Kinetics of the Tantalum-Hydrogen Reaction

Kinetics of reaction of hydrogen with tantalum was studied for atom fraction compositions, N H , 0.05 at 500° to 700°C and N H , 0.10 at 450° to 600°C. The process was one of dissolution and diffusion of hydrogen. The diffusion coefficients obtained are expressed by the following equations: D N H = 0.05 = 1560 exp − 32 , 230 ± 3140 / RT cm 2 / sec D N H = 0.10 = 13 , 960 exp − 33 , 620 ± 1370 / RT cm 2 / sec A single rate was obtained for N H ± 0.25 at 450°C. Regardless of composition, N H 0.05 to N H 0.33 , samples at 300° to 400°C did not achieve surface saturation in the experimental time. The indicated activation energies are higher than the meager literature values for diffusion of hydrogen in most other metals.