Tape casting of aqueous Al2O3 slurries

doi:10.1016/S0955-2219(00)00043-1

Journal of the European Ceramic Society

Volume 20, Issue 11, October 2000, Pages 1691-1697

https://doi.org/10.1016/S0955-2219(00)00043-1 Get rights and content

Abstract

The well-dispersed aqueous Al₂O₃ slurries suitable for tape casting were prepared, the effects of the concentration of dispersant, of the pH value, of solid content etc. on the properties of slurries were investigated, and the results indicated that the rheological of slurries was effected greatly by pH value and organic additives. After cutting, laminating and binder removal, the laminated Al₂O₃ green bodies were sintered by hot-press in a vacuum furnace. SEM micrographs showed that the microstructure of the aqueous green-body and samples were different from that of non-aqueous, and the mechanical properties of aqueous Al₂O₃ samples were much high than that of non-aqueous Al₂O₃.

Introduction

Tape casting is a low cost and an useful process for preparing thin ceramic sheets, It has been widely used to produce ceramic substrate, multilayer structure capacitor, solid electrolytes, solid oxide fuel cell,1, 2, 3, 4, 5 etc. For structure materials, tape casting has already been used to design laminated and multilayered composites to improve the mechanical properties.

The classical tape casting process is made of slurry preparation and tape casting. The stable slurry is composed of ceramic powder dispersed in a solvent which contains dispersant, binder, plasticizer and other surfactant, etc. In generally, tape casting slurry is a typical organic system. Because the volatility and toxicity of organic solvents used in slurries are harmful to the environment and health, and the solvents are difficult to recycle, the development of an aqueous tape casting system is considered to be desirable processing,6, 7 the aqueous slurry system has the advantage of no-flammability, non-toxicity and low cost. In addition, there is widely available knowledge for the aqueous processing system which has been used for other ceramics technologies. Aside from of aqueous tape casting, there are several other new tape casting methods which have been developed to overcome the problems, such as in situ polymerizable slurries8, 9 in which all solvents and organic additives remain in tape; another way to eliminate the solvent evaporation from slurries is to use UV curable binders.¹⁰ The processing does not need solvents and does not involve solvent evaporation. During drying, the process does not cause high shrinkage and cracking, and it is possible to achieve a high powder loading than that of classical tape casting. The aims of this study were to investigate the rheological behaviors and optimized conditions of aqueous slurries and to compare the difference in the mechanical properties between aqueous samples and non-aqueous samples.

Section snippets

Experimental procedure

The high purity Al₂O₃ powder with an average particle size and a specific area 5.7 m²/g and 0.48 μm, respectively (Wushen fertile factory) was used in the experiment. NH₄PAA was used as dispersant, PVA was used as binder, glycerin and PEG were used as plasticizers, NH₄OH and HCl were used to adjust the pH value of slurries in all processing, and double-distilled water was used as solvent in all formulations.

First, Al₂O₃ powder was mixed with NH₄PAA as dispersant and double-distilled water as

Zeta potential of Al₂O₃

The high performance aqueous ceramic slurry can be acquired through adjusting the pH value and selecting the exact dispersant. According to the DLVO theory,¹¹ the Van Der Waals forces and the repulsive forces originated in the electrical double layers surrounding the particles because the counterions have a strong influence on the diffuse electrical double layer. Moreover, the surface charge of the particles has a tight relationship with the pH value and the concentration of other specifically

Conclusion

NH₄PAA was selected as dispersant, PVA as binder, glycerin and PEG were used as plasticizer. The high quality aqueous Al₂O₃ tapes were produced through the tape casting process. For aqueous Al₂O₃ slurries, there were many factors which can affect the rheological of slurries, especially the pH value and ionic strength, but the pH value does not greatly affect the viscosity of slurry stabilized by a polymeric mechanism. For the high concentration of organic additives slurry, the rheological of

Acknowledgements

The work was a cooperative program between the Chinese Academy of Science and the Max-Planck Foundation. The authors were grateful to the Max-Planck Foundation for providing support.

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Tape casting of aqueous Al2O3 slurries

Abstract

Introduction

Section snippets

Experimental procedure

Zeta potential of Al2O3

Conclusion

Acknowledgements

Ceram. Int.

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

The development of high quality alumina substrates

Stress and fracture behavior of monolithic fuel cell tapes

J. Am. Ceram. Soc.

Piezoelectric and Electrooptic Ceramics

Tape casting of aqueous Al₂O₃ slurries

Zeta potential of Al₂O₃