Anode Effect Research Articles

Anodic Processes during the Electrowinning of Niobium from Chloride-Fluoride Melts and the Influence of Oxide Ions on Them

Anodic processes were studied in chloride-fluoride, fluoride melts by voltammetry and gas chromatography mass spectrometry method. It was found that the reason for the occurrence of the anodic effect during the electrolysis of the KCl-KF-K2NbF7 melt is the formation of the compound CxFy on the electrode surface, which has electrical insulating properties. Influence of oxide ions on the anodic processes in the KCl-KF-K2NbF7 melt was investigated. It was determined that oxide ions and oxofluoride complexes of niobium oxidize at a glassy carbon electrode at more negative potentials than fluoride ions. The anodic effect in the chloride-fluoride melt containing oxide ions and oxofluoride complexes of niobium can be reached if the anodic current density will be higher than the limiting current density of electrooxidation of oxide ions and niobium oxofluoride complexes.

Exploring MgO/HA ceramic nano-composites for biodegradable implants: Exploring biological properties and micromechanics

The release of Mg ions from Mg-based implants during biodegradation can promote bone repair through osteoblast migration. However, the high pH values (alkaline stresses) associated with this process can be harmful for osteoblasts. Therefore, surface modifications are required which allow to adjust the Mg ion concentration within a tolerable range. The present work investigates the effect of anodizing of magnesium/hydroxyapatite metal matrix nano composites (Mg/HA-ncomposites) on micromechanical behavior and on biological properties. The results will be implemented into a design strategy for improved Mg/HA-ncomposites. The HIPed Mg/HA-ncomposites with varied content of nano hydroxyapatite (n-HA) particles (0, 0.75, 1.8, and 3 wt%) were anodized in a 6 M KOH solution at 1.50 V and 50 °C for 2 h to develop magnesium oxide/hydroxyapatite surface ceramic matrix nano-composite (MgO/HA-ncomposite). The specimens were evaluated by immersing the materials into simulated body fluid (SBF), seeding of human mesenchymal stem cells on the surfaces, and performing nano-indentation and nano-scratch tests. The results show that the uniform distribution of 1.8 wt% n-HA particles in the MgO converted layer strengthens its adhesion as compared to the other types of MgO/HA-ncomposites. Furthermore, the cell spreading of human mesenchymal stem cells on the composite of 1.8 wt% n-HA improves after the anodizing process and after a one-day cell culture. In summary, the present combined micromechanical and biological study has shown that the MgO/HA-ncomposite of 1.8 wt% n-HA represents a promising biomaterial for bio-absorbable bone implants and that it outperforms pure Mg-surfaces.

Effect of the Current Intensity and Inter-Electrode Distance in Surface Electrical Stimulation: A FEM Simulation Study.

In functional electric stimulation, variables such as electrode size, shape, and inter-electrodes distance can produce different neural and functional responses. In this work, a computational model combining FEM and MRG axon models is implemented to replicate two experimental studies that compare the effect of changing inter-electrode distance when applying FES to induce knee flexion. One work affirms that the stronger torque happens for greater distances, while the other obtain its maximum at lower distances. Using a simplified computational model gave another study perspective to understand why these two stimulation methodologies obtain different results. According to our results, an anodic stimulation occurs with greater current intensities and inter-electrode distances. This anodic effect can activate other nerve or motor points in the vicinity of the anode, explaining that more muscle fibers are recruited and generate an increased torque. Clinical Relevance - This work gives another view to understanding how the distance between electrodes affects neural activation, which has implications for optimizing clinical and exercise protocols using electrical stimulation techniques.

Synergistic effect of Co3O4/Fe2O3 nanoparticles encapsulated with MOFs-derived nitrogen-doped porous carbon for high-performance lithium-ion battery

Using efficient and stable electrode materials for lithium-ion batteries (LIBs) is critical for cleaner and more sustainable energy systems. Choosing a reasonable composite is also critical for obtaining LIBs anode with enhanced performance and stability [1]. Herein, an effective approach for encapsulating Fe2O3 and Co3O4 into nitrogen-doped porous carbon (Fe2O3-Co3O4/NPC) using metal organic frameworks as sacrificial templates is reported. Due to the good conductivity of the carbon material and the synergistic effect stemming from the two components, the electrode had good electron transfer rate, was rich in accessible active sites, and had excellent reaction kinetics. Based on these properties, the electrode was used as an anode for LIBs and found to have long-term stability of 621 mA h g−1 at 1 A g−1 after 1000 cycles, and superior rate performance of 406 mA h g−1 at 2.0 A g−1. Further, the work presents the assessment of synergistic effect of transition metal oxide anodes on the increase of LIBs performances.

Strengthen Synergistic Effect of Soft Carbon and Hard Carbon Toward High-Performance Anode for K-Ion Battery.

Synergistic effect of soft carbon and hard carbon has been proven to be useful for obtaining excellent anode materials for potassium ion battery, which is determined by the mixing degree of precursors. Inspired by the formation of proteins in biology, peptide bonds are used to connect the precursors of the two sort of carbon to prepare soft-hard hybrid carbons with stronger synergistic effects. The hard carbon domain with nanometer size is so highly distributed in the soft carbon that the synergistic effect between two sorts of carbon is significantly enhanced. After the optimization, the diffusion coefficient of as-prepared hybrid carbon (CSHC3-6-1200) is 10 times larger than that of corresponding carbon synthesized by physical method. Consequently, CSHC3-6-1200 can maintain a specific capacity of 71.6 mAh g-1 at a high current density of 1600 mA g-1. It is believed that this new preparation route may bring a new perspective to the development of soft and hard composite carbon material anodes with high power density and ultralong service life.

A Study of Bubble Behavior and Anode Effect on the Graphite and Industrial Carbon Anode in a See-Through Furnace During Aluminium Electrolysis

Anode gas bubble behavior and anode effect on graphite and industrial carbon rod-shaped anode in a cryolite melt have been studied using a see-through furnace. The different carbon materials have different properties which can affect bubble behavior and electrochemical properties. Industrial carbon is more inhomogeneous with respect to structure, pore, aggregates and impurities in comparison to the graphite. More bubbles were nucleated on the industrial carbon than on the graphite for the same current density. The time related to the coalescence process for both anodes was found to be in interval 16 to 24 ms and independent of the current densities. Bubbles detached from the horizontal surface of the anode have similar average diameter value for both anodes for current densities < 1.0 A cm−2, while for current densities > 1.0 A cm−2, the average diameter is lower for the industrial carbon anode. The onset of the anode effect occurred faster on the graphite than on the industrial anode. The PFC-containing gas layer appeared to be thicker and more stable on the graphite anode than on the industrial carbon anode.

Experimental Analysis on Flow Field Pattern of PEM Fuel Cells

The polymer electrolyte membrane (PEM) fuel cells flow fields channels serve the same roles as nutrient and reactant circulation systems in plants and animals, so bio-inspired flow field channels with a similar could improve reactant uniform transport efficiency and boost fuel cell performance. In this analysis, the lung channel configuration of a humane lung and a tree leaf bio-inspired flow field channels are used as an anode and cathode bipolar plate. A channel model is developed for three new flow field patterns designs: leaf design, lung design and triple-serpentine. It has been observed that the performance improvement in terms of power in the bio-inspired flow field is 13.32% more than the triple serpentine. This indicates the bio-inspired design has good performance than other flow field design. Further a parametric steady is carried out experimentally to study the effect of cell operating temperature, anode and cathode humidity, hydrogen and oxygen flow rate on the cell performance.

Effect of electrochemical anodization and growth time on continuous growth of carbon nanotubes on carbon fiber surface

Carbon nanotubes (CNTs)/carbon fiber (CF) reinforcements were prepared by chemical vapor deposition after electrochemical anodization and catalyst impregnation. The results showed that after the electrochemical anodization, the CFs were oxidatively etched and the surface roughness increased, which is helpful to form a uniform catalyst coating on the surface of CF. Under the current of 0.4 A and 0.6 A, CNTs can grow evenly on the surface of CF. Within a certain range, with the increase of growth time, the density and length of CNTs are improved. The CNTs/CF reinforcement prepared at the current intensity of 0.4 A and the growth time of 8 min has the best comprehensive performances compared with other as-fabricated samples. The tensile strength of the sample can reach a high value of 4.56 GPa, and the wettability of resin has an effective improvement.

Application of magnesium alloy sacrificial anode for restraining chloride ingress into mortar

This study aims to restrain the chloride ingress into mortar by magnesium alloy sacrificial anode system. Cube reinforced mortar specimens with embedded magnesium alloy anode meshes were prepared. The output electrochemical parameters of magnesium alloy mesh, the chloride profiles and corrosion electrochemical performance of steel in mortars immersed in chloride-contaminated solutions were detected. Besides, the visual inspection of steel surface after immersion was performed. The results indicate that the magnesium alloy mesh can restrain effectively chloride ingress into mortar. With increasing water-cement ratio and chloride content, the galvanic potential and current density between the steel and magnesium alloy mesh increase. The chloride diffusion coefficient of mortar decreases after the application of magnesium alloy sacrificial anode and the decreased magnitude rises with increasing water-cement ratio, chloride concentration and decreasing steel cover thickness. The mitigation of steel corrosion and morphology of the steel surface after immersion further demonstrate the good effect of magnesium alloy sacrificial anode on reducing chloride ingress into mortar.

THE EFFECT OF HEAT TREATMENT AND SURFACE ANODIZATION ON FRICTION AND WEAR COEFFICIENT OF ALUMINIUM 2024 USING PIN ON DISK METHOD

The use of aluminum alloys as a material for engineering components that rub against each other is increasing, so it is important to know the friction characteristics of these aluminum alloys. In this study, Aluminum 2024 was given heat treatment with variation in aging time and anodization. Then, the wear and friction coefficient tests were carried out using a pin tool on the disc. The effect of aging time and surface anodization on wear tests are carried out to determine the amount of wear and the coefficient of friction test is carried out to determine the coefficient of friction of the material when it rubs against a pin made of AISI 52100 Steel. The coefficient of friction test is carried out by adding lubrication as a parameter. The test results showed that the aluminum material given heat treatment had better resistance than that which was not heat treated. This is because the heat treatment creates precipitates that can increase the aluminum's hardness and wear resistance. Whereas for anodized specimens, the alumina layer can act as an abrasive grain when given a high enough friction and load continuously, so the wear testing mode changes from dry sliding wear to three body abrasive wear and decreased wear resistance. From the friction coefficient test results, the aging time affects the hardness of the aluminum alloy, which leads to the value of the coefficient of friction. The harder the sample surface, the smaller the coefficient of friction obtained. Furthermore, applying lubricant to the sample will also decrease the value of the friction coefficient of the sample. Lubricating oil will provide a more significant reduction in friction coefficient than air. Finally, the anodizing surface on the sample will act as a lubricant reservoir when it occurs.

Anodic oxidation effects at the copper/silicon oxide interface

We report on anodic oxidation effects in memristively switching Cu/SiO2/Pt and Cu/CuOx/SiO2/Pt Electrochemical Metallization Cells. In-depth x-ray photoelectron spectroscopy reveals the formation of a Cu-ion reservoir composed of Cu(OH)2 underneath the anode during oxidation. By using cyclic voltammetry partial redox reactions are observed both in SiO2- and CuOx/SiO2-based devices. From our analysis we conclude that the CuOx layer acts as a reservoir for Cu-ions, similar to the low work-function electrode in valance change mechanism devices, which acts a reservoir for oxygen vacancies. Integration of a CuOx layer may thus allow to tailor the resistive switching performance of cation based memristors.

Effects of Phosphate Anodization and Laser Irradiation on Adhesive Property of AZ91D Magnesium Alloy

Effects of Phosphate Anodization and Laser Irradiation on Adhesive Property of AZ91D Magnesium Alloy

Solar-photovoltaic electrocoagulation of wastewater from a chocolate manufacturing industry: Anodic material effect (aluminium, copper and zinc) and life cycle assessment

Wastewater from a chocolate industry with an acid pH (4.38), and a high content of organic matter (Chemical oxygen demand (COD) = 9566 mg/L), Biochemical oxygen demand (BOD5) of 4666.97 mg/L, biodegradability index (BI) of 0.49 and Total organic carbon (TOC) of 1318.7 mg/L, was treated by solar-photovoltaic electrocoagulation. The effects of anodic material (aluminium, copper or zinc), pH (4.38 and 7) and current density (1.781 mA/cm2 and 0.356 mA/cm2) at 60 min of treatment time were studied. The aluminium system exhibited the best results: 50% and 39% removal efficiency of COD and BOD, respectively. The BI increased considerably from 0.49 to 0.59 while TOC diminished only 26.65%. The copper-based cell also showed an acceptable behaviour in the organic removal that was: 43% COD, 53% BOD, 30.7% TOC and the BI was 0.4. The zinc-based system was slightly less efficient than copper and aluminium, where the removal achieved was: 39% COD, 30% BOD5, and 19% TOC. The BI showed an increase to 0.56, improving the biodegradability of wastewater. The quantification and characterization of sludge was carried out using SEM and EDS. Fourier Transform Infrared Spectroscopy (FTIR spectra) proved the removal of organic and nitrogenous matter by the coagulant. Although costs associated with energy savings were estimated, the use of a solar panel, nevertheless, led to energy reductions. According to Life cycle assessment, the Cu anode provided the highest environmental impact and the use of Zn involved a lower effect in all categories, except for marine ecotoxicity, human non-carcinogenic toxicity and human health.

Microscopic mechanism of perfluorocarbon gas formation in aluminum electrolysis process

In view of the unclear cause of perfluorocarbons (PFCs) emission in the anode effect stage of aluminum electrolysis, the microscopic formation mechanism of PFCs was studied by density functional theory calculation and X-ray photoelectron spectroscopy (XPS). It is found that the discharge of fluorine containing anions ([F]−) on carbon anode first causes the substitution of C—H by C—F and further results in the saturation of aromatic C—C bonds, leading to the appearance of —CF3 or —C2F5 group through six-carbon-ring opening. Elimination of —CF3 and —C2F5 with F atom could be a likely mechanism of CF4 and C2F6 formation. XPS results confirm that different types of —CFx group can be formed on anode surface during electrolysis, and the possibility that [F]− discharges continuously at the C edge and finally forms different C—F bonds in quantum mechanical calculation was verified.

Anode paste consumption for aluminum production

In Russia, most aluminum smelters are equipped with cells with self-baking anodes featuring an urgent problem of lowering the anode paste consumption, since the share of anode materials in the cost of aluminum varies from 8 to 20 %. To solve this problem, it is necessary to determine the anode paste demand. The method for calculating the specific anode paste consumption used at aluminum smelters has a poor accuracy. The paper discusses the main errors of this method, shows the stages of anode paste consumption calculation, assesses the adequacy of calculations and gives recommendations for method improvement. It is shown that in general the considered method adequately reflects carbon consumption processes, but the final result of calculations may differ significantly from the actual one. The values taken constant to simplify the calculation, in fact, may vary during the electrolysis, which leads to a significant change in the final result of calculations. For example, an increase in the CO2 fraction from 0.45 to 0.5 leads to a decrease in the anode paste consumption by 15.3 kg/tonAl. At the same time, it is known that the composition of anode gases changes sharply as the anode effect occurs: the CO2 fraction decreases, and the CO fraction increases. In summer, at high ambient temperatures, the proportion of both vaporized pitch and anodes with an increased surface temperature rise. As the latter changes to 0.25, the consumption increases by 6.6 kg/tonAl. The same applies to air oxidation. The number of depressurized cells may increase with the subsequent increase in the carbon consumption. It is necessary to pay attention to factors affecting the anode quality. Incorrectly selected particle size distribution or worn equipment may significantly degrade the anode quality and lead to an increase in carbon consumption. It is necessary to make adjustments to the calculation in order to consider the peculiarities of carbon monoxide formation properly.

High current density with spatial distribution of Geobacter in anodic biofilm of the microbial electrolysis desalination and chemical-production cell with enlarged volumetric anode

The aim of this study was to establish the relationship between spatial distribution of Geobacter and electric intensity in the microbial electrolysis desalination and chemical-production cell (MEDCC) and to investigate the effect of enlarged volumetric anode on the performance of MEDCC. The MEDCC was constructed with nine carbon brush anodes (length × diameter = 11 cm × 3 cm) as enlarged volumetric anode, and operated by feeding with 1 g/L acetate as substrate and 35 g/L NaCl as artificial seawater under the applied voltages of 1.2–4.5 V. Spatial distribution of Geobacter in the anodic biofilm was determined according to the bacterial community analysis on 27 biofilm samples from the top, middle and bottom layers of anodes (i.e., with distance of 4.5, 10, and 15.5 cm to the cathode, respectively). Results showed that the enlarged volumetric anode significantly improved the performance of MEDCC. The maximum desalination rate and current density reached 338.5 ± 21.8 mg/L∙h and 55.7 ± 3.7 A/m2 in the MEDCC, respectively. The electric intensity values decreased with the distance from the anode to the cathode and formed an uneven distribution in the anode chamber. The samples in the top layer of anodes had the highest average 16S rRNA gene copy number of Geobacter of 1.55 × 107 copies/μL, which was 18 times higher than that in the bottom layer of anodes. A linear relation was established between the spatial distribution of Geobacter and electric intensity (R2 = 0.994–0.999). The electric intensity gradient created the uneven spatial distribution of Geobacter in the biofilms of volumetric anode. Results from this study could be useful to enrich Geobacter in the anodic biofilm thus to improve the performance of MEDCC.

Model and Mechanism of Anode Effect of an Electrochemical Cell for Nd or (Nd, Pr) Reduction

The anode effect can occur during neodymium and didymium oxide electrowinning, causing a surge in the electrochemical cell voltage, interrupting the process, and increasing the greenhouse gas emissions. In this work, we develop a mathematical model, based on the mass balance of gas bubbles evolving from the anode, to understand the influence of some process parameters on the anode effect. The anode effect occurs due to bubble coverage and limitations on the mass transfer of the oxide species. Variables such as current density, oxide content, viscosity, and electrolyte composition play an important role in the anodic process. Finally, we propose a mechanism for the occurrence of the anode effect during Nd or Di (Nd–Pr) oxide electrolytic reduction based on models used in aluminum electrolysis.

Crystallization of TiO2 on sputter deposited amorphous titanium thin films

Titanium and titanium dioxide are both very well-known and commonly used materials in today's world. They would also be very promising materials for years to come as their more novel properties are continued to be investigated. For meeting the demands of today's technology and to fine tune its properties, titanium dioxide is still in the scope of scientists from different branches of science.In our study, sputter deposited amorphous titanium thin films on glass substrates were anodically oxidized at 0.7 V for 250, 750, 1250 s in 0.5 M H2SO4 solution to observe their crystalline structure and electrochemical properties. X ray diffraction analysis revealed rutile and anatase crystalline peaks on 250 s and 1250 s anodized samples. Additionally, electrochemical impedance spectroscopy and atomic force microscopy analysis were carried out for investigating the effect of anodization on electrochemical and surface properties of amorphous titanium thin films. Both analysis showed compressive stress related findings in oxide films due to crystallization process.

Study on the Effect of Low-Temperature Anode Filled with FeCl3 Solution on Electro-Osmotic Reinforcement of Soft Clay

In order to study the effect of FeCl3 solution on the current, soil pH value, drainage volume, anode potential difference, energy consumption, and resistivity of electro-osmosis consolidation of soft clay with different moisture contents under a low temperature environment, we carried out 31 sets of model tests under different working conditions by using a self-made device and an improved Miller Soil Box. The test results showed that, under the same conditions, although the energy consumption coefficient of electro-osmosis had little change in the low temperature environment, the current, displacement, and electro-osmosis coefficient were obviously reduced, and the resistivity and anode potential difference was greatly increased, indicating that the low temperature environment reduces the efficiency of electro-osmosis of soft clay. After the anode was filled with FeCl3 solution, the current, water displacement, and electro-osmotic coefficient were clearly increased; the anode potential difference and electro-osmotic energy consumption coefficient were clearly decreased; and the resistivity was reduced to a certain extent, which indicates that the anode filled with FeCl3 solution is very beneficial in improving electro-osmotic efficiency and in saving energy. The electro-osmotic discharge after the anode filled with FeCl3 solution at low temperature was clearly higher than that after the anode was filled water at normal temperature, indicating that the effect of the anode filled with FeCl3 solution on electro-osmosis is greater than that of temperature. In the process of electro-osmosis of soft clay, the better the electro-osmosis effect, the smaller the pH value of the anode and the larger the pH value of the cathode. The pH value of the cathode and anode can be used as one of the indexes to reflect the electro-osmosis effect.

Comparative Evaluation of Cyclic Fatigue and Corrosion Resistance of Three Different Nickel-Titanium Instruments

Objective: The aims of the study are to investigate the effect of the surface treatment process on prolonging the life of the rotary instruments against cyclic fatigue and the effect of the surface coating process on the corrosion resistance of Ni-Ti files.Methods: This study was carried out in two stages. In the first one, a total of 120 Ni-Ti rotary instruments (25/.04 taper) from 3 brands (HeroShaper, RaCe, and TF) were selected. Sixty of them were anodized then all of them were tested in simulated root canals with two different curvatures. The time until fracture was recorded, and the number of cycles was calculated for each group. The second stage; the effect of anodization on corrosion resistance was assessed. The file groups tested in 5% NaOCl solution at 37° C. Data were subjected to The Mann-Whitney U test. The significance level was set at P= 0.05.Results: There was a statistical difference among the rotary systems in terms of cyclic fatigue. Among the file types, TF instruments were the most resistance to cyclic fatigue and RaCe instruments had the lowest results. The effect of anodization process was different among file groups.Conclusion: Within the limits of this study, the increase in canal curvature reduces the life of the rotary instruments. While the anodization process did not change cyclic fatigue in all file groups in 20° curved canals, it reduced the wear life of RaCe and HeroShaper files and extended the wear life of TF files in canals with 37° curved canals.