As for the air plasma sprayed ZrB_(2)-based coatings,B content change caused by inevitable oxidation is predictable but commonly ignored.Affected by air plasma flame,the B element loss and residual B_(2) O_(3) in the ...As for the air plasma sprayed ZrB_(2)-based coatings,B content change caused by inevitable oxidation is predictable but commonly ignored.Affected by air plasma flame,the B element loss and residual B_(2) O_(3) in the sprayed ZrB_(2) coating were observed.Moreover,how the B content change affects the microstructure,phase evolution,and ablation resistance(2.4 MW/m^(2),60 s)of ZrB_(2)-based coatings with different sec-ondary phases(SiC,MoSi_(2),and TaC)was investigated.The B element loss contributed to the increase in surface temperature and the decline in the sintering degree of the ZrO_(2) layer.The evaporation of residual B_(2)O_(3) caused damage to the coating structure in the form of pores,whose negative effect was enhanced and reduced by MoSi_(2) and TaC secondary phases,respectively.This work will provide some insight into thermally sprayed non-oxide ceramic coatings in the atmosphere.展开更多
Ultra-high temperature ceramics(UHTCs)exhibit a unique combination of excellent properties,including ultra-high melting point,excellent chemical stability,and good oxidation resistance,which make them promising candid...Ultra-high temperature ceramics(UHTCs)exhibit a unique combination of excellent properties,including ultra-high melting point,excellent chemical stability,and good oxidation resistance,which make them promising candidates for aerospace and nuclear applications.However,the degradation of hightemperature strength is one of the main limitations for their ultra-high temperature applications.Thus,searching for mechanisms that can help to develop high-performance UHTCs with good high-temperature mechanical properties is urgently needed.To achieve this goal,grain boundary segregation of a series of carbides,including conventional,medium entropy,and high entropy transition metal carbides,i.e.,Zr_(0.95)W_(0.05)C,TiZrHfC_(3),ZrHfNbTaC_(4),TiZrHfNbTaC_(5),were studied by atomistic simulations with a fitted Deep Potential(DP),and the effects of segregation on grain boundary strength were emphasized.For all the studied carbides,grain boundary segregations are realized,which are dominated by the atomic size effect.In addition,tensile simulations indicate that grain boundaries(GBs)will usually be strengthened due to segregation.Our simulation results reveal that grain boundary segregation may be a universal mechanism in enhancing the high-temperature strength of both conventional UHTCs and medium/high entropy UHTCs,since GBs play a key role in controlling the fracture of UHTCs at elevated temperatures.展开更多
Finding the optimum balance between strength and toughness,as well as acquiring reliable thermal shock resistance and oxidation resistance,has always been the most concerned topic in the discussion of ultra-high tempe...Finding the optimum balance between strength and toughness,as well as acquiring reliable thermal shock resistance and oxidation resistance,has always been the most concerned topic in the discussion of ultra-high temperature ceramic composites.Herein,PyC modified 3D carbon fiber is used to reinforce ultra-high temperature ceramic(UHTC).The macroscopic block composite with large size is successfully fabricated through low temperature sintering at 1300℃without pressure.The prepared PyC modified 3D C_(f)/ZrC-SiC composites simultaneously possess excellent physical and chemical stability under the synergistic effect of PyC interface layer and low temperature 1/2 sintering without pressure.The fracture toughness is increased in magnitude to 13.05±1.72 MPa·m^(1/2)accompanied by reliable flexural strength of 251±27 MPa.After rapid thermal shock spanning from room temperature(RT)to 1200℃,there are no visible surface penetrating cracks,spalling,or structural fragmentation.The maximum critical temperature difference reaches 875℃,which is nearly three times higher than that of traditional monolithic ceramics.The haunting puzzle of intrinsic brittleness and low damage tolerance are resolved fundamentally.Under the protection of PyC interface layer,the carbon fibers around oxide layer and matrix remain structure intact after static oxidation at 1500℃for 30 min.The oxide layer has reliable physical and chemical stability and resists the erosion from fierce oxidizing atmosphere,ensuring the excellent oxidation resistance of the composites.In a sense,the present work provides promising universality in designability and achievement of 3D carbon fiber reinforced ceramic composites.展开更多
In materials science,a significant correlation often exists between material input parameters and their corresponding performance attributes.Nevertheless,the inherent challenges associated with small data obscure thes...In materials science,a significant correlation often exists between material input parameters and their corresponding performance attributes.Nevertheless,the inherent challenges associated with small data obscure these statistical correlations,impeding machine learning models from effectively capturing the underlying patterns,thereby hampering efficient optimization of material properties.This work presents a novel active learning framework that integrates generative adversarial networks(GAN)with a directionally constrained expected absolute improvement(EAI)acquisition function to accelerate the discovery of ultra-high temperature ceramics(UHTCs)using small data.The framework employs GAN for data augmentation,symbolic regression for feature weight derivation,and a self-developed EAI function that incorporates input feature importance weighting to quantify bidirectional deviations from zero ablation rate.Through only two iterations,this framework successfully identified the optimal composition of HfB_(2)-3.52SiC-5.23TaSi_(2),which exhibits robust near-zero ablation rates under plasma ablation at 2500℃ for 200 s,demonstrating superior sampling efficiency compared to conventional active learning approaches.Microstructural analysis reveals that the exceptional performance stems from the formation of a highly viscous HfO_(2)-SiO_(2)-Ta_(2)O_(5)-HfSiO_(4)-Hf_(3)(BO_(3))_(4) oxide layer,which provides effective oxygen barrier protection.This work demonstrates an efficient and universal approach for rapid materials discovery using small data.展开更多
Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,...Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,which facilitated the effective incorporation of ZrB_(2) powder into the carbon fiber preform.A single IVI cycle reduced the porosity of the preform from∼77%to∼40%.Microstructural analysis revealed a preferential distribution of ZrB2 powders within random layers and pyrolytic carbon effectively bridging the ceramic particles and fibers.Due to the hierarchical 0°/90°carbon fiber architecture,as fabricated Cf/ZrB_(2) composites exhibited anisotropy in mechanical and physical properties.Vertically oriented com-posites demonstrated higher compressive strain and low thermal conductivity(1.00-2.59 W m^(−1) K^(−1) from 298 to 1173 K).In contrast,horizontally oriented specimens exhibited higher compressive strength(60.77±20.30 MPa)and thermal conductivity(1.6-4.5 W m^(−1) K^(−1) from 298 to 1173 K).Furthermore,the continuous Cf endowed the composites with a positive temperature-dependent electrical conductiv-ity characteristic,not only contributed to their higher electrical conductivity values,but also was helpful for maintaining the excellent EMI shielding effectiveness(19.80-22.51 dB)of Cf/ZrB_(2) up to 800℃without obvious degradation.Considering the low-density characteristics of as-prepared composites,their specific performance metrics demonstrate good competitiveness compared to those fabricated via alternative processes.展开更多
Carbon fiber reinforced ultra-high temperature ceramic （UHTC） composites, consisting of carbon fibers embedded in a UHTC-matrix or a C-SiC-UHTC-matrix, are deemed as the most viable class of materials that can overc...Carbon fiber reinforced ultra-high temperature ceramic （UHTC） composites, consisting of carbon fibers embedded in a UHTC-matrix or a C-SiC-UHTC-matrix, are deemed as the most viable class of materials that can overcome the poor fracture toughness and thermal shock resistance of monolithic UHTC ma- terials, and also improve the oxidation resistance and ablation resistance of C/C and C/SiC composites at ultra-high temperatures. In this review, we summarize the different processing routes of the compos- ites based on the UHTC introducing methods, including chemical vapor infiltration/deposition （CVI/D）, precursor infiltration and pyrolysis （PIP）, reactive melt infiltration （RMI）, slurry infiltration （SI）. in-sito reaction, hot pressing （HP）, etc; and the advantages and drawbacks of each method are briefly dis- cussed. The carbon fiber reinforced UHTC composites can be highly tailorable materials in terms of fiber. interface, and matrix. From the perspective of service environmental applications for engine propul- sions anti hypersonic vehicles, the material designs （mainly focusing on the composition, quantity, structure of matrix, as well as the architecture of carbon fibers, UHTCs and pores）, their relevant processing routes and properties （emphasizing on the mechanical and ablation properties） are discussed in this paper. In addition, we propose a material architecture to realize the multi-function through changing the distri- bution of carbon fibers, UHTCs and pores, which will be an important issue for future development of carbon fiber reinforced UHTC composites.展开更多
Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densificat...Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures.In order to overcome these obstacles,herein,porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C was prepared by a simple method combing in-situ reaction and partial sintering.Porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm^2·s^-1and good high temperature stability.The combination of these properties renders porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))Cpromising as light-weight ultrahigh temperature thermal insulation materials.展开更多
Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeab...Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeability and high porosity are general requirements for porous media of transpiration cooling systems.In this work,a new porous high entropy metal hexaboride(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 is designed and prepared by the in-situ reaction/partial sintering method.Two reaction routes are designed to synthesize(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6,including boron thermal reduction and borocarbon thermal reduction.The as-prepared porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 ceramics possess homogeneous microstructure and exhibit low density,high porosity,high compressive strength and high permeability.The combination of these properties makes porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 promising as a candidate porous media for various transpiration cooling applications.展开更多
基金supported by the National Key R&D Program of China(No.2021YFA0715800)the Science Center for Gas Turbine Project(No.P2021-A-IV-003-001)+1 种基金the National Nat-ural Science Foundation of China(No.52125203)the Innova-tion Foundation for Doctor Dissertation of Northwestern Polytech-nical University(No.CX2021007)。
文摘As for the air plasma sprayed ZrB_(2)-based coatings,B content change caused by inevitable oxidation is predictable but commonly ignored.Affected by air plasma flame,the B element loss and residual B_(2) O_(3) in the sprayed ZrB_(2) coating were observed.Moreover,how the B content change affects the microstructure,phase evolution,and ablation resistance(2.4 MW/m^(2),60 s)of ZrB_(2)-based coatings with different sec-ondary phases(SiC,MoSi_(2),and TaC)was investigated.The B element loss contributed to the increase in surface temperature and the decline in the sintering degree of the ZrO_(2) layer.The evaporation of residual B_(2)O_(3) caused damage to the coating structure in the form of pores,whose negative effect was enhanced and reduced by MoSi_(2) and TaC secondary phases,respectively.This work will provide some insight into thermally sprayed non-oxide ceramic coatings in the atmosphere.
基金supported by the National Natural Science Foundation of China(No.51672064)。
文摘Ultra-high temperature ceramics(UHTCs)exhibit a unique combination of excellent properties,including ultra-high melting point,excellent chemical stability,and good oxidation resistance,which make them promising candidates for aerospace and nuclear applications.However,the degradation of hightemperature strength is one of the main limitations for their ultra-high temperature applications.Thus,searching for mechanisms that can help to develop high-performance UHTCs with good high-temperature mechanical properties is urgently needed.To achieve this goal,grain boundary segregation of a series of carbides,including conventional,medium entropy,and high entropy transition metal carbides,i.e.,Zr_(0.95)W_(0.05)C,TiZrHfC_(3),ZrHfNbTaC_(4),TiZrHfNbTaC_(5),were studied by atomistic simulations with a fitted Deep Potential(DP),and the effects of segregation on grain boundary strength were emphasized.For all the studied carbides,grain boundary segregations are realized,which are dominated by the atomic size effect.In addition,tensile simulations indicate that grain boundaries(GBs)will usually be strengthened due to segregation.Our simulation results reveal that grain boundary segregation may be a universal mechanism in enhancing the high-temperature strength of both conventional UHTCs and medium/high entropy UHTCs,since GBs play a key role in controlling the fracture of UHTCs at elevated temperatures.
基金supported by Key Program of National Natural Science Foundation of China(No.52032003)National Natural Science Foundation of China(Nos.51872059 and 51772061)+2 种基金Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments(No.6142905202112)China Postdoctoral Science Foundation(No.2021M690817)Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z20144).
文摘Finding the optimum balance between strength and toughness,as well as acquiring reliable thermal shock resistance and oxidation resistance,has always been the most concerned topic in the discussion of ultra-high temperature ceramic composites.Herein,PyC modified 3D carbon fiber is used to reinforce ultra-high temperature ceramic(UHTC).The macroscopic block composite with large size is successfully fabricated through low temperature sintering at 1300℃without pressure.The prepared PyC modified 3D C_(f)/ZrC-SiC composites simultaneously possess excellent physical and chemical stability under the synergistic effect of PyC interface layer and low temperature 1/2 sintering without pressure.The fracture toughness is increased in magnitude to 13.05±1.72 MPa·m^(1/2)accompanied by reliable flexural strength of 251±27 MPa.After rapid thermal shock spanning from room temperature(RT)to 1200℃,there are no visible surface penetrating cracks,spalling,or structural fragmentation.The maximum critical temperature difference reaches 875℃,which is nearly three times higher than that of traditional monolithic ceramics.The haunting puzzle of intrinsic brittleness and low damage tolerance are resolved fundamentally.Under the protection of PyC interface layer,the carbon fibers around oxide layer and matrix remain structure intact after static oxidation at 1500℃for 30 min.The oxide layer has reliable physical and chemical stability and resists the erosion from fierce oxidizing atmosphere,ensuring the excellent oxidation resistance of the composites.In a sense,the present work provides promising universality in designability and achievement of 3D carbon fiber reinforced ceramic composites.
基金supported by the Natural Science Foundation of China[grant numbers 52302093]Natural Science Foundation of Jiangxi Province[grant numbers 20224BAB204021].
文摘In materials science,a significant correlation often exists between material input parameters and their corresponding performance attributes.Nevertheless,the inherent challenges associated with small data obscure these statistical correlations,impeding machine learning models from effectively capturing the underlying patterns,thereby hampering efficient optimization of material properties.This work presents a novel active learning framework that integrates generative adversarial networks(GAN)with a directionally constrained expected absolute improvement(EAI)acquisition function to accelerate the discovery of ultra-high temperature ceramics(UHTCs)using small data.The framework employs GAN for data augmentation,symbolic regression for feature weight derivation,and a self-developed EAI function that incorporates input feature importance weighting to quantify bidirectional deviations from zero ablation rate.Through only two iterations,this framework successfully identified the optimal composition of HfB_(2)-3.52SiC-5.23TaSi_(2),which exhibits robust near-zero ablation rates under plasma ablation at 2500℃ for 200 s,demonstrating superior sampling efficiency compared to conventional active learning approaches.Microstructural analysis reveals that the exceptional performance stems from the formation of a highly viscous HfO_(2)-SiO_(2)-Ta_(2)O_(5)-HfSiO_(4)-Hf_(3)(BO_(3))_(4) oxide layer,which provides effective oxygen barrier protection.This work demonstrates an efficient and universal approach for rapid materials discovery using small data.
基金financially supported by the National Natural Science Foundation of China(Nos.52332003,52293373,52022072 and 52202067)the Hubei Provincial Natural Science Foundation of China(Distinguished Young Scholars No.2022CFA042)Independent Innovation Projects of Hubei Longzhong Laboratory(No.2022ZZ-10).
文摘Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,which facilitated the effective incorporation of ZrB_(2) powder into the carbon fiber preform.A single IVI cycle reduced the porosity of the preform from∼77%to∼40%.Microstructural analysis revealed a preferential distribution of ZrB2 powders within random layers and pyrolytic carbon effectively bridging the ceramic particles and fibers.Due to the hierarchical 0°/90°carbon fiber architecture,as fabricated Cf/ZrB_(2) composites exhibited anisotropy in mechanical and physical properties.Vertically oriented com-posites demonstrated higher compressive strain and low thermal conductivity(1.00-2.59 W m^(−1) K^(−1) from 298 to 1173 K).In contrast,horizontally oriented specimens exhibited higher compressive strength(60.77±20.30 MPa)and thermal conductivity(1.6-4.5 W m^(−1) K^(−1) from 298 to 1173 K).Furthermore,the continuous Cf endowed the composites with a positive temperature-dependent electrical conductiv-ity characteristic,not only contributed to their higher electrical conductivity values,but also was helpful for maintaining the excellent EMI shielding effectiveness(19.80-22.51 dB)of Cf/ZrB_(2) up to 800℃without obvious degradation.Considering the low-density characteristics of as-prepared composites,their specific performance metrics demonstrate good competitiveness compared to those fabricated via alternative processes.
基金supported by the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation NSFC and CASC, China (Grant No. U1537204)the Research Fund of Youth Innovation Promotion Association CAS, China (Grant No. 2014171)
文摘Carbon fiber reinforced ultra-high temperature ceramic （UHTC） composites, consisting of carbon fibers embedded in a UHTC-matrix or a C-SiC-UHTC-matrix, are deemed as the most viable class of materials that can overcome the poor fracture toughness and thermal shock resistance of monolithic UHTC ma- terials, and also improve the oxidation resistance and ablation resistance of C/C and C/SiC composites at ultra-high temperatures. In this review, we summarize the different processing routes of the compos- ites based on the UHTC introducing methods, including chemical vapor infiltration/deposition （CVI/D）, precursor infiltration and pyrolysis （PIP）, reactive melt infiltration （RMI）, slurry infiltration （SI）. in-sito reaction, hot pressing （HP）, etc; and the advantages and drawbacks of each method are briefly dis- cussed. The carbon fiber reinforced UHTC composites can be highly tailorable materials in terms of fiber. interface, and matrix. From the perspective of service environmental applications for engine propul- sions anti hypersonic vehicles, the material designs （mainly focusing on the composition, quantity, structure of matrix, as well as the architecture of carbon fibers, UHTCs and pores）, their relevant processing routes and properties （emphasizing on the mechanical and ablation properties） are discussed in this paper. In addition, we propose a material architecture to realize the multi-function through changing the distri- bution of carbon fibers, UHTCs and pores, which will be an important issue for future development of carbon fiber reinforced UHTC composites.
基金supported by the National Natural Science Foundation of China under Grant Nos. U1435206 and 51672064Beijing Municipal Science & Technology Commission under Grant No. D161100002416001
文摘Porous ultra-high temperature ceramics(UHTCs)are promising for ultrahigh-temperature thermal insulation applications.However,the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures.In order to overcome these obstacles,herein,porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C was prepared by a simple method combing in-situ reaction and partial sintering.Porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1μm,which exhibits high porosity of 80.99%,high compressive strength of 3.45 MPa,low room temperature thermal conductivity of 0.39 W·m^-1K^-1,low thermal diffusivity of 0.74 mm^2·s^-1and good high temperature stability.The combination of these properties renders porous high entropy(Zr(0.2)Hf(0.2)Ti(0.2)Nb(0.2)Ta(0.2))Cpromising as light-weight ultrahigh temperature thermal insulation materials.
基金financial supported by the National Natural Science Foundation of China(Nos.51672064 and U1435206).
文摘Transpiration cooling technique is a reusable and high-efficiency thermal protection system(TPS),which is potential to improve the reusability and security of re-entry space vehicle.Relatively low density,high permeability and high porosity are general requirements for porous media of transpiration cooling systems.In this work,a new porous high entropy metal hexaboride(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 is designed and prepared by the in-situ reaction/partial sintering method.Two reaction routes are designed to synthesize(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6,including boron thermal reduction and borocarbon thermal reduction.The as-prepared porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 ceramics possess homogeneous microstructure and exhibit low density,high porosity,high compressive strength and high permeability.The combination of these properties makes porous HE(Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 promising as a candidate porous media for various transpiration cooling applications.
