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Preforms made of carbon fibers and sacrificial tungsten fibers as a pore forming agent were repeatedly infiltrated with polycarbosilane and pyrolysed for 14 cycles,followed by aqua regia leaching to remove the tungsten fibers to form porous C/SiC composites.The pore structure,mechanical properties and permeability of the porous C/SiC composites to water and kerosene were respectively studied by a scanning electron microscope,a universal materials testing machine and home-made permeation equipment based on a fluid flow model in capillaries.Results showed that the pores of the porous C/SiC composites were mostly straight and that the open porosity can be controlled by the volume fraction of tungsten fibers used.The bend strength,Young's modulus and fracture toughness were 358 MPa,124 GPa and 16.7 MPa·m1/2 respectively when the open porosity of the composite was 23.5%.The fluids permeated through the porous C/SiC composites by linear laminar flow(the osmosis rate value is 1.02×10-3 mm2).The composites exhibited tough fracture behavior and the presence of pores didn't lead to a significant deterioration of their mechanical properties. |
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