C/C-ZrC composites were prepared by precursor infiltration and pyrolysis using the organic zirconium as precursor.The conversion mechanisms of the precursors such as the thermal behavior,structural evolution,phase com...C/C-ZrC composites were prepared by precursor infiltration and pyrolysis using the organic zirconium as precursor.The conversion mechanisms of the precursors such as the thermal behavior,structural evolution,phase composition,microstructure,composition of the precursors and products were analyzed by thermal gravimetric analyzer,Fourier transform infrared spectrometer,X-ray diffraction and scanning electron microscope.The results indicate that the ZrC precursor transforms to inorganic ZrO2 from room temperature to 1200 ℃,then reduces to ZrC at 1600 ℃ through the carbothermal reduction reaction.The microstructure of the C/C-ZrC composites was also investigated.The composites exhibit an interesting structure,a coating composed of ZrC ceramic covers the exterior of the composite,and the ZrC ceramic is embedded in the pores of the matrix inside the composite.展开更多
Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coati...Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.展开更多
HfCeSiC-modified carbon/carbon composite(C/CeHfCeSiC)sharp leading edges(SLEs)were prepared via precursor infiltration and pyrolysis for potential hypersonic applications.The effect of SiC proportion on the ablation b...HfCeSiC-modified carbon/carbon composite(C/CeHfCeSiC)sharp leading edges(SLEs)were prepared via precursor infiltration and pyrolysis for potential hypersonic applications.The effect of SiC proportion on the ablation behavior of the SLEs under oxyacetylene flames with 2.38 MW/m^(2) and 4.18 MW/m^(2) was investigated.The preferred sample with a volume ratio of HfC to SiC of 0.74 possessed almost zero degradation(linear recession rate 0.6 mm/s)up to a temperature of 2371℃.As the temperature increases to 2527℃ in the latter condition,the SLE with less SiC(the volume ratio of HfC to SiC is 1.10)exhibited a linear recession rate of 1.03 mm/s during cyclic ablation of 3×40 s.Relatively more SiC addition is favorable under lower heat flux due to the better oxygen barrier performance of the scale.However,superior ablation resistance is available under higher heat flux with less SiC addition due to the higher thermal stability of the resulting oxide scale.展开更多
Carbon fiber reinforced silicon carbide-hafnium carbide(C/SiC-HfC)composite was prepared by precursor infiltration and pyrolysis process.Then,ablation behavior of C/SiC-HfC was evaluated in plasma wind tunnel.It was f...Carbon fiber reinforced silicon carbide-hafnium carbide(C/SiC-HfC)composite was prepared by precursor infiltration and pyrolysis process.Then,ablation behavior of C/SiC-HfC was evaluated in plasma wind tunnel.It was found that oxide layer formed during ablation significantly influenced the surface temperature.Formation of dense HfO2 SiO2 layer under low heat flux led to stable surface temperature.Silica(SiO2)on the surface was gradually consumed when heat flux increased,resulting in conversion of HfO2-SiO2 on the surface to HfO2.Converted HfO2 with high catalytic cofficient absorbed more energy,causing gradual increase in the surface temperature.Formed oxide layer was destroyed at high heat flux and high stagnation point pressure.After carbon fiber lost the protection of HfO2-SiO2 layer,it burned immediately,leading to surface temperature jump.展开更多
To further improve the oxidation resistance of polymer derived ceramic(PDC)composites in harsh environments,Cf/SiC/SiHfBOC composites were prepared by chemical vapor infiltration(CVI)and precursor impregnation pyrolys...To further improve the oxidation resistance of polymer derived ceramic(PDC)composites in harsh environments,Cf/SiC/SiHfBOC composites were prepared by chemical vapor infiltration(CVI)and precursor impregnation pyrolysis(PIP)methods.The weight retention change,mechanical properties,and microstructure of C/SiC/SiHfBOC before and after oxidation in air were studied in details.Microscopic analyses showed that only the interface between the ceramics and fibers was oxidized to some extent,and hafnium had been enriched on the composite surface after oxidizing at different temperature.The main oxidation products of Cf/SiC/SiHfBOC composites were Hf0_(2)and HfSi04 after oxidation at 1500℃for 60 min.Moreover,the weight retention ratio and compressive strength of the Cf/SiC/SiHfBOC composites are 83.97%and 23.88±3.11 MPa,respectively.It indicates that the Cf/SiC/SiHfBOC composites should be promising to be used for a short time in the oxidation environment at 1500℃.展开更多
A preceramic polymer, polyzirconosaal （PZSA）, was synthesized by the ligand-exchange reaction between polyzirconoxane （PZO） and salicyl alcohol （SA）. The precursor was air-stable and exhibited excellent solubili...A preceramic polymer, polyzirconosaal （PZSA）, was synthesized by the ligand-exchange reaction between polyzirconoxane （PZO） and salicyl alcohol （SA）. The precursor was air-stable and exhibited excellent solubility and rheology. These properties are useful for the processing of C/C-ZrC composites v/a precursor infiltration and pyrolysis （PIP） process. The polymer to ceramic conversion was investigated by TG, XRD and TEM. Nanosized ZrC was formed by pyrolysis of this precursor at 1300 ℃ in argon with ceramic yield of 57.8%.展开更多
Directional thermal transport materials enable anisotropic heat flow,thereby enhancing the efficiency of thermal management systems.These materials have found broad applications in aerospace,elec-tronics,and automotiv...Directional thermal transport materials enable anisotropic heat flow,thereby enhancing the efficiency of thermal management systems.These materials have found broad applications in aerospace,elec-tronics,and automotive industries.Silicon carbide(SiC)based composites,with their exceptional properties including high modulus,thermal stability,and superior thermal conductivity,serve as an ideal structural material.Strategic manipulation over microstructure and composition enables direc-tional thermal management,expanding applicability in thermal management and achieving structural-functional integration.By combining selective laser printing with precursor impregnation and pyrolysis(PIP),this work presents an innovative approach to fabricating thermally anisotropic C_(f)/SiC composites that integrate both structural and functional properties.The optimized composite(20%(in volume)chopped C_(f))exhibited high fiber alignment(f_(p)=0.7677)and pronounced thermal anisotropy,with thermal conductivities of 70.14 W/(m·K)perpendicular and 38.87 W/(m·K)parallel to the printing plane(anisotropy ratio:1.8).This directional heat transport,enabled by fiber orientation and phonon scat-tering control,is critical for advanced thermal management.The composite also maintained good mechanical strength,exhibiting a flexural strength of(150.4±9.8)MPa parallel to the printing plane,finalizing in a structural and functional integration.展开更多
In this paper,a high-yield Hf-modified SiHfBOC ceramic precursor was developed,and a high-pressure assisted impregnation pyrolysis method was proposed to achieve the preparation of 3D PyC–Cf/SiHfBOC composites.This h...In this paper,a high-yield Hf-modified SiHfBOC ceramic precursor was developed,and a high-pressure assisted impregnation pyrolysis method was proposed to achieve the preparation of 3D PyC–Cf/SiHfBOC composites.This high-pressure assisted impregnation method significantly improves impregnation filling effect of the precursor in and between fiber bundles compared to dozens of traditional impregnation cycles.After undergoing just 9 precursor infiltration pyrolysis(PIP)cycles,the composites achieved relative density of approximately 90%and density of 1.64 g/cm^(3).The critical temperature difference of the 3D PyC–Cf/SiHfBOC composites after the shock of room temperature(RT)–1000℃is as high as 650℃,which is twice that of traditional ceramic materials,showing good thermal shock resistance.Under the effect of Hf modification,a dense HfO_(2)–SiO_(2)oxide layer(thickness of 93μm)was formed in situ on the surface of the 3D PyC–Cf/SiHfBOC composites,effectively preventing further erosion of the composite matrix by high-temperature oxidation gas.Even in the ultra-high-temperature oxygen-containing environment at 1800℃,it still exhibits an excellent non-ablative result(with a linear ablation rate of 0.83×10^(−4)mm/s).This work not only enriches the basic research on lightweight ultra-high-temperature ceramic composites converted from Hf ceramic precursors,but also provides strong technical support for their applications in ultra-high-temperature non-ablative thermal protection materials for high-speed aircraft.展开更多
Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation proc...Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation process hinder their broader application.In this study,novel mullite anti-gyroid/SiC gyroid metastructures are designed to integrate the mechanical and electromagnetic wave(EMW)absorption properties of composite materials.Mullite anti-gyroid/SiC gyroid composites are fabricated utilizing a combination of digital light processing(DLP)three-dimensional(3D)printing and precursor infiltration and pyrolysis(PiP)processes.Through the modulation of structural units,the electromagnetic parameters can be effectively regulated,thus improving the impedance matching characteristics of the composites.The structural composites show outstanding EMW absorption properties,with a minimum reflection loss of-54 dB at a thickness of 1.9 mm and an effective absorption bandwidth of 3.20 GHz at a thickness of 2.2 mm.Furthermore,the PIP process significantly enhances the mechanical properties of the composites;compared with those of the mullite/SiC ceramics,the flexural strength of the composites is improved by 3.69-5.85 times(13.28±1.15 MPa vs.(49.05±1.07)-(77.78±3.72)MPa),and the compressive strength is improved by 4.59-13.58 times(8.55±0.90 MPa vs.(39.02±1.63)-(116.13±2.58)MPa).This approach offers a novel and effective method for fabricating structural composites with an expanded range of higher electromagnetic wave absorption properties and improved mechanical properties.展开更多
基金Project (2011CB605801) supported by the National Basic Research Program of ChinaProject (CX2012B042) supported by the Graduated Students' Scientific Research Innovation Project in Hunan Province of China
文摘C/C-ZrC composites were prepared by precursor infiltration and pyrolysis using the organic zirconium as precursor.The conversion mechanisms of the precursors such as the thermal behavior,structural evolution,phase composition,microstructure,composition of the precursors and products were analyzed by thermal gravimetric analyzer,Fourier transform infrared spectrometer,X-ray diffraction and scanning electron microscope.The results indicate that the ZrC precursor transforms to inorganic ZrO2 from room temperature to 1200 ℃,then reduces to ZrC at 1600 ℃ through the carbothermal reduction reaction.The microstructure of the C/C-ZrC composites was also investigated.The composites exhibit an interesting structure,a coating composed of ZrC ceramic covers the exterior of the composite,and the ZrC ceramic is embedded in the pores of the matrix inside the composite.
基金Project(NCET-07-0228)support by the New Century Excellent Talents in University
文摘Two-dimensional plain-weave silicon carbide fiber fabric reinforced silicon carbide(2D-SiC/SiC)composites were molded by stacking method and densified through precursor infiltration and pyrolysis(PIP)process.SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition(CVD)technique.Fiber/matrix debonding and relatively long fiber pullouts were observed on the fracture surfaces.Additionally,the flexural strength and elastic modulus of the composites with and without fiber/matrix interphase layer were investigated using three-point bending test and single-edge notched beam test.The results show that the fiber fraction and the porosity of 2D-SiC/SiC composites with and without coating are 27.2%(volume fraction)and 11.1%,and 40.7%(volume fraction)and 7.5%,respectively.And the flexural strength and elastic modulus of 2D-SiC/SiC composites with and without coating are 363.3 MPa and 127.8 GPa,and 180.2 MPa and 97.2 GPa,respectively.With a proper thickness,the coating can effectively adjust the fiber/matrix interface,thus causing a dramatic increase in the mechanical properties of the composites.
基金supported by the National Natural Science Foundations of China under Grant No.52293372the Key R&D projects in Shaanxi Province under Grant No.2023-YBGY-418the Fundamental Science Center for Aviation and Gas Turbine Engines under Grant No.P2021-A-IV-002-001.
文摘HfCeSiC-modified carbon/carbon composite(C/CeHfCeSiC)sharp leading edges(SLEs)were prepared via precursor infiltration and pyrolysis for potential hypersonic applications.The effect of SiC proportion on the ablation behavior of the SLEs under oxyacetylene flames with 2.38 MW/m^(2) and 4.18 MW/m^(2) was investigated.The preferred sample with a volume ratio of HfC to SiC of 0.74 possessed almost zero degradation(linear recession rate 0.6 mm/s)up to a temperature of 2371℃.As the temperature increases to 2527℃ in the latter condition,the SLE with less SiC(the volume ratio of HfC to SiC is 1.10)exhibited a linear recession rate of 1.03 mm/s during cyclic ablation of 3×40 s.Relatively more SiC addition is favorable under lower heat flux due to the better oxygen barrier performance of the scale.However,superior ablation resistance is available under higher heat flux with less SiC addition due to the higher thermal stability of the resulting oxide scale.
基金The authors greatly acknowledge the financial support from the National Natural Science Foundation of China(Grant No.51972027).
文摘Carbon fiber reinforced silicon carbide-hafnium carbide(C/SiC-HfC)composite was prepared by precursor infiltration and pyrolysis process.Then,ablation behavior of C/SiC-HfC was evaluated in plasma wind tunnel.It was found that oxide layer formed during ablation significantly influenced the surface temperature.Formation of dense HfO2 SiO2 layer under low heat flux led to stable surface temperature.Silica(SiO2)on the surface was gradually consumed when heat flux increased,resulting in conversion of HfO2-SiO2 on the surface to HfO2.Converted HfO2 with high catalytic cofficient absorbed more energy,causing gradual increase in the surface temperature.Formed oxide layer was destroyed at high heat flux and high stagnation point pressure.After carbon fiber lost the protection of HfO2-SiO2 layer,it burned immediately,leading to surface temperature jump.
基金supported by the Key Program of the National Natural Science Foundation of China(No.52032003)the National Natural Science Foundation of China(Nos.519720820 and 51772061)+1 种基金the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments(No.6142905202112)the Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z20144).
文摘To further improve the oxidation resistance of polymer derived ceramic(PDC)composites in harsh environments,Cf/SiC/SiHfBOC composites were prepared by chemical vapor infiltration(CVI)and precursor impregnation pyrolysis(PIP)methods.The weight retention change,mechanical properties,and microstructure of C/SiC/SiHfBOC before and after oxidation in air were studied in details.Microscopic analyses showed that only the interface between the ceramics and fibers was oxidized to some extent,and hafnium had been enriched on the composite surface after oxidizing at different temperature.The main oxidation products of Cf/SiC/SiHfBOC composites were Hf0_(2)and HfSi04 after oxidation at 1500℃for 60 min.Moreover,the weight retention ratio and compressive strength of the Cf/SiC/SiHfBOC composites are 83.97%and 23.88±3.11 MPa,respectively.It indicates that the Cf/SiC/SiHfBOC composites should be promising to be used for a short time in the oxidation environment at 1500℃.
基金supported by"the Fundamental Research Funds for the Central Universities"(No. 2011QNA20)
文摘A preceramic polymer, polyzirconosaal （PZSA）, was synthesized by the ligand-exchange reaction between polyzirconoxane （PZO） and salicyl alcohol （SA）. The precursor was air-stable and exhibited excellent solubility and rheology. These properties are useful for the processing of C/C-ZrC composites v/a precursor infiltration and pyrolysis （PIP） process. The polymer to ceramic conversion was investigated by TG, XRD and TEM. Nanosized ZrC was formed by pyrolysis of this precursor at 1300 ℃ in argon with ceramic yield of 57.8%.
基金support from National Natural Science Foundation of China(Nos.52073299,52172077,U23A20563)the National Key R&D Program of China(No.2024YFB3714704)are gratefully acknowledged.
文摘Directional thermal transport materials enable anisotropic heat flow,thereby enhancing the efficiency of thermal management systems.These materials have found broad applications in aerospace,elec-tronics,and automotive industries.Silicon carbide(SiC)based composites,with their exceptional properties including high modulus,thermal stability,and superior thermal conductivity,serve as an ideal structural material.Strategic manipulation over microstructure and composition enables direc-tional thermal management,expanding applicability in thermal management and achieving structural-functional integration.By combining selective laser printing with precursor impregnation and pyrolysis(PIP),this work presents an innovative approach to fabricating thermally anisotropic C_(f)/SiC composites that integrate both structural and functional properties.The optimized composite(20%(in volume)chopped C_(f))exhibited high fiber alignment(f_(p)=0.7677)and pronounced thermal anisotropy,with thermal conductivities of 70.14 W/(m·K)perpendicular and 38.87 W/(m·K)parallel to the printing plane(anisotropy ratio:1.8).This directional heat transport,enabled by fiber orientation and phonon scat-tering control,is critical for advanced thermal management.The composite also maintained good mechanical strength,exhibiting a flexural strength of(150.4±9.8)MPa parallel to the printing plane,finalizing in a structural and functional integration.
基金the National Natural Science Foundation of China(No.52032003)National Natural Science Foundation of China(Nos.51972082,52102093,and 52172041)+1 种基金Postdoctoral Research Foundation of China(No.2021M690817)the Science Foundation of National Key Laboratoryof Science and Technology on Advanced Composites in Special Environments.
文摘In this paper,a high-yield Hf-modified SiHfBOC ceramic precursor was developed,and a high-pressure assisted impregnation pyrolysis method was proposed to achieve the preparation of 3D PyC–Cf/SiHfBOC composites.This high-pressure assisted impregnation method significantly improves impregnation filling effect of the precursor in and between fiber bundles compared to dozens of traditional impregnation cycles.After undergoing just 9 precursor infiltration pyrolysis(PIP)cycles,the composites achieved relative density of approximately 90%and density of 1.64 g/cm^(3).The critical temperature difference of the 3D PyC–Cf/SiHfBOC composites after the shock of room temperature(RT)–1000℃is as high as 650℃,which is twice that of traditional ceramic materials,showing good thermal shock resistance.Under the effect of Hf modification,a dense HfO_(2)–SiO_(2)oxide layer(thickness of 93μm)was formed in situ on the surface of the 3D PyC–Cf/SiHfBOC composites,effectively preventing further erosion of the composite matrix by high-temperature oxidation gas.Even in the ultra-high-temperature oxygen-containing environment at 1800℃,it still exhibits an excellent non-ablative result(with a linear ablation rate of 0.83×10^(−4)mm/s).This work not only enriches the basic research on lightweight ultra-high-temperature ceramic composites converted from Hf ceramic precursors,but also provides strong technical support for their applications in ultra-high-temperature non-ablative thermal protection materials for high-speed aircraft.
基金The authors gratefully acknowledged the financial support provided by the National Key R&D Program of China(No.2021YFB3701500)the Program of Shanghai Academic/Technology Research Leader(No.22XD1404000).
文摘Sic-based composites are widely used as electromagnetic wave absorbers due to their excellent dielectric properties.However,the constraints associated with structural design and the intricacies of the preparation process hinder their broader application.In this study,novel mullite anti-gyroid/SiC gyroid metastructures are designed to integrate the mechanical and electromagnetic wave(EMW)absorption properties of composite materials.Mullite anti-gyroid/SiC gyroid composites are fabricated utilizing a combination of digital light processing(DLP)three-dimensional(3D)printing and precursor infiltration and pyrolysis(PiP)processes.Through the modulation of structural units,the electromagnetic parameters can be effectively regulated,thus improving the impedance matching characteristics of the composites.The structural composites show outstanding EMW absorption properties,with a minimum reflection loss of-54 dB at a thickness of 1.9 mm and an effective absorption bandwidth of 3.20 GHz at a thickness of 2.2 mm.Furthermore,the PIP process significantly enhances the mechanical properties of the composites;compared with those of the mullite/SiC ceramics,the flexural strength of the composites is improved by 3.69-5.85 times(13.28±1.15 MPa vs.(49.05±1.07)-(77.78±3.72)MPa),and the compressive strength is improved by 4.59-13.58 times(8.55±0.90 MPa vs.(39.02±1.63)-(116.13±2.58)MPa).This approach offers a novel and effective method for fabricating structural composites with an expanded range of higher electromagnetic wave absorption properties and improved mechanical properties.
