Vol.22 - 1 Original
Kinetic Isotope Effects on Hydrogen Absorption by Pd, Pd-4at%Pt and Pd-8at%Pt
Y. Jin, M. Hara, K. Watanabe
Hydrogen Isotope Research Center, Toyama University
Gofuku3190, Toyama 930-8555, JAPAN
Abstract
Absorption of protium and deuterium by Pd, Pd-4at%Pt and Pd-8at%Pt powders under 200 mesh was measured
in a dilute hydrogen concentration region at temperatures from 0 to 82℃ by recording the decline of hydrogen
pressure in an experimental chamber due to hydrogen absorption. These measurements and data analyses gave the
adsorption rate, desorption rate and diffusion constants of hydrogen isotopes for the alloys. The absorption was
very
fast, completed within a few tens of seconds, but there appeared a clear trend of decreases in the rate
constants
for adsorption, desorption and diffusion with increase in the Pt content in the sample. The activation energies
for
these rate processes increased with increase in the platinum content. Regarding isotope effects, protium showed
a higher
adsorption rate but lower desorption rate in the present temperature range. It was also found that protium
diffused
more slowly than did deuterium in all three samples