Experimental investigation of gas diffusion through monomodal materials. Application to geopolymers and Vycor® glasses

•One pore size materials were prepared and characterized in the context of nuclear waste disposal.•Their water saturation level was controlled after placing them in humid chambers until equilibrium.•The hydrogen diffusion coefficient was measured as a function of the water saturation level.•Knudsen diffusion is not negligible for this class of materials.•When the water saturation level is below 60%, %, the pore size repartition has no impact on the diffusion coefficient.

This paper documents the influence of the water saturation level and the pore size distribution of porous materials on the diffusion of hydrogen. The materials are two monomodal materials: geopolymers and Vycor glasses. First, the pore size repartition is measured by means of mercury intrusion porosimetry and nitrogen adsorption porosimetry. Next, the materials are characterized through their water sorption isotherms. Finally, the diffusion coefficients measured as a function of the water saturation degree allows to quantify the impact of water on the gas diffusion through the materials. The results highlight the existence of a threshold value of saturation degree which leads to a decrease of two orders of magnitude in the hydrogen diffusion coefficient.

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