C/C composites with improved mechanical strength were synthesized using a filler constituted by a carbon felt covered with catalytically grown carbon nanofibers(CNFs)and a carbonaceous matrix generated by the pyrolysis of a phenolic resin.First,the synthesis method of the filler allows the homogeneous deposition and anchorage of CNFs on the host microfilaments at a rapid densification rate.Carbon nanofibers grown this way lead to the formation of numerous micro-and nanobridges between the microfilaments,conferring a significant improvement of the mechanical resistance of the CNF/C system allowing one to tailor its dimensions and shape.Thus,further fabrication of C/C composites can be achieved:the CNF/microfilament structure was infiltrated with a phenolic resin and carbonized at 650°C to generate a carbonaceous matrix by thermal decomposition.Similar experiments on the microfilaments carried out at the same synthesis time,without catalyst and at higher reaction temperatures led to the deposition of a pyrolytic carbon sheath and to poor mechanical enhancements.This clearly indicates the advantage of using CNF growth as an efficient densification process before infiltration.Such C/C composites exhibit high-quality bonding between the two carbon phases,the matrix and the CNF/microfilament filler,via the formation of a considerable amount of CNF interphase.
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