Xenotime rare-earth(RE)phosphates are emerging as promising materials for environmental barrier coatings(EBCs)for SiC-based ceramic-matrix composites(CMCs)because of their close coefficients of thermal expansion(CTEs)...Xenotime rare-earth(RE)phosphates are emerging as promising materials for environmental barrier coatings(EBCs)for SiC-based ceramic-matrix composites(CMCs)because of their close coefficients of thermal expansion(CTEs)and resistance to calcium-magnesium-alumina-silicate(CMAS)corrosion.In this work,high-entropy(HE)(Sc_(0.2)Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2))PO_(4) and five single-component REPO4(RE=Sc,Lu,Yb,Er,and Y)compounds were synthesized,and their stability,thermal properties,and CMAS corrosion resistance were investigated.The CTE values of four REPO_(4) compounds(RE=Lu,Yb,Er,and Y;~(5.6-6)×10^(−6)℃^(−1))are close to those of SiC-CMC((4.5-5.5)×10^(−6)℃^(−1)),whereas ScPO_(4)(6.98×10^(−6)℃^(−1))and HE(5RE_(0.2))PO_(4)(6.39×10^(−6)℃^(−1))have slightly higher values in the temperature range of 200-1300℃.HE phosphate has the lowest thermal conductivity due to its size and mass disorder.Systematic CMAS corrosion tests at 1300℃ for 5,45,and 96 h revealed that all RE phosphates formed a continuous and dense reaction layer predominantly composed of Ca_(8)MgRE(PO_(4))_(7),effectively impeding CMAS penetration.Additionally,REPO_(4) with smaller RE³−cations displays a slower reaction rate and reduced corrosion kinetics,as evidenced by the smaller thickness of the reaction layer.A larger negative difference in the optical basicity(OB)value between REPO_(4) and CMAS signifies greater corrosion resistance.A mechanistic understanding of CMAS corrosion and elucidation of the effects of critical parameters such as the ionic mass and ionic radius of RE elements on their thermal properties and CMAS corrosion kinetics are useful for the development of novel xenotime-type phosphates as EBCs for SiC-CMCs.展开更多
Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings(EBCs),offering enormous possibilities and flexibility by controlling and varying their components and fract...Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings(EBCs),offering enormous possibilities and flexibility by controlling and varying their components and fractions to tailor their performance.In this work,the key material parameters(e.g.,ionic size and ionic size disorder)and the elements governing their thermal‒mechanical properties and resistance against calcium‒magnesium‒aluminosilicate(CMAS)corrosion were elucidated.The thermal conductivities of multicomponent rare-earth phosphates correlate well with cation size disorder,but no clear trend is identified for the coefficient of thermal expansion(CTE).Er-containing compositions display low CTEs and high fracture toughness.Rapid formation of a dense interfacial layer occurs for most CAMS corrosion-resistant compositions when tested at 1300°C,e.g.,(Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2)Gd_(0.2))PO_(4) and(Lu_(0.2)Yb_(0.2)Er_(0.2)Dy_(0.2)Gd_(0.2))PO_(4).These multicomponent phosphates also display the least recession upon molten CMAS attack at 1400°C without significant volumetric swelling,which is superior to their single-component counterparts and state-of-the-art EBCs based on rare-earth disilicates.In contrast,Sc-containing multicomponent phosphates display inferior performance against CMAS corrosion and penetration.A mechanistic understanding and understanding of the kinetics of the interfacial interaction at higher temperatures,as well as the key parameters governing their thermomechanical properties and CMAS corrosion,are valuable for designing data-driven materials of multicomponent phosphates for EBC applications.展开更多
基金supported as part of the DMREF:Machine Learning Accelerated Design and Discovery of Rare-earth Phosphates as Next Generation Environmental Barrier Coatings,a standard Grant funded by the Division of Materials Research,National Science Foundation under Award DMREF-2119423.
文摘Xenotime rare-earth(RE)phosphates are emerging as promising materials for environmental barrier coatings(EBCs)for SiC-based ceramic-matrix composites(CMCs)because of their close coefficients of thermal expansion(CTEs)and resistance to calcium-magnesium-alumina-silicate(CMAS)corrosion.In this work,high-entropy(HE)(Sc_(0.2)Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2))PO_(4) and five single-component REPO4(RE=Sc,Lu,Yb,Er,and Y)compounds were synthesized,and their stability,thermal properties,and CMAS corrosion resistance were investigated.The CTE values of four REPO_(4) compounds(RE=Lu,Yb,Er,and Y;~(5.6-6)×10^(−6)℃^(−1))are close to those of SiC-CMC((4.5-5.5)×10^(−6)℃^(−1)),whereas ScPO_(4)(6.98×10^(−6)℃^(−1))and HE(5RE_(0.2))PO_(4)(6.39×10^(−6)℃^(−1))have slightly higher values in the temperature range of 200-1300℃.HE phosphate has the lowest thermal conductivity due to its size and mass disorder.Systematic CMAS corrosion tests at 1300℃ for 5,45,and 96 h revealed that all RE phosphates formed a continuous and dense reaction layer predominantly composed of Ca_(8)MgRE(PO_(4))_(7),effectively impeding CMAS penetration.Additionally,REPO_(4) with smaller RE³−cations displays a slower reaction rate and reduced corrosion kinetics,as evidenced by the smaller thickness of the reaction layer.A larger negative difference in the optical basicity(OB)value between REPO_(4) and CMAS signifies greater corrosion resistance.A mechanistic understanding of CMAS corrosion and elucidation of the effects of critical parameters such as the ionic mass and ionic radius of RE elements on their thermal properties and CMAS corrosion kinetics are useful for the development of novel xenotime-type phosphates as EBCs for SiC-CMCs.
基金supported as part of the DMREF:Machine Learning Accelerated Design and Discovery of Rare-earth Phosphates as Next-Generation Environmental Barrier Coatings,a standard grant funded by the Division of Materials Research,National Science Foundation under Award DMREF-2119423.
文摘Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings(EBCs),offering enormous possibilities and flexibility by controlling and varying their components and fractions to tailor their performance.In this work,the key material parameters(e.g.,ionic size and ionic size disorder)and the elements governing their thermal‒mechanical properties and resistance against calcium‒magnesium‒aluminosilicate(CMAS)corrosion were elucidated.The thermal conductivities of multicomponent rare-earth phosphates correlate well with cation size disorder,but no clear trend is identified for the coefficient of thermal expansion(CTE).Er-containing compositions display low CTEs and high fracture toughness.Rapid formation of a dense interfacial layer occurs for most CAMS corrosion-resistant compositions when tested at 1300°C,e.g.,(Lu_(0.2)Yb_(0.2)Er_(0.2)Y_(0.2)Gd_(0.2))PO_(4) and(Lu_(0.2)Yb_(0.2)Er_(0.2)Dy_(0.2)Gd_(0.2))PO_(4).These multicomponent phosphates also display the least recession upon molten CMAS attack at 1400°C without significant volumetric swelling,which is superior to their single-component counterparts and state-of-the-art EBCs based on rare-earth disilicates.In contrast,Sc-containing multicomponent phosphates display inferior performance against CMAS corrosion and penetration.A mechanistic understanding and understanding of the kinetics of the interfacial interaction at higher temperatures,as well as the key parameters governing their thermomechanical properties and CMAS corrosion,are valuable for designing data-driven materials of multicomponent phosphates for EBC applications.
