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Träfflista för sökning "hsv:(NATURVETENSKAP) hsv:(Kemi) srt2:(1980-1994)"

Sökning: hsv:(NATURVETENSKAP) hsv:(Kemi) > (1980-1994)

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3.
  • Antonsson, H, et al. (författare)
  • VIBRATIONAL MOTION AND GEOMETRICAL STRUCTURE IN ADSORBED CO STUDIED BY CORE LEVEL PHOTOELECTRON-SPECTROSCOPY
  • 1990
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 54, s. 601-613
  • Tidskriftsartikel (refereegranskat)abstract
    • High resolution core level spectra from CO adsorbed on clean and hydrogen precovered Ni(100) and CO adsorbed on Cu(100) are presented. The core level binding energy is shown to be sensitive to the adsorption site. Cluster calculations reproduce the general trend of the binding energy shifts between the on top and hollow sites of CO/Ni(100). In the coadsorption system CO/H/Ni(100) three different adsorption sites have been observed with a maximum binding energy shift of 2.6 eV for the Ols level. The temperature dependence of the Cls and Ols line profiles in CO/Ni(100) has been carefully investigated. The temperature dependent broadening is due to thermal excitations of frustrated translations parallel to the surface. The spectra from CO on Cu(100) show no temperature dependence below 200K.
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4.
  • Elfving, P, et al. (författare)
  • MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .1. INITIAL SURFACE SULFITE FORMATION ON CALCITE
  • 1994
  • Ingår i: Applied Surface Science. - 0169-4332. ; 74:1, s. 91-98
  • Tidskriftsartikel (refereegranskat)abstract
    • An experimental set-up to investigate the reactions at ppm concentrations of pollutants with stone surfaces, involving a minimum of sample tampering, is proposed. In-situ Diffuse Reflectance Infrared Fourier Transform spectrometry (DRIFT) is employed to monitor the time evolution of products formed at a precipitated calcite sample. The powdered sample was exposed to a mixture of air and SO,(g) at different humidities. The nature of the initial sulphite formed is discussed in terms of anhydrous and hemihydrate calcium sulphite and sulphite in solution. In all three cases IR spectra are produced and compared to previous studies. The DRIFT spectra reveal the presence of at least two sulphite species on calcite at humid conditions, one chemisorbed and one dissolved. The relevance of this study to the understanding of calcareous stone deterioration is discussed.
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5.
  • Elfving, P, et al. (författare)
  • MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .2. SULFATE FORMATION ON CALCITE
  • 1994
  • Ingår i: Applied Surface Science. - 0169-4332. ; 78:1, s. 83-92
  • Tidskriftsartikel (refereegranskat)abstract
    • The crucial role of surface water in the formation of surface sulphite was addressed in a previous study by in-situ Diffuse Reflectance Infrared Fourier Transform spectrometry (DRIFT). No sulphate was formed, indicating O2(g) to be too weak an oxidant to oxidize surface sulphite. The usefulness of DRIFT is further emphasized as it is employed to investigate the roles of NO2 and O3 in the formation of gypsum on calcareous stone at close to normal atmospheric conditions. Sulphate formation at calcite, employed to model e.g. marble, is shown to progress via a surface sulphite intermediate. NO2 is found to catalyze surface sulphate formation by activating molecular oxygen, while ozone acts to form sulphate by direct oxidation.
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6.
  • Elfving, P, et al. (författare)
  • MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .3. MANGANESE AND IRON-MEDIATED SULFATION OF NATURAL STONE
  • 1994
  • Ingår i: Applied Surface Science. - 0169-4332. ; 78:4, s. 373-384
  • Tidskriftsartikel (refereegranskat)abstract
    • Transition-metal-mediated sulphation of calcareous stone is investigated. Mixes of iron and manganese compounds with precipitated or ground calcite are employed to model natural calcareous stones containing these metals in trace concentrations. The products are characterized by Diffuse Reflectance Infrared Fourier Transform spectrometry. Sulphation is shown to depend strongly on the amounts of transition metals in the mixture, and calibration curves are constructed. Sulphate formations at natural calcareous stone surfaces are discussed within the framework of the assumed model.
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9.
  • Larsson, Henrik, et al. (författare)
  • Electron transport in quaternized poly(4-vinylpyridine) films containing pentacyanoferrate(II/III) on electrodes. The influence of the binding type of the electroactive complex
  • 1992
  • Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 336:1-2, s. 263-279
  • Tidskriftsartikel (refereegranskat)abstract
    • This study is an attempt to investigate how charge transport in thin redox polymer films spin-coated onto glassy carbon electrode surfaces is affected by the way in which the electroactive group is bound to the polymeric matrix. Two different redox polymers based on methylated and cross-linked poly(4-vinylpyridine) and pentacyanoferrate(II/III) have been synthesized. In the first case, an anionic complex formed by coordinating pyridine to pentacyanoferrate(II) was electrostatically bound to the methylated pyridine groups in the polymer matrix. In the other case, pentacyanoferroate(II) was coordinated directly to unmethylated pyridine groups in the partly methylated polymer film. The film thicknesses were estimated with ellipsometric measurements. Their electrochemical characteristics were investigated using cyclic voltammetry, chronocoulometry and impedance spectroscopy. The apparent charge-transport diffusion coefficient D(app) was almost two orders of magnitude greater in the ion-exchange polymer than in the redox polymer with coordinatively bound electroactive groups. The temperature dependence of D(app) was evaluated using Arrhenius plots.
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10.
  • Larsson, Henrik (författare)
  • Ellipsometric determinations of the thicknesses of dry and electrolyte-immersed poly(4-vinylpyridine) films containing coordinated light-absorbing [Os(bpy)2pvpCl]2+/+ redox groups
  • 1994
  • Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657 .- 1873-2569. ; 365:1-2, s. 229-237
  • Tidskriftsartikel (refereegranskat)abstract
    • Ellipsometry has been used to measure the dimensions of quaternized poly(4-vinylpyridine) films containing [Os(bpy)2pvpCl]2+/+ redox groups on glassy carbon electrodes. Film thicknesses and complex refractive indices were deduced using molar absorptivities obtained from photometry or a combination of photometry and cyclic voltammetry. The precision in the film thicknesses was estimated using data obtained from thick and thin films with the same polymer + redox group compositions and from data recorded at 60-degrees and 70-degrees angles of incidence of 633 nm laser light. The effects of errors in the experimentally determined molar absorptivity of the redox groups on film thickness were also assessed. The results of this study suggest that reliable thicknesses can be obtained for both dry and electrolyte-swollen films, and that the presence of light-absorbing redox groups within coatings such as these presents no real obstacle for ellipsometric determinations.
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