Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures.This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating,performed using high velocity...Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures.This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating,performed using high velocity oxy-fuel(HVOF)spraying technology.The environment temperature plays an important role in the microstructure and phases as well as lubricant properties of NiCoCrAlYTa/Ag/Mo coatings.When the environment temperature is above 600℃,the outer diffusion and oxidation of Ag and Mo lead to the formation of Ag2 MoO4 on the coating surface.Layer-like Ag2 MoO4 could form a continuous lubricant film at 800℃and consequently let the composite coating present the best tribological properties.Meanwhile,a small number of hard particles could play a good bearing role during friction and improve the tribological properties of the composite coating.展开更多
High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practic...High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practical application.In order to improve the poor thermal expansion property and further reduce the thermal conductivity,high-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) is designed and synthesized in this work.The as-prepared multicomponent material is formed in a simple disordered fluorite structure due to the high-entropy stabilization effect.Notably,it exhibits a much higher TEC of approximately 12.0×10^(−6) K^(−1) compared with those of other high-entropy oxides reported in the field of TBCs.Besides,it presents prominent thermal insulation behavior with a low intrinsic thermal conductivity of 0.92 W·m^(−1)·K^(−1) at 1400℃,which can be explained by the existence of high concentration oxygen vacancies and highly disordered arrangement of multicomponent cations in the unique high-entropy configuration.Through high-temperature in-situ X-ray diffraction(XRD)measurement,this material shows excellent phase stability up to 1400℃.Benefiting from the solid solution strengthening effect,it shows a higher hardness of 8.72 GPa than the corresponding single component compounds.The superior thermo-physical performance above enables(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) a promising TBC material.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10774062, 10774061 and 90505007. The authors thank Y. D. Zhang and D. P. Yang for fruitful discussions.
基金the financial supports of National Natural Science Foundation of China(Nos.51771214 and 51705481)the Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences。
文摘Ag-Mo-O ternary oxide has attracted growing attention because of its potential as a solid lubricant at high temperatures.This work designs and prepares NiCoCrAlYTa/Ag/Mo composite coating,performed using high velocity oxy-fuel(HVOF)spraying technology.The environment temperature plays an important role in the microstructure and phases as well as lubricant properties of NiCoCrAlYTa/Ag/Mo coatings.When the environment temperature is above 600℃,the outer diffusion and oxidation of Ag and Mo lead to the formation of Ag2 MoO4 on the coating surface.Layer-like Ag2 MoO4 could form a continuous lubricant film at 800℃and consequently let the composite coating present the best tribological properties.Meanwhile,a small number of hard particles could play a good bearing role during friction and improve the tribological properties of the composite coating.
基金This research was financially supported by Youth Innovation Promotion Association(No.2014378)for Chinese Academy of Sciences.The authors are grateful to the constructive comments of the reviewers.
文摘High-entropy oxides(HEOs)are widely researched as potential materials for thermal barrier coatings(TBCs).However,the relatively low thermal expansion coefficient(TEC)of those materials severely restricts their practical application.In order to improve the poor thermal expansion property and further reduce the thermal conductivity,high-entropy(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) is designed and synthesized in this work.The as-prepared multicomponent material is formed in a simple disordered fluorite structure due to the high-entropy stabilization effect.Notably,it exhibits a much higher TEC of approximately 12.0×10^(−6) K^(−1) compared with those of other high-entropy oxides reported in the field of TBCs.Besides,it presents prominent thermal insulation behavior with a low intrinsic thermal conductivity of 0.92 W·m^(−1)·K^(−1) at 1400℃,which can be explained by the existence of high concentration oxygen vacancies and highly disordered arrangement of multicomponent cations in the unique high-entropy configuration.Through high-temperature in-situ X-ray diffraction(XRD)measurement,this material shows excellent phase stability up to 1400℃.Benefiting from the solid solution strengthening effect,it shows a higher hardness of 8.72 GPa than the corresponding single component compounds.The superior thermo-physical performance above enables(La_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Gd_(0.2))_(2)Ce_(2)O_(7) a promising TBC material.
