Effect Of High Pressure And Temperature Treatment On The Properties Of Metal Oxide

In this paper, effect of high pressure and temperature treatment on the properties of Metal Oxide were main studied. As an example to the microstructure and sintering density of ZnO and Al₂O₃, which under high pressure and temperature.The ZnO and Al₂O₃ nanocrystals were processed under high pressure and temperature on a cubic high pressure apparatus. The treated time was 25 minutes. The microstructure of the obtained ZnO and Al₂O₃ were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), the Sintering density of the samples were measured with drainage method. With the experimental results, effect of high pressure and temperature treatment on the microstructure and Sintering density of ZnO and Al₂O₃ nanocrystals were investigated.Firstly, the variety of morphology, grain sizes, and structure of the samples were studied under different temperature and pressure. The SEM and XRD results show: the phase transformation didn't happen to the samples of Al₂O₃ which were treated under high temperature and high pressure. Under the high pressure, as the temperature increase, the grain sizes of the samples increase. It can be seen uniform grain size of alumina. All of the ZnO samples in the experiment present a hexagonal wurtzite structure. The nanocrystals eventually transform to bulk materials while the grain sizes increase with the temperature increasing under a certain pressure. It indicates that high temperature can obviously promote the growth of the grain. And under the high temperature, the grain size increases with increasing the pressure. Under the 6GPa,850℃treatment, the phase transformation of ZnO was not observed. Therefore, the research on the phase transformation of ZnO should be done under higher pressure and temperature conditions.Then, measuring line-shrinkage rate, density of sintered samples. And effect of high pressure and temperature treatment on the sintering density of ZnO and Al₂O₃ nanocrystals were investigated. The results show that as the temperature and pressure increase, the sintering density of the samples increase. The relative density of Al₂O₃ can achieve 97% under 5GPa,1200℃.The sintering density of ZnO under high pressure sintering was higher than samples under normal temperature and high pressure. It achieved 82.5% under 6GPa and normal temperature while it achieved 95%under 600℃,6GPa. This shows that temperature plays an important role in the high-pressure sintering. While the treated time extended, the sintering density increased. And the results also show: compared with normal pressure sintering, the sintering temperature of the samples decrease remarkably in the high-pressure sintering, as compared with the normal-pressure sintering, which shortens the sintering time. The high-pressure sintering can achieve fast-and low-temperature sintering.