Ceramic composites molded with the aid of selected enzymatic reactions
Anita Tomaszewska-Grzędęda , Mikołaj Szafran Politechnika Warszawska, Wydział Chemiczny, Zakład Technologii Nieorganicznej i Ceramiki, ul. Noakowskiego 3, 00-664 Warszawa
Annals 4 No. 11, 2004 pages 297-301
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abstract The direct coagulation casting by means of enzymatic reactions is the subject of research carried out in the Department of Specialty Ceramics of the Warsaw University of Technology Faculty of Chemistry Division of Inorganic Technology and Ceramics. This method consists in the concentration of the casting slip by internal, slow change of pH (resulting from the decomposition of certain substances by means of enzymes) round each particle of the ceramic powder. This is the reason for the change in the structure of the double electric layer round this powder suspended in a solvent. In the work the results of studies on the obtaining of ceramic composites by direct coagulation casting of slips with Al2O3, nZrO2 or a mixture of zirconium, hafnium and yttrium hydroxides are presented. The work consisted in the obtaining and studying the properties of composites comprising 95 vol.% of aluminum oxide and 5 vol.% of the ZrO2 additive, introduced by two methods - as a powder and as a „gel”, and the comparison of the results obtained. Table 1 shows the results of studies of green samples obtained from ceramic casting slips with aluminum oxide, aluminum oxide with a 5% additive of zirconium oxide nano-powder, and with aluminum oxide with the addition of a gel of total solid phase concentration of 54.3 vol.%. Tables 2-5 show the results of studies of sintered samples. Figures 1-4 show consecutive magnifications of the sintered sample obtained by the DCC method from aluminum oxide and gel. The obtained results of studies show the relevancy of selecting the mixture of zirconium, hafnium and yttrium hydroxides as components of the Al2O3⋅nZrO2 composite, instead of the earlier used nZrO2. Key words: ceramic composites, aluminum oxide, ZrO2 nanopowder, urease, urea