Researchers at The University of Manchester have collaborated with Central South University in China to create a new kind of ceramic coating that could enable hypersonic travel for air, space and defense purposes.
Hypersonic travel means moving at Mach five or above, or at least five times faster than the speed of sound. When a projectile, aircraft or spacecraft moves at such high velocities, the heat generated by air and gas in the atmosphere is extreme, reaching anywhere from 2,000 to 3,000°C, and can have a serious impact on the structural integrity of the vehicle.
The main destructive processes are oxidation and ablation, where the extremely hot air and gas remove surface layers from the materials that make up the surface of the object travelling at such high speeds. Materials known as ultra-high temperature ceramics (UHTCs) are used to combat the problem, and are used in aero-engines and hypersonic vehicles such as rockets, re-entry spacecraft and defence projectiles.
However, currently available conventional UHTCs are unable to stand up to the rigours of hypersonic travel. Now, the multinational team of researchers have designed and fabricated a new carbide coating that is vastly superior in resisting temperatures up to 3,000°C, when compared to existing UHTCs such as Zirconium carbide (ZrC). In fact, the carbide coating is 12 times better than ZrC, an extremely hard refractory ceramic material which is commercially used in tool bits for cutting tools.
According to Philip Withers, a Professor from The University of Manchester, a plane flying at hypersonic speeds could travel between London and New York in just two hours, revolutionising both commercial and commuter travel.
"But at present one of the biggest challenges is how to protect critical components such as leading edges, combustors and nose tips so that they survive the severe oxidation and extreme scouring of heat fluxes at such temperatures cause to excess during flight," he said.
The much improved performance of the coating is due to its unique structural make-up and features. This includes extremely good heat resistance and massively improved oxidation resistance.
The coating is made using a process called reactive melt infiltration (RMI), which dramatically reduces the time needed to make such materials, and has been in reinforced with carbon–carbon composite (C/C composite). This makes it not only strong but extremely resistant to the usual surface degradation.