Brittle star shows the way to tougher ceramics

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Brittle star shows the way to tougher ceramics

December 07, 2017 - 20:39
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An international team of researchers have managed to unlock the secrets of the brittle star's focal lenses, paving the way to the creation of tougher ceramics.

Professor Boaz Pokroy in the experimental hutch of ESRF ID16B beamline with ESRF's scientist Julie Villanova.

The brittle star appears to hold the key to stronger ceramics. The brittle star can be found in coral reefs and has hundreds of focal lenses on its body. These powerful calcite lenses serve as its eyes.

After studying the brittle star for the past three years, a team of researchers led by the Technion-Israel Institute of Technology have deciphered its crystalline and nanoscale structure, and figured out the protective mechanism of its highly resistant lenses. The discovery can be applied to the creation of tougher ceramics.

Scientists from the University of Wisconsin (US), the Natural History Museum of Los Angeles county (US), the University of Trento (Italy) and the Charité Hospital in Berlin (Germany), as well as the ESRF-the European Synchrotron, Grenoble, France, were also part of the research team. The findings of their discovery was published in the recent issue of Science.

"We have discovered a strategy for making brittle material much more durable under natural conditions. It is 'crystal engineering' and tempering without heating and quenching—a process that could be very useful in materials engineering", explained Professor Boaz Pokroy, from the Institute's Department of Materials Science and Engineering.

As an illustration of the process, consider how tempered glass is produced. It is made by rapidly heating it, and then rapidly cooling it. This process causes the outer layer of the glass to cool down faster than the inner layer, thereby compressing the interior and increasing the strength of the glass.

The brittle star's lenses are powerful and accurate, but they are formed in the open sea, at room temperature.

According to the press release: "...the crucial stage in the process of lens formation is the transition from the amorphous phase—the phase between liquid and solid—to the crystalline phase. At this stage, calcite nanoparticles, which are rich in magnesium and characterised by a relatively low density, separate from the rest of the material. The difference in concentration of magnesium in the calcite particles causes various degrees of hardness, density, and pressure in different regions of the material. Magnesium-rich particles press on the inner part of the lens as it crystallises and 'temper' it into a clear and tough crystalline material."

The team's discovery can be applied to strengthen synthetic ceramic materials in items like optical lenses, automatic turbochargers, biomaterial implants, etc.

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