is the common technique for determination of the surface area of porous materials. The process is based on the replacing of materials’ porous by adsorption (physisorption)/desorption of nitrogen gas. There are 2 functions of BET method (Degas sample and Analysis). Nitrogen adsorption - desorption isotherm was measured and then and the samples were degassed. The specific surface area was calculated by BET equation with the obtained adsorption data.