Protection of Metals and Physical Chemistry of Surfaces最新文献

The literature data published in recent years on the functionalization of carbon materials under the influence of HNO₃ are systematized. Graphite, carbon nanotubes, carbon black, and mesoporous carbon material type of the Sibunit^TM were considered as carbon materials. The article presents modern concepts of the mechanism of acid treatment of carbon materials, which determine the efficiency of functionalization and also influence their physicochemical characteristics (structure, strength characteristics, etc.). The conducted analysis allows us to provide recommendations for the functionalization of carbon materials that differ in degree of ordering.

A study was conducted of morphological transformations of C-Gd₂O₃:Eu³⁺ (5 mol %) films obtained by the sol–gel method from solutions of GdCl₃ and EuCl₃ chlorides in water and ethylene glycol with aerosol delivery of the precursor to the substrate surface at room temperature. It has been shown that, at slow stages of chloride hydrolysis and polycondensation of GdO⋅nOH–EuO⋅nOH hydroxides when supplying vapors of the precipitating agent NH₄OH, droplet-shaped films of GdO⋅nOH xerogel with EuO⋅nOH are formed, the morphology of which is practically preserved after annealing at 700°C until the formation of C-Gd₂O₃:Eu³⁺ film with a thickness of ~50–170 nm of the solid part, with a surface roughness of ~186–490 nm. The use of large droplets of precursors that have previously undergone hydration and polycondensation stages with the introduction of the precipitating agent NaOH is accompanied by the formation of dendrites of the GdO⋅nOH xerogel + EuO⋅nOH + mNa⁺ with subsequent annealing to form a phosphor C‑Gd₂O₃:Eu³⁺, mNa⁺. In this case, the solid part of the film thickness reaches a value of ~100–1800 nm with a roughness of ~100–200 nm. The possibilities of using the obtained films as catalysts and optical devices are discussed.

A dual-thioamide molecular design is demonstrated to achieve superior copper corrosion inhibition in 0.5 M H₂SO₄. The synthesized bis-functionalized inhibitor BTHC exhibits exceptional performance, achieving a record 98.5% inhibition efficiency as optimized by response surface methodology (RSM), significantly surpassing its mono-functionalized analogue MTHC (85.8%). Notably, RSM models for BTHC show near-perfect predictability (R² = Q² = 1.000) and identify a robust operational window, where the inhibitor maintains >95% efficiency at a moderate 50.5 µM concentration. Thermodynamic analysis confirmed a spontaneous, exothermic chemisorption process for both inhibitors, with BTHC exhibiting consistently higher adsorption constants and a more negative adsorption enthalpy (−39.36 vs. −24.40 kJ mol^–1), indicating stronger interfacial interactions and enhanced adsorption stability. Density functional theory (DFT) calculations rationalize this enhancement, showing BTHC possesses a narrower HOMO–LUMO gap (4.01 vs. 4.10 eV) and an electronic structure that favors charge transfer. Critically, its dual-anchoring thioamide groups facilitate multidentate coordination, promoting extended surface coverage. This mechanism is directly validated by SEM-EDX analysis, which reveals BTHC forms a compact, coherent film that effectively suppresses corrosive product formation. The integrated methodology establishes a definitive structure-activity relationship, proving that bis-thioamide functionalization offers a validated blueprint for designing high-performance copper corrosion inhibitors.

Using the method of dynamic mechanical relaxation spectroscopy, the relaxation behavior of elastic polyalkyl (meth) acrylates in a free state and as part of compositions involving a metal surface was studied before and after exposure to various types of radiation with different intensities. The results of a study of dissipative processes of α-, β-, and µ-relaxation occurring in polymers under the influence of ultraviolet and radiation are summarized. The analysis is based on a comparison of the intensity of local dissipative relaxation processes occurring in unirradiated and irradiated polymer, as well as its glass transition temperature and elastic properties.

In this work, a coating based on a copolymer of methacrylic acid with acrylamide and zinc compounds (ZnO nanoparticles, zinc nitrate, and hydroxide) was obtained, the properties of which were tested for anticorrosion protection of U8A steel. Using IR spectroscopy, it was shown that the functional groups of the copolymer form complex compounds with zinc ions and are bound to ZnO by weak intermolecular interactions. Based on the data from corrosion diagrams and electrochemical spectra, the optimal ratio of MAC : AA monomers was determined: 1 : 9 wt %, respectively. Testing of coatings in a mixture of nitric and hydrochloric acids and in an environment of saturated hydrochloric acid vapors demonstrated that all types of additives enhance corrosion protection.

Ti–Al–C and Cr–Al–C coatings were produced by spark plasma sintering using MAX-phase powders produced by self-propagating high-temperature synthesis. The 1.6–1.7 mm thick coatings had a dense structure and contained the following phases (wt %): 43 Ti₂AlC, 41 Ti₃AlC₂, 16 TiC, 94 Cr₂AlC, and 6 Cr₇C₃, respectively. The coating hardness was 13–17 GPa, the elastic modulus was 202–283 GPa, and the elastic recovery was 31–39%. Cr–Al–C coating exhibited minimal wear rate of 3.14 × 10^–7 mm³ N^–1 m^–1 and a friction coefficient of 0.17 under sliding friction conditions. Application of Ti–Al–C and Cr–Al–C coatings made it possible to significantly increase the wear resistance of substrates made of titanium and chromium alloys and increase oxidation resistance by 2.5 times.

Oxidative polymerization of aniline is for the first time conducted in aqueous solutions of polynaphthalene sulfonic acid (PNSA) at different ratios of the concentrations of aniline and PNSA. The polymerization is studied by in situ spectroscopy in the UV-vis and near-IR regions. The films of water-dispersible complexes of polyaniline (PANI) with PNSA are obtained by spraying. The electron structure, morphology, and sensor (ammonia) properties of the films of PANI–PNSA complexes are studied for the first time. To increase the stability of the sensor properties under the conditions of humidity close to 100%, the effect of their treatment with aqueous solutions of sodium, calcium, strontium, and aluminum chlorides is studied.

Using electrical discharge machining (EDM) with a non-localized electrode, FeCrWMoSiCB/Al₂O₃ composite coatings of iron-based metallic glasses with aluminum oxide were prepared for grade 35 steel. Coating thicknesses ranged from 36.6 to 48.8 μm. X-ray diffraction patterns of coatings reveal a broad halo, indicating the predominance of the amorphous phase. Elemental mapping data indicate a dispersed distribution of Al₂O₃ particles in the coating. The coating surface exhibited high hydrophobicity, with distilled water contact angles of 108°–127°. An increase in corrosion potential and a decrease in corrosion current density were demonstrated with the introduction of aluminum oxide into the amorphous matrix. Impedance spectroscopy data indicate an increase in the density and stability of barrier film formed in the electrolyte with the introduction of Al₂O₃ into the metallic glass. Heat resistance at 700°C for composite coatings with aluminum oxide was lower than for samples with metallic glass coatings. Tribological tests showed a twofold increase in wear resistance of coatings with dispersion hardening of the amorphous matrix with aluminum oxide.

Olivine-type LiMnPO₄ is a technologically relevant inorganic material whose surface state and microstructure are strongly influenced by carbonaceous surface modifications. While carbon coatings are widely employed, their intrinsic role in regulating crystallite growth and hierarchical particle assembly remains insufficiently clarified. In this work, LiMnPO₄/C composites were synthesized via a sol–gel route using glucose as a sustainable carbon precursor with carbon contents of 5–20 wt %. The influence of glucose-derived carbon on phase formation, crystallite size, surface-related vibrational features, and microstructural evolution was systematically investigated by X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy. All samples retained the single-phase orthorhombic LiMnPO₄ structure, while the average crystallite size decreased progressively from ~173 nm (pristine) to ~73 nm (20 wt % carbon), indicating effective suppression of crystallite growth by the carbonaceous coating. Electron microscopy revealed the formation of hierarchical microstructures, where nanoscale crystallites assemble into micrometer-scale secondary particles, with carbon content governing the balance between growth inhibition and particle aggregation. These results demonstrate that glucose-derived carbon acts not only as a surface coating but also as a microstructural regulator that controls crystallite development and particle assembly. The findings provide a surface-chemistry and microstructure-oriented perspective on carbon-modified LiMnPO₄, relevant to the design of coated inorganic materials where interfacial and structural control is critical.

Understanding the conformational behavior of oligomeric hyaluronans (HAs) is crucial for controlling their physicochemical behavior and cross-linking efficiency in biomedical materials. In this work, conformational changes of oligomeric HAs (with a molecular mass range of 11.2–50.0 kDa) in a wide pH range (4.0–10.0) were investigated by synthesizing HA conjugates labeled with 2-aminobenzoic acid. The labeling strategy used introduces a sensitive internal fluorophore into the hyaluronan structure, which allows for monitoring subtle structural shifts in the macromolecule in real time. The integrity of the HA backbone after conjugation was assessed by measuring the viscosity of the solutions, which confirmed the absence of significant chain degradation during the labeling process. Chemical modification and labeling efficiency were confirmed by fluorescence spectrophotometry and hydrophilic high-performance liquid chromatography with fluorimetric detection. Conformational transitions were characterized using differential scanning fluorimetry (DSF), which allowed us to gain insight into the thermal stability and behavior of oligomers. Additional estimates of the hydrodynamic size distribution were obtained using dynamic light scattering (DLS) and particle trajectory analysis, providing a comprehensive view of the supramolecular organization in solution. Changes in the fluorescence intensity of the label and particle size were assessed for both the initial labeled HAs and the products of their reaction with an epoxy cross-linking agent, 1,4-butanediol diglycidyl ether. The observed pH-dependent shifts in fluorescence and size distribution indicate reversible conformational rearrangements of HA oligomers, probably caused by the protonation/deprotonation state of carboxyl groups. Furthermore, BDDE treatment caused significant changes in size and fluorescence consistent with effective covalent modification and alteration of the supramolecular structure. Based on the obtained data, a scheme of interaction of HA with glycidyl ethers was proposed, emphasizing the essential role of the conformation of the initial HA for the cross-linking processes.