Preparation Of Highly Dispersed Nano Zirconia With Water-soluble Salts As Supports

Nano zirconia has been widely used in structural ceramics,thermal barrier coatings,catalysts and solid electrolytes due to its excellent thermal insulation performance,high temperature stability and high oxygen ion conductivity.High quality nano zirconia powder should have the characteristics of fine particles,good dispersion,good crystallization and stable crystal structure.However,nano-zirconia prepared by the existing technology often has defects such as particle sintering and poor crystallinity.Therefore,it has been the focus in this field to study the high-efficiency preparation technology of highly dispersed and highly crystalline nano zirconia.In order to solve the problem of high temperature sintering of nano particles,this paper studies the preparation of nano zirconia assisted with the water-soluble salt.The high melting point water-soluble salt is used as the isolation phase to inhibit the contact and sintering growth of zirconia nanoparticles at high temperatures,thereby effectively improving the dispersibility of zirconia nanoparticles.This article explored two preparation methods of impregnation and sol-gel with water-soluble salt as supports,and successfully prepared nano-zirconia powder with both high crystallinity and dispersibility at high temperature;self-made yttrium stabilized zirconia(YSZ)nano-powder was used as raw material,YSZ nanocrystalline ceramics were prepared by casting method,and its properties were studied.Firstly,ZrO₂ nanoparticles with controllable size of 5.5-20 nm,uniform size and high dispersibility were prepared by impregnation method with K₂SO₄ as sacrificial carrier at 700-1000?.The results show that compared with micron K₂SO₄,the size of ZrO₂ prepared by nano-K₂SO₄ is smaller.The monoclinic phase ratio and particle size of nano ZrO₂ increase with the increase of precursor solution concentration.As the calcination temperature increases,the particle size of nano ZrO₂ increases.When the temperature is 1000?,the particle size grows to20nm,but still maintains good dispersibility.The crystal structure of nano ZrO₂ prepared by this method is mainly tetragonal phase,and the monoclinic phase ratio slightly increases with the increase of the calcination temperature.YSZ nanoparticles with controllable size of 9-23 nm,uniform size,high dispersibility and good crystallinity were successfully prepared by sol-gel method assisted with water-soluble salt.The results show that the size of YSZ nanoparticles can be reduced significantly by selecting appropriate surfactant and optimizing its addition amount.With the increase of sol concentration,the particle size of YSZ increases gradually.With the increase of calcination temperature,the particle size of YSZ increases,and the size of YSZ prepared at 1000?is about23nm and the particle size distribution is uniform.Using the YSZ nanopowder prepared by the water-soluble salt assisted sol-gel method as the raw material,the YSZ nanocrystalline ceramics with the grain size of 94?339 nm were successfully prepared by the casting method.The results show that the small size of raw material is helpful to improve the density and ionic conductivity of the sintered body.Using11nm YSZ nano powder as raw material,YSZ ceramics sintered at 1300°C have an ionic conductivity of 4.96×10^-5 S/cm at 400°C.With the increase of sintering temperature,the grain size of YSZ ceramics becomes larger and the density increases.The relative density of YSZ ceramics sintered at 1400?can reach 96.8%,and the conductivity at 400?can reach 1.07×10^-4 S/cm?...