Fluorocarbon Pyrolytic Graphite

Abstract

An attempt was made to prepare high density pyrolytic graphite by the decomposition of C2F4 in a flow reactor and to obtain the parameters of the deposition. Sooting pressures, important in defining optimum deposition conditions, were determined for the C Z F~ system as a function of deposition temperature and flow rate. Deposition rates were measured, examined as a function of deposition pressure and temperature, and noted as being relatively temperature insensitive above 1750OC. Deposition rates with C2F4 were up to 50% lower (225OOC.) than CHI depositions under similar circumstances, and the densities of the CzF4 deposits were lower. Consequently, CH4 has superior deposition characteristics. I t was desired to characterize the properties of the cZF4 pyrolytic graphite compared to CH4 pyrolytic graphite prepared under similar conditions. The densities of the deposits from both systems were shown to rise with increase i n deposition temperature and decrease in deposition pressure. Photomicrographs of the deposits contained characteristic microstructures. An attempt was made to produce high density pyrolytic graphite from C2F4 at temperatures below 1500' C. to circumvent some of the residual interlaminar cooldown stresses acquired when the material is produced at 2000' to 225OOC. Production of high-density deposits was not feasible because of the low deposition rates encountered.