LaNi_(4.7)Al_(0.3)储氢合金氧化前后吸放氢性能研究

Hydriding Performance of LaNi_(4.7)Al_(0.3) Alloy before and after Poisoning with Oxygen

研究了LaNi4 .7Al0 .3贮氢合金被微量氧气毒化前后贮氢性能的变化 ,测定了合金的贮氢量 ,吸氢动力学曲线。并采用扫描俄歇电子能谱(AES)原位研究了LaNi4 .7Al0 .3储氢合金中毒前后化学成分变化 ,结果表明 :氧含量较低时 ,不会影响合金的初始吸氢速率 ,但会降低合金的贮氢容量 ;随着O2 的剂量的逐渐增大 ,合金的吸氢速率变慢 ,合金的储氢容量大大降低。原位分析氧毒化LaNi4 .7Al0 .3贮氢合金表明 ,O2 在清洁LaNi4 .7Al0 .3表面吸附离解后 ,优先与表面镧原子结合生成La的氧化物 ,再与部分表面镍原子结合生成Ni的氧化物。氧化过程中La向表面富集 。

The change of hydrogen storage performance of LaNi_(4.7)Al_(0.3) alloy in the hydrogen containing small amount oxygen was studied with measuring hydrogen storage capacity and the kinetics of H_2 absorption. Chemical composition change for poisoned and unposioned hydrogen storage alloy was examined with in situ analysis by Auger electron spectroscopy (AES). Results indicate that oxygen does not effect the initial absorption rate at low level O_2 exposures, but reduces the total amount of hydrogen absorbed. With increasing O_2 exposure, the hydrogen absorption rate and ultimate hydrogen storage capacity of LaNi_(4.7)Al_(0.3) alloy reduce greatly. Analysis in situ shows that oxygen absorbed on the clean LaNi_(4.7)Al_(0.3) surface and dissociation, then associated with La and the oxide lanthanium forms at first, then the residual oxygen associates with Ni and oxide nickel and dissociated forms. During this process, La atoms concentrate onto the surface, and at the same time, metal Ni separate out.