Fabrication and magnetic characteristics of vertical feco nanowire arrayed in Al2O3 insulator of honeycomb bulkhead structure

High-density and uniform-sized FeCo alloy nanowires were prepared by electro deposition of Fe2+ and Co2+ into Anodic aluminum oxide (AAO) templates with two different diameters. These templates were fabricated with three-step anodization method. The additional anodization after the 2nd anodization step resulted in the decrease of the thickness of bottom barrier layer. It found an optimum condition to obtain a successful electrodeposition of Fe2+ and Co2+ into AAO templates. The nanowires with the diameters of 25 nm and 80 nm were homogeneously embedded in the AAO templates and their magnetic properties were strongly affected by diameters of nanowire.     

Effect of process parameters on growth rate and diameter of nano-porous alumina templates

Anodic aluminium oxide (AAO) template with hexagonal shaped nano-pores with high aspect ratio was fabricated by two-step anodization processes from high purity aluminium foil. It was observed that pore dimensions were affected by anodizing voltage, electrolyte temperature and the duration of anodization time. The vertical growth rate of the pores (10?C250?nm/min) was found to vary exponentially with anodizing voltage; however, it exhibits linear increment with the electrolyte temperature. The measured pore diameter (50?C130?nm) shows a linear variation with anodizing voltage. The bottom barrier oxide layer was etched out by pore widening treatment to obtain through holes.     

Cu/AAO复合材料的制备及表征

通过阶梯降压法,成功制备出带有铝基底的有序多孔阳极氧化铝,铝基底与有序多孔氧化铝之间的阻挡层极薄。以该模板为阴极,采用循环伏安法电化学沉积技术制备出Cu/AAO纳米复合材料。分别用场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、X射线衍射(XRD)等测试方法对该纳米复合材料的形貌、组成和结构进行了表征和分析。结果表明,Cu纳米线在模板中填充率高,直径约为70nm,长度可达30μm,具有面心立方单晶结构。     

Highly ordered uniform single-crystal Bi nanowires: fabrication and characterization

A mechanical pressure injection technique has been used to fabricate uniform bismuth (Bi) nanowires in the pores of an anodic aluminum oxide (AAO) template. The AAO template was prepared from general purity aluminum by a two-step anodization followed by heat treatment to achieve highly ordered nanochannels. The nanowires were then fabricated by an injection technique whereby the molten Bi was injected into the AAO template using a hydraulic pressure method. The Bi nanowires prepared by this method were found to be dense and continuous with uniform diameter throughout the length. Electron diffraction experiments using the transmission electron microscope on cross-sectional and free-standing longitudinal Bi nanowires showed that the majority of the individual nanowires were single crystalline, with preferred orientation of growth along the [011] zone axis of the pseudo-cubic structure. The work presented here provides an inexpensive and effective way of fabricating highly ordered single-crystalline Bi nanowires, with uniform size distributions.     

Preparation and characteristics of large-area and high-filling Ag nanowire arrays in OPAA template

Highly ordered porous anodic aluminum oxide (OPAA) on aluminum substrate with an ultrathin barrier layer was prepared by a two-step aluminum anodic oxidation plus a step-by-step voltage decrement process. Ag nanowire arrays have been successfully electrodeposited into the OPAA template through constant current technique. The morphology, composition and structure of the nanowire arrays were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that Ag nanowires possess smooth surface and high aspect ratio up to 330 with a diameter of 70-80 nm. Nearly 100% of the pores were filled by Ag nanowires, which have face center cubic structure and (111) preferential orientation. The branch of originally straight pores at the formation front was demonstrated and the branched pores favor the formation of several nucleation sites in each pore at the beginning of the electrodeposition.     

阳极氧化铝样模法制备纳米线阵列的发展概况

对金属纳米线的研究和发展进行了回顾和展望:在多孔阳极氧化铝模板上可制备出不同直径和长度的纳米管或纳米线阵列;所制备的纳米线有着光、电、磁、催化等特性,具有广泛的用途及发展前景.     

Template assisted synthesis of SnO<Subscript>2</Subscript> nanorods by immerse and filtration technique,vacuum and drop setting

Honeycomb-shaped and ordered arrays of nanopore AAO template with a uniform pores size was produced utilizing a two-step an anodization process. Highly ordered SnO₂ nanorods arrays have been selectively fabricated via a convenient (immerse and filtration) technique and (vacuum and drop) setting using anodic aluminum oxide (AAO) as a hard template. The morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (FESEM), and Energy-dispersive X-ray spectroscopy (EDX) techniques. The optical characterizations were examined by UV-VIS and Photoluminescence (PL). Scanning microscopy images indicate that the SnO₂ nanorods are relatively uniform with the outer diameter matching well with the pore diameter. XRD and EDX indicated that these polycrystalline SnO₂ nanostructures with well-defined composition were obtained.     

多孔阳极氧化铝模板法交流电沉积单晶镍纳米线阵负

一维纳米材料在光学、电学、磁学等领域有着广阔的应用前景。采用二次阳极氧化法,结合逐级降压法制备了多孔阳极氧化铝（AAO）模板,然后在其上交流电沉积了单晶镍纳米线阵列。利用SEM,XRD,TEM等对镍纳米线阵列的形貌和结构进行了表征,探讨了沉积效果与沉积电流密度一时间曲线和稳定沉积电流密度大小之间的关系。结果表明：沉积电...     

用低纯度铝制备AAO模板及其结构研究

在0.3mol/dm3草酸溶液中,通过不同纯度铝的恒电位二次阳极氧化制备了纳米孔氧化铝模板,并用场发射扫描电子显微镜(FE-SEM)和原子力显微镜(AFM)观察模板结构.实验结果表明,一次氧化除膜后低纯度铝基体表面呈现较为规则的六边形结构,这种蜂巢结构有利于二次氧化过程中获得有序度更高的纳米孔模板.低纯度铝制备的模板表面被晶界分隔为微小的区域,只是在较窄区域内才出现六边形规则排列的纳米孔.恒电位40V时所得模板经扩孔处理后,孔径由35nm增大到100nm左右,且孔径大小几乎一致.从纳米孔的有序度来看,由低纯度铝制备模板还需要进一步优化阳极氧化参数.     

Penetrating the oxide barrier in situ and separating freestanding porous anodic alumina films in one step

A simple method for penetrating the barrier layer of an anodic aluminum oxide (AAO) film and for detaching the AAO film from residual Al foil was developed by reversing the bias voltage in situ after the anodization process is completed. With this technique, we have been able to obtain large pieces of free-standing AAO membranes with regular pore sizes of sub-10 nm. By combining Ar ion milling and wetting enhancement processes, Au nanowires were grown in the sub-10 nm pores of the AAO films. Further scaling down of the pore size and extension to the deposition of nanowires and nanotubes of materials other than Au should be possible by further optimizing this procedure.     

Controlled fabrication of gold and polypyrrole nanowires with straight and branched morphologies via porous alumina template-assisted approach

Straight and branched nanowires (NWs) of gold and polypyrrole (PPy) were synthesized inside the pre-designed nanochannels of anodic aluminum oxide (AAO) templates via electrodeposition. The morphologies, diameters and lengths of the NWs could be tailored by tuning the topologies of the nanochannels inside the AAO template and electrodeposition parameters. The present method provides a rational way to build materials that can be electrodeposited inside the nanochannels into NWs with desired architectures, which have potentials in nanoelectronics and nanosystems.     

One-step anodization fabrication and morphology characterization of porous AAO with ideal nanopore arrays

A fabrication method for one-step anodization of an anodic aluminum oxide (AAO) template with nanopore arrays using pretreated high purity aluminum foil is reported in this article. Morphology of the AAO was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed that porous AAO with ideal nanopore arrays can be fabricated by one-step anodization fabrication technology on high purity aluminum foil which had been anodized at 45?V direct current (DC), in 0°C, 0.5?M H₂C₂O₄ solution for 48 hours. The average pore diameter and the interpore distance were 80?nm and 120?nm, respectively. Nanopores in porous AAO had very narrow size distribution and were arranged into hexagonal array. The formation mechanism of nanopore arrays in porous AAO is discussed. Porous AAO with ideal nanopore arrays provide an ideal template for preparation of many one-dimensional nanomaterials. One-step anodization of AAO is a simpler procedure and more applicable in industrial application than the previous two-step anodization technology.     

A kind of synthetic nanopillar arrays for studying single biomolecule

The anodic aluminum oxide (AAO) template with ordered pores was firstly fabricated in oxalic acid solutions using two-step anodization method. Then, a layer of polymethylmethacrylate (PMMA) was uniformly laid on one surface of the AAO template by a Spin-Coater, then baked and cooled them, after that, the H3PO4 solution was utilized to dissolve the residual aluminum and barrier layer, as the result, the functional nanopillar arrays were achieved. Finally, the morphology of the functional PMMA nanopillars was examined with the Scanning Electron Microscope (SEM) and the properties were discussed. The functional nanopillar arrays could be applied to the micro and nano-scale devices as the sensors for the biological, chemical and single molecular detection.     

Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane

The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.     

阳极氧化法制备有序纳米多孔氧化铝膜的研究

利用电化学阳极氧化的方法,在草酸溶液中,精确控制反应条件,在高纯铝片表面有序生长了纳米多孔氧化铝膜。试验中,分别采用一次阳极氧化和二次阳极氧化方法制备氧化铝膜。利用H3PO4溶液浸泡法对氧化铝膜进行扩孔处理。通过扫描电子显微镜对样品进行表征分析。结果发现,二次阳极氧化制备的氧化铝膜的孔洞分布较一次氧化的更为规则有序,并且孔径大小均匀一致。扫描电镜观察显示,氧化铝膜的扩孔过程可以去掉阻碍层,并调节孔径大小,溶去二次氧化后黏附在氧化层表面的一些杂质,从而使氧化铝模板更为规则有序,孔径均一。这种经过二次阳极氧化和扩孔处理得到多孔阳极氧化铝模板的方法简单,成本较低,可以为后续的纳米材料合成提供高质量的合成模板。     

Highly ordered porous alumina with tailor-made pore structures fabricated by pulse anodization

A new anodization method for the preparation of nanoporous anodic aluminum oxide (AAO) with pattern-addressed pore structure was developed. The approach is based on pulse anodization of aluminum employing a series of potential waves that consist of two or more different pulses with designated periods and amplitudes, and provides unique tailoring capability of the internal pore structure of anodic alumina. Pores of the resulting AAOs exhibit a high degree of directional coherency along the pore axes without branching, and thus are suitable for fabricating novel nanowires or nanotubes, whose diameter modulation patterns are predefined by the internal pore geometry of AAO. It is found from microscopic analysis on pulse anodized AAOs that the effective electric field strength at the pore base is a key controlling parameter, governing not only the size of pores, but also the detailed geometry of the barrier oxide layer.     

A comparative study on the NO2 gas sensing properties of ZnO thin films, nanowires and nanorods

ZnO thin films were fabricated using the spin coating method, ZnO nanowires by cathodically induced sol-gel deposition by the means of an anodic aluminum oxide (AAO) template, and ZnO nanorods with the hydrothermal technique. For thin film preparation, a clear, homogeneous and stable ZnO solution was prepared by the sol-gel method using zinc acetate (ZnAc) precursor which was then coated on a glass substrate with a spin coater. Vertically aligned ZnO nanowires which were approximately 65 nm in diameter and 10 μm in length were grown in an AAO template by applying a cathodic voltage in aqueous zinc nitrate solution at room temperature. For fabrication of the ZnO nanorods, the sol-gel ZnO solution was coated on glass substrate by spin coating as a seed layer. Then ZnO nanorods were grown in zinc nitrate and hexamthylenetetramine aqueous solution. The ZnO nanorods are approximately 30 nm in diameter and 500 nm in length. The ZnO thin film, ZnO nanowires and nanorods were characterized by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The NO₂ gas sensing properties of ZnO thin films, nanowires and nanorods were investigated in a dark chamber at 200 °C in the concentration range of 100 ppb-10 ppm. It was found that the response times of both ZnO thin films and ZnO nanorods were approximately 30 s, and the sensor response was depended on shape and size of ZnO nanostructures and electrode configurations.     

Growth and optical properties of silver nanostructures obtained on connected anodic aluminum oxide templates

Ag nanostructures are grown by AC electrodeposition on anodic alumina oxide (AAO) connected membranes acting as templates. Depending on the thickness of the template and on the voltage applied during the growth process, different Ag nanostructures with different optical properties are obtained. When AAO membranes about 1 μm thick are used, the Ag nanostructures consist in Ag nanorods, at the bottom of the pores, and Ag nanotubes departing from the nanorods and filling the pores almost for the whole length. When AAO membranes about 3 μm thick are used, the nanostructures are Ag spheroids, at the bottom of the pores, and Ag nanowires that do not reach the upper part of the alumina pores. The samples are characterized by angle resolved x-ray photoelectron spectroscopy, scanning electron microscopy and UV-vis and Raman spectroscopies. A simple NaOH etching procedure, followed by sonication in ethanol, allows one to obtain an exposed ordered array of Ag nanorods, suitable for surface-enhanced Raman spectroscopy, while in the other case (3 μm thick AAO membranes) the sample can be used in localized surface plasmon resonance sensing.     

Effects of temperature and voltage mode on nanoporous anodic aluminum oxide films by one-step anodization

Many conventional anodic aluminum oxide (AAO) templates were performed using two-step direct current anodization (DCA) at low temperature (0–5 °C) to avoid dissolution effects. This process is relatively complex. Pulse anodization (PA) by switching between high and low voltages has been used to improve wear resistance and corrosion resistance in barrier type anodic oxidation of aluminum or hard anodization for current nanotechnology. However, there are only few investigations of AAO by hybrid pulse anodization (HPA) with normal-positive and small-negative voltages, especially for the one-step anodization, to shorten the running time. In this article, the effects of temperature and voltage modes (DCA vs. HPA) on one-step anodization have been investigated. The porous AAO films were fabricated using one-step anodization in 0.5 M oxalic acid in different voltage modes including the HPA and DCA and the environment temperature were varied at 5–15 °C. The morphology, pore size and oxide thickness of AAO films were characterized by high resolution field emission scanning electron microscope. The pore size distribution and circularity of AAO films can be quantitatively analyzed by image processing of SEM. The pore distribution uniformity and circularity of AAO by HPA is much better than DCA due to its effective cooling at relatively high temperatures. On the other hand, increasing environment temperature can increase the growth rate and enlarge the pore size of AAO films. The results of one-step anodization by hybrid pulse could promote the AAO quality and provide a simple and convenient fabrication compared to DCA.     

长程有序纳米孔氧化铝模板的制备与研究

以硫酸和草酸溶液为电解液,采用二次阳极氧化法制备出高度长程有序的纳米孔氧化铝(AAO)模板,并结合扫描电子显微镜(SEM)对其微观结构及形貌进行了观察和表征.通过研究不同的氧化电压和电解液浓度对AAO模板纳米孔形貌(孔径、孔间距、面密度和长程有序性)的影响,得到了最佳的氧化电压和电解液浓度.