Filters

2011 - 20173

More filters

20233
Reset filters

Settings

Author: Krause, Beate × End date: 2019 × DDC: 540 × Subject: Polymer ×

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Polypropylene-based melt mixed composites with singlewalled carbon nanotubes for thermoelectric applications: Switching from p-type to n-type by the addition of polyethylene glycol
    (Oxford : Elsevier Science, 2017) Luo, Jinji; Cerretti, Giacomo; Krause, Beate; Zhang, Long; Otto, Thomas; Jenschke, Wolfgang; Ullrich, Mathias; Tremel, Wolfgang; Voit, Brigitte; Pötschke, Petra
    The thermoelectric properties of melt processed conductive nanocomposites consisting of an insulating polypropylene (PP) matrix filled with singlewalled carbon nanotubes (CNTs) and copper oxide (CuO) were evaluated. An easy and cheap route to switch p-type composites into n-type was developed by adding polyethylene glycol (PEG) during melt mixing. At the investigated CNT concentrations of 0.8 wt% and 2 wt% (each above the electrical percolation threshold of ∼0.1 wt%), and a fixed CuO content of 5 wt%, the PEG addition converted p-type composites (positive Seebeck coefficient (S)) into n-type (negative S). PEG was also found to improve the filler dispersion inside the matrix. Two composites were prepared: P-type polymer/CNT composites with high S (up to 45 μV/K), and n-type composites (with S up to −56 μV/K) through the addition of PEG. Two prototypes with 4 and 49 thermocouples of these p- and n-type composites were fabricated, and delivered an output voltage of 21 mV and 110 mV, respectively, at a temperature gradient of 70 K.
  • Thumbnail Image
    Item
    Characterization of the state of dispersion of carbon nanotubes in polymer nanocomposites
    (Weinheim : Wiley-VCH Verl., 2011) Buschhorn, Samuel T.; Wichmann, Malte H. G.; Sumfleth, Jan; Schulte, Karl; Pegel, Sven; Kasaliwal, Gaurav R.; Villmow, Tobias; Krause, Beate; Göldel, Andreas; Pötschke, Petra
    A practical overview of possibilities and limits to characterize the state of dispersion of carbon nanotubes (CNT) in polymer based nanocomposites is given. The most important and widely available methods are discussed with practical employment in mind. One focus is the quantitative characterization of the state of dispersion in solid samples using microscopy techniques such as optical microscopy or transmission electron microscopy. For dispersions of CNTs in aqueous media, solvents or monomers a sedimentation analysis is presented. This way dispersability and dispersion state of CNTs can be assessed. Indirect methods such as electrical conductivity measurements and rheological tests, dynamic differential scanning calorimetry and mechanical test are discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Thumbnail Image
    Item
    Methods to characterize the dispersability of carbon nanotubes and their length distribution
    (Weinheim : Wiley-VCH Verl., 2012) Krause, Beate; Mende, Mandy; Petzold, Gudrun; Boldt, Regine; Pötschke, Petra
    Two main properties of carbon nanotube (CNT) materials are discussed in this contribution. First, a method to characterize the dispersability of CNT materials in aqueous surfactant solutions in presented, which also allows conclusions towards the dispersability in other media, like polymer melts. On the other hand it is shown, how the length of CNTs before and after processing, e.g., after melt mixing with thermoplastics, can be quantified. Both methods are illustrated with examples and the practical relevance is shown. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.