Aluminum Anode Research Articles

Blue photoluminescence from active carboxyl adatoms on nanoporous anodic alumina films

Nanoporous anodic alumina (nPAA) films formed on aluminum in lower aliphatic carboxylic acids exhibit blue self-coloring and characteristic properties such as photoluminescence (PL), electroluminescence, and electron spin resonance. The blue colors are seemingly originated from the adsorbed radicals incorporating into the oxide during the aluminum anodization. However, there is lack of reports revealing the detailed activation mechanism of the adatoms in the complexes. This study investigates the blue PL and its correlation with the atomic and electronic structures of the active aluminum surface using multiple theoretical and experimental methods. The results show that the concentration of carboxylates at the nPAA surface is highly correlated with the blue colorization and manifest that unpaired electrons in carbon (derived from the carboxylates) bridging two aluminum atoms at surface can play as an active source of the blue colorization. Therefore, it is suggested that controlling the adsorption of the carboxylate on the alumina membrane having large surface-to-volume ratio can be an efficient way to generate the blue light for the optoelectronic applications.

Harnessing 3D Porous Cobalt Oxide Nanoflakes Grown on Metal for Exceptional Adhesion between Aluminum Surfaces and the Epoxy Matrix

The developments in the automotive and aerospace sectors require alternative structures to metals for diverse applications; therefore, lightweight polymer–metal hybrid composites with outstanding mechanical characteristics are synthesized. Herein, the modern nanoperfusion technology, which involves the in situ growth of 3D porous cobalt oxide nanoflakes (Co3O4 NFs) on the porous aluminum surface, is used. A rough surface with corresponding surface porosities of 21, 48.1, and 49.8% can be produced by anodization of aluminum at 8, 10, and 12 V, respectively. The samples anodized at 10 V are selected as a structure for the growth of 3D Co3O4 NFs at different hydrothermal temperatures (90, 120, and 160 °C). The bond strength and modulus of the toughness of the sample combining aluminum and 3D Co3O4 NF growth at 120 °C exhibit a substantial bonding strength, reaching a value of 14.27 MPa and 3.56 kJ m−3, respectively. The porous nature of the manufactured cobalt oxide nanoflakes allows the epoxy to penetrate, which enhances the bonding strength and thus improves the mechanical properties of the manufactured joints.

Diazo Red B Dye Removal by Electrocoagulation Method using Aluminum Electrode

The removal of diazo red B dye was studied in water using the electrocoagulation method with an aluminum electrode. The study aimed to reduce the presence of harmful diazo red B dyes in the environment and their impact on living organisms. This study was conducted by testing various parameters with specified values. The initial dye concentrations were set at 10, 20, 30, 40, and 50 mg/L, while the electrocoagulation times were varied at 30, 60, 90, 120, 150, and 180 minutes. The initial pH levels were adjusted to 5, 6, 7, and 8. The applied voltages were 2.5, 5, 7.5, 12.5 V, and the distances between electrodes varied at 1, 1.25, 1.5, 1.75, and 2 cm. The study also examined the effects of initial dye concentration on electrocoagulation time, its interaction with pH, and the influence of pH on electrocoagulation time. These parameters aim to determine the optimum conditions for diazo red B removal, as measured by a UV-Vis spectrophotometer at a wavelength of 420 nm. The optimum removal efficiency of diazo red B was achieved with 94.32% for an initial dye concentration of 30 mg/L, 94.13% for an electrocoagulation time of 180 minutes, 96.00% at a pH of 6, 95.32% for a voltage of 7.5 V, and 95,75% for an electrode distance of 1.5 cm. Additionally, the efficiencies were 99.5% for concentration relative to time was 99.5%, for concentration relative to pH was 97.85%, and for pH relative to time was 96.00%. Additionally, the coagulant analysis of the electrocoagulation results was carried out using FTIR and morphological analysis of the surface of the damaged aluminum anode using an optical microscope.

Addressing of Aluminum Anode Based Battery Challenges: Electrochemical Effect of Zn-Mn Electrodeposition

Aluminum (Al) has emerged to become one of the potential anode materials candidates in metal-based batteries due to its abundant resource, inexpensive cost, good safeness and high theoretical energy density. However, thoughtful challenges have been barrier towards huge progress, including easy aluminum hydroxide formation, low practical voltage, and high corrosion rate. To approach those problems, this article proposes to enhance the electrochemical performance of anode side through electrodeposition of Zn-Mn on aluminum surface. The deposition of Zn-Mn consists of citrate and ethylenediaminetetraacetic acid (EDTA) as complexing agent to control the process rate. The effect of various deposition time, 0, 10, and 30 minutes, will be investigated by linear polarization, linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy measurements. The electrochemical measurement exhibits the deposition effect, minimized the impedance of Al surface and improved the electrochemical reactions. Moreover, the appearance of Zn-Mn layer has prolonged the discharge performance with battery analyzer measurements. Therefore, energy density increased from 1270.52 to 3327.68 mWh g-1Al and the specific capacity enhances from 2779.908 to 7291.651 mAh g-1. All the measurements applied 3.5% sodium chloride (NaCl). These results pose the electrical performance enhancement from the anode side, but the development of other sides is also necessary.

Study on the Performance of Aqueous Aluminum‐Ion Battery with Al[TFSI]3 Electrolyte

Aqueous aluminum‐ion batteries have higher energy density and lower cost than traditional rechargeable batteries. Electrolytes play a vital role in aqueous aluminum‐ion battery and are directly related to battery performance. However, ionic liquid electrolytes suitable for aluminum are expensive and have potential environmental problems. To improve the energy density and reduce the environmental impact, this study innovatively proposes a new aqueous electrolyte. In this article, a battery preparation and performance testing bench is built to prepare a new aqueous aluminum‐ion battery. A novel aqueous aluminum‐ion battery is proposed using α‐MnO2 as the positive electrode, eutectic mixture‐coated aluminum anode (UTAl) as the negative electrode, and aluminum bistrifluoromethanesulfonate (Al[TFSI]3) aqueous solution as the electrolyte. The electrochemical performance of the prepared aqueous aluminum‐ion battery is studied under multiple working conditions. The results show that the assembled UTAl/Al[TFSI]3/α‐MnO2 battery exhibits an ultrahigh first‐cycle specific energy of up to 420 mAh g−1 at room temperature and a current density of 50 mA g−1 for 5 mol L−1 Al[TFSI]3. The newly developed battery can achieve a capacity retention rate of 63.4%, a Coulombic efficiency of over 94%, and a stable charge and discharge voltage platform of 1.65 and 1.4 V.

Synthesis of Porous Anodic Alumina Featuring a Periodic Pore Structure by Regulating the Anode Temperature

Abstract Porous anodic alumina (PAA) with a periodic pore structure has been synthesized by using an innovative preparation method. The morphology of PAA pores can be modulated within the same electrolyte by adjusting the temperature of the aluminum anode, enabling periodic variations in pore size (Dp). The formation mechanism of PAA has been elucidated through analyses of micromorphology, anodization current density (ia), interpore distance (Dint), and Dp of the samples. Results indicate that the average Dint for the synthesized PAA is approximately 260–340 nm, while the average Dp ranges from 90 to 260 nm. Both ia and Dp exhibit periodic fluctuations corresponding to changes in anode temperature under consistent electrolyte conditions and anodization voltage (Ua). Lateral pores are generated via a phosphoric acid etching process, resulting in PAA with a distinctive three-dimensional interconnected pore architecture. Furthermore, ridges with an arc-like shape on the outer walls of PAA pores have been observed; their formation mechanism can be effectively explained by the convection model and the viscous flow model. These findings contribute significantly to achieving precise control over the pore structure of PAA.

Removal of microplastics by electrocoagulation

With the gradual increase of microplastics in water bodies, it is essential to understand the current treatment processes for their removal. This study aims to investigate the removal of microplastics in synthetic solution by electrocoagulation (EC). The effects of electrode type, contact time (min), agitation speed (rpm) and current density (A/m²) were evaluated using a fractional factorial design. The results showed that the aluminum anode achieved a higher removal of microplastics than the iron anode, reaching 98.04% removal with the aluminum operational configuration within 15 min at 70 rpm and a current density of 20 A/m². A high correlation between the predicted and observed removal was evidenced, with values of R²= 0.99 and adjusted R²= 0.98, indicating a good agreement between the model and the experimental data, confirming the validity and feasibility of the adopted linear model. This study demonstrates that the electrocoagulation process has a great potential for the removal of microplastics.

Synthesis of Silicon in the Interaction of Aluminum With a Quasi-Neutron and Estimation of the Contribution of the Aluminum Hydride Complex

Among the nuclear fusion reactions of new elements, the simplest reaction refers to the capture of a proton p by the nucleus of the original element ZXA with the formation of the Z + 1YA+1 nucleus (Z and A are the charge and mass number of the element X). In the case of cold fusion, the occurrence of such a reaction is associated with the existence of quasi-neutron (p + e) states in which the proton is “escorted” by the electron e: ZXA + (p + e) ! Z + 1YA+1 + e. For example the synthesis of zinc from copper was established. It is important to note that the ratios of the proportions of synthesized isotopes in most cases should differ significantly from natural ratios, which would certainly confirm their artificial origin. The data of preliminary mass spectrometric measurements for the synthesis of zinc from copper, gallium from zinc, and rhenium from tungsten are consistent with this conclusion. However, for relatively heavy elements, the masses of daughter atoms with Z + 1YA+1 nuclei are difficult to distinguish from the masses of hydride complexes of parent atoms with ZXA nuclei and hydrogen atoms H formed in the course of mass spectrometric measurements. In this regard, the problem of estimating the contributions of daughter atoms and hydride complexes is topical. The solution of this problem was carried out for the case of silicon synthesis from aluminum. In an air environment with water vapor, an electric arc was ignited between an aluminum anode and a tungsten cathode. Aluminum has one stable isotope 13Al27; therefore, the synthesis of only one of the three stable silicon isotopes 14Si28 was expected, which was observed in the mass spectrum of the powder formed on the anode surface (peak at ⇡ 27.977 a.m.u.). The AlH complex corresponds to a peak at ⇡ 27.989 a.m.u. This peak has a height approximately 2.5 times less than the height of the peak for the mass distribution of silicon atoms. Thus, the relatively low intensity for the mass distribution of the AlH complex suggests that it is the isotope ratios of the synthesized daughter nuclei that make the main contributions to the observed isotope mass ratios in the cases of parent atoms having several stable isotopes.

Anodization of Aluminum in a Sodium Hydroxide Solution: Effect of pH on Chemical Dissolution

The chemical dissolution of anodic alumina film was investigated using the re-anodization technique. The formation of thick oxide films in an alkaline electrolyte is thought to be difficult to achieve due to the high pH value and high solubility of anodic alumina. The dissolution rate of anodic film was found to be strongly affected by the pH of the solution used for chemical dissolution; the film dissolved significantly faster in a sodium hydroxide solution having a high pH of 13.11 than in acidic solutions commonly used for anodization, such as sulfuric acid (pH 0.98) and phosphoric acid (pH 1.54). Nevertheless, the addition of glycerol to the sodium hydroxide solution effectively suppressed the chemical dissolution of the anodic film. The change in solubility of the anodic alumina film in solution was greatly affected by the change in the dissociation of the solute in solution. The results demonstrated that oxide films more than 10 μm thick were produced in an alkaline electrolyte by adding glycerol to the solution. The suppression of the chemical dissolution of alumina by the addition of alcohol has thus been shown to occur not only in acid solutions but also in alkaline solutions.

Thermochemical effects in hydrogen production with a dissolvable aluminum anode system

This study presents the results of experimental determination and theoretical calculations of the thermal effect of aluminum dissolution in alkaline solutions accompanied by hydrogen evolution. The experiments were conducted using an EK1 calorimeter, with temperature measurements recorded every 10 seconds. Potassium hydroxide solutions with concentrations ranging from 0.5 to 5 mol/L were utilized. It was demonstrated that the temperature variation curves over time, the temperature dynamics at different solution concentrations, and the aluminum dissolution rate exhibit an S-shaped profile. The rate of aluminum dissolution in aqueous alkaline solutions depends on the KOH concentration. As the KOH concentration increases from 0.5 to 2 mol/L, the thermal effect of the reaction rises. Further increasing the alkali concentration to 5 mol/L results in almost no change in the thermal effect. The thermal effect of aluminum dissolution in 3–5 mol/L sodium hydroxide solutions was found to be 1300 J/g. The experimentally determined thermal effect falls within the range of values calculated from thermodynamic data (from 1165 to 1528 J/g). The results obtained in this study can be applied to the development of relatively low-cost hydrogen production technologies.

Effect of Electrode Configuration on Bipolar Anodization of Aluminum

Anodization of aluminum is a surface treatment employed to protect or decorate its surface for commercial applications. Although preparation of nanoporous film by conventional anodization is conducted in a simple cell, direct energization to the workpiece in an electrolyte is indispensable. Therefore, conventional anodization is unsuitable for the simultaneous surface treatment of a large number of small specimens. Against this background, we have recently studied bipolar electrochemistry as a surface treatment for aluminum. We have already demonstrated that indirect oxidation without a direct electrical connection (so called bipolar anodization) can be used to form a uniform film on aluminum balls which are difficult to ensure electrical continuity 1,2). In this study, the effect of configuration of aluminum object (bipolar electrode, BPE) and driving electrodes in an open bipolar cell on the film formation on the BPE through bipolar anodization. In AC bipolar anodization, the film thickness increased with increasing charge as in conventional anodization, regardless of whether the driving electrode was arranged horizontally or vertically. However, the thickness of the film formed using vertically arranged driving electrodes was thicker than that of the film formed using horizontally arranged driving electrodes despite the same charge. The difference in film formation efficiency may be due to the change in electric field distribution caused by the configuration of the driving electrodes.

Effect of Charge during Current Recovery on Morphology of Anodic Porous Alumina Film/Substrate Interface

Porous-type anodic oxide film, so-called anodic porous alumina, which is formed by the anodization of aluminum, is a typical self-ordered nanoporous material. It is often called a nanochannel or nanohole structure depending on the dimensions of porous-type anodic oxide film. When the formation voltage is suddenly dropped during anodization, the current gradually recovers after a period of almost no current flow and becomes steady state. In other words, the specimen is re-anodized at the new voltage. This phenomenon is known as the current recovery. The morphology of the pore base (i.e., anodic porous alumina film/substrate interface) is affected by the change in voltage. Using this technique, branched channels with various morphology have formed by lowering the formation voltage suddenly. The tree-like morphology of branched channels can be applied to fabricate unique structures such as Y-junction nanodevices. In this study, we investigated the relationship between the morphology of pore branching in anodic porous alumina and the charge consumed during the current recovery from the point of view of decorativeness. Anodic porous alumina films with a thickness of approximately 10 µm were prepared in sulfuric acid by constant current anodization. After that, the voltage was dropped to a predetermined voltage in the same electrolyte. The degree of pore branching in the anodic film, which depended on the charge during the current recovery, was systematically evaluated by SEM observation of the anodic film/substrate interface after removal of the anodic film.

Fabrication of Uniform Porous Anodic Aluminum Oxide by Anodizing Aluminum in Trisodium Phosphate with Higher pH Values

Anodizing of aluminum is an electrochemical process of surface oxidation to form an alumina layer. Porous anodic aluminum oxide (PAAO) possessing self-organized nanopores can be obtained by anodizing aluminum in several acidic electrolyte solutions, and it has been widely used to develop emerging applications, such as nano-filters and optical devices. Recently, we found that anodizing in several alkaline solutions caused the formation of PAAOs with unique nanostructures such as an extremely high porosity and ultra-flat barrier layer. However, the anodizing process in alkaline solutions with higher pH values produced a slightly non-uniform film due to the active dissolution environment of alumina. Herein, we report the fabrication of uniform PAAO film by anodizing aluminum in alkaline solutions and their unique nanostructures.High-purity aluminum specimens were electropolished in 78 vol% CH3COOH/ 22 vol% - 70% HClO4. The electropolished specimens, then, were anodized in a 0.3 M trisodium phosphate (Na3PO4) solution at 274 K (pH = 13.1) and a constant voltage of 2-100 V. A platinum plate was used as the cathode, and the aluminum specimen was placed parallel to and 22 mm from the platinum plate. We investigated the effect of various operating conditions on the formation of PAAO film. The growth behavior and internal structure of anodized specimens were examined by optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM), and scanning transmission electron microscopy (STEM).Figure 1a shows the OM images of the aluminum specimen anodized in a 0.3 M Na3PO4 solution at 274 K and a constant voltage of 20 V for 60 min with and without stirring the solution. A non-uniform appearance with both weak white and metallic luster areas was obtained on the specimen anodized with stirring, whereas a uniform metallic luster can be observed without stirring. The SEM images of four different surface positions (2 mm intervals) of each anodized specimen are shown in Figure 1b. In the case of the stirring condition, the surface of PAAO on the left was dissolved due to the high pH value of the Na3PO4 solution and higher dissolution rate caused by stirring. On the other hand, a uniform PAAO film possessing similar nanoscale pores was successfully fabricated by suppressing non-uniform dissolution without stirring. The PAAO film grew by anodizing in the Na3PO4 solution at extremely low applied voltages less than 10 V. Figure 1

Galvanic and Local Corrosion of Aluminum Alloy 6061-T6 Coupled to Non-Passivating and Passivating Alloys

Marine and aerospace structures sometimes combine lightweight aluminum alloys with dissimilar metals to optimize mechanical performance and reduce costs. Unfortunately, the exposure of such dissimilar couples in a harsh environment can cause severe corrosion damage to the aluminum structure due to its position in the galvanic series. Corrosion of Aluminum Alloy (AA) 6061-T6 coupled to non-passivating and passivating alloys was studied to elucidate galvanic effects on local corrosion. In this work, local and galvanic corrosion were quantified, the effects of cathode material on local electrolyte pH were explored, and a relationship between pH and local-corrosion of AA6061-T6 was established.Experimental studies quantified local and galvanic corrosion of AA6061-T6 coupled to 316 stainless steel, copper, titanium alloy Ti6Al4V, and 316 stainless steel coated with titanium nitride, chromium nitride, and a sol-gel nano-coating. Galvanic couples were misted with 3.15 wt.% sodium chloride solution and exposed in a controlled temperature-humidity chamber. Galvanic currents were measured during exposure, and the total mass loss of the aluminum alloy was determined to quantify the corrosion damage. Exposure tests showed that galvanic corrosion decreases over time and accounts for less than 15% of the total corrosion of AA6061-T6. Therefore, most aluminum corrosion damage was caused by local corrosion. In addition, immersion experiments of AA6061-T6 galvanic couples in gelled 3.15 wt.% NaCl solutions showed that galvanic coupling influences the evolution of electrolyte pH leading to severe acidification at the aluminum anode surface and alkalization around the cathode. The solution pH at the aluminum surface was decreased by galvanic action and severity of pH decrease depends on galvanic couple materials and design. To quantify the effect of acidity on local corrosion of AA6061-T6, potentiodynamic polarization tests were performed in aerated and deaerated 3.15 wt.% NaCl solution adjusted to different pH values. Anodic dissolution reactions and cathodic oxygen reduction reactions show significantly higher anodic and cathodic currents for more acidic solutions due to the instability of the passive oxide film of aluminum. This film is stable in near-neutral solutions and unstable in highly acidic solutions. As a result, the breakdown of the passive film increases the effective area contributing to anodic or cathodic currents resulting in enhanced local corrosion.The series of experimental results show that galvanic interaction leads to a decrease of pH at the aluminum anode, and therefore increasing local corrosion of the aluminum surface. The increase of local corrosion induced in a galvanic couple depends on the cathode material and underlines the importance of accounting for local corrosion and pH-dependent corrosion kinetics when predicting the galvanic compatibility of aluminum alloys.

Formation of Porous Anodic Aluminum Oxide with a Thick Barrier Layer and High Porosity By Anodizing Aluminum in Sodium Metaborate Solutions

Porous-type anodic aluminum oxide (AAO) can be fabricated by anodizing an aluminum substrate in suitable aqueous electrolyte solutions. The morphological properties of the AAO, including the interpore distance, pore size, and thickness, are controlled by various operating parameters, such as the applied voltage, temperature, and anodizing time. However, their structural controllability is limited because the fabrication process is based on the typical anodizing method in acidic solutions. The authors previously found that AAO with a novel nanostructure can be fabricated by anodizing using alkaline ammonium carbonate and sodium tetraborate. Therefore, further research on aluminum anodizing using various alkaline solutions opens the possibility of novel AAO fabrication. Herein, we report the fabrication of a new AAO film, which is different from the typical nanostructure formed in acidic solutions, by anodizing in alkaline sodium metaborate (NaBO2).Electropolished aluminum specimens were anodized at a constant voltage of 0.1-200 V in a 0.3 M sodium metaborate electrolyte solution (pH = 11.9) at 278 K. The surface and cross-section of the anodized specimens were examined by field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Cs-corrected scanning transmission electron microscopy (STEM). The elemental depth profile of the specimens was analyzed by radiofrequency glow discharge optical emission spectroscopy (rf-GDOES).An AAO film consisting of an outer porous layer and an inner hemispherical cap barrier layer, similar to typical AAO films formed in acidic solutions, was formed at lower voltages below 50 V. In contrast, an AAO film with a flat barrier layer, deviating from the typical Keller-Hunter-Robinson model, was obtained at voltages above 100 V. The porosities of the porous layer obtained above 20 V were almost constant (0.16-0.19). However, there was a significant increase in the porosity at lower voltages (0.93 at 0.1 V). The AAO formed in sodium metaborate was composed of amorphous, anion-free aluminum oxide. Figure 1

(Invited) Mild Anodization of Aluminum: From Fundamentals to Industrial Applications

Considering the recent energy crisis and global environmental pollution, the weight reduction of vehicles through the modification of several parts (e.g., engines and wheels) is emerging as an important research area. One strategy for achieving this is the use of aluminum. Aluminum, a lightweight material with excellent recyclability, is widely used in various industrial fields. There are various surface treatment methods for aluminum, depending on the purpose of use in each operating environment. Corrosion resistance and hardness of native oxides are not enough under some environment.To improve the surface properties of aluminum, anodic oxidation of aluminum (so-called anodizing or anodization), is generally applied. The surface treatment has a history of nearly 100 years. In Japan, anodization using oxalic acid was first patented in 1923. A porous-type oxide film formed on aluminum by anodization, or a product covered with the porous alumina film, is industrially called alumite in Japan. The structure of a porous-type oxide film (alumite) determines the various surface properties of aluminum. For instance, to increase the hardness of anodic films on aluminum, the anodization is industrially carried out at low temperature to avoid chemical dissolution of the formed oxide film during anodization.Here, I present an overview of the progress of anodization in common acidic electrolytes (e.g., sulfuric acid, oxalic acid, or phosphoric acid) containing alcohol as an additive [1-6]. Anodization was mainly conducted using various alcohols with different physical properties under mild anodization conditions with a constant current of 100 A·m−2 at 20 °C. The effects of alcohol addition in electrolytes on the anodization behavior of aluminum, the coating ratio, the porosity, the maximum attainable film thickness, and the hardness of anodic films will be discussed in terms of both basic research and commercial applications. H. Asoh, M. Matsumoto, H. Hashimoto, Surf. Coat. Technol., 378, 124947 (2019).M. Matsumoto, H. Hashimoto, H. Asoh, J. Electrochem. Soc., 167, 041504 (2020).H. Asoh, T. Sano, J. Electrochem. Soc., 168, 103506 (2021).H. Asoh, H. Kadokura, R. Murohashi, M. Matsumoto, J. Electrochem. Soc., 169, 073510 (2022).T. Sano, Y. Wakabayashi, H. Asoh, Surf. Coat. Technol., 459, 129399 (2023).H. Asoh, S. Ota, K. Hagiwara, J. Electrochem. Soc., 171, 033502 (2024).

Fabrication of Mid-Infrared Porous Anodic Alumina Optical Microcavities via Aluminum Anodization.

This study reports the production of mid-infrared (MIR) porous anodic alumina (PAA)-based microcavities with tunable optical quality. The spectral position of the cavity resonance peak (λC), along with its intensity (IR) and Q-factor, varies depending on the geometric positioning of the cavity layer within the multilayer stack of alternating low- and high-porosity layers, as well as the type of cavity produced-either by high voltage (CvH-type) or low voltage (CvL-type) pulses. In most cases, PAA microcavities with CvH-type cavity layers exhibited superior light confinement properties compared to those with CvL-type cavities. Additionally, shifting the cavity layer from the center toward the edges of the multilayer stack enhanced the intensity of the resonance peak. For PAA microcavities with CvH-type cavity layers, the highest intensity (IR = 53%) and the largest Q-factor (Q = 31) were recorded at λC of around 5.1 µm. The anodization approach used in this study demonstrates significant potential for designing PAA-based microcavities with high optical performance in the MIR spectral region, especially with further refinement of electrochemical parameters. These findings pave the way for the development of new photonic materials specifically tailored for the MIR spectral range, broadening their applications in various optoelectronic and sensing technologies.

Orthogonal Nano‐Engineering (ONE): Modulating Nanotopography and Surface Chemistry of Aluminum Oxide for Superior Antibiofouling and Enhanced Chemical Stability

AbstractDecoupling certain material surface properties can be key to attaining critical property‐activity relationships that underpin their antibiofouling performance. Here, orthogonal nano‐engineering (ONE) is employed to decouple the influences of nanotopography and surface chemistry on surface antibiofouling. Nanotopography and surface chemistry are systematically varied with a two‐step process. Controlled nanotopography is obtained by electrochemical anodization of aluminum, which generated anodic aluminum oxide (AAO) surfaces with cylindrical nanopores (diameters: 15, 25, and 100 nm). To modify surface chemistry while preserving nanotopography, an ultrathin (≈5 nm) yet stable zwitterionic coating of poly(divinylbenzene‐4‐vinylpyridyl sulfobetaine) is deposited on these surfaces using initiated chemical vapor deposition (iCVD). Antibiofouling performance is assessed by quantifying 48‐h biomass formed by gram positive and negative bacteria. The ONE surfaces demonstrated enhanced antibiofouling performance, with small‐pore nanotopography and zwitterionic chemistry each lowered biomass accumulation by tested species, with potential additive effects. The most effective chemistry‐topography combination (ZW‐AAO15) enabled an overall reduction of 91% for Escherichia coli, 76% for Staphylococcus epidermidis, 69% for Listeria monocytogenes, and 67% for Staphylococcus aureus, relative to the uncoated nanosmooth control. Additionally, the composite ZW coating exhibited encouraging anticorrosion properties under both static and turbulent cleaning conditions, vital to antibiofouling applications in healthcare and food industries.

Electrokinetics-Driven Anodic Oxide Pore Formation: Linear and Weakly Nonlinear Analysis

Anodization of aluminum in an acidic medium facilitates the formation of well-ordered nanoporous anodic oxide films. The mechanism of pore formation is investigated as a morphological instability using a simplified model. The model accounts for the high field conduction law and field-assisted reactions (oxide formation/dissolution) only at the oxide-solution interface. The role of Butler-Volmer electrokinetics, electrolyte pH, anodic efficiency, and interface curvature on reaction kinetics are taken into account. Linear stability analysis suggests that the oxide film is unstable to well-defined wavelengths in specific ranges of parameters such as anodizing efficiency, applied voltage and electrolyte pH. Subsequently, a weakly nonlinear analysis is carried out to determine the nature of bifurcation beyond the stability threshold. Our findings indicate that the instability exhibits a subcritical nature, well in agreement with experimental observations.

Lithium-ion comb—artificial self-regulating lithium-storage film on aluminum anode enabling long cycles of batteries

Al anode can increase battery energy density, but its non-wettability and high Li nucleation hindrance cause uneven Li nucleation to deteriorate the anode structure. Herein, we present a novel in-situ synthesis method for the deposition of molybdenum oxide nanospheres (NMO) onto the surface of Al foil, that is, molybdenum oxide/aluminum (M-Al), which demonstrates a two-stage propulsion effect on Li-ion migration to address the issue at hand. The high wettability and low Li nucleation hindrance of the NMO layer drive the first stage of Li-ion migration. NMO acted as a comb to deliver Li ions uniformly with minor volume expansion. Subsequently, the formation of Li2O-rich solid electrolyte interphase (SEI) film with exceptional desolvation capability, facilitated by the NMO layer and electrochemically activated M-Al to Li molybdate/aluminum (Li-M-Al), represents the second stage in the advancement of Li−ion migration. The embedding of lithium ions makes molybdenum oxide evolve into lithium molybdate, thereby enabling Mo to regulate the storage of Li ions through the valence state. Hence, the Li nucleation overpotential of M-Al is decreased by 0.32 V, leading to a significant enhancement in the cycling performance of the Li-M-Al||LiFePO4 (LFP) battery, with a capacity retention rate of 78.5 % after 400 cycles at 1C.