大长径比有序多孔阳极氧化铝模板的制备及用于镍纳米线阵列

报道一种恒电流二次氧化制备大长径比(>1000)阳极氧化铝(AAO)模板的方法,研究氧化时间和氧化电流密度分别对制备的AAO模板的表面形貌、孔径大小、厚度等的影响.结果表明,AAO模板的表面形貌及厚度n受m氧、厚化度电约流为密2度00及μ氧m、化长时径间比的为影10响0;-当13氧00化的电高流质密量度A为AO8模m板A·.c采m用-2电时化,氧学化沉1积8方h能法在制制备备出的孔A径A为O模15板0-的20孔0中成功制备了Ni纳米线阵列,分别用扫描电镜(SEM)、高分辨透射电镜(HRTEM)、X射线衍射(XRD)和X射线能量散射光谱(EDS)对其进行了表征;结果显示,制备的Ni纳米线排列整齐有序,每根Ni纳米线直径几乎相同,约150nm,长度约为180-200μm,长径比为1200-1300,与AAO模板的参数一致.研究了Ni纳米线阵列的长径比对其磁性能的影响,发现大长径比的Ni纳米线阵列具有明显的磁各向异性,而长径比约为200的Ni纳米线阵列未表现出明显的磁各向异性.本文结果表明,恒电流二次氧化方法能制备大长径比的AAO模板,并能用于制备大长径比的一维纳米材料阵列,可望在制备具有特殊光学、磁学等性能材料方面得到应用.

Preparation of an Ultrahigh Aspect Ratio Anodic Aluminum Oxide Template for the Fabrication of Ni Nanowire Arrays

This work reports a two-step constant-current anodization approach for the fabrication of an anodic aluminum oxide(AAO) template having an aspect ratio>1000.The effects of oxidation current densities and oxidation time on the morphologies,pore size,and thickness of AAO templates were studied.The results indicated that the morphology and thickness were significantly affected by both the oxidation time and the oxidation current density.High-quality AAO templates with 150-200 nm pore sizes,200 μm thicknesses,and 1000-1300 aspect ratios could be prepared under a constant-current density of 8 mA cm-2 and an oxidation time of 18 h.Using the AAO template,Ni nanowire arrays were fabricated by electrochemical deposition and were characterized by scanning electron microscopy(SEM),high resolution transmission electron microscopy(HRTEM),energy-dispersive X-ray spectroscopy(EDS),and X-ray diffraction(XRD) techniques.The Ni nanowire arrays were parallel to each other,with diameters of 150 nm,lengths of 180-200 μm,and aspect ratios of 1200-1300.These parameters compared favorably with those of the AAO template,thus indicating that it can be used for preparation of one-dimensional nanowire arrays with an ultrahigh aspect ratio.The effects of the aspect ratios on the magnetic characteristics of the Ni nanowire arrays were examined by comparing their coercivities and remanence ratios in parallel and perpendicular directions,respectively.The results indicated that Ni nanowire arrays with an aspect ratio>1000 clearly displayed a magnetic anisotropy,while the arrays with an aspect ratio of 200 did not.Thus an AAO template with an ultrahigh aspect ratio can be fabricated using a two-step constant-current anodization method,and that the AAO template may find applications in the fabrication of one-dimensional,high-aspect ratio nanowire arrays with special optical and magnetic properties.