ScMn_(1.6)V_(0.4)合金吸氢热力学和动力学研究

Research on hydrogen absorption thermodyna- mics and kinetics of ScMn_(1.6)V_(0.4) alloy

利用XRD研究了ScMn1.6V0.4合金及其氢化物的晶体结构,利用氢气反应装置测量了合金的吸放氢性能。结果表明:ScMn1.6V0.4合金为理想的密排C14型Laves相结构。合金在实验条件下生成的氢化物晶体结构与原始合金相同,体积膨胀28%。合金在115 kPa和298 K条件下可快速吸氢,孕育期非常短,表现出优异的活化性能。合金不同温度下的P-C-T曲线没有明显的吸放氢平台,吸放氢滞后随温度升高变小,临界滞后温度为523 K。由van’t Hoff方程得到合金在(α+β)相的ΔH和ΔS的变化范围分别为-(29~34) kJ/molH2和-(61~84) J/molH2K;β相分别为-(31~33) kJ/molH2和-(87~88) J/molH2K。合金的吸氢动力学可用JMA模型描述,初次活化的块体样品(α+β)和β相区域的Avrami指数分别为4和1;完全活化的粉体样品两个相区域的Avrami指数分别为1和0.5,表观活化能分别为(15±1) kJ/mol和(7±2) kJ/mol。

The crystal structure of ScMn1.6V0.4 alloy and its hydride were studied by XRD, and the hydrogen absorption and dehydrogenation properties of the alloy were measured by hydrogen reaction device. The results indicated that the crystal structure of ScMn1.6V0.4 alloy is an ideal close-packed C14 type hexagonal Laves phase structure. The crystal structure of hydride was the same as that of the original alloy under experimental conditions, and the volume expanded by 28%. The alloy could absorb hydrogen rapidly at 115 kPa and 298 K, with very short incubation period. The alloy exhibited excellent activation properties. The P-C-T curves of the alloy at different temperatures had no obvious hydrogen absorption and desorption platform. The hysteresis of hydrogen absorption and desorption decreased with the increase of temperature, and the critical hysteresis temperature was 523 K. The ΔH and ΔS of(α+β) phase range respectively-(29-34) kJ/molH2 and-(61-84) J/molH2K obtained by van’t Hoff equation, and the β phase is-(31-33) kJ/molH2 and-(87-88) J/molH2K, respectively. The kinetics of hydrogen absorption of the alloy could be described by JMA model. The Avrami index of the(α+β) and β phases of the first activated block sample were 4 and 1, respectively. The Avrami index of the fully activated powder samples were 1 and 0.5, and the apparent activation energy were 15±1 kJ/mol and 7±2 kJ/mol, respectively.