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
The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and...The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE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Project supported by the National High Technology Research and Development Program of China (No.2007AA04Z322)the State Key Development Program for Basic Research of China (No.2009CB320305)the Hundred Talents Plan of Chinese Academy of Sciences
文摘The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE
