Surface Of Structural Materials Research Articles

Functionalization of structural materials through electro-blown spinning of ultrathin and transparent silk fibroin ionotronic nanofiber skin

Direct functionalization of structural materials can provide an elegant balance between their structure, performance, and function. However, effective direct functionalization techniques are very limited. This work reports a technique to functionalize structural materials in a non-destructive manner, wherein the surface of the materials is selectively etched without compromising their internal structure. In this technique, an ultrathin and transparent silk fibroin ionotronic nanofiber skin (SFINS) is spun on the surface of structural materials through electro-blown spinning, endowing them with electric conductivity and environmental responsiveness. This process is characterized by outstanding scalability, low cost, and high efficiency. In addition, the SFINS can be firmly bonded to the surface of different structural materials, such as glass, metals, polymers, and wood. More importantly, the electro-blown spinning process and the formed SFINS do not alter the structure, properties, and sustainability of the substrate materials. For instance, the transparency of glass and acrylic plates, the texture of wood, the color of plastics, the text of papers, the elasticity of elastomers, as well as their strength are all retained. Consequently, structural materials functionalized under the proposed process can be directly integrated into functional devices that require both structural stability and functional diversity in practice use. In this work, two prototypes are developed to demonstrate the applications of SFINS-functionalized structural materials as tactile receptors for an intelligent sorting manipulator and as a self-powered IntelliSensor for geological hazard early warning. Both examples reveal the advantages of the proposed technique in terms of the balance between the structure, performance, and function of the developed device systems.

Experimentálna analýza tribologických vlastností povrchov konštrukčných materiálov

The presented article deals with the tribological properties of the surfaces of structural materials. Comparing the results of experimental measurements of three different surfaces (chrome steel 100CrMnMoSi8-4- 6, blackened steel surface, DLC coating) and three different balls (chrome steel 100Cr6, silicon carbide, tungsten carbide) made it possible to observe the influence of the materials of the friction pair on the tribological properties.

Parametric Studies of Effect of Cavitation Jet Modes on Wear Rate of Surface of Structural Materials

In this study the kinetic curves of cavitation wear of cast steels 20 GL and 30 L used for production of critical elements of hydraulic machines were obtained. The typical predominance of growth rate of cavitation mark diameter over its depth was found on the surfaces of the investigated cast steels. The revealed phenomenon made it possible to offer a formula for estimating the volume removal of the examined cast steels in order to expand the scope of the method according to ASTM G134-17. This method uses profilometry and microscopy and allows to determine cavitation resistance both for homogeneous and heterogeneous materials, including materials after modification of their surface (with different types of coatings and hardenings).

Preparation and Characterization of SiO2/α‐Al2O3 Tritium Permeation Barriers at Low Temperature

A tritium permeation barrier on the surface of structural materials can effectively solve the problem of tritium fuel penetration and leakage. Herein, SiO2/α‐Al2O3 ceramic coatings are prepared on 316L stainless steel through slurry spin coating method. Different particle sizes of α‐Al2O3 powder are used to prepare three kinds of coatings. The particle sizes of α‐Al2O3 used are 30 nm (sample 1), 200 nm (sample 2), and equal mass ratio of 30 nm and 200 nm mixed (sample 3), respectively. The results show that the ceramic coating is composed of α‐Al2O3 and amorphous SiO2. The coating surface of sample 3 is uniform and compact and exhibits the best microstructure. Compared with samples 1 and 2, sample 3 has better thermal shock resistance. The binding strength of sample 3 is up to 69 N. Electrochemical hydrogen penetration tests indicate that SiO2/α‐Al2O3 ceramic coating can effectively improve the electrochemical hydrogen resistance of 316 L stainless steel substrate. Sample 3 has the lowest stable hydrogen penetration current density and current density difference value. Although the hydrogen resistance of sample 3 is reduced after 50 thermal shocks, it is still better than that of the substrate.

Creation of Hydrophobic Functional Surfaces of Structural Materials on the Basis of Laser Ablation (Overview)

Creation of Hydrophobic Functional Surfaces of Structural Materials on the Basis of Laser Ablation (Overview)

Properties of the Surface of Structural Materials in the Area of a Barcode Formed under the Action of Laser Radiation

Properties of the Surface of Structural Materials in the Area of a Barcode Formed under the Action of Laser Radiation

Preparation and properties of Al2O3/SiO2 composite tritium permeation barrier and its effects on the inner walls of pipelines

A tritium permeation barrier can be prepared on the surface of structural materials to effectively inhibit tritium penetration and leakage. In this study, an Al2O3/SiO2 composite tritium permeation barrier was prepared on the inner wall of a 316L stainless steel tube via the slurry method. The microstructure and phase composition of the coatings were investigated by using SEM, XRD, TEM, and XPS. The thermal shock resistance and hydrogen resistance of the coating were studied. Results show that the coating is continuous and dense, and is composed of Al2O3 and amorphous SiO2. The thickness of the coating is approximately 80 μm and well attaches to the substrate. Compared with thermal shock at 700 °C, the coating exhibits better thermal shock resistance at 500 °C and 600 °C. The Al2O3/SiO2 composite coating has good phase stability after thermal shock. Electrochemical hydrogen permeation tests demonstrate that the Al2O3/SiO2 composite coating effectively improves the hydrogen resistance of the 316L stainless steel substrate.

Modification of the Surface of Structural Materials by Concentrated Energy Flows in Order to Improve their Performance Properties

The work is devoted to the basics of surface modification of structural materials for the effective protection of machine parts and mechanisms operated in extreme conditions from the mechanical impact of aggressive media, by the method of plasma-chemical exposure to concentrated streams of matter and energy by means of plasma generators, which allow for surface renovation and engineering.

On the Physical Interpretation of the Process of Recombination of the Atomic Components of A Gas Mixture on the Surface of Structural Materials

On the Physical Interpretation of the Process of Recombination of the Atomic Components of A Gas Mixture on the Surface of Structural Materials

Phase stability of Cs-Si-O and Cs-Si-Fe-O compounds on stainless steel

ABSTRACT During a severe accident (SA) such as the Fukushima Daiichi Nuclear Power Plant accident, fission products (FPs) can be retained on the surface of structural materials in reactors. Cesium (Cs) is an important FP, and various Cs compounds such as Cs silicates are formed on the surface of stainless steel (SS) in a reactor during a SA. We calculated total energies of Cs-Si-O compounds for evaluation of phase stability within an adiabatic approximation. The calculations indicate that Cs6Si10O23 is the most stable of the Cs-Si-O compounds. We calculated, furthermore, total energies of Cs-Si-Fe-O compounds. These calculations indicate that Cs-Si-Fe-O compounds are more stable than C-Si-O compounds and that CsSi2FeO6 is the most stable of these C-Si-O and Cs-Si-Fe-O compounds within an adiabatic approximation. The results of our present calculations and our previous experiments lead to the conclusion that Cs-Si-Fe-O compounds can be stably formed on SS surface by Cs chemisorption.

Dense-film preparation of zirconium oxide by self-oxidation in air

For the formation of a dense oxide film for use as an anticorrosion film with self-diagnosis and self-healing functions on the surface of structural materials, liquid blankets, and liquid divertors of thermonuclear fusion reactors, we investigated the self-oxidation of zirconium (Zr) at 500°C in air. The microstructure, composition (O/Zr ratio), crystal structure, and formation mechanism of the film were clarified through scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis. It was demonstrated that the dense oxide film could be prepared, and its film exhibited a continuous and layered structure that consists of multiple phases. The outermost surface was unstrained monoclinic ZrO2. The growth of the oxide film adheres to a parabolic rate law.

Методы расчета термодинамических потенциалов при оценке состава оксидного слоя на поверхности металлов

To select proper water chemistry at fossil and nuclear power plants, data on the composition of oxide film formed on the metal surface contacting with aqueous coolant are necessary. By using these data, the processes occurring on the metal surface can be estimated. Calculation of Pourbaix diagrams is one of the methods using which the processes that take place on metal surface depending on the redox potential and pH can be established. To calculate these diagrams, it is necessary to have a certain set of thermodynamic data based on which it is possible to estimate the possibility of various chemical reactions to occur in the “aqueous coolant – metal” system. However, not all thermodynamic data are available from the literature, especially at high parameters. The article discusses two new methods for calculating the thermodynamic potentials of metal oxides and hydroxides. The first one, called the relative deviation method, is used for carrying out calculations in the coolant temperature range 25–327°C, and the second method, called the relative variation method, is used for carrying out calculations in the coolant temperature range 327–827°C and can also be used for more exactly determining the data obtained using the first method. Both methods can be used for estimating the most probable region for forming protective oxide films on structural material surfaces contacting with aqueous coolant.

SURFACE HARDENING OF CONSTRUCTION MATERIALS WITH THE USE OF COMPOSITE SATURATING CHARGES

The article discusses the formation of the structure of protective diffusion layers using composite saturating charges on structural materials with different carbon content. A thermodynamic analysis of the gas phase at saturation has been carried out. The composition of the gas phase has been determined. Gaseous products interact with elements of the powder system (Al, Mo, Cr) and are transformed into the gas phase (CrH, CrOH, CrСl, CrСl2, CrСl3, СrОН, СrОСl2, CrI, CrI2, CrI3, МоСl, МоСl2, МоСl3, МоСl4, МоОСl, МоОСl2, МоI, МоI2, МоI3, МоI4). Using 3D modeling of microstructures, it was possible to more fully establish the nature of the distribution of phases and inclusions in the diffusion layer. The relationship between the 3D microstructure of the material and its physical and mechanical properties made it possible to carry out modeling to obtain the optimal composition of the developed composite charge for saturation. Diffuse layers are formed on the surface of structural materials, which contain Mo2C and α phases - the Cr, Al, Mo phase, the inclusion of Fе7Мо6, (Fe, Сr, Al, Mo)23С6. Carbides of three types were found: hexagonal chromium carbide Сr7C3 and carbides Мо2С, Cr23C, Fe3Mo3C и Fe2Mo2C. The physical, mechanical and operational properties of structural materials with protective diffusion coatings have been investigated. At tests in the conditions of sliding friction the best wear resistance among the considered diffusion coverings has vanadium, titanium and borized. Their wear resistance is 1.8 - 2.3 times greater than that of coatings obtained under isothermal conditions.

H2 generation at metal oxide particle surfaces under γ-radiation in water

ABSTRACT The formation of hydrogen gas in the water circuits of nuclear power plants has implications for the safe and efficient operation of the plant and so requires thorough investigation. Therefore, typical metal oxides found on water circuit structural material surfaces have been subjected to γ-radiation in water, and the production of H2 by radiolysis has been analysed as a function of oxide composition and water content. The observed radiolytic hydrogen yields, G(H2), were analysed as a function of structural material oxide showing that the presence of the metal oxides increased the rate of hydrogen production relative to neat water radiolysis due to energy absorption by the oxides. The increase in the rate of H2 production was dependent on the oxide composition. The G(H2) value increased at low water weight fractions indicating surface effects are important in the H2 production mechanism.

Charge transfer across the Cr2O3, Fe2O3, and ZrO2 oxide/water interface: A pulse radiolysis study

The transfer of electrons across the oxide/water interface has been investigated for oxide particles which are typically found incorporated into structural material surfaces within water circuits of nuclear systems. A pulse radiolysis study was conducted in order to observe the generation and decay kinetics of hydrated electrons in water in the presence of metal oxides. The presence of the oxides was found to have an effect on hydrated electron decay behaviour, with Fe2O3 retarding the decay rate and ZrO2 increasing the decay rate. The presence of Cr2O3 appeared to have negligible effect on the decay rate. The electron yield after the irradiation pulse was found to increase for all oxide/water mixtures relative to neat water, indicating electron transfer from the oxide to the water. The responses were attributed to electronic properties such as the band gap of the materials with respect to redox reactions at the material surface, as well as the effect of hydroxyl radicals on electron behaviour in the presence of the oxides.

Surface chemistry of structural materials subjected to corrosion

Abstract The article describes a comprehensive mass spectrometric approach to the study of surfaces of structural materials. The combined use of thermal desorption mass spectrometry, gas and liquid chromatography, and laser desorption/ionization mass spectrometry (LDI) to provide information about the surface and surface layers of materials is proposed. The suggested method allows one to determine the thermodynamic characteristics of compounds and surface contaminants adsorbed on surfaces, as well as surface layers, to determine the composition of volatile and non-volatile contaminants on the surface, and to determine the nature of the distribution over the surface of these compounds. The method allows to obtain the most complete information about the surface condition and can be used to predict the life of structural materials.

Study of the Properties of Qxide Coatings Formed on Titanium by Plasma Electrolytic Oxidation Method

The development of the modern industry requires to develop high-performance, environmentally friendly methods for the production of light structural material surface coatings. The use of products and structures made of titanium and its alloys with high wear resistance and corrosion resistance prevails in many industries, in particular in the aerospace industry, shipbuilding, and transport engineering. Nowadays, the application of the plasma electrolytic oxidation method, a promising metal surface treatment method, is of increasing interest. Besides this method is called microarc oxidation. The objective of this work is to study the properties of oxide coatings obtained on titanium alloys under the influence of rapid pulsed effects of the plasma electrolytic oxidation process. Oxide composite coatings were obtained in various electrolyte solutions in this work. Oxide coatings are characterized by high wear resistance. It has been established in tribological tests that the wear resistance of the coating is increased by 2–15 times compared with an uncoated sample. The friction coefficient curves obtained for coated samples show that there is no destruction of the coating to the base. The breaking-in area is marked in the curves. The friction surfaces are adjusted to each other and go to a stable friction mode. The latter results in the friction coefficient decrease and wear rate decrease.

Mathematical simulation of low cycle fatigue of high-loaded engine parts

The paper discusses main aspects of low cycle fatigue influence on the lifetime of engine parts. The importance and history of the problem, the main experiments and the effects impacting the low cycle fatigue of structural materials are described. A hypothesis about the existence of a thermomechanical surface of structural material, generalized to the case of a cyclical loading was used to approximate the loops of cyclic nonisothermal elastoplastic deformation curves. The cyclic deformation curve model is based on the following three parameters: the elastic modulus during unloading, the Bauschinger effect and the conversion parameter of the nonlinear part of its first halfcycle. This model also accounts for the accumulated plastic strain, as well as the testing temperature. The criterion of durability is formulated, based on the dependence between the number of halfcycles to failure and the accumulated plastic deformation. Deformation theory of plasticity, generalized to the case of cyclic deformation, in combination with the durability model and technology of "dying" elements is applied to the finite element analysis of low cycle fatigue of gas turbine engine parts. The results of calculations are demonstrated.

Laser-Spark Modification of the Surfaces of Structural Materials by the Example of St3

The paper considers a technology for hardening construction materials using the hybrid (laser-spark) method by the example of steel St3 using hard alloys (VK8, stellite PR-V3K). A significant (several-fold) increase in the wear resistance of the coatings obtained is shown at resistance to abrasive friction due to the good quality of the coating layer and its microhardness (up to 60 GPa). Optimum modes for electrical spark and laser surface modification are proposed. Some physical and chemical properties of the coatings obtained (thickness, roughness, wear resistance, microhardness), as well as their dependence on the hybrid machining modes, are studied. The prospectivity of applying the hybrid (laser-spark) method for hardening of machine parts in order to increase their resistance to abrasive wear during friction is justified.

Sorption of Radionuclides from the Primary Circuits of Reactors with Pb–Bi Coolant onto the Surface of Structural Materials of the Reactor Core

Sorption and phase distribution of 54Mn, 59Fe, 60Со, 106Ru, 125Sb, 137Cs, 144Се, 154,155Eu, and 235,238U radionuclides in contact of the Pb–Bi melt with the steel surface were studied. Radionuclides of the elements with the minimal oxygen affinity (Ru, Te, and Sb) remain mainly in the coolant melt and are weakly sorbed onto the solid phase. The other fission product radionuclides having higher oxygen affinity are sorbed onto the surface of steel structural materials. The sorption increases at 350–400°С.