电解液中钙磷组分对镁合金MAO生物陶瓷膜层特性的影响

Influence of the Ca- or P-containing Electrolyte Compositions on Properties of Micro-arc Oxidation Coatings Fabricated on Mg Alloy

摘要:

采用恒流模式，通过单变量实验改变电解液中乙酸钙、六偏磷酸钠和磷酸二氢钠等钙磷组分的浓度，在AZ31镁合金表面制备微弧氧化生物陶瓷膜，观察分析膜层微观组织结构，测定膜层表面Ca/P比、耐蚀性等，探讨钙磷组分及其浓度对膜层组织和性能的影响，进而对电解液进行优化，并对优化后的膜层性能进行观察和分析。结果表明：乙酸钙、六偏磷酸钠、磷酸二氢钠对膜层Ca、P元素含量及Ca/P比值有决定作用；乙酸钙浓度越高，膜层厚度越小，但是均一性越好；六偏磷酸钠浓度对膜层表面形貌和厚度几乎无影响，其浓度越高，膜层中P元素含量越高；磷酸二氢钠浓度越高，Ca/P比值越小。电解液优化后，制备的膜层较为平整致密，表面均匀分布10.7 μm左右的微孔，但存在微裂纹；膜层主要由MgO、Mg和少量Ca2P2O7、SiO2等物相组成，使硬度和耐蚀性比镁合金基体有明显提高；膜层粗糙度Ra=0.45 μm，润湿角为42.65°，有利于细胞的附着与生长

Abstract:

Micro-arc oxidation was conducted on AZ31 Mg alloy under CC mode by single variable experiments to improve its corrosion resistance and bio-activity. The microstructure, Ca/P ratio and corrosion rate were studied to investigate the influence of the Ca- or P-containing compositions on the coating. Furthermore, the properties of the optimized coating were studied. The results reveal that Ca/P ratio depends on the concentration of Ca(Ac)2, (Na2PO3)6 and NaH2PO4. With the increase of Ca(Ac)2, the coating thickness decreases, but it becomes more uniform; while (Na2PO3)6 has little effects on surface morphology or coating thickness. The content of P increases with (Na2PO3)6. The more NaH2PO4, the bigger the pore size and the smaller Ca/P ratio. The optimized coating possesses a flat and compact surface covered by micropores with diameters of about 10.7 μm and there are microcracks. And the coating phases are mainly MgO, Mg and a small amount of Ca2P2O7 and SiO2, which make the coating harder and more resistant to corrosion. The coating roughness Ra is 0.4482 μm and the wetting angle is 42.65°, which are good for cells to adhere to and grow on.