To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxida...To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxidation stage,CeO_(2) accelerated the formation of a multiphase glass layer on the coating surface.The maximum oxidation rates of CeO_(2)-HfB2-SiC coatings with 1%,3%,and 5%CeO_(2) were 24.1%,20.3%,and 53.2%higher than that of the unmodified HfB2-SiC coating,respectively.In the stable oxidation stage,the maximum oxidation rates of coatings with 1%and 3%CeO_(2) decreased by 31.4%and 21.9%,respectively,demonstrating adequate inert protection.CeO_(2) is a“coagulant”and“stabilizer”in the composite glass layer.However,increasing the CeO_(2) content accelerates the reaction between the SiO_(2) glass phase and SiC,leading to a higher SiO_(2) consumption and reduced self-healing ability of the glass layer.The 1%CeO_(2)-60%HfB2-39%SiC coating showed improved glass layer viscosity and stability,moderate SiO_(2) consumption,and better self-healing ability,significantly boosting the oxidation protection of the coating.展开更多
The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_...The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_(2)-SiC dense layer embedded within a lightweight three-dimensional(3D)needled carbon fiber composite.Utilizing the volatility of ethanol and polycarbosilane,the ceramic slurry is selectively infused into targeted regions of the fibrous structure,optimizing the ZrB_(2)to MoSi_(2)ratio to enhance performance.The resulting dense layer exhibits exceptional emissivity,surpassing 0.90 in the 1-3μm range and exceeding 0.87 in the 2-14μm range.Moreover,it demonstrates remarkable oxidative ablation resistance.Specifically,at an optimized ZrB_(2)to MoSi_(2)ratio of 6:4,the dense layer achieves a minimal linear ablation rate of 0.015μm·s^(-1) under a 1.5 MW·m^(-2)oxyacetylene flame for 1000 s.Even after exposure to oxyacetylene ablation at surface temperatures of approximately 1750℃for 1000 s,the dense layer retains its structural integrity,highlighting its enduring oxidation resistance.The incorporation of MoSi_(2)not only enhances emissivity but also fortifies the ZrO_(2)and SiO_(2)oxide layers,crucial for environments with elevated oxygen levels,thereby mitigating the active oxidation of SiC.This combination of high emissivity and long-term oxidation resistance at ultra-high temperatures positions the ZrB_(2)-MoSi_(2)-SiC dense layer as an exceptionally promising candidate for advanced thermal protection in hypersonic vehicles.展开更多
In order to protect C/C composites from oxidation, SiC-MoSi2 composite coating was synthesized by chemical vapor infiltration /reaction （CVI/CVR） technology. A porous Mo layer was prefabricated on SiC coated C/C com...In order to protect C/C composites from oxidation, SiC-MoSi2 composite coating was synthesized by chemical vapor infiltration /reaction （CVI/CVR） technology. A porous Mo layer was prefabricated on SiC coated C/C composites, and then MoSi2 and SiC were subsequently prepared in a CVI /CVR process using methyltrichlorosilane （MTS） as precursor. The deposition and reaction mechanism of the MoSi2-SiC composite coating was investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The oxidation behavior of SiC-MoSi2 coated specimens was tested. The results show that the porous Mo layer can be densified with SiC phase decomposed from MTS, and transformed into SiC-MoSi2 by reacting with MTS as well. A dense composite coating was prepared with optimized deposition parameters. The coated specimen exhibits a good oxidation resistance with a little mass loss of 1.25% after oxidation at 1500 °C for 80 h.展开更多
文摘To improve the oxidation resistance of HfB_(2)-SiC coatings on carbon/carbon composites at 1700°C in air,CeO_(2) was introduced to improve oxygen blocking and its mechanism was investigated.During the rapid oxidation stage,CeO_(2) accelerated the formation of a multiphase glass layer on the coating surface.The maximum oxidation rates of CeO_(2)-HfB2-SiC coatings with 1%,3%,and 5%CeO_(2) were 24.1%,20.3%,and 53.2%higher than that of the unmodified HfB2-SiC coating,respectively.In the stable oxidation stage,the maximum oxidation rates of coatings with 1%and 3%CeO_(2) decreased by 31.4%and 21.9%,respectively,demonstrating adequate inert protection.CeO_(2) is a“coagulant”and“stabilizer”in the composite glass layer.However,increasing the CeO_(2) content accelerates the reaction between the SiO_(2) glass phase and SiC,leading to a higher SiO_(2) consumption and reduced self-healing ability of the glass layer.The 1%CeO_(2)-60%HfB2-39%SiC coating showed improved glass layer viscosity and stability,moderate SiO_(2) consumption,and better self-healing ability,significantly boosting the oxidation protection of the coating.
基金supported by the National Natural Science Foundation of China(Nos.52272060,51902067,51872066 and 52172041)the Key Program of National Natural Science Foundation of China(No.52032003)+5 种基金the Young Elite Scientists Sponsorship Program by CAST(No.2020QNRC001)China Postdoctoral Science Foundation(Nos.2019M651282 and 2022T150157)Heilongjiang Provincial Postdoctoral Science Foundation(Nos.LBH-Z19022 and LBH-TZ2207)Heilongjiang Touyan Innovation Team Program,Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2019-012)the Fundamental Research Funds for the Central Universities(No.FRFCU5710051022)the Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environments(No.JCKYS2022603C011).
文摘The rapid evolution of hypersonic vehicle technologies necessitates robust thermal protection systems capable of withstanding extreme oxidative ablation.This study introduces a novel gradient-architected ZrB_(2)-MoSi_(2)-SiC dense layer embedded within a lightweight three-dimensional(3D)needled carbon fiber composite.Utilizing the volatility of ethanol and polycarbosilane,the ceramic slurry is selectively infused into targeted regions of the fibrous structure,optimizing the ZrB_(2)to MoSi_(2)ratio to enhance performance.The resulting dense layer exhibits exceptional emissivity,surpassing 0.90 in the 1-3μm range and exceeding 0.87 in the 2-14μm range.Moreover,it demonstrates remarkable oxidative ablation resistance.Specifically,at an optimized ZrB_(2)to MoSi_(2)ratio of 6:4,the dense layer achieves a minimal linear ablation rate of 0.015μm·s^(-1) under a 1.5 MW·m^(-2)oxyacetylene flame for 1000 s.Even after exposure to oxyacetylene ablation at surface temperatures of approximately 1750℃for 1000 s,the dense layer retains its structural integrity,highlighting its enduring oxidation resistance.The incorporation of MoSi_(2)not only enhances emissivity but also fortifies the ZrO_(2)and SiO_(2)oxide layers,crucial for environments with elevated oxygen levels,thereby mitigating the active oxidation of SiC.This combination of high emissivity and long-term oxidation resistance at ultra-high temperatures positions the ZrB_(2)-MoSi_(2)-SiC dense layer as an exceptionally promising candidate for advanced thermal protection in hypersonic vehicles.
基金Projects(51221001,51272213,51072166)supported by the National Natural Science Foundation of ChinaProject(GBKY1021)supported by the Fundamental Research Foundation of Northwestern Polytechnical University,ChinaProject(B08040)supported by Program of Introducing Talents of Discipline to Universities,China
文摘In order to protect C/C composites from oxidation, SiC-MoSi2 composite coating was synthesized by chemical vapor infiltration /reaction （CVI/CVR） technology. A porous Mo layer was prefabricated on SiC coated C/C composites, and then MoSi2 and SiC were subsequently prepared in a CVI /CVR process using methyltrichlorosilane （MTS） as precursor. The deposition and reaction mechanism of the MoSi2-SiC composite coating was investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The oxidation behavior of SiC-MoSi2 coated specimens was tested. The results show that the porous Mo layer can be densified with SiC phase decomposed from MTS, and transformed into SiC-MoSi2 by reacting with MTS as well. A dense composite coating was prepared with optimized deposition parameters. The coated specimen exhibits a good oxidation resistance with a little mass loss of 1.25% after oxidation at 1500 °C for 80 h.
