The effects of SiC whiskers and an SiC film coating deposited by chemical vapor infiltration (CVI) on a porous cordierite substrate

This study was performed with the goal of reducing environmental pollution caused by nano-particle materials. SiC whiskers were grown on a porous cordierite substrate to enhance its filtering efficiency, performance, and durability by controlling pore morphology. We investigated two different methods: SiC whisker growth (A) and SiC film coating after the SiC whisker growth (B). These experiments were performed using the chemical vapor infiltration (CVI) process to grow the whiskers in the inner pore without closing it. After a 1 h deposition at 1200°C, the compressive strength of the whiskered porous cordierite body increased from 24 MPa to 60 MPa (250%) in experiment (A) and to 82 MPa (342%) in experiment (B). The mean pore size was reduced after whisker growth (A) as well as after additional film coating (B). The adhesion strength between the whiskers and the cordierite substrate increased with the additional film coating (B). Consequently, the separation of whiskers from the substrate was minimized. N₂ gas was injected and a permeability change was observed which explains the separation of the whiskers from the substrate. This method makes the filtration of nano-sized particles feasible.