Highly dispersed, fluorite-like solid solutions (Ce0.80Zr0.10La0.05M0.05O2-delta ), where M = Nd, Sm or Gd, were synthesized by co-precipitating metal hydroxides, followed by heat treatment. The chemical composition of the resulting materials was confirmed by inductively coupled plasma optical emission spectroscopy. X-ray phase analysis confirmed the formation of the Ce0.80Zr0.10La0.05M0.05O2-delta -s solid solutions, where M = Nd, Sm or Gd, based on the cerium dioxide crystal lattice. According to transmission electron microscopy data, the average particle size is 13 +/- 2 nm. The synthesised materials have a mesoporous structure with a specific surface area of 83-86 m(2)/g, a total pore volume of 0.101-0.104 cm(3)/g and a pore diameter of 3.6-3.8 nm. The catalysts exhibit high activity in the complete oxidation of methane (model mixture composition: CH4-1 vol.%; O-2-8 vol.%; N-2-balance). A correlation has been established between the catalytic activity of solid solutions and the ionic radius of the rare earth dopant M. The activity of synthesised solid solutions (Ce0.80Zr0.10La0.05M0.05O2-delta ), where M = Nd, Sm or Gd, decreases in the order Gd-> Sm-> Nd. The highest activity is observed in the presence of the Ce(0.80)Zr(0.10)La(0.05)M(0.05)O(2-delta )2-s catalyst, which has the smallest ionic radius of the M(3+ )dopants studied. The temperatures at which 50% and 99% conversion are achieved in the presence of the sample are 356 degrees C and 477 degrees C, respectively. The application of Ce0.80Zr0.10La0.05M0.05O2-delta -s as a carrier for the active component, palladium, shows promise. The catalytic activity of 0.3% PdO/Ce0.80Zr0.10La0.05M0.05O2-delta -s exceeds that of the industrial analogue, 0.3% PdO/y-Al2O3, demonstrating the feasibility of using the synthesized solid solution as a carrier for the active component.
The results of a study on a suspension containing industrial oil I-20A and copper nanopowder at concentrations of 0.05, 0.1, 0.2, 0.3 and 0.5 (wt.%) are presented in the paper. The work simulated a mode of insufficient lubrication in the friction zone - 0.1 ml of lubricant was added to the friction zone and the lubricant was not renewed throughout the experiment. The tests were carried out on a friction machine SRV-3 at a load of 200 N, an amplitude of 3 mm and a frequency of 5 Hz. The addition of 0.1% by weight copper nanoparticles to industrial oil showed the best results in reducing the coefficient of friction and wear compared to the base oil. The mechanism is explained by the deposition of small copper particles in the wear area and the improvement of tribological characteristics, this is confirmed by the analysis of wear surfaces on a scanning electron microscope. At concentrations above 0.1%, particle aggregation occurs and, as a result, abrasive wear increases. At copper concentrations less than 0.1%, only partial film formation occurs, and the uneven distribution of particles does not provide any advantages over the base oil. Copper nanoparticles are a promising material for improving the lubricating properties of oils and restoring surfaces. Their use allows you to reduce friction, reduce wear and extend the service life of mechanisms. However, for widespread adoption, issues of aggregation and cost need to be addressed, and further research into long-term effects needs to be conducted.
By varying the concentration of reinforcing phase particles and the technological parameters of the method for producing functional composite coatings, it is possible to influence their structural state and, consequently, their performance characteristics. This article analyzes the dependencies of the structural parameters of the Inconel 625/WC composite coating, manufactured by laser cladding, on the amount of reinforcing carbide phase and the cladding mode. X-ray phase analysis in the coatings revealed phases present in the initial powders-nickel solid solution and carbides WC and W2C, as well as carbides formed during laser cladding: r11(Ni3Mo3C), (W,Cr)2C, and MoNbC2. It was established that the microhardness of the composite coating matrix primarily depends on the amount of r11-phase in it, which increases with an increase in the initial concentration of carbide and the specific power of the laser radiation. Scanning electron microscopy and X-ray microspectral analysis were used to reveal the structural components and their composition. The structure includes initial spherical tungsten carbide particles containing only W and C, surrounded by a "halo" enriched with W, C, and strong carbide-forming elements of the matrix - Mo and Nb, dendrites with increased concentrations of Ni and Fe, and interdendritic space enriched with Mo, Nb, and W. It is shown that the lattice parameter of the nickel solid solution depends non-monotonically on the amount of reinforcing phase in the coating: up to 30% tungsten carbide, the lattice parameter increases with the concentration of carbide, while higher concentrations show the opposite effect.
This paper presents the results of using synchrotron radiation to study the circumferential and layer-by-layer inhomogeneity of zirconium alloy tubes. Reducing the size of the initial synchrotron beam to 200x200 mu m allows us to analyze the layer-by-layer inhomogeneity of tubes with a wall thickness of 600 mu m and above. Based on the results of the analysis of the circumferential inhomogeneity of the cladding tubes and guide channels for the integral texture f-parameters, the error value was 0.04, which is twice as high as the error when using the standard X-ray method. The maximum error in integral texture f-parameters is achieved for recrystallized samples, i.e. when the number of grains from which the diffraction pattern is formed decreases. The division of Debye rings into individual reflections also leads to a reduction of the statistical significance of the data obtained and an increase in the error in processing the diffraction patterns. Layer-by-layer analysis of the studied cold-rolled and annealed tubes made it possible to identify the features of plastic deformation of the tubes.
The technology of oxygen blowing of pre-hydrogenated aluminum alloy melt allows to obtain a composite material in situ, saturated with submicroscopic Al2O3 particles. The key factor of the technology is the presence of iron in the melt, which negatively affects the strength of the oxide film, which allows to obtain isotropic particles of aluminum oxide, and not extended films. Until now, the technology was used only for cast products based on silumin AlSi7Fe. It is proposed to use an Al-Fe alloy with an iron content above 1.5% for obtaining a composite for cold rolling technology. The alloy is also saturated with titanium due to the introduction of TiH2 for hydrogenation. As a result, a butterfly-shaped structure is formed in the metal, presumably by the following mechanism: the butterfly body is an Al3Ti intermetallic compound, which precipitates in the melt first and collects oxide particles and iron-containing intermetallic compounds. The composite demonstrates grinding of iron intermetallic compounds at least 3 times relative to the original alloy. The content of the oxide component is 8 times lower than on the initial alloy of the AlSi7Fe system due to a significantly smaller thickness of the oxide film. This leads to a significant reduction in the blowing time, the total duration of melt processing, including hydrogen saturation, was 15 min. The samples were subjected to cold rolling, the foil thickness achieved was 19 mu m. The obtained rolled product with a thickness of about 150 mu m exceeds the original alloy in mechanical properties (6u-269 MPa against 174 MPa of the original alloy), and the hot-rolled AlSi7Fe-Al2O3p composite (6u-250 MPa).
