Parameters Of Oxidation Process Research Articles

Synergistic modification of Ti/PbO2 electrodes with metal ions (Nd, Al, Bi) and STAB surfactant for electrocatalytic treatment of desulfurization wastewater

In this study, PbO2 electrodes are modified by co-doping with different metallic elements (Nd, Al, Bi) and stearyl trimethyl ammonium bromide (STAB) using the electrodeposition method. The modified electrodes, designated as Ti/PbO2-Nd-STAB, Ti/PbO2-Al-STAB, and Ti/PbO2-Bi-STAB, are then applied in the electrochemical degradation of desulfurization wastewater. The surface morphology, crystal structure, and elemental valence of the prepared electrodes are analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance and stability are assessed by linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated life testing (ALT). The results reveal that modification with metallic elements and STAB significantly enhances the physicochemical and electrocatalytic performance of the Ti/PbO2 electrode. Among the modified electrodes, the Ti/PbO2-Nd-STAB electrode exhibits the most compact and homogeneous surface morphology, the highest oxygen evolution potential (OEP, 2.33 V vs. SCE), the lowest chlorine evolution potential (CEP, 1.44 V vs. SCE), the largest electrochemically active surface area, the lowest charge transfer resistance, the highest electrochemical stability, and a prolonged accelerated life (65 h, which is 17 h longer than that of the unmodified electrode). Further, the optimal electrochemical oxidation process parameters for desulfurization wastewater are determined as follows: current density = 50 mA/cm2, temperature = 35 ℃, electrode spacing = 3.0 cm, and stirring rate = 300 rpm. After 300 min of electrolysis, the Ti/PbO2-Nd-STAB electrode achieves a Cl− removal rate of 86.9 % and a chemical oxygen demand (COD) removal rate of 71.2 %. After 10 cycles, the Cl− and COD removal rates decrease by 2.8 % and 1.8 %, respectively. Besides, Tafel curve analysis indicates that the chlorine evolution reaction follows the Volmer-Tafel mechanism, with the recombination of adsorbed Cl− ions on the surface oxidation film being the rate-determining step. Overall, the Ti/PbO2-Nd-STAB anode exhibits immense application potential in the treatment of desulfurization wastewater.

A grey relational analysis of the micro arc oxidation process parameters and their effects on Ti-6Al-7Nb coating performance and corrosion resistance for biomedical uses

Abstract In current investigation micro arc oxidation of Ti6Al7Nb alloy was done to improve its surface properties and corrosion resistance. Mixture of Na2SiO3, Na3PO412H2O and KOH is used as electrolyte. MAO treated Ti6Al7Nb specimens were examined using x-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) to examine their morphology and phase composition. It was observed that electrolyte composition is simultaneously included in the growing oxide layer during MAO process. From electrochemical study it was found that corrosion resistance of the Ti6Al7Nb increases during EIS testing in 0.9% NaCl solution. It was found that frequency, duty cycle, current and processing time effect the surface roughness, thickness, hardness and corrosion resistance of coating. Out of above mention parameters frequency and duty cycle has major impact on performance parameters. The objective of current investigation is to find out effects MAO process parameters on coating performance parameters such as coating thickness, hardness, surface roughness and corrosion resistance. At duty cycle of 50%, frequency 500 Hz, current 300 mA and processing duration 7.5 min, highest coating thickness 32.96 μm and surface roughness 3.3680 μm was obtained. Process parameters have the influence on pore size, biggest average pore size 3.8519 μm was obtained at duty cycle of 50%, frequency 500 Hz, current 300 mA and processing duration 7.5 min. Grey relational analysis is done to determine which process variable has the most influence on performance parameters. From grey relational analysis technique, it was observed that duty cycle 50%, frequency 500 Hz, current 300 mA, and processing time 7.5 min are ideal process parameters for higher coating thickness, hardness, surface roughness and better corrosion resistance. From grey relation analysis it was also found that frequency has most significant impact on performance parameters after that duty cycle, then current and at last processing time.

Preliminary treatment of landfill leachate by hydrodynamic cavitation supported by Fenton process

Hydrodynamic cavitation as an effective and environmentally friendly method of treating wastewater. Massive amounts of energy may be released into the surrounding liquid during hydrodynamic cavitation, resulting in mechanical , chemical and thermal impacts. Bacteria and organic materials in sewage can be broken down by these circumstances. Furthermore, a coupling effect may be created by combining hydrodynamic cavitation with other water treatment techniques. In this study it is aim to investigate and improve the hydrodynamic cavitation (HDC) process supported by Fenton process for the pretreatment of landfill leachate. In the second phase of the study, the effectiveness of the hydrodynamic cavitation process was investigated in conjunction with the Fenton process. The parameters such as the number of cavitation events, pH, and temperature were evaluated. The effluent was characterized and monitored for COD measurements. The consequences of operational variables such H2O2, Fe+2 , and pH values were investigated to determine the optimal Fenton oxidation process parameters. The findings of the experiment showed that pH values were ideal for Fenton oxidation of 3.5-4.5, 30 mM H2O2, and 5 mM Fe+2. A combined treatment process of Fe+2+H2O2, HDC + Fenton, and Cavitation alone were conducted for the treatment of landfill leachate. The results showed that the removal rates of chemical oxygen demand (COD) for the combined processes were 32.85%, 44.28%, and 7%, respectively. Temperature, pH, and the number of cavitation events were among the parameters that were assessed. The effluent was measured for COD and was characterized.

Craniofacial reconstruction using 3D personalized implants with enhanced surface properties: Technological and clinical aspects

In this study, the modification of personalized titanium implants was developed using the plasma electrolytic oxidation process. Plasma electrolytic oxidation process parameters were initially optimized using solid samples of the Ti6Al4V alloy. Oxidation was achieved in an electrolyte containing calcium and phosphorus compounds at 250 V. The oxide layer produced was characterized by the use of human osteoblasts and fibroblasts, with high biological activity of the modified titanium alloy in relation to these cells was demonstrated. Based on tomographic examinations, models were made and then personalized implants for three patients were printed from a Ti6Al4V alloy powder. These implants were subjected to plasma electrolytic oxidation treatment within the previously developed parameters and surgically placed in the craniofacial area. On the basis of postoperative studies, surgical interventions were successful, with modification of the surface using the plasma electrolytic oxidation method producing bioactive surfaces for both bone and soft tissue.

Effects of Micro-arc Oxidation Process Parameters on Micro-structure and Properties of Al2O3 Coatings Prepared on Sintered 2024 Aluminum Alloy

Effects of Micro-arc Oxidation Process Parameters on Micro-structure and Properties of Al2O3 Coatings Prepared on Sintered 2024 Aluminum Alloy

Modification of the Ni-NiO-oxidant system by thermo-chemical oxidation with accelerated growth of the p-type dielectric oxide layer, by the action of substituted V2O5 on the system

Nickel is covered with very thin oxide film and is stable against corrosion under normal conditions. Nickel, as Ni-NiO-oxidant system, can make much thicker (even a thousand times) and more corrosion unstable oxides. With certain new oxidation process parameters, nickel can undergo so-called accelerated oxidation. The subject and goal of this work is to find the most favorable conditions for performing of accelerated - catastrophic Ni oxidation process, when substitution of V2O5 is carried out into NiO (2V (Ni)), with significant electron concentration increase and oxygen surplus. Unlimited main and secondary charge carriers transfer is significantly facilitated if oxide film with non-stoichiometric composition and defects is formed. The aim is to avoid compact oxide film formation by chemical-thermal treatments and to obtain porous and defective NiO. By using oxidized system Ni - NiO - oxidant in glass, ceramics and evaporated metal technology, extraordinary usable value of this work is ensured.

Surface Modification of Additively Fabricated Titanium-Based Implants by Means of Bioactive Micro-Arc Oxidation Coatings for Bone Replacement.

In this work, the micro-arc oxidation method is used to fabricate surface-modified complex-structured titanium implant coatings to improve biocompatibility. Depending on the utilized electrolyte solution and micro-arc oxidation process parameters, three different types of coatings (one of them-oxide, another two-calcium phosphates) were obtained, differing in their coating thickness, crystallite phase composition and, thus, with a significantly different biocompatibility. An analytical approach based on X-ray computed tomography utilizing software-aided coating recognition is employed in this work to reveal their structural uniformity. Electrochemical studies prove that the coatings exhibit varying levels of corrosion protection. In vitro and in vivo experiments of the three different micro-arc oxidation coatings prove high biocompatibility towards adult stem cells (investigation of cell adhesion, proliferation and osteogenic differentiation), as well as in vivo biocompatibility (including histological analysis). These results demonstrate superior biological properties compared to unmodified titanium surfaces. The ratio of calcium and phosphorus in coatings, as well as their phase composition, have a great influence on the biological response of the coatings.

New insights into the non-isothermal oxidation of tight oil: Experimental study and theoretical prediction

A better understanding of the influence factor investigation and oxidation behavior prediction for the crude oil could supply valuable insights into the reactivity of crude oil and feasibility of air injection process. In this study, non-isothermal oxidation experiments have been conducted via thermal analyses (thermogravimetry/differential scanning calorimetry/pressurized differential scanning calorimetry, TG/DSC/PDSC) with different heating rates (5, 10, and 15 °C/min) and experimental pressures (1, 3, and 5 MPa) in order to investigate the influences on oxidation behaviors, exothermic characteristics, and kinetic parameters of typical tight oil. In addition, the distributed activation energy method (DAEM) was employed to determine accurate kinetic parameters for whole oxidation process and to further predict the oxidation behavior with the reconstruction of TG and conversion curves. The results showed that, heating-rate increment would lead to inadequate oxidation process with more reaction occurrence in a shorter time. Inversely, more rapid heat release, higher exothermic peaks with lower temperature ranges were detected in PDSC curves, indicating high pressure in actual oil reservoir would strengthen the oxidation progress with more heat generation to enhance oil recovery. Then, based on specific activation energy distribution and DAEM, the calculated TG and conversion curves presented a satisfactory fitting relation with experimental data, demonstrating a reasonable prediction of oxidation behavior and kinetic characteristic for the crude oil under specific heating-rate. The understandings in this study not only provided new insights on the verification of obtained kinetic parameters, but also the accurate prediction of crude oil oxidation behavior.

Galvanic corrosion protection of Al-alloy in contact with carbon fibre reinforced polymer through plasma electrolytic oxidation treatment

Al-alloy/carbon fibre reinforced polymer (CFRP) joint systems offer exceptionally lightweight, superior fatigue behaviour and impact resistance for aerospace applications. Nevertheless, the galvanic corrosion at the joint interfaces accelerates the adhesive failure and strength damage. In this work, oxidation of Al 7075 alloy was studied by employing plasma electrolytic oxidation (PEO) and thin film sulphuric acid anodizing (TFSAA) methods, addressing their galvanic corrosion (GC) protection performance in contact with CFRP. Structural and electrochemical characterisations were carried out in tandem with varied oxidation process parameters, revealing that high voltage PEO resulted in crystallized compact ceramic coating and thus improved GC protection. A decrease in the GC current by ~ 90% has been achieved by using the PEO coating at 700 V compared with the ~ 12% current reduction of commercial TFSAA coating. Further microstructure studies revealed that the improved GC protection of the crystallized PEO coating was realized by suppressing the initiation and propagation of localized pitting due to the improved electrical isolation between the Al-alloy/CFRP interfaces. A high voltage PEO process provides sufficient energy to produce uniform and crystalline ceramic coating consisting of Al2O3 and mullite, which give rise to improved corrosion protection.

Surface modification of titanium and titanium alloy by plasma electrolytic oxidation process for biomedical applications: A review

Titanium (Ti) and its alloys are mostly utilized for orthopedic and dental applications on account of its excellent corrosion resistance, good formability, excellent fatigue strength and lower modulus of elasticity. As Ti is bioinert, it’s not satisfactory for long-term clinical applications and can't attach to living bone straightforwardly at the beginning phase after implantation into a human body. With an end goal to improve implant-cell connection, many surface alterations techniques have been examined in the recent past to quicken osseointegration process and upgrade surface topography with the tissue of host. Plasma electrolytic oxidation (PEO) process likewise called micro-arc oxidation (MAO) can be utilized successfully for surface alteration of Ti and its alloys. PEO is an electrochemical surface modification technique to create defensive oxide coatings on light metal, for example, titanium, aluminum and magnesium. PEO is a basic, single-step surface modification strategy used to create coatings on Ti and its alloys for orthopedic and dental applications. Desired coating properties can be obtained by changing process parameters of PEO process, for example, electrolyte composition, frequency, processing time, duty cycle and applied voltage. Electrolyte concentrations is a significant factor to impact growth mechanism of coating. It has been observed that, porosity decreases as the PEO current density increases due to the higher rate of ionic current and sealing effect on the micro size pores. It was seen that for better wear resistance, temperature during coating should be kept at lower values. It was likewise seen that the safest coating to erosion was acquired in the oxidized titanium alloy specimen deposited at 500 Hz with 30% duty cycle by PEO. This review article is focusing on surface modification of Ti and its alloy by plasma electrolytic oxidation process and process parameters effects on substrate characteristics.

Effects of Micro-Arc Oxidation Process Parameters on Characteristics of Calcium-Phosphate Containing Oxide Layers on the Selective Laser Melted Ti13Zr13Nb Alloy

Titania-based films on selective laser melted Ti13Zr13Nb have been formed by micro-arc oxidation (MAO) at different process parameters (voltage, current, processing time) in order to evaluate the impact of MAO process parameters in calcium and phosphate (Ca + P) containing electrolyte on surface characteristic, early-stage bioactivity, nanomechanical properties, and adhesion between the oxide coatings and substrate. The surface topography, surface roughness, pore diameter, elemental composition, crystal structure, surface wettability, and the early stage-bioactivity in Hank’s solution were evaluated for all coatings. Hardness, maximum indent depth, Young’s modulus, and Ecoating/Esubstrate, H/E, H3/E2 ratios were determined in the case of nanomechanical evaluation while the MAO coating adhesion properties were estimated by the scratch test. The study indicated that the most important parameter of MAO process influencing the coating characteristic is voltage. Due to the good ratio of structural and nanomechanical properties of the coatings, the optimal conditions of MAO process were found at 300 V during 15 min, at 32 mA or 50 mA of current, which resulted in the predictable structure, high Ca/P ratio, high hydrophilicity, the highest demonstrated early-stage bioactivity, better nanomechanical properties, the elastic modulus and hardness well close to the values characteristic for bones, as compared to specimens treated at a lower voltage (200 V) and uncoated substrate, as well as a higher critical load of adhesion and total delamination.

Determining Optimum Anodic Oxidation Parameters for Hardness and Wear Properties of AA7075-T6 Alloys Using Taguchi Design

In this study, the main goal is to determine the effects of the variable anodic oxidation process parameters on the hardness and wear properties of the AA7075-T6 alloy, which is widely used in the gun industry, automotive, aircraft, and space industry. Samples obtained using the process parameters designed by the Taguchi method were subjected to various experiments and the findings obtained from these experiments were compared with S/N graphs determined using ANOVA analysis. As a result of these findings, it was determined that different coating thickness, hardness and wear resistance were obtained by varying the anodic oxidation process parameters. The highest oxide layer thickness obtained was determined as 70.63 µm. In addition, the oxide layer formed by the anodic oxidation process has significantly increased the hardness and wear resistance of the AA 7075-T6 alloy. Also, as a result of the experiments and ANOVA analysis, it was determined that the oxide layer obtained with the parameters of 22V constant voltage, 1.3A/dm2 current density, 2°C temperature, 140 minutes of processing time will have the superior wear performance.

Thermal analysis of carbon nanomaterials: advantages and problems of interpretation

Thermal analysis of carbon nanomaterials is a useful tool to investigate their synthesis and modification techniques. The properties and thermal behavior of carbon nanomaterials, such as carbon nanotubes, carbon nanofibers, graphene, and graphene-related materials mainly determine their fields of application. The parameters of thermal investigation of carbon nanomaterials, such as heating rate, gas atmosphere, heating regime, make it possible to study the important characteristics useful for their further applications: oxidation rate, amount of catalyst, yield, activation energy, and other kinetic parameters of oxidation process, etc. The main advantages of thermal analysis for characterization of carbon nanomaterials were discussed. The important features on the interpretation of differential scanning calorimetry data of graphite oxide and graphene oxide were formulated. A comparison of TGA and DSC data on graphene oxide reduction during heating has been made. In this review, we focus on recent advances in thermal analysis (mainly, thermogravimetric analysis and differential scanning calorimetry) of carbon nanomaterials.

Effect of Anodic Oxidation Process Parameters on TiO2 Nanotube Formation in Ti-6Al-4V Alloys

Effect of Anodic Oxidation Process Parameters on TiO2 Nanotube Formation in Ti-6Al-4V Alloys

Design of graphene oxide by a one‐pot synthetic route for catalytic conversion of furfural alcohol to ethyl levulinate

AbstractBackgroundGraphene oxide (GO) has abundant oxygen‐containing functionalities such as hydroxyl groups and carboxyl groups with distinct acidities. This feature makes GO a potential solid acid catalyst for the acid‐catalyzed reactions such as the production of ethyl levulinate (EL), a platform chemical, from the acid‐treatment of furfuryl alcohol (FA). The structure and functionalities of GO are closely related to its catalytic performance, and thus it is necessary to establish the relationship between the chemical structure and the catalytic properties of GO. To achieve this aim, in this work, the GO catalysts were designed by a facile one‐pot synthetic route with no subsequent modification. By controlling the parameters of oxidation process in preparation, multiple functional groups were immobilized onto graphitic substrate, significantly impacting the catalytic activity of GO in the conversion of FA to EL in an ethanol (EtOH) medium.ResultsThe results showed that, the oxidation process significantly influenced the distribution of oxygen‐containing functionalities on the surface of GO. The amount of the oxygen‐containing functionalities can be adjusted by the oxidation parameters such as oxidizing agent equivalent, reaction time and temperature, while the organosulfate can only be remained at a moderate oxidation temperature. The existence of the synergistic effect between the oxygen‐containing functionalities and the organosulfate functionalities promoted the catalytic activity of GO for the acid‐catalyzed conversion of FA to EL.ConclusionsThis work provides a new strategy of design and development of functional graphene‐based catalysts for the acid‐catalyzed reactions, and lays foundation of the practicability of GO in biomass conversion. © 2019 Society of Chemical Industry

Sulphite Electrooxidation in Alkaline Media on Skeletal Nickel Based 6 Layers Platinum Nanoparticles Electrode

In this paper, anodic oxidation of sulphite ions on skeletal nickel based platinum nanoparticles electrode (6 layers) in aqueous alkaline solution was investigated in order to find the relationship between kinetic parameters and sulphite concentration. The purpose of this research is both to understand the oxidation mechanism and determine optimal parameters for oxidation process. Electrochemical behavior of sulphite ions has been studied by cyclic voltammetry and linear polarization. Tafel method was used in order to determine kinetic parameters and electrochemical impedance spectroscopy studies were performed to confirm the oxidation mechanism. For a complete characterization of sulphite electrooxidation process chrono-electrochemical methods (chronoamperometry, chronopotentiometry, chronocoulometry) were used.

Evaluation of the influence of texture and microstructure of titanium substrates on TiO2 anodic coatings at 60 V

The current paper analyzes the influence of texture and microstructure of Ti substrates on morphology and color of titanium dioxide coatings obtained by anodic oxidation. Substrates of Ti grade 2 and Ti grade 5 with different thermo-mechanical histories were used in the shape of cylindrical bars cut in both longitudinal and transversal directions, and laminated sheets. The crystalline orientation of the surface grains in the substrate before oxidation, were determined by electron backscatter diffraction. The oxide coatings were analyzed by optical and scanning electron microscopy. The results show that different substrate grain orientations produce oxides with different colors, because of different thickness depending on their orientations. An oxide grown on a basal hcp plane, with higher atomic density is thinner than an oxide grown on a transversal hcp plane with lower atomic density. This effect is more pronounced on elongated grains. Different anodic oxidation process parameters and heat treatments of the substrate were applied in order to obtain a more uniform oxide thickness. A specific heat treatment of the substrate was the most efficient, starting from a favorable orientation of crystals, characteristic of rolling texture.

Investigation of Electrochemical Properties of Elemental Sulfur Dissolved in Alkaline Solution on Rhodium Electrode

In this article, the electrochemical properties of elemental sulfur dissolved in alkaline solution has been studied for the first time using the method of removing the anodic and anodic-cathodic potentiodynamic polarization curves on rhodium electrodes. The influences of different parameters for oxidation process of elemental sulfur, namely sulfur component in electrolyte concentration, scan rate and temperature were investigated. The resulting polarogram presented in oxidation reaction of polysulfide ions to elemental sulfur process. This shows that polysulfide-ions in electrolyte at cathodic polarization was restored to monosulfide, and monosulfide –ions oxidized to elemental sulfur. The effective activation energy was calculated which equals 13,67 Kj/mol, indicating the oxidation reaction of sulfur occurred in diffusion mode.

Epinephrine sensing at nanostructured Au electrode and determination its oxidative metabolism

Epinephrine (EP) is a neurotransmitter and hormone involved in an enormous number of processes in living organisms, however its highly active oxidation metabolites can cause hard damages and lead to serious health consequences. This paper described a relatively simple method of fabrication of Au nanotube array electrodes for electrochemical determination of EP, which could be easily transferred to non-laboratory conditions. On the basis of Tafel plot, some parameters of EP oxidation process like number of electrons involved in the rate-determining step (nα=2) and electron transfer coefficient (α=0.45) were evaluated for the studied electrode. The linear sweep voltammetry (LSV) revealed a very good linear response in the EP concentration range of 60–600μM EP, however to 1000μM its linearity differs insignificantly. Using differential pulse voltammetry (DPV), the calibration curve for EP determination is close to linear in the range of 10–150μM, but the detection limit of 2.8μM was evaluated for a lower concentration range 10–60μM. The proposed DPV method was successfully applied to the determination of EP in a pure, ascorbic acid containing and real samples. The DPV results were evaluated and compared with those obtained by the high-performance liquid chromatography (HPLC) method. Combining the ROXY™ EC System with mass spectrometry creates an analytical tool for oxidative products of EP and conjugation of EP reactive potential metabolites characterized for I and II stage of biotransformation. The presence of leucoadrenochrome-o-semiquinone radicals confirmed by mass spectrometry implies that the ECE (electron transfer-chemical reaction-electron transfer) mechanism of EP oxidation at the Au electrode is more feasible.

Use of Multidimensional Data Analysis Method for Developing High-Quality Road Asphalt Production Technology

The possibility of analyzing multidimensional data for predicting properties of petroleum road asphalts is examined. Construction of a prognostic model helped determine the optimal feedstock composition and technological parameters of the oxidation process for getting improved asphalts. The positive and negative correlating variables, viz., feedstock properties, oxidation process parameters, and properties of oxidized asphalts, are determined from the data set. The analysis results were used to develop a technology for producing improved asphalts under conditions of asphalt production by OAO Syzranskii NPZ (OJSC Syzran Refinery).