Papers by Author: Han Zhang

Abstract: Advanced silicon nitride ceramic compact was prepared by colloidal process. The rheological behaviors of the Si3N4 powders were emphatically investigated. At the same time, the effects of the dispersant, pH value and ball milling time on the silicon nitride slurry were discussed. The results showed that the addition of the dispersant could shift the value of Zeta potential and improve the fluidity of silicon nitride slurries. The well fluidity can be achieved when the amount of the dispersant was 1.2wt%. Besides, a ball milling time of 8h was appropriate. Statistic pattern recognition was used to predict the processing parameters. Then the high density of green compact could be attained while the volume fraction of solid powders was up to 40%, and the fracture toughness of the sintered body reached 7.2MPa·m1/2. The microstructure of final sintered ceramic was observed by scanning electron microscope (SEM).

Abstract: Without addition of any thermodynamically stable perovskite compound such as PbTiO3, Pb(Mg1/3Nb2/3)O3 was fabricated by a new sol-gel route, and the processing parameter was studied. The result showed that the chelating effect of ammonium citrate was relatively better than that of citric acid in this system. When the ratio of ammonium citrate to Nb2O5 was 8.33, the colloid of Nb2O5·nH2O was in state of transparency. The effects of heat treatment on the formation of perovskite phase of Pb(Mg1/3Nb2/3)O3 powders were characterized by X-Ray Diffraction (XRD) method. With increasing heat treatment temperature or holding time, pyrochlore phase turned into perovskite phase gradually, and after second calcination, the content of perovskite phase increased significantly from 54% to 72%.