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Silicon (Si) particle with small size used as anode material has been recognized for its ability to reduce the damage caused by volume expansion in liquid lithium-ion batteries. However, whether the same mechanism still exists for different particle sizes of Si in all-solid-state batteries (ASSBs), these have not been systematically investigated. In this work, Si particles with various sizes ranging from 30 to 1000 nm are investigated as regards the effect of Si particle size. It is revealed that the performance of Si particles in ASSBs is influenced by a combination of factors, including uniformity of the Si oxide layer, tap density, and expansion degree, which are all related to size of the Si particles. In order to investigate the effect of different particle sizes of Si, micron, sub-micron, and nano-silicon are set up in this work for electrochemical performance testing of all-solid-state batteries. Among all, sub-micron Si exhibits smaller impedance increase due to its tight contact and fewer voids and cracks after cycle. Such a structure demonstrates excellent conductive network and achieve the high initial Coulombic efficiency (ICE) of Si (78.37%) by exploiting the passivation effect of sulfides (Li6SP5Cl) solid electrolyte (SE) on the Si anode and the high voltage stability of halide SE (Li3InCl6). This work has certain reference significance for improving the conductivity of Si anode in ASSBs. [ABSTRACT FROM AUTHOR]

Abstract—The effect of ion implantation on the surface morphology, structure of oxide layers, and electrochemical properties of nickel titanium TiNi in a 0.9 wt % sodium chloride (NaCl) solution has been studied. It has been established that the modification of the TiNi surface with titanium and niobium ions at an irradiation dose of 1017 ion/cm2 increases the surface roughness and improves the corrosion properties, which manifests itself in the growth of the charge transfer resistance and the drop of the anodic current. The comparative transmission electron microscopy analysis of the structure of the oxide layers and study of their electrochemical properties have shown that the corrosion properties of TiNi are caused by the complex phase composition of the surface. In particular, the niobium ion-beam treatment has resulted in the formation of a thin (~2 nm) continuous amorphous oxide film with a low permittivity (ε = 44) on the TiNi surface. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) consisting of five or more components in an equimolar ratio are attracting increasing attention due to a unique combination of various properties. Doping HEAs with small amounts of certain elements (most often rare earth, trace or noble metals) is a promising way to improve the characteristics of such alloys and to control their properties. This paper reports the results on the microstructure, phase composition, and microhardness of as-cast AgxAl0.5CoCrCuyFeNi HEAs (x = 0, 0.1; y = 0.5, 1.0). The effect of silver addition on the oxidation behavior of the studied HEAs at 700°C was determined. The morphology, phase and chemical composition of the resulting oxide film were studied. It was shown that the introduction of silver improves the mechanical characteristics of the alloys, but deteriorates the oxidation resistance due to the formation of copper-silver eutectic in the alloy microstructure, leading to a change in the morphology and phase composition of the formed oxide layer. Along with the solid solution of (Al, Cr)2O3 oxides and CuCr2O4, NiCr2O4 spinels, the addition of silver leads to the formation of copper oxide CuO and a small amount of silver oxide Ag2O in the surface film. [ABSTRACT FROM AUTHOR]

The chemical and phase composition of oxide layers on U8, U10, and 45 tool steel samples formed by laser treatment is studied by X-ray photoelectron spectroscopy. In the surface layers of the samples, the depth of the oxide layers (Fe2O3, Fe3O4, FeO) is the same, but their thickness is different. That affects the tribological properties. [ABSTRACT FROM AUTHOR]

In this paper, the durability, the wear resistance, the tribological behavior, and the wear particles flow of the Anodic Aluminum Oxide Film 5083 were studied under cyclic loading. Different anodizing durations (reaction times (RT)) and applied currents (J) were tested. Besides, a tribological model with a correlation between the friction coefficient and the wear mechanisms of the oxide layer was established. Postmortem analyses were investigated using scanning electron microscopy (SEM), energy-dispersive x-rays (EDX), and profilometry analyses. Experimental results were shown that the increase in the RT improves the durability of the 5083-aluminum alloy oxide layer. Moreover, when RT increased, the stability of friction coefficient was improved, and the surfaced pores were more filled with micro-sized wear particles, inducing the establishment of a compacted layer. Consequently, the 5083-aluminum alloy oxide layer was shown important tribological characteristics such as the durability and wear resistance after hundreds of rubbing cycles. It was concluded that three stages characterized the friction behavior and the wear particle flow under cycling: firstly, a friction coefficient stable stage with the establishment of an internal flow that feeds the contact (internal source flow); the second stage is the progressive increase in the friction coefficient, while the wear particles were crushed and compacted to form a smooth layer, constituting the continuous internal flow; and the third stage is the return of the stable state of the friction coefficient, where the smooth layers spread, and the pores filled with the powder. [ABSTRACT FROM AUTHOR]

The stable oxide layers formed by chemical or electron-beam treatments of TiNi shape memory alloys are able to provide a good corrosion resistance and prevent release of toxic Ni. The mechanisms responsible for corrosion behavior of Ti-bearing alloys are currently not completely clear. In this work, the structure and electrochemical properties of surface oxides on TiNi alloy and Ti-Ni-Ta-Si surface alloy were examined. The glassy structure of the surface alloy was produced by a liquid phase mixing of Ti60Ta30Si10 (at.%) film with a TiNi substrate using a low-energy high-current electron beam. The reference electropolished TiNi alloy and the Ti-Ni-Ta-Si surface alloy exhibit thin (2-4 nm) glassy-crystalline oxide layers varying by chemistry and phase composition as confirmed using high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy. It is shown that during anodic polarization in 0.9% NaCl and Lock-Ringer solutions, the oxide layer on the Ti-Ni-Ta-Si surface alloy possesses an enhanced passivation ability compared to the reference sample. We have revealed that the absence of oxidation species Ni2+ and the lower nickel concentration in the subsurface layer are closely related with corrosion resistance. A scheme describing the formation of corrosion products via transport of nickel ions through the free volumes (interstitial spaces, interfaces between clusters/particles) inside the oxide layer was proposed. [ABSTRACT FROM AUTHOR]

The effect of the electrolyte composition for hard anodizing of aluminum on the corrosion resistance of the synthesized anodic coatings was studied. The hard anodizing was carried out at temperatures of –4–0°C for 60 min at a current density of 5 A/ dm2. The basic electrolyte was a 20% aqueous solution of H2SO4. Hydrogen peroxide (H2O2) was added to the electrolyte in concentrations of 30; 50; 70 and 100 g/L to determine strong oxidants influence on the characteristics of the anode layers. The concentration of 70 g/L H2O2 in the electrolyte, which ensures the synthesis of the thickest and least porous coating, was optimal. At the initial moment of immersion of anodic coatings synthesized in hydrogen peroxide electrolyte, their corrosion resistance decreases. When peroxide electrolyte concentration increases from 30 to 100 g/L, corrosion currents increase by 30 and 90%, respectively. However, with increasing exposure of coatings in the environment, their corrosion current density decreases more intensively with a decrease in their porosity. After 14 days, no dependence of the coatings corrosion durability on the composition of the electrolyte observed, what indicated a complete closure of the pores. [ABSTRACT FROM AUTHOR]

The present study is an endeavor to understand the wear and friction behavior of EN8 steel and Inconel X-750 alloy tribo-pair under dry and lubricated conditions. Initial experiments were performed under dry conditions at different loads (50–200 N) and sliding speeds (0.14–0.47 m/s). To investigate the effect of lubricants, the experiments were performed under two lubricants (SEA20W40 and SAE20W40 + MoS2) at the same range of loads and speeds. Ex-situ analysis of worn-out surfaces of both disc and pin was performed through scanning electron microscope (SEM). Chemical composition of worn-out surfaces of disc and pin was evaluated through energy disperse x-ray spectroscopy (EDS). Under dry conditions, formation of oxide layer was noticed. The significant improvement in wear and friction was observed under lubricated conditions as compared to dry conditions. Also, by mixing micron-size MoS2 particles to the normal lubricant SAE20W40, significant improvement in wear and friction was perceived due to the formation of boundary layer film. [ABSTRACT FROM AUTHOR]

The processes of oxidation of metal fittings in reinforced concrete structures after a long-term operation are studied using the methods of mathematical modeling. In the calculations, the B25 (M350) concrete, from which monolithic foundations, floor slabs, columns, beams, monolithic walls and other responsible structures are manufactured was used. The corrosion process is a result of oxygen reduction with the formation of an oxide layer, which leads to a gradual fracture of concrete, that is taken into account by a scalar damage model. The influence of the oxide layer thickness on the pressure, normal and tangential stresses at the reinforcement–concrete boundary is determined. The conditions, under which the critical corrosion fracture of the concrete structure has not been reached, are determined. The structure damage decreases with an increase in the diameter of the reinforcement, a decrease in the thickness of the oxide layer as well as the total oxygen content in the concrete structure. [ABSTRACT FROM AUTHOR]

Ozone has attracted more scholars' attention due to its less environmental injury during oxidation. Oxidation with ozone has been more regarded because ozone evaluates oxygen and can form a terrific oxide layer even at lower temperatures compared to oxygen. This work investigated the Al(100) surface oxidation simulations by O2 and O3 molecules at 400, 600, and 800 K temperatures with the reactive force field (ReaxFF) method. In separate simulation boxes, one hundred ozone molecules and 150 oxygen molecules have been placed in a space above the Al(100) surfaces to examine this metal's behavior with them (gases incipient density of 0.47 g/cm3). We found further growth of the oxide layer in the case of ozone-aluminum. Subsequently, we surveyed the correlation between temperatures and the development of alumina layers in the case of oxygen and ozone in separate sets through ReaxFF simulation to untangle the mechanism of oxidation kinetics of the Al(100) surface by ozone. Even though there are demonstrated constraints on growing an oxide layer with ozone and oxygen, it is possible to produce a thicker oxide layer at lower temperatures using ozone. Here, we used LAMMPS as our program package for all simulations and used reactive molecular dynamics simulation, which is a relatively inexpensive tool for studying complex conditions that are impossible to reproduce with other techniques. [ABSTRACT FROM AUTHOR]

Abstract—The state of the surface of a nickel electrode in weakly alkaline medium is studied with the electrochemical impedance-frequency spectroscopy method. An equivalent electrical circuit of the processes that proceed under these conditions is proposed, which describes these processes and the ratings of the elements of the electrical circuit. [ABSTRACT FROM AUTHOR]

Besides process parameters, powder properties such as grain size, morphology, and chemical composition have the highest impact on the material properties of parts produced by powder-based additive manufacturing. These properties are strongly influenced by the production process of the powder and its feedstock. In the scope of this work, the influence of three different powder producers of Ti6Al4V, on density, chemical composition, and mechanical properties of build samples, is investigated. Furthermore, the effects of the varying atomization process on morphology, particle size distribution, chemical composition, and oxide layers are studied. Particle size distribution and flowability seem to have a minor influence on the production process while density depends highly on the surface topology, sphericity, and nature of the oxide layer, which affect energy intake. Tensile properties are highly influenced by chemical composition, mainly dissolved oxygen, and polluting satellites, while notched bar impact strength is additionally influenced by the oxide layer and suspected TiO2 precipitations caused by it. [ABSTRACT FROM AUTHOR]

The amount of aluminium sheets in future body-in-white concepts is still on the rise. There is a need for optimizing the joining techniques, caused by the different characteristics compared to the established steel components. Especially the electrode life for resistance spot welding as a reliable and established process needs to be improved. One reason for the short electrode life when welding aluminium is the insulating effect of the aluminium oxide layer. One possibility to reduce the electrode wear is the mechanical destruction of the oxide layer before the welding. This paper describes the influence of a translational and rotational electrode movement on the electrode wear. The oxide layer destruction is detected by resistance measurement. It could be shown that the destruction of the oxide layer already occurs at low movements. However, a homogeneous, large-area destruction is necessary for a wear reduction. [ABSTRACT FROM AUTHOR]

The regularities of formation of coatings with the particles of β-tricalcium phosphate (β-TCP) by micro-arc oxidation method on the metal substrates of Ti, Ti-40Nb, and Mg0.8Ca alloys were studied. The effect of the electrophysical properties of the transitional oxide layer on the structural-morphological and adhesive properties of the coatings was established. The small values of the band gap and the high dielectric constants of TiO2 and Nb2O5 oxides contributed to the transmission of cascades of micro-arc discharges with a low intensity. In this case, MgO oxide with a low dielectric constant accumulated a large amount of electrical energy, which was released in the form of powerful discharges. Coatings on the Mg0.8Ca alloy were characterized by high thickness and roughness, contained the largest amount of the crystalline phase, and had good adhesive properties. The maximum critical load value of 17 N was noted for the coating on the Mg0.8Ca alloy, and the minimum value of 7 N was observed for the coating on the Ti-40Nb alloy. [ABSTRACT FROM AUTHOR]

We studied the microstructure of the transfer layer and its effect on the wear mechanism and wear properties of an aged Cu-15Ni-8Sn alloy against 100Cr6 bearing steel during dry sliding by changing the applied load. The results indicate that the aged Cu-15Ni-8Sn alloy shows different wear behaviour and wear properties when the applied load changes; specifically, the average friction coefficient and specific wear rate decrease quickly with increasing applied load under steady wear conditions. The sample tested under a relatively high applied load showed the best wear performance because the oxide layer in the transfer layer. The main wear mechanisms were found to change with variation in the applied load. Metallic nanocrystalline particles and relatively ductile copper oxides promoted the formation of a thick and dense oxide layer. Changes in the thickness and morphology of the oxide layer under different loads can significantly affect the wear mechanisms. [ABSTRACT FROM AUTHOR]

The influence of particle impact temperature and size on adhesion of soft particle/hard substrate material in cold spray has been scarcely studied. While the relationship between particle impact conditions and particle/substrate bonding is commonly established through FEM studies, they typically lack comparison to experimental data. In the current study, characterization was performed by post-mortem observation of removed adhered particles and collected rebounded particles contact surfaces. Observations are correlated to interfacial pressure and temperature using FEM, otherwise impossible to measure in situ. The influence of pressure and its temporal evolution with particle deformation on melting and bonding is evaluated. Evidence of anisotropic particle deformation associated with microstructural orientation and grain geometrical features has been observed. Experimental evidence confirms that the particle south pole experiences restricted deformation as the original powder grain morphology was observed even after impact. Interfacial melt features have been detected and the melt zone generation, propagation, stagnation and regression tracked through FEM have shown important influence on single impact adhesion processes. Observed metallic bonding features and FEM indicate that increasing particle velocity, i.e., decreasing particle size, accelerates particle bonding processes to occur within tens of nanoseconds. Contact compressive pressure and interfacial expansion increase with particle increasing velocity and temperature. [ABSTRACT FROM AUTHOR]

Inconel 600 alloy is widely utilized for high temperature environment application due to the corresponding good oxidation and corrosion resistance properties. In order to estimate the high temperature oxidation resistance of Inconel 600 alloy at various temperatures, the oxidation weight gain of all specimens was measured and fitted for the curve at the temperatures of 700, 800 and 900 °C for exposure time of 100 h. The surface morphology and the component of the oxide film were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results indicate that the high temperature oxidation resistance of Inconel 600 alloy is excellent blew 800 °C due to the oxidation kinetic curves at different temperatures corresponding to the parabola dynamic rules. This means that the oxidation film protects the substrate well. The dense oxide layer formation containing Cr2O3 and NiCr2O4 at 700 and 800 °C and MnCr2O4 at 900 °C, respectively, is the main reason for the good oxidation resistance. In contrast, the oxide layer peels off easily under applied force as the temperature increases beyond 800 °C, on account of the complicated compositions of the oxide film and the binding force between the oxide layer and the substrate weakening. Corresponding oxidation mechanism is expected to be understood and the oxidation resistance of Inconel 600 alloy is improved through binding force enhancement. [ABSTRACT FROM AUTHOR]

It is established that, when growing Si nanowires in a H2 flow that has not been additionally purified from residues of O2 and water vapor, SiO2 layers are formed on the crystal surface and growth substrate. The growth of Si nanowires is inhibited because of the presence of an oxide surface layer, and the crystals are characterized by strong morphological instability. The thermodynamic conditions for the formation of an oxide surface layer and its effect on the growth of Si nanowires are determined. At synthesis temperatures of 750–1400 K, Si nanowires are thermodynamically unstable in the gas phase containing any appreciably low O2 concentrations, and Si should completely transform into an oxide under favorable kinetic conditions. The thermal dissociation and hydrogen reduction of SiO2 under Si-nanowire growth conditions are practically unrealizable. [ABSTRACT FROM AUTHOR]

Investigations of the influence of the optimized process of wet chemical treatment on the optical characteristics of the silicon monocrystalline wafers surface have been carried out. It was found that chemical treatment of a silicon wafer surface with a KOH solution with a concentration of 45% in deionized water at a temperature of 75°C for 4 min leads to etching of the damaged surface layer, thereby reducing the number of surface recombination centers of charge carriers. The use of ozone for cleaning from organic and other contaminants and the replacement of isopropyl alcohol in a solution with KOH replaced by ALKATEX surfactant allows the plates to be textured at higher temperatures in a relatively short time and to reduce material costs. The use of an optimized wet chemical treatment process makes it possible to texture monocrystalline silicon wafers and obtain a pyramid on the surface with a base width from 1 to 4 μm and a height of ~1.5–3 μm, which will make it possible to reduce the reflection coefficient of electromagnetic radiation by more than 3 times in relation to plates with a smooth surface, in the spectral range of 600–800 nm, the reflection coefficient decreased to a value of 8.7%. A decrease in the reflection coefficient from the silicon wafer surface should lead to an increase in the transmittance of the supplying electromagnetic radiation of the silicon wafer, which will increase the number of the solar cell quanta penetrating the photoactive region, as a result of which the magnitude of the short-circuit current and the open-circuit voltage should increase. Investigation of the load current–voltage characteristic of a heterojunction with an intrinsic thin-layer (HIT) solar cell based on a textured monocrystalline silicon wafer showed an efficiency value of 22.92% under standard test conditions. [ABSTRACT FROM AUTHOR]

The procedure of hard anodizing is carried out at a temperature of (– 4)–0°C for 60 min. A 20% aqueous solution of H2SO4 is used as the base electrolyte. In the course of anodizing, the current density is equal to 5 A/dm2. To determine the influence of strong oxidants on the characteristics of anode layers (oxides), different amounts (30, 50, 70, and 100 g/liter) of hydrogen peroxide (H2O2) were added to the electrolyte. In some cases, it was blown off with an ozone-air mixture at a rate of 5 mg∙min/liter of ozone. It was discovered that the oxide layer (Al2O3∙H2O) is formed in the course of hard anodizing on aluminum alloys not only by oxygen ions appearing as a result of decomposition of water but also by neutral oxygen atoms formed as a result of decomposition of hydrogen peroxide and ozone. It is shown that both hydrogen peroxide and the procedure of blowing of the electrolyte with an air-ozone mixture increase the thickness and microhardness of the anodized layer by 50% due to the twofold reduction of the number of water molecules in aluminum oxide. Hydrogen peroxide and ozone clearly also decrease the thickness of the barrier layer of the coating through which oxygen and aluminum ions may penetrate and combine to form the oxide layer. It is demonstrated that the maximum microhardness of the anodized layer can be attained as a result of heat treatment, namely, as a result of heating of the anodized samples to 300°C. [ABSTRACT FROM AUTHOR]

This paper investigated the solid particle erosion behavior of partially oxidized NiCrBSiFe and NiCr coatings by varying temperature and impact angle. The challenge in the current situation is to process a new system of powders containing metallic and oxide phases. Partially oxidized powders containing metallic and oxide phases were processed by flame spraying the alloy powders into distilled water and allowing the oxide layer to form while keeping the core in the middle of the particle. Partially oxidized coatings were developed on MDN321 steel using the plasma spray technique with feedstock of partially oxidized powders. An air jet erosion test was carried out using Al2O3 erodent of grit size 50 µm at room temperature, 200, 400, 600, and 800°C by varying 30, 45, 60, 75, and 90° impact angles. Coatings were characterized concerning bond strength, porosity, micro-hardness, and density. The effect of temperature and impact angle on volumetric erosion loss was studied using SEM, EDS, and XRD analysis. Partially oxidized NiCrBSiFe coating exhibited better erosion resistance compare with partially oxidized NiCr coating. NiCr coating demonstrates maximum volumetric erosion loss at 45° impact angle, whereas NiCrBSiFe at 60° impact angle under all tested temperatures. [ABSTRACT FROM AUTHOR]

The AA6061-T6 alloy is used in many industrial applications such as hydraulic pistons, aerospace and marine vehicle fittings, including the nuclear reactors due to their excellent joining and coating properties, high strength, good formability, high resistance to aquatic corrosion and neutron transparency. This study consists of high temperature oxidation for which the samples were oxidized using thermogravimetric analysis, at a temperature of 580°C in an atmosphere that contains air and argon. Exposure of exposure times at 580°C varied from 15 min to 8 h, which permitted to understand the mechanism of oxide formation mechanisms in this alloy and progressive formation of oxide layers on the surface. The chemistry, thickness and the morphology of the oxide layer formed on the surface was characterized by scanning electron microscopy (SEM-EDS), X-ray diffraction which revealed the existence of the following elements in the oxide layer, such as Al2O3, Al9Si, SiO2, MgO and Mg3O4. Results showed that the oxide layer becomes thicker with the increasing exposure time and is accompanied by a loss of weight compared to the mass formed at the beginning of the thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

This study investigates the cracking behavior of oxide layers formed on molten metals and alloys including pure zinc, Zn–4 wt%Al (ZAMAK3) and Al–(0.5–2) wt%Ca in dynamic oxidation condition by injecting gas bubbles into the molten metal during the pouring process. The crack characteristics of the oxide layers were studied using a field emission scanning electron microscope. The results show that various stresses initiated from turbulence flow in the molten metal promote the deformation of the oxide layer, particularly at the initial stages of oxidation. Different coefficients of thermal expansion of the oxide layers and the metals can also result in deformation/cracking the oxide layers. Simultaneous aspiration of the molten metal and solidification phenomenon within the casting process may lead to various morphological changes, e.g. folded-, wrinkled- and cracked-oxide layers. In addition, a splitting and reforming phenomenon of multiple oxide layers is observed, called as strips of 'ruffled tape'. An illustrative mechanism is suggested and discussed quantitatively for the formation of such phenomena. It is assumed that the unique appearance of these strips depends on the formation time and complex stress gradients on the oxide layers. [ABSTRACT FROM AUTHOR]

Photocatalysis-assisted chemical mechanical polishing, in which the photocatalysis oxidation and silica abrasives polishing are combined, is a novel finishing technique for 4H–SiC wafer. This paper characterizes the effect of pressure and abrasives on the MRR and surface quality and discusses mechanical and chemical interaction based three slurries that resulted in maximum material removal rate (1.18 μm/h) with PCMP slurry. The polished silicon carbide wafer was examined with atomic force microscope, transmission electron microscope and X-ray photoelectron spectroscopy for surface quality and material removal mechanism. The results show that an atomically smooth and flat 4H–SiC (0001) surface (Ra about 0.247 nm) was obtained by PCMP. The interface of crystal and amorphous layer of 4H–SiC wafer was flat without introducing crystallographic subsurface damage, and the atoms and lattice fringes of the crystal layer are arranged in regular order. The existence of a thin silicon oxycarbide layer, which are various forms of functional groups such as Si–C, Si–C–O, Si–O, Si4C4O4, C–O, and C = O, at the interface. And, it also demonstrates that the amorphous layer is composed of oxide layer (4–6 nm) and distorted layer. The silicon carbide surface is mechanically activated, oxidized and mechanically removed in turn, which is the main method of material removal. [ABSTRACT FROM AUTHOR]

The characteristics of the oxide layer deposited by microarc oxidation (MAO) on Al – Si alloys in a silicate-alkaline electrolyte are studied. The thermal conductivity of the layer at 50 – 120°C is determined using a special facility by the method of stationary heat flow. The thickness, the porosity, the elemental composition, the content of the amorphous phase, and the size of the crystallites in the oxide layer are determined. The results obtained are analyzed and the conditions for the lowest thermal conductivity of the oxide layer are determined. [ABSTRACT FROM AUTHOR]

Prospects of oxygen alloying of alloys in the process of deposition of rods on parts from titanium alloys aimed at raising their hardness are considered. Experiments on fabrication of samples of titanium alloys with remelting of filler rods with oxide coating formed by plasma electrolytic oxidation are performed. The main mechanical characteristics of the overlay rod material modified by introduction of oxygen from the oxide layer are determined and the structural features of the material are analyzed. [ABSTRACT FROM AUTHOR]

The excellent strength, toughness, and corrosion resistance of high-strength stainless steel has led to its extensive use in the chemical, nuclear, aerospace, and aviation industries. To shape this hard-to-cut material, electrochemical machining is a promising process. However, few reports have focused on the electrochemical dissolution behavior of high-strength stainless steel. Therefore, we focus herein on the electrochemical dissolution behavior of S-04 high-strength stainless steel in NaNO3 aqueous solution. The current efficiency indicates that current density can be divided into three regions (I, II, and III). Interestingly, a black machined surface appears in regions II and III, and the machined surface is shiny for region III. X-ray photoelectron spectroscopy indicates that the black machined surface is mainly due to the presence of Fe3O4. In addition, γ-Fe2O3 was also detected on the black machined surface in region III, whereas both γ-Fe2O3 and α-Fe2O3 were also detected on the black machined surface in regions I and II. Moreover, dissolution morphologies examined by SEM/EDX at different current densities and machining times showed that a good surface finish of the S-04 specimen can be obtained in region III. Finally, grooves with black surfaces in regions II and III were obtained by electrochemical milling. [ABSTRACT FROM AUTHOR]

In this paper, we present the study results of the surface layers of carbon steels U8 and U10 performed by X-ray photoelectron spectroscopy after laser exposure. The thicknesses of oxidized surface layers were determined to be 43 nm and 108 nm for U8 and U10 steels, respectively. Both the total thickness of the formed oxide film and its phase composition (FeO, Fe2O3, Fe3O4) with depth were found to change depending on the concentration of iron, oxygen, and carbon atoms in the considered steels. The "layer" structure effect of the oxides of the layer modified by laser irradiation on the frictional characteristics of steels is shown. In particular, the presence of FeO oxide on the U8 steel surface increases the wear characteristics, while the presence of Fe2O3 and Fe3O4 oxides provides a higher wear resistance of steel U10 compared to an unirradiated steel surface. [ABSTRACT FROM AUTHOR]

Plasma transferred arc additive manufacturing is a growing technology in the additive manufacturing world. The plasma transferred arc additive manufacturing system's ability to produce large samples, compared with other common additive manufacturing techniques, makes it highly desirable in many industrial applications. The selected material in this additive process is 17-4 precipitation hardened stainless steel, which is widely used in numerous fields, such as the aerospace, chemical, and mining industries. However, two types of voids were found in the deposits and these voids are detrimental to the mechanical properties. The identified voids were oxide layers and porosity. The presence of oxide layers was correlated to the interaction of atmospheric oxygen with the chromium present in the stainless steel. A shielding hood was designed to provide continuous shielding with inert gas to prevent oxide layer formation. The other source of voids was attributed to the porosity in the initial powders and to the choice of welding process parameters. Changing the powder supplier and optimizing the process parameters, mainly by increasing the heat input to ensure complete melting of the powders, greatly reduced the amount of porosity in the finished part. Hardness measurements were obtained from multiple samples. Hardness was only affected by the aging process, during which copper precipitates formed within the 17-4 precipitation hardened stainless steel matrix. X-ray diffraction and transmission electron microscopy analyses were conducted to characterize the martensitic matrix before and after the heat treatment and to view copper precipitation after the heat treatment. It is demonstrated that an operating solution to avoid oxide formation is the use of 5% hydrogen in the shield, center, and powder gas feeds. [ABSTRACT FROM AUTHOR]

Experimental methods for protection of metals from corrosion by radiation-oxidative treatment in hydrogen peroxide are considered. It is established that such treatment of stainless steel for 30–50 h (D = 123–205 kGy) leads to the formation of a surface oxide film that passivates the surface of the metal during thermal and radiation-thermal processes of water decomposition. With an increase in the thickness of the oxide film, its defectiveness increases and the oxidation of the metal phase increases. [ABSTRACT FROM AUTHOR]

The production of low-temperature reheated grain-oriented silicon steel is mainly based on the acquired inhibitor method. Due to the additional nitriding process, a high nitrogen content exists in the oxide layer, which changes the structure of the oxide layer. In this study, the structure of the surface oxide layer after nitriding was analyzed by scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), glow discharge spectrometry (GDS), and X-ray diffraction (XRD). The size and orientation of ferritic grains in the oxide layer were characterized, and the distribution characteristics of the key elements along the thickness direction were determined. The results show that the oxide layer of the steel sample mainly comprised particles of Fe2SiO4 and spherical and lamellar SiO2, and Fe4N and fcc-Fe phases were also detected. Moreover, the size and orientation of ferritic grains in the oxide layer were different from those of coarse matrix ferritic grains beneath the oxide layer; however, some ferritic grains exhibited same orientations as those in the neighboring matrix. Higher nitrogen content was detected in the oxide layer than that in the matrix beneath the oxide layer. The form of nitrogen enrichment in the oxide layer was analyzed, and the growth mechanism of ferritic grains during the oxide layer formation is proposed. [ABSTRACT FROM AUTHOR]

Corrosion behavior of 304 stainless steel exposed to a NaCl (3.5 wt %) solution saturated with CO2 has been analyzed using electrochemical techniques including, potentiodynamic polarization, polarization resistance, and electrochemical impedance measurements. The stainless steel samples were evaluated having different surface and pre-oxidation treatments. The oxide scales formed on 304 stainless steel oxidized in different pO2 at 1100°C have also been studied and compared. Different morphologies and chemical composition of the oxide scales were observed after oxidation at low and high oxygen partial pressures. Oxide layers with high chromium content were formed on the ground sample pre-oxidized in Ar while iron-rich oxides were mainly formed under air atmosphere. The electrochemical corrosion results indicate that non-oxidized 304 SS exhibits the best corrosion performance followed by the ground sample heat-treated in argon. For the oxidized stainless steels, the differences in the electrochemical responses are associated to the morphological characteristics and composition of the oxide layer. Homogeneous and dense Cr-rich oxide scale provides protection to 304 SS during exposure to CO2-saturated solutions while the formation of Fe-oxides with porous morphology increases the corrosion rate of 304 stainless steel. [ABSTRACT FROM AUTHOR]

A modification in the chemistry of single-crystal CMSX-4 to produce CMSX-486 superalloy has been reported in the literature to be accomplished without degradation in high-temperature mechanical performance. However, adequate attention has not yet been focussed on the hot corrosion response of the alloy considering its chemical composition modification. This paper reports for the first time that a considerable degradation in the hot corrosion resistance of CMSX-4 occurs by the modification of its chemistry. Corrosion tests at different salt concentrations and temperatures showed that the hot corrosion resistance of CMSX-486 is worse than the conventional CMSX-4 alloy. The difference in the corrosion resistance characteristics of the two alloys is attributable to the nature of the protective oxide layer formed on the materials during hot corrosion. Characterization using various advanced techniques revealed that the oxide layer formed on CMSX-486 consists of less amount of protective and coherent Al2O3 and Cr2O3 film than CMSX-4, and this is the reason for its poor hot corrosion resistance. [ABSTRACT FROM AUTHOR]

The possible formation of a solid phase in the lead coolant in the BREST-OD-300 reactor, a problem common for reactors of such type, is numerically investigated. For modeling unsteady processes in the steam generator operating with a liquid-metal coolant under the conditions involving the occurrence of crystallization–melting phenomena, a procedure that makes it possible to take into account the process ambiguity depending on the state of the heat-transfer contact surface oxide layer was used. Accidents caused by a rupture of the main steam header and by failure of the regenerative feedwater heating system are considered. The influence of certain reactor parameters on the solid phase formation dynamics in such accidents is estimated. If loss of tightness occurs in the main steam header with simultaneous loss of power supply to the reactor and failure of the steam generators' shutoff and control valves and also in the case of regenerative feedwater heating system failure with retaining the supply of feedwater to the steam generators, the solid phase fully blocks the flow section in all four loops of the primary coolant circuit. Depending on the state of the heat-transfer contact surface oxide layer, the flow sections of the steam generators themselves or those of the steam generator cavities in the concrete shell can be blocked. The main factor causing the lead coolant to become solidified in the case of steam header rupture is a sufficiently large amount of feedwater in the secondary coolant circuit pipelines and heat-transfer equipment at high pressure. At the same time, in an accident involving failure of the regenerative feedwater heating system, this volume is not of key importance for the solid phase formation dynamics in the lead coolant. The study results can be used in elaborating the designs of lead cooled reactors. [ABSTRACT FROM AUTHOR]

The emissivity models of aluminum 7075 were studied during the growth of oxide layer over the temperature range from 800 to 910 K at a wavelength of 1.5 μm. In the experiment, the samples were heated to a certain temperature and kept at that temperature for approximately 6 h. To determine the accurate emissivity, the surface temperature of specimens was measured by the two thermocouples, which were symmetrically welded onto the front surface of samples. The average of their readings was regarded as the true temperature. Eleven models were employed to evaluate the variation of emissivity with temperature or growth of oxide film on the specimen surface at a certain condition. The effect of the number of parameters used in the models on the fitting quality was studied at a certain temperature. The conclusion was obtained as more the number of parameters used in the models, the better the fitting quality became on the whole. The variation of emissivity with temperature was investigated at a certain thickness of oxide layer. The three approximate models of variation in emissivity with temperature and thickness of oxide film were proposed. The strong oscillations of emissivity were observed during the initial heating period, which were affirmed to arise from the interference effect between the two radiations stemming from the oxide layer and coming from the substrate. [ABSTRACT FROM AUTHOR]

The microstructure of the oxide layer is studied and the adhesion energy of the metal/oxide interface is determined after high-temperature isothermal oxidation ( T = 1150°C) of a single-crystal commercial René N5 nickel alloy. Experiments upon heating and rapid cooling are performed to initiate failure of the oxide layer. The elastic energy of the metal/oxide interface is determined using the model of circular buckling followed by edge delamination. Calculations are conducted for a homogeneous alumina layer and with allowance for the multilayer structure that forms at the initial stages of alloy oxidation. The adhesion energy is 72 and 27 J/m2 for these cases, respectively. [ABSTRACT FROM AUTHOR]

Based on the ultrasonic vibration technology and the electrochemical principle, the ultrasonic vibration-assisted electrolytic in-process dressing internal (UAEI) grinding is realized on the vertical machining center. The mathematical control model of the UAEI grinding is established to maintain the protrusion height of abrasive grains. Simulations and fittings show that the average current is positively associated with the increase of ultrasonic frequency, grinding speed or workpiece speed, and the decrease of grinding ratio. Concrete control schemes are made by adjusting the controllable parameters. The objective judgments are obtained by comparing the experimental results under different processing conditions. The experimental results show that the surface roughness of workpiece can research 0.0487 μm, the grinding force ratio maintains at relatively stable level, topography of oxide layer presents uniform-distributed cavities, and surface micro-topography of workpiece becomes smoother with the processing parameters determined by the control model of the UAEI grinding, proving the validity of this control model of the UAEI grinding. [ABSTRACT FROM AUTHOR]

A model of the growth of a calcium phosphate coating on a zirconium substrate with respect to the formed oxide sublayer and formation of phases is proposed. The influence of the parameters of the model on the growth of the coating and the evolution of the stresses in the oxide layer and in the coating is investigated. It is shown that the content of the substances formed in the coating increases with the increasing constants of the reaction rates, increasing diffusion coefficients, or with a decreasing voltage of the process. It is shown that the stresses in the vicinity of the interface (the substrateoxide layer) are higher when there is an oxide layer than in its absence. [ABSTRACT FROM AUTHOR]

A series of oxidation experiments were carried out on these novel γ/γ′-strengthened cobalt-based alloys of the systems Co–9Al–10W and Co–9Al–10W–0.02X (X = La, Ce, Dy, Y) at 900 °C. The appropriate amounts’ addition of rare earth elements leads to improved oxidation properties at 900 °C, especially La elements show the best oxidation resistance (129.008 mg/cm2). However, the base Co–9Al–10W alloy shows the worst oxidation performance (151.544 mg/cm2). Multilayer oxide layers formed during the oxidation process, the outer were mainly CoO and Co3O4 oxides, and the middle layer contained complex oxides (containing Co, Al, and W). The inner layer consists of little discontinuous oxides, included few Al2O3 oxides. There existed a different crack width and the base alloy had the widest crack. Moreover, there exists a phase transformation (γ/γ′ to γ/Co3W) at the interface between oxide film and substrate. [ABSTRACT FROM PUBLISHER]

This work investigated the normal spectral emissivity characteristics of Steel 304 over a temperature range from 800 to 1100 K and a wavelength range from 1.4 to 2.1 μm. In the experiments, specimens were heated in air for 6 h at a certain temperature. Two platinum-rhodium thermocouples were symmetrically welded onto the front surface of the specimens near the measuring area for accurate monitoring of the surface temperature. The temperatures measured by the two thermocouples had an uncertainty of 1 K. The average of their readings was regarded as the temperature of the specimen surface. The radiance stemming from the specimens were measured at temperatures from 800 to 1100 K in increments of 20 K by multispectral radiation thermometry. Variation in the normal spectral emissivity with respect to wavelength and temperature was studied for different heating times. The effect of surface oxidization on the accurate prediction of the specimen surface temperature was discussed. Similar variation in the normal spectral emissivity for different heating times showed that the emissivity followed a certain rule. Nine emissivity models were examined for accuracy in the temperature prediction. The results showed that the four-parameter log-linear wavelength and line wavelength emissivity models generated best overall temperature prediction. We concluded that the effect of surface oxidization on the emissivity models of Steel 304 could be dismissed; and that the same models could be used to predict its surface temperature from 800 to 1100 K. [ABSTRACT FROM AUTHOR]

We have presented a method to prepare a uniform anodic nanoporous oxide film on the surface of a cylindrical zircaloy (Zr) tube. The distribution of the electric field around the Zr tube determines the distribution of the thickness of the anodic nanoporous oxide film. The electric field generated when a cylindrical Zr tube is electrochemically anodized was simulated by using commercial code COMSOL. When four Pt wires were used as counter electrodes, a uniform electric field was achieved with minimal use of Pt. Based on the simulation results, a cylindrical Zr tube was anodized and the distribution of the thickness of the anodic nanoporous oxide layer was measured by FESEM. Also, mass production of uniform nanoporous anodic oxide films was possible by symmetrically arranging the zircaloy tubes and Pt wires. [ABSTRACT FROM AUTHOR]

Stainless steel splats were deposited on 304 stainless substrates with different thicknesses of oxide layer to examine the effect of substrate oxidation on splat morphology and splat-substrate interface bonding by inert low-pressure plasma spraying. The cross sections of splats showing the splat-substrate interface were prepared by focus ion beam (FIB). The splat morphology and splat-substrate interface bonding state were characterized by scanning electron microscopy. The interface bonding was also examined by an electrolytic etching process. Results showed that with increasing oxide layer thickness and surface roughness, the morphology of splat changed from disk shape to splashed finger-like shape. The examination into the interface bonding by using FIB-prepared cross-sectional samples revealed that the splat interface bonding depended on the oxide roughness and composition. The interface bonding with a ratio of 44% was formed at the inner part of a splat on the pre-oxidized substrate when iron oxide presented on the surface, and the roughness of oxide scale was <5 nm. When the pre-oxidizing temperature exceeded 800 °C, the surface roughness increased to 14 nm and chromium oxide covered the pre-oxidized surface, resulting in no effective bonding forming at the whole interface. Thus, surface roughness and oxide composition have a significant influence on the splat interface bonding formation. [ABSTRACT FROM AUTHOR]

Satisfactory development of the internal and external oxide layers on piercing-mill mandrels may be ensured by annealing. In addition, strong adhesion of the layers with the metal base is observed. In electron- microscope images, the structure of the boundary layer at the metal surface is seen. It resembles stalagmites. This layer consists of metal oxides, with chaotically distributed particles of the oxides of iron, nickel, and other alloying elements. With increase in the number of piercing cycles, the oxide layer becomes thicker, and its phase composition changes. With high temperature and cooling conditions, the content of wustite FeO in the surface oxide layer increases to 80%. [ABSTRACT FROM AUTHOR]

Oxide layers formed on AK6M2 aluminum-silicon alloy by microarc oxidizing (MO) are studied. The chemical and phase compositions and the morphology of the layers deposited from a base-composition electrolyte with different contents of added SiO powder are determined. It is shown that high-temperature phases form in the oxide layer at a specific concentration of SiO nanoparticles. This indicates elevation of the effective temperature in the zone of synthesis of the oxide layers in the process of MO. The addition of nanosize particles of SiO into the electrolyte influences positively the operating characteristics of the formed oxide layer. [ABSTRACT FROM AUTHOR]

We have presented a mechanism to explain why the resulting oxide morphology becomes a porous or a tubular nanostructure when a zircaloy is electrochemically anodized. A porous zirconium oxide nanostructure is always formed at an initial anodization stage, but the degree of interpore dissolution determines whether the final morphology is nanoporous or nanotubular. The interpore dissolution rate can be tuned by changing the anodization parameters such as anodization time and water content in an electrolyte. Consequently, porous or tubular oxide nanostructures can be selectively fabricated on a zircaloy surface by controlling the parameters. Based on this mechanism, zirconium oxide layers with completely nanoporous, completely nanotubular, and intermediate morphologies between a nanoporous and a nanotubular structure were controllably fabricated. [ABSTRACT FROM AUTHOR]

Multicomponent saturation of low-carbon steel with carbon, nitrogen, and boron was investigated under the anode plasma electrolytic treatment. Optical and scanning electron microscopes with an energy dispersive attachment were used to characterize the composition of the modified layer and its surface morphology. Surface roughness and microhardness were studied with a profilometer-profilograph and a microhardness tester; tribological properties were evaluated using a pin-on-disc tribometer at lubricated testing conditions. It has been established that the thickness of the oxide layer slowed down the diffusion of carbon, nitrogen, and boron as determined by the anode dissolution and high temperature oxidation, which are dependent on the processing temperature. Dissolution prevails over oxidation up to 850°C that results in the sample weight loss. At 900°C, the sample weight increases owing to oxidation which prevails over dissolution. The maximal boronitrocarburising layer thickness (0.11 mm) is observed at 850°C. The maximal microhardness of this layer is 880 HV after saturation at 850°C for 5 min. The friction coefficient and the wear rate of the samples treated at 850°C decrease by a factor of 2 in comparison with those of an untreated sample. [ABSTRACT FROM AUTHOR]

This paper strives to model the normal spectral emissivity of red copper T2 during the growth of oxide layer at 800-1,100 K. For this reason, the normal spectral emissivity of red copper T2 specimens is evaluated at the sixteen definite temperatures during a 6-h heating period. In experiment, the normal radiance is measured using an InGaAs photodiode detector at 1.5 μm, which is perpendicular to the surface of specimens as accurately as possible. The temperature of specimen surface is obtained by averaging the two platinum-rhodium thermocouples, which are welded symmetrically and tightly in the front surface of specimens near the measuring area viewed by the detector. The strong oscillation of normal spectral emissivity occurs only during the initial heating period at each definite temperature, which has been affirmed to be connected with the thickness of oxide layer on the specimen surface. The interference effect between the radiation coming from the oxide layer on the specimen surface and the radiation stemming from the substrate is discussed, which is responsible to the strong oscillations of normal spectral emissivity. The uncertainty of normal spectral emissivity contributed only by the surface oxidization is estimated to be 3.3-10.0 %, and the corresponding uncertainty of temperature is estimated to be about 3.2-10.0 K. The analytical models between the normal spectral emissivity and the heating time are evaluated in detail. A simple functional form with the exponential and logarithmic functions has been found to reproduce well the variation of normal spectral emissivity with the heating time, including the fundamental reproduction of strong oscillation occurring during the initial heating period. [ABSTRACT FROM AUTHOR]

Different mechanisms of how the crystallographic texture affects the corrosion behavior of the cladding tubes made of commercial Zr-based alloys are considered under service conditions. It is shown that the dependence of corrosion resistance of the tubes on the degree of recrystallization correlates with the distribution of prismatic axes in the tube texture, which can be regarded as an indicator of the propensity of the tube to intergranular oxygen diffusion. The effect of the layerwise inhomogeneity of a texture on tensile stresses is studied in the surface layers of the tube. It is shown that tensile stresses enhance oxygen diffusion into internal layers of the tube. It is established that, under the action of tensile stresses arising during oxide formation in the surface layer, twinning of the α-Zr matrix takes place near the front of oxidation. The texture of the monoclinic phase of the oxide layer is stable under tube surface treatment owing to existence of the orientation relationship with the substrate. [ABSTRACT FROM AUTHOR]

This work strives to model the normal spectral emissivity of aluminum 1060 during the growth of oxide layer in air over the temperatures ranging from 800 to 910 K. For this reason, the normal spectral emissivity of aluminum 1060 has been measured over a 6 h heating period at a definite temperature. In our experiment, the radiance coming from the specimen is received by an InGaAs photodiode detector, which works at 1.5 μm with the bandwidth of 20 nm. The temperature of specimen surface is measured by averaging the two platinum-rhodium thermocouples, which are symmetrically welded in the front surface of specimen near the measuring area viewed by the detector. The strong oscillations of normal spectral emissivity have been observed and discussed, which are affirmed to be connected with the thickness of oxide layer on the specimen surface, and originate from the interference effect between the radiation coming from the oxide layer on the specimen surface and the radiation stemming from the substrate. The uncertainty of normal spectral emissivity contributed only by the surface oxidization is about 4.6-10.6%, and the corresponding uncertainty of temperature contributed only by the surface oxidization is about 3.5-8.4 K. The analytical model between the normal spectral emissivity and the heating time is evaluated at a definite temperature. A simple functional form with the exponential and logarithmic functions can be employed to reproduce well the variation of normal spectral emissivity with the heating time at a definite temperature, including the reproduction of strong oscillations. [ABSTRACT FROM AUTHOR]