Effect of aluminum on hydrogen absorption kinetics of tantalum

The isothermal hydrogen absorption kinetics of Ta1−zAlz alloys (z = 0, 1, 1.6 and 2.4 atom%) has been investigated in the temperature range of 673-973 K. The reacted fractions of hydrogen as well as reaction rate constant have been determined from time dependent hydrogen absorption curves using pressure drop method. The variation in rate constant with respect to temperature has been observed for all the alloys. Three-dimensional diffusion processes seems to be the intrinsic rate limiting step of hydrogen absorption. The apparent activation energy of hydrogen absorption has been calculated using Arrhenius equation. With increasing aluminum concentration, the hydrogen absorption kinetics slows down. Consequently, the rate constant decreases and the apparent activation energy of hydrogen absorption increases. The apparent activation energy of hydrogen absorption increases from 53.7 to 57.7 kJ/mol with increasing Al concentration from 0 to 2.4 atom% in tantalum.