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Author: Leuteritz, Andreas × Publisher: Basel : MDPI ×

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Now showing 1 - 3 of 3
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    Preparation of Photoactive Transition-Metal Layered Double Hydroxides (LDH) to Replace Dye-Sensitized Materials in Solar Cells
    (Basel : MDPI, 2020) Naseem, Sajid; Gevers, Bianca R.; Labuschagné, Frederick J. W. J.; Leuteritz, Andreas
    This work highlights the use of Fe-modified MgAl-layered double hydroxides (LDHs) to replace dye and semiconductor complexes in dye-sensitized solar cells (DSSCs), forming a layered double hydroxide solar cell (LDHSC). For this purpose, a MgAl-LDH and a Fe-modified MgAl LDH were prepared. X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy were used to analyze the structural properties, morphology, and success of the Fe-modification of the synthesized LDHs. Ultraviolet-visible (UV-Vis) absorption spectroscopy was used to analyze the photoactive behavior of these LDHs and compare it to that of TiO2 and dye-sensitized TiO2. Current-voltage (I–V) solar simulation was used to determine the fill factor (FF), open circuit voltage (VOC), short circuit current (ISC), and efficiency of the LDHSCs. It was shown that the MgFeAl-LDH can act as a simultaneous photoabsorber and charge separator, effectively replacing the dye and semiconductor complex in DSSCs and yielding an efficiency of 1.56%.
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    Structure, Properties, and Release Kinetics of the Polymer/Insect Repellent System Poly (l-Lactic Acid)/Ethyl Butylacetylaminopropionate (PLLA/IR3535)
    (Basel : MDPI, 2022) Du, Fanfan; Erdmann, Rafael; Petzold, Albrecht; Wutzler, Andre; Leuteritz, Andreas; Nase, Michael; Androsch, René
    The insect repellent ethyl butylacetylaminopropionate (IR3535) was used as a functional additive for poly (l-lactic acid) (PLLA) to modify its structure and mechanical properties and achieve insect repellency. PLLA/IR3535 mixtures at various compositions were prepared via melt extrusion. In the analyzed composition range of 0 to 23 m% IR3535, PLLA and IR3535 were miscible at the length scale represented by the glass transition temperature. Addition of IR3535 resulted in a significant decrease in the glass transition temperature of PLLA, as well as in the elastic modulus, indicating its efficiency as a plasticizer. All mixtures were amorphous after extrusion, though PLLA/IR3535 extrudates with an IR3535 content between 18 and 23 m% crystallized during long-term storage at ambient temperature, due to their low glass transition temperature. Quantification of the release of IR3535 into the environment by thermogravimetric analysis at different temperatures between 50 and 100 °C allowed the estimation of the evaporation rate at lower temperatures, suggesting an extremely low release rate with a time constant of the order of magnitude of 1–2 years at body temperature.
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    Barrier properties of GnP-PA-extruded films
    (Basel : MDPI, 2020) Boldt, Regine; Leuteritz, Andreas; Schob, Daniela; Ziegenhorn, Matthias; Wagenknecht, Udo
    It is generally known that significant improvements in the properties of nanocomposites can be achieved with graphene types currently commercially available. However, so far this is only possible on a laboratory scale. Thus, the aim of this study was to transfer results from laboratory scale experiments to industrial processes. Therefore, nanocomposites based on polyamide (PA) and graphene nanoplatelets (GnP) were prepared in order to produce membranes with improved gas barrier properties, which are characterized by reduced permeation rates of helium. First, nanocomposites were prepared with different amounts of commercial availably graphene nanoplatelets using a semi-industrial-scale compounder. Subsequently, films were produced by compression molding at different temperatures, as well as by flat film extrusion. The extruded films were annealed at different temperatures and durations. In order to investigate the effect of thermal treatment on barrier properties in correlation to thermal, structural, and morphological properties, the films were characterized by differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), optical microscopy (OM), transmission electron microscopy (TEM), melt rheology measurements, and permeation measurements. In addition to structural characterization, mechanical properties were investigated. The results demonstrate that the permeation rate is strongly influenced by the processing conditions and the filler content. If the filler content is increased, the permeation rate is reduced. The annealing process can further enhance this effect.