The Thermal Conductivity of Polymer-Derived Amorphous Si-O-C Compounds and Nano-Composites

Silicon oxycarbide glasses can be produced over a range of Si-O-C compositions by the controlled pyrolysis of polymer precursors. We present measurements of the thermal conductivity of a silicon oxycarbide glass after two different heat treatments and two Si-O-C nano-composites, hot-pressed at 1600 degrees C, up to 1000 degrees C and compare them to fused silica, amorphous carbon, and SiC. The temperature dependence of their thermal conductivities is similar to other amorphous materials. The presence of low volume fractions of nanoparticles of hafnia (4.5 v/o) or zirconia (7.4 v/o) dispersed within the amorphous matrix only modifies the conductivity slightly, consistent with a simple Maxwell model, and does not affect the temperature dependence of the thermal conductivity above room temperature.