The wisdom of ceramics

The institute's scientists discovered that under certain conditions, cerium gadolinium oxide behaves like a kind of rubber, and not like a normal ceramic material: similar to a rubber ball, this material adapts itself to the shape imposed on it from the outside, but as soon as the external restrictions are removed - it returns to its original shape

  
Prof. Igor Lubomirsky. adaptation
smart. flexible. Copes well with pressures. Adapts quickly to new situations. Sound like a top candidate for a challenging role? True, but the "candidate" is an unconventional ceramic material capable of adapting, on its own, to difficult and changing conditions. Prof. Igor Lubomirsky, from the Department of Materials and Surfaces, in the Faculty of Chemistry at the Weizmann Institute of Science, who discovered the surprising properties of this material, says that this discovery may lead, in the future, to
for new research and many industrial applications.
This is a rather surprising discovery, since the substance, cerium gadolinium oxide, has been known for more than 15 years, but was never considered unusual by any means. This material is created by combining gadolinium with cerium oxide. Prof. Lubomirsky: "Imagine if you found out that your neighbor across the street, who for years you thought was of average intelligence, has the IQ of a genius."
The institute's scientists discovered that under certain conditions, cerium gadolinium oxide behaves like a kind of rubber, and not like a normal ceramic material: similar to a rubber ball, this material adapts itself to the shape imposed on it from the outside, but as soon as the external limitations are removed - it returns to its original shape. To discover this surprising feature, the scientists developed a drum-shaped structure, whose "head", which is connected at the edges to the frame, is made of a thin layer (less than one micron) of the ceramic material. At room temperature the layer was flat and fit exactly to the frame. But during heating, unexpected phenomena began to occur.
The scientists expected that, as a result of heating, the ceramic layer would behave differently than the drum frame would react. The frame was supposed to change very little, while the ceramic layer was expected to swell and protrude upwards. But the "smart" ceramic remained flat all the way when heated slowly, even when the heat reached 180 degrees Celsius. Surprisingly, even when it was gradually cooled back down, it kept its original shape and no crack formed in it. From this, the scientists concluded, that this ceramic material has a sophisticated internal mechanism that allows it to adapt itself to the frame at any temperature - provided that the change takes place gradually. When the material was heated to a temperature of 180 degrees Celsius at once, it swelled and protruded. When they cooled it all at once - it cracked. Just like any high-end ceramic.
The time factor seems to have played a crucial role in both scenarios: when it had enough time to adjust to heating or cooling, the ceramic material was soft as rubber, but when it didn't have enough time, it succumbed to the pressures of the rapid change, and broke. A rubber ball also behaves in a similar way: when it is compressed slowly, it changes its shape to adapt to the pressure and returns to its original shape when it is released, but when it is a quick blow - such as, for example, when it is thrown to the floor - it resists the change of shape, which causes Let it float back up.
What is the mechanism that makes the ceramic material so "smart" and adaptable? The secret comes from two types of point defects in the material, which are created in the process of its formation. The first defect is the atoms of gadolinium that penetrate into the cerium oxide. The second defect is the voids that are created when the gadolinium atoms push out the oxygen atoms in the cerium oxide. These spaces allow the defects to move and change places in the material, just like people change places in a movie theater that has many empty seats left.
For example, when the material cools, the elastic energy created as a result of pressure and heat is partially lost, which causes the defects to adhere and organize the material in a more "economical" state, the existence of which requires less energy. As a result, the volume of the material gradually decreases, which allows it to remain flat and crack-free.
Prof. Lubomirski says that many other substances may have similar properties of dealing well with stressful situations. Together with the members of the research group he heads, he developed the theoretical basis for the rubber-like behavior of ceramic materials, and then proved this theory in experiments. Research student Anna Kosovoi from the Department of Materials and Surfaces, Dr. Yishai Feldman and Dr. Alan Wachtel from the Chemical Research Infrastructures Unit at the Weizmann Institute of Science, as well as Prof. Joachim Meyer from the Max Planck Institute participated in this study.
Condensed material in Stuttgart, Germany. The research findings were recently published in the scientific journal Advanced Functional Materials.
A material that is able to maintain its original shape at any temperature can be very useful in many applications - for example, in devices that heat up and cool down alternately. These include certain fuel cells - devices that convert chemical energy into electricity - which are now being built from ceramic materials from the same family to which cerium gadolinium belongs. It is possible that such devices will be used in the future as power supplies for portable computers. It is customary to turn such devices on and off frequently, so they heat up and cool down suits. In these situations, a smart material, which is able to adapt to different and changing temperatures, can prevent the formation of cracks and damage.
The smart ceramic material can help produce microscopic devices designed to perform precise measurements in a repeatable way, such as micro-sensors or micro-pumps in medical equipment. Mass production of identical parts
Such devices pose many engineering challenges, which can be overcome by using a ceramic material that changes its shape to adapt itself exactly to the frame of the device. The demand for microtechnologies will undoubtedly increase in the future, so a smart material, capable of bridging gaps and covering the limitations of existing engineering, may be required for many additional uses.