Catalytic graphitization of wood-based carbons with alumina by pulse current heating

Japanese cedar was preheated at 500 degrees C and subsequently mixed with 40 mu m Al2O3 particles. A pulse current heating method was used for a 5-min carbonization step under a pressure of 50MPa in order to promote the graphitization at temperatures between 2000 and 2200 degrees C. The samples were analyzed in an analytical transmission electron microscope equipped with a GATAN Imaging Filter, in a high resolution transmission electron microscope and in a scanning electron microscope. Transformation into well-ordered graphite could be enforced by the intermediate reaction of Al2O3 and carbon to plate-like Al4C3. This latter compound dissociates under the proper CO pressure and temperature into Al vapor and solid graphite. The addition of Al2O3 and the pressurized heating device improve the graphitization in comparison with the effect of temperature alone. The electron microscopic observations are supported by XPS and XRD spectra.