A note on the crystal growth of hydroxyapatite precipitated from aqueous solutions

Abstract

When the formation of hydroxyapatite in aqueous solution proceeds from the dissolution of non-crystalline calcium phosphate, the crystal growth of the apatite can be divided into two distinct stages. In the presence of the non-crystalline salt, the crystals grow by a diffusion-controlled dendritic mechanism which results in the production of colloidal apatite particles. When the dissolution of the non-crystalline precursor has gone to completion, the apatite crystals continue to grow but now through a consolidation process known as Ostwald ripening. This changeover in growth mechanisms is the result of a decrease in the level of supersaturation occurring concomitantly with the disappearance of the non-crystalline calcium phosphate from the aqueous reaction system.