High-temperature piezoresistive C / SiOC sensors

Here we report on the high-temperature piezoresistivity of carbon-containing silicon oxycarbide nanocomposites (C / SiOC). Samples containing 13.5 vol% segregated carbon have been prepared from a polysilsesquioxane via thermal cross-linking, pyrolysis and subsequent hot-pressing. Their electrical resistance was assessed as a function of the mechanical load (1-10MPa) and temperature (1000-1200 degrees C). The piezoresistive behavior of the C / SiOC nanocomposites relies on the presence of dispersed nanocrystalline graphite with a lateral size <= 2 nm and non-crystalline carbon domains, as revealed by Raman spectroscopy. In comparison to highly ordered carbon (graphene, HOPG), C/ SiOC exhibits strongly enhanced k factor values, even upon operation at temperatures beyond 1000 ffi C. The measured k values of about 80 +/- 20 at the highest temperature reading (T = 1200 degrees C) reveal that C/ SiOC is a primary candidate for high-temperature piezoresistive sensors with high sensitivity