LaNi4.25Al0.75吸氕、氘、氚热力学同位素效应

Thermodynamics Isotope Effects of LaNi_(4.25)Al_(0.75)Absorbing Protium,Deuterium and Tritium

采用自制的全金属氢化物吸放氢实验装置,恒温等容条件下测定LaNi_(4.25)Al_(0.75)材料吸氕、氘、氚单质气体的压力-组成等温线(P-C-T曲线),并根据Van’t Hoff(范特霍夫)方程得到LaNi_(4.25)Al_(0.75)吸氕、氘、氚形成氢化物相的热力学参数焓变ΔH分别为:-44.5、-45.0、-47.1kJ·mol-1,熵变ΔS分别为:-118.0、-121.8、-127.5J·mol^(-1)·K^(-1)。结果表明:LaNi_(4.25)Al_(0.75)材料吸收氕、氘、氚单质气体,在温度较低时,同位素效应不明显;温度高于100℃时,热力学同位素效应显著。相同温度、吸气容量条件下,吸气平衡压力从低到高依次是氕、氘和氚,其反应焓变和熵变从小到大依次是氚、氘和氕。结果表明,LaNiAl合金吸氢的热力学同位素效应依赖于温度的变化。

The P-C-T curves of LaNi4.25 Al0.75 alloy absorbing protium, deuterium and tritium were investigated at constant temperature and volume in our metal hydride research system. According to the Van＇t Hoff Equation, the thermodynamics parameters of the hydride phase were determined. Enthalpy change and entropy change for protium, deuterium and tritium were - 44.5, - 45.0, - 47.1 kJ/mol and - 118.0, -121.8, -127.5 J· mol^-1 · K^-1. The experiments indicated that the isotope effect did not obviously at low temperature, however, as the temperature increasing to 100 ℃, there were obvious thermodynamics isotope effect with hydrogen absorption by LaNi4.25 Al0.75 alloy. The order of equilibrium pressure absorbing gases was T2〉DE〉H2. However, the enthalpy and entropy appeared to be in verse order, T2 〈D2〈H2. The results showed that hydrogen isotope effect with LaNiAl alloys were depended on temperature.