Co-Ni合金納米線的反常共沉積機理研究
發(fā)布時間：2018-08-21 14:43
【摘要】：本論文研究了實驗室制備多孔氧化鋁(AAO)模板的全過程并且采用電化學沉積法以AAO模板為工作電極沉積得到直徑與AAO模板孔徑一致的金屬單質(zhì)或合金納米線陣列;在此基礎上,針對Co-Ni合金納米線反常共沉積現(xiàn)象進行重點研究并科學地分析得出了 Co-Ni合金納米線的反常共沉積機理。金屬納米線的制備通常運用到模板輔助合成的辦法,完成對工業(yè)鋁片的特殊處理之后,在一定的實驗條件下通過二次陽極氧化的方法制備出了多孔氧化鋁模板并對其進行SEM表征。通過AAO模板——電化學沉積法制備出金屬納米線。根據(jù)金屬電化學沉積原理研究了典型的電流——時間極化曲線,分析指出金屬納米線在氧化鋁通道中的生長模式以及該模式下所對應電流的變化情況。從原子尺度上解釋了金屬納米線在AAO模板中的生長機理。通過不同實驗處理手段得到部分固定在氧化鋁模板框架中長度尺徑統(tǒng)一、排列高度有序的金屬納米線陣列或者完全脫離模板框架束縛的金屬納米線。合金的反常共沉積是指在電沉積過程中,含有不同金屬離子的電解液中的次貴金屬原子優(yōu)先得到沉積,從而導致次貴金屬元素在最終沉積產(chǎn)物中的相對含量高于電解液中的相對含量。Co-Ni合金納米線具有優(yōu)秀的磁性能,機械性能以及熱物理性能,因此具有大量潛在的應用前景。得到的Co-Ni合金納米線的功能性質(zhì)主要取決于材料的成分比例,理解Co-Ni合金納米線反常共沉積的機理將有利于調(diào)控合金納米線的成分比例。在本論文的工作中,我們提出了一種新的關于Co-Ni合金納米線反常共沉積的機理,通過進行沉積電壓對Co-Ni合金納米線成分以及內(nèi)在結構的研究成功解釋了Co-Ni合金納米線反常共沉積的機制:沉積電壓為-0.9 V→-1.6 V,形成的Co-Ni合金納米線主要是hcp相,發(fā)生反常共沉積;而沉積電壓為-3.0 V時,形成的Co-Ni合金納米線主要是fcc相,發(fā)生正常的共沉積。我們提出反常共沉積的出現(xiàn)是由于晶化過程受阻。在此研究中,當沉積形成hcp結構時,由于Ni在hcp相存在一定的固溶極限導致Ni原子沉積到hcp晶格中受到阻礙從而造成Co-Ni合金納米線的反常共沉積;而當沉積形成fcc結構時,Ni在fcc相中具有完全固溶性,于是Ni原子沉積到fcc晶格的過程不受阻礙,從而出現(xiàn)Co-Ni合金納米線的正常共沉積。
[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.
【學位授予單位】：華中師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：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.
【學位授予單位】：華中師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB383.1;TQ133.1
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