Rapid Breakdown Anodization Research Articles

Investigation of Copper Anodization Products with Temperature and Chemical Solution Changes

The rapid breakdown anodization (RBA) process was used to modify the copper surface and produce copper oxide powder. The effects of the temperature and inhibitors like glycerol and ethylene glycol were studied. The rate of corrosion increased dramatically at low temperatures, whereas it decreased at high temperatures. Cubic Cu2O particles were formed on the anode. Their volumes increased with increasing temperatures. Scanning electron microscope (SEM) images show the production of semispherical particles in the powder formed at low temperatures, but these particles congregate and combine at high temperatures. After using the glycerol, octahedron and semispherical Cu2O particles were formed on the anode and cathode, respectively. The findings confirm the concept that the anodizing process's temperature may be utilized for controlling the oxide to metal ratio. Significant slowing of the anodic process occurs at high ratios for both inhibitors.

Investigation of Copper Anodization Products with Temperature and Chemical Solution Changes

The rapid breakdown anodization (RBA) process was used to modify the copper surface and produce copper oxide powder. The effects of the temperature and inhibitors like glycerol and ethylene glycol were studied. The rate of corrosion increased dramatically at low temperatures, whereas it decreased at high temperatures. Cubic Cu2O particles were formed on the anode. Their volumes increased with increasing temperatures. Scanning electron microscope (SEM) images show the production of semispherical particles in the powder formed at low temperatures, but these particles congregate and combine at high temperatures. After using the glycerol, octahedron and semispherical Cu2O particles were formed on the anode and cathode, respectively. The findings confirm the concept that the anodizing process's temperature may be utilized for controlling the oxide to metal ratio. Significant slowing of the anodic process occurs at high ratios for both inhibitors.

Preparation of nanoporous TiOx powder and its enhanced photocatalytic N2 to NH3 conversion by solar-driven interfacial water evaporation

At present, the limited efficiency in ammonia generation poses significant challenge to the widespread practical implementation of photocatalytic nitrogen reduction to ammonia (PNRN). In this study, we synthesized a nanoporous TiOx powder (Alloy-RTO) by rapid breakdown anodization of TA13 alloy and subsequent magnesiothermic reduction. The Alloy-RTO exhibited superior photothermal and photocatalytic properties owing to its multicomponent and interconnective nanoporous structure, and the electronic band structure is suitable for efficient PNRN. Notably, through synergistic integration of PNRN with solar-driven interfacial water evaporation technology (SDIWE), the ammonia production rate was further enhanced, and a multifaceted role of SDIWE in enhancing PNRN was proposed: (1) increasing temperature of Alloy-RTO to promote PNRN; (2) raising temperature to accelerate ammonia water decomposition and facilitate PNRN; and (3) generating plenty of gaseous water to accelerate PNRN. This study presents an effective strategy for preparing nanoporous TiOx and highlights the pivotal role of SDIWE in promoting PNRN.

Nanostructure-performance relationships in titania-only electrodes for the selective electrocatalytic hydrogenation of oxalic acid

The preparation of robust and selective hydrogenation electrodes not based on critical raw materials is a relevant goal for the development of sustainable electrocatalytic processes. Oxalic acid is an emerging intermediate produced from CO2 that can be used to produce valuable, added-value monomers for high-performance polymers by selective electrocatalytic reduction. We demonstrated that with the rapid breakdown anodization (RBA) method, superior-performance TiO2-only electrodes can be directly prepared with a fast and low-cost procedure. The electrodes were based on a conductive Ti substrate, used to generate a roughened titania layer by RBA characterized by an ordered array of vertically aligned TiO2 nanotubes (NTs) on top of them and partially reduced TiO2-x nanoparticles stabilized by the interaction with the NTs layer. In addition, the preparation method leads to highly nanoporous NTs. The electrodes obtained by RBA at 60 V led to the best Faradaic efficiency (FE) to glycolic acid (86 %) and oxalic conversion (48 %) at −0.8 V vs. RHE, superior to the existing literature on TiO2-only electrodes at room temperature. The NTs structural features, such as length and surface roughness, were calculated by AFM and linearly correlated with the oxalic acid conversion and the electrochemical active surface area (ECSA). Additionally, the ECSA was found to be correlated with selectivity, indicating the complex interrelations between the NT nanostructure and performance. This finding emphasizes the importance of controlling the nanostructure as a critical factor in tuning the selectivity toward glyoxylic acid or glycolic acid.

Fabrication of Gamma-Ray Shielding Using Rapid Breakdown Anodization

Fabrication of Gamma-Ray Shielding Using Rapid Breakdown Anodization

Separation of tungsten and cobalt from cemented tungsten carbide by rapid breakdown anodization

Cemented tungsten carbide (WC-Co) has been used as an important industrial material and secondary resource of tungsten (W) and cobalt (Co). The recycling methodology of WC-Co scraps has drawn much attention because the recovery of strategic metals such as W and Co are critical. Here, rapid breakdown anodization (RBA) was applied for the first time to the conversion of WC-Co into high-purity hydrated tungsten oxide (WO3-H2O) up to 99.99 wt% and pure Co metal up to 90.43 wt% by using WC-Co as a sacrificial anode. Effective cobalt leaching was achieved in acidic aqueous solution without encountering anodic passivation issue due to the successful removal of tungsten oxidation layer during the electro-dissolution of WC-Co. Based on the particle formation mechanism of RBA, a two-stage reaction was confirmed, including electrochemical dissolution and chemical precipitation. The high purity of recovered WO3-H2O powders was realized by using high current density and high electrolyte concentration. We demonstrate that RBA is a new pathway for effective and environmentally-friendly WC-Co recycling with a significantly simplified process compared to conventional hydrometallurgical methods.

Enhanced visible light sensitized photoreaction by mixed phase titania nanotubes

In this work, we demonstrate the synthesis of mixed crystalline TiO2 nanotubes (TiNT) using a rapid breakdown anodization process and investigate its application in visible light photocatalytic degradation of rhodamine-B (RhB) dye pollutant. Nanotubes with different anatase to rutile crystalline phases were achieved during thermal annealing by tuning the amount of perchlorate ions. Increasing the rutile content decreased the nanotubes' bandgap and surface area. Photocatalytic studies of TiNT with different crystalline phase ratios revealed promising RhB degradation under visible light compared to commercial TiO2. Herein we propose the humidity conditioning (99% relative humidity) of TiNT as a surface modification method to enhance the –OH group on the oxygen defective sites. FTIR and XPS analysis of the TiNT before and after surface modification showed significant change in the surface –OH groups. The surface area normalized apparent-first order kinetic rate constant was higher for all the TiNTs than commercial TiO2. We report for the first time the higher photocatalytic activity of the humidity conditioned nanotubes with high –OH groups compared to the respective catalyst with less –OH group. The simple method proposed for –OH group incorporation shows a possible way of developing an efficient photocatalyst without complex surface modification techniques.

Long term antifouling performance of superhydrophobic surfaces in seawater environment: Effect of substrate material, hierarchical surface feature and surface chemistry

Biofouling is a serious concern for the materials that are in contact with seawater or brackish water. Superhydrophobic (SHP) surfaces have the potential to lower fouling. Although good progress is made on the design of SHP surfaces, the long-term antifouling performance of SHP surfaces is still a major concern. We report the effect of substrate material, hierarchical surface features, chemistry, and the nature of bacteria on the long-term antifouling properties of superhydrophobic for the first time. Three different superhydrophobic coatings on aluminum, Cr-Mo steel, and Ti substrates were studied in a seawater bacterial consortium. Silane based SHP Al with a water contact angle (WCA) ~170 ± 1.5°, cerium myristate based SHP Cr-Mo of WCA ~ 162 ± 2.4° and stearic acid based SHP Ti of WCA ~168 ± 3.3° were prepared by dip coating, electrodeposition, and rapid breakdown anodization, respectively. After 120 h of exposure in seawater bacterial consortium, the cell viability reductions were three, two and one order in SHP Al, SHP Cr-Mo, and SHP Ti, respectively. The SHP Al samples possessed both micron-sized structures (~2 µm) along with nano-sized spherical particles (~ 57 nm). The quat silane-like structures gave better antibacterial resistance to SHP Al. The predominant bacteria present on bare Al,Ti, Cr-Mo and SHP Al, and Ti surfaces after exposure were Bacillus and Pseudomonas sp., whereas cocci bacteria was seen on the SHP Cr-Mo. After 240 h of exposure, a thicker biofilm was seen on the SHP Cr Mo surface due to the densely populated nanostructures of sizes comparable to cocci diameter, which was favorable for the cocci bacterial attachment. Though the average WCA followed the trend SHP Ti> SHP Al>SHP Cr Mo, the bacterial adhesion trend was SHP Ti> SHP Cr Mo> SHP Al, after 120 h of exposure. This suggests that wettability is not the only parameter determining the antifouling performance of an SHP coating but is also influenced by the surface charge density, surface roughness, stiffness, topography, and environmental variables such as fluid dynamics, bacterial motility, and size and morphology of bacteria. Both the surface morphology and the chemical nature were responsible for this reduced cell viability of the SHP Al surface. These findings not only provide new insights into the understanding of long-term biofouling of SHP surfaces but also would provide new directions in the design of robust SHP surfaces.

Optimal condition for fabricating mechanically durable superhydrophobic titanium surface by rapid breakdown anodization: Self cleaning and bouncing characteristics

In this paper, we describe a simple, cost effective, fast, scalable and sustainable method for fabrication of mechanically durable superhydrophobic (SHP) surface of titanium by a rapid breakdown anodization (RBA) followed by molten stearic acid (MSA) chemical modification. In this new approach, the preparation time is only a minute. Instead of stearic acid- ethanol solution, molten stearic acid is the post surface modification, which made the preparation process rapid and simple. The anodized samples showed islands of TiO2 microclusters with complex hierarchical structures with nano pores uniformly distributed in the passive TiO2 matrix. Laser Raman spectroscopy (LRS) analysis revealed the TiO2 microclusters are polycrystalline in nature. The applied voltage, anodization time, immersion time and MSA bath temperature are optimized to obtain a robust mechanically durable SHP surface. FESEM images showed that both anodization and immersion parameters have significant effect on the surface morphology of microclusters. A maximum water contact angle (WCA) of 167.8° with a sliding angle of 6° was obtained for a Ti sample anodized at 50 V for 10 min after molten stearic acid immersion at 125 °C for 30 min. The prolonged anodization for 10 min promoted microcluster growth in all dimensions to form a highly hierarchical micro-nanostructure. The prepared samples showed vertical micro plate-like crystals of stearic acid on the micro clusters, which enhanced the very high WCA. The FTIR results revealed multiple bonding modes of stearic acid with TiO2 microclusters through surface hydroxyl groups. The prepared superhydrophobic samples showed excellent self-cleaning and abrasion resistance.

Controlled synthesis of tungsten trioxide with globular clusters constructed of nanoplates by rapid breakdown anodization

Herein, electrochemical synthesis of tungsten trioxide (WO3) with globular clusters constructed of nanoplates is demonstrated. Under a breakdown anodization potential of 25 V at 50 °C, tungsten foil anode was efficiently electro-oxidized into WO3 nanoplates-aggragated globular clusters powder, rather than a thin film structure as conventional anodization occurs. The WO3 globular clusters were characterized by SEM, TEM, and XRD. Effects of electrolyte composition on the breakdown anodization of the W substrate has been discussed. It is suggested that the growth of the WO3 nanoplates is initiated by localized anodic dielectric breakdown, and followed by an effective crystal growth in the electrolyte at high breakdown field.

A mesoporous ternary transition metal oxide nanoparticle composite for high-performance asymmetric supercapacitor devices with high specific energy.

We report on the optimized fabrication and electrochemical properties of ternary metal oxide (Ti–Mo–Ni–O) nanoparticles as electrochemical supercapacitor electrode materials. The structural, morphological, and elemental composition of the fabricated Ti–Mo–Ni–O via rapid breakdown anodization are elucidated by field emission scanning electron microscopy, Raman, and photoelectron spectroscopy analyses. The Ti–Mo–Ni–O nanoparticles reveal pseudocapacitive behavior with a specific capacitance of 255.4 F g−1. Moreover, the supercapacitor device Ti–Mo–Ni–O NPs//mesoporous doped-carbon (TMN NPs//MPDC) device exhibited a superior specific energy of 68.47 W h kg−1 with a corresponding power density of 2058 W kg−1. The supercapacitor device shows 100% coulombic efficiency with 96.8% capacitance retention over 11 000 prolonged charge/discharge cycles at 10 A g−1.

Properties and Stability Study of Tio2 Nanotube Based Nanofluid Synthetized by Rapid Breakdown Anodization as Lubricants

Properties and Stability Study of Tio2 Nanotube Based Nanofluid Synthetized by Rapid Breakdown Anodization as Lubricants

A simple approach for fabrication of superhydrophobic titanium surface with self-cleaning and bouncing properties

A simple, scalable, rapid and eco-friendly method for the fabrication of superhydrophobic (SHP) titanium surface was developed using rapid breakdown anodization (RBA) for the first time. The desired hierarchical surface morphology for superhydrophobicity is achieved by controlling the RBA process parameters and low surface energy modification by using stearic acid (SA). The prepared samples were characterized using Field emission scanning electron microscope (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA) measurements. The anodized samples showed islands of TiO2 microclusters with complex hierarchical structures randomly distributed in the passive TiO2 matrix. Ti sample anodized at 30 V was hydrophobic with a WCA of ~ 130° and a sliding angle > 30°, whereas the one anodized at 50 V was superhydrophobic with a WCA of ~ 154° and a sliding angle of 10° after the low surface energy modification. The growth mechanism of RBA leading to the formation of pores and microclusters was understood from the current-time transient data analysis. Our results show that the sustained oxidation of titanium and pore growth by chemical or field-assisted dissolution reactions governed the final morphology of the anodized sample. The superhydrophobic sample exhibited excellent self-cleaning, adhesion (bouncing) properties and abrasion resistance.

Evaluation of visible-light driven photocatalytic reaction by porphyrin coupled TiO2 nanotubes obtained via rapid breakdown anodization

The perceived attraction of nanotubular TiO2 in diverse applications has brought the researchers attention to focus on various aspects of nanotube synthesis and modification. In this work, the visible light activity of dye sensitized TiO2 nanotubes obtained in powder form via rapid breakdown anodization was investigated. Tetra (4-carboxy phenyl) porphyrin (TCPP) was used as a visible light sensitizing component on phase pure anatase TiO2 nanotubes (ATiNT). The effect of introducing two different anchoring groups between the dye and TiO2 nanotubes on photocatalytic activity was investigated. The visible light photocatalytic efficiency of the prepared ATiNT/TCPP composites was tested on a pharmaceutical compound, famotidine (FAM) in order to avoid degradation through photosensitization. For the given amount of TCPP load on ATiNT, the presence of a lengthy anchoring group between TCPP and ATiNT had a negative influence on the photocatalytic activity. Direct oxidation through visible-light-generated holes in the ATiNT/TCPP composite appeared to be the most significant pathway for FAM photocatalysis.

The bioactivities of prepared Ti, Zn, TiO2, ZnO and Al2O3 nanoparticles by rapid breakdown anodization technique

Ti and Zn content have essential role in determining the characters of many biomedical alloys and studying their bioactivities is an important issue. These elements with TiO2, ZnO and Al2O3 oxides were synthesized in nano sizes by Rapid Breakdown Anodization (RBA) method. Electrophoretic deposition (EPD) technique was utilized to deposit produced powders on their corresponding metal sheets. Bioactivity tests (BACT) of these materials were accomplished by soaking them inside simulated body fluid (SBF) solution for one month to detect the constructions of apatite layers on their surfaces. X-Ray Diffraction (XRD) and scanning electron microscope (SEM) analysis were utilized to record the bioactivities of these samples. After BACT Hydroxyapatite (HAp) phase was recorded in XRD patterns of Ti, TiO2 and Zn, ZnO. Also SEM images of these materials showed the creations of new HAp particles. These two tests referred to the bioactivities of these nanoparticles. There were no peaks belonged to HAp phase in XRD pattern of Al2O3. This refers to absence of bioactivity for this oxide. Energy dispersive X-ray spectroscopy (EDS) was used to measure weights and atomic percentages of elements before and after BACT. Molar Ca/P ratio was calculated for all samples, their values were 0.97, 1.277 and 0.86 for Ti,TiO2; Zn, ZnO and Al2O3 nanoparticles respectively.

Anion additives in rapid breakdown anodization for nonmetal-doped TiO2 nanotube powders

Nonmetal-doped TiO2 powders consisting of one-dimensional nanotube bundles are prepared using electrolytes containing different kinds of anion additives via a one-step rapid breakdown anodization (RBA) process in a short time. The results show that although no nitrogen species are observed when nitrate is used as an additive, it acts as a catalyst to increase current density during the RBA process. However, substitutional P- or S-doped TiO2 nanotube powders with reduced band gap energy are obtained when electrolytes containing phosphate or sulfate are used. Compared with that of undoped-TiO2 nanotube powders, S-doped TiO2 nanotube powders exhibit significantly reduced band gap energy, from 3.36 eV to 2.93 eV as the concentration of sulfate ions increases.

WO3 Nanorods Supported on Mesoporous TiO2 Nanotubes as One-Dimensional Nanocomposites for Rapid Degradation of Methylene Blue under Visible Light Irradiation

One dimensional (1D) WO3 nanorod (WR)/TiO2 nanotube (TN) composites were fabricated by employing a simple impregnation method for the photodegradation of methylene blue (MB), where WRs and TNs were synthesized by the hydrothermal method and rapid breakdown anodization, respectively. As a comparative study for the photodegradation process, nanocomposites of WRs/TiO2 Degussa P-25 nanoparticles (TPs) were prepared utilizing the same impregnation approach. X-ray diffraction studies confirm the structure of WO3 and TiO2 to be monoclinic and anatase, respectively. Morphological studies revealed the formation of 1D nanocomposite with a mesoporous surface having an increased presence of hydroxyl groups, as indicated by Brunauer–Emmett–Teller and electron paramagnetic resonance analyses. Ultraviolet–diffuse reflectance spectroscopy and photo luminescence profiles displayed a bathochromic shift in wavelength along with a reduction in the electron hole pair recombination rate, signifying the activation of the nanoco...

Fabrication of TiO2 sensor using rapid breakdown anodization method to measure pressure, humidity and sense gases at room temperature

Rapid breakdown anodization (RBA) process was used to fabricate TiO2 sensor to measure pressure and humidity and sense gases at room temperature. This chemical process transformed Ti to its oxide (TiO2) as a powder with amorphous phase as X ray diffraction (XRD) technique confirmed. This oxide consisted from semi spherical nanoparticles and titania nanotubes (TNTs) as Scanning electron microscope (SEM) technique showed. TiO2 powder was deposited on Ti substrates by using electrophoretic deposition (EPD) method. Average pressure sensitivity was 0.34 MΩ/bar and hysteresis area was 1.4 MΩ .bar. Resistance of TiO2 decreased exponentially with the increasing of relative humidity (RH%). The sensitivity% of TiO2 for RH% was greater than 70% in the range of (50-95). TiO2 was tested as a sensor for Ammonia, Ethanol and Methanol. Its sensitivity and selectivity towards Ammonia were the greatest but the shortest response and recovery times were recorded toward Methanol.

Chemo-resistive detection of hydrogen in argon using Pd nanoparticles on TiO2 nanotubes prepared via rapid breakdown anodization

The present work explores palladium sensitized Titania nanotubes (Pd/TiO2 NTs) as a potential sensor material for detecting hydrogen (H2). TiO2 NTs powder was prepared as bundles via rapid breakdown anodization. Pd nanoparticles (NPs) were deposited over TiO2 NTs by sodium borohydride-based chemical reduction of palladium chloride (PdCl2) to form nanocomposite materials. Morphological analysis exposed the tubular architecture and provided the nanoscale dimensions of the synthesized materials. Structural analysis revealed the anatase phase and face-centered cubic crystal structure for TiO2 NTs and Pd nanoparticles (NPs), respectively. The presence of Pd over TiO2 NTs was established with compositional analysis. Thermal stability analysis confirmed that the deformation of phase takes place only after 550 °C, thereby indicating the suitability of the material to sense H2 up to the required 350 °C temperature. A paste of Pd/TiO2 NTs was used to make a thick film sensor to sense H2 in argon (Ar) as a function of Pd loading and temperature. A tremendous change in the sensor response of the sample was witnessed with different percentages of Pd. The sensor material was insensitive to H2 up to a threshold temperature of 100 °C owing to the formation of a surface oxide over Pd NPs. The sensors displayed an elevated response beyond the threshold temperature. The sensing behavior was selective only to H2 gas, amid the presence of reducing gases like ammonia and methane and oxidizing gas like nitrogen oxide.

Influence of noble metal loading and effect of temperature on the hydrogen sensing behavior of the platinum sensitized titania nanotubes

Platinum sensitized titania nanotubes (Pt/TiO2 NTs) is a promising material for hydrogen (H2) sensing. TiO2 NTs powder was prepared through rapid breakdown anodization (RBA) and was sensitized with Pt NPs by chemical reduction of chloroplatinic acid. The morphological characterization revealed the tubular architecture of TiO2 NTs with length around 6 μm, diameter of about 20 nm and wall thickness measuring about 3 to 4 nm. The structural analysis confirmed the TiO2 NTs to be in anatase phase and Pt NPs to be in FCC crystal structure. Compositional studies established the effective presence of Pt NPs over TiO2 NTs. The vibrational spectroscopic analysis indicated that in TiO2, Ti4+ state is present with the tetragonal arrangement. The thermal stability investigation revealed that the Pt/TiO2 NTs nanocomposites are stable up to 550 °C thereby indicating the materials are suitable to be used in the temperatures under present investigation. The thick film H2 sensor made using a paste of Pt/TiO2 and the sensor behaviour towards H2 in argon (H2/Ar) was studied as a function of Pt loading and temperature. Increase in the Pt loading was found to enhance the sensor response initially but at higher loading the response decreased substancially. Sensitivity to hydrogen was found to increase with temperature with the needed linearity. At higher temperatures, the sensor response of the Pt/TiO2 NTs saturated beyond a certain threshold limit. The sensor behaviour was also observed to be selective only to H2 gas amid the presence of methane, ammonia and nitrogen oxide gases.