A study on hydrogen-induced amorphization in the LaNi system
A study on hydrogen-induced amorphization in the LaNi system
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DOI：
10.1016/0022-3093(89)90259-7
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发表时间：
1989-08
影响因子：
3.5
通讯作者：
U. Chung;Jai-Young Lee
中科院分区：
文献类型：
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作者：
U. Chung;Jai-Young Lee
为了探讨氢致非晶化的机理，用X射线衍射研究了La 2Ni 7，LaNi 2，LaNi1.5和LaNi化合物吸氢引起的结构变化。用DSC和氢脱附技术研究了氢化样品的热稳定性。对于La_2Ni_7化合物，氢的吸收导致晶格畸变严重。然而，随着氢吸收-解吸循环的重复，发生非晶化。LaNi_2和LaNi_（1.5）化合物在室温下氢化时完全没有衍射线，即发生了氢致非晶化。氢致非晶合金的DSC曲线显示出一个小的放热峰，与LaH 2和LaNi 5的析出有关。LaNi化合物在室温下氢化后，可以转变为不同于原始LaNi化合物的另一种晶体结构。结果表明，化合物的非晶化取决于化合物的稳定性和分解成LaH_2和LaNi_5的速率。非晶化的机制与金属原子的运动引起的晶格畸变有关，使得处于非晶态的氢原子的周围类似于LaH 2中的氢原子的周围。
In order to investigate the mechanism of hydrogen-induced amorphization, the structure changes by hydrogen absorption in La2Ni7, LaNi2, LaNi1.5and LaNi compounds are investigated by X-ray diffraction. Also thermal stabilities of the hydrogenated samples are examined by DSC and hydrogen desorption technique. In case of La2Ni7compound, the severe lattice distortion is found as hydrogen is absorbed. However, as the hydrogen absorption-desorption cycle is repeated, the amorphization takes place. LaNi2and LaNi1.5compounds show the complete absence of diffraction lines when hydrogenated at room temperature, i.e. the hydrogen-induced amorphization has occurred. The DSC curve of the hydrogen-induced amorphous alloy shows a small exothermic peak related to the precipitation of LaH2and LaNi5. LaNi compound may transform into another crystalline structure by hydrogenation at room temperature, which is different from that of original LaNi compound. It is suggested that the amorphization of a compound is dependent upon the stability of the compound and the decomposition rate to LaH2and LaNi5. The mechanism of the amorphization is related to the lattice distortion caused by the motion of the metal atoms so that the surroundings of the hydrogen atoms in the amorphous state resemble those of hydrogen atoms in LaH2.