Sintering of Insitu Synthesized SiC-TiB2 Composites with Improved Fracture-Toughness

TiB2-particle reinforcement is one of the most successful methods for
improving the fracture toughness of SiC ceramics.1-3 Commercially
available TiB2 powders, however, have a large particle size and/or are
highly reactive so that they are not favorable as a starting powder. In
the present work, TiB2 particles are formed by an in situ reaction
between TiC and boron. The reaction takes place during sintering
between 1000-degrees and 1600-degrees-C and is accompanied by a large
volume expansion. Under optimum conditions, dense composites (>98% of
theoretical) can be obtained by pressureless sintering using B and C as
sintering additives. The in situ reaction method enables, for the first
time, a complete densification of SiC-particulate composites by
pressureless sintering. The fracture toughness of the composites was
approximately 30% higher than that of the monolithic SiC ceramic.