A new way to synthesise high-strength composites based on MAX phases for the aerospace industry and nuclear energy has been developed by scientists from the Engineering School of Nuclear Technologies at the Tomsk Polytechnic University (TPU). MAX phases are a large family of materials with more than 150 different compositions that have been extensively investigated during the last 25 years. They present a layered structure and a unique combination of properties, bridging the gap between metallic and ceramic properties. However, despite their excellent oxidation resistance up to 1400°C under corrosive environment, good damage and radiation tolerance, thermal shock resistance, and self-crack healing, their application has been limited by three main factors: the complexity of this large family of materials; unavailability of highly pure commercial powders; and the extensive time needed to license products in strategic fields such as nuclear or aviation.

The proposed technology at TPU makes it possible to obtain materials with a special structure that ensures their high operational characteristics, the university’s press service said. Ceramic materials are promising for use in the aerospace and transport industries, shipbuilding and nuclear energy. Compared with metals, they have high strength, heat resistance, can withstand sudden temperature drops and can withstand aggressive environments. However, a key disadvantage of ceramics is their fragility, which limits their use. The aim is therefore to develop new types of materials with high operational characteristics and to find effective ways to produce them.

"Scientists of experimental physics at the TPU Engineering School of Nuclear Technology synthesised composites based on MAX phase from mixtures of commercially available domestic powders using the original combined synthesis method, the report noted “First, they subjected the initial components to pre-thermal treatment in a vacuum furnace – powders of titanium, silicon and carbon of domestic production. After vacuum sintering at the second stage of synthesis, scientists applied the technology of spark plasma sintering, which is characterised by a high rate of consolidation of the powders of refractory compounds.”

Synthesised composites, due to their high-performance characteristics, can act both as independent materials and as an additive for new ceramic-matrix composites, able to compete with domestic and foreign counterparts due to the availability of raw materials and the expected high physical and mechanical characteristics. The study was supported by a grant from the Russian Science Foundation.

"Thanks to the quick sintering at the second stage of synthesis with the addition of the necessary components, it was possible to increase the content of the MAX phase by 10-15%. In addition, two-stage heat treatment contributes to the growth of MAX crystals almost twice. The results of mechanical tests showed that such a structure provides improved properties of the resulting composite,” according to Elizaveta Sedanova, an assistant at the experimental physics department of TPU.