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二元双相块体纳米晶Ag-25Ni合金腐蚀性能研究

发布时间:2018-12-26 17:02
【摘要】:有关纳米材料在各种溶液中稳定性的研究,已引起人们的高度关注。迄今为止,国内外在这方面的研究还主要集中在表面纳米化、纳米薄膜及纳米涂层上,而对块体尤其是块体纳米晶二元双相合金腐蚀性能的研究还是相对较少。本文采用机械合金化法(MA)和液相还原法(LPR)通过优化合成参数制备纳米晶Ag-25Ni合金粉末,利用真空热压技术通过优化热压参数制备了块体纳米晶Ag-25Ni合金,并与粉末冶金法(PM)制备的块体常规尺寸Ag-25Ni合金对比,利用电化学工作站,通过极化曲线、交流阻抗谱、平均活化能以及Mott-Schottky曲线等测试,研究了它们在中性NaCl、H_2SO_4和酸性NaCl溶液中的腐蚀性能以及显微组织细化对其腐蚀性能的影响,结果表明:(1)三种合金的显微组织如晶粒尺寸、相的结构与分布存在差异。粉末冶金法制备块体常规尺寸合金显微组织极不均匀,组元间固溶度很低;机械合金化法制备块体纳米晶合金显微组织比较均匀,组元间有一定固溶度,而液相还原法制备块体纳米晶合金显微组织均匀,组元间固溶度较低;(2)向中性Na_2SO_4溶液中加入NaCl、H_2SO_4和酸性Na Cl溶液后,不同方法制备的三种PM Ag-25Ni、LPR Ag-25Ni和MAAg-25Ni合金的腐蚀电流密度增大,且随着溶液浓度的增加,三种合金的腐蚀电流密度均增大。晶粒细化后,纳米晶MAAg-25Ni合金的腐蚀速度降低,而纳米晶LPRAg-25Ni合金腐蚀速度则加快;(3)在中性NaCl溶液中,不同方法制备的三种Ag-25Ni合金的交流阻抗谱均由单容抗弧组成,腐蚀过程受电化学反应控制。在H_2SO_4溶液中,MAAg-25Ni和PMAg-25Ni合金的交流阻抗谱为单容抗弧,而LPRAg-25Ni合金则出现扩散尾,腐蚀过程受扩散控制。在酸性NaCl溶液中,PMAg-25Ni合金的交流阻抗由单容抗弧组成,而LPRAg-25Ni和MA Ag-25Ni合金出现扩散尾。三种合金的电荷传递电阻变化趋势与腐蚀电流密度相反;(4)在中性NaCl、H_2SO_4和酸性NaCl溶液中,不同方法制备的三种Ag-25Ni合金均出现钝化现象,晶粒细化并没有改变钝化膜半导体的类型,均为n型半导体。在中性NaCl和酸性NaCl溶液中,三种合金表面形成的钝化膜的载流子密度大小按LPRAg-25NiPM Ag-25NiMA Ag-25Ni合金的顺序降低。在H_2SO_4溶液中,钝化膜的载流子密度大小按LPRAg-25NiMAAg-25NiPMAg-25Ni合金的顺序降低,与三种合金的维钝电流大小规律相符。
[Abstract]:The study on the stability of nanomaterials in various solutions has attracted much attention. Up to now, the researches in this field have mainly focused on the surface nanocrystalline, nanocrystalline films and nanocrystalline coatings at home and abroad, but the corrosion properties of bulk, especially bulk nanocrystalline binary dual phase alloys, have been relatively few. Nanocrystalline Ag-25Ni alloy powder was prepared by mechanical alloying method (MA) and liquid phase reduction method (LPR) by optimizing synthesis parameters. Bulk nanocrystalline Ag-25Ni alloy was prepared by vacuum hot pressing technology by optimizing hot pressing parameters. Compared with the conventional bulk Ag-25Ni alloy prepared by powder metallurgy method (PM), the electrochemical workstation was used to study their effect on neutral NaCl, by means of polarization curve, AC impedance spectrum, average activation energy and Mott-Schottky curve. The corrosion resistance of H_2SO_4 and acid NaCl solution and the effect of microstructure refinement on their corrosion resistance are discussed. The results show that: (1) the microstructure, phase structure and distribution of the three alloys are different, such as grain size. The microstructure of conventional bulk alloy prepared by powder metallurgy method is very uneven, and the solution between components is very low. The microstructure of bulk nanocrystalline alloy prepared by mechanical alloying method is uniform, and there is a certain solution degree among the components, while the microstructure of bulk nanocrystalline alloy prepared by liquid phase reduction method is uniform, and the solution degree between components is low. (2) the corrosion current density of three kinds of PM Ag-25Ni,LPR Ag-25Ni and MAAg-25Ni alloys prepared by different methods increased after adding NaCl,H_2SO_4 and acidic Na Cl solution to neutral Na_2SO_4 solution, and the corrosion current density increased with the increase of solution concentration. The corrosion current density of the three alloys increased. After grain refinement, the corrosion rate of nanocrystalline MAAg-25Ni alloy decreased, while that of nanocrystalline LPRAg-25Ni alloy accelerated. (3) in neutral NaCl solution, the AC impedance spectra of three kinds of Ag-25Ni alloys prepared by different methods are all composed of single capacitive reactance arc, and the corrosion process is controlled by electrochemical reaction. In H_2SO_4 solution, the AC impedance spectrum of MAAg-25Ni and PMAg-25Ni alloys is single capacitive reactance arc, while that of LPRAg-25Ni alloy is diffusion tail, and the corrosion process is controlled by diffusion. In acidic NaCl solution, the AC impedance of PMAg-25Ni alloy is composed of single capacitive reactance arc, while the diffusion tail of LPRAg-25Ni and MA Ag-25Ni alloys appears. The change trend of charge transfer resistance of the three alloys is opposite to the corrosion current density. (4) in neutral NaCl,H_2SO_4 and acid NaCl solution, the three kinds of Ag-25Ni alloys prepared by different methods all appear passivation phenomenon, the grain refinement does not change the type of passivation film semiconductor, all of them are n-type semiconductors. In neutral NaCl and acidic NaCl solutions, the carrier density of passivated films formed on the surface of the three alloys decreased in the order of LPRAg-25NiPM Ag-25NiMA Ag-25Ni alloys. In H_2SO_4 solution, the carrier density of the passivated film decreases in the order of LPRAg-25NiMAAg-25NiPMAg-25Ni alloy, which is consistent with the law of the magnitude of the three alloys.
【学位授予单位】:沈阳师范大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TB383.1;TG178

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