Remote monitoring of thermal conductivity of a powder by a flash radiometry technique

We study the dependence of the thermal conductivity of a carbon-loaded epoxy powder on its porosity using a noncontact flash radiometry technique. The thermal conductivity is found to be very small when the porosity of the sample is higher than a critical value. Below the critical porosity Pcrit, thermal conductivity increases linearly with packing density. This phenomenon can be explained by a two-phase model; the powder exhibits continuous thermal conduction paths only when the porosity is less than Pcrit.