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.     

Synthesis of anodic aluminum oxide (AAO) at relatively high temperatures. Study of the influence of anodization conditions on the alumina structural features

Anodic aluminum oxide (AAO) is a well known template for nanofabrication. Structural features of AAO like pore diameter, interpore distance, porosity, pore density can be fully controlled by operating conditions of anodization. Typically, self-organized two-step anodization is carried out at low temperature (below room temperature) and is a time consuming process. There are individual experiments describing anodization at temperatures close to room temperature. In our study, furthermore, a systematic analysis of the anodization condition influence on the nanoporous alumina structural features was done. The anodization temperature was ranging from 35 to 50 °C increasing significantly current density of the processes, which has increased oxide film growth rate. The anodizing potential ranged from 20 to 60 V and time of the anodization steps was 30, 60 or 120 min. The data obtained has shown that the pore diameter increases with potential, temperature and time of anodization, while the interpore distance is influenced solely by the potential. Temperature and time changes do not affect the interpore distance. Porosity is also influenced by potential, temperature and duration of anodization. Pore density is influenced only by the potential. The synthesis of AAO reported here gives possibilities to obtain the AAO templates in a faster and cheaper way, essential for researchers applying anodic alumina as a template.     

Porous anodic alumina membranes formed by anodization of AA1050 alloy as templates for fabrication of metallic nanowire arrays

The through-hole porous anodic aluminum oxide (AAO) membranes were fabricated by a two-step anodization of the aluminum alloy (AA1050) in 0.3 M oxalic acid at 45 V and 20 °C followed by removal of Al and pore opening/widening procedures. The effect of duration of the second anodizing step on the porous oxide layer thickness and the influence of the pore opening time on structural features of as-prepared membranes were studied in detail. The prepared membranes with a thickness of about 60 μm were used as templates for fabrication of dense arrays of Ag, Au, and Sn nanowires with various aspect ratios by a DC electrochemical deposition process. The successful synthesis of metallic nanowires by simple DC electrodeposition of metals inside the pores of AAO templates fabricated from the AA1050 alloy was reported for the first time. The fabrication costs of nanowire arrays can be reduced by about 500 times when AAO templates, prepared from the AA1050 alloy, are used instead of those usually formed from expensive high purity Al.     

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.     

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.     

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。     

Alumina nanostructures prepared by two-step anodization process

Alumina nanostructures were obtained by two-step anodization process.The porous anodic aluminum oxide(AAO)membranes were anodized in oxalic acid,which was subsequently treated with chemical etching process with 1.0 mol/L sodiumhydroxide solution,or mixed solution of phosphoric acid(6.0%)and chromic acid(1.8%),respectively.Field emission scanningelectron microscopy(FE-SEM)and transmission electron microscopy(TEM)were employed to character the morphology andstructure of the obtained alumina nanostructure.It is found that alumina nanowires are generated in the acidic chemical etchingsolution,while nanotube structures are formed in the alkaline solution.The influence of acid and alkaline solution on aluminamorphologies in the chemical etching process was discussed.     

阳极氧化铝膜的表面接枝改性及润湿行为

目的通过对阳极氧化铝膜(AAO)表面化学接枝甲基丙烯酸甲酯,改变其表面的粗糙度和分子结构,从而实现AAO膜表面润湿行为的可控。方法采用二步阳极氧化法制备六方柱形的多孔AAO膜,结构高度有序,并对AAO膜表面进行硅烷化(KH-570)处理,采用活性聚合的方法在其表面接枝上甲基丙烯酸甲酯。采用原子力显微镜(AFM)、X射线衍射仪(XRD)和接触角测定仪对AAO膜及改性后的AAO膜进行了结构表征和润湿行为研究。探讨了阳极氧化的工艺条件及接枝甲基丙烯酸甲酯对AAO膜的形貌和润湿性能的影响。结果 AAO膜孔径在100 nm左右,六边形孔洞分布均匀,并且六边形孔洞垂直于AAO膜表面,孔洞与孔洞平行,通过对其表面接枝甲基丙烯酸甲酯,使得AAO膜的表面水接触角先增大后减小。结论 AAO膜表面的润湿行为,可以通过AAO膜表面化学改性和表面粗糙度共同作用而得以调控。     

高质量氧化铝模板的制备及其研究

以5%磷酸为电解液,通过阳极氧化高纯铝片制得了有序性较高的多孔氧化铝模板,结合扫描电镜(SEM)对其结构和行貌进形观察和表征.研究了氧化铝模板的制备工艺,还讨论了氧化铝膜的形成过程,最后比较了一次阳极氧化和二次阳极氧化获得的样品的多孔结构,认为低温下采用二次阳极氧化法可以获得很好的多孔氧化铝模板.     

Regularity control of porous anodic alumina and photodegradation activity of highly ordered titania nanostructures

A two-step anodizing process was used to prepare wide-range highly ordered porous anodic alumina membrane （PAA） in the electrolyte of oxalic acid. The effects of anodic voltage, anodizing time, size of aluminium foil and additives on the regularity of PAA membrane were also studied in the process of two-step anodization. The template method was combined with the sol-electrophoresis deposition and sol-gel method respectively to prepare highly ordered titania nanostructures. The diameter and length of the obtained nanostructures were determined by the pore size and depth of the PAA template. Scanning electron microscopy （SEM） and X-ray diffraction （XRD） were, used to characterize the morphology and phase structure of the PAA template and the titania nanostructures. The results show that the anodizing time and the additive of ethanol have a great effect on the regularity of PAA template. This can be explained from the self-organized process and the current density theory. A theoretical model based on the self-organized process was established to discuss the formation mechanism of PAA template from the chemical perspective. The titania nanostructures prepared with this method has a high specific surface area. Furthermore, the photocatalytic activity of titania nanostructures on methyl orange were studied. Compared with ordinary titania membranes, the titania nanostructures synthesized with this method have higher photodegradation activity.     

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。     

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…     

Microstructural and Optical Properties of Porous Alumina Elaborated on Glass Substrate

A transparent porous anodized aluminum oxide (AAO) nanostructure was formed on a glass substrate using the anodization of a highly pure evaporated aluminum layer. A parametric study was carried out in order to achieve a fine control of the microstructural and optical properties of the elaborated films. The microstructural and surface morphologies of the porous alumina films were characterized by x-ray diffraction and atomic force microscopy. Pore diameter, inter-pore separation, and the porous structure as a function of anodization conditions were investigated. It was then found that the pores density decreases with increasing the anodization time. Regular cylindrical porous AAO films with a flat bottom structure were formed by chemical etching and anodization. A high transmittance in the 300-900 nm range is reported, indicating a fulfilled growth of the transparent sample (alumina) from the aluminum metal. The data showed typical interference oscillations as a result of the transparent characteristics of the film throughout the visible spectral range. The thickness and the optical constants (n and k) of the porous anodic alumina films, as a function of anodizing time, were obtained using spectroscopic ellipsometry in the ultraviolet-visible-near infrared (UV-vis-NIR) regions.     

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.     

Nanowire Array of Rare-Earth Simple Substance Neodymium by DC Electrodeposition with Barrier-Layer-Free Template

A two-step anodization method was adopted to prepare the porous anode alumina (PAA) template through the oxalic acid solution. By adjusting the parameters (such as current density, oxidation time, electrolyte concentration and other factors), the PAA template was obtained, which has the evenly distributed pores with similar diameters and hexagonal-shaped mouth. Meanwhile, by removing the barrier layer without peeling off the film, the residual aluminum becomes the base and acts as electrode. In the non-aqueous system, the nanowire of RE simple-substance (SS) Nd has been prepared with the template DC electrodeposition. The aperture diameter of PAA template is approximately 60 nm, and there is little change before and after the barrier layer is removed. The Nd nanowire given is orderly and in similar size. EDS shows that the nanowires contain simple-substance (SS) Nd and a tiny of Nd2O3, while the content of SS Nd is 92.73 wt%. Both the SS Nd and Nd2O3 nanowire are possessed of hexagonal structure     

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%。     

Co Filled Porous Anodic Alumina Film Fabricated on ECR-Al Film with Silicon Substrate

Magnetic Co nanodots embedded in the porous anodic alumina films(AAFs)on silicon substrate can be used as the magnetic recording material with high area recording density.For this purpose,pure aluminum films were deposited on Si substrate with the Electron Cyclotron Resonance(ECR)plasma sputtering technique,and AAFs with vertical nano holes were synthesized with the two-step anodization process in oxalic acid.Finally magnetic material Co was deposited into the nano holes with electrochemical method.The results showed that polycrystalline ECR-Al films are homogenous and fit for the synthesis of AAFs with uniform distributed nano holes when ion sheath formed in front of the substrate surface.The diameters of AAF nano holes were in the range from 30 to 70 nm,and the hole pitches were approximately 100 nm,the AAF on silicon substrate was about 100 nm thick after two-step anodization.Magnetic Co nanodots filled into the nano holes of AAF exhibited both fcc and hcp structures.     

Influence of the microstructure of the aluminum substrate on the regularity of the nanopore arrangement in an alumina layer formed by anodic oxidation

We investigated the microstructure of aluminum sheets with different purities (Al 99.999%, Al 99.95%, Al 99.5% and AlMg1) before and after different treatments (polishing and annealing) by X-ray diffraction (phase analysis and pole figures) and high-resolution scanning electron microscopy. In a two-step anodisation process within sulfuric acid a nanoporous alumina layer (with mean diameters of 25 nm and mean distances of 30 nm) was formed on the aluminum sheets. We found that the regularity of the nanopore arrangement correlates with the fraction of aluminum grains with (100) orientation in the aluminum substrate. A correlation with the grain boundary and dislocation densities within the aluminum could not be determined.     

Influence of the aluminum surface on the final results of a two-step anodizing

1050 Aluminum alloy sheets were used to analyze the influence of a surface treatment on the characteristics of the alumina layer formed in a two-step anodizing. The study was mainly focused on two pretreatment steps, electropolishing and acid etching, as well as on the intermediate stripping step. The pretreatment procedure was optimized by accounting for the chemical nature of the substrate, with the results indicating that additional pretreatment steps enhanced the self-ordered porous arrangement. The E-t curves recorded during the experiments demonstrated that the best alumina layers were obtained when the first barrier layer had a high resistance; i.e., a high anodizing potential. The application time of the stripping step was optimized to clean the surface from alumina remains, without damaging the aluminum substrate. By optimizing all of these experimental conditions, we were able to obtain porous anodic aluminum oxide layers displaying ordered domains several hundreds of nanometers in length.     

Aluminum alloys anodisation for nanotemplates application

The aim of this investigation was to reveal the processing differences in achieving nanoporous anodized aluminium from aluminium alloys and their application for cobalt nanowires electrodeposition. The following types of aluminium were tested: pure Al (99.99%), and commercial alloys: AA1050, 6082 and 6060. Because of the differences in the surface temperature and high voltages during the anodizing steps, some stresses can be built up in the material. Therefore a strict temperature control should be done to limit thermal stresses in materials. Alloying elements (Si, Mg) cause precipitates that are observed on the surface, especially for 6060 alloy. Nevertheless, a nanoporous structure can be obtained at the end of second anodization step on all aluminium alloys investigated. It was shown that the number density of pores on the surface is practically independent on the aluminium alloys used. However, the degree of hexagonal distribution of the pores depends on the type of anodized aluminium alloy. Also, a successful fabrication of Co nanowire arrays using nanoporous anodic alumina template produced on Al alloy has been demonstrated, and the uniform filling of the template by cobalt nanowires arrays is discussed.