Abstract
We have developed a novel, simple, efficient and economical synthetic route for preparation of carbon nanoparticles and graphite-encapsulated metal nanoparticles in solution. The carbon nanoparticles were prepared in toluene that contains copper wires under microwave irradiation. Graphite-encapsulated metal nanoparticles were prepared similarly after a metal precursor was added. The morphologies of the products were examined using TEM and HRTEM. The crystalline structures of the samples were characterized using SAED, XRD and Raman spectroscopy. The magnetic characteristics of the metallic carbon products were explored using SQUID. Reactions that proceeded in the interior metal core of carbon nanocapsules occurred under focused microwave irradiation are examined. A possible mechanism of the reactions of carbon shells with iron cores was proposed. Results of this study provide further insight into the mechanism of the iron-catalyzed growth of carbon nanotubes. This thesis also presents a technique for rapidly surface functionalization the of carbon nanotubes (CNTs). CNTs were surface-functionalized with various functionalities via a rapid, single-step process that involved ultrasonication-assisted and microwave-induced radical polymerization. Both hydrophobic (such as polystyrenes and poly methyl methacrylate) and hydrophilic (such as poly acrylamide, poly acrylic acids and poly allyl alcohols polymer chains) can be chemically grafted onto the surface of MWCNTs by the same process within ~10 min. The surface grafted polymers were identified by FTIR, TGA, TEM, EELS and Raman spectroscopy. The solubilities of the surface derivatized MWCNTs were in the range 1200~ 2800 mg/L. Iron-filled multi-walled carbon nanotubes (Fe@MWCNTs) can also be functionalized by this strategy. The poly (acrylic acid) modified iron filled MWCNTs have a saturated magnetic dipole moment of ~40 emu/g at room temperature with a coerceive field of nearly zero Gauss. The surface modifying strategy was applied to various graphite materials (such as graphite nanofiber and carbon nanotubes) as catalyst supports for the oxidation of methanol at the anode. The surfaces of various graphite materials were homogenously modified with poly vinyl pyrrolidone(PVP) and used as supports for the oxidation of methanol at the anode. The PVP-carbon supports were characterized by FTIR, TGA and Raman spectroscopy. The HRTEM, XRD and XPS results demonstrated the small (1-2 nm) and narrow size distribution of the Pt nanoparticles catalyst could be deposited on these PVP-carbon supports. Various graphite materials functionalized with PVP radicals and carboxylic acid via acid oxidation were used as supports for the Pt catalyst in a methanol oxidation reaction. The Pt-PVP-herringbone graphite nanofiber (PVP-GNF) nanocomposite gives the best electro-catalytic performance in direct methanol fuel cell among all carbon nanosupports, being nearly four times oxidation current of that from the Pt/acid oxidizing GNF(AO-GNF) nanocomposite, and nearly three times that of the Pt-XC-72 carbon black. The developed methodology is expected to be very useful in future DMFC studies when applied to other metals or metal alloy catalysts. In additional, the various nanocomposited (such as Au/CNT, Pb/CNT, ZnS/CNT and CdS/CNT) with the surface functionalized CNTs can successful be prepared by simple room temperature chemical reaction in this thesis. This method could expect be the generality assembly of nanocrystal-carbon nanotube composite approach.