Design and control of hierarchically structured nanomaterials
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.
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