Electrochemical behavior of hydrogen precipitated Zircaloy-4

2015 ◽  
Vol 29 (32) ◽  
pp. 1550200 ◽  
Author(s):  
Mohsin Rafique ◽  
Naveed Afzal ◽  
K. M. Deen ◽  
Yong-Soo Kim

This work investigates the hydrogen precipitation effects on the electrochemical behavior of Zircaloy-4 in acidic saline media. The specimens of Zircaloy-4 were hydrogen charged at 200, 400 and 600 ppm concentrations for 30 min at 400[Formula: see text]C. X-ray diffraction (XRD) studies confirmed the formation of delta hydrides in the material. Scanning electron microscopy (SEM) results also indicated the presence of elongated hydrides whose density and thickness increased with the increase of hydrogen concentration in the alloy. The corrosion kinetics of the specimens were explored before and after hydrogen precipitation using potentiodynamic anodic polarization (PAP) and electrochemical impedance spectroscopy (EIS) techniques. The results showed that hydrogen precipitation shifts the corrosion potential towards more positive and thus improves the corrosion resistance of the alloy. The charge transfer resistance [Formula: see text] of the alloy was found to increase with increasing hydrogen concentration. This indicates an increased polarization tendency of the Zircaloy-4 surface with a limited dissolution tendency in the presence of delta hydrides.

Author(s):  
Syed Abbas Raza ◽  
Muhammad Imran Khan ◽  
Muhammad Ramzan Abdul karim ◽  
Rashid Ali ◽  
Muhammad Umair Naseer ◽  
...  

Abstract Equiatomic TiNi alloy composites, reinforced with 0, 5, 10 and 15 vol. % ZrO2, were synthesized using conventional sintering approach. Equiatomic TiNi pre-alloyed powder and ZrO2 powder were mixed in planetary ball mill for 6 hours followed by cold compaction and pressure-less sintering, respectively. The sintered density was found to vary inversely with the addition of ZrO2 content. The X-Ray diffraction spectra have shown the formation of multiple-phases which were resulted from the decomposition of the B19'and B2 phases of the equiatomic TiNi alloy due to the addition of ZrO2 and higher diffusion rate of Ni than that of Ti in the alloy composite. An increase in hardness was noted due to the addition of ZrO2, measured by micro and nanoindentation techniques. Potentiodynamic polarization scan revealed a 10% decrease in the corrosion rate of the composite containing 10 vol. % ZrO2. Electrochemical impedance spectroscopy results indicated an increase in passive layer resistance (Rcoat) due to the increase in charge transfer resistance (Rct) caused by the reduced leaching of ions from the surface.


Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 241
Author(s):  
Keishu Miki ◽  
Takeshi Watanabe ◽  
Shinji Koh

In research on enzyme-based biofuel cells, covalent or noncovalent molecular modifications of carbon-based electrode materials are generally used as a method for immobilizing enzymes and/or mediators. However, the influence of these molecular modifications on the electrochemical properties of electrode materials has not been clarified. In this study, we present the electrochemical properties of chemical vapor deposition (CVD)-grown monolayer graphene electrodes before and after molecular modification. The electrochemical properties of graphene electrodes were evaluated by cyclic voltammetry and electrochemical impedance measurements. A covalently modified graphene electrode showed an approximately 25-fold higher charge transfer resistance than before modification. In comparison, the electrochemical properties of a noncovalently modified graphene electrode were not degraded by the modification.


2016 ◽  
Vol 23 (02) ◽  
pp. 1550111 ◽  
Author(s):  
JIBO JIANG ◽  
CHENQI FENG ◽  
WEI QIAN ◽  
LIBIN YU ◽  
FENGYING YE ◽  
...  

The electrodeposition of Ni–nano-Cr2O3 composite coatings was studied in electrolyte containing different contents of Cr2O3 nanoparticles (Cr2O3 NPs) on mild steel surfaces. Some techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness, the potentiodynamic polarization curves (Tafel) and electrochemical impedance spectroscopy (EIS) were used to compare pure Ni coatings and Ni–nano-Cr2O3 composite coatings. The results show that the incorporation of Cr2O3 NPs resulted in an increase of hardness and corrosion resistance, and the maximum microhardness of Ni-nano-Cr2O3 composite coatings reaches about 495 HV. The coatings exhibit an active-passive transition and relatively large impedance values. Moreover, the effect of Cr2O3 NPs on Ni electrocrystallization is also investigated by cyclic voltammetry (CV) and EIS spectroscopy, which demonstrates that the nature of Ni-based composite coatings changes attributes to Cr2O3 NPs by offering more nucleation sites and less charge transfer resistance.


NANO ◽  
2013 ◽  
Vol 08 (06) ◽  
pp. 1350063
Author(s):  
JINXIAN LIN ◽  
PAN WANG ◽  
YUYING ZHENG

A poly(pyrrolyl methane) (Poly[pyrrole-2, 5-diyl(4-methoxybenzylidane)], PPDMOBA)/multiwalled carbon nanotubes (MWNTs) composites are fabricated by in situ chemical polycondensation of pyrrole and 4-methoxybenzaldehyde on MWNTs. The structure, morphology, thermal stability and electrical property of the resulting composites are investigated via fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and a four-probe method. The electrochemical performance of the composites is determined in a three-electrode system using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. FTIR, FESEM and TEM confirm that the composites have been successfully prepared, and PPDMOBA is uniformly dispersed in MWNTs. Electrical conductivity of PPDMOBA/MWNTs composites is 1.39 S cm-1, which is significantly larger than that of pristine PPDMOBA. The specific capacitance and charge transfer resistance of the composites is 56 F g-1 (1 mA cm-2) and 0.3Ω, respectively.


2018 ◽  
Vol 96 (5) ◽  
pp. 477-483 ◽  
Author(s):  
Saeid Panahi ◽  
Moosa Es’haghi

In this work, PANI/MnCo2O4 nanocomposite was prepared via in-situ chemical polymerization method. Materials synthesized were characterized by FTIR spectroscopy, X-ray diffraction, and scanning electron spectroscopy. In addition, surface characterization of samples such as specific surface area, pore volume, and pore size distribution was studied. Supercapacitor capability of materials was investigated in 1 mol L–1 Na2SO4 solution using cyclic voltammetry in different potential scan rates and electrochemical impedance spectroscopy (EIS). The specific capacitance of materials was calculated, and it was observed that the specific capacitance of PANI/MnCo2O4 nanocomposite was 185 F g−1, much larger than PANI. Moreover, the prepared nanocomposite exhibited better rate capability in scan rate of 100 mV s−1 with respect to PANI. The EIS experiments revealed that the nanocomposite has lower charge transfer resistance compared with pure PANI. Subsequently, it was shown that the nanocomposite cycling performance was superior to the PANI cycling performance.


2016 ◽  
Vol 22 (3) ◽  
pp. 171 ◽  
Author(s):  
Malika Diafi ◽  
Said Benramache ◽  
Elhachmi Guettaf Temam ◽  
Adaika Mohamed Lakhdar ◽  
Brahim Gasmi

<p class="AMSmaintitle">Abstract</p><p class="Default">The aim of this research work was to codeposit nano-Al<sub>2</sub>O<sub>3</sub> particles into Zn-Ni alloy coatings in order to improve some surface ,properties, the influence of the concentration of Al2O3 is the principal object in order to improve the corrosion resistance of the deposit, which has been made by electroplating on steel substrates previously treated, have been studied by several characterization methods, as the X-ray diffraction, measurement of micro hardness and scanning electron microscopy (SEM), protection against corrosion properties studied in a solution of 3% NaCl in the potentiodynamic polarization measurements (Tafel), electrochemical impedance spectroscopy (EIS) to the potential of corrosion free. The parameters that characterize the corrosion behavior can be determined from the plots and Nyquist plots and chronopotentiometry. Trends of increasing the charge transfer resistance and the decrease of capacitance values. XRD and SEM results and identify any coatings Zn-Ni and Zn-Ni-Al<sub>2</sub>O<sub>3</sub> alloy composition have similar phase ( γ-phase structure) and the addition of Al<sub>2</sub>O<sub>3</sub> in the Zn-Ni matrix increases the microhardness, and we note the maximum hardness is obtained for 50 g/L Al<sub>2</sub>O<sub>3</sub>.</p><p class="Default"> </p>


2015 ◽  
Vol 15 (10) ◽  
pp. 8042-8047 ◽  
Author(s):  
Minchan Jeong ◽  
Hyun-Soo Kim ◽  
Dong-Sik Bae ◽  
Chang-Woo Lee ◽  
Bong-Soo Jin

In this study, the Li3V2–X YX(PO4)3 compounds have been synthesized by a simple solid state method. In addition, a polyurethane was added to apply carbon coating on the surface of the Li3V2–X YX(PO4)3 particles for enhancement of the electrical conductivity. The crystal structure and morphology of the synthesized Li3V2–XYX(PO4)3/C (LVYP/C) was investigated using an X-ray diffraction (XRD) and a scanning electron microscopy (SEM) systematically. The electrochemical performance of synthesized material, such as the initial capacity, rate capability, cycling performance and EIS was evaluated. The sizes of synthesized particle ranged from 1 to 5 μm. The Li3V2–XYX(PO4)3/C (X = 0.02) delivered the initial discharge capacity of 171.5 mAh · g–1 at 0.1C rate. It showed a capacity retention ratio of 73.0% at 1.0C after 100th cycle. The electrochemical impedance spectroscopies (EIS) results revealed that the charge transfer resistance of the material decreases by Y doping.


2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Nicanor Cimpoeşu ◽  
Lucia Carmen Trincă ◽  
Georgiana Dascălu ◽  
Sergiu Stanciu ◽  
Silviu Octavian Gurlui ◽  
...  

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).


2011 ◽  
Vol 689 ◽  
pp. 350-354 ◽  
Author(s):  
Xiang Li Li ◽  
Chun Hua Xu ◽  
Zhi Lei Wen ◽  
Wen Jie Zhang

TiO2nanotube arrays were fabricated in the electrolyte containing 0.25wt% NH4F, 2.5vol% water and the ethylene glycol for various hours at room temperature by anodization of Ti foil in this paper. Some anodized specimens were annealed at 450°C for 3 hours. Electrochemical Impedance Spectroscopy (EIS) was employed to measure electrochemical parameters of anodized specimens. The morphology and crystalline structure of anodized products were characterized by Field Emission Scanning Electronic Microscopy (FESEM), X-ray Diffraction (XRD) and Transmission Electronic Microscopy (TEM). A non-tube layer appears on nanotube arrays with the increase in anodization time. Anodized TiO2nanotube arrays have an amorphous structure, which transfers to anatase structure after annealing at 450°C. A new equivalent circuit R(CR(R(QR)(CR))) was proposed to fit EIS data. The results show that the charge transfer resistance at the electrode/electrolyte interface controls the electrochemical process of TiO2nanotubes.


2011 ◽  
Vol 700 ◽  
pp. 211-214
Author(s):  
Bhuvaneswari Kannan ◽  
David E. Williams ◽  
Jadranka Travas-Sejdic

Electrochemical DNA sensors can be constructed by understanding basic interfacial electron transfer between solid surface-electrolyte-DNA interfaces. The kinetics of this heterogeneous process can be significantly affected by the microstructure and roughness of the electrode surface. By understanding this concept, in this paper; we compared the performance of micro electrodes containing poly(Py-co-PAA) with macro electrode containing same copolymer, showing that micro electrodes are more sensitive than the macro electrodes for biosensor applications. Sensors based on the copolymer electropolymerised on both micro and macro electrodes were evaluated across a range of oligonucleotide concentrations. The interfacial electron charge transfer resistance between the solution and electrode surface was studied using electrochemical impedance spectroscopy (EIS).


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