Abstract
Si3N4/5-wt% carbon nano/nano-composite was successfully fabricated for the first time by high-energy mechanical milling followed by spark plasma sintering. The milling promoted the amorphization of starting powders; most of the carbon particles were transformed into nano-size and embedded in the amorphous phase. This, combined with low sintering temperature and rapid densification rate, prevented the reactions between carbon and other starting powders, leading to a nano/nano composite microstructure. The nano-sized carbon grains with average diameter of about 10 nm were homogeneously dispersed in nano-sized (about 70 nm) silicon nitride grain boundaries. The hardness of obtained nano-ceramics is comparable with that of conventional silicon nitride, whereas Youngs modulus is significantly decreased.
