Protection of Metals and Physical Chemistry of Surfaces最新文献

The electronic characteristics of the Ga_n (n = 3–6), Be₁₂O₁₂, and GaBe₁₁O₁₂ clusters were examined by applying the DFT calculations with the B3LYP-D3/6-31G(d, p) method. The sensing performances of these clusters to the phenytoin (Phy) molecule were also evaluated in gas and water phases. The results show the adsorption of the Phy molecule over the Ga_n and Be₁₂O₁₂ clusters was viewed as a great chemical adsorption with E_ads which vary from –1.120 to –1.602 eV. While the interaction between the Phy molecule and the surface of the GaBe₁₁O₁₂ fullerene is considered as a moderate chemisorption. Due to the strong interaction between the adsorbent and the adsorbate, the energy gaps of the Ga_n, Be₁₂O₁₂, and GaBe₁₁O₁₂ clusters were significantly altered after the adsorption process, thus leading to a high sensitivity towards the chemisorbed molecule. The presence of water led to a little bit reduction in the adsorption energy of Phy molecule onto the clusters compared with the values observed in the gas phase, while maintaining their high-sensing performances. The comparison of the recovery time of the three types of clusters studied revealed that the Ga_n (n = 4, 5, and 6) and Be₁₂O₁₂ clusters possess a long recovery time, rendering them inappropriate nanomaterials to build regenerable biosensors for the Phy molecule detection, whereas the Ga₃ and GaBe₁₁O₁₂ clusters displayed a short recovery time (8.3 s and 5.7 × 10^–3 s), making them highly efficient nanosensors for capturing the Phy molecule in an aqueous solution.

Ni—TiO₂ composite films were electrodeposited from a nickel-plating bath containing various amounts of TiO₂ particulates of different particle sizes. The films deposited from a bath that contained 10 g/L TiO₂ did not contain any TiO₂. On the other hand, all films deposited from a bath with 40 g/L TiO₂ contained some TiO₂. Current density and cathode rotation speed did not seem to have much effect on the incorporation of TiO₂ in the nickel matrix film, but the amount of TiO₂ powder in the bath and also their particle size appeared to be very influential parameters in the incorporation of TiO₂ particulates. The Ni–TiO₂ composite films showed some “cauliflower-type” globular grains, which were compact without any cracks or pits. They were smaller for the films deposited from a bath containing small particle-size TiO₂ particles. Using Monte Carlo simulation, it can be concluded that in the Ni–TiO₂ composite coating, nickel atoms are first deposited on the TiO₂ particulates and then a Ni–TiO₂ colony will be formed on the surface of the substrate and the final structure of cauliflower was created.

The paper presents the results of interpretation and analysis of IR-ATR spectra of composite ultrafiltration (UF) membranes made of polysulfone (PS) and polyethersulfone (PES) in air-dry and water-saturated states in order to assess structural changes in the active layer caused by static and dynamic water saturation. A comparative analysis of the IR spectra of air-dry and water-saturated samples revealed that no shifts occur in the region of skeletal oscillations of the frequency of absorption bands of the functional groups of PS and PES. This allows us to affirm the stability of the chemical structure of the active layer matrix of membranes of this type. Manifestation in the IR-ATR spectra of UF membranes in the air-dry state of a wide absorption band at ~3305 cm^–1 suggests the presence of a superposition of various OH^– groups in the active layer of the PS and PES involved in the formation of N-dimensional hydrogen bonds. Relative changes in the shape and intensity of the band on the high-frequency side of the spectrum for water-saturated samples conceal the redistribution of hydrogen bonds of adsorbed water and OH^— groups of polyethylene glycol (PEG) and suggest that the structure of water in the pore space of the active layer of the membrane changes significantly, demonstrating an increase in weakly bound “liquid water.” The decrease in the number of PEG molecules is regular, most likely due to significant hydration of PEG molecules in adsorbed water, and indicates partial washing out (leaching), but not complete disappearance.

The paper presents the results of a study of 1,2,3-benzotriazole (BTA) films formed on a real copper surface under various conditions. It has been established that BTA molecules, depending on the conditions, form adsorption (Cu–BTA_ads) or surface-associated (Cu–BTA_surf) films. The coordination forms of BTA molecules on the copper surface were established using Raman spectroscopy and density functional theory (DFT) modeling. By counter synthesis, complex compounds BTA–Cu²⁺ were obtained in aqueous solutions at different pH values and their properties were studied using IR and Raman spectroscopy. On a real copper surface, adsorption and surface-associated films of copper and 1,2,3-benzotriazole complexes were formed at different pH values and temperatures, and their structure and properties were studied. The SERS effect was registered and its explanation was given based on the differences in the structure of the synthesized complexes of BTA–Cu²⁺, Cu–BTA_ads adsorption films, and surface-associated Cu–BTA_surf structures. Quantum-chemical modeling of possible adsorption of Cu–BTA_ads and surface-associated Cu–BTA_surf structures was carried out using the DFT method, and a DFT calculation of their Raman spectra was performed. The geometries of surface structures have been established. Energy states of Cu–BTA_ads and Cu–BTA_surf structures were analyzed. It is shown that the predictions of DFT modeling successfully correlate with experimental results.

Magnesium and its alloys have gained significant prominence as promising biomaterials for healthcare applications due to their advantageous mechanical properties, notably their compatibility with bone tissue. Despite these advantages, their rapid rate of corrosion in physiological environments remains a substantial barrier, leading to the formation of hydrogen gas and elevation of pH levels that impede the process of tissue healing. Plasma electrolytic oxidation (PEO) has emerged as an effective surface treatment to improve the corrosion resistance of magnesium as it creates a protective oxide layer. Recent studies have revealed that the incorporation of hydroxyapatite (HA) and alumina (Al₂O₃) nanoparticles into PEO coatings significantly enhances the mechanical and electrochemical properties of magnesium alloys, improving biocompatibility, corrosion resistance, and surface hardness. This research aims to investigate and optimize the corrosion resistance and mechanical performance of a HA-Al₂O₃ composite coating on AZ31 magnesium alloy, with a focus on composition, morphology, adhesion, and corrosion resistance via advanced characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical testing. Preliminary results demonstrate significant improvements in surface hardness and corrosion resistance, highlighting the potential for this composite coating to enhance the longevity and performance of magnesium-based biomedical implants.

Salicylidene-p-toluidine (SPT) was evaluated in this work as a corrosion inhibitor for APl X70 carbon steel in an acidic setting at 25°C using 1M hydrochloric acid. The study was based on gravimetric analysis, electrochemical techniques and DFT (density functional theory) calculations using the 6-311G+(d,p) basis set carried out in both gas and aqueous phases. This method was employed to investigate the intrinsic properties of corrosion inhibitors and their adsorption mechanisms. The findings revealed that both the molecular structure and the concentration of the SPT, significantly affect the corrosion rate of steel. The highest value of 98.78% is reached by the inhibitory efficiency of SPT at 10^–2 M. Polarization curve shape suggests that SPT functions primarily as an anodic inhibitor.

Multielectrode arrays are a kind of systems which have multiple electrodes on their surfaces to record or stimulate electrical activities in biological cells or tissues. In these systems, the electrodes are typically made of gold, titanium, platinum, carbon-based materials or stainless steel (SS) etc. Among these materials, SS has corrosion resistance, conductive, ease of fabrication and low-cost properties. However, biological properties of SS remain to be improved for its use as an electrode in neuroengineering applications. To enhance its biocompatibility, cellular and tissue interactions, SS could be modified to fabricate nanofeatured topographies on their surfaces. In this study, 65 and 100 nm homogenous nanoporous structures were obtained on the 316L SS surfaces via anodization process. Results indicated that having nanoporous structures on the surfaces (T-65 and T-100) significantly increased surface area compared to NA sample. It was observed that the nanoporous 316L SS surfaces enhanced ~2-folds more glioblastoma proliferation at 5 days in vitro and ~4-folds more neurite extension for T-65 surfaces. Therefore, fabricating nanoporous structures can improve biocompatibility, bioactivity and cellular interactions of the 316L SS surfaces and can be developed as low-cost and widely available electrodes for neuroengineering applications.

A comparative study of the adsorption behavior of methane, ethane, propane and n-butane on the supermicroporous adsorbent ACW with a high micropore volume (1.44 cm³/g) and a wide distribution of pore sizes. The gas adsorption isotherms were measured by the volume–weight method at temperatures of 303, 313, 323, and 333 K in the pressure ranges of methane (0.1–40 MPa), ethane (0.01–3.8 MPa), propane (0.01–0.9 MPa), and n-butane (0.01–0.19 MPa). The IAST method was used to calculate the adsorption of binary mixtures CH₄/C₂H₆, CH₄/C₃H₈, and CH₄/H₁₀ with component contents of 98/2, 95/5, 92/8, and 90/10 mol %, respectively. The potential selectivity of the ACW adsorbent in adsorption gas separation processes was assessed for their further use.

Organic corrosion inhibitors based on heterocyclic compounds provide significant coverage of a metal surface and protect it from corrosion by adsorption. The adsorption of 4-amino-4H-1,2,4-triazole-3,5-dithiol (ATD) on the surface of low-carbon steel in a 1 M solution of sulfuric acid is studied by a set of physicochemical methods including polarization measurements, electric impedance spectroscopy, contact angle method, and optical microscopy. The redistribution of the components of free energy of the surface and its hydrophobization support the existence of a protective film of ATD. The calculation of the activation energy of the corrosion process based on polarization measurements shows a change in the character of adsorption with increasing temperature from mixed to chemical. It is found based on the data of electrochemical impedance spectroscopy and contact angles that multilayer filling occurs at a concentration of 100 mg/L. ATD predominantly inhibits the cathodic partial electrochemical reaction, forming adsorption layers on the energetically heterogeneous surface in accordance with the Redlich–Peterson isotherm model.

Complex polyester urethanes in multicomponent solvents were used as examples for demonstrating the wide possibilities for regulating the morphology of highly-polymeric condensation structures, which were prepared with the aid of diffusional enrichment of these solutions with a nonsolvent. Dynamic light scattering was used to determine the sizes and conformation of the solution elements that determine the diversity of the resulting structures. The obtained results provided the possibility to make the conclusions about the specific features of these structures. When multicomponent solvents are used, the uncertainty of both the compositions and properties of the released phases does not yet make it possible to determine their size via this method.