Now, researchers have discovered that a new class of ceramic coatings could offer jet engines special protection against volcanic ash damage in the future.
For a study published online in the Early View edition of the journal Advanced Materials, the researchers tested two coatings that were originally developed to keep airborne sand from damaging jet engines, and found that the coatings also resist damage caused by ash deposits.
“Of course, it’s best for jets to avoid ash in the first place,” said Nitin Padture, College of Engineering Distinguished Professor at the Ohio State University, who led the study. “That’s not always possible. We determined that these coatings could offer sufficient protection against small amounts of ash ingested by the engine over time.”
However, large amounts of ash can temporarily jam a jet engine and cause it to stall, he explained. These coatings would not be useful in those extreme circumstances.
Temperatures inside an engine reach up to 2,500 degrees Fahrenheit, and ceramic thermal-barrier coatings insulate metallic engine parts from that heat. The ingested ash melts onto the coating and penetrates the coating. Upon cooling, the molten ash forms a brittle glass that flakes off, taking the coating with it.
It’s a familiar story to Padture, who previously invented a new coating composition to prevent similar engine damage caused by sand.
Like sand, ash is made mostly of silica. When the Icelandic volcano Eyjafjallajökull erupted in April 2010, it billowed clouds of silicate ash.
“Ash poses a threat very similar to sand, but ash composition varies widely depending on the type of volcano. After what happened in Iceland, we wanted to see how ash interacted with our new thermal barrier coating, and whether the underlying damage mechanisms were any different,” he said.
Doctoral students Julie Drexler and Andrew Gledhill took samples of the ceramic coatings on pieces of metal, and coated them with ash from the Eyjafjallajökull eruption. Then they heated the samples in a furnace to simulate the high temperatures created in a jet engine.They experimented with a typical jet engine coating and two sand-resistant coatings. One was Padture’s formula, containing zirconia and alumina, and the other was a commercially available new formula based on gadolinium zirconate.
Looking at cross-sections of the samples, the researchers saw why: molten ash had penetrated through the pores of the typical ceramic coating all the way to its base. But in the other two, the molten ash barely penetrated.
Drexler explained why the pores are important.
“Pores give the coating its strain tolerance,” she said. “They make room for the coating to expand and contract as the engine heats up while flying, and as it cools after landing. When all the pores are plugged with ash, the coating can’t adjust to the temperature anymore, and it breaks off.”
On the sand-resistant coatings, the ash filled the pores only near the surface. Chemical analysis revealed that the ash reacted with the alumina in the first coating to produce a thin layer of the mineral anorthite below the surface, while on the gadolinium zirconate it produced a layer of the mineral apatite.
"The chemical reaction arrests the penetration of the ash into the coatings," Gledhill said. "The unaffected pores allow the coating to expand and contract."
Now, the researchers are repeating their experiment with a new setup. They are heating samples over and over with a powerful blowtorch, and letting them cool in between to more closely simulate engine conditions.
Both sand-resistant coatings are more expensive than the typical coating, but the researchers think that the benefits outweigh the cost.
“This study’s not going to solve all the problems of ash clouds and jet engines, but we are making progress, and we’ve learned a lot about the physics of the situation,” Padture said.
But that’s not all they learned.
“We also learned how to pronounce ‘Eyjafjallajökull.’”
Ohio State coauthors on the Advanced Materials paper included postdoctoral scholar Kongara Reddy. The engineers collaborated with Kentaro Shinoda and Sanjay Sampath of Stony Brook University and Alexander Vasiliev of the Russian Academy of Sciences. University of Iceland volcanologist Niels Óskarsson provided samples of Eyjafjallajökull ash.
Funding for this research was provided in part by the Office of Naval Research, the Department of Energy, and the National Science Foundation.Contact: Nitin Padture, (614) 247-8114; Padture.firstname.lastname@example.org
Nitin Padture | EurekAlert!
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
New process produces hydrogen at much lower temperature
01.12.2016 | Waseda University
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy