Microstructure and gas permeation performance of porous silicon nitride ceramics with unidirectionally aligned channels

Porous Si(3)N(4)ceramics with unidirectionally aligned channels were prepared via freezing ceramics suspension with distinct solid contents under different freezing temperatures. The samples obtained using lower solid content in ceramic suspension at higher freezing temperature exhibit larger Darcian and non-Darcian constants due to their higher open porosity, larger pore size and lower tortuosity. Moreover the investigation on individual contributions of viscous energy losses and inertial energy losses on the total pressure drop during permeation process indicates that with decreasing the solid content or the freezing temperature the viscous energy losses increase but the inertial energy losses decrease for samples owing to the differences in their pore structures. It is worth mentioning that porous Si(3)N(4)ceramics with unidirectionally aligned channels exhibit larger Darcian and non-Darcian constants than those with similar pore size distributions and open porosity owing to their lower tortuosity, thus rendering them appropriate for filters and membrane supports.