Electrostatic and electrosteric stabilization of aqueous slips of 3Y-ZrO2 powder

Yttria-doped zirconia powder (3Y-ZrO2) was characterized and dispersed in d istilled water. The state of dispersion was evaluated in terms of zeta pote ntial, apparent viscosity and the mean particle size of solid phase in the slip. Zeta potential, apparent viscosity and the mean particle size as a fu nction of pH indicated the pH range of electrostatic stabilization. These r esults showed that electrostatic stabilization of the slip can be accomplis hed in low acidic and high basic range of pH. Dissolution of yttria from th e powder surface in acidic pH was found to be high and fast, risky to the s tability of the slip as well as the microstructure of the sintered body. El ectrosteric stabilisation by addition of an anionic polyelectrolyte (PMAA-N H3) shifted the isoelectric point (IEP) to lower pH. The state of dispersio n was further investigated by particle size measurements of the solid phase in the slip. The optimum amount of dispersant is discussed in terms of zet a potential and viscosity. The adsorption of polyelectrolyte is considered at pH 4, native pH of suspension and at pH 10, below and above the IEP of p owder and correlated with the dissociation rate of polymer and the net surf ace charge of particles at given pH. Higher adsorption of dissociated polym er to the positively charged surfaces justifies the higher optimum amount o f polyelectrolyte at pH 4. (C) 2000 Elsevier Science Ltd. All rights reserv ed.