Pyrolytic Conversion of Spherical Organo-silica Powder to Silicon Nitride under Nitrogen |
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Authors: | Jae Young Choi Young Tae Moon Do Kyung Kim Chong Hee Kim In-Sig Seog |
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Affiliation: | Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Taejeon 305–701, Korea;New Materials Research Laboratory, Keum Kang Central Institute, Kyunggi-do 449–910, Korea |
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Abstract: | Monodisperse, spherical Si3N4 powder composed of fine particulates was synthesized by pyrolyzing spherical organo-silica powder under nitrogen. The organo-silica powder was prepared by hydrolyzing a mixture of phenyltrimethoxysilane (PTMS) and tetraethoxysilane (TEOS) in a methanol solution of water and ammonia. The organo-silica powder consisted of 81.3 at.% silicon units derived from PTMS and 18.7 at.% silicon units derived from TEOS. During the pyrolysis under nitrogen, the organo-silica powder decomposed to a mixture of free carbon and silica, with an increase of the surface area, at 500°-600°C, followed by the formation of alpha-Si3N4, with ß-Si3N4 as a minor phase, at 1450° and 1500°C and ß-SiC at 1550°C. The pyrolyzed powders, which retained the spherical shape and monodispersity of the organo-silica powders, with a reduction in mean particle diameter, were composed of fine particulates that were ~40 nm in size. |
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