Advanced colloidal techniques for characterization of the effect of electrosteric dispersant on the colloidal stability of nanocrystalline ZrO2 suspension

Abstract

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.

Electrokinetic sonic amplitude measurement of concentrated alumina suspensions: Effect of electrosteric stabilization

“…The calculation of the ζ-potential from the dynamic mobility has to consider the size, density and frequency dependent inertia forces. O'Brien 7) has formulated a Smoluchowski type formula relating the high frequency or dynamic mobility to the particle zeta potential: (2) ε dielectric permittivity of the suspension ζ zeta potential η viscosity f factor considering the diameter relation of particle and double layer G(α) considers the inertia forces of the particles at high frequency The equation for converting the ESA amplitude to the (ζ) zetapotential becomes:…”

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“…Of the different water-soluble anionic polyelectrolyte dispersants available (e.g., PAA, PMAA), a new type of commercially available electrosteric dispersant agent, Dolapix CE64 (Zschimmer & Schwartz GmbH Co., Germany) was found to be the most suitable choice on basis of physical and chemical properties as well as practical experiments reported by different authors [3,[42][43][44][45][46][47][48][49][50][51][52]. According to the manufacturer information and result reported by different authors, Dolapix CE64 contains aqueous solution (~ 70 mass%) and ammonium salt (~ 30 mass%) of poly-(methacrylic acid) (PMAA-NH 4) , with a pH of 9 [3,[43][44][45][46][47][48][49][50][51][52].It has a molecular weight of 660 g/mol with a density (20°C) of approximately 1.2 g/cm 3 [3,[43][44][45][46][47][48][49][50][51][52]. It can easily dissociate in water and produces negatively charged polyions and ammonium counter-ions that create stability based on electrosteric interactions [3,[43][44][45][46][47][48][49]…”

Preparation of spherical calcium phosphate granulates suitable for the biofunctionalization of active brazed titanium alloy coatings

“…The dispersion of the suspensions using Dolapix CE64 is driven by an electrosteric mechanism [16]. The carbonic acid-based polyelectrolyte chains interact with the charged surface of the particles, causing the formation of a thin organic layer on the particles which prevent the attractive van-der-Waals forces between particles, and thus flocculation is avoided [3,16,19]. However, our results have shown that this mechanism is limited, since it was not possible to synthesize slurries containing more than 60 wt% of solids content (TH).…”

“…The presence of organic molecules on the particles caused tightening of the outer shell preventing the remaining water Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 6/19/15 2:33 AM from evaporating and increasing the pressure inside the granules. Since the temperature during the spray drying process (between T in = 230°C and T out = 102°C) was not high enough to cause pyrolysis of the additive Dolapix CE64, which is reported to occur at temperatures between 230 and 490°C [19], granulate defects such as doughnut structure, hollow structure, or fracture of the spheres occurred [14]. The other applied organic deflocculant, trisodium citrate, did not show this effect since its pyrolysis temperature of approximately 150°C (manufacturer data) was surpassed.…”