Browsing by Author "Blom, ACM"

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    The application of neutron reflectometry and atomic force microscopy in the study of corrosion inhibitor films
    (Elsevier B. V., 2006-11-15) John, D; Blom, ACM; Bailey, S; Nelson, A; Schulz, JC; De Marco, R; Kinsella, B
    Corrosion inhibitor molecules function by adsorbing to a steel surface and thus prevent oxidation of the metal. The interfacial structures formed by a range of corrosion inhibitor molecules have been investigated by in situ measurements based on atomic force microscopy and neutron reflectometry. Inhibitors investigated include molecules cetyl pyridinium chloride (CPC), dodecyl pyridinium chloride (DPC), 1-hydroxyethyl-2-oleic imidazoline (OHEI) and cetyl dimethyl benzyl ammonium chloride (CDMBAC). This has shown that the inhibitor molecules adsorb onto a surface in micellar structures. Corrosion measurements confirmed that maximum inhibition efficiency coincides with the solution critical micelle concentration. Copyright © 2006 Elsevier B.V.
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    The application of neutron reflectometry and atomic force microscopy in the study of corrosion inhibitor films
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) John, D; Blom, ACM; Bailey, S; Nelson, A; Schulz, JC; De Marco, R; Kinsella, B
    In the search for new, superior and environmentally friendly corrosion inhibitor molecules, it is important to understand their mechanism of inhibition. Characterising the chemical and physical nature of the adsorbed inhibitor layer is a major part of understanding this mechanism. An accurate account of this character necessitates the use of surface analysis techniques that are capable of in-situ measurements. Ex-situ techniques are likely to cause changes either by oxidation of the metal and corrosion product film or rearrangement and loss of the inhibitor film during exposure to air and during the drying and analysis under vacuum. Neutron reflectometry in combination with atomic force microscopy provides the capability of in-situ surface analysis of thin interfacial layers. These complementary techniques make it possible to investigate the structure and orientation of molecules on a surface. which can ultimately assist in gaining an insight into the inhibitor mechanism. This paper will explore how these techniques can be used to determine the mechanism of corrosion inhibitors, with particular emphasis on surfactant molecules used to prevent carbon dioxide corrosion of steel during petroleum production. Results will be presented from experiments using the aforementioned in-situ surface analysis with generic corrosion inhibitor molecules cetyl pyridinium chloride (CPC), dodecyl pyridinium chloride (DPC), 1-hydroxyethyl-2-oleic imidazoline (OHEI) and cetyl dimethyl benzyl ammonium chloride (CDMBAC). These results will be further discussed with respect to the observed inhibition of carbon dioxide corrosion of carbon steel electrodes. © The Authors
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    Direct visualisation of mesh phases at the solid/solution interface by AFM and neutron reflectometry
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Blom, ACM; Warr, GG; Nelson, A
    Using soft-contact AFM imaging, the adsorbed layer structure of mixed solutions of single-chained dodecyltrimethylammonium bromide (DTAB) and double-chained didodecyldimethylammonium bromide (DDAB) at varying compositions has been studied. On quartz, the observed morphologies as composition was varied from DDAB-rich mixtures to DTAB-rich mixtures changed from a bilayer -> mesh -> rods -> globules. This novel mesh structure is consistent with the average curvature progression from bilayer to rods, and consists of densely branched rods. There was a narrow solution composition over which this mesh structure was observed and a fractional change in solution composition resulted in a film transformation to rods. Neutron reflectometry experiments on multiple contrasts have been performed in ISIS and at ANSTO and confirm the curvature sequence observed using AFM. The composition of the mixed film was determined as were adsorbed amounts, film thicknesses and surface coverages. Despite there being an excess of DTAB in solution, the surface was very enriched in DDAB for the two mixed films. © 2005 The Authors
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    Neutron reflectivity and atomic force microscopy studies on the effect of pH and solubilizate upon the structure of adsorbed cationic surfactant films on quartz
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Schulz, JC; Nelson, A; Blom, ACM; War, GG
    We have examined the adsorbed layer morphology of cationic surfactant, tetradecyltrimethylammonium bromide (TTAB), on the hydrophilic quartz surface using atomic force microscopy (AFM) and neutron reflectometry (NR). We report on the effect of varying the surface charge of quartz by adjusting the bulk solution pH upon the adsorbed surfactant film structure. AFM results show that number density of globular (or spherical) TTAB aggregates on quartz increases, as the pH of the bulk solution is increased, reflecting the increase in surface charge of quartz. NR results also verify the AFM observations. We also report on the effect of the incorporation of a non-adsorbing solubilisate, naphthol, into the adsorbed surfactant film. In the bulk solution the incorporation of naphthol molecules into surfactant micelles promotes in micellar growth. Similarly, in the adsorbed surfactant film a transition to from globular to cylindrical surfactant aggregates was also observed. © 2005 The Authors
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    Phase behavior of amphiphilic diblock co-oligomers with nonionic and ionic hydrophilic groups
    (American Chemical Society, 2013-03-14) Heinen, JM; Blom, ACM; Hawkett, BS; Warr, GG
    The synthesis of a series of co-oligomer amphiphiles by RAFT and their self-assembly behavior in water is described. These novel amphiphiles, comprised of styrene, butyl acrylate, and alkyl hydrophobes together with ionic acrylic acid and nonionic hydroxyethylacrylate hydrophilic moieties and with a total degree of polymerization from 5 to 17, represent a new class of small-molecule surfactants that can be formed from the immense potential library of all polymerizable monomers. Examples of micellar solutions and discrete cubic, hexagonal, lamellar, and inverted hexagonal lyotropic phases, as well as vesicle dispersions and coexisting lamellar phases, are reported and characterized by small-angle scattering. The variation of self-assembly structure with co-oligomer composition, concentration, and solution conditions is interpreted by analogy with the surfactant packing parameter used for conventional small-molecule amphiphiles.© 2013, American Chemical Society.
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    Structure of mixed DTAB/DDAB adsorbed layers on quartz: a neutron reflectometry and atomic force microscopy study
    (Elsevier, 2007-11-15) Blom, ACM; Warr, GG; Nelson, A
    The structure and composition of adsorbed layers formed by mixtures of dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) on quartz have been determined using a combination of atomic force microscopy and neutron reflectometry. The mixed adsorbed layer was found to be substantially enriched in DDAB, stabilising the formation of a laterally unstructured bilayer even when there is only as little as 1 mol% present in the bulk mixed solute. At even higher DTAB content the adsorbed film morphology gradually transforms to globules over a very narrow composition range. DDAB was found to be significantly excluded from the mixed adsorbed film only after it was completely transformed into globular aggregates, the equilibrium adsorbed layer morphology of DTAB. © 2007, Elsevier Ltd.