Protection of Metals and Physical Chemistry of Surfaces最新文献

The article is devoted to the presentation of statistical mechanics as applied to nanomaterials, based on multivariate statistical studies. The fundamentals of statistical nanomechanics and their application to the theory of self-organization of nanodispersed media are presented.

By direct-current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS) methods at peak currents of 50 and 100 A, as well as by applying a negative bias voltage of –500 V to a substrate with a target compound of Ti₂AlC, nanostructured coatings in the Ti–Al–C system with a thickness of 1.8–6.4 μm were obtained. The main phase in the coatings was titanium carbide; when using HIPIMS, the intermetallic compound TiAl was additionally formed. It was found that the coatings deposited by the DCMS method have a maximum hardness of 31 GPa and an elastic modulus of 294 GPa, as well as a low friction coefficient of 0.2, while the HIPIMS method, when using optimal conditions, provides a minimum wear rate of 5.1 × 10^–6 mm³ N^–1m^–1, thermal stability, and oxidation resistance up to 1000°С. The protective properties are associated with the formation of dense surface films based on aluminum oxide. The use of HIPIMS by applying a high negative bias voltage to the substrate promotes the precipitation of Ti₂AlC and Ti₃AlC₂ MAX-phase crystallites with a crystallite size of less than 100 nm during vacuum annealing of coatings at 1000°С.

The review presents the classification, characteristics, and range of sorbents and wound dressings of various natures developed and used in application therapy. New trends and developments in carbon-based vulnerosorption materials are demonstrated.

The effect of the structure on the inhibitory properties of ketoximes in a simulated NACE formation water saturated with carbon dioxide and hydrogen sulfide has been studied. The influence of medium temperature and exposure time on inhibitory properties has been established. The influence of the “structure–property,” kinetic and physico-chemical parameters of interaction, as well as the mechanism of adsorption on the metal surface are investigated. Based on the obtained values, it is proved that the neutral form of acetophenonoxime is more preferable for the adsorption process on the metal surface than the protonated one. This phenomenon is explained by the fact that neutral molecules are more “soft” compounds and have low stability, and, consequently, tend to transfer electrons by iron atoms with electron deficiency.

The sorption capacity of a synthesized polymer based on starch and glycidyl acrylate in relation to heavy-metal ions is studied. It is shown that the sorption of metal ions is reliably described by the Langmuir model, while the process itself has a physical character. It is found by thermogravimetric analysis that the process of thermal destruction of the polymer occurs in three stages, and that of its complex with copper, in four stages. The activation energy of decomposition of the initial polymer is in a range of 24–38 kJ/mol for each stage, while for its complex with copper it is 46–68 kJ/mol. The introduction of Cu(II) increases the thermal stability of the obtained polymer based on starch.

The possibilities of return-path laser ellipsometry for monitoring oxidation–reduction processes on metals and alloys in rarefied environments have been studied. A laser automatic ellipsometer has been built based a return-path autocollimation scheme, which makes it possible to remote monitoring of the growth and degree of oxidation of the surface layer on metal samples through the optical window of the vacuum chamber. It has been shown that kinetic return-path ellipsometry makes it possible to record confidently the onset of a new phase formation based on changes in the slope of the experimental ellipsometric nomogram Δ(t)–ψ(t). As an example, laser-ellipsometric studies of low-temperature vacuum oxidation processes of AISI-321 alloy through the optical window of the vacuum chamber of an Auger electron spectrometer have been performed. A combination of kinetic return-path ellipsometry and Auger electron spectroscopy with layer-by-layer etching has been used to show that after the induction period of oxidation, a kink is recorded on the ellipsometric kinetic curve Δ(t)–ψ(t), which is associated with the onset of formation of a thin (40–50 Å) metal–oxide layer of a new oxide phase in the volume due to the exchange reaction of iron oxides with chromium from the alloy and the resulting conversion of iron oxides into spinel (FeCr₂O₄). In this case, the front of this transition shifts closer and closer to the metal–oxide interface, while the formation of low-protective iron oxides becomes increasingly difficult, and they do not have time to reach their maximal thickness.

The adsorption of methane onto an La–BTC metal–organic framework (MOF)was investigated within a pressure range of 0.1−40 MPa at supercritical temperatures of 303, 313, 323, and 333 K. The isotherms of excess adsorption were measured, the adsorption volumes were evaluated, and the isotherms of the total content were calculated, as well as the differential isosteric and initial heats of methane adsorption. Analysis of the obtained results revealed the incompleteness of the gas-adsorption process in the La–BTC MOF in the studied pressure range, which is indicated by the impossibility of fulfilling the condition of equality of the adsorbate and adsorptive densities. The same effect was observed in the previously studied adsorption systems based on other MOFs (Zr–BDC and Al–BTC) and carbon adsorbents. The porous structure of the La–BTC adsorbent was assumed to be the cause of the observed peculiarities of the methane adsorption process.

In this study, hybrid surface composites were fabricated using friction stirring technique to improve the tribological properties of AA6082 aluminum alloy, which has various industrial applications. Micro-scale SiC and n-Al₂O₃ reinforcements were used in the hybrid composites produced. The rotational and travel speeds were chosen as chosen as 1250 rpm and 40 mm min^–1, respectively. After the double pass production, it was determined that the homogeneous particle distribution in the surface region lost this homogeneity in the lower regions of the surface. The hardness of the hybrid surface composites was found to be approximately 44.2% higher than AA6082 aluminum alloy. It was determined that the wear resistance of SiC/n-Al₂O₃ reinforced hybrid surface composites produced by friction stir processing was up to 68.5% higher than non-reinforced AA6082 alloy.

This study aimed to investigate the corrosion inhibition behavior of zeolitic materials on aluminum in 1 M HCl solution. This investigation used electrochemical methods (polarization curves and electrochemical impedance spectroscopy). Polarization curves indicate that the inhibition mechanism primarily acts as a mixed-type inhibitor, with the corrosion rate of aluminum in 1 M HCl reduced by 99.57% at an inhibitor concentration of 100 ppm. Electrochemical impedance diagrams demonstrate that inhibition occurs through a charge transfer process on a heterogeneous surface across all tested zeolite concentrations. Scanning electron microscopy micrographs revealed that the formed film effectively blocked acid attack through physical and chemical adsorption on the aluminum surface.