Effect of surface impurities and argon sputtering on deuterium permeation of nickel

To clarify the effect of surface impurities upon hydrogen isotope-permeation through nickel, the deuterium permeation rate of variously treated nickel was measured in the pressure range of 3x10-4 to 2x10-1 Pa at 673 K. Surface segregation of sulfur proceeded during a thermal anneal at ∝673 K as was identified with in-situ AES analysis. Even in this low pressure range, the permeation rate of nickel obeyed Richardson's equation: the rate-limiting step is bulk diffusion. Neither carbon nor sulfur on the surface significantly affected the steady state permeation rate, which is different from the case for vanadium. On the other hand, argon ion sputtering decreased the deuterium permeation rate of nickel. This decrease in permeation rate can be recovered to some extent by an anneal at ∝673 K. Such behavior is probably attributable to some sort of irradiation damage produced during argon ion sputtering. (orig.)