HYDROGEN PERMEATION THROUGH GRAPHITE

As a study of the transport processes of hydrogen in graphite, the kinetics of permeation of hydrogen and argon through graphite was investigated in the pressure range of 0.5 to 100 Pa and in the temperature range of 290 to 983 K. The observed results suggested that the hydrogen permeation through graphite can be dealt with as a simple molecular flow. It is remarkable that the gaseous permeability of graphite definitely decreased with the increase of temperature. Such a behavior was mainly attributed to the fact that the permeation of hydrogen in graphite was a molecular flow, while the accommodation effect, which is highly significant in case of the thermal expansion coefficient, was negligibly small. By analyzing the observed temperature dependences, the size of pores in graphite which dominates the gaseous permeation processes was roughly estimated.