Preparation Of Gradient Ceramic/polymer Composites By Pyrolysis-impregination (PIP) Technique

This paper is aimed to prepare for a kind of anti-oxidation ceramic/polymer functional gradient composites at high temperature by numbers of cycles of surface pyrolysis-impregination technique with high heat flux, which heats on the sample's surface to form temperature gradient so that the polymer preceramic pyrolyze gradually vertically across the sample. These works lay foundation to make a sort of polymer composites as antiablative as ceramics.Two kinds of low cost polysilicones SAR-9 and SAR-2 made inbroad was used as polymer preceramics to prepare for antioxidation Si-C-O ceramics and ceramic composites at high temperature after assessing the properties and materials cost of several sorts of polymer ceramics which have been used most often so far. DTA-TG test showed that the pyrolysis temperature range of SAR-9 in the inertia atmosphere is between 230-837℃ , the ceramic yield is more than 85%. The pyrolysis residue at the different temperature was tested by FTIR,XRD及 TDA-TG, which showed that the residue at 1200℃ was best antioxidant, and its weight loss in air at 1000℃ is 0.4%, comparatively, the weight loss of the residue at 900 ℃ and 1600℃ is 2.2% and 2.6% respectively.C_f/Si-C-O ceramic composites have been manufactured by PIP technique from carbone fiber reinforced SAR-9 polymer composite ingot after 7 cycles of pyrolysis-impregination, which different pyrolysis temperatures are choosed, and SAR-2 was used as impregination resin. The bend strength of C_f/Si-C-O ceramic composites prepared at 1200 ℃ is the best of all the samples with the density being 1.920g/cm~3, which is 190.5 MPa at room temperature , and keep up 172.3MPa after keeping at 1000℃ in air for 60min.The chemical reaction between the interface of C_f/Si-C-O ceramic composites took place , and SiC crystal appeared when the sample was put in inertia atmosphere for heat treatment at high temperature up to 1600℃. With increase of the treat temperature, the reaction is more violent, the fiber face destruct more, and the SiC crystal grain become greater.The temperature gradient across the SAR-9 sample with φ/δ being 20/5mm was calculated out when heating its surface by different heat flux after a reasonable calculation modle was built by virtue of the calculation method of ablative...