Co-Ni合金纳米线的反常共沉积机理研究
发布时间：2018-08-21 14:43
【摘要】：本论文研究了实验室制备多孔氧化铝(AAO)模板的全过程并且采用电化学沉积法以AAO模板为工作电极沉积得到直径与AAO模板孔径一致的金属单质或合金纳米线阵列;在此基础上,针对Co-Ni合金纳米线反常共沉积现象进行重点研究并科学地分析得出了 Co-Ni合金纳米线的反常共沉积机理。金属纳米线的制备通常运用到模板辅助合成的办法,完成对工业铝片的特殊处理之后,在一定的实验条件下通过二次阳极氧化的方法制备出了多孔氧化铝模板并对其进行SEM表征。通过AAO模板——电化学沉积法制备出金属纳米线。根据金属电化学沉积原理研究了典型的电流——时间极化曲线,分析指出金属纳米线在氧化铝通道中的生长模式以及该模式下所对应电流的变化情况。从原子尺度上解释了金属纳米线在AAO模板中的生长机理。通过不同实验处理手段得到部分固定在氧化铝模板框架中长度尺径统一、排列高度有序的金属纳米线阵列或者完全脱离模板框架束缚的金属纳米线。合金的反常共沉积是指在电沉积过程中,含有不同金属离子的电解液中的次贵金属原子优先得到沉积,从而导致次贵金属元素在最终沉积产物中的相对含量高于电解液中的相对含量。Co-Ni合金纳米线具有优秀的磁性能,机械性能以及热物理性能,因此具有大量潜在的应用前景。得到的Co-Ni合金纳米线的功能性质主要取决于材料的成分比例,理解Co-Ni合金纳米线反常共沉积的机理将有利于调控合金纳米线的成分比例。在本论文的工作中,我们提出了一种新的关于Co-Ni合金纳米线反常共沉积的机理,通过进行沉积电压对Co-Ni合金纳米线成分以及内在结构的研究成功解释了Co-Ni合金纳米线反常共沉积的机制:沉积电压为-0.9 V→-1.6 V,形成的Co-Ni合金纳米线主要是hcp相,发生反常共沉积;而沉积电压为-3.0 V时,形成的Co-Ni合金纳米线主要是fcc相,发生正常的共沉积。我们提出反常共沉积的出现是由于晶化过程受阻。在此研究中,当沉积形成hcp结构时,由于Ni在hcp相存在一定的固溶极限导致Ni原子沉积到hcp晶格中受到阻碍从而造成Co-Ni合金纳米线的反常共沉积;而当沉积形成fcc结构时,Ni在fcc相中具有完全固溶性,于是Ni原子沉积到fcc晶格的过程不受阻碍,从而出现Co-Ni合金纳米线的正常共沉积。
[Abstract]:In this paper, the whole process of preparing porous alumina (AAO) template in laboratory was studied and the metal or alloy nanowire arrays with the same diameter as that of AAO template were obtained by electrochemical deposition with AAO template as working electrode. The anomalous co-deposition of Co-Ni nanowires was studied and the anomalous co-deposition mechanism of Co-Ni nanowires was scientifically analyzed. The preparation of metal nanowires is usually applied to template assisted synthesis, after special treatment of industrial aluminum, Porous alumina templates were prepared by secondary anodization under certain experimental conditions and characterized by SEM. Metal nanowires were prepared by AAO template-electrochemical deposition method. Based on the principle of electrochemical deposition of metals, the typical current-time polarization curves were studied. The growth mode of metal nanowires in alumina channel and the corresponding current variation in the mode were analyzed. The growth mechanism of metal nanowires in AAO template was explained from atomic scale. Some metal nanowires with uniform length and diameter in the aluminum oxide template frame or metal nanowires which are completely separated from the template frame were obtained by different experimental methods. Anomalous codeposition of alloys means that in the electrodeposition process, the subprecious metal atoms in the electrolyte containing different metal ions are preferentially deposited. As a result, the relative content of sub-precious metal elements in the final deposition products is higher than that in electrolyte. Co-Ni alloy nanowires have excellent magnetic properties, mechanical properties and thermo-physical properties, so they have a large number of potential application prospects. The functional properties of the obtained Co-Ni alloy nanowires mainly depend on the composition ratio of the materials. Understanding the mechanism of anomalous co-deposition of Co-Ni alloy nanowires will help to control the composition ratio of the alloy nanowires. In this paper, we propose a new mechanism of anomalous co-deposition of Co-Ni alloy nanowires. The mechanism of anomalous co-deposition of Co-Ni alloy nanowires was successfully explained by studying the composition and internal structure of Co-Ni alloy nanowires by means of deposition voltage. The deposition voltage was -0.9 V ~ (-1. 6) V, and the formation of Co-Ni alloy nanowires was mainly hcp phase. Anomalous codeposition occurs, and when the deposition voltage is -3.0 V, the Co-Ni alloy nanowires are mainly formed in fcc phase, and normal co-deposition occurs. We suggest that the anomalous codeposition occurs because the crystallization process is blocked. In this study, when the hcp structure was formed, the deposition of Ni atoms into the hcp lattice was hindered due to the existence of a certain solution limit of Ni in the hcp phase, which resulted in the anomalous co-deposition of Co-Ni nanowires. However, when the fcc structure is formed, Ni is completely solid soluble in the fcc phase, so the process of Ni atom deposition into the fcc lattice is unhindered, thus the normal co-deposition of Co-Ni nanowires appears.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TQ133.1
[Abstract]:In this paper, the whole process of preparing porous alumina (AAO) template in laboratory was studied and the metal or alloy nanowire arrays with the same diameter as that of AAO template were obtained by electrochemical deposition with AAO template as working electrode. The anomalous co-deposition of Co-Ni nanowires was studied and the anomalous co-deposition mechanism of Co-Ni nanowires was scientifically analyzed. The preparation of metal nanowires is usually applied to template assisted synthesis, after special treatment of industrial aluminum, Porous alumina templates were prepared by secondary anodization under certain experimental conditions and characterized by SEM. Metal nanowires were prepared by AAO template-electrochemical deposition method. Based on the principle of electrochemical deposition of metals, the typical current-time polarization curves were studied. The growth mode of metal nanowires in alumina channel and the corresponding current variation in the mode were analyzed. The growth mechanism of metal nanowires in AAO template was explained from atomic scale. Some metal nanowires with uniform length and diameter in the aluminum oxide template frame or metal nanowires which are completely separated from the template frame were obtained by different experimental methods. Anomalous codeposition of alloys means that in the electrodeposition process, the subprecious metal atoms in the electrolyte containing different metal ions are preferentially deposited. As a result, the relative content of sub-precious metal elements in the final deposition products is higher than that in electrolyte. Co-Ni alloy nanowires have excellent magnetic properties, mechanical properties and thermo-physical properties, so they have a large number of potential application prospects. The functional properties of the obtained Co-Ni alloy nanowires mainly depend on the composition ratio of the materials. Understanding the mechanism of anomalous co-deposition of Co-Ni alloy nanowires will help to control the composition ratio of the alloy nanowires. In this paper, we propose a new mechanism of anomalous co-deposition of Co-Ni alloy nanowires. The mechanism of anomalous co-deposition of Co-Ni alloy nanowires was successfully explained by studying the composition and internal structure of Co-Ni alloy nanowires by means of deposition voltage. The deposition voltage was -0.9 V ~ (-1. 6) V, and the formation of Co-Ni alloy nanowires was mainly hcp phase. Anomalous codeposition occurs, and when the deposition voltage is -3.0 V, the Co-Ni alloy nanowires are mainly formed in fcc phase, and normal co-deposition occurs. We suggest that the anomalous codeposition occurs because the crystallization process is blocked. In this study, when the hcp structure was formed, the deposition of Ni atoms into the hcp lattice was hindered due to the existence of a certain solution limit of Ni in the hcp phase, which resulted in the anomalous co-deposition of Co-Ni nanowires. However, when the fcc structure is formed, Ni is completely solid soluble in the fcc phase, so the process of Ni atom deposition into the fcc lattice is unhindered, thus the normal co-deposition of Co-Ni nanowires appears.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TQ133.1
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