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Fakultätsübergreifendes Institut für Werkstofftechnik

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Univ.-Prof. Dr. Edda Rädlein


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Caba, Stefan; Koch, Michael
Process design for void-minimized liquid composite molding. - In: Junior Euromat 2016 : 13th FEMS Junior EUROMAT, Lausanne, Switzerland, 10-14 July 2016 : abstract e-book / created by: Margarethe Hofmann-Amtenbrink, Dr.-Ing. ; in collaboration with Nga Wun Chan ; FEMS, Federation of European Materials Societies. - Pully : MatSearch Consulting / Junior EUROMAT ; 13 (Lausanne) : 2016.07.10-14. - Pully : MatSearch Consulting, ISBN 978-2-8399-1926-5, (2016), Abstract number: 2639, Seite 55-56

The production of fiber reinforced lightweight components for automotive and aerospace industry in resin transfer molding (RTM) has achieved considerable progress during the last decade. Cycle times were reduced from hours to minutes and processes are being automated continuously. A major obstacle for industrial serial manufacturing is the formation of voids during the process as injection times tend to be reduced. These defects are usually air entrapments in a microscopic scale. Voids can be formed due to inaccurate molds and material handling as well as process inherent circumstances. Two different categories can be classified. Air entrapments can be measured in the fiber bundles and in the flow channels between the bundles. The parameters effecting these voids in resin transfer molding were examined using a glass wall mold and an inline measurement. It could be shown that void formation is frequently a product of unbalanced flow fronts. The conditions for the two classes can be expressed in the dimensionless modified capillary number. Based on the design of experiments method this number was tested on the predictability of void formation during injection in RTM processes. In the experiments a major effect of the fiber reinforcement setup could be detected. By means of additional wetting analyses in a microscopic scale, characteristic flow front shapes were measured. The bundle geometry and the weave pattern were identified as influencing factors on the flow front. These are not included in the modified capillary number leading to a lower quality level. New key numbers were derived implementing these parameters to improve the accuracy of a prediction of void formation. The key numbers were used to create a process simulation based on analytical approaches. An algorithm was implemented that calculates feasible process parameters referring to process boundary conditions and used materials. The viscosity development of the resin is included using a new Weibull approach characterizing the processing ability of the resin. The outputs of the simulation are all necessary parameters for a production of parts with minimum cycle time at a user specified maximum void level. Means to apply these parameters to industrial processes include the volume flow rate control during injection. The selection of fiber reinforcements and resins based on process design aims is assisted. The results are transferable to other processes and enable a faster start-up of production processes for newly designed lightweight components.
Caba, Stefan; Fiebig, Christian; Koch, Michael
Application of desert sands for polymer concrete. - In: Junior Euromat 2016 : 13th FEMS Junior EUROMAT, Lausanne, Switzerland, 10-14 July 2016 : abstract e-book / created by: Margarethe Hofmann-Amtenbrink, Dr.-Ing. ; in collaboration with Nga Wun Chan ; FEMS, Federation of European Materials Societies. - Pully : MatSearch Consulting / Junior EUROMAT ; 13 (Lausanne) : 2016.07.10-14. - Pully : MatSearch Consulting, ISBN 978-2-8399-1926-5, (2016), Abstract number: 2853, Seite 43

The refugee crisis has shown that the fast construction of medium-term homes in crisis regions is a major challenge. Particularly in the middle east the lacks of suitable construction sands, energy, water and infrastructure leads to the requirement of novel production methods for building blocks. In the present work, methods for the application of local sands in polymer concrete bricks were developed. The basic conditions and requirements for a concept of a mobile production plant for bricks were analyzed. A layout consisting of standard shipping containers was chosen. A production chain with defined mixtures of cleaned quartz sands, rock flour and polyester resin could be configured to manifacture bricks containing 87 % filling material in an inline-process with a cycle time of less than one hour. The adaption for natural desert sands started with an analysis of variying temperatures and humidity. Sands from multiple countries around the earth were analyzed in rheometer experiments. It could be shown that the curing times depend on the filling sand, preventing a simplified implementation into the established processes. The desert sands were characterized for differences in particle size, particle shape, specific heat capacity and chemical composition. Particle analysis showed that a larger angle of repose leads to fewer void content in the brick. The minor differences of specific heat were not sufficient to inhibit the self-acceleration of the exothermic resin reaction. The divergences of the chemical composition were identified as the most important obstacle. The premise is that available sands should be used. Thus the only possibility was to adapt the mixture of the polyester resin to the filling material. The resin is inhibited to ensure adequate time for wetting the sand. MEKP hardeners were combined with cobalt and cobalt-amine accelerators. The analysis showed that especially cobalt-amine accelerators lead to the pursued cycle time of under 60 minutes. On the other hand a correlation between the metallic elements in the sand and the viscosity increase of the polymer concrete could be obtained. These elements impede the effect of the cobalt complex in the accelerator. Particular ratios of hardener and accelerator for every sand must be applied. A user-friendly fast test was developed that can be performed on site. So the suitability of the resin and the filling material is ensured. The mechanical properties of desert sand and quartz sand polymer concrete were measured in standard devices. The results show that the strength of common polymer concrete can almost be achieved. Desert sand bricks could be used even to build two-storey houses. Based on the examinations a mold concept for the establishment of a series process was derived. The comparatively high shrinkage of the polyester resin and the friction of the sand were taken into account to design a manufacturing mold with a reusable core. It could be shown that the application of desert sands for the production of building blocks is possible. The impacting factors were examined and a concept for a process adapted to the natural resources was established. A mobile production plant can now be built to help diminish the harm of refugees in crisis regions.
Ivanov, Svetlozar; Barylyak, Adriana; Besaha, Khrystyna; Dimitrova, Anna; Krischok, Stefan; Bund, Andreas; Bobitski, Jaroslav
Enhanced lithium ion storage in TiO2 nanoparticles, induced by sulphur and carbon co-doping. - In: Journal of power sources : the international journal on the science and technology of electrochemical energy systems. - New York, NY [u.a.] : Elsevier, ISSN 18732755, Bd. 326 (2016), S. 270-278
Im Titel ist "2" tiefgestellt
Sandjaja, Marco; Stolle, Thomas; Bund, Andreas; Lang, Klaus-Dieter
Investigation of all wet chemical process for the barrier formation in high aspect ratio silicon vias. - In: IEEE transactions on electron devices : ED : a publication of the IEEE Electron Devices Society. - New York, NY : IEEE, ISSN 00962430, Bd. 63 (2016), 8, S. 3199-3204
Gruia, Violeta-Tincuta
Preparation and electrochemical performance of PEDOT - AuNPs nanocomposite layers for the seletive detection of neurotransmitters. - Ilmenau : Universitätsbibliothek. - 1 Online-Ressource (119 Seiten)
Technische Universität Ilmenau, Dissertation, 2016

Poly-3,4-ethylendioxythiophen (PEDOT) ist, aufgrund seiner guten elektrochemischen Stabilität und hoher Leitfähigkeit eines der am meistgenutzten leitfähigen Polymere [1]. Es wurde im Jahr 1988 von der Bayer AG, Leverkusen synthetisiert [1]. Jüngst wurde der Erforschung von Verbundmaterialien besondere Aufmerksamkeit zuteil, deren Grundlage leitfähiger Polymere bilden, auf die verschiedene Metalle abgeschieden wurden. Diese Nanoverbundmaterialien haben ein geringes Gewicht, eine große Oberfläche, das Potenzial zur nicht-enzymatischen Detektion und sind preisgünstig. Die Verarbeitung ist unkompliziert und einfach ausbaubar [1]. Catecholamine sind eine Stoffgruppe von Neurotransmittern und ihre Detektion im menschlichen Körper ist für Neurowissenschaftler von großem Interesse. Zu der Stoffgruppe zählen Dopamin, Serotonin, Adrenalin und sie spielen wichtige Rollen in verschiedenen biologischen, pharmakologischen und physikalischen Prozessen. Unter den verschiedenen Analysetechniken haben insbesondere elektrochemische Methoden viel Beachtung erfahren, da sie einfach, selektiv, günstig und weniger zeitaufwändig sind. Zudem können sie in einer Echtzeit-in-situ Bestimmung angewandt werden [2]. Die elektrochemische Analyse auf unmodifizierten Elektroden wie glasartigem Kohlenstoff oder Goldelektroden, wie in unserer Arbeit verwendet, hat ihre Limitierungen aufgrund von überlappenden voltammetrischen Peaks und hohen Konzentrationen von Ascorbinsäure [3]. Das Hauptziel dieser Arbeit war es eine neue Generation von modifizierten Elektroden, PEDOT/Au Nanopartikel, zu entwickeln, die differenzierbare Oxidationspeaks des Analyten aufweisen. Die Sensitivität der Dopamindetektion steigerte sich mit PEDOT/Au Nanopartikeln um das Dreifache, von 0,13+/-0,01/ microA/microM auf 0,3+/-0,03/ microA/microM. Die zweite lineare Region die im nanomolekularen Bereich gefunden wurde weist eine höhere Steigung auf (0,04+/-0,0002/ microA/microM). Dies entspricht einer höheren Sensitivität. Auch für die Serotonindetektion wurde mit PEDOT/Au Nanopartikeln eine höhere Sensitivität erreicht (0,4+/-0,04/ microA/microM). Der Vergleich mit den Daten der PEDOT-Schicht (0,13+/-0,004/ microA/microM) zeigt auch hier eine um das Dreifache gesteigerte Sensitivität. Eine zweite höher sensitive lineare Region wurde für eine Konzentration im nanomolekularen Bereich zwischen 50 nM und 500 nM nur für die Nanokompositschichten gefunden. Die Sensitivität für die Serotonindetektion von Nanokompositelektroden stieg im nanomolaren Bereich um das Hundertfache an. Um die abgeschiedene Metalmasse auf den vorsynthetisierten Polymerfilmen zu berechnen, haben wir ein Model vorgeschlagen, dass auf den EQCM Untersuchungen beruht. Die Reproduzierbarkeit wurde ebenfalls untersucht und diese Daten beweisen auch, dass PEDOT Nanokompositschichten einen vielversprechender Kandidaten für einen amperometrischen Sensor für die elektrochemische Detektion von Catecholaminen darstellt.
Wulfmeier, Hendrik; Omelcenko, Alexander; Albrecht, Daniel; Klimm, Detlef; El Mofid, Wassima; Strafela, Marc; Ulrich, Sven; Bund, Andreas; Fritze, Holger
Thermal stability of materials for thin-film electrochemical cells investigated by thin-film calorimetry. - In: MRS advances : a journal of the Materials Research Society (MRS). - Cambridge : Cambridge University Press, ISSN 20598521, Bd. 1 (2016), 15, S. 1043-1049
Inayat, Alexandra; Reinhardt, Björn; Herwig, Jan; Küster, Christian; Uhlig, Hans; Krenkel, Sharon; Rädlein, Edda; Enke, Dirk
Recent advances in the synthesis of hierarchically porous silica materials on the basis of porous glasses. - In: New journal of chemistry. - London : RSC, ISSN 13699261, Bd. 40 (2016), 5, S. 4095-4114
Dyck, Tobias; Bund, Andreas
An adaption of the Archard equation for electrical contacts with thin coatings. - In: Tribology international. - Amsterdam [u.a.] : Elsevier Science, ISSN 0301679X, Bd. 102 (2016), S. 1-9
Kuriganova, Alexandra B.; Vlaic, Codruta A.; Ivanov, Svetlozar; Leontyeva, Daria V.; Bund, Andreas; Smirnova, Nina V.
Electrochemical dispersion method for the synthesis of SnO2 as anode material for lithium ion batteries. - In: Journal of applied electrochemistry. - Dordrecht [u.a.] : Springer Science + Business Media B.V, ISSN 15728838, Bd. 46 (2016), 5, S. 527-538
Im Titel ist "2" tiefgestellt
Wang, Dong
Preparation and properties of tailored nanomaterials and nanocomposites. - Ilmenau. - 1 Band (verschiedene Zählungen)
Technische Universität Ilmenau, Habilitationsschrift, 2016