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C/ZrB 2 -SiC composites were fabricated by polymer infiltration and pyrolysis combined with slurry impregnation method. Three kinds of coating structures for these composites were applied in order to improve their ablation resistance: pure silicon carbide coatings, ZrB 2 -SiC mixture coatings, and ZrC-SiC alternating multilayer coatings. The ablation experiments were carried out on an oxyacetylene torch flame with a temperature of about 30001C. The ZrC-SiC alternating multilayer showed the best ablation resistance. The linear erosion rate for ZrC-SiC alternating multilayer coatings is half of that for ZrB 2 -SiC mixture and pure SiC coatings. A model was put forward to account for such a result. Fig. 7. Calculation results for temperature distribution on the surface of the ablated specimen.

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In this article, the influence of curing processing on the final ceramic yield of a highly branched polycarbosilane is discussed. Effect of pyrolysis conditions on the ceramic residue is also investigated. The results show that post-treatment can highly increase the crosslinking degree and pyrolysis yield, but has little influence on the final ceramic yield. The heating rate between 170 and 200 A degrees C shows a little effect on the ceramic residue. Adding the catalyst into polymer, pyrolysizing with the gas pressure and improving the heating rate during the pyrolysis process can efficiently increase the final ceramic yield.Natural Science Foundation of Fujian Province of China [E0510002