Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/11500
標題: 鎂合金表面成長碳酸鈣/水滑石複合膜提升抗腐蝕研究及其聚焦離子束定點切割觀察
Calcium carbonate/Layered double hydroxide coating for improving the corrosion resistance of Mg alloy and the focus ion beam cross-section structure observation
作者: 王煥新
Wang, Huan-Hsin
關鍵字: 腐蝕
Corrosion
前驅層
水滑石複合膜
碳酸鈣
化學置換鍍層
聚焦離子束
Precursor layer
Hydrotalcite
Layered double hydroxide
Calcium carbonate
Conversion coating
Focus Ion Beam
出版社: 材料科學與工程學系所
引用: [1] Yu Bing-lung, Lin Jun-kai, Uan Jun-yen. Science Direct, Trans.Nonferrous Met.Soc.China 20(2010) 1331-1339. [2] A.A.Zuleta, E.Correa, C.Villada, M.Sepulveda, J.G.Castano, F.Echeverria, Surface & Coatings Technology, 205(2011)5254-5259. [3] B.L. Yu, X.L.Pan, J.Y.Uan. Corrosion enhancement of Mg alloy, Corrosion Science, 52(2010)1874-1878. [4] Norio Wada, Kimihiro Yamashita, and Takao Umegaki, Journal of Colloid and Interface Science 201,1-6(1998) [5] Jitka MacAdam & Simon A.Parsons, Environmental Science and Bio/Technology 3:159-169,2004. [6] M.Pourbaix,Atlas of electrochemical equilibria in aqueous solutions, National Assosiation of Corrosion Engineers, Houston, 1974,pp.139-145. [7] V.R. Constantino, T.J. Pinnavaia, Inorganic Chemistry, 34 (1995) 883-892. [8] Y. You, G.F. Vance, H. Zhao, Applied Clay Science, 20 (2001) 13-25. [9] U. Olsbye, D. Akporiaye, E. Rytter, M. Ronnekleiv, E. Tangstad, Applied Catalysis A: General, 224 (2002) 39-49. [10] Jun-Yen Uan, Bing-Lung Yu and Xin-Liang Pan, The Minerals, Metals & Materials Society and ASM International 2008. [11] P.Koczon, W.Lewandowski, A.P.Mazurek, Vibrational Spectroscopy 20(1999) 143-149. [12] Yan Feng Zhang, Jiu Xing Zhang, Qing Mei Lu, Qing Yun Zhang, Materials Letters 60(2006) 2443-2446. [13] M.A.Legodi, D.DE WAAL, and J.H.Potgieter, Department of Chemistry, University of Pretoria, South Africa. [14] I.C. Chisem, W. Jones, J. Mater. Chem., 4 (1994) 1737-1744.
摘要: 鎂合金在目前行動及手持式電子產品中,是一種受歡迎的外殼材料,由於夲身電化學活性較大,表面抗腐蝕的能力格外重要. 抗腐蝕有眾多方法,電化學電鍍,陽極處理, 化學置換鍍層等等,其一是以化學置換鍍層法,在表面形成碳酸鈣層,隔絕外界環境可能對鎂合金造成的腐蝕。 實驗樣品以AZ91D鎂鋁合金當試片, 浸泡在碳酸鈣溶液,在表面形成 LDH (Layered Double Hydroxide) 以及碳酸鈣 CaCO3層,藉由層狀披覆保護底材對抗腐蝕,使用不同的檢測儀器SEM/ EDS 對表面形態結構及元素分佈做觀察分析,AZ91D初期經過碳酸水溶液的腐蝕會形成表面龜裂的情形,表面元素已轉換成含有大量的碳(C)及氧(O),使用 FT-IR對形成的物質種類做比對確認,再以 GAXRD低掠角X光繞射分析儀針對表面物質的結晶程度做觀察,峰值從原先前驅層LDH的出現但不明顯的狀態經過鹼性碳酸水溶液浸泡後轉變成峰值明顯的Mg ,Al-hydrotalcite(Mg6Al2(OH)16CO3.4H2O) LDH,顯示前驅層形成結晶的趨勢明確,後段CaCO3階段則顯現出結晶型態大多屬於Calcite,這和浸泡在過飽和的碳酸鈣溶液有密切關係。由電化學極化實驗TAFEL曲線尋找腐蝕電位及電流評估抗腐蝕的能力,經 LDH及碳酸鈣成長的試片,其腐蝕電位上升,腐蝕電流有下降的趨勢,顯示對抗腐蝕能力有明顯提升。 試片在某些區域發現到覆蓋不甚均勻的情形,從表面SEM觀察可看到少量的孔洞,這種結構很可能對抗腐蝕層的功能造成威脅與傷害,針對此使用 FIB做定點切割,再由FE-SEM觀察及比較孔洞和碳酸鈣覆蓋區域的縱切面,藉以瞭解結構上的差異並推論形成的原因,可作為製程上改善的依據。 從觀察及量測的過程發現,試片表面碳酸鈣成長較差的區域,其底下的前驅層則比旁邊成長較佳區域為薄,甚至有區域發現沒有碳酸鈣,其底下也沒出現應有的前驅層,這說明前驅層對碳酸鈣的成長具有很大的影響,亦即試片浸泡初期腐蝕是必然的,但是維持它的腐蝕深度及腐蝕的均勻性卻是必要的。
There are a lot of methods to enhance the anti-corrosion capability of Magnesium alloy. Electrochemical plating, anodizing process, chemical conversion coating etc, are those of them. One method is to use chemical conversion coating to form a CaCO3 layer onto the Mg alloy to isolate it from the surroundings. This could prevent it from the possibilities of corrosion to the base material. This experiment used AZ91D Mg-Al alloy , the widely used in electronic industry, and dip into CaCO3 solutions to form LDH and CaCO3 layer for corrosion resistance. First is to dip samples into carbonic acid to form precursor layer. SEM/EDS show that the surface exists many crack lines and already change to high amount of oxygen and carbon. FTIR and GAXRD detect the LDH grain structure after dipping into alkaline carbonic acid solution. And finally dipping into CaCO3 solutions, SEM show it is mostly calcite grain type and polarization curves indicate the corrosion resistance capability is enhanced. We may observe some pores on the surface by SEM inspection. This kind of structure should decrease the capability of corrosion resistance. Using Focus Ion Beam for digging a hole across the poor and well coated areas, compare the under structure by FE-SEM inspection. Under 4~5kx magnification, a precursor layer with cracks are found between CaCO3 and base substrate. After observation, the poor CaCO3 coating area has thinner precursor layer; furthermore there is an area without CaCO3, the precursor layer could not be found. This indicates the precursor layer plays an important role in the formation of CaCO3 coatings. The preliminary corrosion should be necessary and how to keep corrosion a certain depth and uniformity is essential in the process of CaCO3 coating formation.
URI: http://hdl.handle.net/11455/11500
其他識別: U0005-1408201313075100
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-1408201313075100
Appears in Collections:材料科學與工程學系

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