Due to their low density and good impedance matching with air, the biomass carbon/ferrite nanocomposites could be promising green light-weight EM wave absorbers by adjusting the particle sizes of ferrite nanoparticles.

    (163059)Electrical resistivity and short-range order in rapid-quenched CrMnFeCoNi high-entropy alloy

    Hisanori TanimotoRyo HozumiMari Kawamura
    6页
    查看更多>>摘要:High-entropy alloys (HEAs) are equimolar solid solution alloys composed of more than five elements, and their atomic arrangement is chemically disordered. Some ordering in HEAs, however, is suspected from the characteristic properties, such as high strength with good ductility at low temperatures or sluggish diffusion. Herein, we report that quasi-stable states inherent in nonequilibrium systems can be extracted by applying an electric pulse current to the system (electropulsing). In this study, changes in the electrical resistivity of the rapid-quenched CrMnFeCoNi HEA were investigated after electropulsing. No step-like large decreases reflecting nanocrystallization in amorphous alloys were observed for rapid-quenched CrMnFeCoNi by electropulsing. This indicates that quasi-stable ordered atom clusters do not exist in the CrMnFeCoNi HEA. However, the resistivity showed a slight decrease and increased with increasing electropulsing current density. A tendency to form short-range order, as Cr is preferentially surrounded by Ni, is suggested by comparison with the results of NiCr alloys.

    (162836)Magnetic, structural and magnetocaloric effect investigations on the substituted spinel Mg_(1-x)Zn_xFe_2O_4 (0 ≤ x ≤1) prepared by sol-gel method

    M. BouhbouA. DzubinskaM. Reiffers
    10页
    查看更多>>摘要:Polycrystalline Mg_(1-x)Zn_xFe_2O_4 (0 ≤ x ≤1) ferrites were prepared with sol-gel method. The obtained samples were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mossbauer spectrometry. The X-ray diffraction analysis combined with the Rietveld refinement confirmed that the samples crystallize in a single-phase cubic spinel structure with (SG: Fd3m) and an average grain size in the range of 29.1-40 nm. Lattice parameter increases with increasing Zn concentration, due to the larger ionic radius of Zn~(2+) ions in regard of Mg~(2+) ions. The Curie temperature T_c decreases linearly with substitution. Saturation magnetization (M_s), magnetic moment of iron (u_Fe)) and magnetic entropy change (-ΔS_M) increase for x≤ 0.5 and decrease for x≥ 0.5, this behavior is attributed to the cationic distribution of the ions on tet-rahedral [A] and octahedral [B] sites, where the structure turns from partially inverse spinel to normal spinel, affecting the remanent magnetization and the coercitive field. Moreover, a new empirical relation is acquired performing linear relation between magnetic moment and the inversion parameter 6. Mossbauer spectra show a transformation from sextuple to an only a doublet which indicates a transformation from ferrimag-netic to paramagnetic phase, this ferrimagnetism degradation is confirmed by the negative values of-ΔS_M and the transition of the magnetocaloric effect from normal to inverse through substitution.

    (162994)Spectroscopic and magneto-optical characteristics of erbium doped cerium trifluoride crystal grown by the Bridgman method

    Geng ZhaoMin XuYilun Yang
    6页
    查看更多>>摘要:In this study, a 2 at% erbium doped cerium trifluoride (Er:CeF_3) single crystal was grown using the Bridgman method. The consequent absorption, infrared transmittance, and fluorescence spectra were recorded. The spectroscopic properties of Er:CeF_3 crystals were intensively studied based on the Judd-Ofelt (J-O) theory. The Ω_2, Ω_4, and Ω_6 parameters were fitted to be 5.206 × 10~(-20), 1.805 × 10~(-20), and 3.06 × 10~(-20) cm~2, respectively. The emission cross-section centered at 1564.6 nm was calculated to be 1.053 × 10~(-20) cm~2, and the corresponding fluorescence lifetime was measured to be 1.675 ms. Additionally, the magneto-optical (MO) performance of the Er:CeF_3 crystal was investigated for the first time. The Verdet constants of Er:CeF_3 at 532, 632.8, 1064, and 1310 nm are 231.0,165.4, 43.4, and 24.4 rad-T~(-1)-m~(-1), respectively, which are significantly higher than those of pure CeF_3 and traditional Tb_3Ga_5O_(12). The results show that the Er:CeF_3 crystal can be applied both to solid-state lasers and Faraday devices.

    (163069)Dual-layer carbon protected coaxial cable-like Si-based composites as high-performance anodes for lithium-ion batteries

    Shuling LiuQiuting WangRui Wang
    10页
    查看更多>>摘要:The Si-based composites (NC@Si@CNTs) are synthesized successfully by a facile route. Using tetra-ethylorthosilicate as Si-source, carbon nanotubes (CNTs) and polydopamine as C-source, a dual-layer carbon protected coaxial cable-like structure is achieved. As an anode for Li-ion battery, the dual-layer carbon protection to Si layer gives a initial specific discharge and reversible specific discharge capacity of 2804 and 1752 mAh g~(-1) at 200 mA g~(-1) after 150 cycles. Even at 2 A g~(-1) the NC@Si@CNTs electrode can still display an initial and reversible specific capacities of 2297 mAh g~(-1) and 910 mAh g~(-1). The dual-layer carbon protected coaxial cable-like structure also improves the rate performance and cycling stability greatly compared to Si. This might be ascribed mainly to high conductivity and buffer effect of two carbon layers during cycling, which provide more effective transmission paths for electrons and promote fast diffusion for Li ions. In addition, the N-doping of carbon layer for extra Li ions and more stable structure of the as-prepared coaxial cable also contribute to the enhanced specific capacity and cycle stability during the charging/discharging process.

    (163121)Effects of amine (APTES) and thiol (MPTMS) silanes-functionalized ZnO NPs on the structural, morphological and, selective sonophotocatalysis of mixed pollutants: Box-Behnken design (BBD)

    Reza MahdaviS. Siamak Ashraf Talesh
    15页
    查看更多>>摘要:The lack of selectivity of Zinc oxide nanoparticles (ZnO NPs) in the wastewater purification process is considered a severe limitation. This research aims to use surface-modified ZnO NPs with different surface charges for selective removal of methyl orange (MO) and methylene blue (MB) dyes from an aqueous mixture solution. The sonophotocatalyst process was investigated to improve the selective oxidation of the aqueous mixture. The surface of the ZnO NPs has been modified with a silane coupling agent (APTES and MPTMS) to get active surface functional groups. The synthesized modified ZnO NPs were characterized by XRD, FE-SEM, TEM and FTIR analysis. The surface charge and absorption spectrum were investigated using Zeta potential and UV-Vis spectrophotometer approaches, respectively. The selective sonophotocatalytic of anionic MO and cationic MB dyes was performed via APTES-ZnO and MPTMS-ZnO NPs, respectively. The selective removal was optimized using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD). To this end, the effects of catalyst dosage, dye concentration, and reaction time on selective removal were investigated under various experimental conditions. The results revealed that unmodified ZnO NPs have no selectivity in the decomposition of an MO and MB mixed, whiles the change in surface charges of ZnO NPs has been shown to change significantly the selectivity efficiency of ZnO NPs.

    (163019)Hollow nanostructure boosts the surface capacitive charge storage of NiCo-LDH derived from metal-organic framework for high performance asymmetric supercapacitor

    Huifang ZhangBing YanHeming Zhao
    8页
    查看更多>>摘要:Layered double hydroxide (LDH) has great potential as advanced electrode material for supercapacitor. In this paper, by tuning the reaction temperature, two Ni Co-LDH nanostructures (hollow nanocage and sea urchin) were synthesized through the hydrolysis etching process of ZIF-67 crystals and Ni~(2+) ions. It has been found that the morphology of the electrode material has a great influence on the electrochemical performance and analysis the reason of this behavior is essential for understanding the morphology-related electrochemical performance. Here, a much more capacitive charge storage behavior of hollow Ni Co-LDH than that of sea urchin-shaped product is demonstrated by electrochemical kinetic analysis. The higher capacitive behavior of hollow Ni Co-LDH suggests a rapid surface redox reaction during the electrochemical process, which will lead to excellent electrochemical properties. An asymmetric supercapacitor assembled using hollow NiCo-LDH as the positive electrode displays a high energy density of 88.6 Wh kg~(-1) at 749.9 W kg~(-1), further demonstrating its great application potential. These results provide insights into the reasons for the excellent electrochemical performance of hollow nanostructure.