December 8th, 02008 by Alexander Rose - Twitter: @zander
The MIT Tech Review published an article last week on a new type of engineered ceramic from UC Berekeley that is tough and resilient instead of the usual brittle stuff that allows cracks to propagate. They did this by engineering the structure to be more like that of mother of pearl found in abalone shells. While they laud it for its high performance applications, we are quite interested in it as a long lasting material for the 10,000 Year Clock. We already plan on using engineered ceramics for bearings and other wear components, but the elimination of ceramics only real drawback, that it can shatter, really opens up the engineering possibilities.
From the article:
“To shape their ceramics into nacre-like structures, the Berkeley researchers first create a water suspension of the material to be patterned–in this case, aluminum oxide. Then they chill it in a very controlled way. “You take the heat out at one end,” explains Ritchie. This leads to long, thin structures that the researchers press into microscale, brick-like structures after heating them to evaporate the water. When this process is repeated, it creates a layered, porous structure of aluminum oxide bricks connected to one another by column-like structures–the same shapes found in natural nacre. Then, to mimic the protein glue in the abalone shell, the researchers fill the spaces with a polymer. This process is described online in the journal Science this week. Other groups have made thin films of biomimetic materials; the Berkeley group has succeeded in making large pieces.
The scanning electron microscope image (lower image above), taken during a stress test, shows one source of the material’s toughness: damage is widely distributed in small, contained cracks.”