| ZHU Shi-jie,WANG Jian-feng,LIU Xin-yu,WANG Li-guo,REN Chen-xing,CHANG Lei,WANG Jun,GUAN Shao-kang.Preparation and Properties of Composite Coating by Micro-Arc Electrodeposition and Hydrothermal Synthesis on Surface of Biodegradable Magnesium Bone Screws[J],46(3):20-27 |
| Preparation and Properties of Composite Coating by Micro-Arc Electrodeposition and Hydrothermal Synthesis on Surface of Biodegradable Magnesium Bone Screws |
| Received:November 27, 2016 Revised:March 20, 2017 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2017.03.003 |
| KeyWord:biomagnesium alloy bone screws electrolytic polishing micro-arc electrophoresis hydrothermal synthesis composite coating hydroxyapatite |
| Author | Institution |
| ZHU Shi-jie |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| WANG Jian-feng |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| LIU Xin-yu |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| WANG Li-guo |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| REN Chen-xing |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| CHANG Lei |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| WANG Jun |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
| GUAN Shao-kang |
School of Materials Science and Engineering, Zhengzhou University, Zhengzhou , China |
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| Abstract: |
| The work aims to control the degradation rate effectively by preparing hydroxyapatite coating on the surface of biomagnesium alloy bone screws. Coating was prepared on the surface of bone screws with complex morphology by means of micro-arc electrophoresis and hydrothermal synthesis. First, electrolytic polishing was used to pretreat the surface of bone screws. Subsequently, amorphous hydroxyapatite coating was prepared on the surface by virtue of micro-arc electrophoresis. Finally, the micro-arc electrodeposition coating was sealed by virtue of hydrothermal synthesis to obtain hydroxyapatite composite coating is with high purity and good crystallinity. Microstructures, morphology and composition of the composite coating were characterized by XRD, SEM, AFM etc. In vitro immersion test and electrochemical experiment were carried out in T. Kokubo's stimulated body fluid (SBF) to evaluate the corrosion resistance and the ability to induce the precipitation of calcium orthophosphates of this composite coating. Electrolytic polishing pretreatment was carried out provided with electrolytic polishing current of 0.14 A and polishing time of 2 min, so as to improve binding strength between the substrate and coating. In the process of micro-arc electrophoresis, serious tip discharge was observed on surface due to its specific shape of the bone screws. The addition of glycerol into the micro-arc electrophoresis electrolyte could effectively restrain the electric discharge phenomena in the tip, and prevent porosity of the film structure, deposition of numerous oxides, exfoliation of the coating and even ablation of the matrix by adjusting the content of glycerol in the electrolyte and optimizing the micro-arc electrophoresis process (voltage of 155 V and reaction time of 20 min). Then the micro-arc electrophoresis coating was sealed by optimizing hydrothermal synthesis parameters (pH 8.5, reaction time of 1.5 h and reaction temperature 393k) to form HA composite coating. The morphology of micro-arc electrophoresis/hydrothermal synthesis composite coating is cauliflower-like structure assembled by hydroxyapatite nano rods. The coating is uniform, compact and of good crystallinity. The electrochemical corrosion test shows that, corrosion current density of the bone screws with the composite coating decreases by one order of magnitude, and morphology of the bone screws is still intact after 6 days of immersion in simulated body fluid, indicating that micro-arc electrophoresis/hydrothermal composite coating could improve biocompatibility to some extent and especially the corrosion resistance. However, the fretting friction-wear test shows that the wear resistance decreases after hydrothermal composite sealing. |
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