MmNi 3.6 CoxMnYAl1.4-x-y alloy of melt-spinning and gas-atomization were investigated in the hydrogen absorption characteristics

• Main Authors: chang-yai-huain, 姜雅惠
• Other Authors: chang-wen-chai
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/93679019910307104196

碩士 === 國立中正大學 === 物理系 === 88 === Abstract After petroleum came to a crisis , it is imperative to open up and develop the new energy resources . Additionally , the portable electric products have a large number of requirement in the secondary battery in recent years . The developing of secondary battery already become the tide of science and technology . In the study , AB5-based rare earth alloys using as the negative electrode materials of the secondary batteries have received considerable attention as high capacity . Owing to La is expensive , Mischmetal was normally adopted to replace La in AB5 compound . MmNi5-x-y-zCoxMnyAlz alloys , which were prepared by both melt-spinning and gas atomization , were chosen as our starting materials . The hydrogen absorption characteristics influenced by different additives , quenching speed and method were investigated in details . Experiment results are as follows : （1）Before measuring the hydrogen absorption characteristics , it is needed to activate the sample . When activation temperature is increased , the activation rate can be raised and reduce the activation times , pulverization phenomenon is slightly suppressed . If activation is incomplete , it may decrease hydrogen absorption apparently . Besides , activation times have more influence than the times of hydrogen absorption on the pulverization phenomenon . （2）The partial substitution of Ni with Co , Mn or Al decreases the equilibrium pressure from 48 atm to 0.5~1 atm . The partial substitution of Ni with Mn or Al can improve the stability of equilibrium pressure and hydrogen absorption than additive Co . But additive Co has better contribution to reduce the pulverization phenomenon . （3）Because quenching rate of cast alloy is insufficient , composition segregation makes hydrogen absorption incompolete . To improve segregation phenomenon , melt-spinning method is preferred which can improve hydrogen absorption and activation rate . （4）Higher quenching rate in melt-spinning may induce a finer grain size of the ribbons , which results in a higher activation rate and hydrogen absorption . However , pulverization becomes easily . （5）Gas atomization powders segregate slightly more than that of cast alloys , which led to a small hydrogen absorption and making pulverization easier . The gas atomization powers is needed to homogenize to improve the hydrogen absorption characteristics . （6）The alloy ribbons combination of MmNi3.6Co0.7Mn0.42Al0.28 quenched at Vs =15 m/s shows the optimum hydrogen absorption and equilibrium pressure and a slight pulverization phenomenon .