RESEARCH STUDIES ON SOLID HYDROGEN PURIFICATION MEMBRANES.
Interim technical rept. no. 2, 15 May-15 Nov 66,
TYCO LABS INC WALTHAM MASS
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The permeation rate of hydrogen through tantalum coated with a thin film of palladium was measured over the temperature range 400-600C and at pressures up to 175 psia. The permeation rate is substantially greater than that through pure palladium membranes of the same thickness under the same conditions. The permeation rate through tantalum decays with time, particularly at temperatures 500C or higher. An extensive study of the decay of the permeation rate in relation to the conditions of preparation of the membrane and the conditions of its use was carried out. It appears that at high temperatures extensive recrystallization of the palladium film takes place. This process probably leads to exposure of tantalum to the gas phase and causes a decrease of the rate of hydrogen absorption. Although this process is probably mainly responsible for the loss of activity, there also appears to be a secondary effect contributing to the decrease of the permeation rate arising either from diffusion of palladium into tantalum or from diffusion of an impurity, e.g. interstitially dissolved oxygen, from the bulk of the tantalum membrane to the tantalum-palladium interface. Author
- Industrial Chemistry and Chemical Processing