Studies on the CO poison and cyclic hydrogenation of the ZK60 alloy

• Main Authors: Jhe-yi Lin, 林哲逸
• Other Authors: Kun-ming Lin
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/11205346784817166724

碩士 === 逢甲大學 === 材料科學所 === 100 === In this study, the ZK60 (Mg-5.7Zn-0.57Zr) alloy was severely deformed by equal channel angular pressing (ECAP) with route BA and 12 passes. Then, we used drilling machine to get small scraps, and added various contents of alloying elements to the scraps in ball milling for 20hr to prepare the alloy powders. The powders were used to analyze various hydrogen storage properties. Experimental results show that the hydrogen storage capacity of the ZK60 alloy is only 4.13wt% after 60 mins hydrogen absorption, and its hydrogen absorption rate is very slow. In order to improve the hydrogen storage properties, we added various amounts of activated carbon to the ZK60 alloy during ball milling. It is found that the hydrogen storage capacity and its absorption rate are obviously enhanced with the carbon addition. The alloy with addition of 5wt% activated carbon had the highest hydrogen storage capacity that reaches 6.16wt%. Therefore, we fixed activated carbon content at 5wt%, and added various amounts of vanadium and/or palladium during ball milling for the study of hydrogen storage properties. The results show that the alloys with 5C0.5V, 5C0.5Pd, and 5C0.5V0.75Pd additives, respectively, exhibited better hydrogenation kinetics. The maximum hydrogen storage capacity of the alloys with 5C0.5V additives reaches 7.01wt%. It is found that the addition of palladium during ball milling can effectively enhance hydrogen absorption rate. The hydrogen storage capacity can reach 61%~71% in the first minute as compared with that for 60 minutes hydrogen absorption, and it can reach 90% in the first 3 mins hydrogen absorption. Bseides, the addition of palladium has also a positive effect on cyclic hydrogenation. For the study of the cyclic hydrogenation and poison effect, the alloys with 5C0.5V and 5C0.5V0.75Pd additives were used for the cyclic test. The results show that the decrease percentage of the hydrogen storage capacity of the alloy with 5C0.5V additives is 54.59% after 300 cyclic test. However, the counterpart of the alloy with 5C0.5V0.75Pd additives is only 14.40% under the same condition. It means that the addition of palladium can effectively improve the properties on cyclic hydrogenation. For the hydrogen absorption capacity, the alloy with 5C0.5V0.75Pd is poisoned more seriously than that with 5C0.5V in the CO poison cyclic test. For the hydrogen absorption rate under poison condition, the catalytic effect of the palladium is good when CO concentration is less than 100ppm, but becomes worse when CO concentration is over 200ppm.