Catalytic acceleration of graphitisation of amorphous carbon during synthesis of tungsten carbide from tungsten and excess amorphous carbon in a solar furnace

Amorphous carbon is one of the allotropes of carbon possessing carbon activity a(C) higher than that of graphite (standard state with a(C) = 1). Amorphous carbon is in a metastable state but, under normal circumstances, it takes several hours to be graphitised to an extent detectdble by X-ray diffraction even at temperature higher than 1500 degrees C. In the present work, we report the accelerated graphitisation of amorphous carbon induced apparently by the catalytic action of tungsten (W) or tungsten carbide (WC) during synthesis of WC started from Wand active carbon in solar furnace under controlled atmosphere (Ar or N-2) This degree of graphitisation of amorphous carbon did not proceed by the similar reaction undertaken in the traditional laboratory furnace under the comparable conditions. (C) 1999 Elsevier Science S.A. All rights reserved.