A team of researchers at the Ohio State University headed by Nitin Padture, College of Engineering Distinguished Professor at the university, have invented a new type of ceramic coatings that could effectively protect jet engines from volcanic ash.
During the research, the scientists examined two coatings that were initially developed to offer protection to jet engines against airborne sand. It was established that these coatings can also protect jet engines from ash sediments. The major component of ash is silica. In April 2010, the historic eruption of the Eyjafjallajokull volcano in Iceland generated significant amount of silicate ash.
Padture stated that like sand ash, ash is highly dangerous. However depending on the volcano type, its composition differs widely. Padture added that after Eyjafjallajökull volcano eruption, the team decided to study the interaction of ash with the new heat-resistant coating and to assess if the fundamental damage mechanism were the same or different.
Andrew Gledhill and Julie Drexler, doctoral students, placed specimens of the ceramic coatings on metal pieces and then coated the samples with ash obtained from the Eyjafjallajokull explosion. The elevated temperature in a jet engine was simulated by heating the samples in a furnace. They did the experiment using a standard jet engine coating as well as two sand-resilient coatings. One of the sand-resilient coatings was Padture's formula, comprising d alumina and zirconia and the other was a new formula derived from gadolinium zirconate. They found that the standard jet engine coating was badly impaired by the molten ash and the other two sand-resilient coatings maintained their chemical structure.
The researchers examined the cross-sections of the samples and found that the molten ash had pierced through the apertures of the standard ceramic coating but did not pierce through the other two coatings and just filled the apertures near the coatings’ surface.
Chemical assessment showed that the ash developed an anorthite mineral layer beneath the surface of the alumina and formed a thin layer of the apatite mineral on the gadolinium zirconate. This chemical interaction prohibited the ash from diffusing into the coatings. However huge quantities of ash can block a jet engine briefly, making it to stop. Hence, these coatings would not be beneficial in adverse situations.
The research was published online in the Advanced Materials journal.