Zinc-substituted hydroxyapatite (Zn-HA) powders were prepared by hydrothermal method using Ca(NO(3))(2), (NH(4))(3)PO(4) and Zn(NO(3))(2 )as reagents. X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to characterize the crystalline phase, microstructure, chemical composition, morphology and thermal stability of Zn-HA. The results show that the substitution content of zinc (Zn) in Zn-HA powders prepared in NaOH solution is higher than that prepared in NH(3) solution, and is lower than that of the corresponding amount of starting materials. The substitution of the Zn ion for calcium ion causes a lower crystallinity of Zn-HA and changes the lattice parameters of Zn-HA, since the ionic radius is smaller in Zn(2+) (0.074 nm) than in Ca(2+ )(0.099 nm). Furthermore, the substitution of the Zn ions restrains the growth of Zn-HA crystal and decreases the thermal stability of Zn-HA. Zn-HA powder prepared in NH(3) solution starts to decompose at 800 degrees C when the Zn fraction increases to 15 mol%, while that prepared in NaOH solution start to decompose at 5 mol% Zn. The substitution content of Zn significantly influences the thermal stability, microstructure and morphology of Zn-HA.

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Hydroxyapatite (HA)/polycaprolactone (PCL)-chitosan (CS) composites were prepared by melt-blending. For the composites, the amount of HA was varied from 0% to 30% by weight. The morphology, structure and component of the composites were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The tensile properties were evaluated by tensile test. The bioactivity and degradation property were investigated after immersing in simulated body fluid (SBF) and physiological saline, respectively. The results show that the addition of HA to PCL-CS matrix tends to suppress the crystallization of PCL but improves the hydrophilicity. Adding HA to the composites decreases the tensile strength and elongation at break but increases the tensile modulus. After immersing in SBF for 14 days, the surface of HA/PCL-CS composites are covered by a coating of carbonated hydroxyapatite with low crystallinity, indicating the excellent bioactivity of the composites. Soaking in the physiological saline for 28 days, the molecular weight of PCL decreases while the mass loss of the composites and pH of physiological saline increase to 5.86% and 9.54, respectively, implying a good degradation property of the composites.

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