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The adsorption state and dispersion effect of an anionic polyelectrolyte (Dolapix CE64) dispersant on the stability of nanocrystalline ZrO2 suspensions are studied by using adsorption isotherms, sedimentation, TGA, electrokinetic sonic amplitude (ESA) and Auger electron spectroscopy (AES) techniques. It was found that colloidal stability and surface properties of aqueous ZrO2 suspension are closely related to coverage distribution of polyelectrolyte as a function of pH on nanocrystalline ZrO2 particle surface. The amount of polyelectrolyte adsorbed on nanocrystalline ZrO2 particle surface increases greatly with decreasing pHiep (pH 3.72) and increasing the polymer concentration. The results obtained from electroacoustic (ESA) technique and AES spectra of polyelectrolyte adsorbed on nanocrystalline ZrO2 surface proved that both techniques are very effective ways to measure the distribution state of polyelectrolyte on nanocrystalline ceramic powder and reveal how the distribution affect the stability of the suspension. It was found that stabilization can be achieved only when conditions of both Dolapix CE64 ionization and ZrO2 surface coverage are satisfied, suggesting an electrosteric stabilization mechanism. In conclusion, we hypothesized a stabilization model according to the model of two particles approaching to describe the influence of the adsorbed anionic polyelectrolyte configuration on particle surface and the stability of nanocrystalline ZrO2 suspensions.

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This study reports useful application of the electrokinetic sonic amplitude (ESA) technique in combination with rheometry and electron microscopy techniques for direct probing the stability of low and high-concentrated zirconia (ZrO2) nanosuspensions in the presence of an alkali-free anionic polyelectrolyte dispersant Dolapix CE64. A comparative study of the electrokinetic characteristics and the rheological behavior of concentrated ZrO2 nanosuspensions has been done. Good agreement was obtained from relationship between the electrokinetic characteristics (zeta potential, ESA signal), viscosity, and its pH dependence for each concentrated ZrO2 nanosuspension with different dispersant concentration in the range of 0.9–1.5 mass%. A nanoscale colloidal hypothesis is proposed to illustrate that the addition of different amounts of dispersant influences on both the stability and the electrokinetic and rheological properties of concentrated ZrO2 nanosuspensions. It is found that an optimum amount of 1.4 mass% dispersant at the inherent pH (>9.2) can be attached fully onto the nanoparticles with sufficient electrosteric dispersion effects, suitable for casting applications. Supplementary scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses followed by colorization effect were taken to verify the visible interaction between dispersant and nanoparticles surfaces. SEM and HR-TEM images proved the existence of visible coverage of dispersant on the surface of individual nanoparticles and showed that thin polyelectrolyte layers were physically bound onto the particles’ surfaces. This study will be of interest to materials scientists and engineers who are dealing with dispersion technology, nanoparticle surface treatments, functionalization, characterization, and application of bio/nanoparticle suspensions at various concentrations using different types of polymers.