Distribution of intercalant in copper chloride and iron chloride graphite intercalation compounds
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Distribution of intercalant in copper chloride and iron chloride graphite intercalation compounds Shinn-Shyong Tzenga) and Mei-Hsueh Nien Department of Materials Engineering, Tatung Institute of Technology, Taipei, Taiwan 104, Republic of China (Received 9 January 1998; accepted 24 January 1998)
CuCl2 and FeCl3 graphite intercalation compounds were prepared by a gas phase reaction method using different carbon host materials. The effect of the microstructure of carbon host materials on the amount of intercalation and the distribution of intercalant was investigated using x-ray diffraction and electron microprobe analysis. For a fiber sample with a core region of onion skin structure in the cross section, a lower concentration of intercalant was measured in the core region. For fiber samples with an oriented-core transverse microtexture, different intercalant distributions along the long axis (oriented-core direction) and the short axis of the elliptical cross section were found.
I. INTRODUCTION
Because of weak van der Waal’s bonding between graphite basal planes, many atoms or molecules can be inserted between the basal planes to form graphite intercalation compounds (GIC’s). A number of chemical species, ranging from a simple metal to large organic molecules, have been found to form GIC’s when using different synthesis processes. Because of their special structure and properties, GIC’s have potential for many different applications.1,2 In the early research for the synthesis of GIC’s, graphite powders and highly oriented pyrolytic graphite (HOPG) were often used as host materials. However, due to the development of high modulus pitch-based carbon fibers and vapor grown carbon fibers, which possess a high degree of graphitization, the use of graphite fibers as host materials for intercalation has also received much attention.3 – 6 The novel geometry of graphite fibers facilitates the study of various intercalation phenomena and is of particular importance for practical applications of GIC’s.1 Host effect is an important parameter in the structure and properties of graphite intercalation compounds.7,8 In general, the carbon fibers with better structural order will produce an intercalation compound having higher electrical conductivity. Typically, the increase in conductivity of highly crystalline graphite fibers after intercalation is approximately one order of magnitude. The conductivity increase by the intercalation of graphite fibers is generally lower than that in a HOPG host for the same intercalate species and stages. However, the fiber geometry offers advantages relative to HOPG for increasing the compositional stability of graphite intercalation compounds under ambient condition.9,10 a)
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J. Mater. Res., Vol. 14, No. 1, Jan 1999
In addition to the degree of graphitization, several transverse microtextures in the cross section of graphite fibers could also be developed from diff
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