Structural Studies of Graphite Intercalation Compounds of Fluorine by Transmission Electron Microscopy Tetsuya Isshiki, Fujio Okino, Yoshiyuki Hattori, Shinji Kawasaki and Hidekazu Touhara Department of Chemistry, Faculty of Textile Science and Technology Shinshu University, 3-15-1 Tokida, Ueda 386, Japan Structures of graphite intercalation compounds of fluorine CxF have been investigated using transmission electron microscope (TEM) in combination with XPS and X-ray diffraction (XRD) measurements. TEM lattice fringe images of CxF indicate that the sandwich thickness of semi-ionic C3.2F is smaller than that of ionic C7.3F by ca. 0.05nm in accordance with XRD results. This also supports the semi-covalent character in C-F bonds in the latter observed by XPS which allows closer contact between carbon and fluorine atoms. Although the lattice fringes of CxF are wavy compared with that of pristine graphite, they are much less wavy compared with that of covalent graphite fluoride (C2F) indicating that the planarity of carbon layers in CxF is preserved. The waviness increases from ionic to semi-ionic CxF as the fluorine content increases. A nanobeam electron diffraction of semi-ionic C3.2F is also shown. KEYWORDS: Graphite intercalation compounds, Fluorine, Transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, C-F bonds
Table 1 Reaction conditions, composition, stage number, Ic and di of CxF prepared by the direct reaction of graphite with F2.
Fig.1 C1s and F1, XPS binding energies of fluorine-graphite intercalation compounds and related materials. Fig. 2 C1s and F1s, XPS spectra of (a) C16.8F, (b) C3.2F and (c) C2.1F.
Table 2 Reaction conditions composition stage number Ic and di of CxF prepared by the fluorination of graphite in the presence of AHF. Fig. 3 X-ray diffraction patterns of C3.2F before and after immersion in methanol and acetone.
Fig. 4 C1s and F1s XPS spectra of C3.2F and C16.8F before and after immersion in methanol and acetone. Fig. 5 TEM lattice fringe image of SP-1 graphite. Fig. 6 TEM lattice fringe image of graphite fluoride (C2F)n.
Fig. 7 TEM lattice fringe image of stage-2 C7.3F with ionic C-F. Fig. 8 TEM lattice fringe image of stage-1 C3.2F with semi-ionic C-F.
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