Catalytic graphitization of non-graphitizable carbon by chromium and manganese oxides

Carbon prepared from the benzene-insoluble fraction of a solvent refined coal (non-fusible), an active carbon, a charcoal and PAN carbon fibres have been heat-treated with oxides of chromium, manganese, molybdenum and vanadium to investigate catalytic graphitization in the temperature range 1673–2773 K. Resultant materials were examined by X-ray diffraction, SEM and phase contrast high resolution electron microscopy. The chromia is an effective catalyst at 2273 K at concentration of chromium of 30%, no changes being observed at higher temperatures. With other oxides the extent of catalytic graphitization (using L_c) increased with HTT to 2773 K, values of C₀ being less sensitive to HTT. Soak times are important, equilibration taking 2 hr at 2073 K (SRC-BI: Cr₂O₃) and 10 hr at 1673 K (SRC-BI; MnO₂). Large concentrations of additives (up to 30% of metal) are required. The microscopy reveals the development of flaky graphite (SRC-BI) and the layered stacking arrangements of graphite planes in the SRC-BI graphites.