【作者】 于翠艳；

【导师】 张湘义；

【作者基本信息】 燕山大学 ， 材料学， 2007， 博士

【摘要】 金属镍纳米线阵列在垂直磁记录领域具有广阔的应用前景,如何生长高质量的镍纳米线阵列是其应用要解决的关键问题之一。本文采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和振动样品磁强计(VSM)开展了镍纳米线阵列电沉积动力学参数、电化学沉积机理、纳米线结构与磁性关系的研究。利用二次阳极氧化的方法在不同腐蚀介质中,制备了不同孔径的多孔氧化铝模板,研究了铝的纯度、抛光、温度、氧化电压等因素对氧化铝模板的孔有序性和孔径大小的影响,发现高纯铝、电抛光、低温和适中的氧化电压有利于提高氧化铝模板的有序性。采用恒电位三电极体系进行电沉积制备镍纳米阵列。研究表明,纳米线的直径与模板纳米孔直径相当,随纳米线的直径由小变大,其结构逐渐由单晶变为多晶。通过研究沉积电流与时间的关系(I-t曲线) ,确定了镍纳米线阵列在不同温度下的沉积是一个典型的动力学过程,据此测定了直径为160 nm、40 nm、25 nm的镍纳米线的表观生长激活能分别为1.26 eV、0.71 eV和0.25 eV。纳米线直径越小,其表观生长激活能越小。通过分析沉积过程的I-t曲线和镍纳米线阵列电极的极化曲线,确定电化学反应步骤为整个电沉积过程的控制步骤;通过测定不同浓度下的阴极极化曲线,计算了沉积过程中交换电流密度,发现了纳米微电极直径减小,交换电流密度增大的动力学规律。通过对电极反应的电子转移数的研究,提出了镍纳米线阵列电沉积反应机理。在上述工作基础上,利用正交实验确定了制备单晶镍纳米线阵列的最佳工艺条件,所制备的直径为40 nm的镍纳米线阵列的矫顽力为1036 Oe,剩磁比为0.94。发现镍纳米线的直径越小其磁性能越好,当镍纳米线的直径达到15 nm时,其矫顽力达到1106 Oe。更多还原

【Abstract】 It is of importance to improve the growth quality of the nickel nanowire arrays as it has broad applications as perpendicular magnetic recording media. In the present work, the microstructure and magnetic properties of Ni nanowire arrays have been studied by the employment of an x-ray diffractometer (XRD), a scanning electron microscopy (SEM), a transmission electron microscopy (TEM), and a vibrating sample magnetometer (VSM) measurements. The kinetic parameters during electrodeposition process and mechanism have also been investigated.Porous anodic aluminium oxidation templates with different diameters have been prepared by a two-step anodization process in different corrosive solution. The influence of aluminium purity, polishing, temperature and oxidation voltage on the order and diameter of anodic aluminium oxidation templates were discussed. The results show that electropolished aluminum with high purity, appropriate oxidation voltage and low temperature are favorable for the order of anodic aluminium oxidation templates.Ni nanowire arrays were fabricated by constant voltage deposition with a standard three-electrode electrochemical system. Microstructure analysis indicates that the diameter of nanowires is equal to the nanopores. The crystalline structure of Ni gradually changes from single crystalline to polycrystalline as the increase of diameter. The deposition current-time relation shows that the electrodeposition of Ni nanowire arrays under different temperatures is a typical kinetic process. The calculated apparent growth activation energy of Ni nanowire arrays with diameter of 160 nm, 40 nm and 25 nm are 1.26 eV, 0.71 eV, 0.25 eV respectively, which exhibits that a low value of apparent growth activation energy is corresponding to a nanowire with small diameter.Electrochemical reaction is the dominate step in the electrodeposition process by analyzing the deposition current-time curve and polarization curve of Ni nanowire arrays electrode. The exchange current density was calculated by measuring the cathodic polarization curve with different concentrations, which indicates that the exchange current density increases as the nanosized microelectrode decreases.The optimal properties of Hc=1036 Oe and Mr/Ms=0.94 were obtained for the Ninanowire arrays fabricated under appropriate experimental parameters which educe from orthogonal experiment. The magnetic properties of Ni nanowire arrays with different diameters have also been studied. The results indicate that the nanowire with a smaller diameter is favorable for the better magnetic properties. The coercivity increases to 1106 Oe while the diameter is 15 nm.更多还原