The elasticity of structured surface liquid layers

The notion of “elasticity of structured surface liquid layers” has been introduced and considered in detail for the first time. It is shown to be reasonably connected with the thermodynamics of condensed matter, allowing the logical derivation of the general equations for the surface tension of liquids and solids which had been impossible before.     

Internet expert panel for interdisciplinary problems

The aim of this work is an evaluation of Internet and Worldwide web not only as the sources of scientific information but also as a prospective way for considering and solving the interdisciplinary problems. In order to give this evaluation quantitative character, the notions of “Expert Panel” and “Internet Expert Panel” were analyzed using some selected search engines and databases. Using the real example: “surface tension of solids” as a typical case of intersect of many natural sciences, we demonstrated the possibility of creating the virtual “Online Internet Expert Panel” for solving the interdisciplinary problems. Original Russian Text ? V.A. Marichev, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 1, pp. 107–112.     

Nonlinear Behavior in Compression and Tension of Thermally Sprayed Ceramic Coatings

Mechanical properties of thermally sprayed coatings, especially of ceramics, are strongly influenced by a high density of mesoscopic defects, microcracks of dimensions between fractions of μm up to tens of μm. The anisotropic linear elastic stress–strain relations are valid only at very low deformations, e.g., |e| < 0.05%, with small values of Young’s moduli due to elastic openings and elastic partial closings of microcracks. At higher deformations, e.g., 0.05% < |e| < 0.4%, the stress–strain relations are strongly nonlinear. Under compressive stresses, elastic closing of microcracks leads to a gradual decrease of the microcrack density and to an increase of Young’s modulus in compression. Under tensile stresses, the microcracks slightly grow by inelastic processes; the microcrack density gradually increases and effective Young’s modulus in tension decreases. A two-parametric equation containing linear and quadratic terms is used to describe the nonlinear stress–strain curves of plasma-sprayed ceramic coatings. The effect of nonlinearity on the bending of beams with coatings and the nonlinear combination of external and residual stresses are discussed. The fracture of coatings at higher tensile stresses due to coalescence of the microcracks is mentioned.     

Martensite transformations: History and laws

Conclusions The results of research in the field of martensite transformations reflect the complexity and inexhaustible nature of this many-sided process, which shows the importance and expediency of continuation of the work in this field with the aim of finding new, still unknown possibilities for varying this process and discovering new aspects of its practical use. Concluding the review, I would like to list some fundamental notions formulated in the theoretical work ofG. V. Kurdyumov andA. L. Roitburd “On the nature of martensite transformations” [92], that reflect the large role of the martensite problem in the general theory of phase transformations: “The martensite problem is a cornerstone of the general problem of the structure and properties of crystalline bodies… The formation of substructure in martensite tranformation is a result of relaxation of stresses and a decrease in the elastic energy. This occurs with “pumping” of the elastic energy into the energy of interphase boundaries… There are grounds to assume that isothermal transformation occurs with formation of a more relaxed phase… This is proved indirectly by calorimetric measurements of the stored energy, which turns out to be substantially lower in an isothermal transformation than in an adiathermal one [157]… The main features of martensite kinetics consist in manifestation of the transformation proper rather than reflection of the specific features of the prepared centers of heterogeneous nucleation,”… they are “connected with inherent features of the transformation and, are not brought from outside together with the prepared center.”… “The significance of lattice defects in martensite transformations is similar to the role of impurities in crystallization of liquids. They affect the kinetic parameters substantially but do not change the general laws. In conclusion it should be stressed that many characteristics of martensite transformations are typical of all phase transformations. This is one of the causes of the long-term and fundamental nature of the problem.” Translated from Metallovedenie, i Termicheskaya Obrabotka Metallov, No. 8, pp. 4–22, August, 1999. Ol'ga Pavlovna Maksimova (born 1915) is a candidate of engineering and a senior research worker. From 1946 to 1990 she worked at the Institute of Metal Science and the Physics of Metals of the Bardin TsNIIChERMET, investigating martensite transformation under the guidance of Academician G. V. Kurdyumov. She has published 91 scientific works, some which have been translated in leading foreign journals.     

On the choice of “Geometric” thermodynamic models

A number of “geometric” models have been proposed for estimating the thermodynamic properties of a ternary solution from optimized data for its binary subsystems. Among the most common of these are the Kohler, Muggianu, Kohler/Toop, and Muggianu/Toop models. The latter two are “asymmetric” models in that one component is singled out and treated differently, whereas the first two models are “symmetric.” It is shown that the use of a symmetric model when an asymmetric model is more appropriate can often give rise to large errors. Equations are proposed for extending the symmetric/asymmetric dichotomy into N-component systems (N=3), while still permitting the flexibility to choose either a symmetric or an asymmetric model for any ternary subsystem. An improved general functional form for “ternary terms” in the excess Gibbs energy expression is also proposed. These terms are related to the effect of a third component upon the binary pair interaction energies. All the above considerations also apply when short-range ordering is taken into account by using the modified quasichemical model. Finally, some arguments in favor of the Kohler model over the Muggianu model are presented.     

Mechanisms of plastic deformation in microcrystalline and nanocrystalline TiNi-based alloys

Mechanisms of plastic deformation of a high-temperature B2 phase that act upon tension, compression, and high-pressure torsion in TiNi-based single crystals have been studied depending on the crystal orientation. For the crystals with orientations located near the [$ \bar 1 $ \bar 1 11] and [$ \bar 1 $ \bar 1 12] poles in the standard stereographic triangle, multiple dislocation slip prevails upon both compression and tension. In “hard” crystals with the deformation axis close to the [001] direction, in which the Schmid factors for dislocation slip are close to zero, the main deformation mechanisms are the mechanical twinning in the B2 phase and the stress-assisted B2 → B19′ martensitic transformation. All the above listed mechanisms take part in the formation of the {111}〈hkl〉 texture. The mechanism of the change in the orientation of “hard” polycrystalline grains upon the formation of a nanocrystalline and amorphous-crystalline state has been demonstrated on the example of the evolution of the structure of [001] crystals upon severe plastic deformation in a Bridgman cell.     

Effect of temperature on the inhibition of the acid corrosion of steel by benzimidazole derivatives

The effect of 2-mercaptobenzimidazole (inh. I) and 2-mercapto-5-methylbenzimidazole (inh. II) on the corrosion of mild steel in 1M solutions of sulphuric acid has been investigated in relation to the concentration of the inhibitor as well as temperature by various monitoring corrosion techniques. The results obtained revealed that these compounds are good inhibitors. All the impedance diagrams gave semicircles for both inhibitors indicating that the corrosion of mild steel is controlled by a charge transfer process and the presence of either inhibitor does not alter the mechanism of the dissolution of mild steel. In general, both inhibitors efficiencies increased with increasing the inhibitors concentration at all temperatures used. On the other hand, inhibitors efficiencies were almost constant with increasing the temperature at concentrations 5 × 10⁻⁴ M, 1 × 10⁻³ M and 5 × 10⁻³ M. The best performance was noticed in case of (inh. II) especially at the concentration 5 × 10⁻³ M. Adsorption of both inhibitors was found to follow Langmuir, Flory-Huggins isotherms and kinetic-thermodynamic model. The binding constants “K” were calculated for both inhibitors. On increasing the temperature, the value of “K” increased in both cases indicative of stronger binding of the inhibitor molecule to the mild steel surface and hence higher inhibition efficiency at higher temperatures. The activation energy of the corrosion reaction decreases with increasing the concentration of (inh. I) or (inh. II). The adsorption of both inhibitors on the surface of mild steel is probably chemisorbed on the electrode surface. The thermodynamic parameters were calculated. Mass loss measurements revealed that both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance. DC polarization data reveals that, both inhibitors does not alter the mechanism of anodic behaviour of mild steel and they behave as mixed type inhibitors. Again both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance.     

Fullerenes and spheroidization of graphite in iron alloys

Conclusions The mechanism of layer-by-layer crystallization of globular graphite with the formation of fullerenes suggested by some researchers (and correct in principle) should be supplemented by taking into account the following thermodynamic aspect. A buckeyball like C₆₀ cannot become itself an endogenic center of graphitization, because its diameter of less than 1 nm should be compressed by a very high Laplace pressure due to the effect of the interphase surface tension: then the chemical potential of the carbon will exceed that of cementite and cause “carbonization” instead of “graphitization”. It is more likely that “fullerene” curved layers are deposited on quite coarse tensoactive nonmetallic inclusions (endogenic and exogenic) rather than on the C₆₀ buckeyballs. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 3–6, July, 2000. A. A. Zhukov and P. Ramachandra Rao (Director of the National Metallurgical Laboratory, India) have been awarded a Banergi silver medal in 1995 for their work in the field of fullerenes and graphite spheroidization.     

Soda-fuel metallurgy: Metal ions for carbon neutral CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O reduction

The role of minerals in biomass formation is understood only to a limited extent. When the term “photosynthesis—CO₂ and H₂O reduction of sugars, using solar energy”—is used, one normally thinks of chlorophyll as a compound containing magnesium. Alkali and alkaline earth metals present in leaf cells in the form of ions are equally essential in this solar energy bioconversion coupled with nitrogen fixation. Application of some of these principles can lead to artificial carbon-neutral processes on an industrial scale close to the concentrated CO₂ emission sources.     

Surface tension of solids. Structure-mechanical approach

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. The text was submitted by authors in English.     

Investigation of the structure of compacts and sheets of an Al-Cu-Li alloy strengthened by Al<Subscript>2</Subscript>CuLi (T<Subscript>1</Subscript>) particles

X-ray diffraction and electron microscopy have been used to investigate structural states of the material of compacts and sheets of an aluminum-copper-lithium alloy with a lithium content corresponding to the field of equilibrium of a solid solution with the phase T ₁ (Al₂CuLi). In pressed strips, there arises a multicomponent texture (Bs “110”〈112〉, Cu “211”〈111〉, S “123”〈hkl〉) typical of pressed articles of aluminum-lithium alloys. Their microstructure was characterized by the presence of slip bands oriented in the rolling direction. The formation of lamellar precipitates of the T ₁ phase at slip-band boundaries in the process of deformation is supposedly stimulated by Shockley partial dislocations. In hot-rolled sheets, there arose an unusually intense nearly single-component texture of the Ex ₁ “011”〈111〉 type, whose appearance is mainly caused by the cross rolling of the sheets. The reduced strength characteristics of the sheets examined are connected with a sharply oriented character of the structure of both the matrix phase and the strengthening T ₁ phase. A quasicrystalline phase T ₂ present in the material and the precipitates of the δ′ phase exert no marked effect on the level of mechanical properties.     

On some special features of the structure and properties of metallic “thin” films

Conclusions  

Effect of “melt-crystal” interphase surface energy in iron on its structure in castings

Problems of the influence of “melt-graphite” interphase energy in iron on formation of graphite inclusions of different shapes are considered. The effect of the content of elements surface-active with respect to graphite in the melt on the shape of graphite inclusions is considered. The direction of their action on the variation of the “melt-graphite” interphase energy, which is the main factor of shaping of graphite inclusions in cast iron, is shown and the intensity of this action is evaluated. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 13–15, August, 2007.     

Role of promoting oxide morphology dictating the activity of Au/SiO2 catalyst in CO oxidation

The interfacial interaction of gold nanoparticles deposited on either model SiO₂/Si(100) or high surface area amorphous or mesoporous silica with minute amounts of promoter oxide like “active” FeO_x, TiO₂ and CeO₂ has been discussed. The role of the active oxide, its contribution to the perimeter along the gold nanoparticles has been interpreted. The oxide may invoke electronic interaction and simultaneously the defect structure of oxides likely has a key issue in the formation and stabilization of very small Au particles. The activity of the Au/oxide perimeter depends not only on the size of the Au particles, but also on the size and morphology of the oxide component (likely amorphous structure) regardless of whether it is supporting Au nanoparticles or decorating them. The activity in CO oxidation over Au catalysts is strongly affected by the length of the Au/“active” oxide perimeter which is regarded as the “active interface”. The longer length of the perimeter is evidenced by the enhanced CO oxidation activity.     

Models of the surface of aluminum mirrors bombarded by ions from a deuterium plasma

Changes in the optical properties of samples of aluminum-alloy mirrors caused by ion bombardment with ions from a deuterium plasma, which imitates conditions that can exist upon the operation of the first mirrors for diagnostics of plasma in an ITER, have been investigated. The basic methods of studying the mirror surfaces were ellipsometry and reflectometry; as an additional procedure, Auger electron spectroscopy was used. It has been found that the coefficient of reflection of mirrors decreases as a result of irradiation by ions with an energy of ∼1 keV, but it can be restored by the subsequent irradiation by ions with a lower energy (∼60 eV). The complex of experimental studies that were performed was used as a base for the selection of a mathematical model for a correct interpretation of ellipsometric data. The results of multiple-angle and spectral ellipsometry were analyzed in terms of the models of a clean surface and single-layer films. On the basis of the analysis of experimental data and simulation of the effective medium, we proposed a mechanism, which explains the results of the experiment; this mechanism is based on (1) the chemical processes in the surface layer in the first cycle of “degradation-restoration” and (2) the development of roughness as a result of a sequence of procedures of “degradation-restoration.”     

Physicochemical study of the nanodiamond surface

Suspensions of five types of ultrafine diamond of a detonation synthesis in distilled water and 0.9 mol/l NaCl solution were found to have pHs in the range of 3–6, which results from the intrinsic acidity of their surfaces. The possibility of quantitatively determining the protogenic groups of a surface is found using the pH-potentiometric method. The data on the kinetics of the varying pH of suspensions in water and 0.9 mol/l NaCl solution and the data on the curves of the alkali titration of the suspensions of nanodiamond in the indicated systems make it possible to infer the presence of one or two types of acid groups on the surface of a diamond. The constants of dissociation (pK ₁) of these groups on the assumption of their single-base nature are estimated. From 1 × 10⁻³−5 × 10⁻² mol/l chloride solutions of H[AuCl₄] and RhCl₃ on the surface of diamond, gold(III) and rhodium(III) are found to be adsorbed; the adsorption of methylene blue from its 2.5 × 10⁻⁴−5 × 10⁻⁴ mol/l solutions reaches more than 90% (upon adsorption from 5 ml of the initial solution by a 0.05-g nanodiamond).     

General concept of surface structure and elasticity of liquids

The concept of generalization says: of any two related concepts, such as A and B, A is a “generalization” of concept B if every instance of concept B is also an instance of concept A, but not contrary. So, animal is a generalization of bird since a bird is an animal, and there are many other animals. In this view (and to start) consider a more complicated example: any car has a minimal set of vitally necessary attributes: 1—energy supply (storage), 2—engine, 3—framework, 4—transmission, 5—propulsive device (wheels, tracks ...), 6—command center (a person or computer). Actually, this obvious set has a universal character and may be generalized for all self-moving devices with some proper variations in point (5), e.g. an airplane’s propeller, submarine’s screw and so on. Amazingly, this set of vital attributes is also suitable for many living creatures, at least for mammals, birds, fish and possibly for some others. For instance, it would be essentially the same for humans, cats, dogs, squirrels ... and so on, if: 123—stomach, 23—heart, 3—spine, 4—nerves and muscles, 5—paws, 6—brain.     

On the Self-Affine Fractal Geometry of Plasma-Sprayed Surfaces

Surface roughness strongly controls essential properties of thermally sprayed wear- and corrosion-resistant coatings including their mechanical adhesion to the substrate, tribological performance, efficient retention of lubricating materials, and also the presence of sufficient carrying surface able to support the wear couple along the line of contact expressed by the Abbott-Firestone curve. The determination of the surface fractal geometry may yield useful information on the topography of plasma-sprayed coatings beyond that provided by a single roughness parameter such as R _a or R _z. The fractal geometry of atmospheric plasma-sprayed chromium oxide coatings, deposited according to two different statistical experimental design protocols, was assessed through determination of the Hurst exponent H of fractal Brownian motion (fBM), as well as the area-scaled fractal complexity (ASFC) obtained by triangular tessellation (“patchwork” method). Attempts were made to correlate fractality with coating adhesion strength.     

Surface tension,density, and molar volume of liquid Sb-Sn alloys: Experiment versus modeling

Through the application of the maximum bubble pressure and dilatometric method, density and surface tension were investigated. The experiments were conducted in the temperature range from 583 K≤T≤1257 K. The surface tension was measured for pure antimony and for six liquid Sb-Sn alloys (mole fractions X _Sn=0.2, 0.4, 0.6, 0.8, 0.9, and 0.935 mm²) and measurements of the density were only for alloys. It has been observed that both surface tension and density show linear dependence on temperature. The temperature-concentration relation of both surface tension and density were determined with minimization procedures. The surface tension isotherms calculated at 873 K and 1273 K show slight negative deviations from linearity changes, but the observed maximal differences did not exceed 30 mN · m⁻¹. The surface tension calculated from Butler’s model was higher than the experimental value for most concentrations and also showed curvilinear temperature dependence. The experimental densities and the molar volumes of the Sb-Sn liquid alloys conform very closely to ideal behavior with differences comparable to the experimental errors.     

Surface tension, density, and molar volume of liquid Sb-Sn alloys: Experiment versus modeling

Through the application of the maximum bubble pressure and dilatometric method, density and surface tension were investigated. The experiments were conducted in the temperature range from 583 K≤T≤1257 K. The surface tension was measured for pure antimony and for six liquid Sb-Sn alloys (mole fractions X _Sn=0.2, 0.4, 0.6, 0.8, 0.9, and 0.935 mm²) and measurements of the density were only for alloys. It has been observed that both surface tension and density show linear dependence on temperature. The temperature-concentration relation of both surface tension and density were determined with minimization procedures. The surface tension isotherms calculated at 873 K and 1273 K show slight negative deviations from linearity changes, but the observed maximal differences did not exceed 30 mN · m⁻¹. The surface tension calculated from Butler’s model was higher than the experimental value for most concentrations and also showed curvilinear temperature dependence. The experimental densities and the molar volumes of the Sb-Sn liquid alloys conform very closely to ideal behavior with differences comparable to the experimental errors.