This Synthetic Mother of Pearl is Ten Times Tougher Than Ceramics

By Jamie Condliffe on at

Ceramics are an increasingly common material to work with—from hard-wearing bearings to heat-proof cladding on spacecraft—but they all share one fatal weakness: they're fragile. Now, though, inspired by nature, researchers are making a ceramic that mimics mother of pearl—and is ten times stronger than normal ceramics.

The material, developed by researchers from the Laboratoire de Synthèse et Fonctionnalisation des Céramiques at CNRS, closely mirrors the structure found in mother of pearl—the material created by the small single-shelled marine mollusc abalone, and the one that forms the outer surface of pearls. It's desirable to mimic that because it's strong and resilient—but sadly, it's also incredibly expensive.

The structure of mother of pearl is what makes it so special. Composed of 95 per cent calcium carbonate—which is itself intrinsically fragile—under the microscope it looks like a stack of bricks (on the left in the top image), all stuck together with a kind of mortar made from proteins. The complex structure means it's incredibly hard for cracks to propagate through it—making it extremely tough.

Inspired by mother of pearl, the material scientists decided to build their own miniature bricks out of alumina powder formed into microscopic platelets. They then suspended them in water, left them to form a closely packed sediment, cooled the mixture gradually to grow ice crystals that forced the platelets into neatly ordered stacks, and finally heat-treated the whole thing to drive out water and make the resulting material more dense.

The result, published in Nature Materials, is a substance that is ten times stronger than a conventional ceramic and retains its properties at temperatures up to 600°C. Just like mother of pearl, it resists cracks because of its brick-like structure (on the right in the image above), so cracks have to travel a long way to make any impact on the integrity of the material. Not just that, though: the researchers claim it should be no more expensive to make than other common ceramics, and way cheaper than mother of pearl itself.

The manufacturing technique could also be applied to other base powders, too, as long as they can be used to form the neat little platelets. Regardless, though, the material is super-tough and fairly cheap—so it's likely it will soon start appearing in everything from replacement joints to armour plating. You can thank a mollusc for the inspiration. [Nature via PhysOrg]