The influence of deposition temperature on the microstructure of isotropic pyrocarbon obtained by hot-wall chemical vapor deposition

Bulk isotropic pyrocarbon was successfully prepared by hot-wall chemical vapor deposition. The density of the products was measured by Archimedes method in ethanol. The structural parameters of pyrocarbon were derived from X-ray diffraction (XRD) and Raman spectroscopy. The morphology and texture of pyrocarbon was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the density of pyrocarbon increases from 1.53 to 1.73 g/cm³ with the increase of deposition temperature. The d ₀₀₂ spacing decreases gradually from 0.3487 to 0.3449 nm as temperature rises from 950 to 1100 °C. Lc increases greatly from 6.5 to 10.5 nm, whereas La slightly rises from 4.0 to 3.6 nm. Under TEM, the fringe lattice images are composed of curved graphene layers, and the length of graphene layers is greatly improved with the increasing temperature. The selected area electron diffraction patterns of the products are complete rings, indicating their isotropic feature.