离子液体中电沉积Ni-La合金的研究

发布时间：2018-05-30 00:30

  本文选题：EMIC-EG + 电沉积　； 参考：《昆明理工大学》2015年硕士论文

【摘要】：镧元素具有独特的4f层电子结构,使其金属以及其合金薄膜具有一些独特的功能,例如,Ni-La合金具有优良的耐腐蚀性能,当其成分达到LaNi5时,是典型的储氢合金,它具有储氢量高、吸放氢性能较好、合金循环次数高、不会对环境产生污染等特点。本文以EMIC-EG为电解质,采用循环伏安曲线法、计时电流法等多种电化学测试手段,系统地研究了Ni和Ni-La合金在该体系中的电沉积行为,并运用XRF、 XRD、 SEM、 XPS等检测手段对镀层的成分、形貌进行分析。对EMIC-EG-NiCl2电解液进行电化学分析,研究表明,Ni的沉积过程主要是受扩散控制,扩散系数为4.6×10-7cm2／s,扩散活化能为21.75 kJ/mol。温度升高或浓度增大都有利于Ni的还原。在以玻碳电极或铂电极为工作电极时,Ni的沉积属于扩散控制下的三维瞬时形核模型。对EMIC-EG-NiCl2-LaCl3电解液进行电化学分析,研究表明,La在该体系中发生了氧化还原反应,并且Ni-La的电沉积遵从诱导共沉积的机理。温度升高使Ni-La共沉积的起始还原电位正移,LaCl3摩尔浓度的增加,Ni-La共沉积的起始还原电位负移。Ni-La在玻碳电极上的电沉积是属于扩散控制下的三维瞬时形核模型。在含有0.1mol/LNi (II)的EMIC-EG电解液中,在1 mA/cm2恒电流的条件下,以不锈钢为阴极,沉积得到了光滑有轻微亮度的沉积层,沉积层致密并且粒径在100 nm以下。在EMIC-EG-NiCl2-LaCl3电解液中,以铜片为阴极,石墨为阳极,沉积得到了Ni-La沉积层。沉积层中La的含量随着温度和电流密度的增加而增加,随着La(Ⅲ)浓度的增加呈现先增加后减小的趋势。当温度为373 K、Ni(Ⅱ)浓度为0.1 mol/L、 La (III)浓度为0.2 mol、电流密度为5 mA/cm2时,电沉积得到的沉积层中La含量最高,为7.3 at.%。在Ni-La合金中半径较大的La原子取代了半径较小的Ni原子,产生同晶取代,形成固溶置换体,晶格常数比单质Ni的大。SEM结果表明,随着温度和电流密度的增加,沉积层颗粒逐渐增大,沉积层表面粗糙,随着La(Ⅲ)浓度的升高,沉积层表面由圆球形团簇形貌变为枝状结构。耐腐蚀性能实验表明,随着沉积层中La含量的增加,沉积层的耐腐蚀性能呈现先变好后变差的趋势,当沉积层中La含量在1.00 at.%左右时,沉积层的耐腐蚀性能最好。
[Abstract]:Lanthanum has a unique electronic structure of 4f layer, which makes its metal and its alloy film have some unique functions. For example, Ni-La alloy has excellent corrosion resistance and is a typical hydrogen storage alloy when its composition reaches LaNi5. It has the characteristics of high hydrogen storage, good hydrogen absorption and desorption, high cycle times and no pollution to the environment. In this paper, the electrodeposition behavior of Ni and Ni-La alloys in this system was systematically studied by means of cyclic voltammetry and chronoamperometry with EMIC-EG as electrolyte, and the composition of the coating was measured by XRF, XRD, SEM, XPS and other methods. The morphology was analyzed. The electrochemical analysis of EMIC-EG-NiCl2 electrolyte shows that the deposition process of Ni is mainly controlled by diffusion, the diffusion coefficient is 4.6 脳 10 ~ (-7) cm ~ (2) / s, and the diffusion activation energy is 21.75 kJ 路mol ~ (-1). The increase of temperature or concentration is beneficial to the reduction of Ni. When the glassy carbon electrode or platinum electrode is used as the working electrode, the deposition of Ni belongs to the three-dimensional instantaneous nucleation model under the control of diffusion. The electrochemical analysis of EMIC-EG-NiCl2-LaCl3 electrolyte showed that the redox reaction occurred in the system and the electrodeposition of Ni-La followed the mechanism of induced co-deposition. With the increase of temperature, the initial reduction potential of Ni-La codeposition is positively shifted to LaCl3 molar concentration, and the initial reduction potential of Ni-La codeposition is negatively shifted. The electrodeposition of Ni-La on glassy carbon electrode is a three-dimensional instantaneous nucleation model controlled by diffusion. In the EMIC-EG electrolyte containing 0.1mol/LNi II, under the condition of 1 mA/cm2 constant current and using stainless steel as cathode, a smooth and slight luminance deposit layer was obtained. The deposit layer was compact and its diameter was below 100nm. In the EMIC-EG-NiCl2-LaCl3 electrolyte, the Ni-La layer was deposited with copper as cathode and graphite as anode. The content of La in the deposit increases with the increase of temperature and current density, and then decreases with the increase of La (鈪，

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