Study Of Microstructures And Properities Of Pulsed Laser Depositied Hydroxyapatite Thin Films

Hydroxyapatite (HA or HAP) which widely exists in human bones and teeth, has gained much attention by the biomedical materials researchers owing to its excellent biocompatibility and bioactivity. Nevertheless, man-made HA has a low intensity and toughness and can't be employed as load-bearing applications. So in these cases, HA thin films were coated on Ti and its alloys to combine the mechanical performance of the metallic substrates and the bioactivity of HA. The films can endow the implant with a layer against the release of metallic ions. Recently, many methods have been applied to preparing HA films including plasma spraying, sol-gel and ion beam sputter deposition. These traditional methods have obtained successful application especially plasma spraying. However, there are many drawbacks of these methods including the large grain size not the nanometers HA of bones and low crystallinity of films which need a post-heat treatment to increase their crystallinity. Nevertheless post-heat treatment can decrease the bonding strength between film and substrate. So finding a new method that can precisely control the stoichiometry and crystallinity has important significance. In this paper, pulsed laser deposition and pulsed laser ablation and synthesis deposition were used to prepare HA films. The microstructures of HA films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA), fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM).The results show that surface of HA films consists of many droplets, and there are no cracks and pores. THE films are amorphous examined by means of XRD, FT-IR and TEM. The Ca/P ratio of films is higher than the theoretical value (1.67). From TEM results it can be seen that there are β-Ca₃(PO₄)₂ (β-TCP), CaO in the films. Density of droplets on films is increasing with deposition time increasing. Morphology of the films has no obvious change after post-heat treatment. The heat treated films mainly consist of HA and TiO₂ and the Ca/P ratio of films is closer to theoretical value.The mutual action of laser and the target material decides the ablation composition, production rate, speed and its spatial distribution, thus affects the films...