Relationship between gas permeability and open pore of carbon

Studying gas permeability of carbon materials is very important to use the materials for some applications such as chemical reaction chambers, high vacuum vanes, seal rings, fuel cells and nuclear fusion devices. Although, the relationship between gas permeability and open pore is not fully understood. Gas permeabilities were measured for various carbon materials with different mean pore radius and porosity. The materials include both self-sintering (meso-carbon based) and binder-sintering (binder and coke based) carbons. Empirical equations in which viscous flow permeability constant (Bo) and Knudsen flow permeability constant (Ko) are related to mean pore radius (a) and open porosity (V) are obtained: Bo = 0.745a2.06V2.51, Ko = 6.18a0.96V2.16. We have estimated the effective length of pores in unit volume. The lengths of pores contributed for viscous flow (lBo) and Knudsen flow (lKo) were calculated separately. It is considered that the ratio (lBo/lKo) indicates a tortuosity of open pores. (author)