Carbon/carbon nanocomposites derived from phenolic resin-silica hybrid ceramers: microstructure, physical and morphological properties

Phenolic resin-silica hybrid ceramers were prepared through the sol-gel method. The hybrid ceramers with various inorganic contents were used as matrix precursors to fabricate silica containing carbon/carbon (C/C) composites. The effect of the organic-inorganic mixing ratio on the change of density and porosity was studied. The flexural strength and modulus of the C/C composites was also investigated. Results show that the density of the C/C composites increases with silica content. However, at higher silica content, the density of the composites does not change before and after carbonization. Silica increases the stiffness of the fabricated C/C composites from 12.4 x 10(4) to 3.0 x 10(4) MPa. However, it does not affect the flexural strength. XRD and Raman spectra studies show that the incorporation of inorganic silica into the phenolic resin influences the growth of ordered carbon structures. From SEM morphological observations, it was concluded that the silica particles are dispersed uniformly on the surfaces of the specimens with some particles located at the pores due to the decomposition of the polymer matrix. (C) 2002 Elsevier Science Ltd. All rights reserved.