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Author: Fischer, Dieter × End date: 2019 ×

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    Tuneable Dielectric Properties Derived from Nitrogen-Doped Carbon Nanotubes in PVDF-Based Nanocomposites
    (Washington, DC : ACS Publications, 2018) Pawar, Shital Patangrao; Arjmand, Mohammad; Pötschke, Petra; Krause, Beate; Fischer, Dieter; Bose, Suryasarathi; Sundararaj, Uttandaraman
    Nitrogen-doped multiwall carbon nanotubes (N-MWNTs) with different structures were synthesized by employing chemical vapor deposition and changing the argon/ethane/nitrogen gas precursor ratio and synthesis time, and broadband dielectric properties of their poly(vinylidene fluoride) (PVDF)-based nanocomposites were investigated. The structure, morphology, and electrical conductivity of synthesized N-MWNTs were assessed via Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, and powder conductivity techniques. The melt compounded PVDF nanocomposites manifested significantly high real part of the permittivity (ϵ′) along with low dissipation factor (tan δϵ) in 0.1 kHz to 1 MHz frequency range, suggesting use as efficient charge-storage materials. Longer synthesis time resulted in enhanced carbon purity as well as higher thermal stability, determined via TGA analysis. The inherent electrical conductivity of N-MWNTs scaled with the carbon purity. The charge-storage ability of the developed PVDF nanocomposites was commensurate with the amount of the nitrogen heteroatom (i.e., self-polarization), carbon purity, and inherent electrical conductivity of N-MWNTs and increased with better dispersion of N-MWNTs in PVDF.
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    Characterization of Zahari Zograph’s nave wall paintings in the church “The nativity of the virgin” of Rila Monastery (Bulgaria) by vibrational spectroscopy and SEM–EDX analysis
    (Abingdon, Oxon : Routledge, Taylor and Francis Group, 2018) Yancheva, Denitsa; Tapanov, Stefan; Velcheva, Evelina; Stamboliyska, Bistra; Glavcheva, Zornitza; Stoyanov, Simeon; Haralampiev, Nikifor; Fischer, Dieter; Lederer, Albena
    An analytical study on the nave mural paintings of the church “The Nativity of the Virgin” of Rila monastery, Bulgaria, painted by Zahari Zograph was carried out. Vibrational spectroscopy was applied to identify the pigments and organic materials used in the mural paintings. To complement the spectral information, elemental composition of the samples was determined by SEM-EDX. The data showed that smalt with carbohydrate binder was applied for the blue background, green colour was executed by green earths and red-orange colour – by red lead. Azurite is the pigment used to paint the blue colour of the saints’ hoods. The mordant for gilding was prepared of drying oil, resin and siccative metal oxides as evidenced by SEM-EDX, ATR-FTIR and pyrolysis GC-MS analysis. The use of azurite is related to Zahari Zograph’s works as it was not found in any of the previously studied murals in the church painted by other artists.
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    Tracing microplastics in aquatic environments based on sediment analogies
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2019) Enders, Kristina; Käppler, Andrea; Biniasch, Oliver; Feldens, Peter; Stollberg, Nicole; Lange, Xaver; Fischer, Dieter; Eichhorn, Klaus-Jochen; Pollehne, Falk; Oberbeckmann, Sonja; Labrenz, Matthias
    Microplastics (MP) data collection from the aquatic environment is a challenging endeavour that sets apparent limitations to regional and global MP quantification. Expensive data collection causes small sample sizes and oftentimes existing data sets are compared without accounting for natural variability due to hydrodynamic processes governing the distribution of particles. In Warnow estuarine sediments (Germany) we found significant correlations between high-density polymer size fractions (≥500 µm) and sediment grain size. Among potential predictor variables (source and environmental terms) sediment grain size was the critical proxy for MP abundance. The MP sediment relationship can be explained by the force necessary to start particle transport: at the same level of fluid motion, transported sediment grains and MP particles are offset in size by one to two orders of magnitude. Determining grain-size corrected MP abundances by fractionated granulometric normalisation is recommended as a basis for future MP projections and identification of sinks and sources.