| In order to improve the bioactivity of titanium alloy by controlling the surface phase together with the morphology, an alkalizing and laser texturing combination technology (ALT) was used to improve the surface property of Ti-6A1-4V. The phase analsis, morphology and the microstructure of the samples were investigated with X-ray diffraction, Scanning Electron Microscope (EDS), and Laser Scanning Confocal Microscope (LSCM). Surface free energy was calculated based on the contact angle measurements by senssile drop method. The wettabiligy and in vitro bioactivity were also studied through immersion tests in simulated body fluid (SBF) solution.The influences of alkali concentration, the alkali duration and the temperature of the solution on the surface phases and the morphology were investigated. The results show that the proper alkalizing parameters are as following:temperature of the solution of 80?, the alkali concentration of 5mol/L, and the alkalizing duration of 3 days.An even layer consisting of Na2TiO3 and a little amount of TiO2 was obtained under the above parameters.The alkalized samples were then laser textured.The laser parameters used in this paper are that laser pulse width of 0.2 ms, pulse frequency of 16 Hz, laser scanning speed of 1000 mm/s, defocus distance of 7 cm, and the space of laser beam of 1.5 mm and 0.75 mm, respectively. The results revealed that the space of laser beam has a significant influence on the morphology and surface roughness, but no significant influence on the type of phase. After laser textuing, the alkalized samples presented great differences in phase constituents. No Na2TiO3 was found. The main phases consist of Ti, TiO2,Ti6O and other titanium oxides. The results of LSCM showed that a textured morphology with periodical pits was realized. The surface roughness is about 7.62?m. SEM results of ALT samples revealed the existence of the alkalized layer but with a different microtructure compared with that of the alkalized samples. The ALT sample presented a porous microstructure rather than a dense layer in the alkalized samples. The layer around the laser beam almostly disappeared due to the laser ablation effects.The wettabiligy of the ALT samples were investigated. The results of surface free energy calculation illustrated tha the surface free energy of the alkalized sample is 51.73±0.02 mJ/m, that for the ALT sample is 52.57±0.02 mJ/m2, both of that is higher than that of the titamium control corresponding to 44.94±1.30 mJ/m2. This indicated that the wettability of titanium alloy was improved by alkalizing and ALT processing. The results of contact angle measurement between the samples and the SBF solution indicated that the ALT samples possessed a smaller contact angle compared with titanium control, further indicating the improvement of the wettability by ALT treatment.The in vitro bioactivity was examined by immersion tests in simulated body fluid (SBF) solution. The weight increased with increasing of immersion time and got 5.9 mg after 14 days immersion. Compared with the ALT sample at laser beam space of 0.75 mm, the samples processed at 1.5 mm illustrated a faster deposition rate of 1.79×10-1 mg/h. XRD results showed that no significant peaks corresponding to HA were found after immersion 3 days and 7 days, but a significant widened peak was observed after 14 days immersion. The ALT samples processed at laser beam space of 1.55 mm presented a stronger and wider peak than that of the samples processed at laser beam space of 0.75 mm. The morphology of the immersed sample can be characterized as graphical particles. The ratio of Ca to P for the sample processed at 0.75 mm is 1.06,1.308, and 1.307 after 3 days,7 days, and 14 days immersion, respectively. But for the samples processed at 1.5 mm, that ratio is 1.162,1.375, and 1.703, respectively, which is much higher than the above sample and is more similar with HA. |
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