*3.2.2 Thermal properties*

Thermal conductivity suffers by various factors, and sintering at different pressure is one of them. At low temperature, thermal conductivity is proportional to the square of the temperature, reflecting amorphous like character. This happens because of various scattering phenomenon, especially phonons scattering by pores [30]. On the contrary, at high temperature conductivity rises at different rates, lightly for samples pressed by pressure of 5 GPa, while strongly for pressed at 4 GPa. For a high temperature range with increasing pressure, there is an unusual decrease in the value of thermal conductivity. Porosity as well as quality of graphene and ceramic composites are the of the main concern [31].
