The milling time effect on sintering kinetics of silicon nitride based composites

We have investigated the influence of the milling time on the structure and mechanical properties of the nanocomposite, as well as the effect of grain size on the sintering kinetics (alpha to beta silicon nitride phase transformation). As we observed, by increasing the milling time the mechanical properties of the ceramics may be improved. The reason of this improvement is partly due to the alpha-Si3N4 to beta-Si3N4 transformation facilitated by the smaller grain size, on the other hand it is due to the better dispersion of the carbon nanotubes. The X-ray measurements confirmed that in the case of samples milled for 5 hours, even when sintered at 1700 degrees C, low nitrogen pressure (2MPa) and without holding time, a faster phase transformation occurs, resulting in improved mechanical properties.