Study Of The Fabrication And Application Of Ni Nanowires In AAO Template

In this paper, we polished aluminum for anodic oxidation with three-acid chemical polishing method, and studied the effect of the time and the formula of chemical polishing soluthion on polishing result by visual method, metallurgical microscopy and surface roughometer. Highly ordered porous anodic aluminum template was prepared by the method of two-step anodization in oxalic acid solution, the barrier layer was thinning by the method of step-down depressurization, and the details of the reaction mechanism was discussed. The results indicated that the surface roughness of aluminum was up to 0.155μm when volume ratio of H3PO4-H2SO4-HNO3 is 70:20:10, polishing temperature is 100-105℃, the polishing time is 2 min, which is the best polishing effect.The anodic alumina membrane which fabricated at 4℃,40V in 0.3 M oxalic acid solution was aperture uniform and highly ordered. The average pore size was 69nm, the pitch of holes was 107nm, and the pore density was 1.01×1010 cm-2, wich was suitable for preparing one dimensional nanomaterials.Ni nanowires were fabricated by AC deposition using anodic aluminum oxide template. We studied the effect of template, the concentration of NiSO4, voltage and temperature on the deposition. The morphology and structure of Ni nanowires were characterized by SEM, TEM, XRD. The results indicated that the template which the voltage down to 15V with 1V/min was most suitable for deposition Ni nanowires. The deposition effect was best when the concentration of NiSO4·6H2O was 75g/L, deposition voltage was 15V and temperature was 20～30℃. The diameter of Ni nanowires was uniform and similar to template, the lengths up to 4μm and the morphology depends on the shape of the pore.The mechanism of AC deposition was discussed by measuring the U-I, EIS of anodic alumina membrane and Ni nanowire assembly system. The results show that Ni nanowires has been able to deposited with alternating current was because the rectification characteristic of anodic alumina membrane. When Ni-deposited into the holes of membrane, the barrier layer/Ni appeared rectification characteristic in the opposite direction, which offsetted with the former. The rectification characteristic of assembly system decreased with the growth of Ni nanowires, which cause deposition rate reduced.Ni nanowire electrode was prepared with electroless nickel plating. The morphology of Ni nanowire electrode was characterized by SEM. The electrochemical performance of Ni bulk and nanowire electrode in alkaline solution and the electro-catalytic activity for methanol were studied by cyclic voltammetry. The results showed that:Ni nanowire electrode has great specific surface area. The surface composition of electrode wasβ-Ni(OH)2 after repeated cyclic voltammetry. The electrochemical activity of Ni nanowire electrode in alkaline solution was high an order of magnitude than Ni bulk electrode, and had higher electricity catalytic activity for methanol.