This thesis is concerned with the performance and measurement uncertainty of wire-mesh sensors in different air-water flow regimes in horizontal pipes. It also presents measurements of void fraction and interfacial velocity in such flows. It was found that the interfacial velocity measurements of the wire-mesh sensors were in good agreement with those taken with a high-speed camera and estimates of the uncertainties of these measurements are presented. Drift-flux models were fitted to the measurements and it was found that the parameters of these models were not only sensitive to the flow regime, but also to the liquid superficial velocity.

Understanding the behaviour of polymers which are located in the presence of nuclear materials is important in order to predict the lifespan of the materials. Artificial ageing experiments are undertaken at elevated temperatures to infer how the materials may age. This study was concerned with the monitoring of trace gases (H2O, CO2, CO and acetic acid) within a materials ageing vessel which contained ethylene-vinyl acetate (EVA) polymer and uranium in order to deduce the rate of polymer degradation and/or uptake of the gases by uranium. A novel circular multi-reflective (CMR) cell was designed, developed and deployed in situ in order to extend the optical pathlength within the vessel to improve detection limits of the trace gases. One cell was located at the 6 millimetre solid/solid interfacial region between cylindrical coupons of the EVA polymer and uranium, to enable representative sampling in proximity to where the gases were evolved, adsorbed or reacted. The unique planar star-like beam profile of the CMR cell was crucial in enabling detection within this narrow interfacial region. A second CMR cell was incorporated within the vessel headspace, above the two material coupons, to address a specific research problem which aimed to ascertain whether differences in the gaseous composition existed between the two regions, which would indicate poor gas mixing. Two spectroscopic techniques were employed in conjunction with the CMR cells to monitor the trace gases: these comprised broadband absorption spectroscopy (BBAS) and tunable diode laser absorption spectroscopy (TDLAS). Near-infrared (IR) radiation sources, in the form of diode lasers, a superluminescent light emitting diode (SLED) and supercontinuum (SC) source were utilised in BBAS experiments. TDLAS was used for the detection of CO2, CO and H2O, whilst BBAS was used for the detection of acetic acid, and other potential unknown species. The requirement for using near-IR radiation was a consequence of using flexible silica-based optical fibres to remotely monitor the vessel which was located within a temperature controlled chamber. As a result, this was the first demonstration of CMR cells being used in conjunction with near-IR radiation sources. An optical pathlength of 69 cm was achieved within the materials ageing vessel, which led to the following limits of detection at 75 °C, 150 Torr with a 10 second averaging time: H2O = 3 ppm; acetic acid = 157 ppm; CO2 = 596 ppm and CO = 37500 ppm. Manufacturing issues with the cell optics, coupled with monitoring weak ro-vibrational absorption features led to considerably higher limits of detection than expected. The CMR spectroscopic system was used successfully to observe the outgassing trend of partially cured EVA polymer, which was shown to depend on cure time. A key finding of this research, however, was the observation of a difference between the interfacial gaseous composition versus the headspace gas in a system that contained both a source and sink material (i.e. one that evolved, and one that adsorbed gases). This was only made possible by using the CMR spectroscopic system. This observation was also supported by a computational fluid dynamic (CFD) model.

Raman spectroscopy has been used to monitor the deformation of natural cellulose whisker polymer nanocomposites. Cotton and tunicate whiskers were used as reinforcements in polymer matrices. Raman spectra from the nanocomposites highlight an intense band located at the 1095 cm-1 position. This band is reported to shift towards a lower wavenumber under the application of tensile deformation. On the other hand, the compressive deformation of the composite gives rise to an increase in the position of this Raman band. The shifts correspond to the direct deformation of the molecular backbone of cellulose, which is dominated by a C-O stretching mode. The Raman band located at 1095 cm-1 is shown to shift non-linearly before it reaches a plateau due to the breakdown of the whisker-matrix interface. The initial shift rate is associated with the stiffness of the cellulose whiskers. The stiffnesses of single whiskers of cotton and tunicate are found to be 58 and 155 GPa respectively, assuming two dimensional (2D) in-plane distribution of whiskers. Cyclic deformation tests of the composites provide an insight into understanding the behaviour of the whisker-polymer matrix interface under tension and compression. It is found that residual compressive stress occurs during each cycle of the deformation. The level of disruption at the whisker-matrix interface is determined by estimating the energy dissipation, which is proportional to the hysteresis area. Local orientation is also observed in the nanocomposites produced by solution casting and subsequent melt pressing. Dark regions of the composites viewed under a polarised optical microscopy are found to represent areas in which the cellulose whiskers form a randomly oriented whisker network. A shift rate for the Raman band initially located at 1095 cm-1 obtained in the dark regions of 12.2 vol% tunicate whisker poly(vinyl acetate) nanocomposites is found to be -0.5±0.07 cm-1%-1, which is lower than -1.2±0.04 cm-1%-1 from the bright regions. Exposure to water and temperature during the deformation of the nanocomposites results in significant changes in stress transfer between the whiskers and the matrix. It is shown that the interface can be 'switched-off' for the poly(vinyl acetate)/whisker system in the presence of water and also at temperature above the glass transition.

Knowledge regarding carbon dioxide (CO2)-brine interfacial tension (IFT) is important for petroleum industry and Carbon Capture and Storage (CCS) strategies. In petroleum industry, CO2-brine IFT is especially importance for CO2 – based enhanced oil recovery strategy as it affects phase behavior and fluid transport in porous media. CCS which involves storing CO2 in geological storage sites also requires understanding regarding CO2-brine IFT as this parameter affects CO2 quantity that could be securely stored in the storage site. Several methods have been used to compute CO2-brine interfacial tension. One of the methods employed is by using Density Gradient Theory (DGT) approach. In DGT model, IFT is computed based on the component density distribution across the interface. However, current model is only applicable for modelling low to medium ionic strength solution. This limitation is due to the model only considers the increase of IFT due to the changes of bulk phases properties and does not account for ion distribution at interface. In this study, a new modelling strategy to compute CO2-brine IFT based on DGT was proposed. In the proposed model, ion distribution across interface was accounted for by separating the interface to two sections. The saddle point of tangent plane distance where ( ) was defined as the boundary separating the two sections of the interface. Electrolyte is assumed to be present only in the second section which is connected to the bulk liquid phase side. Numerical simulations were performed using the proposed approach for single and mixed salt solutions for three salts (NaCl, KCl, and CaCl2), for temperature (298 K to 443 K), pressure (2 MPa to 70 MPa), and ionic strength (0.085 mol·kg-1 to 15 mol·kg-1). The simulation result shows that the tuned model was able to predict with good accuracy CO2-brine IFT for all studied cases. Comparison with current DGT model showed that the proposed approach yields better match with the experiment data. In this study, the thermodynamic properties were computed using Cubic Plus Association (CPA) equation of state, and the electrolyte contribution was accounted for by adding Debye-Huckel activity coefficient in the thermodynamic properties computation.

For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4∙105 control volumes. The turbulence was modelled separately for each phase using the k-ω based shear stress transport (SST) turbulence model. The results compare well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow. Furthermore, CFD pre-test calculations were done to show the possibility of slug flow generation in a real geometry and at relevant parameters for nuclear reactor safety. The simulation was performed on a flat model representing the hot-leg of the German Konvoi-reactor, with water and saturated steam at 50 bar and 263.9°C. The results of the CFD-calculation show wave generation in the horizontal part of the hot-leg which grow to slugs in the region of the bend.

In this thesis, we develop a physical understanding of the effects of viscosity and geometry on the dynamics of interfacial flows in drops and bubbles. We first consider the coalescence of pairs of conical water droplets surrounded by air. Droplet pairs can form cones under the influence of an electric field and have been observed to coalesce or recoil depending on the angle of this cone. With high resolution numerical simulations we show the coalescence and non-coalescence of these drop pairs is negligibly affected by the electric field and can be understood through a purely hydrodynamic process. The coalescence and recoil dynamics are shown to be self similar, demonstrating that for these conical droplet pairs viscosity has a negligible effect on the observed behavior. We generalize this result to the coalescence and recoil of droplets with different cone angles, and focus on droplets coalescing with a liquid bath and flat substrate. From the simulations of these droplets with different cone angles, an equivalent angle is found that describes the coalescence and recoil behavior for all water cones of any cone angle. While viscosity is found to negligibly affect the coalescence of conical water drops, it plays a key role in regulating the coalescence process of bursting gas bubbles. When these gas bubbles burst, a narrow liquid jet is formed that can break up into tiny liquid jet drops. Through consideration of the effects of viscosity, we show that these jet drops can be over an order of magnitude smaller than previously thought. Here, viscosity plays a key role in balancing surface tension and inertial forces and determining the size of the jet drops. Finally, we investigate the drainage of surfactant free, ultra-viscous bubbles where surface tension serves only to set the initial shape of the bubble. We use interferometry to find the thickness profiles of draining bubble films up to the point the of rupture. A theoretical film drainage model considering the balance of viscous and gravitational stresses is developed and numerically computed. The numerical results are found to be consistent with the experimentally obtained thickness profiles. In this work we provide insight into the role of viscosity in the outlined interfacial flows. The results of this thesis will advance the understanding of drop production in clouds, the marine climate, and the degassing of glass melts.

The focus of the following research was to provide an optimized particle stabilized foam of Laponite and Pluronic L62 in water by understanding (1) the Laponite-Pluronic interactions and properties for improved performance in a particle stabilized foam and (2) the interfacial properties between air and the Laponite-Pluronic complex. These studies were conducted using both bulk and interfacial rheology, XRD, sessile droplet, TGA and UV-vis. Two novel and simple techniques, lamella break point and capillary breakup extensional rheometry, were used to both understand the Laponite Pluronic L62 interaction and determine a different mechanism for foaming properties. Bulk rheological properties identified an optimal Laponite concentration of 2% with Pluronic L62 ranging from 2.5% and 6.5%, due to the ease of flow for the dispersion. The Pluronic L62 was observed to enhance the Laponite bulk rheological properties in solution. Additionally TGA showed a similar trend in thermal resistance to water with both addition of Laponite and Pluronic L62. XRD demonstrated that 0.25% Pluronic intercalated into Laponite from dried 2% Laponite films. XRD demonstrated that the Laponite matrix was saturated at 1% Pluronic L62. UV-vis demonstrated that a monolayer of Pluronic L62 is observed up to 0.65% Pluronic L62 onto Laponite. Interfacial rheology showed that Laponite enhances Pluronic L62 at the air-liquid interface by improving the storage modulus as low at 0.65% Pluronic L62 with 2% Laponite. The lamella breakpoint of Laponite with Pluronic films indicate strong film interaction due to higher increases in mass. Extensional rheology indicates that 2.5% to 6.5% Pluronic with 2% Laponite show the most filament resistance to stretching.

Abstract: The aim of this research is to fabricate thin-film composite (TFC) membranes using a synthetic derivative of plant-based phenols, as a non-toxic building block for interfacial polymerization. Classical interfacially polymerized composite membranes are heavily integrated in reverse osmosis and nanofiltration applications for water and wastewater treatment and most recently for chemical and pharmaceutical industries. Implementing sustainable practices in membrane fabrication by exploiting greener alternatives to conventional chemicals can directly reduce hazardous waste and ultimately lower the global energy and environmental burdens. In this study, allyl gallate was chosen as a monomer to form selective thin films by the interfacial reaction with trimesoyl chloride on top of an asymmetrically porous polyacrylonitrile support. The advantage of the unreacted allyl groups is that they can be in the future used as post-functionalization sites. The highly volatile organic phase solvents were additionally replaced by an isoparaffinic fluid, commercially known as Isopar G. The chemical composition and morphology of the membrane was evaluated using solid-state 13C NMR, FTIR, and SEM. The optimized membrane resulted in a permeance of 12±2 and 48±14 L m-2 h-1 bar-1 for respectively pure water and methanol with a rejection in the nanofiltration range.

<p>Here presents the studies of polymerization kinetics and crosslinking efficiency of nm-resolution striped phases on surface, which depends on lengths of alkyl segments and headgroup chemistry. While fluorescence readouts offer the overall efficiencies of polymerization and crosslinking transfer, SPM measurements reveal molecular details accounting for reactivity differences. Additionally, this research also demonstrates the utilization of primary amines striped phases on soft materials, achieving post-functionalization and specific  adsorption of nanocrystals, highlighting the versatile applications of this nm-scale chemistry boundary.</p>

In the last decades, there has been a trend towards bio-inspired approaches for the formation of nanocoatings as well as to accomplish energy-intensive industrial separations in a more sustainable fashion. Solvent Resistant Nanofiltration (SRNF) is a pressure driven technology where the operation conditions are moderate and additional waste streams are minimized, making this a favorable energy efficient approach for challenging molecular separations such as purification of active pharmaceutical ingredients, production of specialty chemicals and in the petrochemical industry just to mention a few examples, where this technology can be currently applied. The overall performance of SRNF membranes is determined by solute/solvent interactions with the membrane top layer. Therefore, the modification of the membrane surface becomes crucial to obtain high-performance SRNF membranes, as well as exploring novel and green approaches to improve the separation properties of SRNF membranes, without sacrificing their permeation properties. One alternative for the fabrication of the thin-films in SRNF membranes proposed in this work is the use of biopolyphenolic molecules. Among the many classes of phenolic biomolecules, plant phenols are capable of binding and cross-linking due to their strong interfacial activity. Here, the successful optimization of the interfacial polymerization reaction for the manufacture of SRNF membranes is demonstrated by replacing the common toxic amines used for this method with natural occurring bio-polyphenols such as dopamine, tannic acid, morin hydrate and catechin. These bio-polyphenols can be found in mussels, date fruits, guava fruits and green tea respectively and they were used to form a selective thin film on top of a crosslinked polyacrylonitrile or a cellulose support. These membranes have shown an exceptional performance and resistance towards harsh solvent environments. Due to the incorporation of natural compounds for the manufacture, they provide a cost-effective alternative for industrial separations due to the ease of chemical modification and preparation, which is potentially easy to scale up at low cost taking advantage of the natural compounds for their manufacture.