Structure Domain Size of Carbon Fibers

Abstract

The internal micro-structure is an important factor affecting the thermal conductivity of materials. In this work, the relationship between micro-structure, thermal conductivity, and temperature variation for carbon fibers (CF) are systematically studied by using the transient electrothermal technique. When the temperature is below the critical temperature (about 110 K), the internal structure of carbon fiber deteriorates, resulting in a very different behavior of thermal conductivity variation with temperature. By introducing the thermal reffusivity theory, the structure domain size of CF can be represented by the phonon mean free path at 0 K. The thermal reffusivity change of two temperature ranges is studied, and the mean free path of phonons in CF before and after deterioration can be calculated as 317 nm and 234 nm, respectively. The results are in good agreement with the crystallite grain size of 288 nm determined by Raman study. The thermal reffusivity provides another feasible method to study the relationship between structure domain size and thermophysical properties of materials.