Relation between porosity and pore size or pressure drop of fibrous SiC filter prepared from carbonized cellulose-powder preforms

Using pressure-pulsed chemical vapor infiltration (PCVI), SiC was partially infiltrated into the carbonized cellulose-powder preforms having the initial porosity of 0.93–0.94, and the relation among porosity (ε), pore size and pressure drop (ΔP) was evaluated. After 30 000 pulses of PCVI, fibrous SiC having ε of 0.76 and average pore size (Dp) of 13 μm was obtained. Dp was related with ε and fiber diameter (Df), assuming a model for fiber arrangement at right-angles and regular intervals. The derived relationship showed that Dp increased proportionally with Df under the constant ε. ΔP followed the relationship based on the Kozeny–Carman equation, i.e. it was proportional to (1−ε)2 ε−3 Df−2. ΔP was also related with ε and Dp using the Kozeny–Carman equation and the model for fiber arrangement. From the derived relationship, it was suggested that ΔP of fibrous SiC filter was lower than that of porous carbon or sintered ceramics filter at the same ε and Dp.