Design of carbon fiber reinforced boron nitride matrix composites by vacuum-assisted polyborazylene transfer molding and pyrolysis

In the present study, the vacuum-assisted polyborazylene transfer molding (VAPTM) followed by pyrolysis at 1450 °C under nitrogen was successfully applied to prepare C/BN composites with a relative density of 94.7%, and an open porosity of 5.1 vol%. Rheology measurements combined with TG experiments and measurement of the weight gain of the composites after each polymer impregnation pyrolysis (PIP) cycles allowed fixing elaboration parameters (10 PIP cycles using two types of polyborazylene) to generate C/BN composites as high temperature vacuum compatible materials which demonstrate potentialities for vacuum technology and space applications. Scanning electron micrographs of composites demonstrated that the BN matrix appropriately filled the space between the fibers with a low fiber-matrix bonding which affects the compressive modulus. The thermal diffusivity and electrical conductivity of the BN matrix have been measured and showed that carbon fibers have poor effects on the intrinsic properties of BN.