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Author: Krause, Beate × Type: article × Publisher: Weinheim : Wiley-VCH ×

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    Graphene Derivatives Doped with Nickel Ferrite Nanoparticles as Excellent Microwave Absorbers in Soft Nanocomposites
    (Weinheim : Wiley-VCH, 2017) Pawar, Shital Patangrao; Gandi, Mounika; Arief, Injamamul; Krause, Beate; Pötschke, Petra; Bose, Suryasarathi
    Herein, we report the development of soft polymeric composites containing multiwall carbon nanotubes (MWNTs, 1–3 wt%) and graphene derivatives doped with nickel ferrite nanoparticles (rGO@NF, 10 wt%) as lightweight microwave absorbers. The soft nanocomposites were designed using melt-mixed blends of varying compositions of PC (polycarbonate) and SAN (poly styrene acrylonitrile) by compartmentalized functional nanoparticles in one of the components of the blend (here PC). Maximum attenuation of the incoming electromagnetic (EM) radiation mainly through absorption was achieved. The hetero-dielectric media at microscopic length scale in the PC component provided large interfaces which facilitated multiple scattering thereby attenuating the incoming EM radiation. This strategy of positioning the functional nanoparticles in one of the components in the blends resulted in significantly enhanced shielding effectiveness (SE), at any given concentration of MWNTs, in contrast to PC based composites. This enhancement in SE was realized in the special morphology of the bicomponent PC/SAN=60/40 wt% blends where both the components are continuous. The enhanced SE in co-continuous blends is due to combined effect of enhanced electrical conductivity (more precisely due to interconnected network of the nanoparticles) and the presence of a hetero-dielectric media generating large scattering interfaces. For instance, the PC/SAN (60/40 wt%) co-continuous blend containing 3 wt% MWNTs and 10 wt% rGO@NF manifested in a total shielding effectiveness (SET) of −32.3 dB (i. e. more than 99.9 % attenuation of incoming EM radiation) mainly through absorption.
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    Achieving electrical conductive tracks by laser treatment of non-conductive polypropylene/polycarbonate blends filled with MWCNTs
    (Weinheim : Wiley-VCH, 2014) Liebscher, Marco; Krause, Beate; Pötschke, Petra; Barz, Andrea; Bliedtner, Jens; Möhwald, Michael; Letzsch, Alexander
    Electrical non-conductive polymer blends consisting of a polypropylene (PP) matrix and dispersed particles of polycarbonate (PC) were melt compounded with 3 wt.% multiwalled carbon nanotubes (MWCNTs) loading and processed into plates by injection molding. The morphological analysis confirmed the selective localization of the MWCNTs in the PC component. By local irradiation with a CO2 laser beam, depending on the laser conditions, conductive tracks with dimensions of about 2 mm width, 80 to 370 μm depth and line resistances as low as 1.5 kΩ · cm-1 were created on the surface of the non-conductive plates. The factors affecting the line resistance are the PC content, the laser speed and laser power, as well as laser direction with respect to the melt flow direction. After the irradiation an enrichment of MWCNTs in the laser lines was detected indicating that conductive paths were generated by percolation of nanotubes selectively within these lines in otherwise non-conductive plates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.