Comparative study of the microstructure of the interphases in two SiC fibre/lithium aluminosilicate matrix composites

Abstract

The microstructure of the interfacial region in two Nicalon SiC fibre/lithium aluminosilicate glass (with and without Nb₂O₅) matrix composites (which consists of a carbon layer and possibly NbC crystals) has been investigated by high-resolution electron microscopy. Special attention has been paid to the evolution of this microstructure from the matrix to the fibre. The study has revealed new data which have improved the understanding of these materials. The formation of the carbon layer begins at the surface of the glass and continues on the side of the fibre. A certain amount of carbon diffuses inside the matrix with a heterogeneous distribution. The addition of Nb₂O₅ to the glass results in the formation of a carbon layer with a more amorphous structure. An important feature has been revealed in the composite without Nb₂O₅ which contributes to its brittleness.