X-ray diffraction study of pore structure of pyrocarbon coatings obtained at various temperatures

X-ray diffraction (large- and small-angle scattering) has been used in an investigation of the pore structure and crystal structure of pyrocarbon coatings obtained by pyrolysis of a number of gaseous hydrocarbons at temperatures of 1300–2000°C. The coatings have a well-developed pore structure. The pore dimensions cover a range from fractions of a nanometer to hundreds of nano-meters. The pore volume and distribution depend primarily on the temperature of deposition. This relationship is extremal in nature. The volume of small pores (R=0.5-3.0 nm) is the greatest when T_d=1500°C; owing to the closed nature of the pores, this leads to an anomalous decrease in pycnometric density, the minimum density being observed at this same temperature. With T_d > 1500°C, growth of the crystals is observed, correlating with the decrease in volume of small pores.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya; No. 5, pp. 982–987, May, 1990.