A study on hydrogen-induced amorphization in C15 Laves phase DyNi2 under different hydrogen pressures
A study on hydrogen-induced amorphization in C15 Laves phase DyNi2 under different hydrogen pressures
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DOI：
10.1016/j.jallcom.2005.02.045
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发表时间：
2005-08-16
影响因子：
6.2
通讯作者：
Aoki, K
中科院分区：
文献类型：
--
作者：
Li, HW;Ishikawa, K;Aoki, K
四个放热反应：（1）氢吸收形成晶态（c-）和非晶态（a-）DyNi_2 H_x;（2）c-DyNi_2 H_x向a-DyNi_2 H_x的转变，即，当使用压力差示扫描量热计（PDSC）在2.0MPa H-2或更高的氢气压力下加热C15 Laves相DyNi 2时，依次观察到氢诱导的非晶化（HIA）、（3）DyNi 5在a-DyNi 2 Hx中的沉淀、以及（4）剩余的非晶氢化物分解成DyNi 5和BiF 3型DyH 3。另一方面，在低于2.0 MPa H-2下观察到（1）c-和a-DyNi 2 Hx的形成，（2）部分HIA和（3）a-和c-DyNi 2 Hx的混合物分解成DyNi 5和DyH 3（或DyH 2）。同时形成的c-和a-DyNi 2 Hx在第一个放热峰解释了由低活化能氢吸附形成c-DyNi 2 Hx的局部温度增量。另一方面，考虑到DyNi 2的大生成焓，可以解释分解过程中DyNi 5的形成。此外，根据T-p和T-p/T-m（DyNi 2的峰值温度/熔点）与压力的关系、激活能E-A和焓变Δ H等实验结果，对DyNi 2在氢气气氛中加热时的相变机理进行了讨论。(c)2005 Elsevier B. V.保留所有权利。
Four exothermic reactions of (1) hydrogen absorption forming crystalline (c-) and amorphous (a-) DyNi2Hx (2) the transformation of c-DyNi2Hx to a-DyNi2Hx, i.e., hydrogen-induced amorphization (HIA), (3) the precipitation of DyNi5 in a-DyNi2Hx, and (4) the decomposition of the remaining amorphous hydride into DyNi5 and BiF3-type DyH3 were observed sequentially when the C15 Laves phase DyNi2 was heated using a pressure differential scanning calorimeter (PDSC) at 2.0 MPa H-2 or higher hydrogen pressures. On the other hand, (1) the formation of c- and a-DyNi2Hx, (2) partial HIA and (3) the decomposition of the mixture of a- and c-DyNi2Hx, into DyNi5 and DyH3 (or DyH2) were observed below 2.0 MPa H-2. Simultaneous formations of c- and a-DyNi2Hx at the first exothermic peak were explained by the local temperature increment resulting from the low activation energy for hydrogen absorption forming c-DyNi2Hx. On the other hand, the formation of DyNi5 during the decomposition was explainable in consideration of the large formation enthalpy of DyNi2. Furthermore, the mechanism of the phase transformations of DyNi2 heated in a hydrogen atmosphere was discussed on the basis of the experimental results such as the pressure dependence of T-p and T-p/T-m (the peak temperature/the melting point of DyNi2), the activation energy E-A, and the enthalpy change Delta H. (c) 2005 Elsevier B.V. All rights reserved.