Study and analysis of structural properties of non-crystalline carbon phases prepared from PTFE

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Abstract
The structures of three carbon preparations obtained by different treatments of the products of a low-temperature electrochemical reduction of poly(tetra-fluoroethylene) have been studied by analysing radial electron density distribution (REDD) curves calculated from X-ray scattering intensity data. The basis of the analysis was a comparison of experimental radial distribution functions (RDFs) with theoretically calculated ones, both for diamond-like and for intra- and interlayer graphite-like structures, using a representation of the RDF as a sum of weighted and broadened pair functions. The above-mentioned carbon preparations have several unusual physico-chemical properties, for example a very high specific surface area (3000m2g−1) and a high elasticity of the carbon skeleton when subjected to pressure; moreover, in the native reaction products (a compacted mixture of carbon and LiF) the simultaneous presence of all three theoretically possible bonding modifications of carbon (sp2, sp3, and—in particular—the expected, highly reactive sp modification) has been confirmed. Analysis of the shape of the carbon RDF in the region of the first three coordination spheres has shown that samples of carbon, obtained by melting (950°C) or by leaching out LiF from its mixture with carbon in the reaction products, contained 25% of diamond-like and 75% of graphite-like structure, respectively. The diameters of these graphite-like and diamond-like regions have been estimated to lie in the ranges 1·2–1·6 and 0·6–1·2 nm, respectively.