Electrodeposited Ni,Fe,Co and Cu single and multilayer nanowire arrays on anodic aluminum oxide template

The Ni, Fe, Co and Cu single and multilayer nanowire arrays to make perpendicular magnetic recording media were fabricated with nanoporous anodic aluminum oxide (AAO) templates from Watt solution and additives by the DC electrodeposition. The results show that the diameters of Ni, Fe, Co and Cu single and multilayer nanowires in AAO templates are 40-80 nm and the lengths are about 30 μm with the aspect ratio of 350-750. The magnetic properties of the prepared nanowires are different under different electrodepositing conditions. The remanences (Br) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires, and coercivity (Hc) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires. These are compatible with the required conditions of high density magnetic media devices that should have the low coercivity to easily success magnetization and high remanence to keep magnetization after removal of magnetic field.

Electrochemical Fabrication of Pd-Ag Alloy Nanowire Arrays in Anodic Alumina Oxide Template

The synthesis of Pd-Ag alloy nanowires in nanopores of porous anodic aluminum oxide （AAO） template by electrochemical deposition technique was reported. Pd-Ag alloy nanowires with 16%-25% Ag content are expected to serve as candidates of useful nanomaterials for the hydrogen sensors. Scanning electron microscopy （SEM） and energy dispersed X-ray spectroscopy （EDX） were employed to characterize the morphologies and compositions of the Pd-Ag nanowires. X-ray diffraction （XRD） was used to characterize the phase properties of the Pd-Ag nanowires. Pd-Ag alloy nanowire arrays with 17.28%-23.76% Ag content have been successfully fabricated by applying potentials ranging from -0.8 to -1.0 V （vs SCE）. The sizes of the alloy nanowires are in agreement with the diameter of AAO nanopores. The underpotential deposition of Ag＋ on Pd and Au plays an important role in producing an exceptionally high Ag content in the alloy. Alloy compositions can still be controlled by adjusting the ion concentration ratio of Pd^2＋ and Ag＋ and the electrodeposition processes. XRD shows that nanowires obtained are in the form of alloy of Pd and Ag.

Preparation of well-aligned carbon nanotubes/silicon nanowires core-sheath composite structure arrays in porous anodic aluminum oxide templates

The well-aligned carbon nanotubes (CNTs) arrays with opened ends were prepared in ordered pores of anodic aluminum oxide (AAO) template by the chemical vapor deposition (CVD) method. After then, silicon nanowires (SiNWs) were deposited in the hollow cavities of CNTs. By using this method, CNTs/SiNWs core-sheath composite structure arrays were synthesized successfully. Growing structures and physical properties of the CNTs/SiNWs composite structure arrays were analyzed and researched by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectrum (XRD), respectively. The field emission (FE) behavior of the CNTs/SiNWs composite structure arrays was studied based on Fowler-Nordheim tunneling mechanism and current-voltage (I-V) curve. And the photoluminescence (PL) was also characterized. Significantly, the CNTs/SiNWs core-sheath composite structure nanowire fabricated by AAO template method is characteristic of a metal/semiconductor (M/S) behavior and can be utilized to synthesize nanoscale PN junction or Schottky diode device. This process also could be useful for the fabrication of SiNWs and other nanoscale core-sheath composite structure nanowires with chemically inert interfaces for nanoscale electronic and device applications where surface oxidation is undesirable. The diameters and lengths of nanoscale composite structure arrays can be dominated easily, and the experimental result shows that the curling and twisting structures are fewer than those prepared by other synthesized methods.

Synthesis of ordered Si nanowire arrays in porous anodic aluminum oxide templates

Highly ordered poly crystalline Si nanowire arrays were synthesized in porous anodic aluminum oxide (AAO) templates by the chemical vapor deposition (CVD) method. The morphological structure, the crystal character of Si nanowire arrays and the individual nanowire were analyzed by the transmission electron microscopy (TEM), scanning electron microscopy (SEM), atom force microscopy (AFM) and the X-ray diffraction spectrum (XRD), respectively. It is shown that most fabricated silicon nanowires (SiNWs) tend to be assembled parallelly in bundles and constructed with highly orientated arrays. This method provides a simple and low cost fabricating craftwork and the diameters and lengths of SiNWs can be controlled, the large area Si nanowire arrays can be achieved easily under such a way. The curling and twisting SiNWs are fewer than those by other synthesis methods.

Growth and Optical Absorption Properties of Silver Nanorod Arrays in Porous Anodic Aluminum Oxide Templates

Silver nanorod arrays have been fabricated by alternat-ing current（AC） and pulsed direct current（DC） electrodeposition in porous anodic aluminum oxide（AAO） templates with controlled pore diameters of 19,38,and 65 nm,respectively.The variation of their optical absorption properties with the incident angle and the nanorods length（corresponding to the electrodeposition time） has been investigated.Optical absorption spectra show that the posi-tion of longitudinal surface plasmon resonance（LSPR） peak has a small blueshift with the increase of incident angle of the excitation light.While the aspect ratio of the nanorods increases,the position of LSPR peak first redshifts and then blueshifts to a certain wave-length.Furthermore,the position of LSPR peak can be tuned,ranging from 550 nm to 900 nm,which makes it possible to cou-ple various wavelength of excitation source to assist radiative en-ergy transfer to the acceptor.

Carbon nanotubes prepared by anodic aluminum oxide template method

One of the most unique structural characteristics of carbon nanotubes(CNTs) differentiating from other carbon materials is their hollow nanochannles,which can be utilized for encapsulating and loading foreign matters.The anodic aluminum oxide(AAO) template technique enables the diameter,length,and cap structure control of the replicated CNTs,and thus shows advantages in pore structure control over the traditional CNT growth approaches.This review details the synthesis of CNTs with tunable diameter,length,wall thickness,and crystalline by using the AAO template method.The doping of heteroatoms and filling of foreign matters into AAO-CNTs are also addressed.Moreover,the main challenges and developing trends of the AAO template method are discussed.

Magnetic nanowires fabricated by anodic aluminum oxide template—a brief review

Anodic aluminum oxide （AAO） with highly ordered nanoscale pores which are monodisperse and mutually parallel can be produced through a self-organized electrochemical process. Subsequent deposition of materials into the nanopores produces AA0 embedded nanowire arrays. Whilst the templates can be further removed to obtain free individual nanowires, the em- bedded nanowires form an interesting nanocomposite structure. Recent research activities on the fabrication and characteriza- tion of AAO template based magnetic nanowires are reviewed in this article. Studies of specific systems are given as an exam- ple of the research in the area.

Quantificational Etching of AAO Template

Ni nanowires were prepared by electrodeposition in porous anodized aluminum oxide （AAO） template from a composite electrolyte solution. Well-ordered Ni nanowire arrays with controllable length were then made by the partial removal of AAO using a mixture of phosphoric acid and chromic acid （6 wt pct H3PO4：1.8 wt pct H3CrO4）. The images of Ni nanowire arrays were studied by scanning electron microscopy （SEM） to determine the relationship between etching time and the length of Ni nanowire arrays. The results indicate that the length of nanowires exposed from the template can be accurately controlled by controlling etching time.

Synthesis of carbon nanotube arrays using ethanol in porous anodic aluminum oxide template

Carbon nanotube (CNT) arrays confined by porous anodic aluminum oxide (AAO) template were synthe- sized using ethanol as reactant carbon source at low pressure. Images by scanning electron microscope (SEM) and low magnification transmission electron microscopy (TEM) show that these CNTs have highly uniform outer diameter and length, absolutely controlled by the diameter and depth of nano-channel arrays of the AAO. High resolution transmis- sion electron microscopy (HRTEM) imaging indicates that the graphitization of the CNT walls is better than the results reported on this kind of template-based CNT arrays, al- though it is not so good as that of multiwalled carbon nano- tubes (MWCNTs) synthesized by catalysis. CNTs synthesized using acetylene as reactant gas show much less graphitiza- tion than those prepared using ethanol by comparing the results of HRTEM and Raman spectroscopy. The etching effects of decomposed OH radicals on the amorphous carbon and the roughness of AAO nano-channel arrays on the CNTs growth were employed to explain the graphitization and growth of the CNTs.

Effect of anneal pre-treatment of polycrystalline aluminum sheets on synthesis of highly-ordered anodic aluminum oxide membranes

Anodic aluminum oxide (AAO) membranes with large ordered pore domains were successfully prepared by adopting the anneal pre-treatment of polycrystalline alu- minum sheets. A statistical method with Gaussian distribution was introduced to quantitatively study the size of the domain with ordered pores. The largest average area of ordered pore domains was 2.6 μm2±0.11 μm2. The corresponding AAO membrane was synthesized by aluminum sheets annealed at 893 K for 24 h.

AAO模板的制备及其应用

阳极氧化铝模板由于其价廉,制备工艺简单,以及特殊的结构和多样的组装方法得到了广泛的研究和应用。主要阐述了AAO模板的制备、影响因素,及其在纳米组装体系中的应用,包括量子点、纳米线、纳米管和"同轴电缆式"层状纳米材料等,介绍了AAO组装体系的应用,最后提出了AAO模板的潜在发展。

AAO模板外表面自组织纳米孔洞的差异性研究

以草酸为电解液,分别用一次阳极氧化法和二次阳极氧化法制备了阳极氧化铝(AAO,anodic alu-minum oxide)模板,在较大范围内得到了纳米孔分布均匀、孔洞大小均一、尺寸可控、排列有序的双通模板.采用扫描电镜(SEM)对其形貌进行表征,发现一次阳极氧化法制得的AAO模板的反面孔洞排列较为规则,而正面的孔洞排列规则性明显不如反面;二次阳极氧化法制备得到的模板正、反面孔洞的排列都比较规则.比较了模板正、反面纳米孔洞的差异,并结合阳极氧化过程中电流的变化,探讨了自组织孔洞的形成机理.目前尚未发现关于纳米孔洞差异性及原因分析的文献报道.

Co/AAO纳米有序阵列复合结构的光致发光和光吸收特性

以草酸电解液制备的高度有序的纳米级多孔阳极氧化铝(AAO)为模板,采用交流电化学沉积工艺合成了Co/AAO纳米有序阵列复合结构。分别研究了AAO模板和Co/AAO结构的光致发光和光吸收特性。结果表明,AAO模板在350～550nm范围内存在较强的光致发光带,其峰位在395nm处;Co/AAO纳米有序阵列复合结构的光致发射峰位亦在395nm处,且发光峰强度随Co沉积量的增加而迅速减弱。实验发现,Co/AAO纳米有序阵列复合结构的光吸收边从近紫外至近红外的波段范围内发生大幅度红移,最大红移量甚至超过380nm。文章定性分析并解释了Co/AAO纳米有序阵列复合结构吸收边大幅度红移及其光发射峰位不变、而峰强减弱的主要原因。

在AAO模板上用溶胶—凝胶法制备TiO_2纳米管阵列

用二次阳极氧化法在草酸电解液中制备出有序多孔阳极氧化铝(AAO)模板,采用溶胶-凝胶法在负压辅助条件下用钛酸四丁脂Ti(OC_4H_9)_4为TiO_2前驱体溶胶浸渍AAO模板,450℃下热处理制备长度和孔径可控的TiO_2纳米管的阵列结构.剥离去除模板后,用FE-SEM、XRD对产物形貌、晶型进行表征和分析.结果表明,制备的TiO_2纳米管长约3μm,外径130 nm,内径100 nm,与AAO模板的孔径相当,且单根TiO_2纳米管分散性较好,管与管之间无团聚,说明负压辅助可提高TiO_2纳米管的连续性.XRD分析显示,TiO_2纳米管呈锐钛矿相晶型.

AAO模板为基底CVD法合成孔径可控的碳微球

1000℃下两段炉中裂解乙炔，第一段炉中不放催化剂，第二段炉中放入孔径约为50nm的AAO模板并将炉温设定为700℃，反应时间为10min。产物通过扫描电子显微镜和高分辨透射电子显微镜进行了表征。结果表明：AAO模板表面沉积了很多直径约为50nm的碳微球，碳微球的结构为断断续续的石墨片层组成的波纹状结构，石墨片层的层间距约为0．3～0．35nm。

Electroless Deposition of Nickel Nanowire and Nanotube Arrays as Supports for Pt-Pd Catalyst for Ethanol Electrooxidation

Nickel nanowire and nanotube arrays as supports for Pt-Pd catalyst were prepared by elec- troless deposition with anodic aluminum oxide template. Pt-Pd composite catalyst was de- posited on the arrays by displacement reaction. SEM images show that the nickel nanowires have an average diameter of I00 nm and the nickel nanotubes have an average inner diameter of 200 nm. EDS scanning reveals that elemental Pt and Pd disperse uniformly on the arrays. Cyclic voltammetry study indicates that the nickel nanotube array loaded with Pt-Pd pos- sesses a higher electrochemical activity for ethanol oxidation than the nickel nanowire array with Pt-Pd.

AAO模板制备过程中电化学抛光工艺的研究

研究了在高氯酸/乙醇抛光液体系下,不同抛光电压(5、10、15、20 V)和抛光时间(2、3、4、5 min)的抛光工艺对抛光效果的影响。并且对抛光过程中的电流密度变化及抛光表面的光亮情况进行研究。结果表明,该体系的最佳抛光工艺:抛光电压15 V、抛光时间4 min(分两次抛光,每次时间为2 min)。

AAO模板快速制备方法探究

为了快速制备出高度有序且孔径可调控的AAO(阳极氧化铝)模板应用于工业生产,通过改进传统的两步阳极氧化法,采用逐步提高电解液浓度的硬氧氧化法制备了AAO模板,并确定了最佳制备工艺为初始电解液浓度0.15mol/L,添加电解液浓度0.40mol/L,温度保持在5℃左右,无水乙醇添加比例为1:1,从而使铝片的击穿电压从40V上升到130V左右(模板面积1.5cm×4.5cm),采用DimensionEdge型号的原子力显微镜(AFM)对多孔氧化铝模板进行了表征。结果表明:未经退火处理的铝片,也可以制备出高度有序的AAO模板,但其粗糙度略有增加,并与在高压条件下二次氧化、三次氧化、四次氧化制备AAO模板进行了比较,发现二次氧化制备的AAO模板有序度、孔径、孔间距均优于三次、四次氧化法。

氧化条件对AAO阵列显微形貌与晶体结构的影响及自组织机理研究

以草酸为电解液,分别用一次氧化法和二次氧化法制备了阳极氧化铝(AAO)模板。采用原子力显微镜和X射线衍射仪分别对其显微形貌和晶体结构进行表征。结果表明:一次氧化法制得的AAO模板正面孔洞排列有序性较差,而反面纳米花样排列较为规则;二次氧化法制得的模板孔洞排列很规则,且经扩孔腐蚀后,孔径变大,晶体结构由多晶态Al2O3转变为AlPO4;不同氧化电压下晶体结构存在差异。简要探讨了AAO模板形成机理。

影响AAO生长因素的研究

影响氧化铝阵列模板的因素有很多,包括铝箔的纯度、抛光效果、铝箔是否经过退火处理、电解液类型、电解液浓度、电压、温度以及氧化方法的选用等。研究表明,它们并不是单一地影响着孔洞排布的有序度、孔洞的大小以及膜的厚度等,而是相互作用、共同影响。例如不同的孔洞大小应选取不同的温度、电压和电解液类型等。总的说来,为了得到理想的氧化铝阵列模板,就应尽量优化各影响因素,这就需要对各影响因素有一个系统、全面的了解。作者改变了以前的文章[1-6]中一种因素只影响模板一个条件(包括孔排布的有序状况,孔洞的大小和膜的厚度)的缺点,对其影响因素进行了系统、全面的研究。