- 學位論文
微弧氧化製程之電參數與電解液濃度對於純鈦深色膜層性質之影響
Effect of Electrical Parameters and Electrolyte Concentration on Coating Properties of Dark Micro-Arc Oxidation on Pure Titanium
摘要
由於鈦與鈦合金具有高比強度、良好的抗蝕性、生物相容性等優異特性，而被廣泛應用於航空、軍事、建築、醫療等產業，但其硬度較低，易發生摩擦磨損是其應用上的缺點。透過微弧氧化處理，能在鈦金屬表面形成一層陶瓷氧化膜層，此膜層能提供鈦金屬良好的抗腐蝕及抗磨耗性質。 深色二氧化鈦膜層可用於珠寶或建築等裝飾性用途上，也可應用於光學設備，因而具有發展潛力。本研究透過調整微弧氧化製程中陽極電流密度及工作頻率並使用不同濃度釩酸銨、氫氧化鈉、磷酸二氫鈉，在純鈦上探討不同參數對膜層結構、外觀及其他性質的影響。在分析方面利用掃描式電子顯微鏡、X光繞射儀及X光光電子能譜儀進行膜層微觀結構觀察與成分分析；透過分光色差儀量化膜層外觀顏色；以動電位極化曲線分析膜層的耐腐蝕性質，並以Ball-on-disk形式磨耗試驗評估膜層的耐磨耗性質。 研究結果指出，陽極電流密度影響微弧氧化過程中成膜能量，與膜層厚度與相結構有明顯正相關；工作頻率主要能改善膜層的結構，高頻率下進行微弧氧化能使膜層較緻密。而不同電解液濃度的調整均會影響膜層外觀、結構及成分，但經微弧氧化後均可提供純鈦基材良好保護性。透過添加釩酸銨能使膜層中含有黑色V2O3而使膜層呈現深色；氫氧化鈉濃度影響電解液導電度甚劇，使微弧氧化放電行為有明顯變化；而磷酸二氫鈉為本實驗電解液中主要成膜鹽類，高濃度磷酸二氫鈉所製備的膜層較厚且均勻，並含有良好抗磨耗性的金紅石，因而有較佳的抗磨耗性能。
並列摘要
Titanium and its alloys are widely used in aerospace, military, architecture and biomedical industry due to their excellent performance such as high strength to weight ratio, excellent corrosion resistance and high biocompatibility. However, the inherent disadvantages of titanium alloys have limited their usage. For example, titanium may easily undergo severe friction and wear damage. Titanium and its alloys can be treated to generate ceramic-like oxide coatings on its surface by micro arc oxidation(MAO). This coating can improve the corrosion and wear resistance of titanium. Dark TiO2 coatings on Titanium have attracted scientific interest due to their extensive applications such as jewelry, decorative architectures and optical equipment. In this study of MAO process on pure titanium, the applied positive current density, frequency and the concentrations of ammonium metavanadate, sodium hydroxide, sodium dihydrogen phosphate were carefully controlled. The influences of these controlled parameters on the structures, appearance and properties of the MAO coating were discussed. In order to understand the microstructures and compositions of the coatings, the scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy(XPS) were applied. Furthermore, to evaluate the corrosion resistance properties, wear resistance performance and to define the color of the coatings, the potentiodynamic polarization test, ball-on-disk tribometer and colorimeter were used respectively. The experimental results show that the positive current density has pronounced influence on the thickness and phase composition of the coating because it can supply different intensity of energy during MAO process. Frequency can have a more obvious effect on the microstructure of the coating. The dense coating can be obtained by MAO with high frequency. The concentration adjustment of electrolytes will affect the appearance, structures and compositions of the coatings. All these MAO coatings on pure titanium can exhibit excellent surface protection. The dark coatings can be fabricated by adding ammonium metavanadate during MAO process. Sodium hydroxide dramatically influences the conductivity of electrolyte which apparently changes the discharge types. Sodium dihydrogen phosphate can improve high growth rate of the coating. The thick, uniform and good wear resistance MAO coating can be produced by adding high concentration of sodium dihydrogen phosphate during MAO process.
參考文獻
延伸閱讀
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