Influence of pitch air‐blowing and thermal treatment on the microstructure and mechanical properties of carbon/carbon composites

This paper discusses the optimization of pitch properties as a matrix precursor of C/C composites by subjecting the pitches to different pretreatments to promote polymerization of the molecular components of pitch, which could improve carbon yield and density of the resultant carbon materials. Two series of pitches were prepared by air‐blowing of impregnating coal‐tar pitches at temperatures between 523 and 573 K, and thermal treatment at temperatures between 673 and 703 K, in an inert atmosphere. Effects of pitch treatments on resultant coke texture and porosity were monitored by polarized light microscopy. Unidirectional laminar composites were prepared using the original and treated pitches and commercial PAN‐based carbon fibres. Effects of pitch treatments on the main microstructural features of composites are determined by scanning electron microscopy and polarized light microscopy, and related to the mechanical properties of composites. Results show an improvement of the mechanical properties of composites in both series, particularly for pitch treatments at 523 K/air in the air‐blown series, and at 698 K–5 h in the thermally treated one.