Browsing by Author "Drabarek, E"

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    Flow assurance in a model crude oil: a structural and rheometric study.
    (Australian Nuclear Science and Technology Organisation, 2008-04) Drabarek, E; Muzny, C; Bryant, G; Hanley, HJM
    This report investigates how the technique of small angle neutron scattering (SANS) helps elucidate the phenomenon of wax deposition in a petroleum crude oil. Specifically, we report SANS data, supplemented by results from dynamic light scattering (DLS), obtained from a synthetic petroleum crude oil: a mixture of commercial paraffin wax dissolved in an octane/cyclohexane solvent. The system is a gel below the cloud point. The onset and growth of this waxy gel, and changes in its nanostructure, are recorded here as a function of temperature over the range 10 ≤ T/°C ≤ 65. SANS indicates that the wax has a definite characteristic length of about 100 Å (10 nm) which can be observed at temperatures as high as 57°C, but DLS indicates that the wax also contains very large structures - of the order of a micrometer - over the temperature range 30° - 50°C. The structural studies are supplemented by corresponding sets of viscosity and stress data taken from the gelling wax when subjected to an applied shear. We observe that the stress will increase as the temperature falls - i.e. as the system gels - but, in general, will then reach a maximum and tend to decline. The wax results are compared with those from an equivalent system consisting of a major component of the wax: n-docosane, C22. Significant differences between the behavior of the wax and the pure component in the solvents are noted. The SANS patterns to 20°C from docosane do not give any indication of the nanoscale structure observed from the wax; the DLS patterns for docosane indicate that a solidification occurs over a very narrow temperature range between 10°C and 12°C, accompanied by a dramatic slowing of the dynamics; the large scale structure seen in the wax mixtures is not evident; and the rheological behavior of the two systems is markedly different. The paper also compares and contrasts the rheological behavior of the wax gel with that observed from defined system, gelled colloidal silica. Strong similarities are apparent.
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    Shear-induced alignment of self-associated hemoglobin in human erythrocytes: small angle neutron scattering studies
    (Springer, 2004-11) Garvey, CJ; Knott, RB; Drabarek, E; Kuchel, PW
    Small angle neutron scattering (SANS) was performed on suspensions of actively metabolising human erythrocytes in the constant shear field induced by a Couette cell. The SANS pattern recorded on a two-dimensional detector was a function of the shear rate; at zero shear, the SANS pattern had radial symmetry around the direction of the beam. The radial average of the SANS pattern consisted of a broad intensity maximum superimposed on a decay. The intensity maximum at q = 0.1 Å(-1) supercript stop was attributed to isotropically oriented self-associated complexes of the tetrameric oxygen transport protein hemoglobin inside the erythrocytes. A flow curve of the cell suspension was used to identify at what shear rate a suspension of uniaxially oriented ellipsoidal cells is produced. The radial symmetry of the SANS patterns persisted until the shear rate was sufficient to produce a suspension of uniaxially oriented ellipsoidal cells. Again, an intensity maximum was present in directions parallel and orthogonal to the shear axis, but this intensity maximum was superimposed upon quite different intensity decays in each direction from that of the primary neutron beam. The angular range of the SANS instrument was limited, however the results from shear-induced structural changes is consistent with a model that involves hemoglobin complexes that are aligned with respect to the plasma membranes of the elongated cells. © 2004, Springer.
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    Striving for order and compositional homogeneity in bulk mesoporous zirconium titanium mixed metal oxides from triblock copolymers and metal chlorides
    (Elsevier, 2009-02-01) Luca, V; Soler-Illia, GJAA; Angelome, PC; Steinberg, PY; Drabarek, E; Hanley, TL
    Under consideration in this work is the prospect for the preparation of ordered, thermally stable, compositionally homogenous bulk zirconium titanate mesophases using a triblock copolymer template (F-I 27). As a starting point, well established evaporation-induced self-assembly procedures for the production of thin films have been adapted to the preparation of bulk materials. The composition of the precursor solution was fixed at ZrxTi1-xCl4:40 EtOH:0.005 F127:h H2O (x = 0.28, h = 10) and ambient humidity was varied in a systematic and precise fashion. It has been demonstrated that while it was possible to prepare materials with localized order at humidities exceeding about 20% relative humidity, these materials showed macroscopic phase segregation with very little zirconium entering the mesophase structure instead precipitating as zirconium oxide. This phase segregation resulted in poor thermal stability at 500 degrees C. In contrast, at humidities below about 20%, more thermally stable worm-like materials with compositional homogeneity on the transmission electron microscope length scale could be prepared. For comparison with bulk materials, thin films were also prepared from the similar precursor solutions. The results of these preparations were unexpectedly very similar to those of the bulk preparations. It has been clearly demonstrated that attempts to incorporate about 30 mol% zirconium resulted in destruction of long range mesoscopic ordering under the conditions used. An additional important result of this study is the observation that the pore size distribution (PSD) was shifted from about 2.5 nm to about 6.5 nm for an increase in relative humidity from 0% to 20% and from 6.5 to about 7.6 nm for relative humidity increase from 20% to 70% for a calcination temperature of 300 degrees C. At this temperature all materials remained stable although similar overall trends were observed in the pore diameter with humidity when the calcination temperature was increased to 500 degrees C even though there was evidence of phase segregation and pore collapse at this temperature especially for samples prepared at the higher humidities. The present results suggest therefore that regulation of humidity during evaporation step affords a certain level of control over porosity. © 2008, Elsevier Ltd.
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    Tungstate-based glass-ceramics for the immobilization of radio cesium
    (Elsevier, 2009-02-15) Drabarek, E; McLeod, TI; Hanna, JV; Griffith, CS; Luca, V
    The preparation of tungstate-containing glass–ceramic composites (GCC) for the potential immobilization of radio cesium has been considered. The GCC materials were prepared by blending two oxide precursor compositions in various proportions. These included a preformed Cs-containing hexagonal tungsten bronze (HTB) phase (Cs0.3Ti0.2W0.8O3, P63/mcm) and a blend of silica and other oxides. The use of the HTB phase was motivated on the assumption that a HTB-based adsorbent could be used to remove cesium directly from aqueous high level liquid waste feeds. In the absence of the HTB, glass–ceramics were relatively easily prepared from the Cs-containing glass-forming oxide blend. On melting the mixture a relative complex GCC phase assemblage formed. The principal components of this phase assemblage were determined using X-ray powder diffraction, 133Cs MAS-NMR, and cross-sectional SEM and included glass, various zeolites, scheelite (CaWO4) and a range of other oxide phases and Cs-containing aluminosilicate. Importantly, under no circumstance was cesium partitioned into the glass phase irrespective of whether or not the composition included the preformed Cs-containing HTB compound. For compositions containing the HTB, cesium was partitioned into one of four major phases including zeolite; Cs–silica–tungstate bronze, pollucite (CsAlSi2O6), and an aluminosilicate with an Al/Si ratio close to one. The leach resistance of all materials was evaluated and related to the cesium distribution within the GCC phase assemblages. In general, the GCCs prepared from the HTB had superior durability compared with materials not containing tungsten. Indeed the compositions in many cases had leach resistances comparable to the best ceramics or glass materials. © 2009, Elsevier Ltd.
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    Understanding the supramolecular self-assembly of zirconium titanate mesophases formed from the poly(ethylene oxide) surfactant brij-58
    (American Chemical Society, 2010-07-13) Luca, V; Drabarek, E; Griffith, CS; Hanley, TL
    The evaporation-induced self-assembly of mesoporous zirconium titanium oxide thin films prepared from precursor solutions with the composition ZrxTi1−xCl4:40 EtOH:0.005 Brij 58:h H2O (where x = 0.28, h = 10, and Brij 58 = diblock copolymer C16H33PEO20) by dip coating has been studied as a function of the mole fraction of zirconium (x), the relative humidity (RH), and the drying conditions. Extremely well-ordered mesophases and compositional homogeneity on the atomic scale were consistently obtained when the films were prepared at relative humidities above 60%, under which conditions a cubic phase was identified. The influence of humidity was monitored using a combination of in situ small-angle X-ray diffraction (SAXD) and small-angle X-ray scattering (SAXS). These techniques showed the existence of nanocrystalline phases during the initial drying process for films prepared from precursor solutions with x in the range of 0.20−0.60. The nanocrystalline phases were evidenced as multiple X-ray reflections above 8° 2θ. These reflections were ascribed to relatively crystalline nano building units of the mesophase and displayed only a transient stability in humid air, disappearing after 1 h of film conditioning in any humidity. A clear dependence of the primary d-spacing observed in the SAXD on composition for films dried at 65% RH, stabilized at 200°C, and calcined at 350°C provided strong evidence of the ability to form a complete solid solution of Zr and Ti in the oxide mesophase prepared from the precursor solutions. This compositional homogeneity was confirmed by transmission electron microscopy and further corroborated using Ti K-edge X-ray absorption spectroscopy, which probed the local chemical environment of the embedded Ti atoms. The data provided here are in stark contrast to studies of zirconium titanium mixed oxide film systems using similar preparation procedures but triblock copolymer porogens such as F-127. A hypothesis is tendered to explain the dramatic difference in the products obtained using these distinct but related copolymer templates. © 2010, American Chemical Society