TY - JOUR A1 - de Moraes, Flavia A1 - Müller, Wolfgang A1 - Frischat, G.H. A1 - Müller, Ralf T1 - Corrosion and crystallization at the inner surfaces of glass bricks N2 - Glass bricks are important transparent building materials. They are produced by joining two halves of glass pressings at 600–700 °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 time–temperature 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. KW - Chemical properties KW - Chemical durability KW - Corrosion KW - Crystallization KW - Crystal growth KW - Nucleation KW - Glasses KW - Mass spectroscopy KW - Mechanical properties KW - Hardness KW - Indentation KW - Microindentation KW - Microscopy KW - Optical microscopy KW - Scanning electron microscopy KW - Optical properties KW - Optical spectroscopy KW - Oxide glasses KW - Alkali silicates KW - Soda-lime-silica KW - Surfaces and interfaces PY - 2008 U6 - https://doi.org/10.1016/j.jnoncrysol.2007.07.086 SN - 0022-3093 VL - 354 IS - 2-9 SP - 284 EP - 289 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-16433 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -