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1.
Surface Tension of Solids. Structure-Mechanical Approach1 V. A. Marichev Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7 e-mail:
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Received March 19, 2007 Abstract — Problems of applying the classic and generalized Lippmann equations to adsorption studies on solid electrodes are shortly reviewed. Long-time thermodynamic discussion results in no clear-cut decision. A new nonthermodynamic approach is proposed considering the principal possibility and role of elastic and plastic deformations of the electrode surface during adsorption. The extremely thin electrode surface layers affected electrically and mechanically by adsorbate are supposed to be free of dislocations because of volume restriction. The nearest structure-mechanical analogs of such layers are the whisker crystals whose side surface could have one- and two-dimensional defects, but no active dislocations. Like whiskers, surface metal layers should possess a high ultimate strength close to the theoretical one and a purely elastic deformation. Special attention has been paid to the concepts of “reversible wholly plastic deformation (as in cleavage)” used for derivation of the generalized Lippmann equations for solids. This concept was shown to be an idealized one having no relation to the real plastic deformation of metals. It is a case of mixed notions since “cleavage” is not a kind of deformation. It is a kind of irreversible fracture mostly without the steps of plasticity. Affected only by adsorbate, the thin surface electrode layer should be considered as absolutely elastic body, whose plastic deformation is impossible, i.e. the Lippmann equation and other equations containing terms of plastic deformation cannot be used in thermodynamics of adsorption on the solid metals. PACS numbers: 68.03.Cd DOI: 10.1134/S003317320802001X
03/09/2008 | 1238 Посещения | Печать
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2.
Theory of the Electrolysis of Water R. R. Salem E-mail:
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Received October 16, 2006 Abstract—Based only on simple electrodynamics relations with no use of Arrhenius’ ionic hypothesis, an equation relating the polarization current density to the potential is derived and used in describing the kinetics of electrolysis by an example of water decomposition in a wide range of potentials. PACS numbers: 82.45.Hk DOI: 10.1134/S0033173208020021
03/09/2008 | 1162 Посещения | Печать
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Theory of Pit Nucleation. II. Interaction between Pits at the Early Stage of Development. The Role of Solvent Yu. A. Popov Karpov Institute of Physical Chemistry, ul. Vorontsovo pole 10, Moscow, 103064 Russia Received June 6, 2006 Abstract — A mechanism of interaction between pits is considered. It is shown that at an early stage of their development, the interaction proceeds due to the hydration of metal ions by the solvent, as a result of which electrolyte in a pit and over it becomes dehydrated. Accordingly, the kinetics of mass transfer, which affects the reagent supply to the dissolved surface of the growing pit, changes. As a result, the reagents are in deficit, the growth of weak (i.e., less active) pits is decelerated, and they are repassivated. Equations describing these processes are derived, and a model of interaction between two linearly connected pits is proposed. PACS numbers: 82.45.Bb DOI: 10.1134/S0033173208020033
03/09/2008 | 1202 Посещения | Печать
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Determination of the Thermodynamic Parameters Characterizing the Adsorption and Inhibitive Properties of Surfactants B. N. Afanas’ev, Yu. P. Akulova, and Yu. A. Polozhentseva St. Petersburg State Technological Institute (Technical University), Moskovskii pr., 26, St. Petersburg, 198013 Russia Received June 23, 2007 Abstract — Equations for calculations of the activity coefficients of surfactants in the surface layer and the Gibbs energy changes due to the hydrophobic effect and associated with the metal–surfactant bond energy were derived. An analysis of data on the adsorption of surfactants at  -Fe2O3 and lead showed that the surfactant is an effective corrosion inhibitor when the surfactant–metal bond is sufficiently strong and the activity coefficient of the surfactant in the surface layer is high. This favors the formation of two-dimensional “islets” of adsorbed molecules. PACS numbers: 81.65 Kn DOI: 10.1134/S0033173208020045
03/09/2008 | 1211 Посещения | Печать
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Steel Protection Inhibitors in Electrochemical Machining in Concentrated Sodium Chloride Solutions V. G. Revenko*, V. V. Parshutin*, G. P. Chernova**, and N. L. Bogdashkina *Institute of Applied Physics, Academy of Sciences of Moldova, Akademicheskaya 5, Kishinev, MD-2028 Moldova **Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia Received June 5, 2006 Abstract — Optimal inhibitors for the protection of #38KhN3MFA and #30KhN2MFA steels in concentrated sodium chloride solutions during electrochemical machining (EM) are revealed. Compositions of solutions used in washing of the surface of samples subjected to EM are selected. Corrosion and electrochemical methods are used. The most effective corrosion inhibitors are found and their optimal concentrations are determined, which allows one to reduce the corrosion rate of studied steels by a factor of 5–7. PACS numbers: 81.65.Kn DOI: 10.1134/S0033173208020057
03/09/2008 | 1199 Посещения | Печать
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Hydrogen Adsorption on Model Nanoporous Carbon Adsorbents A. A. Fomkin and V. A. Sinitsyn Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia E-mail:
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Received June 14, 2007 Abstract — Hydrogen adsorption on model nanoporous adsorbents with slit-like micropores of 0.538, 0.878, and 1.218 nm width, which were obtained by successively eliminating one, two, and three layers of hexagonal carbon from a graphite structure treated as a model cell, is estimated. The Dubinin theory of volume pore filling and the linearity of adsorption isosters are used. Hydrogen adsorption isotherms are calculated at temperatures of 20, 33, 77, 200, 300, and 400 K and pressures up to 20 MPa for the structures with mono- and bilayer carbon walls. The maximum hydrogen adsorption for the AC35 structure at a pressure of 20 MPa and a temperature of 300 K was 7.9 wt %. The effect of parameters of the porous adsorbent structure on the temperature dependence of the hydrogen adsorption is discussed. PACS numbers: 68.43.-h DOI: 10.1134/S0033173208020070
03/09/2008 | 1092 Посещения | Печать
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Analysis of Microporous Structure of Carbon Adsorbents in Terms of the Theory of Volume Filling of Micropores G. A. Petukhova Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia E-mail:
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Received June 14, 2007 Abstract — A methodology of using the theory of filling the volume of micropores when evaluating the porous structure of carbon nanomaterials and adsorbents, as well as describing the adsorption of different species, is considered. Potentialities of the mathematical means of a theory of filling the volume of micropores when differentiating homogeneous and irregular microporous structure of activated carbon, determining the micropores’ parameters (their volume and size), evaluating the degree of heterogeneity of microporous structures, and describing adsorption over wide concentration range are analyzed. The perspectives of this approach, based on the theory of filling the volume of micropores, in the prognosis of the microporous structures’ parameters and the activated carbons’ adsorbability in the process of their synthesis are demonstrated. PACS numbers: 68.43.-h DOI: 10.1134/S0033173208020082
03/09/2008 | 1124 Посещения | Печать
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A Gas-Chromatography Study of Adsorption Properties of Silica Modified by Stable Nickel Nanoparticles Obtained in Reverse Micelles under  -Radiation L. D. Belyakovaa, S. V. Gornostaevab, N. A. Pavlovac, O. G. Larionova, A. A. Revinaa, and A. V. Bulanovac a Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia b Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125190 Russia c Samara State University, Samara, Russia Received June 12, 2007 Abstract — Stable nano-sized nickel particles are prepared using the radiation-chemical synthesis in reverse micelles. Adsorption properties of raw silica (silochrome, S-120), the silochrome modified by a micelle-forming compound (AOT), and the silochrome modified by the nano-sized nickel particles are studied using gas chromatography method. The retention times for different test-compounds at different temperatures are determined for these adsorbents. Specific retention volumes of the test-compounds, as well as the thermodynamic adsorption characteristics, are determined. After the modification, the initial adsorption heat for n-hydrocarbons increases, which points out to the higher surface roughness of the modified samples. For the nickel-nanoparticle-modified silica, the contribution of specific interactions of polar compounds is less than that for the unmod-ified silica; this can be explained by screening the active centers (OH-groups) of the silica gel by the metal nano-particles. The silica polarity decreases after the modification. The gas chromatography method allows detecting the difference in the properties of nanocomposites containing Ni- and NiO-nanoparticles. PACS numbers: 68.43.-h DOI: 10.1134/S0033173208020094
03/09/2008 | 1155 Посещения | Печать
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A Changed State of Silver Nanoparticles upon the Adsorption of Acrylic Acid and Low-Temperature Treatment E. A. Kononova, Nghia Nguyen, and I. I. Mikhalenko Peoples Friendship University, ul. Miklukho-Maklaya 6, Moscow, 117923 Russia E-mail:
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Received June 21, 2007 Abstract — Plasma-resonance absorption spectra of silver hydrosol were recorded and analyzed to estimate the influences of acrylic acid (AA) as an additive and subsequent low-temperature treatment (LTT) of the sol at 77K on the state of silver nanoparticles. It was found that AA adsorbs in two forms with different orientations of its molecules. Low-temperature treatment resulted in aggregation of particles because of their more defective surfaces, which is characterized by the damping factor of plasmon vibrations. In the adsorption of AA, the damping factor also increases, but the cryoaggregation of particles decreases. PACS numbers: 68.43.–h DOI: 10.1134/S0033173208020100
03/09/2008 | 1295 Посещения | Печать
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Adsorption of Oxygen-Containing Compounds at Fluorinated Graphite and Fluorinated Carbon Fiber T. M. Roshchina, S. V. Glazkova, N. A. Zubareva, E. A. Tveritinova, and A. D. Khrycheva Department of Chemistry, Moscow State University, Vorob’evy gory 1, Moscow, 119992 Russia E-mail:
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Received May 17, 2007 Abstract — The surface properties of fully fluorinated samples of natural graphite (FG) and carbon fiber (FCF) were studied by gas chromatography, IR spectroscopy, and static adsorption. It was found that for fluorocar-bons, the contributions from the O atom (for ethers) and the OH group (for alcohols) are comparable with the contribution from the methylene unit to the retention parameters, which is typical only of highly homogeneous, hydrophobic, and nonpolar surfaces. Unusual properties of fluorocarbons compared to known hydrophobic adsorbents include weaker adsorption of secondary alcohols than ketones, their dehydrogenation products. An analysis of the retention parameters of isomeric propanols and butanols revealed that the FCF surface is acces-sible to the adsorption of these molecules, and is mainly formed by planar homogeneous fragments. In contrast, the FG structure is porous; the pore width is comparable with the molecule size, which makes the adsorption equilibrium more difficult to reach. PACS numbers: 68.43.–h DOI: 10.1134/S0033173208020112
03/09/2008 | 1295 Посещения | Печать
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