溶胶一凝胶模板法制备氧化镍纳米线

采用二次阳极氧化的方法,以5%磷酸为电解液,制得具有一定厚度有序性较高的阳极氧化铝模板(AAO),结合溶胶-凝胶法在模板微孔内合成氧化镍纳米线.利用扫描电镜(SEM)对模板和纳米线材料的形貌进行了表征,结果表明:采用该方法成功制得线状的氧化镍,长度可达亚微米级,直径约为100nm,与AAO模板的孔径大小基本一致,因此可以通过调节AAO模板的孔径大小来实现氧化镍纳米线的可控生长.     

Research on fabrication and properties of nanoporous GaN epilayers

Gallium nitride (GaN) epilayers with nanopore arrays were fabricated by inductive coupled plasma (ICP) etching using anodic aluminum oxide (AAO) as mask.Nanoporous AAO templates were formed by anodizing the Al films deposited on GaN epilayers.The diameter of the perforations in the AAO masks could be easily controlled by tuning the technique parameters of AAO fabrication process.Cl2/Ar and Cl2/He were employed as etching gas.Scanning electron microscopy (SEM) analysis shows that vertical nanoporous arrays with uniform distribution can directly be transferred from AAO masks to GaN films in some proper conditions.Photoluminescence (PL) spectra, X-ray diffraction (XRD) and Raman spectroscopy were applied to assess properties of the nanoporous GaN films with different average pore diameters and interpore distances.     

Magnetic properties improvement through off time between pulses and annealing in pulse electrodeposited CoZn nanowires

CoZn alloy nanowire arrays embedded in anodic aluminum oxide (AAO) template were fabricated by alternative current (ac) pulse electrodeposition. Various off times between pulses in an electrolyte with constant concentration of Co⁺² and Zn⁺² and acidity of 4 were employed. The effect of deposition parameters on the alloy contents, microstructures and magnetic properties of Co_xZn_1−x nanowires were studied. It is shown that, Co content increased by increasing the off time between pulses. This phenomenon enables us to fabricate Zn and Co-rich nanowires by adjusting the off time during the deposition procedure. Increasing the off time more than 200 ms increased the coercivity and squareness of CoZn nanowire arrays. A significant increase in the coercivity of CoZn nanowires was observed after annealing which was varied for the samples fabricated with different electrodeposition conditions. A coercivity of 1785 Oe was obtained for the annealed sample (a sample fabricated with 50 ms off time) from initially 240 Oe.     

Optical properties of anodic aluminum oxide films on Al1050 alloys

In this study the reflectance and nano-structure of anodized aluminum oxide (AAO) films that formed on Al1050 alloys in a 15% w/w sulphuric acid solution were examined. It was found that AAO films that formed under a high bath temperature and/or low anodic current density had a high pore density (count dm^− 2). The reflectance of AAO films formed at different anodizing times is a function of their thickness. The surface reflectance spectra showed interference when the AAO films exceeded a critical thickness (~ 100 nm). The reflectance curves oscillated and were affected by the pore density. We calculated the refractive index (n) and extinction coefficient (k) of the films based on the measured film thickness and reflectance. We can see from the experimental results that reflectance decreased with increasing thickness, while increasing pore density led to an increased refractive index but decreased extinction coefficient.     

Bi_(3.15)Nd_(0.85)Ti_3O_(12)纳米管阵列的制备与微结构表征

采用溶胶凝胶法,在孔径为200 nm的阳极氧化铝模板中制备了Bi_3.15Nd_0.85Ti_3O_(12)纳米管阵列.通过XRD、SEM、TEM、HRTEM、SAED和Raman光谱测试手段对纳米管阵列的物相、微结构和声子振动特性进行了表征.研究表明,所合成BNdT纳米管为钙钛矿相多晶结构,纳米管外径约为200 nm,管壁厚约10 nm,管径和长度与所用AAO模板尺寸一致.Raman光谱分析表明,Nd离子取代了类钙钛矿层中A位的Bi离子.     

Investigation of the hydrogen gas sensing properties of nanoporous Pd alloy films based on AAO templates

In this study, the hydrogen sensing properties of nanoporous Pd-Ag and Pd-Cu alloy films based on anodic aluminum oxide (AAO) templates were investigated at various temperatures (25-100 °C) and hydrogen with concentrations in the range between 250 and 5000 ppm in high purity nitrogen to determine the temperature-sensitivity relationship. A hexagonally shaped AAO template of approximately 50 nm in diameter and 10 μm in length was fabricated as a substrate for supporting a nanoporous Pd alloy film with an approximate thickness of 80 nm. The morphologies of the AAO template and the Pd alloy films were studied by scanning electron microscopy (SEM). The hydrogen sensing properties of the nanoporous Pd-Ag and Pd-Cu alloy films were measured using a transient resistance method. The sensor responses of the nanoporous Pd-Ag and Pd-Cu films on the AAO template were better than the traditional Pd-Ag and Pd-Cu thin film sensors; the sensitivities of the sensors were approximately 1.6% and 1.2%, respectively, for 1000 ppm H₂, and the detection limit was 250 ppm at room temperature. The highest sensitivity was measured at room temperature for all alloy nanoporous sensors, and the sensitivity of the Pd-Ag nanoporous alloy was higher than that of the Pd-Cu nanoporous alloy.     

Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in Oxalic Acid

Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3?M oxalic acid under the anodizing potential range of 30?C60?V at an electrolyte temperature of ~5°C. The AAO templates were analyzed using scanning electron microscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis. The as obtained layers are amorphous; the mean pore size is between 40?nm and 75?nm and increases with the increase of the anodization potential. Well-defined pores across the whole aluminum template, a pore density of ~10¹⁰?pores/cm², and a tendency to form a porous structure with hexagonal symmetry were observed.     

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 (B_r) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires, and coercivity (H_c) 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.     

Preparation and characterization of La-Co alloy nanowire arrays by electrodeposition in AAO template under nonaqueous system

La-Co alloy nanowires can be made in pulse reversal current（PRC） and direct current（DC） electrodepositions under nonaqueous system, with the porous anodic aluminum oxide（AAO） as template. This membrane is subject to the dual-oxidation （two-step） anodizing. Scanning electron microscope（SEM） examination shows that all of the nanowires have uniform diameter about 200 nm, and their diameters are determined by the pore diameter of applied AAO template. X-ray energy dispersion analysis indicates that the chemical composition of La and Co elements is very close to 1：2 in stoichiometry. X-ray diffraction pattern investigation demonstrates that La-Co nanowire is the face-centered cubic（FCC） LaCo13.     

The effect of n-alcohols on porous anodic alumina formed by self-organized two-step anodizing of aluminum in phosphoric acid

Self-ordered porous anodic alumina films were fabricated by a two-step anodization technique at potentials between 110 and 170 V using different n-alcohols and water mixtures containing 0.3 M H₃PO₄ at the electrolyte temperatures of 0 and − 5 °C. The morphology of the specimens was observed by a field emission scanning electron microscope (FE-SEM). Anodic aluminum oxide (AAO) films fabricated in the absence of n-alcohols exhibit a complex structure with sub-pores, independently of the anodizing potential. The sub-pore structure of films disappeared in the presence of n-alcohols probably due to the cooling effect of alcohol and extended time for the pore interaction (re-arrangement of pores). Additionally, with increasing anodizing potential, the regularity of pore arrangement, uniformity of pore shape and interpore distance of the AAO film increases independently of the electrolyte composition. The order of arrangement and circular shape of pores increases with increasing n-alcohol content for both anodizing temperatures. The best arranged porous structures were obtained in 1:1 methanol-water electrolyte containing 0.3 M H₃PO₄ (lower evaporating point than n-propanol and water) at 0 °C. The interpore distance of porous anodic alumina decreases with increasing n-alcohol content and increasing regularity of pore arrangement.     

Controlled synthesis of highly ordered CuO nanowire arrays by template-based sol-gel route

The highly ordered CuO nanowire arrays of composite-oxides were synthesized within a porous anodic aluminum oxide（AAO） template by a citrate-based sol-gel route. A vacuum system was applied to draw the gel into the template pores, which conquers the only driving force of this technique-capillary action, then the gel was thermally treated to prepare desired CuO nanowires. The results of scanning electron microscopy（SEM） indicate that the CuO nanowires are very uniformly assembled and parallel to each other in the pores of the anodic aluminum oxide（AAO） template membranes. The results of X-ray diffraction（XRD） and the selected-area electron diffraction（SAED） indicate that the CuO nanowires are monoclinic-type crystalline structure. Furthermore, X-ray photoelectron spectroscopy （XPS） demonstrates that the stoichiometric CuO is formed.     

Sol-gel synthesis of Bi3.25La0.75Ti3O12 nanotubes

Ferroelectric Bi_3.25La_0.75Ti₃O₁₂ (BLT) nanotubes were synthesized by sol-gel technique using nanochannel porous anodic aluminum oxide (AAO) templates, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). BLT nanotubes with diameter of around 240 nm and the wall thickness of about 25 nm exhibited a single orthorhombic perovskite structure and highly preferential crystal growth along the [1 1 7] orientation, which have smooth wall morphologies and well-defined diameters corresponding to the diameter of the applied template. The formation mechanism of BLT nanotubes was discussed.     

模板法电沉积钆钴合金纳米线阵列

在草酸电解液中用二次阳极氧化法制备多孔阳极化氧化铝(Anodic Aluminum Oxide,AAO)模板。通过对电流密度、氧化时间、电解液浓度等参数的调整,最终获得孔洞分布均匀、孔径基本一致、孔口呈六边形的AAO模板。采用不去除中间铝,用逐级降压法和电化学法减薄阻挡层,然后利用中间铝作为电极,在非水体系中以AAO为模板,直流电沉积钆钴合金纳米线阵列。经过SEM观测,AAO模板孔径在60nm左右,去阻挡层前后变化不大,制备的钆钴合金纳米线排列有序、尺寸一致;EDS测定表明纳米线为钆钴合金及少量氧化物纳米线,钆钴摩尔质量比为1:7.5,钆钴合金质量分数为90.66%;XRD分析图谱表明所得到的钆钴合金纳米线为非晶态。     

有序多孔氧化铝模板及 ZnO 沉积膜的制备与表征

采用二次阳极氧化法制备有序多孔氧化铝模板(AAO),探讨了氧化时间、磷酸溶液浸泡后处理对氧化铝表面形貌的影响。以AAO为模板沉积ZnO薄膜,通过SEM,XRD,EDS,AFM等技术对氧化铝模板及ZnO薄膜进行表征,结果表明,有序多孔层为非晶态氧化铝。研究了以AAO为模板沉积ZnO薄膜作光阳极的染料敏化太阳电池的光电转换性能,得出其转换效率为0.34%。     

Unique nanostructures in NiCo alloy nanowires

NiCo alloy nanowires have been fabricated by electrodeposition using an anodized aluminum oxide (AAO) template. Single-crystalline and polycrystalline alloy nanowires have been obtained, and their microstructure was strongly dependent on the deposition conditions (current density and composition). In addition, unique nanostructures have been observed in NiCo alloy nanowires. Bamboo or layer structures were found for 15 and 25 at.% Co, respectively. The investigation of the mechanisms shows that these particular structures are related to the different diffusion rates of Ni and Co on the surface of the AAO template. The work demonstrates that as well as single-crystalline and polycrystalline nanowires, other unique nanostructures (layered and bamboo in this work) can be achieved through careful control of the preparation conditions.     

氧化次数对制备多孔阳极氧化铝膜的影响

在8℃、0.3 mol/L浓度的草酸电解液中,施加40 V直流电压,采用两步阳极氧化法在高纯度铝箔上制备了多孔阳极氧化铝（AAO）膜。用场发射扫描电镜（FESEM）对一次、二次氧化制备的多孔氧化铝膜的表面形貌进行了表征。用XRD对原始铝箔及用二次氧化法制备的氧化铝膜的相结构进行了表征。用TEM观察了扩孔后多孔膜的通透性。结果表明,用二次阳极氧化制备的多孔膜明显比用一次法制得的更规则、有序和更厚,为非晶态的Al2O3。     

Fabrication of Pd-Fe nanowires with a high aspect ratio by AAO template-assisted electrodeposition

In this study, vertically oriented Pd_0.86Fe_0.14 nanowires have been fabricated using an anodized aluminum oxide (AAO) template by direct voltage electrodeposition at room temperature. AAO template-assisted electrodeposition of Pd-Fe was carried out in Pd(NH₃)₂Cl₂:FeSO₄·7H₂O solution. The AAO template and the Pd_0.86Fe_0.14 nanowires were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) methods and X-ray diffraction (XRD). It was observed that the Pd_0.86Fe_0.14 nanowires were approximately 65 nm in diameter and 10 μm in length with an aspect ratio of 153 in a relatively large area of about 4 cm². The nucleation rate and the number of atoms in the critical nucleus are determined from the analysis of current transients.     

Formation of unidirectional nanoporous structures in thickly anodized aluminum oxide layer

A series of anodic aluminum oxide(AAO) was grown on the commercially pure 1050 aluminum sheet by controlling electrolyte temperature (2–15 °C) and an odizing time (0.5–6 h), using a fixed applied current density of 3 A/dm² in diluted sulfuric acid electrolyte. A crack-free thick AAO with the thickness of 105–120 μm and containing unidirectional nano sized pores (average pore diameter of 5–7 nm) is successfully achieved in the specimens anodized for 2 h, irrespective of electrolyte temperature. When anodizing time reaches 6 h, very thick AAO with the thickness of 230–284 μm is grown, and average diameter of unidirectional pores is in the range of 6–24 nm. The higher values in both the AAO thickness and pore diameter are attained for the specimens anodized at higher temperatures of 10–15 °C. A crack is observed to exist in the AAO after anodizing up to 4 h and more. A higher fraction (more than 9%) of the crack is shown in the specimens anodized at higher temperatures of 10–15 °C for 6 h and a considerable amount of giant cracks are contained.     

FRICTION PROPERTIES OF OIL-INFILTRATED POROUS AAO FILM ON AN ALUMINUM SUBSTRATE

1. IntroductionA lum inum and its alloys are used in m any engineering applications because of their highstrength-to-w eightratio and high therm alconductivities.H ow ever,high friction coefficient,poorw earresistance and low seizure load ofalum inum allo…     

Tribological properties of nanoporous anodic aluminum oxide film

Friction and wear properties of nanostructured anodic aluminum oxide (AAO)) films were studied in relation to contact load and pore size (pore diameter). Uniformly arrayed nanoporous aluminum oxide films (pores of 28 nm, 45 nm, 95 nm, and 200 nm diameter and 60-100 μm thick) were synthesized by anodization. Reciprocating wear tests using 1 mm diameter steel balls as counterpart were carried out for a wide range of load (from 1 mN to 1 N) at ambient environment. The friction coefficient reduced with the increase of load. The friction coefficient decreased by approximately 30% when the load increased by 3 orders of magnitude. The pore density marginally affected the frictional properties of AAO films. The influence of pore size on the friction coefficient was significant at relatively high loads (0.1 N and 1 N) whereas it was negligible at low loads (1 mN and 10 mN). The worn surface of AAO films tested at low loads did not experience tribochemical reaction and exhibited only mild plastic deformation. Dispersed thick smooth films were formed on the worn surface of all samples at relatively high loads whereas only extremely thin smooth film patches were rarely formed at low loads. These thick smooth films were generated by combined influence of tribochemical reaction at the contact interface and plastic deformation of compacted debris particles as evidenced by energy-dispersive spectroscopy analysis. We suggest that these thick films mainly contributed to the decrease of friction regardless of the pore size.