Catalytic carbonization of wood charcoal : graphite or diamond?

We report on the process of making graphite out of wood by catalytic carbonization. Two different types of microstructure were observed. One type being typical for graphitization of wood without the effect of a catalyst, the main characteristic being the typical fibrillar microstructure related back to the original cellulose morphology. A strong {0002} inner diffraction ring corresponding to the 0.336 nm lattice spacing of graphite dominates its diffraction pattern. The other type being typical for graphitization of wood with aluminum as catalyst, the main characteristic being the large sheets of carbon forced upon by the formation of plate like Al4C3. This compound is formed as an intermediate reaction product, which dissociates into aluminum vapour and solid carbon. The diffraction pattern indicates a differently textured structure. EELS measurements in the areas of catalytic graphitization indicate a significant decrease of the sp(2) bonding typical for graphite. It can be an indication of the presence of metastable diamond. This diamond-like structure is extremely unstable under influence of the electron beam. It decomposed within 250 s of beam exposure. (C) 2003 Elsevier Ltd. All rights reserved.