Kinetics and Characteristics of Isothermal Constant Volume Hydrogen Desorption in TC21 Alloy

Hydrogen desorption kinetics and characteristics, residual hydrogen content and activation energy of TC21 alloy were investigated by the constant volume method. Results show that hydrogen desorption temperature and initial hydrogen pressure affect hydrogen desorption characteristics of TC21 alloy. The hydrogen desorption process is mainly dominated by nucleation and growth process (k1=[-ln(1-alpha)](2/3)), chemical reaction process (k1= (1-alpha)(-1/2)) and three-dimensional diffusion process (k1=[1-(1-alpha)(1/3)](1/2)) when the hydrogenated TC21 alloy is dehydrogenated at temperatures of 700-940 degrees C. When the hydrogenated TC21 alloy releases hydrogen, the following relationship exists among the rate constants of each process: k (chemical reaction process)>k (nucleation and growth process) >k (three-dimensional diffusion process). The residual hydrogen content of the hydrogenated TC21 alloy after hydrogen desorption decreases gradually with the increase in hydrogen desorption temperature, and increases gradually with the increase in the initial hydrogen pressure. The activation energy of TC21 alloy in the process of hydrogen desorption is about 26.663 kJ/mol.