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New process purifies high-temp ceramics.

How annoying when a dinner plate cracks in the dishwasher. But what if that dinner plate were part of a jet engine?

Under intense heat and pressure, ceramics can crack. A big difference between household ceramics (like teacups or sinks) and high-temperature ceramics (like engine parts or capacitors) is purity. For a ceramic to withstand big loads and temperatures (above 1,200 [degrees] C), it must be free of impurities.

Now, a new purification process promises to improve high-temperature ceramics. Developed at NASA's Lewis Research Center in Cleveland, the new method uses compounds derived from guanidine to remove sodium and potassium residues that show up when the ceramics are fired in their molds.

"These [guanidine-derived] chemicals have direct use in the aerospace industry," says senior research chemist Warren H. Philipp, who invented the process. "We can use them to form lightweight, corrosion-resistant ceramic parts leading to more efficient aircraft engines and rocket motors." The process also may improve capacitors and superconductors, he says.

Typically, ceramic parts come from powders, which are mixed with solvents, poured into molds, and fired in kilns. Usually, some sodium and potassium residues remain, compromising the ceramic's integrity. Often this imperfection doesn't matter. But at high temperatures and stress, residues can cause cracks.

The new guanidine-based process, however, removes virtually all sodium or potassium residue. The result, says Philipp: purer, stronger, and more corrosion-resistant ceramic products.
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Title Annotation:new process uses guanidine-derived compounds to remove sodium and potassium residues in high temperature ceramics
Publication:Science News
Article Type:Brief Article
Date:Aug 21, 1993
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