Eyed Shape Changing Ceramics for Medical Devices, Electronics

Researchers have found a way to create ceramic materials that can change shape, which could mean significant improvements for a range of electronic and medical devices, they said.

An international team of researchers from the University of Minnesota Twin Cities and the University of Kiel in Germany have created a way to produce a reversible shape-memory ceramic by changing the chemical structure of the material.

Gu, et al., University of Minnesota and University of Kiel

A diagram shows what happened when researchers attempted to create shape memory ceramics with a sample of ceramic material. Instead of improving the deformability of the ceramic, they observed that some specimens gradually collapsed into a pile of powder, a phenomenon they called “seepage.”

Ceramics are perhaps best known for their use in dishes and plates, but due to their semiconducting, superconducting, ferroelectric and insulating properties, they also have many uses in electronic applications.

Yet, while useful, shape memory has so far been a feature reserved for alloys and polymer-based materials, while ceramics are known to be brittle and break fairly easily. Anyone who has ever dropped their favorite coffee mug in the kitchen has experienced it.

“Shape-memory ceramics would be a whole new type of functional material,” said Richard James, a distinguished professor in the Department of Aerospace Engineering Mechanics at the University of Minnesota. “

Indeed, these types of materials could be used in electronics that can withstand higher temperatures or corrosive environments – such as shape memory actuators – or to create ferroelectric ceramics, in which phase transformation can. be used to generate electricity from small temperature differences, he mentioned.

Opening the way

Creating shape-memory ceramics was not a straightforward process for researchers, they said. First, they attempted to achieve this by using a solution that in the past worked for the discovery of new shape memory metallic materials. This involves adjusting the distances between atoms using changes in composition so that the two phases fit together well, they said.

However, this solution did not give them the expected results. On the contrary, instead of improving the deformability of ceramics, the attempt left them with ceramics that exploded during their passage through the transformation phase, while others collapsed into a pile of powder, a phenomenon that the researchers called “crying”.

Eventually, the researchers achieved a solid-to-solid phase transformation that was reversible, easily transforming between phases, similar to the characteristic of a typical shape memory material, they said.

“More precisely, when cooling kinematically compatible ceramics (Zr / Hf) O2(YNb) O4 Through its transformation from tetragonal to monoclinic phase, the polycrystal slowly and steadily disintegrates at its grain boundaries (a process we call weeping) or even disintegrates explosively, ”they explained in a summary for an article detailing their work in the newspaper Nature. “If, instead, we adjust the network parameters to satisfy a stronger ‘equidistance’ condition (which also takes into account the shape of the sample), the resulting material exhibits reversible behavior with low hysteresis. . “

Although the researchers have not yet fully solved the puzzle, the mathematical conditions under which they achieved a reversible transformation can be widely applied to pave the way for paradoxical shape memory ceramics, they said.

“The theory developed on this basis does not only describe the behavior [of the materials] but also shows the way forward to achieve the desired compatible shape memory ceramics, ”said Eckhard Quandt, co-author of the article and professor at the Institute for Materials Science at the University of Kiel.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for over 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York. In her spare time, she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

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