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.     

End-closed NiCoFe-B nanotube arrays by electroless method

A novel approach is obtained during the fabrication of NiCoFe-B nanotube arrays via electroless method. Porous anodic aluminum oxide (AAO) templates fabricated by anodization of aluminum foil were sensitized using PdCl₂ solution and immersed into electroless plating baths at room temperature to produce nanotube arrays. Compositional and morphological properties of the nanotube arrays are characterized. Results indicates the formation of end-closed nanotubes with the dimension of 100-130 nm in outside diameter, which is determined by the pore size of the AAO template, and about 15 nm in thickness of tube walls. The possible formation mechanism of end-closed metallic nanotube arrays is discussed.     

高度有序多孔阳极氧化铝模板的制备

为了得到纳米孔排列高度有序的多孔阳极氧化铝模板,以0.3 mol·L-1的草酸为电解液研究了模板的制备工艺.采用场发射扫描电子显微镜(FE-SEM)对多孔氧化铝模板的表面形貌进行表征,X射线衍射分析高纯铝及氧化膜的结构.实验结果表明,铝基体不经过高温退火处理,同样能够得到高度有序的氧化铝膜,简化了多孔氧化铝膜的制备工艺.分别讨论了阳极氧化电压和电解液温度对多孔阳极氧化铝膜的形貌及孔径的影响,并对一步法和两步法制得的多孔氧化铝膜进行比较,结果表明,两步阳极氧化法制备的多孔氧化铝模板的有序性优于一步氧化法.XRD分析证实,多孔氧化铝膜由非晶态的Al2O3组成.     

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。     

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.     

Ion-beam pore opening of porous anodic alumina: The formation of single nanopore and nanopore arrays

Anodized aluminium oxide (AAO) fabricated by electrochemical anodization of aluminium is used as the substrate for focused ion-beam (FIB) fabrication of single nanopore and nanopore arrays. The method is based on the controlled and selective removal of AAO barrier oxide film by FIB milling. FIB process with different milling conditions is applied to open single nanopores (diameter of 60 nm) or circular nanopore arrays with a different number of opened pores on AAO substrate. This process combines a low cost AAO substrate and FIB milling, and offers an economically viable alternative for the fabrication of nanopore devices with controlled dimensions for a range of applications in nanofluidics, molecular separations and biosensing.     

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.     

Nanopore gradients on porous aluminum oxide generated by nonuniform anodization of aluminum

A method for surface engineering of structural gradients with nanopore topography using the self-ordering process based on electrochemical anodization of aluminum is described. A distinct anodization condition with an asymmetrically distributed electric field at the electrolyte/aluminum interface is created by nonparallel arrangement between electrodes (tilted by 45°) in an electrochemical cell. The anodic aluminum oxide (AAO) porous surfaces with ordered nanopore structures with gradual and continuous change of pore diameters from 80 to 300 nm across an area of 0.5-1 cm were fabricated by this anodization using two common electrolytes, oxalic acid (0.3 M) and phosphoric acid (0.3 M). The formation of pore gradients of AAO is explained by asymmetric and gradual distribution of the current density and temperature variation generated on the surface of Al during the anodization process. Optical and wetting gradients of prepared pore structures were confirmed by reflective interferometric spectroscopy and contact angle measurements showing the ability of this method to generate porous surfaces with multifunctional gradients (structural, optical, wetting). The study of influence of pore structures on cell growth using the culture of neuroblastoma cells reveals biological relevance of nanopore gradients and the potential to be applied as the platform for spatially controllable cell growth and cell differentiation.     

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.     

Optimization of the Sol–Gel Chemical Route for Fabrication of Densely Packed NiFe2O4 Nanowires in the AAO Template

In this paper we investigate the thermal decomposition of the citrate-based precursors in order to make the chemical and physical properties appropriate for the fabrication of nickel ferrite nanowires (NWs) through the sol?Cgel chemical route. IR spectroscopy (FTIR) along with X-ray diffraction (XRD) has been performed to select the suitable chemical and physical conditions for the sol?Cgel process. The anodic aluminum oxide (AAO) method was used for the template to control the diameter and length of the aligned wires. The morphology of the samples was studied by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The magnetic measurements were also done by a vibrating sample magnetometer (VSM). The results showed that the NiFe₂O₄ NWs were parallel ordered in the AAO template and their mean diameter is 80?C100?nm with high aspect ratio of 600.     

Template synthesis of highly ordered hydroxyapatite nanowire arrays

Highly ordered hydroxyapatite (HA) nanowire arrays were synthesized using porous anodic aluminum oxide (AAO) template from sol-gel solution containing P₂O₅ and Ca(NO₃)₂. Theresults of transmission electron microscopy (TEM) and scanning electron microscopy(SEM) revealed that the obtained HA nanowires had a uniform length and diameter andformed highly ordered arrays, which were determined by the pore diameter and thethickness of the applied AAO template. The results of X-ray diffraction (XRD) and X-rayphotoelectron spectroscopy (XPS) demonstrated that the major component was HA. Theselected-area electron diffraction (SAED) results indicated that HA was a polycrystallinestructure. This novel method of preparing highly ordered HA nanowires with a large areamight be important for many applications in biomaterials.     

Pb(Zr0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties

Herein a useful methodology to synthesize the lead zirconate titanate (PZT) nanotubes via a dip-coating deposition process with anodic aluminum oxide (AAO) template is proposed. The nano-porous AAO templates were produced using a controlled two-step electrochemical anodization technique. The PZT/AAO composite was formed using the dip-coating wetting technique. The prepared PZT precursor solution was driven into the nanopore channels of AAO template under the driving force of capillary action, subsequently the sintering process of the as-filled templates was carefully tuned to obtain Pb(Zr_0.52Ti_0.48)O₃ nanotubes of crystalline tetragonal phase with uniform pore size and ordered arrange. Fourier transform infrared spectroscopy (FTIR) results show that in the 1200–1900 cm⁻¹ band, the composite structure of PZT/AAO has obvious absorption peaks at 1471.56 cm⁻¹ and 1556.09 cm⁻¹, the absorption intensity of the composite structure is about six times of pure AAO template. The unusual optical properties found in PZT/AAO composite will stimulate further theoretical and experimental interests in ferroelectric nanostructures.     

Template-based fabrication of nanowire-nanotube hybrid arrays

The fabrication and structure characterization of ordered nanowire-nanotube hybrid arrays embedded in porous anodic aluminum oxide (AAO) membranes are reported. Arrays of TiO(2) nanotubes were first deposited into the pores of AAO membranes by a sol-gel technique. Co?nanowires were then electrochemically deposited into the TiO(2) nanotubes to form the nanowire-nanotube hybrid arrays. Scanning electron microscopy and transmission electron microscopy measurements showed a high nanowire filling factor and a clean interface between the Co nanowire and the TiO(2) nanotube. Application of these hybrids to the fabrication of ordered nanowire arrays with highly controllable geometric parameters is discussed.     

阳极氧化铝作为铝电解电容器阳极箔用的研究

采用直流电阳极氧化法在高纯铝箔上制备了多孔阳极氧化铝(AAO)膜,同时采用扫描电子显微镜(SEM)、循环伏安(CV)和电化学阻杭谱(EIS)等技术对AAO膜的表面形貌、厚度和比表面电容性质等进行了表征.结果表明,AAO膜由垂直于膜表面的、孔径在60～80nm之间的平行纳米孔道组成,膜的多孔层厚度约为20μm左右;AAO...     

Focused ion beam lithography and anodization combined nanopore patterning

In this study, focused ion beam lithography and anodization are combined to create different nanopore patterns. Uniform-, alternating-, and gradient-sized shallow nanopore arrays are first made on high purity aluminum by focused ion beam lithography. These shallow pore arrays are then used as pore initiation sites during anodization by different electrolytes. Depending on the nature of the anodization electrolyte, the nanopore patterns by focused ion beam lithography play different roles in further pore development during anodization. The pore-to-pore distance by focused ion beam lithography should match with that by anodization for guided pore development to be effective. Ordered and heterogeneous nanopore arrays are obtained by the focused ion beam lithography and anodization combined approach.     

Preparation of superparamagnetic and flexible γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanowire arrays in an anodic aluminum oxide template

Superparamagnetic and flexible Fe₂O₃ nanowire arrays were fabricated by the controlled electrostatic assembly of iron oxide nanoparticles and poly(dimethyldiallylammonium chloride) (PDADMAC) in an anodic aluminum oxide (AAO) template. The micrograph of iron oxide nanowire arrays was characterized by field emission scanning electron microscopy. The magnetic hysteresis loops obtained by a vibrating sample magnetometer confirm that the nanowire arrays have superparamagnetic properties. The filling ratio of iron oxide nanoparticles and polymers in the AAO template was affected by four factors, including the concentration of iron oxide nanoparticles, the pore diameter of the AAO template, the charge ratio of iron oxide nanoparticles and PDADMAC, and the molecular weight of polyacrylic acid. The effect of the AAO template on the diameter and length of the nanowire arrays was also analyzed. In addition, the nanowire arrays were shown to be flexible because of the presence of polymers. These nanowire arrays with superparamagnetic and flexural properties have potential applications in sensor probes.     

Magnetoimpedance Effect on Single NiFe Nanowire

In this study, Ni₈₂Fe₁₈ nanowires were deposited on Au-coated porous anodic alumina oxide (AAO) template by electrochemically. Scanning electron microscopy showed that wires have diameters of about 250–310 nm and length of 50–60 μm. NiFe nanowire arrays embedded in AAO were mechanically polished until nanowires appeared. Later, electrical contacts were made to a single nanowire using a focused ion beam (FIB) system. Magnetoimpedance (MI) properties of single nanowire were investigated, and nearly 3.5 % MI was observed at 4 GHz driving current frequency.     

Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.     

Fabrication of ordered magnetite-doped rare earth fluoride nanotube arrays by nanocrystal self-assembly

We describe a nanocrystal self-assembly method for the preparation of rare earth fluoride nanotube (ReF-NT) arrays and magnetite-doped rare earth fluoride nanotubes (Fe₃O₄-ReF-NTs) by using porous anodic aluminum oxide (AAO) as a hard template. The ReF-NTs can be simply prepared by the impregnation of α-NaYF₄ nanocrystals doped with Yb and Er into the channels of the porous AAO and show a highly ordered nanotube array and excellent upconversion (UC) fluorescence properties. Similarly, the Fe₃O₄-ReF-NTs are obtained by the self-assembly of a mixture of Fe₃O₄ and Yb/Er doped α-NaYF₄ nanocrystals in the AAO pore channels and have a uniform dispersion of magnetite nanocrystals on the rare earth fluoride tube matrix and possess multifunctional magnetic/UC properties. The diameter of these nanotubes can be varied from 60 nm to several micrometers depending on the pore size of the AAO template. The wall thickness can be increased from 10 to 35 nm by increasing the concentration of nanocrystals from 0.02 to 0.4 mmol/L, while the morphology of the nanotubes can be varied from small isolated domain structures to percolating domains and eventually to compact domains. A template-directed formation mechanism is proposed and the quantitative predictions of the model for such self-assembled nanocrystal spreading processes are demonstrated. Strong UC fluorescent emissions are realized for the nanotube arrays and multifunctional nanotubes with UC excitation in the near-infrared (NIR) region. A strong magnetic response of the multifunctional nanotubes is observed, which facilitates their easy separation from solution by magnetic decantation using a permanent magnet.     

The nanoporous structure of anodic aluminum oxide fabricated on the Au/Nb/Si substrate

We have studied the anodization behavior of an Al film evaporated on the Au/Nb/Si substrate and demonstrated an effective approach to fabricate the through-hole anodic aluminum oxide (AAO) template on the conducting substrate. The smoothness of the initial metal films and an appropriate wet etching of the oxide film anodized in the first step were found to be critical factors for successfully anodizing the Al film on Au surface. The barrier layer of the obtained AAO structure presented a convex and thinner characteristic, and the underlying Au surface became porous after the anodization. This phenomenon was similar to the case of anodizing the Al film on an ITO glass substrate and could be explained reasonably by the effect of high pressure O₂ gas impelling and H⁺ etching at the interface of the barrier oxide and the Au layer.