【摘要】：隨著微電機(jī)系統(tǒng)的迅速發(fā)展和組件的微型化趨勢(shì),要求作為系統(tǒng)一部分的磁體必須具有較小的尺寸。永磁薄膜在微電機(jī)系統(tǒng)中有著舉足輕重的作用,廣泛應(yīng)用于微驅(qū)動(dòng)器、微傳感器、微型開關(guān)、微型能量采集器以及微泵、微閥等。由于金屬鈷具有高熔點(diǎn)、高硬度、高耐蝕耐磨性、良好的抗高溫氧化和抗拉強(qiáng)度等優(yōu)異性能,人們發(fā)現(xiàn)Co合金鍍層結(jié)構(gòu)致密、硬度高、耐熱性好、耐磨耐蝕性能優(yōu)良。除了這些優(yōu)點(diǎn)以外,最重要的是Co合金薄膜具有很好的磁性能,不僅可以用來(lái)作為超高密度垂直磁記錄的介質(zhì),而且還可以代替電子設(shè)備中的微磁體。磁場(chǎng)電沉積技術(shù)作為一種新穎的制備技術(shù),在制備薄膜過(guò)程中,可以有效的提高沉積效率,細(xì)化鍍層晶粒,降低表面粗糙度,對(duì)磁性膜層在制備過(guò)程中進(jìn)行取向等優(yōu)點(diǎn),本文研究磁場(chǎng)誘導(dǎo)下的共沉積技術(shù),在電化學(xué)過(guò)程中對(duì)鈷、鎳、鈷鎳薄膜和鈷鎳錳合金電化學(xué)動(dòng)力學(xué)、表面織構(gòu)、成分、電沉積參數(shù)等方面的影響,取得以下結(jié)論:(1)研究發(fā)現(xiàn)鈷的電化學(xué)沉積屬于一種不可逆的擴(kuò)散控制的三維瞬時(shí)成核過(guò)程。磁場(chǎng)對(duì)擴(kuò)散控制體系下的鈷電化學(xué)沉積過(guò)程影響顯著,施加垂直于電場(chǎng)的磁場(chǎng),在鈷電沉積體系中可以“減薄”擴(kuò)散層厚度,提高鈷離子傳質(zhì)速度,促進(jìn)鈷的電化學(xué)沉積過(guò)程。平行磁場(chǎng)下,鈷離子在磁場(chǎng)中會(huì)受到磁場(chǎng)梯度力作用,表現(xiàn)為受磁場(chǎng)驅(qū)動(dòng)力作用遠(yuǎn)離陰極表面,抑制了鈷的電化學(xué)沉積過(guò)程。磁場(chǎng)平行電場(chǎng)下,鈷容易沿著磁場(chǎng)方向磁化生長(zhǎng),出現(xiàn)典型的“山狀”結(jié)構(gòu)顆粒膜。(2)研究發(fā)現(xiàn),鎳的電沉積過(guò)程屬于電化學(xué)控制過(guò)程,隨著陰極極化的增強(qiáng),極化電流隨之增強(qiáng),鎳屬于典型的電化學(xué)控制的連續(xù)成核過(guò)程。鎳的電化學(xué)沉積過(guò)程中施加垂直于電場(chǎng)的磁場(chǎng),有利于提高鎳的沉積電流,促進(jìn)鎳的電化學(xué)沉積,本質(zhì)上是由于擴(kuò)散層厚度的減小。垂直磁場(chǎng)作用下鎳表面出現(xiàn)枝晶狀顆粒,隨著磁場(chǎng)強(qiáng)度的增大,枝晶狀顆粒越發(fā)明顯。磁場(chǎng)平行電場(chǎng)條件下,鎳離子在磁場(chǎng)中會(huì)受到磁場(chǎng)梯度力作用,表現(xiàn)為受磁場(chǎng)驅(qū)動(dòng)力作用加速遷移到陰極表面,在磁驅(qū)動(dòng)力和“微觀洛倫茲力”的作用下,促進(jìn)鎳的電化學(xué)沉積過(guò)程,提高了沉積速率。(3)鈷鎳合金屬于典型的異常共沉積,主要是較活潑的鈷在陰極附近形成氫氧化鈷膠體,抑制了鎳的沉積,導(dǎo)致鍍層中鈷的含量增多,并且鍍液中鈷的含量越高,陰極極化作用越強(qiáng),異常共沉積越明顯,鍍層中鈷的含量越高。鈷鎳的電化學(xué)沉積過(guò)程中施加垂直于電場(chǎng)的磁場(chǎng),磁場(chǎng)的加入有利于提高鈷鎳的沉積電流,促進(jìn)鈷鎳的電化學(xué)沉積。鈷鎳鍍層中鈷含量較高時(shí),XRD結(jié)構(gòu)上可以發(fā)現(xiàn)Co-hcp結(jié)構(gòu),掃描電鏡上呈現(xiàn)出“稻谷”狀形貌。磁場(chǎng)平行電場(chǎng)情況下,CoNi(111)和Co(002)兩個(gè)方向的衍射峰逐漸增強(qiáng),證明(111)和(002)分別是CoNi和Co的兩個(gè)易磁化方向。磁場(chǎng)平行電場(chǎng)作用下,由于鈷鎳容易沿薄膜磁場(chǎng)方向生長(zhǎng),“枝晶”狀結(jié)構(gòu)變得更加明顯。(4)電化學(xué)沉積CoNiMnP中引入垂直電場(chǎng)方向的磁場(chǎng),可以提高極化電流和增加膜層的質(zhì)量。垂直磁場(chǎng)作用下,CoNiMn合金鍍層的鈷含量有所降低,主要認(rèn)為是洛倫茲力的“擾動(dòng)”作用,降低陰極附近的pH值,阻礙鈷的氫氧化物的形成,促進(jìn)了鎳的電沉積。CoNi的衍射峰分別出現(xiàn)在44.5°,51.8°,76.4°和93.1°這個(gè)四個(gè)角度,衍射強(qiáng)度很高,具有較好的晶體結(jié)構(gòu),引入垂直磁場(chǎng)后,制備得到的樣品XRD衍射峰,鈷的雜峰減弱,樣品結(jié)晶度增強(qiáng)。CoNiMn合金的磁性能具有很好的垂直各向異性,磁場(chǎng)的引入有利于增大膜層的矯頑力,提高膜層的比飽和磁化強(qiáng)度。研究發(fā)現(xiàn),1 T磁場(chǎng)下0.8 V沉積電位制備得到的鈷鎳錳鍍層具有最優(yōu)的矯頑力和剩磁。平行磁場(chǎng)下膜層容易沿著CoNi(111)和Co(002)方向磁化生長(zhǎng),使得膜層從顆粒狀轉(zhuǎn)變?yōu)橹睢?br/>[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.
【學(xué)位授予單位】：中國(guó)科學(xué)院寧波材料技術(shù)與工程研究所
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TG132.27;TB383.2
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本文編號(hào)：2216309