|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Fundamental Aspects and Modeling Powder Metal Synthesis and Processing
||Mechanisms of Pore Formation in High-temperature Carbides: Case Study of TaC Prepared by Spark Plasma Sintering
||Olivia A. Graeve, James P. Kelly
|On-Site Speaker (Planned)
||Olivia A. Graeve
The compositionally diverse TaC<sub>1-x</sub> phase is an interstitial carbide having a rocksalt crystal structure and mixed covalent, metallic, and ionic bonding. Therefore, this material has an interesting combination of properties that in some respects are intermediate between typical ceramics and metals. In this study, a detailed analysis of microstructure and pore evolution of TaC has been studied and three pore-forming mechanisms have been discovered: (1) evolution of oxygen impurity, (2) evolution of excess carbon, and (3) incongruent sublimation of TaC. The evolution of oxygen impurities is the predominant mechanism and can be a consequence of the high amount of oxygen impurity typical of nanopowders. We propose that the latter two mechanisms can be facilitated by local hot spots and discuss a possible source. The root cause of the three mechanisms indicates that a limiting sintering temperature (~2173 K) and carefully controlled chemistry are essential for producing TaC without trapped porosity.