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Three types of mesoporous silicon flakes were fabricated by anodization in methanoic hydrofluoric acid from the same substrates (heavily doped p-type). Even though anodization current density, rinsing, drying method, and storage condition were the same for all three wafers, the resulting porous silicon (PSi) structures had very different properties. They had very different colors. Two of them showed quite high luminescence quantum yields (QYs), confirmed by very long luminescence lifetimes. The highest QY exceeded 50% for a peak photoluminescence wavelength of ∼750 nm. To date, this QY is the highest obtained for PSi and very importantly for silicon with large mesopores, which is typically not highly efficient (as opposed to silicon with small mesopores and microporous silicon). Large mesopores (>15 nm diameter) facilitate impregnation of various substances into luminescent material, such as metals for plasmonics and drugs for theranostics. The differing luminescent properties were correlated to electrolyte temperature during anodization, and evolution of the electrolyte batch (lowering of active fluoride content and buildup of hexafluorosilicate) used to anodize several wafers, whose effects are often overlooked when mass-producing PSi. Supercritical drying and completion of the slow growth of native oxide passivation in the dark leading to different final partially oxidized PSi structures are also important factors for the high QYs obtained. The highest QY was obtained with the structure having the most isolated Si nanocrystals in an amorphous Si oxide tissue. [ABSTRACT FROM AUTHOR]

Porous anodic oxides have become a research hotspot, but their formation mechanisms are still controversial. The classical field-assisted dissolution theory (FADT) is a theory of top-down dissolution to form nanotubes. However, certain key problems such as the three-stage current-time curve in anodizing process cannot be explained by this theory. The oxygen bubble mold (OBM) is a new mechanism of bottom-up growth of nanotubes, which can explain the phenomenon that cannot be explained by the FADT. Compared to the anodic TiO 2 nanotubes, ZrO 2 nanotubes have a more complex anodizing current-time curve which is not studied sufficiently. Under certain conditions, there are double complete three-stage current-time curves and two-layer nanotubes. In this study, to explore the formation mechanism of anodic ZrO 2 nanotubes, the current-time curve and the interesting morphology were analyzed, after zirconium anodizing and SEM characterizing. An interesting three-layer structure composed of upper nanotubes, dense layer and lower nanotubes formed by zirconium anodizing is reported for the first time. The lower nanotubes and the dense layer are tightly bonding, which strongly refutes the FADT. The OBM was used to explain this phenomenon, which promoted the development of the formation mechanism of anodic ZrO 2 nanotubes. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) nanotubes were obtained by the anodization process, applying a potential of 30 V for 2 h in an electrolyte composed of NH4F, H2O and ethylene glycol. The nitrogen doping of the obtained nanostructures was studied and the influence of the use of different temperatures during the thermal treatments 400, 500 and 600°C, on the formed nanotubes were evaluated. The morphology and crystalline structure of the obtained materials were determined by field emission gun scanning electron microscopy and X-ray diffraction. The optical properties were evaluated by UV–Vis diffuse reflectance spectroscopy and the photoelectrochemical properties by linear sweep voltammetry curves. The photocatalytic activity of nanotubes was evaluated by degradation of glycerol in aqueous medium using UV and visible radiation. TiO2 nanotubes developed photoactivity, photoelectrochemical behaviour and presented catalytic activity for glycerol degradation, which is more evident with UV radiation. The sample thermally treated at 500°C was the one that presented superior photoelectrochemical behaviour and superior photocatalytic activity when exposed to both UV and visible radiation. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the individual electrochemical transients arising from local anodic events on stainless steel, to uncover the potential mechanisms producing different types of transients and to derive appropriate parameters indicative of the corrosion severity of such transient events. Design/methodology/approach: An equivalent circuit model was used for the transient analysis, which was performed using a local current allocation rule based on the relative instant cathodic resistance of the coupled electrodes, as well as the kinetic parameters derived from the electrochemical polarization measurement. Findings: The shape and size of the electrochemical current transients arising from SS 316 L were influenced by the film stability, local anodic dissolution kinetics and the symmetry of the cathodic kinetics between the coupled electrodes, where the ultralong transient might correspond to the propagation of film damage with a slow anodic dissolution rate. The dynamic cathodic resistance during the final stage of transient current growth can serve as a characteristic parameter that reflects the loss of passive film protection. Originality/value: Estimation of the local anodic current trace opens a new way for individual electrochemical transient analysis associated with the charges involved, local current densities and changes in film resistance throughout localized corrosion processes. [ABSTRACT FROM AUTHOR]

Analytical methods with wide field range and high spatial resolution are required to observe the distribution of the crystal structure in micro‐regions undergoing macroscopic chemical reactions. A recent X‐ray diffraction (XRD) imaging method combines XRD with an X‐ray optical device such as a glass polycapillary consisting of a bundle of numerous monocapillaries. The former provides the crystal structure, while the latter controls the shape of the incident or diffracted X‐rays and retains the positional information of the sample. Although reducing the monocapillary pore size should improve the spatial resolution, manufacturing technology challenges must be overcome. Here, an anodic aluminium oxide (AAO) film, which forms self‐ordered porous nanostructures by anodic oxidation in an electrolyte, is applied as an X‐ray optical device. The AAO film (pore diameter: 110 nm; size of the disc: 11 mm; and thickness: 620 µm) was fabricated by anodization in a mixture of oxalic acid and ethylene glycol. The film was incorporated into a laboratory XRD instrument. Compared with using a glass polycapillary alone, using a combination of a glass polycapillary and the AAO film improved the spatial resolution of the XRD imaging method by 40%. This XRD imaging method should not only provide practical analysis in a laboratory environment but also support various observations of the crystal structure distribution. [ABSTRACT FROM AUTHOR]

Aluminum alloy forms a protective layer of aluminum oxide when exposed to air, which gives it corrosion resistance. But, the layer can be easily damaged, causing metal corrosion. The hard anodizing method is used to solve this issue. Determining the appropriate anodizing parameters, including current density, process time, and electrolyte concentration, is crucial for attaining the desired thickness and hardness of the anodized layer. An experimental design approach utilizing the response surface method (RSM) was employed to investigate the effects of these variables. Quadratic models were presented to predict the hardness and thickness of the layer with an average error of 2.84% and 3.89%, respectively. The models were verified through analysis of variance (ANOVA) to assess the effect of each parameter and their interactions. Oxalic acid concentration, the interaction between process time and oxalic acid concentration, and the square of current density and process time have a significant impact on hardness. Layer thickness is mainly influenced by current density, process time, and the interaction between process time and oxalic acid concentration. Optimization results show that a current density of 1.19 A / dm 2 , a process time of 160 min, sulfuric and oxalic acid concentrations of 26.25 g r / l i t and 36.88 g r / l i t , respectively, leads to hardness of 434 HV and thickness of 93.6 µm. A scanning electron microscope (SEM) image under optimal conditions shows that aluminum porous arrays created by an anodizing process in mixed sulfuric acid and oxalic acid electrolyte, with a hexagonal shape observed across a wide range of grain domains. [ABSTRACT FROM AUTHOR]

Pulsed anodization of a nearly equiatomic NiTi alloy in HNO3 leads to the formation of a nearly Ni‐free oxide layer, resulting in the suppression of Ni‐ion release from the alloy surface. The core technology involves introduction of a lower‐voltage period, which promostes chemical reactions between the alloy and electrolyte, to obtain a surface layer with better corrosion protection. In this study, a higher voltage of 3.5 V was applied, and the lower voltage was varied within 0–3.5 V. As the lower voltage was increased, nanometer‐sized pores present on the anodized surface gradually expanded, while the layer thickness decreased. Although the corrosion protectivity of the layer did not change significantly during the electrochemical experiments, the amount of Ni‐ion released into the physiological solution significantly decreased when the voltage was below 1.8 V. X‐ray photoelectron spectroscopy analyses revealed the presence of Ni (OH)2 on the topmost surface, and its concentration decreased at a voltage <1.8 V. Lower voltages affected the concentration of Ni (OH)2 on the topmost surface and thus considerably influenced the Ni‐ion release behavior. These findings will contribute to the production of NiTi alloys with improved biocompatibility. [ABSTRACT FROM AUTHOR]

In this study, we examined a method for whitening an aluminum surface by anodizing it in a sulfuric acid solution to industrialize the process. Anodic oxidation in a sulfuric acid solution at 2.5Adm-2 for 120 s resulted in the whitening of the aluminum surface, but localized burning occurred. When anodization was performed at a low current density for a short time (2.5Adm-2 for 4.5 s) after a high current density, a white anodic film was successfully obtained without burning. Cross-sectional scanning electron microscopy (SEM) observation of the white film revealed that etching by pretreatment created an uneven surface, and pore branching created an uneven metal-oxide interface. The fluctuating value of the film thickness obtained by length measurements using SEM was 0.2-0.3 µm. This value is sufficient to whiten the anodic film because of increase in diffusion reflection at the film surface and the metal-oxide interface. These results indicate that the difference in the peak voltage between the first and second anodizing resulted in the formation of a branched pore structure and film whitening. [ABSTRACT FROM AUTHOR]

This review delineates the mechanisms of pit nucleation and growth, establishes the foundational principles of etching technology, and presents the findings from investigations on the behavior of anodic dissolution and anodic film formation on high-purity aluminum foils for electrolytic capacitors based on electrochemical analyses and surface electron microscopic observations of etched surfaces. To elucidate pit nucleation and growth mechanisms, the effects of crystalline oxide and small amounts of lead on etching behavior were investigated. Pits initiate at cracks surrounding MgAl2O4 spinel or γ-Al2O3, resulting from the crystallization of the oxide film at metal ridges on the aluminum substrate. Using ultra-high-resolution field-emission scanning electron microscope (FE-SEM), high-angle backscattered electron (BSE) images revealed the presence of lead as the bright nanoparticles, approximately 10 nm in size, at the surface oxidation layer along rolling lines attributable to pick-up inclusions during hot rolling. Pitting attacks predominantly occur in the oxidation layer owing to the less noble potential for tunnel dissolution in the initial DC etching phase. Increased titanium content within the aluminum foil accelerated hydrogen evolution in the pit and hydrous oxide formation during the cathodic half-cycle of alternating current etching. The crystallization of anodic oxide films around MgAl2O4 spinel crystals, formed in a boric acid solution, was observed using transmission electron microscopy (TEM). Round-shaped γA-Al2O3 formed around the MgAl2O4 crystals and expanded across the surface as the formation voltage increased. [ABSTRACT FROM AUTHOR]

Aqueous zinc (Zn) metal batteries have considerable potential as large‐scale energy storage systems. However, cathodic metal ions dissolution and anodic dendrite growth constrain their further development. Here, an ion gradient separator is proposed to stabilize the bi‐electrodes of Zn metal batteries. The results show that the constructed low Zn2+ concentration region in the separator helps the NH4V4O10 (NVO) model cathode to maintain good electrolyte wettability and form a N/ZnS/ZnF2‐rich cathode‐electrolyte interphase (CEI), exhibiting a low vanadium (V) dissolution behavior. Meanwhile, the high Zn2+ concentration region in the separator and the flexible solid electrolyte interphase (SEI) inhibit the dendrite growth and parasitic reactions of the Zn metal anode and further prevent the diffusion of V ions. As a proof‐of‐concept, the NVO||Zn battery with gradient separator can achieve 88.1% capacity retention even after cycling over 800 cycles at 1 A g−1, while the ordinary separator only maintains 14.8%. This work presents an innovative gradient separator strategy for achieving high‐performance Zn metal batteries and sheds light on other rechargeable batteries. [ABSTRACT FROM AUTHOR]

Bioinspired titanium implant nanotexturing achieved via advanced techniques such as lithography, hydrothermal and laser patterning enables modulation of cell functions toward enhanced bioactivity and antibacterial efficacy. However, such costly, multi‐step methods limit clinical translation and benchtop implant modification. For the first time, single‐step, cost‐effective, and translatable electrochemical anodization is reported to fabricate bioinspired nanopillar‐like textures on micro‐rough titanium. In‐depth surface characterization confirms the formation of novel nanostructures, namely nanoscale Spinules, Daggers, Papillae, Spikes, and Flames, exhibiting varied roughness and wettability. Next, in separate experiments, primary human osteoblasts and polymicrobial salivary biofilm are cultured on the implant substrates. Nanotextured surfaces show high protein adhesion and maintain the proliferation, adhesion, and spreading of osteoblasts. Interestingly, all nanotextures exhibit superior antibiofilm abilities compared to control surfaces. Bioactive and antibacterial implant surface nano‐texturing achieved via single‐step anodization has the potential for clinical translation as the next generation of orthopedic and dental implant surface modification. [ABSTRACT FROM AUTHOR]

To enhance the corrosion resistance of magnesium alloys, an anti-corrosion composite film was prepared by combining anodic oxidation and sol-gel technology. Experimental results indicate that after anodization at 17.5V for 3 min, the composite film obtained through sealing with an MPTMS-modified sol exhibited significant improvements in physical properties. The thickness of the film reached 24.3 μm, its hardness was measured at 164.7 HV, and it demonstrated good surface uniformity. Electrochemical impedance spectroscopy revealed that the impedance modulus at low frequency (|Z| at 0.01 Hz) increased by nearly two orders of magnitude. Furthermore, this study thoroughly explores the corrosion protection mechanism of the composite film, highlighting the role of the sol-gel layer in occupying micro-pores and micro-cracks to form a denser and more uniform protective layer. The dual-layer protection provided by the combination of anodic oxidation and sol-gel layers significantly enhances the overall corrosion resistance of the magnesium alloy. [ABSTRACT FROM AUTHOR]

The performance of the lithium (Li) metal anode in rechargeable batteries has been hampered by the formation of unstable solid‐electrolyte interphase layers, which compromise cycle life and pose significant safety concerns. Herein, for the first time, the anodizing oxidation of pure Li in a liquid electrolyte is developed by using tetrahydrofuran with LiNO3. With this novel process, thickness‐controllable Li oxide films with in situ nitrogen doping during the anodizing process can be obtained. The resulting nitrogen‐doped Li oxide film (NLO) exhibits a uniform surface of the Li metal anode, effectively suppressing Li dendrite growth and simultaneously improving Li ionic conductivity. In addition, the Li metal full cells with Li/NLO anodes perform a long stable life of 1100 cycles at 5C. More importantly, this work demonstrates the great potential of NLO films as a solid‐state electrolyte in solid‐state Li metal batteries. The symmetric Li cells with NLO films perform excellent cycling stability for 300 h at 2 mA cm−2 current density and high Li+ ion conductivity of ≈3 ×10−4 S cm−1 at room temperature. This research not only provides a novel Li anodizing process and a stable Li metal anode but also opens up new possibilities for new solid‐state Li metal battery technologies. [ABSTRACT FROM AUTHOR]

Anodizing is a well-documented surface treatment that is inserted in a complex protection system against corrosion applied to Al alloys. In the scientific literature, there are many works about this topic, which are concentrated on: (1) anodic aluminum oxide (AAO) growth mechanism; (2) anodized alloys corrosion behavior, or (3) the influence of anodizing parameters on the following steps of corrosion protection of the anodized layer. However, the effect of the microstructure on the AAO formation is not yet well established. This paper aims to review the effect of the microstructure of Al and its alloys on the anodizing process by a historical, statistical, and electrochemical approach, considering the advantages in understanding the influence of intermetallics in this process. Besides, this review brings a comparison among the number of publications and the types of alloys studied by statistical analyses. Finally, it emphasizes the importance of anodizing in the aeronautical industry, in which a great number of studied alloys are applied, mainly the 2XXX (Al-Cu) and 7XXX (Al-Zn) series alloys. [ABSTRACT FROM AUTHOR]

This study investigates the influence of various anodic oxidation parameters on the photocatalytic activities of the nanostructured titanium dioxide (TiO2) films. TiO2 films were prepared by anodic oxidation of titanium substrate using 1 M Na2SO4 / 5 wt. % NH4F electrolyte, and then annealed at 500 °C. Anatase appears in all calcined samples. The anodic oxidation process was performed in two steps at different voltages (5–80 V) and times (15–480 min) to reveal the relationship between the surface morphologies, wettability and photocatalytic properties. The results showed that the voltage and anodization time can play important role in the surface morphology of nanostructured TiO2 films and thus in various properties. While 40 V showed the most efficient photocatalytic degradation among voltage values, 60 min was the most efficient time for photocatalytic degradation efficiency and lowest contact angle. In addition, a pore area fraction of 39.54%, equal diameter of 96.81 nm, and circularity of 66.7% were obtained from image analysis of the 60-min anodized sample. While increasing the voltage and time benefited up to a point in terms of photocatalytic efficiency, changes in morphology had a negative effect after a point. At low voltage and time values, small pore diameters result in low photocatalytic properties. This titania can be readily utilize to meet application expectations in areas such as gas sensors, photocatalysis and photovoltaic cells. [ABSTRACT FROM AUTHOR]

This paper reports on the coating of heterostructured TiO2 nanopores/nanotubes on Ti substrates by anodizing at high voltages to design surfaces for biomedical implants. As the anodized voltage from 50 V to 350 V was applied, the microstructure of the coating shifted from regular TiO2 nanotubes to heterostructured TiO2 nanopores/nanotubes. In addition, the dimension of the heterostructured TiO2 nanopores/nanotubes was a function of voltage. The electrochemical characteristics of TiO2 nanotubes and heterostructured TiO2 nanopores/nanotubes were evaluated in simulated body fluid (SBF) solution. The creation of heterostructured TiO2 nanopores/nanotubes on Ti substrates resulted in a significant increase in BHK cell attachment compared to that of the Ti substrates and the TiO2 nanotubes. [ABSTRACT FROM AUTHOR]

In this study, a superhydrophobic surface was successfully prepared on Al alloy 5052 using a simple anodic oxidation method followed by fluorination treatment. This study demonstrates the construction of rough structure of Al oxide by an anodic oxidation reaction, which improves the superhydrophobicity of the alloy. The top, tilt, and cross‐views of the samples were characterized by field‐emission scanning electron microscopy and focused ion beam. The chemical composition of the samples was analyzed by energy‐dispersive X‐ray spectroscopy and Fourier‐transform infrared spectroscopy. The structure of the surface was effectively modified as the anodization time increased. The optimum anodic oxidation reaction was carried out for 4 min in a 0.2‐M H3PO4 aqueous electrolyte at 50°C under a constant voltage of 120 V to create a pore‐and‐dendrite hybrid nanostructure. The water contact angle values were maximized in the hybrid nanostructure because their solid fraction area was smaller than that in the porous structure. Corrosion measurements proved that the superhydrophobic surface can significantly inhibit the corrosion of the substrate alloy with an inhibition efficiency of 99.99%. In addition, the prepared superhydrophobic sample exhibited good self‐cleaning properties. [ABSTRACT FROM AUTHOR]

Nitrobenzene liquid-phase catalytic hydrogenation is commonly regarded as one of the most effective technologies for aniline production. The traditional granular catalysts have the disadvantages that the reactor bed pressure drop is large and the mass transfer efficiency between gas and liquid phases is low. In this study, a novel structured mesh-type Pd/γ-Al2O3/Al catalyst was prepared by anodic oxidation and pore structures of γ-Al2O3/Al supports were constructed by acid pore-widening treatments. The results showed that acid pore-widening treatments can improve the pore size of γ-Al2O3/Al supports; the support with HNO3 pore-widening treatment exhibited the largest pore size, being enlarged from 3.7 nm to 4.6 nm. The Pd/γ-Al2O3/Al catalysts prepared with different acid pore-widening treatment supports contribute to the increased active metal Pd loading, more Pd0 content, and better dispersion of the Pd particles. The catalyst prepared with HNO3 pore-widening treatment support exhibited the largest active metal Pd loading, enlarging from 1.82% to 1.95%, the largest Pd0 content being enlarged from 52.1% to 58.5% and the smallest Pd particle size being reduced from 103 nm to 41 nm, resulting in the highest nitrobenzene conversion, increasing from 67.2% to 74.3%. Eventually, we calculated that the pressure drop of structured catalysts was 1/72 of that of granular catalysts, resulting in a better diffusion of the H2 through nitrobenzene solution to active sites on the catalyst surface and a significant increase in the catalytic activity. [ABSTRACT FROM AUTHOR]

The anodic behavior of Ni48Fe47Cu5 and Ni42Fe38Cu20 alloys in NaF-KF-AlF3-Al2O3 electrolyte was studied using electrochemical methods, such as chronopotentiometry, chronoamperometry, and linear sweep voltammetry at 770°C. The cryolite ratio and potassium ratio were 1.3 and 0.7, respectively. The steady-state polarization curves were obtained before and after galvanostatic polarization for 2 h. The current densities in the passivation region were lower for both anodes after polarization than before, indicating the formation of a protective passive layer during polarization. When anodes were subjected to potentiostatic polarization at 2.2 V (vs. reference), a passive film was readily formed. Linear sweep voltammograms were obtained on Ni48Fe47Cu5 and Ni42Fe38Cu20 alloys, and the polarization resistances were 5.227 Ω cm−2 and 5.968 Ω cm−2, respectively. During the galvanostatic electrolysis, the anodic potential (vs. reference) constantly varied with time for the Ni48Fe47Cu5 anode. In contrast, the anodic potential of Ni42Fe38Cu20 remained almost constant throughout the electrolysis. The thickness of the oxide layer formed on the anodes Ni48Fe47Cu5 and Ni42Fe38Cu20 after 2 h of electrolysis were around 90 μm and 30 μm, respectively. [ABSTRACT FROM AUTHOR]

Using carbon‐based super black coatings on optical devices can achieve superior stray light suppression for applications in astronomy. For the first time, the work presents carbon nanofiber‐based black coating on commercial anodized Al(6061), which facilitates the development of a highly effective route to directly integrate the carbon‐based material on the common substrate for optical baffles. The scalable and available structural engineering effect is synergized with the anodized Al(6061) coating with black dye composed of nickel catalyst and the intrinsic broadband light absorption of the CVD‐grown carbon material to ultimately achieve a superior broadband light absorber. Nickel catalysts embedded in anodized Al(6061) offer a practical pathway for carbon nanofiber growth through CVD without additional stacked catalysts. The CVD‐growing mechanism and CNF nanostructures are demonstrated through TEM and EDS element mapping, SEM, and Raman spectroscopy. CNF‐grown Al(6061) substrates offer above 99% broadband light absorption and low light reflectance below 1% in UV–vis–NIR and mid–IR ranges. This facile approach has been useful for super black coating on Al(6061)‐based complicated sculptures, such as concave substrate and an optical baffle. These results have demonstrated a facile method that can significantly impact the industrial scaling‐up of high‐quality, super‐black coating on spaceborne devices. [ABSTRACT FROM AUTHOR]

The lightweight, recyclable aluminum alloy with the "green metal" modifier enhances energy efficiency by substituting various metals; however, its thin natural oxide layer is susceptible to cracking or corrosion in harsh environments, requiring surface treatment, such as anodization. Anodization improves metal's corrosion and wear resistance, hardness, and esthetic impression. Its arrangement of the nanopore structure influences the uniformity of secondary processes, such as coloring, paint, and coating adhesion. This study applied time variables to the three-step process's first anodization and anodic aluminum oxide (AAO) removal steps to confirm AAO pore uniformity. A six-hour anodization formed 8.26 ± 0.10 µm thick AAO. Subsequent removal steps, lasting 0.5, 2, 6, and 10 h, resulted in a 5.04 µm h−1 AAO removal rate. As the AAO removal time increased, pore diameter (Dp) and interpore distance (Dint) changed, and the 6 h AAO removal condition was used for anodization. The AAO's pore uniformity, surface roughness, and wettability were observed after the first anodization for 1, 3, 5, 7, and 9 h; AAO removal; and second anodization. Furthermore, larger, uniform pores formed as the first anodization time increased, and pore structure changes increased AAO's roughness and decreased contact angle. This study introduces an efficient anodization manufacturing method that can be employed across various fields, aiming to enhance material stability and improve energy storage efficiency. [ABSTRACT FROM AUTHOR]

Aluminum technical alloys are well known for their outstanding mechanical properties, especially after heat treatment. However, quenching and aging, which improve the mechanical properties, by the formation of Cu-rich zones and phases that are coherent with the matrix and block the dislocation motion, cause uneven distribution of the elements in the alloy and consequently make it prone to corrosion. One method providing satisfactory corrosion protection of aluminum alloys is anodizing. On an industrial scale, it is usually carried out in electrolytes containing chromates that were found to be cancerogenic and toxic. Therefore, much effort has been undertaken to find substitutions. Currently, there are many Cr(VI)-free substitutes like tartaric–sulfuric acid anodizing or citric–sulfuric acid anodizing. Despite using such approaches even on the industrial scale, Cr(VI)-based anodizing still seems to be superior; therefore, there is an urge to find more complex but more effective approaches in anodizing. The incorporation of anions into anodic alumina from the electrolytes is a commonly known effect. Researchers used this phenomenon to entrap various other anions and organic compounds into anodic alumina to change their properties. In this review paper, the impact of the incorporation of various corrosion inhibitors into anodic alumina on the corrosion performance of the alloys is discussed. It is shown that Mo compounds are promising, especially when combined with organic acids. [ABSTRACT FROM AUTHOR]

In this study, the electrochemical and mechanical characteristics of 6061‐T6 aluminum alloy and hard anodized specimens are investigated after tribocorrosion experiments with rotational speed in dry, distilled water, and sulfuric acid solution. The tribocorrosion experiments indicate that the corrosion potential of aluminum alloys and hard anodized specimens decrease with the initiation of friction/wear. In particular, the increase in the wear track width of an aluminum alloy and the exposure of the base material by completely destroying the anodized layers of the hard anodized specimens dramatically decrease the corrosion potential. Compared to the dry conditions, both the width and depth of damage in the distilled water and sulfuric acid solution increase dramatically. However, damage in the distilled water and sulfuric acid solutions do not present a significant difference. The results are attributed to the fact that the presence of fluid has a greater impact on damage degree in a material than corrosion. In particular, the brittleness and porosity of a hard anodized layer facilitates the impingement and penetration of fluid, making it relatively easy to generate and propagate cracks. These cracks accelerate the degradation and damage to the material by synergistic effects of wear and corrosion. [ABSTRACT FROM AUTHOR]

A nanocomposite of multi-walled carbon nanotubes (MWCNTs) decorated with molybdenum dioxide (MoO2) nanoparticles is fabricated through the reduction of phosphomolybdic acid hydrate on functionalized MWCNTs in a hydrogen–argon (10%) atmosphere in a tube furnace. The MoO2/MWCNTs composite is proposed as an anodic modification material for microbial fuel cells (MFCs). MWCNTs have outstanding physical and chemical peculiarities, with functionalized MWCNTs having substantially large electroactive areas. In addition, combined with the exceptional properties of MoO2 nanoparticles, the synergistic advantages of functionalized MWCNTs and MoO2 nanoparticles give a MoO2/MWCNTs anode a large electroactive area, excellent electronic conductivity, enhanced extracellular electron transfer capacity, and improved nutrient transfer capability. Finally, the power harvesting of an MFC with the MoO2/MWCNTs anode is improved, with the MFC showing long-term repeatability of voltage and current density outputs. This exploratory research advances the fundamental application of anodic modification to MFCs, simultaneously providing valuable guidance for the use of carbon-based transition metal oxide nanomaterials in high-performance MFCs. [ABSTRACT FROM AUTHOR]

Anodic oxidation is a promising method for removing organic pollutants from water due to its high nonselectivity and effectiveness. Nevertheless, its widespread application is limited due to its low current efficiency, high energy consumption and low treatment rates. These problems may be overcome by the optimization of the process parameters, reactor design and electrode geometry, by coupling the experimental investigations with mathematical modeling. Here we review the modeling of anodic oxidation with focus on basics of this process, the competition phenomenon in real wastewater, flow cells and batch cells, historical aspects, general modeling equations, modeling with plate electrodes, modeling with porous 3-dimension electrodes and the density functional theory. Mathematical modeling can provide current, voltage and concentration distributions in the system. Mathematical modeling can also determine the effects on the performance of parameters such as diffusion layer thickness, flow velocity, applied current density, solution treatment time, initial concentration and diffusion coefficients of organic pollutants, electrode surface area, and oxidation reaction rate constant. Mathematical models allow to determine whether the limiting factor of the process is kinetics or diffusion, and to study the impact of competition of phenomena. The density functional theory provides information on probable reaction pathways and by-products. [ABSTRACT FROM AUTHOR]

The current work assessed the corrosion inhibitory efficacy of three ligands, namely methyl 2-((2-hydroxynaphthalen-1-yl)diazenyl)benzoate(MDN), 1-((3,4-dimethylphenyl)diazenyl)naphthalen-2-ol (DDN), and 3-((2-hydroxynaphthalen-1-yl)diazenyl)benzonitrile (HDN). Electrochemical and quantum methodologies, along with UV–Vis, SEM, and EDX, were employed. The anticorrosion process was comprehensively investigated. Potentiodynamic polarization validated the mixed type nature of inhibitors by demonstrating a drop in the cathodic hydrogen evolution reaction and the anodic metal dissolution, resulting to a significant decrease in corrosion current densities. Enhanced rates of effectiveness are achieved with higher inhibitor doses. Electrochemical impedance spectroscopy investigations confirmed the formation of a protective layer at the metal/solution interface, demonstrating that charge transfer was the primary cause of mild steel corrosion. The inhibitory potencies of the studied inhibitors at 10−3 M were 94.65, 94.56, and 93.63% for MDN, DDN, and HDN, respectively. The presence of several attributes in the molecular skeleton, such as nitrogen heteroatoms, aromatic rings, and the ester substituent group (CO2CH3), enhanced the availability of non-bonded and π-electrons and created stable covalent bonds by donating electrons to the iron surface. The inhibitory efficiency was better than 89% across all temperature ranges, suggesting the potential benefits of inhibitors at elevated temperatures. Adsorption trials revealed high effectiveness in corrosion control on mild steel, with Langmuir-based physisorption and chemisorption. The impact of electronegative O and N atoms, along with aromatic rings, in forming protective coatings was demonstrated by quantum chemistry computations which linked molecular structure and charge density patterns to the inhibition potency of MDN, DDN, and HDN, highlighting MDN's strong adsorption capacity. [ABSTRACT FROM AUTHOR]

Silver(I) oxide is considered as one of the promising materials for photoelectrochemical technologies because it has an optimal band gap, relatively low cost, and a wide variety of production methods. However, its characteristics such as quantum efficiency, morphology, and crystal structure parameters require optimization, which can be achieved by applying the most suitable method for the obtaining of the material. One of the fairly simple methods is the anodic oxidation of silver or its alloys in alkaline media, which allows obtaining oxide phases with a controlled composition and predictable properties by varying the concentration of the alloy components and electrolysis mode. The purpose of this work is to reveal the features of anodic formation and to determine the photoelectrochemical characteristics of silver(I) oxide on silver–palladium alloys in deaerated 0.1 M KOH solution. The regularities of the anodic formation of Ag(I) oxide on alloys of the Ag–Pd-system with the palladium atomic fraction from 0.05 to 0.20 in deaerated 0.1 M KOH solution were studied by non-stationary electrochemical methods of cyclic voltammetry, chronoamperometry with synchronous recording of photocurrent, and photopotential measurements. The phase composition of the alloys (alpha phase) was determined from the results of X-ray diffractometry. Chemical composition was determined by energy dispersive microanalysis. Photoelectrochemical parameters were calculated from the results of the photocurrent and photopotential measurements. It was established that the Ag(I) oxide anodically formed on silver–palladium alloys is characterized by n-type conductivity and the predominance of donor defects. On the alloys with a relatively low palladium concentration (5 and 10 at %), Ag(I) oxide with a higher concentration of defects is formed, while on alloys with a relatively high palladium concentration (15 and 20 at %), with a lower concentration of defects than on pure silver. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of the Co–Cr–Mo–W alloy in the Fusayama synthetic saliva was examined as a function of fluoride ion concentration, pH level, and immersion time using open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The OCP results showed that the rate of growth of the air-formed film on the Co–Cr–Mo–W alloy surface lowers as the concentration of the F– ions added to saliva increases. Additionally, in all of the pH values of saliva examined (from 2 to 11), the OCP became more positive over time, indicating the development of the native film on the alloy. The results of impedance and potentiodynamic polarization revealed that the corrosion resistance of the primarily produced oxide layer on the alloy decreased with an increase in the F– ions in saliva, but increased with an increase in saliva pH value. According to the EIS findings, the thickness of the anodic oxide film on the Co–Cr–Mo–W alloy increases with rising pH levels in the formation medium (saliva). By using energy-dispersive X-ray spectroscopy (EDS), it was discovered that as the salvia pH rises, the amount of oxygen on the alloy surface increases, indicating the development of a protective oxide layer. The surface roughness of the mechanically polished alloy surface rises with anodic polarization in an alkaline saliva solution, according to atomic force microscopy. The results of scanning electron microscopy and EIS show that as the alloy is immersed in saliva for a longer time, the thickness of the air-formed film on the alloy increases. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of different abutments and crowns on the color of implant-supported restorations. Methods: Zirconia and lithium disilicate (e.max) disks with A2 shade were fabricated to represent two crowns. The implant abutments were untreated titanium, opaqued titanium, anodized titanium, A2 shade zirconia and white zirconia. 4.0 mm-thickness zirconia and e.max specimens were used as references respectively. The crowns were placed on tested abutments with a drop of clear glycerin between them and the color was measured using a digital spectrophotometer. CIELab values were recorded to evaluate color differences (AE) between tested specimens and the references. Results: Titanium abutments presented higher color differences than zirconia. The AE values with untreated titanium were higher than those with opaqued titanium. No differences were found between untreated titaniurn and anodized titanium for zirconia crowns. The AE values of zirconia crowns showed no significant differences between shade A2 zirconia and white zirconia abutments; e.max crowns showed a significant difference. The zirconia crown AE values were lower than those of e.max for all titanium and A2 zirconia abutments. Lithium disilicate crowns and zirconia abutments may be more suitable for implant-supported restorations. Opaqued titanium abutment may improve color in esthetic regions when a ceramic abutment cannot be used. [ABSTRACT FROM AUTHOR]

Dissimilar joining between carbon fiber reinforced thermoplastic (CFRTP) and metal has attracted attention of transportation equipment industry for reduction of weight and cost by multi-material structure. Friction stir spot welding (FSSW) between anodized A5052 (AO-A5052) and carbon fiber reinforced thermoplastic (CFRTP) was investigated for the improvement of joining strength. Average tensile shear strength of AO-A5052/CFRTP joint was 2505 N and more than 500 N higher than that of untreated-A5052/CFRTP joint. In the AO-A5052/CFRTP joint, probe plunge induced cracks and microwrinkles in the anodic oxide layer on the weld surface. Matrix resin was immersed into the cracks and the microwrinkles underneath of the shoulder of the welding tool. Reinforced carbon fiber and matrix resin was immersed into large crack at the outer peripheral corner of probe. Thus, those increased the joining strength by mechanical anchoring effect. Thermal stress test and machining stress test were performed for revealing the mechanism of cracking of anodic oxide layer. Although thermal stress did not generate cracks in the anodic oxide layer, machining stress by probe plunge generated cracks in the anodic oxide layer. The generated cracks in anodic oxide layer underneath of the shoulder were distorted to the rotating direction of welding tool by the friction stirring. [ABSTRACT FROM AUTHOR]

Anodic aluminum oxide (AAO) has been widely applied for the surface protection of electronic component packaging through a pore-sealing process, with the enhanced hardness value reaching around 400 Vickers hardness (HV). However, the traditional AAO fabrication at 0~10 °C for surface protection takes at least 3–6 h for the reaction or other complicated methods used for the pore-sealing process, including boiling-water sealing, oil sealing, or salt-compound sealing. With the increasing development of nanostructured AAO, there is a growing interest in improving hardness without pore sealing, in order to leverage the characteristics of porous AAO and surface protection properties simultaneously. Here, we investigate the effect of voltage on hardness under the same AAO thickness conditions in oxalic acid at room temperature from a normal level of 40 V to a high level of 100 V and found a positive correlation between surface hardness and voltage. The surface hardness values of AAO formed at 100 V reach about 423 HV without pore sealing in 30 min. By employing a hybrid pulse anodization (HPA) method, we are able to prevent the high-voltage burning effect and complete the anodization process at room temperature. The mechanism behind this can be explained by the porosity and photoluminescence (PL) intensity of AAO. For the same thickness of AAO from 40~100 V, increasing the anodizing voltage decreases both the porosity and PL intensity, indicating a reduction in pores, as well as anion and oxygen vacancy defects, due to rapid AAO growth. This reduction in defects in the AAO film leads to an increase in hardness, allowing us to significantly enhance AAO hardness without a pore-sealing process. This offers an effective hardness enhancement in AAO under economically feasible conditions for the application of hard coatings and protective films. [ABSTRACT FROM AUTHOR]

Tartaric-sulfuric acid anodic (TSA) films were prepared on the surface of the 2024 Al alloy. These films were sealed with cerium salts at 25 °C and 65 °C, hot water, and dichromate. The morphology and corrosion resistance of the anodic films were investigated using a field emission scanning electron microscope/energy-dispersive spectrometer, an electrochemical workstation, an acidic spot test, and an immersion test. The results indicated that the surface of the TSA film sealed with cerium salt at 65 °C had a slightly lower cerium content compared to the TSA film sealed at 25 °C. It was found that increasing the sealing temperature of cerium salt could enhance the corrosion resistance of the TSA film. After immersion in a 3.5 wt.% NaCl solution for 336 h, no obvious corrosion pits were observed on the surface of the TSA film sealed at 65 °C, whereas many larger corrosion pits appeared on the surface of the TSA film sealed at 25 °C. The improved corrosion resistance of the TSA film sealed at 65 °C could be attributed to the synergistic effect of cerium oxide deposition and the hydration reaction. The corrosion resistance of the TSA film sealed at 65 °C was significantly better than that of the film sealed with hot water, but it was still lower than that of the TSA film sealed with dichromate. [ABSTRACT FROM AUTHOR]

Mg-rare earth (RE) alloy, i.e., Mg-1Zn-1Gd (ZG11), was treated by a conventional pulse anodization process. The effect of electrical parameters (processing time, duty cycle and applied current) on the microstructure and corrosion resistance of anodized film was investigated by orthogonal method. SEM and XRD were used to characterize the microstructures and compositions of anodized films. Polarization curve, electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) were performed to evaluate the corrosion resistances of anodized samples. The results show that with the employment of appropriate electrical parameters, corrosion resistance of ZG11 alloy can be significantly enhanced (icorr decreases by nearly three orders of magnitude) after anodized for less than 2 min. Besides, the optimal sample selected from orthogonal experiments in terms of the thickness and porosity of anodized film appropriately matches with the sample with the best corrosion resistance determined by electrochemical corrosion measurements, indicating the strong relationship between the thickness and porosity of anodized film and its corrosion resistance. Additionally, results of cell proliferation tests demonstrate that the varied surface morphologies and microstructure characteristics of the anodized samples in the present study do not necessarily influence the related cytocompatibilities. The study helps to further understand the effect orders of different current parameters on the structure and properties of anodized film and therefore provides a high-efficiency and low-energy consumption way to manufacture Mg alloys with excellent corrosion resistances. [ABSTRACT FROM AUTHOR]

The reliable and durable corrosion protection of commercially attractive aluminum alloys like AA2024-T3 is the subject of world-wide intensive scientific research. Thus, the quality of the preliminary treatments and the coating primers is of key importance in this field. In this aspect, Anodic Aluminum Oxides (AAO) and Cerium Conversion Coatings (CeCC) appear to be the most perspective approaches for the formation of coating primers. The present systematic study offers results of a comparative elucidation of the properties of CeCC deposited under different regimes on AAO formed on the AA2024-T3 aircraft alloy. The formation of CeCC was performed either spontaneously, or under different electrochemical regimes. The samples were subjected to analyses that included: (i) preliminary color characterization and contact angle measurements, (ii) surface observations by optical metallographic (OMM) and scanning electron (SEM) microscopy, (iii) element distribution by means of Energy dispersive X-ray (EDX) and X-ray Photoelectron (XPS) spectroscopy and (iv) corrosion tests. The latter were performed by applying Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Scanning (PDS) after 24 h of exposure to a 3.5% NaCl model corrosive medium (MCM). For completeness, the experiments were extended to 672 h of exposure for the samples with superior barrier ability. The analysis of results obtained from the employed analytical techniques has revealed that spontaneous and cathodic depositions at low current densities are suitable for formation of uniform CeCC layers. Conversely, the application of higher current densities and alternating current (AC) or anodic deposition regimes had adverse effects. [ABSTRACT FROM AUTHOR]

In this work, ordered macropore arrays in n-type silicon wafers were fabricated by anodic etching using a double-tank electrochemical cell. The effects of the wafer thickness, etching time and voltage on the quality of macropore arrays were investigated. Homogeneous macropore arrays could be achieved in 200 μm thick silicon wafers, but could not be obtained from 300 and 400 μm thick silicon wafers. Highly ordered macropore arrays with an aspect ratio of 19 were fabricated in 200 μm thick n-type silicon at 4.5 V. The etching current decreases in 200 μm thick silicon but increases in thicker silicon with an increase in time. It demonstrates that the minority carrier transportation capability from the illuminated surface to the reactive surface is different for silicon wafers with different thicknesses. The minority carrier concentration at the illuminated surface for stable macropore formation and the current under different etching voltages were calculated based on a hole transport model. The results show that appropriately decreasing wafer thickness and increasing voltage can help stable macropore array fabrication in the illumination-limited double-tank cell. [ABSTRACT FROM AUTHOR]

Aluminum (Al) components of high quality often require an optimal ratio of lightness and favorable mechanical properties. In order to improve the physical-mechanical properties of Al, an aluminum oxide (Al2O3) film is usually formed on the surface of Al, which itself is characterized by high strength, hardness, corrosion resistance, and other technical properties. Unfortunately, depending on the conditions, the oxide film may be formed from different crystal phases on the Al surface, which are not always of desirable quality, i.e., the α-Al2O3 phase. The present review demonstrates that the properties of the Al2O3 film may be improved by Al processing with a laser beam according to the scheme: Al (Al alloy) → electrochemical anodizing → treatment with laser irradiation → α-Al2O3. Both Al substrate and the anodizing electrolyte affect the phase transformation of anodic Al2O3. Laser irradiation of the Al2O3 surface leads to high heating and cooling rates, which may promote the formation of a highly crystalline α-Al2O3 phase on anodic Al2O3. [ABSTRACT FROM AUTHOR]

The paper breaks the general concepts and shows that pore formation is possible in anodic aluminum barrier oxide by anodizing of pure Al, and also presents the results of electrochemical anodizing in boric acid and citrate buffer aqueous solutions of homogeneous binary alloys AlCu (4 wt.%), AlZn (3 wt.%) and AlAg (5.2 wt.% and 16.2 wt.%). Barrier anodizing allowed obtaining Al2O3 thin films doped with copper, zinc and silver. The anodizing behavior and the effect of anodic current density on the charge were studied, and scanning electron microscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses were performed. The doped alumina thin films, which are a mixture of Al2O3, Cu2O, ZnO, Ag2O, AgO and promising double metal oxides CuAlO2, AgAlO2 and ZnAl2O4, are promising for use as resistive switching, photoelectron, mechanical, photo-thermoelectric and fluorescence materials; sensors; and transparent conductive and photocatalyst films. [ABSTRACT FROM AUTHOR]

A biphasic anodic oxidation method for aromatic halogenation process was developed, where aqueous metal salts were directly used as halogen source. Ammonium salts serve as both electrolytes and phase transfer catalysis to facilitate anion transport and oxidative transformation. This design allows for chlorination or nitration of multiple types of arenes using NaCl or KNO2. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation (MAO) is one of the most effective techniques for producing ceramic coatings on metal surfaces and is widely used for metal surface modification. However, energy is wasted due to the dispersion of energy when handling large workpieces. Scanning micro-arc oxidation (SMAO) is a coating process developed based on conventional micro-arc oxidation, where electrode confinement is carried out during the scanning process thus saving energy. In this paper, SMAO is further investigated and simulated using simulation software, which greatly saves the experimental cost. The results show that increasing the number of scans increases the thickness of the micro-arc oxidized film, while the scanning speed is the opposite. Both anodic oxidation and passivation zones exist at the periphery of the SMAO region, the roughness of the SMAO film layer decreases from the center to the edge, and the anodic oxidation reaction mainly occurs at the edge zone of the discharge region. The thickness of the film layer is about 17 um in a single scan, and the thickness of the film layer can reach 50 um after several scans, and there is a porous structure on its surface, which is favorable for the adsorption and diffusion of gas molecules. The results show that SMAO is suitable for producing large-volume and large-area metal surface coating, and it is a feasible metal surface coating process. [ABSTRACT FROM AUTHOR]

In this work, the possibility of employing shot peening and laser peening as pre‐treatments to a tartaric–sulfuric anodizing process on the fatigue behavior of 7050‐T7451 aluminum alloy components was investigated. The surface modifications and stress fields induced by the combination of the peening and anodizing processes were evaluated by scanning electron microscopy and residual stress assessment methodologies based on diffraction techniques, respectively. It was found that the anodizing process alone results in a significant reduction in fatigue life compared to the as‐machined condition especially in the high‐cycle fatigue (HCF) region of the S–N diagrams due to the presence of defects within the anodic layer that act as stress concentrators facilitating the initiation of fatigue cracks. The application of both shot and laser peening treatments is demonstrated to offset the negative effects induced by anodizing, offering greater safety margins useful for the design of critical aeronautical structures. Highlights: The possibility to employ peening processes as pre‐treatments to anodizing was studied.No significant influence of anodizing on residual surface stresses was observed.SP and LP provide significant benefits in the fatigue behavior of anodized components.Thicker anodic layers result in greater susceptibility to fatigue crack nucleation. [ABSTRACT FROM AUTHOR]

Some heavy metals such as Pb, Cd, Hg and As are extremely hazardous to the human beings because of their non-biodegradable nature even at very low levels of exposure. Besides the standard methods such as Inductively Coupled Plasma (ICP)-Mass Spectrometry and ICP-Optical Emission Spectrometry, the other methods with fast, accurate and cheap requirements also need to be developed to detect these toxic heavy metals ions in aquatic sources. Recently the application of porous materials in the anodic stripping voltammetry has gained a great attention owing to high selectivity, sensitive and low cost. In the present study, a glassy carbon electrode (GCE) modified by ZnO- electrochemically reduced graphene oxide (ZnO/ErGO) was used for the electrochemical detection of Pd(II) and Cd(II). It is found that the surface area of ZnO/ErGO-GCE is 0.130 cm2 much larger than that of the bare GCE (0.083 cm2).The charge transfer resistance decreases significantly from 3212 Ω for the bare GCE to 924 Ω for ZnO/ErGO-GCE. These results manifest a fast electron transfer ratio of kinetics for the ZnO/ErGO-modified electrode. ZnO/ErGO-GCE exhibits excellent electrochemical performance towards the detection of Pb(II) and Cd(II) compared with ErGO-GCE and bare GCE. The peak current has a linear relationship with the Cd(II) and Pb(II) concentration in the 2.5–200 µM range. The limit of detection for Cd(II) and Pb(II) is 1.69 and 0.45 ppb, respectively. In addition, the electrochemical sensor exhibits excellent selectivity, stability, and repeatability in experimental studies, and it opens up great potential for detecting a trace amount of metals. [ABSTRACT FROM AUTHOR]

TNAs have been synthesized using a two-step anodization method by increasing the second-step voltages. The titanium (Ti) foil was used as the anode, and the first step of anodization layer was removed by sonication in the deionized water. The second anodization step was conducted using the same electrolyte but at a higher potential. The modification of the second-step voltage was discussed with correlation for the morphology and photoelectrochemical performance of TNAs. Increasing the second voltage of two-step anodization leads to a decrease in the bandgap of the anatase phase of TNAs at 3.09 eV. The highly ordered TNAs were formed by increasing the second-step voltage based on the Fast Fourier Transform (FFT) images with a higher regularity ratio (RR) with 30 V for 30 min in the first step and 40 V for 30 min in the second step. The tube length of TNAs was produced in a short time of anodization. The photocurrent density of TNAs prepared by increasing voltage in the second step is higher than that of the one-step anodization. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the surface characteristics and the inner close-to-surface characteristics of die-cast Al-Si-Cu alloy on the anodizing process under steady-state voltage and current modes. Samples of industrial-pressure die-cast aluminium–silicon alloy AlSi12Cu1(Fe) underwent anodization in as-die-cast surface conditions and after surface-grinding operations with material removal of 0.1, 0.5, and 1 mm. After surface grinding operations, the anodic layer thickness was significantly greater when subjected to a steady-state voltage of 35 V compared to that formed under a steady-state voltage of 20 V, showing an increase in the range of 2 to 2.5 times more than the thickness at 20 V. Additionally, anodizing under steady-state current mode (1.6 A·dm−2) yielded thicker layers compared to steady-state voltage mode (35 V, 1.6 A·dm−2 max) across all surface states (as-cast, ground). SEM-EDS analysis with element mapping revealed the subsequent effects of element distribution on anodic layer growth and structure. Grinding prior to anodization resulted in larger cavity sizes and lengths, attributed to microstructural variations induced by grinding. Grinding also exposed areas with slower solidification rates, fostering a homogeneous Al phase that facilitated enhanced oxide growth. Moreover, the formation of oxide was directly correlated with the presence of alloying elements, particularly silicon particles, which influenced the presence of the unanodized aluminium regions. [ABSTRACT FROM AUTHOR]

Titanium anodic memristors were prepared in phosphate buffer (PB) and citrate buffer (CB) electrolytes. Studying their I-U sweeps, the memristors presented self-rectifying and volatile behaviors. Transmission electron microscopic analysis revealed crystalline protrusions inside a semi-crystalline Ti oxide. Grounded in this, a hybrid interfacial memristive switching mechanism relaying on partial filaments was proposed. Moreover, both analyzed memristor types demonstrated multilevel switching capabilities. The memristors anodized in the PB and CB showed high-to-low resistance ratios of 4 × 104 and 1.6 × 102, respectively. The observed (more than two order of magnitude) ratio improvement of the PB memristors suggests their better performance, in spite of their modestly high resistive state instabilities, attributed to the thermal stress caused by consecutive switching. The endurance and retention of both the PB and CB memristors was measured over up to 106 cycles, indicating very good lifetimes. Phosphate incorporation into the anodic oxide was confirmed by photoelectron spectroscopy analysis and was related to the improved memristive behavior of the PB sample. The presence of phosphate inside the memristively active layer modifies the availability of free O species (vacancies and ions) in the oxide. Taking all this into consideration, Ti anodic memristors anodized in PB are emphasized as candidates for neuromorphic computing. [ABSTRACT FROM AUTHOR]

For the application of titanium and titanium alloys in orthopedic implant materials, the antibacterial properties and cell biocompatibility determine whether the implant surgery is successful. In this study, a functional anodic oxidation (AO) coating was successfully prepared to modify the surface of Ti-Ag alloy. The surface characteristics of the anodized Ti-Ag alloy were analyzed using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The corrosion characteristics of Ti-Ag samples were tested by an electrochemical workstation. In addition, the antibacterial properties and cell activity were studied by the plate count method and MC3T3-E1 cell staining. The results indicate that the AO process can generate a multi-functional TiO2/Ag2O coating with a large number of block and flower-like structures on the surface of a Ti-Ag alloy. When the AO voltage of the sample is 120 V, the maximum roughness is 0.73 μm and the minimum wetting degree is 23°, which improves the biocompatibility. The corrosion test results show that AO treatment can improve the corrosion resistance of a Ti-Ag alloy. The oxidation voltage is 20 V and the coating has the best corrosion resistance. The corrosion open circuit potential (Eocp) is 107.621 mV and the corrosion current density (icorr) is 2.241 × 10−8 A·cm−2. This coating can promote ion release and show more than 99% of a strong antibacterial ability against S. aureus. The results of the compatibility evaluation by cultured cells showed that the multifunctional coating formed by the anodic oxidation process did not cause cytotoxicity and promoted the adhesion of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

This research examines the influence of adding a commercial ionic liquid to the electrolyte during the electrochemical anodization of tungsten for the fabrication of WO3 nanostructures for photoelectrochemical applications. An aqueous electrolyte composed of 1.5 M methanesulfonic acid and 5% v/v [BMIM][BF4] or [EMIM][BF4] was used. A nanostructure synthesized in an ionic-liquid-free electrolyte was taken as a reference. Morphological and structural studies of the nanostructures were performed via field emission scanning electron microscopy and X-ray diffraction analyses. Electrochemical characterization was carried out using electrochemical impedance spectroscopy and a Mott–Schottky analysis. From the results, it is highlighted that, by adding either of the two ionic liquids to the electrolyte, well-defined WO3 nanoplates with improved morphological, structural, and electrochemical properties are obtained compared to samples synthesized without ionic liquid. In order to evaluate their photoelectrocatalytic performance, the samples were used as photocatalysts to generate hydrogen by splitting water molecules and in the photoelectrochemical degradation of methyl red dye. In both applications, the nanostructures synthesized with the addition of either of the ionic liquids showed a better performance. These findings confirm the suitability of ionic liquids, such as [BMIM][BF4] and [EMIM][BF4], for the synthesis of highly efficient photoelectrocatalysts via electrochemical anodization. [ABSTRACT FROM AUTHOR]

This study shows that the simple approach of keeping anodic TiO2 nanotubes at 70 °C in ethanol for 1 h results in improved photoelectrochemical water splitting activity due to initiation of crystallization in the material amplified by the light‐induced formation of a Ti3+−Vo states under UV 365 nm illumination. For the first time, the light‐induced Ti3+−Vo states are generated when oxygen is present in the reaction solution and are stable when in contact with air (oxygen) for a long time (two months). We confirmed here that the amorphous or nearly amorphous structure of titania supports the survival of Ti3+ species in contact with oxygen. It is also shown that the ethanol treatment substantially improves the morphology of the titania nanotube arrays, specifically, less surface cracking and surface purification from C‐ and F‐based contamination from the electrolyte used for anodizing. [ABSTRACT FROM AUTHOR]

The porous layer of FeCO3, as a main corrosion product in CO2 aqueous environments, has a critical influence on corrosion kinetics. However, multi‐physicochemical processes are involved in the evolution of the FeCO3 porous layer, such as homogeneous chemical reactions, multi‐component transport, and dissolution/precipitation at the solid–fluid interface, which is notoriously complicated to be totally understood. This study builds a numerical framework based on partial‐bounceback lattice Boltzmann method to investigate the reactive transport in the evolving porous layer. Experimental observations on polarization behavior confirm the model performance. Results show that the formation of a protective FeCO3 film is self‐promoted under anodic polarization in CO2‐saturated alkaline solutions and the "self‐promoted" effect is highly associated with local water chemistry at the interface. The interfacial FeCO3 supersaturation is several orders of magnitude higher than that of the bulk, while the interfacial concentrations of CO32− and HCO3− are slightly changed from bulk. The growing porous layer hinders Fe2+ from transporting away from the interface, promotes the precipitation of FeCO3, and further facilitates a denser film to inhibit anodic processes, which is another manifestation of the self‐promoted effect. [ABSTRACT FROM AUTHOR]