Quasicrystals applications

For the first 15 years after the discovery, quasicrystals were studied purely as a compelling scientific issue. Just recently, applications have begun to appear. 

The many papers in this proceedings are partitioned into very abstruse theoretical analyses of structure and stability of quasicrystals on the one hand, and practical studies of surface structures, mechanical properties and potential applications. The subject shows signs of becoming as deeply divided between theorists and practical investigators, out of touch with each other, as magnetism became in the preceding century. 

Notes on the crystallography of quasi-periodic structures. A general way to face the problems related to the interpretation of quasi-periodic structures (modulated structures, quasicrystals) is based on the introduction and application of higher-dimensional crystallography (de Wolff 1974, 1977, Janner and Janssen 1980, Yamamoto 1982, 1996, Steurer 1995). 

Figure 1.11 Portion of a Penrose tiling based on two rhombuses. Penrose tilings are nonperiodic tilings of the plane and are two-dimensional analogs of quasicrystals. (Diagram created by the free Windows application Bob s Rhombus Walker, v. 3.0.19, JKS Software, Stamford, CT.)...

L. Pauling, Interpretation of so-called icosahedral and decagonal quasicrystals of alloys showing apparent icosahedral symmetry elements as twins of an 820-atom cubic crystal. Computers Math. Applic. 17, 337-339 (1989). 

Industry is highly interested in new materials that possess new or improved properties. The use of structure maps and other diagrammatic tools aid in this quest. Below are described the uses of such maps in the search for property-specific materials. In the sections on stable quasicrystals, high-Tc superconductors, and ferroelectrics, the applications of the quantum structural diagrams (QSD) described above will be used. In these classes of materials, the analysis starts with the compilation of the diagrammatic coordinates as described in equation (6). For these unusual types of order, the existence of diagrammatic regularities implies, at least, that the same factors that control local structure and stability in ordinary compounds also determine the tendency to these types of order and probably a coimection as well. 

Similar results are applicable for any icosahedral quasicrystal described with the M T ) model, in particular for i-AlCuFe [2]. 

P. Pleasants, in Covering of Discrete Quasiperiodic Sets Theory and Applications to Quasicrystals, Springer Tracts in Modern Physics Vol. 180, edited by P. Kramer and Z. Papadopolos (Springer, Berlin, 2002), p. 185. 

The application of LEED is limited to ultrahigh vacuum (UHV) conditions because of the character of the probe and its high surface sensitivity. The main application is the study of single crystal metal and semiconductor surfaces, and adsorption on these surfaces. Study of surfaces of thin insulator films is also possible. Recently, the application extends to study the surface structure of quasicrystals. LEED is widely applied to determine the symmetry and periodicity of surface structures and thus to identify reconstructions and adsorbate phases by observing the diffraction pattern. It is also a technique for quantitative surface structure analysis. LEED is also appHed as the quantitative determination of thermal vibrations at surfaces. 

Notice that rotation symmetry only exists for n = l, 2, 3, 4, and 6 five- and sevenfold rotations are not allowed because bodies with these symmetries cannot fill all space for the same reason that you cannot tile a floor with pentagons or with septagons. Icosahedral quasicrystals with fivefold symmetry can form, but cannot grow into crystalline solids in the strict sense of the word. Even so, such quasicrystals are extremely interesting both theoretically as well as from applications that utilize their unusual properties, as discussed later. 

Suck, J.B., Schreiber, M., and Haussler, P. (eds) (2002) Quasicrystals An Introduction to Structure, Physical Properties and Applications, Springer, Berlin. 

Al-Cr-Fe alloys are of interest as new lightweight alloys for structural apphcations, in particular, for the production of protective coatings formed by alumina scales from alloys of compositions that he in the Al-rich comer of the system. Al-Cr-Fe quasicrystal approximants are also potential candidates for new applications because of their specific properties. Alternatively, the addition of chromium to Fc3Al- and FeAl-based alloys produces excellent candidates for moderate and high temperature apphcations. [2005Pal] showed that... 

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