Filters

2020 - 20213

More filters

2021 - 20223
Reset filters

Settings

Author: Krause, Beate × End date: 2024 × End date: 2024 × Start date: 2020 × Subject: Carbon nanotubes × WGL Institute: IPF ×

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Blend Structure and n-Type Thermoelectric Performance of PA6/SAN and PA6/PMMA Blends Filled with Singlewalled Carbon Nanotubes
    (Basel : MDPI, 2021-4-28) Krause, Beate; Liguoro, Alice; Pötschke, Petra
    The present study investigates how the formation of melt-mixed immiscible blends based on PA6/SAN and PA6/PMMA filled with single walled nanotubes (SWCNTs) affects the thermoelectric (TE) properties. In addition to the detailed investigation of the blend morphology with compositions between 100/0 wt.% and 50/50 wt.%, the thermoelectric properties are investigated on blends with different SWCNT concentrations (0.25–3.0 wt.%). Both PA6 and the blend composites with the used type of SWCNTs showed negative Seebeck coefficients. It was shown that the PA6 matrix polymer, in which the SWCNTs are localized, mainly influenced the thermoelectric properties of blends with high SWCNT contents. By varying the blend composition, an increase in the absolute Seebeck coefficient, power factor (PF), and figure of merit (ZT) was achieved compared to the PA6 composite which is mainly related to the selective localization and enrichment of SWCNTs in the PA6 matrix at constant SWCNT loading. The maximum PFs achieved were 0.22 µW/m·K2 for PA6/SAN/SWCNT 70/30/3 wt.% and 0.13 µW/m·K2 for PA6/PMMA/SWCNT 60/40/3 wt.% compared to 0.09 µW/m·K2 for PA6/3 wt.% SWCNT which represent increases to 244% and 144%, respectively. At higher PMMA or SAN concentration, the change from matrix-droplet to a co-continuous morphology started, which, despite higher SWCNT enrichment in the PA6 matrix, disturbed the electrical conductivity, resulting in reduced PFs with still increasing Seebeck coefficients. At SWCNT contents between 0.5 and 3 wt.% the increase in the absolute Seebeck coefficient was compensated by lower electrical conductivity resulting in lower PF and ZT as compared to the PA6 composites.
  • Thumbnail Image
    Item
    Mixed Carbon Nanomaterial/Epoxy Resin for Electrically Conductive Adhesives
    (Basel : MDPI, 2020) Lopes, Paulo E.; Moura, Duarte; Hilliou, Loic; Krause, Beate; Pötschke, Petra; Figueiredo, Hugo; Alves, Ricardo; Lepleux, Emmanuel; Pacheco, Louis; Paiva, Maria C.
    The increasing complexity of printed circuit boards (PCBs) due to miniaturization, increased the density of electronic components, and demanding thermal management during the assembly triggered the research of innovative solder pastes and electrically conductive adhesives (ECAs). Current commercial ECAs are typically based on epoxy matrices with a high load (>60%) of silver particles, generally in the form of microflakes. The present work reports the production of ECAs based on epoxy/carbon nanomaterials using carbon nanotubes (single and multi-walled) and exfoliated graphite, as well as hybrid compositions, within a range of concentrations. The composites were tested for morphology (dispersion of the conductive nanomaterials), electrical and thermal conductivity, rheological characteristics and deposition on a test PCB. Finally, the ECA’s shelf life was assessed by mixing all the components and conductive nanomaterials, and evaluating the cure of the resin before and after freezing for a time range up to nine months. The ECAs produced could be stored at −18 °C without affecting the cure reaction.
  • Thumbnail Image
    Item
    Nanocomposites with p-and n-type conductivity controlled by type and content of nanotubes in thermosets for thermoelectric applications
    (Basel : MDPI, 2020) Kröning, Katharina; Krause, Beate; Pötschke, Petra; Fiedler, Bodo
    In this work, composites based on epoxy resin and various carbon nanotubes (CNTs) were studied regarding their thermoelectric properties. The epoxy composites were prepared by infiltration of preformed CNT buckypapers. The influence of different types of CNTs on the Seebeck coefficient was investigated, namely lab-made and commercially available multi walled carbon nanotubes (MWCNTs), lab-made nitrogen doped MWCNTs (N-MWCNT) and commercially available single walled carbon nanotubes (SWCNTs). It was found that only by varying the lab-made MWCNT content could both n-and p-type composites be produced with Seebeck coefficients between -9.5 and 3.1 µV/K. The incorporation of N-MWCNTs resulted in negative Seebeck coefficients of -11.4 to -17.4 µV/K. Thus, the Seebeck coefficient of pure SWCNT changed from 37.4 to -25.5 µV/K in the epoxy/1 wt. % SWCNT composite. A possible explanation for the shift in the Seebeck coefficient is the change of the CNTs Fermi level depending on the number of epoxy molecules on the CNT surface. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.