Abstract

Nanosized tungsten carbide powders were synthesized by the chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl(W(CO)_6). The effect of CVC parameters on the formation and the microstructural change of as-prepared powders were studied by XRD, BET and TEM. The loosely agglomerated nanosized tungsten-carbide(WC_1-x) particles having the smooth rounded tetragonal shape could be obtained below 1000°C in argon and air atmosphere respectively. The grain size of powders was decreased from 53 nm to 28 nm with increasing reaction temperature. The increase of particle size with reaction temperature represented that the condensation of precursor vapor dominated the powder formation in CVC reactor. The powder prepared at 1000°C was consisted of the pure W and cubic tungsten-carbide (WC_1-x), and their surfaces had irregular shape because the pure W was formed on the WC_1-x powders. The WC_1-x and W powders having the average particles size of about 5 nm were produced in vacuum.

• Keywords: Tungsten carbide;Chemical vapor condensation;Tungsten hexacarbonyl;Nanosized powders;