March 25, 1996
Five years of work has yielded a ceramics breakthrough-a material
similar to what's used for dinner plates, but so tough it may end up as
armorplate on tanks. "We're also looking at pistons and turbines"
for auto and jet engines, says the material's developer, William W. Predebon
of Michigan Technological University in Houghton. Another possible use:
Industrial cutting tools that easily chew through high-strength metals.
The secret of the new alumina ceramic? Predebon took things out of the usual ceramic mix. Ceramics are difficult to process, so they normally contain sintering aids to help hold the ceramic mix together. But when Predebon inspected ceramic fractures under a microscope, he noticed the breaks often occur in the sintering additives. So he removed that weak link by developing a new processing method, using a hot vacuum press, that doesn't need additives.
The resulting material is to tough it doesn't break until he applies 50% more pressure than alumina ceramic is supposed to tolerate. Under normal conditions, it can withstand almost as much pressure as tungsten-carbide steel, one of the strongest materials around. And under high loading-such as extreme pressure from the impact of an artillery shell-the ceramic's toughness actually increases, beating tungsten-carbide steel by 37%.
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