Plasma driven permeation of hydrogen through Nb: influence of the surface and bulk defects

Plasma driven permeation of hydrogen through 25 μm Nb foils was investigated under low‐energy hydrogen ion irradiation in the range of membrane temperature 450–800 K and at different surface conditions. The interaction of hydrogen at molecular, atomic and ionizated states with niobium was under experimental research. The maximum value of low‐temperature steady state permeation efficiency (SPE) was observed at Ar plasma cleaned inlet surface and with insignificant influence of outlet surface conditions. Such result is unusual and contradicts the developed classical representations and other published data for high‐temperature range plasma‐driven permeation. We explain this phenomenon by influence of defect structure of the polycrystalline membrane. The defects lead to the enhanced diffusion of hydrogen atoms along the crystallite sides. Such diffusion can essentially increase SPE of hydrogen through metal at low temperatures. The validity of this explanation was proved by the comparison of molecular hydrog...