Abstract
The conversion of amorphous calcium phosphate (ACP) into apatites in solutions was studied under conditions of constant pH.
The kinetics for the crystallization of hydroxyapatite (HAp) was determined by measuring the amount of alkaline solutions which were added in order to keep a constant pH of 9.0 in a pH-stat. The formation of fluorine-bearing apatite was examined by analyzing fluoride ion in the reaction products of ACP and fluoride with an ion-selective electrode.
The exponents of the Avrami-Erofeev equation for HAp formation rates changed with the solution products [Ca2+] [PO43-] related to the degrees of supersaturation for the starting mixtures on precipitation of ACP. Fluorine-bearing apatites were obtained by the direct and rapid reactions of ACP and fluoride ion in aqueous solutions of pH 5.5, 7.0 and 9.0.
