Analysis of Stacking Structure of Cup-Stacked Type Carbon Nanofibers
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G7.40.1
Analysis of Stacking Structure of Cup-Stacked Type Carbon Nanofibers Kyoich Oshida, Tatsuo Nakazawa, Kozo Osawa, Takuya Hayashi1, Morinobu Endo1, Takashi Yanagisawa2, and Mildred S. Dresselhaus3 Nagano National College of Technology, 716 Tokuma, Nagano-shi, 381-8550, JAPAN. 1 Shinshu University, 4-17-1 Wakasato, Nagano-shi, 380-8553, JAPAN. 2 GSI Creos Incorporation, 3-1, kudanminami 2-chome, Chiyoda-ku, Tokyo 102-0074, JAPAN. 3 Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ABSTRACT The lattice images of the new type (cup-stacked type) carbon nanofibers were observed by high resolution transmission electron microscopy (HRTEM) and the detailed structure was analyzed by image processing. The angle of opposed graphitic basal planes was measured from power spectrum obtained by 2 dimensional first Fourier transform. The structures of the slanted (00~1) lattice planes, which appear at the cross section of the fiber wall, were shown by means of this image analysis technique. Defects were observed in the ordered structure of this material. The (00~1) lattice planes show large fluctuation in alignment of them and the (10~0) lattice planes make several angles with the (00~1) lattice planes. The average repeat distance d002 was estimated on the basis of d100 by HRTEM image and image analysis. INTRODUCTION Carbon nanotubes generally have a layer structure, which is formed parallel to the fiber axis. The nanotubes of which diameters are over 10nm are called carbon nanofibers. Wall structures of cup-stacking type carbon nanofibers [1,2], variations of carbon nanofibers, are different from that of the conventional multi wall carbon nanotubes [3] and nanofibers [4]. The layer planes of the cup-stacking type nanofibers have an angle to the fiber axis, that is, the layer stacking are slanted from the fiber axis, and many edge sites of stacking layers will exist at the sidewall of the tube. These new type nanofibers have possibilities of wide application, for example, the material for the cathode electrodes of lithium ion secondary batteries and for the other energy storage system, because the fibers can be broken at the cup-stacking splices by milling and small molecules can go into the hollow of the fiber through the open edges or the side wall. In this report, a partial structure of the cup-stacking type carbon nanofibers produced by the vapor growth method was investigated by high resolution transmission electron microscopy (HRTEM) combined with image processing [5], in order to find the suitable application of the fibers. EXPERIMENTALS Preparation of the sample for TEM observation A little lump of the cup-stacking type nanofibers are put into alcohol in test tube and disperse by supersonic wave. The alcohol contained the disperse nanofibers is seeped on the microgrid for TEM observation by pipet several times. The microgrid is dried for about 3 hours.
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TEM Observation Initially, the shape of the cup-stacking type nanofibers are observed at low magnification, and then the lattice images are ob
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