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 activ ity a(C) higher than that of graphite (standard state with a(C) = 1). Amorp hous carbon is in a metastable state but, under normal circumstances, it ta kes several hours to be graphitised to an extent detectdble by X-ray diffra ction even at temperature higher than 1500 degrees C. In the present work, we report the accelerated graphitisation of amorphous carbon induced appare ntly by the catalytic action of tungsten (W) or tungsten carbide (WC) durin g synthesis of WC started from Wand active carbon in solar furnace under co ntrolled atmosphere (Ar or N-2) This degree of graphitisation of amorphous carbon did not proceed by the similar reaction undertaken in the traditiona l laboratory furnace under the comparable conditions. (C) 1999 Elsevier Sci ence S.A. All rights reserved.