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Item-typ:Veröffentlichung, The impact of fibre processing on the mechanical properties of epoxy matrix composites and wood-based particleboard reinforced with hemp (Cannabis sativa L.) fibreThis work investigated the impact that the processing of hemp (C. sativa L.) fibre has on the mechanical properties of unidirectional fibre-reinforced epoxy resin composites loaded in axial tension, and particleboard reinforced with aligned fibre bundles applied to one surface of the panel. For this purpose, mechanically processed (decorticated) and un-processed hemp fibre bundles, obtained from retted and un-retted hemp stems, were utilised. The results clearly show the impact of fibre reinforcement in both materials. Epoxy composites reinforced with processed hemp exhibited 3.3 times greater tensile strength when compared to the un-reinforced polymer, while for the particleboards, the bending strength obtained in those reinforced with processed hemp was 1.7 times greater than the un-reinforced particleboards. Moreover, whether the fibre bundles were processed or un-processed also affected the mechanical performance, especially in the epoxy composites. For example, the un-processed fibre-reinforced epoxy composites exhibited 49% greater work of fracture than the composites reinforced with processed hemp. In the wood-based particleboards, however, the difference was not significant. Additionally, observations of the fracture zone of the specimens showed different failure characteristics depending on whether the composites were reinforced with processed or un-processed hemp. Both epoxy composites and wood-based particleboards reinforced with un-processed hemp exhibited fibre reinforcement apparently able to retain structural integrity after the composite’s failure. On the other hand, when processed hemp was used as reinforcement, fibre bundles showed a clear cut across the specimen, with the fibre-reinforcement mainly failing at the composite's fracture zone.Wissenschaftlicher ArtikelBand:57Heft:392 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The impact of metal doping on fumed silica structure and amino acid thermal condensation catalytic properties(Springer, 2021-08-18); ; ; ; Fumed silica nanoparticles (FSN) are one of the most common synthetic forms of silica, but prolonged exposure leads to cell toxicity and apoptosis due to reactive oxygen species (ROS) generation and cell membrane perturbation resulting from hydrogen bonding and electrostatic interactions. Increasing attention is being put on synthesizing FSN material that is safer both for workers involved in large-scale industrial production, and consumers coming in contact with FSN additives. In the present work, we explore the molecular structural differences and efficacy of Al- and Ti-metal-doped FSN which has previously been shown to reduce toxicity effects of FSN. We use a combination of 29Si and 27Al solid-state magic angle spinning (MAS) NMR, Raman spectroscopy, and thermogravimetric analysis (TGA) to probe the surface and bulk structure and quantify the adsorption capacity and reactivity of the metal-doped FSN with respect to amino acid thermal condensation. Alanine was selected as the amino acid of choice for its simplicity and ubiquity in biochemical reactions. The results indicate that metal doping has a modest impact on the fumed silica molecular structure with a small decrease in amino acid adsorption capacity and thermal condensation reactivity as a function of increased metal doping.Wissenschaftlicher ArtikelBand:5644 72 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Unidirectional solution-based freeze cast polymer-derived ceramics: influence of freezing conditions and templating solvent on capillary transport in isothermal wicking(Springer, 2019-12-23); ; ; Porous SiOC monoliths were prepared by solution-based freeze casting of polysiloxane at constant freezing temperature or constant freezing front velocity. Dendritic and prismatic pore structures were obtained by using cyclohexane and tert-butyl alcohol as solvent, respectively. Gradients in freezing velocity lead to gradients in pore window size, whereas a constant freezing velocity (3.3–6.8 µm/s) generates homogeneous pore structures. The water permeability varies from 1.12 × 10−13 to 1.03 × 10−11 m2 and correlates with the pore window diameter (10–59 µm) and the porosity (51–82%). In wicking tests, the gradient in pore window size is clearly reflected by a pronounced decrease in the wicking speed. Contrary, a homogeneous pore structure results in wicking curves which are closer to the prediction according to the Lucas–Washburn equation. However, this theoretical approach based on the three parameters, pore window size, porosity and permeability, is insufficient to describe complex three-dimensional pore structures. Besides the porosity, the pore morphology was found to be a major influencing factor on the wicking. The filling of secondary dendrites slows down the wicking into the dendritic structure. Fastest wicking was observed for a prismatic pore structure at low freezing front velocity (6.6 µm/s) and high porosity (78%), whereas slowest wicking occurred into the dendritic structure with high porosity (76%) and constant freezing temperature (− 20 °C). The knowledge of the relationship between structural properties and the resulting wicking behavior can address a variety of pivotal applications in chemical engineering for capillary transport.Wissenschaftlicher ArtikelBand:55123 141 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Novel tape-cast SiOC-based porous ceramic electrode materials for potential application in bioelectrochemical systemsOne alternative to improve electrochemical performance and long-term applicability in microbial bioelectrochemical systems (BESs) is the use of porous ceramic electrodes. In this work, electrodes of polymer-derived ceramics based on poly(silsesquioxanes) are synthesized, tailoring the properties by varying pyrolysis temperatures and incorporating conductive phases. Carbon (graphite, carbon black) and metal-based (stainless steel/Cu grids, Co/Ni particles) materials are incorporated into the silicon oxycarbide (SiOC) matrix. The influence of pyrolysis temperature and incorporation of conductive materials on functional properties and electrical conductivity is discussed. Furthermore, this study provides the first investigation of biofilm development on SiOC-based ceramic surfaces with Escherichia coli and Bacillus cereus. SiOC-based ceramics with DC conductivity values at room temperature in the semiconductor range (0.044–0.385 S cm-1) were obtained, with the highest values achieved by Co and Ni particles incorporation and in situ formation of CNTs. Adjustment in hydrophilicity and specific surface areas (6.21–263.45 m2 g-1) is realized by the pyrolysis. The biofilm studies reveal adhesion in the first 2 h for most of the surfaces, with higher bacterial adhesion and biofilm formation with the E. coli. The biocompatibility in terms of bacterial attachment and conductivity values comparable to a commercial carbon felt support the applicability of the developed SiOC-based materials as promising new class of electrodes for BES.Wissenschaftlicher Artikel106 103