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February 13th, 2009

Pill-shaped precipitates

Published on February 13th, 2009 | By: pwray@ceramics.org

Everyone who has paid their dues in a chem lab is familiar with processes that precipitate materials shaped as spheres, cubes, rods and needles. It’s also not unusual to see rhombohedra, whiskers, tubes, flowers and rosette particles of inorganic/organic materials in the micron-scale. But, how about a pill-shaped particle? You know – round, with slightly out-curving sides. Never seen that kind of precipitate? No, neither have I, until now. Apparently, the synthesis of monodisperse, biconvex pill-shaped microparticles, precipitated directly from an aqueous solution, has not yet been reported for any natural or man-made materials. But, ACerS member and Yeditepe University (Istanbul, Turkey) professor A. Cuneyt Tas reports he has synthesized biconvex micropills of CaCO3 (of the vaterite form). Tas says he first cools (at 4°C) aqueous solutions of CaCl2-gelatin-urea and then heats the same at 70°C for 24 hours. He says this yields a products “looking like those cute aspirin tablets everybody know, but synthesized for the first time in water-based solutions at the micron-scale.” (It should be noted that aspirin tablets and the like are produced by a compressing powders into a die formed for the desired pill shape.) CaCO3 powders are widely used in pharmaceutical, cosmetics, toothpaste, rubber, plastic, papermaking, printing ink, food and biomedical industries. An article about Tas’ work appears in the current issue of the International Journal of Applied Ceramic Technology.


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