GENERATION MECHANISM OF FINE METALLIC PAR TICLES IN THE INTERLAYER SPACING OF GRAPHITE

We have proposed a reaction mechanism to form fine metallic particles in the interlayer spacing of graphite. Graphite intercalation compound s (GICs) with metal chlorides were immersed in lithium-naphthalene-org anic solvent mixture. Metal chlorides were reduced in the interlayer s pacing of graphite, and fine particles of corresponding metal were obt ained. The size of metallic particles was estimated from the line widt h of X-ray diffraction profiles and transmission electron microscope ( TEM) images. The particle size is found to depend on the activity of p article precursors (i.e. metal atoms or their aggregates) to move in t he graphite gallery, which is determined by the bulk melting point of the metal and the reaction temperature. If the bulk melting point is l ow and the reaction temperature is high, the precursors move more acti vely and grow to a great size. Assuming this mechanism, the dependence of the stage number of starting GICs on the particle size is also exp licable; the size increases with decreasing stage number. The particle size is also affected by the solvent used for the reduction. When the solvent molecules are co-intercalated together with lithium into the interlayer spacing of the GIG, they facilitate the reduction of metal chloride, and relatively large metallic particles are obtained. Analyz ing closely the TEM images, we predict that the metallic particles gen erated in graphite matrix has a form of a short cylinder, which is acc eptable as the growth of particle is taken place in the two-dimensiona l gallery of graphite interlayer. Fine metallic particles with control led size supported in graphite matrix are expected to be useful for ca talytic applications.