Formation of biocompatible hydroxyapatite thin films deposited by laser ablation

摘要

In this paper, we report that a thin film of hydroxyapatite (Ca_(10)(PO_4)_6(OH)_2), or HA was deposited by means of laser ablation to increase the biological compatibility of a titanium alloy( Ti-6Al-4V). Polished substrates with different microstructures (0.1 approx 3.0 mu m Rmax) were prepared. Depositions were carried out in a water vapor by bubbling O_2 gas through a water bath at 0.1Torr (1.3x10~(-2) Pa). An ArF excimer laser operating at a repetition rate of 10Hz was used for deposition. The substrate temperature was varied from 500 deg C to 560 deg C. The crystal structures of HA film were evaluated by X-ray diffractometry (XRD). At temperatures lower than 500 deg C, the films were amorphous. At temperatures greater than 560 deg C, the films had crystalline alpha -tricalciumphosphate ( alpha -TCP). The crystallized HA was obtained at about 530 deg C. The surface morphology of the HA film was observed using an atomic-force microscopy (AFM). The mechanical properties of the film were measured by the scratch test and the peeling off test by means of a tensile-test machine. In the peeling off test, the adhesive strengths between HA films and the substrates were about 2.3 and 5.4MPa for surface roughness 0.1 and 1.0 mu mRmax, respectively.