scholarly journals Electrochemical Characterization of a New Biodegradable FeMnSi Alloy Coated with Hydroxyapatite-Zirconia by PLD Technique

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Nicanor Cimpoeşu ◽  
Lucia Carmen Trincă ◽  
Georgiana Dascălu ◽  
Sergiu Stanciu ◽  
Silviu Octavian Gurlui ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Zero Current ◽  
Capacitive Effect ◽  
Current Potential

Biodegradable alloys are very attractive biomaterials. Electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization (LPP) techniques were used for the study of the electrochemical behavior of uncoated FeMnSi and coated FeMnSi with hydroxyapatite + zirconia (HA-ZrO2) through pulsed laser deposition (PLD) technique. Experiments were carried out using Hank’s balanced salt solution (HBSS). It has been shown that in HBSS the impedance for uncoated FeMnSi was mainly characterized by one capacitive effect, which related to the alloy charge transfer control. The charge transfer resistance increases for HA-ZrO2-coated FeMnSi alloy. The equivalent circuits simulating the electrochemical behavior of both uncoated and HA-ZrO2-coated FeMnSi alloys in HBSS were proposed. From LPP the corrosion resistance was evaluated by means of the zero current potential (ZCP) and corrosion current density (jcorr). The surface morphology of both uncoated and HA-coated FeMnSi alloys in HBSS obtained after LPP was studied using scanning electron microscopy (SEM).

scholarly journals Electrochemical, Thermodynamic, Surface, and Spectroscopic Study in Inhibition of Iron Corrosion with Turmeric Root Extract (TRE)

2020 ◽  
Author(s):  
Khuloud Almzarzie ◽  
Ayman Almassri ◽  
Ahmad Falah ◽  
Hassan Kellawi
Keyword(s):  
Charge Transfer ◽  
Inhibition Efficiency ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Root Extract ◽  
Iron Corrosion ◽  
Transfer Resistance ◽  
Corrosion Reaction ◽  
Capacitive Loop

Turmeric root extract was tested as corrosion inhibitor for iron in 0.5 M HCl, using potentiodynamic polarization and electrochemical impedance spectroscopy, scanning electron microscope, and energy dispersive X-ray analysis. The inhibition efficiency increases as the time of immersion rises but decreases with temperature rise. The Nyquist plots showed that the charge transfer resistance increases and the double-layer capacitance decreases as the time of immersion increases. Tafel results show that both corrosion current and corrosion speed are reduced with time of immersion. All impedance spectra of EIS tests exhibit one capacitive loop, which indicates that the corrosion reaction is controlled by charge transfer process. Inhibition efficiency increases with the concentration of the inhibitor reaching its maximum value, 88.90%, at 8 g/100 mL. Thermodynamic parameters, Ea, ∆H*, and ∆S*, were estimated, and the mechanism of corrosion and inhibition was discussed. The adsorption of turmeric root extract followed Langmuir adsorption isotherm.

MONITORED DEFORMATION BY POTENTIAL-INDUCED DEFECTS IN CH3(CH2)n−1SH SELF-ASSEMBLED MONOLAYERS ON GOLD: EIS STUDY OF CHAIN LENGTH EFFECT ON SUBDIFFUSION AND SAMs’ HETEROGENEITY

2019 ◽  
Vol 26 (10) ◽  
pp. 1950067 ◽  
Author(s):  
AHMED MOUGARI ◽  
MOKHTAR ZABAT ◽  
SMAIL BOUDJADAR
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance ◽  
Defect Density ◽  
Charge Transfer Resistance ◽  
Electrical Circuit ◽  
Transfer Resistance ◽  
Low Frequencies ◽  
Interface Evolution ◽  
Impedance Measurements ◽  
Self Assembled

From the defects-free self-assembled organic layers (SAMs) of CH3([Formula: see text]SH molecules with short chain lengths ([Formula: see text]) electrodeposited on the (111) surface of monocrystalline gold previously prepared, monitored defects (pinholes) were potential-induced from cyclic partial reduction of SAMs at an appropriate potential. Electrochemical impedance measurements were in-situ conducted and [Fe(CN)6][Formula: see text] ions were used as probes for mass and charge transfer. Interface evolution was modeled with an equivalent electrical circuit containing two distinct constant-phase elements (CPEs). One is a generalized semi-infinite Warburg element in series with a charge transfer resistance attributed to subdiffusion phenomenon through leaky sublayers at low frequencies; the other CPE is used for characterizing the interface heterogeneity at medium and high frequencies. At low frequencies, electrochemical impedance measurements show subdiffusion phenomenon, which depends on the remaining sublayer and its thickness. When the defect density increases, diffusion tends to be ordinary, obeying the Fick’s law.

Corrosion performance of mild steel and epoxy coated rebar in concrete under simulated harsh environment

2019 ◽  
Vol 37 (5) ◽  
pp. 657-678
Author(s):  
Muazzam Ghous Sohail ◽  
Mohammad Salih ◽  
Nasser Al Nuaimi ◽  
Ramazan Kahraman
Keyword(s):  
Mild Steel ◽  
Polarization Resistance ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Charge Transfer Resistance ◽  
Harsh Environment ◽  
Corrosion Performance ◽  
Transfer Resistance ◽  
Content Type ◽  
Rc Structures

Purpose The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides. Design/methodology/approach The blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure. Findings Mild steel BB showed a high corrosion current density of 1.24 µA/ cm2 in Tafel plots and a very low polarization resistance of 4.5 kΩ cm2 in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm2 is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl− solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions. Originality/value The corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.

scholarly journals Electrochemical, Structural and Morphological Characterization of Hydrothermally Fabricated Binary Palladium Alloys PdCo and PdNi

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 796
Author(s):  
Edson Meyer ◽  
Raymond Taziwa ◽  
Dorcas Mutukwa ◽  
Nyengerai Zingwe
Keyword(s):  
Solar Cells ◽  
Charge Transfer ◽  
Binary Alloys ◽  
Dye Sensitized Solar Cells ◽  
Charge Transfer Resistance ◽  
Palladium Alloys ◽  
Transfer Resistance ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

This article details the development and characterization of binary palladium alloys synthesized via a hydrothermal process. Palladium alloys, being good redox catalysts, could potentially replace platinum in many applications such as in dye sensitized solar cells, capacitors and vehicular catalytic converters where platinum is vital for maximum productivity. A good replacement should be cheap, readily available and be able to offer comparable catalytic activity to that of platinum. As such we hereby attempt to hydrothermally fabricate and characterize binary palladium alloys PdNi and PdCo that could be ideal replacements for platinum. XRD analysis of the as-synthesized binary alloys revealed the existence of only palladium peaks at 2θ values of 40.1°, 46.7°, 68.1°, 82.1° and 86.6°, indicative of the successful formation of the binary alloys. SEM micrographs revealed that both alloys consisted of spherical particles with PdCo agglomerating to an extent, whereas PdNi was widely distributed, thus it could enhance electrolyte adsorption during catalytic reduction reactions. Cyclic voltammetry analysis at 50 mV∙s−1 revealed that PdNi is more electrocatalytically active with a reduction current density of 41 mA∙cm−2 compared to 18 mA∙cm−2 for PdCo. Lower charge transfer resistance from electrochemical impedance spectroscopy confirmed the superior catalytic ability of PdNi. The two palladium alloys also produced maximum specific capacitances of 68 and 27 F∙g−1 for PdNi and PdCo respectively. Analysis of the sample stability yielded coulombic efficiency retention of 98.7 and 97% for PdNi and PdCo respectively after 1000 cycles. Results obtained have shown that the palladium alloys with their low charge transfer resistance could be ideal replacements for platinum in dye sensitized solar cells. Modest specific capacitance for PdNi illustrates its potential as an electrode catalyst in capacitors.

scholarly journals Electrochemical behaviour of poly(3,4-ethylenedioxytiophene) modified glassy carbon electrodes after overoxidation − the influence of the substrate on the charge transfer resistance

2018 ◽  
Author(s):  
Dora Zalka ◽  
Soma Vesztergom ◽  
Mária Ujvári ◽  
Gyözö Láng
Keyword(s):  
Charge Transfer ◽  
Glassy Carbon ◽  
Electrochemical Impedance ◽  
Electrochemical Behaviour ◽  
Mechanistic Explanation ◽  
Time Instant ◽  
Charge Transfer Resistance ◽  
Polymer Chains ◽  
Transfer Resistance ◽  
Impedance Measurements

<p class="PaperAbstract">Time dependence of the electrochemical impedance of an overoxidized glassy carbon|poly(3,4-ethylenedioxytiophene) (PEDOT)|0.1 mol·dm<sup>-3</sup> sulfuric acid (aq.) elec­trode has been investigated. To follow the changes occurring at the film/substrate interface after the overoxidation procedure, successive impedance measurements were carried out. Although the system is intrinsically nonstationary, the charge transfer resis­tance (R<sub>ct</sub>) cor<strong>­</strong>res<strong>­</strong>ponding to different time instants could be determined by using the so-called 4-dimensional analysis method. The same post-experimental mathematic­cal/ana­lytical procedure could be used also for the estimation of the charge transfer resistance corresponding to the time instant just after overoxidation of the PEDOT film. The increase of the charge transfer resistance of the overoxidized system with respect to that of the pristine electrode suggests that during overoxidation the electrochemical activity of the film decreases and the charge transfer process at the metal/film interface beco­mes more hindered. After the overoxidation procedure, when the electrode potential was held in the “stability region” (at E = 0.4 V vs. SSCE in the present case) the R<sub>ct</sub> decre­ased continuously with experiment time to a value somewhat higher than that of the pristine electrode.<strong> </strong>By comparing the properties of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> and the Au|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrodes a possible mechanistic explanation for the observed behavior has been proposed. This is based on the assumption that in the case of the GC|PEDOT|0.1 M H<sub>2</sub>SO<sub>4</sub> electrode two processes may occur simultaneously during the impedance measurements: (a) reduction of the oxidized surface of the GC substrate, including the reduction of the oxygen-containing surface functionalities and (b) read­sorption of the polymer chains (polymer chain ends) on the surface.<strong></strong></p>

scholarly journals Electrochemical Impedance Spectroscopy on the Performance Degradation of LiFePO4/Graphite Lithium-Ion Battery Due to Charge-Discharge Cycling under Different C-Rates

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4507 ◽  
Author(s):  
Yusuke Abe ◽  
Natsuki Hori ◽  
Seiji Kumagai
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Specific Capacity ◽  
Lithium Ion ◽  
Performance Degradation ◽  
Charge Transfer Resistance ◽  
Transfer Resistance ◽  
Charge Discharge

Lithium-ion batteries (LIBs) using a LiFePO4 cathode and graphite anode were assembled in coin cell form and subjected to 1000 charge-discharge cycles at 1, 2, and 5 C at 25 °C. The performance degradation of the LIB cells under different C-rates was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. The most severe degradation occurred at 2 C while degradation was mitigated at the highest C-rate of 5 C. EIS data of the equivalent circuit model provided information on the changes in the internal resistance. The charge-transfer resistance within all the cells increased after the cycle test, with the cell cycled at 2 C presenting the greatest increment in the charge-transfer resistance. Agglomerates were observed on the graphite anodes of the cells cycled at 2 and 5 C; these were more abundantly produced in the former cell. The lower degradation of the cell cycled at 5 C was attributed to the lowered capacity utilization of the anode. The larger cell voltage drop caused by the increased C-rate reduced the electrode potential variation allocated to the net electrochemical reactions, contributing to the charge-discharge specific capacity of the cells.

Engineering the ABIO-BIO interface of neurostimulation electrodes using polypyrrole and bioactive hydrogels

2020 ◽  
Vol 92 (6) ◽  
pp. 897-907 ◽  
Author(s):  
Ankita Bhat ◽  
Alexa R. Graham ◽  
Hemang Trivedi ◽  
Matthew K. Hogan ◽  
Philip J. Horner ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Density ◽  
Electrochemical Impedance ◽  
Inverse Correlation ◽  
Membrane Resistance ◽  
Charge Transfer Resistance ◽  
Foreign Body Response ◽  
Transfer Resistance ◽  
Cord Injury ◽  
Interfacial Impedance

AbstractFollowing spinal cord injury, the use of electrodes for neurostimulation in animal models has been shown to stimulate muscle movement, however, the efficacy of such treatment is impaired by increased interfacial impedance caused by fibrous encapsulation of the electrode. Sputter-deposited gold-on-polyimide electrodes were modified by potentiostatic electrodeposition of poly(pyrrole-co-3-pyrrolylbutyrate-conj-aminoethylmethacrylate): sulfopropyl methacrylate [P(Py-co-PyBA-conj-AEMA):SPMA] to various charge densities (0–100 mC/cm2) to address interfacial impedance and coated with a phosphoryl choline containing bioactive hydrogel to address biocompatibility at the ABIO-BIO interface. Electrodes were characterized with scanning electron microscopy (surface morphology), multiple-scan rate cyclic voltammetry (peak current and electroactive area), and electrochemical impedance spectroscopy (charge transfer resistance and membrane resistance). SEM analysis and electroactive area calculations identified films fabricated with a charge density of 50 mC/cm2 as well suited for neurostimulation electrodes. Charge transfer resistance demonstrated a strong inverse correlation (−0.83) with charge density of electrodeposition. On average, the addition of polypyrrole and hydrogel to neurostimulation electrodes decreased charge transfer resistance by 82 %. These results support the use of interfacial engineering techniques to mitigate high interfacial impedance and combat the foreign body response towards epidurally implanted neurostimulation electrodes.

Thermal transitions in hydrated layer-by-layer assemblies observed using electrochemical impedance spectroscopy

Soft Matter ◽  
2014 ◽  
Vol 10 (34) ◽  
pp. 6467-6476 ◽  
Author(s):  
Choonghyun Sung ◽  
Katelin Hearn ◽  
Jodie Lutkenhaus
Keyword(s):  
Charge Transfer ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Electrochemical Impedance ◽  
Charge Transfer Resistance ◽  
Thermal Transition ◽  
Layer By Layer ◽  
Thermal Transitions ◽  
Transfer Resistance ◽  
Hydrated Layer

Layer-by-layer assemblies exhibit increased conductivity and decreased charge transfer resistance upon heating through the thermal transition.

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