Study On Growth Kinetics And Magnetic Properties In Nickel Nanowire Arrays

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.