scholarly journals Electrochemical properties and thermal stability of epoxy coatings electrodeposited on aluminium and modified aluminium surfaces

2001 ◽  
Vol 66 (11-12) ◽  
pp. 871-880 ◽  
Author(s):  
Vesna Miskovic-Stankovic ◽  
Zorica Lazarevic ◽  
Zorica Kacarevic-Popovic
Keyword(s):  
Thermal Stability ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Charge Transfer Resistance ◽  
Epoxy Coatings ◽  
Transfer Resistance ◽  
Protective Properties ◽  
Chemically Modified ◽  
Thermal Stability Of

The corrosion behaviour of epoxy coatings electrodeposited on aluminium, as well as on electrochemically and chemically modified aluminium were investigated during exposure to 3 % NaCl. Electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA) were used for the determination of the protective properties of epoxy coatings on aluminium, anodized aluminium, phosphatized and chromatized-phosphatized aluminium. The protective properties of epoxy coatings on anodized and chromatized-phosphatized aluminium are significantly improved with respect to the same epoxy coatings on aluminium and phosphatized aluminium: higher values of the pore resitance and charge-transfer resistance, lower values of the coating capacitance, double-layer capacitance and relative permittivity (from EIS) smaller amount of absorbed water inside the coating (From TGA). On the other hand, the lower values of the ipdt temperature indicate a lower thermal stability of the epoxy coatings on anodized and chromatized-phosphatized aluminium.

scholarly journals Epoxy coatings electrodeposited on aluminium and modified aluminium surfaces

2002 ◽  
Vol 56 (11) ◽  
pp. 468-472
Author(s):  
Zorica Lazarevic ◽  
Vesna Miskovic-Stankovic ◽  
Zorica Kacarevic-Popovic ◽  
Dragutin Drazic
Keyword(s):  
Thermal Stability ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
The Other ◽  
Nacl Solution ◽  
H2 Evolution ◽  
Epoxy Coatings ◽  
Protective Properties ◽  
Aluminum Surfaces ◽  
Thermal Stability Of

The corrosion behaviour and thermal stability of epoxy coatings electrodeposited on modified aluminum surfaces (anodized, phosphatized and chromatized-phosphatized aluminium) were monitored during exposure to 3% NaCl solution, using electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA). Better protective properties of the epoxy coatings on anodized and chromatized-phosphatized aluminum with respect to the same epoxy coatings on aluminum and phosphatized aluminum were obtained: higher values of Rp and Rct and smaller values of Cc and Cd, from EIS, and a smaller amount of absorbed water inside the coating, from TGA. On the other hand, a somewhat lower thermal stability of these coatings was obtained (smaller values of the ipdt temperature). This behavior can be explained by the less porous structure of epoxy coatings on anodized and chromatized-phosphatized aluminum, caused by a lower rate of H2 evolution and better wet ability.

scholarly journals INFLUENCE OF A PREFABRICATED-CROWN ROLLING PROCESS ON THE CORROSION BEHAVIOUR OF AZ31 MAGNESIUM ALLOY

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Zhiquan Huang ◽  
Jinchao Zou ◽  
Junpeng Wang ◽  
Yanjie Pei ◽  
Renyao Huang ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Plate Thickness ◽  
Az31 Alloy ◽  
Rolling Process ◽  
Charge Transfer Resistance ◽  
Az31 Magnesium Alloy ◽  
Transfer Resistance

The present study aims to investigate the effect of a prefabricated-crown rolling process on the corrosion characteristic of the AZ31 magnesium alloy. Specimens made of the AZ31 alloy were rolled under various crown conditions, and their microstructure evolution and corrosion behavior were analyzed. The corrosion behavior was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion-current density of the AZ31 alloy with a side pressure of 37.5 % of the plate thickness of the precast convexity decreased from 3.79 × 10–6 A/cm2 to 1.80 × 10–6 A/cm2, and the difference between the edge and the middle of the AZ31 alloy was shortened from 2.05 × 10–6 A/cm2 to 1.14 × 10–6 A/cm2. The charge-transfer resistance also increased from 507.1 Ω·cm2 to 581.2 Ω·cm2. The improvement in the corrosion resistance is a result of the more stable corrosion products and microstructure refinement formed after the prefabricated-crown rolling process.

Polyaniline Binder for Functionalized Acetylene Black: A Hybrid Material for Supercapacitor

2014 ◽  
Vol 1024 ◽  
pp. 327-330
Author(s):  
Singh Ajit ◽  
Srinivasan Palaniappan ◽  
S. Gopukumar
Keyword(s):  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Acetylene Black ◽  
Transfer Resistance ◽  
Bonding Effect ◽  
Ft Ir ◽  
Xps Study ◽  
Low Charge ◽  
Electrochemical Impedance Spectroscopic ◽  
Thermal Stability Of

Polyaniline-doped with functionalyzed acetylene black material has been successfully synthesized and used as an electrode material in supercapacitor, wherein, this material contributes both pseudocapacitative (PC) and electrical double layer capacitative (EDLC) behaviour. Functionalization of acetylene black (AB) has been carried out and used as dopant for THF soluble polyaniline base (PANI) to prepare PANI-functionalized acetylene black (PANI-FAB). Formation of FAB and PANI-FAB was confirmed with the help of FT-IR and XPS study. Functionalization of AB results in agglomerated FAB and doping with PANI results in agglomerated fibrous PANI-FAB, as compared to fibrous AB. High thermal stability of AB decreases on functionalization and again slightly increases for PANI-FAB. Functionalization of AB also results good bonding effect with PANI, where PANI acts as both PC and binder, instead of the higher amounts of binder (PVdF > 30 wt%) that are normally needed to hold AB. Electrochemical studies of FAB and PANI-FAB materials were carried out by cyclic voltammetric and electrochemical impedance spectroscopic methods. PANI-FAB supercapacitor cell shows capacitance of 132 Fg1for 0.3 Ag1current density with very low charge-transfer resistance and low time constant.

scholarly journals Developing Activated Carbon Veil Electrode for Sensing Salivary Uric Acid

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 287
Author(s):  
Maria A. Bukharinova ◽  
Natalia Yu. Stozhko ◽  
Elizaveta A. Novakovskaya ◽  
Ekaterina I. Khamzina ◽  
Aleksey V. Tarasov ◽  
...  
Keyword(s):  
Uric Acid ◽  
Electrochemical Impedance ◽  
Linear Sweep Voltammetry ◽  
Cost Effective ◽  
Human Saliva ◽  
Charge Transfer Resistance ◽  
Oxidation Potential ◽  
Transfer Resistance ◽  
Highly Sensitive

The paper describes the development of a carbon veil-based electrode (CVE) for determining uric acid (UA) in saliva. The electrode was manufactured by lamination technology, electrochemically activated and used as a highly sensitive voltammetric sensor (CVEact). Potentiostatic polarization of the electrode at 2.0 V in H2SO4 solution resulted in a higher number of oxygen and nitrogen-containing groups on the electrode surface; lower charge transfer resistance; a 1.5 times increase in the effective surface area and a decrease in the UA oxidation potential by over 0.4 V, compared with the non-activated CVE, which was confirmed by energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, chronoamperometry and linear sweep voltammetry. The developed sensor is characterized by a low detection limit of 0.05 µM and a wide linear range (0.09–700 µM). The results suggest that the sensor has perspective applications for quick determination of UA in artificial and human saliva. RSD does not exceed 3.9%, and recovery is 96–105%. UA makes a significant contribution to the antioxidant activity (AOA) of saliva (≈60%). In addition to its high analytical characteristics, the important advantages of the proposed CVEact are the simple, scalable, and cost-effective manufacturing technology and the absence of additional complex and time-consuming modification operations.

Quantitative Determination of Triiodothyronine by Electrochemical Impedance Spectroscopic Biosensor Using Gold Nanoparticle-Modified Electrode

2020 ◽  
Vol 20 (11) ◽  
pp. 7163-7168
Author(s):  
Huynh Vu Nguyen ◽  
Anna Go ◽  
Min-Ho Lee
Keyword(s):  
Quantitative Determination ◽  
Gold Nanoparticle ◽  
Modified Electrode ◽  
Electrochemical Impedance ◽  
Low Cost ◽  
Charge Transfer Resistance ◽  
Impedance Change ◽  
Label Free ◽  
Transfer Resistance

A label-free electrochemical impedimetric immunosensor for the detection of Triiodothyronine—a thyroid hormone that functions as the biomarker for monitoring for thyroid dysfunction was developed. The gold nanoparticle-modified electrode was employed to achieve the sensitive determination of Triiodothyronine at a low concentration level. The gold nanoparticle layer on the gold electrode was generated by chronoamperometry method and its resulting characteristics were investigated by scanning electron microscopy. Redox probe [Fe(CN)6]3−/4− and electrochemical impedance spec-troscopy was used for both evaluation of the immobilization of anti-Triiodothyronine antibody on the electrode surface and quantitative determination of target Triiodothyronine in different concentrations. The electrode with absorbed antibodies showed significant changes in charge transfer resistance upon binding the antigen, which resulted in an increase in normalized impedance change as the addition of antigen concentrations over a dynamic linear range of 0.01–100 ng/ml. These results indicated that the proposed immunosensor could be a potential alternative method for determination of Triiodothyronine in clinics with the advantage of low cost and less time-consuming.

scholarly journals Impedimetric Determination of Kanamycin in Milk with Aptasensor Based on Carbon Black-Oligolactide Composite

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4738 ◽  
Author(s):  
Tatiana Kulikova ◽  
Vladimir Gorbatchuk ◽  
Ivan Stoikov ◽  
Alexey Rogov ◽  
Gennady Evtugyn ◽  
...  
Keyword(s):  
Carbon Black ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
3D Structure ◽  
Cationic Polyelectrolyte ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Chitosan Matrix ◽  
Negative Effect

The determination of antibiotics in food is important due to their negative effect on human health related to antimicrobial resistance problem, renal toxicity, and allergic effects. We propose an impedimetric aptasensor for the determination of kanamycin A (KANA), which was assembled on the glassy carbon electrode by the deposition of carbon black in a chitosan matrix followed by carbodiimide binding of aminated aptamer mixed with oligolactide derivative of thiacalix[4]arene in a cone configuration. The assembling was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. In the presence of the KANA, the charge transfer resistance of the inner interface surprisingly decreased with the analyte concentration within 0.7 and 50 nM (limit of detection 0.3 nM). This was attributed to the partial shielding of the negative charge of the aptamer and of its support, a highly porous 3D structure of the surface layer caused by a macrocyclic core of the carrier. The use of electrostatic assembling in the presence of cationic polyelectrolyte decreased tenfold the detectable concentration of KANA. The aptasensor was successfully tested in the determination of KANA in spiked milk and yogurt with recoveries within 95% and 115%.

scholarly journals The Experimental Verification of a Generalized Model of Equivalent Circuits

2021 ◽  
Vol 49 (1) ◽  
pp. 1-8
Author(s):  
Zoltán Lukács ◽  
Dávid Baccilieri ◽  
Tamás Kristóf
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Mathematical Treatment ◽  
Frequency Range ◽  
Transfer Resistance ◽  
Generalized Model ◽  
Fitting In ◽  
Adsorption Desorption

The determination of typical parameters of electrochemical systems, e.g. the polarization or charge transfer resistances, can be critical with regard to the application of Electrochemical Impedance Spectroscopy (EIS) if the lower frequency range is biased as a result of transport and/or adsorption/desorption processes. In such cases, the charge transfer resistance should be assessed from the higher frequency range which is typically inadequate in itself as an input for nonlinear parameter fitting. In earlier publications, an alternative mathematical treatment of both the Equivalent Circuit (EC) and of the parameter dispersion was provided using a generalized model of ECs and also a dispersion-invariant model of the electrochemical interface. In the present work, the previously presented experimental EIS results were crosschecked to verify the performance of the generalized model against a series of redox and corrosion systems. The results proved that the applied method is consistent and provides a fairly good correlation between the principal resistance data assessed by different methods.

scholarly journals A Surface Network Based on Polytyramine/ Gold Nanoparticles: Characterization, Kinetics, Thermodynamics and Selective Determination of Norepinephrine

2021 ◽  
Vol 26 (1) ◽  
pp. 8-21
Author(s):  
Emad A. Khudaish ◽  
Arwa Al-Maskari
Keyword(s):  
Gold Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Differential Pulse ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Selective Determination ◽  
Irreversible Reaction ◽  
Nanoparticles Characterization

A solid-state sensor was fabricated by a spontaneous electrochemical deposition of polytyramine (Ptyr) film onto a glassy carbon electrode (GCE) which was further peripherally supported by gold nanoparticles (AuNPs). The surface materials of the developed sensor (AuNPs.Ptyr-GCE) were characterized by X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The rate constant of charge transfers (kct) of the as-prepared sensor (8.77 × 10-4 cm/s) was evaluated by fitting the charge transfer resistance (Rct) data in the presence of ferric-ferrous hexacyanide redox couple solution, [Fe(CN)6]3-/4-. The voltammetric behavior of norepinephrine (NOR) was confirmed to follow an irreversible reaction mechanism at which the estimated diffusion coefficient value was 7.39 × 10-5 cm2/s. The sensor showed a large enhancement on NOR oxidation and comparatively lowered its detection limit (DL3s) to 0.130 mM (22 ppb). It was also applied for selective determination of NOR in the presence of high concentrations of ascorbic acid (AA) and uric acid (UA). The interference study highlighted the great stability of the proposed sensor by generating a similar sensitivity as in the pure NOR solution. The analytical performance of the proposed system was validated successfully for pharmaceutical and biological samples with tolerable recovery percentages.

scholarly journals The effect of Zn-Ni sublayers on the corrosion behaviour and thermal stability of epoxy coatings electrodeposited on steel

2000 ◽  
Vol 65 (12) ◽  
pp. 923-933 ◽  
Author(s):  
Vesna Miskovic-Stankovic ◽  
Jelena Bajat ◽  
Miodrag Maksimovic ◽  
Zorica Kacarevic-Popovic
Keyword(s):  
Thermal Stability ◽  
Pulse Current ◽  
Corrosion Behaviour ◽  
Epoxy Coating ◽  
Epoxy Coatings ◽  
Corrosion Stability ◽  
Ni Alloys ◽  
Protective System ◽  
Thermal Stability Of ◽  
Protective Systems

The electrochemical and transport properties, as well as the thermal stability of epoxy coatings electrodeposited on steel and steel modified by Zn-Ni alloys were investigated during exposure to 3% NaCl. The Zn-Ni alloys were electrodeposited on steel using direct and pulse current. From the time dependence of the pore resistance of the epoxy coating (impedance measurements), the diffusion coefficient of water through the epoxy coating (gravimetric liquid sorption measurements) and the thermal stability of the epoxy coating (thermogravimetric analysis), it was shown that Zn-Ni sublayers significantly improve the corrosion stability of a protective system based on an epoxy coating. The values of the pore resistance were almost unchanged over a long period of immersion time for epoxy coatings on steel modified by Zn-Ni alloys, inidicating the great stability of these protective systems.

scholarly journals Electrochemical DNA Sensor Based on the Copolymer of Proflavine and Azure B for Doxorubicin Determination

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 924
Author(s):  
Anna Porfireva ◽  
Gennady Evtugyn
Keyword(s):  
Polymer Film ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Polymer Surface ◽  
Charge Transfer Resistance ◽  
Dna Sensor ◽  
Transfer Resistance ◽  
Redox Probe ◽  
Azure B

A DNA sensor has been developed for the determination of doxorubicin by consecutive electropolymerization of an equimolar mixture of Azure B and proflavine and adsorption of native DNA from salmon sperm on a polymer film. Electrochemical investigation showed a difference in the behavior of individual drugs polymerized and their mixture. The use of the copolymer offered some advantages, i.e., a higher roughness of the surface, a wider range of the pH sensitivity of the response, a denser and more robust film, etc. The formation of the polymer film and its redox properties were studied using scanning electron microscopy and electrochemical impedance spectroscopy. For the doxorubicin determination, its solution was mixed with DNA and applied on the polymer surface. After that, charge transfer resistance was assessed in the presence of [Fe(CN)6]3−/4− as the redox probe. Its value regularly grew with the doxorubicin concentration in the range from 0.03 to 10 nM (limit of detection 0.01 nM). The DNA sensor was tested on the doxorubicin preparations and spiked samples mimicking blood serum. The recovery was found to be 98–106%. The DNA sensor developed can find application for the determination of drug residues in blood and for the pharmacokinetics studies.

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