Dense high-temperature ceramics by thermal explosion under pressure

Abstract

Near fully dense in-situ particulate reinforced ceramic matrix composites (CMCs) were fabricated from fine Ti–B 4C, Ti–BN, Ti–Al–BN, Ti–SiC, Ti–B 6Si and Al–TiO 2 powder blends with or without the addition of Ni. Two reactive synthesis techniques were employed: thermal explosion/TE (SHS) under pressure, where the compacted reagent blend was placed and rapidly heated in a pressure die preheated slightly above the ignition temperature, and reactive hot pressing/RHP. In both approaches, the processing or preheating temperature (≤1250°C) was considerably lower than those typical of the current methods used for the processing of ceramic matrix composites. Partial to full conversion of reagents into products was achieved during TE, and a moderate external pressure of ≤150 MPa was sufficient to ensure full density of the final products. Rapid cooling from the combustion temperature due to the ‘heat sink’ action of the pressure die resulted in the fine/micronsize microstructures of the in-situ composites synthesized. RHP processing yielded dense materials with even finer microstructures, however full conversion of reagents into products has not been achieved.