本研究利用電化學碳化(Electrochemical carburization, ECC)技術，在0.1 M 硫酸鈉水溶液中通入二氧化碳作為電解液，在水溶液中以定電位的方式，於純鐵電極表面進行碳沈積反應。經電化學處理後的試片利用能量分散X光譜（EDS）以及X光電子能譜（XPS）確認碳沈積反應，並使用掃描式電子顯微鏡(SEM)觀察純鐵表面積碳的影像與形貌，同時從橫截面量測沈積碳的厚度。實驗結果顯示在-1.3 VSCE、-1.5 VSCE、-1.7 VSCE、-1.9 VSCE電位下進行定電位還原反應，能成功地使碳沉積在純鐵的表面，而碳層的厚度隨著碳化的時間增加而增加，其關係大約呈現正比取向，經過360小時的碳化，其厚度可達42 μm。X光電子能譜結果顯示，經電化學碳化過的鐵基材，會在表層形成一層非晶質碳(284.8 eV)，且部分的碳會擴散至基材中，形成鐵碳固溶體(283.0 eV)。另外，碳擴散的深度會隨碳化的時間增加而增加。
本研究亦探討電化學碳化與滲碳熱處理結合的可能性，將碳化過的試片以真空加熱的方式進行熱處理。結果顯示，沉積碳擴散至鐵基材的區域，會在冷卻後形成麻田散鐵組織、碳化物及石墨等新相。另外，因麻田散鐵組織的出現，其硬度會提升至大約750 Hv。

In this study, electrochemical carburization (ECC) technique was employed in an attempt for carbon deposition on a pure iron electrode surface in 0.1 M sodium sulfate solution purged with carbon dioxide. Carbon deposition was confirmed by using energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The morphology of the deposited carbon was examined by a scanning electron microscope (SEM), which was also used for carbon film thickness determination from the cross-section of the specimen. The experimental results indicated that the reduction of carbon dioxide to carbon did occur on iron electrode surface at an applied potential in the range of -1.3 ~ -1.9 VSCE. The thickness of carbon layer increased with increasing processing time. The as-deposited carbon was mainly in amorphous form while a thin layer of carburized iron just beneath the amorphous carbon was also found as identified by XPS. Subsequent heat treatment at various temperature and time was performed. The dissolution of carbon into iron substrate leading to phase transform was confirmed. Depending on the amount of carbon deposited on pure iron surface and the heat treatment condition applied, different phases such as ferrite, martensite, carbide and graphite, etc., were identified. A significant increase in surface hardness up to about 750 Hv could be obtained with the presence of martensite.

[1] B. Kermani Editor, “Carbon Capture, Transport, and Storage [CCTS] Aspects of Corrosion and Material”, NACE, 2014.
[2] M. Henczka and M. Djas, “Reactive extraction of acetic acid and propionic acid using supercritical carbon dioxide”, The Journal of Supercritical Fluids, vol. 110, pp.154-160, 2016.
[3] P. Ratanajiajaroen and M. Ohshima, “Preparation of highly porous β-chitin structure through nonsolvent-solvent extrange-induced phase separation and supercritical CO2 drying”, J. of Supercritical Fluids, vol. 68, pp. 31-38, 2012.
[4] A. M. Vorobei, O. I. Pokrovskiy, K. B. Ustinovich, O. O. Parenago, S. V. Savilov, V. V. Lunin and V. M. Novotortsev, “Preparation of polymer – multi-walled carbon nanotube composites with enhanced mechanical properties using supercritical antisolvent precipitation”, Polymer, vol. 95, pp 77-81, 2016.
[5] I. A. Cuadraa, A. Cabañasa, J. A. R. Chedaa, F. J. Martínez-Casadob and C. Pandoa, “Pharmaceutical co-crystals of the anti-inflammatory drug diflunisal and nicotinamide obtained using supercritical CO2 as an antisolvent”, Journal of CO2 Utilization, vol. 13, pp. 29-37, 2016.
[6] H. Yoshida, M. Sone, A. Mizushima, K. Abe, T. X. Tang, S. Ichihara, et al., “Electroplating of Nanostructured Nickel in Emulsion of Supercritical Carbon Dioxide in Electrolyte Solution”, vol. 31, pp. 1086-1087, 2002.
[7] H. Yoshida, M. Sone, H. Wakabayashi, H. Yan, K. Abe, X. T. Tao, et al., “New electroplating method of nickel in emulsion of supercritical carbon dioxide and electroplating solution to enhance uniformity and hardness of plated film”, Thin Solid Films, vol. 446, pp. 194-199, 2004.
[8] S. T. Chung and W. T. Tsai, “Nanocrystalline Ni–C Electrodeposits Prepared in Electrolytes Containing Supercritical Carbon Dioxide”, Journal of The Electrochemical Society, vol. 156, p. D457, 2009.
[9] S. T. Chung and W. T. Tsai, “Effect of pressure on the electrodeposition of nanocrystalline Ni–C in supercritical CO2 fluid”, Thin Solid Films, vol. 518, pp. 7236-7239, 2010.
[10] S. T. Chung, Y. C. Chuang, S. Y. Chiu, and W. T. Tsai, “Effect of H3PO3 concentration on the electrodeposition of nanocrystalline Ni–P deposited in an emulsified supercritical CO2 bath”, Electrochimica Acta, vol. 58, pp. 571-577, 2011.
[11] W. T. Tsai, C. Y. Lin and C. M. Tseng, “Electrochemical carburization of pure iron in 1 M Na2SO4 aqueous solution with the presence of supercritical carbon dioxide”, Electrochemistry Communications, vol.49, pp. 14-17, 2014.
[12] W. Y. H. Liew, R. Protasius, J. L. J. Ling, N. J. Siambun and N. A. Mohd-Lair, “Reciprocating wear behavior of mild steel carburized using Na2CO3–NaCl”, Tribology International, vol. 95, pp. 406-418, 2016.
[13] A. W. Batchelor, N. L. Lam and M. Chandrasekaran, “Materials Degradation and its Control by Surface Engineering”, Imperial College Press, 3rd Edition, 2011.
[14] Bard, Allen J., “Electrochemical Method”, John Wiley & Sons, Singapore, Chap. 1-3 & 9, 1980.
[15] R. C. Reid, J. M. P. and B. E. Poling, “The properties of Gases and Liquids”, New York: McGraw-Hill, 1986.
[16] T. Clifforo, “Fundamentals of supercritical fluids”, United Kingdom: Oxford University Press, 1999.
[17] G. L. Weibel and C.K.Ober, “An overview of supercritical CO2 applications in microelectronics processing”. Microelectronics Engineering, vol. 65, p. 145, 2003.
[18] H. Yan, M. Sone, A. Mizushima, T. Nagai, K. Abe, S. Ichihara, et al., “Electroplating in CO2-in-water and water-in-CO2 emulsions using a nickel electroplating solution with anionic fluorinated surfactant”, Surface and Coatings Technology, vol. 187, pp. 86-92, 2004.
[19] H. Yoshida, M. Sone, A. Mizushima, H. Yan, H. Wakabayashi, K. Abe, et al., “Application of emulsion of dense carbon dioxide in electroplating solution with nonionic surfactants for nickel electroplating”, Surface and Coatings Technology, vol. 173, p. 285, 2003.
[20] H. Yan, M. Sone, N. Sato, S. Ichihara and S. Miyata, “The effect of dense carbon dioxide on nickel plating using emulsion of carbon dioxide in electroplating solution”, Surface and Coatings Technology, vol. 182, pp. 329-334, 2004.
[21] A. Mizushima, M. Sone, H. Yana, T. Nagaib, L. Shigeharaa, S. Ichiharaa, et al., “Nanograin deposition via an electroplating reaction in an emulsion of dense carbon dioxide in a nickel electroplating solution using nanionic fluorinated surfactant”, Surface and Coatings Technology, vol. 194, pp. 149-156, 2005.
[22] H. Wakabayashi, N. Sato, M. Sone, Y. Takada, H. Yan, K. Abe, et al., “Nano-grain structure of nickel films prepared by emulsion plating using dense carbon dioxide”, Surface and Coatings Technology, vol. 190, pp. 200-205, 2005.
[23] M. Z. Rahman, M. Sone, M. Eguchi, K. Ikeda, S. Miyata, and T. Yamamoto, “Wear properties of nickel coating film plated from emulsion with dense carbon dioxide”, Surface and Coatings Technology, vol. 201, pp. 606-611, 2006.
[24] K. M. Hong, M. S. Kim, and J. G. Chung, “Characteristic of nickel film electroplated on a copper substrate in supercritical CO2”, J. Ind. Eng. Chem., vol. 11-4, pp. 683-689, 2004.
[25] M. S. Kim and C. K. Kim, “Nickel electroplating on copper substrate in plating solution containing high-density CO2”, J. Ind. Eng. Chem., vol. 11-6, pp. 876-882, 2005.
[26] M. S. Kim, J. Y. Kim, C. K. Kim, and N. K. Kim, “Study on the effect of temperature and pressure on nickel-electroplating characteristics in supercritical CO2”, Chemosphere, vol. 58, pp. 459-465, 2005.
[27] S. T. Chung, H. C. Huang, S. J. Pan, W. T. Tsai, P. Y. Lee, C. H. Yang and M. B. Wu, “Material characterization and corrosion performance of nickel electroplated in supercritical CO2 fluid”, Corrosion Science, vol. 50, pp. 2614-2619, 2008.
[28] 鍾松廷，「於含有超臨界二氧化碳流體之電解液中以電鍍法製備鎳基複合鍍層及材料特性研究」，國立成功大學材料科學及工程學系博士論文，2011。
[29] 林承暘，「純鐵在含有超臨界二氧化碳流體之介質中的電化學碳化研究」，國立成功大學材料科學及工程學系碩士論文，2014。
[30] M. Pourbaix, “ Atlas of electrochemical equilibria in aqueous solutions”, National Association of Corrosion Engineers, 1974.
[31] W. D. Callister and D. G. Rethwisch, “Materials Science and Engineering: An Introduction”, 9th Edition, 2014。
[32] J. Chipman, “Thermodynamics and phase diagram of the Fe-C system”, Metallurgical Transactions, 1972.
[33] R. Abbaschian,L. Abbaschian, R. E. Reed-Hill, “Physical Metallurgy Principles”, 4th Edition, 2008。
[34] 賴耿陽 編譯，「鋼鐵表面熱處理」，日本熱處理技術協會編，1981。
[35] 黃振賢，「金屬熱處理第十八版」，新文京開發出版有限公司，2003。
[36] R. J. Kawka, D. H. Herring, P. Roth and R. J. Sitko, “With hydrocarbon and aliphatic alcohol carrier gas”, Patent number: US 4,386,973 A, Term of patent: from May. 8, 1981 to May. 8, 2001, 1981.
[37] L. C. F. Canale, G. E. Totten, R. A. Mesquita, “Failure Analysis of Heat Treated Steel Components”, ASM International, 2008.
[38] T. H. Courtney, “Mechanical Behavior of Materials”, New York, McGraw-Hill, 2nd, 1990.
[39] J. Lian, B Baudelet, A. A. Nazarov, “Model for the prediction of the mechenical behaviour of nanocrystalline material”, Materials Science Engineer, 1993.
[40] E.O. Hall, “The Deformation and Ageing of Mild Steel:ⅡDiscussion of results”, Proc. Phy. Soc., B. 64, 1951.
[41] N. J. Petch, “The cleavage strength of polycrystals”, J. Iron Steel Inst.,174, 1953.
[42] J. F. Moulder, “Handbook of X-ray photoelectron spectroscopy”, Physical Electronics, Inc., 1995.
[43] M. C. Biesinger, B. P. Paynec, A. P. Grosvenor, L. W. M. Laua, A. R. Gersonb and R. S. C. Smart, “Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni”, Applied Surface Science, vol. 257, pp. 2717–2730, 2011.
[44] A.V. Shchukarev and D.V. Korolkov, “XPS Study of Group IA Carbonates”, Central European Journal of Chemistry, vol. 2, pp. 347-362, 2004.
[45] R. G. J. C. Lascovich and S. Scaglione, “Evaluation of the sp2/sp3 ratio in amorphous carbon structure by XPS and XAES”, Applied Surface Science, vol. 47, pp. 17-21, 1991.
[46] Y. Cao, F. Ernst and G. M. Michal, “Colossal carbon supersaturation in austenitic stainless steels carburized at low temperature”, Acta Materialia, vol. 51, pp. 4171-4181, 2003.
[47] S. S. Zumdahl and S. A. Zumdahl, “Chemistry”, Brooks/Cole, 8th, 2009。
[48] H. J. Hibshman, “Diamond growth process”, Patent number: US 3,371,996 A, Term of patent: from Jan. 20, 1964 to Jan. 20, 1984, 1964.
[49] D.A. Porter, K. E. Easterling and M. Sherif, “Phase Transformations in Metals and Alloys”, 3rd, 2009.