In~situ Kinetics Study in Chemical Vapor Deposition of Pyrocarbon from Propylene

The deposition kinetics of pyrocarbon by chemical vapor deposition(CVD)from propylene was investigated by in situ measurements of deposition rates which were measured by Magnetic Sus- pension Balance TG system.The gas phase products that collected by a liquid nitrogen cold trap were analyzed by GC-MS.The apparent activation energy is(201.9±0.6)kJ/mol in the range from 850℃to 1100℃,where dilution ratio a is 4,total pressure is 6kPa and the flow rate of propylene is 20sccm,and the deposition kinetics is controlled by homogenous reactions.The main products of gas phase are single ring aromatic hydrocarbons and polycyclic aromatic hydrocarbons(PAHs)at high and low tempera- tures,respectively.Through the investigation of dependence of propylene partial pressure(0.3-6.5kPa) on deposition rate in 900℃and 1000℃,it can be concluded that the decomposition of propylene is a first order reaction.Related to both of the effective reaction time and the flow rate of propylene,the maximum of the deposition rate is found at residence time of 0.6s.