La含量对Ce-La合金氢化动力学的影响

Effect of La Content on Hydriding Kinetics of Ce-La Alloys

采用压降法结合原位形貌观察研究了La含量(0~10%,质量分数)对Ce-La合金氢化动力学的影响,并利用XRD和Raman光谱仪对Ce-La合金表面氧化膜的结构进行了表征。结果表明,随La含量的增加,Ce-La合金的氢化反应进程不断加快,表现为孕育期时间变短,成核速率和反应速率增大。随着La含量增加,Ce-La合金表面氧化膜中的氧空位增多,Ce O2的晶格常数变大。La掺杂引起的表面氧空位缺陷增强了H原子在氧化膜中的迁移性能,使得具有更高La含量的Ce-La合金的氢化反应进程变快。

Various metals, such as uranium and plutonium, have the potential to form hydride phases while environment develop so that they are exposed to low standard of hydrogen in a long time storage environment. The generation of hydride phases has safety implications, for instance the potential to cause unintended thermal excursions and to adversely alter mechanical properties. So the reaction of alloys between hydrogen is of significant industrial interest. The hydrogenation kinetics characteristics of Ce-La alloys have the similarity with some actinide materials. Investigating the growth kinetics of Ce-La alloy hydride reaction sites is of fundamental importance to the development of predictive model of hydriding behavior. In this work, the effect of La content（0~10%, mass fraction） on hydriding kinetics of Ce-La alloys was studied by pressure consume curve, and the effects of La content on surface morphology and oxidation film structure of Ce-La alloy were observed by in situ OM, XRD and Raman spectra. The results show that doped La can shorten the induction period and accelerate the nucleation rate, so as to accelerate the hydriding rate. Furthermore, doped La can cause the lattice expansion and promote the formation of oxygen vacancy in the oxidation film. The apparent activation energies of pure Ce and Ce-10 La alloy are 51.12 and 41.53 k J/mol, respectively, suggesting that the diffusion barrier of hydrogen in the oxidation film of Ce-10 La alloys is lower. The oxygen vacancy and the lattice expansion caused by doped La may promote the diffusion ability of hydrogen in the oxide film. Hydrogen diffusion through the oxide film decides the hydriding rate. So doped La accelerate the hydrogenation.