RMIT University uses AM in cooling catalysts for hypersonic flight

November 19, 2021

A range of experimental designs for the additively manufactured catalysts (Courtesy RMIT University)

Researchers at RMIT University, Melbourne, Australia, have developed additively manufactured catalysts that could potentially be used to cool airplane systems during hypersonic flight. A research paper on this project was published in ‘Zeolites on 3D-printed open metal framework structure: metal migration into zeolite promoted catalytic cracking of endothermic fuels for flight vehicles the paper’ by Roxanne Hubesch, Maciej Mazur, Karl Föger. Selvakannan Periasamy, and Suresh K Bhargava in Chemical Communications, a Royal Society of Chemistry journal.

Lead researcher Dr Periasamy said this work tackled one of the biggest challenges in the development of hypersonic aircraft: controlling the incredible heat that builds up when planes fly at more than five times the speed of sound.

“Our lab tests show the 3D printed catalysts we’ve developed have great promise for fuelling the future of hypersonic flight,” he stated. “Powerful and efficient, they offer an exciting potential solution for thermal management in aviation and beyond. With further development, we hope this new generation of ultra-efficient 3D printed catalysts could be used to transform any industrial process where overheating is an ever-present challenge.”

Only a few experimental planes have reached hypersonic speed (defined as above Mach 5; over 6,100 km/hour or 1.7 km/second). Theoretically, a hypersonic aircraft could travel from London, UK, to Sydney, Australia, in four hours, but many challenges remain in the development of hypersonic air travel. One such challenge is the extreme heat levels generated. PhD researcher Roxanne Hubesch believes that using fuel as a coolant is one of the most promising experimental approaches to the overheating problem.

“Fuels that can absorb heat while powering an aircraft are a key focus for scientists, but this idea relies on heat-consuming chemical reactions that need highly efficient catalysts,” she stated. “Additionally, the heat exchangers (where the fuel comes in contact with the catalysts) must be as small as possible, because of the tight volume and weight constraints in hypersonic aircraft.”

To make the new catalysts, the team used Laser Beam Powder Bed Fusion (PBF-LB) to additively manufacture tiny heat exchangers made of metal alloys and coated them with synthetic minerals known as zeolites.

The researchers then replicated, at lab scale, the extreme temperatures and pressures experienced by the fuel at hypersonic speeds to test the functionality of their design. When the additively manufactured structures heat up, some of the metal moves into the zeolite framework– a process crucial to the unprecedented efficiency of the new catalysts.

“Our 3D printed catalysts are like miniature chemical reactors and what makes them so incredibly effective is that mix of metal and synthetic minerals,” Hubesch added. “It’s an exciting new direction for catalysis, but we need more research to fully understand this process and identify the best combination of metal alloys for the greatest impact.”

The next steps for the research team from RMIT’s Centre for Advanced Materials and Industrial Chemistry (CAMIC) include optimising the additively manufactured catalysts by studying them with X-ray synchrotron techniques and other in-depth analysis methods. The researchers hope to extend the potential applications of this work into air pollution control for vehicles and miniature devices to improve indoor air quality, something especially relevant in managing airborne respiratory viruses like COVID-19.

CAMIC Director, Professor Suresh Bhargava, said the trillion-dollar chemical industry was largely based on old catalytic technology. “This third generation of catalysis can be linked with 3D printing to create new complex designs that were previously not possible,” Bhargava stated. “Our new 3D printed catalysts represent a radical new approach that has real potential to revolutionise the future of catalysis around the world.”

Study co-author Dr Maciej Mazur, from the RMIT Centre for Additive Manufacturing, said the work was a strong example of innovation made possible through cross-disciplinary collaboration: “Combining Additive Manufacturing with chemical sciences has produced groundbreaking results.”

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