Synthesis And Characterization Of Ordered Mesoporous Transition Metal Oxides And Nitrides
Controlling the structure of inorganic materials on the mesoscale (2-50 nm) is desirable for many applications and can influence the materials' properties and performance in devices. Amphiphilic block copolymers (BCPs) have been used extensively to structure-direct transition metal oxides, controlling their mesoscale morphology. By selectively incorporating metal oxide precursors into one block of the BCP and removing the BCP through thermal decomposition, ordered mesoporous metal oxides with well-defined mesoscale morphologies can be achieved that are interesting, e.g. for energy conversion and storage applications. This dissertation reports on the amphiphilic block terpolymer poly(isoprene)-blockpoly(styrene)-block-poly(ethylene oxide) used in combination with sol-gel metal oxide precursors to generate ordered three-dimensionally (3D) mesoporous metal oxides. 3D cocontinuous cubic network structures such as the alternating gyroid are particularly interesting for energy applications due to their chirality, co-continuity, and high porosity. In particular, the high porosity and mesoscale dimensions can facilitate rapid diffusion of gases/liquids, but limit solid state diffusion lengths in the inorganic structure during chemical conversions of the oxides, e.g. nitriding. Freestanding gyroidal mesoporous metal oxides can be further processed into gyroidal mesoporous metal nitrides by heating under flowing ammonia gas. Transition metal nitrides are of interest due to their electrical conductivity and electrochemical stability. The development of a synthesis for 3D ordered mesoporous nitrides opens paths for studying the effects of welldefined block copolymer mesostructures on superconductivity, an exciting new field.
block copolymers; mesoporous materials; metal nitrides
Disalvo, Francis JWiesner, Ulrich B.
Chemistry and Chemical Biology
Ph.D. of Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis