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Ceramics go to new lengths.

Ceramics go to new lengths

Like unexceptional children who discover exceptional talents later in life, ceramics recently have been revealing abilities that no one suspected they had. In 1986, for example, ceramics became celebrities as high-temperature superconductors. In the March 29 NATURE, Fumihiro Wakai of the Government Industrial Research Institute in Nagoya, Japan, and his co-workers describe another unanticipated talent of certain ceramics: superplasticity. Using mostly silicon nitride and silicon carbide, the scientists fabricated ceramic strips, then stretched the still-hot strips to more than 2-1/2 times their starting lengths.

The ceramic composite's ability to stretch during processing brightens hopes for using silicon nitride and silicon carbide -- already known for their hardness and strength -- where they have never been used before. For example, Wakai and his colleagues suggest engineers might readily mold superplastic ceramics into intricate shapes that require little or none of the expensive post-production machining that has mostly prevented ceramics from replacing metals in large-scale applications such as wear-resistant engine parts.

"Ceramics have always been brittle materials that you could not deform much," observes materials scientist Rishi Raj of Cornell University. "This is something really brand new."
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Title Annotation:superplasticity
Publication:Science News
Date:Mar 31, 1990
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