【作者】 李建梅；

【导师】 刘燕刚；

【作者基本信息】 上海交通大学 ， 应用化学， 2014， 博士

【摘要】 制备兼具较低高频损耗值P、较大饱和磁感应强度Bs及耐磨、耐蚀等优良综合性能的磁性材料，成为未来集高频化、微型化和节能化等特征于一体的微电子工业的重要组成部分。迄今为止，在诸多的材料制备方法中，电化学技术由于其能够较好的通过控制电化学工艺参数及电解液成分调节薄膜材料的组成、织构及性能，业已成为磁性材料制备、结构分析及性能研究等方面最具发展前景的技术之一。本论文可分为三部分，第一部分（第二章、第三章）在通过电化学循环伏安技术（CV）制备了CoNiFe软磁薄膜的基础上，进一步以经化学修饰处理的Si3N4纳米颗粒为前驱体，获得了整体纳米结构的CoNiFe-Si3N4复合薄膜。随后，采用循环伏安法（CV）、电化学阻抗（EIS）等电化学方法结合扫描电镜（SEM）、X射线衍射（XRD）及磁滞回线（VSM）等测试手段，较为系统的研究了CoNiFe与CoNiFe-Si3N4薄膜电沉积的主要参数（如：电解液中金属离子浓度、外加电位区间、pH值等）、材料结构及性能的变化规律，得到如下结论：（1）通过CV技术制备的CoNiFe软磁薄膜呈整体纳米结构，且具有较好的软磁性能（饱和磁感强度高达2.03T，矫顽力为851.2A/m）。（2）经化学修饰处理的Si3N4纳米颗粒对CoNiFe-Si3N4复合薄膜具有较好的诱导作用，该粒子的掺杂使得CoNiFe-Si3N4复合薄膜的综合磁性能保持较高水平的同时（Bs=1.82T，Hc=716.2A/m），整体硬度及耐蚀性能均有较大幅度的提高。论文的第二部分（第四章及第五章）通过CV、EIS、电化学噪声（EN）等电化学技术结合SEM、XRD等测试方法研究了CoNiFe与CoNiFe-Si3N4薄膜在电沉积反应机理及其在中性3.5wt.%NaCl中的腐蚀机理并得出如下结论：（1）在CoNiFe及CoNiFe-Si3N4薄膜的电沉积体系中，两者的EIS特征在开路电位时均由一高频容抗弧和一低频感抗弧组成；外加负偏压的施加导致低频感抗弧消失并由一低频容抗弧取代。在此过程中，后者的反应电阻Rt及双电层电容相较前者均呈增大趋势。（2）在CoNiF薄膜中掺杂纳米Si3N4颗粒前驱体后，其沉积电位发生明显正移且纳米Si3N4颗粒在阴极表面的竞争吸附使得CoNiFe与Si3N4共沉积阴极还原反应的电荷转移电阻Rt增大。说明还原反应的阴极极化提高了晶体成核速度以及空间位阻阻碍铁系金属晶粒长大的协同作用有利于整体薄膜材料的晶粒细化。同时，CoNiFe与CoNiFe-Si3N4薄膜在异质金属上的电沉积过程均遵循3D瞬时形核/长大机制。（3）CoNiFe-Si3N4复合薄膜较CoNiFe薄膜的耐蚀能力大大提高。同时，在对后者的EN研究结果表明，因次分析法获得的两个分别对应腐蚀过程中快速信息（电化学控制下的点蚀等）及慢速信息（扩散控制下的腐蚀产物膜生成、聚集及脱落）的参数SE和SG与CoNiFe-Si3N4薄膜在腐蚀过程中的反应机理及规律有较好的对应关系。论文的第三部分（第六章）对NdFeB稀土永磁薄膜的电沉积工艺及机理进行了探索。研究结果表明：甘氨酸（C2+2H5NO2）可以作为Fe的良好配体以及Nd3+的还原诱导基参与NdFeB薄膜的共沉积反应。同时，Nd3+在水溶液体系中表现出极高的活性且还原反应过程极其剧烈，而沉积液中过高的Nd3+浓度可能是NdFeB薄膜的晶体生长速度过快而导致晶粒难以细化的原因之一。更多还原

【Abstract】 Magnetic materials with low high-frequency loss, high saturationmagnetization intensity, excellent corrosion resistance and resistance arepotential candidates in MEMS applications. Among various methodsemployed to prepare magnetic films, the electrodeposition method is one ofthe most promising technologies. That is because it is easy to control thecomposition, structure and property of the film through the adjustment oftechnical parameters and electrodeposition bath.This dissertation consists of three parts. In the first part (chapter2andchapter3), nanocrystalline CoNiFe soft magnetic film and CoNiFe-Si3N4composite films have been successfully prepared through cyclic voltammetry(CV) method. In addition, the effects of technical parameters such asterminate potential, Si3N4concentration, pH and agitation speed on the filmstructure have been studied. Then the surface morphologies, magneticproperties, constituent phases and hardness of the CoNiFe and CoNiFe-Si3N4films have been characterized by x-ray diffraction (XRD), scanning electronmicroscopy (SEM) and vibrating sample magnetometer (VSM). The optimalcondition has therefore been determined. The conclusions are follows:(1) The CoNiFe soft magnetic thin film with nano-structure has beenelectrodeposited through CV method. It possesses a high magnetization Bsof 2.03T and a low coercivity Hcof851.2A/m.(2) The electrodeposited CoNiFe-Si3N4composite film possesses highermicro-hardness and smaller nanocrystalline particles than the CoNiFe film.Meanwhile, its magnetic properties (Bs=1.82T, Hc=716.2A/m) is comparableto that of the CoNiFe film.In the second part(chapter4-5), the electrodeposition mechanism andkinetics process of nanocrystalline CoNiFe and CoNiFe-Si3N4thin filmshave been studied by using CV, electrochemical impedance spectroscopy(EIS) and chronoamperometry (CHR). In addition, the corrosion evolutionand corrosion resistance of the CoNiFe and CoNiFe-Si3N4thin films in3.5%NaCl solution have been investigated by using Tafel, EIS, EN combinedwith XRD and SEM. The conclusions are as follows:(1) In the electrodeposition bath of CoNiFe and CoNiFe-Si3N4thin films,both EISs consist of a capacitive arc at high frequency and an inductive arcat low frequency, respectively. As negative bias is applied and increased, theinductive component at low frequency is replaced by another capacitive arc.Meanwhile, the charge transfer resistance Rtand CPE of the theCoNiFe-Si3N4sysytem is higher than those of the CoNiFe system.(2) The addition of nano-sized Si3N4particles into the CoNiFeelectrodeposition bath makes the electrodeposition potential shift in apositive direction. Furthermore, the adsorption of the nano-sized Si3N4particles to the cathode leads to an increase in charge transfer resistanceduring the cathodic reduction process of CoNiFe-Si3N4codeposition, andtherefore increases the cathodic polarization. Finally, the synergetic functionof higher cathodic polarization and grain growth obstruction caused by sterichindrance of absorbed nano-sized Si3N4particles results in the grain refinement and surface densification of the CoNiFe-Si3N4film.(3) The electrodeposition of CoNiFe and CoNiFe-Si3N4thin films belongto anomalous co-deposition. Meanwhile, their nucleation-growth procedurefollows the style of3D transient nucleation/growth mechanism.(4) The CoNiFe-Si3N4film possesses higher corrosion resistance than theCoNiFe film. During the corrosion process of the CoNiFe-Si3N4thin films,two corrosion parameters SEand SGobtained by dimensional analysis methodthrough EN parameters can well describe the fast reaction (such as pittingunder electro-chemical control) and slow reaction (such as corrosion productformation under diffusion control).In the third part(chapter6), the electrodeposition of NdFeB rare earthpermanent magnetic film through CV method has been preliminarily explored.The complexing agent (C2H5NO2and NH4Cl) as additive during NdFeBelectrodeposition has been discussed. Then the effects of NdCl3concentrationand terminate potential on the morphologies of NdFeB thin films have beeninvestigated. It has been shown that the rare permanent magnetic NdFeB filmcould be obtained by electrodepositionin aqueous solution as the codepositionof Nd3+could be induced by Fe2+. Meanwhile, high Nd3+content acceleratesthe growth rate of NdFeB and results in grain coarsening. In addition, due tohigh activity of Nd3+in aqueous solution, the electrodeposition reaction of theNdFeB film is radical. This factor lead to crack in the NdFeB filmelectrodeposited in the bath with higher Nd3+concentration.更多还原