Carborane-Catalyzed Graphitization in Polyarylacetylene-Derived Carbon- Carbon Composites
AEROSPACE CORP EL SEGUNDO CA MECHANICS AND MATERIALS TECHNOLOGY CENTER
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Boron in the form of a carborane compound, C2B10H12, was used to catalytically graphitize a polyarylacetylene PAA resin, typically a nongraphitizing carbon, in bulk form and in a carbon-carbon CC composite. In bulk form, significant graphitization was observed after heat treatment to 1800 deg C complete graphitization was realized at 2400 deg C. Similar results were found for a PAA derived carbon matrix in a unidirectional CC composite. The effect of carborane addition on the mechanical properties of CC unidirectional composites of PAA and T-50 carbon fibers was also examined. After heat treatment to 1100 deg C, the tensile strength of unidirectional fiber tows increased significantly with increasing concentration of carborane. The increase in tensile strength was accompanied by increased fiber pullout, suggesting that interface weakening decreases the tendency for matrix-dominated brittle fracture. After heat treatment to 1800 deg C and above, the carborane decreased the strength of the composites but substantially increased the modulus. Catalytic graphitization of PAA offers a major potential advantage of obtaining graphitic matrices in CC without the disadvantages of conventional pitch processing. In addition, the much lower temperatures required for catalytic graphitization would enable processing temperatures for CC to be reduced significantly. Carbon-carbon composites, Graphitization, Catalysis, Processing.
- Physical Chemistry
- Polymer Chemistry
- Laminates and Composite Materials