Microwave-assisted Preparation of Precursor for the Synthesis of Nanocrystalline Boron Carbide Powder

ABSTRACT Nanocrystalline boron carbide was synthesized using a precursor. The precursor was prepared by the thermal decomposition of a condensed product formed by boric acid and mannitol. The condensed product was formed by microwave-assisted heating of the aqueous solution of boric acid and mannitol. The condensed product was thermally decomposed at various temperatures, viz. 400°, 500° and 600°C for 2 h. The thermally decomposed condensed product was further heat treated at temperatures from 1000° to 1600°C for 10-240 min to optimize the temperature and duration of heating in order to synthesize boron carbide with a lower free carbon impurity phase. All the products were characterized for phase purity and chemical composition (boron, total carbon and free carbon contents). The formation of boron carbide was found to occur even at a lower temperature of 1000°C. The free carbon content in the product at 1600°C was found to be <0.5 wt%. GRAPHICAL ABSTRACT