Indian boffin developing fake diamond technology to help jet engines take the heat

March 18th, 2008 - 4:58 pm ICT by admin  

Washington, March 18 (ANI): Soon, engines of military aircrafts and jets will be able to run hotter and more efficiently, thanks to Ohio State University engineers led by an Indian scientist, who are developing a technology to combat high-temperature corrosion.

Nitin Padture, professor of materials science and engineering at Ohio State, and his team is developing a technology to coat jet engine turbine blades with zirconium dioxide, commonly called zirconia, the stuff of synthetic diamonds.

The zirconia chemically converts sand and other corrosive particles that build up on the blade into a new, protective outer coating. In effect, the surface of the engine blade constantly renews itself.

Padture said that ultimately, the technology could enable manufacturers to use new kinds of heat-resistant materials in engine blades, so that engines will be able to run hotter and more efficiently.

He added that he had military aircraft in mind when he began the project.

In the desert, sand is sucked into the engines during takeoffs and landings, and then you have dust storms. But even commercial aircraft and power turbines encounter small bits of sand or other particles, and those particles damage turbine blades, said Padture, who received a B.Tech. in Metallurgical Engineering from the Indian Institute of Technology, Bombay (1985), a M.S. in Ceramic Engineering from Alfred University (1987), and a Ph.D. in Materials Science and Engineering from Lehigh University (1991).

Jet engines operate at thousands of degrees Fahrenheit, and blades in the most advanced engines are coated with a thin layer of temperature-resistant, thermally-insulating ceramic to protect the metal blades. The coating, referred to as a thermal-barrier coating, is designed like an accordion to expand and contract with the metal.

However, one problem is that the sand melts and becomes glass when it hits the hot engine blade.

Molten glass is one of the nastiest substances around. It will dissolve anything, Padture said.

The hot glass chews into the ceramic coating. But the real damage happens after the engine cools, and the glass solidifies into an inflexible glaze on top of the ceramic. When the engine heats up again and the metal blades expand, the ceramic coating cant expand, because the glaze has locked it in place. The ceramic breaks off, shortening the life of the engine blades.

Padture and his colleagues described how the new coating forces the glass to absorb chemicals that will convert it into a harmless — and even helpful — ceramic.

The key, Padture said, is that the coating contains aluminum and titanium atoms hidden inside zirconia crystals. When the glass consumes the zirconia, it also consumes the aluminum and titanium. Once the glass accumulates enough of these elements, it changes from a molten material into a stable crystal, and it stops eating the ceramic.

The glass literally becomes a new ceramic coating on top of the old one. Then, when new glass comes in, the same thing will happen again. Its like its constantly renewing the coating on the surface of the turbine, he said.

Padtures former university has applied for a patent on the technique that he devised for embedding the aluminum and titanium into the zirconia. Hes partnering with Inframat Corp., a nanotechnology company in Connecticut, to further develop the technology.

Padture stressed that the technology is in its infancy. He has yet to apply the coatings to complex shapes, and cost is a barrier as well: the process is energy-consuming.

The technology is described in the recent issue of the journal Acta Materialia. (ANI)

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