Protective coatings for carbon bonded carbon fibre composites

• Published in: Ceramics international 2008-07, Vol.34 (5), p.1297-1301
• Main Authors: Smeacetto, F., Ferraris, M., Salvo, M., Ellacott, S.D., Ahmed, A., Rawlings, R.D., Boccaccini, A.R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Carbon matrix composites; Ceramic and carbon fibers; Ceramic industries; Chemical industry and chemicals; Cross-disciplinary physics: materials science; rheology; D. Glass ceramics; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Glass-ceramics; Glasses; Materials science; Oxidation protection; Physics; Slurry infiltration; Specific materials; Technical ceramics
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2007.03.012

Carbon bonded carbon fibre composites (CBCF) were modified by direct reaction with molten silicon in order to obtain a silicon carbide layer on the composite surface. Subsequently, the Si-infiltrated CBCF material was coated with a silica-based glass containing yttria and alumina by means of a slurry-dipping technique. On heat treatment the glass yielded a glass-ceramic layer thus giving a multi-layered oxidation and erosion protection system. The microstructural characterisation of the coating was conducted by standard microscopy techniques and by X-ray diffraction. The controlled crystallization of the glass-produced cristobalite, yttrium silicate (Y 2Si 2O 7, keiviite, β-form) and mullite as main crystalline phases. These are excellent ceramic materials for oxidation and erosion protection of SiC-coated carbon-based composites since their coefficients of thermal expansion (CTE) closely match that of SiC. The possibility of healing (closure) of micro cracks by a thermal treatment at 1375 °C, thus exploiting the viscous flow of the residual glass in the glass-ceramic, was explored in order to extend the service life of the protection system.