Thesis (M.S. in material science and engineering)--Washington State University, May 2010. / Title from PDF title page (viewed on July 14, 2010). "School of Mechanical and Material Engineering." Includes bibliographical references (p. 90-92).

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 285-298). Also available in electronic version.

Crystallising large, flexible molecules, which are becoming more common in pharmaceutical development, often presents significant challenges for chemists and particle scientists. These difficulties are sometimes attributed to the flexibility of the molecule, and the existence of multiple conformers in solution. Structurally related impurities, frequently present when crystallising these materials, can also impact on growth and habit, and both these aspects are considered in this thesis. This work considers two pharmaceutical compounds, a relatively small but nonetheless flexible molecule, ethenzamide, and a precursor of Amprenavir, a much larger molecule. Both compounds typically grow as thin needles in a wide variety of solvents, and effort was required to grow suitable crystals for structure determination. Ethenzamide has an unusual structure, the amide group being out-of-plane relative to the ring, while in all known co-crystals of the compound, including three new co-crystal structures determined in this work, it has a planar structure with an intramolecular hydrogen bond not seen in the single component crystal. Theoretical structure generation calculations suggest a second polymorph with a planar conformation may exist, though a screen has not found any further solid phases. ab initio work suggests the planar conformation is the stable arrangement in vacuo. Several structures for the Amprenavir intermediate have been determined, as an ethanol solvate, a methanol solvate and a hydrate. A phase diagram has been measured in the industrial solvent mix, and the nucleation and growth properties of this molecule, both pure and in the presence of several structurally related impurities, have been measured. The Cambridge Structural Database has been searched for similar structures, and conformational searches have been carried out for both molecules, using vacuum phase ab initio energy calculations. Infrared spectroscopy has been used to investigate solution phase structure. These theoretical and practical studies will try to relate conformational properties to crystallisation behaviour.

Al4SiC4 est une céramique réfractaire avec une bande d’énergie 2.5eV qui est très intéressant pour diverses applications dans le domaine de l’énergie. Pourtant, la synthèse des monocristaux d’Al4SiC4 n’a pas été étudiée jusqu’à présent.Dans la première partie de ce mémoire, les phénomènes de vaporisation et de condensation dans le système Al4C3-SiC sont étudiés en combinant une analyse de thermodynamique avec une approche d’expérimentale focalisée. Les conditions expérimentales de la synthèse d’Al4SiC4, telles que la composition initiale, la température de recuit et le gradient de température, sont étudiées et optimisées. À partir des résultats obtenus, un diagramme de phase condensée à l’équilibre est établi pour la fraction molaire XAl4C3/(Al4C3+SiC) < 0.5, qui est déterminée comme la condition préférée pour la condensation d’Al4SiC4. En effet, Al4SiC4 pourrait être synthétisée expérimentalement par sublimation à 1900°C avec un gradient de température inférieur à 40°C. Les caractéristiques de base comme la qualité structurale et l’absorption optique des couches cristalline d’Al4SiC4 obtenues sont étudiées.Dans la deuxième partie, les nouvelles structures d’hétéro-épitaxiales du système Al-Si-C sur substrats de SiC hexagonal (orienté [0001]) sont proposées comme Al4C3/SiC et Al4SiC4/SiC. Les caractéristiques des hétérostructures comme le mécanisme de croissance et les relations cristallographiques, sont principalement étudiées à l’échelle nanoscopique par utiliser la TEM à haute résolution. / Al4SiC4 is a refractory ceramic with a reported band gap of about 2.5 eV, making it an interesting semiconductor material for various applications in the field of energy. However, the synthesis of Al4SiC4 single crystals has so far not been investigated.In the first part of this thesis, combining a thermodynamic analysis with a focused experimental approach, the vaporization and condensation phenomena in the Al4C3-SiC system are described. Experimental conditions, such as initial composition, baking temperature and temperature gradient, are investigated and optimized regarding the crystallization of Al4SiC4. From the results obtained, a condensed phase diagram at equilibrium is established for the molar fraction XAl4C3/(Al4C3+SiC) < 0.5, which is determined as the favorite condition for the Al4SiC4 condensation. Indeed, Al4SiC4 single phase could be experimentally synthesized by sublimation at 1900°C with a temperature gradient smaller than 40°C. Some basics characteristics of obtained Al4SiC4 crystalline layers like the structural quality and optical absorption are investigated.In the second part, new hetero-epitaxial structures on [0001] oriented hexagonal SiC are studied like Al4C3/SiC and Al4SiC4/SiC. The characteristics of heterostructures, like growth mechanism and crystallographic relationships are mainly investigated in nanoscopic scale by using high resolution TEM.

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