Halogenated glass systems for the protection of structural carbon-carbon composites Original Research Article

Oxidation protection systems or carbon-carbon composites have met limited success, particularly between 900 and 1500 °C where internal glass inhibitors are relied upon to protect the composite. Thi study investigated potential halogenated glass protection systems for the protection of structural carbon-carbon composites. A series of fluoride and fluoroborate glass compositions were selected based on thermodynamic predictions; specifically, to reduce volatility of current B2O3 based protection systems at elevated temperatures. The halogenated glass candidates examined in this study included a series of fluoroborate glasses containing 5 and 10 mol% CaF2, MgF2 and NaF. Since B2O3 is currently used as the matrix inhibitor, the effectiveness of these glasses was compared to B2O3 based upon their high temperature durability and ability to inhibit oxidation of SP-1 and HLM-85 graphite. The high temperature durability of the glasses were compared during two hour isothermal holds in oxygen at 900, 1100, 1300 and 1500 °C. The ability of the halogenated glasses to inhibit the oxidation of SP-1 and HLM-85 graphite was analyzed by examining the oxidation kinetics of compacts containing 33 wt% of the glass inhibitor and graphite. This study is unique in that the oxidation kinetics of inhibited carbon materials were studied in the temperature range of 900 to 1500 °C. This temperature range is of critical importance in the application of these materials.