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Flocculation after injection molding in ceramic suspensions

Published online by Cambridge University Press:  03 March 2011

J.H. Song  and
J.R.G. Evans
J.H. Song
Affiliation:
Department of Materials Technology, Brunel University, Uxbridge Middlesex, UB8 3PH, United Kingdom
J.R.G. Evans
Affiliation:
Department of Materials Technology, Brunel University, Uxbridge Middlesex, UB8 3PH, United Kingdom
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Abstract

The flocculation of an unstabilized suspension of fine ceramic particles is advanced as the explanation for the formation of cracks in a “liquid” suspension. The development of cracks was observed several minutes after reheating wax-based ceramic moldings above the melting point of the wax and was accompanied by phase separation of the wax from the molding. Calculations of the acceleration of particles under London dispersion forces in a viscous fluid show the “time to impact” as a function of initial separation distance, fluid viscosity, and particle size. This is compared with the intercollision time calculated from classical flocculation theory, and it is shown that for crowded suspensions initial interparticle distances are such that the London force field cannot be neglected. Methods of preventing the flocculation are described.

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Articles
Information
Journal of Materials Research , Volume 9 , Issue 9 , September 1994 , pp. 2386 - 2397
Copyright
Copyright © Materials Research Society 1994

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