Browsing by Author "Gao, Wei"

Now showing 1 - 4 of 4
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    Graphite oxide coated particulate material and method of making thereof
    (2016-08-02) Majumder, Mainak; Gao, Wei; Ajayan, Pulickel Madhavapanicker; Narayanan, Tharangattu; Pradhan, Bhabendra K.; Rice University; United States Patent and Trademark Office
    A process for conversion of conventional sand granules (or other particulates) to a ‘core-shell’ adsorbent granules in which GO (or GO-f) coating imparts nano structural features on the surface of the sand granules (or other particulates). Such materials are useful in a variety of engineering applications such as water purification, catalysis, capacitors, proppants, casting, and magnetic shielding.
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    Graphite Oxide: Structure, Reduction and Applications
    (2012-09-05) Gao, Wei; Ajayan, Pulickel M.; Weisman, R. Bruce; Barrera, Enrique V.
    This thesis proposes a modified structure model for graphite oxide (GO), an important precursor in graphene chemistry, develops a new strategy to convert GO back to graphene-like structure, and demonstrates its possible applications in both water purification and supercapacitor technologies. GO, a nontraditional compound first obtained from graphite oxidation over 150 years ago, is now becoming an important player in the production of graphene-based materials, which has high technological relevance. GO structure and reduction have been vigorously investigated, but its precise chemical structure still remains obscure, and the complete restoration of the sp2 carbon lattice has not yet been achieved. In our work, solid state 13C NMR (MAS) analysis offered a piece of evidence for five or six-membered ring lactol structure existing in GO that had never been assigned before, leading to a modified Lerf-Klinowski model for GO. A three-step reduction strategy, involving sodium borohydride (NaBH4), sulfuric acid, and high temperature thermal annealing, described in the thesis, successfully reduced GO back to chemically converted graphene (CCG) with the lowest heteroatom abundance among all those previously reported. In addition to the chemical significance of graphene/CCG production, GO and its derivatives were used as novel adsorbents in water purification. GO-coated sand showed higher retention than ordinary sand for both Rhodamine B and mercuric ion (Hg2+) contaminants in water. Further functionalization of GO with thiophenol resulted in better adsorption capacity toward Hg2+ than that of activated carbon. In addition, free-standing films of GO were treated and reduced with a CO2 laser beam into different conductive reduced GO (RGO) patterns, and directly used as supercapacitor devices which showed good cyclic stability and energy storage capacities comparable to that of existing thin film ultracapacitors. GO turned out to be a solid electrolyte with anisotropic proton conductivity similar to Nafion, while the large amount of trapped water in GO played an important role.
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    Paintable Battery
    (Springer, 2012) Singh, Neelam; Galande, Charudatta; Miranda, Andrea; Mathkar, Akshay; Gao, Wei; Reddy, Arava Leela Mohana; Vlad, Alexandru; Ajayan, Pulickel M.
    If the components of a battery, including electrodes, separator, electrolyte and the current collectors can be designed as paints and applied sequentially to build a complete battery, on any arbitrary surface, it would have significant impact on the design, implementation and integration of energy storage devices. Here, we establish a paradigm change in battery assembly by fabricating rechargeable Li-ion batteries solely by multi-step spray painting of its components on a variety of materials such as metals, glass, glazed ceramics and flexible polymer substrates. We also demonstrate the possibility of interconnected modular spray painted battery units to be coupled to energy conversion devices such as solar cells, with possibilities of building standalone energy capture-storage hybrid devices in different configurations.
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    Patterned graphite oxide films and methods to make and use same
    (2016-04-12) Ajayan, Pulickel M.; Pradhan, Bhabendra K.; Gao, Wei; Rice University; United States Patent and Trademark Office
    The present invention relates to patterned graphite oxide films and methods to make and use same. The present invention includes a novel strategy developed to imprint any required conductive patterns onto self-assembled graphene oxide (GO) membranes.