Interfacial Microstructure and Chemistry of SiC/BN Dual‐Coated Nicalon‐Fiber‐Reinforced Glass‐Ceramic Matrix Composites

Abstract

Glass‐ceramic composites with improved high‐temperature mechanical properties have been produced by incorporating continuous SiC fibers into a barium magnesium aluminosilicate matrix. Control of the fiber/matrix interface was achieved by a dual‐layer coating of SiC/BN(C) applied to the fibers by CVD. The weakly bonded interface resulted in composites with high fracture toughness and strength up to 1100°C, and the composite system was oxidatively stable during long‐term exposure to air at high temperatures. Composites with different thermal and mechanical histories were studied, and interfaces were characterized using transmission electron microscopy (TEM), Auger electron spectroscopy, and fiber pushout tests. Observations of interfacial microstructure were correlated with the mechanical properties of the composite and with interface properties determined from fiber push‐out tests.