以TiMnx (x = 1.4, 1.5, 1.6, 1.7)非计量比合金为对象,系统研究了储氢容量与其内在结构之间的相关性。结果表明,所有合金的主相均为C14型Laves相,但其储氢容量却存在显著差异。其中TiMn1.4合金的储氢量约为0.65% (w,质量分数),吸/放氢平台较倾斜,且存在明显的滞后;而TiMn1.5合金的可逆储氢量达到1.2% (w),平台较为平坦;但继续增加x,其储氢量反而降低,如x = 1.6合金的储氢量仅为0.30% (w),而x = 1.7合金则几乎不吸氢。进一步结构解析表明,上述储氢容量的迥异主要归因于部分Ti原子占据Mn(2a)位置,且其占位率随x的增加而降低,随之C14相中贮氢四面体间隙体积减小;而引起贮氢四面体间隙体积发生变化的主要因素是Ti―Ti键和Mn(2a)―Mn(2a)键的键长,其中Mn(2a)―Mn(2a)键长的增加对合金储氢容量的提升起关键作用。
The correlation between structural factors and hydrogen storage capacity of nonstoichiometric TiMnx (x = 1.4, 1.5, 1.6, 1.7) alloys was investigated systematically. The capacities of TiMnx alloys were different with changing the x value, although all the alloys show a C14-type Laves phase. The TiMn1.4 alloy shows 0.65% (w, mass fraction) capacity and a sloping plateau with hysteresis, and the TiMn1.5 alloy exhibits the highest capacity of 1.2% (w) and a flat plateau. By further increasing the x value, the hydrogen storage capacity was reduced significantly, such as approximately 0.30% (w) and zero for the alloys with x = 1.6, 1.7, respectively. Structural analysis shows that the Ti atoms partially occupy the Mn(2a) site in the nonstoichiometric TiMnx alloys, and the increasing occupation factor (g) exhibits a negative effect on the volume of tetrahedron interstitials for hydrogen storage. The key factors for changing the volume of tetrahedron interstitials are the bond lengths of Ti―Ti and Mn(2a)―Mn(2a), where Mn(2a)―Mn(2a) bonds play a dominant role in improving the hydrogen storage capacity