Topic 7 – UHTCs and MAX phases
Ultra-high temperature ceramics (UHTCs) and nano-laminated ternary carbides and nitrides (MAX phases) are families of compounds that display a range of potentially very useful properties. For the UHTCs this includes extremely high melting temperatures (>3000°C), high hardness and good chemical stability and strength at high temperatures. For the MAX phases it includes unusual combinations of chemical, physical, electrical, and mechanical properties; these materials exhibit both metallic and ceramic characteristics under various conditions.
UHTC materials are typically considered to be the carbides, nitrides and borides of the transition metals, but the Group IV compounds (Ti, Zr, Hf) plus TaC are generally considered to be the main focus of research due to the superior melting temperatures and stable high-melting temperature oxide that forms in situ. The combination of properties make these materials potential candidates for a variety of high-temperature structural applications, including engines, hypersonic vehicles, plasma arc electrodes, advanced nuclear fuels, fusion first walls and divertors, cutting tools, furnace elements and high temperature shielding. Recently, work has been focused on producing ultra-high temperature ceramic matrix composites, UHTCMCs. These materials are typically reinforced with carbon fibres and offer most of the advantages arising from UHTCs but also including much higher toughness and hence capability to resist both mechanical and thermal shock. They are being investigated for a range of applications, from rocket nozzles to thermal protection systems.
MAX phases can have quite complex compositions and their properties include high electrical and thermal conductivity, thermal shock resistance, damage tolerance, machinability, high elastic stiffness, and low thermal expansion coefficients. Some MAX phases are also highly resistant to chemical attack (e.g. Ti3SiC2) and high-temperature oxidation in air (Ti2AlC, Cr2AlC, and Ti3AlC2). They are useful in technologies involving high efficiency engines, damage tolerant thermal systems, increasing fatigue resistance, and retention of rigidity at high temperatures. These properties can be related to the electronic structure and chemical bonding in the MAX phases.
The purpose of this Topic is to bring together interested parties from academia, government and industry in a single forum that allows the bench researchers to interact with designers and engineers to discuss state-of-the-art research and development efforts, what the results mean in a broader context and how to move the technology forward toward near-term and longer term use.
Key words :
Scientific Committee :
- Nataliya Baklanova, ISSCM, Russia
- Diletta Sciti, ISTEC-CNR, Italy
- Yanchun Zhou, Aerospace Res. Inst. of Materials & Processing Technology, China
- Bill Fahrenholtz, Missouri Univ. of Sci. & Techn., USA
- Hejun Li, Northwestern Polytechn. University, China
- Marianne Balat-Pichelin, CNRS – PROMES, France
- Per Eklund, Linköping University, Sweden
- Carolina Tallon, Virginia Tech, USA
- Raffaele Savino, University of Naples, Italy
- Chris Weinberger, Colorado State University, USA
Point of contact:
Prof. Jon Binner, University of Birmingham, UK