63. Scanning transmission electron microscopy of mukiphases in graphite-interactioncompounds H. Mazurek and M. S. Dresselhaus (M.I.T., Center for Material Science and Engineering 13-3017, Cambridge, MA 02139). Results of a systematic study of various
stages of graphite-alkali metal intercalation compounds by scanning transmission electron microscopy will be presented. Bright and dark field real space images indicate that at room temperature the observed island domains are in an ordered, incommensurate phase. Related X-ray fluorescence data show these domains to be of higher intercalant density than the background regions. 64. In-plane melting transitions in graphite-halogens K. K. Bardhan and D. D. L. Chung (Department of Metallurgy and Materials Science, Carnegie-Mellon University, Pittsburgh, PA 15213). X-Ray diffraction has
shown that the in-plane melting transition in graphite-Br, is continuous, whereas that in graphite-ICI is first order. The transition occurs at 373.7”C on heating and cooling for graphite-Brz. For graphite-ICI, it occurs with hysteresis at 314S”C on heating and at 313S”C on cooling. 65. The effect of intercalation on lattice constants of graphite T. Krapchev, S. Y. Leung, R. Ogilvie and M. S. Dresselhaus (M.I.T., Center for Material Science and Engineering 13-2090, Cambridge, MA 02139). A series of (h, k, 0) X-ray scans has been carried out on well staged intercalation compounds formed from HOPG. The results are consistent with the interpretation of the Raman data, namely, the a spacing in graphite increases for donors and decreases for acceptors. In contrast, no observable change in the graphite-graphite c-spacing has been detected with intercalation. 66. X-ray diffraction studies of the intercalate layers in antimony chloride-graphite M. L. Saylors, M. H. Boca, D. S. Smith and P. C. Eklund (Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506). We have analyzed the integrated intensities of the (001)diffraction spots in SbCl,:graphite in terms of a structural model based on intercalate layers comprised of SbC&- and SbC& molecules. The presence of these molecules in our intercalated HOPG samples has been confirmed by “‘Sb MGssbauer spectroscopy[l]. The results of the X-ray data analysis will be presented and include: (1) the relative intercalate layer population of the two molecular species, (2) the c-axis positions of the two molecular centers of mass, and (3) the orientation of the molecular axes relative to the c-axis.
versity of Kentucky, Lexington, KY 40506). “‘Sb M&sbauer experiments on stage 2 samples of SbC&:graphite have been performed as a function of temperature and sample thickness. The measurements show the presence of SbCI,- and SbCI, in the intercalate layers. Their relative population in the layers has been determined; and the connection of this result with the intercalation chemistry will be made.
68. Order-disorder transition in the intercalation compounds Ag,Ti& R. Leonelli, G. Jackie, M. Plischke and J. C. Irwin (Physics Department, Simon Fraser University, Bumaby, B.C., VSA IS6 Canada). The transition from a commensurate g/3 x d3 Ag superlattice to a disordered lat-
tice gas has been studied by Raman spectroscopy and differential calorimetry for x = < 0.4. The intensity of light scattered from zone folded phonon modes is proportional to the square of the order parameter. The transition is found to be second order and well described by a two dimensional lattice gas model. V.INTERCALATION OFGRAPHITE:
CHEMICAL ASPECTS 69. Oxidative intercalation of graphite by antimony pentafhtoride W. C. Forsman and D. E. Carl (Department of Chemical Engineering and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, PA 19104), and T. Birchall (Department of Chemistry, McMaster University, Hamilton, Ontario L85 4M 1 Canada). Intercalation of graphite by SbFS
gives SbF3 as a byproduct indicating that oxidation is the driving force for the insertion reaction. Since Mijssbauer spectra of the intercalation compound indicates that no SbFS is present in the lattice, it is concluded that attack by the SbF, is at the internal basal planes. 70. Vapor-phase intercalation of graphite with nitronium and nitrosonium salts W. C. Forsman and H. E. Mertwoy (Department of Chemical Engineering, University of Pennsylvania, Philadelphia, PA 19104). The vapor in equilibrium with
nitronium and nitrosonium salts are effective intercalation reagents. It is suggested that the mechanism is through attack on the graphite surface by species such as N02+. . . BF.,-. 71. Vapor-phaseintercalationby AIC&-HCImixtures Kam Leong and W. C. Forsman (Department of Chemical Engineering, University of Pennsylvania, Philadelphia, PA 19104). Vapor mixtures of AICI, and
HCI effect intercalation of graphite. The mechanism is thought to be the same as was suggested for inter67. Intercalantspecies in SbCI,: graphite from Miissbauer calation by AIt&-Cl2 mixtures-attack at the graphite spectroscopy surface by an adsorbed, highly electrophylic anion. P. Boolchand, W. J. Bresser, K. Sisson (Department of Physics, University of Cincinnati, Cincinnati, OH 4.5221), 72. Stage dependence of the exfoliation of intercalated D. McDaniel (Department of Chemistry, University of graphite Cincinnati, Cincinnati, OH 45221) and P. C. Eklund and S. H. Anderson, H. H. Lee and D. D. L. Chung V. Yeh (Department of Physics and Astronomy, Uni- (Department of Metallurgy and Materials Science and