Carbon fiber-reinforced SiC matrix (Cf/SiC) composites were fabricated using a chemical vapor infiltration + polymer infiltration and pyrolysis (CVI+PIP) hybrid process. In an effort to improve the yield of SiC pyrolyzed during PIP, we conducted pyrolysis under high pressure using polycarbosilane as a precursor. We investigated the effects of the high-pressure pyrolysis of the polycarbosilane infiltrate on the efficiency of the PIP process and the physical characteristics of the fabricated Cf/SiC composites. The CVI+PIP hybrid process under high-pressure pyrolysis reduced the processing time by a factor of ten, minimized the oxygen content (< 10 at %) and improved the crystallinity of the nano β-SiC crystal. These results are due to the pressure in the polycarbosilane pyrolysis, which resulted in a high polycondensation. The ceramic yield of polycarbosilane infiltrated into Cf-preform was increased and the inter-facial bonding between the matrix and fibers was improved. Consequently, the Cf/SiC composites fabricated by the CVI+PIP hybrid process under high-pressure pyrolysis exhibited a high density of 2.15 g/cm 3 .
>> Carbon materials are mainly used as catalyst supports for polymer exchange membrane fuel cell (PEMFC). Catalyst supports are required specific characteristics of the carbon materials, such as large surface area and high electrical conductivity. Attempted were to improve electrical conductivity and to maintain high surface area of carbon materials using a microwave treatment. Microwave treatment, as a relatively new technique, takes short reaction time and reduce the consumption of the gases used for carbon treatment compared to a traditional heat treatment. Hybrid carbon (ACF/Graphene) as catalyst supports by microwave-irradiation method for PEMFC increase the cell performance because of increased electrical conductivity resulting in triple-phase contact and reduced the interfacial resistance. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-Ray Diffraction (XRD) were employed to analyze carbon materials. The performance of microwave-treated carbon materials was evaluated by measuring current-voltage (I-V) characteristics and electrode impedance.
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