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

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Техническая литература
Год издания: 0
isbn: 9781118799499
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Graphs depict the contrast between the radially averaged local structure T(r) of directionally and metallically bonded structures as exemplified by the network glass SiO2 (a) and the bulk metallic glass Ca60Mg25Cu15 (b). The short, intermediate, long, and medium range orders are identified alongside 2-D schematics of local atomic arrangements.

      Source: Courtesy of A. Hannon (http://alexhannon.co.uk/DBindex.htm).

      Compared with diffraction techniques used for crystalline materials, diffuse scattering methods seriously underdetermine the extended structure of glass, even for monatomic systems. Other independent structural measurements are needed in order to increase the credibility of atomistic models. Although X‐ray and neutron S(Q)′s are independent measures of the same radially averaged structure, until recently X‐ray measurements lacked the extensive Q‐range of neutron instruments. However, with the arrival of high‐energy X‐ray scattering [8], both methods are now compatible and are generally applied sequentially to the same material.

Graphs depict the contrast between the network structure of SiO2 (a) and the metallic structure of Ca60Mg25Cu15 (b) manifest in the scattered intensities i(Q), from which the T(r)'s of Figure 2 were obtained. The SRO as defined by the principal peak (PP) and IRO defined by the first sharp diffraction peak (FSDP) are labeled alongside LRO and MRO for each glass.

      Source: Data courtesy of A. Hannon (http://alexhannon.co.uk/DBindex.htm).

      In adding further confidence to modeling extended glass structure, studies of dynamic properties, using inelastic spectroscopies like inelastic neutron scattering (INS) and Raman spectroscopy, have played an important part [1, 5, 16] – principally in highlighting stretching and bending optic mode vibrations between the atom pairs in network glasses and providing fingerprints of the polyhedra and small molecular groups that constitute SRO and aspects of IRO.