磁场诱导下CoNi基合金永磁膜的制备及其机理研究
发布时间：2018-09-01 05:53
【摘要】：随着微电机系统的迅速发展和组件的微型化趋势,要求作为系统一部分的磁体必须具有较小的尺寸。永磁薄膜在微电机系统中有着举足轻重的作用,广泛应用于微驱动器、微传感器、微型开关、微型能量采集器以及微泵、微阀等。由于金属钴具有高熔点、高硬度、高耐蚀耐磨性、良好的抗高温氧化和抗拉强度等优异性能,人们发现Co合金镀层结构致密、硬度高、耐热性好、耐磨耐蚀性能优良。除了这些优点以外,最重要的是Co合金薄膜具有很好的磁性能,不仅可以用来作为超高密度垂直磁记录的介质,而且还可以代替电子设备中的微磁体。磁场电沉积技术作为一种新颖的制备技术,在制备薄膜过程中,可以有效的提高沉积效率,细化镀层晶粒,降低表面粗糙度,对磁性膜层在制备过程中进行取向等优点,本文研究磁场诱导下的共沉积技术,在电化学过程中对钴、镍、钴镍薄膜和钴镍锰合金电化学动力学、表面织构、成分、电沉积参数等方面的影响,取得以下结论:(1)研究发现钴的电化学沉积属于一种不可逆的扩散控制的三维瞬时成核过程。磁场对扩散控制体系下的钴电化学沉积过程影响显著,施加垂直于电场的磁场,在钴电沉积体系中可以“减薄”扩散层厚度,提高钴离子传质速度,促进钴的电化学沉积过程。平行磁场下,钴离子在磁场中会受到磁场梯度力作用,表现为受磁场驱动力作用远离阴极表面,抑制了钴的电化学沉积过程。磁场平行电场下,钴容易沿着磁场方向磁化生长,出现典型的“山状”结构颗粒膜。(2)研究发现,镍的电沉积过程属于电化学控制过程,随着阴极极化的增强,极化电流随之增强,镍属于典型的电化学控制的连续成核过程。镍的电化学沉积过程中施加垂直于电场的磁场,有利于提高镍的沉积电流,促进镍的电化学沉积,本质上是由于扩散层厚度的减小。垂直磁场作用下镍表面出现枝晶状颗粒,随着磁场强度的增大,枝晶状颗粒越发明显。磁场平行电场条件下,镍离子在磁场中会受到磁场梯度力作用,表现为受磁场驱动力作用加速迁移到阴极表面,在磁驱动力和“微观洛伦兹力”的作用下,促进镍的电化学沉积过程,提高了沉积速率。(3)钴镍合金属于典型的异常共沉积,主要是较活泼的钴在阴极附近形成氢氧化钴胶体,抑制了镍的沉积,导致镀层中钴的含量增多,并且镀液中钴的含量越高,阴极极化作用越强,异常共沉积越明显,镀层中钴的含量越高。钴镍的电化学沉积过程中施加垂直于电场的磁场,磁场的加入有利于提高钴镍的沉积电流,促进钴镍的电化学沉积。钴镍镀层中钴含量较高时,XRD结构上可以发现Co-hcp结构,扫描电镜上呈现出“稻谷”状形貌。磁场平行电场情况下,CoNi(111)和Co(002)两个方向的衍射峰逐渐增强,证明(111)和(002)分别是CoNi和Co的两个易磁化方向。磁场平行电场作用下,由于钴镍容易沿薄膜磁场方向生长,“枝晶”状结构变得更加明显。(4)电化学沉积CoNiMnP中引入垂直电场方向的磁场,可以提高极化电流和增加膜层的质量。垂直磁场作用下,CoNiMn合金镀层的钴含量有所降低,主要认为是洛伦兹力的“扰动”作用,降低阴极附近的pH值,阻碍钴的氢氧化物的形成,促进了镍的电沉积。CoNi的衍射峰分别出现在44.5°,51.8°,76.4°和93.1°这个四个角度,衍射强度很高,具有较好的晶体结构,引入垂直磁场后,制备得到的样品XRD衍射峰,钴的杂峰减弱,样品结晶度增强。CoNiMn合金的磁性能具有很好的垂直各向异性,磁场的引入有利于增大膜层的矫顽力,提高膜层的比饱和磁化强度。研究发现,1 T磁场下0.8 V沉积电位制备得到的钴镍锰镀层具有最优的矫顽力和剩磁。平行磁场下膜层容易沿着CoNi(111)和Co(002)方向磁化生长,使得膜层从颗粒状转变为枝晶状。
[Abstract]:With the rapid development of micro-motor systems and the trend of miniaturization of components, magnets as part of the system are required to have smaller sizes. Permanent magnet films play an important role in micro-motor systems and are widely used in micro-actuators, micro-sensors, micro-switches, micro-energy collectors, micro-pumps, micro-valves and so on. Cobalt has excellent properties such as high melting point, high hardness, high corrosion resistance and wear resistance, good high temperature oxidation resistance and tensile strength. It has been found that the Co alloy coating has compact structure, high hardness, good heat resistance, excellent wear and corrosion resistance. In addition to these advantages, the most important thing is that the Co alloy film has very good magnetic properties, not only can be used as a super-high temperature oxidation resistance and tensile strength. Magnetic field electrodeposition, as a novel preparation technology, can effectively improve the deposition efficiency, refine the grain size of the coating, reduce the surface roughness, and orient the magnetic film in the preparation process. The effects of magnetic field-induced co-deposition on the electrochemical kinetics, surface texture, composition and deposition parameters of Co, Ni, Co, Ni and Co-Ni-Mn alloys were investigated. The following conclusions were obtained: (1) The electrochemical deposition of cobalt is an irreversible diffusion-controlled three-dimensional transient nucleation process. Cobalt electrodeposition process under the diffusion control system is significantly affected by applying a magnetic field perpendicular to the electric field. In the cobalt electrodeposition system, the thickness of diffusion layer can be "thinned", the mass transfer rate of cobalt ions can be increased, and the electrodeposition process of cobalt can be accelerated. The electrochemical deposition process of cobalt is inhibited by the field driving force acting far from the cathode surface. Under the magnetic field parallel to the electric field, cobalt tends to magnetize along the direction of the magnetic field, and a typical "hilly" structure granular film appears. Nickel is a typical electrochemical controlled continuous nucleation process. The application of magnetic field perpendicular to the electric field during the electrochemical deposition of nickel is beneficial to increase the deposition current and promote the electrochemical deposition of nickel. Essentially, the thickness of diffusion layer decreases. Dendritic particles appear on the surface of nickel under the action of vertical magnetic field, with the increase of magnetic field intensity. Under the magnetic field parallel to the electric field, the nickel ion will be subjected to the magnetic field gradient force, which accelerates the migration to the cathode surface. Under the magnetic driving force and the "micro Lorentz force", the electrochemical deposition process of nickel is promoted and the deposition rate is increased. Cobalt hydroxide colloid formed near the cathode inhibited the deposition of nickel, resulting in the increase of cobalt content in the coating. The higher the content of cobalt in the bath, the stronger the cathodic polarization, the more obvious the anomalous co-deposition, and the higher the cobalt content in the coating. Adding a magnetic field perpendicular to the electric field, the magnetic field can improve the deposition current of cobalt and nickel and promote the electrochemical deposition of cobalt and nickel. (111) and (002) are the two easy magnetization directions of CoNi and Co, respectively. The dendritic structure becomes more obvious due to the growth of cobalt and nickel along the magnetic field direction under the magnetic field parallel to the electric field. (4) The magnetic field perpendicular to the electric field can improve the polarization current and increase the quality of the film. The cobalt content in the coating of CoNiMn alloy decreases under the action of vertical magnetic field, which is mainly attributed to the disturbance of Lorentz force, which reduces the pH value near the cathode, hinders the formation of cobalt hydroxide and promotes the electrodeposition of nickel. The XRD diffraction peaks of the samples were weakened and the crystallinity of the samples was enhanced by introducing a vertical magnetic field. The magnetic properties of CoNiMn alloy were very vertical anisotropy. The introduction of a magnetic field was conducive to increasing the coercivity of the films and increasing the specific saturation magnetization of the films. Cobalt-nickel-manganese coating prepared by deposition potential has the best coercivity and remanence. The film is easy to grow along the direction of CoNi(111) and Co(002) in parallel magnetic field, which makes the film change from granular to dendritic.
【学位授予单位】：中国科学院宁波材料技术与工程研究所
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG132.27;TB383.2
，
本文编号：2216309
[Abstract]:With the rapid development of micro-motor systems and the trend of miniaturization of components, magnets as part of the system are required to have smaller sizes. Permanent magnet films play an important role in micro-motor systems and are widely used in micro-actuators, micro-sensors, micro-switches, micro-energy collectors, micro-pumps, micro-valves and so on. Cobalt has excellent properties such as high melting point, high hardness, high corrosion resistance and wear resistance, good high temperature oxidation resistance and tensile strength. It has been found that the Co alloy coating has compact structure, high hardness, good heat resistance, excellent wear and corrosion resistance. In addition to these advantages, the most important thing is that the Co alloy film has very good magnetic properties, not only can be used as a super-high temperature oxidation resistance and tensile strength. Magnetic field electrodeposition, as a novel preparation technology, can effectively improve the deposition efficiency, refine the grain size of the coating, reduce the surface roughness, and orient the magnetic film in the preparation process. The effects of magnetic field-induced co-deposition on the electrochemical kinetics, surface texture, composition and deposition parameters of Co, Ni, Co, Ni and Co-Ni-Mn alloys were investigated. The following conclusions were obtained: (1) The electrochemical deposition of cobalt is an irreversible diffusion-controlled three-dimensional transient nucleation process. Cobalt electrodeposition process under the diffusion control system is significantly affected by applying a magnetic field perpendicular to the electric field. In the cobalt electrodeposition system, the thickness of diffusion layer can be "thinned", the mass transfer rate of cobalt ions can be increased, and the electrodeposition process of cobalt can be accelerated. The electrochemical deposition process of cobalt is inhibited by the field driving force acting far from the cathode surface. Under the magnetic field parallel to the electric field, cobalt tends to magnetize along the direction of the magnetic field, and a typical "hilly" structure granular film appears. Nickel is a typical electrochemical controlled continuous nucleation process. The application of magnetic field perpendicular to the electric field during the electrochemical deposition of nickel is beneficial to increase the deposition current and promote the electrochemical deposition of nickel. Essentially, the thickness of diffusion layer decreases. Dendritic particles appear on the surface of nickel under the action of vertical magnetic field, with the increase of magnetic field intensity. Under the magnetic field parallel to the electric field, the nickel ion will be subjected to the magnetic field gradient force, which accelerates the migration to the cathode surface. Under the magnetic driving force and the "micro Lorentz force", the electrochemical deposition process of nickel is promoted and the deposition rate is increased. Cobalt hydroxide colloid formed near the cathode inhibited the deposition of nickel, resulting in the increase of cobalt content in the coating. The higher the content of cobalt in the bath, the stronger the cathodic polarization, the more obvious the anomalous co-deposition, and the higher the cobalt content in the coating. Adding a magnetic field perpendicular to the electric field, the magnetic field can improve the deposition current of cobalt and nickel and promote the electrochemical deposition of cobalt and nickel. (111) and (002) are the two easy magnetization directions of CoNi and Co, respectively. The dendritic structure becomes more obvious due to the growth of cobalt and nickel along the magnetic field direction under the magnetic field parallel to the electric field. (4) The magnetic field perpendicular to the electric field can improve the polarization current and increase the quality of the film. The cobalt content in the coating of CoNiMn alloy decreases under the action of vertical magnetic field, which is mainly attributed to the disturbance of Lorentz force, which reduces the pH value near the cathode, hinders the formation of cobalt hydroxide and promotes the electrodeposition of nickel. The XRD diffraction peaks of the samples were weakened and the crystallinity of the samples was enhanced by introducing a vertical magnetic field. The magnetic properties of CoNiMn alloy were very vertical anisotropy. The introduction of a magnetic field was conducive to increasing the coercivity of the films and increasing the specific saturation magnetization of the films. Cobalt-nickel-manganese coating prepared by deposition potential has the best coercivity and remanence. The film is easy to grow along the direction of CoNi(111) and Co(002) in parallel magnetic field, which makes the film change from granular to dendritic.
【学位授予单位】：中国科学院宁波材料技术与工程研究所
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG132.27;TB383.2
，
本文编号：2216309
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