Gas permeability of SiC/SiC composites as fusion reactor material

Abstract

Permeability of helium gas in SiC/SiC composites material, which is one of the most important properties in application of SiC/SiC composite for first wall and blanket of fusion reactors, was studied by using a vacuum apparatus. Three tubular and two flat plate SiC/SiC composites were prepared by different preparation processes. The measurement of permeability coefficient of helium gas was carried out with pressure ranging from 10 2 to 10 5 Pa at room temperature. The permeability coefficient of the SiC/SiC composite largely depended on the preparation method. In three tubular materials, the SiC/SiC composite made by both polymer impregnation and pyrolysis (PIP) and melt infiltration (MI) methods showed the lowest permeability, 9.1×10 −7 m 2/s, which was approximately two orders of magnitude smaller than one of the material made only by PIP method. The permeability of the flat plate SiC/SiC composites made by both liquid phase sintering (LPS) and hot pressing (HP) was approximately 1.5×10 −9–4.0×10 −11 m 2/s. The difference of permeability was related to the microscopic structure, i.e. pores and cracks.