Diphenylborosiloxane (PBS), a kind of organometallic compound, was compounded with carbon fiber (CF) to form CF/ceramics composites. These composites have excellent mechanical properties with a possibility of their use at high temperatures. So the CF/ ceramics composites were heat-treated at high temperatures, and the change of their structure and the behavior of interface were investigated.
The CF/ceramics composites were prepared by impregnating pitch-type or PAN-basedCF strand with acetone solution of PBS containing SiC powder (as a filler), and by heattreatingthem at 1000°C. Then they were heat-treated at high temperatures of 1250°, 1500°, 1750° and 2000°C. The weight decreasing rates of the composite at 1250°Cwere 4% for that prepared from pitch-type CF, and 8% for that from PAN-based CF.
In the X-ray diffraction patterns of the composites prepared from pitch-type CF and from PAN-based CF, when heat-treated at high temperatures up to 2000°C, only the diffraction peaks by carbon and β-SiC were observed. The higher the treating temperature was, the greater the intensity of diffraction peak by carbon (002) was. The graphitization was more noticeable with pitch-type CF than with PAN-based CF. For any treating temperature, no diffraction peaks by boron or its compounds, such as B4C, were noticed.
Moreover, the diffusion profile of silicon into CF in the composites heat-treated at high temperatures, was inspected by X-ray microanalyzer. The results showed that the existence of silicon was slightly observed only in the vicinity of CF surface, which indicated no diffusion of silicon into CF regardless of its kind and the treating temperature.