|Autor||Vázquez, P. and Thomachot-Schneider, C. and Mouhoubi, K. and Gommeaux, M. and Fronteau, G. and Barbin, V. and Bodnar, J.L.|
|Titel||Study of NaCl crystallization using Infrared Thermography|
|Link||Datei:21 SWBSS-2014 Vazquez etal.pdf|
|Bemerkungen||In: De Clercq, Hilde (editor): Proceedings of SWBSS 2014. Third International Conference on Salt Weathering of Buildings and Stone Sculptures Royal Institute for Cultural Heritage, Brussels, Belgium, 14-16 October 2047, S. 289-303|
Eintrag in der Bibliographie
|[Vazquez.etal:2014]||Vázquez, P.; Thomachot-Schneider, C.; Mouhoubi, K.; Gommeaux, M.; Fronteau, G.; Barbin, V.; Bodnar, J.L. (2014): Study of NaCl crystallization using Infrared Thermography. In: Hilde De Clercq (Hrsg.): Proceedings of SWBSS 2014 3rd International Conference on Salt Weathering of Buildings and Stone Sculptures,KIK-IRPA, Royal Institute for Cultural Heritage Brussels 289-303, 10.5165/hawk-hhg/274|
Infrared Thermography, emissivity, creeping, NaCl, temperature
The Infrared Thermography (IRT) technique has been widely developed during the last years. IRT is useful to observe changes in the fields of physics and chemistry, and has turned out to be an important and indispensable non-destructive technique used for investigation of civil engineering works, with special attention to cultural heritage. In this research IRT has been used to study the crystallization of NaCl solution droplets with different initial concentrations (3.5, 14 and 26% weight). The crystallization was induced by evaporation of the solvent (water). Tests were carried out at two temperatures (25 and 50°C). We explained how the crystallization process is observed with IRT. The variations in emissivity recorded by the IRT described distinctly the different stages of salt crystallization. IRT allowed observing three phases. In phase I the mass diffusion within the droplet and differences in concentration and volume of the solution around the crystal germs nuclei were observed. Phase II is related to the final crystallization step, with the crystal growth and the complete evaporation of the solution. Phase III describes creeping associated with efflorescence formation. This phenomenon takes place as an intermittent decrease in the IR thermosignal which can be repeated up to 100 times in a 10 minutes interval. Different morphologies corresponded to different IRT phases. Thus, if only phases I-II are present, crystals have cubic shape or efflorescence-like with fan-shape. If phase III occurs, efflorescence-like crystals with spherulite shape develop. These spherulites can crystallize on the substrate or on previous crystals, growing by top-supplied creeping and showing an intermittent decrease of thermosignal. The study and comprehension of salt droplets crystallization by IRT is the first step in our research. Currently, we are testing different salt types and the response of salt crystallization in porous stones.
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Als Phase wird ein stofflicher Zustand bezeichnet, der in sich, makroskopisch betrachtet, homogen ist.