Browsing by Author "Zhang, Xueyi"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Directed synthesis and characterization of zeolite nanoparticles(2013-10) Zhang, XueyiZeolites are a class of materials with ordered micropores (smaller than 2 nm), that can be used for gas separation, catalysis, and adsorption. Structurally, zeolites are composed of SiO4 tetrahedra sharing corners in an ordered manner. The numerous arrangements of these SiO4 tetrahedra give zeolites micropores in the forms of channels and cages. Although the applications of each zeolite depends on the spatial arrangements and the sizes of these micropores, size and morphology of zeolite particles are equally important. By preparing zeolite nanoparticles, diffusion paths of zeolite particles can be shortened, total surface area of zeolite particles can be increased, which are beneficial to reducing energy consumption in gas separation, reducing deactivation in catalytic reactions, and increasing adsorption capacities. This dissertation introduces various methods to prepare zeolite nanoparticles. Zeolite nanoparticles prepared with the help of mesoporous carbon templates (hard template) are firstly introduced where the shape and size of zeolite particles are imprinted from the templates. In addition to hard templates, the use of bifunctional surfactant (soft templates) to prepare ultra-small zeolite nanoparticles and lamellar zeolite membrane is also introduced. With only one structure-directing agent that is less intuitive than hard or soft templates, the preparation of hierarchical lamellar zeolite with 2 nm lamellae, the self-pillard pentasil (SPP) zeolite, is introduced, where the intrinsic growth patterns of the crystal played an important role. Finally, template-free synthesis of zeolite nanoparticles, where zeolite formation is totally driven by the intrinsic growth patterns, is introduced. In addition to the preparation methods, a series of computational methods to determine and study the structures of zeolite nanoparticles are also introduced.Item Item Structure determination of zeolite nanosheets(2012) Zhang, Xueyi; Tsapatsis, MichaelMFI and MWW zeolite nanosheets are building units for state-of-the-art zeolite thin films for gas separation. In this study, the structures of exfoliated MFI and MWW zeolite nanosheets were determined using a combination of experimental and simulation methods. Based on characterization results from atomic force microscopy and transmission electron microscopy, the structures and thicknesses of the exfoliated zeolite nanosheets were proposed. After optimization with Car-Parrinello molecular dynamics, X-ray diffraction patterns and electron diffraction patterns are simulated from these structures. The agreement between experimental and simulated characterization data suggested that the proposed structures should represent the actual structures of the exfoliated zeolite nanosheets. The methods used in this study can be extended to determining structures of other zeolite nanostructures.