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(17/04) Курс “Анализ геномных данных”, Москва, 2 – 11 июля 2012
Уважаемые коллеги, Со 2 по 11 июля 2012 года Учебный центр Института биологии гена РАН организует практический десятидневный курс по статистическому анализу геномных дан...
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(12/03) Впервые получено изображение атомов, движущихся в молекуле
Исследователи из Университетов Огайо и Канзаса впервые смогли получить изображения атомов, движущихся в молекуле. С помощью ультрабыстрого лазера исследователи выбивали элек...
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(12/03) Наблюдение за распределением зарядов в молекуле
Исследователи из Швейцарии впервые с помощью экспериментов смогли визуализировать распределение зарядов отдельной молекуле. Предполагается, что результаты работы могут при...
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(22/01) Простой способ разделения углеродных нанотрубок
Существуют одностенные углеродные нанотрубки [single-walled carbon nanotubes (SWCNT)] с металлическим и полупроводниковым типом проводимости, однако для использования этих...
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Результаты 1 - 10 из 14
1.

Factors Influencing the Long-term Corrosion of Bronze Artefacts in Soil1

A. G. Nord, E. Mattsson, and K. Tronner

 

National Heritage Board, P.O. Box 5405, SE-11484 Stockholm, Sweden

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Received January 5, 2005

 

Abstract — The investigation was undertaken to determine the main factors causing deterioration of bronze objects in soil by studying artefacts from archaeological excavations in progress. Objects that had been buried for 300–3000 years were examined. The composition of the metal, corrosion products, and surrounding soil was determined by chemical analysis. The possible effect of polluting sources and the environment in general was also taken into account. In total, 82 variables were coded, and their effects were statistically evaluated by multivariate analysis. Acidic soil, large deposits of sulfur pollutants in relation to the critical load, the presence of soot and soluble salt, and conditions giving access to water and air were found to accelerate the deterioration. A major part of the corrosion is likely to have occurred during the latest century. The results are of importance for the understanding and estimation of long-term corrosion of bronze objects in soil.

 

Key words: bronze corrosion, long-term corrosion, environment, soil acidity, multivariate analysis.
23/09/2008 | 890 Посещения | Печать

2.

Marine Corrosion and Protection of Aluminum Alloys According to Their Composition and Structure

V. S. Sinyavskii and V. D. Kalinin

 

All-Russian Institute of Light-Weight Alloys (OAO), ul. Gorbunova 2, Moscow, 121596 Russia

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Received August 19, 2004

 

Abstract — Based on long-term tests of aluminum alloys in seawater of various climatic zones from the Arctic to the tropics, the peculiarities of their corrosion behavior are revealed. In contrast to other alloys, hydrogen sulfide has a beneficial effect on their corrosion resistance due to the passivation. However, deep in the Black Sea, the alloys, which are susceptible to structural types of corrosion, were subjected to strong exfoliation corrosion, because hydrogen sulfide excluded fouling with microorganisms that inhibits exfoliation corrosion. Alloys of the Al–Mg system exhibit the highest corrosion resistance in seawater. Alloy of an frame0frame1frame261 type (ul= 340 MPa, 0.2 = 180–210 MPa, = 11–15%) has shown a good performance. Alloying with scandium and ther-momechanical treatment make possible further simultaneous improvement of mechanical properties and corrosion resistance. It is shown that crevice corrosion is more typical of corrosion-resistant low aluminum alloys possessing lower free-corrosion and pitting potentials compared to high alloys, which are susceptible to structural types of corrosion, in particular, exfoliation corrosion. The methods of the aluminum alloys protection against marine corrosion are considered. It is shown that, in contrast to carbon steels, the anodic–cathodic protection is used for aluminum alloys.
23/09/2008 | 980 Посещения | Печать

3.

Solid-Phase Diffusion at a Potentiostatic Dissolution of Silver Alloyed with Gold

O. A. Kozaderov, O. V. Sazhneva, O. V. Koroleva, and A. V. Vvedenskii

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

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Received August 17, 2004

 

Abstract — In an acidic nitrate solution containing no less than 10–4 mol/l Ag+, potentiostatic anodic dissolution of silver from its alloy with gold (up to 35 at. %) already in about 10 s is limited by the solid-phase mutual diffusion of the components. A number of diffusion-kinetic dissolution models taking into account contribu-tions from the liquid-phase mass transfer, segregation in the surface layer, microroughness of the surface, shift of the alloy–solution interface, as well as the relaxation of nonequilibrium vacancies into a transient dissolution current are considered. The diffusivities and mutual diffusivities of the components, concentrations of nonequilibrium vacancies, and thickness of the diffusion zone estimated in terms of these models are compared. The effect of the overpotential and alloy composition is discussed. The main source of nonequilibrium monovacancies in the amount 14 orders as high as the equilibrium one is found to be the dissolution of silver. The efficiency of the sinks, among which the formation of bivacancies seemingly dominates, is not high, which predetermines the slowness of relaxation processes in the solid-phase diffusion zone.
23/09/2008 | 1038 Посещения | Печать

4.

The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

L. F. Kozin and B. I. Danil’tsev

 

Vernadsky Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine,
pr. Akad. Palladina, 32/34, Kiev-142, 03680 Ukraine

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Received February 18, 2003

 

Abstract — The effect of thiocyanate on the corrosion dissolution rate of silver in thiosemicarbazide (TSC) ammonium–chloride–bromide solutions was studied by using gravimetry and rotating disc electrode technique. The corrosion dissolution of silver was shown to be preceded by the formation of dithiosemicarbazide molecules due to the oxidation with iron (III) ions. The “second ligand” phenomenon is discussed, which consists in an increase in the corrosion dissolution rate of silver upon adding sodium thiocyanate (STC) to a TSC solution because of the decrease in the adsorption layer thickness. A synergism was discovered in the case of the corrosion dissolution of silver in a solution containing both thiosemicarbazide and sodium thiocyanate. The composition of the adsorption layer formed on a silver electrode and involving silver, sulfur (AgHS and Ag2S), as well as carbon, nitrogen, and oxygen forming the base of adsorption layers, was investigated by means of Auger spectrometry. The kinetic parameters (rate constants and reaction orders) were determined and a mechanism of the corrosion dissolution of silver in TSC, STC, and TSC + STC solutions is proposed.
23/09/2008 | 967 Посещения | Печать

5.

The Mechanism of the Cobalt Anodic Ionization in Chloride Solution

F. D. Manilevich, L. F. Kozin, A. K. Bogdanova, and B. I. Danil’tsev

 

Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine,
pr. Palladina 32/34, Kiev, 03680 Ukraine

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Received March 18, 2004

 

Abstract — The mechanism of the cobalt anodic ionization in 2.5 M CoCl2 solution (pH 3.5 0.2, t = 15–60°C) is studied with the use of rotating disk electrode and rotating ring–disk electrode methods. The experimental data showed that the ionization proceeds by stages, of which the first is an intermediate CoAads species formation (A is Cl or OH), in which the cobalt oxidation state is 1+. Further CoAads transformation involves rapid parallel reactions of the Co+ ions electrochemical oxidation or disproportionation. An oxidation current wave was revealed at the platinum ring electrode for the species formed during the cobalt anodic ionization at the disk electrode. Judging by the wave potential, these species can be either finely dispersed elemental cobalt or the intermediate Co+ ions.
23/09/2008 | 925 Посещения | Печать

6.

Electropolishing of Silver in Waterframe0Organic Solutions of Potassium Thiocyanate

A. V. Balmasov*, E. V. Koroleva*, and S. A. Lilin**

 

* Ivanovo State University of Chemistry and Technology,
pr. F. Engel’sa 7, Ivanovo, 153000 Russia

** Institute of Chemistry of Solutions, Russian Academy of Sciences,
ul. Akademicheskaya 1, Ivanovo, 153045 Russia

Received August 19, 2004

 

Abstract — The anodic behavior of silver in aqueous and water–glycerol solutions of potassium thiocyanate is studied on motionless and rotating-disk electrode. The appearance of the limiting current is explained. Optimal solution compositions and conditions for the process (which ensure metal polishing) are suggested.
23/09/2008 | 968 Посещения | Печать

7.

Corrosion of Hydrides of Nickel and Cu30Ni Alloy in Oxygen Containing Solutions

 

G. N. Markos’yan, D. S. Sirota, and A. P. Pchel’nikov

Karpov Institute of Physical Chemistry State Scientific Center of the Russian Federation,
ul. Vorontsovo Pole 10, Moscow, 103064 Russia

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Received July 27, 2004

 

Abstract — Corrosion behavior of nickel hydride is studied in alkaline, neutral, and weakly acidic oxygen-containing solutions by compensating oxygen consumed in corrosion and spectrophotometric analysis of solution for nickel. It is shown that in the course of nickel hydride corrosion in alkaline solutions, oxygen is consumed solely in its interaction with hydrogen formed at hydride decomposition, while nickel remains at the surface. It is concluded that, in a pH range from 7 to 14, hydrogen oxidation is limited by its solid-phase diffusion, whereas the rate of nickel hydride decomposition is pH-independent. The difference in the corrosion behavior of the original alloy and its hydride is attributed to the fact that the original alloy evolves copper ions, whereas the hydride evolves hydrogen.
23/09/2008 | 988 Посещения | Печать

8.

Electrochemical Estimation of Developed Roughness of Galvanic Nickel CoatingsA. N. Podobaev*, S. S. Kruglikov**, P. Becker***, and M. Mattiesen***

 

* Karpov Institute of Physical Chemistry, State Scientific Center of the Russian Federation
ul. Vorontsovo Pole 10, Moscow, 103064 Russia

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** Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125190 Russia

*** Tyco Electronics Corp., Menlo Park, California, USA

Received April 2, 2004

 

Abstract — The roughness of nickel coatings with highly developed surface (constituted from dendrites) can be estimated by measuring their differential capacitance under cathodic polarization in weakly acid sulfate solution. For the same purpose, using diffusion- or kinetics-controlled electrochemical reactions yields underestimates.
23/09/2008 | 969 Посещения | Печать

9.

Formation, Retention, and Loss of the Metals Atmospheric Corrosion Products. 1. The Integral Weight Modelof the Products Formed

Yu. M. Panchenko and P. V. Strekalov

 

Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

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Received May 20, 2004

 

Abstract — Changes of the total weight of tested samples, as well as changes in the weight of the retained atmospheric corrosion products, are studied as functions of corrosion losses in different climate zones and different test duration, for carbon steel, zinc, copper, magnesium, aluminum, frame016 and frame1frame2 alloys, and brass. An experimen-tal mathematical model for integral weight of formed corrosion products is suggested. Climate effects on the change in the weight of corrosion products retained by metals are studied during long-term exposure of plates and wire spirals recommended by the ISO 9226-92 Standard for the monitoring of atmospheric corrosivity.
23/09/2008 | 1101 Посещения | Печать

10.

Biocorrosion of Oil and Gas Field Equipment and Chemical Methods for Its Suppression. I

L. S. Moiseeva* and O. V. Kondrova**

 

* Scientific and Engineering Center, LUKOIL Oil Company, ul. Usacheva 11, Moscow, 119048 Russia

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** Dneprodzerzhinsk State Technical University, ul. Dneprostroevskaya 2, Dneprodzerzhinsk, Russia

Received in final form, October 14, 2004

 

Abstract — Main groups of corrosive microorganisms are considered. The parameters of the medium that intensify biocorrosion and the conditions for the formation of biofilms are described. The mechanisms of biocorrosion induced by the main groups of unicellular microorganisms are proposed, and the characteristic types of biodamage, specified.
23/09/2008 | 1146 Посещения | Печать

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