Effect of pyrolysis temperature on the microstructure and thermal conductivity of polymer-derived monolithic and porous SiC ceramics

The present work investigates the influence of pyrolysis temperature on the microstructure and thermal conductivity (λ) of polymer-derived SiC ceramics. For the study, both monolithic thin ceramic disks and highly porous reticulated foams were considered. The λ of the polymer-derived SiC disks were measured, in the temperature range 100 °C–1000 °C, to amount between 0.5 W.m−1. K−1 and 47 W.m−1. K−1, depending from the maximum pyrolysis temperature. While, the λ measured at RT on the SiC foams (porosity 79.5 %–99.0 %), ranges between 0.03 W.m−1. K−1 and 0.19 W.m−1. K−1. The thermal transport in polymer-derived SiC ceramics was observed to be more significantly governed by the nanocrystalline to crystalline transition which occurs at pyrolysis temperatures above 1200 °C as compared to mesopore formations or the nature and amount of free carbon.