Processing and Consolidation of TaC/HfC Based Composites Using MoSi2 and Carbon Nanotubes
Tantalum and hafnium carbides are classified as Ultra High Temperature Ceramics (UHTC) because of their extreme melting temperatures (above 3900 degrees C). Therefore, these materials can safely operate in the range of temperature that any other materials could hardly exist. However, these applications can be strongly restricted due to (1) processing difficulties and (2) low fracture toughness. In this work, to address these two difficulties we have used two additives, which are multi-walled carbon nanotubes (CNTs) and molybdenum disilicide (MoSi2). The CNTs were added aimed to improve the fracture toughness of the composites, and the MoSi2 to facilitate sintering. Application of such a sintering aid, add to the novel SPS technique, allowing quick processing at relatively lower temperature, results in (1) fully densified specimens (> 99%) and (2) well-surviving CNTs after sintering. Moreover, microstructural analysis points out fair-enough dispersion of the CNTs within the ceramics particles, in both the green and sintered bodies. Also the specimens phase characterization shows inter dissolution of TaC and HfC and formation of binary carbides solid solution.