Papers by Keyword: Polycarbosilane

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Authors: Jing Jing Wang, Wen Song Lin, Li Hui Duan, Xue Zeng Yan
Abstract: SiC nanopowder, polycarbosilane and divinylbenzene mixed slurries were prepared for viscosity measurement, which were used as matrix source of ceramic matrix composites. Results showed that apparent viscosity of the slurries increased with the increase of the content of SiC particles. The slurries with 50 nm SiC particles showed a low viscosity as compared with those slurries with 20 nm or 120 nm SiC particles at the same content of SiC. In particular, when the viscosity of slurry was higher than 30 mPa•s, the slurry could not be used in the test. Three-dimensional carbon fiber (3D-Cf) preforms were infiltrated with the aforementioned slurries. Addition of the nanoSiC powder as the inert filler in the slurries led to reduce the porosity and the infiltration–curing–pyrolysis cycles to manufacture 3D-Cf/SiC composites by the subsequent polymer impregnation and pyrolysis (PIP) process. Characterizations of the composites showed that the maximum flexural strength of specimen in the composites was 326 MPa and its fracture toughness was 10.5 MPa•m1/2.
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Authors: Xin Xing, Lin Liu, Xiao Zhong Huang, Xiao Dong Li
Abstract: Silicon carbide coatings on graphite were prepared through polymer vapor pyrolysis deposition process (PVPD) under N2 atmosphere. During this process, some low molecular weight substances that polycarbosilane (PCS) pyrolyzed can be deposited on graphite, and they can convert into SiC in high temperature. The results of XRD showed that amorphous SiC coatings were formed on graphite when the pyrolysis temperature was 1000°C, andβ-SiC phase formed in the coatings when the temperature up to 1250°C. Effects of the coatings on the microstructure and properties were investigated. It was shown that the uniform dense SiC coatings could be obtained by carefully controlling the pyrolysis temperature and ramping rate when the number molecular weight of PCS was in the range of 1,000~1,500.
1297
Authors: Roger R. Naslain, R. Pailler, G. Chollon, R. Bodet, H. Hannache
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Authors: Da Xiang Yang, Yong Cai Song, Xian He Mao, Wei Li
Abstract: A new curing method, chemical vapour curing (CVC) for polycarbosilane (PCS) fibers using unsaturated hydrocarbon (cyclohexene) vapour was studied. The low oxygen content SiC fibers were prepared and when the oxygen content in fibers was lower than 4.0%, the maximum tensile strength reached to 3.8GPa. The relationship between the tensile strength and the oxygen content of the fibers was investigated. The structure and composition of SiC fibers were also characterized by element analysis, FT-IR, XRD and XPS. Compared with that by air curing method, SiC fibers with less oxygen and better mechanical properties were prepared by CVC method.
1297
Authors: Lu Jiao Yang, Xuan Cheng, Ying Zhang, Jia Liu
Abstract: Polycarbosilane (PCS), an important precursor for manufacture of silicon carbide (SiC) ceramics, was prepared and analyzed to determine its chemical composition. The major elements of silicon (Si) and carbon (C) in Si-C backbones and side chains in PCS represent more than 80% with minor elements of oxygen and hydrogen being less than 20%. In this work, a conventional potassium silicofluoride volumetric method was explored and modified for establishing a standard routine procedure to evaluate Si content in PCS. The optimal conditions were investigated using an orthogonal designed four-factor-three-level normal experimental scheme. The suitable parameters and standard procedure to analyze Si in PCS were obtained.
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Authors: Zi Qing Zhu, Liu Ying Huang, Xuan Cheng, Ying Zhang
Abstract: As an important precursor in preparation of silicon carbide ceramic fibers by polymer precursor-derived method, it is very difficult to find the zero shear viscosity through the conventional steady test for the oligomer-like polycarbosilane (PCS) because of the possible oxidation and a prolonged time required to attain a steady state of the samples. In this work, a steady test and a series of transient tests were performed for the PCS melts. The limitation of the steady test is discussed. An averaging method based upon data from the transient tests is developed to determine the zero shear viscosity for the melt. The reliability of the results from the method is discussed and the zero shear viscosity of the pretreated PCS melt was obtained.
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Authors: Masaki Sugimoto, Y. Morita, T. Seguchi, Kiyohito Okamura
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Authors: Radoslaw A. Wach, Masaki Sugimoto, Masahito Yoshikawa
Abstract: Production of reinforced surface ceramic material was investigated by radiation curing-oxidation method. The originality of this research is to use along with polycarbosilane (PCS) an admixture of another preceramic polymer, polyvinylsilane (PVS). PCS, PVS or their combination in cyclohexane solution were spin-coated onto Al2O3 plates or deposited onto porous substrate by dipping method. After radiation oxidation step, used to preserve the coat on the substrate, a heat treatment was applied for crosslinking of the polymer. Thickness and quality of silicon carbide (SiC) film were investigated after pyrolysis.
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Authors: Masaki Sugimoto, Akira Idesaki, Shigeru Tanaka, Kiyohito Okamura
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Authors: K.J. Lee, Shin Hyuk Kang, Deug Joong Kim
Abstract: The sintering of TiB2 was limited due to its high degree of covalent bonding and low self diffusion coefficient. To solve this problem, hot pressing has been used for fabricating TiB2 ceramics, but this process was expensive and limited to the production of simple shapes. Pressureless sintering has also been studied, but its sintering temperatures is, as high as more than 2000°C, resulting in exaggerated grain growth and decrease of mechanical properties. The addition of SiC was found to be effective in improving the densification. However, a supplementary HIP process was needed to enhance the mechanical properties. In this study, the densification behavior and microstructural change of TiB2 ceramics infiltrated by the polycarbosilane of SiC precusor were investigated. The infiltrated polycarbosilane was converted to SiC during heating and densification was accelerated.
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