Production of replicated porous materials based on SiC: Microstructure, mechanical behavior & thermal shock resistance

Abstract

High strength, thermal shock resistance, and suitable thermal conductivity of silicon carbide foams has led to their widespread applications. Doing that, in this research, SiC foams were produced using the slurry contains SiC as the main material with bentonite, alumina, zirconia, and silica sol. This slurry covered the PU foam one to five times during the replication process. Afterward, samples were sintered at three low sintering temperatures, i.e. 900, 1000, and 1100 °C. The microstructure, phases, compressive strength, and thermal shock resistance of these multi-layered porous structures were studied. It was found that the number of coating layers and sintering temperature influenced the type, extent, and size of defects. Applying multi-layer coating changed the morphology of the worst defect of the replication method, i.e. triangular hollow struts, to circular ones, which impressively enhanced the mechanical strength and thermal shock resistivity. Comparing nine types of samples indicated that the maximum strength was obtained in a five-layer coated sample sintered at 1000 °C, and not at the maximum sintering temperature. Notably, burning off bentonite and silica soles results in blister generation at 1100 °C, which reduced strength, and thermal shock resistance. The optimum strength of the porous sample after exposure to 11 sequences of thermal shock test was obtained in a four-layer-coated sample sintered at 1000 °C, which highlighted the critical strut thickness in porous structures.