Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"Crystalline solid"”.
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Dynamical effects in crystalline solid state systems: theory of temperature dependent optical response of bulk gaAs and vibrational modification of C(111) 2 x 1 Surface in Comparison to Experiment
This thesis presents a new theoretical formalism which incorporates dynamical effects in atomistic electronic structure and related calculations. This research, fundamental by nature, brings about a deeper understanding of the dynamical processes in a range of materials. This establishes …
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Development and verification of the relationship between atomic vibrational amplitude and thermal expansion of crystalline solids
… square vibrational amplitude of the atoms of a crystalline solid and the thermal expansion of that solid is derived from basic principles, assuming a simple potential energy function between atoms. The functional accuracy of this relationship is proven for several cubic lattice elements and …
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Diffusion and the thermal stability of amorphous copper-zirconium
… to the coefficient of self-diffusion in crystalline Cu at the same temperatures. The activation energies for diffusion in the amorphous alloy are 0.72 to 1.55 ev/atom, much closer to the activation energy for self-diffusion in liquid Cu, 0.42 eV/atom, than that for the crystalline solid, …
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Eigenvalue Statistics for Random Block Operators
… Hamiltonian for a single electron in a crystalline solid with independent, identically distributed (i.i.d.) single-site potentials has been well studied. It has the form of a diagonal potential energy operator, which contains the random variables, plus a kinetic energy operator, which is …
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Optical, electronic, and dynamical phenomena in the shock compression of condensed matter
… 2, the nature of electronic excitations in crystalline solid nitromethane are examined under conditions of shock compression. Density functional theory calculations are used to determine the crystal bandgap under hydrostatic stress, uniaxial strain, and shear strain for pure and defective …
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Characterization of Fluoropolymer Powders Made By Supercritical Assisted Mixing With Crystalline Additives
… investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the …
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Core excitons in amorphous magnesium alloys
… the formation of intermetal1ic compounds in the crystalline solid, and are thought to be due to the formation of core excitons. Variation in the strength of the excitonic resonance is explained by a simple screening argument. Variation in the line shape of the threshold is described by a critical …
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Kinetics based characterization of struvite dissolution
… Dittmarite (MgNH4PO4*H2O) and another unknown crystalline solid were found to potentially lead to enhanced solubility. The importance of characterizing plant specific struvite was noted when instances of enhanced solubility were seen in samples which exhibit distinct FTIR bands when comparing …
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A structural database for pharmaceutical salt selection
… different counterions for the formation of a crystalline salt. This approach is necessitated by the limited understanding of the relationships between molecular and supramolecular structure and properties and the stoichiometry and ionisation state of the resultant crystalline solid. Presented …
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Optimization of High Entropy Borides for Advanced Applications
… percentages to generate a single phase crystalline solid solution, i.e. (Hf0.2Mo0.2Ti0.2Ta0.2Zr0.2)B2, were found to display peculiar properties that could provide a possible further advancement in this field. In particular, preliminary investigations evidenced that members of the HEB …
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Organic electrodes and solid-state electrolytes for lithium electrochemical energy storage
… design guidelines for positive electrodes and solid-state electrolytes to address these challenges. The positive electrode is one of the main limitations to improving both the capacity and cost of lithium-ion batteries. Organic molecules represent a class of materials, which if selected …
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Order Under Pressure: Structural and Magnetic Characterization at Extreme Stresses
… magnetism. Despite over a century of research on solid-state materials over one gigapascal (GPa), experimental and theoretical obstacles remain for structural and physical characterization of complex phases which only persist at these conditions. We begin to address the wide-reaching challenge of …
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Phonon Dispersion Relations in Chrystals
… much information about the thermal motions in solids and liquids. Neutrons which have been thermalised by the moderator of a nuclear reactor have energies similar to those associated with these thermal motions. It so happens that they also have wavelengths similar to the interatomic spacing in …
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Magnetic Ionic Liquids: Design, Properties and Application
… in nature. Starting from the design of dimeric solids, we demonstrate that by tuning of anion and cation structures we can lower the melting points below room temperature, while maintaining the dimeric structure. Magnetic measurements were able to establish the spin-spin interactions of the …
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Polymer Crystallization: Micro- and Nano- Filler Effects on Isotactic Polypropylene
… application field. Since the features of semi-crystalline polymers depend on the crystallinity degree and crystallite morphology, studies about the effects of fillers on the crystallization behavior of composites are of great interest. Nucleated crystallization has been the subject of several …
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Compositional tuning, crystal growth, and magnetic properties of iron phosphate oxide
Iron phosphate oxide, Fe3PO4O3, is a crystalline solid featuring magnetic Fe3+ ions on a complex lattice composed of closely-spaced triangles. Previous work from our research group on this compound has proposed a helical magnetic structure below T = 163 K attributed to J1-J2 competing interactions …
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New Fluorescence Sensors for Critical Materials
… phonons (quantised lattice vibrations in a crystalline solid that may enable non-radiative energy relaxation). This opens an additional dimension to mineral fluorescence investigation, and this thesis will report one luminescent response under low-temperature conditions from a mineral …
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Polymorphism control and the formation of organic molecular nanocrystals
… involved in those methods, producing amorphous solids and if crystalline solid is obtained making control of desired polymorphs difficult. The aim of this thesis is to: (1) Evaluate practical methods to produce organic molecular nano-crystals of the desired form; (2) determine the change in …
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Impact of mixed solvent on co-crystal solubility, ternary diagrams and crystallisation scale-up. Crystallisations of Isonicotinamide ¿Benzoic Acid Co-crystals from Ethanol ¿Water Co-solvent System.
The production of stable solid crystalline material is an important issue in the pharmaceutical industry and the challenge to control the desired active pharmaceutical ingredient (API) with the specific chemical and physical properties has led to more development in the drug industry. Increasing …
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Characterization of different hydrophilic polymers and their applicability in hot melt extrusion technology
… administration, and mainly include conventional solid dosage forms such as pellets, tablets, and/ or milled material filled in capsules. Since most of the actives studied under current research have low aqueous solubility, it was necessary to utilize a novel technology such as hot melt extrusion …
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