ULTRASTRUCTURAL ANALYSIS OF HYDROXYAPATITE NANO-PARTICLES SYNTHESIZED UNDER DIFFERENT INITIAL PH CONDITIONS USING HIGH-RESOLUTION TRANSMISSION ELECTRON MICROSCOPY

Hydroxyapatite (HAp) nano-particles were synthesized by a hydrothermal process under different initial pH conditions (pH 9.00~10.50). All resulting particles were identified to be single-phase HAp. With increasing of initial pH values, Ca/P molar ratios increased closely to that of the stoichiometric HAp value of 1.67. The morphologies and ultrastructures of these particles were observed using high-resolution transmission electron microscopy. These results indicated that the resulting particles were fiber-shaped single crystals with preferred orientation to the a-plane at low pH values. However, at high pH values, the resulting particles were plate-shaped polycrystalline crystals with preferred orientation to the c-plane. (Received February 17, 2012; Accepted February 28, 2012)