Preparation Of Al₂O₃ Doped 3Y-TZP Nanopowders And Investigation Into The Strengthening Mechanics Of The Composite Materials

In this research, we mainly discussed two major points: 1, mechanism and processing parameters of peroxyl complex coprecipitation (PCC) applied in preparing Al₂O₃ doped 3Y-TZP (AYTZP) nanopowders; 2, the influences of different composition, different sintering temperature and different synthesizing methods of resultant AYTZP nanopowders upon sintering activity and mechanical properties of composite AYTZP materials. Samples of AYTZP powders and sintered bodies were analyzed by means of FT-IR, TG-DSC, TEM, BET, XRD, SEM, et al.Results showed: the effect of PCC on improving properties of AYTZP nanopowders was built upon the modification of groups within resultant precursors, the group of–OOH was produced by the introduction of H₂O₂ into the precursor solutions as complexant; exorbitant microwave power caused severely hard agglomerations and partial crystallization within PCC yielded precursors, whereas, at a lower microwave drying power of 600 W the resultant dried precursors had light agglomerations and was made up of dried amorphous precipitates; the ball-milling treatments before calcinations produced high quality resultant powders with good dispersibility, the nonlinear heating-up during calcination treatments refined the particle size of resultant powders, and reduced the agglomerations between nanoparticles; the dosage of added Al₂O₃ had great influences on sintering and densification of AYTZP composite materials, when sintering temperature was 1450℃, the tendency of the densification process of the AYTZP composite materials was nonlinearly varied with the accumulation of added Al₂O₃, when the dosage of doped Al₂O₃ was 0.5 wt%, the volume and relative densities of the AYTZP composite materials reached the peak values of 5.98 g·cm^-3 and 98 %, respectively; the dosage of added Al₂O₃ and sintering temperature also had great influences on mechanical properties of AYTZP composite materials, the amplitude of variation of undoped 3Y-TZP materials'bending strength was narrow, which was significant when 3Y-TZP was doped with Al₂O₃, the optimum values of AYTZP's bending strength of 778 MPa was reached when the dosage of added Al₂O₃ was 0.5 wt% and the sintering temperature was 1450℃; the sintering and mechanical properties of resultant materials comprised by nanopowders prepared by PCC were better than those of resultant materials comprised by ball-milling mixing and packing PCC methods; through the studies of AYTZP by XRD and SEM, we found the proportion of t-ZrO₂ within AYTZP sintered body was lifted and transgranular microcrack was found within morphology of fracture surface of AYTZP doped with Al₂O₃ by the dosage of 0.5 wt% and sintered at 1450℃, it was supposed that the toughing effect brought by the microdosaged doping of Al₂O₃ was due to the higher proportion of t-ZrO₂, which would give birth to more stress-induced phase transformation within inner structure of the composite materials, and the existence of transgranular microcrack, which would enhance the fracture energy of the toughed materials; moreover, we also investigated the mechanisms of the different phenomena taken place in this research.