The Quasicrystal Laureate
Dan Shechtman, the Philip Tobias professor of materials engineering at the Haifa Technion Israel Institute of Technology, was awarded the 2011 Nobel Prize in Chemistry last week for his discovery of quasicrystals—a form of matter with an atomic structure that was previously thought impossible.
In 1982, Shechtman discovered a new atomic structure when studying a rapidly cooled mix of aluminum and manganese. Unlike a regular crystal, which has an orderly, repeating structure, this material contained a pattern that never repeated. Many other kinds of quasicrystals have been discovered since then.
In 1992, the International Union of Crystallography changed the official definition of the crystal to incorporate Shechtman’s discovery.
TR: Are there opportunities to invent new types of materials because of quasicrystals?
Shechtman: There is always something new in quasicrystals. There are so many people working on it around the world, so every month there are new developments. If you use a material for an application, then you need a special property that will be better than other materials—otherwise, why use this material? Quasi-periodic materials have certain properties which are unique, such as electrical properties, optical properties, hardness and nonstick properties. The direction of light through this material is different. Electrically, they behave in a very peculiar way depending on temperature. Some of these properties have been put to use.
What was the first product based on quasicrystals?
The first application was nonstick coating on frying pans and cooking utensils. If you cook on quasicrystals, your omelet will not stick to it, like Teflon. But unlike Teflon, if you use a knife in the [quasicrystal] skillet, you will ruin the knife. When you have Teflon and you use a knife, you ruin the Teflon. Ruined Teflon is not healthy. I have a frying pan which is plasma-coated with quasicrystals and it works fine. It was made by a French company, Sitram. They closed the production line because they had a few problems in the reaction of the coating with salt. If people cook with a lot of salt it will etch the quasicrystalline coating. People didn’t like it, so they did not continue.
The Nobel citation says that quasicrystals are brittle but they can reinforce steel “like armor.” What are the practical applications?
Sandvik, a company in Sweden, produces a precipitation-hardened stainless steel that has interesting properties. The steel is strengthened by small quasicrystalline particles and it does not corrode. It is an extremely strong steel. It is used for anything that touches the skin, for instance, razor blades or surgery tools. When a material deforms in such a way that it will not spring back, in most cases, the deformation is due to a process called dislocation glide. There are defects in the material that cause dislocations. If they are free to move, then it is easy to bend the material. But if something stops them, then it is more difficult and the material is harder and stronger. These little quasicrystalline particles impede the motion of dislocation in the material.
The citation also says quasicrystals are being used to develop heat insulation, LEDs, diesel engines, and new materials that convert heat to electricity. What new applications do you think are most promising?
Because some of these materials have a low coefficient of friction, and they have nonstick properties and are also hard, imagine what would happen if you produce quasicrystalline powder in tiny little balls by rapid solidification process, a gas-atomizing process, then you can embed the fine powders in plastic. Because these particles are strong and can withstand friction and wear, you can make gears from this plastic and the gears will not erode because of these embedded particles. It’s like a protection from erosion. This can serve in ventilators and fans that have plastic gears. Also, the heat conductivity of some of these quasicrystals is very poor. It’s almost an insulator. So you can coat with it and it will insulate against heat transfer.
Icosahedrite, a naturally occurring quasicrystalline mineral, has been identified in a sample from the Khatyrka River in Chukhotka, Russia. Will it be useful?
This is an important discovery, because it’s the first one found in nature, but there are no practical applications. There are many, many metals, but if you think that all the metals can be used for something useful, think again. Look at construction materials. We have steel, which is based on iron, we have aluminum alloys, magnesium alloys, titanium-based alloys, nickel-based alloys, copper alloys, and that’s about all, if I haven’t forgotten any. What do all the other metals do? What are the applications of ytterbium? What are the applications of all the other metals? So to have an application for a material is not trivial.
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