Corrosion Characteristics of an Ultrafine-Grained Al-Mg-Si Alloy (AA6082)

2008 ◽  
Vol 584-586 ◽  
pp. 988-993 ◽  
Author(s):  
Bernhard Wielage ◽  
Daniela Nickel ◽  
Thomas Lampke ◽  
Gert Alisch ◽  
Harry Podlesak ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Before And After ◽  
Eis Measurements

The corrosion behaviour of the aluminium alloy, AA6082, processed by equal-channel angular pressing (ECAP) after different passes (route E, room temperature) was studied in comparison to the coarse-grained counterpart. The results of the electrochemical investigations (cyclovoltammetry; electrochemical impedance spectroscopy, EIS) are presented in correlation with the microstructure before and after the corrosion examinations. Both, chemical (precipitations, phases) and physical (dislocations, high-angle grain boundaries, grain size, low-angle grain boundaries) inhomogeneities characterize the microstructure of this commercially used Al-Mg-Si alloy. Results indicate an improved resistance against pitting of the ECAP material expressed by a reduced pitting density of up to 50 % and lower pit depths. EIS measurements and microstructural examinations (scanning electron microscopy, transmission electron microscopy, 3D topography measurement) confirm that ECAP modifies the number, size and distribution of these inhomogeneities, which leads to a more favourable corrosion behaviour.

scholarly journals Study on Corrosion Behavior of Ultrafine-Grained Ti-6Al-7Nb Fabricated by Equal Channel Angular Pressing

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 950 ◽  
Author(s):  
Zequn Yu ◽  
Yuecheng Dong ◽  
Xin Li ◽  
Jingzhe Niu ◽  
Igor Alexandrov ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Oxide Film ◽  
Equal Channel Angular Pressing ◽  
Corrosion Behavior ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Electrochemical Measurement ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Ultrafine Grained

The aim of this study was to investigate the corrosion resistance of ultrafine-grained (UFG) Ti-6Al-7Nb fabricated by equal channel angular pressing (ECAP) and coarse-grained (CG) Ti- 6Al- 7Nb. The microstructure of each specimen was investigated by the electron backscattered diffraction (EBSD) method. The corrosion behavior of each specimen was determined by electrochemical measurement in Ringer’s solution. The surface corroded morphologies and oxide film formed on Ti-6Al-7Nb alloy after electrochemical measurement were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). EBSD investigation shows that the grain size of UFG Ti-6Al-7Nb decreased to ~0.4 µm, accompanied by low angle grain boundaries (LAGBs) accounting for 39%. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicated that UFG Ti-6Al-7Nb alloy possessed a better corrosion resistance. The surface corroded morphologies revealed many small and shallow corrosion pits, which can be attributed to the good compactness of the oxide film and a rapid self- repairing ability of the UFG Ti-6Al-7Nb alloy.

Microstructure and Corrosion Behaviour of Ultrafine-Grained Copper

2006 ◽  
Vol 503-504 ◽  
pp. 883-888 ◽  
Author(s):  
Branislav Hadzima ◽  
Miloš Janeček ◽  
Ralph Jörg Hellmig ◽  
Yulia Kutnyakova ◽  
Yuri Estrin
Keyword(s):  
Microstructure Evolution ◽  
Current Density ◽  
Corrosion Behaviour ◽  
Corrosion Damage ◽  
Corrosion Current ◽  
Good News ◽  
Coarse Grained ◽  
Anodic Current Density ◽  
Angular Pressing ◽  
Ultrafine Grained

Microstructure evolution and corrosion behaviour of ultrafine-grained copper processed by equal channel angular pressing (route Bc) were studied. The results of TEM investigation of the microstructure evolution are presented along with the measurements of the corrosion potential, the corrosion current density and the anodic current density for two aggressive media, viz. 3% NaCl and 1M H2SO4. An important finding and a good news is that the corrosion behaviour of ECAP copper is not inferior to and does not qualitatively differ from that of the coarse grained material. Moreover, it was shown by SEM investigation that the corrosion damage is more homogeneous in ultrafine grained ECAP processed copper than in its coarse grained counterpart.

scholarly journals A Sensitive Impedimetric Aptasensor Based on Carbon Nanodots Modified Electrode for Detection of 17ß-Estradiol

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1346 ◽  
Author(s):  
Mohd Hazani Mat Zaid ◽  
Jaafar Abdullah ◽  
Normazida Rozi ◽  
Aliff Aiman Mohamad Rozlan ◽  
Sharina Abu Hanifah
Keyword(s):  
Water Samples ◽  
Electrochemical Impedance ◽  
Carbon Nanodots ◽  
Visible Absorption ◽  
Transmission Electron ◽  
Relative Standard ◽  
Before And After ◽  
Average Recovery Rate ◽  
Aptamer Probe ◽  
Eis Measurements

A simple and sensitive aptasensor based on conductive carbon nanodots (CDs) was fabricated for the detection of 17ß-Estradiol (E2). In the present study, the hydrothermal synthesis of carbon nanodots was successfully electrodeposited on a screen-printed electrode (SPE) as a platform for immobilization of 76-mer aptamer probe. The morphology and structure of the nanomaterial were characterized by UV-visible absorption spectra, Fluorescence spectra, Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Moreover, cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the electrochemical performance of the prepared electrodes. Subsequently, impedimetric (EIS) measurements were employed to investigate the relative impedances changes before and after E2 binding, which results in a linear relationship of E2 concentration in the range of 1.0 × 10−7 to 1.0 × 10 −12 M, with a detection limit of 0.5 × 10−12 M. Moreover, the developed biosensor showed high selectivity toward E2 and exhibited excellent discrimination against progesterone (PRG), estriol (E3) and bisphenol A (BPA), respectively. Moreover, the average recovery rate of spiked river water samples with E2 ranged from 98.2% to 103.8%, with relative standard deviations between 1.1% and 3.8%, revealing the potential application of the present biosensor for E2 detection in water samples.

Investigation of corrosion behavior on plastically deformed aa 7075 t651 by shot peening process

2021 ◽  
Author(s):  
Abeens M ◽  
R Murugananthan
Keyword(s):  
Electron Microscopy ◽  
Corrosion Resistance ◽  
Dislocation Density ◽  
Aluminium Alloy ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
X Ray ◽  
Transmission Electron ◽  
Aa 7075 ◽  
Micro Structures

Abstract As AA 7075 T651 comprehensively is used in the marine naval vessels, the factor of corrosion performance always plays a significant role. In this work, an investigation is carried out to study the effect of corrosion behaviour of shot peened AA 7075 T651 in 3.5% solution. From the potentiodynamic polarization study, a 27.72% decrease is ascertained in the Icorr in shot peened specimen in correlation to unpeened aluminium alloy. A drop in Icorr from 1.883 to 1.480 mA/cm2 in shot peened specimen, indicates enhanced pitting corrosion resistance. An electrochemical impedance spectroscopy reveals a surge in the oxide layer formation on the peened surface aiding the drop in corrosion rate. Resistance to pit formations and improvement in oxygen deposition in the peened specimen is observed availing a Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray analysis (EDX). The micro structures of the peened and unpeened specimen are captured using optical microscopy and Transmission electron microscopy (TEM). Micro-strain, dislocation density is also calculated from the X- ray diffraction analysis (XRD), in which grain size reduces by 28.07%, dislocation density surges by 38.65% and micro strain increases by 21.95% in peened specimen in correlation to unpeened AA 7075 T651, resulting in a surge in corrosion resistance by 27.92% in the peened specimen in correlation to unpeened aluminium alloy.

Synthesis and Densification of Nanometric Ce0.8Sm0.2O1.9-δ

2006 ◽  
Vol 972 ◽  
Author(s):  
Vincenzo Esposito ◽  
Marco Fronzi ◽  
Enrico Traversa
Keyword(s):  
Electron Microscopy ◽  
Liquid Phase ◽  
Electrochemical Impedance ◽  
Liquid Phase Sintering ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Conventional Sintering ◽  
Eis Measurements ◽  
Co Precipitation

AbstractNanometric 20% molar Sm-doped ceria (SDC20) powders were synthesized by tetrametylethylen ammine (TMDA) co-precipitation method. SDC20 was sintered in several conditions to control the final microstructure. Fast firing and conventional sintering were performed. LiNO3was used as an additive to promote liquid phase sintering of ceria at low temperatures (900-1200°C). Powders and dense pellets were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) measurements were performed on dense pellets in air to estimate the contribution of grain boundary and bulk to the electrical conductivity. Liquid phase sintering produced the densest samples with the highest conductivity.

Metals Microstructure Improving under Hard Cyclic Viscoplastic Deformation

2008 ◽  
Vol 584-586 ◽  
pp. 361-366
Author(s):  
Lembit A. Kommel
Keyword(s):  
Grain Boundaries ◽  
Combined Treatment ◽  
Pure Copper ◽  
Metal Flow ◽  
Coarse Grained ◽  
Materials Testing ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Crystallite Sizes ◽  
Dislocations Density

Annealed pure copper was subjected to equal-channel angular pressing (ECAP) by route Bc for different passes number. Tensile test specimens were manufactured and subjected to hard cyclic viscoplastic (HCV) deformation by means of the materials testing installation Instron 8516 in strain control regime at room temperature. The specimens were cyclically deformed with a frequency of 0.5Hz at different strain amplitudes, step-by-step increased from ±0.05 to ±2.5% for 30 cycles, up to seven test series in this study. The microstructure of ECAP and HCV deformed samples were characterized by optical- and transmission electron microscope, X-ray diffraction, tensile- and hardness testing methods. The ECAP processed metal has mainly elongated subgrains with low-angle grain boundaries and texture, oriented in direction of metal flow during latest pressing. We demonstrate that during HCV deformation the dislocations density of ECAP processed UFG copper was decreased. The ECAP texture was reoriented under cyclic load applied as elongated subgrains were jointed to small pieces under this same angle to axis as texture before. The grain- and crystallite sizes were decreased, which were accompanied with dislocation ribbons forming nearby new formed high-angle grain boundaries. This paper builds on knowledge that the combined treatment by ECAP and followed HCV deformation enable to improve UFG microstructure and ductility with lowering the strength and hardness of UFG metals due to the lower dislocation density while coarse grained copper exhibits increasing the strength and hardness.

scholarly journals An amperometric H2O2 biosensor based on hemoglobin nanoparticles immobilized on to a gold electrode

2017 ◽  
Vol 37 (4) ◽  
Author(s):  
Vinay Narwal ◽  
Neelam Yadav ◽  
Manisha Thakur ◽  
Chandra S. Pundir
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Impedance ◽  
Uv Spectroscopy ◽  
Colorimetric Method ◽  
High Sensitivity ◽  
Electrochemical Impedance Spectra ◽  
Sodium Phosphate Buffer ◽  
Transmission Electron ◽  
Before And After ◽  
Optimum Response

The nanoparticles (NPs) of hemoglobin (Hb) were prepared by desolvation method and characterized by transmission electron microscopy (TEM), UV spectroscopy and Fourier-transform IR (FTIR) spectroscopy. An amperometric H2O2 biosensor was constructed by immobilizing HbNPs covalently on to a polycrystalline Au electrode (AuE). HbNPs/AuE were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) before and after immobilization of HbNPs. The HbNPs/AuE showed optimum response within 2.5 s at pH 6.5 in 0.1 M sodium phosphate buffer (PB) containing 100 μM H2O2 at 30°C, when operated at –0.2 V against Ag/AgCl. The HbNPs/AuE exhibited Vmax of 5.161 ± 0.1 μA cm−2 with apparent Michaelis-Menten constant (Km) of 0.1 ± 0.01 mM. The biosensor showed lower detection limit (1.0 μM), high sensitivity (129 ± 0.25 μA cm−2 mM−1) and wider linear range (1.0–1200 μM) for H2O2 as compared with earlier biosensors. The analytical recoveries of added H2O2 in serum (0.5 and 1.0 μM) were 97.77 and 98.01% respectively, within and between batch coefficients of variation (CV) were 3.16 and 3.36% respectively. There was a good correlation between sera H2O2 values obtained by standard enzymic colorimetric method and the present biosensor (correlation coefficient, R2 =0.99). The biosensor measured H2O2 level in sera of apparently healthy subjects and persons suffering from diabetes type II. The HbNPs/AuE lost 10% of its initial activity after 90 days of regular use, when stored dry at 4°C.

Corrosion Resistance of Ultrafine-Grained Pure Cu

2014 ◽  
Vol 912-914 ◽  
pp. 69-72
Author(s):  
D.R. Fang ◽  
L.W. Quan ◽  
J. Yang
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Corrosion Rate ◽  
Electrochemical Impedance ◽  
Coarse Grained ◽  
Nacl Solution ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Pure Cu

Pure Cu samples were subjected to equal channel angular pressing (ECAP), and the corrosion resistance of the samples was investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy measurements in 3.5% NaCl solution. The results show that the corrosion rate of the ultrafine-grained Cu decreases, in comparison with the coarse-grained Cu.

IN SITU TEMPLATE SYNTHESIS OF PoPD–TiO2 NANOCOMPOSITES FOR ACTIVE ANTI-CORROSIVE COATINGS ON 316L SS

2011 ◽  
Vol 10 (04n05) ◽  
pp. 1147-1152 ◽  
Author(s):  
P. MUTHIRULAN ◽  
N. RAJENDRAN
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Impedance ◽  
Material Loss ◽  
Transmission Electron ◽  
Corrosion Studies ◽  
Protective System ◽  
Ft Ir ◽  
Eis Measurements ◽  
Thermal Stability Of

Corrosion is one of the major destruction processes involved in material loss, and its prevention is paramount in protecting investments. The present work shows a new contribution to the design of a new protective system based on poly(orthophenylenediamine) (PoPD)–nano- TiO2 composites. The structure and properties of PoPD– TiO2 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), Cyclicvoltammetry (CV), Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. Thermal stability of the composite was studied by Thermogravimetric analysis (TGA). The anti-corrosion behavior of PoPD– TiO2 nanocomposites has been investigated in 3.5 wt.% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) measurements. Corrosion studies revealed that PoPD– TiO2 nanocomposites coating exhibited excellent anti-corrosive properties compared with PoPD coated and uncoated 316L SS.

scholarly journals Electro-Oxidation of Ammonia at Novel Ag2O−PrO2/γ-Al2O3 Catalysts

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 257
Author(s):  
Mariam Khan ◽  
Naveed Kausar Janjua ◽  
Safia Khan ◽  
Ibrahim Qazi ◽  
Shafaqat Ali ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Impedance ◽  
Precipitation Method ◽  
Impregnation Method ◽  
X Rays ◽  
Kinetic And Thermodynamic Parameters ◽  
Catalytic Support ◽  
Transmission Electron ◽  
Electro Oxidation ◽  
Oxidation Of Ammonia

An Ag2O(x)−PrO2(y)/γ-Al2O3 electrocatalyst series (X:Y is for Ag:Pr from 0 to 10) was synthesized, to use synthesized samples in electrochemical applications, a step in fuel cells advancements. Ag2O(x)−PrO2(y)/γ-Al2O3/Glassy-Carbon was investigated for electrochemical oxidation of ammonia in alkaline medium and proved to be highly effective, having high potential utility, as compared to commonly used Pt-based electrocatalysts. In this study, gamma alumina as catalytic support was synthesized via precipitation method, and stoichiometric wt/wt.% compositions of Ag2O−PrO2 were loaded on γ-Al2O3 by co-impregnation method. The desired phase of γ-Al2O3 and supported nanocatalysts was obtained after heat treatment at 800 and 600 °C, respectively. The successful loadings of Ag2O−PrO2 nanocatalysts on surface of γ-Al2O3 was determined by X-rays diffraction (XRD), Fourier-transform Infrared Spectroscopy (FTIR), and energy dispersive analysis (EDX). The nano-sized domain of the sample powders sustained with particle sizes was calculated via XRD and scanning electron microscopy (SEM). The surface morphology and elemental compositions were examined by SEM, transmission electron microscopy (TEM) and EDX. The conductive and electron-transferring nature was investigated by cyclic voltammetry and electrochemical impedance (EIS). Cyclic voltammetric profiles were observed, and respective kinetic and thermodynamic parameters were calculated, which showed that these synthesized materials are potential catalysts for ammonia electro-oxidation. Ag2O(6)−PrO2(4)/γ-Al2O3 proved to be the most proficient catalyst among all the members of the series, having greater diffusion coefficient, heterogeneous rate constant and lesser Gibbs free energy for this system. The catalytic activity of these electrocatalysts is revealed from electrochemical studies which reflected their potentiality as electrode material in direct ammonia fuel cell technology for energy production.

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