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| 1 | Effect of C/SiC Volume Ratios on Mechanical and Oxidation Behaviors of C_(f)/C-SiC Composites Fabricated by Chemical Vapor Infiltration Technique显示文摘C/SiC volume ratios in carbon fiber-reinforced carbon-silicon carbide(C_(f)/C-SiC)composites may influence greatly mechanical and oxidation properties of the composites,but have not been well investigated yet.Herein,C_(f)/C-SiC composites with different C/SiC volume ratios were fabricated by chemical vapor infiltration(CVI)technique through alternating the thickness of a pyrocarbon(PyC)interlayer.The composites with C/SiC volume ratios of 0.37 and 0.84 exhibited the better comprehensive mechanical properties.The CS0.37 showed the highest flexural strength of 340.6 MPa,and CS0.84 had the maximum tensile strength of 139.1 MPa.The excellent mechanical properties were closely related to the relatively low C/SiC volume ratios and porosities,optimum interfacial bonding and reduced matrix micro-cracks.The composite with a low C/SiC volume ratio of 0.10 showed the best anti-oxidation performance due to its high SiC content.The oxidation mechanisms at 1100℃and 1400℃were discussed by considering the effect of the C/SiC volume ratios,pores and matrix micro-cracks,oxidation of carbon phase and SiC. | Jinjin Yao Shengyang Pang Yuanhong Wang Chenglong Hu Rida Zhao Jian Li Sufang Tang Hui-Ming Cheng | 2022 | Acta Metallurgica Sinica(English Letters)2022，35，5： | 1 |
| 2 | Deposition kinetics and mechanism of pyrocarbon for electromagnetic-coupling chemical vapor infiltration process显示文摘Although the electromagnetic-coupling chemical vapor infiltration(E-CVI)has been proven of a highefficiency technique for producing carbon fiber reinforced pyrocarbon(Py C)matrix(C/C)composites,a deep understanding of the deposition kinetics and mechanism of Py C matrix is still lack.In this work,a deposition model with uniform electric field but gradient magnetic field was set up by using unidirectional carbon fiber bundles as the substrates to investigate the deposition kinetics and mechanism.Meanwhile,the polarizability,and the chemical adsorption and dehydrogenation barriers of hydrocarbon were simulated based on the density functional theory(DFT)and the Climb-image nudged elastic band method,respectively.The E-CVI process exhibited extremely high Py C deposition rates of 8.7,11.5,16.5 and 22.7 nm/s at 700,750,800 and 850℃,respectively,together with a significantly low apparent activation energy of 57.9 k J/mol within the first 5 min.The Py C deposited at different temperatures with different time shows a smooth laminar structure with low coherent length and graphitization degree.The theoretical calculation and simulation results indicated that the electrons existing on the carbon fibers and the accelerated motion of radicals with preferred orientation forced by the derived magnetic field have reduced the energy barrier for the deposition process,thereby resulting in low apparent activation energy and high Py C deposition rate.The results of this work may shed a light on how to better direct the preparation of C/C composites by E-CVI process with high quality and efficiency. | Chenglong Hu Rida Zhao Sajjad Ali Yuanhong Wang Shengyang Pang Jian Li Sufang Tang | 2022 | Journal of Materials Science & Technology2022，，6： | 1 |
| 3 | Capillary infiltration of liquid silicon in carbon nanotubes:A molecular dynamics simulation显示文摘In this work,by simplifying the nanopores of porous C/C preform with single-walled carbon nanotubes(SWCNT)or double-walled carbon nanotubes(DWCNTs),the infiltration of liquid Si in the SWCNTs and DWCNTs was studied by molecular dynamics(MD)simulations.As a result,a quantitative relationship between tube diameter and liquid Si infiltration rate was established,which has been successfully ap-plied to reproduce the available experiment result.The obtained relationship indicates that the capillary infiltration of liquid Si at the nanoscale still conforms to the classic Lucas-Washburn law,however,the liquid Si infiltration quickly stops in small tubes with a diameter of less than 3 nm due to an obvious contraction of the tube wall.This work may provide theoretical guidance for pore structure optimization of porous C/C preform to fabricate high-density C/SiC composites. | Kangyu Zhang Rida Zhao Yongqiang Yang Lichang Yin Sufang Tang | 2023 | Journal of Materials Science & Technology2023，，13： | 0 |
| 4 | Mechanical Properties and Oxidation Behaviors of Self-Healing SiCf/SiC-SiBCN Composites Exposed to H_(2)O/O_(2)/Na_(2)SO_(4)Environments显示文摘The oxidation behaviors and their influence on the mechanical properties of self-healing SiCf/SiC-SiBCN composites were investigated in H_(2)O/O_(2)and H_(2)O/O_(2)/Na_(2)SO_(4)environments at 1200‒1350℃for 100 h.As the temperatures increase from 1200 to 1350℃,the oxidation rate constants increase from 0.45×10^(–7)to 1.58×10^(–7)mg^(2)/(mm^(4) h)in H_(2)O/O_(2),and from 1.02×10^(–7)to 3.42×10^(–7)mg^(2)/(mm^(4) h)in H_(2)O/O_(2)/Na_(2)SO_(4).The involvement of Na_(2)SO_(4)leads to the formation of a loose lamellar oxide layer,the breakage of the SiBCN/CVI-SiC interface and the decrease in the oxide viscosity,thus accelerating the oxidation of the composites.The composites show the maximum retention rate of strength(102%,535.71 MPa)after oxidation in H_(2)O/O_(2)at 1200℃due to the good self-healing capacity of the produced glass,while the minimum(82%,430.56 MPa)in H_(2)O/O_(2)/Na_(2)SO_(4)at 1350℃caused by the severe microstructural corrosion derived from Na_(2)SO_(4). | Suya Ji Bin Liang Chenglong Hu Shengyang Pang Rida Zhao Jian Li Sufang Tang | 2023 | Acta Metallurgica Sinica(English Letters)2023，36，11： | 0 |
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