Zirconium titanate ceramic pigments: Crystal structure, optical spectroscopy and technological properties

Spark plasma sintered Al₂O₃-YSZ-TiO₂ composites: processing, characterization and in vivo evaluation

Al2O3 and Al2O3-YSZ composites containing 3 and 5 wt.% TiO2 were prepared by spark plasma sintering at temperatures of 1350-1400°C for 300s under a pressure of 40 MPa. The grain growth of alumina was suppressed by the addition of YSZ. Al2O3-YSZ composites showed higher hardness than monolithic Al2O3. There was not a considerable difference in hardness values for Al2O3-YSZ composites containing 10 and 20 vol.% YSZ and the addition of TiO2 decreased the hardness of the composites. The fracture toughness of Al2O3 increased from 2.8 MPa·m(1/2) to 4.3 MPa·m(1/2) with the addition of 10vol.% YSZ, further addition resulted in higher fracture toughness values. The fracture toughness values were increased with TiO2 addition and the highest value of fracture toughness, 5.3 MPa·m(1/2), was achieved with the addition of 20 vol.% YSZ and 5 wt.% TiO2. Preliminary in vivo tests demonstrated the biocompatibility and osseointegration of the composites after 6 week post-implantation in femur of Wistar rats.

Characterization of Zr-doped TiO2 nanocrystals prepared by a nonhydrolytic sol-gel method at high temperatures

Highly crystalline and surface-modified Zr-doped TiO(2) nanorods were successfully prepared using a nonhydrolytic sol-gel method that involves the condensation of metal halides with alkoxides in anhydrous trioctylphosphine oxide (TOPO) at either 320 or 400 degrees C. In addition, the interaction of the cross-condensation between the Ti and Zr species was studied by characterizing the morphologies, crystalline structures, chemical compositions, surface properties, and band gaps of the nanocrystals obtained at different reaction temperatures and Zr-to-Ti stoichiometric ratios. Increases in the concentration of Zr(4+) and in the reaction temperature led to large nanorods and regular shapes, respectively. In addition, only the anatase form was observed in the Zr-doped TiO(2) nanorods. The Zr-to-Ti ratios obtained ranged from 0.01 to 2.05, all of which were far below the stoichiometric ratios used during the preparation of the samples (0.25-4). Moreover, the Zr(4+) units accumulated mainly at the surface of the TiO(2) nanocrystals. The band gaps of the Zr-doped TiO(2) nanorods ranged from 2.8 to 3.8 eV, which are smaller than those of pure TiO(2) (3.7 eV) or ZrO(2) (5.2 eV). The Zr-doped anatase TiO(2) nanorods prepared at 400 degrees C at an initial stoichiometric Zr-to-Ti ratio of 2:3 exhibited the highest photoactivities for the decomposition of rhodamine B because of the presence of trace amounts of Zr(4+) (Zr/Ti = 0.03) in the TiO(2) and the regular shapes of these particles. DSC analysis indicated that the temperatures for forming nanocrystalline TiO(2) and ZrO(2) were 207 and 340 degrees C, respectively. Moreover, the reactivities of condensation between the Ti species were reduced when Zr species were involved in the NHSG reactions. The results obtained in this study clearly demonstrate that the faster kinetics for the generation of TiO(2) controls the material properties as well as the photoactivities of the nonhydrolytic sol-gel-derived nanocrystals.