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In this talk I will summarize our recent results on the synthesis and characterization of carbon nanosheets — a new two-dimensional nanostructure of micron-scale height and length but atomic-scale thickness. Scanning electron microscopy of carbon nanosheet samples shows that the nanosheets have a flake-like structure and stand perpendicular from the growth surface with a linear contact point -- similar to CVD nanotubes and in contrast to intercalated graphene sheets which have planar contact with the substrate. Raman spectroscopy, Transmission electron diffraction, and X-ray diffraction indicate that the nanosheets are graphite in nature and have a high degree of order which can be tuned by via growth parameters. Transmission electron microscopy confirms that the nanosheets are atomic-scale in thickness in that they are made up of 1-10 graphene layers stacked in a parallel arrangement. Auger electron spectroscopy, X-ray photoelectron spectroscopy, and particle induced X-ray emission spectroscopy all confirm that nanosheets do not contain catalyst or contaminants to ppm sensitivity. Thermal desorption spectroscopy results show that the as-produced hydrogen to carbon ratio can be as high as 1:4. Browning Emmet Teller surface area measurements provide a specific surface area of ~1300m2/g, which is the theoretical maximum value for a 2-layered graphene sheet.
Carbon nanosheets synthesized by radio-frequency plasma enhanced chemical vapor deposition from a mixture of methane (CH4) and hydrogen (H2) have been deposited on Si, SiO2, Al2O3, Mo, Zr, Ti, Hf, Nb, W, Ta, Cu and 304 stainless steel, without any catalyst or substrate pre-treatment. The high surface area makes nanosheets a potential candidate of catalyst support and hydrogen storage in fuel cell applications. Field emission testing shows that nanosheets have threshold fields as low as 1.1 V/ìm (10 nA threshold), can sustain current densities as high as 0.2 A/cm2, and are able to produce maximum DC current as high as 20 mA.
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