Preparation And Property Of C_F/SiOC-ZrB₂High Temperature Composite

Carbon-carbon composite material which has low density, high temperature mechanical properties of stability, low thermal expansion coefficient, ablation resistance, withstand changes in extreme hot and cold environments and so on has been widely used in military, aerospace, aviation and other fields, which makes it the most promising material in high-temperature thermal protection in future.Therefore, carbon-carbon composite material is widely reseached by researchers in aviation, aerospace, civil application and other fields who are making great efforts to overcome its shortcomings.My thesis takes example by the process route and synthetize principles of carbon-carbon composites and abandons the high density of compact carbon-carbon composites. Just prepare a porous skeleton of carbon fiber from the perspective of lightweight and easy for matrix modification. The density of the carbon fiber skeleton is0.20g/cm3,its maximum compression strength is anisotropy:0.94Mpa and3.01Mpa respectively. The next work is based on the carbon fiber skeleton.This paper takes example by the anti-oxidation methods and matrix-modification of the carbon-carbon composite material, adopts precursor pyrolysis method and introduces ceramic precursors into the carbon fiber skeleton to improve the high temperature oxidation resistant ability and strength of carbon fiber skeleton.Select SiOC ceramic precursor and ZrB2ceramic precursor as the anti-oxidation ceramic coating, we can make different content carbon fiber reinforced composites by means of dipping different eramic precursors, changing the number of dipping ceramic precursors and the sequence of dipping ceramic precursors.Among those composite materials prepared through carbon fiber skeleton dipping different pyrolysis ceramic precursors, five kinds of materials are representative:Cf/SiOC composite prepared through carbon fiber skeleton dipping SiOC ceramic precursors and then getting through pyrolysis three times; Cf/SiOC composite prepared through carbon fiber skeleton dipping SiOC ceramic precursors and then getting through pyrolysis twice; Cf/ZrB2composite prepared through carbon fiber skeleton dipping ZrB2ceramic precursors and then getting through pyrolysis twice; Cf/SiOC-ZrB2composite prepared through the Cf/SiOC composite dipping ZrB2ceramic precursors and then getting through pyrolysis twice; Cf/ZrB2-SiOC composite prepared through Cf/ZrB2composite dipping SiOC ceramic precursors and then getting through pyrolysis twice.Then the compression strength of these representative materials were tested, the result showed that Cf/SiOC-ZrB2composite owned the best comprehensive property,such as:its maximum compression strength is2.58MPa and5.48Mpa, having improved174%and82%respectively comparing to the carbon fiber skeleton while its density is only0.62g/cm3.Select composite materials that own better comprehensive property to carry out static oxidation experiments. set the static oxidation temperature as800℃.The carbon fiber skeleton could be burned down in0.5hour while the oxidation weight loss of Cf/SiOC-ZrB2composite was only5.4wt.%when oxy-genated at800℃after1hour in the air. In addition, it is found that Cf/SiOC-ZrB2composite can retain the oxidation weight loss at about5wt.%for a longer time according to the shape of the curve of oxidation weight loss of Cf/SiOC-ZrB2composite. Besides its maximum compression strength decreased slowly and its maximum compression strength was4.29MPa to1.76MPa after it had been oxy-genated for one hour.