Browsing by Author "Gadd, GE"

Now showing 1 - 7 of 7
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    Biodegradable polyhydroxyalkanoates/SWNT nanocomposite spheres and films prepared by spray-drying method
    (American Chemical Society, 2008-04-06) Yun, SI; Gadd, GE; Russell, RA; Holden, PJ
    The nanocomposite microspheres and films of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) with single wall carbon nanotubes (SWNTs), were prepared by spray-drying method. The TEM immages showed that SWNTS well dispersed in PHB abd PHO indicating that rapid evaporation by spray drying effectively prevents aggregation of SWNTs. The Optical microscopy showed that the crystalline size substantially decreased for PHB/SWNTs nanocomposites with a 1% weight fraction of SWNTs relative to PHB (PHB/(1%)SWNTs), indicating the effective nucleation of PHB crystallization by SWNTs. Mechanical properties of the nanocomposite films were measured by nanoindentation. Both polymer nanocomposite films showed an increase in hardness (H) and Young's modulus (E), with SWNTs concentration.
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    Mechanical properties of biodegradable polyhydroxyalkanoates/single wall carbon nanotube nanocomposite films
    (Springer Nature, 2008-04-15) Yun, SI; Gadd, GE; Latella, BA; Lo, V; Russell, RA; Holden, PJ
    The nanocomposite films of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) with single wall carbon nanotubes (SWCNTs), were prepared. The Optical microscopy showed that the crystalline size substantially decreased for PHB/SWCNTs nanocomposites with a 1 % weight fraction of SWCNTs relative to PHB (PHB/(1%)SWCNTs), indicating the effective nucleation of PHB crystallization by SWCNTs. Mechanical properties of the nanocomposite films were measured by nanoindentation. Both polymer nanocomposite films showed an increase in hardness (H) and Young’s modulus (E), with SWCNTs concentration. The PHB/SWCNTs nanocomposite films are found to be more brittle than neat PHB films. © 2008 Springer-Verlag
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    Morphology of composite particles of single wall carbon nanotubes/biodegradable polyhydroxyalkanoates prepared by spray drying
    (Springer, 2010-01) Yun, SI; Lo, V; Noorman, J; Davis, J; Russell, RA; Holden, PJ; Gadd, GE
    Spray drying was investigated as a strategy for producing single wall carbon nanotube (SWCNT)/polymer composites. The spray-drying method produced SWCNT/poly(3-hydroxybutyrate) and SWCNT/poly(3-hydroxyoctanoate) composite particles in which the SWCNTs have been trapped in a well-dispersed state throughout the polymer matrix. Increasing SWCNT content in the composite led to a change in particle morphology from spherical and smooth to rosette shape with angular distortions. The technique shows potential for bulk carbon composite fabrication. © 2010, Springer.
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    PAMAM dendrimers as potential agents against fibrillation of α-synuclein, a parkinson's disease-related protein.
    (Wiley-VCH Verlag Berlin, 2009-03-10) Rekas, A; Lo, V; Gadd, GE; Cappai, R; Yun, SL
    The effect of PAMAM dendrimers (generations G3, G4 and G5) on the fibrillation of α-synuclein was examined by fluorescence and CD spectroscopy, TEM and SANS. PAMAM dendrimers inhibited fibrillation of α-synuclein and this effect increased both with generation number and PAMAM concentration. SANS showed structural changes in the formed aggregates of α-synuclein - from cylindrical to dense three-dimensional ones-as the PAMAM concentration increased, on account of the inhibitory effect. PAMAM also effectively promoted the breaking down of pre-existing fibrils of α-synuclein. In both processes-that is, inhibition and disassociation of fibrils-PAMAM redirected α-synuclein to an amorphous aggregation pathway. © 2009, Wiley-VCH Verlag Berlin
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    Spray-dried microspheres as a route to clay/polymer nanocomposites
    (Wiley-Blackwell, 2008-05-05) Yun, SI; Attard, DJ; Lo, V; Davis, J; Li, HJ; Latella, BA; Tsvetkov, F; Noorman, H; Moricca, SA; Knott, RB; Hanley, HJM; Morcom, M; Simon, GP; Gadd, GE
    A new strategy for the preparation of well-dispersed clays in a polymer matrix by a spray-drying method is presented. Scanning electron microscopy and transmission electron microscopy measurements show that the spray-drying process produces clay/polymer microspheres in which the clay is trapped in a well-dispersed state throughout the polymer matrix. The microspheres have been successfully extruded into clay/poly(methyl methacrylate) nanocomposite bulk structures without any perturbation of the well-dispersed clay nanostructure in the original microspheres. Transmission electron microscopy and small-angle X-ray scattering show that the clay particles in the extruded materials range from single platelets to simple tactoids composed of a few stacked clay platelets, indicating an excellent degree of dispersion. The results show that sprayed microspheres are very good precursors for further processing such as extrusion or melt blending with other polymers for bulk nanocomposite fabrication. © 2008, Wiley-Blackwell. The definitive version is available at www3.interscience.wiley.com
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    Thermal expansion of solutions of deuteromethane in fullerite C60 at low temperatures. Isotopic effect
    (American Institute of Physics, 2009-03) Dolbin, AV; Vinnikov, NA; Gavrilko, VG; Esel'son, VB; Manzheliĭ, VG; Gadd, GE; Moricca, SA; Cassidy, DJ; Sundqvist, B
    The thermal expansion of CD4 solutions in the orientational glass C60 with molar concentration of deuteromethane 20 and 50% has been investigated in the temperature range 2.5–23 K. The orientational glass CD4–C60 undergoes a first-order phase transition in the temperature interval 4.5–55 K. This transition is manifested as hysteresis of the linear thermal expansion coefficient α as well as maxima in the temperature dependences α(T) and τ1(T), where τ1 is the characteristic thermalization time of the experimental samples. The characteristic re-orientation times of the C60 molecules and the characteristic phase transformations occurring in the experimental solutions are determined. The results of the present study are compared with the results of a similar study of the solution CH4–C60. It is concluded that tunneling rotation of the CH4 and CD4 molecules occupying interstitial positions in the fullerite C60 lattice occurs. © 2009, American Institute of Physics
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    The world's smallest gas cylinders?
    (American Association for the Advancement of Science (AAAS), 1997-08-15) Gadd, GE; Blackford, MG; Moricca, SA; Webb, N; Evans, PJ; Smith, AM; Jacobsen, GE; Leung, S; Day, A; Hua, Q
    Argon gas was trapped at high pressure within hollow carbon tubes grown in vapor that have an outer diameter of between 20 and 150 nanometers. The gas was forced into the tubes by hot isostatically pressing (HIPing) the carbon material for 48 hours at 650°C under an argon pressure of 170 megapascals. Energy dispersive x-ray spectroscopy maps and line scans across the tubes show that the argon is trapped inside the bore and not in the tube walls. The room temperature argon pressure in these tubes was estimated to be about 60 megapascals, which indicates that equilibrium pressure was attained within the tubes at the HIPing temperature. These findings demonstrate the potential for storing gases in such carbon structures. © 1997 American Association for the Advancement of Science