TY - JOUR AB - This new Special Issue of Materials entitled “3D/4D Printing Application for Shape Memory Materials” aims to publish original and review papers dealing with basic and applied research on this emerging technology [...] AU - Ehrmann, Andrea ID - 2280 IS - 17 JF - Materials TI - 3D/4D Printing Application for Shape Memory Materials VL - 15 ER - TY - JOUR AB - The effects of climate change are becoming increasingly clear, and the urgency of solving the energy and resource crisis has been recognized by politicians and society. One of the most important solutions is sustainable energy technologies. The problem with the state of the art, however, is that production is energy-intensive and non-recyclable waste remains after the useful life. For monocrystalline photovoltaics, for example, there are recycling processes for glass and aluminum, but these must rather be described as downcycling. The semiconductor material is not recycled at all. Another promising technology for sustainable energy generation is dye-sensitized solar cells (DSSCs). Although efficiency and long-term stability still need to be improved, the technology has high potential to complement the state of the art. DSSCs have comparatively low production costs and can be manufactured without toxic components. In this work, we present the world’ s first experiment to test the recycling potential of non-toxic glass-based DSSCs in a melting test. The glass constituents were analyzed by optical emission spectrometry with inductively coupled plasma (ICP-OES), and the surface was examined by scanning electron microscopy energy dispersive X-ray (SEM-EDX). The glass was melted in a furnace and compared to a standard glass recycling process. The results show that the described DSSCs are suitable for glass recycling and thus can potentially circulate in a circular economy without a downcycling process. However, material properties such as chemical resistance, transparency or viscosity are not investigated in this work and need further research. AU - Schoden, Fabian AU - Schnatmann, Anna Katharina AU - Davies, Emma AU - Diederich, Dirk AU - Storck, Jan Lukas AU - Knefelkamp, Dörthe AU - Blachowicz, Tomasz AU - Schwenzfeier-Hellkamp, Eva ID - 1513 IS - 21 JF - Materials TI - Investigating the Recycling Potential of Glass Based Dye-Sensitized Solar Cells—Melting Experiment VL - 14 ER - TY - JOUR AB - Electrospun poly(acrylonitrile) (PAN) nanofibers are typical precursors of carbon nanofibers. During stabilization and carbonization, however, the morphology of pristine PAN nanofibers is not retained if the as-spun nanofiber mats are treated without an external mechanical force, since internal stress tends to relax, causing the whole mats to shrink significantly, while the individual fibers thicken and curl. Stretching the nanofiber mats during thermal treatment, in contrast, can result in fractures due to inhomogeneous stress. Previous studies have shown that stabilization and carbonization of PAN nanofibers electrospun on an aluminum substrate are efficient methods to retain the fiber mat dimensions without macroscopic cracks during heat treatment. In this work, we studied different procedures of mechanical fixation via metallic substrates during thermal treatment. The influence of the metallic substrate material as well as different methods of double-sided covering of the fibers, i.e., sandwiching, were investigated. The results revealed that sandwich configurations with double-sided metallic supports not only facilitate optimal preservation of the original fiber morphology but also significantly accelerate the carbonization process. It was found that unlike regularly carbonized nanofibers, the metal supports allow complete deoxygenation at low treatment temperature and that the obtained carbon nanofibers exhibit increased crystallinity. AU - Storck, Jan Lukas AU - Hellert, Christian AU - Brockhagen, Bennet AU - Wortmann, Martin AU - Diestelhorst, Elise AU - Frese, Natalie AU - Grothe, Timo AU - Ehrmann, Andrea ID - 1594 IS - 16 JF - Materials KW - electrospinning KW - stabilization KW - carbonization KW - metallic substrates KW - shrinkage KW - fiber morphology TI - Metallic Supports Accelerate Carbonization and Improve Morphological Stability of Polyacrylonitrile Nanofibers during Heat Treatment VL - 14 ER - TY - JOUR AB - Electrospun poly(acrylonitrile) (PAN) nanofibers are typical precursors of carbon nanofibers. During stabilization and carbonization, however, the morphology of pristine PAN nanofibers is not retained if the as-spun nanofiber mats are treated without an external mechanical force, since internal stress tends to relax, causing the whole mats to shrink significantly, while the individual fibers thicken and curl. Stretching the nanofiber mats during thermal treatment, in contrast, can result in fractures due to inhomogeneous stress. Previous studies have shown that stabilization and carbonization of PAN nanofibers electrospun on an aluminum substrate are efficient methods to retain the fiber mat dimensions without macroscopic cracks during heat treatment. In this work, we studied different procedures of mechanical fixation via metallic substrates during thermal treatment. The influence of the metallic substrate material as well as different methods of double-sided covering of the fibers, i.e., sandwiching, were investigated. The results revealed that sandwich configurations with double-sided metallic supports not only facilitate optimal preservation of the original fiber morphology but also significantly accelerate the carbonization process. It was found that unlike regularly carbonized nanofibers, the metal supports allow complete deoxygenation at low treatment temperature and that the obtained carbon nanofibers exhibit increased crystallinity. AU - Storck, Jan Lukas AU - Hellert, Christian AU - Brockhagen, Bennet AU - Wortmann, Martin AU - Diestelhorst, Elise AU - Frese, Natalie AU - Grothe, Timo AU - Ehrmann, Andrea ID - 2580 IS - 16 JF - Materials TI - Metallic Supports Accelerate Carbonization and Improve Morphological Stability of Polyacrylonitrile Nanofibers during Heat Treatment VL - 14 ER - TY - JOUR AB - Electrospinning can be used to create nanofibers from diverse polymers in which also other materials can be embedded. Inclusion of magnetic nanoparticles, for example, results in preparation of magnetic nanofibers which are usually isotropically distributed on the substrate. One method to create a preferred direction is using a spinning cylinder as the substrate, which is not always possible, especially in commercial electrospinning machines. Here, another simple technique to partly align magnetic nanofibers is investigated. Since electrospinning works in a strong electric field and the fibers thus carry charges when landing on the substrate, using partly conductive substrates leads to a current flow through the conductive parts of the substrate which, according to Ampère’s right-hand grip rule, creates a magnetic field around it. We observed that this magnetic field, on the other hand, can partly align magnetic nanofibers perpendicular to the borders of the current flow conductor. We report on the first observations of electrospinning magnetic nanofibers on partly conductive substrates with some of the conductive areas additionally being grounded, resulting in partly oriented magnetic nanofibers. AU - Storck, Jan Lukas AU - Grothe, Timo AU - Mamun, Al AU - Sabantina, Lilia AU - Klöcker, Michaela AU - Blachowicz, Tomasz AU - Ehrmann, Andrea ID - 2904 IS - 1 JF - Materials TI - Orientation of Electrospun Magnetic Nanofibers Near Conductive Areas VL - 13 ER - TY - JOUR AB - Textile-based dye-sensitized solar cells (DSSCs) can be created by building the necessary layers on a textile fabric or around fibers which are afterwards used to prepare a textile layer, typically by weaving. Another approach is using electrospun nanofiber mats as one or more layers. In this work, electrospun polyacrylonitrile (PAN) nanofiber mats coated by a conductive polymer poly(3,4-ethylenedioxythiopene) polystyrene sulfonate (PEDOT:PSS) were used to produce the counter electrodes for half-textile DSSCs. The obtained efficiencies were comparable with the efficiencies of pure glass-based DSSCs and significantly higher than the efficiencies of DSSCs with cotton based counter electrodes. The efficiency could be further increased by increasing the number of PEDOT:PSS layers on the counter electrode. Additionally, the effect of the post treatment of the conductive layers by HCl, acetic acid, or dimethyl sulfoxide (DMSO) on the DSSC efficiencies was investigated. Only the treatment by HCl resulted in a slight improvement of the energy-conversion efficiency. AU - Juhász Junger, Irén AU - Wehlage, Daria AU - Böttjer, Robin AU - Grothe, Timo AU - Juhász, László AU - Grassmann, Carsten AU - Blachowicz, Tomasz AU - Ehrmann, Andrea ID - 1074 IS - 9 JF - Materials TI - Dye-Sensitized Solar Cells with Electrospun Nanofiber Mat-Based Counter Electrodes VL - 11 ER - TY - JOUR AU - Fafenrot, Susanna AU - Grimmelsmann, Nils AU - Wortmann, Martin AU - Ehrmann, Andrea ID - 1078 IS - 10 JF - Materials TI - Three-Dimensional (3D) Printing of Polymer-Metal Hybrid Materials by Fused Deposition Modeling VL - 10 ER -