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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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    Size-dependent magnetocaloric effect in GdVO4 nanoparticles

    Ruan, M. Y.Yang, C. Q.Wang, L.Jin, P. B....
    8页
    查看更多>>摘要：We investigated the magnetization and electron spin resonance (ESR) in nanocrystals of antiferromagnet GdVO4 with the grain size ranging from 30 nm to 5 mu m. Our nanoparticles with an average size reduction from 5 pm to 300 nm exhibited enhanced paramagnetic-like behavior, in which the weakly coupled spins can be well aligned along the direction of an external magnetic field, resulting in a giant entropy change of -Delta S-M = 45 J/kg K at 3 K for Delta H = 7 T. Moreover, with a further reduction of grain size to similar to 30 nm, the saturation magnetization together with the negative entropy change -Delta S-M,S- max decreased dramatically. The aggregation effect is believed to be responsible for the decline in -Delta S-M,S- max in which small nanoparticles agglomerating to 'large' grains made them behave like bulk material. Finding the critical point of positive size effect on magnetocaloric effect offered a new way to achieve large magnetic entropy change. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Synthesis and study of transport and magnetic properties of magnesium cage compounds RNi2Mg20(R = Pr and Nd)

    Kusanose, YukaOnimaru, TakahiroYamane, YuUmeo, Kazunori...
    7页
    查看更多>>摘要：We have synthesized magnesium cage compounds RNi2Mg20 (R = Pr and Nd). We report the measurements of electrical resistivity rho, magnetic susceptibility chi, isothermal magnetization M, and specific heat C. Polycrystalline samples with R = Pr and Nd were obtained by annealing, while the counterparts for R = La, Ce, and Y were found to be absent. The rho(T) data for R = Pr and Nd monotonically decrease on cooling from 300 K to 40 K and exhibit shoulders at around 13 K and 15 K, respectively. The Curie-Weiss behaviors of the chi(T) data indicate the trivalent states of both the Pr and Nd ions. For R = Pr, the maximum in C(T) at around 7 K is reproduced by a doublet-triplet two-level model with an energy gap of 14 K. The peak in C(T) at 0.7 K is attributed to a short-range order of quadrupolar degrees of freedom in the non-Kramers ground doublet. On the other hand, for R = Nd, a maximum in C(T) at around 9 K is explained by thermal excitation from a ground state doublet to an excited quartet separated by 23 K. Upon further cooling, C(T) shows a lambdashaped peak at 1.5 K. By applying magnetic fields up to 2 T, the peak becomes broad and shifts to higher temperatures, which is a characteristic of a ferromagnetic order. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Fabrication and compressive properties of directional porous titanium scaffold by freeze casting TiH2 powders

    Loboda, PetroShu, ChangqingZhang, ShashaDu, Wenbo...
    10页
    查看更多>>摘要：Porous titanium scaffold has been prepared by freeze casting of TiH2 aqueous slurry for the application of structural core of sandwiches, filters, heat exchangers and bones due to the directional lamellar structure. The effects of freezing temperature and solid content, which are decisive parameter in freezing casting process, on porous structure are revealed. As freezing temperature drops and solid content increases, the porosity ranges from 15% to 73%, wall thickness increases from 8 mu m to more than 15 mu m. Different structures provide different mechanical properties. With the decrease of porosity, the yield strength in the direction parallel to the freezing direction rose from 60 MPa to 286 MPa while Young's modulus is from 0.8 GPa to 11.2 GPa. The fracture mode changes from surface fragmentation to body fragmentation along with partial splitting. The modified Gibson -Ashby formula was used to describe the relationship between the mechanical properties and the relative density. The constant and exponents of mechanical properties with porosity are much higher than the conventional process, which indicated excellent mechanical properties compared with other processes. (c) 2021 Published by Elsevier B.V.
      原文链接:
    • NSTL
    • Elsevier

    SiC reinforced AlSi10Mg composites fabricated by selective laser melting

    Zhang, DongyunYi, DenghaoWu, XupingLiu, Zhiyuan...
    11页
    查看更多>>摘要：In this study, a 10 wt% SiC-reinforced AlSi10Mg-based composites is prepared by selective laser melting (SLM) process. The effect of laser linear energy density on phase morphology, microstructure, and mechanical properties of AlSi10Mg-10SiC composite is investigated. There is relatively higher density, no obvious pores and cracks in the SLM-fabricated AlSi10Mg-10SiC composites with laser linear energy densities ranging from 90.64 J/mm(3) to 104.16 J/mm(3). The high laser linear energy density promotes the in-situ reaction between SiC particle and Al melt in the melt pool, the Al4SiC4 phase forms during SLM fabrication process. Driven by Marangoni convection, the fine SiC particles and Al4SiC4 phase distributes uniformly. When the laser linear energy density is 104.16 J/mm(3), the composite exhibits the highest average micro hardness of 208.5 HV0.1. When the laser linear energy density is 90.64 J/mm(3), the composite displays the highest yield strength and modulus with values of 408 MPa and 90 Gpa, respectively. During the deformation process of tensile test, the higher modulus SiC particles could withstand greater load transfer, which improves the modulus and yield strength of the composites. (C) 2021 Published by Elsevier B.V.
      原文链接:
    • NSTL
    • Elsevier

    Hot oscillating pressed FGH4096 nickel-based alloy with enhanced ductility and strength

    Sun, DejianZhao, KeLi, GuizhongKang, Jiachen...
    5页
    查看更多>>摘要：FGH4096 Nickel-based superalloy was prepared by hot oscillating pressing (HOP) and hot pressing (HP). Compared with HPed sample, the sample prepared by HOP exhibits lightly higher yield strength and ultimate tensile strength, but greatly improved elongation. The elongation of the HOPed sample is as high as 36.9%, which is not only much higher than that of the HPed sample, but also higher than that of the sample prepared by hot isostatic pressing (HIP). The improvement in the elongation of the HOPed sample is likely due to the application of the oscillatory pressure, which enhanced inter-particle boundary sliding and/or plastic deformation during densification process. (c) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Effects of different holding pressures on the microstructure and mechanical properties of Al-5.9Zn-2.2Mg-1.8Cu alloy

    Yan, XuanjieTan, PanSui, YudongJiang, Yehua...
    6页
    查看更多>>摘要：In this study, a low-pressure casting process was used to examine the influence of the holding pressure on the Al-5.9Zn-2.2Mg-1.8Cu alloy. The study aimed to refine the grain structure and optimize the micro structural homogeneity and mechanical properties of the alloy. The phase composition, microstructure, chemical composition, and fracture morphology of the alloy were determined using optical microscopy, SEM, inductively coupled plasma spectroscopy, and XRD. As the holding pressure increased, the theoretical crystallisation temperature of the alloy increased, which increased the degree of undercooling during solidification and the effective number of nuclei, resulting in grain refinement. In addition, increase in the holding pressure strengthened the feeding ability of the alloy melt and reduced the occurrence of shrinkage porosity defects. When the optimal pressure was exceeded, the nucleation rate as well as the denseness of the alloy decreases. When the holding pressure was 0.035 MPa, the grain refining effect was the best and the microstructure was the most uniform. The yield strength, tensile strength, and elongation of the alloy reached the maximum values of 264.6 MPa, 290.8 MPa, and 7.7%, respectively. When the holding pressure was >0.035 MPa, the structure was not further refined; in contrast, the grains were larger, and the mechanical properties were inferior. (c) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Research implementing different dopants (M = Al, Sn, and Eu) on the properties of Schottky diodes with structure TCO/CdS/C and TCO/CdS:M/C

    Chavez-Urbiola, E. A.Ramirez-Bon, R.Vorobiev, P.Vorobiev, Yu V....
    10页
    查看更多>>摘要：A metal-semiconductor interface is an integral part of numerous electronic devices such as Schottky barrier diodes, photodetectors, photovoltaic detectors, photoelectric converters for UV radiation, among others. On the other hand, semiconductor thin films of cadmium sulfide have been applied to several electronic devices. This study presents the synthesis of semiconductor thin films of pure cadmium sulfide and those doped with Al, Sn, and Eu by a chemical bath deposition technique. XRD, SEM, EDS, XPS, UV-Vis spectroscopy, I-V, and photocurrent measurement analyzed these semiconductor thin films. Afterwards, the doped and undoped CdS thin films were applied to the manufacture of Schottky diodes. The doped CdS thin films reveals differences in the size of the crystallites, which decreased by 5.7%, 11.5%, and 60.1% after doping with aluminum, tin, and europium, respectively. The CdS thin films show morphological differences, decreasing grain size by 5.3% in the case of tin doping and increasing by 21.9% with aluminum and 32.6% after being doped with europium. Additionally, the energy bandgap of the doped CdS thin films show a blue shift, except when doped with Eu, which shows a red shift. This enables the design of window layers by choosing the suitable dopant of CdS. The effect of the CdS doping on the electrical photoresponse of the Schottky diodes was also analyzed. Due to the incorporation of dopants, the photoresponse of the aluminum-doped CdS Schottky diodes improved by 176% compared to its undoped counterpart and by up to 493% with other reports in the literature. The Schottky diodes manufactured in this work show variation in height of the potential barrier, increasing by 6% in the case of aluminum doping and decreasing by 5% and 25% after being doped with europium and tin respectively. These results demonstrated the beneficial impact of dopants on the characteristics of the CdS-based Schottky diodes and elaborated photodiodes, exhibiting an impressive enhancement in their photoresponse, in the potential barrier reached for photosensitivity and in the energy band gap value. Overall, our extensive study reveals that there is great potential in the design of affordable multifunctional optoelectronic devices. (c) 2021 Published by Elsevier B.V.
      原文链接:
    • NSTL
    • Elsevier

    Surface modification for AlCoCrFeNi2.1 eutectic high-entropy alloy via laser remelting technology and subsequent aging heat treatment

    Miao, JunweiYao, HongweiWang, JunLu, Yiping...
    10页
    查看更多>>摘要：Eutectic high-entropy alloys (EHEAs) are a class of prospective structural material in advanced engineering applications due to their excellent mechanical properties and castability. However, few researchers focused on the surface modification of these EHEAs. This study aimed to propose an effective method combining laser remelting and heat treatment to modify the surface of classical AlCoCrFeNi2.1 EHEA. After surface modification, the surface microhardness of the EHEA increased by 59%, and the average friction coefficient and wear rate decreased by 26% and 68%, respectively. The improved performance was mainly attributed to the decrease in lamellar spacing between face-centered cubic (FCC)/body-centered cubic (BCC) (B2) and coherent precipitation of nanoparticles in both FCC and B2 phases. A semi-empirical model was built to estimate the contribution of lamellar spacing to microhardness. The method and model might be applied to modify the surface properties of other EHEAs with lamellar structures. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Neutron vibrational spectroscopic evidence for short H center dot center dot center dot H contacts in the RNiInH1.4; (1.6) (R = Ce, La) metal hydride

    Klein, Ryan A.Balderas-Xicohtencatl, RafaelMaehlen, Jan PetterUdovic, Terrence J....
    8页
    查看更多>>摘要：Intermetallic metal hydrides are critical materials for hydrogen storage applications, however, metal hydrides with greater storage capacities are still needed. Within metal hydrides, the volumetric storage capacities are limited by the number of hydrogen-accommodating interstitial sites which can be simultaneously occupied given a minimum hydride nearest-neighbor distance of approximate to 2.1 angstrom, according to the Switendick-Westlake criterion. To date, violations of this criterion are rare. Perhaps the most well studied compounds violating this criterion are the RNiInHx compounds (R = Ce, La, Nd). Previous neutron diffraction studies on the deuterated species revealed the presence of Ni-D center dot center dot center dot D-Ni-D center dot center dot center dot D-Ni chains with anomalously close D center dot center dot center dot D contacts of approximate to 1.6 angstrom. Yet there are no neutron vibrational spectroscopic investigations reported for these atypical hydrides. Here we use neutron vibrational spectroscopy (NVS) measurements to probe the hydrogen dynamics in LaNiInHx (x = 0.67, 1.6) and CeNiInH1.4. For x > 0.67, the presence of close H center dot center dot center dot H contacts yields two related features in the vibrational spectrum centered near approximate to 90 meV corresponding to the oscillations of paired H atoms simultaneously occupying neighboring R3Ni tetrahedra. Notably, these features are energetically distinct from comparable vibrational motions for "unpaired" H atoms when x <= 0.67. To compare, we also present powder neutron diffraction and NVS measurements for the newly characterized, chemically similar Sn compounds CeNiSnH, CeNiSnH2, and CeNiSnD2. These compounds also contain R3Ni tetrahedra, however, the H-occupied tetrahedra are well separated from each other with the closest H center dot center dot center dot H distances exceeding 2.1 angstrom, and the Switendick-Westlake criterion is not violated. Consequently, the spectral signature of the close H center dot center dot center dot H contacts is absent in these hydrides. Published by Elsevier B.V.
      原文链接:
    • NSTL
    • Elsevier

    Microstructure evolution and mechanical properties of Cu-3Ag-xZr alloys processed by equal channel angular pressing

    Yue, ShipengQu, JianpingLi, GuoliangLiu, Shichao...
    12页
    查看更多>>摘要：In the present study, microstructure evolution and mechanical properties of the Cu-3Ag-xZr alloys processed by equal channel angular pressing (ECAP) at room temperature were investigated. The results indicated that significant grain refinement can be achieved, and the average grain sizes are remarkably refined to 0.41 +/- 0.1 mu m and 0.39 +/- 0.05 mu m after 8 P for Zr-free and Zr-containing alloys, respectively. The continuous dynamic recrystallization (CDRX) should be responsible for such refinement mechanism. For Zr-containing alloy, the original coarse island-like Cu4AgZr particles are crushed into nearly spherical particles with the average size less than 5 mu m during the subsequent deformation process. In addition, the Cu-3Ag-xZr alloys processed by ECAP after 8 P present the excellent comprehensive properties with yield strength of 587 MPa and 627 MPa, as well as the electrical conductivity of 84.5%ICAS and 70.7%ICAS for the Zr-free and Zr-containing alloys, respectively. Accordingly, a quantitative calculation based on the established strengthening mechanism was conducted, indicating that the significant strengthening effect originates from the formation of subgrain structure. It is anticipated that this research would provide a feasible way for the preparation of high-performance Cu-3Ag-xZr alloys. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier