TiVNbTa难熔高熵合金的吸放氢动力学

Hydrogen absorption-desorption kinetics of TiVNbTa refractory high-entropy alloy

通过真空电磁感应悬浮熔炼技术制备TiVNbTa难熔高熵合金试样,采用多通道储氢性能测试仪测试合金的吸放氢性能,并研究该合金的吸(放)氢行为及其动力学机制。结果表明:单相BCC结构的TiVNbTa难熔高熵合金吸氢后生成TiH_(1.971),Nb_(0.696)V_(0.304)H和Nb_(0.498)V_(0.502)H_(23)种氢化物新相。氢化高熵合金粉末在519,593 K和640 K分别发生氢化物的分解反应,放氢后恢复单相BCC结构,因此TiVNbTa合金的吸氢反应属于可逆反应。该合金在423~723 K温度区间具有较高的吸(放)氢速率,其吸(放)氢动力学模型分别符合Johnson-Mehl-Avrami(JMA)方程和二级速率方程,吸(放)氢的表观活化能Ea分别为-21.87 J/mol和8.67 J/mol。

TiVNbTa refractory high-entropy alloy was prepared by vacuum electromagnetic levitation melting technology.The hydrogen absorption and desorption properties of the alloy were tested by multichannel hydrogen storage tester,the hydrogen absorption-desorption behavior and corresponding kinetic mechanisms were investigated.The results show that BCC single-phase structure in the alloy is transformed into three new phases including TiH_(1.971),Nb_(0.696)V_(0.304)H and Nb_(0.498)V_(0.502)H_(2)after the hydrogen absorption process.The hydrides in the hydrogenated high-entropy alloy decompose at 519,593 K and 640 K,respectively and change to BCC phase again after hydrogen desorption process.Therefore,the hydrogenation reaction is reversible.The alloy exhibits high hydrogenation(dehydrogenation)rates at 423-723 K.The kinetics of hydrogen absorption and desorption can be described by Johnson-Mehl-Avrami(JMA)model and second-order rate model,respectively.The apparent activation energies Ea of hydrogen absorption and desorption are-21.87 J/mol and 8.67 J/mol,respectively.