Papers by Keyword: Preceramic

Abstract: Foam-type porous silicon carbide (SiC) ceramics without cracks and hollow struts were fabricated using the polymer replica method with polycarbosilane (PCS) and polyurethane (PU) foam as the starting materials. The synthesized porous SiC was analyzed using X-ray diffraction and scanning electron microscopy. The results revealed that a porous SiC ceramic structure was formed with a dense framework at a low temperature of 1200°C. During the heat-treatment process, the PCS experienced an organic–inorganic transformation and then converted to the SiC ceramics. It was determined that the organic–inorganic transformation of PCS, which was the stage of silicon oxycarbide formation, is affected by the curing condition. In this study, the optimum curing condition was determined to be an air atmosphere at 200°C for 7 h.

Abstract: Iron-containing SiC ceramics have low specific resistivity and excellent electromagnetic properties. In this work, hyperbranched polyferrocenylsilane as the precursor of Fe/Si/C ceramics was prepared by the reaction of ferrocenyl dilithium, dichlorodimethylsilane and trichloromethylsilane. The ceramization process of the preceramic polymer from organic to inorganic was then investigated. Precursor microspheres were prepared by emulsion method, which were then pyrolyzed to obtain Fe/Si/C ceramic microspheres.The composition, structure and morphologies of the precursor and ceramics were characterized by ¹H-NMR, FT-IR, TG-MS, XRD, SEM and EDS. Experimental results showed that the hyperbranched precursor was successfully synthesized, the pyrolytic process of which started at 350 °Cand almost completed above 600 °C. There was crystalline transformation from Fe₅Si₃ to Fe₃Si as the sintering temperature increased from 1000 °C to 1400 °C. Moreover, the crystalline phase of β-SiC appeared at 1400 °C. Precursor microspheres were prepared by emulsion method. Porous ceramic microspheres were obtained after the precursor microspheres being sintered at 1400 °C, which can be applied in gas adsorption and catalyst supports.

Abstract: Polyphenylcarbosilane (PPCS) was synthesized from thermal rearrangement of the polymethylphenylsilane around 350 ~ 430°C. Characterization of synthesized PPCS was performed with FT-IR spectroscopy analysis. From FT-IR data, the band at 1035cm^-1 is very strong and assigned to CH₂ bending vibration in Si-CH₂-Si group, indicating the formation of the PPCS. Ceramic thin film was fabricated onto stainless substrate by dip coating using a 20wt% PPCS in toluene. Heat treatment of the samples was performed at various temperatures (600°C and 800°C) under nitrogen atmospheres. The prepared PPCS samples and the coating layers on SUS316 after heat treatment were analyzed using FT-IR and XPS, respectively.