The high temperature compressive strength of non-oxide ceramic foams

The compression strengths of five coated vitreous carbon foams under development were measured at 25, 1000, 1200 and 1400°C. Only qualitative trends in the measured strengths were obtainable due to a numerical lack of specimens. One developmental foam was a pyrolytic carbon (PC)-coated reticulated vitreous carbon (RVC) foam, and it was tested in argon at the three elevated temperatures. Four developmental RVC foams had chemical vapor infiltration (CVI)-SiC coatings on them, each with different coating thicknesses and consequential different bulk densities; these SiC-RVC foams were tested in ambient air at the elevated temperatures. The strength of the PC-RVC foam was independent of temperature up to 1400°C in argon. The compressive strengths of the SiC-RVC foams having the two thinnest coatings (or the two smallest bulk densities) were equivalent in ambient air to those of the PC-RVC foam in argon up to 1400°C, while the SiC-RVC foams having the two thickest coatings (or the two greatest bulk densities) were consistently stronger. These results show thin-SiC layered SiC-RVC foams grant oxidation protection that PC-RVC foams do not possess to 1400°C, and that thicker SiC layers on SiC-RVC foams are required for added strength.