Hydrogen absorption kinetics of V4Cr4Ti alloy prepared by aluminothermy

The hydrogen absorption kinetics of V4Cr4Ti alloy, synthesized by aluminothermy process has been investigated in the temperature range of 373–773 K. The obtained hydrogen absorption kinetic curves were linearly fitted using a series of mechanism function to reveal the kinetics parameter and reaction mechanism. Nucleation and growth, one dimensional diffusion and three-dimensional diffusion processes are the intrinsic rate limiting steps of hydrogen absorption at 373 K. It was found that nucleation and growth processes disappear between 413 K–473 K. However at higher temperatures (>473 K), nucleation and growth as well as one dimensional diffusion process disappear. In the temperature ranges investigated (473 K–773 K), three-dimensional diffusion process was the intrinsic rate limiting step. The apparent activation energy was calculated using Arrhenius equation and found to be 6.1 kJ/mol. This value appears to be relatively higher which can be attributed to the presence of aluminium, which has blocked the absorption sites and increased the activation energy.

► Hydrogen kinetics is a function of surface properties and temperature.
► Presence of Al increases the activation energy.
►  Aluminothermy process could be used for synthesize of VTiCr master alloy.
► Three dimension diffusion process control the reaction at high temperature.