Papers by Author: Hai Feng Hu

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Authors: Min Mei, Xin Bo He, Xuan Hui Qu, Hai Feng Hu, Yu Di Zhang
Abstract: Characterizations of a liquid polycarbosilane used as SiC matrix precursor were investigated by TG-DTA, FTIR, XRD, etc, which indicated the feasibility of using LPCS as precursor for CLVD process to prepare C/SiC composites. The results show that the inorganic conversion of LPCS to SiC is almost completed at 900 °C, and the crystallization of β-SiC appears at 855 °C approximately. As the temperature increases, the deposit becomes more pure and the crystallinity of β-SiC also increases. The atomic ratio of C/Si in the deposit attained at 1200 °C is near-stoichiometric, the crystallite size of β-SiC is about 33.4 nm.
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Authors: Dan Zhao, Chang Rui Zhang, Hai Feng Hu, Yu Di Zhang, Qi Kun Wang, Xin Bo He
Abstract: Stitched carbon fiber cloth reinforced zirconium carbide composite (C/ZrC) was prepared by polymer infiltration and pyrolysis (PIP) process. C/ZrC-SiC composite was obtained by further introduction of SiC with PIP process in order to improve anti-oxidation property. The results show that 1.9vol% SiC addition improves the mechanical and anti-oxidation properties of C/ZrC composite. The flexural strength of C/ZrC is 247.9MPa, while that of C/ZrC-SiC is 273.1MPa. After oxidation in a muffle furnace at 1200°C for 30 minutes, the mass loss rate was reduced from 30.6% (C/ZrC) to 20.1% (C/ZrC-SiC), and the flexural strength and elastic modulus of C/ZrC were 56.7MPa and 5.7GPa, respectively, while those of C/ZrC-SiC were 122.9MPa and 17.2GPa, respectively.
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Authors: Feng Zhang, Hai Feng Hu, Qi Kun Wang, Yu Di Zhang, Chang Rui Zhang
Abstract: In this paper, 2D C/SiC composites with different carbon cloth filaments (1K, 3K) were prepared via precursor infiltration and pyrolysis (PIP) process. The flexural strength of 2D-1K C/SiC composites was 380MPa, and fracture toughness was 16.8MPa-m1/2, while those of 2D-3K C/SiC were 305MPa and 14.4MPa-m1/2, respectively. The differences of these two composites were analyzed from fiber volume ratio in the composites, density, and fracture surface (SEM) of the samples.
1041
Authors: Si’an Chen, Hai Feng Hu, Yu Di Zhang, Chang Rui Zhang, Guang De Li
Abstract: Zirconium carbide (ZrC) coatings were prepared on C/C composite via molten salt reaction process at relatively low temperatures of 800-1000°C. During the reaction process, potassium fluorozirconate (K2ZrF6) played a role transporting zirconium from the molten salt to the C/C composite surface. Elevating reaction temperature increased the growth rate of coatings, simultaneously leaded to rougher coatings. The coatings growth rate increased with reaction time at first and then decreased gradually. The ZrC coatings prepared at 900°C for 5h was ~2m thickness. At the early stage, the low solubility of zirconium in the molten salt leaded to the low coatings growth rate. Secondly, the growth rate of the ZrC coatings was controlled by the chemical reaction between C/C composites and zirconium once zirconium was saturated in the molten salts. Thirdly, the control step of coatings formation turned into the diffusion of carbon through the formed ZrC coatings and which leaded to a gradual decrease of growth rate.
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Authors: Song Wang, Zhao Hui Chen, Fan Li, Hai Feng Hu
Abstract: 3D C/SiC composites were fabricated by polycarbosilane (PCS) infiltration and pyrolysis process. The influence of pretreatment of carbon fiber, including pyrolytic carbon coating and thermal treatment, on mechanical properties of C/SiC composites was investigated. The results showed that the composites without fiber pretreatment had a flexural strength of 154MPa and a fracture toughness of 4.8 MPa•m1/2, while those with carbon coating or thermal treatment had much higher strength and toughness, that is, more than 400MPa and 15MPa•m1/2 respectively. Weak interfacial bonding and better in-situ strength of carbon fiber were main reasons for mechanical property improvement with pretreated carbon fiber.
1245
Authors: Chang Cheng Zhou, Chang Rui Zhang, Hai Feng Hu, Yu Di Zhang, Zhi Yi Wang
Abstract: 2D-C/SiC composites with high performance were prepared at temperatures as low as 900 °C. The flexural strength of the composites reached 329.61MPa, the same level as the composites prepared at 1200°C, and shear strength and fracture toughness were 32.14MPa and 14.65MPa·m1/2, respectively. The microstructure and mechanical properties of the composites after heat-treatment at 1600°C were also investigated to determine the potential applications at high temperature.
849
Authors: Yang Wei Lu, Yu Di Zhang, Hai Feng Hu, Chang Rui Zhang
Abstract: A novel, online-joining of C/SiC-C/SiC method, precursor infiltration and pyrolysis, was used to obtain high temperature stable joining SiC composition, while joining process was highly consistent with C/SiC preparation process. The compositions of joining ingredients and process parameters were investigated to determine the maximum joining strength of C/SiC-C/SiC at room and high temperatures. The optimum weight ratio of (polycarbosilane/divinyl benzene)/SiC powder is 3/1, and ramping rate of pyrolysis is 2°C/min, and cycles of infiltration and pyrolysis is 6. The flexural strengths of joining components remained stable up to 1200°C (50.8MPa), but decreased to 30.5MPa at 1500°C, while the tensile strengths remained rather stable (20.5MPa) up to 1500°C, and decreased to 8.4MPa at 1800°C.
1044
Authors: Yu Di Zhang, Hai Feng Hu, Chang Rui Zhang, Guang De Li
Abstract: C/SiC composites have widely application prospects in the field of aeronautic and aerospace for their excellent properties. The joining of C/SiC composites is a key to fabricate large and complex components. In this paper, 1D C/SiC pins were prepared by precursor infiltration and pyrolysis (PIP) process and used to join C/SiC composites by Slurry react (SR) and PIP process. The shear strength of the C/SiC pins with different carbon fiber volumes was investigated with the maximum shear strength as high as 339.46MPa. Influences of C/SiC pins on the joining properties of C/SiC composites were studied. The shear strength and flexural strength of C/SiC-C/SiC joining are improved from 9.17MPa and 30.41MPa without pins to 20.06MPa and 75.03MPa with one C/SiC pin (diameter 2mm), respectively. The reliability of C/SiC-C/SiC joining is also improved with C/SiC pins in that the fracture mode changes from catastrophic without pins to non-catastrophic. The SEM photos show a strong bond between joining layer and C/SiC composites without obvious interface.
135
Authors: Si’an Chen, Hai Feng Hu, Chang Rui Zhang, Yu Di Zhang, Xin Bo He, Min Mei
Abstract: Chemical liquid-vapor deposition (CLVD) process is a new style of fast densification, which combines the advantages of PIP process and CVI process. 2D C/SiC composites were prepared at 800~1200°C for 3~4 hours with liquid polycarbosilane and carbon fiber cloth by CLVD process with induction heating, and had the density of 1.7 g/cm3, the flexural strength of 84.6MPa, and the flexural modulus of 20GPa. XRD pattern of the sample proved that the matrix was β-SiC. It was found that SiC deposited mainly around single fiber instead of among fiber bundles and layers.
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Authors: Yu Di Zhang, Chang Rui Zhang, Hai Feng Hu, Yong Lian Zhou
Abstract: Ultra high temperature ceramic matrix composites (UHTCC) are being considered as the most promising materials for leading edge and nose cap of hypersonic spacecrafts, reusable space vehicles and so on. In the paper, 2D carbon fiber cloth reinforced silicon carbide-tantalum carbide (2D SiC-TaC) UHTCC was fabricated by slurry-pasting and precursor infiltration pyrolysis process (PIP). Influences of the volume ratio (10, 20, 30, 60, 80 and 100%) of TaC powder on mechanical properties and ablative resistance of 2D C/SiC-TaC composites were studied. The results showed that the relative density of composites with 60vol% TaC powder was the highest, the flexural strength of the composites reached 356MPa and the mass loss rate and recession rate were 0.0116g/s and 0.026mm/s respectively, while those of C/SiC composites were 0.0166g/s and 0.062mm/s respectively. Moreover, the higher TaC powder content, the smaller the fracture toughness of the composites was. The fracture toughness of the 2D C/SiC-TaC composites with 100vol% TaC powder was only 8.69 MPa-m1/2, while that of C/SiC composites was over 15.0 MPa-m1/2.
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