Technologie-Entwicklungsgruppe TEG

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  • Publication
    Multiwalled carbon-nanotubes-sheet actuators
    ( 2005)
    Haque, Mohammed H.
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    Kolaric, Ivica
    ;
    Vohrer, Uwe orcid-logo
    ;
    Wallmersperger, Thomas
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    D'Ottavio, Michele
    ;
    Kroplin, Bernd
    In this paper we present experimental measurements as well as a theoretical model for the chemo-electro-mechanical behavior of multi walled (MWNT) carbon nanotubes sheet actuators. Investigations of MWNT paper as an actuator and the analysis of the experimental and theoretical characteristics are special features of the presented work. The influencing parameters of the actuation behavior such as thickness of sheet materials and electrolyte concentration have been investigated. We report the experimentally measured active displacement varying quadratically with the applied electric field and non-linearly with the electrolyte concentration. In the theoretical part, we present a macroscopic actuation model for the global displacement behavior of MWNT materials. Finally, a comparison between the theoretical and the experimental investigations has been conducted.
  • Publication
    Carbon-nanotube-sheet actuator - theoretical and experimental investigations
    ( 2004)
    Haque, M.H.
    ;
    Kolaric, I.
    ;
    Vohrer, Uwe orcid-logo
    ;
    Wallmersperger, T.
    ;
    Kröplin, B.
    In this paper we present experimental measurements as well as a theoretical model for the electro-mechanical behavior of single walled carbon nanotube (SWNT) sheet actuators. The SWNT material exhibits elongation and contraction of the carbon bond length due to electro-chemically induced surface charge and works at a relatively low operating voltage. The use of carbon nanotube sheet material sandwich with porous ceramic is a special feature of the presented work. In the experiment, two layers of SWNT with a ceramic layer in between were placed between two working-electrodes in an electrolyte solution bath. The counter electrode has been placed within the solution away from the composite. The charge transfer takes place between the working and the counter electrodes. The displacement of the composite was measured in the thickness direction, i.e. between the fixed and the mobile working electrodes. Depending on the applied voltage, different displacement values up to 0.8% of its original thickness were obtained. As influencing factors, the parameters such as applied electric field, thickness of the composite, solvent and electrode type were investigated. A clear dependency of the actuation on the applied potential was observed within the electro-chemical window. It is remarkable that an applied electric voltage exceeding the window leads to a hydrolysis of the solvent, i.e. generation of gas bubbles. In the theoretical part, a macroscopic model for the actuation of the SWNT material has been developed. A mechanical field equation which uses the applied electric potential as input gives the elongation and contraction of the material. Depending on the parameters given above, the time-behavior of the actuator has been simulated. Thus, by various numerical simulations and experimental investigations, the actuator-characteristics can be optimized. In conclusion, a good corelation between the experimental and the numerical results has been determined.
  • Publication
    Carbon nanotube sheets for the use as artificial muscles
    ( 2004)
    Vohrer, Uwe orcid-logo
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    Kolaric, I.
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    Haque, M.H.
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    Roth, S.
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    Detlaff-Weglikowska, U.
    Low voltage artificial muscles are of great importance for an enormous variety of industrial applications. In 1999 a new material, carbon nanotube sheets also called bucky paper, was described with suitable electromechanical properties. We developed an experimental set-up which allows, for the first time, the analysis of actuation forces vertical to the sheet plane. Single walled carbon nanotubes (SWNT) from arc discharge or HiPco process as well as multi walled carbon nanotubes (MWNT) were used as received or after further purification steps to produce carbon nanotube sheets by the filtration technique. The fastest actuation time of three seconds could be, up to now, obtained with the HiPCo-material, which is free of amorphous carbon particles. Several parameters influence the electromechanical properties like the sheet thickness, the used electrolyte, the applied voltage and so on. But also the nanotube material itself and the procedure for the bucky paper production must be considered intensively to avoid large differences between different batches and to produce indiscriminate and reproducible carbon nanotube sheets. We characterized the material, among others, by TGA, SEM/EDX, and BET analysis.