Zirconia Powder Surface Modification Of The Injection Molding Process

In CIM process, the poor wettability between zirconia powder and wax-based binder results in high feedstock viscosity,low loading,low debinding rate,low dimension precision and defects easily. Organic/ inorganic coating ceramic powders were prepared by applying surface modifying reagent S to modify the zirconia particle's surface. The influence of surface modification on both powder properties and process of ceramic injection molding was studied. The rheological property of binder and feedstocks was discussed. Two different debinding processes, direct thermal debinding and solvent debinding+ thermal debinding, were researched particularly. In addition, the effects of sintering temperature on densification and transparence of zirconia ceramic were analysed in detail. The conclusions have showed that, (1) The polarity of the modified particles was changed, the wetting contact angle of the modified powder with dimethylbenzene were reduced ,the agglomeration of the modified powder was also reduces, meanwhile, surface modification influenced the rheological property of ceramic feedstocks markedly. Viscosity was reduced evidently and the sensitivity to stealing speed and temperature was also weakened by the surface modification.The feedstock prepared by the modified powder not only exhibits low viscosity but also has excellent formability.The ceramic injection molding feedstocks made of the modified powder exhibited good homogeity, high powder loading and low injection molding temperature, which make the zirconia powder suit for ceramic injection molding.(2)Binder was debinded gradually in direct thermal debinding process. It takes 66 hours to debind all binders by direct thermal debinding which is far longer than by solvent debinding and thermal debinding (34hours). (3) The density and transparence of samples were different when the sintering temperature changed. At 1550℃the sample had ideal property with density 5.94g/cm~3(99%), subtransparent. (4)After surface modification, the defects which present in CIM were reduced, the dispersion of sample's bending strength was decreased, the reliability and three-dimensional shrinkage were improved.