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(11/10) Ученые из ИФХЭ РАН и МГУ под руководством Ольги Виноградовой поняли, как «полосатая» гидрофобность..
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Results 31 - 40 of 118
31.

Thermodynamics of Chemical and Electrochemical Stability of Aluminum, Silicon, and Tin Bronze

A. G. Tyurin

 

Chelyabinsk State University, ul. Br. Kashirinykh 129, Chelyabinsk, 454021 Russia

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Received December 20, 2006

 

Abstract—Phase diagrams copper–element–oxygen and potential–pH diagrams are plotted for alloys of the Cu–Al, Cu–Si, and Cu–Sn systems at 25frame0C. Thermodynamic peculiarities of the corrosion and electrochemical behavior of phase components of aluminum, silicon, and tin bronzes are analyzed. The surface activity of alloying elements is assessed.

PACS numbers: 81.65.Kn

DOI: 10.1134/S0033173208030132
03/09/2008 | 845 Hits | Print

32.

Determining the Partial Currents of Silver Ionization, its Oxide Formation, and Chemical Dissolution by Multicycle Chronoammetry with an RRDE

D. A. Kudryashov, S. N. Grushevskaya, and A. V. Vvedenskii

 

Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia

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Received May 17, 2007

 

Abstract — A multicycle chronoammetry with a rotating disc electrode with a ring (RRDE) enables one to experimentally discriminate between the partial currents of the substrate metal ionization, anodic formation of the oxide, and chemical dissolution of the oxide in the summary polarization current of the disc. The technique is approved by an example of AgAg2OOHframe0(H2O) system. In a range of relatively small anodic potentials of the Ag disc (0.48 to 0.51 V), the active dissolution of silver at the open surface sites and via pores in the surface film dominates; the phase formation current and, accordingly, the current efficiency of the process rapidly drop. At the potentials of the voltammogram maximum (0.52 to 0.53 V) when the silver active dissolution current is suppressed, the phase formation currents prevail and substantially exceed the chemical dissolution rate of the oxide. The thickness of an Ag2O film rapidly increases under these conditions, and the current efficiency of the oxide formation is close to 100% for the whole polarization period. The rate constant of the chemical dissolution of an Ag(I) oxide is practically independent of the anodic phase-formation potential, but slightly depends on the oxide film thickness, reflecting changes in the film structure and, possibly, in its composition, from AgOH to Ag2O.

PACS numbers: 82.45.Qr

DOI: 10.1134/S0033173208030144
03/09/2008 | 898 Hits | Print

33.

Acid-Basic, Adsorption, and Photosorption Properties of Magnesia Samples

I. A. Ekimova and T. S. Minakova

 

Tomsk State University, pr. Lenina 36, Tomsk, 634050 Russia

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Received June 14, 2007

 

Abstract—The acid-basic, adsorption, and photosorption properties of differently prepared magnesia samples were studied. It was found that the less basic magnesia surface photosorbs better oxygen and adsorbs better the water vapor.

PACS numbers: 68.47.Gh

DOI: 10.1134/S0033173208030156
03/09/2008 | 945 Hits | Print

34.

Surface Tension of Solids. Structure-Mechanical Approach1

V. A. Marichev

 

Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7

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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 | 1170 Hits | Print

35.

Theory of the Electrolysis of Water

R. R. Salem

 

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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 | 1097 Hits | Print

36.

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 | 1139 Hits | Print

37.

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 | 1142 Hits | Print

38.

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 | 1126 Hits | Print

39.

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

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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 | 1029 Hits | Print

40.

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

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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 | 1059 Hits | Print

  

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