| 1. |
- Daniel, Geoffrey, et al.
(författare)
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Pushing the theoretical capacity limits of iron oxide anodes: capacity rise of γ-Fe2O3 nanoparticles in lithium-ion batteries
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4, s. 18107-18115
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles (NPs) of g-Fe2O3 are successfully prepared via facile hydrolysis of a complex iron iodide precursor with subsequent oxidation under mild conditions. When evaluated as an anode material in lithium ion half-cells, electrodes made with gamma-Fe2O3 NPs exhibit excellent rate capabilities with high capacities and good coulombic efficiencies. Electrodes of gamma-Fe2O3 NPs initially deliver capacities of 1100 mA h g1 at 100 mA g1 current density and 980 mA h g1 at 1000 mA g1. Following an activation step of the electrodes, the capacities increase by up to 300 mA h g1 while coulombic efficiencies also improve slightly. At a high current density of 4000 mA g1, a stable capacity of 770 mA h g1 is achieved. In this study, dQ/dv plots are employed to graphically illustrate the capacity breakdown of each cycle into intercalation, conversion, and extra capacity regions. Upon prolonged cycling, the extra capacity region expands to yield higher capacities; this phenomenon has been attributed to both pulverizationinduced particle size reduction and high-rate lithiation-induced activation processes. This study concludes that gamma-Fe2O3 NPs could serve as a promising anode material with comparable results to widely studied alpha-Fe2O3 and Fe3O4 NPs.
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| 2. |
- Etman, Ahmed S., et al.
(författare)
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A one-step water based strategy for synthesizing hydrated vanadium pentoxide nanosheets from VO2(B) as free-standing electrodes for lithium battery applications
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:46, s. 17988-18001
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of two dimensional (2D) materials from transition metal oxides, chalcogenides, and carbides mostly involve multiple exfoliation steps in which hazardous solvents and reagents are used. In this study, hydrated vanadium pentoxide (V2O5 center dot nH(2)O) nanosheets with a thickness of a few nanometers were prepared via a facile environmentally friendly water based exfoliation technique. The exfoliation process involved refluxing the precursor, vanadium dioxide (VO2(B)), in water for a few days at 60 degrees C. The proposed exfoliation mechanism is based on the intercalation/insertion of water molecules into the VO2(B) crystals and the subsequent cleavage of the covalent bonds holding the layers of VO2(B) together. The thermal and chemical analyses showed that the approximate chemical composition of the nanosheets is H0.4V2O5 center dot 0.55H(2)O, and the percentage of V-V content to that of V-IV in the nanosheets is about 80(3)% to 20(3)%. The exfoliated aqueous suspension of the V2O5 center dot 0.55H(2)O nanosheets was successfully deposited onto multi-walled carbon nanotube (MW-CNT) paper to form free-standing electrodes with a thickness of the V2O5 center dot 0.55H(2)O layer ranging between 45 and 4 mu m. A series of electrochemical tests were conducted on the electrodes to determine the cyclability and rate capability of lithium insertion into V2O5 center dot 0.55H(2)O nanosheets. The electrodes with the thinnest active material coating (similar to 4 mu m) delivered gravimetric capacities of up to 480 and 280 mA h g(-1) when cycled at current densities of 10 and 200 mA g(-1), respectively.
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| 3. |
- Wu, Qiong, et al.
(författare)
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Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:48, s. 20996-21009
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, where, according to protein solubility measurements and infrared spectroscopy, the presence of silica had prohibited full aggregation of the proteins. The foams with "built-in" flame-retardant properties had thermal insulation properties similar to those of common petroleum- and mineral-based insulation materials. The foams, with a porosity of 87 to 91%, were obtained by freeze-drying the liquid mixture. Their internal structure consisted of mainly open cells between 2 and 144 mu m in diameter depending on the foam formulation, as revealed by mercury intrusion porosimetry and scanning electron microscopy. The foams prepared with >= 30% TEOS showed excellent fire-retardant properties and fulfilled the criteria of the best class according to UL94 fire testing standard. With increasing silica content, the foams became more brittle, which was prevented by cross-linking the materials (using gluteraldehyde) in combination with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2 .
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