Experimental Preforms made of PAN based carbon fibres were used in this work. (a) Preforms were impregnated with 10 vol. % distilled water solution of orthophosphoric acid. The samples were then dried in air at 150°C for 2 hours and treated at 600°C under an argon atmosphere. In order to understand the chemical phenomena occurring between H3PO4 and carbon, C/C composite materials (tablets) were carefully polished and treated with a H3PO4 solution. (b) Preforms were coated with SiC using a methyltrichlorosilane (MTS)/H2 mixture (950°C-3 kPaH2/MTS=0,7). Thermogravimetric analyses (TGA) were performed on the treated preforms under argon or dry air atmospheres in the 650-1000°C temperature range. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), Raman and Fourier transform infrared (FTIR) spectroscopies were carried on C/C composites polished surfaces.
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Labruquère et al. (1997) studied this question.