Hypersonic Aircraft are now More Likely Thanks to a Newly Developed Ceramic Coating

There are a few reasons why you aren't flying across the country in hypersonic aircraft, but the simplest of them is heat: when you travel at speeds over Mach 5, the ultra-high temperatures (around 3,600F to 5,400F) strip layers from metal. How do you protect a vehicle when even the toughest ceramic tiles can't handle those conditions? A team of British and Chinese researchers might have the answer. They've engineered a carbide-based ceramic coating that's about 12 times more effective than current ceramics, making hypersonic aircraft more realistic.

The structural problems are primarily caused by processes called oxidation and ablation. This occurs when extremely hot air and gas remove surface layers from the metallic materials of the aircraft or object travelling at such high speeds. To combat the problem materials called ultra-high temperature ceramics (UHTCs) are needed in aero-engines and hypersonic vehicles such as rockets, re-entry spacecraft and defense projectiles.

The trick was to rely on a different manufacturing technique, reactive melt infiltration, to give the coating a unique structure that's both extremely strong and resistant to oxidization. The next-best conventional coating, zirconium carbide, can withstand heat but is prone to degrading.

Professor Ping Xiao, Professor of Materials Science, who led the study in University of Manchester explains: 

“Current candidate UHTCs for use in extreme environments are limited and it is worthwhile exploring the potential of new single-phase ceramics in terms of reduced evaporation and better oxidation resistance. In addition, it has been shown that introducing such ceramics into carbon fibre- reinforced carbon matrix composites may be an effective way of improving thermal-shock resistance.”

Any commercial use of the coating is a long ways off, if just because the hypersonic vehicles themselves are still a distant prospect. If it works well in practice, though, those extreme speeds would be feasible without compromising safety, especially in the long term. You'd see hypersonic aircraft that could fly you to another side of the planet within a couple of hours, and spacecraft that could return to Earth without needing frequent ceramic tile inspections and replacements. In short, flights that were once extra-risky could become virtually commonplace.

Advanced Materials

Advanced materials is one of The University of Manchester’s research beacons - examples of pioneering discoveries, interdisciplinary collaboration and cross-sector partnerships that are tackling some of the biggest questions facing the planet.

Referecne: "Ablation-resistant carbide Zr0.8Ti0.2C0.74B0.26 for oxidizing environments up to 3,000 °C" Yi Zeng, Dini Wang, Xiang Xiong, Xun Zhang, Philip J. Withers, Wei Sun, Matthew Smith, Mingwen Bai & Ping Xiao Article number: 15836 (2017) doi:10.1038/ncomms15836 

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