Protection of Metals and Physical Chemistry of Surfaces最新文献

The method of stability control is considered of ZrBDC, LaBTC, Cu₃(BTC)₂, and Basolite Z205 (BASF) metal–organic framework (MOF) structures exposed to solvent vapors of acetone and water. The principle of microweighing on quartz-crystal resonators of longitudinal oscillations is proposed as a control tool. It is shown that, based on changes in the resonant frequency and dynamic resistance of the resonator, it is possible not only to monitor changes in the stability of the MOF in real time, but also to record the concentration of the solvent at which the destruction of the structure framework begins to occur. The use of the method found ZrBDC and Cu₃(BTC)₂ to be resistant to acetone and water vapor for long periods of time and over a wide range of solvent concentrations, while LaBTC and Basolite Z205, while resistant to one solvent, were not resistant to the other: Basolite Z205 began to degrade after 37 h in acetone vapor at a volume concentration of 0.9%, and LaBTC after 7 h in water vapor with a relative humidity of 7%.

Composite electrochemical coatings (CECs) based on nickel modified with multilayer graphene oxide (GO) are obtained in a steady-state electrolysis mode from a sulfate–chloride electrolyte. The microstructure of these CECs is studied by X-ray diffraction analysis and scanning electron microscopy. It is found that the microhardness of nickel–GO CECs increases approximately 1.20-fold in comparison with nickel without a disperse phase. The corrosion electrochemical behavior of the nickel–GO composite coatings in a 0.5M solution of H₂SO₄ is studied. Tests in a 3% solution of NaCl show that including GO particles into the composition of electrolytic deposits of nickel results in a 1.45- to 1.50-fold increase in their corrosion resistance.

The effect of temperature and composition of inhibitor compositions based on aqueous extracts of aspen bark (EXA), spruce (EXS), and pine (EXP) on the corrosion of St3 carbon steel in 2M sulfuric acid, used for etching steel products, and 10X18N10T(10Cr18Ni10Ti) austenitic steel in 1.4 M hydrochloric acid, used with the addition of an inhibitor for washing and chemical cleaning of cooking and heat exchange equipment, was studied for the first time using gravimetric and electrochemical methods. New data on the kinetics and mechanism of acid corrosion of the studied steels were obtained and analyzed. It has been shown that with the same content of 1 g/L inhibitory action Z water-extractive substances (WESs) of tree bark on acid corrosion of steels increases in the series EXP < EXS < EXA, as well as with an increase in the concentration of WES to 4.0 g/L and temperatures from 20 to 60°C, when mixing bark extracts of different species and even more significantly (Z = 90–97%) when hexamethylenetetramine or potassium iodide synergists are introduced into aqueous extracts¹.

In the present study, the changes in microstructure, thermal conductivity (K), melting properties and microhardness (HV) adding of 0.05 wt % Al, Ag and Sb into Zn–5Sn–2Cu–1.5Bi (ZSCB) high temperature solder alloy were investigated. The addition of trace amounts of Al, Ag and Sb caused a significant improvement in K and HV values. Addition of 0.05 wt % of Al and Ag into the ZSCB alloy increased the K and HV values by 62% and in the range of 19–21%, respectively. The addition of 0.05 wt % of Sb increased the K and HV values by 32 and 36%, respectively.

Magnesium alloys have garnered significant gained attention in the scientific community due to their low density, superior damping capacity, impressive strength-to-weight ratio, and recyclability. The biocompatible Mg alloys attracted the researchers to use them as permanent implants in the body. But Mg alloys were positioned low in the electromotive series, have a high affinity for corrosion, and will be degraded in the presence of corrosive anions. Surface modification methods could be adopted to protect the Mg surface from corrosive environments. Among various surface treatment processes, plasma electrolytic oxidation (PEO) process is environmentally friendly for providing a robust anti-corrosion and wear-resistant coating on the Mg alloys. Presence of the pores and cracks on the PEO surfaces reduced the corrosion and wear resistance of the alloys. Surface morphology, corrosion and wear characteristics of the PEO-coated Mg surfaces can be improved by various composite coatings. The mechanisms of corrosion inhibition, wear characteristics, wetting characteristics, biofunctionality and finally the degradation of various composite coatings over Mg‑PEO surfaces in the presence of corrosive environments are elaborated in this review paper.

A molecular analysis of two-phase distributions within slit-shaped and cylindrical pores with homogeneous walls has been conducted across a wide range of pressures and temperatures, where both liquid and vapor phases coexist. The pore walls are assumed to be nondeformable, acting as an external field for the fluid. The equilibrium states of both phases—“liquid in pore” and “vapor in pore”—satisfy the equality of their chemical potentials with that of the bulk phase and with each other. Molecular distributions were calculated using the lattice gas model (LGM) with a simplified nearest-neighbor pairwise interaction potential. The distribution of molecular density within the inhomogeneous field of the pore walls is associated with two types of pressure: isothermal pressure, linked to the system’s chemical potential, and internal mechanical pressure (or expansion pressure in LGM terminology). The difference between each of these pressures and the corresponding pressure in the bulk phase defines the disjoining pressure. This parameter is widely employed in the thermodynamic interpretation of thin film properties as a function of film thickness. The theory accounts for the effects of the adsorbent–adsorbate interaction potential and its range, deviations in pore geometry from the ideal slit-shaped form, and temperature on the values of disjoining pressure. The molecular theory based on the LGM framework provides a thermodynamic analysis of disjoining pressure as a characteristic of confined systems, distinguishing them from macroscopic systems. It is demonstrated that the concept of disjoining pressure in two-phase systems can be extended to all fluid densities, ranging from vapor to liquid, and to any pore geometry.

We present on the elaboration and characterization of p-type Mn₃O₄ thin film grown on ITO substrate, using spray pyrolysis as a low cost growth method. The structural, surface and optical properties of Mn₃O₄/ITO heterostructure were studied by using (XRD) X-ray diffraction, atomic force microscopy techniques and ultraviolet–visible-near infrared spectrophotometer. It turned out that the optical characteristics of this heterostructure exhibits an improved transmittance in the blue-green spectral range. Moreover, we found that the average grain size for hausmannite films deposited on ITO is equal to 220 nm. The I–V curve of p-Mn₃O₄/ITO thin film revealed a linear behavior, which can be positively used for optoelectronic devices.

This paper presents the development of a composite sorbent based on cellulose and carbon nanotubes and its sorption properties towards Cu(II) ions. Carbon nanotubes were sequentially modified with concentrated sulfuric acid, thionyl chloride, and ethylenediamine, and subsequently attached to cellulose pretreated with citric acid. The formation of new functional groups on the surface of the composite cellulose sorbent was confirmed through FTIR spectroscopy. Scanning electron microscopy revealed differences in the surface structure of cellulose-based sorbents before and after modification. The kinetics and equilibrium of Cu(II) ion sorption were investigated in a heterogeneous “aqueous solution–modified sorbent” system. The kinetic data were more accurately described using the pseudo-second-order kinetic model. Analysis of sorption isotherms using the Langmuir equation allowed determination of the maximum sorption capacity of the original sorbent and its composite derivative. It was found that the sorption capacity of the composite sorbent is approximately six times greater than that of unmodified cellulose.

Self-cleaning materials performed a vital function in our daily lives, but there remained some critical challenges such as complex fabrications, non-transparency, and poor long-term stability, which limited their applications. In this paper, ST-402 reagent was used to construct roughness on the surface of the slide, then low surface energy materials (HDTMS, POTS) were uniformly sprayed. And finally a layer of QX-18 fluorocarbon nano coating was deposited on the surface of the coating to obtain an interface with excellent wear-resistant and hydrophobic properties. The surface micromorphology and elements of the treated interface, contact angle to water, wear resistance, acid and alkali resistance stability, and self-cleaning performance of dirt were characterized. The results showed that the hydrophobic effect of the coating prepared by using POTS as modifier was better. The hydrophobic coating had good wear resistance, transparency, self-cleaning and acid resistance, but poor alkaline resistance.

In this paper, we studied the influence of alumina particles addition, 5, 10, and 15 wt %, on the microstructure after elaboration of Al–Al₂O₃ MMC composite, morphology and kinetic of corrosion, hardness, texture evolution of aluminum matrix. The results show distribution of alumina particles in shape of petal-like phase in some zones , in form of flack in another region for sample with 5% addition alumina, and in mixture between truncated petal-like phase and flake form particles for the sample with 10% addition of alumina, of flake in zone 1 one and a mixture of petal-like phase and flake in zone 2 for the sample with 15% addition of Al₂O₃, the samples with 5 and 10% Al₂O₃ were undergo generalized corrosion almost in the all surfaces, but for the sample with 15% addition of was undergo the corrosion which don’t tends to generalized corrosion. The corrosion resistance increase when the Al₂O₃ addition increases. The texture of aluminum changes slightly when the alumina powders are added to aluminum. The hardness change when alumina powders are added to aluminum.