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  • 101.
    Halldin Stenlid, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Campos dos Santos, Egon
    Stockholm University, Faculty of Science, Department of Physics. Universidade Federal de Minas Gerais, Brazil.
    Johansson, Adam Johannes
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    On the Nature of the Cathodic Reaction during Corrosion of Copper in Anoxic Sulfide Solutions2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 6, p. C196-C208Article in journal (Refereed)
    Abstract [en]

    Sulfide-induced corrosion is expected to be the dominating long-term corrosion process for copper containers in technical concepts for deep geological disposal of spent nuclear fuel (SNF), adapted in several waste management programs around the world. The present study investigates the atomic-scale mechanism of the cathode side of the corrosion reaction using Density Functional Theory (DFT) calculations. Despite the central role of the reaction, neither the site of reaction nor the active species has been previously established. Here we compare the cathodic reaction leading to H-2-evolution on pure copper and on chalcocite (Cu2S) surfaces. The considered H-donors are OH-/H2O and HS-/H2S which are all available at the neutral to alkaline conditions anticipated at the SNF disposal sites. Assuming Volmer-Tafel-Heyrovsky kinetics, we find that the cathodic reactions are many orders of magnitude faster on copper compared to copper sulfide. Although we find that HS-/H2S have lower reaction barriers than H2O, our kinetic analysis suggest that H2O is expected to be the main H-source for the cathodic reaction under SNF repository conditions as results of the low sulfide concentrations (less than or similar to 10 mu M) expected in SNF repositories in Sweden, Finland and Canada.

  • 102.
    Harnden, Ross
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Peuvot, Kevin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Multifunctional Performance of Sodiated Carbon Fibers2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 13, p. B616-B622Article in journal (Refereed)
    Abstract [en]

    An investigation is conducted into the potential for sodiated PAN-based carbon fibers (CFs) to be used in multifunctional actuation, sensing, and energy harvesting. Axial CF expansion/contraction is measured during sodiation/desodiation using operando strain measurements. The reversible expansion/contraction is found to be 0.1% - which is lower than that of lithiated CFs. The axial sodiation expansion occurs in two well-defined stages, corresponding to the sloping and plateau regions of the galvanostatic cycling curve. The results indicate that the sloping region most likely corresponds to sodium insertion between graphitic sheets, while the plateau region corresponds to sodium insertion in micropores. A voltage-strain coupling is found for the CFs, with a maximum coupling factor of 0.15 +/- 0.01 V/unit strain, which could be used for strain sensing in multifunctional structures. This voltage-strain coupling is too small to be exploited for harvesting mechanical energy. The measured axial expansion is further used to estimate the capacity loss due to solid electrolyte interphase (SEI) formation, as well as capacity loss due to sodium trapped in the CF microstructure. The outcomes of this research suggest that sodiated CFs show some potential for use as actuators and sensors in future multifunctional structures, but that lithiated CFs show more promise.

  • 103.
    Hatamie, Amir
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering. Shvrif Univ Technol, Iran.
    Angizi, Shayan
    Shvrif Univ Technol, Iran.
    Kumar, Saurabh
    Indian Inst Sci, India; Delhi Technol Univ, India.
    Pandey, Chandra Mouli
    Delhi Technol Univ, India.
    Simchi, Abdolreza
    Shvrif Univ Technol, Iran.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering.
    Malhotra, Bansi D.
    Delhi Technol Univ, India.
    Review-Textile Based Chemical and Physical Sensors for Healthcare Monitoring2020In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 167, no 3, article id 037546Article, review/survey (Refereed)
    Abstract [en]

    The emergence of textile-based wearable sensors as light-weight portable devices to monitor desired parameters, has recently gained much interest and has led to the development of flexible electronics on non-rigid substrates. The flexible biosensors may result in improved sports performance, to monitor the desired bodies for injuries, improved clinical diagnostics and monitor biological molecules and ions in biological fluids such as saliva, sweat. In addition, they could help users with different types of disorders such as blindness. In this context, new composite and nanomaterials have been found to be promising candidates to obtain improved performance of the textile based wearable devices and to optimize the structures for intimate contact with the skin for better functionality. This review aims to provide the most recent cutting-edge information on emergence, fabrication, materials, and applications of chemical and physical flexible and stretchable textile-based (bio)sensors. Besides this, we discusss the recent key innovations and applications of textile-based sensors in healthcare.

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  • 104.
    Hedberg, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Baldelli, Steven
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques II. Two and Three-Dimensional Growth of Reaction Products Induced by Formic and Acetic Acid2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 10, p. C363-C373Article in journal (Refereed)
    Abstract [en]

    In an effort to obtain a more molecular view of atmospheric corrosion, we present experimental data from three complementary acting vibrational spectroscopy techniques that have been used in parallel exposures to follow the initial atmospheric corrosion of zinc during exposure in dry or humid air to which formic acid or acetic acid was added, with the primary aim to simulate indoor exposure conditions. The techniques used were vibrational sum frequency spectroscopy (interface sensitive), IR reflection absorption spectroscopy (near-surface sensitive), and confocal Raman microspectroscopy (bulk sensitive with submicrometer surface lateral resolution). The growth of two-dimensional interface species of zinc formate or zinc acetate could be monitored in situ and distinguished from three-dimensional growth of ZnO and zinc hydroxy formate or acetate. These interface species are believed to act as precursors of the dissolution of aqueous zinc carboxylate species that subsequently deposit at the surface and result in local growth of crystalline or amorphous ZnO and local zinc hydroxy carboxylate. Differences in the growth of corrosion products induced by acetic or formic acid were mainly attributed to differences in pH of the aqueous adlayer and in different deposition velocities of the acids into the aqueous adlayer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479255] All rights reserved.

  • 105.
    Hedberg, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Baldelli, Steven
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Tyrode, Eric
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques I. Experimental Approach2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 10, p. C357-C362Article in journal (Refereed)
    Abstract [en]

    As the nature of the interactions taking place on a metal surface during atmospheric corrosion is inherently complex, it imposes demands on the analytical studies that are needed to understand the fundamentals on a molecular level. Corrosion products may spread on the metal surface forming two-and three-dimensional structures. Thus, it is imperative to use different techniques to resolve the different types of growth. In this first part of a series of two papers, a systematic investigation is made to obtain detailed information on the mechanisms of the onset of atmospheric corrosion of zinc exposed to 115 ppb acetic acid in either dry or humidified air. The vibrational spectroscopy techniques used were vibrational sum frequency spectroscopy (VSFS, interface sensitive), infrared reflection absorption spectroscopy (IRAS, near-surface sensitive), and confocal Raman microspectroscopy (CRM, bulk sensitive). The VSFS selectively targeted the two-dimensional structures, IRAS followed the growth of three-dimensional corrosion products, and CRM could provide a laterally resolved chemical map on localized aggregates of zinc hydroxy acetate and ZnO with bulk character. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479207] All rights reserved.

  • 106.
    Hedenstedt, Kristoffer
    et al.
    Göteborgs Universitet; AkzoNobel.
    Bäckström, Joakim
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Göteborgs Universitet.
    Ahlberg, Elisabet
    Göteborgs Universitet.
    In-Situ Raman Spectroscopy of α- and γ-FeOOH during Cathodic Load2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 9, p. H621-H627Article in journal (Refereed)
    Abstract [en]

    Water reduction on corroded iron surfaces is technologically and fundamentally important. Here, the technological interest originatesfrom the chlorate process where water reduction is the main cathodic process. Fundamentally, water reduction on oxide surfaces raisesquestions on the stability of the oxide and the nature of electrocatalytic surface sites. Two iron oxyhydroxides,α-andγ-FeOOH,were electrodeposited on titanium substrate and their reduction processes were followed in detail with in-situ Raman spectroscopy,using low incident laser power to avoid sample damaging. Polarization to negative potentials show two reduction peaks forγ-FeOOHand one peak forα-FeOOH prior to hydrogen evolution. The characteristic Raman peaks gradually disappear as the potential ismade more negative but no new peaks can be observed.δ-FeOOH was detected as an intermediate phase upon oxidation of thereduced surface layer. This indicates that Fe(OH)2is formed during cathodic polarization and initially re-oxidized to the isostructuralδ-FeOOH. Characteristic Raman signals of the original phases appear upon further oxidation in air.

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  • 107.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jacques, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    PAN-based carbon fiber negative electrodes for structural lithium-ion batteries2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 12, p. A1455-A1460Article in journal (Refereed)
    Abstract [en]

    Several grades of commercially-available polyacrylonitrile (PAN)-based carbon fibers have been studied for structural lithium-ion batteries to understand how the sizing, different lithiation rates and number of fibers per tow affect the available reversible capacity, when used as both current collector and electrode, for use in structural batteries. The study shows that at moderate lithiation rates, 100 mA g-1, most of the carbon fibers display a reversible capacity close to or above 100 mAh g-1 after ten full cycles. For most of the fibers, removing the sizing increased the capacity to some extent. However, the main factor affecting the measured capacity was the lithiation rate. Decreasing the current by a tenth yielded an increase of capacity of around 100 for all the tested grades. From the measurements performed in this study it is evident that carbon fibers can be used as the active negative material and current collector in structural batteries. © 2011 The Electrochemical Society.

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  • 108.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zavalis, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Electrochemical characterization of lithium intercalation processes of PAN-based carbon fibers in a microelectrode system2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 9, p. A1473-A1481Article in journal (Refereed)
    Abstract [en]

    A full electrochemical investigation of the lithium intercalation processes in a commercially available PAN-based carbon fiber, Toho Tenax IMS65 (unsized and sized) primarily intended to be used in structural lithium-ion batteries, has been performed. In order to extract the electrochemical properties, a specially designed microelectrode system consisting of a single fiber working electrode, lithium-foil counter electrode and well-characterized battery materials were utilized. The properties, for 5 to 100% state-of-charge (SOC), were mainly determined from electrochemical impedance spectroscopy (EIS) measurements by fitting of a physics-based model, and electronic conductivity examination. The study shows excellent mass transport and kinetic properties, especially at high SOCs for this specific carbon fiber compared to other negative electrode materials. Some electrochemical parameters vary depending on sizing, but are too small to affect the actual electrochemical performance. A strong SOC dependence is shown for most electrochemical properties, including the electronic conductivity.

  • 109.
    Herting, Gunilla
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    A comparison of release rates of Cr, Ni and Fe from stainless steel alloys and the pure metals exposed to simulated rain events2005In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, no 1, p. B23-B29Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to demonstrate differences in metal release rates of Cr, Ni, and Fe from pure metals and stainless steels alloys (grades 304 and 316) exposed to identical simulated rain events. Panels were exposed to two 8 h continuous rain periods, separated by a 40 day dry period, in a specially designed rain chamber which permits artificial rain of known composition to be introduced at a given intensity. The study is intended to provide further knowledge of the behavior of stainless steels exposed to atmospheric corrosion and to show the discrepancy between estimated release rates based on nominal alloy composition and actual, measured release rates. Release rates of Fe and Ni were found to be substantially higher from the pure metals than from the stainless steels due to the presence of a chromium-rich surface film. The release rate of Cr was similar for stainless steel alloys and pure chromium. X-ray photoelectron spectroscopy investigations after single-rain events showed chromium to be enriched in the surface film upon rain exposure resulting in decreasing release rates of Cr, Ni, and Fe. Comparison between actual release rates of alloy constituents and calculated rates based on the pure metals and the nominal alloy composition, showed calculated data to substantially overestimate release rates of Ni and Fe.

  • 110.
    Hitova, L.
    et al.
    Inst. Semiconduct. Phys. Technol., St. Kliment Ohridski Univ. of Sofia, 1164 Sofia, Bulgaria.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Trifonova, E.P.
    Faculty of Physics, St. Kliment Ohridski Univ. of Sofia, 1164 Sofia, Bulgaria.
    Lenchev, A.
    Faculty of Chemistry, St. Kliment Ohridski Univ. of Sofia, 1164 Sofia, Bulgaria.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Heat capacity of 4H-SiC determined by differential scanning calorimetry2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 9, p. 3546-3547Article in journal (Refereed)
    Abstract [en]

    The thermochemical properties of monocrystalline 4H-SiC was studied. Differential scanning calorimetry was used to measure the heat capacity. The powders used were nitrogen doped. The powder is synthesized from pure Si and C. The heat capacity measurements were performed using a DSC-4 Perkin Elmer device. The data obtained were analyzed statistically using the computer program. The experimental data fitted the curves. The measured data and the extrapolated data for monocrystalline 4H-SiC are lower than those of monocrystalline 6H-SiC.

  • 111.
    Hollmark, H.M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Duda, Laurent-Claudius
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Dahbi, Mohammed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Saadoune, Ismael
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O22010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 8, p. A962-A966Article in journal (Refereed)
  • 112.
    Hollmark, H.M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Vegelius, J.R.
    Kristiansen, P.T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Werme, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Duda, Laurent-Claudius
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 1, p. C1-C5Article in journal (Refereed)
  • 113.
    Hollmark, Håkan M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Dahbi, Mohammed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Saadoune, Ismael
    LCME, University Cadi Ayyad, Marrakech, Morocco.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Resonant Soft X-Ray Emission Spectroscopy and X-Ray Absorption Spectroscopy on the Cathode Material LiNi0.65Co0.25Mn0.1O22010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 8, p. A962-A966Article in journal (Refereed)
    Abstract [en]

    We present a study of the charge-state behavior of the Li-ion battery cathode material LixNi(0.65)Co(0.25)Mn(0.1)O(2) as observed by X-ray absorption spectroscopy (XAS) and resonant soft X-ray emission (RSXE). A set of six identical Li//LixNi0.65Co0.25Mn0.1O2 batteries has been cycled and is studied in different states of charge in the range of x = 1.0, ... ,0.2 before disassembly in an Ar glove box. Site and symmetry selective information about the electronic structure of the conduction and valence bands reveals that Ni as well as Co ions participate in the uptake and release of the extra electron charge that the inserted Li ions provide, but the Ni ion is much less than expected. The net amount of charge on the oxygen varies approximately 0.24 charge units in the range of x, and dramatic changes in the hybridization are evident in XAS and in particular in RSXE at the O K edge. We attribute this to a strong screening behavior of the Li ions between the oxide layers. Structural integrity effects limit the extraction of Li ions to a value of about x = 0.2-0.4. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3454739] All rights reserved.

  • 114.
    Hollmark, Håkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Vegelius, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Kristiansen, Paw
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Werme, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Duda, Laurent
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Soft X-Ray Physics.
    Exposure of Oxidized Copper Surfaces to Aqueous Na2S Solution Studied with Soft X-Ray Spectroscopy2011In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 1, p. C1-C5Article in journal (Refereed)
    Abstract [en]

    We present results from X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) of oxidized polycrystalline copper surfaces [Cu(I) and Cu(II), respectively] exposed to a 1.0 mM aqueous solution of Na2S (sodium sulfide) for several hours. Scanning electron microscopy reveals that the Cu oxide surfaces attain a much rougher texture upon sodium sulfide exposure, and that the exposed Cu(II) oxide sample exhibits areas with crystallites. The XAS spectra show that sodium sulfide effectively reduces Cu(II) oxide to Cu(I) compounds. The RIXS spectra of the exposed surfaces closely resemble those of the Cu2O reference sample with the notable exception of their Cu LIII,II-RIXS spectra. We conclude that copper evidently forms a Cu(I) compound with oxygen but with a Cu 3d-band of much reduced width, pointing to the possibility of a more complex compound containing both oxygen and sulfur.

  • 115.
    Holmström, Nicklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wiezell, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Studying Low-Humidity Effects in PEFCs Using EIS I: Experimental2012In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, no 8, p. F369-F378Article in journal (Refereed)
    Abstract [en]

    A suitable electrochemical characterization technique for studying water effects at low-humidity conditions is electrochemical impedance spectroscopy (EIS). In general, an EIS spectrum for a PEFC shows one or several capacitive loops and in some situations an inductive loop at the lowest frequencies depending on operating conditions. In this study, low-humidity effects in an operating polymer electrolyte fuel cell have been investigated by using electrochemical impedance spectroscopy (EIS), with the focus on the low-frequency impedance. Measurements have been carried out using several membranes with different thicknesses at various current densities and operating conditions. At frequencies, around 1 Hz down to 5 mHz a pseudo-inductive loop was seen. The magnitude of this loop increased with thicker membranes and at lower humidities. Based on the results the pseudo-inductive loop was attributed to water transport characteristics in the membrane, where the capacitive part is attributed to drying out of the anode and parts of the membrane closest to the anode while the inductive part is attributed to rehydration of the membrane and the anode by product water from the oxygen reduction reaction on the cathode. In addition, both the magnitude and the top-frequencies of the pseudo-inductive loop were affected by the flow rate.

  • 116.
    Hosseinpour, Saman
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Self-Assembled Monolayers as Inhibitors for the Atmospheric Corrosion of Copper Induced by Formic Acid: A Comparison between Hexanethiol and Hexaneselenol2014In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 161, no 1, p. C50-C56Article in journal (Refereed)
    Abstract [en]

    The corrosion protection by self-assembled monolayers (SAMs) of hexanethiol and hexaneselenol has been explored on copper exposed to humid air containing formic acid, a corrosive environment relevant for indoor atmospheric corrosion. The kinetics of the formation of corrosion products on SAM covered copper was followed using in-situ infrared reflection/absorption spectroscopy (IRAS) and compared with that of bare copper. Both SAMs initially showed a corrosion protection ability. The prolonged exposure of hexanethiol copper resulted in a reduced formation rate of copper formate and copper hydroxide compared to bare copper, while on bare and hexaneselenol covered samples copper (I) oxide, copper formate, and copper hydroxide were observed. To assess the quality of the SAMs during the sample exposure, vibrational sum frequency spectroscopy (VSFS) was used. It was found that hexaneselenol molecules are locally removed from the surface during corrosion in contrast to their thiol counterparts. This created localized galvanic effects which resulted in an accelerated corrosion of selenol covered copper. X-ray photoelectron spectroscopy at elevated pressure demonstrated that the hexanethiol removed thin oxide layers upon adsorption. A contributing parameter to the enhanced corrosion inhibiting ability of hexanethiol could be its greater ability than hexaneselenol to bind to the copper surface during its deposition and sample exposure.

  • 117.
    Hosseinpour, Saman
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Alkanethiols as inhibitors for the atmospheric corrosion of copper induced by formic acid: Effect of chain length2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 6, p. C270-C276Article in journal (Refereed)
    Abstract [en]

    Self assembled monolayers (SAMs) of n-alkanethiols of different chain length (4, 6, 8, 12, and 18 carbons in the chain) have been explored as corrosion inhibitors for copper exposed to humidified air containing formic acid, an environment used to mimic accelerated indoor atmospheric corrosion. Near-surface sensitive in-situ infrared reflection/absorption spectroscopy combined with interface sensitive vibrational sum frequency spectroscopy revealed unique molecular information on the role of each SAM during ongoing corrosion. All SAMs protect copper against corrosion, and this ability increases continuously with chain length. Their structural order is high prior to exposure, but an increased disorder is observed as a result of the corrosion process. The protection ability of the SAMs is attributed to a selective hindrance of the corrosion stimulators water, oxygen gas, and formic acid to reach the copper-SAM interface through each SAM, which results in different corrosion mechanisms on SAM protected copper and unprotected copper. This significantly retards the formation of the corrosion products copper hydroxide and copper formate, and results in essentially no formation of cuprite.

  • 118.
    Hu, Lan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ekström, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. COMSOL AB, Sweden.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A Model for Analysis of the Porous Nickel Electrode Polarization in the Molten Carbonate Electrolysis Cell2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 8, p. H5197-H5201Article in journal (Refereed)
    Abstract [en]

    It is important to know the electrode kinetics of hydrogen production as well as to understand the effect of the mass transport in the gas phase for the analysis of the molten carbonate electrolysis cell (MCEC). A one-dimensional model based on the Maxwell-Stefan diffusion equations was applied to predict the mass transfer behavior in gas phase of the porous nickel electrode in the MCEC, combined with equations describing the current distribution in the electrolyte phase. The model gave a fair match to the experimental polarization data of the Ni electrode for varied inlet gas compositions of H2O, CO2 and H-2 between 10 and 40%. The model was also deployed to evaluate the effect of the water-gas shift reaction (WGSR). The fitted kinetic coefficients and electrode porosity differed in the case when including the WGSR compared to when not including the WGSR. In both cases the model was able to well describe the porous nickel electrode behavior in the molten carbonate electrolysis cell.

  • 119.
    Hu, Lan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Electrode Kinetics of the Ni Porous Electrode for Hydrogen Production in a Molten Carbonate Electrolysis Cell (MCEC)2015In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, no 9, p. F1020-F1028Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to elucidate the kinetics of a porous nickel electrode for hydrogen production in a molten carbonate electrolysis cell. Stationary polarization data for the Ni electrode were recorded under varying gas compositions and temperatures. The slopes of these iR-corrected polarization curves were analyzed at low overpotential, under the assumption that the porous electrode was under kinetic control with mass-transfer limitations thus neglected. The exchange current densities were calculated numerically by using a simplified porous electrode model. Within the temperature range of 600-650 degrees C, the reaction order of hydrogen is not constant; the value was found to be 0.49-0.44 at lower H-2 concentration, while increasing to 0.79-0.94 when containing 25-50% H-2. The dependence on CO2 partial pressure increased from 0.62 to 0.86 with temperature. The reaction order of water showed two cases as did hydrogen. For lower H2O content (10-30%), the value was in the range of 0.47-0.67 at 600-650 degrees C, while increasing to 0.83-1.07 with 30-50% H2O. The experimentally obtained partial pressure dependencies were high, and therefore not in agreement with any of the mechanisms suggested for hydrogen production in molten carbonate salts in this study.

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  • 120. Hu, Ronggang
    et al.
    Ornberg, Andreas
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Investigation of Influence of Small Particles in MP35N on the Corrosion Resistance in Synthetic Biological Environment2009In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 156, no 10, p. C341-C344Article in journal (Refereed)
    Abstract [en]

    A cobalt-based alloy, MP35N, is currently used as a conductor material for thin wires in pacemaker leads. In this study, electrochemical impedance spectroscopy and cyclic polarization measurements of the alloy in a phosphate-buffered saline solution with 100 mM H2O2 indicated a high corrosion resistance and no passivity breakdown. Scanning electron microscopy and energy-dispersive spectroscopy analyses showed the existence of micrometer-sized TiN particles in the microstructure. Volta potential mapping by scanning Kelvin probe force microscopy revealed that the Volta potential of the TiN particles wits several tens of millivolts higher than that of the alloy matrix. By in situ atomic force microscopy measurements in the solution, small pitlike holes were observed in the vicinity of TiN particles and in other areas after 2 weeks of exposure. However, deposition of corrosion products within the pits was observed in the following days, and the pitlike holes were sealed upon further exposure. The results indicated a negligible risk for localized corrosion of this alloy despite the TiN particles present in the microstructure.

  • 121.
    Hultquist, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Graham, M. J.
    Wee, A. T. S.
    Liu, R.
    Sproule, G. I.
    Dong, Q.
    Anghel, C.
    Effects of O-2 dissociation on a porous platinum coating in the thermal oxidation of GaAs2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 2, p. G182-G186Article in journal (Refereed)
    Abstract [en]

    A 20-30-nm-thick porous Pt layer has been sputter-coated on a portion of a GaAs sample and subsequently the sample was oxidized at 500 degrees C in O-16(2) followed by O-18-enriched O-2. The oxide formed was characterized by Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy, all with a lateral resolution of about 100 mu m. Away from the Pt area, a mm-ranged gradually decreasing degree of As oxidation was observed in the outermost oxide layer. In the Pt area, Ga was preferentially oxidized at the oxide/substrate interface producing a five to seven times thicker oxide than in an area without the influence of Pt. A strongly enhanced dissociation rate of O-2 on Pt particles and a subsequent O spillover to adjacent oxide explain the experimental observations. The mm-ranged spillover is believed to take place via fast lateral surface diffusion and results in the observed variation of oxidized As at the gas/oxide interface. In the Pt area, a high concentration gradient of dissociated oxygen across the oxide layer supplies a high flux of dissociated oxygen to the GaAs substrate where Ga is preferentially oxidized. The results clearly demonstrate that both a surface reaction and solid-state diffusion influence the oxidation rate. A localized high effective oxygen (O) activity that spills over to a nearby oxide area is believed to be a general phenomenon that is operating in oxides where a dissociating element such as Pt is present at O-2/oxide interfaces.

  • 122.
    Hultquist, Gunnar
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sproule, G. I.
    Moisa, S.
    Graham, M. J.
    Sodervall, U.
    Influence of deuterium and platinum on the thermal oxidation of GaAs2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 10, p. G617-G623Article in journal (Refereed)
    Abstract [en]

    The thermal oxidation of GaAs at 500 degreesC in O-18 labeled O-2 has been studied with gas phase analysis, Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy. The influence of a few hundred atomic parts per million of deuterium in the GaAs substrate and of surface platinum have been evaluated with respect to oxide growth mechanisms and the degree of As buildup. Deuterium increased the transport from the substrate interface of both Ga and As toward the gas interface thereby lowering the degree of preferential Ga oxidation and As buildup at the substrate interface. Platinum, on the other hand, catalyzed the dissociation of the oxygen molecule at the gas interface and thereby facilitated an increased transport of oxygen toward the substrate interface. That results in an increased overall oxidation rate with a high degree of preferential Ga oxidation and concomitant As buildup. When the oxygen pressure was increased from 20 to 720 mbar, a lowered degree of As buildup was observed due to the lower degree of preferential Ga oxidation.

  • 123. Hurley, P. K.
    et al.
    Cherkaoui, K.
    O'Connor, E.
    Lemme, Max C.
    AMO GmbH, AMICA, Aachen, Germany.
    Gottlob, H. D. B.
    Schmidt, M.
    Hall, S.
    Lu, Y.
    Buiu, O.
    Raeissi, B.
    Piscator, J.
    Engstrom, O.
    Newcomb, S. B.
    Interface defects in HfO2, LaSiOx, and Gd2O3 high-k/metal-gate structures on silicon2008In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, no 2, p. G13-G20Article in journal (Refereed)
    Abstract [en]

    In this work, we present experimental results examining the energy distribution of the relatively high (> 1 X 10(11) cm(-2)) electrically active interface defects which are commonly observed in high-dielectric-constant (high-k) metal-insulator-silicon systems during high-k process development. This paper extends previous studies on the Si(100)/SiOx/HfO2 system to include a comparative analysis of the density and energy distribution of interface defects for HfO2, lanthanum silicate (LaSiOx), and Gd2O3 thin films on (100) orientation silicon formed by a range of deposition techniques. The analysis of the interface defect density across the energy gap, for samples which experience no H-2/N-2 annealing following the gate stack formation, reveals a peak density (similar to 2 X 10(12) cm(-2) eV(-1) to similar to 1 X 10(13) cm(-2) eV(-1)) at 0.83-0.92 eV above the silicon valence bandedge for the HfO2, LaSiOx, and Gd2O3 thin films on Si (100). The characteristic peak in the interface state density (0.83-0.92 eV) is obtained for samples where no interface silicon oxide layer is observed from transmission electron microscopy. Analysis suggests silicon dangling bond (P-bo) centers as the common origin for the dominant interface defects for the various Si(100)/SiOx/high-k/metal gate systems. The results of forming gas (H-2/N-2) annealing over the temperature range 350-555 degrees C are presented and indicate interface state density reduction, as expected for silicon dangling bond centers. The technological relevance of the results is discussed. (c) 2007 The Electrochemical Society.

  • 124. Ihonen, J.
    et al.
    Jaouen, F.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sundholm, G.
    Investigation of mass-transport limitations in the solid polymer fuel cell cathode - II. Experimental2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 4, p. A448-A454Article in journal (Refereed)
    Abstract [en]

    In this work, we investigated the kinetics and mass-transport limitations of the oxygen reduction reaction in the solid polymer fuel cell. The information obtained from electrochemical experiments and electrode characterization was analyzed with an agglomerate model presented in Part I of this paper. The electrochemical behavior of the cathode was studied by polarizing vs. a hydrogen reference electrode at a low sweep rate. For each potential, the iR-drop was measured with the current-interrupt technique. The cathode structure was investigated by porosimetry and electron microscopy techniques. The effects on the cathode polarization curves of the active layer thickness, oxygen partial pressure, and humidity of the oxygen gas were investigated. On the basis of the model results, conclusions could be drawn regarding the nature of mass-transport limitations because of the characteristic shape of the experimental polarization curves. The simulated curves were fitted to the experimental ones to give the kinetic and masstransport parameters. Finally, we discuss the validity of the model with regard to the values obtained for the transport and structural parameters.

  • 125.
    Ihonen, Jari
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Mikkola, M.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Flooding of gas diffusion backing in PEFCs - Physical and electrochemical characterization2004In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 151, no 8, p. A1152-A1161Article in journal (Refereed)
    Abstract [en]

    In polymer electrolyte fuel cells (PEFCs) gas diffusion backings (GDBs) have a significant effect on water management and cell performance. In this study, methods for characterizing GDB performance by fuel cell testing and ex situ measurements are presented. The performance of four different commercial GDB materials was tested and significant differences were found between the materials. While the performance and behavior are almost similar in the single-phase region, the flooding behavior of different GDBs in the two-phase region varies widely. The results show that using high clamping pressures increases cell flooding, but the increase varies from material to material. Increased flooding is caused by the combination of decreased porosity and a temperature difference between GDB and current collector. Furthermore, it was observed that the decrease in porosity due to cell compression and corresponding increase in mass-transfer resistance should be studied in the single-phase region, because flooding of the GDB easily becomes the dominating source of mass-transfer resistance. In addition, a literature review on GDB studies and characterization methods was carried out. The review revealed a lack of an established GDB testing regime and the absence of a relation between physical properties of the GDB and fuel cell performance.

  • 126. Ipek, N.
    et al.
    Cornell, Ann M.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Vynnycky, M.
    A mathematical model for the electrochemical pickling of steel2007In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, no 10, p. P108-P119Article in journal (Refereed)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen. To obtain a better understanding of this process, we derive in this paper a mathematical model for predicting the potential, current density and ionic species distributions in a vertical pickling cell, as well as the oxide dissolution rate at the steel strip. The model is two dimensional, steady state and isothermal, and is based on the conservation equations for ionic species in dilute solution, involving convection, diffusion, migration and reaction. Kinetic Tafel expressions for the electrochemical gas evolving reactions at the lead anode, stainless steel cathode and at the bipolar steel strip surface are introduced. The derived model comprises six ionic species; numerical solutions for a full version and two reduced versions of this model are then obtained. Finally, the implications of the results for the actual pickling process are discussed.

  • 127. Ipek, N.
    et al.
    Vynnycky, M.
    Cornell, Ann M.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A coupled electrochemical and hydrodynamical two-phase model for the electrolytic pickling of steel2008In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, no 4, p. P33-P43Article in journal (Refereed)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen bubbles. In this paper, we extend an earlier mathematical model for the electrochemical aspects of the process, which took account only of the liquid phase, to include the effect of the gas phase. The model is two-dimensional, steady-state and isothermal, and comprises five ionic species, the mixture velocity, pressure, and the gas fraction; numerical solutions of this model are then obtained. The results of the single and two-phase models are compared, and their implications for the actual pickling process are discussed.

  • 128.
    Isheden, Christian
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Radamson, Henry H.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Suvar, Erdal
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hellström, Per-Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Östling, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Formation of shallow junctions by HCl-based Si etch followed by selective epitaxy of B-doped Si1-xGex in RPCVD2004In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 151, no 6, p. C365-C368Article in journal (Refereed)
    Abstract [en]

    Formation of shallow source/drain junctions by using HCl-based Si etch followed by selective deposition of in situ heavily B-doped SiGe in a reduced pressure chemical vapor deposition reactor is presented. The etching parameters were optimized to obtain a smooth surface prior to deposition of the SiGe layers. In the epitaxy process, SiGe layers with a resistivity of 5 x 10(-4) Omega cm were obtained by tuning the partial pressure of the B and Ge precursors. A problem with selectivity in the epitaxy step was encountered when combing the etch and growth processes, but a practical solution is presented. Integration issues such as loading effect, pile-up, and defect generation have also been investigated.

  • 129. Jahan, D.
    et al.
    Soderstrom, D.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kinetic study of InP: Fe growth by LP-HVPE with ferrocene as Fe source2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 2, p. 744-746Article in journal (Refereed)
    Abstract [en]

    A kinetic study of InP:Fe growth has been carried out in a low pressure hydride vapor phase epitaxy (LP-HVPE) reactor using Ferrocene as iron source. The influence of the ferrocene partial pressure on the growth behavior has been investigated. A drastic decrease of the growth rate in the presence of ferrocene has been experimentally measured. This effect is explained to be due to cyclopentadiene adsorption. A kinetic model, that takes into account this adsorption, is proposed, which explains the observed experimental results.

  • 130. Jaouen, F.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Transient techniques for investigating mass-transport limitations in gas diffusion electrodes - I. Modeling the PEFC cathode2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 12, p. A1699-A1710Article in journal (Refereed)
    Abstract [en]

    The use of electrochemical impedance spectroscopy and current-interruption techniques with the scope of determining mass-transport limitations in PEFC gas-diffusion electrodes is investigated. The porous electrode is assumed to be composed of spherical agglomerates consisting of a homogeneous mixture of the electrolyte and the electronic phase. The model is applied to the O-2 reduction reaction in the cathode and includes Tafel kinetics for the O-2 reduction, Ohm's law for proton migration, Fick's law for O-2 diffusion, and capacitive current due to the contribution of the double layer. A novel impedance is defined, enabling the results to be presented in a simpler manner than with the usual one. It is shown how these transient techniques can be employed to qualitatively separate diffusion from migration effects. The parameter groups that can be quantitatively determined from the processing of experimental data are presented. The effect of O2 pressure and electrode thickness on the predicted electrode response is also investigated.

  • 131. Jaouen, F.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Sundholm, G.
    Investigation of mass-transport limitations in the solid polymer fuel cell cathode - I. Mathematical model2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 4, p. A437-A447Article in journal (Refereed)
    Abstract [en]

    In this paper, a one-dimensional, steady-state agglomerate model was used to describe the functioning and the mass transport limitations of the cathode in the solid polymer fuel cell (SPFC). This mathematical model is then compared to experimental results obtained on cathodes in an SPFC. The following processes were considered: Tafel kinetics of the oxygen reduction reaction, proton migration, oxygen diffusion in the agglomerates, and diffusion of a ternary gas mixture O-2/N-2/water vapor in the pores of the active layer and of the gas backing. The model shows that limitation by proton migration in the active layer or by oxygen diffusion in the agglomerates leads to a doubling of the Tafel slope at higher current densities. For those two types of transport limitations, the dependence of the reaction rate on the active-layer thickness, oxygen partial pressure, and relative humidity of the gas were simulated. When additional limitation due to slow gas phase diffusion appears, the double Tafel slope is distorted. A mathematical expression for the limiting current density due to this process is presented. By using this expression, it is possible to correct the polarization curves for slow gas phase diffusion.

  • 132.
    Jaouen, Frédéric
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Wiezell, Katarina
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Transient techniques for investigating mass-transport limitations in gas diffusion electrodes: II. Experimental characterization of the PEFC cathode2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 12, p. A1711-A1717Article in journal (Refereed)
    Abstract [en]

    The current-interrupt technique and electrochemical impedance spectroscopy were employed in order to study the behavior of a polymer electrolyte fuel cell (PEFC) cathode containing 30 wt % Nafion and 70 wt % Pt/C. The steady-state polarization curves were also recorded. The experimental results were analyzed with help of the mathematical models developed in Part I of this paper. The effect of a varying oxygen pressure and humidity on the dynamic response of the cathode was investigated. The double-layer capacitance, Tafel slope, oxygen solubility, a group containing the effective O-2 diffusion coefficient and agglomerate size, and finally, the effective proton conductivity in the cathode were obtained. The parameter values were reasonable and attest the robustness of the agglomerate model for describing the PEFC cathode. At low humidity, a second, low-frequency loop was observed that was attributed to the membrane behavior.

  • 133.
    Jensen, J.A.D.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Moller, P.
    Møller, P., Department of Mfg. Eng. and Mgmt., The Technical University of Denmark, Lyngby DK-2800, Denmark.
    Bruton, T.
    BP Solar, European Technology Centre, Sunbury, United Kingdom.
    Mason, N.
    BP Solar, European Technology Centre, Sunbury, United Kingdom.
    Russell, R.
    BP Solar, European Technology Centre, Sunbury, United Kingdom.
    Hadley, J.
    Enthone, s-Herrogenbosch, Netherlands.
    Verhoeven, P.
    Enthone, s-Herrogenbosch, Netherlands.
    Matthewson, A.
    The Natl. Microelectronics Res. Ctr., University College Cork, Cork, Ireland.
    Electrochemical deposition of buried contacts in high-efficiency crystalline silicon photovoltaic cells2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 1Article in journal (Refereed)
    Abstract [en]

    This article reports on a newly developed method for electrochemical deposition of buried Cu contacts in Si-based photovoltaic (PV) cells. Contact grooves, 20 µm wide by 40 µm deep, were laser-cut into Si PV cells, hereafter applied with a thin electroless NiP base and subsequently filled with Cu by electrochemical deposition at a rate of up to 10 µm per min. With the newly developed process, void-free, superconformal Cu-filling of the laser-cut grooves was observed by scanning electron microscopy and focused ion beam techniques. The Cu microstructure in grooves showed both bottom and sidewall texture, with a grain-size decreasing from the center to the edges of the buried Cu contacts and a pronounced lateral growth outside the laser-cut grooves. The measured specific contact resistances of the buried contacts was better than the production standard. Overall performance of the new PV cells was equal to the production standard with measured efficiencies up to 16.9%.

  • 134.
    Jeschull, Fabian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Maibach, Julia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    On the Electrochemical Properties and Interphase Composition of Graphite: PVdF-HFP Electrodes in Dependence of Binder Content2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 7, p. A1765-A1772Article in journal (Refereed)
    Abstract [en]

    Poly(vinylidene-difluoride) (PVdF) based polymers constitute the most commonly used binders for lithium-ion battery electrodes. In scientific studies, the binder content often exceeds commercially meaningful amounts. At the same time, the battery electrode performance can in various ways be coupled to its binder content, partly due to its influence on the surface properties. For example, an optimum binder content of around 5 wt% has been reported. In this study, graphite: PVdF-HFP electrodes containing 2.5, 5 and 10 wt% of PVdF-HFP are investigated, and their electrochemical behavior are put into context of the electrode-electrolyte interphase of the different formulations. Although the electrodes display similar electrochemical behavior, the SEI layer composition and thickness, analyzed by photoelectron spectroscopy, vary notably depending on binder content. It was found that a binder content of 5 wt% maintained the best cycling stability and also exhibited a thinner SEI layer with a larger fraction of inorganic components. In contrast to higher binder contents, where the binder covers most of the surface, larger parts of the active material are exposed directly to the electrolyte with binder contents of 2.5-5 wt%. The formation of a thinner, yet protective, SEI layer is beneficial for cycling performance of the graphite electrode. (C) 2017 The Electrochemical Society. All rights reserved.

  • 135.
    Jin, Ying
    et al.
    University of Science and Technology Beijing, National Center for Materials Service Safety.
    Liu, Min
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. University of Science and Technology Beijing, National Center for Materials Service Safety.
    Zhang, Chuanhui
    University of Science and Technology Beijing, National Center for Materials Service Safety.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Electrochemical Society, United States.
    Wen, Lei
    University of Science and Technology Beijing, National Center for Materials Service Safety.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Electrochemical Society, United States.
    First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 9, p. C465-C473Article in journal (Refereed)
    Abstract [en]

    This work presents a theoretical assessment of galvanic (relative) nobility of four intermetallic particles (IMPs), Al2Cu, Al2CuMg, Mg2Si andMgZn(2), in aluminum alloys through work function calculation based on density functional theory (DFT). The concepts of work function, Volta potential and relative nobility are discussed with respect to the IMPs and aluminum matrix. The calculated Volta potentials are compared with reported experimental Volta potentials measured by scanning Kelvin probe forcemicroscopy (SKPFM). Various crystal faces and terminal types are examined in the DFT calculation, showing that these two factors have a significant effect on the work function value. Considering the large divergence in the reported experimental data, the comparison shows a general agreement between the calculated and experimental Volta potential data for the investigated IMPs. The DFT calculations provide theoretical explanations for several experimental phenomena. The results demonstrate that DFT calculation is a valuable theoretical approach for assessment of the relative nobility of different phases in the alloys, providing complementary information to experimental data from SKFPM. Moreover, the implications of the calculated Volta potentials are discussed with respect to the corrosion potentials.

  • 136. Jogi, Indrek
    et al.
    Tamm, Aile
    Kukli, Kaupo
    Kemell, Marianna
    Lu, Jun
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sajavaara, Timo
    Ritala, Mikko
    Leskelä, Markku
    Investigation of ZrO2-Gd2O3 Based High-k Materials as Capacitor Dielectrics2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 10, p. G202-G210Article in journal (Refereed)
    Abstract [en]

    Atomic layer deposition (ALD) of ZrO2-Gd2O3 nanolaminates and mixtures was investigated for the preparation of a high permittivity dielectric material. Variation in the relative number of ALD cycles for constituent oxides allowed one to obtain films with controlled composition. Pure ZrO2 films possessed monoclinic and higher permittivity cubic or tetragonal phases, whereas the inclusion of Gd2O3 resulted in the disappearance of the monoclinic phase. Changes in phase composition were accompanied with increased permittivity of mixtures and laminates with low Gd content. Further increase in the lower permittivity Gd2O3 content above 3.4 cat. % resulted in the decreased permittivity of the mixtures. Leakage currents generally decreased with increasing Gd content, whereby laminated structures demonstrated smaller leakage currents than mixed films at a comparable Gd content. Concerning the bottom electrode materials, the best results in terms of permittivity and leakage currents were achieved with Ru, allowing a capacitance equivalent oxide thickness of similar to 1 nm and a current density of 3 X 10(-8) A/cm(2) at 1 V. Charge storage values up to 60 nC/mm(2) were obtained for mixtures and laminates with thickness below 30 nm. In general, at electric fields below 2-3 MV/cm, normal and trap-compensated Poole-Frenkel conduction mechanisms were competing, whereas at higher fields, Fowler-Nordheim and/or trap-assisted tunneling started to dominate.

  • 137.
    Johansson, Tomas
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Persson, Nils-Krister
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Moving Redox Fronts in Conjugated Polymers Studies from Lateral Electrochemistry in Polythiophenes2004In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 151, no 4Article in journal (Refereed)
    Abstract [en]

    The propagation speed of the front of electrochemical conversion, from semiconductor to highly doped polymer, in films of regioregular poly(3-hexylthiophene) spin cast on insulating substrates was analyzed. Propagation of the p-doped zone in polymer electrochromic devices was imaged simultaneously with recording of electrochemical data. The current is proportional to the propagation speed and has a Tafel-like behavior when taking the resistive drop in the film into account. The resistivity in the film, which gradually lowers the propagation speed, was used for determination of the conductivity of the p-doped polymer. By combining these values with the doping charge injected into the film during front migration we estimated the hole carrier mobility for different doping levels. © 2004 The Electrochemical Society.

  • 138. Johnsen, S. E.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundqvist, A.
    Tunold, R.
    A single particle investigation on the kinetics of metal hydride materials2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 5, p. A629-A637Article in journal (Refereed)
    Abstract [en]

    Potential step chronoamperometry and electrochemical impedance spectroscopy measurements were performed on single metal hydride (MH) particles. For the alpha phase, the bulk diffusion coefficient and the absorption/adsorption rate parameters were determined. Materials produced by atomization, melt spinning, and conventional casting were investigated. The melt spun and conventional cast materials were identical and the atomized material similar in composition. The particles from the cast and the melt spun material were shaped like parallelepipeds. A corresponding equation for this geometry, for diffusion coupled to an absorption/adsorption reaction was developed. It was found that materials produced by melt spinning exhibited lower bulk diffusion (1.7 x 10(-14) m(2) s(-1)) and absorption/adsorption reaction rate (1.0 x 10(-8) ms(-1)), compared to materials produced by conventional casting (1.1 x 10(-13) m(2) s(-1) and 5.5 x 10(-8) ms(-1), respectively). In addition, the influence of particle active surface and relative diffusion length were discussed. It was concluded that there are uncertainties connected to these properties, which may explain the large distribution in the kinetic parameters measured on MH particles.

  • 139.
    Johnson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Atmospheric corrosion of zinc by organic constituents - III. An infrared reflection-absorption spectroscopy study of the influence of formic acid2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 12, p. B547-B550Article in journal (Refereed)
    Abstract [en]

    The initial corrosion of a zinc surface exposed to formic acid at various relative humidities has been investigated by in situ infrared reflection-absorption spectroscopy. The major corrosion product observed was zinc formate, as evidenced in particular by the two strong carboxylate stretching vibrations. The importance of the thickness of the water adlayer always covering a metal surface was confirmed by the more rapid corrosion process monitored at higher relative humidities. Nonetheless, significant corrosion rates were observed even at low (25%) relative humidities. The corrosion rate at a given humidity was observed to initially be very fast, followed by slower kinetics at longer exposure times. This indicates a protective ability of the corrosion products formed compared to the initially more reactive fresh zinc surface.

  • 140.
    Johnson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Atmospheric corrosion of zinc by organic constituents II. Reaction routes for zinc-acetate formation2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 12, p. B542-B546Article in journal (Refereed)
    Abstract [en]

    The acetic acid and acetaldehyde-induced atmospheric corrosion of a zinc surface was investigated by in situ infrared reflection-absorption spectroscopy. Independent of the relative humidity, both corrosive gases yielded zinc oxide and zinc acetate as reaction products. However, faster kinetics for the acetate formation was observed for acetic acid, which was attributed to an acetate-induced zinc dissolution mechanism as the rate determining step, and a more complicated reaction path for acetaldehyde to form the zinc-acetate surface species. Additionally, the rate varied significantly with the relative humidity, and an enhanced corrosion rate was observed under more humid conditions, when the water adlayer that always covers a metal surface is thicker. Scanning electron microscopy revealed the formation of radial growth of corrosion products in the case of acetic acid and filiform corrosion for acetaldehyde. By X-ray diffraction of the powderlike corrosion products, solely zinc oxide was detected. This implies a minute production of zinc acetate in comparison to zinc oxide, or a noncrystalline phase of the acetate. Reaction paths for acetic acid and acetaldehyde were proposed.

  • 141.
    Johnson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Tyrode, Eric
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Atmospheric corrosion of zinc by organic constituents I. The role of the zinc/water and water/air interfaces studied by infrared reflection/absorption spectroscopy and vibrational sum frequency spectroscopy2006In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 3, p. B113-B120Article in journal (Refereed)
    Abstract [en]

    The zinc oxide/water and water/air interfaces have been investigated in order to elucidate the role of these two interfaces in an atmospheric corrosion process. Vibrational sum frequency spectroscopy (VSFS) has been used to study the water/air interface of aqueous acetic acid and acetaldehyde solutions. The VSFS studies revealed that the interfacial region of the acetic acid solutions is dominated by various species formed by hydrogen bonding, whereas acetaldehyde underwent a hydration process to form a gem-diol. In both cases, even small additions resulted in a breakdown of the surface structure found in pure water. Infrared reflection/absorption spectroscopy (IRAS) has been utilized to examine the zinc oxide/ water interface upon exposure of gaseous acetic acid and acetaldehyde at various relative humidities. The in situ IRAS investigations indicated a formation of zinc acetate both when the zinc oxide surface was exposed to acetic acid and acetaldehyde. Thus, despite being different in nature, these compounds resulted in the same end product in the corrosion process studied.

  • 142.
    Jönsson, Martin
    et al.
    Corrosion and Metals Research Institute (KIMAB), Stockholm.
    Persson, Dan
    Corrosion and Metals Research Institute (KIMAB), Stockholm.
    Gubner, Rolf
    Corrosion and Metals Research Institute (KIMAB), Stockholm.
    The Initial Steps of Atmospheric Corrosion on Magnesium Alloy AZ91D2007In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, no 11, p. C684-C691Article in journal (Refereed)
    Abstract [en]

    Magnesium, with its low density, is a very interesting metal in applications in which weight is important. In this work the initiation of corrosion attacks on magnesium alloy AZ91D has been investigated under atmospheric conditions, using confocal laser scanning microscopy and SKPFM. The corrosion attack starts in the alpha phase in larger grains and is under atmospheric conditions initiated at the boundary between the alpha phase and the eutectic alpha-/beta phase. The SKPFM measurement shows that a high Volta potential difference exists between the larger grains and the surrounding eutectic alpha-/beta phase and the beta phase. A microgalvanic element is formed in the thin adlayer on the surface, with anodic Mg dissolution in the alpha phase and the cathodic reaction primarily in the eutectic alpha-/beta phase. The initiation in the larger grains could be explained by the smaller aluminum content in the larger grains due to the solidification process. Even though intermetallic Al-Mn particles show a high Volta potential difference with the connecting alpha phase, they are not involved in the initiation of the corrosion. This is explained by the position within the microstructure of Al-Mn particles embedded in the beta phase and located away from the alpha phase.

  • 143.
    Karlsson, L M
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Back-side etching A tool for making morphology gradients in porous silicon2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 12Article in journal (Refereed)
    Abstract [en]

    A new method for preparing morphology gradients in electrochemically etched porous silicon layers in presented. The idea is to etch on the back side of the anode and thus utilize and inhomogenous electric field to control the pore size along a surface. The etching procedure resulted in a complex gradient in pore size, porosity, and porous layer thickness, which was studied by spectroscopic ellipsometry and scanning electron microscopy. The gradients are of interest, e.g., for biomaterials research, bio-sensor applications, and for basic studies of adsorption of organic molecules, like proteins. In order to investigate the potential of the gradient surfaces for protein adsorption studies, these were exposed to human serum albumin, and a gradient in the amount of adsorbed protein was observed.

  • 144.
    Kayambaki, M.
    et al.
    Found. for Res. and Technol.-Hellas, Heraklion, Crete 71110, Greece.
    Tsagaraki, K.
    Found. for Res. and Technol.-Hellas, Heraklion, Crete 71110, Greece.
    Cimalla, V.
    Found. for Res. and Technol.-Hellas, Heraklion, Crete 71110, Greece.
    Zekentes, K.
    Found. for Res. and Technol.-Hellas, Heraklion, Crete 71110, Greece.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Crystal quality evaluation by electrochemical preferential etching of p-type SiC crystals2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 7, p. 2744-2748Article in journal (Refereed)
    Abstract [en]

    An electrochemical etching process is used for evaluating the types and the distribution of crystal defects on both the Si and C faces of p-type 6H and 4H-SiC. The surface morphology of the etched area is different for the two surface polarities. Dislocation-related etch-pits appeared on the etched surfaces due to a preferential etching process. The etching experiments were conducted in a commercial apparatus in combination with accurate capacitance-voltage profiling, showing that this characterization method is highly useful and simple for evaluating SiC material quality.

  • 145.
    Kharitonov, Dmitry S.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Belarusian State Technol Univ, Chem Technol & Engn Fac, Dept Chem Electrochem Prod Technol & Mat Elect Eq, Minsk 220006, BELARUS..
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB, Dept Corros Energy & Proc Ind, SE-16440 Kista, Sweden..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Sommertune, Jens
    RISE Res Inst Sweden, Chem Mat & Surfaces, SE-11486 Stockholm, Sweden..
    Zharskii, Ivan M.
    Belarusian State Technol Univ, Chem Technol & Engn Fac, Dept Chem Electrochem Prod Technol & Mat Elect Eq, Minsk 220006, BELARUS..
    Kurilo, Irina I.
    Belarusian State Technol Univ, Organ Subst Technol Fac, Dept Phys Colloid & Analyt Chem, Minsk 220006, BELARUS..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 3, p. C116-C126Article in journal (Refereed)
    Abstract [en]

    Corrosion inhibition of aluminum alloy AA6063-T5 by vanadates (NaVO3) in 0.05 M NaCl solution has been investigated by electrochemical and weight loss measurements, and associated with microstructure and Volta potential data. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses confirmed the presence of micrometer-sized Fe-rich Al4.01MnSi0.74, Al1.69Mg4Zn2.31, and FeAl3 intermetallic phases (IMPs) and nanometer-sized CuAl2, ZnAl2, and Mg2Si precipitates in the microstructure. Scanning Kelvin probe force microscopy measurements showed Volta potential differences of up to 600 mV between the microstructure constituents indicating a high susceptibility to micro-galvanic corrosion, with interphase boundary regions exhibiting the highest propensity to corrosion. Most IMPs had cathodic character whereas some nanometer-sized Mg-rich particles exhibited anodic nature, with large Volta potential gradients within interphase regions of large cathodic particles. Electrochemical potentiodynamic polarization measurements indicated that the vanadates provided mixed corrosion inhibition effects, mitigating both oxygen reduction, occurring on cathodic IMPs, and anodic metal dissolution reaction, occurring on anodic sites, such as Mg2Si and interphase boundary regions. Electrochemical measurements indicated that the sodium metavanadate inhibitor blocks active metal dissolution, giving high inhibition efficiency (>95%) during the initial exposure, whereas long-term weight loss measurements showed that the efficacy decreases after prolonged exposure.

  • 146.
    Kharitonov, Dmitry S.
    et al.
    KTH Royal Institute of Technology, Sweden; Belarusian State Technological University, Belarus.
    Örnek, Cem
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB. KTH Royal Institute of Technology, Sweden.
    Claesson, Per M
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. KTH Royal Institute of Technology, Sweden.
    Sommertune, Jens
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Zharskii, Ivan M.
    Belarusian State Technological University, Belarus.
    Kurilo, Irina I.
    Belarusian State Technological University, Belarus.
    Pan, Jinshan
    KTH Royal Institute of Technology, Sweden.
    Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 5, no 3, p. C116-C126Article in journal (Refereed)
    Abstract [en]

    Corrosion inhibition of aluminum alloy AA6063-T5 by vanadates (NaVO3) in 0.05 M NaCl solution has been investigated by electrochemical and weight loss measurements, and associated with microstructure and Volta potential data. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses confirmed the presence of micrometer-sized Fe-rich Al4.01MnSi0.74, Al1.69Mg4Zn2.31, and FeAl3intermetallic phases (IMPs) and nanometer-sized CuAl2, ZnAl2, and Mg2Si precipitates in the microstructure. Scanning Kelvin probe force microscopy measurements showed Volta potential differences of up to 600 mV between the microstructure constituents indicating a high susceptibility to micro-galvanic corrosion, with interphase boundary regions exhibiting the highest propensity to corrosion. Most IMPs had cathodic character whereas some nanometer-sized Mg-rich particles exhibited anodic nature, with large Volta potential gradients within interphase regions of large cathodic particles. Electrochemical potentiodynamic polarization measurements indicated that the vanadates provided mixed corrosion inhibition effects, mitigating both oxygen reduction, occurring on cathodic IMPs, and anodic metal dissolution reaction, occurring on anodic sites, such as Mg2Si and interphase boundary regions. Electrochemical measurements indicated that the sodium metavanadate inhibitor blocks active metal dissolution, giving high inhibition efficiency (>95%) during the initial exposure, whereas long-term weight loss measurements showed that the efficacy decreases after prolonged exposure.

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  • 147.
    Kiros, Yohannes
    KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Electrocatalytic Properties of Co, Pt, and Pt-Co on Carbon for the Reduction of Oxygen in Alkaline Fuel Cells1996In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 143, p. 2152-2157Article in journal (Refereed)
    Abstract [en]

    The effect of cobalt, platinum, and cobalt-platinum, alloys on high surface area carbons for oxygen reduction in alkaline electrolyte was investigated. The Pt-Co catalyst with ca. 1:3 atomic ratio was prepared by addition of H2PtC16 solution to a mixture of methanol and a 5% surfactant in deionized water containing cobalt acetate and carbon suspension. This was followed by drying and heat-treatment at 700 and 900°C in a flow of hydrogen and nitrogen gas mixtures. Polarization curves and kinetic parameters for Pt, Co, and Pt-Co were conducted and compared in 6 M KOH and at 80°C. Higher activities were observed for the Pt-Co alloy, that had been heat treated at 900°C. In addition to increased activity of this catalyst, the unalloyed base metal (Co) contributes to total performance improvement of the oxygen reduction process. Furthermore, surface, structural, and chemical characterizations of the catalysts were carried out using transmission electron microscopy, x-ray diffraction, Brunauer, Ermnett, and Teller method, and atomic absorption spectroscopy. Dissolution of cobalt from the electrodes, both from the single cobalt phase and Pt-Co alloy catalysts, has been established. The x-ray results demonstrated a shift to lower lattice parameters (3.618 A) by the Pt-Co alloys, prepared at 90 0°C, than the pure platinum catalyst (3.9 19 A).

  • 148.
    Klass, Verena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Evaluating Real-Life Performance of Lithium-Ion Battery Packs in Electric Vehicles2012In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 159, no 11, p. A1856-A1860Article in journal (Refereed)
    Abstract [en]

    In regard to the increasing market launch of plug-in hybrid electric vehicles (PHEVs), understanding battery pack performance under electric vehicle (EV) operating conditions is essential. As lifetime still remains an issue for battery packs, it is a necessity to monitor the battery pack's state-of-health (SOH) on-board. Standard laboratory performance tests for health evaluation do not apply since operation interruptions and additional testing equipment are out of the question during ordinary EV usage. We suggest a novel methodology of performance estimation from real-life battery data. On the basis of battery pack data collected during PHEV operation, a support vector machine model capturing battery behavior characteristics is constructed. By virtually testing this battery model, access to standard performance evaluation figures can be gained. The SOH indicator "10 s discharge resistance" as known from hybrid pulse power characterization (HPPC) tests is chosen to exemplify how performance can be followed over a year.

  • 149.
    Ko, Jing Ying
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Varini, Maria
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Ekström, Henrik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. COMSOL AB, Sweden.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Porous Electrode Model with Particle Stress Effects for Li(Ni1/3Co1/3Mn1/3)O2 Electrode2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111Article in journal (Refereed)
    Abstract [en]

    A porous electrode model, incorporating particle stress effects, is developed for the electrode kinetic processes in the positive Li(Ni1/3Mn1/3Co1/3)O2 or NMC111 electrode. The model is used to analyze experimental data from galvanostatic intermittent titration technique (GITT) during charging at the beginning of life. The equilibrium potential accounts for the influence of mechanical stress in the electrode particles. While the standard Newman-based model proves unable to capture the dynamic performance of NMC111, the extended model with stress allows good fits of the GITT responses for NMC half cells for a voltage range from 3.7–4.1 V vs Li/Li+ at 10°C, 25°C and 40°C. Four physical parameters are extracted to analyze the underlying diffusive, kinetic, thermodynamic and stress phenomena from polarization to relaxation during a GITT transient. Strong dependencies of the kinetic rate constant k, slope of the open-circuit potential curve dEconc/dxpos and stress proportionality factor ϒstress with lithium concentration are found. The effective diffusion coefficients Ds,eff are ∼10−14 – 10−13 cm2/s across voltages and temperatures. Diffusion limitation and particle surface stress are more profound at higher voltages and at higher temperatures. This leads to large lithium concentration gradient near particle surface, requiring longer relaxation time during GITT.

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  • 150.
    Kolahdouz, Mohammadreza
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Adibi, P. Tabib Zadeh
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Farniya, Ali Afshar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Shayestehaminzadeh, Seyedmohammad
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Trybom, Erik
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Di Benedetto, Luigi
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Radamson, Henry H.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Selective Growth of B- and C-Doped SiGe Layers in Unprocessed and Recessed Si Openings for p-type Metal-Oxide-Semiconductor Field-Effect Transistors Application2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 6, p. H633-H637Article in journal (Refereed)
    Abstract [en]

    This work presents the pattern dependency of the selective epitaxial growth of boron- and carbon-doped SiGe layers in recessed and unprocessed openings. The layer profile is dependent on deposition time, chip layout, and growth parameters. Carbon and boron doping compensates for the strain in SiGe layers, and when both dopants are introduced, the strain reduction is additive. The incorporation of boron and carbon in the SiGe matrix is a competitive action. The concentration of carbon decreases, whereas the boron amount increases in SiGe layers with higher Ge content. In recessed openings, the Ge content is independent of the recess depth. The strain amount in the grown layers is graded vertically, which is due to the thickness of the epilayer exceeding the critical thickness.

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