Protection of Metals and Physical Chemistry of Surfaces最新文献

A highly active microporous carbon adsorbent, KAUSORB-VA, with a micropore volume of 0.68 cm³/g and a specific BET surface of 1640 m²/g, was synthesized from nut shells for systems of adsorption storage of natural gas. Methane adsorption onto the adsorbent was measured at pressures up to 40 MPa and at temperatures of 303, 313, 323, and 333 K. The methane adsorption was found to achieve a maximum value of ~13.5 mmol/g (21.5 wt %) at a temperature of 303 K. The average differential molar isosteric heat of methane adsorption at 303 K was found to be ~16 kJ/mol.

The effect of silicon contained in aluminum alloys on the structure, phase composition, and thermophysical properties of coatings formed by microarc oxidation has been demonstrated. The studies have been performed using samples made of AK12pch eutectic alloy with a silicon content of ~12% of Si and foreign-produced M244 hypereutectic alloy with a silicon content of ~26% of Si. Microarc oxidation coatings have been formed on all samples in a capacitive setup in a silicate-alkaline electrolyte using the same process conditions for all samples. The structure of the alloys and the resulting coatings has been analyzed. The coating thickness, porosity, microhardness, phase composition, and heat capacity have been determined. It has been found that silicon in the aluminum alloy contributes to an increase in the coating thickness, porosity, and heat capacity. Silicon in the alloy also contributes to an increase in the fraction of the amorphous phase in the coating and the amount of silicon oxide.

Methane adsorbed natural gas (ANG) is a promising technology applicable to gas storage and transportation. ANG provides higher capacity at relatively low operating pressures compared to CNG, as well as increased fire and explosion safety and energy efficiency of the charge/discharge processes. This allows us to move to new engineering principles for gas accumulators based on conformal designs instead of cylindrical cylinders. A scaled natural gas accumulator (SNGA) of a conformal design with a volume of 24 L loaded with a compacted industrial carbon adsorbent, KS-HAM, was developed, and the comprehensive study of its cyclic operation was carried out. As part of the experiment, the cyclic operation of SNGA was studied under conditions of high-speed charge (up to 2 min) and slow discharge with gas flow rates of 5 and 10 L (NTP)¹/min in two modes: with active temperature control and natural convection. For theoretical studies of the cyclic operation of the SNGA, a lumped parameter model was developed and verified using experimental data. The investigations resulted in the characteristics of the cyclic operation of the SNGA that are essential for the purposes of actual usage on passenger vehicles.

This study assesses recent advances in the preparation and microstructure, oxidation, and hot corrosion properties of diffusion coatings on super alloys for turbine applications. Surface alloying of super alloys by diffusion coating is regarded as an effective method of protecting super alloys against oxidation and hot corrosion degradation. A co-deposition of Pt, Ge, Ta, Ni, Ti, and Ru with a diffusion coating is stated to give outstanding protection against hot corrosion and cyclic oxidation. The review articles start by diffusion coatings, diffusion coating synthesis techniques, various types of diffusion coatings, recent advancements in diffusion coatings, and diffusion coating degradation mechanisms. Diffusion coatings are classified as aluminide, chromide, silicide, boronizing, and nitriding. Pack cementation, chemical vapor deposition (CVD), molten salt bath, and slurry coating process are the several types of diffusion coating synthesis processes. Degradation mechanisms of coatings involve cyclic oxidation, hot corrosion, mixed oxidant corrosion, interdiffusion, and erosion.

Nano-surface modification and the introduction of residual compressive stress can enhance the service performance of materials. This study investigates the surface integrity of steel Q345R used for pressure vessels after ultrasonic peening, elucidating the evolution of the surface microstructure and its impact on mechanical properties. The experimental results indicate that as the peening time increases, the surface roughness first increases and then decreases, while the surface hardness increases, with a maximum increase of approximately 21.1% compared to the unpeened specimens. As the shot diameter increases, the surface roughness decreases, and the surface hardness decreases, with a minimum increase of about 5.7% compared to the unpeened specimens. As the peening height increases, the surface roughness decreases, and the surface hardness continues to decrease, with a minimum increase of about 11.6% compared to the unpeened specimens. EBSD characterization revealed that peening induced significant plastic deformation on the specimen surface, with a noticeable refinement of grains, reducing in size by about 83.8%, and a significant increase in dislocation density compared to the unpeened areas. Through tensile testing and data analysis, the peening process parameters were optimized. Under the conditions of 8 min of peening time, a shot diameter of 5 mm, and a peening height of 10 cm, the tensile strength and yield strength of Q345R increased by 3.8 and 10.4%, respectively, resulting in the best comprehensive tensile performance.

Based on the concepts of physicochemical mechanics of contact interaction, a materials-science analysis of the tribological efficiency of a number of synthetic lubricant compositions containing a surface-active additive, lithium 12-hydroxystearate, was carried out. Tests of the “CuAl5 bronze–С45 steel” friction pair were carried out on an MT-8 reversible sliding friction machine under conditions corresponding to the operating modes of heavily loaded friction units. The role of the lubricating medium was revealed using criterial approaches based on an experimentally obtained set of macroscopic integral criteria (phenomenological indicators of friction and wear) and microscopic (microstructural) criteria (physical broadening of X-ray lines, crystal lattice period, elemental composition of the surface layer of the material of the contact deformation zone) determined using modern metallophysical research methods. For the first time, it has been experimentally proven that the use of dispersion-lubricating media containing surfactants in tribocouplings promotes the formation of a wear-resistant structure in the antifriction material aluminum bronze.

The corrosion inhibition properties of Lavandula angustifolia (LA) extract for C45 steel in a 1 M HCl solution were investigated using weight loss measurements to determine the optimal inhibitor concentrations at room temperature. The performance of LA at deferent temperature (20–50°C) was further evaluated using electrochemical impedance spectroscopy (EIS), including polarization measurements and open circuit potential analysis. The corrosion rates were corroborated by UV-Vis spectroscopy and scanning electron microscopy (SEM). The results demonstrated that LA extract effectively inhibits the corrosion of carbon steel in acidic environments, achieving a maximum inhibition efficiency of 93.87% at an inhibitor concentration of 7 g/L and a temperature of 50°C. Potentiodynamic polarization studies revealed that the inhibitor adsorbs onto the carbon steel surface following the Langmuir adsorption isotherm model, classifying LA as a mixed-type inhibitor. Additionally, the low equilibrium constant K_ads values for the adsorption–desorption process suggest that the inhibition mechanism involves physical adsorption. The LA inhibitor effectively protects the surface against additional corrosion attacks, according to SEM and UV studies. Because the computed quantum parameters agreed with the experimental findings, LA can be utilized as a substitute inhibitor to prevent corrosion in carbon steel.

Ta–Si–C–(N) coatings were obtained by magnetron sputtering of a TaSi₂–30% SiC target in an Ar, N₂, and Ar + 15% N₂ gas mixture. The structure and mechanical characteristics of coatings were studied, with special attention paid to the tribological properties of coatings under liquid friction conditions. Results showed that the coatings have a dense, low-defect nanocomposite structure. The Ta–Si–C coating’s main structural component was the TaC phase. Introduction of nitrogen into the gas-medium composition promoted the formation of Ta(C,N) phase. In the coating deposited in N₂, the silicon-nitride-based phase was predominant. An increase in the nitrogen concentration led to a decrease in hardness from 27 to 16 GPa and in elastic modulus from 265 to 160 GPa. Coatings had a friction coefficient of 0.12–0.13. A coating obtained in an Ar + 15% N₂ environment was characterized by a minimum reduced wear of 6.1 × 10^–6 mm³ N^–1 m^–1.

This study examines the durability and performance of high-performance self-compacting concrete (HP-SCC) incorporating supplementary cementitious materials (SCMs) such as natural pozzolan, blast furnace slag, and silica fume when exposed to aggressive acidic environments (HCl and H₂SO₄). In addition to standard tests for fresh concrete properties (slump flow, L-box, V-funnel, sieve stability) and compressive strength, the research integrates analytical chemistry techniques to investigate the degradation mechanisms. Mass loss was measured to quantify acid attack, while X-ray diffraction (XRD) analysis was used to monitor mineralogical changes, such as the dissolution of portlandite and formation of secondary salts due to leaching. Chemical analysis of the immersion solutions provided insight into the dissolution behavior of cementitious phases and shifts in chemical equilibria under acidic conditions. The experimental data were used to calibrate a predictive computational model simulating the kinetics of degradation. Results demonstrated that mixtures containing silica fume and blast furnace slag exhibited superior chemical stability, retaining mechanical strength and microstructural integrity over time. These findings highlight the value of incorporating analytical methods in concrete durability studies, especially for designing materials intended for harsh industrial environments.

In order to broaden the effective absorption bandwidth (EAB) of the electromagnetic wave absorption material (YSPM) prepared in our previous work, carbon fibers (CF) were introduced to effectively optimized the dielectric constant of YSPM. Polydopamine (PDA) was used as adhesive agent to facilitate the attachment of YSPM onto the CF surface, constructing a structurally stable and high-performance fiber-based electromagnetic wave absorbing material (CF@YSPM). By optimizing the concentration of DA·HCl, the weight ratio of CF to YSPM, and the reaction time, the performance of CF@YSPM electromagnetic wave absorbing composite was systematically enhanced. The results revealed that the incorporation of CF established an efficient conductive network, and significantly improved the loss characteristics of CF@YSPM, enabling effective electromagnetic energy absorption and dissipation without increasing thickness or additives. Through range analysis, the optimal preparation parameters were determined as follows: DA·HCl concentration of 1.5 mol/L, CF-to-YSPM weight ratio of 1 : 3, and reaction time of 24 h. At 8.45 GHz, the composite achieved superior absorption with a minimum reflection loss (RL_min) of –51.23 dB. With a thickness of 2.2 mm, EAB extended to 14.02 GHz, covering multiple important electromagnetic wave frequency bands. Consequently, this study successfully developed a novel carbon fiber-based composite with exceptional broadband electromagnetic wave-absorbing properties through hierarchical structural design and compositional optimization.