The development and application about Quasicrystals

Posted by beauty33 on November 17th, 2021

Development path

The structure of quasi-crystals has been well-known by architects before the 20th century. For example, in the mosque in Isfahan, Iran, the patterns on the tiles are arranged in quasi-crystal patterns.

In 1961, mathematician Wang Hao proposed the puzzle problem of covering a plane with puzzles of different shapes. Mathematicians already know that it is possible to fill a plane with a single-shaped puzzle, such as a quadrilateral or a regular hexagon of any shape, but when the types of puzzle units are increased, more ways to fill a plane can be constructed. Two years later, Wang Hao\'s student Robert Berger constructed a series of jigsaw puzzle methods that are not periodic. Later, there were fewer and fewer types of puzzles needed to cover the plane. In 1976, Roger Penrose constructed a series of methods that only required two puzzles. The patterns created by this method had five-fold symmetry.

At the end of 1984, D. Shechtman et al. announced that they had discovered an alloy image with five-fold rotational symmetry but no translational periodicity in the rapidly solidified Al Mn alloy, that is, a 20-hedral quasicrystal. The puzzle form of this quasicrystal is Two different rhombus composition. This article was published in 1984 with the title \"Metallic Phase with Long-Range Orientational Order and No Translational Symmetry\" (Metallic Phase with Long-Range Orientational Order and No Translational Symmetry). The five-fold symmetry structure they discovered was produced in Al-Mn alloys that rapidly cooled after melting. It caused a great shock in crystallography and related academic circles. Soon, this kind of crystal with no translational periodicity but with positional order was called a quasi-crystal.

Quasicrystals were discovered in 1982. They have a regular shape of convex polyhedrons, but unlike solid crystals, they have a five-fold axis that crystalline materials do not have. The regular dodecahedron shape of quasicrystals containing holmium-magnesium-zinc. The known quasicrystals are all intermetallic compounds. All the hundreds of quasicrystals discovered before 2000 contained at least three metals, such as Al65Cu23Fe12, Al70Pd21Mn9 and so on. However, it has been recently discovered that only two metals can also form quasicrystals, such as Cd57Yb10 [Nature, 2000,408:537].

In 2009, a mineralogical discovery provided evidence for whether quasicrystals can be formed under natural conditions: quasicrystal particles composed of Al63Cu24Fe13 were found on a piece of aluminum-zinc-copper ore in Russia. Like those synthesized in the laboratory, the crystallinity of these particles is very good.

The composition and structure of quasicrystals are still under study. It is worth paying attention to the fact that the composition is worthy of attention: the composition of Al70Pd21Mn9 is a quasicrystal, while the composition of Al60Pd25Mn15 is a crystal. Regarding structural issues, it is generally believed that the existence of quasi-crystals deviates from the three-dimensional periodic structure of crystals, because the monotonic periodic structure cannot have a five-fold axis, but the structure of quasi-crystals is still regular, unlike amorphous substances. Nearly disordered, it is still a kind of near-ordered structure.

Although the composition and structure of quasicrystals have not yet been fully elucidated, its discovery has had a great impact on classical crystallography in theory, so that the International Crystallographic Union recently proposed to define a crystal as a solid with a clear pattern in its diffraction pattern (any solid having an essentially discrete diffraction diagram) to replace the original definition of periodic structure in microscopic space. In fact, quasicrystals have been developed as useful materials. For example, it has been found that the quasicrystal composed of aluminum-copper-iron-chromium has low friction coefficient, high hardness, low surface energy and low heat transfer. It is being developed as a coating for cooking pots; Al65Cu23Fe12 is very wear-resistant and has been developed as a coating for cooking pots. Coating of high temperature arc nozzle.

Application

Quasicrystals have unique properties: they are hard, flexible, and very smooth. Moreover, unlike most metals, their electrical and thermal conductivity are very poor, so they are very useful in daily life. Scientists are trying to apply it to other products, such as non-stick pans and light-emitting diodes. In addition, despite their poor thermal conductivity, because they can convert heat into electricity, they can be used as ideal thermoelectric materials to recycle the heat. Some scientists are trying to use them to capture the heat of waste cars.

Discoverer

The Israeli scientist Daniel Shechtman alone won the 2011 Nobel Prize in Chemistry for his discovery of quasicrystals.

In 2011, 70-year-old Shechtman will receive a bonus of 10 million Swedish kronor (about 1.4 million US dollars). Shechtman discovered quasicrystals, the peculiar structure of this material, which overturned the established concept of crystallography. For many years, condensed matter physicists were only concerned with crystalline solid matter. However, in the past few decades, they have gradually turned their attention to \"amorphous\" materials, such as liquids or amorphous materials. The atoms in these materials are only in short-range order, which is known as the lack of \"spatial periodicity.\"

In 1982, Shechtman discovered quasicrystals while working at Hopkins University in the United States. This new structure is not crystals due to lack of spatial periodicity, but unlike amorphous crystals, quasicrystals exhibit perfect long-range properties. Order, this fact has brought a huge impact to the crystallographic community, and it challenges the basic concept of the equivalence of long-range order and periodicity.

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