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  • 1.
    Bergman, Susanna L.
    et al.
    Yale NUS Coll, Sci Div, Singapore 138529, Singapore.;Princeton Univ, Dept Chem, Princeton, NJ 08540 USA..
    Granestrand, Jonas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Technology.
    Xi, Shibo
    ASTAR, ICES, Singapore Synchrotron Light Source, Singapore 117603, Singapore..
    Du, Yonghua
    ASTAR, ICES, Singapore Synchrotron Light Source, Singapore 117603, Singapore..
    Tang, Yu
    Univ Kansas, Dept Chem, Lawrence, KS 66045 USA..
    Tang, Chunhua
    Natl Univ Singapore, Mat Sci & Engn, Singapore 117575, Singapore..
    Kienkas, Liene
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Pettersson, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Bernasek, Steven L.
    Yale NUS Coll, Sci Div, Singapore 138529, Singapore.;Princeton Univ, Dept Chem, Princeton, NJ 08540 USA..
    Probing the Oxidation/Reduction Dynamics of Fresh and P-, Na-, and K-Contaminated Pt/Pd/Al2O3 Diesel Oxidation Catalysts by STEM, TPR, and in Situ XANES2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 5, p. 2945-2952Article in journal (Refereed)
    Abstract [en]

    This study examines the oxidation and reduction behavior of Pt/Pd/Al2O3 diesel oxidation catalysts at temperatures and gas compositions that model the conditions of the working diesel oxidation catalyst in a truck exhaust system. In situ measurements using Pt L-3 X-ray edge absorption spectroscopy are coupled with temperature-programmed reduction (TPR) and scanning transmission electron microscopy measurements to characterize the catalyst. The fresh catalyst is compared with chemically aged catalysts, exposed to Na, K, and P contaminants. Phosphorus exhibits strong, spatially localized interactions with the Pt/Pd catalyst nanoparticles that are reflected in a strong shift to lower energy of the Pt L-3 edge under CO oxidation conditions. The Na and K poisons are spread more uniformly throughout the catalyst washcoat and do not strongly affect the edge spectra or the TPR-determined catalyst reducibility.

  • 2.
    Horne, Gregory P.
    et al.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Zarzana, Christopher A.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Grimes, Travis S.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Rae, Cathy
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Ceder, Joakim
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering. Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Mezyk, Stephen P.
    Calif State Univ Long Beach, Dept Chem & Biochem, Long Beach, CA 90804 USA..
    Mincher, Bruce J.
    Idaho Natl Lab, Ctr Radiat Chem Res, POB 1625, Idaho Falls, ID 83415 USA..
    Charbonnel, Marie-Christine
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Guilbaud, Philippe
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Saint-Louis, George
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Berthon, Laurence
    Univ Montpellier, CEA, DEN, DMRC, Marcoule, France..
    Effect of chemical environment on the radiation chemistry of N,N-di-(2-ethylhexyl)butyramide (DEHBA) and plutonium retention2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 38, p. 14450-14460Article in journal (Refereed)
    Abstract [en]

    N,N-di-(2-ethylhexyl)butyramide (DEHBA) has been proposed as part of a hydro-reprocessing solvent extraction system for the co-extraction of uranium and plutonium from spent nuclear fuel, owing to its selectivity for hexavalent uranium and tetravalent plutonium. However, there is a critical lack of quantitative understanding regarding the impact of chemical environment on the radiation chemistry of DEHBA, and how this would affect process performance. Here we present a systematic investigation into the radiolytic degradation of DEHBA in a range of n-dodecane solvent system formulations, where we subject DEHBA to gamma irradiation, measure reaction kinetics, ligand integrity, degradation product formation, and investigate solvent system performance through uranium and plutonium extraction and strip distribution ratios. The rate of DEHBA degradation in n-dodecane was found to be slow (G = -0.31 +/- 0.02 mu mol J(-1)) but enhanced upon contact with the oxidizing conditions of the investigated solvent systems (organic-only, or in contact with either 0.1 or 3.0 M aqueous nitric acid). Two major degradation products were identified in the organic phase, bis-2-ethylhexylamine (b2EHA) and N-(2-ethylhexyl)butyramide (MEHBA), resulting from the cleavage of C-N bonds, and could account for the total loss of DEHBA up to similar to 300 kGy for organic-only conditions. Both b2EHA and MEHBA were also found to be susceptible to radiolytic degradation, having G-values of -0.12 +/- 0.01 and -0.08 +/- 0.01 mu mol J(-1), respectively. Solvent extraction studies showed: (i) negligible change in uranium extraction and stripping with increasing absorbed dose; and (ii) plutonium extraction and retention exhibits complex dependencies on absorbed dose and chemical environment. Organic-only conditions afforded enhanced plutonium extraction and retention attributed to b2EHA, while acid contacts inhibited this effect and promoted significant plutonium retention for the highest acidity. Overall it has been demonstrated that chemical environment during irradiation has a significant influence on the extent of DEHBA degradation and plutonium retention.

  • 3.
    Kim, Hyeyun
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Mattinen, Ulriika
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering. Åbo Akademi.
    Guccini, Valentina
    Salazar-Alvarez, German
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Cornell, Ann M.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Feasibility of chemically modified cellulose nanofiber membrane as lithium ion battery separatorManuscript (preprint) (Other academic)
    Abstract [en]

    Chemical modification of cellulose contributes to its fibrillation to nanofibers and consequently production of a mesoporous membrane, desirable for lithium ion battery separator. Nevertheless, the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidized cellulose nanofibers (TOCN) based separator with high charge density (650 μmol COO-/gCNF) has high risk of cell failure in lithium ion battery (LIB), compared to the counterpart with lower charge density (350 μmol/g). In this study, the influence of sodium carboxylate or carboxylic acid functional groups in TOCN as lithium ion battery separator was investigated. In-operando mass spectrometry measurements were used to elucidate the cause of cell failure by analyzing the gas evolved, from batteries containing different types of separators. For the TOCN separator with sodium carboxylate functional groups, it seems that Na deposition is the dominant reason for poor electrochemical stability of the cell thereof. The poor performance of the protonated TOCN separator is attributed to a high amount of gas evolution, mostly H2, originating from the reduction of trace water and H+ released from COOH and OH surface groups. Nonetheless, the electrochemical performance of the separator could be dramatically improved by adding 2 wt% of vinylene carbonate (VC) to the electrolyte, which effectively suppressed the generation of gas. Furthermore, the separator demonstrated excellent cycling stability in the pouch cell and sufficiently high specific capacity at ≈ 2C of discharging rate.

  • 4.
    Kim, Hyeyun
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Mattinen, Ulriika
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering. Åbo Akademi.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Cornell, Ann M.
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Spray-coated nanocellulose based separator/electrode assemblyManuscript (preprint) (Other academic)
    Abstract [en]

    A separator-electrode assembly (SEA) made of wood-based cellulose nanofibers (CNF) and Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was fabricated by a facile spray-coating process. CNF building blocks were prepared by homogenizing enzymatically pretreated cellulose fibers dispersed in a non-hazardous solvent, 2-propanol (IPA). The porous composite separator was made by spray-coating thin layers CNF-IPA, followed by a PVDF-HFP spray coating, on a lithium ion battery electrode. A CNF substrate was crucial for making a highly porous and thermally stable separator and PVDF-HFP coating enhanced its mechanical stability. The SEA maintained dimensional integrity when subjected to high temperature and when used in lithium ion batteries. A CNF-LiNi1/3Co1/3Mn1/3O2 (NMC) SEA showed excellent electrochemical stability, especially at fast charging/discharging rate, whereas a graphite counterpart showed poor electrochemical performance, resulting in cell failure. A SiO2 layer overcoated on the top of CNF-NMC SEA enabled its application for a proof-of-concept lithium metal battery and for a high energy‐density LiNi0.6Co0.2Mn0.2O2 (NMC622) lithium‐ion battery with excellent electrochemical stability and performances. The utilization of biodegradable materials and non-hazardous solvents such as IPA and acetone makes the development of the CNF based SEA attractive, as an eco-friendly lithium ion battery manufacturing process.

  • 5.
    Winberg-Wang, Helen
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Water density impact on water flow and mass transport in rock fractures2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One way of taking care of spent nuclear fuel is to place it in a geological repository. In Sweden, a three-barrier system is planned. The system is based on encapsulating the fuel in copper canisters. These are surrounded by bentonite clay and buried under 500 m of bedrock. As a part of the safety assessment, the Q-equivalent model is used to quantify the possible release of radioactive material. This model also describes the rate at which corrosive agents carried by seeping water in rock fractures can reach the canisters, which may affect the longevity of the canisters.

    The aim of this thesis was originally to develop an experimental, phys- ical model to visualize and validate the Q-equivalent model. However, the overarching theme of this work has been to study the effect of minor density differences that might be overlooked in experiments, both concentration- dependent and density-difference induced by light absorption.

    In the initial diffusion and flow-experiment and associated calculations and simulations, it was found that simple Q-equivalent can describe and quantify the mass transport in both parallel and variable aperture fractures. However, this is the case only if the density difference between seeping water and clay pore water is insignificant. It was found in experiments with dyes used to visualise the flow and diffusion patterns that even minimal density differences could significantly alter the flow pattern. Density differences can result from concentration gradients or be induced by light absorption. TheQ-equivalent model was extended to account for density-induced flow. The importance of density-induced flow due to concentration gradients at the setting of a long-term repository for nuclear waste was evaluated. It was found that concentration gradients are able to induce rapid vertical up- or downward flow. This could increase the overall mass transport of radioactive material up to the biosphere or carry it downward to larger depths.

  • 6.
    Winberg-Wang, Helen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Visualisation of mass transfer between source and seeping water in a variable aperture fracture-Impact of tracer densityManuscript (preprint) (Other academic)
    Abstract [en]

    An experiment with a vertical slot with horizontally seeping water with a dye diffusing from below was performed to help validate and visualise the Q-equivalent model, which describes the mass transfer rate from a source into flowing water such that in a repository for nuclear waste. The Q-equivalent model is used for quantifying mass transport in geological repositories. However, the tracer propagated much slower and to a lesser extent than predicted by the model. It was found that the tracer gave rise to a small density gradient, which induced buoyancy-driven flow, overwhelming that driven by the horizontal hydraulic gradient. This dramatically changed the mass transfer from the dye source into the water in the slot. For the release of contaminants, this can have detrimental as well as beneficial effects, depending on positive or negative buoyancy is induced. These observations led to an analysis of when and how density differences in a repository can influence the release and further fate of escaping radionuclides in waste repositories. This and other experiments also showed that laboratory experiments aimed to visualise flow and mass transfer processes in fractures could be very sensitive to the heating of the dye tracers by the lighting in the laboratory. 

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