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Titolo:
SODIUM AND SILVER ENVIRONMENTS AND ION-EXCHANGE PROCESSES IN SILICATEAND ALUMINOSILICATE GLASSES
Autore:
HOUDEWALTER SN; INMAN JM; DENT AJ; GREAVES GN;
Indirizzi:
UNIV ROCHESTER,INST OPT ROCHESTER NY 14627 SERC,DARESBURY LAB WARRINGTON WA4 4AD CHESHIRE ENGLAND UNIV MANCHESTER,DEPT GEOL MANCHESTER M13 9PL LANCS ENGLAND
Titolo Testata:
Journal of physical chemistry
fascicolo: 37, volume: 97, anno: 1993,
pagine: 9330 - 9336
SICI:
0022-3654(1993)97:37<9330:SASEAI>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
MIXED ALKALI GLASSES; CURVED-WAVE THEORY; EXAFS CALCULATIONS; X-RAY; COORDINATION; DIFFUSION; MINERALS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
53
Recensione:
Indirizzi per estratti:
Citazione:
S.N. Houdewalter et al., "SODIUM AND SILVER ENVIRONMENTS AND ION-EXCHANGE PROCESSES IN SILICATEAND ALUMINOSILICATE GLASSES", Journal of physical chemistry, 97(37), 1993, pp. 9330-9336

Abstract

X-ray absorption fine structure (XAFS) was used to determine the local environments of sodium in sodium silicate and aluminosilicate glasses. Silver environments were also measured after Ag/Na ion exchange in the same glasses. Na-O distances were found at a characteristic first-shell distance of 2.30-2.32 angstrom. The coordination number of approximately 5 oxygen in binary silicates dropped, however, when Al2O3 wasadded to the glass. We ascribe this to changes in the geometry of available oxygen cages in the glass structure as nonbridging oxygens are replaced by bridging oxygens. In comparison, ion exchange with silver led to cation environments with much shorter cation-oxygen distances of 2.08-2.23 angstrom and even smaller coordination numbers approaching2 oxygen, resembling the immediate environment of Ag in Ag2O. This geometry was shown to persist in one of the ion-exchanged glasses despite a variety of thermal history and processing conditions. In detail, though, as the glass composition was varied, disorder in the oxygen shell surrouding Ag was affected. This increased as Al2O3 was added, indicating a more rigid environment as the network polymerized. The different ion-exchange rates of the sodium and silver have been compared andare reconciled in terms of the effects different cation oxygen ratii and the number of available nonbridging oxygen have on diffusion mechanisms in the glass.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/09/20 alle ore 06:11:59