Mechanochemical synthesis of nanocrystalline carbonate-substituted hydroxyapatite

Carbonate-substituted hydroxyapatite has been produced by solid-state reactions using a mechanochemical synthesis method. Ammonium phosphate monobasic and calcium carbonate were used as raw materials. Mixtures of the initial powders were prepared using a Ca/P molar ratio similar to that of non-substituted hydroxyapatite, Ca10(PO4)6(OH)2. Dry milling of the powders was performed by using a ball to powder weight ratio equals 20:1. The obtained product was characterized by means of infrared spectroscopy, transmission electron microscopy and X-ray diffraction. Under the employed synthesis conditions hydroxyapatite is obtained after 2 h of milling. The crystallinity and the amount of the hydroxyapatite increase as milling time does. After milling for 6 h, nanosized apatite which has a possible composition Ca9+y(CO3)(PO4)5(OH)1+2y is obtained.