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2024 | OriginalPaper | Buchkapitel

18. The Non-Crystalline State

verfasst von : Rick Ubic

Erschienen in: Crystallography and Crystal Chemistry

Verlag: Springer International Publishing

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Abstract

This chapter discusses the non-crystalline state. In it, we make a distinction between amorphous and disordered materials, and we introduce the concept of short-range order. Models of amorphous materials based on either hard spheres or networks are explored, and polymers are specifically discussed in terms of structure, applications, and recyclability. Brief biographies of John Desmond “Des” Bernal and Georgy Theodosiyovych Voronoï are also included.

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Vorheriges Kapitel Line Defects

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The same definition was used by the Mesopotamians and, as molten metals also flow, led to the confusion that glass was always metal or contained metal.

Correlation is a consequence of long-range order and means that if the position of just one unit (atom/ion/molecule) is known, the positions of all other units can be precisely determined.

Boris Nikolayevich Delaunay (1890–1980) was a Soviet/Russian mathematician and mountain climber. His surname derives from his ancestor, a French army officer who was captured during Napoleon’s invasion of 1812 and subsequently married a woman from the Tukhachevsky noble family and stayed in Russia. A peak in the Katun Mountains of southern Siberia is named after him.

from the Greek olígos (ὀλίγος), “few,” and méros (μέρος), “part”

Zachariasen’s first scientific paper, on the crystal structure of BeO, was published in 1925 when he was just 19 years old. He was the sole author. At age 20, he published six more papers, mostly also as sole author. In 1928, at the age of just 22, he became the youngest person to receive a PhD from the University of Oslo.

Topology in this context describes the physical arrangement of vertices and polyhedra in a network.

Note that V/P ≠ (P/V)⁻¹.

The smallest actual repeating unit here is CH₂, so one might be tempted to call this polymer polymethylene, (CH₂)_n, and the systematic structure-based name according to the IUPAC is indeed poly(methylene); however, PE is prepared by polymerizing ethene (CH₂=CH₂), the double bond here being key to the polymerization process. There is no stable methene/methylene compound, so the traditional name is derived from the smallest unit which is actually used to synthesize the polymer.

a state of matter in which long-range order exists along just one or two axes, resulting in properties intermediate between those of conventional liquids and those of solid crystals

from the ancient Greek déndron (δένδρον), meaning “tree”

An elastomer is a polymeric substance that possesses the quality of elasticity, i.e., the ability to regain its shape after deformation.

Natural rubber is derived from latex, which is the sap of the rubber tree (Hevea brasiliensis).

from the Greek taktikótiita (τακτικότητα), meaning “regularity”

Isomers are molecules or polyatomic ions with identical molecular formulae but distinct arrangements of atoms. Recall that polymorphs are crystalline materials that exist in more than one form.

A few other materials also exhibit a negative thermal expansion coefficient, α, including the metastable cubic Zr(WO₄)₂ phase which has an average α of −7.2 ppm/°C) from absolute zero all the way to its decomposition temperature of 777 °C. It crystallises in space group P2₁3 (No. 198) with zirconium octahedra which are corner-shared to tungsten tetrahedra.

now the Plastics Industry Association

Phthalates are a group of chemicals used to make plastics softer and more flexible, increase plasticity, decrease viscosity, or decrease friction during manufacture. They are often called plasticizers.

Polycarbonate is a group of thermoplastic polymers containing carbonate groups (CO₃²⁻) in their chemical structures.

Hydrolysis is a chemical reaction in which a water molecule breaks one or more chemical bonds. In this case, –(–OC₆H₄)₂C(CH₃)₂CO–)–_n (PC) + H₂O (CH₃)₂C(C₆H₄OH)₂ (BPA) + CO₂. Leaching is the selective removal of a material component, in this case BPA, by dissolution in a liquid.

over the objections of the American Chemistry Council, an industry trade association for US chemical companies

For example, despite PVDC’s impenetrable barrier to odor and superior heat resistance (i.e., microwavability), SC Johnson removed it from its Saran Wrap product in 2004 because when items containing chlorine end up in municipal incinerators, they can emit toxic chemicals into the environment. Saran Wrap is now made of LDPE.

Fluorocarbons, also known as perfluorocarbons or PFCs, are organofluorine compounds with the general formula C_xF_y.

C. L. Losq, M. R. Cicconi, G. N. Greaves and D. R. Neuville, “Chapter 13: Silicate Glasses,” in Springer Handbook of Glass, J. D. Musgraves, J. Hu and L. Calvez, Eds., Cham, Springer Nature Switzerland AG, 2019, pp. 441–503.CrossRef

N. A. Krishnan, B. Wang, Y. Le Pape, G. Sant and M. Bauchy, “Irradiation- vs. vitrification-induced disordering: The case of α-quartz and glassy silica,” Journal of Chemical Physics, vol. 146, no. 20, p. 204502, 2017.CrossRefPubMed

W. H. Zachariasen, “The Atomic Arrangement in Glass,” Journal of the American Chemical Society, vol. 54, no. 10, p. 3841, 1932.CrossRef

A. R. Cooper, “W.H. Zachariasen – The Melody Lingers On,” Journal of Non-Crystalline Solids, vol. 49, pp. 1–17, 1982.CrossRef

Titel: The Non-Crystalline State
verfasst von: Rick Ubic
Verlag: Springer International Publishing
Buch: Crystallography and Crystal Chemistry
Print ISBN: 978-3-031-49751-3

Electronic ISBN: 978-3-031-49752-0

Copyright-Jahr: 2024
DOI: https://doi.org/10.1007/978-3-031-49752-0_18

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