Effect of Chloride Ions on the Electrochemical Oxidation of Chalcopyrite at 340 °C and 21 MPa

Understanding the oxidative mechanisms of chalcopyrite in various hydrothermal fluids is of great significance to improve copper extraction and to model the geochemical cycling of copper, iron, and sulfur. This paper investigated the effect of NaCl on the electrochemical oxidation of chalcopyrite at 340 °C and 21 MPa using polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. The experimental results showed that NaCl can promote chalcopyrite leaching. As NaCl concentration increases, the protective property of the oxidation layer degraded. In the absence of NaCl, the oxidation layer that consisted of CuSn, (n ≥ 1), probably with some Fe2O3 and Fe(OH)3 and also in the presence of NaCl, Fe2O3, is the principal oxidation product. More rapid ionic diffusion and further chemical reaction contributed to the improvement of chalcopyrite dissolution with increasing NaCl concentration. A dissolution mechanism is proposed in this paper to explain the chalcopyrite leaching processes which is dependent on NaCl concentration.

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Preparation of novel Ti-based MnOx electrodes by spraying method for electrochemical oxidation of Acid Red B

Water Science & Technology ◽

10.2166/wst.2019.282 ◽

2019 ◽

Vol 80 (2) ◽

pp. 365-376

Author(s):

Xuelu Xu ◽

Jiao Zhao ◽

Subei Bai ◽

Rongrong Mo ◽

Yan Yang ◽

...

Keyword(s):

Electrochemical Oxidation ◽

Photoelectron Spectroscopy ◽

Manganese Oxides ◽

Electrochemical Impedance ◽

Charge Transfer Resistance ◽

Cell Potential ◽

Transfer Resistance ◽

X Ray ◽

Concentration Changes ◽

Spraying Method

Abstract At different calcination conditions, titanium-based manganese oxides (MnOx) electrodes were fabricated by spraying method without adhesive. The MnOx/Ti electrodes were applied in electrochemical oxidation of wastewater treatment for the first time. The surface morphologies of electrodes were tested by scanning electron microscopy. The formation of different manganese oxidation states on electrodes was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties of the electrodes have been performed by means of cyclic voltammetry and electrochemical impedance spectroscopy. The characterizations revealed that the MnOx/Ti-350(20) electrode, prepared at calcination temperature of 350 °C for 20 min, exhibited fewer cracks on the electrode surface, larger electrochemically effective surface area and lower charge transfer resistance than electrodes prepared at other calcination conditions. Moreover, Acid Red B was used as target pollutant to test the electrode activity via monitoring the concentration changes by UV spectrophotometer. The results showed that the MnOx/Ti-350(20) electrode presented the best performance on decolorization of Acid Red B with the lowest cell potential during the process of electrochemical oxidation, and the chemical oxygen demand (COD) conversion was 50.7%. Furthermore, the changes of Acid Red B during the electrochemical oxidation process were proposed by the UV–vis spectra.

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Effect of Zn Content on Structure, Roughness and Corrosion Behavior of Zn-Ni Alloys

Scientific Bulletin of Valahia University - Materials and Mechanics ◽

10.2478/bsmm-2019-0013 ◽

2019 ◽

Vol 17 (17) ◽

pp. 17-22

Author(s):

Hayette Faid

Keyword(s):

Corrosion Behavior ◽

Electrochemical Impedance ◽

Stripping Voltammetry ◽

X Ray Diffraction ◽

X Ray ◽

Ni Alloys ◽

Sulfate Bath ◽

Zn Content ◽

Polarization Test ◽

Δ Phase

AbstractIn this work, Zn-Ni alloys have been deposited on steel from sulfate bath, by electrodeposition method. The effect of Zn content on deposits properties was studied by cyclic voltammetry (CV), chronoaperometry (CA), linear stripping voltammetry (ALSV) and diffraction (XRD) and scanning electronic microscopy (SEM). The corrosion behavior in 3.5 wt. NaCl solution was examined using anodic polarization test and electrochemical impedance spectroscopy. X-ray diffraction of show that Zn-Ni alloys structure is composed of δ phase and γ phase, which increase with the decrease of Zn content in deposits. Results show that deposits obtained from bath less Zn2+ concentration exhibited better corrosion resistance.

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Characterizations of Synthetic 8mol% YSZ with Comparison to 3mol %YSZ for HT-SOFC

Engineering and Technology Journal ◽

10.30684/etj.v38i4a.351 ◽

2020 ◽

Vol 38 (4A) ◽

pp. 491-500

Author(s):

Abeer F. Al-Attar ◽

Saad B. H. Farid ◽

Fadhil A. Hashim

Keyword(s):

Ionic Conductivity ◽

Electrochemical Impedance ◽

Structural Information ◽

Impedance Analysis ◽

High Energy ◽

Yttria Stabilized Zirconia ◽

X Ray Diffraction ◽

Stabilized Zirconia ◽

Powder Morphology ◽

X Ray

In this work, Yttria (Y2O3) was successfully doped into tetragonal 3mol% yttria stabilized Zirconia (3YSZ) by high energy-mechanical milling to synthesize 8mol% yttria stabilized Zirconia (8YSZ) used as an electrolyte for high temperature solid oxide fuel cells (HT-SOFC). This work aims to evaluate the densification and ionic conductivity of the sintered electrolytes at 1650°C. The bulk density was measured according to ASTM C373-17. The powder morphology and the microstructure of the sintered electrolytes were analyzed via Field Emission Scanning Electron Microscopy (FESEM). The chemical analysis was obtained with Energy-dispersive X-ray spectroscopy (EDS). Also, X-ray diffraction (XRD) was used to obtain structural information of the starting materials and the sintered electrolytes. The ionic conductivity was obtained through electrochemical impedance spectroscopy (EIS) in the air as a function of temperatures at a frequency range of 100(mHz)-100(kHz). It is found that the 3YSZ has a higher density than the 8YSZ. The impedance analysis showed that the ionic conductivity of the prepared 8YSZ at 800°C is0.906 (S.cm) and it was 0.214(S.cm) of the 3YSZ. Besides, 8YSZ has a lower activation energy 0.774(eV) than that of the 3YSZ 0.901(eV). Thus, the prepared 8YSZ can be nominated as an electrolyte for the HT-SOFC.

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Hydrophobic Modification of Graphene Oxide and Its Effect on the Corrosion Resistance of Silicone-Modified Epoxy Resin

Metals ◽

10.3390/met11010089 ◽

2021 ◽

Vol 11 (1) ◽

pp. 89

Author(s):

Wei Yuan ◽

Qian Hu ◽

Jiao Zhang ◽

Feng Huang ◽

Jing Liu

Keyword(s):

Contact Angle ◽

Corrosion Resistance ◽

Graphene Oxide ◽

Physical Properties ◽

Epoxy Resin ◽

Electrochemical Impedance ◽

Salt Spray ◽

X Ray ◽

Modified Graphene Oxide ◽

Modified Epoxy

This study modified graphene oxide (GO) with hydrophilic octadecylamine (ODA) via covalent bonding to improve its dispersion in silicone-modified epoxy resin (SMER) coatings. The structural and physical properties of ODA-GO were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle tests. The ODA-GO composite materials were added to SMER coatings by physical mixing. FE-SEM, water absorption, and contact angle tests were used to evaluate the physical properties of the ODA-GO/SMER coatings, while salt spray, electrochemical impedance spectroscopy (EIS), and scanning Kelvin probe (SKP) methods were used to test the anticorrosive performance of ODA-GO/SMER composite coatings on Q235 steel substrates. It was found that ODA was successfully grafted onto the surfaces of GO. The resulting ODA-GO material exhibited good hydrophobicity and dispersion in SMER coatings. The anticorrosive properties of the ODA-GO/SMER coatings were significantly improved due to the increased interfacial adhesion between the nanosheets and SMER, lengthening of the corrosive solution diffusion path, and increased cathodic peeling resistance. The 1 wt.% ODA-GO/SMER coating provided the best corrosion resistance than SMER coatings with other amounts of ODA-GO (including no addition). After immersion in 3.5 wt.% NaCl solution for 28 days, the low-frequency end impedance value of the 1 wt.% ODA-GO/SMER coating remained high, at 6.2 × 108 Ω·cm2.

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Influence of HAP on the Morpho-Structural Properties and Corrosion Resistance of ZrO2-Based Composites for Biomedical Applications

Crystals ◽

10.3390/cryst11020202 ◽

2021 ◽

Vol 11 (2) ◽

pp. 202

Author(s):

Réka Barabás ◽

Carmen Ioana Fort ◽

Graziella Liana Turdean ◽

Liliana Bizo

Keyword(s):

Electrochemical Impedance ◽

Artificial Saliva ◽

Synergetic Effect ◽

Composite Layer ◽

Charge Transfer Resistance ◽

Processing Route ◽

Dental Alloys ◽

Metallic Electrode ◽

Transfer Resistance ◽

X Ray

In the present work, ZrO2-based composites were prepared by adding different amounts of antibacterial magnesium oxide and bioactive and biocompatible hydroxyapatite (HAP) to the inert zirconia. The composites were synthesized by the conventional ceramic processing route and morpho-structurally analyzed by X-ray powder diffraction (XRPD) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Two metallic dental alloys (i.e., Ni–Cr and Co–Cr) coated with a chitosan (Chit) membrane containing the prepared composites were exposed to aerated artificial saliva solutions of different pHs (i.e., 4.3, 5, 6) and the corrosion resistances were investigated by electrochemical impedance spectroscopy technique. The obtained results using the two investigated metallic dental alloys shown quasi-similar anticorrosive properties, having quasi-similar charge transfer resistance, when coated with different ZrO2-based composites. This behavior could be explained by the synergetic effect between the diffusion process through the Chit-composite layer and the roughness of the metallic electrode surface.

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Protection of Carbon Steel Rebars by Epoxy Coating with Smart Environmentally Friendly Microcapsules

Coatings ◽

10.3390/coatings11020113 ◽

2021 ◽

Vol 11 (2) ◽

pp. 113

Author(s):

Jacob Ress ◽

Ulises Martin ◽

Juan Bosch ◽

David M. Bastidas

Keyword(s):

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Corrosion Protection ◽

Corrosion Potential ◽

Electrochemical Impedance ◽

Pore Solution ◽

Control Sample ◽

Chloride Ions ◽

Epoxy Coating ◽

Transfer Resistance

The protection of mild steel by modified epoxy coating containing colophony microencapsulated corrosion inhibitors was investigated in this study. The corrosion behavior of these epoxy coatings containing colophony microcapsules was studied by electrochemical analysis using cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. The microcapsule coating showed decreased corrosion current densities of 2.75 × 10−8 and 3.21 × 10−8 A/cm2 along with corrosion potential values of 0.349 and 0.392 VSCE for simulated concrete pore solution and deionized water with 3.5 wt.% NaCl, respectively, indicating improved corrosion protection in both alkaline and neutral pH. Electrochemical impedance spectroscopy analysis also showed charge transfer resistance values over one order of magnitude higher than the control sample, corroborating the electrochemical corrosion potential and current density testing results. Overall, the use of colophony microcapsules showed improved corrosion protection in simulated concrete pore solution and DI water solutions containing chloride ions.

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Electrochemical Investigation of Curcumin–DNA Interaction by Using Hydroxyapatite Nanoparticles–Ionic Liquids Based Composite Electrodes

Materials ◽

10.3390/ma14154344 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4344

Author(s):

Merve Uca ◽

Ece Eksin ◽

Yasemin Erac ◽

Arzum Erdem

Keyword(s):

Electrochemical Impedance ◽

Differential Pulse ◽

Dna Interaction ◽

Composite Electrodes ◽

Hydroxyapatite Nanoparticles ◽

Graphite Electrodes ◽

X Ray ◽

Pulse Voltammetry ◽

Polymerase Chain

Hydroxyapatite nanoparticles (HaP) and ionic liquid (IL) modified pencil graphite electrodes (PGEs) are newly developed in this assay. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV) were applied to examine the microscopic and electrochemical characterization of HaP and IL-modified biosensors. The interaction of curcumin with nucleic acids and polymerase chain reaction (PCR) samples was investigated by measuring the changes at the oxidation signals of both curcumin and guanine by differential pulse voltammetry (DPV) technique. The optimization of curcumin concentration, DNA concentration, and the interaction time was performed. The interaction of curcumin with PCR samples was also investigated by gel electrophoresis.

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Comparison of Biocompatible Coatings Produced by Plasma Electrolytic Oxidation on cp-Ti and Ti-Zr-Nb Superelastic Alloy

Coatings ◽

10.3390/coatings11040401 ◽

2021 ◽

Vol 11 (4) ◽

pp. 401

Author(s):

Ruzil Farrakhov ◽

Olga Melnichuk ◽

Evgeny Parfenov ◽

Veta Mukaeva ◽

Arseniy Raab ◽

...

Keyword(s):

Plasma Electrolytic Oxidation ◽

Electrochemical Impedance ◽

Pure Titanium ◽

Commercially Pure Titanium ◽

X Ray ◽

Kinetic Coefficients ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Cp Ti ◽

Peo Coatings

The paper compares the coatings produced by plasma electrolytic oxidation (PEO) on commercially pure titanium and a novel superelastic alloy Ti-18Zr-15Nb (at. %) for implant applications. The PEO coatings were produced on both alloys in the identical pulsed bipolar regime. The properties of the coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The PEO process kinetics was modeled based on the Avrami theorem and Cottrell equation using a relaxation method. The resultant coatings contain TiO2, for both alloys, and NbO2, Nb2O5, ZrO2 for Ti-18Zr-15Nb alloy. The coating on the Ti-18Zr-15Nb alloy has a higher thickness, porosity, and roughness compared to that on cp-Ti. The values of the kinetic coefficients of the PEO process—higher diffusion coefficient and lower time constant for the processing of Ti-18Zr-15Nb—explain this effect. According to the electrochemical studies, PEO coatings on Ti-18Zr-15Nb alloy provide better corrosion protection. Higher corrosion resistance, porosity, and roughness contribute to better biocompatibility of the PEO coating on Ti-18Zr-15Nb alloy compared to cp-Ti.

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Effect of Molybdenum Content on the Corrosion and Microstructure of Low-Ni, Co-Free Maraging Steels

Metals ◽

10.3390/met11060852 ◽

2021 ◽

Vol 11 (6) ◽

pp. 852

Author(s):

Asiful H. Seikh ◽

Hossam Halfa ◽

Mahmoud S. Soliman

Keyword(s):

Corrosion Resistance ◽

Electrochemical Impedance ◽

Microstructural Analysis ◽

Xrd Analysis ◽

X Ray Diffraction ◽

Alloying Element ◽

X Ray ◽

Maraging Steels ◽

Eds Analysis ◽

Electroslag Refining

Molybdenum (Mo) is an important alloying element in maraging steels. In this study, we altered the Mo concentration during the production of four cobalt-free maraging steels using an electroslag refining process. The microstructure of the four forged maraging steels was evaluated to examine phase contents by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Additionally, we assessed the corrosion resistance of the newly developed alloys in 3.5% NaCl solution and 1 M H2SO4 solution through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Furthermore, we performed SEM and energy-dispersive spectroscopy (EDS) analysis after corrosion to assess changes in microstructure and Raman spectroscopy to identify the presence of phases on the electrode surface. The microstructural analysis shows that the formation of retained austenite increases with increasing Mo concentrations. It is found from corrosion study that increasing Mo concentration up to 4.6% increased the corrosion resistance of the steel. However, further increase in Mo concentration reduces the corrosion resistance.

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Chemisorbed Oxygen or Surface Oxides Steer the Selectivity in Pd Electrocatalytic Propene Oxidation Observed by Operando Pd Ledge X‐ray Absorption Spectroscopy

Catalysis Science & Technology ◽

10.1039/d0cy02134b ◽

2021 ◽

Author(s):

Sergey Koroidov ◽

Anna Winiwarter ◽

Oscar Alfonso Diaz-Morales ◽

Mikaela Gorlin ◽

Joakim Halldin Stenlid ◽

...

Keyword(s):

Electrochemical Oxidation ◽

Absorption Spectroscopy ◽

Propene Oxidation ◽

X Ray ◽

Chemisorbed Oxygen ◽

Oxidation Of Hydrocarbons ◽

Surface Oxides ◽

X Ray Absorption

Controlled electrochemical oxidation of hydrocarbons to desired products is an attractive approach in catalysis. Here we study the electrochemical propene oxidation under operando conditions using Pd L‐edge X‐ray absorption spectroscopy...

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