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This document describes an experimental investigation of two different particle systems under conditions of oscillatory flow. The 1st system being concentrated suspensions of non-motile particles and the 2nd system being dilute suspensions of swimming algae. This document focuses on the study of the jamming of concentrated suspensions of particles (primarily in oscillatory flows), and the response of swimming algae to oscillatory shear flows. The flow characteristics of concentrated colloidal and granular suspensions are known to display a variety of interesting flow characteristics such as shear thinning and discontinuous shear thickening. These depend on a wide range of parameters such as concentration, particle size, rate of deformation and many more. During the flow of concentrated suspensions, they can change from behaving like a fluid and flowing to behaving like a solid which can fracture or yield. Many aspects of this transition are still not understood. This phenomenon has important applications in process flow of slurries, the development of light weight bullet proof vests and as a dampening fluid within vehicle suspensions. This thesis shows that when concentrated colloidal and granular suspensions are subjected to oscillatory squeeze film flow, they display reversible local flow field distortions and macroscopic shape changes which are likely related to jamming. It highlights a range of unreported behaviours of suspensions in oscillatory squeeze film flows. This document also provides rheological data on the discontinuous shear thickening and jamming of a wide variety of different suspensions in both continuous and oscillatory shear flows. Swimming micro-organisms are currently used in a wide variety of health and cosmetic products. They are also being researched for use in the production of biodiesel. Swimming algae are grown within photo-bioreactors where their swimming characteristics can have a major impact on the reactors overall efficiency. Additionally a major issue in the production of swimming algae is the need for them to be concentrated using centrifugation which is energy intensive. This thesis shows that in oscillatory shear flows, gravitactic swimming algae can order their swimming directions in the vorticity directions of the oscillating flow field. This has potential applications in the development of a method to encourage micro-swimmers to self-concentrate. Suggestions of other investigations into the ordering behaviour of swimming micro-organisms are also provided. This document also displays a unique and cheap method for applying oscillatory squeeze film flows while allowing samples to be viewed underneath a microscope. It also makes suggestions on how this method could be enhanced. This device has applications in carrying out squeeze film tests to examine the rheological properties of fluids.

Resorcinol-Formaldehyde (RF) xerogels are a type of porous material used in many applications, such as gas storage. These applications often require fine control of the material's porosity, and while it is known that the porosity of a xerogel can be changed through altering synthesis variables, it is not clear why these changes have such an impact. To understand this effect, the gelation process was studied using dynamic light scattering (DLS), with the xerogel products undergoing low temperature nitrogen adsorption measurements to determine textural properties. RF gels are composed of cross-linked clusters and DLS was used to study changes in how these clusters grow. It was found that cluster growth was a thermodynamically controlled process, and for a given catalyst, how the cluster size grows with time was independent of the catalyst concentration. However, the catalyst did kinetically control the number concentration of clusters initially formed, and in turn, the size to which they, therefore, had to grow to reach a critical volume fraction to form the gel, such that higher catalyst concentrations led to smaller clusters making up the gel. This resulted in smaller intercluster voids, hence, smaller pores. The catalysts used also demonstrated a range of different abilities to stabilise the colloidal suspension of clusters. This also affected cluster size, with less stabilising catalysts resulting in larger clusters. This knowledge led to the ability to further tailor the porosity by introducing a secondary catalyst, in various forms, into a separate gelling mixture. The different catalysts, with their varied abilities to stabilise the growing clusters, and the range of concentrations used, resulted in a variety of cluster sizes within the final gel, which changed the porosity of the xerogel products formed.

Hollow fiber gas separation membranes manufactured from Poly(vinyl chloride) (PVC) have been produced via a dry/wet spinning method for end use in ozone/oxygen gas separations. Ambient temperature production mechanisms were initially targeted. A number of spin runs were undertaken changing aspects of the dope solution and the spinning conditions but produced only very low selectivity membranes. It was concluded that ambient condition spinning was unattainable for the solutions used. In order to explain the low selectivity a rheological study was undertaken which considered flow, oscillatory and creep rheological conditions and modelling of the flow patterns observed across the spinneret annulus. This study showed large differences between the dope at 20°C and 60°C in terms of viscosity and viscoelastic nature. These differences were predicted to make spinning difficult through slippage on the spinneret walls and viscoelastic nature of the solution. Spinning at elevated temperature was undertaken and used to produce membranes under different spinning conditions according to a Taguchi model and which would allow graphical comparisons also in order to assess the validity of the Taguchi analysis in these applications. The membranes produced an array of results all of which indicated solution diffusion through PVC as the controlling transport mechanism under the spinning conditions. Both graphical and Taguchi analysis concluded the same conditions to be optimal; low dope extrusion rate but high convective gas flow rate and residence time producing the best selectivity. The membrane permeation results were used alongside scanning electron microscopy images to model the active layer thickness in the membranes. This concluded that the higher selectivity membranes exhibited lower active layer thicknesses and porosity resulting from the quick formation of a dense surface layer for nodule coalescence preventing further mass transport and hence halting penetration of the active layer. Ozone/oxygen binary gas mixtures showed qualitative evidence of separation. Unfortunately due to equipment limitations it was not possible to provide quantitative data to support this. The membranes have displayed good resistance to oxidative environment and therefore they perhaps offer a viable solution for processes occurring in this type of environment which more common membrane materials may not be suitable for.

In this study, a suite of novel CO₂ capture sorbents were prepared employing three facile synthetic routes: amine assimilation (co-synthesis), wet impregnation and in situ-impregnation synthesis, to develop a range of materials capable of efficiently adsorbing CO₂ while demonstrating their applicability as alternative materials for CO₂ capture from coal and gas fired power plants via post-combustion carbon capture. Prepared sorbents were characterised for individual physical and chemical properties, using, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, elemental analyses and N₂ sorption at 77 K. CO₂capture capacities were determined using gravimetric analysis under a range of analysis conditions (different temperature and pressure), with the corresponding effects of materials characteristics on CO₂ capacities investigated. The effect of amine incorporation was explored in detail, with findings first bench-marked against the corresponding amine free counterparts, and, then, the effect of increasing amine content analysed. So far, within the context of this study, results suggest that materials prepared via the synthetic routes adopted, exhibit high degrees of synthetic control; in addition, CO₂ capture capacities were determined to be dependent upon both textural properties but, more importantly, the basic nitrogen functionalities contained within these materials. This observation was prominent with amine in-situ impregnated silica and melamine resorcinol formaldehyde samples, but not wholly for bio-inspired amine silica samples, as the degree of amine functionalisation could not be controlled by the synthetic route chosen. Irrespective, all materials have shown enhanced adsorption performance as a result of the incorporation of basic nitrogen functionalities into the sorbent structures. Furthermore, prepared materials exhibited easy regeneration and maintained stable sorption capacities ≤ 99.9% over the cycles analysed, with results obtained suggesting new strategies for carbon capture materials development for efficient CO₂ capture from power plant flue gas and other relevant applications.

Crystallisation is an important separation and purification technology in the pharmaceutical and fine chemical industry. Crystallisation processes are designed to generate and control supersaturation, nucleate desired polymorphs as well as crystal shapes and growing product crystals to the required particle size distribution and purity. Traditionally crystallisation is carried out in batch mode, due to the necessary process flexibility, although continuous processing can offer advantages of reproducible product quality, more sustainability as well as lesser waste and lower carbon footprint. This work describes a route towards the development of continuous crystallisation processes for small organic molecules. Supersaturation is the ultimate requirement for nucleation and in processes where mixing of two or more solutions is required to generate supersaturation, this step can affect nucleation. This thesis shows that higher mixing intensities yield higher solid recoveries over time and a smaller particle size. However, this phenomenon only applies to low and medium mixing flow rates, whereas results for high mixing flow rates are at the same level as for the medium ones. Furthermore, this effect was only observed in Valine - water:isopropanol (1:1) and at high supersaturations in Glycine - water:isopropanol (1:1) systems. In L-Glutamic acid - water:isopropanol (1:1) or L-Asparagine - water:isopropanol (1:1) systems this effect was not observed at all. Even the reactive precipitation of L-Glutamic acid (H-Glu) from Na-Glutamate and H2SO4 did not show any effects of mixing intensity on solid recovery over time. The mixing insensitive reactive precipitation of H-Glu was used to study the effect of post-mixing flow treatment on solid recovery over time and final polymorphic population. Micromixed samples were exposed to different batch flow units with hydrodynamics of a quiescent crystalliser (QC), stirred tank crystalliser (STC), magnetically stirred crystalliser (MSC), peristaltic pump recirculation loop (PPL) and an oscillatory baffled crystalliser (OBC). Harsh hydrodynamic conditions or mechanical impact like in the STC, MSC or OBC yield the metastable prismatic Alpha H-Glu polymorph and significantly increase solid recovery over time. Milder hydrodynamics like in a QC or PPL yield the stable platelet/needle like Beta H-Glu polymorph, where the PPL shows enhanced solid recovery over the QC. Despite XRPD analysis indicating pure Beta phase, the QC samples also contain about 0.1 % of the Alpha form, which growth kinetics suggest that they must have formed very shortly after mixing. Connecting the continuous mixing setup with a Beta enhancing flow-through PPL unit and a sample collection vessel made a fully continuous Beta H-Glu crystalliser. However, this system never reached steady-state operation, fouling and blockage was a major challenge and an unexpected change in the polymorph population from the stable Beta to the metastable Alpha was observed. This system did not perform satisfactorily and therefore experiments were discontinued. For the mixing insensitive antisolvent crystallisation of H-Glu, a novel rapid continuous antisolvent crystallisation setup was developed to produce crystal suspension of the Beta polymorph with a small size and narrow particle size distribution. The system jetinjects aqueous H-Glu solution into the bulk of isopropanol antisolvent and its performance was characterised with respect to different antisolvent mass fraction, bulk supersaturation, polymorphic population, steady-state operation, solid recovery over time, crystal size, particle size distribution and scale-up capabilities. Results show that increasing the antisolvent mass fraction reduces the final crystal size and particle size distribution, crystal product is of pure Beta form with a high yield, the system rapidly achieves very high supersaturation and reaches steady-state operations after about 20-30 min. Higher total flow rates and scale-up of the system did not show any effect on particle and system properties. The produced crystal slurry exhibits ideal properties of a Beta H-Glu seeding suspension for further crystal growth. Continuously seeded continuous crystal growth cooling crystallisation experiments were carried out in a tubular continuous oscillatory baffled crystalliser (COBC). H-Glu solution of two different concentrations was pumped through the system and Beta H-Glu seeding suspension of two different seed loadings were injected into the saturated solution. Mass balance calculations, supersaturation data, seed loading & solution concentration, crystal morphology information, crystal growth rates and mean residence time in each temperature section along the rig were used to predict solution concentration, desupersaturation behaviour and the temperature profile of the process. Online Focused Beam Reflectance Measurement (FBRM) analysis and offline laser diffraction particle sizing measurements recorded crystal growth in the system. Offline solid recovery analysis over time at various points along the rig successfully confirmed the predicted solution concentrations and desupersaturation profile of the COBC. However, micrographs and Scanning Electron Microscopy (SEM) analysis indicated that final product crystals are agglomerated. The effect of seed loading & solution concentration on the final agglomerated particle size distribution and solid recovery over time was investigated. Higher solution concentration led to larger product crystals, whereas different seed loadings did not show a clear trend. Steady-state crystallisation was demonstrated based on particle size distribution as well as supersaturation data after each crystalliser residence time and was achieved within 20 min after the system was conditioned with crystal slurry. Fouling and secondary Alpha nucleation was not a problem as long as the supersaturation did not exceed a level of 3.7 in the bulk solution.

This thesis describes work done to investigate the effects of flow on concentrated suspensions. The work is largely about the effects of flow on concentrated colloidal suspensions, however, a short section on the effects of flow on concentrated granular suspensions is also given. Concentrated suspensions show a variety of complex flow behaviour. They can show Newtonian, shear thinning or shear thickening behaviour, depending on the applied stress or shear rate and concentration. The shear thickening behaviour may be discontinuous and this is characterised by a dramatic increase in viscosity above a certain threshold of stress. This is thought to be closely related to flow induced jamming, which can be defined as the conversion of a liquid system into a solid by imposed stress. This behaviour is not well understood and can cause significant complications in industry. It also has potential applications, for example in shock absorption. Due to their complexities and potential applications, gaining a better understanding of how shear thickening and jamming materials behave is of interest and forms the basis of this thesis. In this work, bespoke shear cells and a novel method to detect flow induced jamming were designed and utilised. This allowed jamming to be visualised and evaluated quantitatively. Conditions where jamming occurs were mapped out and the effects of parameters such as concentration, shear stress, system geometry and system confinement were investigated. This, and an analysis of jamming statistics, allowed ways to prevent and control jamming to be identified and a better understanding of the system to be achieved. Such an analysis is lacking in literature. The conditions where jamming was detected using the novel equipment matched well with measurements using a commercial rheometer. This supported the idea of discontinuous shear thickening and flow induced jamming being closely related. The studies allowed a mechanism for flow induced jamming and discontinuous shear thickening to be proposed. By designing and using novel equipment that is not commercially available, a better understanding of the effects of flow on concentrated suspensions was achieved. This could ultimately lead to a better understanding of complex flow systems and lead to more efficient processes.

The ability to alter the nanostructure of resorcinol formaldehyde (RF) gels by varying the synthesis conditions, along with the obtainable properties, makes them valuable for a number of applications. Consequently, optimising the synthesis process is important to produce high quality gels that possess desired properties for the desired application. In order to control the formation of RF gels, it is vital to understand the specific role of the catalyst (C), with previous studies suggesting that its function is to alter the initial sol pH [1, 2], enabling gel formation to take place. It has been reported that controlling sol pH, allows the nanostructure of the final gel to be controlled [3], with lower initial pHs resulting in gels with higher surface areas, pore volumes and wider pore size distributions, where the inverse is true for higher pHs. This theory, however, does not explain why gels prepared from sols with equivalent initial pH possess significantly different characteristics, for example average pore diameters and pore volumes. Furthermore, studies into the effect of initial sol pH alter the alkalinity of the sol by modifying the molar ratio of R to C, subsequently, making it difficult to differentiate between the effects of catalyst and sol pH. In this study organic xerogels were prepared using the pre described poly-condensation method, however, a wide range of base catalysts (Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, NaOH, KOH, CaCO₃, SrCO₃, BaCO₃ and (NH₄)₂CO₃) were employed, at varying concentrations, with all other experimental variables kept constant. Through the use of HPLC, titration and DLS the RF polymerisation reaction was monitored allowing effects of R/C ratio, initial sol pH, cation size, charge and presence, as well as base type and deprotonating ability to be identified, differentiated and comprehensively studied. It was found that, in general, for each individual catalyst, increasing R/C ratio caused an increase in average pore diameter and total pore volume, and a decrease in specific surface area. When all catalysts were considered together it became apparent that, rather than initial sol pH influencing the final properties, the xerogel nanostructure was dependent on the potential deprotonation ability (DPA) of the catalyst. Comparing RF gels prepared with Group I and Group II metal catalysts confirmed that cation size and charge affects the polymer stability and aggregation, subsequently, influencing overall structure. Monitoring the reaction of gels catalysed with no catalyst or (NH₄)₂CO₃ demonstrated that the presence of a metal cation is vital for base catalysed sol-gel polymerisation of R and F. Identifying and distinguishing the specific role of the basic catalyst, will allow RF polymerisation to be studied in full, using Design of Experiments (DoE). This approach will not only determine the effects of individual variables, but will also establish the combined influence of experimental conditions. Understanding the polymerisation fully will offer complete control of RF structure, permitting gels to be prepared with precise desired properties.

In nature, a number of organisms and organelles are capable of self-propulsion at the micro- and nano-scale. Inspired by biological motors, this investigation aims to induce self-propulsion of an enzyme, by the biocatalytic self-assembly of aromatic peptide amphiphile molecules into supramolecular fibre structures. The individual motion of enzymes is measured directly using fluorescence microscopy, by the covalent attachment of alkaline phosphatase to fluorescing quantum dots. Enzyme-quantum dot conjugates represent nanoparticulate ‘vehicles’ transported by the enzyme 'motor'. Two aromatic peptide substrate ‘fuels’, initially assembled in a micellar form, are studied for their ability to propel enzyme-quantum dot conjugates, by biocatalytic dephosphorylation causing self-assembly into one-dimensional fibres. The effect of the ‘fuel’ on conjugate motion is compared with controls consisting of no fuel, a non-self-assembling substrate and a non-directional self-assembling substrate (i.e. one that assembles into spheres, but not fibres). Significant quantities of data were obtained for each substrate scenario and speed distribution plots revealed that enzyme-conjugates exhibit faster transport with the fibre forming system, compared to controls. Further to this, upon increasing the concentration of the fibre-forming fuel, the average speed of the conjugates increases, although directionality remains random. An initial investigation for directional control is carried out using 'fuel' reservoirs consisting of substrate saturated polyacrylamide gels. Substrates diffuse from the gel into surrounding motility medium creating a concentration gradient, which the enzyme-motors are proposed to travel along in a directional manner. The proposed propulsion model for self-assembly-driven motion of enzyme-conjugates is that short bursts of fibre growth provides linear propulsion which increases the diffusion rate of the enzyme-conjugate. Simultaneous visualisation of self-assembled fibres and enzyme-quantum dot conjugates is attempted, using extrinsic and intrinsic fluorescent methods, to investigate the mechanism proposed for fibre-propulsion. Finally, enzymes thermolysin and α-chymotrypsin are investigated as a step toward generalising the method for other enzymes and for their potential use in a multi-enzyme/multi-coloured quantum dot system for future applications in nano-separation of enzymes.

Sooting laminar flames at atmospheric pressure present a very complex chemical environment with numerous sources of interference for optical measurement techniques. Absolute concentration profiles of ¹CH₂ and HCO have been measured under a range of flame conditions in a sooting laminar premixed C₂H₄-air flat-flame by Cavity-Ring Down Spectroscopy performed at wavelengths in the range 615 to 625 nm. Also, concentration profiles of the OH radical have been detected via the band of A² ∑(v' = 0) ← X² ∏(v'' = 0) system by Laser-Induced Fluorescence and quantitatively calibrated by Cavity-Ring Down Spectroscopy. In situ measurements of these radicals in sooting flames have hitherto been lacking and are essential for validation of chemical kinetic models of aromatic hydrocarbon and soot formation in flames. The experimental results are compared to simulated concentration profiles generated using the Appel-Bockhorn-Frenklach mechanism. Temperature profiles obtained using OH LIF thermometry are used in interpreting the CRDS data and as input for flame simulation. Additionally, weak broadband absorption is observed by CRDS in the region between the reaction zone and the onset of soot formation; this may be attributable to low concentrations of large aromatic species.