Effects of dispersants and soluble counter-ions on aqueous dispersibility of nano-sized zirconia powder

doi:10.1016/S0272-8842(03)00092-0

Ceramics International

Volume 30, Issue 2, 2004, Pages 219-224

https://doi.org/10.1016/S0272-8842(03)00092-0 Get rights and content

Abstract

The effect of different dispersants and water leaching on aqueous dispersibility of zirconia powder was studied. Zeta potentials of aqueous solutions containing nano-sized zirconia powder and different dispersants, such as ammonium polyacrylic acid (PAA-NH₄) and tetramethyl ammonium hydroxide (TMAH) and water leaching were characterized. Better dispersion of nano-sized zirconia powder in aqueous solutions was achieved with the addition of dispersant and water leaching.

Introduction

Tetragonal zirconia ceramics have been widely used as an advanced structural material for their excellent mechanical properties [1], [2], [3]. For many applications, it is desirable to obtain a fine grain microstructure and to fabricate components with complex shapes. This can be accomplished by using ultrafine powders combined with shaping by colloidal processing. In colloidal processing techniques such as direct coagulation casting (DCC), gelcasting, slip casting, tape casting and centrifugal casting, it is imperative to have a slurry with good dispersion and a desirable rheological behavior because the quality of dispersion controls the casting behavior and the resulting green-body properties [4]. Powder dispersion in water relies on the adjustment of surface charge of ceramic particles by dispersant and elimination of the soluble counter-ions (especially the high-valence counter-ions).

Colloidal processing has attracted great interests in forming green bodies containing submicron powder, but it has not been successful applied to the nano-sized zirconia system [5], [6], [7], [8]. It is known that the dispersion of ceramic particles is closely related to the role of the dispersant on the particle surface and the soluble counter-ions. In this study the effect of dispersant on a nano-sized ZrO₂ powder was investigated in order to achieve good dispersion of the powder in water. In addition, the soluble counter-ions of the powder were analyzed and their effect on the rheological behavior of the system was investigated after their elimination by water leaching.

Section snippets

Experimental procedure

The as-received nano-sized zirconia powder (3 mol% Y₂O₃–ZrO₂) was provided by Jingdezhen Advanced Ceramics Company in China. The average particle size of the powder analyzed by a particle analyzer (Model BI-XDC, Brookhaven Instruments Corp., Holtsville, NY) was about 50 nm (Fig. 1). Fig. 2 shows the TEM micrograph of the zirconia powder obtained by a Model H-800 TEM (Hitachi Instrument Corporation, Japan).

To prepare zirconia suspensions, deionized water was used as a liquid medium, and a 10

Effect of dispersants on aqueous dispersibility of the powder

The effect of dispersant on the dispersibility of the nano ZrO₂ powder was investigated by measuring the viscosity and the zeta potential of the suspension. In general, the dispersion of ceramic powders in suspensions can be improved when the absolute value of the zeta potential is increased after an addition of dispersant. The higher the absolute value of the zeta potential, the higher the charge density is on surface of powders and the larger the repulsion among particles. Fig. 3 shows the

Conclusions

Both the addition of dispersant and elimination of soluble counter-ions are effective ways to improve the dispersion of nano-sized zirconia powder in deionized water. The dispersion of zirconia powder was described by measuring zeta potential, agglomerate particle size and rheological property of suspensions. The isoelectrical point of the zirconia powder in deionized water without a dispersant is near pH 8.0, and zeta potential decreases under both strong acidic and basic conditions. However,

Acknowledgements

The authors thank the National Science Foundation of China (two-base project, Grant No. 50140120423) and National Key Basic Research Development Program of China (973 program: G2000067204-01) for the grants that support this research.

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Effects of dispersants and soluble counter-ions on aqueous dispersibility of nano-sized zirconia powder

Abstract

Introduction

Section snippets

Experimental procedure

Effect of dispersants on aqueous dispersibility of the powder

Conclusions

Acknowledgements

J. Eur. Ceram. Soc.

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