Chemical vapour infiltration of pyrolytic carbon—an electron spin resonance analysis

Abstract A carbon fibre felt with a fibre volume fraction of 7% was densified by chemical vapour infiltration of pyrolytic carbon from methane at about 1100 °C using an isothermal, isobaric process. Specimens of 1 mm 3 size were cut out and analysed by electron spin resonance (ESR) in as-infiltrated form and after annealing at 2200 or 2900 °C. The temperature and orientation dependence of ESR line shape, width, intensity, and g -tensor are derived. Preferred orientation and degree of graphitisation of the deposited pyrolytic carbon are discussed.