Adsorption, rheology, packing, and sintering of nanosize ceramic powders

Nanosize zirconia particles stabilised with a water-soluble polyelectrolyte in an aqueous medium were characterised in terms of adsorption behaviour, suspension rheology, and subsequent green/sintered compact microstructure. A monolayer surface coverage of the particle by adsorption was experimentally verified. The thickness of the adsorbed polyelectrolyte onto the powder particles was calculated to be 6.2 nm, which increases the "bare" particles by 14.6% in size. This adsorption increases the effective solid loading by as large as 51%. Rheological behaviour of the suspensions was experimentally determined which was well-described by an exponential function up to solid fractions of 20 vol%. The particle packing efficiency in the green consolidates appears to be solid-loading dependent; the higher the solid loading, the better the particle packing efficiency can be achieved. Green density as good as 52% theoretical can be obtained in suspensions containing 40% solid loading in this study. The sintered ceramic with an ultrafine microstructure of as fine as 0.14 mu m in average grain size is obtained. (C) 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved.