STUDY OF CATALYTIC GROWTH OF OLEFIN NANO FIBRILS AND CARBON NANO FIBRILS OVER SOLID SURFACE AND ITS APPLICATION
Choi, Kyu Yong
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In this dissertation, the catalytic growth of nano fibrils over solid surface of different geometric types is studied and their applications are also investigated. The new experimental results on olefin polymerization with metallocene catalyst over silica supports of different geometries are presented. Flat surface silica, nano-sized spherical silica, straight cylindrical pore silica, macroporous silica, and conventional silica are used as support materials. The presence or absence of intraparticle monomer diffusion resistance and particle fragmentation has been shown to have significant effects on the catalytic activity. Also the effects of support geometry on the morphology of polymers and intrinsic catalytic activity are analyzed. The catalytic growth of olefin nano fibrils are applied in micro/milli reactors. Unlike many conventional olefin reactors, the reaction temperature, heat transfer and bimodal distribution of polymer molecular weight can easily be controlled in the micro/milli reactor systems developed during this study. The catalytic growth of carbon nano fibrils on silicon has been investigated for application as anode materials in Li-ion batteries. This research is aimed at developing a binder free silicon anode system that consists of a modified Cu foil (current collector), Si nanoparticles (SiNPs), and carbon nanotubes (CNTs). This anode system includes the nanostructured Cu surface layer as a hub for the Si nanoparticles that undergo deformation and fragmentation during the charge/discharge cycles. SiNPs are deposited with Fe-Co bimetallic catalyst and CNTs are grown in situ at the catalyst sites. The surface layer of the Cu is modified via an oxidation and reduction processes to have knife-like nanostructures with high void fractions. The SiNPs are deposited on/in to the nanostructured Cu foil without any binders. The CNTs growing at the surface of the SiNPs serve as the electron conductor and also holds the SiNP during the lithiation/delithiation cycles. Since Si/CNT particles are surrounded by thin protrusions on the surface of Cu current collector, the maximum connectivity between silicon and current collector can be obtained, and excellent cycle stability of the battery can be maintained without any binders.