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124 results on '"Rätzke, Klaus"'

11. Liquids with permanent porosity

Author

Giri, Nicola, Del Pópolo, Mario G., Melaugh, Gavin, Greenaway, Rebecca L., Rätzke, Klaus, Koschine, Tönjes, Pison, Laure, Costa Gomes, Margarida F., Cooper, Andrew I., and James, Stuart L.

Published
2015
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29. Temperature-Dependent Ultrastructure Transformation of Au–Fe Nanoparticles Investigated by in SituScanning Transmission Electron Microscopy

Author

Kamp, Marius, Tymoczko, Anna, Schürmann, Ulrich, Jakobi, Jurij, Rehbock, Christoph, Rätzke, Klaus, Barcikowski, Stephan, and Kienle, Lorenz

Abstract

Three-dimensional morphology changes of bimetallic nanoparticles (NPs) with nominal composition Au50Fe50and Au20Fe80, generated by pulsed laser ablation in liquid, are monitored in situand ex situvia scanning transmission electron microscopy and electron tomography. The samples are made up of a chemically segregated core–shell (CS) NPs structure, with an Au-rich shell and Fe-rich core, and solid solution (SS) NPs in the pristine state. Further, the examinations reveal information about a sequence of characteristic changes from the pristine metastable and intermediate ultrastructures up to thermodynamically stable products. In the case of the Au20Fe80sample, a metastable spherical CS morphology is transformed at equilibrium conditions into a cube-shaped Fe-rich core faceted by truncated Au-rich pyramids. For the Au50Fe50sample, the Au-rich shell is solved into the Fe-rich core, and chemically homogeneous (SS) NPs are formed. Interestingly, this transformation was proven to occur via an intermediate ultrastructure with lamellar segregation, not previously reported as a transient state during in situheating. On the basis of these observations, a correlation between the composition and the morphology at equilibrium is suggested, in accordance with the bulk phase diagram of Au–Fe. At the same time, our examinations directly prove that laser ablation synthesis creates nonequilibrium NP morphologies, frozen in metastable, spherical core–shell particles.

Published
2018
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40. Correlation of gas permeation and free volume in new and used high free volume thin film composite membranes.

Author

Koschine, Toenjes, Rätzke, Klaus, Faupel, Franz, Khan, Muntazim Munir, Emmler, Thomas, Filiz, Volkan, Abetz, Volker, Ravelli, Luca, and Egger, Werner

Subjects
*GAS separation membranes, *MULTIWALLED carbon nanotubes, *DETERIORATION of materials, *THIN film research, *MICROPOROSITY
Abstract

ABSTRACT Polymeric gas separation membranes frequently undergo the phenomenon of aging, that is, performance parameters like permeability decrease with storage or usage time. Here, we report on a new approach of reducing aging by incorporation of functionalized multiwalled carbon nanotubes into a polymer of intrinsic microporosity. Free volume and permeability measurements clearly show a reduced aging with incorporation of the carbon nantubes. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 213-217 [ABSTRACT FROM AUTHOR]

Published
2015
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44. Diffusion in metallic glasses and supercooled melts

Author

Faupel, Franz, primary, Frank, Werner, additional, Macht, Michael-Peter, additional, Mehrer, Helmut, additional, Naundorf, Volkmar, additional, Rätzke, Klaus, additional, Schober, Herbert R., additional, Sharma, Suman K., additional, and Teichler, Helmar, additional

Published
2003
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