| 1. |
- Wagner, Annemarie, 1954, et al.
(författare)
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Carbon Dioxide Capture from Ambient Air Using Amine-Grafted Mesoporous Adsorbents
- 2013
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Ingår i: International Journal of Spectroscopy. - : Hindawi Limited. - 1687-9457 .- 1687-9449. ; 2013
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic emissions of carbon dioxide (CO2) have been identified as a major contributor to climate change. An attractive approach to tackle the increasing levels of CO2 in the atmosphere is direct extraction via absorption of CO2 from ambient air, to be subsequently desorbed and processed under controlled conditions. The feasibility of this approach depends on the sorbent material that should combine a long lifetime with nontoxicity, high selectivity for CO2, and favorable thermodynamic cycling properties. Adsorbents based on pore-expanded mesoporous silica grafted with amines have previously been found to combine high CO2 adsorption capacity at low partial pressures with operational stability under highly defined laboratory conditions. Here we examine the real potential and functionality of these materials by using more realistic conditions using both pure CO2, synthetic air, and, most importantly, ambient air. Through a combination of thermogravimetric analysis and Fourier transform infrared (TGA-FTIR) spectroscopy we address the primary functionality and by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy the observed degradation of the material on a molecular level.
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| 2. |
- Adebahr, Josefina, 1973, et al.
(författare)
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Ab initio calculations, Raman and NMR investigation of the plastic crystal di-methyl pyrrolidinium iodide
- 2003
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Ingår i: Electrochimica Acta. - 0013-4686. ; 48:14-16, s. 2283-2289
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Tidskriftsartikel (refereegranskat)abstract
- Above 110 °C the symmetric di-methyl-pyrrolidinium iodide salt forms a plastic crystal phase of interest in the area of new electrolyte materials. In this study ab initio calculations of this material has been conducted in order to assign the vibrational spectra. Raman spectroscopy measurements on the solid salt as well as on the salt dissolved in different solvents has been performed and these have been compared to the theoretical spectra. Furthermore, Raman spectra as a function of temperature have been recorded to investigate possible changes in inter-ionic interaction and/or structure through the phase transition. 1 H NMR linewidth measurements as a function of temperature showed a large decrease in linewidth above 100 °C, attributed here to an increase in mobility in agreement with a previously reported phase transition at ∼ 110 °C. © 2003 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Bismarck, A., et al.
(författare)
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Multifunctional epoxy resin for structural supercapacitors
- 2012
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Ingår i: 15th European Conference on Composite Materials: Composites at Venice, ECCM 2012; Venice; Italy; 24 June 2012 through 28 June 2012. - 9788888785332
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Konferensbidrag (refereegranskat)abstract
- Polymer-based electrolytes based on commercially available epoxy resins were prepared through the addition of a liquid electrolyte, a solution of a lithium salt in an ionic liquid. The polymer monoliths were characterized using impedance spectroscopy, 3-point bending test, scanning electron microscopy (SEM) and nitrogen adsorption (BET). The balance of ionic conductivity and flexural modulus is crucially dependent on the relative proportions of epoxy resin to electrolyte. Also the effect of the liquid electrolyte on curing kinetics and processing was assessed by complex viscosity measurements and differential scanning calorimetry (DSC). Only one out of the three resins investigated exhibited a significant acceleration effect.
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| 4. |
- Ciosek Högström, Katarzyna, 1984-, et al.
(författare)
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Impact of the flame retardant additive triphenyl phosphate (TPP) on the performance of graphite/LiFePO4 cells in high power applications
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 256, s. 430-439
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Tidskriftsartikel (refereegranskat)abstract
- This study presents an extensive characterization of a standard Li-ion battery (LiB) electrolyte containing different concentrations of the flame retardant triphenyl phosphate (TPP) in the context of high power applications. Electrolyte characterization shows only a minor decrease in the electrolyte flammability for low TPP concentrations. The addition of TPP to the electrolyte leads to increased viscosity and decreased conductivity. The solvation of the lithium ion charge carriers seem to be directly affected by the TPP addition as evidenced by Raman spectroscopy and increased mass-transport resistivity. Graphite/LiFePO4 full cell tests show the energy efficiency to decrease with the addition of TPP. Specifically, diffusion resistivity is observed to be the main source of increased losses. Furthermore, TPP influences the interface chemistry on both the positive and the negative electrode. Higher concentrations of TPP lead to thicker interface layers on LiFePO4. Even though TPP is not electrochemically reduced on graphite, it does participate in SEI formation. TPP cannot be considered a suitable flame retardant for high power applications as there is only a minor impact of TPP on the flammability of the electrolyte for low concentrations of TPP, and a significant increase in polarization is observed for higher concentrations of TPP. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
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| 6. |
- Holber, Mikael, 1982, et al.
(författare)
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Raman investigation of degradation and ageing effects in fuel cell membranes
- 2009
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781566777384 ; 25:1 PART 1, s. 807-811
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Tidskriftsartikel (refereegranskat)abstract
- Increased life-time of the proton conducting membrane of polymer electrolyte membrane fuel cells is the key to improve the endurance of fuel cell stacks. Here we present a Raman spectroscopy investigation of a fully fluorinated sulfonated membrane from a 1500h FC steady-state experiment compared with Nafion® membranes aged in hydrogen peroxide and Fenton's solution. The latter approach as an attempt to develop a screening method based on accelerated ageing. In all membranes degradation is evident. The Raman results of the fuel cell tested membrane demonstrate a loss of functional sulfonic acid groups throughout the membrane. The accelerated ageing, on the other hand, results in degradation readily observed: e.g. loss of polymer material, opaque areas, and brittleness. Notably, the relative concentration of functional sulfonic groups stays constant, indicating that the accelerated ageing methods primarily attack the backbone of the membrane. ©The Electrochemical Society.
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| 7. |
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| 8. |
- Holber, Mikael, 1982, et al.
(författare)
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Raman Spectroscopy of an Aged Low Temperature Polymer Electrolyte Fuel Cell Membrane
- 2011
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Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 11:3, s. 459-464
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Tidskriftsartikel (refereegranskat)abstract
- The cost and durability of the membrane electrode assembly (MEA) are today limiting factors for large-scale commercialisation of the polymer electrolyte membrane fuel cell (PEMFC). The MEA durability in a real working fuel cell (FC) is closely linked to specific operating conditions such as temperature, gas humidity, load dynamics, etc. This often results in both chemical and mechanical degradation of the ion-conducting membrane and subsequent operation failure of the FC. In this study, Raman spectroscopy is used to identify and distinguish between two different degradation processes for a 1,500 h in situ aged FC membrane. The primary process is due to the loss of proton conducting sulphonic acid end groups over the entire membrane. The secondary process is a degradation of the fluorinated backbone concentrated to the cathode interface; making possible the collapse of carbon into the resulting voids of the membrane. Using spatially resolved Raman spectroscopy we can unambiguously observe both the localisation and the state of the carbon inside the membrane; being similar/identical to the microporous layer (MPL).
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| 9. |
- Holomb, Roman, et al.
(författare)
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Ionic liquid structure: the conformational isomerism in 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4])
- 2008
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:7, s. 793-805
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Tidskriftsartikel (refereegranskat)abstract
- As a probe of local structure, the vibrational properties of the 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim]+ conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim] + conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim] + conformers and the [bmim]+- [BF4]- interactions to the vibrational spectra are discussed.
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| 10. |
- Holomb, Roman, et al.
(författare)
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Vibrational spectroscopy and ab initio studies of lithium bis (oxalato) borate (LiBOB) in different solvents
- 2006
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 110:40, s. 11467-11472
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Tidskriftsartikel (refereegranskat)abstract
- The effect of lithium ion coordination with the bis(oxalato)borate (BOB ) [6(0204)2] anion in DMSO, PEG, PPG, and d-PPG has been studied in detail by IR and Raman spectroscopy. Ab initio calculations were performed to allow a consistent analysis of the experimental data. The main features observed in the IR and Raman spectra correspond to the presence of "free", un-coordinated, BOB - anions. Only with use of d-PPG as solvent a small amount of Li + ⋯BOB - ion pairs were detected. The Raman spectra and the calculations together indicate that Li + coordinates bidentately with two end-oxygen atoms of the BOB - anion. The identification of ion pairs can be used to reveal limitations of LiBOB based electrolytes. The results for LiBOB are compared with literature on other Li salts. © 2006 American Chemical Society.
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