The synthesis of a scandium aluminium methylphosphonate ScAl₃(CH₃PO₃)₆ isostructural to the aluminium methylphosphonate AlMePO-α and with permanent microporosity is reported here for the first time. Structural characterisation of three lanthanide bisphosphonate structures (I,II,III) with the light lanthanides and N,N'-piperazine bis-(methylenephosphonic acid) and its 2-methyl and 2,5-dimethyl derivatives is described. The framework of structure type I shows considerable flexibility upon dehydration with a symmetry change from C2/c, a = 23.5864(2) Å, b = 12.1186(2) Å, c = 5.6613(2) Å, β = 93.040(2)˚) in the hydrated state to P2₁/n, a = 21.8361(12) Å, b = 9.3519(4) Å, c = 5.5629(3) Å, β = 96.560(4)˚ after dehydration. This cell volume reduces by 27% on dehydration and is accompanied by a change in the conformation of the piperazine ring from chair to boat configuration. The structures of type I (hydrated and dehydrated) were refined against synchrotron powder X-ray diffraction data. Despite the reversible hydration and flexibility, the structures possess no permanent porosity. Investigation of the solvothermal chemistry of scandium carboxylates identified routes to 7 framework structures 5 of which were previously unreported in the scandium system. Lower temperature solvothermal reactions using terephthalic acid (80 - 140°C using dimethylformamide and diethylformamide) yielded two scandium terephthalates, MIL-88B(Sc) and MIL-101(Sc), identified by laboratory X-ray powder diffraction. Whereas higher temperature (160 – 220°C), reactions gave MIL-53(Sc) and Sc₂BDC₃. Further study with the tri- and tetra-carboxylate linkers, trimesic acid, 3,3',5,5'-azobenzenetetracarboxylic acid and pyromellitic acid yielded MIL-100(Sc), Sc-ABTC and Sc₄PMA₃ respectively. Structural identification of MIL-100(Sc) and Sc-ABTC was performed by means of X-ray powder diffraction analysis and of Sc₄PMA₃ by single crystal X-ray diffraction. The structure of a small pore scandium terephthalate Sc₂BDC₃ was investigated as a function of temperature and of functionalization. In situ synchrotron X-ray diffraction data, collected on a Sc₂BDC₃ in vacuo, enabled a phase change from orthorhombic Fddd to monoclinic C2/c and the associated structural effects to be observed in detail. The orthorhombic structure displayed a negative thermal expansivity of 2.4 × 10⁻⁵ K⁻¹ over the temperature range 225 – 523 K which Rietveld analysis showed to be derived from carboxylate group rotation. Motion within the framework was studied by ²H wide-line and MAS NMR on deuterated Sc₂BDC₃ indicating π flips can occur in the phenyl rings above 298 K. The effects of functionalization on the Sc₂BDC₃ framework were investigated by reactions using the 2-amino- and 2-nitroterephthalic acid and gave evidence for a strong structural effect resulting from inclusion of the functional groups. The structure of Sc₂BDC₃ and the functionalised derivatives were solved using Rietveld analysis on synchrotron X-ray powder diffraction data. Sc₂(NH₂-BDC)₃ was solved using the orthorhombic Sc₂BDC₃ framework starting model and, over the temperature range studied, stayed orthorhombic Fddd. Sc₂(NO₂-BDC)₃, was shown to be monoclinic C2/c over the same temperature range, a result of the steric effects of the bulky –NO₂ group in a small pore framework. Partial ordering of the functional groups was observed in both Sc₂(NH₂-BDC)₃ and Sc₂(NO₂-BDC)₃. The strength of interaction for the Sc₂(NH₂-BDC)₃ with CO₂ was higher than that of the parent Sc₂BDC₃ due to the strong –NH₂•••CO₂ interaction. Despite the inclusion of a relatively large –NO₂ group along the walls of a channel ~4 Å in diameter the Sc₂(NO₂-BDC)₃ still showed permanent microporosity to CO₂ (2.6 mmol g⁻¹) suggesting that there must be some motion in the -NO₂ group to allow the CO₂ molecules to diffuse through the channels. The scandium analogue of the flexible terephthalate MIL-53, a competitive phase in the synthesis of Sc₂BDC₃, was prepared and characterised by Rietveld analysis on synchrotron X-ray powder diffraction data using a combination of literature structural models and models obtained from single crystal X-ray diffraction experiments. Experimental solid state ⁴⁵Sc, ¹³C and ¹H NMR data combined with NMR calculations on the structural models produced from diffraction analysis were used to identify the hydrated (MIL-53(Sc)-H₂O), calcined (MIL-53(Sc)-CAL) and high temperature (MIL-53(Sc)-HT) structures of MIL-53(Sc). Further to this the 2-nitroterephthalate derivative, MIL-53(Sc)-NO₂, was prepared and characterised using single crystal X-ray diffraction. The adsorptive properties of the parent terephthalate and the functionalised derivative were compared and in both cases showed a breathing behaviour, exemplified by steps in the adsorption isotherms. MIL-53(Sc)-CAL was found to possess a closed pore configuration in the dehydrated state, a previously unreported structural form for the MIL-53 series, and its presence can be observed in the low pressure region of the CO₂ adsorption isotherm as a non-porous plateau. The selectivity and separation properties of two MOFs, the nickel bisphosphonate, STA-12(Ni) and the scandium carboxylate, Sc₂BDC₃ were measured using breakthrough curves on mixtures of CH₄ and CO₂. The results showed both materials to be highly selective in the adsorption of CO₂ over CH₄. Column testing using a PLOT column of STA-12(Ni) and a packed column of Sc₂BDC₃ showed promising preliminary results with STA-12(Ni) displaying effective, baseline separation on low boiling point hydrocarbon mixtures (C1 – C4) while the smaller pore channels of Sc₂BDC₃ were effective in the size selective separation of higher boiling point branched and straight-chain hydrocarbons (C5 – C7).

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Strong electron-electron correlations and lattice frustration are two physical interactions that pose serious challenges to condensed matter physics. A variety of exotic physical phenomena, for example, charge ordering, spin liquid, and unconventional superconductivity, are believed to arise from the interplay of the two interactions. In this dissertation, I examine two families of systems which exhibit both electron-electron correlations and lattice frustration – charge transfer solids and layered cobaltates. The half-filled band Hubbard model on the triangular lattice has been proposed by mean-field theories as the minimal model for the superconductivity in the charge transfer solids. In the first part of this dissertation, by using exact calculations, I prove the absence of superconductivity in this model. This result calls for a new theoretical approach to describe the rich physics in charge transfer solids. In the second part of this dissertation, I study charge transfer solids by focusing on its real bandfilling ¼. I show that a new kind of insulating phase, paired electron crystal, emerges from antiferromagnetism as the frustration is increased. The paired electron crystal state can explain the various insulating states adjacent to the superconducting state, thus provides a new avenue towards the understanding of the unconventional superconductivity in charge transfer solids and other ¼ filled systems. In the third part of this dissertation, I investigate the carrier concentration-dependent electronic behavior in layered cobaltates. I provide a natural yet simple explanation for this behavior. I show that it can be described within correlated-electron Hamiltonians with finite on-site and significant nearest neighbor hole-hole Coulomb repulsions. I also point out the similarities between organic charge transfer solids and layered cobaltates, which may involve superconductivity.

No description available.

No description available.

In Chapter 2, we consider the hydrostatic equilibrium figure of a rotating earth model with arbitrary radial density profile. We derive an exact non-linear partial differential equation describing the equilibrium figure. Perturbation theory is used to obtain approximate forms of this equation, and we show that the first-order theory is equivalent to Clairaut's equation. In Chapter 3, a method for parametrizing the possible equilibrium stress fields of a laterally heterogeneous earth model is described. In this method a solution of the equilibrium equations is first found that satisfies some desirable physical property. All other solutions can be written as the sum of this equilibrium stress field and a divergence-free stress tensor field whose boundary tractions vanish. In Chapter 4, we consider the minor vector method for the stable numerical solution of systems of linear ordinary differential equations. Results are presented for the application of the method to the calculation of seismic displacement fields in spherically symmetric, self-gravitating earth models. In Chapter 5, we present a new implementation of the direct solution method for calculating normal mode spectra in laterally heterogeneous earth models. Numerical tests are presented to demonstrate the validity and effectiveness of this method for performing large mode coupling calculations. In Chapter 6, we consider the theoretical basis for the viscoelastic normal mode method which is used in studies of seismic wave propagation, post-glacial rebound, and post-seismic deformation. We show how the time-domain solution to the viscoelastodynamic equation can be written as a normal mode sum in a rigorous manner.

In this thesis, the problem of well-posedness of nonlinear viscoelasticity under the assumptions allowing for phase transformations in solids is considered. In one space dimension we prove existence and uniqueness of the solutions for the quasistatic version of the model using approximating sequences corresponding to the case when initial data takes finitely many values. This special case also provides upper and lower bounds for the solutions which are interesting in their own rights. We also show equivalence of the existence theory we develop with that of gradient flows when the stored-energy function is assumed to be -convex. Asymptotic behaviour of the solutions as time goes to infinity is then investigated and stabilization results are obtained by means of a new argument. Finally, we look at the problem from the viewpoint of curves of maximal slope and follow a time-discretization approach. We introduce a three-dimensional method based on composition of time-increments, as a result of which we are able to deal with the physical requirement of frame-indifference. In order to test this method and distinguish the difficulties for possible generalizations, we look at the problem in a convex setting. At the end we are able to obtain convergence of the minimization scheme as time step goes to zero.

Afin de caractériser la physico-chimie des matières en suspension de la Moselle et de ses affluents, ce travail s’est appuyé sur une approche géochimique et minéralogique. Notre étude s’est concentrée sur l’analyse des polluants dans les compartiments dissous et particulaire. Ces études ont notamment permis de déterminer (i) la composition des constituants inorganiques dans les particules et colloïdes du milieu aquatique de la Moselle et d’un de ses affluents : la Fensch, (ii) l’évolution des contributions inorganiques le long de la Moselle et de la Fensch ainsi que leur transfert à la confluence Fensch-Moselle, tout en déterminant les sources principales de contamination, (iii) les associations organo-minérales et l’organisation des agrégats présents et (iv) d’étudier la spéciation de certains éléments par des microanalyses. Ce travail a ainsi permis de mettre en évidence l’importance des matières en suspension, souvent négligées par rapport aux autres compartiments Eau et Sédiments / This work uses geochemical and mineralogical approaches to characterize physical and chemical properties of suspended solids in the Moselle and its tributaries. The study focused on analyzing the pollutants in dissolved and particulate compartments. This allowed (i) the identification of inorganic components composition in particles and colloids in the aquatic environment of the Moselle and one of its tributaries: the Fensch, (ii) the determination of the evolution of inorganic contributions along Moselle and the Fensch and their transfer to the confluence Fensch-Moselle in addition to the determination of main contamination sources, (iii) the identification of organo-mineral associations and the determination of the organization of aggregates, (iv) the analysis of the speciation of some elements by microanalysis. This work highlighted the importance of studying suspended solids that are often neglected compared to water and sediments compartments

Bulk metallic glasses (BMGs) have received significant research interest due to their completely amorphous structure which results in unique structural and functional properties. Absence of grain boundaries and secondary phases in BMGs results in high corrosion resistance in many different environments. Understanding and tailoring the corrosion behavior can be significant for various structural applications in bulk form as well as coatings. In this study, the corrosion behavior of several Zr-based and Fe-Co based BMGs was evaluated to understand the effect of chemistry as well as quenched in free volume on corrosion behavior and mechanisms. Presence of Nb in Zr-based alloys was found to significantly improve corrosion resistance due to the formation of a stable passive oxide. Relaxed glasses showed lower rates compared to the as-cast alloys. This was attributed to lowering of chemical potential from the reduced fraction of free volume. Potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) techniques helped in quantifying the corrosion rate and polarization resistance. The effect of alloy composition was quantified by extensive surface analysis using Raman spectroscopy, energy dispersive x-ray spectroscopy and auger spectroscopy. Pitting intensity was higher in the as-cast glasses than the relaxed glasses. The electrochemical behavior of a Zr-Ti-Cu-Ni-Be bulk metallic glass subjected to high strain processing was studied. High strain processing caused shear band formation and an increase in the free volume. Potentiodynamic polarization and EIS showed a strong correlation between the enthalpy of structural relaxation and corrosion rate and polarization resistance. Pitting was observed to preferentially occur on shear bands in the processed samples, while it was stochastic in unprocessed glass. The corrosion analysis of Co-Fe glasses showed an increase in corrosion current density when Fe content was increased from 0 to 7 at%. The corrosion resistance improved when Fe content was further increased to 15 at%. Similar trend was seen in EIS studies. The improved corrosion resistance at 15 at% Fe can be attributed to the large supercooled region that facilitates the formation of completely amorphous alloy, in contrast to lower Fe containing alloys, where short range ordering may deteriorate the corrosion resistance. Porous metallic glass structure was developed by electrochemical dealloying via cyclic voltammetry. Mechanical properties and changes in electrical conductivity were measured as a function of depth from surface by nano-indentation and nano electrical contact resistance technique. The nanoporous layer was found have hardness of 0.41 GPa and elastic modulus of nearly 22 GPa. The resistivity of the nanoporous layer continuously decreased when moving towards the substrate as the indentation depth increased which is attributed to the gradient in pore size.

Biofuels production and utilisation can reduce the emission of greenhouse gases, dependence on fossil fuels and also improve energy security. Ethanol is the most important biofuel in the transportation sector; however, its production from lignocelluloses faces some challenges. Conventionally, lignocellulosic hydrolysis and fermentation has mostly been performed by separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). SHF results in product inhibition during enzymatic hydrolysis and increased contamination risk. During SSF, suboptimal conditions are used and the fermenting organism cannot be reused. Bacterial contamination is another major concern in ethanol production, which usually results in low ethanol yield. In these studies, the above-mentioned challenges have been addressed. A novel method for lignocellulosic ethanol production ‘Simultaneous saccharification filtration and fermentation (SSFF)’ was developed. It circumvents the disadvantages of SSF and SHF; specifically, it uses a membrane for filtration and allows both the hydrolysis and fermentation to be carried out at different optimum conditions. SSFF also offers the possibility of cell reuse for several cultivations. The method was initially applied to pretreated spruce, with a flocculating strain of yeast Saccharomyces cerevisiae. SSFF was further developed and applied to pretreated wheat straw, a xylose rich lignocellulosic material, using encapsulated xylose fermenting strain of S. cerevisiae. High solids loading of 12% suspended solids (SS) was used to combat bacterial contamination and improve ethanol yield. Oil palm empty fruit bunch (OPEFB) was pretreated with fungal and phosphoric acid in order to improve its ethanol yield. An evaluation of biofuel production in Nigeria was also carried out. SSFF resulted in ethanol yield of 85% of the theoretical yield from pretreated spruce with the flocculating strain. Combination of SSFF with encapsulated xylose fermenting strain facilitated simultaneous glucose and xylose utilisation when applied to pretreated wheat straw; this resulted in complete glucose consumption and 80% xylose utilisation and consequently, 90% ethanol yield of the theoretical level. High solids loading of 12% SS of pretreated birch resulted in 47.2 g/L ethanol concentration and kept bacterial infection under control; only 2.9 g/L of lactic acid was produced at the end of fermentation, which lasted for 160 h while high lactic acid concentrations of 42.6 g/L and 35.5 g/L were produced from 10% SS and 8% SS, respectively. Phosphoric acid pretreatment as well as combination of fungal and phosphoric pretreatment improved the ethanol yield of raw OPEFB from 15% to 89% and 63% of the theoretical value, respectively. In conclusion, these studies show that SSFF can potentially replace the conventional methods of lignocellulosic ethanol production and that high solids loading can be used to suppress bacterial infections during ethanol productions, as well as that phosphoric acid pretreatment can improve ethanol yield from lignocellulosic biomass. / <p>Thesis for the degree of Doctor of Philosophy at the University of Borås to be publicly defended on 31 October 2014, 10.00 a. m. in room E310, University of Borås, Allégatan 1, Borås.</p>