An Experimental Investigation Of Metal Oxide Micro-particles Production By Supercritical Hydrolysis

Nano-sized materials have been developed since early years of 80's of last century. Because of their peculiar performance and wide application prospect they have drawn much attention in both academia and industry. Metal oxide micro-particles are the most important raw materials of cermet, and the production processes of them have been well developed and are various in the laboratory. A new process using supercritical hydrolysis to prepare metal oxide micro-particles is studied in this thesis, and the effects of the process parameters on the particle size are investigated experimentally.The experiment setup is builded up by the reconstruction of an experimental setup for supercritical fluids extraction. The collector, dying and filtration equipment are designed, and some pipelines and valves are added. Two high-pressure mass flowmeters are introduced in the process to measure the flux. The setup can be used for many purposes, and operated easily. The four process parameters, such as pressure, total flux, ratio of brach flux and temperature, could be controlled and measured conveniently after the reconstruction.The experimental investigation of preparing TiO₂ micro-particles by supercritical hydrolysis using tetraisopropyl titanate and deionized water is carried out. The TiO₂ micro-particles with minimal average particle size of 31.6nm are successfully obtained. Some experiments are conducted to produce other metal oxide micro-particles, and Al₂O₃ and ZrO₂ micro-particles are prepared successfully with aluminium-iso-propoxide and Zirconium n-Butoxide. The effect of process parameters are also studied experimentally.Analyses of the particles are made by XRD, SEM and Particle-size Analyzer, from which the satisfactory experiment data are obtained.In the experiment range of this thesis, the influences of process parameters to particle size are examined. The particle size increases with the increase of pressure, and decreases with the increase of total flux. The effect of branch flux ratio on particle size is not remarkably. The particle size increases with the increase of temperature. The pressure, total flux and temperature are the key factors to effect the particle size.Through this work, the experimental technique for the process is established. The process of preparing metal oxide micro-particles and the effects of the process parameters on the particle size are understood more deeply. The basic data for further investigation are obtained, and the correct direction could be found for theoretical study with this technique.