Solid State Phenomena Vol. 380

Abstract: This study investigates the combined effects of Alumina/SiC hybrid nanoreinforcements and surface pre-treatment on the mechanical strength of adhesive joints. A two-component epoxy adhesive was reinforced with 1.0 wt% Alumina/SiC nanoparticles at ratios of 10:0, 7:3, 5:5, 3:7, and 0:10 to bond aluminum alloy substrates. The adherends were pre-treated with P320 and P3000 sandpapers to generate distinct surface roughness profiles. Joint performance was strongly influenced by the interaction between nanoparticle ratio and surface roughness, reflecting the complex mechanisms governing bonding strength. To quantify these effects, Pearson correlation and heatmap analyses were employed, enabling assessment of the relationships between experimental variables and joint properties. The optimal configuration was identified as a 5:5 Alumina/SiC ratio with a surface roughness of Ra = 0.18 ± 0.01 µm, which achieved the highest bonding strength, showing a 47.0% improvement over pristine adhesive. At the same roughness, this hybrid also outperformed single-nanofiller systems, with shear strength gains of 25.7% over Alumina (10:0) and 11.8% over SiC (0:10). Pearson analyses effectively captured these trends, providing a comprehensive evaluation of variable interdependencies and quantitatively highlighting the influence of nanoparticle composition and surface pre-treatment on adhesive joint performance.

Abstract: Ni and Ni-containing nanoparticles exhibit promising magnetic properties. In a preliminary experiment, these nanoparticles aggregated after synthesis. Because nanoparticle aggregation may degrade their unique properties, a method to prevent their aggregation is required. In this study, Ni-Pt nanoparticles were synthesized and coated with silica to suppress aggregation. A colloidal solution of Ni-Pt nanoparticles was synthesized in water exposed to air using nickel(II) acetate tetrahydrate (Ni source), hexachloroplatinate(IV) hexahydrate (Pt source), sodium borohydride (reducing agent), and citric acid (stabilizer). Silica-coated Ni-Pt nanoparticles (Ni-Pt/SiO₂) were synthesized by adding a tetraethylorthosilicate (TEOS)/ethanol solution to the colloidal Ni-Pt nanoparticle solution. The morphology of the Ni-Pt nanoparticles varied with reaction time. The Ni-Pt/SiO₂ nanoparticles consisted of Ni-Pt cores and SiO₂ shells, with their morphology dependent on the TEOS concentration. Furthermore, the Ni-Pt/SiO₂ nanoparticles were more dispersed than the uncoated Ni-Pt nanoparticles, suggesting that the silica coating suppressed aggregation.

Abstract: Ni₈₀Fe₂₀ thin films have been manufactured onto monocrystalline silicon substrates, utilizing a physical vapor evaporation technique under vacuum. The thickness of these Permalloy films fluctuates between 16 and 45 nm. The structure and morphology of the Permalloy film are studied as a function of the thickness of the deposited magnetic layer. Rutherford’s backscattering spectroscopy technique was used to quantify the samples. X-ray diffraction method has been used to examine the structure, and the atomic force microscope scrutinizes the surface topography and performs the film roughness. These techniques allowed to infer that all the films crystallize in the face-centered cubic structure and exhibit <111> preferred orientation. The size of the crystallites is directly proportional to the thickness of the magnetic layer. The films are under stress and the lattice parameter increases with thickness. The 45 nm thickest film exhibits the roughest topographic surface with root mean square roughness near 2.4 nm, while the 16 nm thinnest film exhibits the smoothest topographic surface, not exceeding 3 Å. These results, and others, will certainly contribute to a better understanding of the physical properties of Permalloy material, and improve their technological applications

Abstract: The 8-inch silicon carbide crystals prepared by physical vapor transport (PVT) offer a low-cost pathway for chip production, significantly enhancing the economies of scale. However, point defects， such as vacancies, interstitial atoms, and dislocated atoms produced by the temperature gradient mismatch and the fluctuation of the C/Si ratio during the growth process, seriously affect the residual stresses and the crystalline quality of the crystals. Using stress birefringence optical path difference and X-ray diffraction rocking curve detection methods, we characterized crystals annealed at different temperature. It is well-known that the residual stress of the wafer exhibits an uneven distribution, with the residual stress at the edge of the wafer significantly higher than that at the center. When the post-growth annealing temperature is below 2000°C, the residual stress of the crystal decreases rapidly due to the annihilation and transformation of point defects. However, when the temperature is increased further to 2200°C, a large number of irreparable and large-sized point defect clusters form, which severely degrade the crystalline quality of the crystal, induces lattice distortion, and lead to the generation of residual stress. Overall, the best residual stress relief is achieved at a post-growth annealing temperature of 2000°C.

Abstract: In this paper, the problem of sheath is investigated using the fluid model in a magnetized four-component dusty plasma system comprising positive ions, variable charge of the dust grains and two species of electron populations with two different temperatures, low temperature electrons (LTEs) and high temperature electrons (HTEs). Both electrons are assumed to be a sum of two superthermal electrons which are related at superextensive electrons distribution. The effects of temperature ratio of HTE to LTE superextensive electrons on the plasma sheath parameters are studied numerically. A significant modification is observed in the quantities characterizing the sheath as sheath thickness, sheath potential and dust velocity in the presence of the two groups of superthermal electrons.

Abstract: This work investigates the radiation pattern of a 5 GHz antenna composed of a metal dipole antenna and surrounded by fluorescent tubes which act as reflectors (plasma medium). The study emphasizes the role of plasma reflectors in improving the antenna’s efficiency by controlling the radiation pattern. The electrical parameters of the plasma medium are modeled by Drude model in Comsol Multyphysics for different voltage discharges. Also, a CST software is used to simulate metallic dipole antenna reconfigurability. The results show that the plasma can be used as a good reflector when its permittivity is negative () and . Moreover, it is shown that with increasing the discharge voltage, the plasma reflectivity increases, this is because the gain increases and the directivity of the antenna considerably changes. Keywords: Reflector, Plasma, COMSOL, CST, Gain, Directivity.

Abstract: In this paper, we have developed a numerical model of a magnetized plasma sheath comprising positive ions, electrons and neutral particles. The electrons are considered, following a non-extensive distribution based on Tsallis statistics, while the ions are described using a fluid approach taking into account the ion source term. Using the Sagdeev potential method, the sheath formation criterion was established. Also, the floating electric potential was determined. The obtained results show a significant effect of ionization frequency and magnetic field orientation on the modified Bohm velocity as well as the floating electric potential. It is also shown that the floating potential is considerably affected by the super extensive electrons (q<1).

Abstract: The article presents a calculation method developed for assessing the strength characteristics of building structures constructed using 3D printing technology. The method takes into account the physical and mechanical properties of the material, including modulus of deformation, creep, and compressive strength. A comparative analysis between traditional brick masonry and 3D-printed sand concrete walls of the M300 grade demonstrated the higher load-bearing capacity of additive structures. The study also identifies the limitations of the proposed method when applied to wall fragments with complex geometries and highlights the lack of specialized standards in Ukraine. Particular attention is drawn to the need for adapting regulatory documents to account for the anisotropy of the material and the 10–30 % reduction in interlayer strength. Overall, the results confirm the promising potential of 3D printing for the rapid reconstruction of buildings and emphasize the importance of ensuring the safety and durability of such structures.

Abstract: A variant of the mathematical theory of deformation of multilayer nonlinearly elastic (according to Kauderer) plates of arbitrary constant thickness with non-symmetric structure in thickness has been constructed. The transverse load on the horizontal faces can be arbitrary static. The components of the stress-strain state (SSS) and the boundary conditions on the lateral surface are functions of three spatial coordinates. Spatial boundary value problems for multilayer plates are reduced to two-dimensional using three-dimensional equations of the theory of elasticity, the Reissner variational principle, and the expansion of the components of the SSS into infinite mathematical series by combinations of Legendre polynomials within each layer. This approach differs significantly from the approaches of other authors. The main dependencies, boundary conditions and systems of equilibrium differential equations with high-order partial derivatives with respect to the displacement components are derived. All dependencies and equations contain nonlinear terms. The new methodology for constructing a variant of the nonlinear theory makes it possible to accurately satisfy the boundary conditions on the horizontal faces of the plate and on the lateral surface, and to accurately satisfy the conditions of rigid conjugation of adjacent layers. The system of equilibrium equations has a high order. An analytical method for solving these systems is proposed and developed. The method is based on algebraic, differential and operator transformations of the initial systems. They are reduced to two convenient defining systems: one describes the vortex edge effect with a refinement of the SSS, and the other describes a refined internal SSS with a potential edge effect. The order of the systems of differential equations does not depend on the number of layers, but depends only on the number of retained terms in the mathematical seriess. The internal SSS is separated from the potential edge effect. By the method of order reduction, the determining systems are reduced to second-order differential equations. This significantly simplifies the solution of boundary value problems. General solutions for all components of the SSS were found through general solutions of second-order differential equations. For plates with non-symmetric structure, the equations of skew-symmetric and symmetric deformation are interconnected, unlike plates with a symmetric structure. Numerical results are presented for a two-layer linearly elastic plate under cylindrical bending.