Study Of The Co-precipitation Process For YSZ Powder Preparation

Yttria stabilized zirconia(YSZ)is a kind of zirconium-based ceramic material,which has good resistance to chemical corrosion.Its thermal expansion coefficient is close to the metal materials.Yttrium zirconium powder has a huge market for industrialized production.Considering the cost,equipment,operation and other factors,this paper chooses the co-precipitation preparation method.In order to get the ideal crystal size distribution,both experiment method and CFD(Computational Fluid Dynamics)method were used to explore the best condition for YSZ preparation.The commercial CFD software FLUENT15.0 and parallel computing system graphics workstation were used to study the both the single phase and solid-liquid two phase flow systematically.Based on the improved design,better effect of the reactor was achieved.First,we established a diagnosis and a detailed study on the hydrodynamic flow behavior,and on the agitation performance in the co-precipitation reactor.We can conclude that this reactor is an efficient and well-designed one without any dead zones under the shaft speed of 400rpm.Three layers inclined blade propeller was used during the design of a more effective reactor.On the one hand,the low-priced inclined blade is easy to load and unload;On the other hand,the three layers can fully strengthen the axial flow.The paddle away from the bottom height is 30mm.According to the simulation results,4-leafs-impellers(other conditions unchanged)can be adopted to get a narrow particle size distribution,which is an ideal one.It was concluded that the increase of stirring speed was beneficial to the uniform distribution of particles and 500rpm is a good choice.The experiment shows that when pH<6.0,the material deposits down quickly and it turns out to be something like solid sand;when pH=6.0-9.5,the deposition is slower;when pH>10,there is no obvious precipitation.Therefore,in the process of co-precipitation,the feed rate of the sodium hydroxide is adjusted to keep the solution controlled in pH=7.Keeping the deposition still after reaction for a relatively short time,the particle size of the YSZ will not change.