Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 73: Surface Dynamics: Reactions and Elementary Processes
O 73.10: Poster
Mittwoch, 9. März 2016, 18:15–20:30, Poster A
Investigation of Calcium-Silicate surfaces with UHV-IRRAS to understanding the first step in the corrosion of concretes — •Carsten Natzeck, Peter Weidler, Christof Woell, and Peter Thissen — Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
The well-oriented Calcium-Silicate substrate Wollastonite as our model sample is a chemically well characterized mineral (CaSiO3). It has versatile physical properties for use in industry, reaching from medicine with the formation of artificial bones due to its bioactivity to construction chemistry with Calcium-Silicates (CS) as model system e.g. for cement and concrete. The surface chemistry of this CS substrate has been studied using infrared reflection-absorption spectroscopy under ultrahigh-vacuum conditions (UHV-IRRAS) using water and methanol as probe molecules. Exposure of the cooled substrate (100 K) to H2O leads to the formation of surface OH-species. This proton transfer, which is a crucial step in the corrosion of concrete, is found to be absent when the same surface is exposed to methanol. These results are analyzed on the basis of a detailed, first-principles computational study employing densitiy function theory (DFT) and allow to derive a consistent picture on the chemical properties of this important mineral surface. Implications for corrosion protection of concrete in harsh environments will be discussed.