La_(1.8)Ca_(0.2)Mg_(14)Ni_3+x% Ti合金的微结构和储氢性能

Microstructure and Hydrogen Storage Properties of La_(1.8)Ca_(0.2)Mg_(14)Ni_3+x% Ti Composites

研究了机械球磨La1.8Ca0.2Mg14Ni3＋x％Ti（质量分数，下同）（x=0，5，10）合金的微结构和储氢性能。气态吸放氢研究表明。加入钛粉球磨能有效提高合金的活化性能、储氢容量和吸放氢速率。铸态合金经过6次活化后，在613K时放氢量为4．12％（质量分数，下同）。加Ti球磨改性10h后，随着X增加，合金经过2次～3次循环基本完全活化。吸放氢性能也相应提高。Ti含量在x=0，5，10时合金在613K的放氢量分别为4．69％，4．80％，4．83％：当x=10时合金在373K的吸氢量达到3％以上，在600K经过2min就能达到4．81%（为最大吸氢量的97％）。微结构分析表明。具有表面催化活性的Ti粉与合金基体表面进行复合，并使合金发生部分非晶转变，能有效改善La1.8Ca0.2Mg14Ni3合金的储氢性能。

The hydrogen storage properties of La1.8Ca0.2Mg14Ni3 were modified by mechanical ball-milling with addition of x wt%Ti （x=0,5,10）. X-ray diffraction （XRD）, scanning electron microscopy （SEM） and hydrogen absorption/desorption tests were carried out to study the effect of Ti. The results show that the hydrogen storage properties of La1.8Ca0.2Mg14Ni3 are remarkably improved after ball-milling with addition of small amount of Ti. For the as-cast alloy, 6 cycles of hydriding/dehydriding are needed to activate it at 613 K, and the maximum hydrogen storage capacity is around 4.12 %. After modification by ball-milling with addition of Ti, the activation behavior and the hydrogen storage capacity and the absorption/desorption kinetics are all improved. The effective desorption capacities of the alloys with x=0, 5 and 10 at 613 K are 4.69 %, 4.80% and 4.83%, respectively. As x=10, the alloys can absorb more than 3% hydrogen at 373 K, and 4.81% hydrogen （97% of the maximum hydrogen storage capacity） at 600 K within 2 min. The microstructure analysis indicated that the titanium powder on the alloy surface played the role of surface-catalysis, accelerated the hydrogen decomposition and formation, and provided more channels for hydrogen diffusion from surface, were partly transformed into amorphous structure. As a result, the hydrogen storage properties of La1.8Ca0.2Mg14Ni3 were improved.