Porous Alumina Films Research Articles

Fabrication of Pt-Nanoparticle-Loaded Mesoporous Alumina Coating through Anodizing of an Al-Pt Alloy

Noble metal nanoparticles, usually dispersed in a mesoporous support, have widespread applications. However, uploading nanoparticles into mesoporous materials and preventing the nanoparticles from aggregation during the fabrication and application processes remain major challenges. Herein, we report a novel, simple and low-cost method for fabrication of Pt-nanoparticle-loaded mesoporous alumina coating through anodizing of an Al-Pt alloy (98.5 at% Al and 1.5 at% Pt) prepared by magnetron sputtering. It was found that the Al-Pt alloy could be effectively anodized at voltages between 2.8 and 4.5 V (SCE), in 0.4 M sulfuric acid solution, at room temperature. The anodizing processes resulted in Pt-nanoparticles of 5∼50 nm dimensions uniformly-dispersed in the porous anodic alumina film. The proposed method can be implemented on a large scale and extended to other alloy systems consisting of a valve metal and different alloying elements with Gibbs free energy of oxide formation less negative than that of the valve metal.

Fabrication of an artificial ionic gate inspired by mercury-resistant bacteria for simple and sensitive detection of mercury ion

Bioremediation of mercury pollution by mercury-resistant bacteria requires the key steps of mercury ions (Hg2+) capture and transportation. Inspired by the functions of mercury transporters in mercury-resistant bacteria, we have fabricated an artificial ionic gate, which may further behave as an Hg2+ biosensor. The gate is constructed by using the asymmetrically modified porous anodic alumina (PAA) film capable of forming Hg2+-activated complexes to control ionic current, while the gate works due to the changes between graphene oxide (GO) and different DNA structures. Specifically, single strand poly(T)n DNA on PAA film may transform into duplex structure through T-Hg2+-T coordination chemistry when Hg2+ exists. Compared with the ring by ring delivery via S-Hg intermediates in bacteria, this artificial gate may show better flexibility for Hg2+ transport, because the poly(T)n-Hg2+ complex can be wrapped in a chain structure with controllable DNA length. Furthermore, with the advantages of simple structure, convenient operation and good practicality, the constructed artificial Hg2+-activated ionic gate has been developed as a biosensor for sensitive detection of Hg2+, with the limit of detection (LOD) down to 0.07 fM. The fabricated ionic gate may be used for building an instrument that can absorb and detect Hg2+ from wastewater in the future.

High-speed galvanostatic anodizing without oxide burning using a nanodimpled aluminum surface for nanoporous alumina fabrication

Rapid formation of a porous alumina film without oxide burning was achieved by anodizing in etidronic acid at large current densities using a nanodimpled aluminum surface. After the electropolished aluminum specimens were galvanostatically anodized in a 0.3 M etidronic acid solution at 293 K, a uniform porous alumina film without oxide burning was formed at relatively low current densities of up to 20 Am−2. After the first anodizing process, an array of dimples was fabricated on the aluminum surface by oxide film removal in a chromic acid/phosphoric acid solution. After the nanostructured aluminum specimen was galvanostatically anodized once again under the same conditions, the possible applied current density without burning increased with the size of the nanodimples, and the current density during the high-speed anodizing process of the dimpled aluminum specimen increased by five times. Many pores grew on the whole surface of the aluminum dimples from the initial anodizing stage; then, pores that grew from the bottom of the dimples survived the anodizing process, and a clear porous alumina film was formed as the voltage reached the maximum value.

Fast growth of highly ordered porous alumina films based on closed bipolar electrochemistry

Highly ordered porous anodic alumina (PAA) is widely used as a template for preparing one-dimensional nanostructured materials. At present, research efforts to prepare PAA templates with straight channels mainly focus on improving their regularity or increasing the efficiency of the preparation methods. Herein, we introduce a novel anodization method to fabricate highly ordered PAA films based on closed bipolar electrochemistry. To the best of our knowledge, there have been no reports of the use of closed bipolar electrochemistry in PAA film fabrication. Compared to traditional anodization, a faster PAA film growth rate of 1.67 μm min−1 was obtained in 0.75 M oxalic acid when a voltage of 62 V was applied to the driving electrodes. Furthermore, different electrolyte solutions can be employed in the anodic and cathodic cells in the closed bipolar electrochemical system. In addition, no direct electrical connection to the aluminum sheets is required in this approach.

Effect of Nanoconfinement on the Kinetics of Phase Transitions in Organic Ferroelectric DIPAI

Linear and nonlinear dielectric properties of new organic ferroelectric diisopropylammonia iodide (DIPAI) introduced into porous aluminum oxide films have been studied in comparison with the properties of a bulk DIPAI. In DIPAI, in pores 300 and 60 nm in diameter, it has been found that the ferroelectric phase forms on heating and on cooling in the temperature range between two structural phase transitions above room temperature. No marked temperature hysteresis is observed for both the phase transitions. The boundaries of the intermediate polar phase in the nanostructured DIPAI is shown to shift to lower temperatures as the pore size decreases. For the bulk DIPAI, two structural transitions are observed on heating with the formation of an intermediate polar phase and only one transition below which the ferroelectricity forms is observed on cooling. This transition temperature is significantly lower than the corresponding temperature on heating. It is assumed that the observed differences of the phase transition in DIPAI in pores and in the bulk DIPAI are related to an acceleration of the kinetics of the phase transitions in the nanoconfinement conditions.

Aluminum ASA 6061 Anodizing Process by Chromic Acid Using Box–Wilson Central Composite Design: Optimization and Corrosion Tendency

The behavior of anodic porous alumina film formed on an aluminum surface by anodizing in chromic acid solutions was optimized using Box–Wilson experimental design. The film thickness was correlated as a function of temperature, acid concentration, applied voltage, and time. A mathematical model was suggested and optimized. Results of coating thickness indicate that both temperature and time play an important role in the anodizing process. The interaction effect of variables on the film thickness is less pronounced compared with the effect of the main variables. Optimum film thickness obtained during the anodizing process was 10.43 µm at the optimum value of temperature (45 °C) and time (68 min). The polarization measurement of anodized aluminum ASA 6061 in chromic acid shows a high corrosion resistance in the presence of coating. The results confirmed by using surface morphology investigations.

Energetic Films Realized by Encapsulating Copper Azide in Silicon-based Carbon Nanotube Arrays with Higher Electrostatic Safety.

Since copper azide (Cu(N3)2) has high electrostatic sensitivity and is difficult to be practically applied, silicon-based Cu(N3)2@carbon nanotubes (CNTs) composite energetic films with higher electrostatic safety were fabricated, which can be compatible with micro-electro mechanical systems (MEMS). First, a silicon-based porous alumina film was prepared by a modified two-step anodic oxidation method. Next, CNTs were grown in pores of the silicon-based porous alumina film by chemical vapor deposition. Then, copper nanoparticles were deposited in CNTs by electrochemical deposition and oxidized to Cu(N3)2 by gaseous hydrogen azide. The morphology and composition of the prepared silicon-based Cu(N3)2@CNTs energetic films were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The electrostatic sensitivity of the composite energetic film was tested by the Bruceton method. The thermal decomposition kinetics of the composite energetic films were studied by differential scanning calorimetry (DSC). The results show that the exothermic peak of the silicon-based Cu(N3)2@CNTs composite energetic film is at the temperature of 210.95 °C, its electrostatic sensitivity is significantly less than that of Cu(N3)2 and its 50% ignition energy is about 4.0 mJ. The energetic film shows good electric explosion characteristics and is successfully ignited by laser.

Characterization of Bulk Nanobubbles Formed by Using a Porous Alumina Film with Ordered Nanopores.

Nanobubbles (NBs), with their unique physicochemical properties and promising applications, have become an important research topic. Generation of monodispersed bulk NBs with specified gas content remains a challenge. We developed a simple method for generating bulk NBs, using porous alumina films with ordered straight nanoscaled holes. Different techniques, such as nanoparticle tracking analysis (NTA), atomic force microscopy (AFM), and infrared absorption spectroscopy (IRAS), are used to confirm NB formation. The NTA data demonstrate that the minimum size of the NBs formed is less than 100 nm, which is comparable to the diameter of nanoholes in the porous alumina film. By generating NBs with different gases, including CO2, O2, N2, Ar, and He, we discovered that the minimum size of NBs negatively correlated with the solubility of encapsulated gases in water. Due to the monodispersed size of NBs generated from the highly ordered porous alumina, we determined that NB size is distributed discretely with a uniform increment factor of [Formula: see text]. To explain the observed characteristic size distribution of NBs, we propose a simple model in which two NBs of the same size are assumed to preferentially coalesce. This characteristic bubble size distribution is useful for elucidating the basic characteristics of nanobubbles, such as the long-term stability of NBs. This distribution can also be used to develop new applications of NBs, for example, nanoscaled reaction fields through bubble coalescence.

On the Prediction of Well-Ordered Porous Anodic Alumina Films

Porous hexagonal ordered anodic alumina (PAOX) is a long-known porous oxide material. Despite its straightforward experimental approach, a precise understanding of the microscopic processes that le...

(Invited) Highly Durable Platelet-Type Carbon Nanofibers for Oer in Alkaline Electrolyte

Porous anodic alumina films formed by anodizing of aluminum in acid electrolytes have a highly ordered, nanopore channels, which have attracted increased attention as template for various nanomaterials. Utilizing this template, platelet-type carbon nanofibers (pCNFs) have been successfully prepared by simply heating a mixture of the template and polymer powders, such as polyvinyl chloride and polyvinyl alcohol, in argon atmosphere via liquefied intermediate of the polymers (1, 2). The graphitization degree of pCNFs increases with annealing temperature, and interestingly, the neighboring reactive carbon edge sites at the sidewall of pCNFs form loops of several carbon layers at above 2000ºC. Here, we demonstrate that such pCNFs with high graphitization degree and loop structure exhibit extremely high oxidation resistance under oxygen evolution reaction (OER) conditions in highly alkaline electrolyte for a zinc-air secondary battery application.During galvanostatic OER on the state-of-the-art highly active Ca2FeCoO5 electrode with a conventional carbon black conductive agent in 4 mol dm-3 KOH electrolyte consumed the carbon black almost completely within a few days, whereas that with pCNFs annealed at 2400ºC exhibited almost no consumption of the pCNFs even after one month. The carbon nanofibers with platelet structure and high graphitization degree are promising for the air electrode materials in a zinc-air battery. Acknowledgment This work was supported in part by the RISING2 (Research and Development Initiative for Science Innovation of New Generation Batteries 2) of the New Energy and Industrial Technology Development Organization (NEDO), Japan. 1. H. Konno, S. Sato, H. Habazaki and M. Inagaki, Carbon, 42, 2756 (2004).2. H. Habazaki, M. Kiriu, M. Hayashi and H. Konno, Mater. Chem. Phys., 105, 367 (2007).

Ultra-fast fabrication of porous alumina film with excellent wear and corrosion resistance via hard anodizing in etidronic acid

This paper describes a fast-fabrication strategy for hard-anodized film prepared on 6063T5 aluminum alloy in environmentally friendly etidronic acid (HEDP). The mild HEDP anodizing was first investigated at a temperature range of 15–45 °C, just under the burning current densities. The voltage curves and microstructures of the anodized film prepared in HEDP (Eti-film) indicate that 35 °C is the most appropriate temperature for the fast fabrication of Eti-film, in contrast to the micro-arc oxidation (MAO) coating and the seriously surface-corroded Eti-film prepared at 15 and 45 °C, respectively. Then, the HEDP hard anodizing without burning was successfully conducted via a gradient-increase-current approach, resulting in a high growth rate (~ 2.1 μm/min), low porosity (< 10%), thick barrier layer (~510 nm) and branched nanoholes structure of the hard anodized Eti-film. The Eti-films were systematically investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and a nanoindentation tester. In addition, the wear and corrosion resistance of the Eti-film and the hard sulfuric acid anodized film (Sul-film) were compared. The results indicate that the hardness of the Eti-film can reach ~ 11 GPa (~ 1000 HV0.01). The better wear resistance of the Eti-film as compared to the currently widely used Sul-film is attributed to the low porosity and less hydrated alumina content of the Eti-film. Moreover, the corrosion resistance of the Eti-film has been found to be 10 times higher than that of the Sul-film. In general, our results suggest a possibility of replacing the pollution-carrying anodizing methods currently used in the industry with the etidronic acid anodizing.

Hydrothermal treatment of metallic-monolith catalyst support with self-growing porous anodic-alumina film

Metallic-monolith catalyst support with self-growing porous anodic alumina (PAA) film was prepared by anodizing Al plate. The effect of hydrothermal treatment (HTT) on the crystalline state and textural properties of PAA film was investigated by XRD, BET, SEM and TG. The HTT treatment above 50 °C and the subsequent calcination above 300 °C could convert the amorphous skeleton alumina into γ-alumina and increase the specific surface area ( S BET ). However, SEM images showed the HTT modification was a non-uniform process along the thickness of PAA film. The promotion effect of HTT on S BET was non-linear, and the slope of S BET gradually decreased with the HTT temperature or time increased. The limited HTT effect should be attributed to a changed pore structure caused by an unfavorable pore sealing limitation. Pore widening treatment (PWT) before HTT could break the pore sealing limitation, because of the reduced internal diffusion resistance of hydrothermal reaction. The synergistic combination of PWT and HTT developed a PAA support with a large S BET comparable to commercial γ-alumina. In the catalytic combustion of toluene, the Pt-based catalyst prepared by using the PWT and HTT co-modified PAA support gave higher Pt dispersion and more favorable catalytic activity than that treated by HTT alone. The presence of a bimodal pore structure was suggested to be a decisive reason.

Initial Structural Changes of Porous Alumina Film via High-Resolution Microscopy Observations

The initial growth of a porous alumina film with a large-scale cell structure formed by galvanostatic anodizing in etidronic acid was investigated in detail by high-resolution microscopy. High-purity aluminum plates were galvanostatically anodized in etidronic acid at 2.5–20.0 Am−2. The formation of an anodic oxide and the subsequent instability of the outer oxide simultaneously occurred at the early stage of the linear voltage increase during the anodizing process. Accordingly, a wavy interface boundary between the aluminum oxide that contained incorporated anions and the nearly pure aluminum oxide formed in the anodic oxide. The surviving pores grew as the thickness of the oxide film increased, and a clear porous alumina film with a pore at the center of each cell formed until the voltage reached its maximum value. Finally, steady-state growth of the porous alumina film occurred at the plateau voltage region after a slight voltage decrease. Eggplant-like anion distributions were measured at the head of the pores due to the viscous flow of the anodic oxide. The nanomorphology of the porous alumina film strongly depended on the current density due to the difference in the degree of oxide formation and localized oxide dissolution.

Depth dependent X-ray diffraction of porous anodic alumina films filled with cubic YAlO3:Tb3+ matrix

The presented paper deals with the measurement methodologies of the structural properties of porous anodic alumina (PAA) films filled with YAlO3:Tb3+ composite using X-ray diffraction, atomic force microscopy and scanning electron microscopy. It shows that the deposited material does not uniformly fill the porous volume of the anodic alumina film and the part of it forms a thick layer on the PAA surface. The aim of this work is to show the differences in the XRD response obtained at different angles of incidence of the excitation beam for the PAA/YAlO3:Tb3+ system. Furthermore, this simple approach enables separation of the signal from both regions on the surface and inside the PAA pores, providing more accurate data interpretation. It reveals that the crystallization of the material on the PAA surface and within the pores is different.

Влияние наноконфайнмента на кинетику фазовых переходов в органическом сегнетоэлектрике DIPAI

The results of studying the linear and nonlinear dielectric properties of a new organic ferroelectric diisopropylammonium iodide (DIPAI), embedded in porous alumina films, in comparison with bulk DIPAI, are presented. It was found, for DIPAI in pores 300 and 60 nm in diameter the ferroelectric phase is formed in the heating and cooling modes in the temperature interval between two structural phase transitions above room temperature. No noticeable temperature hysteresis was observed for both phase transitions. It was shown that the boundaries of the intermediate polar phase for nanostructured DIPAI shift to low temperatures with decreasing pore size. For bulk DIPAI, two structural transitions were revealed during heating with the formation of an intermediate polar phase and only one transition during cooling, below which ferroelectricity occurred. The temperature of this transition was much lower than the corresponding temperature during heating. It is assumed that the observed differences in phase transitions for DIPAI in pores and bulk DIPAI are associated with acceleration of the phase transitions kinetics under conditions of nanoconfinement.

The growth and unique electronic properties of the porous-alumina-assisted hafnium-oxide nanostructured films

Hafnium-oxide nanostructures of controlled composition and properties are in demand for modern electronic and optical engineering. Here hafnium-oxide nanostructured films are synthesized on substrates via the anodizing/re-anodizing of a thin Hf layer through a porous anodic alumina (PAA) film at 150/400 V in 0.2 m H3PO4 electrolyte and examined by SEM, EIS, and Mott-Schottky analysis. The films are composed of HfOx nanorods, which grow in the pores, anchored to a continuous HfO2 bottom layer by tiny HfOx nanoroots penetrating the alumina barrier layer. The understanding of film nucleation and growth is advanced through disclosing the hidden features and field-assisted modifications of the metal-oxide interfaces, such as O2-filled nanosized voids and individual hafnium-oxide nanoroots dominating within the alumina barrier layer and securing electron transport to each nanorod. The films reveal a unique combination of electrical properties, such that the bottom oxide behaves like an ideal dielectric whereas the roots and rods show semiconducting behavior. A 600 °C annealing at atmospheric pressure surprisingly leaves the rods and roots semiconducting and still amorphous while the annealing at 10−5 Pa transforms the entire film to a nanocrystallite-containing n-type semiconductor, of a high doping density of up to 2 1021 cm−3. Further anodic polarization of the PAA-free vacuum-annealed film generates dielectric anodic oxide over the film, of thickness proportional to applied potential until the thinner roots and finally the dominating root become fully blocked for electron conduction. Potential applications include high-k dielectrics for high-voltage electrolytic capacitors, semiconducting active layers for gas sensing, or photoanodes for photoelectrochemical water splitting.

High temperature oxidation behavior of low temperature aluminized Mirrax® ESR steel

The aim of this study was to investigate the effect of aluminizing process on the oxidation resistance of mirrax steel. The oxidation behavior of pack cemented aluminizing coatings on Mirrax ESR Steel was investigated at 1000 °C for 5, 25 and 70 h. Low temperature aluminizing process was carried out at 700 °C for 2, 4 and 6 h by pack cementation method. The microstructures, surface morphologies and phase distribution of both coatings before and after oxidation were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and x-ray diffractometry (XRD). Analysis of the coating layer showed that the coating was homogeneous, non-porous and had a good bond at the interface of the coating-matrix. Coating layer was mainly composed of aluminum-rich Fe2Al5 phase. Depending on the increased process time, the coating thickness varied approximately from 17 to 58 microns. The aluminizing process could greatly improve the oxidation resistance of the substrate. Al diffused outward to form multi-layer oxide films, which prevented the diffusion of oxygen. A sticky, protective, non porous alumina film layer was obtained successfully. The results show that oxidation resistance increased with the increased aluminizing time.

Structural Characterization of Anodic Porous Alumina Formed By Galvanostatic Anodizing in Etidronic Acid

Anodizing aluminum in etidronic acid (1-hydroxyethane-1,1-diphosphonic acid) causes the formation of porous alumina at higher voltage more than 200 V. Highly ordered porous alumina with a large-scale cell can be easily fabricated via two-step constant voltage anodizing in etidronic acid. However, extremely little has been reported on the growth behavior during galvanostatic anodizing in etidronic acid and its structural characterization. In the present investigation, we demonstrate the details of the anodizing behaviors and nanostructures of the porous alumina formed via galvanostatic anodizing in etidronic acid under various operating conditions. High-purity aluminum plates were electrochemically polished, and then were anodized at a constant current density of 0.005-500 Am-2 in 0.03-3 M etidronic acid solutions (273-333 K). After anodizing, the specimens were immersed in a 0.20 M CrO3/0.51 M H3PO4 solution (353 K) to dissolve the porous alumina, and the aluminum dimple array was exposed to the surface. The surface and cross-section of 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. As the electropolished aluminum specimens were anodized galvanostatically under various conditions, the voltage linearly increased, gradually decreased, and then reached plateau value (U p). However, excess current density led to a burning phenomenon and the formation of non-uniform porous alumina. Figure 1 shows the changes in the plateau voltage, U p, and the current density, i a, during anodizing in a 0.3 M etidronic acid solution. The plateau voltage greatly increased with the current density at each temperature, and various porous alumina films were successfully fabricated by anodizing at a wide voltage range measuring 7-218 V. Figure 2 shows the relationship between the cell size, D c and the anodizing voltage, U a. The cell size linearly increased with the anodizing voltage at each solution temperature and current density. A linear proportional constant of 2.5 nmV-1 was obtained, which is similar to the self-ordering condition via constant voltage anodizing. Figure 1

Alkaline Corrosion-Resistant Anodic Aluminum Oxide Formed By Etidronic Acid Anodizing

A newly discovered electrolyte for anodizing aluminum, etidronic acid (CH3C(OH)[PO(OH)2]2), operates at high voltages of more than 200 V, and ordered porous alumina measuring 400-670 nm in cell diameter (interpore distance) can be fabricated via constant voltage anodizing. Because such porous alumina film formed at high voltages possesses a thick barrier layer, etidronic acid anodizing may be useful for corrosion protection of aluminum. Here, we describe the alkaline corrosion-resistant porous alumina formed by high voltage anodizing in an etidronic acid solution, and its hydration behavior in boiling water was investigated. Highly pure aluminum plates (99.999 wt%) were anodized in 0.3 M sulfuric acid, 0.3 M oxalic acid, 0.3 M citric acid, and 0.3 M etidronic acid solutions (293 K) at a constant current density of 30 Am-2 or a constant voltage of 250 V. The anodized specimens were immersed in a 2.5 M NaOH solution (293 K). The nanostructural changes were examined by electrochemical impedance spectroscopy (EIS). The anodized specimens were immersed in boiling water to seal the pores in the porous alumina film. The surface and cross-section of the specimens were characterized by field-emission scanning electron microscopy (FE-SEM) The plateau voltages during anodizing aluminum at a constant current density of 30 Am-2 in sulfuric and etidronic acid solutions exhibited approximately 16 V and 197 V, respectively. As the specimen anodized in sulfuric acid was immersed in a 2.5 M sodium hydroxide solution, H2 gas evolution was observed from the surface at the beginning of immersion, and the amount increased with the immersion time. In contrast, the specimen anodized in etidronic acid did not result in hydrogen gas evolution during immersion until 8 min. Here, the capacitance (Cb ) is inversely proportional to the thickness of the barrier layer. Figure 1 shows the changes in the reciprocal Cb with the immersion time, ti . Complete dissolution of porous alumina formed in etidronic acid takes 15 times longer than dissolution of the alumina formed by sulfuric acid anodizing due to the formation of a thick barrier layer. As the porous alumina formed by etidronic acid anodizing is immersed in boiling water, plate-like hydroxides were formed at the bottom of the pores in the initial immersion stage. The thickness of the hydroxide layer increased with the immersion time, and the nanopores are completely sealed by long-term immersion. Figure 1

Formation of Porous Alumina Film By Indirect Oxidation Under AC Electric Field

In recent years, there has been renewed interest in bipolar electrochemistry, which deals with reactions occurring on unconnected conductive objects placed between outer electrodes, due to its potential applications in various fields ranging from sensing to the fabrication of functional materials. In most of the studies regarding bipolar electrochemistry, a direct current (DC) electric field is applied between the driving electrodes, and an inhomogeneous reaction field on the bipolar electrode is used. Based on the polarization of both sides of a bipolar electrode under a DC electric field, the electrochemical redox reactions on each part of a bipolar electrode can be controlled. In our previous study, we investigated the application of an alternating current (AC) electric field for surface coating of aluminum and successfully formed porous alumina films on unconnected aluminum by indirect oxidation under an AC electric field without a direct electrical connection (“AC-bipolar anodization”) 1, 2). A common strategy applied in bipolar anodization is to use the interfacial potential differences between the driving electrodes under a DC electric field, resulting in the asymmetrical formation of oxide films (e.g., gradients in the thickness of the porous layer and pore diameter) on a metal substrate used as a bipolar electrode. On the other hand, we focused on bipolar anodization under an AC electric field as uniform surface treatment for aluminum. With the above background, we continued our preliminary work and tried to fabricate Pt/alumina composite on an unconnected aluminum substrate using one-pot electrochemical synthesis in a single electrolyte 3). This synthetic approach overcomes the drawbacks of conventional methods in terms of the operation efficiency and will lead to the development of various functional composites using one-pot synthesis. In terms of basic research, potential applications of our developed method will be also discussed. H. Asoh, M. Ishino, H. Hashimoto, RSC Adv., 6, 90318 (2016).H. Asoh, M. Ishino, H. Hashimoto, J. Electrochem. Soc., 165, C295 (2018).H. Asoh, S. Miura, H. Hashimoto, ACS Appl . Nano Mater., in press (2019).