Diamondlike Paint Makes Jet Engines Faster

The latest use for zirconia -- similar to the cubic zirconia found in those ubiquitous faux diamonds -- won't be sold in any mall boutiques. Scientists at Ohio State University have developed a way to protect jet engines by coating turbine blades with the stuff, helping the engines burn hotter and cleaner.
The new zirconia-based coating stops sand from damaging the engines, making them faster, more fuel efficient and longer lasting.
"A hotter engine means you aren't wasting heat and using up all the energy...It also burns better, hotter and cleaner," said Nitin Padture, one of the study's authors and a professor at Ohio State.
The blades Padture and his colleagues plan to coat are on the front of the engine. Their job is to suck air into the engine and increase the pressure inside, where fuel is injected and ignited. The super-heated, high-pressure air then shoots out of the engine, propelling the aircraft forward.
The temperature extremes inside the engine can cause it to expand and contract like an accordion. A special coating of zirconia dioxide inside already protects engines as they heat up and cool.
The new coating adds aluminum and titanium to the zirconia on the blades outside.
"As the hot glass penetrates the coating, there is now a reservoir of titanium and aluminum, which crystallizes the glass" made by infiltrating sand, said Padture. "Once it's a crystal, it halts its progress into the engine."

The molten glass eats away at the protective coating during flights, exposing the vulnerable metal beneath. When the engine cools, so does the glass, sometimes causing cracks in the coating the next time the engine expands.
Aircraft undergo a rigorous inspection before flights, which picks up on these kinds of problems, said Ben Nagaraj, an engineer at General Electric who works on aircraft engines.
According to Nagaraj, there have been no in-flight failures of the kind that the new zirconia coating would stop.
But the coating, if adopted by commercial and military jets, could let jets burn their engines at higher temperatures, saving fuel and increasing speed.
"This coating would typically be used in helicopter engines, maybe some jets in the Middle East, both commercial and military engines," said Nagaraj.
"It will help increase the efficiency and lifetime of engines," said Nagaraj, "but it will be several years before the coating sees the light, or heat, of an engine."
The research appeared in a recent issue of the journal Acta Materialia.