A new role for phosphorus in graphitization of phenolic resin

A phosphorus containing phenolic resin, in which the phenolic moieties were cross-linked by a phosphorus compound, tetrakis-(hydroxymethyl)-phosphonium sulfate (THPS) and formaldehyde, was prepared and the effects of phosphorus on the graphitization of the polymer were studied. The chemical forms of the introduced phosphorus were found to vary in the course of hear treatment by P 2p XPS and solid state P-31 NMR. After heat treatment up to 2000 degrees C, the phosphorus species were incorporated in cyclic systems and no signs of graphitization were found. After heat treatment at 3000 degrees C, the XRD diffractogram was found to be drastically changed from a broad (002) line to a sharp but asymmetric one, nevertheless the content of phosphorus in the heat treated sample was almost completely reduced to zero. This finding suggests a new role for phosphorus in graphitization, as this element has been recognized as an inhibitor of graphitization. (C) 1999 Elsevier Science Ltd. All rights reserved.