Processing character of MgO-partially stabilized zirconia (PSZ) in size grading prepared by injection molding

The effects of the mixture of coarse/fine ZrO2 powders in various ratios on the properties of injection-molding feedstocks, the degree of debinding, dimension reproducibility, sintering and phase formation of the Mg-partially stabilized zirconia (PSZ) were studied. The feedstocks and injection molded pieces with 3.5 wt% MgO were tested by capillary rheometry, thermal analysis (DSC), and the injection-molded pieces were analyzed by mercury porosimetry, Archimedes' method. After sintered, the density and m-phase were analyzed by SEM and quantitative XRD techniques. Experimental results show when the feedstocks contained greater than or equal to 50 vol% of coarse powder, the viscosity is lower and the activation energies of the feedstocks are in the same range as that of pure binder admixture. The flowing properties are controlled by the ratio of fine to coarse as the concentration of fine powder was over 50 vol%. In addition, the formulations with a higher content in fine powder would enhance the de-polymerization of PP, improve the dimensional reproducibility, homogeneity, and degree of debinding. With the appropriate controls on the ratio of fine to coarse powders, Mg-PSZ with 60 to 93% theoretical density and uniform microstructure can be produced. (C) 1998 Elsevier Science Limited. All rights reserved.