2026-03-29
Zh.B. Sagdoldina, L.G. Sulyubaeva, D.B. Buitkenov, A.B. Nabioldina, S.D. Bolatov, D.K. Sarzhanov
The article presents the results of research into the structure and tribological testing of WC-Co detonation coatings with a barrel filling volume of 64 % and 74 %. X-ray diffraction analysis of the WC-Co coating re vealed that undesirable Co and W2C peaks disappear after detonation spraying. Morphological analysis showed that with 64 % and 74 % detonation barrel filling, the coatings had a dense structure with a thickness of 136 μm and 161 μm, respectively. EDS mapping showed a uniform distribution of elements. Tribological tests of the coating revealed that the friction coefficient of the samples ranged from 0.48 to 0.53 for 74 % and 0.55–0.57 for 64 %. Based on the results obtained, the optimal technological regime for obtaining wear resistant WC-Co coatings by detonation spraying was established.
2026-03-29
V.N. Kossov, S.A. Krasikov, M.K. Asembaeva, E. Meirambekuly
Isothermal diffusion and convective mixing in a ternary He–Ar–N2 mixture at varying pressures and initial compositions were examined experimentally by means of the two-flask method. The study was conducted under strictly controlled laboratory conditions to ensure precise, comparable, and reproducible results across all experiments. It was found that when the density decreases with height, the mechanical equilibrium of the mixture can be disturbed, causing gravitational flows and partial convection within the system. Anomalous transfer of the component with the greatest molecular mass was detected at particular pressures and starting compositions, pointing to the influence of supplementary convective processes beyond ordinary diffusion. When the experimental results were plotted in the phase space of the three variables — pressure, initial com position, and diffused component concentration — a pronounced wave-like iso-concentration surface emerged. This surface appeared in regions corresponding to well-developed convective flows. Its formation correlated with the highest intensity of partial component mixing, highlighting the combined influence of pressure, composition, and gravitational effects on the mixture’s dynamic equilibrium. These findings provide insight into the interplay between diffusion and convection in multicomponent gas systems, revealing condi tions under which gravitationally induced flows significantly alter component transport and overall mixture behavior.
2026-03-29
Sh. Afroze, A.M. Kabyshev, A.A. Aimakhanova, M.S. Reza, M.S. Islam, K.A. Kuterbekov, A.K. Azad
In this study, a novel perovskite-type oxide SrFe0.6Cu0.3Mo0.1O3–δ was synthesized via a conventional solid state reaction route and comprehensively characterized using neutron powder diffraction (NPD), scanning electron microscopy (SEM), and thermal analysis. The application of NPD enabled precise determination of the atomic structure and differentiation between cations with similar atomic numbers. Rietveld refinement of the NPD data confirmed the formation of a single-phase cubic perovskite with the space group Pm-3m (no. 221) and a lattice parameter of a = b = c = 3.8997(1) Å. SEM images revealed a highly porous, intercon nected microstructure with uniform elemental distribution, while thermogravimetric analysis (TGA) demon strated a two-step oxygen loss up to 1000 °C, confirming excellent thermal stability. The oxide exhibited a low thermal conductivity of 1.986 W·m–1·K–1 at 900 °C, attributed to enhanced phonon scattering induced by Cu and Mo co-doping and lattice disorder. These findings indicate that controlled B-site co-doping can effec tively tailor defect chemistry and phonon transport, resulting in materials with reduced thermal conductivity and improved structural integrity. Therefore, SrFe0.6Cu0.3Mo0.1O3–δ shows great potential for high-temperature energy conversion applications, including thermoelectric devices and solid oxide fuel cells.