Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

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Издательство: John Wiley & Sons Limited
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Жанр произведения: Техническая литература
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isbn: 9781118799499
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Shelby, J.E. (1997). in Introduction to Glass Science and Technology, 38–45. Cambridge: The Royal Society of Chemistry.

      15 15 Pye, L.D., Montenero, A., and Joseph, I. (eds.) (2005). Properties of Glass‐Forming Melts. Boca Raton: CRC Press.

      16 16 Johnson, W.W. Gas generation and transport within a reacting batch pile. In: Proceedings of the 12th International Seminar on Furnace Design – Operations & Process Simulation, 2013. Velke Karlovice, Czech Republic: Glass Service.

      17 17 Jiao, J., Bamiro, O., Lewis, D., and Zhu, X. (2014). 3‐D transient non isothermal cfd modeling of gob formation. In: 75th Conference on Glass Problems (ed. S.K. Sundaram), 185–200. Columbus: Wiley.

      18 18 Tiwary, R. (2015). An overview of float glass forming modeling. In: GMIC Symposium on Glass Forming. Columbus: GMIC.

      Note

      1 Reviewers: W. W. Johnson, Corning Incorporated, Corning, NY, USAE. Muijsenberg, Glass Service, Inc., Vsetin, Czech Republic

Photo depicts the atomic disorder of the glass structure (left) giving way to crystalline order (right): the boundary between a Zr-bearing magnesium aluminosilicate glass and a ZrO2 crystal that precipitated in it. Bar scale: 5 nm.

      Structural studies are nonetheless useful either at a small scale, for example, to figure out how the local environment of an ion determines its optical properties (Section VI), or at a larger scale to gain insights on property–composition relationships when the specific influence of chemical entities on the properties of interest can be evaluated in terms of well‐defined structural elements such as rings or coordination polyhedra. The method was pioneered in Antiquity by Plato (‐428–347): to each of the four elements then acknowledged, he assigned geometrical shapes accounting for their properties, namely the tetrahedron for fire, octahedron for air, icosahedron for water, and cube for earth. Of course, such assignments are no longer purely intellectual constructs; they have an experimental basis. Interestingly, however, one should realize that the first atomic models of glass were devised shortly before any experimental tool was available to determine their structural components (Chapter 10.11). In other words, glass structure represents a good example of a situation where theory not only preceded experiments but also defined their paradigmatic framework.

      From the results obtained with these methods, the next three chapters focus on the glass structure. Short‐range order is dealt with by J.F. Stebbins in a chapter where he defines such concepts as network formers and modifiers, bridging and nonbridging oxygens and their tetrahedral distribution around the network‐forming cations they coordinate, and he also discusses how they change with temperature and composition (Chapter 2.4). From the scale of atoms to that of macroscopic bodies, the increasing complexity found at longer distances is then examined by G.N. Greaves who also points out the basic differences found between oxide and metallic systems (Chapter 2.5). Because glasses have generally complex chemical compositions in both industrial and geological contexts, the relationships between the structures of simple and multicomponent systems are finally described by B.O. Mysen in a perspective aimed at understanding composition–property relationships (Chapter 2.6).

      Returning to more theoretical aspects, the next chapter by P.K. Gupta stresses with the constraint theory the importance of simple topological considerations and of temperature‐dependent bond strengths to understand the glass structure and composition–property relationships. To conclude this section, two chapters review the rapid advances made in the growing field of atomistic simulations in two complementary ways. In the Monte‐Carlo and molecular‐dynamics simulations presented by A. Takada (Chapter 2.8), the interatomic potentials used to simulate the structure and properties of glass‐forming systems are determined a priori, with the advantage that up to a few thousand particles can be considered with current computing power. As reviewed by W. Kob and S. Ispas, atomic interactions are determined instead from first principles in the more fundamental and precise ab initio approaches, such as density functional theory; the price is that only relatively small systems can be currently investigated (Chapter 2.9). Ascertaining the energetics of a glass‐forming melt is fraught with considerable difficulties, however, because phase transformations, in which one is interested, are driven by small differences of typically a few kJ between the very large numbers yielded with significant uncertainties by ab initio methods.

      Throughout this section the emphasis is generally put on oxide glasses. Metallic glasses are specifically dealt with in Chapter 7.10 and organic polymers in three other contributions (Chapters 8.8–8.10).

      1 Plato, T. 55e–56d, transl. by D.J. Zeyl p. 1224–91 in Plato Complete Works. Indianapolis: Hackett Pub. Co., 1997.

       Alex C. Hannon

       ISIS Facility, Rutherford