臺灣博碩士論文加值系統

本實驗以仿生法製備CaCO3/Mg,Al-hydrotalcite複合結構於鎂合金AZ91D表面，探究其抗腐蝕性質之研究。將鎂合金AZ91D試片表層先形成Mg,Al-hydrotalcite(Mg6Al2(OH)16CO3•4H2O)，再將具Mg,Al-hydrotalcite層之鎂合金AZ91D試片以懸吊方式浸置在通有二氧化碳之氯化鈣(CaCl2)溶液中，一方面通入二氧化碳可提供形成碳酸鈣所需的碳酸根，另一方面藉由Mg,Al-hydrotalcite之陰離子交換性質，在鎂合金基材表面上形成緻密之碳酸鈣層。
由X-Ray繞射分析結果發現，在室溫下，Mg,Al-hydrotalcite層之鎂合金AZ91D試片浸置在氯化鈣溶液中所形成之碳酸鈣為Calcite相。由SEM之微結構觀察發現，所形成的Calcite相之碳酸鈣會隨著浸置時間的增加而增加。藉由橫截面觀察顯示碳酸鈣也夾雜在Mg,Al-hydrotalcite層中缺陷與裂縫中生長。
由電化學測試顯示，鎂合金AZ91D基材(無碳酸鈣層和Mg,Al-hydrotalcite之鎂合金試片)之腐蝕電位約在-1.45V/Ag/AgCl，腐蝕電流密度約為250μA/cm2；而CaCO3/Mg,Al-hydrotalcite複合結構於鎂合金AZ91D表面之腐蝕電位約在-1.35 V/Ag/AgCl，其腐蝕電流密度約在7.8μA/cm2，除了電化學測試外，也利用鹽水噴霧測試、模擬海水腐蝕試驗及伽凡尼腐蝕測試，其試驗結果顯示，以仿生法製備CaCO3/Mg,Al-hydrotalcite複合結構於鎂合金AZ91D表面，有助於提高鎂合金AZ91D試片的抗腐蝕能力。

This work discussed the corrosion resistance of the CaCO3/Mg,Al-hydrotalcite-coated Mg alloy. The CaCO3/Mg,Al-hydrotalcite composite layer was formed on Mg alloy (AZ91D) by means of biomimetic approach. At first the Mg,Al-hydrotalcite layer was developed on Mg alloy. Afterward, the thick and fast CaCO3 layer was coated on Mg sample, which take advantage of anion-exchangeability of Mg,Al-hydrotalcite by immersing the AZ91D sample in CaCl2 solution. In order to provide the needed CO32- for the formation of CaCO3, CO2 was add into the CaCl2 solution.
The X-Ray diffraction results revealed that a calcium carbonate (CaCO3) layer was coated on the Mg alloy sample surface in 0.1 M CaCl2 solution. The calcium carbonate was calcite phase. The scanning electron microscope (SEM) observation results found that the content of calcium carbonate (CaCO3) increased with increasing of times in 0.1 M CaCl2 solution. The cross-section of samples observation indicated that the calcium carbonate (CaCO3) also was formed on defect and crack areas of the Mg,Al-hydrotalcite layer.
The electrochemical polarization test results showed that the corrosion potential (Ecorr) and current density (Icorr) of the Mg alloy substrate were -1.45 V/Ag/AgCl and 250 μA/cm2. The Ecorr and Icorr of the sample with the CaCO3/Mg,Al-hydrotalcite composite layer were -1.35 V/Ag/AgCl and 7.8 μA/cm2. Several corrosion testing results presented that the sample with the CaCO3/Mg,Al-hydrotalcite composite layer had a much greater corrosion resistance than the sample with the Mg,Al-hydrotalcite layer and the Mg alloy substrate. Therefore the CaCO3/Mg,Al-hydrotalcite composite layer could form on Mg alloy (AZ91D) by biomimetic approach. The composite layer substantially improved the corrosion resistance of the Mg alloy substrate.

致謝i
中文摘要ii
英文摘要iii
總目錄iv
表目錄vi
圖目錄vii
第一章前言1
第二章實驗步驟與方法6
2-1實驗流程6
2-2實驗材料與試片前處理6
2-3Mg,Al-hydrotalcite(Mg6Al2(OH)16CO3•4H2O)之製備方法6
2-4碳酸鈣之形成機制7
2-5顯微組織觀察7
2-5-1掃描式電子顯微鏡（SEM）7
2-5-2場發射掃描式電子顯微鏡（EF-SEM）7
2-6X-Ray繞射分析8
2-7溶液測定8
2-7-1鈣、鎂離子濃度分析儀8
2-7-2pH值測定儀8
2-8腐蝕測試9
2-8-1電化學測試法9
2-8-2鹽水噴霧測試9
2-8-3模擬海水腐蝕測試10
2-8-4伽凡尼腐蝕測試10
第三章實驗結果17
3-1將形成Mg,Al-hydrotalcite層之鎂合金AZ91D試片浸置在氯化鈣 溶液中17
3-1-1XRD分析結果17
3-1-2顯微組織觀察17
(一)表面型態17
(二)橫截面18
3-1-3Mapping之元素分佈19
(一)表面型態19
(二)橫截面19
3-1-4EDS之成份分析19
3-1-5浸置溶液測試20
(一)pH值測定20
(二)鈣、鎂離子分佈20
3-1-6腐蝕試驗20
(一)極化實驗20
(二)鹽霧試驗21
(三)模擬海水之腐蝕測試21
(四)伽凡尼腐蝕測試22
第四章討論37
4-1鎂合金AZ91D在水中自我保護機制38
4-2鎂合金AZ91D之 Mg,Al-hydrotalcite層探討38
4-3碳酸鈣形成機制 39
4-4浸置過程中，pH值與碳酸鈣形成之關係39
4-5鈣、鎂離子對碳酸鈣生成之影響39
4-6腐蝕試驗40
第五章結論46
第六章參考文獻47

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