Nanosized zirconia (ZrO₂) is a well-know nanostructured oxide material with excellent electrical, optical and catalysis related properties. It is known that the properties of nanosize particles are determined by their phase composition, morphological features, the nature of interparticle interaction and the level of aggregation.

In the present work the peculiarities of formation of a nanopowder hydroxide system and connection between the state of hydrate shell of hydroxide nanoparticles and their aggregation were studied. The wet gel hydroxide system ZrO₂–3 mol% Y₂O₃ was obtained by the method of chemical precipitation of the corresponding ammonium hydrate salts. Various physical influence (high pressure, microwave heating) were used to form nanoparticles with the defined state of hydrate shell. The structure of zirconia and evolution of the surface hydroxyl groups on amorphous nanosize powders was examined by FTIR spectral analysis, XRD, small-angle X-Ray scattering and by rheology methods.

The anomalies of physical properties (density, specific surface, rheological properties and other) are observed under the high pressure influence at 6 kbar. The physical model is offered which considers the nanoparticle as a heterogeneous system containing the closed and opened pores. It is shown, that the aggregation of nanoparticles is determined by correlation of the external pressure P and pressure inside closed pore P_p. A rapprochement of particles at P < 6 kbar promotes to a communications between them and results in formation of big conglomerates of particles with decreased density of material. When P > 6 kbar the pressure inside closed pores increases, the “misfit” stresses appeared because of substantial distinction in compressibility increase that leads to destruction of agglomerates on more small fragments.

This research was performed with the framework of complex program basic research NAS Ukraine “Nanosystems, Nanomaterials, Nanotechnology”.

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