PREPARATION AND CHARACTERIZATION OF CALCIUM PHOSPHATE PARTICLES FROM FORCED HYDROLYSIS OF Ca(OH)₂-TRIPHOSPHATE-K₂S₂O₈ MIXED SOLUTION

摘要

The effects of potassium peroxodisulfate (K_(2)S_(2)O_(8)) on the formation of calcium phosphate particles produced by aging Ca(OH)_(2) and sodium triphosphate (sodium tripolyphosphate, Natpp: Na_(5)P_(3)O_(10)) mixed solution at 100～160°C for 18 h were examined. Spherical and monodispersed particles were produced at low K_(2)S_(2)O_(8) concentration ([K_(2)S_(2)O_(8)]) region ([K_(2)S_(2)O_(8)]≤4 mM) and their size was increased by increase in [K_(2)S_(2)O_(8)]. On the contrary, fine irregular particles were produced at [K_(2)S_(2)O_(8)]≥6 mM. The monodispersed spherical particles produced at [K_(2)S_(2)O_(8)]≤4 mM were amorphous, though small irregular particles produced at [K_(2)S_(2)O_(8)]≥6 mM were poorly crystallized calcium pyrophosphates (β-Ca_(2)P_(2)O_(7)). The Ca/P atomic ratios of these samples were 0.79～0.90, fairly closed to the Ca/P atomic ratio of 1.0 for β-Ca_(2)P_(2)O_(7). A high adsorption selectivity of H_(2)O was observed on amorphous monodispersed spherical particles. On the other hand, the β-Ca_(2)P_(2)O_(7) particles with small amounts of hydrated H_(2)O produced at [K_(2)S_(2)O_(8)]≥6 mM exhibited no selective adsorption of H_(2)O. With increase in the aging temperature, small numbers of transparent balloon-like hollow spheres were obtained at 120～140°C. However, the fraction of hollow spheres was less than 5%. Aging above 150°C, no balloon-like hollow sphere was precipitated but finally calcium hydroxyapatite (Ca_(10)(PO_(4))_(6)(OH)_(2), Hap) particles with small rod-like shape could be precipitated. These Hap particles produced at 150 and 160°C did not exhibit selective adsorption of H_(2)O.