scholarly journals Electrochemical characterization of the passive films formed on niobium surfaces in H2SO4 solutions

2006 ◽  
Vol 71 (2) ◽  
pp. 177-187 ◽  
Author(s):  
Irena Arsova ◽  
Abdurauf Prusi ◽  
Toma Grcev ◽  
Ljubomir Arsov
Keyword(s):  
Cyclic Voltammetry ◽  
Passive Film ◽  
Chemical Structure ◽  
Open Circuit ◽  
Passive Films ◽  
Anodic Films ◽  
Potential Region ◽  
Passive Transition ◽  
Cyclic Voltammetry Data

The electrochemical formation and characteristics of passive films on niobium surfaces in aqueous H2SO4 solutions were studied using open circuit potential and cyclic voltammetry. In the potential region between -1.0 and 1.2 V(NHE), the cyclic voltammetry data showed that the active/passive transition involves slow metal dissolution followed by the formation of semiconducting passive oxide films. The possible electrochemical reactions and the change of the oxidation steps of some niobium oxides occurring in the passive film during the polarization are proposed. A strong influence of the natural air-formed oxide film on the chemical composition of the passive film was shown. This influence makes chemical structure of thin passive films more complicated than that of thick anodic films. It is shown that the passive films consists of more or less stable oxides, such as NbO, NbO2 and Nb2O5. The Raman spectra revealed that the thin passive films were amorphous, while the films formed at higher voltages consist, primarily, of well-crystallized Nb2O5.

Electrochemical Behaviour of Cobalt in NaOH Solutions

1994 ◽  
Vol 59 (11) ◽  
pp. 2383-2389 ◽  
Author(s):  
Sayed S. Abd El Rehim ◽  
Ahmed A. El Basosi ◽  
Salah M. El Zein ◽  
Magda M. Osman
Keyword(s):  
Cyclic Voltammetry ◽  
Passive Film ◽  
Polarization Curve ◽  
Anodic Polarization ◽  
Electrochemical Behaviour ◽  
Anodic Polarization Curve ◽  
Potential Region ◽  
Voltammetric Techniques ◽  
Scan Rate ◽  
Reverse Scan

The electrochemical behaviour of cobalt in 0.001 - 1 M NaOH was investigated by voltammetric techniques coupled with ESCA examination. The anodic polarization curve exhibits a well defined peak which corresponds to the formation of Co(OH)2 or CoO. Further peaks in the transpassive potential region correspond to the electrooxidation of Co(II) species to Co3O4 and CoOOH, respectively. The heights of the anodic peaks increase with the increase of NaOH concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan consistently shows three cathodic peaks which are ascribed to the reduction of CoOOH, Co3O4 and CoO oxides, respectively. ESCA examination confirmed the presence of these oxides in the passive film.

scholarly journals Formation of Gd-Al Alloy Films by a Molten Salt Electrochemical Process

2008 ◽  
Vol 63 (1-2) ◽  
pp. 98-106
Author(s):  
Concha Caravaca ◽  
Guadalupe De Córdoba
Keyword(s):  
Cyclic Voltammetry ◽  
Intermetallic Compounds ◽  
Surface Characterization ◽  
Electrochemical Techniques ◽  
Open Circuit ◽  
Electrochemical Process ◽  
Single Step ◽  
Al Alloy ◽  
Cathodic Potential

The electrochemistry of molten LiCl-KCl-GdCl3 at a reactive Al electrode has been studied at 723 to 823 K. Electrochemical techniques such as cyclic voltammetry and chronopotentiometry have been used in order to identify the intermetallic compounds formed. Cyclic voltammetry showed that, while at an inert W electrode GdCl3 is reduced to Gd metal in a single step at a potential close to the reduction of the solvent, at an Al electrode a shift towards more positive values occurs. This shift of the cathodic potential indicated a reduction of the activity of Gd in Al with respect to that ofW, due to the formation of alloys. The surface characterization of samples formed by both galvanostatic and potentiostatic electrolysis has shown the presence of two intermetallic compounds: GdAl3 and GdAl2. Using open-circuit chronopotentiometry it has been possible to measure the potentials at which these compounds are transformed into each other. The values of these potential plateaus, once transformed into e. f. m. values, allowed to determine the thermodynamic properties of the GdAl3 intermetallic compound.

Synthesis and characterization of conducting copolymer of (N 1,N 3-bis(thiophene-3-ylmethylene)benzene-1,3-diamine-co-3,4-ethylenedioxythiophene)

2010 ◽  
Vol 64 (1) ◽  
Author(s):  
Altuğ Kümbül ◽  
Ersen Turaç ◽  
Tuğba Dursun ◽  
Ertuğrul Şahmetlioğlu
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Nuclear Magnetic Resonance ◽  
Cyclic Voltammetry ◽  
Chemical Structure ◽  
Synthesis And Characterization ◽  
Conductivity Measurements ◽  
Electrochemical Copolymerization ◽  
Scanning Electron

AbstractElectrochemical copolymerization of N 1,N 3-bis(thiophene-3-ylmethylene)benzene-1,3-diamine (TMBA) with 3,4-ethylenedioxythiophene (EDOT) was carried out in a CH3CN/LiClO4 (0.1 M) solvent-electrolyte via potentiodynamic electrolysis. Chemical structure of the monomer was determined by nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectroscopy. The resulting copolymer was characterized by cyclic voltammetry (CV), FTIR, scanning electron microscopy (SEM), and thermogravimetry analyses (TGA). Conductivity measurements of the copolymer and PEDOT (poly(3,4-ethylenedioxythiophene)) were carried out by the four-probe technique.

scholarly journals Ellipsometric study of passive and anodic oxide films formed on Ti and Nb electrodes

2016 ◽  
Vol 5 (4) ◽  
pp. 221 ◽  
Author(s):  
Ljubomir Dimitar Arsov ◽  
Irena Mickova
Keyword(s):  
Barrier Properties ◽  
Anodic Oxide ◽  
Passive Films ◽  
Potential Cycling ◽  
Potential Region ◽  
Passive Transition ◽  
Multiple Cycle ◽  
Pre Treatment ◽  
Voltammetry Methods

<p class="PaperAbstract"><span lang="EN-US">Electrochemical formation of passive films and active/passive transition on Ti and Nb metal surfaces in various concentrations of H<sub>2</sub>SO<sub>4</sub> and KOH solutions was investigated using potentiostatic and cyclic voltammetry methods. By simultaneous electrochemical and in-situ ellipsometric measurements the coefficients of film thickness growth of passive films in the potential region from -1.5 V to 4 V were determined. Results indicate the strong influence of the concentration and electrolyte nature to the active/passive transitions and stability of passive films. The influence of cathodic pre-treatment on the passive films dissolution and appearance of the reactivation peaks during the reverse potential cycling were shown. By multiple cycle sequences in which the final anodic potential was gradually enlarged, the barrier properties of passive films on investigated electrodes were confirmed. The electrochemical and ellipsometric data showed that the passive films formed on Nb electrode are more resistant that passive films formed on Ti electrode, especially in higher concentrations of investigated aggressive solutions.</span></p><br />

Preparation and Characterization of Soybean Oil-based Flame Retardant Rigid Polyurethane Foams Containing Phosphaphenanthrene Groups

2020 ◽  
Vol 17 (10) ◽  
pp. 760-771
Author(s):  
Qirui Gong ◽  
Niangui Wang ◽  
Kaibo Zhang ◽  
Shizhao Huang ◽  
Yuhan Wang
Keyword(s):  
Soybean Oil ◽  
Flame Retardant ◽  
Chemical Structure ◽  
Cell Structure ◽  
Polyurethane Foams ◽  
Limiting Oxygen Index ◽  
Rigid Polyurethane Foams ◽  
Degradation Activation Energy ◽  
Ft Ir

A phosphaphenanthrene groups containing soybean oil based polyol (DSBP) was synthesized by epoxidized soybean oil (ESO) and 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Soybean oil based polyol (HSBP) was synthesized by ESO and H2O. The chemical structure of DSBP and HSBP were characterized with FT-IR and 1H NMR. The corresponding rigid polyurethane foams (RPUFs) were prepared by mixing DSBP with HSBP. The results revealed apparent density and compression strength of RPUFs decreased with increasing the DSBP content. The cell structure of RPUFs was examined by scanning electron microscope (SEM) which displayed the cells as spherical or polyhedral. The thermal degradation and flame retardancy of RPUFs were investigated by thermogravimetric analysis, limiting oxygen index (LOI), and UL 94 vertical burning test. The degradation activation energy (Ea) of first degradation stage reduced from 80.05 kJ/mol to 37.84 kJ/mol with 80 wt% DSBP. The RUPF with 80 wt% DSBP achieved UL94 V-0 rating and LOI 28.3. The results showed that the flame retardant effect was mainly in both gas phase and condensed phase.

Optimization and characterization of flavonoids extracted from Cannabis sativa fibers

2021 ◽  
pp. 004051752110277
Author(s):  
Qilu Cui ◽  
Jiawei Li ◽  
Chongwen Yu
Keyword(s):  
Chemical Structure ◽  
Cannabis Sativa ◽  
Ethanol Concentration ◽  
Extraction Process ◽  
Test Results ◽  
Hemp Fiber ◽  
Hemp Fibers ◽  
Structure Surface ◽  
Degumming Process

In this paper, the extraction process of flavonoids from hemp fibers was studied. Response surface methodology (RSM) analysis of the extraction parameters indicated that optimized results would be ethanol concentration 76 vol.%, bath ratio 1:50, and reaction time 139 min; therefore, an optimal extraction rate of flavonoids of 0.2275% can be obtained. The chemical structure, surface morphology and element composition of flavonoid extracts were analyzed. The test results indicated that hemp extract contains flavonoids, which can be used to extract flavonoids from hemp fiber, so as to comprehensively develop hemp fiber and reduce the discharge of waste liquid in the traditional degumming process.

scholarly journals Isolation and chemical structure characterization of enzymatic lignin frompopulus deltoidswood

2013 ◽  
Vol 130 (1) ◽  
pp. 710-710
Author(s):  
Ali Abdulkhani ◽  
Alinaghi Karimi ◽  
Ahmad Mirshokraie ◽  
Yahya Hamzeh ◽  
Nathalie Marlin ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Structure Characterization

Synthesis and characterization of novel functionalized perarylated polysiloxane for proton exchange membrane fuel cells

MRS Advances ◽  
2019 ◽  
Vol 4 (64) ◽  
pp. 3579-3585
Author(s):  
Guillermo M. González Guerra ◽  
Alejandro Alatorre-Ordaz ◽  
Gerardo González Garcia ◽  
Jesus S. Jaime-Ferrer
Keyword(s):  
Cyclic Voltammetry ◽  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Area Under The Curve ◽  
Chlorosulfonic Acid ◽  
Proton Exchange ◽  
Synthesis And Characterization ◽  
A Value ◽  
Exchange Membrane

ABSTRACTThis work presents the synthesis and characterization of a pearylated polysiloxane material (PAP) from a polycondensation reaction, followed by functionalization with HClSO3 by an electrophilic substitution reaction. According to the characterization techniques applied, a sulfonated pearylated polysiloxane was also obtained, (SPAP). The purpose of this sulfonated material is to obtain an ionomer able to be applied in hydrogen fuel cells of the proton exchange membrane kind (PEMFC). The reaction to produce the polysiloxane precursor was carried out with the commercial reagents: PhSiCl3, Ph2SiCl2 and Ph3SiCl in anhydrous THF at 75 °C and the SPAP material was obtained by sulfonation of the precursor with chlorosulfonic acid. PAP and SPAP were characterized by 1H, NMR for liquids, 29Si NMR for solids, IR-ATR, SEM, and cyclic voltammetry. The NMR 29Si spectra show that PAP and PAPS contain crosslinking regions due to PhSiCl3, growing chain zones due to Ph2SiCl2 and polymer termination zones due to Ph3SiCl, obtaining a mixture of siloxanes. The analysis by cyclic voltammetry indicates that by integrating the area under the curve of the adsorption peaks of H2, a value of 0.062 mC/cm2 is obtained, a value close to the commercial ionomer of Nafion®.

A photoelectrochemical characterization of passive films on stainless steels

1986 ◽  
Vol 26 (11) ◽  
pp. 935-948 ◽  
Author(s):  
Agatino Di Paola ◽  
Francesco Di Quarto ◽  
Carmelo Sunseri
Keyword(s):  
Stainless Steels ◽  
Passive Films ◽  
Photoelectrochemical Characterization
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