Technische Universität Bergakademie Freiberg

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Browsing Technische Universität Bergakademie Freiberg by Subject "4::43::406::406-01"

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  • ItemOpen Access
    Additional data: Impact of Chitosan's Degree of Deacetylation, Molecular Weight, and Crystallinity on the Photoresponsive Properties of Azobenzene-modified Films and Membranes.
    (Technische Universität Bergakademie Freiberg, 2024-11-15) von Seggern, Nils; M. Thiebes, Yannick; Niewa, Rainer; Cord-Landwehr, Stefan; Moerschbacher, Bruno; Tovar, Günter E.M.; Stegbauer, Linus
    A profound understanding of how the degree of deacetylation (DDA), polymerization degree (DP) and photoswitch concentration impact the photomodulation of properties of chitosan(CS)-based responsive materials can serve as a framework for future applications. Herein, we report responsive thin-films manufactured from chitosans with DDA ranging from 70-94% and DP between 170-3380, incorporating 10 30mol% of the light-responsive azobenzene derivative Sodium-4-[(4-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)phenyl)diazenyl]-benzenesulfonate (TEGABS). During UV-irradiation of the 10 30% TEGABS|CS thin-films, e.g. a significant increase of the indentation modulus by 10 ± 5% is observed. UV illumination leads to a decrease of the water vapor permeability (WVP), reducing it by up to 81 ± 17% compared to native state. We demonstrate that TEGABS up to 10% remains as a solid-solution in CS films with differing amount of H-aggregates depending on the DDA and DP. TEGABS in concentrations >10% in CS leads to phase separation of TEGABS crystallites with a diameter of 21 ± 8 nm. To conclude the photothermal heating by UV irradiation and the resulting water evaporation are identified as the primary driving force for the variation in mechanical properties and WVP, with photoisomerization playing a subordinate factor. These findings provide a new pathway for the design of polysaccharide-based water vapor permeable photoresponsive membranes.
  • ItemPublic Metadata
    GRK 2802: Extra-carbonization of biochar pellets obtained after co-torrefaction and co-pyrolysis with bituminous coal
    (Technische Universität Bergakademie Freiberg, 2025-11-28) Koveria, Andrii; Zuber, Jan; Himcinschi, Cameliu; Vogt, Carla; Richter, Julia
    The paper investigates the chemical and structural changes in biochar pellets resulting from the co-torrefaction and co-pyrolysis of pine wood (Pinus sylvestris) pellets with bituminous coal at a 1:1 ratio at 300, 500, and 700 °C. At 500 °C co-pyrolysis, noticeable changes occur in biochar during co-treatment with coal, as observed by Fourier-transform infrared spectroscopy (FT-IR), graphite-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (GALDI-FT-ICR-MS), and Raman spectroscopy compared to individual pyrolysis. Proximate and ultimate analyses show an increase in carbon content and decreases in volatile matter, oxygen, and hydrogen in co-treated biochar pellets. FT-IR and van Krevelen plots indicate compounds with lower O/C ratios and fewer oxygen-rich functionalities. Raman spectroscopy shows that, at 300 and 500 °C, co-pyrolyzed biochar pellets have slightly more structural ordering and less disorder than biochar pellets from individual pyrolysis. This suggests that co-processing allows the creation of a more ordered aromatic carbon structure. GALDI-FT-ICR-MS indicates an increase in condensed aromatic hydrocarbons at the expense of lignin-like and oxygen-rich structures compared with individual pyrolysis. Specifically, 500 °C co-pyrolysis shifts biochar pellets composition toward lower O/C ratios (0–0.3); products are enriched in condensed aromatic hydrocarbons and occupy van Krevelen regions with low O/C (0–0.2) and H/C (0.4–0.8). The results demonstrate extra-carbonization effects in biochar pellets during co-pyrolysis with bituminous coal at 500 and 700 °C.