Preparation And Properties Of MAO/ZrO₂-Y₂O₃ Composite Coating On The Surface Of Zirconium Hydride

In order to solve the problem of hydrogen loss of zirconium hydride moderator material in high temperature environment,MAO/ZrO₂-Y₂O₃ composite hydrogen permeation barrier film was prepared on the surface of zirconium hydride material by micro-arc oxidation and sol-gel technology.The morphology,surface element distribution,phase structure and hydrogen barrier properties of the composite film were analyzed by SEM/EDS,XRD and quadrupole mass spectrometer.The effects of precursor sol type,yttrium oxide content in sol and heat treatment temperature on the microstructure,surface quality,porosity,binding force and hydrogen barrier properties of the composite film were systematically studied.The main results obtained are as follows:MAO/ZrO₂-Y₂O₃ composite coatings were prepared by controlling the mole fraction of yttrium oxide in the precursor sol with zirconium nitrate as precursor.The results show that with the increase of yttrium oxide content in the precursor sol,the micropores and microcracks on the surface of MAO/ZrO₂-Y₂O₃ composite film decrease,and the compactness is significantly improved.However,when the yttrium oxide content exceeds 8 mol%,the surface quality of the composite film decreases.The XRD analysis of the composite film shows that the phase structure of the composite film is mainly composed of m-ZrO₂,t-ZrO_2,Zr_1-xY_xO_2-0.5x,and the relative volume content of the tetragonal phase（t-ZrO₂）is more than 10%,indicating that the addition of yttrium oxide in the precursor sol can stabilize the tetragonal phase zirconia.When the content of yttrium oxide in the composite film is 0 mol%-16 mol%,the hydrogen permeation reduction factor（PRF value）of the composite film is between 11.5-16.3.When the content of yttrium oxide is 8mol%,the composite film is more continuous and dense,the lowest porosity is 7.8%,the content of tetragonal zirconia is 15.88%,the hydrogen resistance effect of the film is ideal,the PRF value can reach 16.3,and the hydrogen loss temperature increases to 675°C.A continuous and dense MAO/ZrO₂-Y₂O₃ composite film can also be obtained on the surface of zirconium hydride by controlling the molar ratio of zirconium oxide to yttrium oxide.The content of tetragonal zirconia（t-ZrO₂）in the composite film is above14%.When the content of yttrium oxide changes from 0 mol%to 12 mol%,with the increase of yttrium oxide content,the surface porosity roughness and porosity of the composite film decrease,the thickness increases first and then decreases,and the binding force decreases first and then increases.When the content of yttrium oxide exceeds 12 mol%,the surface quality of the composite film decreases.Comprehensive comparison,when the yttrium oxide content is 12 mol%,the surface quality of the composite film is the best,the porosity is 2.9%,the PRF value is 19.3,the hydrogen loss temperature is 682°C,and the hydrogen resistance effect is the best.The heat treatment temperature affects the compactness of the composite film.When the end temperature of the composite film heat treatment is in the range of 300°C-600°C,the composite film undergoes gel transformation and crystallization.When the heat treatment temperature is 600°C,the composite film with crystalline,dense and uniform surface can be obtained.