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Ever-finer powders for improved ceramics.

Many materials stretch life taffy: They get weaker as they are pulled and eventually beak. But some metals and a few ceramics are "superplastic": They can deform quite a bit before losing any of their integrity. This means that scientists or manufacturers can mold these materials into desired shapes, something they have difficulty doing with most ceramics.

Canadian scientists have now worked out a way to create new superplastic ceramics by using much finer starting materials than those typically used. The finer the starting powder, the finer the grain in the finished ceramic and the more likely it is to be superplastic, explains David S. Wilkinson, a materials engineer at McMaster University in Hamilton, Ontario.

In a process known as tape-casting, he and his colleagues use a slurry of aluminum powder to make a thin film. In order for this process to work, the researchers first had to figure out how to make the slurry liquid enough to pour on a plate, where the film then forms, Wilkinson says. They also add zirconium to help prevent clumping of the powder grains. To make the finished material, they then stack layers of film.

Tape-cast superplastic ceramics may prove useful for making wear-resistant coatings or cutting tools, Wilkinson says.
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Title Annotation:Materials Research Society report
Author:Pennisi, Elizabeth
Publication:Science News
Date:Dec 21, 1991
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