Electrolyte Temperature Research Articles

Amorphous coatings on tantalum formed by plasma electrolytic oxidation in aluminate electrolyte and high temperature crystallization treatment

In this paper, amorphous coatings on tantalum obtained by plasma electrolytic oxidation (PEO) in alkaline sodium aluminate electrolyte (2–10 g/l NaAlO2 + 2 g/l KOH) are investigated. It was found that the amorphous component of the oxide coatings increased with NaAlO2 concentration in the electrolyte. The coatings obtained in the electrolyte of 10 g/l NaAlO2 + 2 g/l KOH are completely amorphous. Subsequently, the amorphous coatings were subjected to vacuum heat treatment at 600, 800, 900 and 1300 °C to study their crystallization behavior. The results show that crystallization does not occur at 600 °C. However, crystallization occurred partially at 800 °C and completed at 1300 °C, with orthorhombic AlTaO4 as the main phase structure. Nanoindentation tests show that hardness of the coating at dense regions increases after crystallization, but defects and cracks in the coating are also increased after heat treatment. The amorphous coatings have excellent corrosion resistance, but the defects generated in the crystallized coatings are detrimental to the corrosion performance. The reason for the formation of amorphous coatings may be derived from rapid cooling and the glass-forming ability of the binary system of Ta2O5 and Al2O3.

Corrosion behaviour of Zn-Co alloy and multilayered metallic coatings: a comparative insight

ABSTRACT Zinc layers are widely used for the protection of various classes of steel in atmospheric conditions. An improvement in corrosion performance of these layers may qualify them to be used in harsh marine conditions. In this study, two practical approaches, including alloying Zn with Co at different current densities and electrolyte temperatures, as well as deposition of multilayered Zn-Co films with various numbers of interlayers, were applied to fabricate corrosion barrier coatings on St 37 steel. The surface and cross-sectional morphologies of the coatings were studied using scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation tests were employed to compare the corrosion resistance of the alloy and multilayered coatings. Results illustrated that the best protection performance is obtained for multilayered coatings with top Co layer showing promise to be used in marine applications.

Research on multiphysics coupling fields in electrochemical trepanning of lateral flow

Electrochemical trepanning (ECTr) is an effective method for machining the ruled surface parts. Generally, the forward flow mode is used in ECTr, under which the streamlines at the outlet are divergent, resulting in the obvious flow patterns at the outlet and the instability of the machining process. In ECTr of a diffuser with a special structure, the lateral flow mode is adopted to improve the uniformity of the flow field, thereby improving the surface quality at the hub. ECTr is a complicated multiphysics coupling process. To investigate the distributions of electric field, two-phase flow field and thermal field in ECTr with lateral flow, a multiphysics coupling field model was established. In this model, a coupling relationship was formed between the various physical fields through the change of the electrolyte conductivity. And a coupled multiphysics simulation was performed to show how the gas bubbles volume fraction, electrolyte temperature, electrolyte conductivity and current density change along the flow path. Compared with the inlet of the electrolyte, the gas bubbles volume fraction and the temperature at the outlet increased by 38.8% and 6.3 K, respectively. Under the combined influence, the conductivity decreased by 7.227 S/m at the outlet, resulting in a decrease of 57.81 A/cm2 in the current density. The simulation results were then verified against those from a corresponding experiment involving lateral flow ECTr. Along the flow path, the thickness of the machined blade gradually increased, varying from 2.09 mm to 2.76 mm. The surface quality gradually deteriorated along the flow path and the surface roughness varied from Ra 0.72 μm to Ra 1.05 μm. Combining the simulation and the experiment, the correctness and the effectiveness of the multiphysics coupling model and simulation were confirmed. The results can be applied to other ECM processes.

Machine learning‐based analysis and prediction of the interfacial corrosion processes of copper cathode plates during the electrolytic production of copper powders

AbstractPresent efforts to support the essential industrial‐scale electrolytic production of copper‐based metal powders urgently require approaches to the real‐time predicting of corrosion of copper cathodes employed in electrolytic production processes. However, current approaches are extremely limited owing to the difficulty of accurately modeling the complex cathode corrosion process. In this study, the corrosion process under different parameters was analyzed by a self‐designed continuous electrolytic corrosion experimental device, clarify the influence mechanism of current density on the corrosion of the solid–liquid–gas interface area, and addresses this issue by applying a random forest machine learning approach based on three process parameters, including the electrolyte temperature, liquid‐level fluctuation cycle period, and current density. The dataset employed in the model is obtained using a novel experimental corrosion test method based on electrode arrays. The experimental results include the corrosion rates of copper cathode plates at different positions relative to the liquid electrolyte level during the electrolysis process. The resulting stochastic model is demonstrated to obtain a high prediction accuracy of 97% for the various regions of copper cathode plates defined according to liquid electrolyte level.

Discharge Characteristic of Micro-Arc Oxidation on Aluminum Alloy under the Changing Electrolyte Temperature

The electrolyte temperature has a great influence on the performance of the coating prepared by micro-arc oxidation (MAO). The behavior of MAO discharge in the changing electrolyte temperature has been investigated. Compared to constant electrolyte temperature in conventional MAO process, the process has different discharge characteristics under the changing electrolyte temperature. The amplitude of pulse voltage was detected to study the change of discharge characteristic under the constant-current control of MAO power supply. Three successive discharge stages were differentiated by the variable the pulse voltage versus process time. Since there were significant changes in the sound, the sound signals were acquired and the audio analysis was used to describe the changing of the MAO discharge at different stages. Optical emission spectroscopy (OES) was employed in situ to unveil how the micro-discharge changed with the temperature increasing. Scanning electron microscopy (SEM) was used to characterize the morphology of the coatings on 6N01 aluminum alloy prepared by normal process with the constant-temperature control of the MAO electrolyte and by the process under the changing electrolyte temperature. A mode of film growth and micro-discharge was given to describe the effects of the changing electrolyte temperature in the whole MAO process.

Cadmium sulphide thin films deposition and characterization for device applications

Thin films of metal chalcogenides (sulphides, selenides, and tellurides) are investigated, and group II-VI semiconducting materials are more attracted to the thin films, and researchers are more interested in group II-VI semiconducting materials because of their use in photovoltaic cells, photoconductors, optical filters, solar cells, sensors, and other optoelectronic devices. Cadmium sulphide is a semiconducting material that corresponds to the II-VI family and has an energy bandgap of 2.42 eV. It is significant because of their numerous applications in optoelectronic devices, solar cells, LEDs, photoconductors, and other fields. It's also beneficial for window layers in CdTe or CuInSe2-based high-efficiency thin-film solar cells. It can be prepared by several techniques like chemical bath deposition (CBD), electrodeposition, thermal evaporation, spray pyrolysis, molecular beam epitaxy, etc. We have prepared CdS thin films over Molybdenum substrate using a non-aqueous medium by the CBD method. The electrolyte was made by combining the AR grade of cadmium acetate (0.24 M) dissolved with ethylene glycol and ethanol (ratio = 1:2) and the electrolyte temperature was kept at 130 °C with 220 rpm. Molybdenum substrate was dipped into the electrolyte using rigid support and thiourea (0.35 M) was influenced by the prepared electrolyte. The film was deposited for 20 min, and the deposited films was found to be well adherent to the substrate and free of voids, pinholes, and pits. XRD, FESEM, EDS, AFM, and FTIR were used to see into the solid-state features of the films which have been deposited. The deposited film shows a significant peak at 2θ = 26.240 with the (002) plane, suggesting that the film has a crystalline hexagonal structure. Using AFM, RMS roughness value is equal to 92 nm. Compositional analysis peaks reveal the availability of Cd and S.

On the electrodeposition of conically nano-structured nickel layers assisted by a capping agent

• Systematic study of capping agent concentration during electrodeposition of Ni nanostructures. • Optimum deposition conditions for conical growth are derived. • New modeling approach to simulate and quantify local growth of cones. Capping agents are frequently used in electrodeposition to support spatially inhomogeneous mass transfer at small scales. As such, chloride ions are known to support the deposition of conically nanostructured nickel layers. This work presents a systematic experimental study of the impact of a capping agent on the electrochemical growth of conically-shaped nickel deposits. Furthermore, a modeling approach on the scale of cones for numerical simulations of electrodeposition with capping agents is provided for the first time to give deeper insight on how the capping agent influences the local growth of the deposit. The growth rates of the nano-cones obtained numerically are compared with experimental data, and a good agreement is found. The impact of the capping agent concentration, the deposition time, the electrolyte temperature and the current density are investigated systematically, and optimum conditions for conical growth are derived.

Исследование факторов, влияющих на внутреннее сопротивление автомобильных аккумуляторных батарей

The study of the factors affecting the internal resistance of automobile storage batteries will reduce the negative consequences of sudden failures. Despite the large number of publications on this subject, there are almost no studies in which the change of structural and diagnostic parameters is investigated by means of physical modeling of batteries` characteristic failures. The purpose of this work is to analyze the change in the internal resistance of automobile storage batteries based on data processing in the mode of starter discharge. As a result of the study, it was experimentally established that the value of the internal resistance of automobile storage batteries is affected by the electrolyte temperature, operating time, the degree of charging and the degree of serviceability. The author proposes a mathematical model of the battery internal resistance taking into account the change of operation factors. The practical use of this model will allow assessing the technical condition of the automobile storage battery on board the vehicle.

Deposition of Cu-based composite coatings on mild steel substrate via electrodeposition method

The mild steel (MS) is a commonly used material in various structural industries due to its low cost and good strength (relatively lower than other processed steel). But, poor corrosion resistance, relatively low hardness, and wear resistance lead to a limit of its application. To enhance these properties, surface engineering with coating are preferred. The present article investigates the synthesis, microstructural and mechanical properties of copper-based electrodeposited coatings on the mild steel. The direct current (DC) power source is used to deposit the pure copper and copper-based composite reinforced with carbonaceous materials, such as graphene (Gr), graphite (Gt), and carbon nanotubes (CNTs). The coatings were deposited using two types of bath containing reinforcement, non-cyanide alkaline glycerol complex and acidic (sulphuric acid) bath. Various deposition parameters, such as bath temperature, time, current density, pH, and stirring of electrolyte were used to get an optimised uniform coating. The wetting agent was added with carbonaceous particles to make it mix and distribute uniform in the electrolyte. The cube-shaped morphology of copper crystals was witnessed in the electrodeposited coatings along with the plate-like structures of graphene and graphite. The morphology and chemical composition of the deposited coatings were analysed with the help of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) respectively. The microhardness and elastic modulus of the electrodeposited coatings were measured using instrumented microindentation test. Among the composite coatings, copper/graphite (Cu/Gt-MS) coating showed the superior hardness of ∼ 5 GPa, due to the uniform distribution of reinforcement.

ЕНЕРГОЗАБЕЗПЕЧЕННЯ ПУСКУ ХОЛОДНОГО ДВИГУНА ВНУТРІШНЬОГО ЗГОРАННЯ З ВИКОРИСТАННЯМ ТЕРМОЕЛЕКТРИЧНОГО ГЕНЕРАТОРА

Based on the analysis of the energy capabilities of the electric starter system for starting an internal combustion engine at low ambient temperatures, it was found that this process is significantly affected by the temperature of the battery electrolyte and the degree of its charge. A technical solution has been proposed to improve the start of a cold engine, which during operation allows maintaining the optimum temperature of the battery during storage of the car at low temperatures. The description and principle of operation of the proposed system are presented. Experimental studies of the efficiency of the developed power supply system for starting a cold internal combustion engine have been carried out. The object of experimental research is the power supply system for starting a cold internal combustion engine based on a phase transition heat accumulator and a thermoelectric generator.

INFLUENCE OF SURFACTANTS ON THE SCATTERING ABILITY OF SULPHATE ELECTROLYTES OF CADMIUM PLATING AND THE QUALITY OF CADMIUM COATINGS

The effect of surfactants - calcium phenolate (phenolates of tertiary aminophenols), which has a significant size (1286 g/mol) and high activity (adsorbability) in electrolytes and has a positive effect on the scattering ability of the cadmium electrolyte, as well as on the quality of cadmium coatings was studied in this work. In the work, the usual parameters of the cadmium electrodeposition process, such as electrolyte composition, current density, temperature, and deposition time were used. The quality of the obtained cadmium coatings by using a new surfactant in the process of electrocrystallization of cadmium was determined on a JSM-6490LV scanning electron microscope with INSAEnergu energy dispersive microanalysis and HKL-Basic structural analysis systems with a useful magnification of 300.000.

БОРТОВОЙ МОНИТОРИНГ ТЕХНИЧЕСКОГО СОСТОЯНИЯ СТАРТЕРНЫХ АККУМУЛЯТОРНЫХ БАТАРЕЙ

The analytical model of starter batteries state of function, which considers the change of output voltage parameters and electrolyte (ambient air) temperature, is worked out. The correlation between the success of starting the automobile engine and the state of function of batteries has been established.

Pengaruh temperatur elektrolit terhadap ketebalan dan kuat lekat baja karbon rendah pada proses elektroplating

The development of industry as well as science and technology requires humans to fulfill various kinds of needs in their lives. One of them is the need for metal-based goods. Many objects around us, both in the automotive industry and in the steel-based industry for household purposes, etc., are given a metallic finish to protect and beautify the metal. The metal coating technique that is often used in the metal industry is electroplating. Electroplating comes from two words, namely electro and plating or electricity and coating that uses a deposition system. The purpose of this study was to determine the effect of electrolyte temperature on the thickness and adhesive strength of low carbon steel in the electroplating process. The cathode used is low carbon steel with dimensions of 70 mm x 25 mm x 20 mm, while the anode used is Nickel (Ni) and the bath for plating is 60 cm long, 30 cm depth, and 30 cm wide. Two anodes on the right and left side of the anode with an anode-cathode distance of 10 cm, and using an electric voltage of 7.5 Volts, and using variations in electrolyte temperature of 45 0 C, 50 0 C, 55 0 C, 60 0 C, 65 0 C and room temperature. From the results of the study found the optimal thickness value with 0.021 mm at a temperature of 60 0 C. Meanwhile, the optimal value for coating adhesive strength from electroplating research is 60℃ with a very high adhesive strength value of 26.53 MPa.

Clean preparation of V2O3 by one-step molten salt electrochemical reduction of soluble NaVO3

Vanadium oxides, such as V2O5 and V2O3, are important metallurgy products and mainly used to prepare V-based alloys for steelmaking. At present, vanadium oxides are mainly produced by complex sodium salt roasting process. Serious environmental pollution, such as emission of ammonia nitrogen wastewater and NH3, are restrictive problems. Here, a clean and sustainable method for V2O3 preparation is proposed by one-step molten salt electrochemical reduction of soluble NaVO3, i.e. an indispensable intermediate in traditional V metallurgy. The pollution issues are well solved. The theoretical decomposition voltages of different vanadate to various low-valence vanadium oxides were calculated. NaVO3 with a solubility of 14.7 wt% is the most suitable vanadate for the direct preparation of V2O3 by molten salt electrolysis. The effects of cathode structure, NaVO3 content, electrolysis temperature and voltage on current efficiency and electricity consumption were systematically studied. High-purity V2O3 with uniform particle distribution is obtained and the lowest electricity consumption is only 2.86 kWhkg−1. V2O3 is mainly produced by one-step electrochemical reduction of soluble NaVO3 through two-electron transfer process. The economic evaluation for ferrovanadium production is preliminarily carried out. Compared with the traditional process, the cost for ferrovanadium production is lower by the aluminothermic reduction of V2O3 which is prepared by clean one-step electrolysis of soluble NaVO3.

The potential of tantalum as an efficient electrocatalyst for green hydrogen production

Worldwide, discovering a low-cost, highly active and durable electrocatalyst for green hydrogen production is an attractive research field for future renewable energy. Herein, we study the suitability of utilizing metallic Ta as promising electrocatalytic material for hydrogen creation from acidic solutions. The morphological structure and crystal lattice system, as well as the chemical composition and oxidation states of Ta are examined using scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy, respectively. Hydrogen evolution reaction (HER) on Ta is investigated using cathodic polarization and electrochemical impedance techniques as a function of electrolyte concentration, applied potential, and temperature. Various kinetic parameters distinguishing catalytic activity of the process on Ta including Tafel slope, exchange current density, cathodic transfer coefficient, and HER rates are determined. At −1500 mV cathodic potential in 0.5 M H2SO4 solution, the results confirm well that, to reach a similar HER rate of say 100 mA cm-2, the overpotential on Ta cathode is found equal -520 mV, which is lower than the value of -940 mV attained on the platinum cathode, indicating high electrocatalytic activity of the HER on Ta surface. The obtained results also demonstrated that, for the hydrogen production process the overpotential greatly diminishes and its current density significantly improves with increasing either the electrolyte concentration or its temperature. Additionally, Tafel slope analysis and impedance parameters establish that HER proceeds by the Volmer–Heyrovsky mechanism. The outcome of this study reveals that the valve metal Ta is a sustainable, efficient, and promising cathode for green hydrogen generation fuel from sulphuric acid electrolytes.

Effect of electrolysis parameters on corrosion resistance of extra-low carbon high silicon iron-based alloy

PurposeHigh silicon iron-based alloys possess excellent corrosion resistance in certain specific media, but the effects of electrolysis parameters on corrosion resistance remain unknown. This study aims to guide the development and application of an extra-low carbon high silicon iron-based alloy (ECHSIA) in electrode plates.Design/methodology/approachThe corrosion resistance of ECHSIA and a conventional high-silicon cast iron (CHSCI) was analyzed through experimental characterizations. The morphology was observed by scanning electron microscopy. The influence of electrolysis parameters on the corrosion resistance of ECHSIA was investigated through corrosion experiments. The relationship between the electrolysis parameters and the corrosion resistance of ECHSIA was statistically investigated using the grey correlation analysis method.FindingsThe corrosion resistance of the ECHSIA is better than that of the CHSCI. The corrosion rate showed an increasing tendency with the increase in the nitric acid concentration (CHNO3), electrolyte temperature and current density. The grey correlation analysis results showed that the CHNO3 was the main factor affecting the corrosion rate of the ECHSIA.Originality/valueAn ECHSIA with a single ferrite microstructure was prepared. This study provides a guideline for the future development and application of ECHSIAs as electrode plates.

Studies on electrochemical dissolution of sintered molybdenum discs as a potential method for targets dissolution in 99mTc production

Electrochemical dissolution of pressed into discs and sintered metallic molybdenum powder with the mass of 712 ± 10 mg (n = 15) in potassium hydroxide solution was studied in detail. The technique was considered to apply for dissolution of irradiated 100Mo target in the 99mTc production. The effect of various parameters, e.g., the concentration of the electrolyte solution, temperature, current density, and surface area of the platinum cathode, was investigated. The shortest time for total dissolution of molybdenum target was 70 min. This result was achieved using an electrolyte solution of 5 M KOH, temperature 55 °C and the current density of 365 mA/cm2.

Low-temperature constrained sintering of YSZ electrolyte with Bi2O3 sintering sacrificial layer for anode-supported solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have strong potential for next-generation energy conversion systems. However, their high processing temperature due to multi-layer ceramic components has been a major challenge for commercialization. In particular, the constrained sintering effect due to the rigid substrate in the fabrication process is a main reason to increase the sintering temperature of ceramic electrolyte. Herein, we develop a bi-layer sintering method composed of a Bi2O3 sintering sacrificial layer and YSZ main electrolyte layer to effectively lower the sintering temperature of the YSZ electrolyte even under the constrained sintering conditions. The Bi2O3 sintering functional layer applied on the YSZ electrolyte is designed to facilitate the densification of YSZ electrolyte at the significantly lowered sintering temperature and is removed after the sintering process to prevent the detrimental effects of residual sintering aids. Subsequent sublimation of Bi2O3 was confirmed after the sintering process and a dense YSZ monolayer was formed as a result of the sintering functional layer-assisted sintering process. The sintering behavior of the Bi2O3/YSZ bi-layer system was systematically analyzed, and material properties including the microstructure, crystallinity, and ionic conductivity were analyzed. The developed bi-layer sintered YSZ electrolyte was employed to fabricate anode-supported SOFCs, and a cell performance comparable to a conventional high temperature sintered (1400 °C) YSZ electrolyte was successfully demonstrated with significantly reduced sintering temperature (<1200 °C).

Temperature Effect on Photoelectrochemical Water Splitting: A Model Study Based on BiVO4 Photoanodes.

Photoelectrochemical (PEC) water splitting is typically studied at room temperature. In this work, the temperature effect on PEC water splitting is studied using crystalline BiVO4 thin film photoanode as a model system. Systematic temperature-dependent electrochemical study demonstrates that the PEC activity is boosted at elevated electrolyte temperatures and indicates that thermal energy plays a main role in improving charge carrier transport in the bulk of BiVO4. Irreversible surface reconstruction is observed after PEC reactions at elevated temperature in the presence of hole scavengers, with regularly spaced stripes emerging on BiVO4 grains. The surface-reconstructed photoanode exhibits up to 40% improvement in photocurrent densities and ∼ 0.25 V shift of photocurrent onset to favorable direction. Detailed investigation shows the formation of an amorphous layer without stoichiometric change at the reconstructed surface. This work provides insights of the temperature effect on the photoelectrode in solar water splitting and reveals the non-negligible effect of hole scavengers in photoelectrochemical measurement.

Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions

The development of alcohol-based electrolysis to enable the concurrent production of hydrogen with low electricity consumption still faces major challenges in terms of the maximum anodic current density achievable. Whilst noble metals enable a low electrode potential to facilitate alcohol oxidation, the deactivation of the catalyst at higher potentials makes it difficult for the obtained anodic current density to compete with water electrolysis. In this work the effect of significant parameters such as mass transport, glycerol and OH− concentration and electrolyte temperature on the glycerol electrooxidation reaction (GEOR) in alkaline conditions on a bimetallic catalyst PdNi/NiRDE (Pd0.9Ni0.1) has been studied to discern experimental conditions which maximise achievable anodic current density before deactivation occurs. The ratio of NaOH:glycerol in the electrolyte highly affects the rate of the GEOR. A maximum current density of 793 mA cm−2 at -0.125 V vs. Hg/HgO through steady state polarisation curves was achieved at a moderate and intermediate rotation rate of 500 RPM in a 2 M NaOH and 1 M glycerol (ratio of 2) electrolyte at 80 °C. Shown here is a method of catalyst reactivation for enabling the long-term use of the PdNi/NiRDE for electrolysis at optimal conditions for extended periods of time (3 h at 300 mA cm−2 and 10 h at 100 mA cm−2). Through scanning electron microscopy (SEM), X-ray photon electron spectroscopy (XPS) and X-ray diffraction (XRD) it is shown that the electrodeposition of Pd and Ni forms an alloy and that after 10 h of electrolysis the catalyst has chemical and structural stability. This study provides details on parameters significant to the maximising of the GEOR current density and the minimising of the debilitating effect that deactivation has on noble metal based electrocatalysts for the GEOR.