Pore geometry of 3D-Cf/SiC composites by mercury intrusion porosimetry

The 3D-Cf/SiC composites fabricated via precursor infiltration and pyrolysis (PIP) are porous inside due to their specific processing. To evaluate the porosity of 3D-Cf/SiC, a novel procedure of mercury intrusion porosimetry (MIP) was adopted to extract information from the hysteresis and entrapment. This method is able to eliminate the temporarily retained Hg at atmospheric pressure from the real entrapment due to topological reasons. From the interpretation of the MIP primary and secondary intrusion–extrusion data, accompanied by scanning electron microscopy (SEM) analysis and bubble point measurement, the pore geometry of 3D-Cf/SiC is supposed to be a 3D network originating from the architecture of braided carbon fabrics. This network is composed of hundreds of micron-sized large chambers between bundles, micro-cracks below 0.1 μm and medium-sized channels about 20–4 μm that bridge the former two and provide passages for fluids permeating the material.