Browsing by Subject "Templating"

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    Advances in nanostructured materials via templated sol-gel structure control and self-assembly
    (2015-04) Rudisill, Stephen Gabriel
    This dissertation describes a body of work focused on understanding and improving morphology control of nanoporous structures via their aqueous chemistry. Synthesis of materials was carried out primarily using the Pechini process with metal nitrates and colloidal crystal templates. CeO2 and CeO2-derived compounds were used for a substantial portion of the dissertation as they are useful for thermochemical cycling experiments. Templated CeO2 shows a tenfold improvement over an untemplated material as well as a nanoparticle powder under lab-scale thermochemical cycling experiments.The Pechini process itself was then investigated as a means to obtain greater structural control over colloidal crystal templated materials. The process was demonstrated to involve phase separation, which allowed for the production of microspheres and bicontinuous networks of templated CeO2-based solids. Microspheres produced were between 1-3 µm in size, with polydispersity less than 15%. Further experimentation demonstrated that this phase separation methodology was generalizable to Fe2O3 and Mn3O4, though higher polydispersities were obtained for these materials.The final research project accomplished in this dissertation involves a method to produce ordered collagen fibrils through the incorporation of nanocrystalline cellulose during fibrillogenesis. Results were verified via scanning electron microscopy and a mechanism was proposed based on infrared spectroscopy results indicating a decrease in collagen-collagen hydrogen bonding.
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    Manipulating colloids and surfactants as co-templates for porous nanostructures and nanocomposites.
    (2010-02) Li, Fan
    Templating is a general and efficient strategy for creating nanostructured, particularly nanoporous materials. Two commonly employed classes of templates are colloidal crystals and surfactants. Colloidal crystals typically have an opal-like structure and have been used to produce macroporous (>50 nm pores) solids; surfactants generate various mesoporous structures (2−50 nm pores) as a result of their versatile phase behavior. One aim of this study is to combine colloidal crystals and surfactants to realize simultaneous templating at two length scales. A series of hierarchically structured porous silica samples were synthesized under different synthetic conditions, comprehensive TEM characterization was conducted to reveal the detailed hierarchical porous structures, and simulation was performed to correlate the structures to the surfactant phase behavior within the colloidal crystal confinement. The dual templating approach was further extended to synthesize functional materials with composite porous architectures, in which functional cores were embedded in a hierarchically porous framework for optical ionsensing application. A second aim of this study is to develop a template-based strategy for sculpting nanoparticles of desired shapes and sizes. Owing to the ordered structure and symmetry of the template, a templating-disassembly process was found to produce uniform, nanometer-level, multipodal particles. This method is applicable to a variety of compositions, including oxides, phosphates and carbon, and it could further lead in-situ organization of particles following a self-reassembly process. In addition, through a coupled passivation-disassembly process, site-specific functionalization was achieved to modify only the tips of the multipods with a range of functional groups, and therefore to enable their directional bonding to other colloidal particles. (256 words)