R. Vangelisti, A. Herold
1977
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0
Influential Citations
10
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Journal
Carbon
Abstract
Abstract The intercalation of gold trichloride has been studied in the classical manner by the action of the vapour on graphite in a sealed tube[12]. Tables 1 and 5 summarize the results obtained with various samples of natural and artificial graphite and with carbon materials graphitized at high temperatures. Under optimal reaction conditions (245°C), a blue, richest ( Δm mo = 200% ) product is obtained, of formula C12.6AuCl3: gold trichloride intercalates in the pure state (Table 2). Comparison of the results obtained by thermogravimetry (Fig. 1), dialatometry (Fig. 2) and X-ray analysis (Fig. 3) indicates that this final product C12.6AuCl3 is of first stage with an interplanar distance of 6.80A (Table 3). Study of the relative intensities[17] of the (001) reflections allows stating that the gold trichloride intercalates are in the form of planar molecules Au2Cl6 (Table 4). Macroscopic observation of the pyrographite samples shows that the insertion occurs in an “all or nothing” manner[18]: during the reaction the layers are gradually deformed in the neighbourhood of the “invasion front” (Fig. 4) and when the intercalation is terminated, a pleating of the layers appears very clearly at the surface (Figs. 5 and 6). These dislocations visible on the edges of the samples (Fig. 7) are a manifestation of the “separation work” necessary for the intercalation which practically excludes the possibility of reagent layers inserted with a lower ratio than in C12.6AuCl3.Graphite and its intercalation compounds lend themselves only with difficulty to a microstructural study by visualization of the lattice planes (instability of the products under an electron beam, basal carbon planes invariably parallel to the grid support). Carbon blacks (Sterling MTG 3000°C) are small circular rods (θ Δm mo = 140% ), almost of the second stage. With these carbons, it was not possible to intercalate ferric or chromic trichloride[21]. The lattice distances measured on micrographs of the intercalated products (Fig. 9) allowed to identify the most contrasted fringes as direct representations of gold trichloride layers inserted between those of the carbon (the finer fringes). The different types of layers observed along the segment AB (Fig. 9) indicate a succession of different stages from A to B (1st-1st-2nd-3rd-4th-3rd-5th) which indicates the inhomogeneity of the products studied[10]. These results seem to corroborate the “statistical definition” of stage identifiable in the combination of graphite with the halogenides[8,19,22].