| 31. |
- Hosseini Bab Anari, Elham, 1982
(författare)
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Toward Safer Energy Storage Solution by Development of Fluorine-Free Battery Electrolyte
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Portable electronic devices such as mobile phones, laptops, cameras and electronic vehicles (EVs) which contain lithium-ion batteries (LIBs), are indispensable part of our modern society. The safety of conventional electrolytes of LIBs, composed of fluorinated lithium salts and organic solvents is the source of some concerns. While the former is meta-stable at room temperature, quite expensive to synthesis and unsafe in the presence of moisture, the latter have high vapor pressure and are also flammable. Therefore, development of more stable salts and electrolytes are highly desirable, especially in the light of increased use of battery technology in e.g. electric vehicles (EVs).In order to mitigate the challenges with current fluorine containing electrolytes, we set out to develop a new class of safer, fluorine-free anions based on the concept of pseudo-delocalized Mickey MouseTM anions. Their Lithium and sodium salts have been synthesized for the first time, and fully characterized by different analytical methods such as NMR, mass spectroscopy and elemental analysis. Thermogravimetry analysis and X-ray crystallography were conducted to reveal both basic properties in terms of thermal stability and solubility of the salts. To further assess their properties as electrolytes, ion conductivity and electrochemical stability windows (ESWs) were performed.
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| 32. |
- Jansson, Jonas, 1973, et al.
(författare)
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A mechanistic study of low temperature CO oxidation over cobalt oxide
- 2001
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Ingår i: Topics in Catalysis. - 1572-9028 .- 1022-5528. ; 16-17:1-4, s. 385-389
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Tidskriftsartikel (refereegranskat)abstract
- The CO oxidation over Co3O4 and Co3O4/Al2O3 has been investigated using flow reactor and in situ FTIR studies. Cobalt oxide shows very high activity even at room temperature. However, a gradual deactivation takes place during reaction. The deactivated catalyst shows the presence of two different carbonate species and one graphite-like species. A possible mechanism for the deactivation is discussed.
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| 33. |
- Jeihanipour, Azam, 1982, et al.
(författare)
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Enhancement of solubilization rate of cellulose in anaerobic digestion and its drawbacks
- 2011
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 46:7, s. 1509-1514
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Tidskriftsartikel (refereegranskat)abstract
- Hydrolysis is widely acknowledged as the rate-limiting step in anaerobic digestion of solid cellulose to biogas, and pretreatment is generally considered to facilitate the process. However, few studies have investigated how such pretreatment may affect the rest of this complex process. The present study compared the solubilization rate in anaerobic digestion of cotton linter (high crystalline cellulose), with that of regenerated cellulose (amorphous cellulose), using pretreatment with NMMO. Batch digestions were performed, with the initial cellulose concentrations ranging between 5 and 40 g/l, and during 30 days of incubation, biogas and VFAs production as well as pH and COD changes were measured. The lag time before digestion started was longer for the high crystalline cellulose than for the amorphous one. The maximum solubilization ratesof treated cellulose were 842 and 517 mg sCOD/g cCOD/day at the initial cellulose concentration of 5 and 30 g/l respectively, while the solubilization rate of untreated cellulose never exceeded 417 mg sCOD/g cCOD/day. The difference between the two cellulose types was a direct result of the high rate of hydrolysis inhibiting the acetogenesis/methanogenesis microorganisms, a drawback to the rest of the process.
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| 34. |
- Karkela, T., et al.
(författare)
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RECENT FINDINGS ON RUTHENIUM CHEMISTRY IN A SEVERE ACCIDENT
- 2015
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Ingår i: Proceedings of the International OECD-NEA/NUGENIA-SARNET Workshop on the Progress in Iodine Behaviour for NPP Accident Analysis and Management.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The chemistry of radiotoxic ruthenium in a severe nuclear power accident has actively been investigated especially during the last decades. The Ru studies have covered the release from a fuel, the transport in the primary circuit and the behaviour in the containment building. The gathered experimental data have been utilized to understand the key parameters governing the Ru chemistry in a severe accident (SA) and to check the ability of the existing models of SA analysis codes to explain the experimental results. To further increase the knowledge on Ru behaviour, the collaboration on international level has been intensive. Lately, the widest and most active networks have been EU SARNET and EU SARNET2. The valuable effort of these networks on sharing information of e.g. national programs and on interpreting the experimental results is continued in EU NUGENIA program. More detailed studies on separate phenomena have been conducted e.g. as part of OECD/NEA STEM/START and ISTP/VERDON programs. Furthermore, Phébus FP tests have produced valuable data on integral phenomena.The large-scale integral and semi-integral experiments have confirmed that Ru release depends strongly on carrier gas. Ru is significantly released from an irradiated fuel sample under oxidizing conditions, in particular when air is involved. In addition, the oxidation of UO2 fuel seems to lead to a higher Ru release than in case of MOX fuel. Ruthenium can be transported to the containment atmosphere both in gaseous and particulate forms. The small-scale separate-effect experiments gave a detailed view on Ru transport. A high fraction of ruthenium was detected as particles at the outlet of the model primary circuit in an air atmosphere. However, the observed gaseous Ru fraction is higher than what could be expected based on thermodynamic equilibrium calculations. Further studies on the effect of flow residence time in a temperature gradient for the equilibrium of Ru oxides have been conducted.The effect of other fission products in the gas phase, as well as FP deposits on the surface of primary circuit, on the Ru transport has been investigated. For example, caesium containing deposits seemed to trap gaseous ruthenium effectively. Similarly in case of control rod residues, silver particles in the gas phase of the circuit acted as a sink for gaseous Ru. In an air ingress accident, the effect of air radiolysis products on the Ru chemistry becomes important. As the main air radiolysis products can be considered as oxidizing agents, their ability to oxidize the lower oxides of Ru to higher oxidation state has been examined.Most of Ru in the containment building ends up as deposits on the containment surfaces and in the sump. Experiments on the radiolytical revaporisation of ruthenium deposits on the epoxy paint surface indicated the release of gaseous ruthenium and it was enhanced under humid atmosphere and elevated temperature. It appeared that the products of air radiolysis caused by γ-radiation promoted the formation of gaseous ruthenium from Ru oxide deposits on paint in a higher amount than could be expected by pure ozone action. Concerning the irradiation tests of perruthenate aqueous solutions, they indicated the formation of gaseous Ru by γ-radiolysis products in solution.
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| 35. |
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| 36. |
- Kassman, Håkan, 1962, et al.
(författare)
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Measures to reduce chlorine in deposits: Application in a large-scale circulating fluidised bed boiler firing biomass
- 2011
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Ingår i: Fuel. - Amsterdam : Elsevier BV. - 0016-2361 .- 1873-7153. ; 90:4, s. 1325-1334
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of biomass with a high content of alkali (mainly potassium, K) and chlorine (Cl) can result in operational problems including deposit formation and superheater corrosion. Among the measures applied to decrease such problems are co-combustion and the use of additives. The positive effects of these measures are to a large extent either sulphation of the alkali chlorides (KCl) to less corrosive alkali sulphates or capture of alkali from KCl during release of HCl. A test campaign was carried out in a large-scale circulating fluidised boiler fired with biomass where the measures applied were sulphation by ammonium sulphate and co-combustion with peat. Their performance was evaluated by means of several advanced measurement tools including: IACM (on-line measurements of gaseous KCl); a low-pressure impactor (size distribution and chemical composition of extracted fly ash particles) and deposit measurements (chemical composition in collected deposits). The overall performance was better for ammonium sulphate, which significantly lowered KCl in the flue gas. Meanwhile no chlorine was found in the deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion with peat although the chlorine content in the deposits was greatly reduced. These findings were supported by the results from the impactor measurements. (C) 2010 Elsevier Ltd. All rights reserved.
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| 37. |
- Kihlman, Martin, et al.
(författare)
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Cellulose Dissolution in an Alkali Based Solvent : Influence of Additives and Pretreatments
- 2013
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Ingår i: Journal of the Brazilian Chemical Society. - : SOC BRASILEIRA QUIMICA, Brazil. - 0103-5053 .- 1678-4790. ; 24:2, s. 295-303
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Tidskriftsartikel (refereegranskat)abstract
- The distinction between thermodynamic and kinetics in cellulose dissolution is seldom considered in the literature. Therefore, herein an attempt to discuss this topic and illustrate our hypotheses on the basis of simple experiments was made. It is well-known that cellulose can be dissolved in a aqueous sodium hydroxide (NaOH/H2O) solvent at low temperature but it is here shown that such an alkaline solvent can be considerably improved regarding solubility, stability and rheological properties as a whole if different additives (salts and amphiphilic molecules) are used in the dissolution stage. This work probes new aqueous routes to dissolve cellulose, thereby improving the potential to commercially dissolve cellulose in an inexpensive and environmentally friendly manner.
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| 38. |
- Lindberg, Jonas, et al.
(författare)
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The effect of O2 concentration on the reaction mechanism in Li-O2 batteries
- 2017
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 797, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The promising lithium-oxygen battery chemistry presents a set of challenges that need to be solved if commercialization is ever to be realized. This study focuses on how the O2 reaction path is effected by the O2 concentration in the electrolyte. An electrochemical quartz crystal microbalance system was used to measure current, potential, and change in electrode mass simultaneously. It is concluded that the mass reversibility is O2 concentration dependent while the coulombic efficiency is not. The mass reversibility is higher at low O2 concentration meaning that more of the deposited Li2O2 is removed during oxidation in relation to the amount deposited during reduction. The first step of the reduction is the formation of soluble LiO2, which is then either reacting further at the electrode or being transported away from the electrode resulting in low current efficiency and low deposited mass per electrons transferred. During the oxidation, the first step involves de-lithiation of Li2O2 at low potential followed by bulk oxidation. The oxidation behavior is O2 concentration dependent, and this dependence is likely indirect as the O2 concentration effects the amount of discharge product formed during the reduction. The O2 concentration at different saturation pressures was determined using a mass spectrometer. It was found that the electrolyte follows Henry's law at the pressures used in the study. In conclusion, this study provides insight to the O2 concentration dependence and the preferred path of the O2 electrochemical reactions in lithium-oxygen batteries.
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| 39. |
- Mahmoudkhani, Maryam, 1971, et al.
(författare)
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Recycling of Solid Residues to the Forest: Experimental and theoretical study of the release of sodium from lime mud and green liquor dregs aggregates
- 2004
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Ingår i: Process Safety and Environmental Protection: Transactions of the Institution of Chemical Engineers, Part B. - : Elsevier BV. - 1744-3598 .- 0957-5820. ; 82:3, s. 230-237
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Tidskriftsartikel (refereegranskat)abstract
- In order to optimize the recycling of solid residues back to the forest, it is necessary to measure and characterize the dissolution rate of the product under well-defined conditions. In this study, inorganic solid residues from a kraft pulp mill were characterized physically and chemically. The effect of pH, as well as physical characteristics and chemical composition, on the leaching rate was investigated. It was shown that the leaching behaviour differed depending on the production method of the aggregates. A model based on mass transfer was fitted to the experimental leaching data. It was shown that the leaching rate for the easily soluble species was reasonably well described using the concentration gradient of these species within the pellet. It was also shown that mass transfer within and from the pellet/granule was the rate-determining step.
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| 40. |
- Marra, Eva, et al.
(författare)
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Oxygen reduction reaction kinetics on a Pt thin layer electrode in AEMFC
- 2022
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 435, s. 141376-141376
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Tidskriftsartikel (refereegranskat)abstract
- The study of the catalytic activity in a fuel cell is challenging, as mass transport, gas crossover and the counterelectrode are generally interfering. In this study, a Pt electrode consisting of a thin film deposited on the gasdiffusion layer was employed to study the oxygen reduction reaction (ORR) in an operating Anion Exchange Membrane Fuel Cell (AEMFC). The 2D Pt electrode was assembled together with a conventional porous Pt/Ccounter electrode and an extra Pt/C layer and membrane to reduce the H2 crossover. Polarization curves atdifferent O2 partial pressures were recorded and the resulting reproducible ORR activities were normalized withrespect to the active surface area (ECSA), obtained by CO stripping. As expected, decreasing the O2 partialpressure results in a negative shift in open circuit voltage (OCV), cell voltage and maximum attainable currentdensity. For cell voltages above 0.8 V a fairly constant Tafel slope of 60 mV dec−1 was recorded but at lowervoltages the slope increases rapidly. The observed Tafel slope can be explained by a theoretical model with anassociative mechanism where charge- and proton-transfer steps are decoupled, and the proton transfer is the rate-determining step. A reaction order of 1 with respect to O2 was obtained at 0.65 V which corresponds well withthe mechanism suggested above. Based on the obtained catalyst activities, the electrode performance is comparable to good porous electrodes found in the field. The methodology presented in this study is expected to beuseful in future kinetic studies of other catalysts for AEMFC.
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