Structure and oxidation resistance of micro-cellular Si-SiC foams derived from natural resins

Microcellular Si-SiC porous ceramics were prepared from rigid foams derived from tannin-based natural resins. Such natural foams were used either as such, i.e. in the green state, or after conversion at 900 degrees C into vitreous cellular carbon foams. Various preparation methods were tested: replica with preceramic polymers followed by pyrolysis, liquid silicon infiltration (LSI) and vapour silicon infiltration (VSI). Depending on the method, very different materials have been obtained, whose morphology and microstructure have been investigated by SEM, XRD and Raman, whereas oxidation resistance has been evaluated by weight loss measurements in dry air at high temperature. The resulting porous ceramics' properties were discussed in relation to the preparation methods and their morphology and conversion of tannin-based foams into SiC. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.