Browsing by Author "Kealley, CS"

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    Application of small-angle scattering to study the effects of moisture content on a native soy protein
    (Wiley-Blackwell, 2008-06) Kealley, CS; Elcombe, MM; Wuhrer, R; Gilbert, EP
    The nano-and microstructure of glycinin, a soybean protein, has been investigated as a function of moisture for moisture contents between 4 and 21 wt%. Glycinin exhibits peaks in the small-angle region whose positions show minimal change with X-rays for samples up to 13% moisture. However, the use of neutron scattering, and the associated enhancement in contrast, results in the Bragg peaks being well resolved up to higher moisture contents; the associated shift in peak positions between 4 and 21% moisture are consistent with the expansion of a hexagonal unit cell as a function of moisture content. A Porod slope of similar to-4 indicates that the interface between the 'dry' protein powder and the surrounding medium at a length-scale of at least 3 mm down to similar to 20 nm is smooth and sharp. Scanning electron microscopy indicates that the powders, with low moisture content, have a porous appearance, with the porosity decreasing and microstructure expanding as the moisture content increases. © 2008, Wiley-Blackwell.
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    AuCuAl shape memory alloys for use in nano-actuators
    (Australian Institute of Physics, 2010-02-02) Bhatia, VK; Kealley, CS; Thorogood, GJ; Dowd, A; Cortie, MB
    Although Al, Au and Cu each has the face centered cubic structure in elemental solid form, they do not readily alloy with one another, and instead form a series of binary and ternary intermetallic compounds. The ternary system is very interesting and contains, amongst other features, an 18-carat shape memory electron compound sometimes called ‘Spangold’ [1] ( Figure 1). Shape memory alloys are remarkable in that they have the ability to return to their initial state and shape after being deformed. This ability arises from a martensitic (displacive) phase transformation (see Figure 2), which is strongly influenced by temperature, crystal structure and degree of ordering. It is already known that the parent phase of ‘Spangold’ must contain at least a minimum degree of ternary ordering before the reversible displacive transformation needed for the shape memory effect can take place [3]. Furthermore, the parent phase has been found to have the L21 ordered body-centered cubic packing arrangement [4], while it has been reported that the martensite can be described using a monoclinic unit cell [5]. Here we examine the possibility of using this compound as a nano-actuator. Magnetron sputtering was used to deposit the Au, Cu and Al. The films were then characterized using x-ray reflectometry (see figure 3), grazing incidence X-ray diffraction, scanning electron microscopy and atomic force microscopy. The properties of these films are compared with that of bulk samples.
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    Determination of martensite structures of the Au7Cu5Al4 and Au7Cu5.7Al3.3 shape-memory alloys
    (Elsevier, 2014-10-15) Elcombe, MM; Kealley, CS; Bhatia, VK; Thorogood, GJ; Carter, DJ; Avdeev, M; Cortie, MB
    The β-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation for which several conflicting martensite phases have been reported. Here we show the significance of the cooling temperature used to obtain the martensite. If Au7Cu5Al4 is cooled from the parent phase condition to cryogenic temperatures, e.g. below 200 K, the martensitic phase is orthorhombic (space group Pcmn, a = 4.4841 Å, b = 5.8996 Å, c = 17.8130 Å); however, when this composition is cooled to only ∼260 K it will in general consist of a mixture of orthorhombic and monoclinic phase (the latter has space group P21/m, a = 4.4742 Å, b = 5.9265 Å, c = 13.3370 Å, β = 91.425°). In contrast, a sample with decreased Al content (Au7Cu5.7Al3.3) transforms fully to monoclinic phase if cooled to ∼260 K. © 2014 Acta Materialia Inc.
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    Development of carbon nanotube reinforced hydroxyapatite bioceramics
    (Elsevier B. V., 2005-11-27) Kealley, CS; Elcombe, MM; Ben-Nissan, B; van Riessen, A
    This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single phase synthetic hydroxyapatite (HAp) have been determined. Neutron and X-Ray diffraction have been used extensively to follow the effects of drying and heat treatments on the process and to confirm that the final material is single phase. The neutron diffraction data has enabled the positions of the hydroxide bonds to be determined. Subsequent development of a technique to produce a HAp + carbon nanotube composite material is also reported. A method has been determined to remove the soot impurity from the nanotubes with minimal degradation of the nanotube. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained in the structure while most of the remaining soot has burnt off. Small angle neutron scattering, in conjunction with transmission electron microscopy, also shows preservation of the carbon nanotubes. Mechanical property testing is in progress and results will be reported. © The Authors
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    Development of carbon nanotube-reinforced hydroxyapatite bioceramics
    (Elsevier B. V., 2006-11-15) Kealley, CS; Elcombe, MM; van Riessen, A; Ben-Nissan, B
    This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single-phase synthetic hydroxyapatite (HAp) and a HAp and carbon nanotube (CNT) composite material have been optimised. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained intact within the structure, while most of the remaining soot has burnt off. Small-angle neutron scattering, in conjunction with scanning electron microscopy (SEM), also shows preservation of the CNTs. Hot isostatically pressed samples showed excellent densification. Neutron diffraction data has enabled the positions of the hydroxide bonds to be determined, and shown that the addition of the CNTs has had no effect on the structural parameters of the HAp phase, with the exception of a slight reduction in the unit cell parameter α . © 2006 Elsevier B.V.
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    Dynamical transition in a large globular protein: macroscopic properties and glass transition
    (Elsevier, 2010-01) Kealley, CS; Sokolova, AV; Kearley, GJ; Kemner, E; Russina, M; Faraone, A; Hamilton, WA; Gilbert, EP
    Hydrated soy-proteins display different macroscopic properties below and above approximately 25% moisture. This is relevant to the food industry in terms of processing and handling. Quasi-elastic neutron spectroscopy of a large globular soy-protein, glycinin, reveals that a similar moisture-content dependence exists for the microscopic dynamics as well. We find evidence of a transition analogous to those found in smaller proteins, when investigated as a function of temperature, at the so-called dynamical transition. In contrast, the glass transition seems to be unrelated. Small proteins are good model systems for the much larger proteins because the relaxation characteristics are rather similar despite the change in scale. For dry samples, which do not show the dynamical transition, the dynamics of the methyl group is probably the most important contribution to the QENS spectra, however a simple rotational model is not able to explain the data. Our results indicate that the dynamics that occurs above the transition temperature is unrelated to that at lower temperatures and that the transition is not simply related to the relaxation rate falling within the spectral window of the spectrometer. © 2010, Elsevier Ltd.
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    Effects of thermal denaturation on the solid-state structure and molecular mobility of glycinin
    (American Chemical Society, 2011-06-01) Huson, MG; Strounina, EV; Kealley, CS; Rout, MK; Church, JS; Appelqvist, IAM; Gidley, MJ; Gilbert, EP
    The effects of moisture and thermal denaturation on the solid-state structure and molecular mobility of soy glycinin powder were investigated using multiple techniques that probe over a range of length and time scales. In native glycinin, increased moisture resulted in a decrease in both the glass transition temperature and the denaturation temperature. The sensitivity of the glass transition temperature to moisture is shown to follow the Gordon-Taylor equation, while the sensitivity of the denaturation temperature to moisture is modeled using Flory's melting point depression theory. While denaturation resulted in a loss of long-range order, the principal conformational structures as detected by infrared are maintained. The temperature range over which the glass to rubber transition occurred was extended on the high temperature side, leading to an increase in the midpoint glass transition temperature and suggesting that the amorphous regions of the newly disordered protein are less mobile. C-13 NMR results supported this hypothesis. © 2011, American Chemical Society
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    High temperature transformations of the Au7Cu5Al4 shape-memory alloy
    (Elsevier, 2011-02-24) Cortie, MB; Kealley, CS; Bhatia, VK; Thorogood, GJ; Elcombe, MM; Avdeev, M
    The β-phase of Au7Cu5Al4 undergoes a reversible shape-memory phase transformation, however there has been some uncertainty regarding the crystal structure or structures of the parent phase. Here we show that, under equilibrium conditions, the parent phase possesses the L21 structure between its Ap (about 79°C) and 630°C, and the B2 primitive cubic structure between 630°C and its melting point. It melts directly from B2 into the liquid state and hence never achieves the random bcc A2 structure that has been previously mooted. Splat-cast samples of the alloy are martensitic, proving that development of equilibrium order and defect concentration are not pre-requisites for the A → M transformation to occur. © 2011, Elsevier Ltd.
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    Hydration induced structural changes in native, denatured and protected soy glycinin (11s)
    (Institute of Food Technologists, 2007-07) Appelqvist, IAM; Rout, MK; Chanvrier, H; Dezfouli, M; Kelly, M; Htoon, AK; Kealley, CS; Gilbert, EP; Strounina, E; Whittaker, AK; Gidley, MJ; Lillford, PJ
    Proteins and other biomolecules undergo a dynamic transition to a glass-like solid state with small atomic fluctuations. This dynamic transition can inhibit biological function and alter their material properties.
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    Martensite destabilization in Au7Cu5Al4 shape-memory alloy
    (Elsevier, 2011-03) Bhatia, VK; Kealley, CS; Prior, MJ; Cortie, MB
    Aging-induced changes in the austenite peak (Aρ) temperature of Au7Cu5Al4 shape-memory alloy are investigated. Whereas heat treating the parent phase at temperatures >140°C or aging the martensite for long times at room temperature both stabilized the Aρ to ~80°C, low-temperature excursions into the parent phase caused the subsequent Aρ to drop to ~60°C and the transformation hysteresis to decrease. The evidence indicates that this destabilization of the martensite is caused by time-dependent relaxation of elastic constraint due to parent-phase lath migration during the preceding low-temperature austenitizing treatment. This mechanism of aging is different from that of the better-known symmetry-conforming short-range order phenomenon. © 2011, Elsevier Ltd.
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    Micro- and nano-indentation of a hydroxyapatite-carbon nanotube composite
    (American Scientific Publishers, 2008-08) Kealley, CS; Latella, BA; van Riessen, A; Elcombe, MM; Ben-Nissan, B
    The mechanical properties of pure synthetic hydroxyapatite and hydroxyapatite-carbon nanotube composites were examined. Vickers microhardness and nanoindentation using a Berkovich tipped indenter were used to determine the hardness, fracture toughness and Young's modulus of the pure hydroxyapatite matrix and the composite materials. Microscopy showed that for the composites produced the carbon nanotubes were present as discrete clumps. These clumps induced a detrimental effect on the hardness of the materials, while the fracture toughness values were not affected. This would be undesirable in terms of using the material for biomedical implant applications. It should be noted that the carbon nanotubes used contained free graphite. As the properties of the composite materials studied were not greatly improved over the matrix, it is speculated that if the graphite phase were removed from the reagent, this could in-turn enhance the properties of the material. © 2008, American Scientific Publishers
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    Microstrain in hydroxyapatite carbon nanotube composites
    (Wiley-Blackwell, 2008-01-15) Kealley, CS; Elcombe, MM; van Riessen, A
    Synchrotron radiation diffraction data were collected from hydroxyapatite–carbon nanotube bioceramic composites to determine the crystallite size and to measure changes in non-uniform strain. Estimates of crystallite size and strain were determined by line-profile fitting of discrete peaks and these were compared with a Rietveld whole-pattern analysis. Overall the two analysis methods produced very similar numbers. In the commercial hydroxyapatite material, one reflection in particular, (0 2 3), has higher crystallite size and lower strain values in comparison with laboratory-synthesized material. This could indicate preferential crystal growth in the [0 2 3] direction in the commercial material. From the measured strains in the pure material and the composite, there was a degree of bonding between the matrix and strengthening fibres. However, increasing the amount of carbon nanotubes in the composite has increased the strain in the material, which is undesirable for biomedical implant applications. © 2008, Wiley-Blackwell
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    Small-angle x-ray scattering study of the effect of pH and salts on 11S soy glycinin in the freeze-dried powder and solution states
    (American Chemical Society, 2010-01-27) Sokolova, AV; Kealley, CS; Hanley, TL; Rekas, A; Gilbert, EP
    The nanostructures from powders of native protein, glycinin, and corresponding solutions from which the powders have been formed, have been studied as a function of pH and 1 M salts using small-angle X-ray scattering. All powders showed Porod scattering with the exception of that prepared from the solution close to pl which displayed fractal behavior. Well-defined Bragg peaks in the powder scattering at pH 5, pH 7, and 1 M NaCl indicate the presence of long-range order. The scattering from solutions at pH 7, pH 9, and 1 M NaCl can be described well on the basis of particles derived from the known atomic structures of homohexameric glycinin. Extreme acidic (pH 2) and basic (pH 11) environments lead to the partial denaturation of glycinin. Decreasing the pH to 2 initiates dissociation of the hexameric structure, while increasing the pH to 11, as well as the presence of 1 M NaSCN, results in the formation of large unimodal particles. This is reflected by "featureless" SAXS patterns for both powders and solutions. © 2010, American Chemical Society
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    Structure and molecular mobility of soy glycinin in the solid state
    (American Chemical Society, 2008-10) Kealley, CS; Rout, MK; Dezfouli, MR; Strounina, E; Whittaker, AK; Appelqvist, IAM; Lillford, PJ; Gilbert, EP; Gidley, MJ
    We report a multitechnique study of structural organization and molecular mobility for soy glycinin at a low moisture content (<30% w/w) and relate these to its glass-to-rubber transition. Small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy are used to probe structure and mobility on different length and time scales. NMR (similar to 10(-6) to 10(-3) s) reveals transitions at a higher moisture content (> 17%) than DSC or SAXS, which sample for much longer times (similar to 10 to 10(3) s) and where changes are detected at > 13% water content at 20 degrees C. The mobility transitions are accompanied by small changes in unit-cell parameters and IR band intensities and are associated with the enhanced motion of the polypeptide backbone. This study shows how characteristic features of the ordered regions of the protein (probed by SAXS and FTIR) and mobile segments (probed by NMR and DSC) can be separately monitored and integrated within a mobility transformation framework. © 2008, American Chemical Society
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    Structure determination of gold-based shape memory alloy
    (Australian Institute of Physics, 2009-02-04) Kealley, CS; Bhatia, VK; Thorogood, GJ; Elcombe, MM; Cortie, MB
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