吸、放氢循环对V及V0.9Cr0.1合金储氢性能的影响

通过添加少量LaNi5对V以及V0.9Cr0.1合金进行有控制的机械合金化处理,改善了材料的活化性能.吸、放氢循环测试表明,吸、放氢循环超过100次并脱氢后,V和V0.9Cr0.1合金仍然保持单一bcc结构.随着吸、放氢循环的进行,V的吸、放氢平台压力不断增加,相同压力下吸氢量减小,且吸氢动力学有所下降.这与吸、放氢过程中晶格应变的降低和晶胞体积的减小有关.SEM观察表明,随着吸、放氢循环次数的增加,材料表面和内部形成大量的深裂纹,这对提高放氢平台压力和改善放氢动力学有促进作用.吸、放氢循环过程中,V比V0.9Cr0.1合金放氢容量衰减更快的原因是:吸、放氢循环前、后V的晶格应变降低和晶胞体积下降程度均比V0.9Cr0.1合金的要大,导致吸、放氢循环后V的吸氢量下降更大.

EFFECTS OF ABSORPTION/DESORPTION CYCLES ON HYDROGEN STORAGE PROPERTIES OF V AND V0.9Cr0.1 ALLOY

Through mechanical alloying treatment for V and V0.9Cr0.1 alloy with small amount of LaNi5, the activation properties of the both materials were improved. After more than 100 absorption/desorption cycles followed by thorough desorption, both V and V0.9Cr0.1 still maintained the single bcc structure. During the cycling the absorption plateau pressures of V increased, the absorption capacities decreased under the same hydrogen pressure and the absorption kinetics declined, which could be attributed to the relaxation of the internal strain introduced by ball milling and the contraction of the cell volumes. SEM observation revealed that with increasing cycle, a large amount of deep cracks formed on the surface and in the inner of the samples, which are beneficial to the enhancement of the hydrogen desorption plateau pressures and the improvement of the desorption kinetics. V showed greater degradation rate of effective hydrogen desorption capacity than V0.9Cr0.1 because of more decreases of the lattice strain and bcc cell volumes of V than those of V0.9Cr0.1, which induced more sever decrease of absorption capacity of V after absorption/desorption cycle.