研究了不同浸渍工艺对2D高硅氧织物增强甲基硅树脂复合材料结构与性能的影响。结果表明,复合材料的密度及抗氧化性随着浸渍循环次数和热裂解温度的增加而增加;当热裂解温度不高于400℃时,复合材料仍具有较好的假塑性;但当热裂解温度高于...研究了不同浸渍工艺对2D高硅氧织物增强甲基硅树脂复合材料结构与性能的影响。结果表明,复合材料的密度及抗氧化性随着浸渍循环次数和热裂解温度的增加而增加;当热裂解温度不高于400℃时,复合材料仍具有较好的假塑性;但当热裂解温度高于400℃时,复合材料表现为典型的脆性断裂。当浸渍过程中热裂解温度为400℃、循环次数为2次时,500℃热处理20 m in的复合材料的室温弯曲强度最高,为49.8 MPa,比未处理的提高了150%。展开更多
To improve the oxidation resistance of short carbon fiber(C_(sf))-reinforced mechanically alloyed SiBCN(MA-SiBCN)(C_(sf)/MA-SiBCN)composites,dense amorphous C_(sf)/SiBCN composites containing both MA-SiBCN and polymer...To improve the oxidation resistance of short carbon fiber(C_(sf))-reinforced mechanically alloyed SiBCN(MA-SiBCN)(C_(sf)/MA-SiBCN)composites,dense amorphous C_(sf)/SiBCN composites containing both MA-SiBCN and polymer-derived ceramics SiBCN(PDCs-SiBCN)were prepared by repeated polymer infiltration and pyrolysis(PIP)of layered C_(sf)/MA-SiBCN composites at 1100℃,and the oxidation behavior and damage mechanism of the as-prepared C_(sf)/SiBCN at 1300–1600℃ were compared and discussed with those of C_(sf)/MA-SiBCN.The C_(sf)/MA-SiBCN composites resist oxidation attack up to 1400℃ but fail at 1500℃ due to the collapse of the porous framework,while the PIP-densified C_(sf)/SiBCN composites are resistant to static air up to 1600℃.During oxidation,oxygen diffuses through preexisting pores and the pores left by oxidation of carbon fibers and pyrolytic carbon(PyC)to the interior of the matrix.Owing to the oxidative coupling effect of the MA-SiBCN and PDCs-SiBCN matrices,a relatively continuous and dense oxide layer is formed on the sample surface,and the interfacial region between the oxide layer and the matrix of the as-prepared composite contains an amorphous glassy structure mainly consisting of Si and O and an incompletely oxidized but partially crystallized matrix,which is primarily responsible for improving the oxidation resistance.展开更多
Recrystallized silicon carbide（ RSi C）,a high purity Si C material sintered by the process of evaporation-condensation without any additives,is one of the most important structural materials in the fields of high te...Recrystallized silicon carbide（ RSi C）,a high purity Si C material sintered by the process of evaporation-condensation without any additives,is one of the most important structural materials in the fields of high temperatures. However,its low density and porous structure caused by the sintering mechanism in the absence of shrinkage,restrict its wide applications in engineering.This paper reviews the research progress and related technologies on the preparation of high-density RSi C and its composites. RSi C with relative high density up to 2. 75g·cm- 3can be obtained by a combination of pretreatment to Si C raw materials such as reshaping,modification and particle size distribution,and appropriate forming method. Post treatments such as cyclic pyrolysis and impregnation- recrystallization,and slurry impregnation- recrystallization are needed for the further density increase of RSi C（ 2. 99 g·cm- 3）. In addition,high performance RSi C- Mo Si2 and RSi C- Al composites obtained by melt infiltration are also reviewed.展开更多
Continuous silicon carbide fiber reinforced silicon carbide matrix(SiC_f/SiC) composites are attractive candidate materials for aerospace engine system and nuclear reactor system. In this paper, SiC_f/SiC composites w...Continuous silicon carbide fiber reinforced silicon carbide matrix(SiC_f/SiC) composites are attractive candidate materials for aerospace engine system and nuclear reactor system. In this paper, SiC_f/SiC composites were fabricated by polymer infiltration and pyrolysis(PIP) process using KD-S fiber as the reinforcement and the LPVCS as the precursor, while the BN interface layer was introduced by chemical vapor deposition(CVD) process using borazine as the single precursor. The effect of the BN interface layer on the structure and properties of the SiC_f/SiC composites was comprehensively investigated. The results showed that the BN interface layer significantly improved the mechanical properties of the KD-S SiC_f/SiC composites. The flexure strength and fracture toughness of the KD-S SiC_f/SiC composites were evidently improved from 314±44.8 to 818±39.6 MPa and 8.6± 0.5 to 23.0±2.2 MPa·m^(1/2), respectively. The observation of TEM analysis displayed a turbostratic structure of the CVD-BN interface layer that facilitated the improvement of the fracture toughness of the SiC_f/SiC composites. The thermal conductivity of KD-S SiC_f/SiC composites with BN interface layer was lower than that of KD-S SiC_f/SiC composites without BN interface layer, which could be attributed to the relative low thermal conductivity of BN interface layer with low crystallinity.展开更多
Using liquid poly(methylvinyl)borosilazanes(PMVBSZ)as precursor,carbon fiber reinforced SiBCN matrix composites(C_f/SiBCN)were fabricated by a modified polymer infiltration and pyrolysis(PIP)process.With dicumyl perox...Using liquid poly(methylvinyl)borosilazanes(PMVBSZ)as precursor,carbon fiber reinforced SiBCN matrix composites(C_f/SiBCN)were fabricated by a modified polymer infiltration and pyrolysis(PIP)process.With dicumyl peroxide added as cross-linking agent,the PMVBSZ could be solidified at a low temperature of 120℃,leading to a high ceramic yield of～70%.The cross-linking mechanism and ceramization processes of the precursor were investigated in detail.Moreover,a modified infiltration technology was developed,which improved the efficiency and protected the precursor against moist air during PIP.Consequently,the obtained C_f/SiBCN composites had an oxygen content of around 1.22 wt%.Benefiting from the high ceramic yield and high efficiency of the modified PIP,C_f/SiBCN composites with an open porosity of～10%and uniform microstructure were obtained after only 7 cycles of PIP.The flexural strength and fracture toughness of the derived C_f/SiBCN composites were 371 MPa and 12.9 MPa·m^(1/2),respectively.This work provides a potential route for the fabrication of high performance C_f/SiBCN composites.展开更多
The SiBCN matrix via chemical vapor infiltration(CVI)or/and polymer infiltration pyrolysis(PIP)technologies was orderly introduced to SiC_(f)/SiC composites to optimize the mechanical property and electromagnetic(EM)s...The SiBCN matrix via chemical vapor infiltration(CVI)or/and polymer infiltration pyrolysis(PIP)technologies was orderly introduced to SiC_(f)/SiC composites to optimize the mechanical property and electromagnetic(EM)shielding effectiveness simultaneously.The BN interface with the thickness of 350 nm was designed to obtain a little stronger interface bonding.The flexural strength of SiC_(f)/SiC-SiBCN composites reached 545.45±29.59 MPa thanks to the crack deflection between the CVI SiC and CVI SiBCN,as well as CVI SiBCN and PIP SiBCN matrix because of the modulus difference between them.The fracture toughness(KiC)with the value of 16.02±0.94 MPa·m^(1/2) was obtained owing to the extension of crack propagation path.The adverse effect of stronger interface bonding was eliminated by the design of matrix microstructure for SiC_(f)/SiC-SiBCN composites.The thermal conductivity in the thickness direction was 7.64 W·(m·K)^(-1) at 1200℃and the electric resistivity decreased to 1.53×10^(3) Ω·m.The tunable dielectric property was obtained with the coordination of wave-absorption CVI SiBCN matrix and impedance matching PIP SiBCN matrix,and the total shielding effectiveness(SE_(T))attained 30.01 dB.It indicates that the SiC_(f)/SiC-SiBCN composites have great potential to be applied as structural and functional materials.展开更多
In the present paper,MoSi2(Cr5Si3)–RSiC composites were prepared via a combination of precursor impregnation pyrolysis(PIP) and MoSi2-Si-Cr alloy active melt infiltration(AAMI) process. Composition, microstructure, m...In the present paper,MoSi2(Cr5Si3)–RSiC composites were prepared via a combination of precursor impregnation pyrolysis(PIP) and MoSi2-Si-Cr alloy active melt infiltration(AAMI) process. Composition, microstructure, mechanical retention characteristics, and oxidation behaviors of the composites at elevated temperature were studied. X-ray diffraction(XRD) pattern confirms that the composites mainly compose of 6 H–SiC, hexagonal MoSi2, and tetragonal Cr5Si3. Scanning electron microscopy(SEM) image reveals that nearly denseMoSi2(Cr5Si3)–RSiC composites exhibiting three-dimensionally(3D) interpenetrated network structure are obtained when infiltrated at 2173 K, and the interface combination of the composites mainly depends on the composition ratio of infiltrated phases. Oxidation weight gain rate of the composites is much lower than that of RSiC matrix, where MoSiCr2 possesses the lowest value of 0.1630 mg×cm-2, about 78% lower than that of RSiC after oxidation at 1773 K for 100 h. Also, it possesses the highest mechanical values of 139.54 MPa(flexural strength σf and RT) and 276.77 GPa(elastic modulus Ef and RT), improvement of 73.73% and 29.77% as compared with that of RSiC, respectively. Mechanical properties of the composites increase first and then decrease with the extension of oxidation time at 1773 K, due to the cooperation effect of surface defect reduction via oxidation reaction and thermal stress relaxation in the composites, crystal growth, and thickness increase of the oxide film. Fracture toughness of MoSiCr2 reaches 2.24 MPa·m1/2(1673 K), showing the highest improvement of 31.70% as compared to the RT value.展开更多
文摘研究了不同浸渍工艺对2D高硅氧织物增强甲基硅树脂复合材料结构与性能的影响。结果表明,复合材料的密度及抗氧化性随着浸渍循环次数和热裂解温度的增加而增加;当热裂解温度不高于400℃时,复合材料仍具有较好的假塑性;但当热裂解温度高于400℃时,复合材料表现为典型的脆性断裂。当浸渍过程中热裂解温度为400℃、循环次数为2次时,500℃热处理20 m in的复合材料的室温弯曲强度最高,为49.8 MPa,比未处理的提高了150%。
基金the National Natural Science Foundation of China(Nos.52372059,52172068,52232004,and 52002092)the Heilongjiang Natural Science Fund for Young Scholars(No.YQ2021E017)+3 种基金the Fundamental Research Funds for the Central Universities(No.2022FRFK060012)the Heilongjiang Touyan Team Program,and the Advanced Talents Scientific Research Foundation of Shenzhen:Yu Zhou.the Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology and Advanced Space Propulsion Laboratory of BICE(No.LabASP-2023-11)the Huiyan Action(No.1A423653)the Key Technologies R&D Program of CNBM(No.2023SJYL05).Ralf Riedel also gratefully acknowledges the financial support provided by the Research Training Group 2561“MatCom-ComMat:Materials Compounds from Composite Materials for Applications in Extreme Conditions”funded by the Deutsche Forschungsgemeinschaft(DFG),Bonn,Germany.
文摘To improve the oxidation resistance of short carbon fiber(C_(sf))-reinforced mechanically alloyed SiBCN(MA-SiBCN)(C_(sf)/MA-SiBCN)composites,dense amorphous C_(sf)/SiBCN composites containing both MA-SiBCN and polymer-derived ceramics SiBCN(PDCs-SiBCN)were prepared by repeated polymer infiltration and pyrolysis(PIP)of layered C_(sf)/MA-SiBCN composites at 1100℃,and the oxidation behavior and damage mechanism of the as-prepared C_(sf)/SiBCN at 1300–1600℃ were compared and discussed with those of C_(sf)/MA-SiBCN.The C_(sf)/MA-SiBCN composites resist oxidation attack up to 1400℃ but fail at 1500℃ due to the collapse of the porous framework,while the PIP-densified C_(sf)/SiBCN composites are resistant to static air up to 1600℃.During oxidation,oxygen diffuses through preexisting pores and the pores left by oxidation of carbon fibers and pyrolytic carbon(PyC)to the interior of the matrix.Owing to the oxidative coupling effect of the MA-SiBCN and PDCs-SiBCN matrices,a relatively continuous and dense oxide layer is formed on the sample surface,and the interfacial region between the oxide layer and the matrix of the as-prepared composite contains an amorphous glassy structure mainly consisting of Si and O and an incompletely oxidized but partially crystallized matrix,which is primarily responsible for improving the oxidation resistance.
基金the financial support from the National Science Foundation of China ( Grant Nos. 51302076, 51372078 )the China Postdoctoral Science Foundation ( Grant No. 2013M531783)
文摘Recrystallized silicon carbide（ RSi C）,a high purity Si C material sintered by the process of evaporation-condensation without any additives,is one of the most important structural materials in the fields of high temperatures. However,its low density and porous structure caused by the sintering mechanism in the absence of shrinkage,restrict its wide applications in engineering.This paper reviews the research progress and related technologies on the preparation of high-density RSi C and its composites. RSi C with relative high density up to 2. 75g·cm- 3can be obtained by a combination of pretreatment to Si C raw materials such as reshaping,modification and particle size distribution,and appropriate forming method. Post treatments such as cyclic pyrolysis and impregnation- recrystallization,and slurry impregnation- recrystallization are needed for the further density increase of RSi C（ 2. 99 g·cm- 3）. In addition,high performance RSi C- Mo Si2 and RSi C- Al composites obtained by melt infiltration are also reviewed.
基金supported by the National Natural Science Foundation of China with Grant Nos.51502343 and 91426304
文摘Continuous silicon carbide fiber reinforced silicon carbide matrix(SiC_f/SiC) composites are attractive candidate materials for aerospace engine system and nuclear reactor system. In this paper, SiC_f/SiC composites were fabricated by polymer infiltration and pyrolysis(PIP) process using KD-S fiber as the reinforcement and the LPVCS as the precursor, while the BN interface layer was introduced by chemical vapor deposition(CVD) process using borazine as the single precursor. The effect of the BN interface layer on the structure and properties of the SiC_f/SiC composites was comprehensively investigated. The results showed that the BN interface layer significantly improved the mechanical properties of the KD-S SiC_f/SiC composites. The flexure strength and fracture toughness of the KD-S SiC_f/SiC composites were evidently improved from 314±44.8 to 818±39.6 MPa and 8.6± 0.5 to 23.0±2.2 MPa·m^(1/2), respectively. The observation of TEM analysis displayed a turbostratic structure of the CVD-BN interface layer that facilitated the improvement of the fracture toughness of the SiC_f/SiC composites. The thermal conductivity of KD-S SiC_f/SiC composites with BN interface layer was lower than that of KD-S SiC_f/SiC composites without BN interface layer, which could be attributed to the relative low thermal conductivity of BN interface layer with low crystallinity.
基金financial supports from the National Key Research and Development Program of China (No. 2017YFB0703200) National Natural Science Foundation of China (No. 51702341)Chinese Academy of Sciences Innovative Funding (No. CXJJ-17-M169)
文摘Using liquid poly(methylvinyl)borosilazanes(PMVBSZ)as precursor,carbon fiber reinforced SiBCN matrix composites(C_f/SiBCN)were fabricated by a modified polymer infiltration and pyrolysis(PIP)process.With dicumyl peroxide added as cross-linking agent,the PMVBSZ could be solidified at a low temperature of 120℃,leading to a high ceramic yield of～70%.The cross-linking mechanism and ceramization processes of the precursor were investigated in detail.Moreover,a modified infiltration technology was developed,which improved the efficiency and protected the precursor against moist air during PIP.Consequently,the obtained C_f/SiBCN composites had an oxygen content of around 1.22 wt%.Benefiting from the high ceramic yield and high efficiency of the modified PIP,C_f/SiBCN composites with an open porosity of～10%and uniform microstructure were obtained after only 7 cycles of PIP.The flexural strength and fracture toughness of the derived C_f/SiBCN composites were 371 MPa and 12.9 MPa·m^(1/2),respectively.This work provides a potential route for the fabrication of high performance C_f/SiBCN composites.
文摘以分子结构单元为[Si H2NH]n的全氢聚硅氮烷作先驱体,采用聚合物浸渍裂解法制备了三维石英织物增强氮化硅基复合材料(3DSi O2f/Si3N4)。研究了复合材料的致密化工艺与力学性能。结果表明:全氢聚硅氮烷与石英纤维润湿性好,浸渍效率高,陶瓷产率高;经5个浸渍裂解周期后复合材料密度达1.96g/cm3,孔隙率为10.9%,复合材料室温弯曲强度为33.5MPa,弹性模量为16.3GPa。由断口形貌看出:材料呈现脆性断裂,无纤维拔出现象,纤维与基体发生了较强的界面结合,基体内部和纤维表面均出现微裂纹。界面结合过强是导致3D Si O2f/Si3N4复合材料力学性能不佳的主要原因。
基金supported by the National Natural Science Foundation of China(Grant Nos.52072304,51632007,and 51872229)the 111 Project of China(B08040)the National Science and Technology Major Project(Grant No.2017-VI-0007-0077).
文摘The SiBCN matrix via chemical vapor infiltration(CVI)or/and polymer infiltration pyrolysis(PIP)technologies was orderly introduced to SiC_(f)/SiC composites to optimize the mechanical property and electromagnetic(EM)shielding effectiveness simultaneously.The BN interface with the thickness of 350 nm was designed to obtain a little stronger interface bonding.The flexural strength of SiC_(f)/SiC-SiBCN composites reached 545.45±29.59 MPa thanks to the crack deflection between the CVI SiC and CVI SiBCN,as well as CVI SiBCN and PIP SiBCN matrix because of the modulus difference between them.The fracture toughness(KiC)with the value of 16.02±0.94 MPa·m^(1/2) was obtained owing to the extension of crack propagation path.The adverse effect of stronger interface bonding was eliminated by the design of matrix microstructure for SiC_(f)/SiC-SiBCN composites.The thermal conductivity in the thickness direction was 7.64 W·(m·K)^(-1) at 1200℃and the electric resistivity decreased to 1.53×10^(3) Ω·m.The tunable dielectric property was obtained with the coordination of wave-absorption CVI SiBCN matrix and impedance matching PIP SiBCN matrix,and the total shielding effectiveness(SE_(T))attained 30.01 dB.It indicates that the SiC_(f)/SiC-SiBCN composites have great potential to be applied as structural and functional materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51372078 and 51302076)Natural Science Foundation of Hunan Province of China (Grant No. 12JJ4054)+2 种基金Natural Science Foundation of Hunan Province (Grant No. 2018JJ4011)Jiangsu Province Innovative Talent Plan 2016, ChinaYancheng City 515 Talent Plan, China
文摘In the present paper,MoSi2(Cr5Si3)–RSiC composites were prepared via a combination of precursor impregnation pyrolysis(PIP) and MoSi2-Si-Cr alloy active melt infiltration(AAMI) process. Composition, microstructure, mechanical retention characteristics, and oxidation behaviors of the composites at elevated temperature were studied. X-ray diffraction(XRD) pattern confirms that the composites mainly compose of 6 H–SiC, hexagonal MoSi2, and tetragonal Cr5Si3. Scanning electron microscopy(SEM) image reveals that nearly denseMoSi2(Cr5Si3)–RSiC composites exhibiting three-dimensionally(3D) interpenetrated network structure are obtained when infiltrated at 2173 K, and the interface combination of the composites mainly depends on the composition ratio of infiltrated phases. Oxidation weight gain rate of the composites is much lower than that of RSiC matrix, where MoSiCr2 possesses the lowest value of 0.1630 mg×cm-2, about 78% lower than that of RSiC after oxidation at 1773 K for 100 h. Also, it possesses the highest mechanical values of 139.54 MPa(flexural strength σf and RT) and 276.77 GPa(elastic modulus Ef and RT), improvement of 73.73% and 29.77% as compared with that of RSiC, respectively. Mechanical properties of the composites increase first and then decrease with the extension of oxidation time at 1773 K, due to the cooperation effect of surface defect reduction via oxidation reaction and thermal stress relaxation in the composites, crystal growth, and thickness increase of the oxide film. Fracture toughness of MoSiCr2 reaches 2.24 MPa·m1/2(1673 K), showing the highest improvement of 31.70% as compared to the RT value.
