Oxide/oxide composites with fibres produced by internal crystallisation

Sapphire fibres produced by the internal crystallization method were introduced into an alumina matrix. The fibres were coated with pyrolitic carbon to provide weak bonding to the matrix which is expected to enhance the fracture toughness of the material. The composite fabrication process exploited a powder-cloth technique. Evaluation of the strength and fracture toughness values of the specimens revealed an increase in the fracture toughness of the composites compared to that of the matrix, although the strength is not affected by the reinforcement. The main conclusion is that the internal crystallization-process yields single-crystal fibres suitable for the reinforcement of oxide-matrix composites.