【摘要】：金屬腐蝕普遍存在于國民經濟、國防建設和科學技術等領域,其危害十分嚴重,有必要采取一定的防護措施。緩蝕劑作為一種簡單有效的添加劑能有效地抑制金屬的腐蝕,已成為一種最常用的防腐手段。離子液體因其分子中存在雜環(huán)結構、雜原子(如N、O、S)和多重鍵,成為潛在的良好緩蝕劑并已被應用于金屬的防腐領域。近幾年來已取得了不少進展,但目前離子液體緩蝕劑的研究主要集中在緩蝕性能和效率方面,對于緩蝕過程的微觀機理研究較少。本文以三組體系(氯化1-烷基-3-甲基咪唑[XMIM][C1]體系,1-烷基-3-甲基咪唑乙酸鹽[XMIM][Ac]體系和1-辛基-3-甲基咪唑鹽[OMIM][Y]體系,其中X為乙基、丁基、己基和辛基,Y為Cl、BF4、HS04、Ac和TfO)共11種離子液體作為抑制低碳鋼腐蝕的研究對象,采用量子化學計算的方法系統(tǒng)地分析了離子液體的電子結構和反應活性、鐵表面的表面能和電子結構,采用分子動力學模擬的方法研究了離子液體在鐵表面的吸附行為、揭示了緩蝕過程的微觀機制。取得了如下研究成果:計算發(fā)現(xiàn),對于同一陰離子不同陽離子的[XMIM][C1]和[XMIM][Ac]體系,隨烷基鏈長的增加,最高占有軌道能量(EHOMO)、最低空軌道能量(ELUMO)、軟度(5)和極化率(α)逐漸增大,能隙差(△E)、偶極矩(μ)、硬度(η)和親電指數(shù)(ω)逐漸降低。在同一陽離子不同陰離[OMIM][Y]體系中,離子液體的量子化學參數(shù)差異較大,只有極化率(α)呈增大的趨勢。Fe(100)、Fe(110)和Fe(111)面的表面能γ的大小順序為γFe(111)γFe(100)γFe(110),說明Fe(110)面的結構最為致密、穩(wěn)定。鐵表面的3d軌道最為活潑。Fe(110)不僅易與離子液體的含氧陰離子相互作用,也能與離子液體陽離子的咪唑環(huán)相互作用。因此,選取Fe(110)面作為離子液體的吸附面。結果表明,對于[XMIM][C1]體系,起到緩蝕作用的主要是陽離子[XMIM]+,緩蝕效率的排序為[OMIM][Cl][HMIM][C1][BMIM][C1][EMIM][C1]。[XMIM][Ac]體系的陽離子[XMIM]+和陰離子Ac-均有緩蝕的作用,緩蝕效率的順序為[OMIM][Ac][HMIM][Ac][BMIM][Ac][EMIM][Ac]。在[OMIM][Y]體系中,陽離子[XMIM]+和陰離子 BF4-、HSO4-、Ac-、TfO-均有緩蝕的作用,緩蝕效率的排序為[OMIM][TfO][OMIM][Ac][OMIM][HS04][OMIM][BF4][OMIM][C1]。無論哪種體系,均有離子液體的陽離子或陰陽離子吸附且覆蓋在Fe(110)面形成一層保護膜,阻礙腐蝕介質(H2O、H3O+、Cl-)與金屬表面相互作用,以達到緩蝕的目的。綜上所述,[OMIM][TfO]是所研究11種離子液體中的最佳緩蝕劑。
[Abstract]:Metal corrosion is common in the fields of national economy, national defense construction, science and technology, and its harm is very serious, so it is necessary to take some protective measures. As a simple and effective additive, corrosion inhibitor has become the most commonly used anticorrosion method. Ionic liquids have been used as potential corrosion inhibitors because of their heterocyclic structure, heteroatoms (such as Nu OS) and multiplex bonds, and have been used in the field of metal corrosion protection. A lot of progress has been made in recent years, but at present, the research of ionic liquid corrosion inhibitor is mainly focused on the corrosion inhibition performance and efficiency, and the microscopic mechanism of the inhibition process is less studied. In this paper, three systems (1-alkyl-3-methylimidazole [XMIM] [C1] system) of 1-alkyl-3-methyl imidazole acetate [XMIM] [Ac] and 1-octyl -3-methyl imidazolium salt [OMIM] [Y] system, in which X is ethyl, Ding Ji, Eleven kinds of ionic liquids, hexyl and octyl (Cl,BF4,HS04,Ac and TfO), were used to inhibit corrosion of low carbon steel. The electronic structure and reaction activity of ionic liquids, surface energy and electronic structure of iron surface were systematically analyzed by quantum chemical calculation. The adsorption behavior of ionic liquids on iron surface was studied by molecular dynamics simulation, and the microscopic mechanism of corrosion inhibition process was revealed. The results are as follows: it is found that for [XMIM] [C1] and [XMIM] [Ac] systems with different cations of the same anion, with the increase of alkyl chain length, the maximum occupied orbital energy, (EHOMO), and the lowest orbital energy, (ELUMO), softness (5) and polarizability (偽), increase gradually. The energy gap difference (E), dipole moment 渭), hardness (畏) and electrophilic index (蠅) decreased gradually. The quantum chemical parameters of ionic liquids vary greatly in the same cationic [OMIM] [Y] system. Only the polarizability (偽) tends to increase. The order of surface energy 緯 of Fe (100) Fe (110) and Fe (111) surfaces is 緯 Fe (111) 緯 Fe (100) 緯 Fe (110), which indicates that the structure of Fe (110) surface is the most compact and stable. The 3D orbital on iron surface is most active. Fe (110) is easy to interact with not only the anion containing oxygen but also the imidazole ring of ionic liquid cationic. Therefore, the Fe (110) surface is selected as the adsorption surface of ionic liquids. The results show that for [XMIM] [C1] system, the inhibition efficiency is mainly cationic [XMIM], and the order of inhibition efficiency is [OMIM] [Cl] [HMIM] [BMIM] [C1] [EMIM] [C1] [EMIM] [C1]. [XMIM] [Ac] the order of inhibition efficiency is [OMIM] [Ac] [HMIM] [Ac] [BMIM] [Ac] [EMIM] [EMIM] [Ac]. The order of inhibition efficiency is [OMIM] [Ac] [HMIM] [Ac] [BMIM] [Ac] [EMIM] [EMIM] [Ac]. In [OMIM] [Y] system, both cation [XMIM] and anionic BF4-,HSO4-,Ac-,TfO- can inhibit corrosion. The order of inhibition efficiency is [OMIM] [TfO] [OMIM] [Ac] [OMIM] [HS04] [OMIM] [BF4] [OMIM] [C1]. In either system, cationic or anion ions of ionic liquids are adsorbed and covered on the surface of Fe (110) to form a protective film, which hinders the interaction between the corrosion medium (H _ 2O _ H _ 3O _ 3O _ (Cl-) and the metal surface in order to achieve the purpose of corrosion inhibition. In conclusion, [OMIM] [TfO] is the best corrosion inhibitor in 11 ionic liquids studied.
【學位授予單位】：昆明理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.42

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