Mixing excipients is a common way to produce pharmaceutical materials with suitable properties for drug formulation. An understanding of the basic mechanisms involved in the formation and transformation of the structures of solid state mixtures is crucial if one is to be able to produce materials with the desired properties in a reliable way. In the first part of the thesis, the atomic force microscopy (AFM) technique was used to visualise the re-crystallisation of spray-dried amorphous particles comprised of lactose and PVP. The transformation was quantified on a single particle level and analysed with a common kinetic model, the JMAK-equation. The way in which the PVP was incorporated into the particles and the impact this had on their physical stability on exposure to increasing levels of humidity was investigated. The amount and, to a certain extent, the molecular weight of the PVP affected the moisture induced crystallisation of the particles. The inhibition was further discussed in terms of nucleation and growth. In the second part of the thesis, the formation of phases in solid dispersions of monoolein (MO) in PEGs was studied by the use of SAXS and DSC. Upon solidification of a melt, the components phase separated, resulting in a PEG-rich phase and an MO phase. MO was intercalated into the amorphous domains of the lamellar structure of PEG. A second MO phase appeared in the mixtures where the average molecular weight of PEG was 1500 and 4000 g/mol. It was hypothesised that this second phase was formed in conjunction with the expulsion of MO as the PEG unfolded. This thesis describes the application of two relatively unexplored solid state techniques on two different solid mixtures of pharmaceutical interest and, in so doing, contributes to the knowledge of phase formation and transformations in the solid state.

Properties of magnetic thin film devices cannot be understood without detailed knowledge of their structure. For this purpose, a variety of thin film and multilayer systems have been studied. Both reciprocal space (low energy electron diffraction, reflection high energy electron diffraction, X-ray diffraction and reflectometry) and direct space (transmission electron microscopy) as well as Rutherford backscattering spectrometry have been applied. To gain understanding of an oxidation procedure for the growth of magnetite layers, thermal stability of iron layers on molybdenum seed layers has been investigated. Following the mosaicity and the out-of-plane coherence length over different ratios between the constituting layers allowed a deeper understanding of the limits of metallic superlattices. This, together with an approach to use hydrogen in the process gas during magnetron sputter epitaxy, opens routes for the growth of metallic superlattices of superior quality. A non-isostructural multilayer/superlattice system, Fe/MgO, has been investigated. In turn, this gave more understanding how superlattice diffraction patterns are suppressed by strain fields. As an alternative route to single-crystalline superlattices, amorphous multilayers present interesting opportunities. In this context, crystallization effects of iron/zirconium layers on alumiunium oxide were studied. Understanding these effects enables significant improvement in the quality of amorphous multilayers, and allows avoiding these, growing truly amorphous layers. Both the substantial improvement in quality of metallic superlattices, approaching true single-crystallinity, as well as the improvements in the growth of amorphous multilayers give rise to opportunities in the field of magnetic coupling and superconducting spin valves.

In bulk-heterojunction solar cells, device performance is influenced by both the intrinsic properties of the individual components - typically conjugated polymers and fullerene derivatives - and how they assemble and interact at their interface. The ability of fullerene to intercalate within the side-chains of a conjugated polymer can significantly affect the microstructure and overall device performance. Here, a series of computational chemistry approaches are applied to investigate the relationships between structure and property in intercalated polymer:fullerene blend. Using a combination of molecular mechanics (MM) calculation and simulations of 2D grazing incidence X-ray diffraction (GIXD) patterns, we have determined the molecular packing configuration of poly (2,5-bis (3-tetradecyl thiophene-2-yl) thieno[3,2-b]thiophene) (PBTTT-C₁₄) and a blend of PBTTT-C₁₄ and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). Based on the confirmed packing structures, the electronic properties and morphological disorder were examined using density functional theory (DFT) and molecular dynamics (MD) calculations, respectively; we also investigated the intermolecular interaction energies behind the structure formation. Finally, we examined the vibrational, redox, and optical properties of the pristine polymer and a series of fullerene derivatives to understand the characteristic modes related to the various charged states of the systems.

Expansive clay mineral contamination of road aggregate materials in Texas is a persistent problem. Hydrous layer silicate minerals - particularly smectites - in concretes are associated with decreased strength and durability in Portland cement and asphalt concretes. The Texas Department of Transportation (TXDOT) and Texas A&M Transportation Institute (TTI) evaluated the methylene blue adsorption test for its potential to identify and estimate quantities of expansive clays in aggregate stockpiles. Clay mineral quantification was completed for 27 geologically-diverse aggregate materials from Texas, Oklahoma, and Arkansas. X-ray diffraction analysis (XRD) of separated clays on glass was conducted, and NEWMOD was utilized to model the resulting diffraction patterns. Methylene blue adsorption (MBA) and cation exchange capacity (CEC) of clay fractions (< 2µm) and -40 mesh screenings (< 400 µm) were determined for most aggregates. Many of the aggregates exhibited significant quantities of expansive clay minerals such as smectite, which are linked to deleterious performance properties in concretes. While the majority of aggregates were derived from crushed limestone or calcareous river gravel parent materials, severalexhibited uncommon origins and unusual clay mineralogy. Due to the relatively low number of aggregates tested and diverse geological origins of the different aggregates,it proved difficult to formalize any conclusions abouttrendsbetweenthedifferent aggregate performance properties.

The objective of this dissertation is to shed light on the physical properties of InN epilayers grown by High-Pressure Chemical Vapor Deposition (HPCVD) for optical device applications. Physical properties of HPCVD grown InN layers were investigated by X-ray diffraction, Raman scattering, infrared reflection spectroscopies, and atomic force microscopy. The dependencies of physical properties as well as surface morphologies of InN layers grown either directly on sapphire substrates or on GaN/sapphire templates on varied growth conditions were studied. The effect of crucial growth parameters such as growth pressure, V/III molar ratio, precursor pulse separation, substrate material, and mass transport along the flow direction on the optical and structural properties, as well as on the surface morphologies were investigated separately. At present, growth of high-quality InN material by conventional growth techniques is limited due to low dissociation temperature of InN (~600 ºC) and large difference in the partial pressures of TMI and NH3 precursors. In this research, HPCVD technique, in which ambient nitrogen is injected into reaction zone at super-atmospheric growth pressures, was utilized to suppress surface dissociation of InN at high temperatures. At high pressures, long-range and short-range orderings indicate that c-lattice constant is shorter and E2(high) mode frequency is higher than those obtained from low-pressure growth techniques, revealing that InN structure compressed either due to a hydrostatic pressure during the growth or thermal contraction during the annealing. Although the influence of varied growth parameters usually exhibit consistent correlation between long-range and short-range crystalline orderings, inconsistent correlation of these indicate inclination of InN anisotropy. InN layers, grown directly on α-sapphire substrates, exhibit InN (1 0 1) Bragg reflex. This might be due to a high c/a ratio of sapphire-grown InN epilayers compared to that of GaN/sapphire-grown InN epilayers. Optical analysis indicates that free carrier concentration, ne, in the range of 1–50 × 1018 cm–3 exhibits consistent tendency with longitudinal-optic phonon. However, for high ne values, electrostatic forces dominate over inter-atomic forces, and consistent tendency between ne and LO phonon disappears. Structural results reveal that growth temperature increases ~6.6 ºC/bar and V/III ratio affects indium migration and/or evaporation. The growth temperature and V/III ratio of InN thin films are optimized at ~850 ºC and 2400 molar ratio, respectively. Although high in-plane strain and c/a ratio values are obtained for sapphire-grown epilayers, FWHM values of long-range and short-range orderings and free carrier concentration value are still lower than those of GaN/sapphire-grown epilayers. Finally, vibrational and optical properties of chalcopyrite ZGP crystal on the (001), (110), and (10) crystalline planes were investigated by Raman scattering and infrared (IR) reflection spectroscopies. Raman scattering exhibits a nonlinear polarizability on the c-plane, and a linear polarizability on the a- and b-planes of ZGP crystal. Also, birefringence of ZGP crystal was calculated from the hydrostatic pressure difference between (110) and (10) crystalline planes for mid-frequency B2(LO) mode.

No description available.

Pervaporation (PV), a non-porous membrane separation process, is gaining considerable attention for solvent separation in a variety of industries ranging from chemical to food and pharmaceutical to petrochemicals. The most successful application has been the dehydration of organic liquids, for which hydrophilic membranes are used. However, during pervaporation, excessive affinity of water towards hydrophilic membranes leads to undesirable swelling (water absorption) of the membrane matrix. To control swelling, often hydrophilic membranes are crosslinked to modify physicochemical (surface and bulk) properties. Since the transport of species in pervaporation is governed by sorption (affected by surface and bulk properties) and diffusion (affected by bulk properties), it is essential to study the effect of crosslinking on the surface and bulk physicochemical properties and their effects on separation performance. This thesis focuses on the effect of crosslinking on the physicochemical properties (e.g., crystallinity, hydrophilicity, surface roughness) of hydrophilic polymeric membranes and their dehydration performance alcohol-water mixtures. Poly(vinyl alcohol), PVA was used as the base polymer to prepare membranes with various morphologies such as homogeneous, blended (with Chitosan, CS) and composite (with poly(sulfone), PSf) structures. Before applying the crosslinked membranes for the PV dehydration of alcohols, the physicochemical characterization were carried out using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), tensile testing, contact angle and swelling experiments. The crosslinked membranes showed an increase in surface hydrophobicity from the contact angle measurements as compared to the uncrosslinked membranes. AFM surface topography showed that the membrane surfaces have nodular structures and are rough at the nanometer scale and affected by the crosslinking conditions such as concentration and reaction time. Surface hydrophobicity and roughness was found to increase with increasing degree of crosslinking. DSC measurements showed an increase in melting temperature of the polymer membranes after crosslinking. For the PV dehydration of ethanol, a decrease in flux and an increase in selectivity were observed with increase in the degree of crosslinking. Effects of membrane thickness (of PVA layer) for crosslinked PVA-PSf composite membranes were studied on PV dehydration of ethanol. Total flux and selectivity were statistically analyzed as a function of the membrane thickness. In general, the outcome agrees with the solution-diffusion (S-D) theory: the total flux was found to be significantly affected by the PVA layer thickness, while the selectivity remains nearly unaffected. Using the S-D theory, the mass transfer resistance of the selective layers was calculated and found to increase with thickness. The relatively small change observed for selectivity has been related to the crosslinking of the PVA layer that increases the surface hydrophobicity of the membrane. Chitosan-Poly(vinyl alcohol), or CS-PVA, blended membranes were prepared by varying the blending ratio to control membrane crystallinity and its effect on the PV dehydration of ethylene glycol. The blended membranes were crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The crystallinity of the membrane was found to decrease with increasing CS wt% in the blend. Although the crosslinked CS-PVA blend membranes showed improved mechanical strength, they became less flexible as detected in tensile testing. The resulting crosslinked CS-PVA blended membranes showed high flux and selectivity simultaneously, for 70-80wt% CS in the blend. The effect of feed flow-rate was studied to find the presence of concentration polarization for 90wt% EG in feed mixture as well. The crosslinked blend membrane with 75wt% CS showed a highest total flux of 0.46 kg/m2/h and highest selectivity of 663 when operating at 70oC with 90wt% EG in the feed mixture. Effects of crosslinking concentration and reaction time of trimesoyl chloride (TMC) were studied on poly(vinyl alcohol)-poly(sulfone) or PVA-PSf composite membranes. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophilicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with PV dehydration of ethylene glycol-water mixtures at a range of concentrations (30 to 90wt% EG). The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. A central composite rotatable design (CCRD) of response surface methodology was used to analyze PV dehydration performance of crosslinked poly(vinyl alcohol) (PVA) membranes. Regression models were developed for the flux and selectivity as a function of operating conditions such as, temperature, feed alcohol concentration, and flow-rate. Dehydration experiments were performed on two different alcohol-water systems: isopropanol-water (IPA-water) and ethanol-water (Et-water) mixtures around the azeotrope concentrations. Judged by the lack-of-fit criterion, the analysis of variance (ANOVA) showed the regression model to be adequate. The predicted flux and selectivity from the regression models were presented in 3-D surface plots over the whole ranges of operating variables. For both alcohol-water systems, quadratic effect of temperature and feed alcohol concentration showed significant (p < 0.0001) influence on the flux and selectivity. A strong interaction effect of temperature and concentration was observed on the selectivity for the Et-water system. For the dehydration of azeotropic IPA-water mixture (87.5wt% IPA), the optimized dehydration variables were found to be 50.5oC and 93.7 L/hr for temperature and flow-rate, respectively. On the other hand for azeotropic Et-water mixture (95.5wt% Et), the optimized temperature and flow-rate were found to be 57oC and 89.2 L/hr, respectively. Compared with experiments performed at optimized temperature and feed flow-rate, the predicted flux and selectivity of the azeotropic mixtures showed errors to be within 3-6 %.

Pervaporation (PV), a non-porous membrane separation process, is gaining considerable attention for solvent separation in a variety of industries ranging from chemical to food and pharmaceutical to petrochemicals. The most successful application has been the dehydration of organic liquids, for which hydrophilic membranes are used. However, during pervaporation, excessive affinity of water towards hydrophilic membranes leads to undesirable swelling (water absorption) of the membrane matrix. To control swelling, often hydrophilic membranes are crosslinked to modify physicochemical (surface and bulk) properties. Since the transport of species in pervaporation is governed by sorption (affected by surface and bulk properties) and diffusion (affected by bulk properties), it is essential to study the effect of crosslinking on the surface and bulk physicochemical properties and their effects on separation performance. This thesis focuses on the effect of crosslinking on the physicochemical properties (e.g., crystallinity, hydrophilicity, surface roughness) of hydrophilic polymeric membranes and their dehydration performance alcohol-water mixtures. Poly(vinyl alcohol), PVA was used as the base polymer to prepare membranes with various morphologies such as homogeneous, blended (with Chitosan, CS) and composite (with poly(sulfone), PSf) structures. Before applying the crosslinked membranes for the PV dehydration of alcohols, the physicochemical characterization were carried out using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), tensile testing, contact angle and swelling experiments. The crosslinked membranes showed an increase in surface hydrophobicity from the contact angle measurements as compared to the uncrosslinked membranes. AFM surface topography showed that the membrane surfaces have nodular structures and are rough at the nanometer scale and affected by the crosslinking conditions such as concentration and reaction time. Surface hydrophobicity and roughness was found to increase with increasing degree of crosslinking. DSC measurements showed an increase in melting temperature of the polymer membranes after crosslinking. For the PV dehydration of ethanol, a decrease in flux and an increase in selectivity were observed with increase in the degree of crosslinking. Effects of membrane thickness (of PVA layer) for crosslinked PVA-PSf composite membranes were studied on PV dehydration of ethanol. Total flux and selectivity were statistically analyzed as a function of the membrane thickness. In general, the outcome agrees with the solution-diffusion (S-D) theory: the total flux was found to be significantly affected by the PVA layer thickness, while the selectivity remains nearly unaffected. Using the S-D theory, the mass transfer resistance of the selective layers was calculated and found to increase with thickness. The relatively small change observed for selectivity has been related to the crosslinking of the PVA layer that increases the surface hydrophobicity of the membrane. Chitosan-Poly(vinyl alcohol), or CS-PVA, blended membranes were prepared by varying the blending ratio to control membrane crystallinity and its effect on the PV dehydration of ethylene glycol. The blended membranes were crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The crystallinity of the membrane was found to decrease with increasing CS wt% in the blend. Although the crosslinked CS-PVA blend membranes showed improved mechanical strength, they became less flexible as detected in tensile testing. The resulting crosslinked CS-PVA blended membranes showed high flux and selectivity simultaneously, for 70-80wt% CS in the blend. The effect of feed flow-rate was studied to find the presence of concentration polarization for 90wt% EG in feed mixture as well. The crosslinked blend membrane with 75wt% CS showed a highest total flux of 0.46 kg/m2/h and highest selectivity of 663 when operating at 70oC with 90wt% EG in the feed mixture. Effects of crosslinking concentration and reaction time of trimesoyl chloride (TMC) were studied on poly(vinyl alcohol)-poly(sulfone) or PVA-PSf composite membranes. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophilicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with PV dehydration of ethylene glycol-water mixtures at a range of concentrations (30 to 90wt% EG). The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. A central composite rotatable design (CCRD) of response surface methodology was used to analyze PV dehydration performance of crosslinked poly(vinyl alcohol) (PVA) membranes. Regression models were developed for the flux and selectivity as a function of operating conditions such as, temperature, feed alcohol concentration, and flow-rate. Dehydration experiments were performed on two different alcohol-water systems: isopropanol-water (IPA-water) and ethanol-water (Et-water) mixtures around the azeotrope concentrations. Judged by the lack-of-fit criterion, the analysis of variance (ANOVA) showed the regression model to be adequate. The predicted flux and selectivity from the regression models were presented in 3-D surface plots over the whole ranges of operating variables. For both alcohol-water systems, quadratic effect of temperature and feed alcohol concentration showed significant (p < 0.0001) influence on the flux and selectivity. A strong interaction effect of temperature and concentration was observed on the selectivity for the Et-water system. For the dehydration of azeotropic IPA-water mixture (87.5wt% IPA), the optimized dehydration variables were found to be 50.5oC and 93.7 L/hr for temperature and flow-rate, respectively. On the other hand for azeotropic Et-water mixture (95.5wt% Et), the optimized temperature and flow-rate were found to be 57oC and 89.2 L/hr, respectively. Compared with experiments performed at optimized temperature and feed flow-rate, the predicted flux and selectivity of the azeotropic mixtures showed errors to be within 3-6 %.

A comprehensive investigation was reported into the synthesis, characterization and photoluminescence properties of calcium metaniobates and associated alkali earth alloy systems. Previous studies have shown that calcium metaniobate exhibits a strong self-activated blue luminescence at room temperature in stark contrast to the pyroniobates which are known to exhibit a temperature dependent luminescence that quenches above 100 K. The mechanism of this behavior has been studied by measuring the spectral characteristics of the photoluminescence and photoluminescence excitation spectra on the crystalline and morphological properties of the powders as determined from x-ray diffraction and scanning electron microscopy. By correlating the synthesis parameters with the physical, chemical and optical properties of calcium metaniobate, the optimum conditions for efficient blue-visible emission and chemical stability under vacuum ultraviolate (VUV) radiation has been determined. These materials have the potential to replace Barium Magnesium Aluminate, which is currently used as the blue phosphor in plasma displays.

In order to truly understand the process-property behavior of polymer systems it is essential to identify the three dimensional structure of the materials fabricated. For heterogeneous polymer systems such as nanoparticle filled systems, determination of the three dimensional optical properties are particularly difficult. Such information is essential, however, if the behavior of these systems are to be understood and formalized. The purpose of the present research was to develop methods for measuring the optical characteristics of heterogeneous polymer systems nondestructively, in order to characterize their three dimensional behavior. The thesis contains three parts: Part A: Study of an Oriented Uniformly Distributed System: Stretched Isotactic Polypropylene- nano Carbon Black Films (IPP-CB). Three nondestructive optical methods: optical waveguide coupling, Fourier Transform Infrared (FTIR) spectroscopy and x-ray diffraction, were used to investigate the effect of the carbon black on the phase behavior and orientation of the films. It was found that the carbon black has little effect on the crystal form and crystallinity, but has a significant effect on the three dimensional orientation behavior of the polypropylene in the IPP-CB systems. Part B: Study of a non-Uniformly Distributed System: Compression Molded Poly (Methyl Methacrylate) with Nano Indium Tin Oxide (PMMA-ITO) The PMMA-ITO sample is an un-oriented and non-uniformly mixed system which has a grain structure. A unique Break Point Waveguide Method was developed to deal with this problem. It was found that both the refractive index and the extinction coefficient increased with ITO concentration and the samples were three dimensionally random. Part C: Development of Computational Improvements in System Operations Four methods were developed to improve the accuracy of the waveguide methods. They are the Bootstrap Method, the Two-Line Method, the Big Area Method and the Modified Knee method. In conclusion, the three dimensional optical characteristics of two different kinds of heterogeneous polymer systems, oriented uniformly distributed IPP-CB films and non-uniformly distributed PMMA-ITO composites, are obtained and their structures evaluated. Further, several new methods were developed to improve the accuracy of the current optical waveguide methods.