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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Sn-containing (La,Mm)Ni_(5-x)Sn_xH_(5-6) intermetallic hydrides: thermodynamic, structural and kinetic properties
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Sn-containing (La,Mm)Ni_(5-x)Sn_xH_(5-6) intermetallic hydrides: thermodynamic, structural and kinetic properties

机译:含锡(La,Mm)Ni_(5-x)Sn_xH_(5-6)金属间氢化物:热力学,结构和动力学性质

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摘要

This work focused on studies of the phase composition and crystal structure of La_xMm_(1-x)Ni_(4.7)Sn_(0.3) (x=0, 0.5 and 1.0) alloys, where Mm denotes La-rich mischmetal produced by Norsk Hydro ASA. The alloys have been studied using conventional powder and synchrotron X-ray diffraction (XRD), powder neutron diffraction and scanning electron microscopy (SEM). After annealing at 950 deg C the alloys were nearly single-phase materials with small precipitations of RENiSn equiatomic intermetallics formed at grain boundaries. Hydrogen absorption-desorption studies at 298, 323 and 348 K showed (a) a 'flat' structure of the pressure-composition isotherms; (b) a rather broad range of working H storage capacities; (c) an increase of the plateau pressures and decrease in both enthalpy and entropy changes following an increase of the Mm content in the alloy; and (d) fast formation-decomposition rate. Desorption isotherms were approximated by a recently developed model of phase equilibria in the metal-hydrogen systems. In situ powder neutron diffraction studies of the system MmNi_(4.7)Sn_(0.3)-D_2 show that in the region of a-solid solution deuterium insertion leads to a gradual increase of the unit cell volume reaching 1.9 percent. In the hexagonal beta-MmNi_(4.7)Sn_(0.3)D_(4.51) deuteride D atoms occupy two of four available types of tetrahedral interstices including 6m RE_2(Ni,Sn)_2 and 12n RE(Ni,Sn)_3.
机译:这项工作专注于研究La_xMm_(1-x)Ni_(4.7)Sn_(0.3)(x = 0、0.5和1.0)合金的相组成和晶体结构,其中Mm表示由Norsk Hydro ASA生产的富含La的混合金属。已经使用常规粉末和同步加速器X射线衍射(XRD),粉末中子衍射和扫描电子显微镜(SEM)对合金进行了研究。在950摄氏度下退火后,合金几乎是单相材料,在晶界处形成了少量的RENiSn等原子金属间化合物沉淀。在298、323和348 K上的氢吸收-解吸研究表明:(a)压力组成等温线的“平坦”结构; (b)相当大的工作H储存能力范围; (c)随着合金中Mm含量的增加,平台压力增加,焓变和熵变降低; (d)快速的分解速度。解吸等温线可以通过最近开发的金属-氢系统中的相平衡模型来近似。 MmNi_(4.7)Sn_(0.3)-D_2系统的原位粉末中子衍射研究表明,在a固溶体区域中,氘的插入导致单位晶胞体积逐渐增加,达到1.9%。在六边形β-MmNi_(4.7)Sn_(0.3)D_(4.51)中,氘核D原子占据了四种可用的四面体间隙中的两种,其中包括6m RE_2(Ni,Sn)_2和12n RE(Ni,Sn)_3。

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