X-ray diffraction and Raman spectroscopy characterization of isotropic pyrocarbon obtained by hot wall chemical vapor deposition

Varying the flow rate of natural gas from 50 to 80 to 120 1/h,isotropic pyrocarbon produced by hot wall chemical vapor deposition at 1000 °C were examined by X-ray diffraction and Raman spectroscopy. The X-ray data were evaluated by Scherrer equation,and the intensity ratio of D to G band derived from Raman data was used to evaluate the lateral extension of isotropic pyrocarbon. The experimental results show that the d₀₀₂-spacing of isotropic pyrocarbon decreases from 0.3499 nm to 0.3451 nm,while the stack height increases from 6.5 to 8.4 nm with the increase of flow rate of natural gas. The intensity ratio of D to G band and lateral extension of isotropic pyrocarbon increases with natural gas flow rate increasing. After heat treatment,all the crystallite parameters (stack height,lateral extension,and d₀₀₂-spacing) decrease,indicating the improvement of the arrangement of the basic structural units of isotropic pyrocarbon.