China
Africa
Explore chapters and articles related to this topic
Electrization of Liquids
Published in Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin, Cavitation and Associated Phenomena, 2021
Dmitry A. Biryukov, Denis N. Gerasimov, Eugeny I. Yutin
When two media which have free electrons are put into contact, then an electron in the given body must not overcome the work function A of the surface of that body. The question is: the work function of which body is higher? If A1< A2, electrons will leave the medium #1; the medium #2 therefore will be charged negatively while the medium #1 would obtain a positive charge (since electrons left it). The increased electron density in medium #2 will stop the process sooner or later, when the emission currents will be balanced. Besides, there exist another way to interrupt the electron transfer: by establishing the outer contact potential difference, called the Volta potential, ΔφV=A2−A1e which locks the current.
Electrostatic and Thermodynamic Potentials of Electrons in Materials
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
Assuming that both materials are good electronic conductors, if they are brought into contact with a wire, before making the junction, the transference of charge will produce sheets of charges in the surface that result in a Volta potential difference. When the two materials are joined to form the junction, the Volta potential difference has to be accommodated at the interface (in metals) or across extended space charge layer in semiconductors, so that the Fermi levels remain aligned and the bulk energy levels become flat. The lineup of the Fermi levels of two conductors in electronic equilibrium implies changes of the Volta potential on the surface of each conductor, Δψi. The relative amount of the change for each conductor depends on the relative sizes of the conductors (Trasatti, 1986; Hansen and Hansen, 1987a, b) and in the case of semiconductors, on the relative values of the DOS at the Fermi level (Gerischer et al., 1994).
Principles of Electrochemistry
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
Volta potential differences are determined by the work required for moving an electrically charged probe in vacuum or in an inert gas from one point close to the surface of a condensed phase I to a point close to the surface of another phase II. The distance of the probe from the surface should be large enough that all chemical interaction and the effect of electric polarization (image force) can be neglected. This situation is illustrated for a contact between two metals in vacuum in Figure 2.3.
Numerical analysis of topographic and Volta potential profiles during corrosion of duplex stainless steel in chloride solution
Published in Corrosion Engineering, Science and Technology, 2022
Yuan Li, Shan Qian, Boxin Wei, Y. Frank Cheng
The SKPFM, a combination of scanning Kelvin probe (SKP) and atomic force microscopy (AFM), possesses a unique ability to in-situ characterise surface topography and measure Volta potential of a metal specimen at micro – or nanoscale in aqueous environments [8–13]. The Volta potential is related to the corrosion potential of the specimen, capable of distinguishing the electrochemical corrosion activity of different microphases and metallurgical features contained in the metal [5,8]. Generally, the Volta potential is analysed to provide qualitative information of metallic corrosion. For example, the Volta potential with a high (positive) or low (negative) value with respect to the Kelvin probe tip indicates net anodic or net cathodic activity, respectively. A big Volta potential difference measured between a specific microphase and the Kelvin probe is associated with a great corrosion activity of the microphase. A major gap exists in further exploration of the Volta potentials to understand the corrosion at a more mechanistic level.
On the Volta potential measured by SKPFM – fundamental and practical aspects with relevance to corrosion science
Published in Corrosion Engineering, Science and Technology, 2019
Cem Örnek, Christofer Leygraf, Jinshan Pan
The discussion so far does not involve any effect of the electrolyte. For a metal in an electrolyte, the situation is more complicated. The electrochemical potential of an electrode in an electrolyte depends on the structure of the electrochemical double layer at the electrode/electrolyte interface and the electrochemical reaction(s) taking place on the electrode surface. According to Trasatti’s notation, the electrochemical electrode potential includes the Volta potential and the Volta potential difference at the electrode/electrolyte interface so that the interfacial parameters also have an influence on the electrode potential [45]. A similar concept was seen also in earlier communication by Rüetschi and Delahay [30]. Moreover, the corrosion potential of a metal in an electrolyte is a mixed potential reached at the open-circuit condition, which depends on the coupled anodic and cathodic reactions (mixed-potential theory), and also on other parameters such as the surface film formed as well as the Ohmic resistance of the electrolyte. These factors should be kept in mind when correlating the measured Volta potential with the corrosion potential [46].
Effect of grain structures and precipitation characteristics on the corrosion behaviour of Sc-containing Al-Cu-Li alloy
Published in Corrosion Engineering, Science and Technology, 2023
Yuankang Xie, Shengdan Liu, Yunlai Deng, Xiaobin Guo
The surface Volta potential was measured by scanning Kelvin probe force microscope (SKPFM) technique. The surface of the sample was polished and cleaned with alcohol before testing. The probe model SCM-PIT-V2 was used as the reference electrode. Bruker Dimension Icon atomic force microscope (AFM) was used for testing. The experiment was conducted in an atmospheric environment at a scanning frequency of 0.5 Hz. The data were analysed using NanoScope Analysis 1.8.