Preparation And Properties Of High Temperature Stabilized Zirconia Powder And Thermal Barrier Coating

Zirconia ceramic is regarded as one of the best thermal barrier coatings because of its excellent physicochemical properties such as high hardness,low heat capacity and thermal conductivity,high coefficient of thermal expansion,high melting point,stable chemical properties,and good corrosion resistance.In this research,zirconia ceramic powders were synthesized by sol-gel method and studied the influences of process parameters,doping concentration of different rare earth elements?La,Ce,Gd,Yb,Y?;doping concentration of Yttrium oxide,and doping RE2O3?RE=La,Yb,Ce,Gd?and Y2O3 co-doped ZrO₂ powders on the phase stability and morphology of the powder;and Select Yb-YSZ,Gd-YSZ and YSZ Powders for Thermal Barrier Coating by Plasma Thermal Spraying and discuss their high temperature oxidation performance and high temperature corrosion performance.The main findings are as follows:?1?The Zirconia powder is prepared by using Zirconium oxychloride as a precursor and a sol-gel preparation method,using a mixed solution of absolute ethanol and water as a solvent,adding formamide as a dry chemical control additive,using glacial acetic acid as a chelating agent and drying at normal pressure of 110?.By adjusting the process parameters,the influence of different process parameters on the phase composition of zirconia powder was determined.And it was confirmed that n?Zr4+?=0.025mol/L,the content of formamide and the proportion of n?Zr4+?is 1:1,the proportion of absolute ethanol and water is 1:3,gelation temperature is 80?.?2?The oxides of rare earth elements La,Ce,Gd,Yb,and Y were selected as doping agents.The doping amount was 12%?wt.?.By studying the phase composition of zirconia powder prepared by adding different dopants,it was found that all the selected rare earth elements can stabilize the tetragonal zirconia?t-ZrO₂?at room temperature.It was confirmed that yttria-stabilized zirconia?YSZ?powder had the best high-temperature phase stability and was stable at 1200?.After heat-treatment by 1300? at 2h,the tetragonal content?volume fraction?is 5.88%,10.86%,52.22%,74.30%and 100%,respectively.?3?The doping of yttrium oxide can suppress the transformation of the tetragonal phase to the monoclinic phase and improve the thermal stability of the zirconia.When the doping concentration amount is less than 12%?wt.?,the higher the doping amount of yttrium oxide,the better the high temperature phase stability of the zirconium oxide.12YSZ powder was stable at 1200?.?4?Through the study of rare earth element?La,Ce,Gd,Yb?synergistic yttrium oxide stabilized zirconia?RE-YSZ?powder,it was found that different kinds of rare earth elements stabilizing YSZ have a certain influence on the high-temperature stability of zirconia's tetragonal phase.The rare earth elements which Ion radius similar to Zr4+,doped YSZ powders have higher tetragonal phase high-temperature stability.This paper successfully prepared Lanthanum oxide,Cerium oxide,Gadolinium oxide,Ytterbium oxide and put doped yttrium oxide to stabilized zirconia powder and analyzed the phase stability,crystal growth behavior,microstructure morphology and thermal conductivity of zirconia powder.It is shown that Yb-YSZ,Gd-YSZ and YSZ powders can all be stable at 1200 ? and Yb-YSZ powder can be stable at 1300?.Its high temperature phase stability is significantly better than other selected rare earth element stable YSZ powders.?5?Yb-YSZ thermal barrier coating has the best high temperature ant-oxidation performance,and after heat treatment at 1200?,the composition of the phase is not changed.The Yb-YSZ,Gd-YSZ and YSZ thermal barrier coatings have excellent resistance to corrosion at 1200?,and the corrosion products were not found after heat treatment at 1200 C for 50h.