Preparation Of Zirconia-based Dental Bioceramics And Measurement Of Its Mechanical Performance

Zirconia (ZrO₂), with high strength and toughness, excellent biocompatibility and corrosion resistance, is one of the potential dental repair materials. Especially, tetragonal zirconia possessing the property of phase-transformation toughening, can significantly improve the strength and toughness of zirconia-based all-ceramic teeth, which has become the research focus in recent years. This thesis mainly involves the following several aspects: purification of industrial zirconium oxychloride; the preparation of nano-sized tetragonal zirconia powder using hydrothermal method and solid-state suspension reaction; the synthesis of CaZr₄(PO₄)₆ (abbreviated as CZP) powder using coprecipitation-ultrasound technique; hydrothermal- precipitation synthesis and mechanical performance of the composite ceramic ZrO2/HA .First, industrial grade zirconium oxychloride, including some impurities, was purified in order to meet the needs of preparation of high purity zirconia. The purified composition of zirconium oxychloride was characterized by FT-IR and thermoanalysis, and its purity was measured by chemical analysis. Nano-sized zirconia was synthesized by CTAB-assisted hydrothermal method and solid-state suspension reaction respectively, using zirconium oxychloride as raw materials. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Transmission electron microscopy (TEM) were used to analyze the composition and morphology. Second, CZP powder was prepared using coprecipitation–ultrasound technique, and the bioactivity of CZP ceramics was reasonably evaluated by in vitro test. Finally, ZrO₂/HA composite powder was prepared using hydrothermal- precipitation method. The XRD, TEM were employed to analyze the phase and particle size of the as-synthesized powders. Zirconia-based composite ceramic was fabricated using ZrO₂/HA powders, and its mechanical properties was decided.It has been confirmed that the purity of zirconium oxychloride was raised from 52.0% to 99.0%, and can fully meet the requirement of experiment. The loss of water molecules and other component was observed in different temperature scope according to the comprehensive thermal analysis, and the pyrolysis mechanism of ZrOCl₂·8H₂O is suggested. The tetragonal-phase zirconia with good crystallinity and purity, average particle diameter of 12nm and no obvious agglomeration can be synthesized by hydrothermal treatment at 200℃for 12h via the template control effect of the CTAB.The precursor of zirconia can be obtained via microemulsion-assisted solid-state reaction at 150r·min^-1, the single tetragonal zirconia with verage particle diameter of 40nm can be obtained by thermal decomposition of the precursor at 500℃for 2h; the monoclinic zirconia with verage particle diameter of 30nm can be expected by sintering the precursor at 800℃for 2h.The CZP powder with good crystallization can be synthesized by thermal decomposition of CZP precursor at 860℃using a coprecipitation–ultrasound technique. The crystallization of the sample is improved by calcining at 1370℃. The bioactivity of the CZP ceramics was evaluated via in vitro test in simulated body fluid (SBF). It is showed that the CZP ceramic calcined at 860℃possesses bioactivity to some extent, but almost no bioactivity if calcined at 1370℃. The sharp XRD diffraction peaks of ZrO2/HA composite powder implies the good crystallity and the TEM images show the core-shell structure of ZrO2/HA. Zirconia-based composite ceramics prepared using ZrO2/HA composite powder possesses good mechanical performance, i.e. bending strength and vickers hardness, which is more advantageous in the field of ceramic teeth.