Fluorination of Ceramic Fiber with Chlorotrifluoromethane, especially <CCl_3F>

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In order to obtain some information regarding the preparation of fluorinated ceramics, <SiO_2> powder calcinated at high temperatures(1000-1500゜C) was treated with gaseous chlorofluoromethanes or <CF_4> at 450-550゜C in a closed circulation system. In addition, <CF_4> -plasma treatment was applied to the same <SiO_2> sample to perform an intensive surface fluorination.The treatments at 550゜C showed the order of the fluorination activity as following, <CCl_3F> (4.2) > <CCl_2F_2> (2.5) > <CClF_3> (0.3) > <CF_4> (0). (Here, the numbers in parentheses designate F content(%) in the surface layer of the treated <SiO_2> sample.) The F content in the surface layer of the <CCl_3F> -treated <SiO_2> increased linearly from 1.5 to 4.2% with an increase in the treatment temperature. Whereas, <SiF_4> -formation became remarkable at temperatures higher than 600゜C. The surface OH groups completely disappeared and Si-F bond appeared after the <CCl_3F> -treatment at 500゜C. The Cl component was not found for all the flon-treated sample.The adsorptive activities of <SiO_2> for water and hexane decreased with the <CCl_3F> -treatment, suggesting that the <SiO_2> surface became more hydro- and lipo-phobic with the treatment.The <CF_4> -plasma treatment was more effective for the more intensive fluorination of <SiO_2> surface. Thus, an atomic ratio of the treated <SiO_2> attained about 0.75 after the <CF_4> (0.5 Torr)-plasma treatment for 10 min.