High-entropy oxides(HEOs)are considered promising thermal barrier coating(TBC)materials due to their unique thermophysical performances induced by the entropy effects.In this work,(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(...High-entropy oxides(HEOs)are considered promising thermal barrier coating(TBC)materials due to their unique thermophysical performances induced by the entropy effects.In this work,(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)high entropy hafnate,as a thermal barrier coating(TBC)material,was successfully synthesized by solution combustion method for the first time.From the X-ray diffraction,scanning electron microscopy,and transmission electron microscopy results,it is confirmed that(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)has pure single-phase ordered pyrochlore structure with highly homogeneous composition at both micrometer and nanometer scales.The synthesized(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))2 Hf2O7 possesses excellent phase stability at 1600℃and demonstrates a low thermal conductivity(1.0-1.24 W·m^(-1)·K^(-1))which is lower than those of rare earth hafnates(RE2Hf2O7,RE=La,Ce,Pr,Sm,Eu).Therefore,it provides a new perspective and potential to prompt the next generation TBC materials with better performance.展开更多
Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)h...Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)high-entropy ceramic(HE-RE2 Hf_(2)O_(7))for control rod was prepared by solid-state reaction method.The ion irradiation of HE-RE_(2) Hf_(2)O_(7)with 400 keV Kr+at 400℃was investigated using a 400 kV ion implanter and compared with single-component pyrochlore Gd2 Hf_(2)O_(7)to evaluate the irradiation resistance.For HE-RE2 Hf_(2)O_(7),the phase transition from pyrochlore to defective fluorite is revealed after irradiation at 60 dpa.After irradiation at 120 dpa,it maintained crystalline,which is comparable to Gd2 Hf_(2)O_(7)but superior to the titanate pyrochlores previously studied.Moreover,the lattice expansion of HE-RE2 Hf_(2)O_(7)(_(0.2)2%)is much lower than that of Gd2 Hf_(2)O_(7)(0.62%),indicating excellent irradiation damage resistance.Nanoindentation tests displayed an irradiation-induced increase in hardness and a decrease in elastic modulus by about 2.6%.Irradiation-induced segregation of elements is observed on the surface of irradiated samples.In addition,HE-RE2 Hf_(2)O_(7)demonstrates a more sluggish grain growth rate than Gd2 Hf_(2)O_(7)at 1200℃,suggesting better high-temperature stability.The linear thermal expansion coefficient of HE-RE2 Hf_(2)O_(7)is 10.7×10-6 K-1 at 298–1273 K.In general,it provides a new strategy for the design of the next advanced nuclear engineering materials.展开更多
The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE4Hf3Oi2 (RE=Ho, Er, Tm) with defect fluorite structure was investigated for ...The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE4Hf3Oi2 (RE=Ho, Er, Tm) with defect fluorite structure was investigated for potential use as top TBC layer. Dense pellets were fabricated via a hot pressing method and the mechanical and thermal properties were characterized. RE4Hf3Oi2 (RE=Ho, Er, Tm) possessed a high Vickers hardness of 11 GFa. The material retained high elastic modulus at elevated temperatures up to 1773 K, which made it attractive for high temperature application. The coefficient of thermal expansion (CTE) of RE4Hf3Oi2 (RE = Ho, Er, Tm) laid in the range between 7× 10^-6K^-1 to 10×10^16K^-1 from 473 K to 1673 K. In addition, the rare earth hafnates exhibited lower thermal conductivity which rendered it a good candidate material for thermal barrier applications.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51872234,51502242,51432008,51802244,and 51821091)the Key R&D Program of Shaanxi Provence(No.2019ZDLGY04-02)。
文摘High-entropy oxides(HEOs)are considered promising thermal barrier coating(TBC)materials due to their unique thermophysical performances induced by the entropy effects.In this work,(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)high entropy hafnate,as a thermal barrier coating(TBC)material,was successfully synthesized by solution combustion method for the first time.From the X-ray diffraction,scanning electron microscopy,and transmission electron microscopy results,it is confirmed that(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))_(2)Hf_(2)O_(7)has pure single-phase ordered pyrochlore structure with highly homogeneous composition at both micrometer and nanometer scales.The synthesized(La_(0.2)Ce_(0.2)Pr_(0.2)Sm_(0.2)Eu_(0.2))2 Hf2O7 possesses excellent phase stability at 1600℃and demonstrates a low thermal conductivity(1.0-1.24 W·m^(-1)·K^(-1))which is lower than those of rare earth hafnates(RE2Hf2O7,RE=La,Ce,Pr,Sm,Eu).Therefore,it provides a new perspective and potential to prompt the next generation TBC materials with better performance.
基金supported by the Lingchuang Research Project of China National Nuclear Corporation,the National Key Research and Development Program of China(No.2022YFB3504302)the key core technology research project in Beicang District,Ningbo(Grant No.2021BLG009)+4 种基金the key deployment project of the Chinese Academy of Sciences(Grant No.ZDRW-CN-2021-3)the Fujian Provincial Natural Fund Project(Grant No.2021J05101)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2021QNRC001)the independent deployment project of Ganjiang Innovation Research Institute of Chinese Academy of Sciences(Grant No.E055A002)In addition,thanks for the assistance of Jinchi Huang from the School of Energy,Xiamen University for the ion irradiation experiment.
文摘Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)high-entropy ceramic(HE-RE2 Hf_(2)O_(7))for control rod was prepared by solid-state reaction method.The ion irradiation of HE-RE_(2) Hf_(2)O_(7)with 400 keV Kr+at 400℃was investigated using a 400 kV ion implanter and compared with single-component pyrochlore Gd2 Hf_(2)O_(7)to evaluate the irradiation resistance.For HE-RE2 Hf_(2)O_(7),the phase transition from pyrochlore to defective fluorite is revealed after irradiation at 60 dpa.After irradiation at 120 dpa,it maintained crystalline,which is comparable to Gd2 Hf_(2)O_(7)but superior to the titanate pyrochlores previously studied.Moreover,the lattice expansion of HE-RE2 Hf_(2)O_(7)(_(0.2)2%)is much lower than that of Gd2 Hf_(2)O_(7)(0.62%),indicating excellent irradiation damage resistance.Nanoindentation tests displayed an irradiation-induced increase in hardness and a decrease in elastic modulus by about 2.6%.Irradiation-induced segregation of elements is observed on the surface of irradiated samples.In addition,HE-RE2 Hf_(2)O_(7)demonstrates a more sluggish grain growth rate than Gd2 Hf_(2)O_(7)at 1200℃,suggesting better high-temperature stability.The linear thermal expansion coefficient of HE-RE2 Hf_(2)O_(7)is 10.7×10-6 K-1 at 298–1273 K.In general,it provides a new strategy for the design of the next advanced nuclear engineering materials.
基金supported financially by the National Key R&D Program of China (No. 2017YFB0703201)the National Natural Science Foundation of China (Nos. 51402311, 51372252 and 51772302)the International Cooperation Key Program (No. 174321KYSB20180008)
文摘The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE4Hf3Oi2 (RE=Ho, Er, Tm) with defect fluorite structure was investigated for potential use as top TBC layer. Dense pellets were fabricated via a hot pressing method and the mechanical and thermal properties were characterized. RE4Hf3Oi2 (RE=Ho, Er, Tm) possessed a high Vickers hardness of 11 GFa. The material retained high elastic modulus at elevated temperatures up to 1773 K, which made it attractive for high temperature application. The coefficient of thermal expansion (CTE) of RE4Hf3Oi2 (RE = Ho, Er, Tm) laid in the range between 7× 10^-6K^-1 to 10×10^16K^-1 from 473 K to 1673 K. In addition, the rare earth hafnates exhibited lower thermal conductivity which rendered it a good candidate material for thermal barrier applications.