Preparation And Properties Of Scandium-Cerium Co-Stabilized Zirconia Ceramic Materials

Thermal barrier coating materials are widely used in high temperature components of gas turbines,which can effectively improve the service life and operating temperature of engine blades.The zirconia material has high phase stability,high thermal expansion coefficient,low thermal conductivity and excellent mechanical properties,which has attracted wide attention.In this thesis,cerium oxide(CeO₂)and scandium oxide(Sc₂O₃)were used as stabilizers for zirconium oxide and a series of scandium-cerium co-stabilized zirconium oxide ceramic materials(SCZ)are prepared by hydrothermal synthesis-high temperature solid phase synthesis.The thermophysical properties,mechanical properties,Na₂SO₄+V₂O₅ molten salt corrosion resistance and CMAS(CaO,Mg O,Al₂O₃ and Si O₂)corrosion behavior of these materials have been systematically studied.The research content is as follows:(1)The effect of the change of CeO₂ addition on the thermophysical properties,mechanical properties and thermal cycle life of SCZ ceramic materials was studied.After the SCZ ceramic material was heat-treated at 1500?for 100 h,both 4S12CZ and4S16CZ maintained a single tetragonal phase structure.In the test temperature range,the thermal conductivity of SCZ ceramic materials decreases with the increase of CeO₂addition,and the thermal expansion coefficient increases with the increase of CeO₂addition.When the amount of CeO₂ added reaches 16 mol%,the thermal expansion coefficient of 4S16CZ material is between 9.25-12.26×10^-6 K^-1,and the thermal conductivity is between 1.90-2.30 W/(m·K).In addition,the addition of CeO₂ can effectively inhibit the sintering of ceramic granite,so that the SCZ material has better sintering resistance,mechanical properties and thermal cycle life.(2)The corrosion experiment of SCZ ceramic material in Na₂SO₄+V₂O₅ molten salt at 750°C,900°C and 1100°C was carried out for 20 h.In the hot corrosion experiment,the corrosion product and the degree of corrosion depend on the ratio of corrosion temperature and stabilizer.At 750°C,the main corrosion products of SCZ ceramics are m-ZrO₂ and Ce VO₄.When the temperature rises to 900°C and 1100°C,SCZ ceramics become unstable in the Na VO₃ environment,Ce⁴⁺precipitates in the material and mineralization occurs to form new corrosion products CeO₂.The addition of the stabilizer Sc₂O₃ can enhance the strength of the M-O bond and reduce the size mismatch,which effectively improves the corrosion resistance of SCZ ceramic materials.(3)The corrosion experiment of SCZ ceramic material was carried out for 12-100 h in CMAS molten salt corrosion at 1200°C.The experimental results show that the corrosion degree of 4S16CZ ceramic material and 16S4CZ ceramic material is equivalent.During the corrosion process of the powder material,the Sc³⁺in the material precipitates from the inside of the SCZ material due to its high solubility and affinity,and diffuses into the CMAS molten salt,prompting t-ZrO₂ to generate Sc-poor m-ZrO₂ and c-ZrO₂.In the corrosion test of the SCZ bulk material,because the surface of the SCZ ceramic material has a relatively high content of CMAS molten salt,the surface is dissolved and corroded by the molten salt under the action of the CMAS molten salt to generate corrosion products.Although CMAS molten salt will also enter the ceramic interior along the corrosion channel,the corrosion salt will interact with the precipitated Sc³⁺and Ce⁴⁺when entering the ceramic interior to generate apatite corrosion products Ca₂RE₈(Si O₄)₆O₂(RE=Sc and Ce).This corrosion product will be deposited on the lower end of the corrosion area or in the channel,which can effectively resist the continuous penetration of the CMAS molten salt,so as to achieve the effect of resisting CMAS corrosion.