Journal of Advanced Materials in Engineering (Esteghlal)

Electrophoretic Deposition (EPD) weight is highly affected by electrophoretic mobility of powders in suspension. In theoretical aspect, electrophoretic mobility is influenced by suspension viscosity in opposite direction, and increasing in viscosity can decrease electrophoretic mobility and consequently can decrease EPD weight. In non-aqueous suspension, viscosity is determined by ion strengths of suspension. In this study, viscosity, electrical conductivity and deposit weight were determined for electrophoretic deposition (EPD) of alumina suspended in ethanolic solvent of Y-, Mg-, Ce- and La- salts, prepared in dispersant level between 350 to 1350 ppm. The concentration of XCly, (X: Mg, Y, Ce and La), is also found to be a critical factor to control  the viscosity. It is shown that the deposit weight is influenced by precursor concentration, and on the other hand, electrical conductivity, viscosity or the pH of the suspension cannot change the yield. All concentrations interactions, except Mg × Ce concentration are significant in ANOVA model. The viscosity of suspension reached 2.5 mPa.s with Mg-, Y-, La- and Ce- decreased to 100, 100, 100 and 0 ppm in low iodine concentration (400 ppm). The reason is that heavier cations can be adsorbed to alumina surface with iodine adsorption, but lighter Mg- cations can be adsorbed under the influence of OH groups excited on alumina surface.
 

In this study, Spark Plasma Sintering (SPS)  of both slip casted and powder specimens of alumina/ yttria core-shell nanocomposite were utilized for fabricating transparent Yttrium Aluminum Garnet (YAG) ceramics. Phase evolution, optical transmittance and the microstructure of sintered samples were compared. In slip casting process, Dolapix CE64 was used as a dispersant for preparing the stable aqueous slurry of this nanocomposite powder. The effect of Dolapix concentration and pH value on the stability of the suspension was described, and the viscosity diagrams were investigated at different pH value and different weight percents of Dolapix. The rheological behavior of the nanocomposite powder slipped at 60-70 wt% solid loading was studied by measuring their viscosity and shear stress as a function of shear rate of the slurry. The results showed that, the suspension has a minimum viscosity at pH of 10 by addition of 2.5 wt% Dolapix. Also, the slurry with solid loading of 60 wt% showed the Newtonian behavior and this rheological behavior was preserved even above this solid loading values. Slip casting technique caused the uniform size and pores distribution as well as eliminating large pores in the green body. Consequently, transparent YAG ceramic with 60% optical transmittance was achieved after SPS process of slip casted green body which was much higher than that of nanocomposite powder, i.e. about 30% at the same sintering conditions.