Multicomponent(Hf,Zr,Ta)C ceramics are promising candidates for ablation-resistant coating materials applied in ultrahightemperature environments.However,the influence of compositional variations on their ablation beh...Multicomponent(Hf,Zr,Ta)C ceramics are promising candidates for ablation-resistant coating materials applied in ultrahightemperature environments.However,the influence of compositional variations on their ablation behavior remains insufficiently understood.In this study,the effect of Ta content on the ablation resistance of(Hf,Zr,Ta)C coatings was systematically investigated.Moderate Ta addition promotes the densification of oxide scales,whereas excessive Ta reduces the thermochemical stability of the oxide scale,leading to increased ablation damage.The optimized composition,the T15 coating,exhibits superior ablation resistance,maintaining structural integrity for 300 s under an~2160℃oxyacetylene flame.This enhancement is attributed to the co-formation of the(Hf,Zr,Ta)O_(2)and(Hf,Zr)_(6)Ta_(2)O_(17)phases.Ta5+partially dissolves into(Hf,Zr)O_(2)(~5 at%),reducing the oxygen vacancy concentration and improving the oxidation resistance.Additionally,the Ta-rich liquid phase generated from the decomposition of(Hf,Zr)_(6)Ta_(2)O_(17)enhances oxide scale densification and contributes to structural stability during cooling through peritectic transformation.These results demonstrate that non-equimolar multicomponent carbides offer a feasible strategy for improving the ablation resistance of ultrahigh-temperature coatings.展开更多
Sesquioxides such as Y_(2)O_(3)and Sc_(2)O_(3)are important optical materials,but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400℃.In this work,a ser...Sesquioxides such as Y_(2)O_(3)and Sc_(2)O_(3)are important optical materials,but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400℃.In this work,a series of(Y_(1−x)Scx)_(2)O_(3)transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives,and the effect of scandium(Sc)content(x)on the crystal structure and optical/thermal/mechanical properties was evaluated.Y_(2)O_(3)and Sc_(2)O_(3)form a complete solid solution with a cubic bixbyite structure.The formation of(Y_(1−x)Scx)_(2)O_(3)solid solution promotes the densification of ceramics,leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35–8μm.In particular,the in-line transmittance in the range of 0.6–6μm remains above 80%for(Y_(1−x)Scx)_(2)O_(3)with x=0.23–0.31,while the pristine Y_(2)O_(3)and Sc_(2)O_(3)are opaque.Moreover,the mechanical properties including Vickers hardness(HV),fracture toughness(KIC),and biaxial flexural strength(δb)are evidently enhanced due to the solid solution strengthening,while the thermal conductivity(k)is reduced due to the reduction of photon free path.This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxide transparent ceramics with high optical and mechanical quality.展开更多
基金supported by the National Key R&D Program of China(No.2021YFA0715803)the National Natural Science Foundation of China(Nos.52293373,52302091,and 52130205)+1 种基金the Joint Fund of Henan Province Science and Technology R&D Program(Nos.225200810002 and 235200810030)the Fundamental Research Funds of Henan Academy of Sciences(No.240621061).
文摘Multicomponent(Hf,Zr,Ta)C ceramics are promising candidates for ablation-resistant coating materials applied in ultrahightemperature environments.However,the influence of compositional variations on their ablation behavior remains insufficiently understood.In this study,the effect of Ta content on the ablation resistance of(Hf,Zr,Ta)C coatings was systematically investigated.Moderate Ta addition promotes the densification of oxide scales,whereas excessive Ta reduces the thermochemical stability of the oxide scale,leading to increased ablation damage.The optimized composition,the T15 coating,exhibits superior ablation resistance,maintaining structural integrity for 300 s under an~2160℃oxyacetylene flame.This enhancement is attributed to the co-formation of the(Hf,Zr,Ta)O_(2)and(Hf,Zr)_(6)Ta_(2)O_(17)phases.Ta5+partially dissolves into(Hf,Zr)O_(2)(~5 at%),reducing the oxygen vacancy concentration and improving the oxidation resistance.Additionally,the Ta-rich liquid phase generated from the decomposition of(Hf,Zr)_(6)Ta_(2)O_(17)enhances oxide scale densification and contributes to structural stability during cooling through peritectic transformation.These results demonstrate that non-equimolar multicomponent carbides offer a feasible strategy for improving the ablation resistance of ultrahigh-temperature coatings.
基金This research was supported by Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZZ113)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA22010301)。
文摘Sesquioxides such as Y_(2)O_(3)and Sc_(2)O_(3)are important optical materials,but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400℃.In this work,a series of(Y_(1−x)Scx)_(2)O_(3)transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives,and the effect of scandium(Sc)content(x)on the crystal structure and optical/thermal/mechanical properties was evaluated.Y_(2)O_(3)and Sc_(2)O_(3)form a complete solid solution with a cubic bixbyite structure.The formation of(Y_(1−x)Scx)_(2)O_(3)solid solution promotes the densification of ceramics,leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35–8μm.In particular,the in-line transmittance in the range of 0.6–6μm remains above 80%for(Y_(1−x)Scx)_(2)O_(3)with x=0.23–0.31,while the pristine Y_(2)O_(3)and Sc_(2)O_(3)are opaque.Moreover,the mechanical properties including Vickers hardness(HV),fracture toughness(KIC),and biaxial flexural strength(δb)are evidently enhanced due to the solid solution strengthening,while the thermal conductivity(k)is reduced due to the reduction of photon free path.This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxide transparent ceramics with high optical and mechanical quality.
