Kinetics of tantalum hydriding: the effect of palladization

Abstract

The kinetics of tantalum hydriding under isothermal conditions, at six different temperatures in the range 573-823 K, was investigated. The kinetic parameters: rate constant, reaction order, activation energy and pre-exponential factor, were determined. The reaction order was found to amount 1, rate constants were found to vary in the range 5 × 10-6-2 × 10-4 s-1 in the temperature range under investigation, and an apparent activation energy was estimated to amount 56.2 kJ/mol Ta. No change in kinetical parameters was registered after multiple repetition of hydriding/dehydriding cycles. The same investigations were repeated with palladized samples. The palladization caused an abrupt increase in the rate constant value, but maximal hydriding capacity was found to remain unaffected.