Ceramic cores are utilised during turbine blade manufacture to develop cooling channels within the finished component. These cores, fabricated by ceramic injection moulding, must possess an array of properties to ensure minimal defect development during casting. The carrier system, powder interactions and component forming, critical in ceramic injection moulding, have been investigated within this project. The binder systems were developed using paraffin wax, ethylene vinyl acetate and polyethylene with stearic acid incorporated as a surfactant. Binder system development illustrated that a wide range of melting, rheological and mechanical properties could be produced by binder blending. The moulding success was improved by feedstock optimisation, with optimal surfactant levels determined between five and ten ‘layers’ upon the powder surface. Optimisation maximised the achievable ceramic solids loading, measured and estimated by density and rheological methods. Binder systems illustrating a good resistance to fracture with adequate flow characteristics have been shown to successfully form complex cores to high yields. Success in component forming was limited by feedstock fluidity, final components were more prone to crack development when the binder system had reduced crack resistance and success of the wicking process was limited in some systems by formulation with proposed mechanisms explained.

The mixing of complex fluids in stirred reactors is widly used in many industries. Mechanically agitated vessels are widely used in these industries such as wastewater treatment, pharmaceuticals, nuclear and food processing. Complex fluids are frequently encountered in these industries. There is growing interest in developing and studying these fluids, especially for those of shear thickening (ST) behaviour, due to the importance of their industrial applications such as flexible body armor and force damping applications which can protect a person from danger or risk and ultimately saveone’s life. Little work has been done to understand how to mix complex fluids effectively, mainly because of their opaque nature. In this thesis, new ST fluids formulations were developed and these fluids were used as a model fluid for mixing studies. The flow field in an opaque ST fluid was determined experimentally using the positron emission particle tracking (PEPT). In addition, the performance of axial, radial and mixed flow impellers in mixing complex fluids have been also studied using different experimental techniques and the computational fluid dynamics (CFD) simulations. Moreover, for the first time, PEPT has been used to investigate the flow field of floating particles in a stirred vessel. PEPT was used to investigate the two-phase flow field inside a stirred vessel of polypropylene particles in different types of rheological fluids, at the just drawdown speed for a wide range of solid concentrations from 1.8 vol% up to 46 vol%. The outcomes of this thesis are beneficial to many chemical processes, such as e.g. formulation processes in the pharmaceutical industry, whereby an essential step in the product development involving powder mixing is the ability to drawdown the floating solids. In addition, the outcome of this thesis can also be beneficial in identifying the ideal configuration of stirred vessels used in chemical processes where mixing is the central feature, for example, in the food and rubber industries. Moreover, the newly developed complex fluids (shear thickening fluids) can be used in many industrial and commercial applications such as in the defence industry (as liquid body armor) and also as part of the protective devices designed to minimise head and neck injuries that occur in some sports accidents such as in car racing, football, ice hockey etc.

A formulation process for CaCO3 spheres (D50 of 5.1 μm) for use as a functional filler in decorative paints was optimised. This increased the yield of CaCO3 spheres 20-fold and made the process less hazardous, with organic oils, namely rapeseed oil, being used successfully as a replacement for toluene. The CaCO3 spheres contained a multitude of < 250 nm nanovoids, with some spheres containing a core void > 800 nm. These pores formed because the crystals nucleated at the interface of emulsion droplets, resulting in CaCO3 spheres (2.42 g cm-3; 2,420 kg m-3) composed of calcite and vaterite, with a density lower than either mineral (2.71 g cm-3 (2,710 kg m-3) and 2.65 g cm-3 (2,650 kg m-3), respectively). The characterisation and performance of CaCO3 spheres in paint formulations were compared against commercially available products, namely Microdoll H600 (5 μm dolomite). There was no opacity benefit, however a 4-fold scrub resistance benefit was observed. Different oils can be used in the emulsification step in CaCO3 spheres production whilst others cannot, most likely because of the ratio of mono- to poly-unsaturated fatty acids. A technique for improving scrub resistance of other mineral extenders was developed, with AkzoNobel continuing the research into this area.

This thesis considers the role fluids play in improving the efficiency and reducing the environmental impact of modern gas turbines. This includes gas turbines used in aviation, marine propulsion and power generation applications. There are two discrete means of lowering the environmental impact of gas turbines. Improving the thermal efficiency of the gas turbine is one possible route which works by reducing the required fuel consumption. Another route which is indirectly related to engine technology is the use of renewable fuels (biofuels) which have reduced lifecycle carbon dioxide emissions when compared to crude oil derived fuels. As such this thesis examines both the potential of renewable fuels for use in gas turbines and also the impact of increased efficiency on the fluids contained within a gas turbine.

The handling properties of dough were assessed by subjecting a wide variety of dough types to compression. The parameters varied included our variety, mixing time and addition of ingredients such as enzymes, to give doughs with a range of softness and stickiness behaviour. Approximately spherical dough samples were compressed at a constant speed, between lubricated and non-lubricated plates, to a set strain, with contact area assessed using image analysis. Various parameters from the test were compared to baker's assessments of softness and stickiness. A stickiness ratio based on the ratio of adhesive to cohesive components was investigated. Farinograph values were considered but found not to relate to dough behaviour. Compression energy per unit area gave strong correlations with baker's assessments, with softness giving the strongest correlations. Compression was found to give better results than pull-off. Level of water addition had the greatest influence on results. This compression method was assessed against a Quantitative Dough Handling Assessment (QDHA) developed in this work. The energy per unit area correlated well with the QDHA suggesting the potential for the compression method to be used to predict dough handleability. This supports the hypothesis that rheology is key to dough stickiness.

This work investigates the laminar mixing performance of viscoelastic fluids in laboratory-scale batch stirred tanks agitated by “butterfly” impellers and in-line Kenics KM static mixers. Constant-viscosity viscoelastic (Boger) fluids were formulated to investigate viscous and elastic effects separately; multiphase viscoelastic suspensions were formulated from 40-50 volume% glass spheres in glycerol. Particle Image Velocimetry in stirred tanks agitated by high impeller-to-tank diameter ratio butterfly impellers (D/T=0.98) showed that secondary flows in Boger fluid increased solid body rotation and reduced local shear rates (≤16 s-1) compared to equivalent viscosity Newtonian fluids, though the effect was non-monotonic. Mixing times obtained from Planar Laser Induced Fluorescence (PLIF) increased by ≤23%. Positron Emission Particle Tracking in multiphase suspensions showed increased axial mixing due to more dominant secondary flows. In static mixers, Boger fluid striation patterns at the mixer outlet obtained from PLIF showed time dependence and flow instability due to reduced local shear rates. Energy consumption in all geometries displayed an increase of ≤200% with viscoelastic fluids. Using a generalised Reynolds number Reg enabled viscoelastic power draw prediction, previously only possible through empirical relationships. Overall, viscoelasticity generally increases energy consumption whilst reducing blending performance though the link between elasticity and mixing quality is highly non-linear.

The power draw and emulsification performance of in-line rotor-stator mixers were investigated experimentally and theoretically, to predict droplet size as a function of process and formulation variables and to establish scale-up rules. The effect of process conditions, three mixer scales and thirteen rotor-stator geometry configurations on emulsification performance were investigated. Emulsions of a wide range of silicone oil viscosities of varying phase volumes, dispersed in aqueous surfactant and non-surfactant solutions were studied. For lab to factory scale in-line rotor-stator mixers, the most appropriate scaling parameter for mean drop size was tip speed at constant residence time for single and multiple passes. At a single scale, the stator open area was the rotor-stator geometry parameter which had the greatest effect on power draw and emulsification in turbulent flow. Mean drop size was a strong function of the rotor speed, dispersed phase viscosity, interfacial tension, and less dependent upon the mixer flow rate, continuous phase viscosity and dispersed phase volume fraction (for surfactant systems). Correlation of mean drop size with energy dissipation rate indicated that droplet break-up mainly depends on turbulent inertial stresses. Energy dissipation rate profiles were calculated theoretically using numerical simulations to calculate power draw and to solve population balance model equations. This is the first study in open literature where power consumption and drop size distributions in three scales of in-line rotor-stator mixer are reported.

A novel extrusion binder system was developed to enable the manufacture of tungsten carbide drill blanks greater than I 4 mm in sintered cross-sectional diameter at Sandvik Hard Materials Coventry. The binder system comprised primarily of methyl cellulose and water, which was capable of being removed from the extrudate with no adverse effects on extrudate quality or increases in drying and de-binding times. The tungsten carbide feedstock was prepared by z-blade mixing on laboratory, pilot and production plant scales. Extrudates were manufactured either as solid cylindrical rods or as rods formed with internal coolant channels following a helical rotation up to 20 mm sintered diameter. Extrusion tooling was modified to aid the forming process and maintain the desired tolerances of internal properties of the drill blanks. Such properties included coolant hole diameter, coolant hole relative concentricity and the distance between the coolant hole centres (pitch circle diameter). Controlled stress rheometry and oscillatory rheometry techniques were used in the selection of the methyl cellulose and water based binder for further analysis. Contro lled stress and oscillatory rheological techniques were a lso used to determine how modifications to the binder systems could be used to improve the extrus ion feedstock behaviour.

Food, while it is essential for survival, is a dynamic and complex marketplace. The drive to be innovative and popular, combined with ever changing public perception and scientific knowledge, makes the food industry fascinating. One of the recent trends, including sugar and salt, has been the reduction of fat in our diets. However, consumers like to treat themselves and fatty foods give a pleasurable eating experience. These two things are often at odds. This work focusses on the development and use of a novel fat replacement technology known as air filled emulsions (AFEs) as a substitute for the function, both structurally and organoleptically, of the fats present within emulsion products. AFEs are micron sized pockets of air coated in a protective protein coat. This work demonstrates that they can be produced reliably at kilogram scales with great potential for further scale-up. This work successfully supplemented emulsions with AFEs and demonstrated the possibility of reducing the fat concentration by over 45%. AFE substitution also had the advantage of significantly improved resistance to separation.

A Positron Emission Particle Tracking (PEPT) based technique was developed and used to study laboratory grinding of calcium carbonate in a vertically stirred media mill. The PEPT data along with particle fracture data obtained by micromanipulation were used to understand the grinding mechanisms. The PEPT methodology allowed measurements of grinding media occupancy, velocity, force, stress and media–media collisions at different positions within the mill. The stresses exerted by the media were compared with calcium carbonate strength measurements made using the micromanipulator to determine the percentage of the grinding media with sufficient stress to overcome the strength of the calcium carbonate particle. The collision frequency and total number of collisions were estimated using a modified Arrhenius equation approach by measuring the mean relative velocity of the grinding media (estimated to be the standard deviation of velocity measurements made in a block volume) and the number of media particles in a unit volume. This approach was used to characterise the behaviour of a benchmark grinding experiment performed under standard conditions and to understand the effect different operating conditions had on the number of collisions and stress exerted at these collisions. A number of suggestions for improved mill performance are given.