The insulation effect of ceramic coating in a turbine blade is of great importance for the service of engine in the field of aviation industry. Fabricating microstructure in the thermal barrier coatings(TBCs) is consi...The insulation effect of ceramic coating in a turbine blade is of great importance for the service of engine in the field of aviation industry. Fabricating microstructure in the thermal barrier coatings(TBCs) is considered to be able to enhance the thermal insulation effect. In this study, the traditional three-layer structure, containing ceramic top coat, bonding coat and substrate, is firstly simplified into a double-layer structure, where only ceramic layer and substrate are left, for analyzing the thermal insulation. Afterwards, the thermal insulation effect of the designed microstructure in the bonding coat of the three-layer structure is further studied. Column-like microstructures, filled with hollow ceramic microspheres in the interspace, are designed to improve the thermal insulation effect. The size parameters of the designed microstructure were optimized. The existence of the designed microstructure can significantly prolong the efficiency of thermal barrier coatings. The insulation temperature between the heating surface and lower surface of the substrate can exceed 300℃ and the thermal balance time has a big improvement of 240 s, more than 50%, than the traditional TBCs structure. Compared with the TBCs structure without microstructure, the designed microstructure can significantly improve the insulation temperature of more than 110℃.展开更多
Opaque thermal barrier materials play a pivotal role in thermal radiation shielding of turbine blades,since the intensity of thermal radiation rapidly increases with the increase of operating temperature of gas turbin...Opaque thermal barrier materials play a pivotal role in thermal radiation shielding of turbine blades,since the intensity of thermal radiation rapidly increases with the increase of operating temperature of gas turbines and has become a new and major concern for the durability of metallic blades.The conventional thermal barrier coating(TBC)materials such as YSZ and Gd_(2)Zr_(2)O_(7),however,are almost translucent to thermal radiation and are unable to protect the blades at such harsh environment.Although searching for new thermal barrier materials is significant,it is still a challenge to make the current TBC materials opaque without significantly modifying the composition or other physical properties.To cope with this challenge,GdMnO_(3) is incorporated as an absorptive second phase into Gd_(2)Zr_(2)O_(7) in this work,which is originally translucent(absorption coefficient 10^(1)-10^(2) m^(-1))in the near-infrared wavelengths.Intriguingly,with less than 5 wt.%GdMnO_(3),the Gd_(2)Zr_(2)O_(7)/GdMnO_(3) becomes opaque to thermal radiation and successfully refrains the rise of thermal conductivity at high temperatures.Meanwhile,the lattice thermal conductivity and mechanical properties are almost unchanged.The small polaron mechanism is confirmed for GdMnO_(3),leading to a high absorption coefficient(>10^(6) m^(-1))for near-infrared radiation.To understand the underling mechanism,a theoretical model is built to estimate the absorption coefficient of the Gd_(2)Zr_(2)O_(7)/GdMnO_(3) composites(>10^(4) m^(-1)).This paper proposes a powerful strategy to design thermal-radiation-shielding TBCs through incorporating minor second-phase particles with high-absorption mechanism,such as polaron excitation.展开更多
With continuous enhancement of gas-turbine inlet temperature and rapid increase of radiant heat transfer,thermal barrier coating(TBC)materials with a combination of low thermal conductivity and good high-temperature t...With continuous enhancement of gas-turbine inlet temperature and rapid increase of radiant heat transfer,thermal barrier coating(TBC)materials with a combination of low thermal conductivity and good high-temperature thermal radiation shielding performance play vital roles in ensuring the durability of metallic blades.However,yttria-stabilized zirconia(YSZ),as the state-of-the-art TBC and current industry standard,is unable to meet such demands since it is almost translucent to high-temperature thermal radiation.Besides,poor corrosion resistance of YSZ to molten calcia-magnesia-alumina-silicates(CMAS)also impedes its application in sand,dust,or volcanic ash laden environments.In order to improve the hightemperature thermal radiation shielding performance and CMAS resistance of YSZ and further reduce its thermal conductivity,two medium-entropy(ME)oxide ceramics,ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),were designed and prepared by pressureless sintering of binary powder compacts in this work.ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)presents cubic structure but a trace amount of secondary phase,while ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)displays a combination of tetragonal phase(81.6 wt.%)and cubic phase(18.4 wt.%).Both ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)possess better high-temperature thermal radiation shielding performance than YSZ.Especially,the high-temperature thermal radiation shielding performance of ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)is superior to that of ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)due to its narrower band gap and correspondingly higher infrared absorbance(above 0.7)at the waveband of 1 to 5μm.The two ME oxides also display significantly lower thermal conductivity than YSZ and close thermal expansion coefficients(TECs)to YSZ and Ni-based superalloys.In addition,the two ME oxides possess excellent CMAS resistance.After attack by molten CMAS at 1250℃for 4 h,merely~2μm thick penetration layer has been formed and the structure below the penetration layer is still intact.These results demonstrate that ME(Me,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)(Me=Y and Ta),especially ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),are promising thermal barrier materials for high-temperature thermal radiation shielding and CMAS blocking.展开更多
Plasma spray physical vapor deposition(PS-PVD)(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)thermal barrier coatings(TBCs)exhibited better silicate-phobicity than coatings produced by electron beam physical vapor depo-sition...Plasma spray physical vapor deposition(PS-PVD)(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)thermal barrier coatings(TBCs)exhibited better silicate-phobicity than coatings produced by electron beam physical vapor depo-sition.In combination with PS-PVD and ultrafast laser direct writing technology,biomimetic structured GYbZ TBCs,with a triple-scale micro/nano surface microstructure,were obtained.Laser ablating on the PS-PVD GYbZ coating enhanced the surface roughness,improving its wear resistance without increasing the surface hardness.Furthermore,during the laser ablation processing,numerous nanoparticles were deposited in-situ in the gaps between columns of the coating,reducing the coating Young’s modulus.The simulated temperature field and heat flux field demonstrated that the presence of numerous interfaces between small columns of the PS-PVD coatings is beneficial to thermal insulation.However,laser ablation decreased the coating thickness,reducing the thermal insulation by around 20%-30%as compared to its PS-PVD counterpart,suggesting that a moderate increase in the coating thickness should be considered when designing an efficient TBC system.展开更多
Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects...Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects of conventional plasma sprayed and nanostructured yttria stabilized zirconia （YSZ） thermal barrier coatings （TBCs） are investigated. Remarkable increase in thermal conductivity occurs to both typical coatings after heat treatment, The change of porosity is just the opposite. The grain size of the nanostructured zirconia coating increases more drastically with annealing time compared to that of the conventional plasma sprayed coating, which indicates that coating sintering makes more contributions to the thermal conductivity of the nanostructured coating than that of the conventional coating. Thermal barrier effect tests using temperature difference technique are performed on both coatings. The thermal barrier effects decrease with the increase of thermal conductivity after heat treat- ment and the decline seems more drastic in low thermal conductivity range. The decline in thermal barrier effects is about 80℃ for nanostructured coating after 100 h heat treatment, while the conventional coating reduces by less than 60 ℃ compared to the as-sprayed coating.展开更多
High fracture toughness,low thermal conductivity,and thermal expansion coefficient(TEC)matching substrate are essential for thermal barrier coatings(TBCs)and abradable seal coatings(ASCs).In this work,TmNbO_(4)/Tm_(3)...High fracture toughness,low thermal conductivity,and thermal expansion coefficient(TEC)matching substrate are essential for thermal barrier coatings(TBCs)and abradable seal coatings(ASCs).In this work,TmNbO_(4)/Tm_(3)NbO_(7) composites are designed and synthesized to increase their fracture toughness(KIC)and thermal insulation performance.Compared with those of TmNbO_(4)(KIC=2.2±0.1 MPa·m^(1/2))and Tm3NbO7(KIC=1.7±0.2 MPa·m^(1/2)),the increments in fracture toughness are as high as 50.0%and 91.1%,respectively.The highest toughness reaches 3.3±0.4 MPa·m1/2,which is attributed to the superior combination of grains between TmNbO4 and Tm3NbO7,as well as the simultaneous effects of microcracks and crack bridging and bifurcation.Accurate estimation of the effect of the interfacial thermal resistance on the thermal conductivity at low temperatures was achieved using the minimum interfacial thermal resistance model.A novel method is proposed to inhibit radiative heat transfer by utilizing oxides with glass-like thermal conductivity to suppress thermal radiation.Consequently,the TmNbO4/Tm3NbO7 composite maintains a low thermal conductivity(1.19–2.02 W·m^(−1)·K^(−1))at 1000°C.The high TECs(10.4×10^(−6)–11.8×10^(−6)·K^(−1) at 1500°C)and excellent high-temperature stability ensure that the designed TmNbO_(4)/Tm_(3)NbO_(7) composites can be used at temperatures reaching 1500°C.Accordingly,simultaneous enhancement of fracture toughness and thermal insulation in TmNbO_(4)/Tm_(3)NbO_(7) composites is effective,and the revealed mechanisms are useful for various materials.展开更多
基金financially supported by the National Natural Science Foundation of China(11372037,11572041,and 11232008)
文摘The insulation effect of ceramic coating in a turbine blade is of great importance for the service of engine in the field of aviation industry. Fabricating microstructure in the thermal barrier coatings(TBCs) is considered to be able to enhance the thermal insulation effect. In this study, the traditional three-layer structure, containing ceramic top coat, bonding coat and substrate, is firstly simplified into a double-layer structure, where only ceramic layer and substrate are left, for analyzing the thermal insulation. Afterwards, the thermal insulation effect of the designed microstructure in the bonding coat of the three-layer structure is further studied. Column-like microstructures, filled with hollow ceramic microspheres in the interspace, are designed to improve the thermal insulation effect. The size parameters of the designed microstructure were optimized. The existence of the designed microstructure can significantly prolong the efficiency of thermal barrier coatings. The insulation temperature between the heating surface and lower surface of the substrate can exceed 300℃ and the thermal balance time has a big improvement of 240 s, more than 50%, than the traditional TBCs structure. Compared with the TBCs structure without microstructure, the designed microstructure can significantly improve the insulation temperature of more than 110℃.
基金financially supported by the National Natural Science Foundation of China(Nos.52022042 and 51590893)National Science and Technology Major Project(J2019-VII-00080148)。
文摘Opaque thermal barrier materials play a pivotal role in thermal radiation shielding of turbine blades,since the intensity of thermal radiation rapidly increases with the increase of operating temperature of gas turbines and has become a new and major concern for the durability of metallic blades.The conventional thermal barrier coating(TBC)materials such as YSZ and Gd_(2)Zr_(2)O_(7),however,are almost translucent to thermal radiation and are unable to protect the blades at such harsh environment.Although searching for new thermal barrier materials is significant,it is still a challenge to make the current TBC materials opaque without significantly modifying the composition or other physical properties.To cope with this challenge,GdMnO_(3) is incorporated as an absorptive second phase into Gd_(2)Zr_(2)O_(7) in this work,which is originally translucent(absorption coefficient 10^(1)-10^(2) m^(-1))in the near-infrared wavelengths.Intriguingly,with less than 5 wt.%GdMnO_(3),the Gd_(2)Zr_(2)O_(7)/GdMnO_(3) becomes opaque to thermal radiation and successfully refrains the rise of thermal conductivity at high temperatures.Meanwhile,the lattice thermal conductivity and mechanical properties are almost unchanged.The small polaron mechanism is confirmed for GdMnO_(3),leading to a high absorption coefficient(>10^(6) m^(-1))for near-infrared radiation.To understand the underling mechanism,a theoretical model is built to estimate the absorption coefficient of the Gd_(2)Zr_(2)O_(7)/GdMnO_(3) composites(>10^(4) m^(-1)).This paper proposes a powerful strategy to design thermal-radiation-shielding TBCs through incorporating minor second-phase particles with high-absorption mechanism,such as polaron excitation.
基金financially supported by the National Natural Science Foundation of China(No.51772275 and No.51972089)Distinguished Young Foundation of Henan Province(No.202300410355)。
文摘With continuous enhancement of gas-turbine inlet temperature and rapid increase of radiant heat transfer,thermal barrier coating(TBC)materials with a combination of low thermal conductivity and good high-temperature thermal radiation shielding performance play vital roles in ensuring the durability of metallic blades.However,yttria-stabilized zirconia(YSZ),as the state-of-the-art TBC and current industry standard,is unable to meet such demands since it is almost translucent to high-temperature thermal radiation.Besides,poor corrosion resistance of YSZ to molten calcia-magnesia-alumina-silicates(CMAS)also impedes its application in sand,dust,or volcanic ash laden environments.In order to improve the hightemperature thermal radiation shielding performance and CMAS resistance of YSZ and further reduce its thermal conductivity,two medium-entropy(ME)oxide ceramics,ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),were designed and prepared by pressureless sintering of binary powder compacts in this work.ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)presents cubic structure but a trace amount of secondary phase,while ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)displays a combination of tetragonal phase(81.6 wt.%)and cubic phase(18.4 wt.%).Both ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)and ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)possess better high-temperature thermal radiation shielding performance than YSZ.Especially,the high-temperature thermal radiation shielding performance of ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)is superior to that of ME(Y,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)due to its narrower band gap and correspondingly higher infrared absorbance(above 0.7)at the waveband of 1 to 5μm.The two ME oxides also display significantly lower thermal conductivity than YSZ and close thermal expansion coefficients(TECs)to YSZ and Ni-based superalloys.In addition,the two ME oxides possess excellent CMAS resistance.After attack by molten CMAS at 1250℃for 4 h,merely~2μm thick penetration layer has been formed and the structure below the penetration layer is still intact.These results demonstrate that ME(Me,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2)(Me=Y and Ta),especially ME(Ta,Ti)_(0.1)(Zr,Hf,Ce)_(0.9)O_(2),are promising thermal barrier materials for high-temperature thermal radiation shielding and CMAS blocking.
基金supported by Nature Science Foun-dations of China(NSFC)under grant Nos.U21B2052 and 52102057。
文摘Plasma spray physical vapor deposition(PS-PVD)(Gd_(0.9)Yb_(0.1))_(2)Zr_(2)O_(7)(GYbZ)thermal barrier coatings(TBCs)exhibited better silicate-phobicity than coatings produced by electron beam physical vapor depo-sition.In combination with PS-PVD and ultrafast laser direct writing technology,biomimetic structured GYbZ TBCs,with a triple-scale micro/nano surface microstructure,were obtained.Laser ablating on the PS-PVD GYbZ coating enhanced the surface roughness,improving its wear resistance without increasing the surface hardness.Furthermore,during the laser ablation processing,numerous nanoparticles were deposited in-situ in the gaps between columns of the coating,reducing the coating Young’s modulus.The simulated temperature field and heat flux field demonstrated that the presence of numerous interfaces between small columns of the PS-PVD coatings is beneficial to thermal insulation.However,laser ablation decreased the coating thickness,reducing the thermal insulation by around 20%-30%as compared to its PS-PVD counterpart,suggesting that a moderate increase in the coating thickness should be considered when designing an efficient TBC system.
基金National Natural Science Foundation of China (50771009, 50731001, 51071013)
文摘Thermal barrier coatings （TBCs） are mostly applied to hot components of advanced turbine engines to insulate the compo- nents from hot gas. The effect of sintering on thermal conductivity and thermal barrier effects of conventional plasma sprayed and nanostructured yttria stabilized zirconia （YSZ） thermal barrier coatings （TBCs） are investigated. Remarkable increase in thermal conductivity occurs to both typical coatings after heat treatment, The change of porosity is just the opposite. The grain size of the nanostructured zirconia coating increases more drastically with annealing time compared to that of the conventional plasma sprayed coating, which indicates that coating sintering makes more contributions to the thermal conductivity of the nanostructured coating than that of the conventional coating. Thermal barrier effect tests using temperature difference technique are performed on both coatings. The thermal barrier effects decrease with the increase of thermal conductivity after heat treat- ment and the decline seems more drastic in low thermal conductivity range. The decline in thermal barrier effects is about 80℃ for nanostructured coating after 100 h heat treatment, while the conventional coating reduces by less than 60 ℃ compared to the as-sprayed coating.
基金support from Yunnan Major Scientific and Technological Projects(No.202302AG050010)the General Project in Yunnan Province(Nos.202201AT070192 and 202101BE070001-011)+2 种基金the Open Project of Yunnan Precious Metals Laboratory(No.2023050240)the Yunnan Fundamental Research Projects(No.202201BE070001-008)Project of Innovation Team in Yunnan Province(No.202305AS350018).
文摘High fracture toughness,low thermal conductivity,and thermal expansion coefficient(TEC)matching substrate are essential for thermal barrier coatings(TBCs)and abradable seal coatings(ASCs).In this work,TmNbO_(4)/Tm_(3)NbO_(7) composites are designed and synthesized to increase their fracture toughness(KIC)and thermal insulation performance.Compared with those of TmNbO_(4)(KIC=2.2±0.1 MPa·m^(1/2))and Tm3NbO7(KIC=1.7±0.2 MPa·m^(1/2)),the increments in fracture toughness are as high as 50.0%and 91.1%,respectively.The highest toughness reaches 3.3±0.4 MPa·m1/2,which is attributed to the superior combination of grains between TmNbO4 and Tm3NbO7,as well as the simultaneous effects of microcracks and crack bridging and bifurcation.Accurate estimation of the effect of the interfacial thermal resistance on the thermal conductivity at low temperatures was achieved using the minimum interfacial thermal resistance model.A novel method is proposed to inhibit radiative heat transfer by utilizing oxides with glass-like thermal conductivity to suppress thermal radiation.Consequently,the TmNbO4/Tm3NbO7 composite maintains a low thermal conductivity(1.19–2.02 W·m^(−1)·K^(−1))at 1000°C.The high TECs(10.4×10^(−6)–11.8×10^(−6)·K^(−1) at 1500°C)and excellent high-temperature stability ensure that the designed TmNbO_(4)/Tm_(3)NbO_(7) composites can be used at temperatures reaching 1500°C.Accordingly,simultaneous enhancement of fracture toughness and thermal insulation in TmNbO_(4)/Tm_(3)NbO_(7) composites is effective,and the revealed mechanisms are useful for various materials.
