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 t o characterize thermal properties of silicon-epoxy composite materials in t he volume range 0% < x < 32 vol% (50 mum). PA detection was used to study t he variation of the thermal diffusivity as a function of Si volume fraction , and PTR was used to determine the influence of the electronic carrier con tribution to the thermal transport with the optical properties taken into c onsideration. The combined PA and PTR measurements show that there exists n o 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 exhi bit anomalous behavior in the 16% Si volume fraction range, corroborating t he existence of a particle percolation threshold for three-dimensional rand om close packed (rep) solids. (C) 2001 Elsevier Science B.V. All rights res erved.