Thermal Lagging in Random Media

Abstract

The lagging behavior of heat transport in amorphous materials is studied by the use of temperature formulation along with surface heating. The percolating network is alternatively viewed as the physical mechanism causing delayed responses between the heat flux vector and temperature gradient in transporting heat. Experimental results of microsecond responses in rough carbon samples and submillisecond responses in weakly bonded copper spheres are re-examined with emphasis on the possible thermal lagging. Picosecond anomalous diffusion predicted by the fractal and fracton models are compared for silica aerogels and silicon dioxides. It has been shown that the fractal behavior in space can be interpreted in terms of the lagging behavior in time. Nomenclature