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Viewings: 7885Recently scientists of Japan have managed to grow the perfect crystals of solid helium that in terrestrial laboratories to make very difficult - they are easily deformed under the action of gravity. However, the researchers did a very original way - they grew helium crystals in microgravity conditions that were created on Board a jet plane.
Before you start the story about the crystals of solid helium, it is necessary to remind about why scientists they needed. As we know, among the different aggregate States of matter except liquid, solid and gaseous there is also another, which is called condensate Bose-Einstein. In this state, the matter is not made up of molecules and atoms, and of bosons cooled to temperatures close to absolute zero.
One of the interesting properties of the condensate Bose-Einstein is superfluidity - the state in which he has zero viscosity, i.e. when passing through different holes on the surface between it never occurs to friction. You know, this feature can be very useful. In addition, it is proved that in the superfluid state of matter can be even and high-temperature superconductors.
In short, if scientists were able to translate without any problems known substances in the superfluid state, it would be possible to solve many problems. But to do this yet quite difficult. At the same time in the 60-ies of the last century there has been speculation that the superfluidity can have some solid body, especially those that form crystals. And the first candidates for such was the name of the crystals of solid helium, which are formed at a pressure of more than 25 atmospheres.
In 2004 the American physicists from the University of Alberta said on experimental observation totally unexpected effect of superfluidity in solid helium. But their experiments failed to reproduce in other laboratories, resulting in the reliability of the results of this work was questioned. Later, in 2009, physicists at the University of California at Berkeley managed to get a gas of rubidium in the state of a superfluid solid.
However, this direction was recognized unpromising - the fact that with the rubidium difficult to work. Although it on prevalence in the earth's crust is about 20-th place (as copper, Nickel and zinc), however, the nature of this metal exists in the scattered state, without its own minerals and meeting mainly together with other alkaline elements, for example, with potassium. That is, it is quite difficult to produce, making all research with him quite expensive.
Because of this, scientists have once again decided to return to your loved all of helium. But to investigate its property of superfluidity in solid form, first it is necessary to grow the crystals. In principle it is not difficult to do this, just need to create the pressure is higher than 25 atmospheres and lowered the temperature to -272 degrees Celsius. It has been repeatedly shown that in such "the freezer" crystal is formed practically in seconds. However, there is another "but": when the helium crystals grow in the presence of gravity, they are easily deformed. And this greatly affects all their properties, including on superfluidity.
And recently, scientists from Japan offered a very original way to deal with this problem - you just need to grow the crystals in zero gravity! Moreover, it is not necessary to do it in space - the researchers used for their experiments small jet. In these specific tracks, for example, in a parabolic flight, the airplane could situated in weightlessness for about 20 seconds, which is enough time to grow the normal crystal. In total 20 hours of flight physics managed to spend eight experiments!
The experiments took place: first, by the standard technology was grown primary crystals, and after they were adorning "drops" helium-4, which was already in the superfluid state. All this happened in a special on-Board refrigerator. Large helium crystals were placed in the lower chamber high pressure, and then crushed them acoustic wave to break into small pieces. After they were sprashivali superfluid helium-4, crystals smaller melted, and large grew rapidly, reaching a total of approximately 10 mm
As a result, the researchers managed to fully observe the process of formation of the crystal. Interestingly, it was similar to the phenomenon that is called Ostalowska maturation. It is possible to observe in their everyday life on the example of ice cream: with time it larger ice crystals attached to itself small, and eventually the entire product becomes hard and crunchy. But in this case Osvaldova maturation is quite slow, but with helium effect turned out very fast - the process took seconds.
"The helium crystals can quickly grow out of superfluid matter. It is the perfect material for studying the fundamental properties of these crystals as they are formed very quickly" - commented on the results of the work of lead author of the study Professor Nomura Ryuuji. Now, when physicists finally managed to grow the perfect crystal solid helium, you can try to test it on superfluidity.
By the way, American scientists who discovered this property in 2004, in response to criticism of the work indicated that their opponents did not work due to the fact that crystals, with which they worked were deformed. Now Japanese researchers will be able to double-check the results of their colleagues, using the already absolutely normal crystal grown in zero gravity...
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