Studies On The Preparation Of ZrO₂/Al₂O₃ Composite Ceramic For Dental Application

Aluminum oxide bio-ceramic as a kind of prosthetic material has excellent natural appearance and the best biocompatibility, excellent corrosion resistance and abrasive resistance. With the increasing of aesthetic demands, all-ceramic restorations will become the main method of fixed prosthodontias. It is generally accepted that the mechanical shortcoming of ceramic materials including their inherent brittleness and lower strength limit the application of all-ceramic restorations. It has been proved that nanometer zirconia-toughened alumina with excellent fracture strength and toughness for dental application. In this study, effects of prepare techniques on properties of composite ceramic were investigated. The (Y)ZrO2/Al2O3 composite powder have been prepared by improved-coating precipitate techniques with ZrOCl2 and micrometer Al2O3 as raw materials. The ceramics with high fracture strength and low temperature sinter property have been prepared by iso-pressure and add some CaO-MgO-SiO2-TiO2 composite additives. The fracture strength of ceramics sample satisfied to dental crown and bridge materials. The effect of zeta potential on dispersion of nanometer ZrO2 has been discussed, and the sintering behavior of composite powder has been also studied. Some conclusions could be obtained as follow from the experimental results: The electrokinetic properties of nano-scale zirconia precursor were determined by using model 3000HS surface Zetasizer. The effects of ZrOCl2 concentration, pH value and dispersant were mainly studied. The change of zeta potential by pH value is more sensitive at the lower ZrOCl2 concentration. The Zeta potential of zirconia precursor would reduce when the system contain 2wt% PEG6000 and PEG20000. The dental (Y)ZrO2/Al2O3 ceramics with CaO-MgO-SiO2-TiO2 composite as additives could be sintered at lower temperature because of liquid phase sintering mechanism. It was obvious that some liquid appeared in the samples sintered at 1350 ℃for 2 hours from SEM photograph. The bending strength of the sample , with 3.5% and 5% (in mass) CaO-MgO-SiO2-TiO2 as additive, sintered at 1400 ℃for 4hours, were 514Mpa and 497Mpa. It was satisfied to dental ceramics requirement. Content of additive appeared dominant effect on the microstructures of Al2O3/ ZrO2 composite ceramic, and 3.5%(in mass) might be a limited point. The crystal boundary was unclear when the content of additive excessed 3.5%(in mass). The un-perfect crystal boundary was the mainly conjoint mechanism when content low this limit.