NaBr Solution Research Articles

Studies on Electrochemical Behavior of Copper in Aerated NaBr Solutions with Schiff Base, N , N ′ ­ o-phenylen-bis(3-methoxysalicylidenimine)

The electrochemical behavior of copper in the aerated 0.5 mol dm−3 sodium bromide solutions with or without a Schiff base, -phenylen-bis(3-methoxysalicylidenimine) (V-o-Ph-V) were investigated by means of the steady-state polarization and impedance techniques. V-o-Ph-V acted as a mixed-type inhibitor in NaBr media, and it adsorbed easily on the copper surface at potentials near the corrosion potential. The adsorbed V-o-Ph-V formed a thin protective film which reduced both anodic and cathodic reaction rates significantly. The impedance spectra for copper measured at the corrosion potentials in the presence of V-o-Ph-V displayed two capacitive loops due to different influences of the protective film on the anodic and cathodic reactions occurring at the copper surface. V-o-Ph-V could self-assemble on the copper surface and the self-assembled film also exhibited a good inhibition on copper in halide solutions. The dissolution mechanism of copper and the inhibition mechanism of V-o-Ph-V on the copper in NaBr solution are interpreted. In addition, the inhibiting action of V-o-Ph-V is compared with that of the other two Schiff bases, -phenylen-bis (3-methoxysalicylidenimine) (V-p-Ph-V) and N-[(2-hydroxy-3-methoxyphenyl)methylene]-histidine (V-His) in order to investigate the effect of Schiff bases’ geometric structures on their inhibition ability. © 2001 The Electrochemical Society. All rights reserved.

Titanium alloy grade 7 under the influence of micro-organisms in diluted NaBr solution

The behavior of titanium alloy grade 7 under the influence of micro-organisms in diluted NaBr solution was studied. The exposure of the tested titanium alloy to aqueous environments combined with micro-organisms was carried out in a unique test cell under induced potential. During the exposure, the potential between the anodic surface and the reference electrode was recorded. A heavily polluted environment with micro-organisms resulted in a sharp drop of the steady potential after an incubation period of ≈2–4 h. Potentiodynamic polarization measurements show that increasing the total bacterial counts (TBC) to a value >10 4/ml results in higher sensitivity to localized corrosion attack. As the TBC increases, the anodic breakdown potential decreases from ≈950 mV in 10 2/ml to ≈800 mV in 10 7/ml. The results clearly indicate that the aqueous media polluted with micro-organisms inhibits the anodic passivation process and depolarizes the cathodic process, resulting in higher corrosion current density. SEM observation of Ti 7 alloy that was exposed to heavily polluted environments with micro-organisms for ≈3 months revealed a massive growth of biofilm on the metal surface.

Multifrequency bioelectrical impedance analysis to assess human body composition

Multifrequency bioelectrical impedance analysis (MF-BIA) was validated as a method to predict total body water (TBW), extracellular water (ECW), fat free mass (FFM) and fat mass (FM) with other laboratory based methods. Twenty-two healthy adult male volunteers were selected from the staffs of International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B). Ten mL of deuterium oxide (D 2O) along with 1 mL/Kg of 3 g% NaBr solution were given orally to each subject. In order to validate the method, deuterium- and bromide-dilution principles were utilized by using isotope-ratio mass spectrophotometer (IRMS), high performance liquid chromatography (HPLC) and spectrophotometer (SP). Data obtained by these methods were compared to assess the accuracy between the methods. The mean±SD BMI was 24.2±1.7 which indicates that the volunteers were not obese or overweight anthropometrically. A significant correlation of TBW was observed between MF-BIA and IRMS techniques ( r 2= 0.44, p<0.001). However, the ECW volume was 7% higher by MF-BIA and 2% by HPLC in relation to the D 2O dilution method whereas SP method gave the most accurate volume of ECW. The findings of the study indicate that MF-BIA method overestimated ECW although TBW by MF-BIA and IRMS correlated well. The co-efficient of variation (CV%) of ECW measured by HPLC was 9% and by SP method was 27%, indicating that ECW measured by HPLC was more accurate. In summary it could be concluded that MF-BIA is a rapid and useful technique to assess the body composition and its usefulness could be increased if ECW measurement by this method is improved further.

Salt-Induced Sphere-to-Disk Transition of Octadecyltrimethylammonium Bromide Micelles

We have used surface tension measurements, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and cryo-transmission electron microscopy (cryo-TEM) to investigate the dynamic and structural behavior of octadecyltrimethylammonium bromide (C18TAB) micelles in water and NaBr solution. The surface tension data for fixed C18TAB concentrations of 25 mM and varied NaBr additions (0−50 mM) shows that the critical micelle concentration (cmc) increases after an initial decrease at 0.5 mM NaBr. This unusual effect has been explained using results from DSC and DLS. At low salt concentrations (below ca. 25 mM) the relaxation time distribution is bimodal with a dominant fast mode due to spherical micelles. Above ca. 35 mM NaBr disklike structures are favored and the relaxation time distribution is more closely unimodal. The postulated sphere-to-disk transition is supported by cryo-TEM micrographs. A pronounced increase in the micellar effective hydrodynamic radius (RH) is observed as the NaBr conce...

The cyclotron production of carrier-free 77Br via the 79Br(p,3n) 77Kr→ 77Br reaction using a liquid target and on-line extraction

In this investigation, 77Br was produced with a 40 MeV proton cyclotron. 77Br emits a 240 keV photon and has a half life of 56 h. In this method a p,3n reaction on 79Br produces 77Kr which decays with a 1.2 h half life to 77Br. A 40 MeV proton beam is incident on a NaBr or LiBr solution through which helium is flowed to extract 77Kr gas. The mixture is moved through a trap cooled in liquid nitrogen where the 77Kr freezes and is allowed to decay to 77Br. Eight production runs were performed with produced activities of 40, 104, 180, 679, 1080, 685, 762, and 118 μCi respectively.

Pitting Corrosion Behavior of Type 904L Stainless Steel in Sodium Bromide Solutions

Abstract Potentiodynamic cyclic anodic polarization, scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) techniques were used to study pitting corrosion behavior of type 904L (UNS N08904) stainless steel (SS) in aerated or argon-deaerated 0.6 M sodium bromide (NaBr) solutions at 25°C. Type 904L SS was shown to undergo pitting corrosion even though the steel has a high molybdenum content (4.5% Mo). Effects of temperature, air, pH, bromide ion concentration (CBr−), and bromide/chloride ratio on pitting corrosion were studied. The critical pitting potential (Epit) was found to decrease with increasing temperature and CBr−. Changing the pH of the 0.6 M NaBr solution did not affect Epit from pH 2 to 11. At pH ≥ 12, pitting corrosion was prevented. Addition of chloride ions to bromide at a fixed halide concentration of 0.6 M inhibited pitting corrosion attack. Morphology of the pits produced was inspected by SEM after anodic polarization treatment in different bromide solutions.

Morphological and electrochemical studies of polypyrrole/Nafion ®

Polypyrrole (PPy) was electrochemically synthesized from a NaBr solution onto a gold electrode coated with a thermally treated Nafion ® film (Nf). In the reproducibly formed composite Nf/PPy, PPy was doped both by bromide and the sulfonate groups of Nf which can be seen in the cyclic voltammogram (CV) by a double peak in the first scans and by microprobe analysis. CVs and impedance spectroscopy indicate that, in NaBr solution, ion transport in the composite is maintained by sodium ions. The shape of the voltammograms is interpreted on a semi-quantitative base. It was shown by lateral force microscopy for the first time that PPy grows from the electrode side into the ionic areas of Nf which, up to now, has only been an assumption. Composite films polarized to the redox potential (− 583 ± 10 mV) are mechanically free-standing membranes with both ionic and electronic conductivity.

Water soluble polymers: 69. pH and electrolyte responsive copolymers of acrylamide and the zwitterionic monomer 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate: synthesis and solution behaviour

A novel carboxybetaine monomer, 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate (AMPDAB), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM ( M 1)/AMPDAB( M 2) was varied from 90 10 to 0 100 mol% . Low conversion samples were collected and copolymer compositions were determined with 13C n.m.r. by integration of the carbonyl resonances. Reactivity ratios were determined and the nonlinear least-squares method yielded values of r 1 = 1.01 and r 2 = 0.99, indicating random incorporation of monomers into the final copolymer. Molecular weights were determined and range from 3.9 to 12.0 × 10 6 g mol −1. The solution behaviour of the above copolymers was studied as a function of pH and added electrolytes. With the exception of the copolymers containing 60 and 75 mol% AMPDAB, homogeneous solutions were obtained in deionized water. At high pH, the polyzwitterions show an enhancement in viscosity as the concentration of added electrolyte is increased. In deionized water, as the pH of the aqueous media is lowered, the copolymers exhibit a dramatic increase in viscosity as the carboxylate groups are protonated and charge-charge repulsions of the quaternary ammonium groups induce polyelectrolyte behaviour. The solution behaviour is compared to structurally similar sulfobetaines which do not exhibit any responsiveness to changes in pH.

Water-soluble polymers. 72. synthesis and solution behavior of responsive copolymers of acrylamide and the zwitterionic monomer 6-(2-acrylamido-2-methylpropyldimethylammonio) hexanoate

A novel carboxybetaine monomer, 6-(2-Acrylamido-2-methylpropyldimethylammonio) hexanoate (AMPDAH), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM (M1): AMPDAB(M2), was varied from 98.5 : 2.5 to 0 : 100 mol %. The polymerizations were carried out to 20–30% conversion. Copolymer compositions were determined with 13C NMR by integration of the amido carbonyl resonances. Reactivity ratios determined from the nonlinear least-squares method gave values of r1 = 0.98 and r2 = 0.85, indicating random incorporation of the comonomers into the final copolymer. Molecular weights ranged from 7.3 to 4.7 × 106 g/mol. The solubility behavior of the copolymers is dependent on the mol % AMPDAH incorporated into the copolymers. When 25 mol % or more is incorporated, the copolymers are only swellable in aqueous media and attempts to solubilize these systems were unsuccessful. AMPDAH incorporation of 10 mol % or less resulted in copolymers soluble in aqueous media under a variety of conditions. The viscometric properties of copolymers with 10 mol % or less is reported as a function of pH and added electrolytes. At high pH in deionized water, the polyzwitterions show both inter- and intramolecular associations, which are disrupted by the addition of sodium chloride. In deionized water, as the pH of the aqueous medium is lowered, the copolymers exhibit dramatic increases in viscosity as the carboxylate groups are protonated and charge–charge repulsions of the quaternary ammonium groups induce polyelectrolyte behavior. © 1997 John Wiley & Sons, Inc.

Adsorption of Cationic Surfactants on a Hydrophilic Silica Surface at Low Surface Coverages: Effects of the Surfactant Alkyl Chain and Exchangeable Sodium Cations at the Silica Surface

The influence of the alkyl chain length and the concentration of exchangeable sodium cations at the solid/water interface on the energetics of cationic surfactant adsorption on a hydrophilic silica surface at free pH has been studied. Adsorption isotherms, electrophoretic mobilities of the silica particles, and differential molar enthalpies of displacement for benzyldimethyldodecylammonium bromide (BDDAB) on the original silica sample (SilNa) at different ionic strengths (pure deionized water and 0.1 M NaBr solution) were compared, as well as those on a washed silica sample (SilH). The stability of silica suspensions, as characterized by the changes in turbidity, was analyzed with the intention of shedding light on the possible orientation of the adsorbed surfactant ions. Adsorption of BDDAB was also compared with that of benzyldimethyloctylammonium bromide (BDOAB) on SilNa. Individual surfactant adsorption occurs by ion pairing or cation exchange mechanisms, depending on the purity of silica sample and c...

Use of Surfactant-Specific Electrodes in the Study of Adsorption of Cationic Amphiphilic Ions onto Clays

The adsorption isotherms of dodecyltrimethylammonium ions (DTA+) adsorbed onto a laponite clay colloid were studied in water and in NaBr solution (at 0.1, 0.3, and 0.5 mol · liter-1), at 298 K, using amphiphilic ion-specific electrodes. This potentiometric method can be used to measure concentrations in situ and to follow the decrease in the amount of surfactant in the solution as the surfactant is adsorbed onto the clay. This paper describes a method for characterizing adsorption isotherms of DTA+ onto laponite by determining the amount adsorbed at a fixed surfactant activity in solution. By repeating this process for various DTA+ activities, the adsorption isotherm can be plotted. Adsorption isotherms obtained with or without NaBr in the solution were continuous curves which increased with the surfactant activity. The field of study is limited by the CMC value for the surfactant and the curves have a common intersection point, which can be attributed to the isoelectrical point of the laponite/adsorbed surfactant system. This method can be generalized to other cations and obviously to other solids.

The effect of flow velocity on the pitting potential of anodized titanium

The pitting potential of titanium which was anodized at 3 V in 0.5 M H 2SO 4 solution has been measured in 1 M NaBr solution as function of flow velocity. The distribution of pitting potential follows the normal probability distribution and pitting potential increases with flow velocity.

The effect of film formation temperature on the stochastic processes of pit generation on anodized titanium

The anodic oxide films on titanium were formed potentiostatically in 0.5 M H 2SO 4 solution at various temperatures ranging from 303 to 363 K. The effect of film formation temperature on the pit generation on anodized titanium was investigated in 2 M NaBr solution by the stochastic approach. The distribution of pitting potential approximately follows the normal probability distribution and the pit generation process occurs in accordance with the parallel birth and death stochastic model. The pitting potential increases significantly above 343 K due to the decrease in the pit generation rate and to the increase in the pit repassivation rate. The dependence of the pitting potential on film formation temperature can be explained by the change in the properties of the film.

Critical behavior of a cationic surfactant in an aqueous salt solution

The critical behavior of a cationic surfactant, butyl-tetradecyldimethylammonium bromide, in an aqueous 4M–NaBr solution was investigated concerning the isothermal osmotic compressibility and long-range correlation length by means of light scattering, coexistence curve, and turbidity. The critical exponents were obtained as γ′=1.39±0.04 and ν′=0.70±0.03 together with ξ0=(2.48±0.06) nm, and β′=0.375±0.01. The temperature dependence of turbidity showed a good accordance with the result of light scattering measurement. Negative α′ was obtained from the scaling relation. The critical exponents are in good agreement with the Fisher-renormalization prediction for the ternary system (almost fully renormalized Ising exponents).

Forces between Alumina Surfaces in Salt Solutions: Non‐DLVO Forces and the Implications for Colloidal Processing

Direct measurements of the forces between basal (0001) surfaces of sapphire in salt solutions are presented. The measurements reveal the presence of forces in addition to those described by classical DLVO theory. At pH 7.2 in 0.01M NaBr solution, we find an additional short‐range oscillatory force with periodicity approximately equal to twice the diameter of a water molecule. At pH 3 we find an additional strong, short‐range, monotonic, repulsive force and a long‐range attractive force over a range of NaBr concentrations from 0.001 M to 0.1 M. Both monotonic forces are approximately exponential, with decay lengths of 0.55 and 12 nm, respectively. The short‐range force is analogous to hydration forces previously measured on negatively charged surfaces. This force would provide plasticity to alumina slurries and is suggested to be the force responsible for the anomalous viscosity and consolidation behavior of alumina slurries at high salt concentrations.

The effect of film formation potential on the stochastic processes of pit generation on anodized titanium

Pit generation on titanium with anodic oxide film which is formed potentiostatically in 0.5 M H 2SO 4 solution has been studied in 1 M NaBr solution by using the stochastic approach. The distribution of pitting potential obeys the normal probability distribution and pitting potential exhibits a maximum around a formation potential of 6.0 V. The pit generation process occurs by the parallel birth and death stochastic model and depends on film formation potential, i.e. the film thickness and properties.

Effect of Widmanstatten Structure on Protection Potential of Ti-6Al-2Sn-4Zr-2Mo (0.1Si) Alloy in 1 M NaBr Solution

Abstract Three different microstructures, Widmanstatten structure, acicular martensite, and α-plates, have been produced through suitable heat treatments for alloy Ti-6Al-2Sn-4Zr-2Mo (0.1Si). The influence of these microstructures on pitting corrosion in 1 M NaBr solution has been studied using polarization technique. It is found that the parameters, pitting potential (Epit) and protection potential (Epp), are significantly influenced by the heat treatment conditions. Epit increases in the order α-plate < Widmanstatten structure < acicular martensite, while in the case of Epp, the value increases in the order Widmanstatten structure < α-plates < acicular martensite. The poor Epp value in the case of Widmanstatten structure is attributed to the inherent variations in Mo and Al content between the plates accompanied by the formation of this phase.

Potential-Current Oscillations of Titanium Alloy Exposed to 1N NaBr Solution under Applied Potential Conditions

Potential-Current Oscillations of Titanium Alloy Exposed to 1N NaBr Solution under Applied Potential Conditions

Adsorption isotherms for cationic surfactants on silica determined by in situ ellipsometry

The adsorption of tetradecyltrimethylammonium bromide (C 14TAB) on oxidized silicon plate has been determined in water and in 10 mmol·dm −3 NaBr solutions by in situ ellipsometry as a function of pH. The shape of the isotherms changes and the adsorbed amount increases as the pH of the solution is increased. Isotherms for C 14TAB in water and in NaBr solution at pH 5 and for C 12TAB in water at pH 9.6 obtained by ellipsometry are compared with results obtained by a different method (solution-depletion). The aggreement between the two methods is found to be satisfactory.

Cyclic voltammetric behaviour and some surface characteristics of the lead electrode in aqueous NaBr solutions

AbstractThe anodic behaviour of the lead electrode in aqueous 0.05–3.00 M NaBr solutions was investigated by means of linear sweep voltammetry. The voltammograms showed one anodic peak current density (jap) corresponding to the formation of a thin passivating layer of PbBr2. The obtained data depicted a gradual increase of jap and shifting of the corresponding potential (Eap) to more negative values with increase of CNaBr.A detailed study of the formation/reduction of PbBr2 on the surface of lead electrodes in aqueous 0.10–1.00 M NaBr solution was carried out by cyclic voltammetry. The results indicated that the formation of PbBr2 is controlled by diffusion of Br− ions to the anode surface. Irrespective the voltammetric conditions, the study proved that the formation/reduction of the PbBr2 surface layer is a reversible process. The role played by the operating voltammetric conditions in the building up of a relatively thick PbBr2 surface layer that could resist rupture and/or breakdown is discussed.The as‐formed PbBr2 layers were examined by scanning electron microscopy and X‐ray diffractometry. The microstructure showed some morphological modifications which could be correlated to the operating conditions. On the other hand, X‐ray diffiaction analysis proved that, under all conditions, the anodic surface products consist solely of PbBr2 in the orthorhombic crystalline structure.