多组元稀土硅酸盐环境障涂层材料研究进展OA

Rare-earth silicates have emerged as leading candidates for environmental barrier coatings(EBCs)on SiCf/SiC ceramic matrix composites because of their low thermal conductivity,adjustable thermal expansion behavior,and comparatively high environmental stability.However,single-component RE2SiO5 and RE2Si2O7 systems generally cannot simultaneously satisfy the coupled requirements of thermal-expansion compatibility,high-temperature phase stability,low heat transport,and resistance to water-vapor and calcium-magnesium-aluminosilicate(CMAS)attack.This review summarizes recent progress in multi-component rare-earth silicate EBC materials,with particular emphasis on the relationships among composition,crystal structure,thermophysical properties,and high-temperature corrosion behavior.The structural characteristics and thermal properties of RE2SiO5 and RE2Si2O7 are firstly compared.RE2SiO5 generally exhibits relatively high chemical and environmental stability,but its thermal expansion coefficient is often higher than that of SiCf/SiC substrates,increasing the risk of thermally induced interfacial stresses during cyclic exposure.By contrast,β-RE2Si2O7,especially silicates containing small-radius rare-earth cations,provides better thermal-expansion compatibility with substrates,whereas phase transformation,Si-containing species volatilization,and grain-boundary penetration may compromise its long-term stability in aggressive environments. The review then focuses on the multi-component design of rare-earth monosilicates and disilicates.Multi-cation occupation of the rare-earth sublattice expands the available compositional space and enables simultaneous regulation of phase constitution,lattice parameters,local bonding environments,and defect structures.Appropriate control of the average rare-earth ionic radius can promote the formation and retention of structurally favorable X2-type RE2SiO5 or β-RE2Si2O7 phases.Differences in atomic mass and ionic size,together with lattice distortion and local chemical complexity,enhance phonon scattering and can substantially suppress thermal conductivity.The resulting thermophysical response is not governed solely by configurational entropy.Rather,the effects of specific elemental combinations,defect evolution,phonon anharmonicity,and high-temperature structural reconstruction must also be considered,particularly because some highly disordered systems may lose their low-thermal-conductivity advantage at elevated temperatures. Recent studies on high-temperature water-vapor corrosion and CMAS attack are further reviewed.Multi-component design can modify Si-O and RE-O bonding,surface wettability,grain-boundary structure,and cation migration behavior,thereby affecting hydrolysis,volatile hydroxide formation,Si depletion,and the integrity of corrosion-product layers.In CMAS environments,the corrosion resistance of rare-earth silicates depends not only on whether interfacial reactions occur,but also on whether apatite-or garnet-type reaction products form continuous and dense barriers capable of suppressing further melt penetration and ionic diffusion.Multi-component chemistry may therefore improve environmental durability by slowing elemental transport,altering grain-boundary penetration pathways,and regulating the composition and compactness of protective reaction layers. Finally,the remaining challenges for multi-component rare-earth silicate EBCs are discussed,including phase stability above 1 500℃,degradation under coupled thermal,water-vapor,and CMAS conditions,the lack of long-duration and coating-level validation,and the difficulty of reproducible large-scale processing.Future research should move from single-property optimization toward coordinated control of thermal matching,heat transport,phase stability,and corrosion resistance.Integrated composition-structure-process design,low-cost manufacturing,first-principles calculations,high-throughput screening,and machine-learning-assisted materials discovery are expected to accelerate the development of next-generation rare-earth silicate EBC systems for extreme aero-engine environments and support the reliable service of SiCf/SiC hot-section components at increasingly higher operating temperatures.