Optical Measurements of the Thermal Conductivity of Porous SiO₂ Films

Nanocomposites offer unique capabilities of controlling thermal transport through the manipulation of various structural aspects of the material. However, measurements of the thermal properties of these composites are often difficult, especially porous nanomaterials. Optical measurements of these properties, although ideal due to the noncontact nature, are challenging due to the large surface variability of nanoporous structures. Recently, a novel pump-probe geometry was used in Time Domain Thermoreflectance (TDTR) to determine the thermal conductivity of liquids. In this work, we develop a thermal algorithm to solve for the temperature change and heat transfer in this TDTR geometry in which a thin film which is subjected to a modulated heat source is sandwiched between two thermally conductive pathways. We validate our thermal algorithm with TDTR measurements of the thermal conductivity and on a series of porous SiO₂-based nanostructured films.