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Material Innovation : The incomparable lightness of the gel

Lightweight, stable, and incredibly hollow: researchers at the University in Los Angeles, it is possible to develop an Aerogel, the extremely strong temperature fluctuations, can withstand. It could be for Isolation, under conditions as they occur among others in the erdnahem Orbit, is used. The new Material, its preparation describe the researchers in the journal "Science", consists of 99 percent air, and is thus easier to use than known aerogels. At the same time it is very stable against force effects and high temperatures.

aerogels are fascinating materials, they are extremely light and still keep a lot of. Some you can see through it, what helped you with the nickname "frozen smoke". Others are bright green, blue, or pitch black. They are mainly made of air, in very many, very small pores, which are formed of a metal or of carbon compounds or inorganic materials. Thus, one can produce the super lightweight materials such as graphite, Gold, or various ceramics. However, the term "ceramic materials for the latter," with cups or bowls rather little to do. He rather describes certain inorganic Compounds, which are often very resistant to chemicals and fire, and so for a number of applications.

result of a bet between chemists

The first of these materials was produced in 1931 in America. A certain Samuel Kistler worked with classic Gels in which the liquid is stored in a sponge-like network made up of a solid body. The most well-known example is gelatin. The Tradition to bet Kistler and his colleague Charles Learned, who would be first will be able to replace the liquid by a Gas, without changing the structure of the gel is lost.

Trying to evaporate the liquid, simply, meant, however, that the Material, such as a failed Soufflé fell. Finally, Kistler developed the method used in the chemical laboratory equivalent of a pressure cooker and a so-called water glass. This scientific and technical performance was still very time-consuming. However, the development step after that. Soon Sol-Gel "processes"in which, in a liquid reaction solid products. These particles crosslink, wherein the liquid remains in the Holräumen. Drying the Gel under high pressure, so that the Material does not shrink together, results in an Aerogel.

cubic meter weighs as much as a chocolate bar

The researchers to Xiangfeng Duan of the University of California in Los Angeles used for your new fabric, a more complex procedure. The scaffolding consists of boron nitride, a boron-nitrogen compound, which can form a honeycomb-shaped structures. This is a very stable, flat structures, the gangs, the scientists in a three-dimensional, network-like Structure, which can be very well deform elastically. As a support structure, a variant of pure carbon in which the atoms with a honeycomb structure are associated will first be used to graph.

The graph is burned after the vapor deposition of boron nitride at about 600 degrees. Back to an Aerogel, with a density of 0.1 milligram per cubic centimeter, it is extremely light remains: A cubic metre of the material weighs just as much as a bar of chocolate. Unlike chocolate it does not melt but, if you heated it – a whole week at 1400 degrees Celsius, the Gel supernatant without any problems. Short-term changes in temperature could cope with it. Unlike other ceramic aerogels, in the case of such loads, fragile, and could withstand variations in temperature of 275 degrees per second, the boron nitride material. Thus, the new Material is recommended for the construction of probes for the exploration of the universe.

Perfect insulators

And it only remains itself intact, it protects very well against heat. This is a fundamental property of the Aerogels and the reason why they are often used as insulation materials. Since the air in the porous lattice very little room to move, you can heat via convection, therefore, simply the movement of heated molecules are hardly passed on. Also heat conduction through the boron nitride occurs due to the low density of the material only slowly. Duan and his colleagues have also noticed breaks in the range of nanometers in the Material, which will hinder the heat conduction. Only by heat radiation, heat can be passed – this is, however, considerably less effective than heat conduction.

the insulating effect of your Aerogels, placed the flower on a two-inch-thick piece of the material, which she held directly over an alcohol flame. After 15 minutes, the flower was still beautiful - the surface on which she lay, which had been heated to only 45 degrees.

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Frozen smoke

Frank Schubert

mechanically, the new Aerogel is something Special: How just a few ingredients in the world, it has a negative Poisson's ratio. This means that, if one pulls apart, not thin, but as long as thicker, until it is broken. The cause of this strange property is that the Material is folded in its normal state, so to speak, and when the final acts unfolded. Longer research about whether you could use such a "auxetischen" materials, for example in bullet-proof vests. They would, as the opposite phenomenon of expansion in train, and when it hits a projectile - that is, a compression - immediately harden. As a result, the pulse would be spread extremely effectively, and so the projectile its energy.

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