The Direct Coagulation Casting (DCC) is a new and very interesting method of molding samples from ceramic casting slips of high concentration of the solid phase. It consists in concentrating the casting slip via internal slow change of pH round each ceramic powder particle, which causes changes in the electrostatic repulsion forces of double electric layers in favor of the Van der Waals attraction forces.
The role of enzymes in the DCC process consists in the decomposition of an appropriately selected substance which results in slow liberation over the whole volume of molecules changing the pH or also in the synthesis of salts modifying the double electric layer.
The 15 nm grain size nanopowder of zirconia used in the study was purchased from "CEREL" Boguchwała as was the "gel", the hydrated mixture of zirconia salts, which produces nZrO2 upon calcination. The paper discusses the differences between the properties of Al2O3 grains modified with the additions of: a) zirconia nanopowder, b) the "gel", and c) zirconia powder of grain size comparable to that of Al2O3. The addition of zirconia is intended to increase the fracture toughness of alumina. It is assumed that the addition of the nanopowder of zirconia, due to its small particle size, may form nanolayers around the grains of Al2O3 or fill the spaces between them.
The results of using the urease-urea system and the properties of ceramic casting slips, green samples and after sintering with aluminium oxide, Al2O3-ZrO2, and Al2O3-nZrO2 composites are presented in the paper.
The obtained results of studies show a considerable probability of obtaining on the future Al2O3-ZrO2 and Al2O3-nZrO2 composites.

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