STABILITY OF A NANOMETRIC ZIRCONIA COLLOIDAL DISPERSION UNDER COMPRESSION - EFFECT OF SURFACE COMPLEXATION BY ACETYLACETONE

The stability of a colloidal dispersion of nanometric zirconia particl es has been studied during a compression process. Using the osmotic st ress method, cycles of compression and reswelling were applied to the dispersion to test the reversibility of the process. Original dispersi ons are stable in a very limited pH range (0.5-2). At pH 3, the bare p articles aggregate irreversibly under compression as checked by osmoti c pressure and light and X-ray scattering measurements. To improve the stability, small organic complexing molecules (acetylacetone) were ad ded to the original dispersion. The adsorbed monolayer on the particle surfaces acts as a steric barrier and prevents the two colloids from contacting. As a consequence, the dispersion becomes more compressible and the compression cycle is totally reversible. The experimental dat a are quantitatively reproduced with a classical theory of statistical mechanics of liquids based on a DLVO-like colloid-colloid potential. (C) 1997 Academic Press.