Papers by Keyword: Tetragonal Zirconia Polycrystal

Abstract: In previous papers, the present authors observed grain motion in tetragonal zirconia polycrystal during superplastic deformation, and showed the displacement vector map of 748 grains. The map had an interesting feature such as transient domain structure. However, the authors did not pay much attention to the measurement error at that time. In this paper, the influence of measurement error on the map was quantitatively investigated. After precise calibration, it was revealed that measurement error did not have much influence on the feature, and statistics of grain motion was discussed on the calibrated map.

Abstract: Three mole percent Y2O3 doped tetragonal polycrystals (TZP) and stainless steel functionally graded materials (FGMs) were fabricated by slip casting. The optimal conditions for control of interfacial cracks by adjusting shrinkage of each component and temperature gradient were investigated. Experimental results showed that sintering shrinkage mismatch of adjacent intermediate interlayer could cause interface cracks, as well as speedy temperature dropping rate in the cooling process. Based on suitable adjusting of sintering shrinkage and controlling of cooling rate, a satisfying interfacial microstructure without apparent cracks for FGM of 3Y-TZP/SUS with three intermediate layers was obtained.

Abstract: The mechanical properties and the phase stability in yttria and ceria stabilized zirconia containing 0-20wt% A12O3 during aging in air (300°C) and in water vapor (150°C, 180°C, 200°C and 250°C) are investigated in this paper. It is found that water can greatly accelerate the degradation of Y-Ce-TZP. The addition of Al2O3 to Y-Ce-TZP prevents the low temperature degradation in air. Also Al2O3 particles can restrain the phase transformation of tetragonal to monoclinic in Y-Ce-TZP under water vapor condition when the temperature is below 200°C.

Abstract: High temperature creep and superplastic flow in high-purity oxide ceramics such as alumina and tetragonal zirconia polycrystals is very sensitive to a small amount of doping by various oxides. High-resolution transmission electron microscopy and an energy-dispersive X-ray spectroscopy analysis revealed that grain boundaries in high-purity oxide ceramics are free from amorphous phase, and that the doped cations tend to segregate along the grain boundaries. Since the high temperature plastic flow in oxide ceramics takes place mainly by grain boundary matter transport by atomic diffusion, the grain boundary nano-structure control must be a useful way to develop new high-performance functional ceramics in the near future.