New Surprise "Super Material": From Silent Cloak to Elastic Ceramic
Beijing time on March 6 news, according to foreign media reports, "Hyper-materials" is a kind of artificial material that has special properties and does not exist in nature. Physicists and material scientists are studying the exotic properties of metamaterials and exploring their possibilities in life applications. By changing the structure of the material, we can manipulate the appearance and other properties of the material. Next, scientists hope to change the mechanical properties of the material. At present, we have seen many ideas, designs, and preliminary applications for these materials, including elastic ceramics, captive cloaks, and programmable rubber sponges.
The emergence of these new materials will help build spacecraft protective tiles and even develop terrain-sensitive shoes.
“I think the concept of metamaterials has been gradually diversified into many different areas,†said Professor Martin Wegener of the Karlsruhe Institute of Technology in Germany. “Initially, it was an explosion in the field of electromagnetism. Later it entered some Completely different areas, such as thermodynamics, and then later in mechanical mechanics."
Professor Wegner said that the term "metamaterial" has been used to refer to almost all quirky and miraculous designs. They are usually of an extraordinary nature and are not possessed by the original material.
I can't feel it
Professor Wegner studied cloaks, but not to make objects invisible. His purpose is to hide physical forces. Last year, his lab developed a honeycomb-like material that made objects impossible to feel. This particular metamaterial is a solid lattice that resembles a liquid in certain properties and can deflect externally applied pressure.
In the demonstration, this metamaterial can hide a small cylinder (less than 1mm in diameter) from the fingers. Physicists and engineers from France referred to the work of Wegener et al. They pointed out that by carefully and carefully drilling holes according to a certain pattern, it is possible to transfer the more destructive seismic fluctuations. In other words, this is turning the ground itself into a kind of metamaterial, which may make the power plant safe from earthquakes.
At the March meeting of the American Physical Society, Prof. Wegener showed the latest work, including a metamaterial that could make the hole in the tablet center undetectable. He said: "The design principle here is that you can apply it to anything you need."
Set the sole
Also at the March meeting of the American Physical Society, Bastiaan Florijn, a doctoral student at Leiden University in the Netherlands, presented his research results, which he called the world's first mechanical mechanics. Programmable material.
From an appearance point of view, this material is like a porous rubber plate, and it does not seem to have much technological content. However, these holes - which come in two sizes - are actually specially designed and can be compressed longitudinally and laterally. This change in direction is achieved by adding a small clip.
So, what we end up with is an oversized sponge. In the extrusion process, its texture can be very stiff, it can be very soft, or somewhere in between. If it is in the process of transitioning to a soft form and is still under pressure, it exhibits the so-called "negative stiffness" nature. Florin said that this property is very strange and he has not yet thought of how to apply it.
However, another feature of this rubber sheet may be of great use: it absorbs energy. "Imagine that you can program a car bumper. If you drive into a place with many kids, you want to have a very soft bumper," Florin said. "But if it's at high speed, Driving on the highway, you will want it to be strong enough.†At present, Florin and colleagues have also made contact with shoe-making enterprises, hoping to produce shoes that are adjusted according to different terrains.
Save the engine
Professor Katia Bertoldi of Harvard University is also working on a similar exotic elastic material, which is said to have a negative Poisson ratio. This means that when compressing, the material will shrink from all directions instead of extruding to the other two sides, becoming wider and flatter. When stretching, it will also be in all directions. extend. Professor Beltodi’s team has developed a variety of useful properties for this material, including the ability to absorb different frequencies of sound when squeezed.
Poisson's ratio can also affect metal fatigue. Professor Beltodi has worked with Rolls-Royce to design engine parts with complex slot structures that can withstand more compression cycles. Similar principles can be further applied to everyday life. Professor Bertodi said that in order to obtain unique properties, we can develop composite structural building bricks, or use ordinary bricks, but combine them in a special way. .
Rebound ceramic tube
A team at the California Institute of Technology developed a very exotic ceramic material. They made very small ceramics and bounced back after being compressed to 50%. The technology used by the research team can construct atomic layers of material one at a time, thus creating a network of hollow ceramic tubes. The walls of these ceramic tubes are only a few nanometers thick (1 nanometer is 1 millionth of a millimeter), and the thickness of the entire product is even thinner than a sheet of paper.
The raw material they use is alumina, which is higher in strength than steel, but like most ceramic materials, it is very brittle. However, these tiny samples can recover from a heavy blow when the thickness of the ceramic wall is appropriate. Although it is still far from the stage of practical application, with sufficient investment, it is believed that this kind of ceramic material can play an important role in some fields. For example, spacecraft or aircraft engines may use ceramic tiles to insulate rather than use metal shields.
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