Large anisotropic thermal conductivity and excellent thermoelectric properties observed in carbon foam

Abstract

Using first-principles calculations in combination with the Boltzmann transport equation and empirical potential models, we investigate the thermal transport and thermoelectric properties of carbon foam. The results show that large anisotropic thermal conductivity can be observed in carbon foam. The Z direction of carbon foam has the highest thermal conductivity of 22.97 W/m K at room temperature, which is about 25 times greater than that of the Y direction. This is due to the lower phonon group velocity and stronger anharmonic interaction in the Y direction than those in the Z direction. Moreover, we find that the carbon form has excellent thermoelectric properties in the Y direction, the ZT can reach 0.5 at room temperature, and the ZT can be further improved to 0.84 at 800 K, which is two orders of magnitude higher than that in the Z direction. This results from the large power factor and ultralow thermal conductivity in the Y direction.