Rare-earth phosphates(REPO4)are regarded as one of the promising thermal/environmental barrier coating(T/EBC)materials for SiCf/SiC ceramic matrix composites(SiC-CMCs)owing to their excellent resistance to water vapor...Rare-earth phosphates(REPO4)are regarded as one of the promising thermal/environmental barrier coating(T/EBC)materials for SiCf/SiC ceramic matrix composites(SiC-CMCs)owing to their excellent resistance to water vapor and CaO–MgO–Al_(2)O_(3)–SiO_(2)(CMAS).Nevertheless,a relatively high thermal conductivity(κ)of the REPO_(4) becomes the bottleneck for their practical applications.In this work,novel xenotime-type high-entropy(Dy_(1/7)Ho_(1/7)Er_(1/7)Tm_(1/7)Yb_(1/7)Lu_(1/7)Y_(1/7))PO4(HE(7RE_(1/7))PO_(4))has been designed and synthesized for the first time to solve this issue.HE(7RE_(1/7))PO_(4) with a homogeneous rare-earth element distribution exhibits high thermal stability up to 1750℃and good chemical compatibility with SiO_(2) up to 1400℃.In addition,the thermal expansion coefficient(TEC)of HE(7RE_(1/7))PO_(4)(5.96×10^(−6)℃^(−1) from room temperature(RT)to 900℃)is close to that of the SiC-CMCs.What is more,the thermal conductivities of HE(7RE_(1/7))PO_(4)(from 4.38 W·m^(−1)·K^(−1) at 100℃to 2.25 W·m^(−1)·K^(−1) at 1300℃)are significantly decreased compared to those of single-component REPO4 with the minimum value ranging from 9.90 to 4.76 W·m^(−1)·K^(−1).These results suggest that HE(7RE_(1/7))PO_(4) has the potential to be applied as the T/EBC materials for the SiC-CMCs in the future.展开更多
Mechanical properties consisting of the bulk modulus,shear modulus,Young’s modulus,Poisson’s ratio,etc.,are key factors in determining the practical applications of MAX phases.These mechanical properties are mainly ...Mechanical properties consisting of the bulk modulus,shear modulus,Young’s modulus,Poisson’s ratio,etc.,are key factors in determining the practical applications of MAX phases.These mechanical properties are mainly dependent on the strength of M–X and M–A bonds.In this study,a novel strategy based on the crystal graph convolution neural network(CGCNN)model has been successfully employed to tune these mechanical properties of Ti_(3)AlC_(2)-based MAX phases via the A-site substitution(Ti_(3)(Al1-xAx)C_(2)).The structure–property correlation between the A-site substitution and mechanical properties of Ti_(3)(Al1-xAx)C_(2)is established.The results show that the thermodynamic stability of Ti_(3)(Al1-xAx)C_(2)is enhanced with substitutions A=Ga,Si,Sn,Ge,Te,As,or Sb.The stiffness of Ti_(3)AlC_(2)increases with the substitution concentration of Si or As increasing,and the higher thermal shock resistance is closely associated with the substitution of Sn or Te.In addition,the plasticity of Ti_(3)AlC_(2)can be greatly improved when As,Sn,or Ge is used as a substitution.The findings and understandings demonstrated herein can provide universal guidance for the individual synthesis of high-performance MAX phases for various applications.展开更多
基金supported by the National Key R&D Program of China(No.2021YFB3701404)the National Science Fund for Distinguished Young Scholars(No.52025041)the National Natural Science Foundation of China(Nos.51904021 and 52174294).
文摘Rare-earth phosphates(REPO4)are regarded as one of the promising thermal/environmental barrier coating(T/EBC)materials for SiCf/SiC ceramic matrix composites(SiC-CMCs)owing to their excellent resistance to water vapor and CaO–MgO–Al_(2)O_(3)–SiO_(2)(CMAS).Nevertheless,a relatively high thermal conductivity(κ)of the REPO_(4) becomes the bottleneck for their practical applications.In this work,novel xenotime-type high-entropy(Dy_(1/7)Ho_(1/7)Er_(1/7)Tm_(1/7)Yb_(1/7)Lu_(1/7)Y_(1/7))PO4(HE(7RE_(1/7))PO_(4))has been designed and synthesized for the first time to solve this issue.HE(7RE_(1/7))PO_(4) with a homogeneous rare-earth element distribution exhibits high thermal stability up to 1750℃and good chemical compatibility with SiO_(2) up to 1400℃.In addition,the thermal expansion coefficient(TEC)of HE(7RE_(1/7))PO_(4)(5.96×10^(−6)℃^(−1) from room temperature(RT)to 900℃)is close to that of the SiC-CMCs.What is more,the thermal conductivities of HE(7RE_(1/7))PO_(4)(from 4.38 W·m^(−1)·K^(−1) at 100℃to 2.25 W·m^(−1)·K^(−1) at 1300℃)are significantly decreased compared to those of single-component REPO4 with the minimum value ranging from 9.90 to 4.76 W·m^(−1)·K^(−1).These results suggest that HE(7RE_(1/7))PO_(4) has the potential to be applied as the T/EBC materials for the SiC-CMCs in the future.
基金This work was supported by the National Science Fund for Distinguished Young Scholars(No.52025041)the National Natural Science Foundation of China(Nos.51904021,51974021,and 52174294)the National Key R&D Program of China(No.2021YFB3700400).
文摘Mechanical properties consisting of the bulk modulus,shear modulus,Young’s modulus,Poisson’s ratio,etc.,are key factors in determining the practical applications of MAX phases.These mechanical properties are mainly dependent on the strength of M–X and M–A bonds.In this study,a novel strategy based on the crystal graph convolution neural network(CGCNN)model has been successfully employed to tune these mechanical properties of Ti_(3)AlC_(2)-based MAX phases via the A-site substitution(Ti_(3)(Al1-xAx)C_(2)).The structure–property correlation between the A-site substitution and mechanical properties of Ti_(3)(Al1-xAx)C_(2)is established.The results show that the thermodynamic stability of Ti_(3)(Al1-xAx)C_(2)is enhanced with substitutions A=Ga,Si,Sn,Ge,Te,As,or Sb.The stiffness of Ti_(3)AlC_(2)increases with the substitution concentration of Si or As increasing,and the higher thermal shock resistance is closely associated with the substitution of Sn or Te.In addition,the plasticity of Ti_(3)AlC_(2)can be greatly improved when As,Sn,or Ge is used as a substitution.The findings and understandings demonstrated herein can provide universal guidance for the individual synthesis of high-performance MAX phases for various applications.
