Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 116-126).

This research is focused on the synthesis and characterization (BET, transmission electron microscopy and optical spectroscopy) of aluminum oxide condensates via a static sintering process and dynamic process of pulse laser ablation (PLA) and pulse laser ablation in liquid (PLAL). For a start, the static route of an onset coarsening-coalescence event based on the incubation time of cylindrical mesopore formation and a significant decrease of specific surface area by 50% and 70% relative to the dry pressed samples was determined by N2 adsorption-desorption hysteresis isotherm for two Al2O3 powders having 50 and 10 nm in diameter respectively on an average and with £^-type related structures, i.e. £^- and its distortion derivatives £_- and/or £c-types with {100}/{111} facets and twinning according to transmission electron microscopy. In the temperature range of 1100 to 1400oC, both powders underwent onset coarsening-coalescence before reconstructive transformation to form the stable £\-type. The apparent activation energy for such a rapid coarsening-coalescence event was estimated as 241 ¡Ó 18 and 119 ¡Ó 19 kJ/mol, for 50 and 10 nm-sized particles, respectively indicating easier surface diffusion and particle movement for the latter. The size dependence of surface relaxation and onset coarsening-coalescence of the £^−type related Al2O3 nanoparticles agrees with their recrystallization-repacking upon electron irradiation and accounts for their assembly into nano chain aggregates or a close packed manner under the radiant heating effect in a dynamic laser ablation process. In addition, ultrafine (5 nm) Al2O3 nanoparticles having a predominant £\-type structure and with an internal compressive stress up to ca. 15 GPa were synthesized by pulsed laser ablation on Al target under a very high peak power density (1.8x1011 W/cm2) with oxygen flow in vacuum. The ultrafine £\-Al2O3 was alternatively formed from the minor £^-Al2O3 nanocondensates upon electron irradiation. In such a case, the polymorphs follow a special crystallographic relationship [110]£^//[2110]£\; (111) £^//(0114)£\ with a mixed mismatch strain yet nonparallel close packed planes indicating a reconstructive type transformation. The formation of metastable £\-Al2O3 in the dynamic processes can be rationalized by the kinetic phase change from the amorphous lamellar and/or £^-Al2O3 depending on their free energy versus cell volume curves. The dense and ultrafine sized Al2O3 polymorphs with a rather low minimum band gap of 3.7 eV shed light on their natural occurrence in dynamic settings and abrasive as well as catalytic/optoelectronic applications. Furthmore, pulsed laser ablation in water under a high peak power density of 1.8 ¡Ñ 1011 W/cm2 using Q-switch mode and 1064 nm excitation was used to fabricate (H+,Al2+)-codoped Al2O3 nanocondensates having £^- and its derivative £c-type structure as characterized by electron microscopy and spectroscopy. The as-formed £^- and £c-Al2O3 nanocondensates are mainly 10 to 100 nm in size and have a significant internal compressive stress (> 10 GPa) according to cell parameters and vibrational spectroscopy, due to a significant shock loading effect in water. The £^-Al2O3 nanocondensates are nearly spherical in shape but became cubo-octahedra when grew up to ca. 100 nm to exhibit more facets as a result of martensitic £^¡÷£c transformation following the crystallographic relationship (3 11 )£c //(02 2)£^; (0 2 4 )£c//(3 11)£^. The formation of dense and (H+,Al2+)-codoped £^/£c-Al2O3 rather than aluminum hydrates sheds light on the favored phases of the Al2O3-H2O binary at high temperature and pressure conditions in natural dynamic settings. The nanocondensates thus formed have a much lower minimum band gap (5.2 eV) than bulk £\-Al2O3 for potential optocatalytic applications. Moreover, the Al2O3 nanocondensates of spinel-type related structures, i.e. £^- and £c- type with a significant internal compressive stress via pulsed laser ablation in water were subjected to prolonged dwelling in water to form columnar bayerite plates for further transformation as platy £^-Al2O3. Transmission electron microscopic observations indicated the £^-Al2O3 follows the crystallographic relationship (100)b//(011)£^; [001]b//[111]£^ with relic bayerite (denoted as b). The £^-Al2O3 also shows {111} twin/faults and rock salt-type domains due to dehydroxylation of bayerite which involves {111} shuffling and disordering of the Al ions in the octahedral and tetrahedral sites. The combined evidences of X-ray photoelectron spectroscopy, vibrational spectroscopy and UV-visible absorbance indicated that the H+, Al+ and Al2+ co-doped bayerite and £^-Al2O3 composite plates have a minimum band gap as low as ~ 5 eV for potential catalytic and electro-optical applications in water environment. Finally, pulsed laser ablation in aqueous solution of NaOH up to 1 M was employed to fabricate epitaxial NaAlO2 and £^-Al2O3 nanopartricles for electron microscopic and spectroscopic characterizations. The NaAlO2 phase (denoted as N), presumably derived from NaAlO2 .5/4H2O, was found to form intimate intergrowth with the £^-Al2O3 following a specific crystallographic relationship [211]£^//[110]N; ( 2 22) £^//(002)N and (0 2 2) £^//(110)N for a parallel close packed planes in terms of corner linked AlO4 tetrahedra and a beneficial lower interfacial energy and/or strain energy. The composite phases have significant internal compressive stress up to 7 and 40 GPa according to cell volume and IR shift results and a low minimum band gap of 5.9 eV for potential applications in UV region.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 82 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 75-78).

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A novel way of producing nanostructures in the past decade has been through the use of an anodized alumina template. This template has dense, self-ordered nanometric pores that grow in the oxide as the aluminum is being anodized. This technique is a fairly new method of processing nanostructures, and much study and research is presently being done to understand the formation mechanisms of the highly ordered pores. Ultra-pure aluminum foil and pure aluminium single crystal plates were anodized to create porous anodized alumina, and using it as a template to electro-deposit Nickel nanostructures. The effects different anodizing parameters have on oxide creation were studied, and the results obtained from studying the effects of substrate purity and texture of the anodized aluminum substrate on the morphology of the alumina template, through the use of X-ray diffraction and scanning electron microscopy. / Nickel nanowires were prepared by DC electrodeposition inside the porous alumina template with a gold-palladium coating serving a conductive base. The nanowires have a diameter of 65 nm, and their length depends on the deposition time. The nanowires can uphold a position perpendicular to the substrate by partially dissolving the alumina template. They also have a tendency to gather together once the template is partially removed.

Thesis (Ph.D.)--McMaster University, 2004. / Supervisor: D.S. Wilkinson. Includes bibliographical references (leaves 164-170). Also available via World Wide Web.

Thesis (M.S.)--Ohio University, March, 1993. / Title from PDF t.p.

Thesis (Ph. D.)--Lehigh University, 1997. / Includes vita. Includes bibliographical references (leaves 218-227).