Effect of sputtering on the samples of ITER-grade tungsten preliminarily irradiated by tungsten ions: Optical investigations

The simultaneous effect of sputtering and neutron irradiation on the optical properties of tungsten mirrors has been considered, which was simulated by bombardment by 20-MeV W⁺⁶ ions. The action of charge-exchange atoms was imitated using Ar⁺ ions with an energy of 600 eV. The dependence of the structure of the surface and optical properties of tungsten on the fluence of Ar ions has been studied using optical microscopy, interferometry, reflectometry, and ellipsometry. It has been shown that irradiation with neutrons should introduce a significant additional contribution to the processes at the tungsten surface that occur under the effect of charge-exchange atoms. An analysis of experimental data obtained by using reflectometry and ellipsometry made it possible to suggest a realistic model of the process of surface modification for samples of ITER-grade tungsten (that were preliminarily irradiated by tungsten ions) using prolonged sputtering by Ar⁺ ions.     

Surface free energy and surface stress as elastic components of the surface tension of condensed matter

The “surface free energy” and “surface stress” are basic notions in the current theory of the surface tension of solids; they were used online together or separately thousands times, but never “as elastic components of surface tension”. Most of experts highlight that these different notions cannot be mixed or confused since the first one is of the “plastic” and second is of “elastic” nature. Below these opinions are shown to be incorrect. Sufficient evidences, both theoretical and experimental, demonstrate the elastic nature of both the “surface energy” and “surface stress”. In this way, we considered the most convincible models of the metal surface based on the Coulomb interaction and purely elastic surface deformation. The reminiscent of the cantilever-beam-technique data and electrocapillary curves of mercury in combination with the specific adsorption data has logically led to the formulation of the “optimum surface electron density” notion (for the first time in the field of surface tension).     

Heat transfer at the condensation of a gas-vapor mixture in an electric field

The problems associated with the investigation of heat transfer processes at the condensation of vapor from a vapor-air mixture in the presence of an electric field have been considered. It is established that even very small additions of air impair vapor condensation and, hence, the heat transfer. It is shown that the application of an electric field to a vapor-air mixture can be an effective factor for eliminating the negative effects of the presence of air on the condensation process. It has been found out that a corona discharge specially created by means of notches on the surface of the inner electrode of a cylindrical system and its effects are the main reason for this. The experimental characteristics of the relative heat transfer coefficient at condensation as functions of the air concentration, the rate of the mixture’s delivery into the vapor condenser, and the specific heat flux at different electric field intensities have been obtained. The results are explained by the electric charging of the medium in the corona charge field, by the electric wind, and by the charging of the “vapor-liquid” interface. There has been derived a formula according to which the process of condensation is strongly influenced by the molecule effective diameter (ψ∼d _*⁶) increasing in the electric field due to the solvation of ions by water molecules resulting in a new mechanism for the intensification of the condensation process in an electric field.     

In-flight oxidation of aluminum in the twin-wire electric arc process

This paper examines the in-flight oxidation of aluminum sprayed in air using the twin-wire electric arc (TWEA) thermal spray process. Aerodynamic shear at the droplet surface increases the amount of in-flight oxidation by promoting entrainment of the surface oxides within the molten droplet and continually exposing fresh fluid available for oxidation. Mathematical predictions herein confirm experimental measurements that reveal an elevated, nearly constant surface temperature (∼2273 K) of the droplets during flight. The calculated oxide volume fraction of a “typical” droplet with internal circulation compares favorably to the experimentally determined oxide content (3.3–12.7%) for a typical TWEA-sprayed aluminum coating sprayed onto a room temperature substrate. It is concluded that internal circulation within the molten aluminum droplet is a significant source of oxidation. This effect produces an oxide content nearly two orders of magnitude larger than that of a droplet without continual oxidation.     

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

Conclusions  

Anodic treatment of strengthening coatings in electrolytes for electrochemical machining: II. Micromachining of steel surfaces nitrated by electrochemical thermal treatment: Chloride solutions

The anodic dissolution of the nitrated layer of steel 45 specimens at small depths after the chemical thermal treatment is studied. Investigations of the anode dissolution in 2 M NaCl were carried out using a rotating disk electrode with a partially isolated surface. The correlation between the macrokinetics of the anode processes and the technological parameters such as the roughness and microhardness of the nitrided steel surface is registered. The values of the minimal surface roughness and the maximal microhardness are shown to be almost equal to those of the initial surface prior to the treatment and be reached under high current densities (∼50 A/cm²) and intense hydrodynamic modes of treatment, i.e., in a state of thermokinetic instability (upon the constant formation and destruction of surface layers induced by the critical temperature drop and a “thermal explosion”), which arises upon an excess of the anodic limiting current.     

Reactions of small molecules on gold single crystal surfaces

Supported heterogeneous gold catalysts (also called “real” catalysts) have been far more studied than gold single crystal surfaces. However, the surface science approach — fundamental studies of chemistry on well defined gold surfaces under controlled conditions — is extremely important, as it contributes to the understanding of the reaction mechanisms and of the nature of active centers, which allows a better knowledge of the “real” systems. This paper presents a brief overview concerning the work carried out on gold single crystal surfaces from 2004 until recently. Results on the reactions of several molecules on gold surfaces, experimental and computational (DFT) are discussed.     

Effect of irradiation by heavy ions on the nanostructure of perspective materials for nuclear power plants

An imitation experimental technique on the irradiation with heavy ions of structural materials of nuclear power plants using tomographic atom probe analysis has been elaborated. The scheme of irradiation of specimens for atom probe analysis has been realized on a MEVVA ion source of an TIPr accelerator (ITEP) with ion energy 75 keV per charge. Test experiments with irradiation and analysis of samples of the EK-181 steel by aluminum ions to a fluence of ∼2 × 10¹⁵ ion/cm² have been performed. Experiments on the Fe-ion irradiation of the samples of ODS EUROFER perspective steel for fission and fusion reactors to different damaging doses have been carried out. The analysis of distribution of different chemical elements in the volumes tested has revealed that under ion irradiation a change in the composition of nanosized clusters, which are present in the initial material takes place. Comparison of the data obtained with the results of reactor irradiation of the ODS EUROFER steel has been carried out. These data testify a correspondence between nanoscale changes in the steels oxide dispersion strengthened in imitation experiments and under the conditions of reactor irradiation.     

Kinetics of codeposition of copper with N-methylpyrrolidone in sulfate water-dimethylsulfoxide electrolytes

The electrolyte composition is found to affect the composition and density of the adsorption layer on the electrode. The lowest process rate is observed in the water structure stabilization range under conditions of the preferential adsorption of the additive and organic solvent molecules. The electroreduction of copper(II) ions involves the stage of their penetration through the adsorption film, while the dissociation of electroactive species, which precedes their discharge, has the “forced” nature. The increase in the adsorption activity of sulfate ions (which is due to the “salting-out” effect of the mixed solvent and the selective solvation) is accompanied by the acceleration of the process (the ψ effect or the formation of surface associated products, in which anions play the role of bridge ligands). Original Russian Text ? V.V. Kuznetsov, L.M. Skibina, E.F. Kuznetsova, I.N. Loskutnikova, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 6, pp. 632–639.     

Achieving Carbon Neutrality in the Global Aluminum Industry

In the 21st century, sustainability is widely regarded as the new corporate culture, and leading manufacturing companies (Toyota, GE, and Alcoa) and service companies (Google and Federal Express) are striving towards carbon neutrality. The current carbon footprint of the global aluminum industry is estimated at 500 million metric tonnes carbon dioxide equivalent (CO_2eq), representing about 1.7% of global emissions from all sources. For the global aluminum industry, carbon neutrality is defined as a state where the total “in-use” CO_2eq saved from all products in current use, including incremental process efficiency improvements, recycling, and urban mining activities, equals the CO_2eq expended to produce the global output of aluminum. This paper outlines an integrated and quantifiable plan for achieving “carbon neutrality” in the global aluminum industry by advocating five actionable steps: (1) increase use of “green” electrical energy grid by 8%, (2) reduce process energy needs by 16%, (3) deploy 35% of products in “in-use” energy saving applications, (4) divert 6.1 million metric tonnes/year from landfills, and (5) mine 4.5 million metric tonnes/year from aluminum-rich “urban mines.” Since it takes 20 times more energy to make aluminum from bauxite ore than to recycle it from scrap, the global aluminum industry could set a reasonable, self-imposed energy/carbon neutrality goal to incrementally increase the supply of recycled aluminum by at least 1.05 metric tonnes for every tonne of incremental production via primary aluminum smelter capacity. Furthermore, the aluminum industry can and should take a global leadership position by actively developing internationally accepted and approved carbon footprint credit protocols.     

Modeling of plasma spraying of two powders

The behavior of metal and ceramic powders co-sprayed through a plasma jet was simulated using a commercial fluid dynamics model in which the particles are considered as discrete Langrangian entities. Computations were carried out for the plasma jet and the injected particles using (a) a steady-state three-dimensional (3-D) jet and (b) a simplified two-dimensional (2-D) model. An analytical method was used to estimate the appropriate injection velocities for the metal and ceramic particles, injected through opposing nozzles perpendicular to the plasma flow, so that their “mean” trajectories would impinge on the same area on the target surface. Comparison of the model projections with experimental measurements showed that this method of computation can be used to predict and control the behavior of particles of widely different properties.     

Laser sintering of ultradispersed iron-base powder materials

Experimental data on the formation of the structure and mechanical properties of layers produced from ultradispersed Fe-base powder mixtures under laser irradiation (λ ∼ 1 μm) with a radiation density q ∼ 10³ W/cm² and pulse duration 10⁻⁵ s are reported. The results of the study provide a background for the development of a method of producing complex metal alloys in a metastable condition with the help of high-concentration energy sources. The field of application of this method is the production of thin layers on the surface of highly loaded friction units.     

Influence of Plasma Intensity on Wear and Erosion Resistance of Conventional and Nanometric WC-Co Coatings Deposited by APS

The effects of plasma intensity and powder particle size on wear and erosion resistance have been evaluated for WC-12 wt.%Co coatings deposited by Air Plasma Spraying. Coatings were deposited from micrometric and nanostructured powders. SEM and XRD characterization showed the presence of WC, W₂C, W, and an amorphous Co-rich matrix. The performance of the different coatings was compared in sliding wear tests (ball-on-disk), under dry friction conditions. Wear debris and tracks were analyzed by SEM. The debris generated during the test was found to have a great influence on the sliding properties. Wear follows a “three-body abrasive mechanism” and is dominated by coating spallation because of sub-surface cracking. In order to evaluate erosion behavior, solid particle erosion tests were conducted. Eroded coatings were analyzed by SEM, and erosion mainly occurs by a “cracking and chipping mechanism.” The study shows that wear and erosion behavior is strongly affected by plasma arc intensity.     

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.     

Microstructure and abrasion resistance of plasma sprayed titania coatings

Agglomerated titania nanopowder and a “classical” titania were sprayed by the high throughput water-stabilized plasma (WSP) and thoroughly compared. Optical microscopy with image analysis as well as mercury intrusion porosimetry were used for quantification of porosity. Results indicate that the “nano” coatings in general exhibit finer pores than coatings of the “conventional” micron-sized powders. Mechanical properties such as Vickers microhardness and slurry abrasion response were measured and linked to the structural investigation. Impact of the variation in the slurry composition on wear resistance of tested coatings and on character of the wear damage is discussed. The overall results, however, suggest that the “nano” coatings properties are better only for carefully selected sets of spraying parameters, which seem to have a very important impact. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

Two Approaches to the Problem of A. Griffith on the Strength of Solids

Two approaches to the development of physical models of fracture of solid bodies with cracks are compared, i.e., an energy approach based on the model of A. Griffith and a force approach considering breakage of atomic bonds at the tip of ideally sharp crack. It is shown that it is expedient to amend the contribution of the process of breakage of interatomic bonds into the spent energy by introducing a factor equal to 3 into the classical Griffith formula. An original “force” model of fracture of solid bodies due to ideally sharp cracks of natural origin with allowance for the factor of “rigidity” of interatomic bonds at the tip of the crack is suggested. Results of theoretical computations by both models are compared with experimental data presented in the literature. Explanation of the effect of nanosize cracks on the strength of carbon steels and on the strength of cracked glass tubes and bulbs in Griffith's experiments is suggested as an example. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 11 – 17, August, 2005.     

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.     

Electrohydrodynamics of liquids and gases: Similarities and distinctions

The overview and correlation of electrohydrodynamic flows in liquids and gases based on the published experimental data and computer models are presented. An original interpretation of the ions “freezing” in the medium effect is given; estimates of some freezing-in characteristics are presented. A new dimensionless parameter permitting one to evaluate the importance of the freezing-in effect under particular conditions is suggested.     

Nonlinear waves in magnetic films and layered structures: Propagation and interaction

This review presents the results of investigations into the conditions of the emergence, characteristic features of the internal structure, and propagation of soliton states of magnetization in a composite ferromagnet-insulator-metal structure in the magnetostatic approximation. Structure of nonlinear states with a fine internal structure (two-parameter breathers and their periodic generalizations) are analyzed. The possibility of the formation of coupled states—“compound solitons” consisting of a kink-antikink pairs—is shown. The problems of the interaction of two magnetostatic waves simultaneously propagating in a film in a nonlinear regime, as well as of the interaction of “bright” and “dark” solitons with an external monochromatic radiation, are discussed. Results of a numerical simulation and some experimental investigations are given.     

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.