籾殻からのSiO_2の製造及びその性状

概要

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Dry rice hull contains 13-29 wt% inorganic matter depending on the species, climate and geographic location. The inorganic matter is composed of silica (87-97 wt%) with small amounts of alkali and other trace elements. Properties of ash obtained by combustion of between 400° and 1500℃ were investigated. The SiO_2 in the rice hull was localized in the outer and inner epidermis of rice hull. The SiO_2 in rice hull ash formed by combustion below 800℃ of rice hull powder with a particle size below 152μm was amorphous. Particles of the ash having an average diameter of 20μm were aggregates of small particles with a diameter of 2-5μm. At combustion temperatures above 900℃, the SiO_2 in rice hull ash consisted of cristobalite and a small amount of tridymite. The surface of ash particles melted and the particles bonded to each other. The particle size was 40-60μm. It was found that potassium contained in the rice hull ash caused surface melting of SiO_2 particles and accelerated the crystallization of amorphous SiO_2 to cristobalite.
社団法人日本セラミックス協会の論文
1989-08-01