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Settling Behavior of Alumina Dispersions and Resultant Green Body Characteristics: Solvent, Binder, and Dispersant Competition in Model Systems

Published online by Cambridge University Press:  25 February 2011

Anthony A. Parker ,
Mei-Yuan Tsai ,
Girma Biresaw ,
Todd T. Stanzione ,
George H. Armstrong  and
Joseph J. Marcinko
Anthony A. Parker
Affiliation:
Aluminum Company of America, Alcoa Center, PA 15069
Mei-Yuan Tsai
Affiliation:
Aluminum Company of America, Alcoa Center, PA 15069
Girma Biresaw
Affiliation:
Aluminum Company of America, Alcoa Center, PA 15069
Todd T. Stanzione
Affiliation:
Aluminum Company of America, Alcoa Center, PA 15069
George H. Armstrong
Affiliation:
Aluminum Company of America, Alcoa Center, PA 15069
Joseph J. Marcinko
Affiliation:
University of Akron, Akron. Ohio 44325
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Abstract

The chemical functionality of binders, dispersants, and solvents will influence competitive adsorption/desorption behavior on alumina powder, and hence will affect both slurry and ultimate green tape properties. Given that multiple competitive interactions are common to most dispersions, it is usually difficult to ascertain mechanisms from simple settling density experiments. However, this problem can be partially overcome with the choice of model systems that minimize the number of competitive processes. This criterion is met to a first approximation with a model system of toluene solvent, polystyrene binder, and a C8 aliphatic dispersant with an anchor group of variable functionality. Plateau adsorption concentrations from settling experiments in toluene show that surface coverage for efficient dispersants is typically achieved at about 6μmoles/m2. Less efficient dispersants adsorb at higher plateau concentrations, and are eventually displaced after repeated washing steps in toluene. The settling densities of dispersions prepared with C8 dispersants are consistently higher than densities achieved in toluene alone, and as seen in a case study with n-octylsilane, the settling densities are independent of the presence of polystyrene. Green bodies cast from a polystyrene/Al2O3 slurry also show increased densities in the presence of n-octylsilane dispersant. However, despite the apparent low levels of interaction between polystyrene and n-octylsilane in the dispersion state, solid state NMR and dynamic mechanical results show that the solid state molecular motional behavior of polystyrene is strongly affected by the presence of n-octylsilane dispersant.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 249: Symposium Q – Synthesis and Processing of Ceramics: Scientific Issues , 1991 , 273
Copyright
Copyright © Materials Research Society 1992

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References

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