Optimising Ambient Setting Bayer Derived Fly Ash Geopolymers.

The Bayer process utilises high concentrations of caustic and elevated temperature to liberate alumina from bauxite, for the production of aluminium and other chemicals. Within Australia, this process results in 40 million tonnes of mineral residues (Red mud) each year. Over the same period, the energy production sector will produce 14 million tonnes of coal combustion products (Fly ash). Both industrial residues require impoundment storage, yet combining some of these components can produce geopolymers, an alternative to cement. Geopolymers derived from Bayer liquor and fly ash have been made successfully with a compressive strength in excess of 40 MPa after oven curing. However, any product from these industries would require large volume applications with robust operational conditions to maximise utilisation. To facilitate potential unconfined large-scale production, Bayer derived fly ash geopolymers have been optimised to achieve ambient curing. Fly ash from two different power stations have been successfully trialled showing the versatility of the Bayer liquor-ash combination for making geopolymers.

Effects of thermal denaturation on the solid-state structure and molecular mobility of glycinin.

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. (13)C NMR results supported this hypothesis.

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.

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 pI 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.

The versatile colour gamut of coatings of plasmonic metal nanoparticles.

We have investigated the colour gamut of coatings produced by the growth of plasmonically-active coatings of cap-shaped Au or Ag nanoparticles on a transparent substrate. The control of colour and spectral selectivity that can be obtained by the manipulation of the rates of nucleation and growth were explored using a combination of experiment and calculation. In our experimental work the Au nanoparticles were grown in situ using a wet chemical electroless plating technique while the Ag nanoparticles were produced by physical vapour deposition. The optical properties were numerically simulated using the discrete dipole approximation. The resulting measured or calculated transmission spectra were mapped to the CIE L-a -b colour space. The aspect ratio of the nanoparticles was the primary factor in determining the colours in both cases. However, increasing the nucleation rate of the particles resulted in them becoming more closely packed, which also red-shifted the optical extinction peak of the structure due to interactions of their near-fields. This caused an enhancement in the blue component of the transmitted light. Coatings of Ag particles had a significantly wider and brighter colour gamut than those of Au.

Micro- and nano-indentation of a hydroxyapatite-carbon nanotube composite.

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.

Structure and molecular mobility of soy glycinin in the solid state.

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 (approximately 10(-6) to 10(-3) s) reveals transitions at a higher moisture content (>17%) than DSC or SAXS, which sample for much longer times (approximately 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.