THERMAL MEASUREMENTS USING LASER FLASH ANALYSIS AND FREQUENCY-DOMAIN THERMOREFLECTANCE

Abstract

Thermal measurement is a critical part of determining the thermal properties of materials. Conventional steady-state thermal conductivity measurements have strict requirements on the sample dimensions and states, making it hard to measure most unconventional samples. Laser flash analysis (LFA) is a convenient and reliable method of determining different materials' thermal diffusivity and thermal conductivity. Apart from LFA, FDTR (Frequency Domain Thermoreflectance) is a much more powerful tool for thermal measurements, where samples with almost all dimensions and states can be measured. FDTR is thermal property microscopy that utilizes two lasers (pump and probe lasers) to measure the samples' thermal properties. The periodically modulated pump laser locally heats the sample. The probe laser detects the surface reflectivity of the sample, which can be used to calculate the thermal properties of the sample with models. Instead of only measuring the sample's thermal conductivity, the FDTR system can measure up to two properties at once – including volumetric heat capacity, thermal conductivity, thickness, interfacial conductivity, and the anisotropic ratio of thermal conductivity of the sample. This thesis demonstrates how LFA works and how it conducts measurements for polymeric composites and polymer blend samples. Also, this thesis concludes on how to set up an FDTR system and how it works on thermal measurements.