Thermal Conductivity Mapping of Oxidized SiC SiC Composites by Time Domain Thermoreflectance with Heterodyne Detection

TL;DR

This paper employs advanced time domain thermoreflectance with heterodyne detection to map the thermal conductance of oxidized SiC composites at high spatial resolution, revealing differences in oxide layers and improving measurement speed.

Contribution

It introduces a heterodyne detection method in TDTR for faster, high-resolution thermal conductance mapping of SiC composites in oxidizing environments.

Findings

Heterodyne detection improves TDTR data acquisition speed.

Oxide on fibers has lower thermal conductance than on the matrix.

Noise analysis identifies preamplifier noise as dominant at low signal levels.

Abstract

Silicon carbide silicon carbide (SiC SiC) composites are often used in oxidizing environments at high temperatures. Measurements of the thermal conductance of the oxide layer provide a way to better understand the oxidation process with high spatial resolution. We use time domain thermoreflectance (TDTR) to map the thermal conductance of the oxide layer and the thermal conductivity of the SiC SiC composite with a spatial resolution of 3 {\mu}m. Heterodyne detection using a 50 kHz modulated probe beam and a 10 MHz modulated pump suppresses the coherent pick-up and enables faster data acquisition than what has previously been possible using sequential demodulation. By analyzing the noise of the measured signals, we find that in the limit of small integration time constants or low laser powers, the dominant source of noise is the input noise of the preamplifier. The thermal conductance of the oxide that forms on the fiber region is lower than the oxide on the matrix due to small differences in thickness and thermal conductivity.