Pressure-less Sintering of ZrB-SiC Ceramics
A pressureless sintering process was developed for the densification of zirconium diboride ceramics containing 10-30 vol% silicon carbide particles. Initially, boron carbide was evaluated as a sintering aid. However, the formation of a borosilicate glass led to significant coarsening, which inhibited densification. Based on thermodynamic calculations, a combination of carbon and boron carbide was added, which enabled densification (relative density >98%) by solid-state sintering at temperatures as low as 1950°C. Varying the size of the starting silicon carbide particles allowed the final silicon carbide particle morphology to be controlled from equiaxed to whisker-like. the mechanical properties of sintered ceramics were comparable with hot-pressed materials with Vickers hardness of 22 GPa, elastic modulus of 460 GPa, and fracture toughness of ∼4 MPa·m1/2. Flexure strength was ∼460 MPa, which is at the low end of the range reported for similar materials, due to the relatively large size (∼13 μm long) of the silicon carbide inclusions.
S. C. Zhang et al., "Pressure-less Sintering of ZrB-SiC Ceramics," Journal of the American Ceramic Society, Wiley-Blackwell, Jan 2008.
The definitive version is available at http://dx.doi.org/10.1111/j.1551-2916.2007.02006.x
Materials Science and Engineering
Air Force Research Laboratory (Wright-Patterson Air Force Base, Ohio)
Keywords and Phrases
Densification; Fracture Toughness; Particle Morphology; Solid-State Sintering; Zirconium Diboride Ceramics; Sintering
Article - Journal
© 2008 Wiley-Blackwell, All rights reserved.