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Fakultätsübergreifendes Institut für Werkstofftechnik

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Univ.-Prof. Dr. Edda Rädlein


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El Mofid, Wassima
Synthesis and characterization of novel cathode material with improved specific capacity and safety for lithium ion batteries. - Ilmenau : Universitätsbibliothek. - 1 Online-Ressource (xix, 121 Seiten)
Technische Universität Ilmenau, Dissertation, 2016

Die steigenden Anforderungen an Lithium-Ionen-Batterien mit hoher spezifischer Leistung und Energie haben zur Entwicklung von mehreren Klassen von Materialien für die positive Elektrode geführt. Darunter sind unter anderem die vielversprechenden LiNixMnyCo1-x-yO2 (NMC) Materialien. In diesem Zusammenhang ist das Thema dieser Arbeit eine umfangreichen Studie der elektrochemischen und strukturellen Eigenschaften des ursprünglichen Materials NMC (3:1:1) (LiNi0.6Mn0.2Co0.2O2) und der drei neuen Materialien, die entweder durch Mono-Substitution von Co mit Al oder Fe: NMCA (LiNi0.6Mn0.2Co0.15Al0.05O2) und NMCF (LiNi0.6Mn0.2Co0.15Fe0.05O2) oder durch doppelte Substitution von Co mit Al und Fe NMCAF (LiNi0.6Mn0.2Co0.15Al0.025 Fe0.025O2) hergestellt wurden. Im ersten Schritt wurde eine Optimierung der Synthesebedingungen durchgeführt. Dazu wurden verschiedene Verfahren (z.B. Röntgenbeugung, Rasterelektronenmikroskopie) verwendet, um homogene Phasen mit gut geordneter Struktur zu erhalten. Im zweiten Schritt wurden Struktur, morphologische und elektrochemische Eigenschaften der vier Materialien untersucht. Eine detailliertere Untersuchung wurde NMCAF gewidmet. Dieses Material zeigte die besten elektrochemischen Eigenschaften im Vergleich zu den ursprünglichen und den mono-substituierten Materialien. Ziel ist es zu verstehen, was die Mechanismen hinter der Verbesserung des elektrochemischen Verhaltens des doppelsubstituierten Materials sind. Schließlich wurde der Sicherheitsaspekt von NMCAF auf Basis einer detaillierten Untersuchung der thermischen Stabilität während der Lithium-Ionen-Deinterkalation diskutiert.
Caba, Stefan; Koch, Michael
Modeling the viscosity development of epoxy resins during injection of the RTM process. - In: AIP conference proceedings. - Melville, NY : Inst, ISSN 15517616, Bd. 1779 (2016), S. 070002, insges. 5 S.

The development of, in particular RTM, processes for fiber reinforced composite parts is driven by cost reduction that can be achieved by shorter cycle times. The main sub processes are the injection and the curing time of the resin. Both depend directly on resin properties. During the injection phase the viscosity of the resin is a main factor for the flow rate. Additionally, the wetting of fibers and within that the void formation is influenced. The cure of the resin is the most time intensive sub process. In this paper a new model for the description of the resin viscosity development during the injection phase using the cumulative Weibull distribution function is presented. A study of the isothermal viscosity development of numerous resins has been conducted in a wide temperature range ascertaining the applicability. New possibilities for advanced resin selection and a more accurate modeling of the void formation during an injection phase of the RTM process are shown to confirm the benefit of this model.
Düngen, Matthias; Hartung, Sascha; Koch, Michael
Energy balance analysis of the feed zone of grooved barrel single screw extruders. - In: AIP conference proceedings. - Melville, NY : Inst, ISSN 15517616, Bd. 1779 (2016), S. 030011, insges. 5 S.

The energy balance in the feed zone of grooved barrel single screw extruders is important for design and operation of such extruders. Experimental investigations with different bulk materials were undertaken to obtain further insight into the energy balance of the feed zone. The energy balance considers the enthalpy change resulting from temperature and density increase as a result of screw drive power and heat flow in the barrel. Experimental results show a decreasing solid bed temperature for decreasing residence times. In addition, with a reduced gap in the throttle with constant throughput, the pressure increases resulting into various deformation mechanisms of solid particles. The energy required for the deformation of solid particles into a solid bed elevates the specific screw drive power and heat generation. It is shown that the compression behavior of bulk materials is temperature-dependent and influences the energy balance in the feed zone.
Woyan, Felix; Bruchmüller, Matthias; Koch, Michael
Process parameters affecting the bonding of in-mold decoration of injection molded components. - In: AIP conference proceedings. - Melville, NY : Inst, ISSN 15517616, Bd. 1779 (2016), S. 020008, insges. 5 S.

This paper studies the fundamental parameters affecting bonding strength of injection molded parts by an in- mold decoration process (IMD). In order to investigate the influence of materials used and a variety of processing conditions, a test mold was created for experiments. The impact of each factor was examined quantitatively by a full factorial design of experiment (DOE). The DOE covered as processing parameters melt temperature, mold temperature and packing pressure and for product related parameters film thickness and thermoplastic material. Furthermore, the temperature in the boundary layer was experimentally determined and the thermal conditions calculated with a transient simulation. In addition, the results of the experiment were compared with the simulation.
Schneidmadel, Stefan; Koch, Michael; Bruchmüller, Matthias
Effects of fiber orientation on the electrical conductivity of filled plastic melt. - In: AIP conference proceedings. - Melville, NY : Inst, ISSN 15517616, Bd. 1779 (2016), S. 030007, insges. 5 S.

The substitution of conventional materials using technical plastic materials offers a high potential for integration of functions into plastics products. In this context, the light-weight design aspect as well as the simplification of complex production processes can be addressed. As an example, plastics can be modified to transfer an electrical charge by adding conductive particles. The conductivity of these plastic materials depends on the used particle system, processing parameters and part geometry. Today's simulation programs offer the possibility of forecasting fiber orientation in plastic parts as a result of processing. This work analyses the relation between simulated fiber orientation and conductivity in the plastic part. Therefore test specimen were produced on an injection molding machine with different processing parameters. Simulations were executed and the fiber orientation tensor for different processing parameters was calculated. In comparison between simulated and experimentally effected fiber orientation, the possibility of forecasting the electrical conductivity was analyzed and it could be shown that there is a good correlation.
Herz, Andreas; Wang, Dong; Schaaf, Peter
Hats off to self-organisation and self-assembly!. - In: German research : magazine of the Deutsche Forschungsgemeinschaft. - Weinheim : Wiley-VCH, ISSN 15222322, Bd. 38 (2016), 2, S. 26-29
Wiederhold, Andreas; Ebert, Reschad; Weidner, Markus; Halbedel, Bernd; Fröhlich, Thomas; Resagk, Christian
Influence of the flow profile to Lorentz force velocimetry for weakly conducting fluids - an experimental validation. - In: Measurement science and technology : devoted to the theory, practice and application of measurement in physics, chemistry, engineering and the environmental and life sciences from inception to commercial exploitation. - Bristol : IOP Publ, ISSN 13616501, Bd. 27 (2016), 12, S. 125306, insges. 9 S.

The Lorentz force velocimetry (LFV) is a highly feasible contactless method for measuring flow rate in a pipe or in a channel. This method has been established for liquid metal flows but also for weakly conducting electrolytes where the Lorentz force amplitudes are typically six orders smaller than the ones from liquid metal flows. Due to an increased resolution of the Lorentz force measurements which was the main focus of research in the last years, now it is possible to investigate the influence of the flow profile on the amplitude of the Lorentz force. Even if there is a semi-theoretical approach an experimental validation is still outstanding. Therefore we have tested symmetric and asymmetric flow profiles to test the LFV for weakly conducting fluids for typical industrial flows. Salt water has been used as a test electrolyte with constant values of the electrical conductivity from 0.035 to 20 S m-1 and of the flow velocity in a range of 0.5-3 m s-1. We confirmed by extensive measurements that LFV is a suitable method for flow measurements even for different flow profiles within 5% measurement uncertainty. For a wide range of applications in research and industry the LFV should be not sensitive to various flow profiles.
Yan, Yong; Radu, Andreea Ioana; Rao, Wenye; Wang, Hongmei; Chen, Ge; Weber, Karina; Wang, Dong; Cialla-May, Dana; Popp, Jürgen; Schaaf, Peter
Mesoscopically Bi-continuous Ag-Au hybrid nanosponges with tunable plasmon resonances as bottom-up substrates for surface-enhanced Raman spectroscopy. - In: Chemistry of materials. - Washington, DC : American Chemical Society, ISSN 15205002, Bd. 28 (2016), 21, S. 7673-7682

Ag-Au hybrid nanosponges (NSs) with controlled porosity and composition ratio were fabricated through the cyclic electroless deposition of Ag into the porous Au NSs. In the Ag-Au hybrid NSs, both Au and Ag components with mesoscaled ligament size are bicontinuously percolated over the entire structure. The plasmonic properties of the Ag-Au hybrid NSs differ clearly from those of the Au NSs and the solid Au-Ag alloy nanoparticles, and two distinct plasmon peaks were observed which can be attributed to Au and Ag components, respectively. The plasmonic properties can be well tuned by controlling the cycles of Ag deposition. Both plasmon peaks attributed to Au and Ag components blue shift with increasing amount of Ag. The volume porosity decreases upon increasing amount of deposited Ag. The results of the theoretical calculations reveal that the deceasing porosity could play an important role in the blue shift. Moreover, the Ag-Au hybrid NSs exhibit higher sensitivity in surface-enhanced Raman spectroscopy (SERS) detection of butter yellow (BY) than the Au NSs due to the presence of Ag and of the porous structure. Also, the as-prepared structures present a built-in preference for hydrophobic analytes.
Ivanov, Svetlozar; Vlaic, Codruta; Bund, Andreas; Efimov, Igor
In situ analysis of surface morphology and viscoelastic effects during deposition of thin silicon layers from 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide. - In: Electrochimica acta : the journal of the International Society of Electrochemistry (ISE). - New York, NY [u.a.] : Elsevier, Bd. 219 (2016), S. 251-257
Wojciechowski, Jarosław; Szubert, Karol; Peipmann, Ralf; Fritz, Mathias; Schmidt, Udo; Bund, Andreas; Lota, Grzegorz
Anti-corrosive properties of silane coatings deposited on anodised aluminium. - In: Electrochimica acta : the journal of the International Society of Electrochemistry (ISE). - New York, NY [u.a.] : Elsevier, Bd. 220 (2016), S. 1-10