Corrosion and crystallization at the inner surfaces of glass bricks
- Glass bricks are important transparent building materials. They are produced by joining two halves of glass pressings at 600700 °C. During this production process alkali oxides evaporate and are redeposited at the cooler inner front surfaces of the bricks. This surface layer reacts with H2O and CO2 from the residual brick atmosphere, leading to the formation of an alkali-rich silicate-hydrate layer of ≥50 nm thickness, which could be evidenced leading to a reduced nano-hardness of similar thickness, and from which NaHCO3 crystals can finally grow. Climate chamber experiments (repeated cooling between at -8 and -14 °C and reheating to 0 to 15 °C) resulted in reversible NaHCO3 crystallization and redissolution, presumably influenced by water evaporation or condensation and driven by the NaHCO3 supersaturation of the silicate-hydrate layer. Depending on the timetemperature schedule, different crystal morphologies became visible in this closed system, e.g. isolated spherical crystals,Glass bricks are important transparent building materials. They are produced by joining two halves of glass pressings at 600700 °C. During this production process alkali oxides evaporate and are redeposited at the cooler inner front surfaces of the bricks. This surface layer reacts with H2O and CO2 from the residual brick atmosphere, leading to the formation of an alkali-rich silicate-hydrate layer of ≥50 nm thickness, which could be evidenced leading to a reduced nano-hardness of similar thickness, and from which NaHCO3 crystals can finally grow. Climate chamber experiments (repeated cooling between at -8 and -14 °C and reheating to 0 to 15 °C) resulted in reversible NaHCO3 crystallization and redissolution, presumably influenced by water evaporation or condensation and driven by the NaHCO3 supersaturation of the silicate-hydrate layer. Depending on the timetemperature schedule, different crystal morphologies became visible in this closed system, e.g. isolated spherical crystals, crystals arranged in chains and in double-chains, respectively, which can limit already the transmittance of the glass bricks. When a crack occurs or the brick is opened, the hygroscopic NaHCO3 crystals take up more H2O from the ambient, react irreversibly with the glass surface, finally leading to a total loss of transmittance.…
Autor*innen: | Flavia de Moraes, Wolfgang Müller, G.H. Frischat, Ralf Müller |
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Dokumenttyp: | Zeitschriftenartikel |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Deutsch |
Titel des übergeordneten Werkes (Deutsch): | Journal of non-crystalline solids |
Jahr der Erstveröffentlichung: | 2008 |
Verlag: | North-Holland Publ. Co. |
Verlagsort: | Amsterdam |
Jahrgang/Band: | 354 |
Ausgabe/Heft: | 2-9 |
Erste Seite: | 284 |
Letzte Seite: | 289 |
Freie Schlagwörter: | Alkali silicates; Chemical durability; Chemical properties; Corrosion; Crystal growth; Crystallization; Glasses; Hardness; Indentation; Mass spectroscopy; Mechanical properties; Microindentation; Microscopy; Nucleation; Optical microscopy; Optical properties; Optical spectroscopy; Oxide glasses; Scanning electron microscopy; Soda-lime-silica; Surfaces and interfaces |
DOI: | 10.1016/j.jnoncrysol.2007.07.086 |
ISSN: | 0022-3093 |
Verfügbarkeit des Dokuments: | Physisches Exemplar in der Bibliothek der BAM vorhanden ("Hardcopy Access") |
Bibliotheksstandort: | Sonderstandort: Publica-Schrank |
Datum der Freischaltung: | 19.02.2016 |
Referierte Publikation: | Ja |
Datum der Eintragung als referierte Publikation: | 20.12.2007 |