透過雙極脈衝電參數調控鎂鈣合金微弧氧化膜層之抗腐蝕性質

The Anti-corrosion Properties of Micro-Arc Oxidation Coating on Mg-Ca Alloy Adjusted by Bipolar-Pulse Electrical Parameters

林祐亘(Yu-Hsuan Lin)

指導教授 ： 林新智

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100578

摘要

鎂是人體骨骼、牙齒與軟組織中含量豐富的元素，近年來對於鎂合金作為可降解人體植入物引起廣泛的關注，其中鎂鈣二元合金體系由於機械性質佳且楊氏模數與骨骼相近，是極具潛力的植入物材料。然而鎂鈣合金在人體內高含氯的環境中會快速被腐蝕，因此以微弧氧化技術在其表面生長膜層來調控溶解速率及延後腐蝕過程。
微弧氧化法是將金屬至於電解液中並施加電壓使其表面生長陶瓷氧化膜之技術，具有強附著力、高硬度、極佳的耐蝕性。本研究首先對鎂鈣合金做基礎的微結構、機械性質及成分分析，接著通過掃描式電子顯微鏡、能量色散X射線光譜和X光繞射分析對膜層進行微結構與成分分析，利用交流阻抗分析、動電位極化試驗和浸泡試驗進行腐蝕性能測試，以刮痕測試和接觸角量測評估膜層附著特性和親疏水特性，並研究調變個參數對微弧氧化塗層的影響。
研究結果顯示鎂鈣合金由α-Mg與Mg2Ca鎂鈣介金屬化合物共同組成，機械性質佳。微弧氧化膜層附著力佳且表面親水，隨著陰極電流密度增加，雖膜層成膜速率降低但氧化膜層變的緻密，抗蝕性質提升；隨著放電時間延長，膜層外部多孔層厚度增加但內部緻密層變的鬆散，將會有一個最佳的放電時間；提高頻率會傾向產生溫和的放電使的膜層變緻密但同時成膜速率不足；隨t_on^+/t_on^-比值上升膜層表面有由大量噴發溶溶氧化物所構成的突起構造，同時造成貫穿膜層的大型孔洞，最佳的t_on^+/t_on^-比值落在1。

關鍵字

鎂鈣合金 ； 人體植入物 ； 生物降解 ； 微弧氧化 ； 抗腐蝕性能

並列摘要

Magnesium is a rich element in human bones, teeth and soft tissues. In recent years, magnesium alloys as biodegradable human implants have attracted extensive attention. Mg-Ca binary alloy system is a potential implant material due to its good mechanical properties and similar Young's modulus to bone. However, Mg-Ca alloys will be corroded rapidly in human body, so micro arc oxidation technology is widely used to control the degradation rate and delay the corrosion process.

Micro arc oxidation (MAO) is a technology of placing metal into electrolyte and applying voltage to grow ceramic oxide layer on the surface of metal. It presents strong adhesion, high hardness and excellent corrosion resistance. First of all, the microstructure, mechanical properties and composition of Mg-Ca alloy were analyzed in this research. Second, the microstructure and composition of the MAO coating were analyzed by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Third, the corrosion resistance of the coating was tested by AC impedance analysis, potentiodynamic polarization test and immersion test. The surface properties of the coating was evaluated by adhesion test and contact angle measurement. The influence of parameters on the properties of MAO coating was studied.

The results show that the Mg-Ca alloy is composed of α-Mg and Mg2Ca and has good mechanical properties. With the increase of cathode current density, although the film formation rate decreases, the oxide film becomes denser and the corrosion resistance improves; with the increase of discharging time, the thickness of the outer porous layer increases, but the inner dense layer becomes looser, there will be an optimal discharge time. With the increase of frequency, the film tends to produce a mild discharge, which makes the film denser yet lower the formation rate simultaneously. With the increase of t_on^+/t_on^- ratio, there are many protrusions on the MAO surface and large holes through the MAO layer. The coating has the best properties when the t_on^+/t_on^- ratio is 1.

並列關鍵字

magnesium calcium alloy ； human implants ； biodegradation ； micro arc oxidation ； corrosion resistance

參考文獻

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