脈衝電源波形對微弧氧化二氧化鈦微觀組織之影響

Effect of Pulsed Waveforms on the Microstructure of Micro-arc Oxidized Titanium Dioxide

電源參數設定是新式陽極處理技術-微弧氧化製程操作上重要的關鍵。本研究採用單極脈衝電源搭載任意波形產生器調控脈衝波形週期為30000μs的條件下，使用磷酸二氫鈉電解液，在固定微弧處理時間20 min，分別在定電壓450 V、改變輸出時間（Ton= 250 ~ 15000μs）的條件下，以及在定功率225 W、同時改變電壓（300 ~ 900 V）和輸出時間（Ton= 11250 ~ 340μs ）的條件下，於鈦金屬表面進行微弧氧化試驗。研究結果顯示：在定電壓條件下，隨著輸出時間提高，微弧氧化層微觀組織孔洞尺寸及數量皆有逐漸增大與增加的趨勢，且在長脈衝時間的條件下呈現出較疏鬆並產生了開放式孔洞的鍍層形態，近似於傳統直流模式之生長行為，鍍層結構以銳鈦礦相二氧化鈦為主。在定功率條件下高電壓和短脈衝時間的搭配下，鍍層仍以銳鈦礦相二氧化鈦結構為主，但微弧氧化層生長速率提高，並且通孔形貌消失。

The power delivering mode is a key parameter in the micro-arc oxidation (MAO) process. We applied different pulsed waveforms during the MOA process to grow titanium dioxide (TiO2) coatings on α-Ti and investigated the effect of pulsed waveforms on the microstructures of the TiO2 coatings in this study. A unipolar power supply equipped with an arbitrary waveform generator was used to generate pulsed waveforms. The periods of all waveforms were set at a constant value of 30000 μs. The MAO treatment was carried out in a NaH2PO4 electrolyte for 20 min. The first part of this study involved a constant working voltage of 450 V with varying treating times (Ton) ranging from 250 μs to 15000 μs. The second part involved a constant power input of 225 W with varying working voltages and Tons ranging from 300 V to 900 V and from 11250 μs to 340 μs, respectively. Experimental results showed that under a constant working voltage, with increasing Ton and average delivered power, both the pore size and the number of pores of which some were even open ones in the MAO coating increased. They were close to those obtained by using the traditional DC mode. On the other hand, under a constant power input, the growth rate significantly increased at high working voltages and short Tons, and no open pores in the coating were found. The coating structure was mainly composed of anatase TiO2.