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  • 1. Abele, S
    et al.
    Sjöberg, M
    YKI – Ytkemiska institutet.
    Hamaide, T
    Zicmanis, A
    Guyot, A
    Reactive surfactants in heterophase polymerization. 10. Characterization of the surface activity of new polymerizable surfactants derived from maleic anhydride1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, p. 176-181Article in journal (Refereed)
    Abstract [en]

    Characterization of the surface activity of previously obtained polymerizable dialkyl maleates is performed to find out the relation between the structure of surfactants and their performances. The given polymerizable surfactants were synthesized for using in the emulsion polymerization. Three groups of dialkyl maleates-nonionic, cationic and zwitterionic-with different chain lengths of hydrophobic alkyl groups are investigated. Critical micelle concentration (cmc) values are determined for water soluble surfactants. It is found that cmc decreases with increasing chain length of the hydrophobic alkyl group. For nonionic and cationic surfactants interfacial tension at the interface between water and dodecane is measured. Droplet size in oil-in-water (O/W) emulsions is determined for all given surfactants. Cationic and zwitterionic dialkyl maleates with the longest investigated alkyl chain (R=C16H33, C17H35) provide good stability of O/W emulsions. In order to compare the obtained results, measurements with well-known surfactants-nonionic nonylphenol-poly(ethylene oxide) (NPEO10) and cationic hexadecyltrimethyl ammonium bromide (CTAB)-are performed.

  • 2. Abletshauser, C
    et al.
    Klüssendorf, D
    Schmidt, A
    Winkler, K
    März, W
    Buddecke, E
    Malmsten, M
    YKI – Ytkemiska institutet.
    Biosensing of arteriosclerotic nanoplaque formation and interaction with an HMG-CoA reductase inhibitor2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 176, p. 131-146Article in journal (Refereed)
    Abstract [en]

    Proteoheparan sulphate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. As a result of electrostatic repulsion, its anionic glycosaminoglycan side chains are stretched out into the blood substitute solution, thereby representing one receptor site for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques suggesting that high-density lipoprotein (HDL) has a high binding affinity and a protective effect on interfacial heparan sulphate proteoglycan layers with respect to low-density lipoprotein (LDL) and Ca2+ complexation. Low-density lipoprotein was found to deposit strongly at the proteoheparan sulphate-coated surface, particularly in the presence of Ca2+, apparently through complex formation 'proteoglycan-LDL-calcium'. This ternary complex build-up may be interpreted as arteriosclerotic nanoplaque formation on the molecular level responsible for the arteriosclerotic primary lesion. On the other hand, HDL bound to heparan sulphate proteoglycan protected against LDL deposition and completely suppressed calcification of the proteoglycan-lipoprotein complex. In addition, HDL was able to decelerate the ternary complex deposition. Therefore, HDL attached to its proteoglycan receptor sites is thought to raise a multidomain barrier, selection and control motif for transmembrane and paracellular lipoprotein uptake into the arterial wall. Although much remains unclear regarding the mechanism of lipoprotein depositions at proteoglycan-coated surfaces, it seems clear that the use of such systems offers possibilities for investigating lipoprotein deposition at a 'nanoscopic' level under close to physiological conditions. In particular, Ca2+-promoted LDL deposition and the protective effect of HDL even at high Ca2+ and LDL concentrations agree well with previous clinical observations regarding risk and beneficial factors for early stages of atherosclerosis. Considering this, the system was tested on its reliability in a biosensor application in order to unveil possible acute pleiotropic effects of the lipid lowering drug fluvastatin. The very low-density lipoprotein (VLDL)/intermediate-density lipoprotein (IDL)/LDL plasma fraction from a high risk patient with dyslipoproteinaemia and type 2 diabetes mellitus showed beginning arteriosclerotic nanoplaque formation already at a normal blood Ca2+ concentration, with a strong increase at higher Ca2+ concentrations. Fluvastatin, whether applied to the patient (one single 80 mg slow release matrix tablet) or acutely in the experiment (2.2 μmol L-1), markedly slowed down this process of ternary aggregational nanoplaque complexation at all Ca2+ concentrations used. This action resulted without any significant change in lipid concentrations of the patient. Furthermore, after ternary complex build-up, fluvastatin, similar to HDL, was able to reduce nanoplaque adsorption and size. These immediate effects of fluvastatin have to be taken into consideration while interpreting the clinical outcome of long-term studies.

  • 3. Abraham, T
    et al.
    Kumpulainen, A
    Xu, Z
    Rutland, M
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Masliyah, J
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw ~ 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale RG of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Å due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH ~8.0-9.0, in contrast to the case of 3 mM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Å followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 4. Adal, M
    et al.
    Flodin, P
    Gottberg-Klingskog, E
    Holmberg, K
    YKI – Ytkemiska institutet.
    Determination of monomer reactivity ratios in the copolymerization of ethylene oxide and propylene oxide1994In: Tenside Surfactants Detergents, ISSN 0932-3414, E-ISSN 2195-8564, Vol. 31, p. 9-11Article in journal (Refereed)
    Abstract [en]

    The reactivity ratios r1 (EO) and r2 (PO) for the copolymerization of ethylene oxide (EO) and propylene oxide (PO) have been determined. The reactions were carried out in dry dimethyl formamide at 90°C using the potassium salt of ethylene glycol as initiator. The polymer composition at different EO/PO ratios in the feed was determined by 1H-NMR. Using the Fineman-Ross method to calculate reactivity ratios from the values of polymer composition, rl- and r2-values of 1.8 and 0.3, respectively, were obtained.

  • 5. Adhikari, A
    et al.
    Claesson, P
    YKI – Ytkemiska institutet.
    Pan, J
    Leygraf, C
    Dedinaite, A
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, p. 4239-4247Article in journal (Refereed)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani–MeSA polymer was characterized by FT-IR, UV–vis, X-ray diffraction (XRD) and impedance spectroscopy. The polymer was dispersed in polyvinylacetate and coated on carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating on carbon steel in 3% NaCl were investigated using open-circuit potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating a certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel throughout the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 6.
    Adhikari, Arindam
    et al.
    YKI – Ytkemiska institutet.
    Radhakrishnan, S
    Dopant induced effect on electrocatalytic reduction of nitrobenzene using conducting polypyrrole thin film electrodes2011In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 120, no 2, p. 719-724Article in journal (Refereed)
    Abstract [en]

    Conducting polypyrrole electrodes were prepared by electrochemical polymerization of pyrrole on vacuum-metallized glass substrates. These electrodes were modified by doping with a range of metal halides as dopant ions having different electronegativity. Electrochemical reduction of nitrobenzene using these electrodes was studied by means of cyclic voltammetry technique in acetonitrile medium containing aqueous HClO4 (0.1M) as supporting electrolyte. It was found that the electronegativity of the dopant ion played a very important role in the electrocatalytic activity. Polypyrrole doped with nickel chloride gave the highest anodic current at the reduction potential of nitrobenzene. The results were explained on the basis of charge transfer efficiency at the electrode-electrolyte interface, which was associated with the acceptor state created by the dopant in the semi-conducting polymer.

  • 7.
    Agerkvist, I
    YKI – Ytkemiska institutet.
    Mechanisms of flocculation with chitosan in Escherichia coli distintegrates: effects of urea and chitosan characteristics1992In: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 69, p. 173-187Article in journal (Refereed)
    Abstract [en]

    Four different chitosans with different charge densities and different molecular weights were used for investigation of the mechanisms involved in selective flocculation of cell debris particles in E.coli disintegrates. It was found that the main mechanism for flocculation is a "non-equilibrium" bridging process in which a very efficient removal of cell debris particles can be achieved with highly charged chitosans. The high molecular weight (6.5-6.6x105) chitosans produce very large and shear resistant flocs suitable for filtration as well as settling and centrifugation. The low molecular weight (1x105) product forms smaller and more shear sensitive flocs best suited for centrifugation. There are small differences in flocculation dosages depending on molecular weight, but large differences are found with significant changes in charge densities. A decrease in the deacetylation degree from 93 to 39% increased the flocculation dosages by 100 to 150%. A low molecular weight chitosan gave a much broader flocculation region than that of a high molecular weight. Flocculation by addition of urea revealed a hydrogen bonding capacity of chitosan toward cell debris particles which was not involved in chitosan´s interaction with proteins or nucleic acids. The purification of the enzyme -galactosidase could be increased by a factor of 3.7 when using a two step flocculation procedure. The enzyme yield was 82% and the enzyme solution was essentially free of both nucleic acids and cell debris particles.

  • 8.
    Agerkvist, I
    et al.
    YKI – Ytkemiska institutet.
    Eriksson, LB
    YKI – Ytkemiska institutet.
    Selective flocculation with chitosan in E.Coli disintegrates: effects of ionic strength and multivalent metal ions1993In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 14, p. 269-293Article in journal (Refereed)
    Abstract [en]

    The effects of ionic strength and multivalent metal ions on the flocculation performance in Escherichia coli cell disintegrates using the polycationic chitosan as a flocculant were investigated. The study showed that ionic strength could be used to optimize the selectivity in flocculation. The best selectivity was obtained at 0.5 M sodium chloride where 95% of the cell debris and 88% of the nucleic acids could be removed from the disintegrate by sedimentation, leaving 99% of proteins and 86% of -galactosidase enzyme activity in clarified solution. We will also discuss the mechanisms for interaction between chitosan and different groups of components in the disintegrate: cell debris particles, nucleic acid polymers and proteins.

  • 9. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Catalysis in micellar and liquid crystalline phases1973In: Chemie, Physikalische Chemie und Anwendungstechnik der Grenzflächenaktiven Stoffe, Munchen: Carl Hanser Verlag GmbH, 1973, p. 917-924Conference paper (Refereed)
  • 10. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Catalysis in micellar and liquid-crystalline phases : I. the system water-hexadecyltrimethylammonium bromide-hexanol1972In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, p. 5196-5199Article in journal (Refereed)
  • 11. Ahmad, SI
    et al.
    Friberg, S
    YKI – Ytkemiska institutet.
    Phase equilibria and foam stability in solutions of cationic surfactants1971In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 102, p. 3-14Article in journal (Refereed)
  • 12. Ahmad, SI
    et al.
    Shinoda, K
    Friberg, S
    YKI – Ytkemiska institutet.
    Microemulsions and phase equilibria1974In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 47, p. 32-37Article in journal (Refereed)
  • 13. Alander, J
    et al.
    Wärnheim, T
    YKI – Ytkemiska institutet.
    Model microemulsions containing vegetable oils Part 1: Nonionic surfactant systems1989In: Journal of the American Oil Chemists Society, ISSN 0003-021X, E-ISSN 1558-9331, Vol. 66, p. 1656-1660Article in journal (Refereed)
    Abstract [en]

    Nonionic microemulsions containing triglucerides and fatty acid esters as lipophilic components have been studied. The phase inversion temperature (PIT) of the systems was determined by a conductometric method. Partial phase diagrams were constructed in the phase inversion temperature range. Water solubilization capacity of the nonionic surfactant systems studied was dependent on surfactant and oil types in analogy to ordinary hydrocarbon systems. The PIT:s increased with increased molecular weight for both esters and triglycerides.

  • 14. Alander, J
    et al.
    Wärnheim, T
    YKI – Ytkemiska institutet.
    Model microemulsions containing vegetable oils Part 2: Ionic surfactant systems1989In: Journal of the American Oil Chemists Society, ISSN 0003-021X, E-ISSN 1558-9331, Vol. 66, p. 1661-1665Article in journal (Refereed)
    Abstract [en]

    The phase behavior and the structure of ionic microemulsions, stabilized by sodium oleate and different alcohol cosurfactants, containing fatty acid esters or triglycerides as lipophilic components, have been investigated. Microemulsions containing triglycerides display a smaller stability region than microemulsions containing hydrocarbons or fatty acid esters. From structural investigations, using the NMR FT pulsed gradient spin echo method for measuring self-diffusion coefficients, differences in the microstructure are revealed as well. Adding an ester (or a hydrocarbon) to a microemulsion containing sodium oleate/pentanol will at certain compositions lead to a gradual transition from a bicontinuous to an oilcontinuous system, while this behavior cannot be detected when adding a triglyceride. Instead, a phase-separation occurs, and it is suggested that the larger molecular size of the triglyceride is responsible for the diffirence.

  • 15.
    Alberius, Peter
    et al.
    YKI – Ytkemiska institutet.
    Andersson, N
    Spray drying functionalized mesostructured colloids2003In: Self-Assembled Nanostructured Materials / [ed] Yunfeng Lu, C J Brinker , M Antonietti, Materials Research Society, 2003, p. 53-58Chapter in book (Refereed)
  • 16. Alexandrova, L
    et al.
    Hanumantha Rao, K
    Forsberg, KSE
    Grigorov, L
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Three-phase contact parameters measurements for silica-mixed cationic-anionic surfactant systems2009In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 348, no 1-3, p. 228-233Article in journal (Refereed)
    Abstract [en]

    The stability and interactions in thin wetting films between the silica surface and air bubble containing (a) straight chain C10 amine and (b) cationic/anionic surfactant mixture of a straight chain C10 amine with sodium C8, C10 and (straight chain) C12 sulfonates, were studied using the microscopic thin wetting film method developed by Platikanov [D. Platikanov, J. Phys. Chem. 68 (1964) 3619]. Film lifetimes, three-phase contact (TPC) expansion rate, receding contact angles and surface tension were measured. The presence of the mixed cationic/anionic surfactants was found to lessen contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants heterocoagulation could arise through the formation of positively charged interfacial complexes. Mixed solution of cationic and anionic surfactants shows synergistic lowering in surface tension. The formation of the interfacial complex at the air/solution interface was confirmed by surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants system controls the strength of the interfacial complex. The observed phenomena were discussed in terms of the electrostatic heterocoagulation theory, where the interactions can be attractive or repulsive depending on the different surface activity and charge of the respective surfactants at the two interfaces.

  • 17. Alexandrova, L
    et al.
    Hanumantha, Rao K
    Forsberg, KSE
    Grigorov, L
    Pugh, Robert J
    YKI – Ytkemiska institutet.
    The influence of mixed cationic-anionic surfactants on the three-phase contact parameters in silica-solution systems2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 373, p. 145-151Article in journal (Refereed)
    Abstract [en]

    The formation of thin wetting films on silica surface from aqueous solution of (a) tetradecyltrimetilammonium bromide (C14TAB) and (b) surfactant mixture of the cationic C14TAB with the anionic sodium alkyl- (straight chain C12-, C14- and C16-) sulfonates, was studied using the microscopic thin wetting film method developed by Platikanov. Film lifetimes, three-phase contact (TPC) expansion rates, receding contact angles and surface tension were measured. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetimes, as compared to the pure C14TAB. This behavior was explained by the strong initial adsorption of interfacial complexes from the mixed surfactant system at the air/solution interface, followed by adsorption at the silica interface. The formation of the interfacial complexes at the air/solution interface was proved by means of the surface tension data. It was also shown, that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex and causes synergistic lowering in the surface tension. The film rupture mechanism was explained by the heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface, which remained negatively charged.

  • 18. Alexandrova, L
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Tiberg, F
    YKI – Ytkemiska institutet.
    Grigorov, L
    Confirmation of the heterocoagulation theory of flotation1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, p. 7464-7471Article in journal (Refereed)
    Abstract [en]

    To model the flotation process, we have used the microscopic method developed by Scheludko to study the stability of an aqueous thin film containing tetradecyltrimethylammonium bromide ( C14TAB ) between an air bubble and a silica substrate. Experiments were performed at a range of C14TAB concentrations and pH values. Spontaneous rupture of the thin aqueous film was interpretated in terms of heterocoagulation resulting from the preferential adsorption of relatively low surfactant concentrations at the vapour/solution interface causing a net positive charge while the solution/silica interface remained negatively charged. In addition, during the the three-phase-contact (TPC) expansion or de-wetting step following film rupture, the movement of TPC across the silica substrate leads to transfer of amine from the vapour/solution interface to the vapour/silica. This process resembles a Langmuir-Blodgett deposition process and emphasized the importance of the solution/vapour interface in the de-wetting process.

  • 19. Allen, LT
    et al.
    Fox, EJP
    Blute, I
    YKI – Ytkemiska institutet.
    Kelly, ZD
    Rochev, Y
    Keenan, AK
    Dawson,
    Interaction of soft condensed materials with living cells: Phenotype/transcriptome correlations for the hydrophobic effect2003In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 100, p. 6331-6336Article in journal (Refereed)
    Abstract [en]

    The assessment of biomaterial compatibility relies heavily on the analysis of macroscopic cellular responses to material interaction. However, new technologies have become available that permit a more profound understanding of the molecular basis of cell-biomaterial interaction. Here, both conventional phenotypic and contemporary transcriptomic (DNA microarray-based) analysis techniques were combined to examine the interaction of cells with a homologous series of copolymer films that subtly vary in terms of surface hydrophobicity. More specifically, we used differing combinations of N-isopropylacrylamide, which is presently used as an adaptive cell culture substrate, and the more hydrophobic, yet structurally similar, monomer N-tert-butylacrylamide. We show here that even discrete modifications with respect to the physiochemistry of soft amorphous materials can lead to significant impacts on the phenotype of interacting cells. Furthermore, we have elucidated putative links between phenotypic responses to cell-biomaterial interaction and global gene expression profile alterations. This case study indicates that high-throughput analysis of gene expression not only can greatly refine our knowledge of cell-biomaterial interaction, but also can yield novel biomarkers for potential use in biocompatibility assessment

  • 20. Almstrand, A-C
    et al.
    Ljungström, E
    Lausmaa, J
    YKI – Ytkemiska institutet.
    Bake, B
    Sjövall, P
    YKI – Ytkemiska institutet.
    Olin, A-C
    Airway Monitoring by Collection and Mass Specrometric Analysis of Exhaled Particles2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 2, p. 662-668Article in journal (Refereed)
    Abstract [en]

    We describe a new method for simultaneously collecting particles in exhaled air for subsequent chemical analysis and measuring their size distribution. After forced exhalation, particles were counted and collected in spots on silicon wafers with a cascade impactor. Several phospholipids were identified by time-of-flight secondary ion mass spectrometric analysis of the collected spots, suggesting that the particles originated from the lower airways. The amount of particles collected in ten exhalations was sufficient for characterizing the phospholipid composition. The feasibility of the technique in respiratory research is demonstrated by analysis of the phospholipid composition of exhaled particles from healthy controls, patients with asthma, and patients with cystic fibrosis. We believe this technology will be useful for monitoring patients with respiratory disease and has a high potential to detect new biomarkers in exhaled air.

  • 21. Andersson, C
    et al.
    Ernstsson, M
    YKI – Ytkemiska institutet.
    Järnström, L
    Barrier properties and heat sealability/failure mechanisms of dispersion coated paperboard2002In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 15, p. 209-224Article in journal (Refereed)
    Abstract [en]

    Plate-like fillers are often added to improve barrier properties and to prevent blocking of dispersion coatings on paper and board. We have studied the effects of clay addition, neutralizing agent and drying conditions on water vapour permeability, water absorption, oxygen permeability and heat sealability of carboxylated styrene/butyl acrylate dispersion coatings on a pilot scale. The barrier dispersions were applied on a pre-coated side of a three-ply board, using a pre-metering roll coater. Coated strips were sealed under specified conditions of temperature, time and pressure and the sealability was assessed by measuring the peak load necessary to break the joints. The surface composition of the barrier-coated board was analysed and the mode of failure was characterized by ESCA. The occurrence of pinholes in the barrier coatings was assessed by both staining tests and ESEM/EDX analysis of the surface topography. The resulting barrier properties were satisfactory as far as resistance to water transport in both liquid and vapour form is concerned. The oxygen permeability was similar to that of similar amorphous polymers. Heat-sealing tests showed that the mode of failure was mainly cohesive in nature, as fibre tear occurred when sealed strips were separated. Neutralization with sodium hydroxide gave poor adhesion and had a negative effect on the seal strength. Barrier measurements and ESEM/EDX analysis both showed that the pinholes present extended only through the barrier coating

  • 22. Andersson, C
    et al.
    Järnstrom, L
    Fogden, A
    Mira, I
    YKI – Ytkemiska institutet.
    Voit, W
    Zywicki, S
    Preparation and incorporation of microcapsules in functional coatings for self-healing of packaging board2009In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 22, no 5, p. 275-291Article in journal (Refereed)
    Abstract [en]

    The replacement of flexible polyolefin barrier layers with novel, thin, functional polymer coatings in the production of paperboard packaging involves the risk of deteriorated barrier and mechanical properties during the converting process. Local defects or cracks in the protective barrier layer can arise because of the stress induced in creasing and folding operations. In this study, the incorporation of microencapsulated self-healing agents in coating formulations applied both by spot- and uniform-coating techniques was studied. The preparation process of microcapsules with a hydrophobic core surrounded by a hydrophobically modified polysaccharide membrane in aqueous suspension was developed to obtain capsules fulfilling both the criteria of small capsule size and reasonably high solids content to match the requirements set on surface treatment of paperboard for enhancement of packaging functionality. The survival of the microcapsules during application and their effectiveness as self-healing agents were investigated. The results showed a reduced tendency for deteriorated barrier properties and local termination of cracks formed upon creasing. The self-healing mechanism involves the rupture of microcapsules local to the applied stress, with subsequent release of the core material. Crack propagation is hindered by plasticization of the underlying coating layer, while the increased hydrophobicity helps to maintain the barrier properties.

  • 23. Andersson, K
    et al.
    Kizling, J
    YKI – Ytkemiska institutet.
    Holmberg, K
    YKI – Ytkemiska institutet.
    Byström, S
    A ring-opening reaction performed in a microemulsion1998In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 144, p. 259-266Article in journal (Refereed)
  • 24.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    Density measurements of single granules using the atomic force microscope2005In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 88, p. 2322-2324Article in journal (Refereed)
    Abstract [en]

    The density of single spray-dried granules has been determined with a new method based on the atomic force microscopy (AFM). Spherical granules with a well-defined diameter are attached to the AFM cantilever, which acts as a beam type spring, and the mass of a granule is estimated from the shift in the resonant frequency. The error of the measurements associated with the method was estimated to vary between 1-5% depending on the size and shape of the granule. Density measurements of spray-dried WC-Co granules are presented and the effect of a polymeric binder and dispersant on the consolidation during drying is discussed

  • 25.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    DLVO interactions of tungsten oxide and cobalt oxide surfaces measured with the colloidal probe technique2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 246, p. 309-315Article in journal (Refereed)
    Abstract [en]

    We have investigated the DLVO surface forces of oxidised tungsten and cobalt surfaces using the atomic force microscope (AFM) colloidal probe technique. It was shown by X-ray Photoelectron Spectroscopy (XPS), and electrokinetic measurements that this model system is representative for industrial WC and Co powders used in the production of hard metals. We found that the attractive van der Waals forces are well described by Hamaker constants, calculated from optical data for WO3 and CoOOH. The repulsive electrostatic double layer forces between WO3 surfaces increase with increasing pH due to an increasingly negative surface potential. This surface potential decreases with increasing ionic strength at pH 7.5. The electrostatic interaction between WO3 and CoOOH is attractive at pH 10, suggesting a positively charged CoOOH surface.

  • 26.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    Effect of cobalt ion and polyethyleneimine adsorption on the surface forces between tungsten oxide and cobalt oxide in aqueous media2002In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 85, p. 2404-2408Article in journal (Refereed)
    Abstract [en]

    We used the colloidal probe technique with the atomic force microscope (AFM), to study the interactions between a tungsten oxide sphere, WO3, and flat oxidized tungsten and cobalt surfaces in aqueous electrolytes. We have investigated the effects of adsorption of cobalt ions to tungsten oxide surfaces and adsorption of polyethyleneimine (PEI). Low concentrations of cobalt ions to a WO3system resulted in extended hydration forces and lower absolute value of the surface potential. It was shown that PEI adsorbs to the WO3 surfaces and induces an electrosteric repulsion in both the symmetric (WO3-WO3) and asymmetric (WO3-CoOOH) system. The possible complexation of cobalt ions with PEI does not significantly influence the thickness of the adsorbed layer

  • 27.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet. Stockholms Universitet.
    Bergström, L
    Stockholms Universitet.
    Friction and adhesion of single spray-dried granules containing a hygroscopic polymeric binder2005In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 155, p. 101-107Article in journal (Refereed)
    Abstract [en]

    The atomic force microscope has been used to study the friction and adhesion of single spray dried granules containing a mixture of fine tungsten carbide and cobalt powders and various amounts of a polymeric binder, polyethylene glycol (PEG). The adhesion or the pull-off force and the friction force between two single granules (representing intergranular friction) and between a granule and a hard metal substrate (representing die-wall friction) have been determined as a function of relative humidity. We found that the granule-wall friction increases with binder content and relative humidity. The small friction force at the lowest addition of PEG was related to a small contact area due to the high surface roughness of the granules. The substantial increase in the friction coefficient at PEG-addition>1wt% was related to the plasticity of the binder-rich granule surface where an increase in binder content or relative humidity increases the deformability. The granule-granule friction and adhesion is independent of the relative humidity and substantially lower than the granule-wall friction at all PEG contents, which has important implications for the handling of granular matter

  • 28.
    Andersson, KM
    et al.
    YKI – Ytkemiska institutet.
    Bergström, L
    YKI – Ytkemiska institutet.
    Oxidation and dissolution of tungsten carbide powder in water2000In: Int J Refract Met Hard Mater, ISSN 0263-4368, Vol. 18, p. 35-43Article in journal (Refereed)
    Abstract [en]

    The oxidation and dissolution of tungsten carbide powder dispersed in water was investigated using XPS and leaching studies. We found that the WO3 surface layer on the oxidised tungsten carbide powder dissolves readily at pH>3 with the tungsten concentration increasing linearly with time. Adding cobalt powder to the tungsten carbide suspension resulted in a significant reduction of the dissolution rate at pH<10, when the concentration of dissolved Co is high in the solution phase. Electrokinetic studies indicate that the reduced dissolution rate may be related to the formation of surface complexes; experiments showed that Co species in solution adsorb on the oxidised tungsten carbide powder. The experimental data were discussed in relation to theoretical modelling of the WO3 solution chemistry and the Co2+ adsorption at oxide/water interfaces

  • 29.
    Andersson, M
    et al.
    YKI – Ytkemiska institutet.
    Hillerström, A
    YKI – Ytkemiska institutet.
    Svensk, A
    Younesi, SR
    Sjöström, E
    YKI – Ytkemiska institutet.
    Blute, I
    A new class of labile surfactants that break down to non-surface active products upon heating or after a pre-set time, without the need for a pH change2007In: Tenside Surfactants Detergents, ISSN 0932-3414, E-ISSN 2195-8564, Vol. 44, no 6, p. 366-372Article in journal (Refereed)
  • 30.
    Andersson, M
    et al.
    YKI – Ytkemiska institutet.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Lockowandt, C
    Vignes-Adler, M
    Foaming mechanisms in transient foams under microgravity conditions2001In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 11, p. Pr6-227Article in journal (Refereed)
  • 31. Andersson, M
    et al.
    Kronberg, Bengt
    YKI – Ytkemiska institutet.
    Development of advanced foams in microgravity2005In: Microgravity Applications Programme: Successful Teaming of Science and Industry, European Space Agency / [ed] Andrew Wilson, Noordwijk: ESA Publications Division , 2005, p. 589-596Chapter in book (Refereed)
  • 32.
    Andersson, M
    et al.
    YKI – Ytkemiska institutet.
    Sjöström, E
    YKI – Ytkemiska institutet.
    Svensson, B
    Karaktärisering av stenytor - tre användbara tekniker2001In: Sten, ISSN 0346-1866, no 3, p. 38-41Article in journal (Refereed)
  • 33. Andersson, N
    et al.
    Alberius, P
    YKI – Ytkemiska institutet.
    Örtegren, J
    Lindgren, M
    Bergström, L
    Photochromic mesostructured silica pigments dispersed in latex films2005In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 15, no 0149-2136, p. 3507-3513Article in journal (Refereed)
    Abstract [en]

    We have incorporated the photochromic dyes spiropyran and spirooxazine in surfactant templated mesostructured silica particles. Spherical inorganic–organic hybrid pigments with varying dye content were produced by a one-pot synthesis in an aerosol reactor where the internal mesostructure could be controlled. The mesostructured inorganic–organic hybrid pigments provide a mechanically and chemically rigid framework that protects the dyes and facilitate handling. We show that an organic latex binder can be used to prepare transparent photochromic films of varying thickness. Changing the dye loading in the pigments and the pigment content in the films provides a versatile route for tuning the photochromic response. The pigmented films show both fast and direct photochromism, where the decay time for thermal bleaching is very fast in the case of spirooxazine doped pigments (kSO= 0.094 s–1), being in the range of the best reported values for solid state composites.

  • 34.
    Andersson, N
    et al.
    YKI – Ytkemiska institutet.
    Alberius, PCA
    YKI – Ytkemiska institutet.
    Pedersen, JS
    Bergström, L
    YKI – Ytkemiska institutet.
    Structural features and adsorption behaviour of mesoporous silica particles formed from droplets generated in a spraying chamber2004In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 72, p. 175-183Article in journal (Refereed)
    Abstract [en]

    Spherical mesoporous particles have been produced by spraying hydrolysed alkoxide solutions containing templating amphiphilic molecules. The modified spray drying method produces up to 10 g/h of spherical non-hollow particles with a size of 1–5 m. Transmission electron microscopy and X-ray diffraction showed that well ordered internal 2D hexagonal mesostructures could be prepared using both nonionic block copolymers and cationic surfactants as the templating molecules. Disordered cubic and well ordered lamellar, onion like, particles were prepared from the block copolymer templates. Nitrogen sorption data and mercury porosimetry show that pore size distribution of the mesoporous particles is very narrow with pore sizes varying from 2.5 to 8.5 nm as a function of templating amphiphiles. We have shown that the mesoscopic pores are accessible after calcination and can be filled with relatively large molecules; the particles adsorbed more than 20% (by weight) of the cationic dye Janus Green B from aqueous solutions.

  • 35. Andersson, N
    et al.
    Kronberg, B
    YKI – Ytkemiska institutet.
    Corkery, R
    YKI – Ytkemiska institutet.
    Alberius, P
    YKI – Ytkemiska institutet.
    Combined emulsion and solvent evaporation (ESE) synthesis route to well-ordered mesoporous materials2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 3, p. 1459-1464Article in journal (Refereed)
    Abstract [en]

    Control over morphology and internal mesostructure of surfactant templated silicas remains a challenge, especially when considering scaling laboratory syntheses up to industrial volumes. Herewereport a method combining emulsification with the evaporation-induced self-assembly (EISA) method for preparing spherical, mesoporous silica particles. This emulsion and solvent evaporation (ESE) method has several potential advantages over classic precipitation routes: it is easily scaled while providing superior control over stoichiometric homogeneity of templating surfactants and inorganic precursors, and particle sizes and distributions are determined by principles developed for manipulating droplet sizes within water-in-oil emulsions. To demonstrate the method, triblock copolymer P104 is used as a templating amphiphile, generating unusually well-ordered 2D hexagonal (P6mm) mesoporous silica, while particle sizes and morphologies were controlled by varying the type of emulsifier and the method for emulsification

  • 36. Andersson, Nina
    et al.
    Corkery, Robert W
    YKI – Ytkemiska institutet.
    Alberius, Peter CA
    YKI – Ytkemiska institutet.
    One-pot synthesis of well ordered mesoporous magnetic carriers2007In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 17, no 26, p. 2700-2705Article in journal (Refereed)
    Abstract [en]

    The facile preparation of a mesoporous magnetic carrier technology is demonstrated. The micron-sized spherical mesostructured particles are prepared using a newly-developed, one-step, combined emulsion and solvent evaporation (ESE) method. The surfactant-templated silica matrix display a well-ordered internal pore architecture. Very limited pore blocking, and only to a limited degree disordered- or worm-like structures are observed, induced by the iron oxide nanoparticles added to provide the superparamagnetic properties.The iron oxide content was precisely controlled, and the magnetic properties were well preserved during the process. Finally we demonstrate the applicability of the magnetically separable mesoporous material as an adsorbent for specific dissolved materials from dilute aqueous solutions.

  • 37. Andersson, P
    et al.
    Koskinen, J
    Varjus, S
    Gerbig, Y
    Haefke, H
    Georgiou, S
    Zhmud, B
    YKI – Ytkemiska institutet.
    Microlubrication effect by laser-textured steel surfaces2007In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 262, p. 369-379Article in journal (Refereed)
    Abstract [en]

    The beneficial effect on lubrication achieved through microtexturing by laser ablation was investigated. The investigation was based on two independent experimental approaches with oil-lubricated smooth and laser-textured steel surfaces in oscillating sliding contact with a steel ball. Two types of laser-textured patterns of microcavities were studied. It was found that, in comparison with smooth steel surfaces, the laser texturing significantly reduces friction and wear. The most significant improvement in the tribological performance was achieved with an oil of high viscosity combined with a texture comprising a low density of deep microcavities.

  • 38. Ardebrant, H
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Surface acidity/basicity of road stone aggregates by adsorption from non-aqueous solutions1991In: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 53, p. 101-116Article in journal (Refereed)
    Abstract [en]

    The surface of several road stone aggregates were characterized by the adsorption of organic probe molecules (with acidic and basic functional groups) from cyclohexane. The results show differences in the adsorption affinity and adsorption capacity of the molecules for the different mineral surfaces. In most cases it was found convenient to represent the data by a Langmuir-Freundlich type of isotherm, which defines a quasi-Gaussian energy distribution around a peak value. From the theory a range of adsorption free energies and surface coverages (site densities) were calculated, and the heterogenity of the surfaces evaluated. Generally the interaction strengths were rationalized in terms of Lewis acid-base theory.

  • 39. Ardebrant, H
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Wetting studies on silicate minerals and rocks used in bituminous highways1991In: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 58, p. 111-130Article in journal (Refereed)
    Abstract [en]

    A study has been made on the wetting characteristics of quartz and several other silicate minerals and road stones used in bituminous roads. From contact angle measurements using the "two-liquid phase" method the nondispersive interaction energy between the mineral or road stone and water (I_S(p;sw)) with and without heat treatment was obtained. The results indicate a wide range of I_S(p;sw)-values, which appear to depend on the chemical composition of the aggregate. It was also suggested that the result may be related to the degree of contamination. From these studies it also appears that I_S(p;sw) is a useful parameter defining the vulnerability of stripping.

  • 40.
    Arleth, L
    et al.
    YKI – Ytkemiska institutet.
    Bergström, M
    YKI – Ytkemiska institutet.
    Pedersen, JS
    Small-angle neutron scattering study of the growth behavior, flexibility, and intermicellar interactions of wormlike SDS micelles in NaBr aqueous solutions2002In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, p. 5343-5353Article in journal (Refereed)
    Abstract [en]

    SDS wormlike micelles in water with NaBr are studied using small-angle neutron scattering. SDS concentrations ranging from 0.08 to 8.6 % vol in NaBr aqueous solutions at salinities from 0.6 to 1.0 M are covered. The scattering data are analyzed using a novel approach based on polymer theory and the results of Monte Carlo simulations. The method makes it possible to give a full interpretation of the scattering data, even for the entangled micellar solutions occurring at high concentrations and high salinities. Analysis of the scattering data at zero scattering angle demonstrates that the length of the micelles increases according to a power law as a function of concentration in the studied interval. The analysis furthermore shows that the length of the micelles increases exponentially with increasing salinity. The scattering data in the full range of scattering angles are analyzed using a model for polydisperse wormlike micelles where excluded volume effects are taken into account via an expression based on the polymer reference interaction site model (PRISM). This part of the analysis show that the micelles become more flexible as the salinity increases, which is due to an increased screening of the ionic micelles

  • 41.
    Arnebrant, Thomas
    YKI – Ytkemiska institutet.
    Protein adsorption in the oral environment: Chapter 292003In: Biopolymers at Interfaces, CRC Press, 2003, 2nd, p. 811-855Chapter in book (Refereed)
  • 42. Arnold, Celine
    et al.
    Klein, Guillaume
    Maaloum, Mounir
    Ernstsson, Marie
    Larsson, Anders
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Marie, Pascal
    Surfactant distribution in waterborne acrylic films. 2 Surface Investigation2011In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 374, no 1-3, p. 58-68Article in journal (Refereed)
    Abstract [en]

    This paper presents results on sodium dodecyl sulfate (SDS) enrichment at the surface of pure acrylic or acrylic/laponite composite latex films. Surface concentrations were measured by Confocal Raman Spectroscopy leading to higher values than the nominal concentration of 6 wt%. X-ray Photoelectron Spectroscopy (XPS) analyses showed uppermost surface layers saturated with SDS in most cases. High resolution Atomic Force Microscopy (AFM) revealed a variety of morphologies for these surfactant top layers, highlighting the occurrence of SDS bilayers in different configurations. In an attempt to check for a correlation between the surface concentration of the surfactant in dry films and the concentration of free surfactant in water in the initial latex, this latter concentration was determined from the level of the plateau in adsorption isotherms. Adsorption studies by conductimetry showed an unexpected increase of the amount of adsorbed SDS with pH. The proposed interpretation is that, upon acrylic acid neutralization, the chains at the surface become more hydrophilic and spread out in water, revealing more sites for SDS to adsorb on. No correlation between free surfactant and surface enrichment could be established, indicating that the enrichment process is more complex than expected.

  • 43. Asencio, RA
    et al.
    Cranston, ED
    Atkin, R
    Rutland, Mark W.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Ionic liquid nanotribology: Stiction suppression and surface induced shear thinning2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 26, p. 9967-9976Article in journal (Refereed)
    Abstract [en]

    The friction and adhesion between pairs of materials (silica, alumina, and polytetrafluoroethylene) have been studied and interpreted in terms of the long-ranged interactions present. In ambient laboratory air, the interactions are dominated by van der Waals attraction and strong adhesion leading to significant frictional forces. In the presence of the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waals interaction is suppressed and the attractive/adhesive interactions which lead to "stiction" are removed, resulting in an at least a 10-fold reduction in the friction force at large applied loads. The friction coefficient for each system was determined; coefficients obtained in air were significantly larger than those obtained in the presence of EAN (which ranged between 0.1 and 0.25), and variation in the friction coefficients between systems was correlated with changes in surface roughness. As the viscosity of ILs can be relatively high, which has implications for the lubricating properties, the hydrodynamic forces between the surfaces have therefore also been studied. The linear increase in repulsive force with speed, expected from hydrodynamic interactions, is clearly observed, and these forces further inhibit the potential for stiction. Remarkably, the viscosity extracted from the data is dramatically reduced compared to the bulk value, indicative of a surface ordering effect which significantly reduces viscous losses.

  • 44. Attard, P
    et al.
    Carambassis, A
    Rutland, MW
    YKI – Ytkemiska institutet.
    Dynamic surface force measurement. 2. Friction and the atomic force microscope1999In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 15, p. 553-563Article in journal (Refereed)
    Abstract [en]

    The mechanism and geometry of force measurement with the atomic force microscope are analyzed in detail. The effective spring constant to be used in force measurement is given in terms of the cantilever spring constant. Particular attention is paid to possible dynamic effects. Theoretical calculations show that inertial effects may be neglected in most regimes, the exception being when relatively large colloidal probes are used. Model calculations of the effects of friction show that it can cause hysteresis in the constant compliance region and a shift in the zero of separation. Most surprising, friction can cause a significant diminution of the measured precontact force, and, if it actually pins the surfaces, it can change the sign of the calibration factor for the cantilever deflection, which would cause a precontact attraction to appear as a repulsion. Measurements are made of the van der Waals force between a silicon tip and a glass substrate in air. The evidence for friction and other dynamic effects is discussed. Interferometry is used to characterize the performance of the piezoelectric drive motor and position detector used in the atomic force microscope. It is shown that hysteresis in the former, and backlash in the latter, preclude a quantitative measurement of friction effects. The experimental data appear to underestimate the van der Waals attraction at high driving velocities, in qualitative agreement with the model friction calculations.

  • 45. Attard, P
    et al.
    Pettersson, T
    Rutland, MW
    YKI – Ytkemiska institutet.
    Thermal calibration of photodiode sensitivity for atomic force microscopy2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, article id Art No 1161107/1-116110/4Article in journal (Refereed)
    Abstract [en]

    The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.

  • 46. Attard, P
    et al.
    Schulz, JC
    Rutland, M
    YKI – Ytkemiska institutet.
    Dynamic surface force measurement. I. van der Waals collisions1999In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 69, p. 3852-3866Article in journal (Refereed)
    Abstract [en]

    Theoretical calculations and experimental measurements are used to show that hitherto neglected inertial effects can be significant in computer- controlled surface force measurement devices such as the atomic force microscope. The problem is analyzed in detail for the case of the van der Waals attraction in air. It is demonstrated that equating the cantilever deflection to the surface force systematically underestimates the magnitude of the surface force, increasingly so as the speed of approach is increased. It is also shown that the surface separation becomes lost at high accelerations due to a dynamic uncoupling of the cantilever deflection and angle. The effects of elastic deformation of the bodies are taken into account, including the collision-induced elastic vibrations in the solids. Experimental data are obtained for the van der Waals attraction and collision of glass surfaces in air using the measurement and analysis of surface forces device. All of the effects found in the theoretical calculations are identified in the experimental data.

  • 47. Auer, F
    et al.
    Schubert, DW
    Stamm, M
    Arnebrant, T
    YKI – Ytkemiska institutet.
    Swietlow, A
    Zizlsperger, M
    Switchable assembly of stable, ordered molecular layers1999In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 5, p. 1150-1159Article in journal (Refereed)
    Abstract [en]

    Bisamidines can be assembled on self-assembled monolayers of mercaptoalkanoic acids on gold to form stable and ordered but pH-switchable layers (see diagram). At basic pH the layers are stable and charge selective towards charged surfactants and plasma proteins. The system can potentially be used to reversibly introduce new surface properties for given applications that use one single substrate.

  • 48. Aulin, C
    et al.
    Varga, I
    Claesson, PM
    YKI – Ytkemiska institutet.
    Wågberg, L
    Lindström, T
    Buildup of polyelectrolyte multilayers of polyethyleneimine and microfibrillated cellulose studied by in situ dual-polarization interferometry and quartz crystal microbalance with dissipation2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 2509-2518Article in journal (Refereed)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concentrations of the components. Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements. The adsorption data obtained from both the techniques showed a steady buildup of multilayers. High pH and electrolyte concentration of the PEI solution was found to be beneficial for achieving a high adsorbed amount of PEI, and hence of MFC, during the buildup of the multilayer. On the other hand, an increase in the electrolyte concentration of the MFC dispersion was found to inhibit the adsorption of MFC onto PEI. The adsorbed amount of MFC was independent of the bulk MFC concentration in the investigated concentration range (15-250 mg/L). Atomic force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements. The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC. The surface roughness expressed as the rms-roughness over 1 m2 was calculated to be 4.6 nm (1 bilayer). The adsorbed amount of PEI and MFC and the amount of water entrapped by the individual layers in the multilayer structures were estimated by combining results from the two analytical techniques using the de Feijter formula. These results indicate a total water content of ca. 41% in the PEM.

  • 49.
    Axberg, C
    et al.
    YKI – Ytkemiska institutet.
    Eriksson, L
    Koagulation and sedimentation vid kemisk fällning1978In: Vatten, ISSN 0042-2886, Vol. 34, p. 220-229Article in journal (Refereed)
  • 50. Ayyala, S
    et al.
    Subrahmanyam, TV
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Forssberg, KSE
    Effect of corrosion inhibitors on grinding and flotation of a lead-zinc ore1993In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 6, p. 929-935Article in journal (Refereed)
    Abstract [en]

    Grinding and flotation experiments on a Pb-Zn ore were carried out to evaluate : 1) wear of the grinding media both in the presence and absence of an inhibitor and 2) effect of the inhibitor on the flotation of Pb-Zn minerals. The percentage reduction in the wear of the grinding media was observed to be between 25-36%, depending on the type of the inhibitor and its critical concentration. The inhibitors used in the investigation were sodium sulphite, sodium nitrite, sodium chromate and sodium silicate. The results indicate that a specific corrosion inhibitor, for example sodium sulphite, may give better recoveries and grades in flotation but is not as efficient as sodium chromate in inhibiting the wear of the grinding media. Pulp solutions (after grinding) analysed for metal ion concentrations showed low Fe. Iron released into the solution as a result of corrosion reactions subsequently forms insoluble hydroxy complexes and may coat the mineral surfaces. Such hydrophilic coatings may adversely affect the floatabilities of minerals. The particle size analysis of the ground product has been carried out and the results are discussed.

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