The present thesis explores the volumetric and transport properties of complex fluid mixtures under pressure in order to develop a better, more holistic understanding of the relationship between the volumetric properties, derived thermodynamic properties, and viscosity. To accomplish this broad objective, two different categories of fluid mixtures were examined using a combination of experimental data and models. These included base oils and their mixtures with polymeric additives, used in lubricants and ionic liquids, with cosolvent addition, for use in biomass and polymer processing. Experimental density data were collected using a variable-volume view-cell at pressures up to 40 MPa and temperatures up to 398 K. A unique high pressure rotational viscometer was developed to study the effect of pressure, temperature, and shear rate on viscosity while also allowing for the simultaneous examination of phase behavior. Viscosity data were collected at pressures up to 40 MPa, temperatures up to 373 K, and shear rates up to 1270 s-1. Experimental density and viscosity data were fit to a pair of coupled model equations, the Sanchez-Lacombe equation of state and the free volume theory respectively. From density, derived thermodynamic properties, namely isothermal compressibility, isobaric thermal expansion coefficient, and internal pressure, were calculated. By generating these models, viscosity could be viewed in terms of density, allowing for a direct link with thermodynamic properties. In the first part of the study, the effect of composition on density, thermodynamic properties, and viscosity was examined for base oils used in automotive lubricants. Six different base oils, four mineral oils and two synthetic oils, were studied to develop a better understanding on how the thermodynamic properties, particularly isothermal compressibility and internal pressure, vary with the concentration of cyclic molecules in the oil stock. Isothermal compressibility was found to decrease with cycloalkane content, while internal pressure increased. Additionally, the effect of two different polymeric additives on the volumetric properties and viscosity of a base oil composed of poly(α olefins) was examined. Both additives are polymethacrylate based, one with amine functionality, and are used as viscosity index modifiers in engine oils and automatic transmission fluids. The polymer with amine functionality was found to have a significant effect on internal pressure, seen as a large drop at high polymer concentration (7 mass percent), due to the addition of repulsive intermolecular interactions. In the second part of the study, six ionic liquids with the 1-alkyl-3-methylimidazolium cation and their mixtures with ethanol were examined. Two anions were used, chloride and acetate. The effect of ethanol addition on the derived thermodynamic properties and viscosity was studied in terms of chain length of the alkyl group on the cation. In addition, a method of estimating Hildebrand solubility parameter was employed, allowing for solubility parameter to be put in terms of pressure, temperature, and composition. The effect of cosolvent addition on the thermodynamic properties was changed by the length of the alkyl group on the cation. As the cation became bulkier, anion-cation interactions weakened, allowing for an increase in the anion-cosolvent interactions. / Doctor of Philosophy / The present thesis aims to understand both the density and viscosity of various fluid mixtures at high pressures and temperatures through both experiments and modeling. By studying these properties simultaneously, a more holistic view of a fluid can be developed to predict its usefulness for a specific application. This is especially important in the case of fluid mixtures, where, in addition to temperature and pressure, composition needs to be taken into account. To accomplish the experimental portion of this work, a new high pressure rotational viscometer was developed to measure viscosity as a function of temperature and pressure in conjunction with a preexisting technique for measuring density. This experimental data was used to create models, allowing for a better understanding of the effect of temperature, pressure, and composition on both density and viscosity along with certain thermodynamic properties. In the first part of the study, oils and additives used to make lubricants with automotive applications, such as engine oils and automatic transmission fluids, were studied. By studying the properties of these mixtures under pressure, a better understanding of how properties key to lubricant effectiveness are related to temperature, pressure, and composition can be developed. In the second part of the study, ionic liquids, salts with melting points below 100oC, and their mixtures with ethanol were studied. Ionic liquids have unique properties and have been studied for use in batteries, polymer processing, biomass processing, and gas capture. Due to the wide range of potential ionic liquids with various properties that can be made, these salts have been described as tailorable solvents. By adding an additional solvent, the resulting mixture can be tuned through temperature, pressure, and composition. Using the set of tools employed in the present work, important properties for process design were calculated. In particular, the Hildebrand solubility parameter was estimated as a function of temperature, pressure, and composition. The solubility parameter is a useful tool in predicting whether or not a material will dissolve in the solvent of choice.

Ion-containing block copolymers blend ionic liquid properties with well-defined polymer architectures. This provides conductive materials with robust mechanical stability, efficient processability, and tunable macromolecular design. Conventional free radical polymerization and anion exchange achieved copolymers containing n-butyl acrylate and phosphonium ionic liquids. These compositions incorporated vinylbenzyl triphenyl phosphonium and vinylbenzyl tricyclohexyl phosphonium cations bearing chloride (Cl), or bis(trifluoromethane sulfonyl)imide (Tf2N) counteranions. Differential scanning calorimetry and dynamic mechanical analysis provided corresponding thermomechanical properties. Factors including cyclic substituents, counteranion type, as well as ionic concentration significantly influenced phosphonium cation association. 1, 1\'-(1, 4-Butanediyl)bis(imidazole) neutralized NexarTM sulfonated pentablock copolymers and produced novel electrostatically crosslinked membranes. Variable temperature FTIR and 1H NMR spectroscopy confirmed neutralization. Atomic force microscopy and small angle X-ray scattering studied polymer morphology and revealed electrostatic crosslinking characteristics. Tensile analysis, dynamic mechanical analysis, thermogravimetric analysis, and vapor sorption thermogravimetric analysis investigated polymer properties. The neutralized polymer demonstrated enhanced thermal stability, decreased water adsorption, and well-defined microphase separation. These findings highlight NexarTM sulfonated pentablock copolymers as reactive platforms for novel, bis-imidazolium crosslinked materials. 4-Vinylbenzyl piperidine is a novel styrenic compound that observably autopolymerizes. In situ FTIR spectroscopy monitored styrene and 4-vinylbenzyl piperidine thermal polymerizations. A pseudo-first-order kinetic treatment of the thermal polymerization data provided observed rate constants for both monomers. An Arrhenius analysis derived thermal activation energy values. 4-Vinylbenzyl piperidine exhibited activation energy 80 KJ/mol less than styrene. The monomer differs from styrene in its piperidinyl structure. Consequently, in situ FTIR spectroscopy also monitored styrene thermal polymerization with variable N-benzyl piperidine concentrations. Under these circumstances, styrene revealed activation energy 60 KJ/mol less than its respective bulk value. The similarities in chemical structure between styrene and 4-vinylbenzyl piperidine suggested thermally initiated polymerization occurred by the Mayo mechanism.  The unique substituent is proposed to offer additional cationic effects for enhancing polymerization rates. Living anionic polymerization of 4-vinylbenzyl piperidine achieved novel piperidinyl-containing polymers.  Homopolymer and copolymer architectures of this design offer structural integrity, and emphasize base stability.  Sequential anionic polymerization afforded a 10K g/mol poly(tert-butyl styrene-co-4-vinylbenzyl piperidine) diblock and a 50K poly(tert-butyl styrene-co-isoprene-co-4-vinylbenzyl piperidine) triblock. Alkylation studies involving a phosphonium bromide salt demonstrated the future avenues for piperidinium based polymer designs. These investigations introduce piperidinyl macromolecules as paradigms for a new class of ammonium based ionic materials. / Master of Science

In this work, the development of parameters for a series of imidazolium-based ionic liquids molecules, now included in the AMOEBA force field, is discussed. The quality of obtained parameters is tested in a variety of calculations to reproduce structural, thermodynamic, and transport properties. First, it is proposed a novel method to parameterize in a faster, and more efficient way parameters for the AMOEBA force field that can be applied to any imidazolim-based cation. Second, AMOEBA-IL polarizable force field is applied to study the N-tert-butyloxycarbonylation of aniline reaction mechanism in water/[EMIM][BF4] solvent via QM/MM approach and compared with the reaction carried out in gas-phase and implicit solvent media. Third, AMOEBA-IL force field is applied in alchemical calculations. Free energies of solvation for selected solutes solvated in [EMIm][OTf] are calculated via BAR method implemented in TINKER considering the effect of polarization as well as the methodology to perform the sampling of the alchemical process. Finally, QM/MM calculations using AMOEBA to get more insights into the catalytic reaction mechanism of horseradish peroxidase enzyme, particularly the structures involved in the transition from Cp I to Cp II.

La recherche de phases magnétiques exotiques de la matière qui fondent même à T=0 uniquement sous l'action des fluctuations quantiques a été long et ardu, à la fois théoriquement et expérimentalement. La percée est venue récemment avec la découverte de l'Herbertsmithite, un composé formant un réseau kagome parfait avec des moments magnétiques de spin-1/2. Des expériences pionnières, mêlant des mesures de NMR, µSR et de diffusion de neutrons, ont montré une absence totale de gel ou d'ordre des moments magnétiques de spin, fournissant ainsi une forte signature d'une phase paramgnétique quantique. Théoriquement, l'Herbertsmithite est extrêmement bien modélisé par le modèle de Heisenberg quantique antiferromagnétique pour des spins-1/2 sur le réseau kagome, problème qui n'a pas été résolu jusqu'à présent. Plusieurs méthodes approximatives numériques et analytiques ont donné différents états fondamentaux, allant des liquides de spins Z2 gappés et un liquide de spins exotique algébrique U(1) de Dirac aux liquides de spins chiraux et les cristaux à liaisons de valence. Dans cette thèse, le problème est traité dans le cadre d'une approche particule-esclave fermionique, à savoir le formalisme des fermions de Schwinger SU(2). Il est conclu qu'un liquide de spins sans gap algébrique de Dirac a l'énergie variationnelle la plus basse et peut en fait constituer un vrai état fondamental physique de liquide de spins. Une implémentation sophistiquée de méthodes numériques de pointes comme le Monte-Carlo variationnel, le Monte-Carlo fonctions de Green et l'application de pas Lanczos dans un schéma variationnel ont été utilisés. Il est montré que contrairement à la croyance habituelle, le liquide de spins de Dirac U(1) projeté en "2+1" dimensions est remarquablement robuste par rapport à une large classe de perturbations, incluant les liquides de spins topologiques Z2 et les cristaux à liaisons de valence. De plus, l'application de deux pas Lanczos sur la fonction d'onde du liquide de spins de Dirac U(1) montre que son énergie est compétitive avec celles proposées pour les liquides de spins topologiques Z2. Ce résultat, combiné avec les indications expérimentales qui pointent vers un liquide de spins sans gap pour l'Herbertsmithite, appuie l'affirmation que le vrai état fondamental de ce modèle est en fait un liquide de spins algébrique de Dirac.

No description available.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In light of the rapid depletion of the world’s oil reserves, concerns about energy security prompted the exploration of alternative sources of liquid fuels for transportation. One such alternative is the production of synthetic fuels with the indirect coal liquefaction process or Coal-To-Liquids (CTL) process. In this process, coal is burned in a gasifier in the presence of steam and oxygen to produce a synthesis gas or syngas, consisting mainly of hydrogen and carbon monoxide. The syngas is then converted to liquid fuels and a variety of useful chemicals in a Fischer Tropsch synthesis reactor. However, the traditional process for syngas production also produces substantial amounts of carbon dioxide. In fact, only about one third of the carbon in the coal feedstock ends up in the liquid fuel product using traditional CTL technology. If additional hydrogen was available, the carbon utilisation of the process could be improved significantly. The high temperature reactor (HTR) is a gas cooled Generation IV nuclear reactor ideally suited to provide electrical power and high temperature heat for the production of carbon neutral hydrogen via high temperature electrolysis. The integration of an HTR into a CTL process therefore provides an opportunity to improve the thermal and carbon efficiency of the CTL process significantly. This thesis presents a possible process flow scheme for a nuclear assisted CTL process. The system is evaluated in terms of its thermal or syngas production efficiency (defined as the ratio of the heating value of the produced syngas to the sum of the heating value of the coal plus the HTR heat input) as well as its carbon utilisation. If the hydrogen production plant is sized to produce only enough associated oxygen to supply in the needs of the gasification plant, syngas is produced at about 63% thermal efficiency, while 71.5% of the carbon is utilised in this process. It was found that the optimum HTR outlet temperature to produce hydrogen with a high temperature steam electrolysis process is 850°C. If enough process heat and electrical power are available and process equipment capacities are sufficient, the carbon utilisation of the process could be improved even further to values in excess of 90%. / AFRIKAANSE OPSOMMING: Die uitputting van die wêreld se olie-reserwes, asook kommer oor energiesekuriteit het daartoe gelei dat alternatiewe bronne van vloeibare brandstowwe vir vervoer ondersoek moes word. Een so 'n alternatief is die produksie van sintetiese brandstof d.m.v. die indirekte steenkool vervloeiing proses of sogenaamde Coal-To-Liquids (CTL) proses. In hierdie proses word steenkool in die teenwoordigheid van stoom en suurstof in 'n vergasser gebrand om 'n sintesegas of singas te produseer, wat hoofsaaklik uit waterstof en koolstofmonoksied bestaan. Die sintesegas word daarna omgeskakel na vloeibare brandstowwe en 'n verskeidenheid van nuttige chemikalieë in 'n Fischer-Tropsch-sintese reaktor. Ongelukkig produseer die tradisionele proses vir sintesegas produksie ook 'n beduidende hoeveelheid koolstofdioksied. Trouens, slegs sowat een derde van die koolstof in die steenkool roumateriaal eindig in die vloeibare brandstof produk indien van tradisionele CTL-tegnologie gebruik gemaak word. Indien addisionele waterstof beskikbaar was, kon die koolstofbenutting van die proses aansienlik verbeter word. Die hoë temperatuur reaktor (HTR) is 'n gas-verkoelde Generasie IV kernreaktor wat by uitstek geskik is om elektrisiteit en hoë temperatuur hitte te verskaf vir die produksie van koolstofneutrale waterstof d.m.v. hoë temperatuur elektrolise. Die integrasie van 'n HTR in 'n CTL-proses bied dus 'n geleentheid om die termiese- en koolstofdoeltreffendheid van die CTL-proses aansienlik te verbeter. In hierdie ondersoek word 'n moontlike proses vloeidiagram vir 'n kern-gesteunde CTL-proses voorgestel. Die stelsel is geëvalueer in terme van sy termiese- of sintesegas produksie doeltreffendheid (gedefinieer as die verhouding van die hittewaarde van die geproduseerde sintesegas gedeel deur die som van die hittewaarde van die steenkool en die HTR hitte-insette) sowel as sy koolstof-effektiwiteit. Indien die waterstof produksie-aanleg ontwerp word om net genoeg geassosieerde suurstof te voorsien om in die behoeftes van die vergassing-aanleg te voorsien, word sintesegas teen ongeveer 63% termiese doeltreffendheid vervaardig, terwyl 71.5% van die koolstof in hierdie proses benut word. Daar is bevind dat 850°C die optimum HTR uitlaat temperatuur is om waterstof d.m.v. hoë temperatuur stoom-elektrolise te vervaardig. Indien daar genoeg proses hitte en elektrisiteit beskikbaar is en die proses toerusting kapasiteite voldoende is, sou die koolstof-benutting van die proses tot meer as 90% verbeter kon word.

Thesis (MScEng)--Stellenbosch University. / ENGLISH ABSTRACT: Carbon dioxide (CO2) is classified as the main greenhouse gas (GHG) contributing to global warming. Estimates by the Intergovernmental Panel on Climate Change (IPCC) suggest that CO2 emissions must be reduced by between 50 to 85% by 2050 to avoid irreversible impacts. Carbon capture and storage (CCS) strategies can be applied to de-carbonize the emissions from fossil-fueled power plants. Compared to other CCS techniques, post-combustion capture (PCC) is most likely to be implemented effectively as a retrofit option to existing power plants. At present however CCS is not yet commercially viable. The main challenge with CCS is to reduce the inherent energy penalty of the CO2 separation stage on the host plant. Seventy-five to eighty percent of the total cost of CCS is associated with the separation stage. There are several technologies available for separating CO2 from power plant flue gas streams. Reactive absorption with aqueous amine solutions has the ability to treat low concentration, low pressure and large flux flue gas streams in industrial-scale applications. It is most likely to be the first technology employed commercially in the implementation of CCS. The energy required for solvent regeneration however, is high for the standard solvent used in reactive absorption processes, i.e. MEA. This leads to a reduction in thermal efficiency of the host plant of up to 15%. Alternative solvent formulations are being evaluated in an attempt to reduce the energy intensity of the regeneration process. The main objective of this study was to establish a novel, simplified thermodynamic method for solvent screening. Partial solubility parameters (PSPs) were identified as the potential basis for such a method. The major limitation of this approach is that the model doesn’t account for effects from chemical reaction(s) between materials, e.g. CO2 reacting with aqueous alkanolamine solutions; considering only the effects from dissolution. The EquiSolv software system was developed based on PSP theory. The Hansen 3-set PSP approach was used to describe the equilibrium behaviour of CO2 absorbing in task specific solvents. The Hansen theory was expanded to a 4-set approach to account for contributions from electrostatic interactions between materials. The EquiSolv program was used successfully to screen large sets of solvent data (up to 400 million formulations) in the search for suitable alternative solvent formulations for CO2 absorption. The secondary objective of this study was to evaluate the ability of the proposed PSP model to accurately predict suitable alternative solvents for CO2 absorption through preliminary experimental work. A series of CO2 absorption experiments were conducted to evaluate the absorption performance of predicted alternative solvent formulations. The predicted alternative solvent formulations exhibited a significant improvement in absorption performance (up to a 97% increase in the measured absorption capacity) compared to conventional solvent formulations. Statistical analysis of the experimental results has shown that there is a statistically significant concordant relationship between the predicted and measured rankings for the absorption performance of the predicted solvent formulations. Based on this it was concluded that PSP theory can be used to accurately predict the equilibrium behaviour of CO2 absorbing in task specific solvents. Recently ionic liquids (ILs) have been identified as potential alternatives to alkanolamine solutions conventionally used for CO2 absorption. Absorption experiments were conducted as a preliminary assessment of the absorption performance of ILs. Results have shown ILs to have significantly improved performance compared to conventional alkanolamine solvents; up to a 96% increase in the measured absorption capacity compared to conventional solvents. Future work should focus on developing task specific ionic liquids (TSILs) in an attempt to reduce the energy intensity of solvent regeneration in CO2 absorption processes. / AFRIKAANSE OPSOMMING: Koolsuurgas (CO2) word geklassifiseer as die vernaamste kweekhuis gas (GHG) wat bydra to globale verwarming. Beramings deur die Interregeringspaneel oor Klimaatsverandering (IPKV) toon aan dat CO2 emissies teen 2050 verminder moet word met tussen 50 en 85% om onomkeerbare invloede te vermy. Verskeie koolstof opvangs en bergings (KOB) strategieë kan toegepas word ten einde die koolstof dioksied konsentrasie in die emissies van kragstasies wat fossielbrandstowwe gebruik, te verminder. Naverbranding opvangs (NVO) is die mees aangewese KOB tegniek wat effektief toegepas kan word op bestaande kragstasies. Tans is KOB egter nog nie kommersieël lewensvatbaarvatbaar nie. Die hoof uitdaging wat KOB in die gesig staar is om die energie boete inherent aan die CO2 skeidingstap te verminder. Tussen vyf-en-sewentig en tagtig persent van die totale koste van KOB is gekoppel aan die skeidingstap. Daar is verskeie metodes beskikbaar vir die skeiding van CO2 uit die uitlaatgasse van kragstasies. Reaktiewe absorpsie met waterige oplossings van amiene kan gebruik word om lae konsentrasie, lae druk en hoë vloei uitlaatgasstrome in industriële toepassings te behandel. Dit is hoogs waarskynlik die eerste tegnologie wat kommersieël aangewend sal word in die toepassing van KOB. Die oplosmiddel wat normalweg vir reaktiewe absorpsie gebruik word (d.w.s. MEA) benodig egter ‘n groot hoeveelheid energie vir regenerasie. Dit lei tot ‘n afname in die termiese doeltreffendheid van die voeder aanleg van tot 15%. Alternatiewe oplosmiddelstelsels word tans ondersoek in ‘n poging om the energie intensiteit van die regenerasieproses te verminder. Die hoof doelwit van hierdie studie was om ‘n nuwe, ongekompliseerde termodinamiese metode te vestig vir die keuring van alternatiewe oplosmiddels. Parsiële oplosbaarheidsparameters (POPs) is geïdentifiseer as ‘n moontlike grondslag vir so ‘n metode. Die model beskryf egter slegs die ontbindings gedrag van materiale. Die effekte van chemise reaksie(s) tussen materiale, bv. die tussen CO2 en waterige oplossings van alkanolamiene, word nie in ag geneem nie. Die POP teorie het gedien as grondslag vir die ontwerp van die EquiSolv sagteware stelsel. Die Hansen stel van drie POPs is gebruik om die ewewigsgedrag te beskryf van CO2 wat absorbeer in doelgerig-ontwerpte oplosmiddels. Die Hansen teorie is verder uitgebrei na ‘n stel van vier POPs om die bydrae van elektrostatiese wisselwerking tussen materiale in ag te neem. Die EquiSolv program is verskeie kere met groot sukses gebruik vir die sifting van groot stelle data (soveel as 400 miljoen formulasies) in die soektog na alternatiewe oplosmiddels vir CO2 absorpsie. Die sekondêre doelwit van die studie was om die vermoë van die voorgestelde POP model om geskikte alternatiewe oplosmiddels vir CO2 absorpsie akkuraat te voorspel, te ondersoek deur voorlopige eksperimentele werk. ‘n Reeks CO2 absorpsie eksperimente is gedoen ten einde die absorpsie werkverrigting van die voorspelde alternatiewe oplosmidels te ondersoek. ‘n Verbetering in absorpsie werkverrigting van tot 97% is gevind vir die voorspelde oplosmiddels vergeleke met die van oplosmiddels wat tipies in die industrie gebruik word. Statistiese ontleding van die eksperimentele resultate het getoon dat daar ‘n beduidende ooreenstemming tussen die voorspelde en gemete rangskikking van die voorspelde oplosmiddels se werkverrigting bestaan. Dus kan POP teorie gebruik word om die absorpsie van CO2 in doelgerig-ontwerpte oplosmiddels akkuraat te beskryf. Ioniese vloeistowwe (IVs) is onlangs geïdentifiseer as moontlike alternatiewe oplosmidels vir die alkanolamien oplossings wat normaalweg gebruik word vir CO2 absorpsie. Absorpsie eksperimente is gedoen ten einde ‘n voorlopige raming van die absorpsie werkverrigting van IVs te bekom. Daar is bevind dat IVs ‘n beduidende verbetering in werkverrigting toon in vergelyking met die alkanolamien oplosmiddels wat normaalweg gebruik word. ‘n Verbetering in absorpsie werkverrigting van tot 96% is gevind vir die voorspelde IV-bevattende oplosmiddels vergeleke met die van oplosmiddels wat tipies in die industrie gebruik word. Die fokus van toekomstige navorsing moet val op die ontwikkeling van doelgemaakte ioniese vloeistowwe (DGIVs) in ‘n poging om die energie intensiteit van oplosmiddel regenerasie in CO2 absorpsie prosesse te verminder.

An exploration of some organic-inorganic hybrid metal fluorides and lanthanide containing metal organic frameworks (Ln-MOFs) has been carried out under ionothermal conditions. In this synthesis technique an ionic liquid (IL) or deep eutectic mixture (DES) is used as the solvent and in many cases as the provider of the organic structure directing agent. A wide range of ILs and DESs have been investigated as the reaction solvent for the synthesis of organically templated vanadium fluorides and oxyfluorides (VOFs), and initially this has proved to be successful with the isolation of 13 phases, including eight new materials. In the VOFs synthesis the IL acts as a solvent, however the DES acts as a solvent and also as a template delivery agent, where the expected template is provided by the partial breakdown of the urea derivative component. Interestingly, it has been shown that the same structure can be accessible via two different ways; either by using IL with an added templating source, or simply through the use of a DES without any other additive; since the template is provided by the in situ breakdown of the DES. The synthesis of VOFs with extended structures was achieved by the use of the hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM Tf₂N) as the solvent. [HNC₅H₅][V₂O₂F₅] represents the first VOF with a 2D network that contains exclusively V⁴⁺. This material may be considered as arising via condensation of the previously known ladder-like chains. Furthermore, using imidazole as an added template has produced another layer material that has significant similarities to the [HNC₅H₅][V₂O₂F₅] structure, but with some key differences. Within the same system three other phases were also isolated, including two novel materials displaying the known ladder-type building units. Further investigations in the ionothermal synthesis of VOF using EMIM Tf₂N resulted in a successful synthesis of [NH₄]₂[HNC₇H₁₃][V₇O₆F₁₈], a novel material displaying a unique double layered topology featuring a S = ½ kagome type lattice of V⁴⁺ ions (d¹). Two of the V⁴⁺ based kagome sheets are pillared by V³⁺ ions to form a double layered structure templated by both ammonium and quinuclidinium cations. This compound exhibits a high degree of magnetic frustration, with significant antiferromagnetic interactions but no long range ordering was observed above 2 K. This material presents an interesting comparison to the famous Herbertsmithite, ZnCu₃(OH)₆Cl₂, and may provide an excellent candidate for realising a quantum spin liquid (QSL) ground state. Interestingly, in this system the use of EMIM Tf₂2N as a solvent produces mainly V⁴⁺-containing materials, despite the high reaction temperature (170 °C). This characteristic is unprecedented in VOFs synthesis, as rising the reaction temperature above 150 °C in other techniques (i.e. hydrothermal synthesis) would often result in further reduction of V⁴⁺ to V³⁺. Using the ionothermal technique in the synthesis of hybrid iron fluorides resulted in the isolation of three chain-type materials. Again, the IL acts as the solvent and the DES acts as the solvent and also as the template provider where the expected template is released by the partial breakdown of the urea derivative component of the DES. The synthesis of Ln-MOF using a choline chloride/ 1,3-dimethylurea deep eutectic mixture has produced three novel isostructural materials. Usually, in ionothermally prepared materials (i.e. zeolites) the urea portion of the DES is unstable and breaks down in situ to form ammonium or alkylammonium cations. In the ionothermal synthesis of Ln-MOF, 1,3-dimethyurea (DMU) remains intact and is occluded in the final structure. Using a choline chloride/ethylene glycol deep eutectic solvent led to the isolation of a Ln-MOF with interesting structural properties, however none of the DES components appeared in the final structure. These results demonstrate once more the usefulness and applicability of the ionothermal synthesis method and emphasise how this synthesis technique can be further extended and applied in the preparation of important structures with unique properties and functionalities.

<p>The electronic and geometrical structure of free neutral clusters and liquids have been studied using synchrotron-radiation based photoelectron and Auger electron spectroscopy in combination with lineshape modeling. A novel experimental setup has been developed for studies of liquids, based on the liquid microjet technique. Theoretical lineshapes have been computed using both classical (molecular dynamics) and quantum mechanical (mainly density functional theory) methods.</p><p>Clusters are finite ensembles of atoms or molecules, ranging in size from a few to several thousand atoms. Apart from being fundamentally interesting, clusters are also promising as building blocks for nano-technology. In this thesis results are presented for rare-gas and molecular clusters, ranging from weakly van-deer-Waals bonded to hydrogen bonded. It is shown that the combination of core-level photoelectron spectroscopy (XPS) and lineshape modeling can be used to estimate the sizes of clusters. A model for treating the effect of inter-molecular nuclear relaxation upon ionization is proposed. The structure of single-component molecular clusters are investigated by molecular dynamics simulations, validated against XPS data. Finally, the radial structure of a two-component molecular cluster is investigated by XPS.</p><p>Liquids have been studied for centuries, but still many questions remain regarding the microscopic properties. With the recent development of the liquid microjet technique, new insight into the atomic structure can be obtained. In this thesis we study aqueous solutions using photoelectron and Auger electron spectroscopy (AES). We investigate the structure of surface active molecules by XPS, study the Auger decay after core-level ionization in aqueous potassium chloride (KCl), and follow the changes in molecular structure of glycine as a function of pH.</p>

Thermochemical water splitting cycles have been conceptualized and researched for over half a century, yet to this day none are commercially viable. The heavily studied Sulfur-Iodine cycle has been stalled in the early development stage due to a difficult HI-H₂O separation step and material compatibility issues. In an effort to avoid the azeotropic HI-H₂O mixture, an imidazolium-based ionic liquid was used as a reaction medium instead of water. Ionic liquids were selected based on their high solubility for SO₂, I₂, and tunable miscibility with water. The initial low temperature step of the Sulfur-Iodine cycle was successfully carried out in ionic liquid reaction medium. Kinetics of the reaction were investigated by I₂ colorimetry. The reaction also evolved H₂S gas, which led to the conceptual idea of a new Sulfur-Sulfur thermochemical cycle, shown below: / 4I₂(l)+4SO₂(l)+8H₂O(l)↔4H₂SO₄(l)+ 8HI(l) / 8HI(l)+H₂SO₄(l)↔ H₂S(g)+4H₂O(l)+4I₂(l) / 3H₂SO₄(g)↔ 3H₂O(g)+3SO₂(g)+1½O₂(g) / H₂S(g)+2H₂O(g)↔ SO₂(g)+3H₂(g) / The critical step in the Sulfur-Sulfur cycle is the steam reformation of H₂S. This highly endothermic step is shown to successfully occur at temperatures in excess of 800˚C in the presence of a molybdenum catalyst. A parametric study varying the H₂O:H₂S ratio, temperature, and residence time in a simple tubular quartz reactor was carried out and Arrhenius parameters were estimated. All reactive steps of the Sulfur-Sulfur cycle have been either demonstrated previously or demonstrated in this work. A theoretical heat-to-hydrogen thermal efficiency is estimated to be 55% at a hot temperature of 1100 K and 59% at 2000 K. As a highly efficient, all-fluid based thermochemical cycle, the Sulfur-Sulfur cycle has great potential for feasible process implementation for the transformation of high quality heat to chemical energy. / Graduation date: 2012