Polarisation effects of surface films at the dropping and streaming mercury electrodes

1951 ◽  
Vol 16 ◽  
pp. 455-464 ◽  
Author(s):  
J. Heyrovský ◽  
M. Matyáš
Keyword(s):  
Surface Films ◽  
Mercury Electrodes

The anodic formation of calomel films on mercury electrodes—an ellipsometric-galvanostatic study

1964 ◽  
Vol 279 (1378) ◽  
pp. 327-345 ◽  
Keyword(s):  
Current Density ◽  
Induction Time ◽  
Film Growth ◽  
Polarization State ◽  
Chloride Ions ◽  
Surface Films ◽  
Anodic Current ◽  
Precipitation Model ◽  
Current Densities ◽  
Mercury Electrodes

The mechanism of formation of calomel films on mercury electrodes in 1 M potassium chloride solutions has been investigated by combining conventional galvanostatic techniques with a new application of ellipsometry. In this application, the ability of surface films to alter the polarization state of light reflected from metals has been used to monitor optically the state of the mercury surface and to signal the formation of a calomel film on a mercury mirror anode. The cell has been designed for simultaneously obtaining potential-time and ellipsometer intensity-time transients. A potentiostat has been used to maintain the mirror electrode at a potential such that it is kept free of anodically-formed films—this is the optical reference state. The cessation of potentiostatic control of the potential and the imposition of a constant anodic current makes calomel formation possible and ellipsometrically detectable in situ . The essential observation is that the mercury anode attains the ‘calomel potential’ in a time significantly less than the ‘induction time’ ( T i ) which is necessary for the formation of a calomel film on the anode. This induction time increases if an inert gas is bubbled during the passage of an anodic current. Further, it depends on the galvanostatic current density; the product iT increases linearly with current density at low current densities, but is constant at current densities > ~ 0.1 mA/cm 2 . The ellipsometer showed that, even when the anodic current was turned off during film growth, calomel growth continued for some time after which the film thickness became fairly steady over several minutes. Under these conditions (of steady thickness), the refractive index of a particular film has been shown to be that of calomel and its thickness ≈ 35 Å. The experimental results are discussed in terms of a dissolution-precipitation model in which a Hg/KCl interface is charged to the ‘calomel potential’ by a process involving the formation of mercurous adions and specifically adsorbed chloride ions. The transformation of the polarizable interface into a non-polarizable interface occurs through the passage into solution of chloro-mercurous ions, Hg 2 Cl + . The accumulation of these ions is subject to diffusion away from the electrode and to disproportionation into chloro-mercuric ions, HgCl + , and other mercuric entities. When the chloro-mercurous ions attain a critical con­centration (corresponding to the solubility product of calomel with respect to Hg 2 Cl + ) in the vicinity of the anode, a film of calomel is precipitated on to the electrode. On the basis of a diffusion precipitation model, the authors have previously derived an expression for the dependence of iT on i by solving the boundary-value problem. The predictions of this equation are in conformity with the plot of iT against i experimentally observed for calomel formation.

scholarly journals Application of Hierarchical Nanostructured WO3 and Fe2O3 Composites for Photodegradation of Surfactants in Water Samples

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1039 ◽  
Author(s):  
Ewa Biaduń ◽  
Sylwia Gajewska ◽  
Krzysztof Miecznikowski ◽  
Beata Krasnodębska-Ostręga
Keyword(s):  
Water Samples ◽  
Anodic Stripping Voltammetry ◽  
Sodium Dodecyl ◽  
Stripping Voltammetry ◽  
Xrd Analysis ◽  
Surface Films ◽  
Layer By Layer ◽  
Layer System ◽  
Water Contact ◽  
Mercury Electrodes

This study describes the utilization of hierarchical photoactive surface films for the decomposition of surfactants in water samples (with different pH). Photoactive films, containing tungsten (VI) oxide and iron (III) oxide (hematite), were deposited in a systematic and controlled manner using a layer-by-layer method. Physicochemical properties of the photoactive materials were developed and characterized using XRD analysis, Raman spectroscopy, water contact angle, voltammetry, and microscopic (SEM) techniques. The resulting multilayer films showed attractive performances in the photodegradation of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton™ X-144) under solar light irradiation. The efficiency of the surfactants’ photodegradation was evaluated with a “test” based on a method, which is extremely sensitive to surfactants’ interference, with trace analysis of Pb using anodic stripping voltammetry on mercury electrodes (recovery study). The usefulness of hierarchical photoactive systems in the photodegradation of both surfactants is demonstrated in the presence and absence of the applied bias voltage. The maximum decomposition times were 2–3 h and 30 min, respectively. Furthermore, a properly designed layer system may be proposed, matching the pH of the water sample (depending on the treatment on the sampling side).

Surface Films on Zircaloy-2 Samples Cracked in Neutral Aqueous NaCl by Stress Corrosion

1973 ◽  
Vol 31 ◽  
pp. 46-47
Author(s):  
R.A. Ploc
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Stress Corrosion ◽  
Zirconium Dioxide ◽  
Surface Film ◽  
Surface Films ◽  
Continuous Layer ◽  
Transmission Electron ◽  
Product Film

Samples of low-nickel Zircaloy-2 (material MLI-788-see(1)), when anodically polarized in neutral 5 wt% NaCl solutions, were found to be susceptible to pitting and stress corrosion cracking. The SEM revealed that pitting of stressed samples was occurring below a 2000Å thick surface film which behaved differently from normal zirconium dioxide in that it did not display interference colours. Since the initial film thickness was approximately 65Å, attempts were made to examine the product film by transmission electron microscopy to deduce composition and how the corrosion environment could penetrate the continuous layer.

TEM studies of amorphization processes and amorphous structures

1988 ◽  
Vol 46 ◽  
pp. 448-449
Author(s):  
T. E. Mitchell ◽  
R. B. Schwarz
Keyword(s):  
Amorphous Materials ◽  
Fission Products ◽  
Rapid Quenching ◽  
Surface Films ◽  
List Type ◽  
Oxide Glasses ◽  
Crystalline Materials ◽  
Amorphous Structures ◽  
Amorphous Surface ◽  
Interfacial Films

Traditional oxide glasses occur naturally as obsidian and can be made easily by suitable cooling histories. In the past 30 years, a variety of techniques have been discovered which amorphize normally crystalline materials such as metals. These include [1-3]:Rapid quenching from the vapor phase.Rapid quenching from the liquid phase.Electrodeposition of certain alloys, e.g. Fe-P.Oxidation of crystals to produce amorphous surface oxide layers.Interdiffusion of two pure crystalline metals.Hydrogen-induced vitrification of an intermetal1ic.Mechanical alloying and ball-milling of intermetal lie compounds.Irradiation processes of all kinds using ions, electrons, neutrons, and fission products.We offer here some general comments on the use of TEM to study these materials and give some particular examples of such studies.Thin specimens can be prepared from bulk homogeneous materials in the usual way. Most often, however, amorphous materials are in the form of surface films or interfacial films with different chemistry from the substrates.

Corrections for surface films in microanalysis by EDS and EELS

1992 ◽  
Vol 50 (2) ◽  
pp. 1230-1231
Author(s):  
J. Bentley ◽  
E. A. Kenik
Keyword(s):  
Hydrocarbon Contamination ◽  
Specimen Preparation ◽  
Surface Films ◽  
Ion Milling ◽  
Preferential Sputtering ◽  
Electron Energy Loss Spectrometry ◽  
Composition Determination ◽  
Analytical Electron ◽  
First Order Correction ◽  
Electron Energy Loss

Common artifacts on analytical electron microscope (AEM) specimens prepared from bulk materials are surface films with altered structure and composition that result from electropolishing, oxidation, hydrocarbon contamination, or ion milling (preferential sputtering or deposition of sputtered specimen or support material). Of course, the best solution for surface films is to avoid them by improved specimen preparation and handling procedures or to remove them by low energy ion sputter cleaning, a capability that already exists on some specialized AEMs and one that is likely to become increasingly common. However, the problem remains and it is surprising that surface films have not received more attention with respect to composition determination by energy dispersive X-ray spectrometry (EDS) and electron energy loss spectrometry (EELS).For EDS, an effective first-order correction to remove the contribution of surface films on wedge shaped specimens is to subtract from the spectrum of interest a spectrum obtained under identical conditions (probe current, diffracting conditions, acquisition live time) from a thinner region of the specimen.

Sampling and analysis of the air-water interface with SEM and EDS of microlayers

1989 ◽  
Vol 47 ◽  
pp. 1004-1005
Author(s):  
Randall W. Smith ◽  
John Dash
Keyword(s):  
Heavy Metals ◽  
Surface Microlayer ◽  
Surface Films ◽  
Water Interface ◽  
Physical Processes ◽  
Infrared Spectroscopic Analysis ◽  
Eds Analysis ◽  
Air Water Interface ◽  
Significant Area ◽  
Bulk Chemical

The structure of the air-water interface forms a boundary layer that involves biological ,chemical geological and physical processes in its formation. Freshwater and sea surface microlayers form at the air-water interface and include a diverse assemblage of organic matter, detritus, microorganisms, plankton and heavy metals. The sampling of microlayers and the examination of components is presently a significant area of study because of the input of anthropogenic materials and their accumulation at the air-water interface. The neustonic organisms present in this environment may be sensitive to the toxic components of these inputs. Hardy reports that over 20 different methods have been developed for sampling of microlayers, primarily for bulk chemical analysis. We report here the examination of microlayer films for the documentation of structure and composition.Baier and Gucinski reported the use of Langmuir-Blogett films obtained on germanium prisms for infrared spectroscopic analysis (IR-ATR) of components. The sampling of microlayers has been done by collecting fi1ms on glass plates and teflon drums, We found that microlayers could be collected on 11 mm glass cover slips by pulling a Langmuir-Blogett film from a surface microlayer. Comparative collections were made on methylcel1ulose filter pads. The films could be air-dried or preserved in Lugol's Iodine Several slicks or surface films were sampled in September, 1987 in Chesapeake Bay, Maryland and in August, 1988 in Sequim Bay, Washington, For glass coverslips the films were air-dried, mounted on SEM pegs, ringed with colloidal silver, and sputter coated with Au-Pd, The Langmuir-Blogett film technique maintained the structure of the microlayer intact for examination, SEM observation and EDS analysis were then used to determine organisms and relative concentrations of heavy metals, using a Link AN 10000 EDS system with an ISI SS40 SEM unit. Typical heavy microlayer films are shown in Figure 3.

Adsorption of chlorate and bromate ions on mercury electrodes from constant ionic strength solutions

1988 ◽  
Vol 85 ◽  
pp. 523-527
Author(s):  
M.M. Zuleika ◽  
Palhares SILVA ◽  
Ernesto Rafael GONZALEZ ◽  
Luis Alberto AVACA ◽  
Artur de Jesus MOTHEO
Keyword(s):  
Ionic Strength ◽  
Constant Ionic Strength ◽  
Mercury Electrodes

Coadsorption of bulky ions by surfactants. Monomolecular layers of tris(2,2'-bipyridyl)ruthenium(II) complex with sodium lauryl sulphate on glassy carbon, platinium, n-SnO2, and n-Si electrodes

1984 ◽  
Vol 49 (10) ◽  
pp. 2187-2196 ◽  
Author(s):  
Jan Lasovský ◽  
František Grambal ◽  
Miroslav Rypka
Keyword(s):  
Glassy Carbon ◽  
Complex Cation ◽  
Radiant Energy ◽  
Electric Energy ◽  
Sodium Lauryl Sulphate ◽  
Surface Films ◽  
Order Of Magnitude ◽  
Monomolecular Layers ◽  
Self Association ◽  
Semiconductor Electrodes

The electrochemical and photochemical behaviour of tris(2,2'-bipyridyl)ruthenium(II) complex (I) on glassy carbon, platinium, n-SnO2, and n-Si electrodes in the presence of sodium lauryl sulphate (II) was investigated. The surfactant in low concentrations induces self-association of the complex cation and its accumulation in the electrode-solution interface. At the optimum concentrations of sodium lauryl sulphate (cII ~0.6 mmol l-1) and of the complex (cI < 0.1 mmol l-1), monomolecular layers composed of I, II counterions are formed on the electrodes. The formation of the surface films does not depend on the kind of the electrode and improves the sensitivity of the voltammetric determination of I by as much as an order of magnitude. For the semiconductor electrodes, the surface films enhance the efficiency of conversion of radiant energy into electric energy. The effect under study may participate in the photosynthesis of green plants.

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