直流及脈衝式水溶液電漿之診斷及其相關製程研究

Abstract

本研究對於直流式及脈衝式水溶液電漿進行診斷，並以水溶液電漿進行材料製程。以脈衝式電源驅動之水溶液電漿與以直流或交流電源驅動之水溶液電漿相比有較良好之再現性，其高穩定性在製程方面相當有利，並可藉由調整電漿參數進行氣泡模式之轉換，因此在各種製程方面具有相當大的彈性及潛力。實驗上分為兩個部分，第一部分對於脈衝式水溶液電漿進行診斷；第二部分對於水溶液電漿之製程進行研究。脈衝式水溶液電漿診斷部分分為水溶液電漿殘餘效應研究、水溶液電漿模式轉換研究與硫雙原子分子光譜分析。在水溶液電漿殘餘效應研究中發現當殘餘效應產生時，每一週期電漿之電流波形會逐漸產生變化。在實驗中也發現殘餘效應在不同休止時間下有共同的穩態特徵時間，此時間約在 10^-1 秒至 10^0 秒間，實驗中也對殘餘效應之機制進行研究，並提出可能之機制。此研究對於維持水溶液電漿製程之穩定有一定之重要性。在水溶電漿模式轉換研究中針對脈衝式水溶液電漿在電漿生成時的不同模式轉換進行研究，實驗中探討在電漿生成時不同工作時間與休止時間下之不同操作模式、模式間之轉換行為以及其性質檢測。三種伴隨電漿生成的不同模式：噴流模式(JM)、過渡模式(TM)以及固定氣泡模式(FBM)會在固定工作時間時隨著休止時間之減少而陸續出現。實驗中也對於不同操作模式下之電流波形以及電漿放射光強度進行研究。此研究對於未來水溶液電漿製程最適化提出另一種可能性。在硫雙原子分子光譜分析中發現水溶液電漿在含有硫酸根之電解質溶液中可以觀察到硫雙原子分子光譜。研究中發現硫雙原子分子放射光傾向於低電壓及高工作週期中生成，且在特定的操作時間後，此放射光強度會突然迅速減少而後消失。實驗中也發現水溶液電漿中之鈉原子與硫雙原子分子有反向消長關係，但對其消長機制尚未有明確之定論。此放射光譜並未在任何水溶液電漿之文獻中出現，結果顯示水溶液電漿在特定操作時間後不但操作模式可能有所改變，而各原子的激發態組成會有所改變。 水溶液電漿製程研究主要為氧化石墨烯製備。研究中發現水溶液電漿無法成功直接將石墨轉化為氧化石墨烯，但若將石墨進行化學前處理再經水溶液電漿處理後，可增加氧化石墨之層間距、結晶性、分散性以及氧化程度。研究結果證明水溶液電漿可進一步對於經由化學法前處理後之氧化石墨造成化學性質之改變，並且可有效製備出氧化石墨烯。

The diagnosis of plasma generated by a pulsed voltage in NaNO3 electrolytic solution and its potential applications are studied. The pulsed power driven solution plasma system has better stability and cycle-to-cycle reproducibility than the solution plasma driven by DC or AC power, and the bubble behavior of the pulsed power driven solution plasma can be controlled by optimizing the parameter of the pulse power, which shows its potential application for material fabrication. These experimental investigations include two parts: Diagnostic study of pulsed power solution plasmas and potential applications of solution plasma. In the first part, the history effect of the pulsed power driven solution plasma system is studied. With a sufficiently short Toff, the history effect, i.e. the plasma generated in one power cycle is consistently affected by that generated in the previously cycle, is observed. In the experiment, the time to reach steady state is about 0.1 to 1 s. The mechanism of history effect is studied and probable mechanism is also proposed. The transition of bubble behavior of the pulsed power driven solution plasma with different Ton and Toff is also studied. Three different types of bubble behaviors with plasma formation are observed: The jetting mode, the transitional mode and the fixed bubble mode. The different current waveforms and the plasma emission behaviors in different modes are also studied. This study proposes another method to optimize the solution plasma processing. Molecular emission of diatomic sulphur (S2) when the plasma is sustained in low concentration solution containing sulfate ion is also studied. The intensity of S2 emission gradually drops to the noise level with a specific operating time. This observation suggests that the optical emission emanating from the plasma involves a more complex pathway than those suggested in the literature. It shows both bubble behaviors and excited state species change with processing time. In the second part, the fabrication of graphene oxide by solution plasma is studied. Solution plasma cannot directly transform graphite into graphene oxide. However, with chemical pretreatment of graphite, the interlayer spacing, crystallinaty, dispersion and oxidized extent of graphene oxide can be further improved by solution plasma.