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  • 1.
    Beattie, D.A.
    et al.
    Ian Wark Research Institute, University of South Australia.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    In situ total internal reflection Raman spectroscopy of surfactant adsorption at a mineral surface2006Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 41, nr 2, s. 198-204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the first attempt to characterise surfactant adsorption from solution onto a particle film using total internal reflection Raman spectroscopy. Three surfactant collectors of interest to the mineral processing industry were studied in their adsorption onto sphalerite: heptyl xanthate, 2-mercaptobenzothiazole (MBT), and O,O-dibutyldithiophosphate (DTP). All three surfactants adsorbed to the surface of the sphalerite. Adsorption of heptyl xanthate was monitored as a function of time and increasing concentration. The spectrum of heptyl xanthate indicated the presence of a small amount of dixanthogen on the surface of the sphalerite. MBT adsorption studies were complicated due to the fluorescence of the adsorbed layer. However, peaks due to the adsorbed MBT were observed on top of the fluorescent background, allowing the identification of the adsorbed species to be confirmed as the oxidised dimer species. Spectra obtained from MBT and DTP co-adsorption studies did not display the strong adsorbate layer fluorescence, indicating that the fluorescence spectrum of the adsorbed MBT is most likely affected by ring-ring interactions.

  • 2.
    Billes, Ferenc
    et al.
    Department of Physical Chemistry, Budapest University of Technology and Economics, Budapest.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Molecular geometry and vibrational spectroscopy of potassium O,O-diethyldithiophosphate2006Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 40, nr 1, s. 89-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to build a good theoretical and experimental basis for the further study of changes in structure and spectra of the O,O-diethyldithiophosphate anion upon its adsorption on the surfaces of transition metal sulfides.Infrared and Raman spectra of potassium O,O-diethyldithiophosphate were recorded. High level quantum chemical calculations were carried out to optimize the molecular geometry of both the potassium salt and its anion. Vibrational force constants were calculated from the second derivative of the molecular energy function with respect to the Cartesian coordinates of the atoms. With the aid of the optimized geometry and the calculated vibrational force constants a normal coordinate analysis was carried out to characterize the molecular vibrational modes and to assign the vibrational frequencies.

  • 3.
    Billes, Ferenc
    et al.
    Department of Physical Chemistry and Material Science, Budapest University of Technology and Economics, H-1025 Budapest, Budafoki út 8, Hungary; Institute for Chemical Technologies and Analytics, Vienna University of Technology, A-1060 Wien, Getreidemarkt 9/164/EC, Austria.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Mikosch, Hans
    Institute for Chemical Technologies and Analytics, Vienna University of Technology, A-1060 Wien, Getreidemarkt 9/164/EC, Austria.
    A combined DFT and vibrational spectroscopy study of the nickel and zinc O,O-diethyldithiophosphate complexes2010Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 53, nr 2, s. 296-306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Based on our earlier results on the theoretical and experimental study of potassium O,O-diethyldithiophosphate, the normal modes of nickel and zinc O,O-diethyldithiophoshate complexes were elucidated. Infrared and Raman spectra of these compounds were recorded. Quantum chemical calculations resulted in optimized structures, electric charge distributions, vibrational force constants, and fundamental frequencies. Normal coordinate analysis was applied to characterize the vibrational modes. Based on the results of these calculations vibrational spectra were simulated. The largest spectral differences between the two complexes appeared in vibrational modes encompassing the central part of the formula unit viz. PS2MS2P, where M is the metal atom. Namely, this central part of the Ni complex has D2h symmetry, while that of the Zn one has D2d symmetry.

  • 4.
    Ildikó, Száraz
    et al.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    PVP and azelaic acid adsorption on γ-alumina studied by FT-IR spectroscopy2002Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 29, nr 1-2, s. 15-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adsorption mechanism of poly(1-vinyl-2-pyrrolidone) (PVP) and azelaic acid on synthetic γ-aluminium oxide surfaces was investigated using FT-IR spectroscopy. It was found that PVP adsorption from both aqueous and ethylene glycol (EG) solutions, was negligible, but the presence of the dicarboxylic acid enhances the adsorption of the PVP, due to a hydrophobic interaction between the carbon chains of the polymer and the dicarboxylic acid. The carbon chain of the adsorbed dicarboxylic acid is lateral to the surface and attached to it by both carboxylic groups. The simultaneous adsorption of PVP and azelaic acid was studied as a function of time, pH, solvent and ionic strength of the suspension in order to establish a more detailed surface complexation model. Three main surface complexes were found on the surface of the γ-alumina at low pH in aqueous as well as in EG solutions, while at high pH one of them namely the outer-sphere complex dominates.

  • 5. Lidström-Larsson, Margareta
    et al.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Reversible phase transition in Zn₂(O,O-di(cyclohexyl)dithiophosphate)₄, studied by Raman spectroscopy and compared with NMR results2004Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 34, nr 2, s. 243-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It was recently shown by solid state ³¹P NMR spectroscopy that the number of phosphorous signals from the complex Zn₂(O,O-di(cyclohexyl)DTP)₄ varied reversibly with the temperature. According to the present study, Raman spectra of the same metal complex were also temperature dependent. Spectral features affected by the temperature changed reversibly upon raising and lowering the temperature. It was shown that conformational change of the hexyl rings and the P---O---C entities occurred in the temperature range between 40 and 55°C.

  • 6.
    Mohammed-Ziegler, Ildikó
    et al.
    Luleå tekniska universitet. Chemical Research Center of the Hungarian Academy of Sciences, Institute of Chemistry, Budapest, Hungary.
    Holmgren, Allan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Forsling, Willis
    Luleå tekniska universitet.
    Lindberg, Mats
    Luleå tekniska universitet.
    Ranheimer, Maine
    Luleå tekniska universitet.
    Mechanism of the adsorption process of pinosylvin and some polyhydroxybenzenes onto the structure of lignin2004Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 36, nr 1, s. 65-72Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The lignin Induline AT was used as model substrate to observe the adsorption of pinosylvin, trans-stilbene, pyrocatechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol. Prior to adsorption the adsorbates were dissolved in diethylether. Infrared spectra of adsorbed compounds were recorded using the diffuse reflectance infrared Fourier transform (DRIFTS) technique. Far IR spectra of the adsorbed pinosylvin and polyhydroxybenzenes were used to facilitate the interpretation on the mechanism of adsorption. Vibrational analysis by quantum chemical calculations, available for most of the polyhydroxybenzenes, were utilized. The interaction between adsorbed species and lignin was found to be mainly mediated through the formation of hydrogen bonds.

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