Ceramic composites of the Al2O3-ZrO2 type obtained by the direct coagulation casting method
Anita Tomaszewska-Grzęda, Mikołaj Szafran Politechnika Warszawska, Wydział Chemiczny, ul. Noakowskiego 3, 00-664 Warszawa
Annals 3 No. 8, 2003 pages 428-433
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abstract 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 structure of the double electric layer around the powder suspended in the slip. This results in a reduction of 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 results of using the urease-urea system and the properties of ceramic casting slips, green samples and after sintering with aluminum oxide and Al2O3-nZrO2 composites are presented in the paper. In Figures 1-3 are presented the results of studies of casting slips obtained by the DCC method with Al2O3 and Al2O3- nZrO2. In Tables 1 and 2 are presented the results of studies of green and sintered samples, whereas their picture obtained by means of a scanning microscope are presented in Figures 4-9. The obtained results of studies show a considerable probability of obtaining in the future of Al2O3-nZrO2 composites of good strength parameters resulting from their high degree of thickening, providing that a deglomeration method of nZrO2 in the above presented process will be elaborated. Key words: ceramic composites, aluminum oxide, enzymes, zirconium dioxide nanopowder