6 Materialchemie
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Erscheinungsjahr
- 2020 (3) (entfernen)
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- Englisch (3)
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Schlagworte
- Alkali-activated materials (1)
- Corrosion (1)
- Geothermal (1)
- Polymer membranen (1)
- Saline brine (1)
- Sewer structures (1)
- Sulfuric acid resistance (1)
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- 7 Bauwerkssicherheit (3) (entfernen)
Eingeladener Vortrag
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The aim of the work presented was the evaluation of corrosion resistance
of various materials in geothermal Waters as a base to create a catalogue of suitable materials for applications in (not only) German geothermal power plants.
Users shall be enabled to have a basis for designing such facilities. High alloyed corrosion resistant alloys are suitable and do not cause copper or lead deposition. They shall be chosen for future design of the piping system, either in massive or in cladded form, if crevices formation with non-metallic materials can be prevented!
Alkali-activated materials have been repeatedly reported to exhibit high acid resistance, but no generally accepted hypothesis regarding the underlying mechanisms has emerged yet. To contribute to this issue, K-waterglass-activated metakaolin specimens, with and without the addition of CuSO4·5H2O in the starting mix, were exposed to either a chemically aggressive sewer environment (mortars) or sulfuric acid (pastes). The mode of copper incorporation in the materials and the formation of copper phases in the corroded layers were studied by XANES at the Cu K-edge, and 29Si, 27Al and 1H MAS NMR was employed to understand the processes during acid attack. Copper was found as a spertiniite-like phase in the as-cured materials, while in the deterioration layers of the pastes it was present as copper sulfate. In the corroded regions of the mortars, unequivocal identification of Cu phases was not possible, but the results were reconcilable with the presence of copper carbonate hydroxide. The solid-state NMR results revealed virtually complete dissolution of the K-A-S-H gel and the formation of silica gel, interpreted to be a central mechanism determining the acid resistance. No significant differences between the microstructural alterations of the pastes with and without Cu addition on (chemical) sulfuric acid attack were observed.
Polymers with intrinsic microporosity are promising candidates for the active separation layer in green gas separation membranes and as active materials for electronic applicatons. Here, by means of inelastic neutron scattering, the vibrational density of states (VDOS) and the molecular mobility were investigated for PIM-1, the prototypical polymer with intrinsic microporosity. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid).
The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers.
Elastic fixed window scans were measured on a neutron backscattering spectrometer to have an overview about the molecular dynamics at a time scale of ca. 1 ns. The temperature dependence of the estimated mean squared displacement shows a step-like increase in the temperature range from 100 K to 250 K indicating the onset of some molecular mobility. The nature of this motional process was analysed in detail by quasielastic neutron scattering combining Time-of-Flight and backscattering where the data are discussed with regard to both the q- and the temperature dependence.