本文選題：氧化鈰 + 涂層��； 參考：《重慶大學(xué)》2016年博士論文

【摘要】：金屬材料的腐蝕與防護(hù)一直是航空航天、汽車等工業(yè)領(lǐng)域的研究熱點。國內(nèi)外大量研究集中于采用表面涂層工藝增強(qiáng)鋁合金的耐腐蝕性能。其中,鋁合金表面沉積鉻基涂層是過去80年里在航空航天和汽車工業(yè)領(lǐng)域應(yīng)用最廣泛的、耐腐蝕效果最好的、研究最透徹的涂層工藝。但近年來,六價鉻化合物因具有劇毒性和致癌性而被限制使用,此后,國內(nèi)外大量的研究集中于鉻膜替代物的研究與開發(fā)。其中稀土轉(zhuǎn)化膜,特別是鈰基轉(zhuǎn)化膜,是去鉻化涂層中給鋁合金提供腐蝕保護(hù)效果最好的涂層體系。然而,現(xiàn)有的關(guān)于鋁合金表面鈰基防腐涂層的研究都是采用基于液相反應(yīng)的化學(xué)法來沉積鈰基涂層,這些化學(xué)方法的制備過程都涉及鈰基化合物及其他酸性或堿性溶液的使用和廢棄,對環(huán)境有較大的影響。采用化學(xué)法制備的氧化鈰基涂層存在較多微米級尺度的裂紋及缺陷,且與鋁合金基體的結(jié)合力不佳。此外,由于現(xiàn)有的基于液相反應(yīng)的制備工藝不能控制氧化鈰基涂層的化學(xué)組成,特別是其中Ce基團(tuán)的價態(tài),至今鈰基涂層覆蓋的鋁合金基材對腐蝕介質(zhì)的響應(yīng)機(jī)制未能得到透徹的研究。因此,采用綠色環(huán)保的制備工藝,改善鈰基涂層的表面形貌和膜基結(jié)合強(qiáng)度,深入探討涂層中Ce基團(tuán)的價態(tài)、涂層的微觀結(jié)構(gòu)與腐蝕性能間的關(guān)系,對鈰基涂層在高強(qiáng)鋁合金防腐領(lǐng)域的推廣應(yīng)用具有重要意義,也能為鈰基防腐涂層在其他金屬腐蝕保護(hù)領(lǐng)域的應(yīng)用帶來一定的啟發(fā)。本文采用磁控濺射技術(shù)在Al 2024-T3合金表面沉積了CeO_2涂層,研究了的涂層的厚度、表面形貌、晶型結(jié)構(gòu)、膜基結(jié)合強(qiáng)度及電化學(xué)腐蝕性能,并分析比較了磁控濺射法制備的CeO_2涂層與化學(xué)法所制氧化鈰基涂層在形貌、結(jié)構(gòu)和腐蝕特性上的異同。實驗結(jié)果表明,與化學(xué)法制備的氧化鈰基膜層相比,磁控濺射沉積的CeO_2涂層為Al合金基材提供了效果相當(dāng)或更佳的陰極抑制效應(yīng),且具有更少的表面缺陷和更高的膜基結(jié)合強(qiáng)度,可以為2024-T3鋁合金基材提供較好的腐蝕保護(hù)。然而,本實驗條件下制備的CeO_2涂層并不具備磷化后期處理的氧化鈰轉(zhuǎn)化涂層所具有的動態(tài)電化學(xué)活性,只能充當(dāng)腐蝕介質(zhì)和鋁合金基體間的靜態(tài)物理阻隔層。采用共濺射法在CeO_2涂層的沉積過程中引入Al原子制備了Ce-Al-O涂層,分析比較了鋁合金基材表面沉積的Al、CeO_2和Ce-Al-O三種涂層的晶體結(jié)構(gòu)、微觀結(jié)構(gòu)、化學(xué)組成及電化學(xué)腐蝕特性的異同,結(jié)果表明2024-T3鋁合金表面沉積的Al涂層為三維島狀晶態(tài)結(jié)構(gòu),CeO_2涂層為柱狀晶態(tài)結(jié)構(gòu),二者均是作為腐蝕介質(zhì)和鋁合金基體間的物理阻隔層來為鋁合金基體提供一定的腐蝕保護(hù),對Al合金基體的點蝕特性無改善。而對于Ce-Al-O涂層,Al原子在沉積過程中的引入使得柱狀晶態(tài)CeO_2結(jié)構(gòu)轉(zhuǎn)變?yōu)橹旅芫鶆虻姆蔷Щ虺?xì)納米晶Ce-Al-O結(jié)構(gòu),使純Al 2024-T3合金基材的耐腐蝕性能提高三個多數(shù)量級,并大幅降低了鋁合金基體發(fā)生點蝕破壞的傾向。通過改變CeO_2靶材的功率,研究了Ce-Al-O涂層化學(xué)組成的改變對膜基體系電化學(xué)腐蝕性能的影響;并在保持Ce-Al-O涂層化學(xué)組成不變的條件下,研究了Ce-Al-O涂層的厚度對Ce-Al-O涂層的微觀結(jié)構(gòu)和耐腐蝕性能的影響。結(jié)果表明,Ce-Al-O涂層厚度的改變不會改變涂層在電化學(xué)測試中的動態(tài)腐蝕響應(yīng)特性的本質(zhì),但Ce-Al-O涂層對鋁合金基體的電化學(xué)腐蝕過程的抑制效果,特別是對鋁合金基體陽極點蝕過程的改善取決于涂層對樣品的有效覆蓋、涂層內(nèi)致密層厚度、及Ce(III)基團(tuán)的比例和含量。通過長期鹽浴浸泡實驗研究了Al 2024-T3合金基材表面磁控濺射沉積的CeO_2和Ce-Al-O涂層的長期腐蝕響應(yīng),提出了CeO_2和Ce-Al-O涂層對基材不同的腐蝕保護(hù)機(jī)制。當(dāng)涂層內(nèi)的Ce基團(tuán)主要以Ce(IV)形式存在時,晶態(tài)CeO_2涂層具有很好的化學(xué)惰性,是鋁合金基體和腐蝕介質(zhì)間優(yōu)異的阻隔層,涂層完好的情況下能為鋁合金基體提供良好的腐蝕保護(hù),但破損的涂層不具備自修復(fù)能力;當(dāng)涂層內(nèi)的Ce基團(tuán)主要以Ce(III)形式存在時,所沉積的非晶態(tài)Ce-Al-O涂層具有致密的微觀結(jié)構(gòu)和良好的膜基結(jié)合強(qiáng)度,在腐蝕過程中基于Ce、Al、O原子間的氧化還原反應(yīng)和Ce離子的選擇性釋放而實現(xiàn)對腐蝕介質(zhì)的動態(tài)響應(yīng),涂層在一定程度上具有自修復(fù)的特性。
[Abstract]:Corrosion and protection of metal materials have been a hot spot in aerospace, automotive and other industrial fields. A large number of studies have focused on the corrosion resistance of aluminum alloys with surface coating technology. The chromium based coating on the surface of aluminum alloy is the most widely used in the field of aerospace and automobile industry in the past 80 years. The best effect is to study the most thorough coating process. However, in recent years, six valence chromium compounds have been limited to use because of their highly toxic and carcinogenicity. After that, a large number of studies at home and abroad have focused on the research and development of chromium film substitutes. However, the existing research on the cerium based anticorrosive coating on the aluminum alloy surface is to use the chemical method based on liquid phase reaction to deposit cerium based coating. The preparation process of these chemical methods involves the use and discarding of cerium based compounds and other acidic or alkaline solutions, which has a great influence on the environment. The cerium oxide based coating prepared by the method has many micron scale cracks and defects, and the bonding force to the aluminum alloy matrix is not good. In addition, the chemical composition of the cerium oxide based coating can not be controlled by the existing preparation process based on the liquid phase reaction, especially the valence state of the Ce group, so far the aluminum alloy substrate covered by the cerium base coating is so far. The response mechanism of the corrosive medium has not been thoroughly studied. Therefore, the green and environmental preparation technology is adopted to improve the surface morphology and bond strength of the cerium based coating. The valence state of the Ce group in the coating, the relationship between the microstructure and corrosion properties of the coating are discussed, and the application of the cerium based coating in the field of high strength aluminum alloy anticorrosion is applied. It is of great significance and can enlighten the application of cerium based anticorrosion coating in the field of other metal corrosion protection. In this paper, the CeO_2 coating was deposited on the surface of Al 2024-T3 alloy by magnetron sputtering. The thickness, surface morphology, crystal structure, bond strength and electrochemical corrosion properties of the coating were studied and compared. The morphology, structure and corrosion characteristics of the CeO_2 coating prepared by the magnetron sputtering and the cerium oxide based coating made by chemical method are different. The experimental results show that the CeO_2 coating deposited by magnetron sputtering provides a better or better cathodic inhibition effect for Al alloy substrate than the cerium oxide base film prepared by chemical method. The surface defects and higher bond strength can provide better corrosion protection for the 2024-T3 aluminum alloy substrate. However, the CeO_2 coating prepared under this experimental condition does not possess the dynamic electrochemical activity of the cerium oxide conversion coating treated by the later phosphating process, only as the static physics between the corrosion medium and the aluminum alloy matrix. The Ce-Al-O coating was prepared by Al atom in the deposition process of CeO_2 coating by CO sputtering. The crystal structure, microstructure, chemical composition and electrochemical corrosion characteristics of the three coatings deposited on the surface of aluminum alloy substrate were analyzed and compared. The results showed the Al coating deposited on the surface of 2024-T3 aluminum alloy. For the three-dimensional Island crystalline structure, the CeO_2 coating is a columnar crystalline structure. The two are both as the physical barrier between the corrosion medium and the aluminum alloy matrix to provide certain corrosion protection for the aluminum alloy matrix, and the pitting characteristics of the Al alloy matrix are not improved. For the Ce-Al-O coating, the introduction of Al atoms in the deposition process makes the columnar crystalline state Ce. The structure of O_2 is transformed into a compact and uniform amorphous or ultrafine nanocrystalline Ce-Al-O structure. The corrosion resistance of the pure Al 2024-T3 alloy substrate is increased by three orders of magnitude, and the pitting damage tendency of the aluminum alloy matrix is greatly reduced. By changing the power of the CeO_2 target, the change of the chemical composition of the Ce-Al-O coating on the membrane based system electricity is studied. The influence of chemical corrosion properties and the influence of the thickness of the Ce-Al-O coating on the microstructure and corrosion resistance of the Ce-Al-O coating on the condition of keeping the chemical composition of the Ce-Al-O coating unchanged. The results show that the change of the thickness of the Ce-Al-O coating will not change the nature of the dynamic corrosion response characteristic of the coating in the electrochemical test, but Ce-Al The inhibition effect of -O coating on the electrochemical corrosion process of aluminum alloy matrix, especially the improvement of the corrosion process of the aluminum alloy matrix anode depends on the effective coverage of the coating to the sample, the thickness of the coating in the coating and the proportion and content of the Ce (III) group. The magnetron sputtering on the substrate surface of the Al 2024-T3 alloy substrate was studied by a long-term salt bath immersion test. The long-term corrosion response of the deposited CeO_2 and Ce-Al-O coatings shows that the corrosion protection mechanism of the CeO_2 and Ce-Al-O coatings on the substrate is different. When the Ce group in the coating mainly exists in the form of Ce (IV), the crystalline CeO_2 coating has good chemical inertness. It is an excellent barrier layer between the aluminum alloy and the corrosion medium, and the coating is in good condition. It can provide good corrosion protection for the aluminum alloy substrate, but the damaged coating does not have self repairing ability. When the Ce group in the coating mainly exists in the form of Ce (III), the amorphous Ce-Al-O coating deposited in the coating has a compact microstructure and good bonding strength of the membrane base. In the corrosion process, the redox reaction between the Ce, Al, and O atoms is based on the corrosion process. The dynamic response of corrosive medium should be achieved with the selective release of Ce ions.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG174.4

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