OXIDATION AND REDUCTION SYNTHESIS OF SURFACE ENHANCED TITANIUM-BASED ELECTRODES FOR ELECTROLYTIC CAPACITORS

Capacitors are important for use in electrical energy management in low and high-frequency applications. Electrolytic capacitors with high energy density have the potential to be used for efficient energy management in electrical power supplies and for supplying power pulses, for example in spot welders. Titanium-based oxides with high dielectric constants are candidate for the dielectric layer in electrolytic capacitors. The research in the thesis focuses on fabrication methods to form surface-enhanced titanium-based electrodes with sub-micrometer branch and pore sizes for highly surface-enhanced capacitor electrodes. When anodized they can serve as potential anodes in electrolytic capacitors. Oxidation of the surface layer on titanium followed by reduction is a conversion method by which fine-porous, highly surface-enhanced electrodes can be made. Alkali earth metals with high oxygen affinity were selected to reduce titanium dioxide. The experiments reveal that mostly alkali–earth-metal-titanates were formed during the reduction process. Full reduction to metallic porous titanium is achieved only with calcium as a reductant and with calcium chloride as a catalyst for dissolving CaO reaction barrier. The dielectric properties of subsequently formed anodic oxide films on these electrodes depend on retained alkali-earth element in the reduced titanium or partially reduced titanate oxides. Both CaTiO3-x and SrTiO3-x formed during the calcium- and strontium-reduction processes improved the capacitances of anodized electrodes. When calcium chloride was included during the calcium reduction process TiO2 was fully reduced to porous titanium. The fine-porous structure yielded electrodes with high surface areas and high capacitances.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Materials Science and Engineering

Grantor dc:publisher

Case Western Reserve University School of Graduate Studies

Year dc:date

2013

Author dc:creator

• Chen, Li-Ju

Contributors dc:contributor

• Welsch, Gerhard
• Liu, Chung-Chiun

• Materials Science

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=case1364983500

OAI identifier oai:identifier

oai:etd.ohiolink.edu:case1364983500