| Core-shell nano-sized strontium/calcium hydroxyapatite powder was prepared by chemical precipitation method. The particle morphology, phase composition and the granularity distribution of CaHA andβ-Sr3(PO4)2 prepared with diferent process were studied by means of environmental scanning electron microscope(ESEM), field emission transmission electron microscopy(FTEM), thermogravimetric(TG) and differential scanning calorimetry(DSC), X-ray diffraction (XRD) and laser particle size analysis. The Core-shell structure was characterized by line analysis using energy dispersive X-ray fluorescence spectrometer (EDX) and inductively-coupled plasma atomic emission spectrometer (ICP-OES).CaHA were synthesized from the calcium nitrate hydrated and di-ammonium hydrogen phosphate by chemical precipitation method. The Results showed that the obtained CaHA grain had a small size and good dispersibility from the initial concentration of 0.25mol/L and 0.15mol/L respectively. Particle size of CaHA nanocrystalline gradually increased but morphology unchanged when temperature increased from 37 to 70℃.β-Sr3(PO4)2 powders were obtained from strontium-deficient hydroxyapatite after calcined at 700℃for 2h, which were prepared by chemical precipitation method with Sr(NO3)2 and (NH4)2HPO4 used as the reactants. The experiment proved that pH value and the temperature of synthesis had an important influence on the chemical composition. When the pH value was adjusted to 7 and reaction temperature was maintained at 45℃, the amorphous strontium phosphate at the molar ratio Sr/P=1.5 was attained after aging for 10h. The conversion rate increased quickly with the pH value increased to 8. When the pH value decreased to 6, the conversion rate was too slow and needed a long aging time.Core-shell needle-like hydroxyapatite nanoparticles with a length of 50～100nm and a diameter of 6nm were prepared by precipitation method from the addition of Sr(NO3)2 solution into a reactor containing a low concentration of (NH4)2HPO4 which was added into the CaHA suspending liquid in advance, and about 1nm thick of strontium hydroxyapatite deposited on the surface of CaHA nanoparticles was detected by EDX analysis. Whenβ-Sr3(PO4)2 added into the CaHA suspending liquid,β-TCP phase solid solution was obtained. Because particle size ofβ-Sr3(PO4)2 was large, Ca2+ in small CaHA size replaced the Sr2+ in the strontium phosphate before theβ-Sr3(PO4)2 particle had not been completely dissolved.
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