Densification kinetics and mechanical properties of tantalum carbide

Sintering kinetics and densification of tantalum carbide (TaC) based ultra-high temperature ceramics (UHTC) processed using spark plasma sintering (SPS) were investigated. Samples sintered in the temperature ranging from 1600 degrees C to 2300 degrees C for 15 min under uniaxial pressure of 50 MPa showed increasing densification (similar to 77% to 99% from 1600 degrees C to 2300 degrees C) accompanied by substantial grain growth (similar to 0.57 mu m to similar to 4.05 mu m). Below 1900 degrees C, the densification mechanism was grain-boundary sliding with an apparent activation energy of 97.3 +/- 10.2 kJ/mol, However above 1900 degrees C, the activation energy was found to be 232.7 +/- 19.6 kJ/mol with grain boundary diffusion to be an active densification mechanism. The flexural strength (from 161.3 +/- 10.4 MPa to 326.5 +/- 10.5 MPa) and elastic modulus (from 375.7 +/- 3.1 GPa 535.4 +/- 4.7 GPa) was observed to increase with the increasing sintering temperature. The study explicitly establishes that the dense bulk TaC ceramic can be produced by SPS in a shorter time and lower sintering temperature, while maintaining the compositional stoichiometry.