本研究嘗試以含有超臨界二氧化碳流體之電解液進行電化學碳化反應，在純鐵基材上完成電化學碳沉積，使金屬表面產生碳化，使用的電解液為1 M之硫酸鈉水溶液。本實驗採用的電化學方法有兩種，第一種為定電流製程，施加-5 A/dm2之電流密度，進行五小時的電化學碳化，第二種為定電位製程，施加的電位為 -1.5 VPt、-1.8 VPt、-2.1 VPt及-2.4 VPt，進行三小時的電化學碳化反應。實驗結果顯示，於固定電流密度下反應，可以成功的還原碳原子，使用X射線光電子能譜儀、掃描穿透式電子顯微鏡及歐傑電子能譜儀進行分析，結果顯示經過電化學碳化的試片，在表面形成一層非晶質碳的結構，並在純鐵內部有碳固溶的現象發生。若以定電位的方式進行電化學碳化，於電位-1.5 VPt、-1.8 VPt、-2.1 VPt及-2.4 VPt均可在表面發生碳還原，經過X射線光電子能譜儀及歐傑電子能譜儀的縱深分析，結果顯示碳還原之速率和還原電位的絕對值呈現正相關，電位越負時，表面之非晶質碳有較厚的趨勢，但是碳還原速率太快時，表面的非晶質碳會阻擋初生態碳的擴散，進而導致內部形成鐵碳固溶體狀態的深度較淺。

In this research, electrochemical carburization (ECC) of iron in supercritical CO2 (sc-CO2) containing aqueous electrolyte was attempted and studied. The deposition of carbon on pure iron substrate, which was reduced electrochemically from the 1 M Na2SO4 aqueous electrolyte mixing with sc-CO2. There are two electrochemical methods in this study. The first one is galvanostatic mode which applied constant current density of -5 A/dm2 for 5 hours. The second one is potentiostatic mode which conducted with constant voltage 3 hours at -1.5 VPt, -1.8 VPt, -2.1 VPt and -2.4 VPt respectively. The experimental results showed when electrochemical carburization at -5 A/dm2, an obviously reduction reaction of carbon could be found. The formation of carbon film and subsequent carburization of iron substrate was analyzed employing X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The amorphous carbon layer on metal surface and Fe-C solid solution form in iron substrate was confirmed. In potentiostatic test, C 1s signal of the carbon-bearing filmsform at -1.5 VPt, -1.8 VPt, -2.1 VPt and -2.4 VPt was observed by XPS. In addition, the reduction rate of carbon depended on the cathodic potential applied in ECC treatment which is manifested by XPS and AES depth profile results. The thickness of amorphous carbon is increasing with a relative negative potential. However, the amorphous carbon film grew too fast and resisted the nascent carbon diffusing into iron substrate, resulting in a relative thin Fe-C solid solution layer.

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