Low thermal conductivity,compatible thermal expansion coefficient,and good calcium–magnesium–aluminosilicate(CMAS)corrosion resistance are critical requirements of environmental barrier coatings for silicon-based ce...Low thermal conductivity,compatible thermal expansion coefficient,and good calcium–magnesium–aluminosilicate(CMAS)corrosion resistance are critical requirements of environmental barrier coatings for silicon-based ceramics.Rare earth silicates have been recognized as one of the most promising environmental barrier coating candidates for good water vapor corrosion resistance.However,the relatively high thermal conductivity and high thermal expansion coefficient limit the practical application.Inspired by the high entropy effect,a novel rare earth monosilicate solid solution(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)was designed to improve the overall performance.The as-synthesized(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)shows very low thermal conductivity(1.07 W·m-1·K-1 at 600℃).Point defects including mass mismatch and oxygen vacancies mainly contribute to the good thermal insulation properties.The thermal expansion coefficient of(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)can be decreased to(4.0–5.9)×10^(-6)K^(-1)due to severe lattice distortion and chemical bonding variation,which matches well with that of SiC((4.5–5.5)×10^(-6)K^(-1)).In addition,(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)presents good resistance to CMAS corrosion.The improved performance of(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)highlights it as a promising environmental barrier coating candidate.展开更多
Rare earth(RE)silicate is one of the most promising environmental barrier coatings for silicon-based ceramics in gas turbine engines.However,calcium-magnesium-alumina-silicate(CMAS)corrosion becomes much more serious ...Rare earth(RE)silicate is one of the most promising environmental barrier coatings for silicon-based ceramics in gas turbine engines.However,calcium-magnesium-alumina-silicate(CMAS)corrosion becomes much more serious and is the critical challenge for RE silicate with the increasing operating temperature.Therefore,it is quite urgent to clarify the mechanism of high-temperature CMAS-induced degradation of RE silicate at relatively high temperatures.Herein,the interaction between RE_(2)SiO_(5) and CMAS up to 1500℃was investigated by a novel high temperature in-situ observation method.High temperature promotes the growth of the main reaction product(Ca_(2)RE_(8)(SiO_(4))6O_(2))fast along the[001]direction,and the precipitation of short and horizontally distributed Ca_(2)RE_(8)(SiO_(4))6O_(2) grains was accelerated during the cooling process.The increased temperature increases the solubility of RE elements,decreases the viscosity of CMAS,and thus elevates the corrosion reaction rate,making RE_(2)SiO_(5) fast interaction with CMAS and less affected by RE element species.展开更多
基金This work was financially supported by Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Grant No.2021B1515020083)Guang Dong Basic and Applied Basic Research Foundation for Young Scholars(Grant No.21201910240002803)+1 种基金Shenzhen Science and Technology Program(Grant Nos.GXWD20201231165807008,20200831172254001)Fundamental Research Funds for the Central Universities,Sun Yat-sen University(Grant No.2021qntd10).
文摘Low thermal conductivity,compatible thermal expansion coefficient,and good calcium–magnesium–aluminosilicate(CMAS)corrosion resistance are critical requirements of environmental barrier coatings for silicon-based ceramics.Rare earth silicates have been recognized as one of the most promising environmental barrier coating candidates for good water vapor corrosion resistance.However,the relatively high thermal conductivity and high thermal expansion coefficient limit the practical application.Inspired by the high entropy effect,a novel rare earth monosilicate solid solution(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)was designed to improve the overall performance.The as-synthesized(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)shows very low thermal conductivity(1.07 W·m-1·K-1 at 600℃).Point defects including mass mismatch and oxygen vacancies mainly contribute to the good thermal insulation properties.The thermal expansion coefficient of(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)can be decreased to(4.0–5.9)×10^(-6)K^(-1)due to severe lattice distortion and chemical bonding variation,which matches well with that of SiC((4.5–5.5)×10^(-6)K^(-1)).In addition,(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)presents good resistance to CMAS corrosion.The improved performance of(Ho_(0.25)Lu_(0.25)Yb_(0.25)Eu_(0.25))_(2)SiO_(5)highlights it as a promising environmental barrier coating candidate.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.52202078 and 52202126)Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholars(Grant No.2021B1515020083)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021A1515110293 and 2022A1515012201)Shenzhen Science and Technology Program(Grant Nos.202206193000001 and 20220818183014003).
文摘Rare earth(RE)silicate is one of the most promising environmental barrier coatings for silicon-based ceramics in gas turbine engines.However,calcium-magnesium-alumina-silicate(CMAS)corrosion becomes much more serious and is the critical challenge for RE silicate with the increasing operating temperature.Therefore,it is quite urgent to clarify the mechanism of high-temperature CMAS-induced degradation of RE silicate at relatively high temperatures.Herein,the interaction between RE_(2)SiO_(5) and CMAS up to 1500℃was investigated by a novel high temperature in-situ observation method.High temperature promotes the growth of the main reaction product(Ca_(2)RE_(8)(SiO_(4))6O_(2))fast along the[001]direction,and the precipitation of short and horizontally distributed Ca_(2)RE_(8)(SiO_(4))6O_(2) grains was accelerated during the cooling process.The increased temperature increases the solubility of RE elements,decreases the viscosity of CMAS,and thus elevates the corrosion reaction rate,making RE_(2)SiO_(5) fast interaction with CMAS and less affected by RE element species.
