oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
EQCM Study of Influence of Anion Nature on Electrochemical Reduction of Bismuth Sulfide in Nickel Plating Solution
Loreta TAMA?AUSKAIT?-TAMA?IūNAIT?,Leonas NARU?KEVI?IUS,Albina ?IELIEN?,Birut? ?IMKūNAIT?-STANYNIEN?
Materials Science , 2011, DOI: 10.5755/j01.ms.17.1.244
Abstract: The influence of anion nature on the reduction of bismuth sulfide film deposited on gold using the successive ionic layer adsorption and reaction method in solutions containing Ni2+ ions has been investigated by electrochemical quartz crystal microbalance combined with cyclic voltammetry and X-ray photoelectron spectroscopy. It has been determined that the reduction of bismuth sulfide film in the nickel plating solution depends on the anion nature: larger cathodic current and mass changes (D ) are observed in the solution containing acetate anion as compared to those in the solution containing sulfate anion. As the reduction of bismuth sulfide film in the background solutions depends on the nature of anion, it influences the cathodic reduction of Ni2+ ions prior to OPD of Ni. A greater current and mass change (D ) is conditioned by simultaneously occurring reduction of bismuth sulfide film when the film is reduced in the acetate nickel plating electrolyte in contrast to that in the sulfate one. http://dx.doi.org/10.5755/j01.ms.17.1.244
Electrochemical Behavior of Malachite Green in Aqueous Solutions of Ionic Surfactants  [PDF]
Mohammad Mijanur Rahman,M. Yousuf A. Mollah,M. Muhibur Rahman,Md. Abu Bin Hasan Susan
ISRN Electrochemistry , 2013, DOI: 10.1155/2013/839498
Abstract: Electrochemical behavior of malachite green (MG) oxalate in aqueous solution was studied in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS) at a glassy carbon electrode using cyclic voltammetry. The electrochemical oxidation of MG has been characterized as an electrochemically irreversible diffusion-controlled process. Oxidative peak current sharply decreased with increasing SDS concentration, while a slight increase with increasing [CTAB] was apparent. The apparent diffusion coefficient, the surface reaction rate constant, and the electron transfer coefficient of MG clearly show correlation of the electrochemical behavior with the dissolved states of the surfactants. Electrochemical observations together with spectrophotometric results at varying surfactant concentrations provide evidence of interaction of MG with the surfactants to varying extent depending on the type of the surfactant and the concentration. 1. Introduction Triphenylmethane (TPM) dyes, an important class of synthetic organic compounds, have been a promising material for diverse applications, which inter alia include the following: as fungicides in aquaculture, as parasiticides in pharmaceuticals, as dye materials in industry, and as redox mediators, bioprobes, and pH indicators in both fundamental and applied sciences [1–6]. A proper understanding and development of fundamental knowledge base of physicochemical properties of TPM dyes have therefore attracted significant attention. Techniques so far employed for this are polarography [7], conductometry [8, 9], potentiometry [10], spectrophotometry [11, 12], electrochemical methods [13], membrane selective electrode [14], and so on. Dyes of TPM backbones such as malachite green (MG), crystal violet [15], ethyl violet [16], and victoria blue B [17] are electrochemically active, and recent surge of interest has been the exploration of the redox behavior of such dyes. Among the TPM dyes the prospect of MG (chemical structure shown in Scheme 1) for versatile applications [1] prompted many researchers to study the electrochemical behavior of MG for development of electrochemically switchable devices. The electrochemical oxidation of MG occurs at -containing lone-pair electron, and the reduction process is due to reduction of oxidized tertiary amino group of MG [2, 10]. In acidic aqueous solutions, the anodic oxidation of MG leads to the formation of the oxidized form of -tetramethylbenzidine (TMB) ([ -biphenyl]- -diamine), that is, TMBOx whereas the
Dezincification of Brass in Sulfide Polluted Sodium Chloride Medium: Evaluation of the Effectiveness of 2-Mercaptobenzothiazole
Satendra Kumar, T.S.N. Sankara Narayanan, M. Suresh Kumar and A. Manimaran
International Journal of Electrochemical Science , 2006,
Abstract: The present paper addresses the effectiveness of 2-mercaptobenzothiazole (MBT) in preventing the dezincification of brass in sulfide polluted 3.5% NaCl solution. The dezincification behaviour of brass in 3.5% NaCl solution containing 100-1000 ppm of sulfide ions and 1 x 10-6 to 1 x 10-3 M MBT was studied by potentiodynamic polarization, electrochemical impedance spectroscopy, current-time transient and accelerated leaching studies. The presence of sulfide ions in 3.5% NaCl solution has caused a significant increase in the extent of corrosion attack on brass. The inhibiting effect of MBT is markedly reduced in the presence of sulfide ions in the medium. The easy replacement of Cu-MBT complex by Cu2S film on the surface of brass is responsible for the inability of MBT to prevent corrosion attack in the presence of sulfide ions. The study concludes that the effectiveness of MBT in preventing the dezincification of brass is dependent on the concentration of the sulfide ions in the medium and the effectiveness is nullified at higher concentrations of sulfide ions.
Electrochemical oxidation of sulfide ions on platinum electrodes  [cached]
Ibrahim Mohamed Ghayad,Faiza M Al Kharafi,Ayman Y Saad,Badr G Ateya
Modern Applied Science , 2010, DOI: 10.5539/mas.v4n3p2
Abstract: This paper treats the electrochemical oxidation of sulfide ions on platinum using cyclic voltametry. An electrolyte of 3.5% NaCl containing sulfide ions was used as the testing medium. The effects of scan rate, concentration of sulfide ions and temperature on the cyclic voltamograms were investigated. Cyclic voltamograms show small currents in the absence of sulfide ions. In the presence of sulfide ions, the magnitude of the anodic currents in the forward sweep is much more than these in the reverse sweep. Cyclic voltamograms show three features appear in the forward sweep at potentials of -0.1, 0.475 and 1.0 V vs Ag/AgCl, respectively. Peaks currents are increased upon the increase of either the scan rate or temperature. These peaks are explained to show the possible formed species and the possible electrochemical oxidation reactions at the electrode surface.
Influence of Surfactants on the Characteristics of Nickel Matrix Nanocomposite Coatings  [PDF]
Abbas Fahami,Bahman Nasiri-Tabrizi,Mohsen Rostami,Reza Ebrahimi-Kahrizsangi
ISRN Electrochemistry , 2013, DOI: 10.1155/2013/486050
Abstract: Nickel-based nanocomposite coatings were prepared from a Watts-type electrolyte containing reinforcement’s particles (silicon carbide and graphite) to deposit onto the steel St-37 substrate. The electrochemical plating of the coatings in absence and presence of surfactants and reinforcements particles was carried out to optimize high quality coatings with appropriate mechanical and morphological features. The surfactants such as cetyltrimethylammonium bromide (CTAB), sodyumdodecyl sulfate (SDS), and saccharine affected electrodeposition plating and subsequently changed mechanical characteristics. Based on XRD results, the dominant phases in the absence of surfactants were nickel oxide (NiO), nickel, and silicon carbide (SiC), while the main phases in presence of surfactants were nickel (Ni) and SiC. The hardness of the resultant coatings was found to be from 332 to 593 (Hv) depending on the bath parameter and the reinforcements weight percentage (wt%) in the Ni matrix. Microscopic observations illustrated a cluster-like structure which consisted of some fine sphere particulates with average particle size of 65–150?nm. According to elemental mapping spectra, a homogenous distribution of nickel, silicon, and carbon particles appeared into the nickel matrix coating. Finally, the experimental outcomes demonstrated that the surfactants have significant influence on the composition of coatings, surface morphology, and mechanical properties. 1. Introduction The recent researches in surface engineering were significantly focused on the development of low carbon steels (St-37) surfaces which can meet the industrial request [1–4]. The mechanical properties of many parts of surfaces were promoted by coating of numerous pure metals, ceramics, and alloys which can be deposited with fine grain sizes, for example, Ni, Pd, Cu, Ni–P, Ni–W, and Ni–Fe–Cr [5, 6]. Furthermore, various methods such as electrodeposition, ion implantation, chemical vapor deposition (CVD), laser beam deposition, physical vapor deposition (PVD), plasma, and high-velocity oxygen fuel (HVOF) spraying have been developed [7, 8]. Among these procedures, electrochemical plating is a proper method with remarkable features such as easy maintainability, easy low working temperatures, low cost, and high production rate [9]. In chemical techniques, surfactants have been used to absorb much more fine particles into the matrix, so that the repulsion force between particles with the same charges can be increased. This, in turn, reduces the agglomeration and provides a solution with more stable particles. It
Electrochemical and Stress Corrosion Cracking Behavior of Alpha-Al Bronze in Sulfide-Polluted Salt Water: Effect of Environmentally-Friendly Additives  [PDF]
Elsayed A. Ashour, Lobna A. Khorshed, Gehan I. Youssef, Hossam M. Zakria, Tarek A. Khalifa
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.51002
Abstract:

The stress corrosion cracking (SCC) behavior of α-Al bronze alloy (Cu7Al) was investigated in 3.5% NaCl solution in the absence and in the presence of different concentrations of Na2S under open circuit potentials using the constant slow strain rate technique. Also, the addition of different concentrations of cysteine (cys), and alanine (ala) to the test solution, as corrosion inhibitors, was studied. Increasing the sulfide ions concentration in polluted salt water resulted in a reduction in the maximum stress (σmax) and an increase in the susceptibility of α-Al bronze towards SCC. The addition of ala and cys to the test electrolyte increased the time to failure by changing the mode of failure from brittle transgranular cracking to ductile failure. Electrochemical tests were performed to assist the interpretation of the SCC data. Electrochemical impedance spectroscopy (EIS) was used to investigate the mechanism of corrosion inhibition. The results support film rupture and anodic dissolution at slip steps as the operating mechanism of the SCC process. Therefore, cys and ala can be considered as potential environmentally-friendly corrosion inhibitors for the SCC of α-Al bronze in 3.5% NaCl solution containing sulfide ions.

INFLUENCE OF SULFIDE ON PASSIVE FILMS ON STAINLESS STEEL IN BORATE BUFFER SOLUTION
硼酸-硼砂介质中硫离子对不锈钢钝化膜的侵蚀性

GE Hong-hua,ZHOU Guo-ding,WU Wen-quan Environmental Engineering,
葛红花
,周国定,吴文权

腐蚀科学与防护技术 , 2004,
Abstract: The passive films formed on stainless steel in borate buffer solution contained certain among of sulfide,the influence of which on corrosion behavior of the passive film has been studied using Mott-Schottky plots,Nyquist plots and anodic polarization curves.It is shown that the impedance of the stainless steel electrode increases with immersing time,but decreases sharply due to the presence of sulfide.With the increase of sulfide,the passive current of stainless steel electrode rises,and the Mott-Schottky plots change in the region of chromium oxide.It is concluded that sulfide is detrimental to the formation of passive film on stainless steel and the passive film is less protective in the presence of sulfide.
Electrochemical Fabrication of Shape-Controlled Copper Hierarchical Structures Assisted by Surfactants
Huaping Dong,Yajun Wang,Feifei Tao,Linxia Wang
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/901842
Abstract: Various copper hierarchical structures assisted by surfactants were successfully fabricated combined with the electrodeposition technique. To the best of our knowledge, it is the first report on the controlled synthesis of metal copper hierarchical structures. All of the products synthesized in the presence and absence of surfactants, such as cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), or polyvinylpyrrolidone (PVP), were face-centered cubic copper, characterized by X-ray diffraction (XRD), indicating the surfactant-independent crystal structure. However, supplementing surfactants is helpful to construct hierarchical structures and exerts an important influence on copper morphologies. The absence of surfactants led to the formation of the nubby structures, while the use of surfactants resulted in the synthesis of the flower, dendrite, and sphere-like hierarchical morphologies. The effect of deposition time on the copper morphologies was investigated by scanning electron microscopy (SEM), and the possible formation mechanism of the copper hierarchical structures with various morphologies was discussed.
Investigation on solution properties of surfactants in mixed solvent media: Landmark towards Surface Chemistry in Eastern Nepal  [PDF]
Ajaya Bhattarai
BIBECHANA , 2014, DOI: 10.3126/bibechana.v11i0.10400
Abstract: Surfactants are amphiphilic molecules having a hydrophilic or water soluble moiety (head group) and a hydrophobic, or water insoluble moiety (tail group). Surfactants are not only related to soaps and detergents, they are also in heavy demand for industrial processes requiring colloid stability, metal treatments, mineral flotation, pesticides, oil production, pharmaceutical formulation, emulsion polymerization, particle growth and many more. That is why surfactants have been and continue to be a very active area of scientific research and commercial growth for several decades. One interesting property of surfactants is that at low concentrations, they exist solely as monomers. The formation of micelles, begins at a specific surfactant concentration termed the critical micelle concentration (cmc), where the physical properties of the solution, such as interfacial tension, electrical conductivity, and light scattering behaviour, often changes abruptly due to the existence of micelles. The formation of micelles will be able to calculate various thermodynamic parameters. These parameters make surfactants not only an interesting and rich area for the exploration of novel phenomena but also an area of research which can lead to new applications in a variety of fields. However, most of the previous studies on surfactants are limited to aqueous media only. Studies in mixed solvent media are very natural one as one can modulate the conformations of surfactants and their interactions easily by simply varying the composition of the media. With this concept, the research team of Eastern Nepal has started to work the solution properties of surfactants in different mixed solvent media in presence and absence of salts and has also investigated cationic and anionic surfactant interaction in mixed solvent media.
Electrochemical depression of galena aiming at selective sulfide flotation
Dutra, Achilles Junqueira Bourdot;Espínola, Aida;Sampaio, Jo?o Alves;
Journal of the Brazilian Chemical Society , 1997, DOI: 10.1590/S0103-50531997000200019
Abstract: in this article, the potential at which galena depression occurs is related to the formation of hydrophilic compounds on its surface. reactions are proposed based on analyses by cyclic voltammetry, thermodynamic data, and x-ray photoelectron spectroscopy (xps). electrochemical variables, such as the redox potential, present good perspectives for selectivity in the flotation of galena and sphalerite, because in a given range of potentials, the galena surface becomes hydrophilic, as shown by measurements of the contact angle and floatability tests.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.