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829 results on '"Kemnitz, E."'

110. Inorganic-organic nanocomposites based on sol-gel derived magnesium fluoride

Author

Noack, J., Schmidt, L., Gläsel, H.J., Bauer, M., Kemnitz, E., and Publica

Abstract

Monodispersed magnesium fluoride nanoparticles are utilized for the first time to prepare transparent inorganic-organic nanocomposite materials with improved mechanical properties. The fluorolytic sol-gel synthesis route has been modified for the preparation of monodispersed magnesium fluoride nanoparticles with a size of 2-3 nm. MgF(2) particles are effectively stabilised against agglomeration by phosphonic acids, which strongly bind to the particles and lead to an increased compatibility of the inorganic particles with the organic polymers. This way, highly transparent nanocomposite materials with up to 20 wt% magnesium fluoride in different acrylates are obtained, featuring high dispersion of MgF(2) particles in the polymer matrix and an increased hardness by the factor of 2. The nature of interaction between phosphonic acids and magnesium fluoride is thoroughly investigated by IR and NMR showing a monodentate coordination of phosphonates to the particle's surface.

Published
2011

111. Nanoscopic metal fluorides as promising sintering aids for high-performance alumina ceramics

Author

Stosiek, C., Ludwig, H., Reichel, U., Scholz, G., Kemnitz, E., and Publica

Subjects
hard alumina ceramic, nano aluminium fluoride, mechanical strength, transparent, nano magnesium fluoride, sintering additive
Abstract

Nanoscopic aluminium fluoride and magnesium fluoride were investigated as sintering additives for high-purity alumina ceramic production.Nanoscopic magnesium fluoride has been found to be an excellent sintering additive. It enables an effective limitation of grain growth compared to standard ceramic production, thus resulting in ceramics with high density, sub-µm grain size and low concentration of defects, which are perfect preconditions for an improvement of mechanical strength, transparency as well as optical properties. As a result, transparent corundum ceramics with a Vickers hardness of about 3200 were obtained. A mechanistic interpretation of the possible chemical role of nano-MgF2 in the course of texture formation, crystal growth, and densification of the corundum particles is presented based on DTA-TG and 19F MAS NMR-investigations. However, in contrast to literature reports, AlF3 is not suitable for the preparation of slurries and spray granulates with application of the standard technology mainly due to its strong tendency toward pyrohydrolysis, resulting altogether in outgassing effects.

Published
2011

115. Pt-Supported Nanocrystalline Ceria-Zirconia Doped with La, Pr or Gd: Factors Controlling Syngas Generation in Partial Oxidation/Autothermal Reforming of Methane or Oxygenates

Author

Sadykov, V. A., Mezentseva, N. V., Alikina, G. M., Lukashevich, A. I., Borchert, Y. V., Kuznetsova, T. G., Ivanov, V. P., Trukhan, S. N., Paukshtis, E. A., Muzykantov, V. S., Kuznetsov, V. L., Rogov, V. A., Julian Ross, Kemnitz, E., Mirodatos, C., Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and IRCELYON, ProductionsScientifiques

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [SDE.ES] Environmental Sciences/Environmental and Society, [CHIM.CATA]Chemical Sciences/Catalysis, [SDE.ES]Environmental Sciences/Environmental and Society, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2007

116. Design of nanostructured catalysts for syngas generation by autothermal reforming of fuels: approaches to control of the oxygen mobility in complex oxide supports and Pt dispersion

Author

Mirodatos, C., Van Veen, A.C., Sadykov, V. A., Mezentseva, N. V., Alikina, G. M., Lukashevich, A. I., Kuznetsova, T. G., Bunina, R.V., Batuev, L. C., Muzykantov, V. S., Paukshtis, E. A., Rogov, V. A., Ivanov, V. P., Parmon, V. N., Kemnitz, E., Ross, H., IRCELYON, ProductionsScientifiques, Institut de recherches sur la catalyse (IRC), and Centre National de la Recherche Scientifique (CNRS)

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Published
2006

119. Fuel-rich methane combustion: role of the Pt dispersion and oxygen mobility in a fluorite-like complex oxide support

Author

Sadykov, V.A., Kuznetsova, T.G., Frolova, Y.V., Alikina, G.M., Lukashevich, A.I., Rogov, V.A., Muzykantov, V.S., Pinaeva, L.G., Sadovskaya, E., Ivanova, Y.A., Paukshtis, E.A., Mezentseva, N.V., Parmon, V.N., Neophytides, S., Kemnitz, E., Scheurel, K., Mirodatos, C., van Veen, A.C., Institut de recherches sur la catalyse (IRC), Centre National de la Recherche Scientifique (CNRS), P. Forzatti, G. Groppi, P. Ciambelli and D. Sannino, Eds., IRCELYON, ProductionsScientifiques, and P. Forzatti, G. Groppi, P. Ciambelli and D. Sannino, Eds.

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Published
2005

120. Application of calcined Mg-Al hydrotalcites for Michael additions: an investigation of catalytic activity and acid-base properties

Author

Prescott, H. A., Li, Z. -J., Kemnitz, E., Trunschke, A., Deutsch, J., Lieske, H., Auroux, A., Institut de recherches sur la catalyse (IRC), Centre National de la Recherche Scientifique (CNRS), and IRCELYON, ProductionsScientifiques

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Abstract

Mg-Al hydrotalcite catalysts with different Mg/Al molar ratios (0.6, 1.4, 2.2, 3.0) were calcined and tested in liq.-phase Michael addns. at room temp. The catalysts and pure oxides (MgO and Al2O3) were characterized by XRD, XPS, N2 adsorption expts., 27Al MAS NMR, and TG-DTA. The acid-base properties of the samples were investigated by (a) FTIR spectroscopy after pyridine and CO2 adsorption and (b) microcalorimetry with CO2 and benzoic acid. Both acid sites (Lewis) and base sites (Lewis and Bronsted) are present on the surface of calcined hydrotalcites. The calcined hydrotalcites (CHT) catalyzed the Michael addns. of CH-acid compds. to Me vinyl ketone to give high product yields with 100% selectivity; the Al-rich sample exhibited the highest activity.

Published
2005

124. Sulfated zirconia: different syntheses, characterization and catalysis

Author

Quaschning, V., Kemnitz, E., Deutsch, J., Lieske, H., Auroux, A., IRCELYON, ProductionsScientifiques, Institut de recherches sur la catalyse (IRC), and Centre National de la Recherche Scientifique (CNRS)

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [CHIM.CATA]Chemical Sciences/Catalysis
Published
2001

126. Struktur und Eigenschaften von nanoskopischen Metall(hydroxid)fluorid-Aluminiumoxid-Kompositen

Author

Kemnitz, E., Braun, T., Stosiek, Christoph, Kemnitz, E., Braun, T., and Stosiek, Christoph

Abstract

Durch die Verwendung der fluorolytischen Sol-Gel Synthese ist es möglich, röntgenamorphe bzw. partiell nanokristalline Metallhydroxidfluoride und Metallfluoride zu erhalten. Diese Verbindungen unterscheiden sich in ihren Eigenschaften stark von „klassisch“ hergestellten, kristallinen Metall(hydroxid)fluoriden. In der vorliegenden Promotionsarbeit wurden deshalb in vier aufeinander folgenden Kapiteln sowohl die Synthese und Charakterisierung von Aluminium– und Magnesium(hydroxid)fluoriden beschrieben als auch die Auswirkung dieser Verbindungen auf das Phasentransformationsverhalten von böhmitischen Xerogelen zu Korund sowie ihre Wirksamkeit als Sinterhilfsmittel bei der Korundkeramikherstellung untersucht., The application of the fluorolytic sol-gel method with aqueous hydrofluoric acid enables the synthesis of X-ray amorphous or rather partially nanocrystalline metal hydroxide fluorides and metal fluorides. These compounds strongly differ in their characteristics from “classically” manufactured, crystalline metal hydroxide fluorides. In the present dissertation both, the synthesis and characterisation of aluminium and magnesium hydroxide fluorides were described and the effect of these compounds on the phase transformation behaviour from pseudoboehmites to corundum was examined as well as their effectiveness as sintering aid during the corundum ceramics production.

Published
2010

131. Et3GeH versusEt3SiH: controlling reaction pathways in catalytic C–F bond activations at a nanoscopic aluminum chlorofluorideElectronic supplementary information (ESI) available: Experimental procedures, analytical data. See DOI: 10.1039/c7cy00845g

Author

Meißner, G., Dirican, D., Jäger, C., Braun, T., and Kemnitz, E.

Abstract

Catalytic C–F bond activation reactions of mono- and polyfluoroalkanes at Lewis acidic amorphous aluminum chlorofluoride (ACF) are presented. The hydrogen sources Et3GeH or Et3SiH control the selectivity of the conversions. The immobilization of Et3GeH at ACF resulted in catalytic dehydrohalogenation reactions to yield olefins under very mild conditions. In contrast, if Et3SiH is immobilized at ACF, C–C coupling occured and the formation of Friedel–Crafts products was observed. MAS NMR spectroscopic studies revealed information about the surface binding of the substrates.

Published
2017
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