炭酸カルシウム六水和物とその脱水物の形態制御

概要

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The morphological control of calcium carbonate hexahydrate and its dehydrate was investigated. Synthetic calcium carbonates were characterized by means of X ray diffraction pattern, thermal analysis (TG DTA) , in frared spectrum and scanning electron microscopic observation. The hexahydrate was synthesized by aging amorphous calcium carbonate which formed by adding aqueous ammonia into calcium hydrogen carbonate so lution at 0-9℃. The crystal shape and particle size of the hexahydrate were remarkably affected by synthetic conditions such as temperature (0-9℃), calcium ion concentration (2.94-11.34 x 10^<-3> mol dm^<-3>) and stir ring speed (150 250rpm) . For example, the particle size of hexahydrate having hexagonal platelike crystals was controlled to approximately 5 25pm below 3℃. The hexahydrate unstable above room temperature was easily changed to spherical vaterite at 30-60℃ and to needlelike aragonite above 90℃ by dipping the hexahydrate in water at 30 100℃. Moreover, an amorphous calcium carbonate hydrate containing 5% methoxyl group in skeleton structure of original hexagonal platelike particles was formed by dipping the hexahydrate in methanol for I min. This compound was converted to hexagonal platelike calcite by heating at 300℃.
社団法人日本セラミックス協会の論文
1995-12-01