CHARACTERIZATION OF A BASAL-PLANE-ORIENTED GRAPHITE

We have employed scanning electron microscopy (SEM), scanning tunnelli ng microscopy (STM), wide-angle X-ray scattering (WAXS), small-angle n eutron scattering (SANS) and adsorption isotherms to characterise the recompressed, exfoliated graphite 'Papyex'. The substrate is found to consist of ca. 60% void space, most of which is associated with galler ies with a thickness of ca. 300 Angstrom. The substrate contains ca. 7 0% rhombohedral and 30% hexagonal graphite crystallites with dimension s of the order of several hundred angstroms. We confirm that Papyex ha s preferentially oriented graphite (0001) planes whose surfaces mainly contribute to the total available surface area. Using the theory of D ebye et al., the substrate may be classed as a random two-phase struct ure. SANS experiments employing contrast variation show that the voids in Papyex are connected and fillable. A Guinier analysis is inappropr iate to apply to the present system owing to the large scale and inter connected nature of the void space of the galleries. BET analysis show s Papyex is a non-porous or macroporous material giving a Type II isot herm with a surface area of ca. 20 m(2) g(-1) and negligible micropore s. This suggests that the substrate consists of voids and macroscopic cracks and fissures with dimensions of the order of ca. 500 Angstrom o r more. Pored analysis of the SANS data gives a surface dimension of 2 .5 and a surface area comparable to that obtained from the BET analysi s. However, the limited range in which power-law behaviour is observed makes conclusions about fractal dimensions and polydispersity questio nable.