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Structural investigation of hydrous phosphate glasses

  • Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O–MgO–Al2O3–P2O5. Glasses containing 0–8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass Transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules,Dissolved water has major impact on the physical and chemical properties of phosphate glasses. In the present study we have investigated the structural response to water incorporation for glasses in the system Li2O–MgO–Al2O3–P2O5. Glasses containing 0–8 wt% H2O were synthesised at 500 MPa confining pressure in internally heated gas pressure vessels at 1323 K (LMP, Al-poor glass) and 1423 K (LMAP, Al-enriched glass). Water contents of glasses were determined by pyrolysis and subsequent Karl-Fischer titration (KFT) and/or by infrared spectroscopy. Density varies nonlinearly with water content implying large structural changes when adding up to 2 wt% H2O to the dry glass. Glass Transition temperatures measured by differential thermal analysis (DTA) continuously decrease with water content. The trend can be explained by depolymerisation of the phosphate network. Near-infrared spectroscopy shows that even in Al poor glasses only a minority of dissolved water is present as H2O molecules, but the largest amount is present as OH Groups formed by hydrolysis of P–O–P bonds. The network is stabilised by aluminium which is predominantly six-coordinated in these glasses as shown by 27Al MAS NMR spectroscopy. With increase of Al in the glasses, breaking up of the Phosphate network through hydrolysis is depressed, i.e. much lower OH Contents are formed at same total water content. Network depolymerisation upon addition of H2O is evident also from 31P MAS NMR spectroscopy. While Phosphate tetraheda are crosslinked by two to three bridging oxygen in dry glasses, diphosphate Groups are dominant in glasses containing 8 wt% H2O.zeige mehrzeige weniger

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  • 2019 Balzer Phys Chem Glasses 60_2.pdf
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Metadaten
Autoren/innen:R. Balzer, H. Behrens, Stefan Reinsch, M. Fechtelkord
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Physics and Chemistry of Glasses: European Journal of Glass Science and Technology B
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.6 Glas
Jahrgang/Band:60
Ausgabe/Heft:2
Erste Seite:49
Letzte Seite:61
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:NMR spectroscopy; high pressure; infrared spectroscopy; phosphate glasses; water speciation
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen und Materialien
Veranstaltung:2. INT. CONF. ON PHOSPHATE GLASSES
Veranstaltungsort:Oxford, UK
Beginndatum der Veranstaltung:26.07.2017
Enddatum der Veranstaltung:28.07.2017
DOI:https://doi.org/10.13036/17533562.60.2.041
URL:http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=WOS_CPL&DestLinkType=FullRecord&UT=WOS:000467889500002
ISSN:1753-3562
Verfügbarkeit des Volltexts:Volltext-PDF im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:03.06.2019
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:03.06.2019