The Effect of Pressure Modulation on the Flow of Gas through a Solid Membrane: Permeation and Diffusion of Hydrogen through Nickel

The attenuation and phase lag of pressure modulations transmitted through a solid foil from one chamber to another may be used to assess the diffusion and solubility coefficients of diffusant gas in the solid. A linear approximation is used to describe the cases of flow into (1) pumped and (2) equilibrated output chambers. It is shown that experiments based on this kind of system allow self-consistency checks to confirm diffusion limited flow and that pumped systems allow direct estimation of the index of the power law describing permeation. Experiments with hydrogen in nickel using a pumped system demonstrate close adherence, over a wide range of experimental parameters, to the expected frequency variation of output. Formerly with The Open University, Oxford, United Kingdom