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Heterogeneous nanostructures such as coaxial nanotubes, nanowires and nanorods have been of growing interest due to their potential for high energy-conversion efficiencies and charge/discharge rates in solar cell, energy storage and fuel cell applications. Their superior properties at nanoscale as well as their high surface area, fast charge transport along large interfacial contact areas, and short charge diffusion lengths have made them attractive components for next generation high efficiency energy-conversion devices. The primary focus of this work was to understand the doping mechanism of TiO2 nanotube exclusively with strontium as an alkaline earth metal to shine light on the relation between the observed enhancement in photocatalytic properties of doped TiO2 nanotubes and its structural and electronic characteristics. The mechanism of Sr incorporation into the TiO2 nanotube structure with the hypothesis of possibility of phase segregation has been explored in low concentrations as a dopant and in very high concentrations by processing of SrTiO3 nanotube arrays. Detailed experimental examination of the bulk and surface of the Sr-doped nanotubes has been performed to understand the effect of dopant on electronic structure and optical properties of the TiO2 nanotubes. Moreover, in order to minimize the polarizations associated with the ionic/electronic charge transport in the electrolyte and anode of solid oxide fuel cells (SOFCs), a new platform is developed using vertically oriented metal oxide nanotube arrays. This novel platform, which is made of coaxial oxide nanotubes on silicon substrates, has the potential to simultaneously lower the operating temperature and production cost leading to significant enhancement in the performance of micro-SOFCs.

[Truncated abstract] In this dissertation an investigation into the utility of mechanochemically synthesized nanopowders for intermediate temperature solid oxide fuel cell components is reported. The results are presented in the following parts: the synthesis and characterisation of precursors for ceramic and cermet components for the fuel cell; the physical and electrical characterisation of the electrolyte and electrodes; and the fabrication, operation and analysis of the resulting fuel cells. Samarium-doped (20 mol%) ceria (SDC) nanopowder was fabricated by the solid-state mechanochemical reaction between SmCl3 with NaOH and Ce(OH)4 in 85 vol% dilution with NaCl. A milling time of 4 hours and heat treatment for 2 hours at 700°C yielded a material with equivalent particle and crystallite sizes of 17 nm. The existence of a complete solid solution was affirmed by electron energy loss spectroscopy and x-ray diffraction analysis. Doped-ceria compacts were sintered for 4 hours at 1350°C forming ceramics of 88% theoretical density. The ionic conductivity in flowing air was 0.009 S/cm, superior to commercially supplied nanoscale SDC. Anode precursor composite NiO-SDC nanopowder was synthesized by milling Ni(OH)2 with the previously defined SDC formulation ... Anode-supported fuel cells were fabricated on a substrate of at least 500 'm 55wt%NiO-SDC with 17vol% graphite pore formers. Suspensions of SDC were deposited by aerosol on the sintered bilayer at a thickness around 5 'm. A cathode of 10% SDC (SmSr)0.5CoO3 was deposited onto the sintered electrolyte and after firing had a thickness of around 25 'm. Operation of fuel cells in single-chamber mixtures of CH4 and air diluted in argon were successful and gave power outputs of 483 'W/cm2. Operation in undiluted 25 vol% CH4:air gave a power output of 5.5 mW/cm2. It was shown that a large polarisation resistance of 4.1 Ω.cm2 existed and this was assigned to losses in the anode, namely mass transport limitation associated with the catalytic combustion of methane and insufficient porosity. The large surface area of Ni appeared to allow more methane to combust and hence prevented its electrochemical reaction from occurring, thus limiting the performance of the cell. The synthesis procedures, ceramic processing and fabrication techniques and testing methods are discussed and contribute significant understanding to the fields of ceramic science and fuel cell technology.

Dissertation (Ph. D.)--University of Akron, Dept. of Chemical Engineering, 2007. / "December, 2007." Title from electronic dissertation title page (viewed 03/12/2008) Advisor, Steven S. C. Chuang; Committee members, Lu-Kwang Ju, Edward Evans, W. B. Arbuckle, Stephen Z. D. Cheng; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiv, 273 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 184-189).

Thesis (Ph.D.) - School of Engineering and Science, Swinburne University of Technology, 2002. / Submitted in fulfillment of the requirements for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2002. Typescript. Includes bibliographical references (p. 229-239).

Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 111-119).

Thesis (MS)-Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Stephen w. Sofie. Includes bibliographical references (leaves 88-90).

Thesis (M.Phil.) - University of St Andrews, September 2007.

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiii, 126 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 120-126).