Design and control of hierarchically structured nanomaterials

by Carr, Charles Shane

Abstract (Summary)
Hierarchically ordered porous oxides have garnered much interest because of

the numerous applications that can be developed from these materials. The catalytic

properties, separation ability, and ion exchangeability of these materials, specifically

zeolites, make them great candidates for applications. One area which has not been

heavily studied is ways to control the morphology and particle size of these materials

through soft chemistry approaches.

This dissertation looks at two methodologies which can be used to alter

zeolitic particle morphology. The first is a dual templating approach which attempts to

incorporate microporous walls within a mesoporous structure. The zeolitic material,

silicalite-1, is used as a siliceous precursor for the formation of the mesoporous SBA-15

material. A battery of characterization techniques were used to identify the structural

properties of the material, including porosimetry, diffraction, microscopy, and

spectroscopy. The overall conclusion was that a material with different properties than

the parent SBA-15 were obtained, but that no characterization technique could be used to

show the definitive presence of the zeolite in the walls. Another technique studied is the growth of zeolitic materials within the water

domains of microemulsions. The concept of a reverse microemulsion, a confined water

droplet in a continuous oil phase makes it an interesting system for morphological

control. The zeolitic materials should only be able to grow within the water domain, and

the reactive materials should be less available as they are trapped in separate micelles.

Zeolite A (LTA) and zeolite L (LTL), two technologically important zeolites, were

studied. Enhanced growth, larger particles, and unique material aggregates are just a few

of the observations made for the two systems. The development of these materials

should facilitate the application of zeolite in emerging technologies. In particular,

preliminary work has been done on the development of large zeolite crystals with tuned

orientations and particle sizes.

This research shows multiple ways in which particle size and morphology can

be tuned simply by altering the chemistry and reaction conditions of the system. This

research has led to unique findings dealing with large zeolite crystals, and should open

the door for continued research in this area.

Bibliographical Information:

Advisor:Shantz, Daniel F.; Cagin, Tahir; Crooks, Richard M.; Ford, David M.

School:Texas A&M University

School Location:USA - Texas

Source Type:Master's Thesis

Keywords:zeolites microemuslions morphological control


Date of Publication:08/01/2005

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