Research heats up in Princeton Materials Institute

Anthony Evans, director of the Princeton Materials Institute, wants to add some heat to the electric power industry. About 200 degrees, to be exact.

Anthony Evans, director of the Princeton Materials Institute, holds a small cross-section of a turbine that has been coated with sophisticated ceramics to deflect heat. Evans is leading a consortium of six universities in an effort to develop protective materials that could allow gas-fired electric power plants and jet engines to run at considerably higher temperatures, burn less fuel and produce less pollution.


Evans is leading a consortium of six universities in an effort to develop protective materials that could allow gas-fired electric power plants and jet engines to run at considerably higher temperatures, burn less fuel and produce less pollution. Materials and knowledge created in the project also could solve a range of problems related to semiconductor design in the electronics industry.

"We're fairly confident we'll have a new class of materials within the next five years," said Evans.

In gas-fired power plants, exhaust from burning natural gas drives turbines, which spin and generate electricity. The hotter the gas, the more efficient the plant is, said Evans. State-of-the-art cooling systems already allow plants to run at about 1,200 degrees centigrade, which is hotter than the melting point of their metal parts, but the approach results in pollution. Under a five-year, $5 million grant from the Office of Naval Research, Evans and his colleagues hope to push that temperature to as much as 1,400 degrees. "Even 100 degrees in that industry is a big deal, so 200 degrees would be spectacular," he said.

The most promising approach, the researchers believe, is to develop materials called "thermal barrier coatings" -- sophisticated ceramics that coat the surfaces of the gas turbines and deflect heat. These materials are such poor conductors of heat that a sheet just one-tenth of a millimeter in thickness would outperform a freezer door -- the equivalent of allowing ice cubes and boiling water to exist side by side.

The challenge, said Evans, is finding materials that will stay attached to the turbines. A critical problem is that the metal turbine and the protective coating are likely to expand at different rates as the temperature increases, which would tend to make the coating flake off.

"At that stage, the heat gets to the underlying metal and you've got a real problem," said Evans.

The researchers are investigating the physical processes that cause these failures. Based in those insights, they are developing new ceramic materials using a technique called "combinatorial synthesis."

By mixing and matching molecules in different combinations, they create a "library" of hundreds of compounds, each slightly different from the next, and deposit small quantities of each on a chip. They use lasers to heat each sample and measure how they respond. The technique is similar to that used by pharmaceutical developers looking for candidates for new drugs.

Apart from improving power generation, one result of the research could be improved materials and techniques for building electronic components, which can fail or perform poorly when exposed to heat.

It's a tall order, but the project, while still in its first year, already has some candidate materials in development. Researchers from the participating institutions met on campus Sept. 20-22 for a three-day workshop to discuss their results and plan their next steps. "We're making progress," said Evans.

Collaborators in the project include Case Western University, Harvard University, the University of California Santa Barbara, the University of Pittsburgh and the University of Virginia, in addition to several government labs and private companies.

The Princeton Materials Institute is a multidisciplinary center for education and research in materials science. It fosters collaborations between nearly 60 affiliated faculty members from chemistry, physics and the different branches of engineering.

October 9, 2000
Vol. 90, No. 5
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Spotlight / People
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