Abstract

Boron nitride (BN) matrix composites reinforced by a number of different ceramic fibers have been prepared using a low‐viscosity, borazine oligomer which converts in very high yield to a stable BN matrix when heated to 1200°C. Fibers including Nicalon (SiC), FP (A12O3), Sumica and Nextel 440 (Al2O3‐SiO2) were evaluated. The Nicalon/BN and Sumica/BN composites displayed good flexural strengths of 380 and 420 MPa, respectively, and modulus values in both cases of 80 GPa. On the other hand, FP/BN and Nextel/BN composites exhibited very brittle behavior. Nicalon fiber with a carbon coating as a buffer barrier improved the strength by 30%, with a large amount of fiber pullout from the BN matrix. In all cases except for Nicalon, the composites showed low dielectric constant and loss.

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