Control of the thermal conductivity of SiC by modifying the polymer precursor

Compared to other methods, the fabrication of SiC from precursors allows designing the microstructure and thus the properties of the ceramic material by adjusting the microstructure of the precursor materials. In this study, we used a divinylbenzene (DVB) isomer mixture to modify the polycarbosilane (PCS) precursor via the chemical modification method. The ceramics derived from the modified precursors showed different thermal conductivities. The SiC prepared from PCS without DVB exhibited a very low thermal conductivity at low and at high temperatures. A proper doping with DVB led to clean SiC grain boundaries, resulting in the typical thermal conductivity behaviour of coarse SiC ceramics. An excess doping with DVB led to the precipitation of free carbon around the SiC grains, resulting in a still suitable thermal conductivity which was between the other two values. The results clearly demonstrate that adjusting the thermal properties by modifying the microstructure is a promising approach.