Thermophysical properties of an amorphous polymer-derived Si/B/N/C ceramic

The thermophysical properties of an amorphous, multinary precursor derived Si/B/N/C ceramic with the approximate composition of SiBN3C were determined experimentally. Thermal diffusivity a(T) was determined from 77 to 300 K with an alternative laser-flash setup using the resistance change of a thin (circa 100 nm) gold strip as fast temperature probe. From 300 to 873 K a standard laser-flash setup was used. Specific heat capacity cp(T) was determined by temperature modulated differential scanning calorimetry (MDSC) in the temperature range between 190 and 773 K. Using the relation λ(T) = a(T)·cp(T)·ρ with the specimen density of ρ = (1561 ± 47) kg m−3, which was considered to be temperature-independent, the thermal conductivity λ(T) was calculated. The analysis yielded values for the thermal conductivity at room temperature of λ(296 K) = (0.490 ± 0.042) W m−1 K−1, and at the highest investigated temperature of λ(773 K) = (0.706 ± 0.063) W m−1 K−1. Furthermore, space-resolved laser-flash measurements with a lateral resolution of about 1.5 mm were performed at 300 K to examine local inhomogeneities on the specimen. Within the given measurement uncertainties, no inhomogeneities could be found.