Preparation Of Highly Concentrated SiC Slurry

With wet or colloidal processing method, ceramics can be produced with high reliability and complicated shapes, which have the advantages of easy control of agglomeration, impurities, and the defects. In order to achieve a uniformly consolidated compact, it is desired to use dispersed colloidal suspensions containing upwards of 50 vol% solids while still maintaining relatively low viscosities of less than 1 Pa s. The realization of this object depends on controlling the zeta potentials, pH values, rheological properties, dispersant contents, etc. of the slurries.By using of TEM, XRD, XPS, FTIR, TG, SDTA, etc., through careful analysis and comparison the properties including particle size distribution, particle shape, colloidal properties, composition of domestic and imported SiC powders, the way of improving the properties of domestic SiC powders has been suggested by an investigation on the effects of zeta potentials, pH values, particle size distribution, dispersants and highly valence counter ions on the rheological behavior.The results indicate that SiC slurry is tend to coagulate near isoelectric point (EP), and, on the other hand, it is favorably for the dispersion of the slurry and obtaining slurry of high stability and low viscosity at around pH=10l 1 with the relatively high zeta potential. The addition of electrolyte can increase zeta potentials, decrease the IEP, and improve the rheological properties of SiC slurry. Leaching SiC with acid can reduce the content of impurities, remarkably improve the maximum solids volume loading (J. With addition of dispersant together with acid leaching, highly concentrated Slurry (55vol%) of low viscosity has been prepared. However, thermal treatment is unfit for the preparation of high solids loading SiC suspensions.