Synthesis and physicochemical characterization of nanocrystalline chitosan-containing calcium carbonate apatites

The CaCl(2)-(NH(4))(2)HPO(4)-NH(4)HCO(3)-(C(6)H(11)NO(4)) (n) -H(2)O system at 25A degrees C has been investigated by the solubility (Tananaev's residual concentration) method and pH measurements. Coprecipitation conditions have been determined for nanocrystalline type A and B calcium carbonate apatites. Type A: Ca(10)(PO(4))(6)(CO(3)) (x) (OH)(2 - 2x) center dot yC(6)H(11)NO(4) center dot zH(2)O (x = 0.2, 0.5, 1.0; y = 0.1, 0.3, 0.5; z = 5.3-6.7); type B: Ca(10)[(PO(4))(5.7)(CO(3))(0.45)]CO(3) center dot 0.3C(6)H(11)NO(4) center dot 9H(2)O, and Ca(10)[(PO(4))(5.55)(CO(3))(0.675)]CO(3) center dot 0.3C(6)H(11)NO(4) center dot 9.2H(2)O. The solid phases have been characterized by chemical analysis, X-ray diffraction, thermogravimetric analysis, and IR spectroscopy.