Filters

20212

More filters

2021 - 20222
Show more
Reset filters

Settings

Author: González-García, Lola × Author: Kraus, Tobias × Author: Kuttich, Björn × End date: 2024 × Start date: 2020 × DDC: 540 × WGL Institute: INM ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Percolation of rigid fractal carbon black aggregates
    (Melville, NY : American Institute of Physics, 2021) Coupette, Fabian; Zhang, Long; Kuttich, Björn; Chumakov, Andrei; Roth, Stephan V.; González-García, Lola; Kraus, Tobias; Schilling, Tanja
    We examine network formation and percolation of carbon black by means of Monte Carlo simulations and experiments. In the simulation, we model carbon black by rigid aggregates of impenetrable spheres, which we obtain by diffusion-limited aggregation. To determine the input parameters for the simulation, we experimentally characterize the micro-structure and size distribution of carbon black aggregates. We then simulate suspensions of aggregates and determine the percolation threshold as a function of the aggregate size distribution. We observe a quasi-universal relation between the percolation threshold and a weighted average radius of gyration of the aggregate ensemble. Higher order moments of the size distribution do not have an effect on the percolation threshold. We conclude further that the concentration of large carbon black aggregates has a stronger influence on the percolation threshold than the concentration of small aggregates. In the experiment, we disperse the carbon black in a polymer matrix and measure the conductivity of the composite. We successfully test the hypotheses drawn from simulation by comparing composites prepared with the same type of carbon black before and after ball milling, i.e., on changing only the distribution of aggregate sizes in the composites.
  • Thumbnail Image
    Item
    Hybrid Dielectric Films of Inkjet-Printable Core-Shell Nanoparticles
    (Weinheim : Wiley-VCH, 2021) Buchheit, Roman; Kuttich, Björn; González-García, Lola; Kraus, Tobias
    A new type of hybrid core-shell nanoparticle dielectric that is suitable for inkjet printing is introduced. Gold cores (dcore  ≈ 4.5 nm diameter) are covalently grafted with thiol-terminated polystyrene (Mn  = 11000 Da and Mn  = 5000 Da) and used as inks to spin-coat and inkjet-print dielectric films. The dielectric layers have metal volume fractions of 5 to 21 vol% with either random or face-centered-cubic structures depending on the polymer length and grafting density. Films with 21 vol% metal have dielectric constants of 50@1 Hz. Structural and electrical characterization using transmission electron microscopy, small-angle X-ray scattering, and impedance spectroscopy indicates that classical random capacitor-resistor network models partially describe this hybrid material but fail at high metal fractions, where the covalently attached shell prevents percolation and ensures high dielectric constants without the risk of dielectric breakdown. A comparison of disordered to ordered films indicates that the network structure affects dielectric properties less than the metal content. The applicability of the new dielectric material is demonstrated by formulating inkjet inks and printing devices. An inkjet-printed capacitor with an area of 0.79 mm2 and a 17 nm thick dielectric had a capacitance of 2.2±0.1 nF@1 kHz .