1996 Volume 29 Issue 4 Pages 669-674
Carbon fiber-reinforced carbon matrix (C/C) composites are useful engineering materials because they have a high strength to weight ratio and good creep resistance at high temperature. They are stable up to very high temperatures in inert or vacuum environments, but have a serious drawback of reaction with oxidizing atmospheres at temperatures as low as 773 K.
In this study, the effects of double coating of SiC and glass materials on the oxidation resistance of C/C composites were investigated. The first coating of SiC was made by pack cementation in a graphite crucible with metallic silicon, and the second coating of glass materials was applied with ceramics mixtures in order to seal cracks in the SiC layer. The components of the mixtures were m-Si (metallic Si), Al2O3, B4C, SiC and ZrSi2. SiC/Si-B4C-SiC-ZrSi2 coatings were found to provide very effective oxidation resistance at 1773 K in air for 10 hrs. Furthermore, the effects of seven kinds of silicide additive on oxidation resistance of C/C composites were also studied. It was found that ZrSi2 and HfSi2 were very effective on the resistance compared with other silicides.
