Two-step Anodization Research Articles

Effect of Silane Coupling Treatment on the Joining and Sealing Performance between Polymer and Anodized Aluminum Alloy

In the fabrication of joined materials between anodized aluminum alloy and polymer, the performance of the metalpolymer joining is greatly influenced by the chemical properties of the oxide film. In a previous study, the dependence of physical joining strength on the thickness, structure, pore formation, and surface roughness of films formed on aluminum alloys is investigated. In this study, we investigated the effect of silane coupling treatment on the joining strength and sealing performance between aluminum alloy and polymer. After a two-step anodization process with additional treatment by silane, the oxide film with chemically modified nanostructure is strongly bonded to the polymer through physical and chemical reactions. More specifically, after the two-step anodization with silane treatment, the oxide film has a three-dimensional (3D) nanostructure and the silane components are present in combination with hydroxyl groups up to a depth of 150 nm. Accordingly, the joining strength between the polymer and aluminum alloy increases from 29 to 35 MPa, and the helium leak performance increases from 10−2-10−4 to 10−8-10−9 Pa m3 s−1.

Effects of Two-Step Anodization on Surface Wettability in Surface Treatment of Aluminum Alloy

Industrial anodizing of aluminum alloys is widely employed for various products, to improve corrosion and contamination protection as well as aesthetic appearance. At the same time, nanostructure fabrication using highly ordered porous aluminum oxides has been increasingly investigated in academic research for diverse micro-/nano applications. This approach is based on two-step anodization with limited process conditions, such as extended process time and low temperature. In this study, two-step anodizing was employed to anodize hairline-finished Al 1050 with sulfuric acid considering industrial processing conditions. The method is particularly suited for anodized products that require post-processing such as printing, dyeing and/or bonding. Porous anodized layers that were fabricated using conventional single anodizing, and twostep anodizing under identical processing conditions were compared. Variations in porosity, pore diameter, and inter-pore distance were examined in relation to the anodizing parameters, such as temperature and voltage. The results showed that two-step anodizing caused an increase in all measured pore-related measurements, and produced a much more uniform porous layer than the conventional anodizing process. Water contact angles were evaluated on the anodized surface of the previously machined hairline specimen. It was found that the water contact angles clearly decreased on the surfaces treated by two-step anodization, compared to the conventional anodizing process.

A novel sealing and high scratch resistant nanorod Ni-P coating on anodic aluminum oxide

High scratch resistant nanorod nickel-phosphorous (Ni-P) sealing was fabricated using electroless deposition method on nanoporous anodic aluminum oxide (AAO-np). A two-step anodization process was preferred to develop an AAO-np template on Al alloy. Sensitization and activation processes were proceeded using SnCl2, PdCl2 respectively before Ni-P deposition. Concrete Ni-P was filled in and grown on AAO-np with a pore diameter of 40–60 nm at 6–7 μm height. A top view morphology confirms that the initial Ni-P clusters were transformed into a well-grown cauliflower-like structure during 1hr and 2 hr deposition times, respectively. Symmetric Ni-P nano-rods are formed at the beginning of porous structure in a side view. A possible formation of Ni-P nano-rods on AAO structure results in a potential improvement in indentation and scratch hardness as 3100 MPa and 3350 MPa, respectively.

Influence of sub-10 nm anodic alumina nanowire morphology formed by two-step anodizing aluminum on water wettability and slipping behavior

The influence of the nanomorphology of alumina nanowires (ANWs) fabricated by a two-step anodizing process on the superhydrophobicity was investigated through advancing contact angle (ACA) and receding contact angle (RCA) measurements. Aluminum nanobowl specimens were anodized in pyrophosphoric acid to fabricate an ordered ANW structure with an average diameter of 7.1 nm, and the outermost surface of the ANWs was chemically bonded with fluorinated self-assembled monolayers. The growing ANWs bent immediately their own weight, and pyramidal ANW structures were formed as they joined the surrounding nanowires together. The ACA value increased with the number density of pyramidal ANW structures due to the reducing area fraction of ANWs, and an increased superhydrophobicity with a contact angle of approximately 165° was measured on the low-density pyramidal structure with a density of 8.1 × 1011 m−2. Additional anodizing led to complete nanowire bending; thus, the advancing contact angle decreased. The pyramidal nanowire structure exhibited a large slipping property with a contact angle hysteresis (CAH) < 10°, whereas the bent nanowire structure exhibited a decreased slipping property with a CAH > 100°. Superhydrophobic surfaces with opposite water slipping properties were demonstrated by a water dropping experiment.

Zinc-doped iron oxide nanostructures for enhanced photocatalytic and antimicrobial applications

A simple, cost-effective method of two-step anodization is used to prepare environmentally benign zinc-doped iron oxide nanostructures for photocatalytic and antimicrobial applications. The effect of zinc doping on the structure and morphology of iron oxide nanostructure is analysed with the help of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy. A detailed analysis of the changes in the binding energy positions of Fe 2p, O 1s, Zn 2p and valence band maximum with variation in doping concentration is carried out with X-ray photoelectron spectroscopy. A combined analysis of valence band X-ray photoelectron spectra and optical reflectance spectra indicates a shift in Fermi level characteristic to a conversion from n-type in pure α-Fe2O3 to p-type in 5-s zinc-doped α-Fe2O3. The room-temperature electrical conductivity of the doped is improved by five orders compared to the undoped nanostructures. The zinc-doped iron oxide nanostructures with p-type conductivity are found to show high photocatalytic degradation efficiency for the organic dye methylene blue. Significant antimicrobial activity is observed with the nanostructures for the microbes Pseudomonas aeruginosa, Bacillus subtilis and E. coli.

Nondestructive characterization of nanoporous alumina films using terahertz scattering imaging

Ordered nanoporous (NP) alumina (Al 2 O 3 ) films were grown on Al substrates through a two-step electrochemical anodization process. The morphology as well as the roughness are characterized by terahertz (THz) reflectometry and scattering imaging. In particular, we show that before the second anodization, irregular surface morphology of the NP Al 2 O 3 films leads to significant THz scattering, whereas the far more homogeneous films following the second anodization show far less scattering. The regularity of the surface morphology is not readily ascertained using visible-light optical microscopy. The THz results are corroborated by field-emission scanning electron microscopy (SEM) and atomic-force microscopy (AFM), both of which are time-consuming, not easy to operate, and can only provide the local characterization of NP Al 2 O 3 films on Al substrate. THz-based techniques allow for the nondestructive characterization of the surface morphology of the entire NP Al 2 O 3 films on the 10–100 μm length scale important for a range of applications while providing information over macroscopic scan areas, and obviate the need for sample preparation required by other common surface-morphology characterization techniques. • Terahertz scattering imaging is applied to characterize the homogeneity of nanoporous alumina films after anodization. • Irregular surface morphology of nanoporous alumina films observed in terahertz images is corroborated by FE-SEM and AFM. • The stratigraphy and thickness of nanoporous alumina films are obtained nondestructively based on terahertz images. • Terahertz imaging may provide a reliable nondestructive and contactless modality to evaluate the quality of nanoporous films.

Fabrication of nanoporous free standing anodic alumina using two-step anodization for applicability in microhydraulic system as nano filter using surface acoustics

The current trend in nano/micro structured array fabrication for a variety of applications in microsystems development nanoporous anodic alumina (Al2O3) gained tremendous attention. In this research paper, Freestanding (FS) nanoporous anodic alumina were fabricated using a two-step anodization technique. Nanoporous honeycomb structure having an average 85 nm pore diameter and 135 nm distance between pores were achieved by electrochemical anodization at identical constant DC voltage 60 V. Nanoporous membrane thickness 0.25 µm were obtained with 36% porosity. Scanning electron microscopy (SEM) analysis investigation was done and it confirms honeycomb nanoporous structures were formed on the surface of FS AAO membrane. Additionally, Energy dispersive x-ray spectroscopy (EDS) microanalysis was conducted for the FS AAO membrane to analyze the chemical component after anodization. Finally, fabricated FS nanoporous AAO membrane response was presented under electrical excitation to enables its applicability as a nano filter in microhydraulic systems.

Synthesized and characterization of open-ended Ta3N5 nanotube arrays for the preparation of growth template

In this article, a two-step anodization method was applied to tantalum foils to grow compact open-ended tantalum oxide nanotube arrays, which were subsequently subject to high temperature nitridation. The nitride nanotube arrays were characterized with SEM, XRD, and electrochemical tests including I-V and Mott-Schottky analysis. The phases in the nitrided nanotube arrays may consist of Ta3N5, TaN, TaN0.5, N-Ta2O, or the amorphous oxide. The duration of the second anodization step was found to play a key role on the microstructure and the carrier density of the nitride nanotube arrays. It is found that the duration of the second anodization has to be more than 20 min to obtain a specimen with a top layer of Ta3N5, which can work as a photo electrode or a template for the growth of photo catalyst nanomaterials.

Анизотропные алюмооксидные нанопористые мембраны.

In the present study, we report the development of a new type of anodic aluminium oxide membranes. Nanoporous alumina films have been fabricated by galvanostatic two-step anodizing technique. For the 1stgroup of samples at both stages was used water solution of oxalic acid as an electrolyte; and for the 2ndgroup at the 2ndstage was used a special multicomponent electrolyte. Using atomic force microscopy, it was found that a method of barrier layer thinning “from above” in combination with chemical removal of metal enables permeable anisotropic alumina membranes fabrication.

Nanostructure of Anodic Porous Alumina Fabricated By Galvanostatic Anodizing in Etidronic Acid

Galvanostatic and potentiostatic anodizing processes of aluminum leads to the formation of large-scale porous alumina. It is previously reported that self-ordered porous alumina measuring above 500 nm in cell diameter can be fabricated via two-step anodizing in etidronic acid at higher voltage more than 200 V. On the other hand, extremely little has been reported on the growth behavior and their nanostructure during galvanostatic anodizing in etidronic acid. Herein, we investigate the nanostructural characterization of the porous alumina film formed via galvanostatic anodizing in etidronic acid under various operating conditions. Electropolished aluminum specimens were anodized at a constant current density of 0.005-500 Am-2 in 0.03-3 M etidronic acid solutions at 273-333 K. After anodizing, the porous alumina film was dissolved in a 0.20 M CrO3/0.51 M H3PO4 solution at 353 K, and the aluminum dimple array, which corresponded to the bottom shape of porous alumina, was exposed to the surface. The anodized specimens were examined by field-emission scanning electron microscopy (FE-SEM). The cell size (interpore distance) of the porous alumina was calculated using image analysis software. Typical voltage-time curves for the formation of anodic porous alumina were obtained during galvanostatic anodizing in etidronic acid: The voltage linearly increased, gradually decreased, and then reached plateau value. However, excess current density caused oxide burning with unstable oscillation in the voltage-time curve, and non-uniform porous alumina was formed on the aluminum surface. The plateau voltage greatly increased with the current density at each operating temperature, and various porous alumina films with different nanostructures were successfully fabricated by anodizing at a wide voltage range measuring 7-218 V. Figure 1 shows the changes in the average, maximum, and minimum cell sizes with the anodizing voltage under various operating conditions. The cell sizes are directly proportional to the anodizing voltage with proportionality constants of 2.5 (average), 3.5 (maximum), and 0.7 (minimum), respectively. Figure 1

Effect of Sulfurization Time and Temperature on the Properties of Lead Nano/Sub-Micro Wires Fabricated By Vacuum Injection Molding Process

In this research, lead (Pb) nano/sub-micro wire arrays were fabricated with Anodic Aluminum Oxide (AAO) templates of 30,100 and 300nm in diameters. Through vacuum injection molding process, Pb/AAO composite was obtained, and lead sulfide (PbS) could further synthesized after exposed to vaporized sulfide. The AAO templates with different pore size were produced by using 99.999% high purity aluminum in two-step anodization. Three types of solutions include 10vol.% sulfuric acid, 3wt.% oxalic acid and 1vol.% phosphoric acid solutions were adopted to achieve AAO of various pore size. Different sulfurization temperatures and time periods were applied for studying on the properties of PbS. Finally, the morphology, composition, structure and elements distribution of the as-prepared Pb and PbS nano/sub-micro wires were confirmed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X -ray diffraction (XRD) and element-mapping analysis. The results indicated that Pb nano/sub-micro wires obtained successfully after vacuum injection molding process with 50 kgf/cm2 hydraulic pressure and PbS nano/sub-micro arrays formed completely by sulfurization at 500℃ for 5 hours.

Highly Ordered TiO2 Nanotube Electrodes for Efficient Quasi-Solid-State Dye-Sensitized Solar Cells

Free-standing TiO2 nanotube (NT) electrodes have attracted much attention for application in solid- or quasi-solid-state dye-sensitized solar cells (DSSCs) because of their suitable pore structure for the infiltration of solid electrolytes. However, few studies have been performed on the relationship between nanostructures of these NT electrodes and the photovoltaic properties of the solid- or quasi-solid-state DSSCs. Here, we prepare vertically aligned and highly ordered TiO2 NT electrodes via a two-step anodization method for application in quasi-solid-state DSSCs that employs a polymer gel electrolyte. The length of NT arrays is controlled in the range of 10–42 μm by varying the anodization time, and the correlation between NT length and the photovoltaic properties of quasi-solid-state DSSCs is investigated. As the NT length increases, the roughness factor of the electrode is enlarged, leading to the higher dye-loading; however, photovoltage is gradually decreased, resulting in an optimized conversion efficiency at the NT length of 18.5 μm. Electrochemical impedance spectroscopy (EIS) analysis reveals that the decrease in photovoltage for longer NT arrays is mainly attributed to the increased electron recombination rate with redox couples in the polymer gel electrolyte.

Influence of Annealing Time of Aluminum AA1050 on the Quality of Cu and Co Nanocones

Anodization is a widespread surface treatment method for aluminum and its alloys; it also allows the formation of 1D nanostructures by a two-step process. Microstructure of the Al substrate and crystallographic texture after rolling and annealing have influence on the properties of AAO templates with conical nanopores. Synthesized free-standing 1D nanostructures ensure better electrocatalytic properties than bulk materials due to larger active surface area. In this work, the influence of annealing time at 500 °C on Vickers hardness and microstructure of aluminum AA1050 used in a two-step anodization process was investigated. The geometrical features of the templates such as interpore distance and number of pores per 1 μm2 were determined and compared. There is dependence between the time of the annealing process and surface quality of synthesized 1D Cu nanocone layers. The template, after 1 h of annealing, due to the largest active area and satisfactory quality of the nanocone surface, was chosen for synthesis of Co nanocones. The electrocatalytic properties of samples were measured in 1 M NaOH solution and compared with bulk material electrodeposited in the same conditions. The open circuit potential, connected with starting of hydrogen evolution reaction, was determined from the LSV curves. Active surface areas were determined for all samples using SEM photographs and taken into consideration during electrocatalytic tests. Possible behavior of hydrogen bubbles for the formation of nanostructures was considered.

FORMATION OF ANODIC POROUS ALUMINA IN OXALIC ACID AND ELECTRODEPOSITION OF NI.

Nanoporous anodic aluminum oxide (AAO) tubular membranes were fabricated from aluminum alloy tubes in sulfuric and oxalic acid electrolytes using a two-step anodization process. The membranes were investigated for characteristics such as pore size, interpore distance and thickness by varying applied voltage and electrolyte concentration. Morphology of the membranes was examined using light optical and scanning electron microscopy and characterized using Image software. Results showed that membranes having narrow pore size and uniform pore distribution with parallel channel arrays were obtained. The pore sizes were ranging from 10 to 100 nm and the wall thicknesses 60 μm. The catalysts are obtained by impregnation of 3d metals into nanosized pores of aluminum oxide. The obtained catalysts based on nickel and porous Al2O3 are studied by scanning microscopy (SEM-EDX). The results of SEM-EDX analysis shows that a spongy structure with filament sizes of 100 nanometers containing particles of 3d metals formed on the surface of the aluminum oxide matrix.

Growth of Zr–BiFeO3 nanostructures on two step anodized porous alumina for estimation of optical and dielectric response

Abstract Nanostructures decorated with perfectly ordered porous anodic aluminum oxide templates have attained recent research interest for the production of highly efficient energy storage devices. Anodic aluminum oxide porous templates were synthesized using a two-step anodization technique in this work. Pure BiFeO3 and Zr–BiFeO3 nanostructures were grown on these ordered templates by well-controlled fluoride ions assisted autoclave enclosed hydrothermal method. Crystallographic information discloses the presence of rhombohedral crystal structure with geometric space group R3c belongs to BiFeO3. The morphological analysis depicts the formation of an average pore size of approximately 75 nm in anodic aluminum oxide templates. BiFeO3 contains fibrous nanoflakes like morphology with minute content of the monoclinic zirconia phase in Zr–BiFeO3. Optical measurements demonstrate a considerable variation in absorption and bandgap of anodic aluminum oxide with the growth of nanostructures. A significant increase in dielectric permittivity from 17.17 for anodic aluminum oxide to 187.19 for Zr incorporated compositions with a relatively low tangent loss of 0.66.

Stable resistive switching characteristics from highly ordered Cu/TiO2/Ti nanopore array membrane memristors

This article focuses on the fabrication of highly ordered Cu/TiO2/Ti nanopore array membrane memristors by using two-step anodization and vacuumevaporation methods and exploration the effects of oxidation parameters such as anodization voltage and electrolyte temperature on device performance. The performance test results show that this novel ordered TiO2 nanopore array membrane structure can effectivelyregulate the distribution of the local electric fieldthatrestrictsthe growth path of the conductive filaments (CFs), which thereby greatly improves the stability and yield of the devices. In addition, it is found that through adjusting the process parameters, such as anodization voltage and electrolyte temperature, the lateral (pore diameter) and longitudinal (pore depth) dimensions of the TiO2 nanopores can be regulated for further optimizing device performance. These exciting results demonstrate that the highly ordered TiO2 nanopore array structure can offer atangible effectiveness and controllability for improving the stability of memristors, suggesting the strategy seems to have an important scientific significance and application value.

Electrodeposition-assisted formation of anodized TiO2–CuO heterojunctions for solar water splitting

The anatase phase titanium dioxide nanotubes (ATNTs) are investigated for photocatalytic water splitting with and without the formation of copper oxide (CuO) heterojunctions. ATNTs have been grown on titanium substrate by one- and two-step anodization, followed by annealing at 450 oC for transformation to anatase phase. Anodization was performed in an electrolyte containing ammonium fluoride, ethylene glycol and deionized water. The ATNTs were then modified with CuO nanoparticles by dip-coating and electrochemical deposition. The growth of ATNTs and incorporation of CuO nanoparticles in it were confirmed with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) spectroscopy. Well-organized and vertically aligned nanotubes were observed in the FESEM results. Contact angle measurements proved that the thin film of nanotubes is hydrophilic in nature. Linear sweep voltammetry (LSV) technique was performed for photocurrent responses, using distilled water in the dark environment as well as in the light of solar simulator at applied potential of 1.0 V. The photocurrent densities in the dark were negligible, while it became significant under the influence of simulated visible light. The ATNTs grown with two-step anodization offered promising results for photocatalytic water splitting compared to single-step anodization. The CuO modification in ATNTs exhibited a reasonable increase in photocurrent densities compared to pristine ATNTs. Furthermore, the electrochemical deposition process for modification of ATNTs with CuO afforded much better photocurrent responses compared to the dip coating method. The electrochemical deposition of CuO in ATNTs was performed at 0.7 V, 0.9 V and 1.1 V, among which the sample prepared at 0.7 V exhibited the highest photocurrent densities.

Zn0.5Cd0.5S nanoparticles modified TiO2 nanotube arrays with efficient charge separation and enhanced light harvesting for boosting visible-light-driven photoelectrochemical performance

Vertically aligned TiO2 nanotube arrays (TiO2 NTAs) modified with uniformly dispersed Zn0.5Cd0.5S (ZCS) nanoparticles as novel heterojunction photoanodes have been prepared for the first time through a typical two-step anodization followed by successive ionic layer adsorption and reaction (SILAR) process. The photoelectrochemical (PEC) performance of ZCS nanoparticles modified TiO2 NTAs (TiO2 NTAs/ZCS) photoanodes strongly depends on the loading amount of ZCS. By optimizing the amount of ZCS in TiO2 NTAs/ZCS photoanodes, the highest photocurrent density of 10.95 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE) under visible-light illumination is obtained. The optimum photoconversion efficiency is up to 4.54% at 0.49 V vs. RHE, while it is only 0.04% at 0.67 V vs. RHE for bare TiO2 NTAs photoanode. The maximum incident photon-to-current efficiency (IPCE) value in TiO2 NTAs/ZCS photoanodes is 65.0% at 390 nm, which is 2.3-fold as high as that of bare TiO2 NTAs photoanode (28.1% at 340 nm). The formed heterostructure structure between TiO2 NTAs and ZCS possesses a typical type-II band alignment, which is beneficial to drastically promote the improvement of PEC performance due to the efficient charge separation and increased light harvesting.

Evaluation of the electrochemical corrosion behavior of anodic aluminum oxide produced by the two-step anodization process

Purpose This study aims to investigate the effect of different pore diameter and pore length on corrosion properties of anodic aluminum oxide (AAO) film. Design/methodology/approach AAO layer was produced by two-step anodization aluminum in oxalic acid. The surface morphology was investigated using field emission scanning electron microscopy. The pore diameters were ranging from 25 ± 5 to 65 ± 5 nm and the pore length ranging from 5 to 17 µm. The corrosion properties of the AAO films was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy tests. Corrosion properties and morphology of the anodic films depending on anodization times and pore expansion times were evaluated. Findings All highlights of this work can be summarized with the following specified below: more treatment with the protective barrier layer of the solution as the pore diameter increases depends on the morphology of the nanotube structured AAO layer. The excellent corrosion resistance renders AAO films without pore expansion very promising. The oxide layer thickness does not affect the corrosion resistance. The better corrosion resistance of AAO films at low pore length can be ascribed to the barrier layer thickness and the more homogeneous structure. The presence of defects for the higher pore length decreases its corrosion resistance. Originality/value The AAO films were fabricated by a two-step anodization method in oxalic acid. The anodization times and pore expansion times affect the corrosion performance. The AAO film without pore expansion has good corrosion resistance. The corrosion resistance decreases as the pore length increases.

Optimization of process parameters of anodic aluminium oxide using an orthogonal array technique for thermal management applications

The semiconductor packaging field is evolving rapidly due to strong competition in customer demands for increased functionality and performance, further miniaturization, heightened reliability and lower costs. The lifetime reliability and sequential performance of solid-state products are mainly based on the device junction temperature (Tj). The main concerns of efficient thermal management in heat source-based electronic packages are controlling and reducing the device junction temperature and total thermal resistance (Rth). The optimization of process parameters to develop an anodic aluminium oxide nanopore (AAO-np) structure on an Al5052 alloy substrate using an electrochemical process (two-step anodization) is proposed based on the Taguchi orthogonal array (L9). The four major parameters are the electrolyte, anodization time, bath temperature, and applied voltage, which are varied at three different levels. This experiments aim to finalize suitable process parameters and their levels towards optimum Rth and Tj. The morphology of the step-wise preparation of AAO-np structure is discussed for the optimized conditions of 0.3 M oxalic acid, a 3 h anodization time, a 30 V applied voltage, and a bath at room temperature. The resulting AAO-np structure has a pore diameter of 40 to 55 nm and a height of 6 to 7 μm. This formation significantly reduces Rth by 24.58% and Tj by 24.66% for the electronic package compared to a bare Al substrate.