Dense high-temperature ceramics by thermal explosion under pressure

Near fully dense in-situ particulate reinforced ceramic matrix composites ( CMCs) were fabricated from fine Ti-B4C, Ti-BN, Ti-AI-BN, Ti-SiC, Ti-B6Si an d Al-TiO2 powder blends with or without the addition of Ni. Two reactive sy nthesis techniques were employed: thermal explosion/TE (SHS) under pressure , where the compacted reagent blend was placed and rapidly heated in a pres sure die preheated slightly above the ignition temperature, and reactive ho t pressing/RHP. In both approaches, the processing or preheating temperatur e (less than or equal to 1250 degrees C) was considerably lower than those typical of the current methods used for the processing of ceramic matrix co mposites. Partial to full conversion of reagents into products was achieved during TE, and a moderate external pressure of less than or equal to 150 M Pa was sufficient to ensure full density of the final products. Rapid cooli ng from the combustion temperature due to the 'heat sink' action of the pre ssure die resulted in the fine/micronsize microstructures of the in-situ co mposites synthesized. RHP processing yielded dense materials with even fine r microstructures, however full conversion of reagents into products has no t been achieved. (C) 1999 Elsevier Science Ltd. All rights reserved.