Combined photothermal and photoacoustic characterization of silicon-epoxy composites and the existence of a particle thermal percolation threshold
Photoacoustic (PA) and photothermal radiometric (PTR) detection were used to characterize thermal properties of silicon-epoxy composite materials in the volume range 0%< x<32 vol% ( 50 μm). PA detection was used to study the variation of the thermal diffusivity as a function of Si volume fraction, and PTR was used to determine the influence of the electronic carrier contribution to the thermal transport with the optical properties taken into consideration. The combined PA and PTR measurements show that there exists no linear relation between thermal diffusivity and silicon volume fraction. Thermal diffusivity and optical absorption coefficient measurements can be obtained by means of combined PA and PTR measurements. Both parameters exhibit anomalous behavior in the 16% Si volume fraction range, corroborating the existence of a particle percolation threshold for three-dimensional random close packed (rcp) solids.