Preparation of Porous Alumina Film on Aluminum Substrate by Anodization in Oxalic Acid

Self-ordering of the cell arrangement of the anodic porous alumina was prepared in oxalic acid solution at a constant potential of 40V and at a temperature of 20C. The honeycomb structure made by one step anodization method and two step anodization method is different. Pores in the alumina film prepared by two step anodization method were more ordered than those by one step anodization method.

Effect of Anodization on the Graphitization of PAN-based Carbon Fibers of PAN-based Carbon Fibers

One-step pretreatment,anodization,is used to activate the polyacrylonitrile （PAN）-based carbon fibers instead of the routine two-step pretreatment,sensitization with SnCl2 and activation with PdCl2.The effect of the anodization pretreatment on the graphitization of PAN-based carbon fibers is investigated as a function of Ni-P catalyst.The PAN-based carbon fibers are anodized in H3PO4 electrolyte resulting in the formation of active sites,which thereby facilitates the following electroless Ni-P coating.Carbon fibers in the presence and absence of Ni-P coatings are heat treated and the structural changes are characterized by X-ray diffraction and Raman spectroscopy,both of which indicate that the graphitization of PAN-based carbon fibers are accelerated by both the anodization treatment and the catalysts Ni-P.Using the anodized carbon fibers,the routine two-step pretreatment,sensitization and activation,is not needed.

Fast Growth of Highly Ordered TiO2 Nanotube Arrays on Si Substrate under High-Field Anodization

Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field(90–180V) anodization method to grow highly ordered TiO_2 NTAs on Si substrate,and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO_2 NTAs. The current density–time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO_2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields(40–60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.

Formation of TiO_(2) Nanotube Layer by Anodization of Titanium in Ethylene Glycol-H_(2)O Electrolyte

In orthopaedics and orthodontics, the growth of nanotubes of titanium oxide on titanium implants is a promising route for improving the osseointegration. Among the fabrication routes to produce nanotubes, anodization was generally preferred due to its simplicity and low cost. TiO2 nanotubes are formed by the simultaneous anodic reaction and chemical dissolution due to the fluoride species present in the anodization bath. In this work, the formation of TiO2 nanotubes was studied in stirred ethylene glycol-H2O electrolyte (90 - 10 v/v) containing NH4F at room temperature. In order to study the effect of NH4F concentration, voltage and anodization time, and to reduce the number of experiments, a design of experiments (DOE) based on a 2k factorial design with four replicates at the center point was used. The analysis of variance (ANOVA) was used to evaluate the effects of the factors of control and their interactions on the percentage of the titanium surface coated by nanotubes. The dimensions of nanotubes (length and diameter) were also evaluated using field emission gun scanning electron microscopy. The cristallinity and phase composition of the oxide layers was investigated by X-ray diffractometry. The electrochemical behavior of as-received and anodized titanium specimens was studied in Ringer’s solution. The statistical analysis showed that fluoride concentration is the most significant factor. The best condition according to the response surface analysis is the center point (1% NH4F, 20 V, 2 h). The nanotubular oxide layers presented an amorphous structure. Electrochemical tests showed that TiO2 nanotubes coated titanium is less corrosion resistant than as-received titanium.

STUDY OF THE ANODIZATION OF Al FILM ON InP SUBSTRATE AND ITS PROPERTIES

The anodization of Al film on InP substrate and properties of anodic Al2O33/InPhave been investigated by AES,DLTS,I-V,C-V and ellipsometer.The results show that theanodic oxide Al2O3 has a permittivity of 11～12 and a resistivity of 1.3×1013 ohm-cm.Interfacestate density at Al2O3/InP is about 1011 cm-2·eV-1.DLTS reveals that there is a continuouslydistributed interface electron traps at Al2O3/InP interface.Anodic Al2O3 exhibits good stabilityand electrical properties and could be used for passivation,diffusion mask and gate insulator,etc.

Two-Step Anodization of Maltilayer TiO_2 Nanotube and Its Photocatalytic Activity under UV Light

A double-layer TiO2 nanotube arrays were formed by two-step anodization of Ti foils in different electrolytes. First, Ti in 0.5 wt% HF was anodized to form thin nanotube layer. Afterwards a second anodization was conducted in a formamide based electrolyte, which allowed the second layer of nanotube growing directly underneath the first one. From FESEM investigation we found that the thickness of second layer corresponded to the anodization time, the increasing of which would lead to the excessive etching on the first layer. The first layer protected the lower one from fluoride corrosion during anodization process. The double layer TiO2 nanotube arrays showed no benefit to photodegradation effect in methyl orange degradation experiments.

Temporal Evolution of Anodization Current of Porous Silicon Samples

Temporal evolution of the anodization current of porous silicon samples was studied by means of a model of resistances connected in series that represented the temporal changes of the substrate and of the interface between the substrate and the electrolyte during the porous sample formation process. The porous samples were obtained by means of photoelectrochemical etching of (100) n-type silicon wafers with different resistivity values, all in the range of 1 - 25 Wcm. The samples were formed at room temperature in an electrolytic bath composed by a mixture of hydrofluoric acid (48%) and ethanol having a composition ratio of 1:1 in volume under potentiostatic condition (10 V and 20 V) and an etching time of 2 minutes using back illumination provided by a laser beam with a wavelength of 808 nm.

Ultrasonic Corrosion-Anodization: Electrochemical Cell Design and Process Range Testing

Titanium was used in the present work as the test metal for the first ultrasonic corrosion anodization (UCA) study, because of its important photonics and biomedical applications. The electrochemical cell design was implemented and tested under various experimental conditions combinations (e.g. electrolyte concentration, duration, temperature, ultra-sound presence or absence, oxygen presence, etc) in order to investigate the effect of those parameters in the cracks propagation in Ti-foils. It was found that an increase of cracks takes place when oxygen is provided in the electrolyte solution and when ultrasound is applied. The results presented in the current study could be exploitable towards design of materials having dendritic morphologies, applicable in a wide range of processes from photovoltaics to biocompatible materials.

Electrochemical anodization of cast titanium alloys in oxalic acid for biomedical applications

Titanium and its alloys have numerous biomedical applications thanks to the composition and morphology of their oxide film.In this study,the colorful oxide films were formed by anodizing cast Ti-6Al-4V and Ti-6Al-7Nb alloys in a 10%oxalic acid solution for 30 s at different voltages(20–80 V)of a direct current power supply.Atomic force microscopy was used as an accurate tool to measure the surface roughness of thin films on the nanometer scale.Scanning electron microscopy and X-ray diffraction were performed to analyze surface morphology and phase structure.According to the results,the produced titanium oxide layer showed high surface roughness,which increased with increasing anodizing voltage.The impact of anodizing voltages on the color and roughness of anodized layers was surveyed.The corrosion resistance of the anodized samples was studied in simulated body fluid at pH 7.4 and a temperature of 37℃ utilizing electrochemical impedance spectroscopy and the potentiodynamic polarization method.The anodized samples for both alloys at 40 V were at the optimal voltage,leading to a TiO_(2) layer formation with the best compromise between oxide thickness and corrosion resistance.Also,findings showed that TiO_(2) films produced on Ti-6Al-7Nb alloys had superior surface roughness properties compared to those of Ti-6Al-4V alloys,making them more appropriate for orthopedic applications.From the obtained data and the fruitful discussion,it was found that the utilized procedure is simple,low-cost,and repeatable.Therefore,anodization in 10%oxalic acid proved a viable alternative for the surface finishing of titanium alloys for biomedical applications.

Single-step nano-engineering of multiple micro-rough metals via anodization

Anodization is a cost-effective technique to nano-engineer various metals,however,optimizations have been mostly restricted to Al and Ti,and for easy to manage polished and flat substrates,limiting industrial translation.Here,we aim at standardizing and simplifying anodization of ten metals,attempting to make metal nano-engineering more accessible.In a world-first attempt,we synthesize a standard electrolyte to fabricate controlled nanostructures on various metals,taking a close look at the influence of the substrate topography,electrolyte composition,and electrolyte aging(repeated use of same electrolyte)towards designing a standard nano-engineering strategy.Anodization of curved substrates(metal wires)with micro-roughness allows for ease of industrial translation across various applications.This study is a step closer to standardizing anodization and fabrication of controlled nanotopography on various metallic surfaces,while maintaining scalability and ease of use.

Corrosion protection of magnesium alloys anode by cerium-based anodization coating in magnesium-ait battery

CeN_(3)O_(9)·6H_(2)O(0.5,1.0,1.5,and 2.0 g/L)was added into an 8.0%NaCl electrolyte solution to investigate this electrolyte for use in a Mg-air battery.The effects of the amount of CeN_(3)O_(9)-6H_(2)O on the corrosion resistance of an AZ31 Mg alloy anode and battery performance were investigated using microstructure,electrochemical(dynamic potential polarization method and electrochemical impedance spectroscopy),and battery measurements.The re sults show that the addition of CeN_(3)O_(9)·6H_(2)O to the electrolyte leads to the formation of a Ce(OH)_(3)protective film on the surface of the AZ31 Mg alloy that improves the corrosion resistance of the Mg alloy.An increase in the concentration of CeN_(3)O_(9)·6H_(2)O results in a denser Ce(OH)_(3)protective film and decreases corrosion rate of the AZ31 Mg alloy.When the concentration of CeN_(3)O_(9)·6H_(2)O is 1.0 g/L,the corrosion rate of the Mg alloy is the lowest with a corrosion inhibition rate of70.4%.However,the corrosion rate increases due to the dissolution of the Ce(OH)_(3)protective film when the concentration of CeN_(3)O_(9)-6H_(2)O is greater than 1.0 g/L.Immersing the Mg alloy in the electrolyte solution containing CeN_(3)O_(9)-6H_(2)O for 50 h leads to the formation of the Ce(HO)_(3)protective film on its surface,which was confirmed by scanning electron microscopy of the AZ31 alloy.The Mg^(2+)charge transfer resistance increases by 69.5Ωfrom the equivalent circuit diagram,which improves the corrosion resistance of the Mg alloy.The discharge performance of CeN_(3)O_(9)·6H_(2)O improves according to a discharge test,and the discharge time increases by 40 min.

Facile anodization approach derived low-crystalline NiCoeOH/NiCoOOH composite films for ultra-high areal capacity and mass loading supercapacitors

The design of supercapacitor materials with both high areal capacity(C)and high mass loading is vitally important for enhancing energy density(E).Herein,we prepared a NiCosingle bondOH/NiCoOOH composite film consisting of NiCosingle bondOH/NiCoOOH nanosheets on an expanded graphite paper(EGP)by using a facial anodization method.The as-prepared NiCosingle bondOH/NiCoOOH film exhibits ultra-high C of 11 mA·h·cm^(-2)at a mass loading of 165 mg·cm^(-2),high rate capability of 71%and excellent cycling stability of 95%after 12000 cycles.The outstanding performance is ascribed to the low-crystalline feature of the NiCosingle bondOH/NiCoOOH nanosheets,and the synergistic effect of the NiCosingle bondOH and NiCoOOH phases and high conductive porous EGP.An aqueous asymmetric supercapacitor,assembled with the NiCosingle bondOH/NiCoOOH on EGP and Fe_(2)O_(3)on EGP as positive-and negative-electrode,respectively,shows a highest E of 3.8 mW·h·cm^(-2)at a power density(P)of 4 mW·cm^(-2)and a maximum P of 107 mW·cm^(-2)at an E of 2.7 mW·h·cm^(-2).

Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium‑Ion Battery Anode

With graphite currently leading as the most viable anode for potassium-ion batteries(KIBs),other materials have been left relatively underexamined.Transition metal oxides are among these,with many positive attributes such as synthetic maturity,longterm cycling stability and fast redox kinetics.Therefore,to address this research deficiency we report herein a layered potassium titanium niobate KTiNbO5(KTNO)and its rGO nanocomposite(KTNO/rGO)synthesised via solvothermal methods as a high-performance anode for KIBs.Through effective distribution across the electrically conductive rGO,the electrochemical performance of the KTNO nanoparticles was enhanced.The potassium storage performance of the KTNO/rGO was demonstrated by its first charge capacity of 128.1 mAh g^(−1) and reversible capacity of 97.5 mAh g^(−1) after 500 cycles at 20 mA g^(−1),retaining 76.1%of the initial capacity,with an exceptional rate performance of 54.2 mAh g^(−1)at 1 A g^(−1).Furthermore,to investigate the attributes of KTNO in-situ XRD was performed,indicating a low-strain material.Ex-situ X-ray photoelectron spectra further investigated the mechanism of charge storage,with the titanium showing greater redox reversibility than the niobium.This work suggests this lowstrain nature is a highly advantageous property and well worth regarding KTNO as a promising anode for future high-performance KIBs.

An Electrochemical Perspective of Aqueous Zinc Metal Anode

Based on the attributes of nonflammability,environmental benignity,and cost-effectiveness of aqueous electrolytes,as well as the favorable compatibility of zinc metal with them,aqueous zinc ions batteries(AZIBs)become the leading energy storage candidate to meet the requirements of safety and low cost.Yet,aqueous electrolytes,acting as a double-edged sword,also play a negative role by directly or indirectly causing various parasitic reactions at the zinc anode side.These reactions include hydrogen evolution reaction,passivation,and dendrites,resulting in poor Coulombic efficiency and short lifespan of AZIBs.A comprehensive review of aqueous electrolytes chemistry,zinc chemistry,mechanism and chemistry of parasitic reactions,and their relationship is lacking.Moreover,the understanding of strategies for suppressing parasitic reactions from an electrochemical perspective is not profound enough.In this review,firstly,the chemistry of electrolytes,zinc anodes,and parasitic reactions and their relationship in AZIBs are deeply disclosed.Subsequently,the strategies for suppressing parasitic reactions from the perspective of enhancing the inherent thermodynamic stability of electrolytes and anodes,and lowering the dynamics of parasitic reactions at Zn/electrolyte interfaces are reviewed.Lastly,the perspectives on the future development direction of aqueous electrolytes,zinc anodes,and Zn/electrolyte interfaces are presented.

Formation and Characterization of Ceramic Nanocomposite Crystalline Coatings on Aluminium by Anodization

Ceramic nanocomposite coatings have been synthesized on aluminium by using lithium sulphate electrolyte with zirconium silicate additive by anodization. The effects of current density （CD） on microhardness, structure, composition and surface topography of the oxide layer formed at various CDs （0.1-0.25 A/cm^2） have been studied. Crystalline coatings formed at 0.25 A/cm^2 have been （width 95 nm） observed with a relatively uniform distribution confirmed by scanning electron microscopy. Additionally, the average microhardness value of ceramic nanocomposite coatings fabricated from lithium sulphate-zirconium silicate bath is approximately 8.5 times higher than that of the as-received aluminium. The surface statistics of the coatings is discussed in detail to explain the roughness and related parameters for better understanding. These observations demonstrate the importance of surface statistics in controlling the morphology of the coatings and its properties. From the X-ray diffraction investigations, it can be concluded that the formed nanocomposite coatings are crystalline in nature and that the crystallinity of the coatings decreases with increasing applied current density.

Anodization of titanium alloys for orthopedic applications

In recent years, nanostructured oxide films on titanium alloy surfaces have gained significant interest due to their electrical, catalytic and biological properties. In literature, there is variety of different approaches to fabricate nanostructured oxide films. Among these methods, anodization technique, which allows fine-tuning of oxide film thickness, feature size, topography and chemistry, is one of the most popular approaches to fabricate nanostructured oxide films on titanium alloys, and it has been widely investigated for orthopedic applications. Briefly, anodization is the growth of a controlled oxide film on a metallic component attached to the anode of an electrochemical cell. This review provides an overview of the anodization technique to grow nanostmctured oxide films on titanium and titanium alloys and summarizes the interactions between anodized titanium alloy surfaces with cells in terms of cellular adhesion, proliferation and differentiation. It will start with summarizing the mechanism of nanofeatured oxide fabrication on titanium alloys and then switch its focus on the latest findings for anodization of titanium alloys, including the use of fluoride free electrolytes and anodization of 3D titanium foams. The review will also highlight areas requiring further research to successfully translate anodized titanium alloys to clinics for orthopedic applications.

Selective inhibition effects on cancer cells and bacteria of Ni–Ti–O nanoporous layers grown on biomedical NiTi alloy by anodization

Stents made of nearly equiatomic NiTi alloy are used to treat malignant obstruction caused by cancer,but prevention of re-obstruction after surgery is still a challenge because the bare stents possess poor anticancer and antibacterial properties to inhibit cancer/bacteria invasion.The present work aims at endowing the NiTi alloy with anticancer and antibacterial abilities by surface modification.Ni–Ti–O nanoporous layers with different thicknesses were prepared on NiTi by anodization,and biological experiments were conducted to evaluate the effects on gram-positive Staphylococcus aureus,human lung epithelial cancer cells(A549),as well as human endothelial cells(EA.hy926).The nanoporous layer with a thickness of 10.1 lm inhibits growth of cancer cells and kill bacteria but shows little adverse effects on normal cells.Such selectivity is related to the larger amount of Ni ions leached from the sample in the acidic microenvironment of cancer cells in comparison with normal cells.The Ni–Ti–O nanoporous layers are promising as coatings on NiTi stents to prevent re-obstruction after surgery.

Recent progress in Li-ion batteries with TiO_(2) nanotube anodes grown by electrochemical anodization

Self-organized titanium dioxide(TiO_(2))nanotubes,which are prepared by electrochemical anodizing,have been widely researched as promising anodes for Liion batteries.Both nanotubular morphology and bulk structure of TiO_(2)nanotubes can be easily changed by adjusting the anodizing and annealing parameters.This is provided to investigate different phenomena by selectively adjusting a specific parameter of the Li^(+)insertion mechanism.In this paper,we reviewed how the morphology and crystallography of TiO_(2)nano tubes influence the electrochemical performance of Li^(+)batteries.In particular,electrochemical performances of amorphous and anatase titanium dioxide nanotube anodes were compared in detail.As we all know,TiO_(2)nanotube anodes have the advantages of nontoxicity,good stability,high safety and large specific surface area,in lithium-ion batteries.However,they suffer from poor electronic conductivity,inferior ion diffusivity and low theoretical capacity(335 mAh·g^(-1)),which limit their practical application.Generally,there are two ways to overcome the shortcomings of titanium dioxide nanotube anodes,including doping and synthesis composites.The achievements and existing problems associated with doped TiO_(2)nanotube anodes and composite material anodes are summarized in the present review.Based on the analysis of lithium insertion mechanism of titanium dioxide nanotube electrodes,the prospects and possible research directions of TiO_(2)anodes in lithiumion batteries are discussed.

Fabrication of TiO_2 Nanotube Arrays by Rectified Alternating Current Anodization

Anodization is a popular method of preparing TiO2nanotube array films（TiNTs） by using direct current（DC）power as the driving voltage.In this study,three driving voltage modes,namely,the sine alternating current（sine） mode,the full-wave rectification of sine waves via four diodes（sine-4D,where D means diode） mode,and the DC mode,were used to prepare TiNTs by anodization.At 20 V,TiNTs were formed under sine-4D mode but only irregular porous TiO2films were formed under DC mode.At 50 V,TiNTs formed under both the sine-4D and DC modes.No TiNTs formed in the sine mode anodization at either 20 or 50 V.Compared with the DC mode,the sine-4D mode required a lower oxidation voltage for TiNT formation,which suggests that sine-4D is an economical,convenient,and efficient driving voltage for TiNT preparation by anodization.The morphologies and structures of TiNT samples anodized at 50 V in the sine-4D and DC modes at different oxidation time（1,5,10,30,60,and 120 min） were analyzed.TiNT growth processes were similar between the studied modes.However,the growth rate of the films was faster under the sine-4D mode than the DC mode during the first 30 min of anodization.

Morphology dependence of TiO_2 nanotube arrays on anodization variables and buffer medium

Vertically oriented TiO_2 nanotube arrays were prepared by potentiostatic anodization of Ti foils in HF/acetic acid（HAC） aqueous solution.Anodization variables including anodization electrolyte concentration,anodization voltage, anodization time and buffer medium can be chosen and adjusted to manipulate the nanotube arrays to give the required length and morphology.