Subsequent Anodization Research Articles

Three-Dimensional Photonic Crystals Based on Porous Anodic Aluminum Oxide.

Photonic crystals (PCs) consisting of a periodic arrangement of holes in dielectric media have found success in light manipulation and sensing. Among them, three-dimensional (3D) PCs are in high demand due to their unique properties originating from multiple photonic band gaps (PBGs) and even full ones. Here, 3D PCs based on porous anodic aluminum oxide (AAO) were fabricated for the first time. Our approach involves prepatterning of the aluminum surface by a focused ion beam to form a hexagonal array of pore nuclei. Subsequent anodization in 1 M H3PO3 using a sine wave profile of voltage provides AAO with a defect-free in-plane porous structure and out-of-plane porosity modulation. The ability to tune the position, width, and depth of the PBGs is demonstrated. The combination of the flexibility of the proposed approach with the unique properties of AAO extends the range of practical applications of 3D PCs far beyond the current achievements.

Effect of chemical milling and anodizing on the high cycle fatigue behaviour of 2024-T3 aluminium alloy

Aluminium 2024-T3 alloy, widely employed in transport aircraft wing and fuselage skin structures, necessitates thickness reduction for weight optimization. Chemical milling is utilized for this purpose; however, it removes Cladding (as a standard corrosion protection layer), prompting subsequent anodizing and sealing to provide corrosion protection. Literature indicates that anodizing or chemical milling can significantly reduce fatigue life, and limited data have been available on the life of chemically milled anodized materials. In this study, constant amplitude stress-life (S-N) testing was performed on two sets of fatigue samples: Cladded Aluminium Alloy (CAA) 2024-T3 sheet specimens (1.6 mm thick) and chemically milled, anodized and sealed (CMAS-AA) Aluminum Alloy sheet specimens (1 mm thick). S-N curves were generated at R=0.1 and room temperature under stress control. SEM micrographs showed micropores in CMAS-AA and a standard plain surface in CAA, consistent with prior findings. Both types exhibited 3-5 times shorter fatigue life than electropolished samples, as reported in MIL Handbook HDBK-5J, highlighting the importance of corrosion protection techniques for structural integrity. Residual stresses were observed, with cladded samples displaying compressive and CMAS-AA exhibiting tensile stresses. Fractography revealed no abnormal fatigue fracture features, and computed plane stress fracture toughness values estimated using measured crack size from the failed specimens matched standard values of aluminium alloys.

Enhancing oxygen evolution functionality through anodization and nitridation of compositionally complex alloy

Compositionally complex materials (CCMs) have recently attracted great interest in electrocatalytic applications. To date, very few materials were systematically developed and tested due to the highly difficult preparation of high-surface-area CCMs. In this work, a surface of a compositionally complex FeCoNiCuZn alloy (CCA) was nitridated with subsequent anodization leading to morphological and compositional modifications. Notably, the electrochemical surface area and surface roughness as well as the electrocatalytic activity of the anodized material exhibit significant enhancement. Oxygen evolution reaction (OER) activity by the anodized CCN (CCN–AO) proceeds with remarkably small overpotential (233 mV) at 10 mA cm−2 in 1 M KOH. Experimental characterization indicates that the oxidation state of Co plays a critical role in the Fe–Co–Ni electrocatalyst. The developed approach and design strategy open up immense prospects in the preparation of a new, affordable, scalable and effective type of complex and high-performance electrocatalytic electrodes with tunable properties.

Electrochemical and surface characterization of anodized and fs-laser treated Ti6Al4V for osseo-repellent bone screws and dental implants

The surfaces of titanium grade 5 (Ti6Al4V) samples were altered on a micro and nano scale by femtosecond laser irradiation and subsequent electrochemical anodization. The produced micro-cones and nano-ripples covered by the additional oxide layer were characterised and their influence on osteoblast-like Saos-2 cell growth was studied. Surface topography and morphology were studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). From the wettability experiments, it was found that the contact angle vs. roughness follows the Wenzel equation and that the wettability increases after the anodization. The composition of the formed oxide layer was determined by X-ray photoelectron spectroscopy (XPS) and oxide incorporation of phosphate ions could be confirmed. Moreover, estimated electrochemical surface area (ECSA) of the femtosecond laser treated sample was 14 times larger compared to a polished sample. The anodic oxide film formation factors for different electrolytes were determined and were in the range of 1.3 nm V−1–2.0 nm V−1. Finally, the samples anodized with 0.1 M H2SO4 and 3 M H3PO4 showed decreased Saos-2 cell growth.

Fabrication of Ideally Ordered Anodic Porous Alumina on Glass Substrates by Stamping Process Using Flexible Stamps

Establishing a process to fabricate anodic porous alumina with an ordered array of uniform-sized pores on a substrate is an important challenge of fabricating various functional devices. In this study, ordered anodic porous alumina was fabricated on glass substrates by a stamping process using a flexible stamp. This process enables the formation of a resist mask at a low pressure on the sample surface to pattern the starting point for pore generation during anodization. Therefore, it is possible to pattern samples without breaking the glass substrate, and subsequent anodization can generate ordered anodic porous alumina on the substrate. The stamping process using flexible stamps can be applied regardless of the roughness of the Al film on a substrate because the stamp deforms according to the Al surface shape, even when there is a protruding structure on the Al surface. In addition, it was shown that this process could be used to form ordered anodic porous alumina even on Al surfaces with three-dimensional curvatures, such as convex lenses.

Anodizing aluminum in a viscous electrolyte to produce one-dimensional photonic crystals

In the paper, the possibility to produce anodic aluminum oxide (AAO) featuring one-dimensional photonic crystal along the normal to the surface is shown. The AAO structure is represented by alternating layers of different porosity and is formed in a viscous electrolyte based on sulfuric acid and ethylene glycol at the periodically varying from high (1.8 mA/cm2) to low (0.4 mA/cm2) current density with a rectangular pulse shape. The pore sizes and interpore distance, pore density and porosity, thickness and period of the AAO structure have been determined. The specular reflection spectra features for single layers that make up the AAO structure and for one-dimensional photonic crystals structures consisting of 165 periods have been studied. An increase in the porosity of the upper layers of the structure due to chemical etching of the pores during the oxide growth is noted. It is shown that the invariance of the spectral position of the photonic band gap for AAO structures is achieved by a 0.1 % decrease in charge at each subsequent anodizing cycle during their formation, which leads to a decrease in the period of the structure in the lower layers, compensating for the increase in the upper layers porosity. The reflection spectra have been analyzed for the incidence angles of 10° and 30° and used to calculate the period of the structure and the effective refractive index. The effective refractive index of the single layers that make up the AAO structure is calculated using the optical Fabry–Perot oscillations. For AAO with the properties of one-dimensional photonic crystal, a green color is observed at normal light incidence, and an iridescent color is observed when the angle changes. AAO can be used as a decorative coating on the housings of electronic devices (tablets, laptops, phones, etc.) and when creating design objects made of aluminum and its alloys.

Concomitant abatement of ciprofloxacin, sulfamethoxazole and cefadroxil in synthetic wastewater using hybrid photoelectrochemical ozonation driven on TiO2 containing C, N and P species

Ciprofloxacin (CIP), sulfamethoxazole (SMX) and cefadroxil (CFX) are herein degraded in synthetic wastewater (SWW) composed of 20 mg L−1 of each pharmaceutical compound, Na2SO4, MgSO4 and biodegradable organic matter. Photoelectrocatalytic ozonation (PECO) is used to generate multiple routes of oxidizing agents (i.e. ●OH), attacking the recalcitrant pollutants, and compared against individual oxidation processes: ozonation (O3), photolysis (PH) and photoelectrocatalysis (PEC). A TiO2 electrode with N, P and C incorporated in its structure (CNP-TiNST) is synthesized throughout two subsequent anodization methods: a first electrolyte made up of ethylene glycol and ethylenediamine as C and N sources, and a second electrolyte containing phosphoric acid to introduce P. The synthesized electrode presents a significant absorption in the visible light region, according to the Diffuse Reflectance Spectroscopy (DRS) analysis, obtaining two band gaps with values of 1.62 and 2.79 eV, which are considerably reduced in the pristine TiO2 phase. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) evaluations indicate the formation of mostly anatase phase and heterogeneous short nanostructures, respectively. XPS study reveals Ti-O, Ti-C and Ti-N bonds, confirming its successful incorporation into the photoanode. A photo-current density of 0.35 mA cm−2 is reached by the photoelectrode under Xe lamp irradiation while applying 1 V of potential vs Ag/AgCl. Contaminant removals in all systems are monitored by UV-Vis spectroscopy, High-Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC). The highest degree of contaminant removal in SWW occurs with the PECO process (80% according to HPLC analysis), decreasing TOC by 43% in SWW; and 98% TOC removal of these pollutants in distilled water, after 240 min of treatment. A germination toxicity test is performed on Lettuce Sativa, where 100% germination is achieved in the seeds grown in the treated SWW using PECO.

New insight into anodization of aluminium with focused ion beam pre-patterning

The self-ordered anodic aluminium oxide (AAO) structure consists of micron-scale domains—defect-free areas with a hexagonal arrangement of pores. A substantial increase in domain size is possible solely by pre-patterning the aluminium surface in the form of a defect-free hexagonal array of concaves, which guide the pore growth during subsequent anodization. Among the numerous pre-patterning techniques, direct etching by focused gallium ion beam (Ga FIB) allows the preparation of AAO with a custom-made geometry through precise control of the irradiation positions, beam energy, and ion dosage. The main drawback of the FIB approach includes gallium contamination of the aluminium surface. Here, we propose a multi-step anodizing procedure to prevent gallium incorporation into the aluminium substrate. The suggested approach successfully covers a wide range of AAO interpore distances from 100 to 500 nm. In particular, anodization of FIB pre-patterned aluminium in 0.1 M phosphoric acid at 195 V to prepare AAO with the interpore distance of about 500 nm was demonstrated for the first time. The quantification of the degree of pore ordering reveals the fraction of pores in hexagonal coordination above 96% and the in-plane mosaicity below 3° over an area of about 1000 μm2. Large-scale defect-free AAO structures are promising for creating photonic crystals and hyperbolic metamaterials with distinct functional properties.

Nanostructured Superhydrophobic Titanium-Based Materials: A Novel Preparation Pathway to Attain Superhydrophobicity on TC4 Alloy.

This study develops the nanostructured superhydrophobic titanium-based materials using a combined preparation method of laser marking step and the subsequent anodizing step. The structural properties were determined using an X-ray diffractometer (XRD) and scanning electron microscope (SEM), while the performance was explored by wear and corrosion tests. The laser marking caused a rough surface with paralleled grooves and protrusions, revealing surface superhydrophobicity after organic modification. The anodizing process further created a titanium oxide (TiO2) nanotube film. Both phase constituent characterization and surface elemental analysis prove the uniform nanofilm. The inert nanosized oxide film offers improved stability and superhydrophobicity. Compared to those samples only with the laser marking process, the TiO2 nanotube film enhances the corrosion resistance and mechanical stability of surface superhydrophobicity. The proposed preparation pathway serves as a novel surface engineering technique to attain a nanostructured superhydrophobic surface with other desirable performance on titanium alloys, contributing to their scale-up applications in diverse fields.

Preparation of Ideally Ordered Anodic Porous Alumina by Prepatterning Process Using a Flexible Mold

Ideally ordered anodic porous alumina with controlled interpore distances was formed by fabricating a resist mask using a flexible mold and subsequent anodization. Prior to forming the resist pattern on the surface of an Al substrate, Al was pre-anodized at 10 V to prepare the fine porous structure, which acts as a resist adhesive layer. After the formation of the resist mask using a flexible mold, an arranged array of cavities with Al exposed at the bottom was formed by the selective dissolution of the oxide layer at resist openings. The subsequent anodization of the sample with the cavity array generated ideally ordered anodic porous alumina because alumina holes were formed at the bottom of cavities during anodization. This process allows the preparation of ideally ordered anodic porous alumina even on a curved Al surface owing to the flexibility of the mold. In addition, this process can also be applied to the preparation of an ideally ordered anodic porous alumina with a large sample area because the Al substrate can be patterned without high pressure. The obtained sample can be used for various applications requiring an ideally ordered hole array structure.

Differences between the untreated and treated diffusion zone in the Alclad 2024-T3 aluminum alloy and hard anodic films

Chemical treatment with NaOH, followed by HNO 3 is commonly performed during the surface preparation of aluminum alloys for their subsequent anodization. In the present work, the properties of the diffusion zone of Alclad 2024-T3 aluminum alloy and its hard anodic films without/with preliminary chemical treatment were examined. The studied surfaces were characterized morphologically, compositionally, and electrochemically to determine the changes caused by the treatment procedure. The obtained results revealed that the untreated diffusion zone exhibited a heterogeneous surface distribution of intermetallic compounds mostly containing silicon, copper, and magnesium elements, due to the presence of 1230 cladding and 2024-T3 core in the diffusion zone of Alclad 2024-T3 aluminum alloy. Furthermore, the non-treated hard anodic films had pores with angular shape and contained additional corundum and diasporic crystalline structures. While chemical treatment with NaOH, followed by HNO 3 removed many intermetallic compounds or partially dissolved them, silicon atoms were preferentially eliminated making the alloy magnesium-rich, and the hard anodic films had pores with circular shape and completely amorphous. Finally, both films possessed a predominance of dielectric behavior, with minor p-type semiconducting contributions due to Al–Si–O intermetallic compounds. • Chemical treatment with NaOH followed by HNO 3 enriches the surface with Mg and eliminates Si in the diffusion zone. • The diffusion zone of Alclad 2024-T3 alloy favors the incorporation of Si, Mg, Fe, Zn to anodic film surfaces. • Avoiding the chemical treatment gives angular pores and more crystalline hard anodic films. • Chemical treatment favors higher charge and capacitance in the anodizing process and a more orderly porous layer.

Improving the Specific Surface Area of Etched Aluminum Foil by Fabricating the Micro/Nano Structure

Aluminum foil with micro/nano structure has been prepared by electrochemical DC etching and a subsequent anodization treatment followed by removal of the alumina film. When the micron-sized tunnels were generated on the etched aluminum foil, the size and distribution of the nano-concave formed on the sidewall of the etched tunnels varied with the anodized time in H2SO4 and C4H6O6 electrolyte. The optimal value of the specific surface area for the aluminum foil with micro/nano structure is approximately four times larger than that of the only etched aluminum foil. It is indicated from the chronoamperometry and BET measurements that the specific capacitance of aluminum foil with micro/nano structure can be significantly improved by suitable anodization in H2SO4 electrolyte, in comparison with a comparatively small increasement in C4H6O6 electrolyte. This can be attributed to the fact that the tardy anodization process will consume a considerable amount of aluminum substrate, resulting in the aggravation of the merged tunnels.

Ideally Ordered Anodic Porous Alumina on Si Substrate Prepared by Anodization of Sputtered Al–Mg Thin Film

Anodic porous alumina with an ideally ordered hole arrangement was formed on a Si substrate by nanoimprinting and subsequent anodization. In this process, the arrayed shallow dimples formed by nanoimprinting using a mold act as initiation sites of hole development during the anodization. To realize the precise transfer of the mold patterns to the Al surface during nanoimprinting, we used sputtered Al alloy film as a starting material. This is because the Al alloy with appropriate impurities as a sputtering target can suppress the crystal grain growth during sputtering and allow the formation of Al alloy films with smooth surfaces on the substrate. Dimple arrays with 100 nm intervals could be formed on the flat surface of the Al–Mg film on the Si substrate. Ideally ordered anodic porous alumina with an interpore distance of 100 nm was successfully obtained by subsequent anodization. A Co/alumina composite was also obtained by the electrodeposition of Co into the alumina holes. The obtained samples are expected to be applied to various functional devices requiring an ideally ordered structure on a substrate.

Effect of Interface Pretreatment of Al Alloy on Bonding Strength of the Laser Joined Al/CFRTP Butt Joint.

In the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and bonding strength of the corresponding Al/CFRTP butt joint were investigated. The results show that the laser micro-texturing has fabricated the micro-pit or micro-furrow in the Al joining interface. With the increasing of laser scanning times, the size of the micro-pit or micro-furrow decreases, when the laser scanning distance is constant. The bonding strength of the Al/CFRTP butt joint with Al joining interface pretreated by micro-texturing fluctuates with the increasing of laser scanning distance and times, reaching the maximum value of 20 MPa at laser scanning distance of 0.1 mm and 1 time. The anodizing pretreatment has formed the Al2O3 oxide layer on the Al joining interface. The Al/CFRTP butt joint with Al joining interface pretreated by anodizing obtains the maximum bonding strength of 11 MPa at anodizing time of 10 min. The hybrid pretreatment of micro-texturing and subsequent anodizing fabricates the regular grid structure with smooth micro-furrow and micro-pit, while the hybrid pretreatment of anodizing and subsequent micro-texturing fabricates the Al joining interface with explosive micro-pit and micro-furrow. The bonding strength of the Al/CFRTP butt joint with hybrid-pretreated Al joining interface is relative better than that of the Al/CFRTP butt joint with anodizing-pretreated Al joining interface but almost lower than that of the Al/CFRTP butt joint with micro-texturing pretreated Al joining interface. Such results should be attributed to the surface morphology of the Al joining interface.

Drug release from polymer-coated TiO2 nanotubes on additively manufactured Ti-6Al-4V bone implants: a feasibility study

Insufficient osseointegration, inflammatory response and bacterial infection are responsible for the majority of bone implant failures. Drug-releasing implants subjected to adequate surface modification can concurrently address these challenges to improve the success of implant surgeries. This work investigates the use of Ti-6Al-4V (Ti64) with a dual-scale surface topography as a platform for local drug delivery. Dual-scale topography was obtained combining the inherent microscale roughness of the Ti64 samples manufactured by selective laser melting (SLM) with the nanoscale roughness of TiO2 nanotubes (TNTs) obtained by subsequent electrochemical anodization at 60 V for 30 min. TNTs were loaded with a solution of penicillin-streptomycin, a common antibiotic, and drug release was tested in vitro. Three biocompatible and biodegradable polymers, i.e. chitosan, poly(ε-caprolactone) and poly(3-hydroxybutyrate), were deposited by spin coating, while preserving the microscale topography of the substrate underneath. The presence of polymer coatings overall modified the drug release pattern, as revealed by fitting of the experimental data with a power-law model. A slight extension in the overall duration of drug release (about 17% for a single layer and 33% for two layers of PCL and PHB) and reduced burst release was observed for all polymer-coated samples compared to uncoated, especially when two layers of coatings were applied.

Highly ordered anodic porous oxides of transition metals fabricated by anodization combined with a pretexturing process

In this study, highly ordered anodic porous metal oxides of transition metals (W, Fe, Co, and Nb) were prepared by anodization combined with a pretexturing process. The formation of an array of dimples on the metal surface was achieved by dry etching using ordered anodic porous alumina as a mask. Subsequent anodization of the pretextured metals generated metal oxides (WO3, Fe2O3, Co3O4, and Nb2O4) with an ordered hole array structure because each dimple acted as a starting point for hole development. The hole periodicity of the resulting ordered anodic porous metal oxide could be controlled by changing the periodicity of the dimples formed on the substrate. Ordered anodic porous films obtained by this process could be used in various functional devices that require ordered hole array structures.

Metalizadora Construída em Laboratório: Deposição de Filme de Alumínio sobre Substrato de Vidro e Posterior Anodização para Obtenção de Óxido de Alumínio

In this work, the assembly of a low-cost metallizer is presented, based on physical vapor deposition, to obtain metallic aluminum film deposited over a glass substrate. Later, the Al film is anodized and converted into a porous nanostructured oxide film. The metallic film thickness was measured by profilometry, and the sample position inside the chamber was evaluated. Samples positioned at the center of the sample holder showed considerable thickness and best homogeneity compared to those samples positioned at the edges of the sample holder. A thick metallic film of Al (6 to 7 µm) was deposited over the glass substrate for subsequent anodizing treatment. Mild anodization allowed the total conversion of metallic Al after 7000 s, producing a transparent anodic aluminum oxide (AAO) film adhered to the glass substrate. The AAO morphology was investigated by SEM. Some factors have been listed to describe the low regularity and homogeneity of nanopores in the outer layer of AAO, such as internal defects, compaction of deposited Al film layers and the glass substrate roughness.

Structure – Reactivity - Relationship in Nanostructured and Amorphous Aluminium Lanthanoid Material Libraries

The lanthanoids are a consequent series of elements and with their 3 valence electrons they prefer the trivalent state while continuously filling the inner f-shell. A specific energetically stabilizing effect is observed so that the empty, the half-filled or the completely filled f-shell show extraordinary low energies resulting in a stabilizing effect so that neighboring valence states such as divalent or tetravalent can be also observed. Interestingly with increasing atomic number the atomic and ionic radii decrease - counter intuitively. As a result of the electronic shielding effect of the f-electrons the so-called lanthanoid contraction is observed.Aluminium is another element that forms preferentially trivalent ions. A combinatorial approach in which aluminium-lanthanoid-alloys are investigated both in terms of the alloy itself but in particular for the passivity based on the mixed oxides forming on these alloys is presented here. A complex attempt was made not only to cover the various elements themselves but also their concentration ratios in material thin film libraries. These material libraries are prepared in a large preparation and analysis cluster the so-called CALMAR. Asymmetrical physical codeposition of the constituting elements is used in HV and UHV chambers to prepare these libraries and to characterize them by a scanning EDX system as well as XRD.Theoretical considerations were used to compute the Pourbaix diagrams. Also phase diagrams of the Al-Lx alloys are consulted to identify intermetallics and regions of solid solution mixing.Passivation studies were performed using a flow type scanning droplet cell microscope FT-SDCM. This method allows the subsequent stepwise anodization and electrochemical impedance spectroscopy characterisation of a single spot of a library having a single composition. Spatial scanning of the library yields detailed information of the systematically changing alloy compositions. To understand not only the anodic oxide formation but also the chemical and electrochemical reactions during anodization a complementary investigation of the electrolyte is performed using inductively coupled plasma spectrometry.Various lanthanoids were mixed with aluminium and electrochemically studied. It is found that the large ionic radii mismatch is likely to cause strong amorphisation. In this way already binary alloys were found to form metallic glasses in some regions i.e. for some compositions. This has a strong impact on the passivation behavior and electrochemical stability. Some distinct intermetallic compounds in these binary alloys were found with the expected consequence for the stability.

Ti–5Al–5Mo–5V–3Cr bone implants with dual-scale topography: a promising alternative to Ti–6Al–4V

Modifications to the compositional, topographical and morphological aspects of bone implants can lead to improved osseointegration, thus increasing the success of bone implant procedures. This study investigates the creation of dual-scale topography on Ti–5Al–5Mo–5V–3Cr (Ti5553), an alloy not presently used in the biomedical field, and compares it to Ti–6Al–4V (Ti64), the most used Ti alloy for bone implants. Dual-scale surface topography was obtained by combining selective laser melting (SLM) and electrochemical anodization, which resulted in micro- and nanoscale surface features, respectively. Ti5553 and Ti64 samples were manufactured by SLM and showed comparable surface topography. Subsequent electrochemical anodization succeeded in forming titania nanotubes (TNTs) on both alloys, with larger nanotubes obtained with Ti5553 at all investigated anodization voltages. At an anodization voltage of 40 V, a minimum time of 20 min was necessary to have nanotube formation on the surface of either alloy, while only nanopores were evident for shorter times. Seeded Saos-2 cells showed ideal interactions with surface-modified structures, with filopodia extending to both surface microparticles characteristic of SLM and to the interior of TNTs. Attractiveness of Ti5553 lies in its lower elastic modulus (E = 72 GPa) compared to Ti64, which should mitigate stress-shielding phenomena in vivo. This, combined with the analogous results obtained in terms of dual-scale surface topography and cell-substrate interaction, could indicate Ti5553 as a promising alternative to the widely-employed Ti64 for bone implant device manufacturing.

Inverse‐direction Growth of TiO2 Microcones by Subsequent Anodization in HClO4 for Increased Performance of Lithium‐Ion Batteries

AbstractThe effect of second anodization on anodically fabricated TiO2 microcones is investigated with the aim of enhancing the lithium‐ion battery performances; these microcones are treated with a trace concentration of an electrolyte of HClO4. Unlike in the case of second anodization in H2SO4 or H3PO4, which leads to breakdown of the structures of the microcones, the HClO4‐treated TiO2 microcones maintain their unique morphological crystalline structures; this enables the inverse growth of an oxide layer. Particularly, protruding nanoparticles provide a large surface area and thus a higher areal capacity, wherein lithium ions can be stored; these particles are formed on the back‐hemisphere layers of the microcones with an increase in the overall thickness of the barrier oxide layer. The HClO4‐treated TiO2 microcones exhibit an areal capacity of approximately 1.6 times than that of pristine TiO2 microcones as well as an excellent cycling stability and capacity retention.