Condensed-Matter Physics & Materials Science Seminar

"Oxide thin films and nanostructures: Chemical, electrochemical and template synthesis"

Presented by Steven Limmer, University of Missouri-Rolla

Monday, May 22, 2006, 1:30 pm — Bldg. 480 Conference Room

In this talk, I will present an overview of several research projects in the synthesis of oxide nanorods and thin films. Nanorods of several oxides were grown in templates, by means of a combination of sol-gel processing and electrophoretic deposition. Both single metal oxides (TiO2, SiO2) and complex oxides (BaTiO3, Sr2Nb2O7, and Pb(Zr0.52Ti0.48)O3) have been grown by this method. Uniformly sized nanorods of about 50-200 nm in diameter and 10-100 m in length were grown over large areas with near unidirectional alignment. Desired stoichiometric chemical composition and crystal structure of the oxide nanorods was readily achieved by an appropriate procedure of sol preparation, with a heat treatment for crystallization and densification. Thin films of oxides such as CeO2, Fe3O4 and ZnO were formed by electrochemical deposition from aqueous solutions. Crystalline films of CeO2 with thickness in the 10-70 nm range were formed by the electrochemical oxidation of Ce(III) acetate complexes at 65 °C, while ~7 nm CeO2 powders were precipitated when O2 was bubbled through the solution. Films of Fe3O4 can be deposited by the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution, and the films can also be doped with Zn to form ZnxFe3-xO4. The amphoteric nature of ZnO is used to produce the material from strongly alkaline solution. The solution pH is lowered globally to produce ZnO nanostructures, and it is lowered locally at a surface to produce films. ZnO powder is precipitated by adding HNO3 to the solution, while films are electrodeposited by electrochemically oxidizing the ascorbate dianion.

Hosted by: Stan Wong

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