Study On The Preparation And Properties Of Electrodeposited Nanowire Arrays Base On AAO Templates

In this dissertation, the highly ordered anodic aluminum oxide (AAO) templates were prepared by a two-step anodic anodization. Ni, Co and CoPt magnetic metal nanowire arrays were fabricated in the porous alumina templates by electrodeposition. The related parameters that affect the structure and magnetic properties of nanowire arrays have been investigated and discussed.1. Highly ordered aluminum anodic oxide templates were fabricated in the oxalic acid electrolyte by two-step anodic oxidation of aluminum foils. The pore diameter of aluminum oxide templates is about70nm. The anodic oxide films were characterized by at scanning electron microscopy (SEM). The corresponding growth mechanisms of the anodic oxide templates have been analyzed.2. Ni nanowire arrays had been electrodeposited into anodic aluminum oxide (AAO) templates. The influence of the applied voltage and pH value of electrolytes on the structure and magnetic properties of Ni nanowire arrays has been studied. Single crystalline Ni nanowire arrays with growing along the [220] direction have been obtained. The larger coercivities and Squareness ratio (1090Oe and0.91respectively) were achieved in the single crystalline Ni nanowire arrays. For all Ni nanowire, the coercivity and squareness with the external magnetic field parallel to the wire major axis are much larger than those at the perpendicular direction; the easy axis of the wires is parallel to the wire axis. It found that the microstructure and magnetic properties of Ni nanowire arrays can be influenced by the applied voltage and pH value of electrolytes. The mechanisms of applied potential and pH valus of electrolytes determining the microstructure and magnetic properties of Ni nanowires have been discussed.3. Co nanowire arrays were fabricated into anodic aluminum oxide (AAO) templates by pulse DC electrodeposition and AC electrodeposition respectively. Experiments confirmed that the nanowire arrays obtained by pulse DC electrodeposition have better crytallinity, larger coercivity and squareness (2118Oe,0.81). Under pulse DC electrodeposition, we investigated the impact parameters that affect the crystallography phase, crystallinity and texture properties. It is found that the fcc and hcp mixtured Co nanowires can be obtained by choosing proper electrodeposition parameters. Furthermore, single crystalline hcp Co nanowire arrays with [1010] growth direction can be obtained by choosing appropriate applied frequency, voltage and pH value. The magnetic property of Co nanowire arrays is closely related to the nanowire microstructure. The corresponding reasons have been analyzed4. CoPt alloy nanowire arrays were fabricated by pulsed DC electrodepisited. The influence of the electrolyte concentration and pulse frequency on the microstructure and magnetic property of nanowire arrays has been investigated. After annealing, the crystallinity of CoPt nanowires is improved, crystalline grain size increased and the coercivity along the easy axis is weaker. The possible reasons of the observed weaker coercivity along the easy axis in nanowire arrays have been discussed.The one-dimensional nanowire arrays prepared in AAO templates by electrodeposition are highly ordered, uniform in diameter and with large aspect ratio. All nanowire arrays exhibit obviously magnetic anisotropic along the wire growth direction, namely, the easy axis of the wire arrays is perpendicular to the matrix of the film, which is especially useful for their application in the high-density perpendicular magnetic recording media.