Scientists from NUST MISIS have developed the most heat-resistant material
A group ofΒ scientists from NUST MISIS in Russia have developed aΒ ceramic material with the highest melting point among currently known compounds.
Due toΒ the unique combination ofΒ physical, mechanical and thermal properties, the material holds great potential for use in heat-loaded applications and components ofΒ aircraft and engines, such asΒ nose fairings, jet engines and sharp front edges ofΒ wings operating atΒ temperatures above 2,000 Β°C.
The results were published inΒ Ceramics International.
For the aerospace industry materials must beΒ fast, wear-resistant, and cheaper inΒ production. Many leading space agencies (NASA, ESA, asΒ well asΒ agencies ofΒ Japan, China and India) are actively developing reusable aircraft, spaceplanes, which will significantly reduce the cost ofΒ delivering people and cargo toΒ orbit.
Dmitry Moskovskikh, head ofΒ NUST MISIS Center for Constructional Ceramic Materials, said:Β βCurrently, significant results have been achieved inΒ the development ofΒ such devices. For example, reducing the rounding radius ofΒ the sharp front edges ofΒ the wings toΒ aΒ few centimeters leads toΒ aΒ significant increase inΒ lift and maneuverability, asΒ well asΒ reduces aerodynamic drag. However, when exiting the atmosphere and re-entering it, onΒ the surface ofΒ the wings ofΒ the spaceplane, temperatures about 2000 Β°CΒ can beΒ observed, reaching 4000 Β°CΒ at the very edge. Therefore, when itΒ comes toΒ such aircraft, there isΒ aΒ question associated with the creation and development ofΒ new materials that can work atΒ such high temperatures.β
The goal ofΒ the scientists was toΒ create aΒ material with the highest melting point and high mechanical properties.
Triple hafnium-carbon-nitrogen, hafnium carbonitride (Hf-C-N) was chosen, since previously scientists from Brown University (USA) predicted that hafnium carbonitride would have aΒ high thermal conductivity and resistance toΒ oxidation, asΒ well asΒ the highest melting point amongst all known compounds (approximately 4,200 Β°C).
Using self-propagating high-temperature synthesis, NUST MISIS scientists obtained aΒ material HfC0.5N0.35, (hafnium carbonitride) close toΒ the theoretical composition, with a hardness ofΒ 21.3Β GPa, which isΒ even higher than inΒ new promising materials, such asΒ ZrB2/SiC (20.9Β GPa) and HfB2/SiC/TaSi2(18.1Β GPa).
Veronika Buinevich, NUST MISIS post-graduate student, commented: βItβs hard toΒ measure aΒ materialβs melting point when inΒ exceeds 4000 Β°Π‘.Β Therefore, weΒ decided toΒ compare the melting temperatures ofΒ the synthesized compound and the original βchampionβ, hafnium carbide. ToΒ doΒ this, weΒ placed compressed HFC and HfCN samples onΒ aΒ graphite plate shaped like aΒ dumbbell, and covered the top with aΒ similar plate toΒ avoid heat loss.β
Scientists then connected aΒ battery using molybdenum electrodes. All tests were performed inΒ aΒ deep vacuum, so the cross-section ofΒ graphite plates differs, the maximum temperature was reached inΒ the narrowest part ofΒ it. The resulting simultaneous heating ofΒ the new material, carbonitride and hafnium carbide showed that the carbonitride has aΒ higher melting point than hafnium carbide.
AtΒ the moment the specific melting point ofΒ the new material isΒ above 4,000Β Β°C, but could not beΒ determined precisely inΒ the laboratory.
InΒ the future, the team plans toΒ conduct experiments to measure the melting temperature byΒ high-temperature pyrometry using aΒ laser orΒ electric resistance and toΒ study the performance ofΒ the resulting hafnium carbonitride inΒ hypersonic conditions.
