Development of vapor grown carbon fibers (VGCF) reinforced carbon/carbon composites

• Published in: Journal of materials science 2006-07, Vol.41 (13), p.4123-4131
• Main Authors: Dhakate, S. R, Mathur, R. B, Dhami, T. L
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Bulk density; carbon; Carbon fiber reinforced plastics; Carbon fibers; Carbonization; Ceramic and carbon fibers; Ceramic industries; Chemical industry and chemicals; Composite materials; Compressive strength; Cracks; Densification; Exact sciences and technology; Fibers; Graphitization; hardness; Heat treatment; Inert atmospheres; Interfacial cracks; Isostatic pressure; Materials science; Mechanical properties; Morphology; Nanomaterials; Nanostructure; Porosity; scanning electron microscopy; Shrinkage; Sintering (powder metallurgy); Static pressure; Structural ceramics; Technical ceramics; temperature; vapors
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-006-6320-6

C/C composites are developed using vapor grown carbon fibers (VGCF) with two types of pitches as matrix precursor. The composites are carbonized at 1000°C by applying the isostatic pressure throughout the carbonization process and further heat treated at different temperatures up to 2500°C in the inert atmosphere. By applying iso-static pressure one can able to developed VGCF based C/C composites possessing the very high bulk density (1.80 g/cm³) and apparent density (2.01 g/cm³) only by heat treatment up to 2500°C without any densification cycle. This high value of density is due to the extremely strong fiber-matrix interactions and self sintering between the VGCF fibers during carbonization process under iso-static pressure. From the SEM study it reveals that, fiber-matrix interactions are strong and fiber boundaries merges with each other, also there is not a evidence of matrix shrinkage cracks in case 1500°C heat treated composites. On the other hand, in 2500°C heat treated composites, there is evidence of uniform fiber-matrix interfacial cracks and porosity in nanometer dimensions. This is due to the change in fiber morphology above HTT 1500°C. But the formation of nano width cracks does not affect on the mechanical properties of composites. The compressive strength increases from 95MPa of 1500°C to 105 MPa of 2500°C heat treated composites. However, hardness decreases due to the increase in the degree of graphitization of composites on 2500°C. The study reveals that by controlling processing condition and the uniform dispersion of VGCF fibers in the matrix phase, it can be possible to developed nano porosity at fiber-matrix interface.