摘要
用电位阶跃法和恒流充放电法研究了贮氢合金凝固组织中氢的扩散行为和合金氢化物电极放电的速度特性。研究表明，合金ＭｌＮｉ３．４５（ＣｏＭｎＴｉ）１．５５各凝固组织中氢的扩散系数Ｄｈ和其氢化物的电极性能均明显不同。随合金凝固时冷却速度增大，晶胞体积和氢扩散系数减小。雾化快凝合金粉末随颗粒尺寸由２００目变化至３６０目（冷却速度增大）时，其Ｄｈ由３．０６×１０－７（ｃｍ２·ｓ－１）减小至７．４７×１０－９（ｃｍ２·ｓ－１）；定向凝固组织随凝固速率Ｒ＝４８μｍ／ｓ增大时，Ｒ＝２２０μｍ／ｓ时，其Ｄｈ则由７．０３×１０－９（ｃｍ２·ｓ－１）增大至１．３１×１０－８（ｃｍ２·ｓ－１）。合金电极的高倍率放电效率主要取决于氢在合金中的扩散速度和电极表面的电催化活性。
Diffusion behaviour of H atom in solidified microstructure of the metal hydride electrodes are investigated by using electrochemical potential step method and galvanostatic charge/discharge respectively.The results show that for MlNi 3.45 -(CoMnTi) 1.55 the diffusion coefficient of H atom(D h) and the properties of the metal hydride electrodes related to different microstructure are remarkablely different,the cell volume and D h decrease with increasing cooling rate of solidification.For the gas atomized powder alloy,the drop of D h from 3.06×10 -7 (cm 2·s -1 ) to 7.47×10 -9 (cm 2·s -1 ) will take place with size of powder decreased from 200 to 360 meshes.Whereas D h of the unidirectionally solidified alloys has a increase from 7.03×10 -9 (cm 2·s -1 ) to 1.31×10 -8 (cm 2·s -1 ) with increase of the solidifing rate from R=48μm/s to R=220μm/s.The high rate discharge efficiency of the electrodes depends mainly on the diffusion kinetics of H atom in the alloys and electrocatalytic activity on the electrode surface.The high rate discharge capability of unidirectionally solidified microstructure is associated with the enrichment and segregation of Ni element in the microstructure as well as the anisotropically crystal growing.
出处
《电源技术》
CAS
CSCD
北大核心
1997年第4期147-152,共6页
Chinese Journal of Power Sources
关键词
贮氢合金
合金凝固组织
氢扩散
电极放电速度
hydrogen storage alloys,mischmetal nickel based alloys,solidified microstructure,diffusion of hydrogen,discharge rate of electrode
