Browsing by Author "Attard, DJ"

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    Characterisation and properties of low temperature ALD TiO2 films
    (Pielaszek Research, 2007-09-18) Triani, G; Evans, PJ; Campbell, JA; Latella, BA; Atanacio, AJ; Attard, DJ; Burford, RP
    The atomic layer deposition of films under conditions outside the ALD window involves additional processes that have to be accounted for in order to achieve good quality films. [1] In the present study, the growth of ALD TiO2 films on silicon and polycarbonate in the temperature range 80 - 120°C has been investigated in detail for two combinations of pulsing times. Furthermore, both substrate materials were exposed to a low-pressure water plasma to investigate the effect of pre-treatment on the deposited films. A suite of characterisation techniques including XRD, SIMS, RBS, AFM, XTEM and spectroscopic ellipsometry was used to probe the physical and chemical properties of the films. In addition, microtensile testing of the films enable the interface energy and toughness to be determined. These measurements showed water plasma treatment prior to deposition increased the interface energy and interface toughness from 11 to 26 Jm-2 and 1.24 to 1.96 MPa.m1/2 respectively. The contact angle of the TiO2 films was measured to assess their wettability. These tests involved subjecting the films to single and cumulative exposures of UV radiation followed by measurement of the contact angle. For an 85 nm film on polycarbonate, the contact angle decreased from 60° for the as-deposited surface to 10° following a 15 minute exposure. A 25 nm film yielded a similar decrease though this was only achieved after a 50 minute exposure. 1.M. Ritala and M. Leskelä, in Handbook of Thin Film Materials, Volume 1: Deposition and Processing of Thin Films, H.S. Halwa (ed.), Chap. 2, Academic, NY, 2002. © 2007 Pielaszek Research
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    Characterisation of epitaxial TiO2 thin films grown on MgO(0 0 1) using atomic layer deposition
    (Elsevier, 2005-11-15) Mitchell, DRG; Attard, DJ; Triani, G
    Thin films of TiO2 have been deposited onto MgO(0 0 1) substrates using atomic layer deposition at 300 °C. Plan and cross-sectional transmission electron microscopy (TEM), X-ray diffraction and atomic force microscopy have been used to understand the nature of the films. X-ray and electron diffraction showed that a polycrystalline, epitaxial anatase film was produced. The c-axis of the anatase was parallel to the MgO(0 0 1) surface with two orientational variants at right angles to each other in the plane of the film, each aligned with an MgO cube axis. Plan-view and cross-sectional TEM showed that the grain structure of the film reflected this orientation relationship, with the grain morphology comprising two sets of roughly tetragonal grains. Also present was a small fraction of equiaxed, anatase grains which were randomly oriented. Roughness measurement using atomic force microscopy showed that the epitaxial anatase films were quite smooth, in comparison to equivalent non-aligned films grown on silicon. Crown copyright © 2005. Published by Elsevier B.V.
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    The effect of a rapid heating rate, mechanical vibration and surfactant chemistry on the structure–property relationships of epoxy/clay nanocomposites
    (Multidisciplinary Digital Publishing Institute (MDPI), 2013-08-20) Nuhiji, B; Attard, DJ; Thorogood, GJ; Hanley, TL; Magniez, K; Bungur, J; Fox, B
    The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy) to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave manufacturing process equipped to generate rapid heating rates and mechanical vibration. The results suggested that the quaternary ammonium surfactant on C30B clay reacted with the epoxy during cure, while the primary ammonium surfactant (I.30E) catalysed the polymerisation reaction. These effects led to important differences in nanocomposite clay morphologies. The use of mechanical vibration at 4 Hz prior to matrix gelation was found to facilitate clay dispersion and to reduce the area fraction of I.30E clay agglomerates in addition to increasing flexural strength by over 40%. © 2013 by the Authors. This is an open access article distributed under the Creative Commons Attribution License.
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    The effect of alternate heating rates during cure on the structure-property relationships of epoxy/MMT clay nanocomposites
    (Elsevier, 2011-10-24) Nuhiji, B; Attard, DJ; Thorogood, GJ; Hanley, TL; Magniez, K; Fox, B
    This paper investigates the effect of both the mixing technique and heating rate during cure on the dispersion of montmorillonite (MMT) clay in an epoxy resin. The combination of sonication and using a 10 degrees C/min heating rate during cure was found to facilitate the dispersion of nanoclay in epoxy resin. These processing conditions provided a synergistic effect, making it possible for polymer chains to penetrate in-between clay galleries and detach platelets from their agglomerates. As the degree of dispersion was enhanced, the flexural modulus and strength properties were found to decrease by 15% and 40%, respectively. This is thought to be due to individual platelets fracturing in the nanocomposite. Complementary techniques including X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). transmission electron microscopy (TEM) and optical microscopy were essential to fully characterise localised and spatial regions of the clay morphologies. (C) 2011 Elsevier Ltd.
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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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    TEM of atomic layer deposition TiO2
    (Australian Society for Electron Microscopy, 2002-02-04) Mitchell, DRG; Attard, DJ; Triani, G
    Since the development of the atomic layer deposition (ALD) technique in the 1970s it has been widely used for the deposition of a range of binary, ternary and quaternary thin film systems (Niinisto 1996). The distinguishing feature of ALD is that the surface reactions are self limiting. Precursors saturate the adsorption sites, excess precursor is purged, followed by a pulse of reactant to form the film in-situ. Repetition of this deposition cycle permits films to be deposited to the desired thickness. Since the process is driven by adsorption, it produces films with outstanding conformality with the substrate (Ritala and Leskela, 1999), albeit at the expense of very slow deposition rates ( 50nm/hour). Following the recent commissioning of an ALD deposition system, we have been developing our expertise in the deposition and characterisation of TiO2 films in the first instance. These have potential uses in applications such as optical coatings, photovoltaics, sensors and catalysts. The focus of this paper is to report our plan view and cross-sectional transmission electron microscopy (TEM) studies on these films. Despite the power of the TEM technique, it has enjoyed very limited application to the study of any ALD films to date. Our results describe a detailed picture of the evolution of the film morphology under the influence of deposition temperature and surface chemistry of the substrate. These factors influence the nucleation of crystallisation within the films. Plasmon imaging, energy filtered imaging and electron energy loss spectroscopy enable the films to be characterised at the nanometer scale. ©2002 Australian Society for Electron Microscopy Inc