Protection of Metals and Physical Chemistry of Surfaces最新文献

The pseudo-first and pseudo-second order equations used to describe the kinetics of adsorption in solutions are considered. It is shown that they are mainly empirical approximating equations. Based on the mathematical analogy with adsorption isotherms, new expressions for approximating kinetic adsorption curves are proposed. Molecular kinetic analysis of monomolecular adsorption in solutions was performed. A new model of this process has been obtained, taking into account the influence of temperature, hydrodynamics, and other factors on its kinetics. As a consequence, the proposed model yields the Langmuir equation and a number of expressions that allow one to calculate the value of equilibrium adsorption, as well as to estimate the parameters of the adsorption process based on data on its kinetics. It is shown that the integral form of the pseudo-second order equation is also a consequence of the proposed molecular kinetic model. A comparison was made with experimental data on the kinetics of adsorption in solutions published in the literature.

A new catalytic system based on manganese phthalocyanine and nitrogen-doped carbon nanotubes (CNTNs) was synthesized and studied as a platinum-free electrocatalyst in the oxygen reduction reaction (ORR) in an alkaline medium. The synthesized MnPc/CNTN electrocatalyst showed high activity in the ORR both under model conditions using a rotating disk electrode and as part of an alkaline fuel cell (AFC) with a membrane-electrode assembly (MEA) with an anion-exchange membrane. Results obtained were compared with a commercial monoplatinum catalyst’s characteristics under the same conditions. The maximum power density values were 30 and 51 mW/cm² for an MEA with 60Pt/C and MnPc/CNTN, respectively. It has been shown that the MnPc/CNTN system under the operating conditions of an AFC with an MEA is characterized by a higher tolerance to toxic agents (including the ionomer) than the platinum catalyst, which is an important advantage of an MEA based on MnPc/CNTs.

The results of studies of the effect of metals on the physicochemical and physicomechanical properties of polyacrylates based on the analysis of the energy characteristics of the polymer are generalized. For this purpose, the effect of introduced into a polymer composition highly dispersed metal/metal-containing inorganic fillers on the relaxation behavior of the polymers is studied. An analysis of the properties of polyacrylates with different elasticities in the presence of a metal was performed based on the internal friction spectra and temperature–frequency dependences of the oscillatory process of a composite that are obtained using dynamic relaxation spectroscopy based on the determination of the temperature regions of materialization of the elastic properties of a composite at –150 to 100°C. The results of studies of the effect of metal powders of iron and zinc and zinc oxide on the physicochemical and physicomechanical properties of acrylic elastomers are presented and generalized versus an unfilled polymer.

Thin films of tungsten oxide were obtained by cathodic electrodeposition from an electrolyte based on sodium tungstate at a potential of –0.45 V versus an Ag/AgCl reference electrode. WO₃ photoanode film consists of a monoclinic modification (ε-WO₃) with a crystallite size of 10–12 nm. The electrocatalytic activity of WO₃ photoanode in reactions of photoelectrochemical oxidation of mono-, di-, and trihydric alcohols was studied. It was shown that the photoelectrocatalytic activity of WO₃ photoanodes is explained by an increase in the photoelectrooxidation rate symbatically with the number of alcohol adsorption sites.

Ti/CrN/TiN coatings were deposited by cathodic arc deposition at substrate bias voltages ranging from 20 to 60 V. The study examined the effect of bias voltage on the topography and the mechanical and corrosion properties of the coatings using laser and scanning electron microscopy, X-ray diffraction, nanohardness testing equipment and electrochemical testing. The results show that bias voltage significantly affects the morphology of Ti/CrN/TiN coatings. With an increase in bias voltage from 20 to 60 V, the concentration of macroscopic defects decreased significantly, and average surface roughness R_a, measured by the contact method, decreased from 0.227 to 0.179 μm per 4 mm of length. Nanoindentation showed that coatings deposited at a bias voltage of 60 V have maximum hardness and elastic modulus. Corrosion tests in 3.5 wt % NaCl solution showed that coatings deposited at 20- and 40-V bias voltages had better corrosion resistance than coatings deposited at 60 V, probably due to a denser microstructure acting as a barrier to the diffusion of aggressive substances.

Data on the effect of a metal substrate on the physicochemical and physicomechanical properties of polyacrylate coatings are generalized taking into account the energy characteristics of the metal and relaxation behavior of the polymer. An analysis of the properties of polyacrylates with different elasticities in the presence of a metal is based on the experimental data on the internal friction spectra and temperature–frequency dependences of the oscillatory process obtained using dynamic relaxation spectroscopy based on the determination of the temperature regions of materialization of the elastic properties of the polymer at from −150 to 100°C. To confirm the effect of the characteristics of the metal surface on the physicomechanical properties of the film-forming polymer, this paper generalizes the data of the works of the authors, in which the characteristic features of the occurrence of dissipative processes in film-forming latex polyacrylates localized on metal substrates of different chemical natures are analyzed taking into account their surface energy.

This paper presents the results of quantum-chemical modeling and experimental study of the optical properties of amphiphilic spironaphthoxazines in organic solvents. For the first time, a predictive model has been developed for calculating the spectral characteristics of photochromes of this class. It is shown that taking into account multiconfigurational interaction by the CASSCF method allows obtaining information about the complex nature of photo-induced electronic transitions in spironaphthoxazines.

This paper studies phenol sorption on VSK-400 and Norit GAC 1240W activated carbons obtained from various raw materials at different temperatures under static conditions. Sorption capacity for a number of inorganic substances is determined, indicating the number of functional acid and basic groups, and also giving a preliminary characteristic of the surface area of sorbents by the amount of adsorbed molecular iodine. Surface morphology of carbon particles from various raw materials is assessed using microphotographs obtained by scanning electron microscopy. When comparing the equilibrium characteristics in the studied concentration range, a greater ability to extract phenol for VSK-400 carbon is noted. At the same time, its sorption characteristics are not affected by temperature and the presence of mineral salt.

In this work, nine new binder compositions were synthesized based on a cycloaliphatic epoxy matrix (EP) modified with methylene diphenyl diisocyanate (MDI) and polydimethylsiloxane rubber (PDMS) with different ratios of components. The modification of the composition was confirmed by IR and NMR spectroscopy. A correlation was established between hardness, contact angle and coating composition based on binder data. Fillers such as muscovite mica and titanium dioxide were introduced into the composition of the developed binders to evaluate the physical and mechanical properties of the coatings. The influence of curing conditions (hardener, curing temperature) on the physical and mechanical properties of the coating was studied. The corrosion resistance of coatings was assessed using electrochemical methods. The weather resistance of the filled composition EP-10MDI-10PDMS was studied under humid tropical climate conditions. The coating composition is EP-10MDI-10PDMS with fillers (muscovite mica, ({text{Ti}}{{{text{O}}}_{2}})) previously synthesized biologically active substances ({text{Cu}}left( {{text{II}}} right)), ({text{Zn}}left( {{text{II}}} right),) and ({text{Co}}left( {{text{II}}} right)) complexes of tris(2-hydroxyethyl)amine (hydrometallatranes) were also introduced to enhance antifouling properties and their evaluation in the natural conditions of Nha Trang Bay (Dam Bai Bay).

The structure and properties of a nickel–boron coating with an immersion-deposited gold–cobalt film were studied. It has been shown that the application of a thin gold film (30–32 nm) protects the functional nickel–boron coating from oxidation during long-term storage under normal conditions and annealing for 1 h in an air atmosphere in the temperature range of 250–350°C. It has been established that, during annealing of the modified coating, no mutual diffusion of the elements of the substrate and coating occurs. X-ray structural analysis of the modified Ni–B coating showed that the diffraction patterns contain diffraction lines from gold, broadened lines from a solid solution of boron in nickel of the interstitial-substituted type. Low temperature annealing (250–300°C) the Ni–B coating modified with an Au–Co film leads to a decrease in the width of the diffraction lines of the matrix solid solution of boron in nickel, as well as to an increase in the values of its crystal lattice parameter and an increase in the microhardness of the coating to 850–890 HV 0.025. Annealing of the coating at 350°C leads to the release of nanosized particles of the nickel boride phase and is accompanied by a decrease in microhardness to 720–750 HV 0.025. It was concluded that the nickel–boron coating with a gold–cobalt protective film applied after annealing has increased microhardness (850–890 HV 0.025), high wear resistance under boundary friction conditions (linear wear intensity of the coating I_h = 1.6 × 10¹⁰ µm/m) and a low coefficient of friction (f = 0.15), which makes Ni–B/Au–Co coatings comparable in their tribotechnical characteristics to chromium coatings. Modified Ni–B/Au–Co coatings retain the ability to be soldered using low-temperature solder and non-active alcohol–rosin flux, and also have low contact electrical resistance after long-term storage.