The influences of target properties and deposition times on pulsed laser deposited hydroxyapatite films
Introduction
Hydroxyapatite (HA) had been widely used as biomaterials for many applications in both dentistry and orthopaedics, because it forms a real bond with the surrounding bone tissue when implanted. Nevertheless, man-made HA has a low intensity and toughness and cannot be employed as load-bearing applications. Hydroxyapatite coated Ti and its alloys were prepared by different methods to combine the mechanical performance of the metallic substrates and the bioactivity of HA [1], [2], [3], [4]. Among them, pulsed laser deposition (PLD) has been pointed out to be one of the most encouraging techniques.
In this study thin HA films on Ti were prepared by pulsed laser deposition under an atmosphere of Ar. The structures of films were analyzed by EPMA, XRD and Raman spectroscopy.
Section snippets
Experimental
HA powder was made into disks of 2-mm thick and 25 mm in diameter by uniaxial and cold isostatical pressing at 300 MPa. Then the target was divided into three kinds by un-sintered, sintered at 600 °C and 1200 °C. Grade two Ti was selected as substrate material. Before deposition, they were ground to 600 grits and cleaned in a sequence of ultrasonic baths of acetone and ethanol. After that, they were placed 4 cm in front of the target and kept at a temperature of 575 °C for deposition. The films were
Results and discussion
Fig. 1 shows morphologies of films prepared by HA target sintered at different temperature and deposited with 1 h. There are many droplets with different sizes onto the film surface. It is a typical phenomenon of pulsed laser deposited thin films. Droplets with bigger size were mainly formed by splashing of the molten layer caused by the presence of a subsurface superheated layer or from the laser-induced recoil pressure due to rapid surface evaporation. Density of droplets of film prepared by
Conclusion
The films prepared by pulsed laser deposition under Ar atmosphere were amorphous which mainly composed of droplet-like particles and vibration of PO43− groups. Films prepared by target sintered at 1200 °C had little droplets onto film, while there were more droplets in film prepared by target sintered at 600 °C. And with deposition times increasing, the density of droplets is increasing, too. With the target sintering temperature and deposition time increasing, the ratio of Ca/P is increasing and
Acknowledgements
This work is part of a research program financed by Promotional Fund of Scientific Research for Middle-aged and Youthful Scientists of Shandong Province (Project No. 02BS056), by Young Teachers Foundation of Anhui Province (2007jq1026) and by the Natural Science Foundation of Anhui Province (KJ2008B271).
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