Combined photothermal and photoacoustic characterization of silicon-epoxy,and the existence of a particle percolation threshold.

Photoacoustic and Photothermal Radiometric detection were used to determine the thermal properties of silicon-epoxy composite materials in the volume range of 0 < x < 32 vol. % (50 mum). Photoacoustic detection was used to st udy the evolution of the thermal diffusivity as a function of the Si volume fraction, and PTR was used to determine the role of the electronic carrier s in thermal transport by taking the optical properties into consideration. The combined PA and PTR measurements show that there exists no linear rela tion between thermal diffusivity and silicon volume fraction. The thermal d iffusivity and optical absorption coefficient measurements can be obtained by means of combined photoacoustic and photothermal radiometric probes. Bot h parameters exhibit anomalous behavior in the 16 % Si volume fraction rang e, corroborating the existence of an electrical particle percolation thresh old for the three dimensional random close-packed solids.