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This project was focused on the synthesis of novel Polymers of Intrinsic Microporosity (PIMs) that are soluble in common low boiling point solvents so that self-standing films can be prepared for gas permeability measurements. The common building unit of these novel PIMs was triptycene and its derivatives. Modification of these triptycene compounds enabled the alteration of the polymeric backbone, so that we could tune the gas permeability properties. Modifications included the substitution of different functional groups (e.g. addition of methyl groups) and also the extension via benzoannulation of the triptycene structure. The synthesis of the PIMs was based around three different polymerisation techniques. The first one involved the formation of triptycene-based polyimides (PIs) using a triptycene based dianhydride, prepared in a multistep synthesis. Shorter and cheaper synthetic routes were attempted, but all to no avail. The resulting triptycene monomer was reacted with a variety of commercial and non-commercial bisanilines for the formation of several PIM-PIs, all exhibiting different performances. Robust self-standing films were obtained for two of these PIM polyimides. In addition to the formation of polyimides, the synthesis of Tröger’s Base (TB) polymers, also based on triptycene components, were achieved. This type of polymerisation involves the reaction between a “bisaniline” monomer and a source of “formaldehyde”, such as dimethoxymethane (DMM), in a strong acid media, typically trifluoroacetic acid (TFA). Modification of these triptycene-based bisanilines has led to the formation of TB-PIMs, all with distinctive gas permeation properties. TB-PIM copolymers (reaction between two different bisaniline monomers with DMM and TFA) were synthesised in an attempt to further tune the performance of the polymers. Finally, the preparation of polybenzodioxan polymers based around extended triptycene monomers (i.e. benzotriptycenes) was studied. By using a variety of substituted benzotriptycene biscatechol monomers and performing the polymerisation using tetrafluoroterephthalonitrile, in the presence of K2CO3, the synthesis of a series of substituted benzotriptycene polybenzodioxane polymers was successfully achieved and the polymers showed enhanced gas permeation properties.

The research aimed to develop chemically modified PIM-1s for use in adsorption and gas separation processes. In particular, the nitrile group in PIM-1 was converted to several different functional groups to manipulate the interaction ability of PIM-1 with different species. Synthesis of PIM-1 was achieved by two different methods, using both the low (72h, 65 °C) and the high temperature (40 min, 160 °C) methods. Hydrolysis of PIM-1 was performed in the presence of 20% and 10% NaOH solutions (1:1 H2O/ethanol) at 120 and 100 °C, respectively. The reaction resulted in a mixture of hydrolysis products. The composition of the polymer has a profound effect on the final performance of the polymer. Powder samples of hydrolysed PIMs were used in the research. The reduction of nitrile to primary amine was achieved using borane dimethyl sulphide complex, resulting in amine PIM-1. Both membrane and powder forms of amine PIMs were studied. The reaction of PIM-1 with ethanolamine and diethanolamine produced hydroxyalkylaminoalkylamide PIMs. The combination of all available techniques (ATR-IR, solution and solid state NMR, TGA, Elemental analysis, UV, GPC, MALDI-ToF, low pressure N2 sorption) was used to characterise the polymers. Gas sorption studies of modified PIMs showed that the sorption capacities of polymer altered depend on the modification. Hydrolysed PIMs showed reduced CO2 uptake. Ethanolamine modified PIM showed reduced CO2 uptake along with even more reduced N2 uptake, leading to enhanced CO2/N2 ideal selectivity at 1 bar. Amine modification increased the CO2 uptake of the polymer, while showing the same N2 uptake. Enhanced sorption selectivity was also achieved by amine PIM-1. Although chemical modifications reduced the permeability of the membranes, enhanced gas selectivity was obtained. Enhanced H2/CO2 selectivity placed amine PIM-1 above the 2008 Robeson upper bound. The relationship between the degree of conversion and permeability of amine PIM-1 was studied in detail. The effect of temperature and pressure on the permeability of amine PIM was studied, using several different temperatures and pressures. Ethanolamine modified PIM showed size selective behaviour by enhanced H2/N2 and H2/CH4 selectivities, and it crossed the 2008 Robeson upper bounds. Dye adsorption studies revealed that chemical modification manipulated the interaction ability of PIM-1. PIM-1 showed high affinity for neutral dye. While hydrolysed PIMs showed high affinity for cationic species, amine and ethanolamine modified PIMs displayed high affinity for anionic dyes. The factors affecting the uptake capacity of PIM-1, including temperature and pH, were studied along with kinetics of dye adsorption. Thermal treatments of modified PIMs and their structural characterisation were performed. The adsorption and separation performances of thermally treated and untreated modified PIMs were compared.

Membrane-based gas separation processes are an area of interest owing to their high industrial demand for a wide range of applications, such as natural gas purification from CO2 or H2, and N2 or O2 separation from air. This thesis is focused on developing and investigating polymeric-based membranes. Firstly, novel mixed matrix membranes (MMMs) were prepared, incorporating few-layer graphene in the polymer of intrinsic microporosity PIM-1. Secondly, novel polyphenylene-based polymers of intrinsic microporosity (PP-PIMs) were synthesised. An optimum preparation method of graphene/PIM-1 MMMs (GPMMMs) was established from numbers of experiments. In this study, graphene exfoliation was a step towards GPMMM preparation. Starting from graphene exfoliation in chloroform, as a good solvent for PIM-1, enhancement in graphene dispersibility was obtained with addition of PIM-1. This result helped in GPMMM preparation with high graphene content (up to 4 wt.%). Characterizations techniques such as Raman spectroscopy and scanning electron microscopy (SEM) of GPMMMs, confirmed the few layer graphene content, with morphology changes in the polymeric matrix compared to pure PIM-1.Gas permeability results of GPMMMs showed an enhancement in permeability with low loading graphene (0.1 wt.%) using a relatively low permeability PIM-1 batch, due to high water content. However, less influence of graphene incorporation on permeability was observed with a highly permeable PIM-1 batch. Reduction in permeability over time, termed an ageing effect, is known for a polymer of high-free volume like PIM-1. However, the enhancement of GPMMMs permeability after eight months storage was shown to be retained. Novel PP-PIMs were prepared from novel precursors using a series known organic reactions. PP-PIMs were divided into two groups of polymers based on their polymerization reactions. A group of polymers were prepared from condensation polymerization between bis-catecol monomers and tetrafluoroterephthalonitrile (TFTPN). Another group of polymers were prepared from Diels Alder polymerization between monomers of terminal bisphenylacetylene groups and bis tetraphenylcyclopentadienones (TPCPDs). All of which yielded polymers with apparent BET surface area in the range 290-443 m2 g-1.

This thesis describes the synthesis of soluble Polymer of Intrinsic Microporosity (PIM-1), fluoro-endcapped PIM-1 (F-PIM-1) and copolymers of F-PIM-1 with poly(ethylene glycol) monomethyl ether (MeOPEG). The main aim of the project was to alter the porosity of microporous PIM-1 in three ways: (a) synthesis of copolymers of F-PIM-1 with MeOPEG (b) blending of PIM-1 with MeOPEG in various proportions; and (c) adsorption of MeOPEG from aqueous solution byPIM-1. PIM-1 and F-PIM-1 were synthesized by step growth polymerization of tetrafluoroterephthalonitrile (TFTPN) with 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (THSB), using the conventional method and a newly reported high shear mixing method. F-PIM-1 oligomers were then coupled to poly(ethylene glycol) monomethyl ether (MeOPEG). The products were analyzed by NMR, IR, MALDI ToF MSS, TGA and polystyrene based GPC as well as multidetector GPC techniques. The high shear technique generally produced high molar mass products and yields. This method was also more successful for copolymerization.Blending of PIM-1 and MeOPEG in different proportions resulted in macrophase separation. Copolymer products were used to facilitate mixing of blends (as compatibilizers), however only 5% of MeOPEG could be solubilised into a PIM-1 phase. The effect of compatibilizer was found to be affected by interaction between PIM-1 and copolymer. However, N2 adsorption studies showed that after thermal removal of MeOPEG, PIM-1 regained stable porosity with significant BET surface area.Fluorescence studies were aimed at applications of PIM-1 and copolymers in sensors. PIM-1 and copolymers, spin-coated on the polyester-based substrate Melinex, were studied with and without methanol treatment in an environment of different solvent vapours. The effect of time and volume on wavelength shift and change in intensity was studied. Polar solvents tended to cause a red shift with decrease in intensity while less polar solvents behaved otherwise. Based on fluorescence experiments, solvent profiles for PIM-1 and copolymers were established.

Gas transport properties of PIM-1 (the first ladder polymer with intrinsic microporosity) and TC-PIM-1 (thermally cross-linked PIM-1) at 35°C and different pressures were thoroughly studied. The purpose of this study was to evaluate and compare the performance of the TC-PIM-1 membranes with PIM-1 for natural gas separation. The TC-PIM-1 polymer was prepared by post-modification of PIM-1 at 300°C for a period of two days. Sorption isotherms of seven gases, including N2, O2, CH4, CO2, C2H6, C3H8 and n-C4H10, were determined for PIM-1 and TC-PIM-1 using the dual-volume barometric sorption technique at 35°C at different pressures. The sorption isotherms followed the dual-mode sorption model, which is typical for glassy polymers. Moreover, permeability (P) of eight gases, including He, H2, N2, O2, CH4, CO2, C3H8 and n-C4H10, were determined for PIM-1 and TC-PIM-1 at 35°C and 2.0 atm. Furthermore, average diffusion coefficients (D ̅) were calculated from the permeability and solubility data for all tested gases for both polymers. The sorption (S), permeability (P) and average diffusion coefficients (D ̅) for the TC-PIM-1 membrane exhibited lower values than the PIM-1 membrane. However, the TC-PIM-1 membrane showed exceptional gas separation performance. The TC-PIM-1 membrane had a helium (He) permeability of 1218 barrer with He/CH4 and He/N2 ideal selectivities of 27.1 and 23.9 respectively, and carbon dioxide (CO2) permeability of 1088 barrer with CO2/CH4 and CO2/N2 ideal selectivities of 24.2 and 21.3 respectively. Additionally, the TC-PIM-1 membrane showed a hydrogen (H2) permeability of 2452 barrer with an ideal H2/CH4 selectivity of 54.5.

Abstract: In this work, carbon molecular sieve (CMS) membranes were prepared based on a polymer of intrinsic microporosity, named PIM-6FDA-OH. The goal of this work was to examine the effect of the fabrication parameters of the CMS membranes on the gas separation performance of the final CMS membranes produced. Furthermore, the performance changes are reported for membranes physically aged over 7, 30, 60, and 90 days. The membranes prepared consisted of thin-film (about 3 !m thick) CMS selective layers supported by a stainless-steel tube. The experiments were split into four projects. The first project aimed to determine the effect the layer thickness had on the final performance of the produced CMS membranes. Five pairs of membranes were prepared using different coating solution concentrations, and different number of layers. The concentrations used were 5 (1 layer), 7.5 (1 layer), and 9 wt% (1, 2, and 3 layers) polymer in THF. The membranes had the same soak time of 15 minutes and pyrolysis temperature of 650 °C. The results showed that the increase in number of layers did not provide any benefits and was unnecessary. Moreover, the decrease in concentration produced membranes with higher permeances but with a greater loss in selectivity. Therefore, the 9 wt% concentration solution with one layer was chosen for the remaining experiments. The second project examined the effect of the pyrolysis temperature on the performance of the final membranes produced. All membranes were made with the 9 wt% solution and the soak time was held constant at 15 minutes. The soak temperatures tested were: 700, 750, 850, and 950. °C. The membranes pyrolyzed at temperatures above 650 °C were severely defective. This suggests that either the precursor polymer could not form defect-free thin membranes using high soak temperatures, or another potential reason is related to interfacial defect formation between the CMS layer and the porous stainless-steel support. Further experiments are required to fully understand the soak temperature effect on the formation of thin CMS films on porous supports. The third project examined the effect of the soak time (i.e. time the membranes are held isothermally at the pyrolysis temperature) on the final performance of the membranes. The same 9 wt% solution was used, and the pyrolysis temperature was 650 °C. The pyrolysis soak times were 15 minutes, 1 hour, 3 hours, and 10 hours, respectively. The results showed that as the soak time increased the membranes became denser and provided higher selectivities and lower permeances. Furthermore, the membranes with longer soak times became more size-sieving earlier during physical aging than the membranes made with shorter soak times. Physical aging was accelerated with an increase in soak time, i.e., membranes made by soaking over 10 hours reached stable permeance over time starting at day 7. The fourth project aimed to investigate the preparation process, as well as to test the performance of the membranes under different environments. Two types of polyimide precursor membranes were made, one set with the pristine polyimide and the other one with a PDMS top coating. The results showed that the membranes with PDMS had similar selectivities but far slower permeances than the CMS membranes, the membranes made without PDMS coating had much lower selectivities and permeances. CMS membranes soaked for 15 minutes and 3 hours, respectively, were tested to check the permeances of all the five gases (H2, O2, N2, CH4, and CO2) under pressure cycles from 2 to 8 bar. The membranes passed the tests and their permeances were not affected by exposing them to high pressures and back, except for the membranes soaked for 3 hours when tested with CO2.

Microporous carbonates host a significant portion of the remaining oil-in-place in the giant carbonate reservoirs of the Middle East. Improved understanding of petrophysical and multi-phase flow properties at the pore-scale is essential for the development of better oil recovery processes. These properties strongly depend on the 3D geometry and connectivity of the pore space. In this study, we harnessed the unique capabilities of fluorescence confocal laser scanning microscopy (CLSM) to capture both macroporosity and microporosity, down to 0.1 µm, to provide a more representative 3D representation of pore space compared to traditional methods. The experimental procedure developed was specifically designed to enable highresolution confocal 3D imaging of the pore space of carbonate systems. The protocol aims to render carbonates more "transparent" to CLSM by imaging etched epoxy pore casts of the sample and minimizing CLSM signal scattering. The resulting highquality 3D images of the multi-scale pore space allow more reliable petrophysical interpretation and prediction of transport properties. Additionally, we present a robust pore imaging approach that correlates 2D images produced by scanning electron microscopy (SEM) with the 3D models produced by CLSM that cover a range of scales, from millimeters in 3D to micrometers in 2D. For the first time, multi-color fluorescence confocal imaging was employed to characterize the geometric attributes of a porous medium. We foresee that the protocol developed in this study could be used as a standard protocol for obtaining high-quality 3D images of epoxy pore casts using confocal microscopy, and could contribute to improved characterization of micritic carbonate reservoirs and oil recovery methods. We also demonstrate the advantages of multi-scale and multi-color confocal images in realizing more accurate evaluations of petrophysical properties. Finally, we demonstrate that micro 3D printing (two-photon polymerization) can potentially be used to fabricate micromodels with sufficient resolution to capture the geometric attributes of micritic carbonates and that can replicate the inherent 3D interconnectivity between macro- and micro-pores.

Manufacturing of light-weight materials is associated with several types of casting defects during solidification. Porosity defects are common, especially in aluminum and its alloys, which initiate crack propagation and thereby cause drastic deterioration in the mechanical properties. These defects, classified as micro and macro defects (based on their sizes), are mainly governed by release of hydrogen into the liquid at the solid-liquid interface, which triggers the nucleation and growth of hydrogen bubbles in the melt. Subsequently, these bubbles interact with solidifying interfaces such as dendritic arms and eutectic fronts, leading to the formation of pores. Macroscopic defects in the form of voids are created due to solidification shrinkage. The primary focus of the present work is to develop phenomenological models for the evolution of microporosity and microstructures during solidification. The issues outlined above typically occur in multi-phase environments comprising of solid, liquid and gaseous phases, and over a range of length and time scales. Any phenomenological prediction would, therefore, require a multi-phase-scale approach. Principles of volume averaging are applied to equations of conservation to obtain single-field formulations. These are then solved with appropriate interface tracking techniques such as Enthalpy, Level-set, Volume-of-fluid and Immersed-boundary methods. The framework is built up on a standard pressure based incompressible fluid flow solver (SIMPLER algorithm) and coupled modeling strategies are proposed to address the interfacial dynamics. A two-dimensional framework is considered with a fixed-grid Cartesian co-ordinate system. Scaling analyses are performed to bring out the relative effects of various competing parameters in order to obtain further insights into this complex phenomenon. The numerical results and scaling predictions are validated against experimental observations published in literature. In literature, numerical predictions of microporosity mainly include criteria based models based on empirical relations and deterministic/stochastic models based on diffusion driven growth assuming spherical bubbles. The dynamic evolution of non-spherical bubble-metal interface in a three-phase system is yet to be captured. Moreover, several in-situ experiments have shown elongated bubble shapes during the engulfment phase, therefore a criterion to define the dependence on cooling rates and the resulting bubble morphology can possibly deliver further practical insights. We propose a numerical model for hydrogen bubble growth, its movement and subsequent engulfment by a solidifying front, combining the features of level-set and enthalpy methods for tracking bubble-metal and solid-liquid interfaces, respectively. The influx of hydrogen into heterogeneously nucleated bubbles results in growth of bubbles to sizes up to a few hundreds of microns. In the first part of this numerical study, a methodology based on the level-set approach is developed to simultaneously capture hydrogen bubble growth and movement in liquid aluminum. The solidification is first assumed to occur outside the micro-domain providing a specified hydrogen influx to the bubble-in-liquid system. The level-set equation is formulated in such a way as to account for simultaneous growth and movement of the bubble. The growth of a bubble with continuous and fixed hydrogen levels in the melt is studied. The rates of growth of bubble-liquid and solidifying interfaces are compared using an order of magnitude analysis. This scaling analysis explains the thought experiment proposed in the literature, where difference in bubble shapes was attributed to the cooling rate. Moreover, it shows explicit dependence on bubble radius and cooling rate leading to a new criterion for bubble elongation proposed in this thesis. This also highlights the comparison between solidification and hydrogen diffusion time-scales which primarily govern the competitive growth behavior. The bubble-in-liquid model is coupled with microscopic enthalpy method to incorporate effects of solidification and study the interaction of solid-liquid and bubble-liquid interfaces. The phenomena of bubble engulfment and elongation are successfully captured by the proposed model. A parametric study is carried out to estimate the bubble elongation based on different initial bubble sizes and varying cooling rates encountered in typical sand, permanent mold and die casting processes. Although simulation of microstructures has been extensively studied in the literature, very few models address the phenomena of simultaneous growth and movement of equiaxed dendrites. The presence of different flow environments and multiple dendrites are known to alter the position and shape of the dendrites. The proposed model combines the features of the following methods, namely, the Enthalpy method for modeling growth; the Immersed Boundary Method (IBM) for handling the rigid solid-liquid interfaces; and the Volume of Fluid (VOF) method for tracking the advection of the dendrite. The algorithm also performs explicit-implicit coupling between the techniques used. Validation with available literature is performed and dendrite growth in presence of rotational and buoyancy driven flow fields is studied. The expected transformation into globular microstructure in presence of stirring induced flows is successfully simulated. A simple order estimate for time required for stirring is performed which agrees with numerical predictions. In buoyancy driven environment of a settling dendrite, the arm tip speeds show expected higher velocity of the upstream tip compared to its counterpart. The model is extended to study thermal and hydrodynamic interactions between multiple dendrites with appropriate considerations for different orientations and velocities of the dendritic solid entities. The present model can be used for the prediction of grain sizes and shapes and to simulate morphological transformations due to different melt flow scenarios. In the final part, the methodology presented for growth and engulfment of hydrogen bubbles is extended to study the phenomenon of diffusion driven bubble growth occurring in direct foaming of metals. The source of hydrogen is determined by the rate of decomposition of the blowing agent. This is accounted for by a source term in the hydrogen species conservation equation, and growth rate of hydrogen bubbles is calculated on the basis of diffusive flux at the interface. The level-set method is used for tracking the bubble-liquid interface growth, and the macroscopic enthalpy model is used for obtaining heat transfer and solid front position. The model is validated with analytical solution by comparing the front position and the solidification time. The variation of foam density with a transient hydrogen generation source is studied and qualitatively compared with results reported in literature. The modeling strategies proposed in this work are generic and therefore have potential in simulating a variety of complex multi-phase problems.

This thesis deals with the heat evolution duringsolidification and its relation to the formation of porosity.It intends to improve the current understanding of theformation of porosity in cast materials with special interestin nodular cast iron and the spray forming process. Twodifferent systems, a Fe-based alloy, Cast iron, and a Ni-basedalloy, Inconel 625, are examined. The effect on the heatevolution of the morphology and the processing parameters inspray forming are treated. An evaluation of the microstructural features, segregationbehavior and physical properties such as latent heat of fusionis performed byusing thermal analysis under cooling ratesranging from 0.1 to 104 K/s. In order to achieve this amodified differential thermal analysis (DTA) equipment, amirror furnace and levitation casting are used. Results arepresented in terms of the fraction of solidified, the coolingrate and the microstructure observed. The measured latent heatof fusion is not constant throughout the solidificationprocess. Variations in morphology and cooling rate affect therelease of the latent heat. A thermodynamic model is used to describe the experimentalobservations and to explain the formation of pores in nodularcast iron by taking into consideration the formation of latticedefects during the liquid/solid transformation. In this casethe formation of porosity is regarded as a consequence ofchanges in the volume fraction ratio graphite/ during thesolidification process. A numerical model of the spray forming process is developedby means of CFD modelling and compared with experimentalmeasurements performed in an industrial facility. Stagnationpressure measurements provided information about the gas flowvelocity and an analysis of the overspray powder providedinformation about the particle thermal history. Evaluation ofthe deposit was also performed. It is observed that the processconditions in spray forming promote non-equilibriumsolidification even though solidification at the deposit occursat a lower rate. In this case the porosity formed near theinterface substrate/deposit depends largely on the substratetemperature. The presence of certain reactive elements, such astitanium, affects the porosity levels in the rest of thedeposit. <b>Keywords:</b>Thermal Analysis, Nodular Cast Iron, Inconel625, CFD, Flow Assesment, Multiphase Flow, Spray Deposition,Microporosity, Superalloys