Off-target contamination (or spray drift) during agricultural chemical application, arising from removal of small (diameter < 100 m) droplets from sprays by atmospheric or vehicle-generated cross flows, is investigated experimentally. The primary requirement for realistic wind tunnel studies is identified from background review as matching the full-scale logarithmic man velocity profile with suitable surface roughness parameters. A general calculation scheme is presented for spacing horizontal flat plates to simulate weakly-sheared mean velocity profiles. Adequate full-scale matching of logarithmic mean velocity profiles is achieved after systematic equipment modification. Comparative field and wind tunnel experiments using single nozzles show adequate agreement following the above approach, indicating that air entrained into the liquid spray stabilizes the spray to the cross flow action. Measurements within an agricultural spray in still air show that small droplets are passively transported within the entrained air field, whose characteristic turbulence length scale is too small to contribute to droplet dispersion. Wind tunnel studies employing conventional sprays show small droplet removal associated with regions where the entrained air velocity is less than the cross flow velocity, with essentially passive downwind transport. Numerical simulations of spray drift must clearly incorporate characteristics of the entrained air velocity field.

Bacteria are used to ‘grow’ and scaffold precious metal nanoparticles possessing certain catalytic activities. Focusing on Escherichia coli, this thesis aims to investigate the catalytic behaviours of E. coli-supported palladium (bio-Pd/E. coli) or bimetallic gold-palladium (bio- AuPd/E. coli) in hydrogenations and oxidations operated in laboratory-scale three-phase slurry reactors. A discussion of hydrodynamics, mass transfer, reaction mechanisms and corresponding reaction performance is systematically presented for two major industrially important reactions: soybean oil hydrogenation and benzyl alcohol oxidation. Thermogravimetric analysis indicated a suitable operating temperature of below 175\(^0\)C for the E. coli-supported catalyst. A loading of 5 wt%Pd on E. coli showed an average particle size of 4.31 nm estimated by TEM measurements and a crystallite size of 4.12 nm using Scherrer’s equation from obtained X-ray powder diffraction data. This was smaller than an active particle diameter of 12.77 nm for 5wt%Pd/Al\(_2\)O\(_3\) (determined by CO chemisorption). It is concluded that biomass-supported precious metal catalyst is an environmentally attractive alternative to conventional heterogeneous catalyst for application in industrial catalytic processes.

Aggregation of asphaltenes has attracted interest due to the impact on the crude-oil industry. Despite extensive studies on the molecular-structure of natural asphaltene, fundamental knowledge of their aggregation is incomplete. It is unclear how the driving forces of association are related to the molecular architecture and the solvent species, which ultimately affect the aggregation mechanism. In this dissertation, dynamic-light-scattering (DLS) experiments and molecular-dynamics (MD) simulations were performed to investigate the relation between asphaltene chemical-structure and solvent species. The model compounds studied isolate the driving forces of aggregation by varying the peripheral chain-length and functional-groups (triphenylene-cored models) in organic solvents. The results isolate the structure-function relationships. Increasing the chain length imposes restriction upon the nanoaggregate formation, while non-centrosymmetric models appear to be more prone to aggregation. Furthermore, polar components in asphaltene molecular-architecture are observed to increase aggregation potential, more than π-stacking. Hexabenzocoronene-cored models exhibit a structurally selective aggregation mechanisms, as the planar molecules are more liable to aggregate and precipitate than the non-planar models due to π-stacking hindrance. The motivation behind the development and testing of model polyaromatic compounds lies in the pursuit of isolating the source structural-dependence of the compounds interactions. This is done by assessing the solute-solute and solute-solvent associations by experimental and computational approaches, to underpin the structure-to-function relation dictated by aromatic and/or polar molecules in aromatic or aliphatic solvents. This dissertation provides insight for the aggregation of model compounds of varying molecular architectures, and sheds light on the intermolecular interactions affected by these variations and the solvent species.

The modelling of two key areas of transport phenomena in a new polymetallic smelter has been achieved by using both mathematical andphysical models to investigate optimum operating conditions. A study of oxygen mass transfer caused by multiple top-blown, subsonic gas jets contacting water flowing in a full-scale channel model of the smelter converting hearth has been carried out. A liquid phase solute mass transfer model that incorporates a flowing liquid phase has been developed. It has been used to compare mass transfer for both open-packed and close-packed multiple lance arrays of 2.26 mm, 4.95 mm, 10.95 mm and 24.40 mm nozzles delivering the same quantity of gas. It was found that for fewer lances of the larger nozzle diameters, up to a 75% reduction in liquid phase mass transfer occurred especially for the close-packed configurations. This restriction of mass transfer will result in reduced metal losses in the analogous smelter situation. Over a wide range of channel flowrates the mass transfer coefficient was found to be independent of water velocity. A computer model that predicts the amount of fog formation in the zinc vacuum condenser of the smelter for binary vapour/gas mixtures has identified operating conditions most susceptible to vapour fogging and subsequent metal losses. A fog problem is most likely to occur in condensable mixtures with high vapour concentrations and low initial quantities of superheat, and at low cooling wall temperatures as well as at high total pressures. Any lead in a Pb/Zn/N\({_2}\) condensable mixture will fog heterogeneously at least 400°C before zinc droplets form and act as condensation nuclei for the zinc vapour. An engineering approach to estimating quantities of homogeneous fog formation has been developed and is used to analyse the performance of the Imperial Smelting Furnace zinc condenser and the Port Pirie Vacuum Dezincing Unit.

Nanostructured MoS\(_2\) and ZnFe\(_2\)O\(_4\) were synthesised and tested as catalytic water splitting photoelectrodes. MoS\(_2\) was nanopatterned from a bulk crystal using a combination of nanosphere lithography and plasma etching. Three morphologies were produced: nanospheres deposited with interstices between them produced nanopillars, nanospheres squashed into hexagons imprinted a nanowell pattern, and linked nanopillars resulted from parts of each. The MoS\(_2\) was tested as a photocathode and morphologies with linkages between features had improved catalysis than those without. This was attributed to the layered structure of MoS\(_2\). These samples degraded in air to MoSxO(\(_2\)\(_-\)\(_x\)), and an electrochemical technique utilising Na\(_2\)S\(_2\)O\(_3\) was used to re-sulfidate the MoSxO(\(_2\)\(_-\)\(_x\)). The technique decreased the onset potential from -0.27 V SHE to -0.17 V SHE, and the Tafel slope from 282 mV dec\(^{-1}\) to 87 mV dec\(^{-1}\). ZnFe\(_2\)O\(_4\) electrodes were deposited by AACVD from a precursor molecule. The deposition solvent composition was systematically altered between methanol and ethanol to examine its effect on the nanostructure. ZnFe\(_2\)O\(_4\) electrodes deposited from predominantely methanol solvent had compact morphologies due to heterogenous nucleation, while the electrodes deposited from predominantly ethanol solvent had high surface area structures due to homogeneous nucleation. The more exothermic enthalpy of combustion of ethanol was deemed responsible.

Hydrocolloid materials have been used for some time in the fields of regenerative medicine and drug delivery. Despite a significant body of work, to date the majority of research in the area has focused on relatively simple compositions and microstructures. In comparison, the food industry has long used refined and often subtle methods to structure and thereby tailor the release and handling properties of a vast range of similar materials. In this thesis, a range of processing methodologies has been used to generate novel materials intended for use in the regenerative medicine and drug delivery using gellan and kappa carrageenan. The thesis demonstrates how even small changes in process conditions can result in significant changes in the way a material handles and may deliver therapeutic molecules. This thesis has demonstrated that gellan can be used to form robust quiescent structures, as well as shear thinning fluid materials by changing the processing and formulation. Furthermore, it was demonstrated that it was possible to generate a novel cell delivery device by the hydration of kappa carrageenan in warm biomedical buffers. Overall this thesis demonstrates the range and complexity of structures that can be produced using the relatively small number of polymers.

Tightening legislation for vehicles across the world has caused the use of monolith catalysts in automotive emission control to become ubiquitous. Control of the adherence and homogeneity of the platinum group metal (PGM) coating onto the monolith block, to maximise catalytic performance for a minimum PGM loading, is therefore paramount. In this study, an automatic film application is used for coating γ–alumina slurries onto Fecralloy®, an integral component of metallic monolith catalysts, to achieve the desired coating properties. Upon coating of the Fecralloy® coupons, the samples preoxidised for 10 h gave the best performance in terms of coating loading (7.94 mass %) and adherence (< 10 mass % loss) based on ultrasonic vibration test. These conditions produced the optimal surface topography, typified by conspicuous and randomly-oriented α–alumina whiskers which promote coating adherence. The optimal coating loading and adherence were achieved at a pH of 4 and solids concentrations not exceeding 40 wt%. A newly devised technique using the electromechanical testing system showed that finest particle coatings of 40 wt% solids concentration produced the best coating adherence. At solids concentration of 45 wt% the coating adherence was poor and insensitive to the blends of different particle size distributions.

The studies of biointerfaces, interfaces between synthetic materials and biological systems, such as bacteria, represent, by definition, a highly interdisciplinary field spanning across the disciplines of physics, materials science, engineering, chemistry, biology, bioinformatics and medicine. The main approach in biointerfacial science involves the preparation and characterisation of functional surfaces for specific interactions with bio-systems, and studies of the molecular and kinetic processes occurring at such interfaces, ranging from small molecules and biomolecular interactions, to cell and bacteria adhesion. Advanced material engineering techniques, such as self-assembly can structure surfaces that allow dynamic tuning of their properties (i.e. wettability and superficial charge). Recently, switchable surfaces able to undergo conformational switching in response to an applied external stimulus were shown to be suitable platforms for controlling cellular responses. In this context, the design and fabrication of a two-component electrical switchable SAM able to undergo conformational reorientation upon an applied electrical stimulus will be described. This dynamic platform will be used for the first time to gain new insights on the non-specific bacterial adhesion to surfaces in real-time.

Moromi fermentation is an essential part of soy sauce production. This thesis aimed to characterize and control the growth and interaction of two predominant microorganisms, Tetragenococcus halophilus and Zygosaccharomyces rouxii for enhancing the aroma development during moromi fermentation. Antagonism was observed between T. halophilus and Z. rouxii, regardless of the inoculation sequence. However, sequential inoculation of Z. rouxii resulted in more complex aroma profile than simultaneous inoculation. To eliminate antagonism, chitosan-coated alginate and water-oil-water (W1/O/W2) double emulsions (DEs) were tested for their ability to encapsulate Z. rouxii and stability in high NaCl solutions. Alginate was unstable in high NaCl solutions and chitosan exhibited undesirable antimicrobial activity towards Z. rouxii. DEs minimized the antagonism between T. halophilus and Z. rouxii, by segregation in the external W2 and internal W1 phase, respectively. Physicochemical changes in the fermentation medium indicated that DEs affected microbial growth and cell physiology, contributing to the elimination of antagonism. The destabilization of DEs over 30-day storage depended on glucose concentration in W2, which indicated a possibility of sustained release mechanism of Z. rouxii into the moromi. Furthermore, the application of DEs was tested in a moromi model, formulated with reduced NaCl and/or substitution with KCl. DEs resulted in moromi with similar microbiological and aroma profile to that of high-salt. Overall, this thesis demonstrates the potential of DE for delivering mixed cultures in moromi fermentation, which could be applicable in any fermentation process where multiple species are required to act sequentially.

This thesis investigates how the properties of foams can be modulated by the addition of particles to the foam solution. As a model system hydrophobic and hydrophilic silica particles were used. The de-agglomeration of hydrophilic silica particles in water and surfactant solutions was studied. Two methods are investigated: ultrasound cavitation (UC) and mechanical agitation (MA). The efficiency of these two methods was compared with respect to their ability to produce foams and to de-agglomerate both hydrophilic and hydrophobic silica particles. The same particles were used as additions to protein and surfactant foaming solutions. In the experiments, the amount and types of particles, proteins and surfactants were varied in the foaming dispersions. Then UC and MA were used to foam the dispersions and the drainage, breakage and microstructure of the resulting foams were examined. In the protein foaming solutions, both casein and whey protein foams were considered. In the surfactant foaming solution, C12LAS and CTAB were used. Partially hydrophobic silica particles were used in pure water to generate foam. Foamability and foam stability both increased with increasing concentration of particles. Moderately hydrophobic particles gave optimum foamability whilst no foam could be produced with fully hydrophilic particles. In the foam rheology test, a transition from solid-like to liquid-like behaviour was found while the foam with addition of SCMC exhibited no such transition.