Changes in surface morphology and work function caused by corrosion in aluminum alloys

Corrosion behavior of a material is complicated and can affect strongly its surface physical and chemical properties. In this study, the effect of corrosion on surface morphology and electron work function (EWF) of various Al alloys was comparatively investigated using a scanning electron microscopy and a scanning Kelvin probe. The experimental results showed that the change in EWF with corrosion time was not linear, but firstly increased and then decreased. The theoretical treatments demonstrated that such a change in EWF did not only depend on the surface roughness, but also correlate with oxide layers formed at the surfaces of Al alloys. The present results can also be used to reasonably explain the correlation between surface roughness and EWF reported previously.     

Dependence of electron work function of Al-Mg alloys on surface structures and relative humidity

In many fields the determination of electronic structures of a solid material is a prerequisite in order to investigate its physical/chemical properties as well as related applications. The effect of surface structures and ambient environment on the electronic behavior is of both fundamental and practical significance. In this study, the electron work function (EWF) of Al-Mg alloys is investigated using a scanning Kelvin probe. The results show that the EWF decreases with the increase of surface smoothness, whereas surface oxidation layers would result in the increase of the EWF. Furthermore EWF is strongly dependent on the relative humidity, especially when the relative humidity is higher than 70%, implying that considerable care should be takenon such dependence in order to gain a meaningful parameter for the characterization of surface behavior.     

Patterns in the distribution of the electron work function at deformed surfaces of metals

Results of an experimental study of the patterns in the formation and evolution of the electron work function (EWF) on deformed metal surfaces are given. It is shown that the distribution of the EWF over the metal surface shows the deformational contours and allows one to determine the degree of deformability of various parts of the sample. The kinetic dependence of the EWF during the relaxation and vacuum annealing processes is found. Zaporozhe State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 59–63, June, 1998.     

Electron work function in alloys from the tin-lead system

The temperature and concentration dependences of the electron work function in Sn-Pb alloys are determined by the Fowler photoelectric method. It is shown that alloying of Sn with Pb decreases the electron work function rather than increasing it, as was reported in the literature. From the published data and experimental data obtained by the authors for the electron work function in the tin-lead system, it follows that the rate of decrease of the electron work function with increasing Pb concentration depends on the vacuum quality in the measuring cell and features in the electron work function isotherms are the more distinct the higher the vacuum.     

Theory of the residual electrical resistivity of binary actinide alloys

A system of self-consistent equations has been proposed for the coherent potential approximation of the multiband conductivity model for the case of conduction electron scattering from chaotic electric fields of ions of disordered binary alloy components at zero temperature. It has been qualitatively demonstrated that the deviation of the concentration dependence of the residual electrical resistivity of actinide alloys with multiband conductivity from the Nordheim rule is caused by the explicit dependence of the electrical resistivity of the alloy on the magnitude and sign of the real part of the Green’s function at the Fermi level. The derived system of equations for the multiband coherent potential approximation has been used to calculate the concentration dependence of the density of states and the residual electrical resistivity of the alloys of neptunium and plutonium. The results of the calculations have been compared with the available experimental data.     

Effects of elastic and plastic deformations on the electron work function of metals during bending tests

The high sensitivity of the electron work function (EWF) to surface conditions has attracted increasing interest in the application of the electron work function (EWF) to investigate tribological phenomena using the Kelvin probing technique. In this study, the correlation between the EWF and both the elastic and plastic deformation of copper and aluminium during bending tests was investigated. It was demonstrated that, in the elastic range, tensile strain decreased the EWF, while compressive strain increased the EWF. However, in the plastic range, the EWF always decreased with plastic deformation irrespectively of whether it was tensile or compressive. The mechanism responsible for the variation in EWF with elastic and plastic deformation is analysed and discussed.     

Model calculation of the surface tension of liquid Ga-Bi alloy

A convenient model, based on some assumptions, for calculating the composition and temperature dependence of the surface tension of binary liquid alloys is reported. The theoretical calculations of the surface tension of gallium-rich-bismuth alloys are presented. The calculated results are compared with the reported experimental data. A relatively good agreement with experimental behavior of the composition dependence of the surface tension was found, but a disagreement was observed with experimental temperature behavior of the surface tension of these alloys. The calculations were conducted in the temperature range from almost 320 K to about 800 K. The surface tension was calculated from eutectic composition (x_Bi = 0.0022) to x_Bi = 0.1, and worked out by linear equations. The model calculation and analysis indicate a first order surface phase transition in this system, which is in accord with experimental findings. For this system, γ decreases linearly with increasing temperature at fixed Bi mole fraction x_Bi, and thus, suggesting a positive surface excess entropy. It is also found that the surface tension isotherms show the linear dependence on the concentration, in the logarithm scale of x_Bi, in the very narrow concentration range.     

Correlation between the wear resistance of Cu-Ni alloy and its electron work function

This article reports our studies on the performance of isomorphous Cu–Ni alloy during sliding and erosive wear processes with attempt to correlate its wear behaviour with the electron work function (EWF). EWF, mechanical behaviour and wear resistance of the Cu–Ni alloy with respect to the concentration of Ni were measured using ultraviolet photoelectron spectroscopy, micro-indenter, pin-on-disc and air-jet testers, respectively. It was demonstrated that EWF, hardness and Young’s modulus of the alloy increased as the concentration of Ni increased. During solid-particle erosion tests, the wear resistance of the alloy was enhanced with an increase in the Ni concentration, corresponding to an increase in EWF. However, an opposite trend was observed during sliding wear tests, which was ascribed to the formation of oxide scale that affected the sliding wear resistance.     

Electric fields gradients and diffusion in Rb-Cs alloys

The EPG for Kb in statistically disordered Rb-Cs alloys was measured by Kb PAD. Complementary Kb (and Cs) NMR experiments gave information about the nuclear quadrupole moment and Knight shift inhomogeneities. From the motional narrowing observed in all experiments at high temperature the activation energy of diffusion was determined.     

Temperature and concentration dependences of the electrical resistivity for alloys of plutonium with americium under normal conditions

The temperature and concentration dependences of the electrical resistivity for alloys of americium with plutonium are analyzed in terms of the multiband conductivity model for binary disordered substitution-type alloys. For the case of high temperatures (T > Θ_D, Θ_D is the Debye temperature), a system of self-consistent equations of the coherent potential approximation has been derived for the scattering of conduction electrons by impurities and phonons without any constraints on the interaction intensity. The definitions of the shift and broadening operator for a single-electron level are used to show qualitatively and quantitatively that the pattern of the temperature dependence of the electrical resistivity for alloys is determined by the balance between the coherent and incoherent contributions to the electron-phonon scattering and that the interference conduction electron scattering mechanism can be the main cause of the negative temperature coefficient of resistivity observed in some alloys involving actinides. It is shown that the great values of the observed resistivity may be attributable to interband transitions of charge carriers and renormalization of their effective mass through strong s-d band hybridization. The concentration and temperature dependences of the resistivity for alloys of plutonium and americium calculated in terms of the derived conductivity model are compared with the available experimental data.     

Hall coefficient of alloys of the Nd-Y system at temperature range 100–800°K

Studies were conducted on the concentration and temperature dependence of the Hall coefficient of alloys of the Nd-Y system within the entire region of concentrations and in the temperature range from 100 to 800°K. The results obtained are discussed from the point of view of electron theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 32–36, January, 1973.The authors wish to express their thanks to G. F. Kobzenko for supplying the alloys, and to A. E. Bryukhanov and V. F. Nemchenko for their assistance in the work.     

Electron work function in alloys with alkali metals

The electron work function in alloys and compounds containing alkali metals, which are of interest for the designing of new photocathode materials and further development of the theory of electron emission, is studied. It is shown that a number of applied and theoretical issues in this field are poorly understood. These are the temperature and concentration dependences of the electron work function in binary metallic systems, the surface activity of components that are inactive in alloys with alkali metals, and some others.     

Investigation of local work function distribution of field emission cathode from carbon materials doped by Ba with the help of AFM/SEM/X-ray

The joint application of atomic force microscopy (AFM) and SEM/X-ray micro-analyzer for investigation of electron work function (EWF) distribution over the surface of field emission cathode (FEC) is described in the paper. This method was used to investigate the graphite cathodes surface after barium doping. The possibility of defining the average value of EWF over the surface of FEC is shown. The results of AFM measurements are compared with results of field emission tests. The reduction of work function down to 3–3.2 eV was found after barium doping.     

Characteristics of atomic structure and electron scattering in copper-germanium melts

Melts of the Ge-Cu system containing 16.6, 25.0, 36.0, and 60 at.% Ge are studied by x-ray diffraction. The partial structure factors are calculated. It is shown that the rigid-sphere model cannot be applied to describe the structure of Cu-Ge melts. The temperature and concentration dependence of the resistance and thermo-emf are measured. A differential thermal analysis is carried out for alloys containing intermetallic phases. On the basis of these experimental data a model is proposed for the electron spectrum in melts of the Cu-Ge system.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 33–39, November, 1975.     

Fe-Al系统磁性及其压力效应

采用紧束缚线性muffin-tin轨道方法,研究了Fe-Al系统的磁性与Al组分的关系及其压力效应. bcc Fe-Al合金的铁磁磁矩随Al组分增大而单调减小,且会出现Al组分引起的铁磁—顺磁相变. bcc Fe-Al合金的铁磁磁矩随体积压缩单调减小,但与γ-Fe及某些fcc铁基合金不同的是bcc Fe-Al合金不会出现压力诱导的铁磁—顺磁相变.计算结果与实验符合. 关键词：     

Theoretical calculation of surface tension and its temperature coefficient associated with liquid Cu–Ti alloys

In this work, the surface tension of Cu–Ti binary liquid alloys is calculated in the framework of Eyring theory as a function of composition and temperature. It is observed that for all investigated alloys the surface tension can be described by a linear function of the temperature with negative slope, and the temperature coefficient of surface tension decreases as Ti-content of the alloys increases linearly. The obtained theoretical results are compared to the experimental data available in the literature as well as to the theoretical results evaluated by using four models, such as the compound formation model, the quasi-chemical approximation for regular solutions, ideal solution model and Butler model treated in literature frequently.     

The surface tension and density of the Cu-Ag-In alloys

The surface tension and the densities of the Cu-Ag-In alloys have been measured by means of the sessile drop method. The density of these alloys depends linearly on temperature in the case of all the investigated compositions. The surface tension shows a linear dependence on temperature except for the lowest temperatures. For most of the alloys, the surface tension at the lowest temperature is lower than that predicted by the straight line. The experimental values of the surface tension of the Cu-Ag-In alloys are compared with those computed from the model, and quite good agreement is observed.     

The limiting electron activity of cesium in potassium-based alloys

Temperature and concentration dependences of the electron work function in cesium-potassium alloys were studied by the Fowler photoelectric method for the first time. Our results indicate that the limiting electron activity of cesium in potassium-cesium alloys is six times larger than that obtained by extrapolating the work function isotherm to pure potassium.     

Physical properties and electron spectrum of solid solutions (Co1−xNix)5Ge3

Data are presented from an experimental investigation of physical properties (paramagnetic susceptibility, electrical conductivity, Hall coefficient) and their temperature dependence in alloys (Co_1?xNi_x)₅Ge₃, where 0≤x≤1, crystallized in the filled nickel arsenide type. Data obtained are used to define the zone structure of the electron energy spectrum in these crystals, which is based initially on theoretical group analysis with use of Goodenough's concept. It is shown that upon change in external parameters (electron concentration, temperature) shifting of zones relative to each other occurs.     

Thermal atomic vibrations in Cu-Ni alloys

Copper radiation has been used in an x-ray study of the temperature dependence of the effective characteristic x-ray temperature _p(T) for the alloys of the Cu-Ni system over the temperature range 293–1073 °K and in a determination of the concentration dependence of d ln_p/dT for the alloys. It is shown that _p(c) is additive. The concentration dependence of d ln_p/dT is linear. The agreement between the experimental results and data in the literature is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 75–80, September, 1970.