Key Engineering Materials Vol. 1062

Abstract: MXenes are 2D carbides and nitrides of transition metals whose layers are kept by van derWaals forces. These materials are generally metallic and easily intercalate several types ofmolecules and ions, so that they are studied for various types of applications, from energystorage to corrosion resistance. We measured the dynamic Young’s modulus of self-standingfilms of Ti3C2Tx with the free flexural resonance and with the DMA, finding evidence of a previouslyunnoticed phase transition at T_C = 350 K. In a previous paper it is argued that the transition should be related to the onset of sliding ferroelectricity. This is a new type of ferroelectricity known in bilayers of graphene, BN and few chalcogenides, with which ultrafast andstable ferroelectric memories have already been realized. If confirmed, Ti₃C₂T_x would the firstMXene exhibiting sliding ferroelctricity and metallic conduction. The present work is focusedon the effect of the intercalatation of molecules, mainly water, in the intralayer space. Theinterlayer nature of the transition at 350 K is demonstrated by suppressing it through intercalationof H2O. Preliminary results are also presented on composite Ti₃C₂Cl₂-KBr, where giantsoftening upon heating up to 800 K and a final stabilization with elastic anomalies around250 K might be due to intercalation of K and its subsequent ordering/disordering. This mightopen new perspectives in the study of the behaviour of intercalated ions in electrodes forsupercapacitors and batteries.

Abstract: Young’s modulus and internal friction of bulk GaN single crystal samples were measured as a function of temperature in 100 K to 700 K range. The internal friction strongly depends on sample dimensions and measurement frequency (3 – 10 kHz). The experimental values are compared to the theoretical model for thermoelastic damping. The model and the experimental data match very well in the whole temperature range and for different frequencies indicating that the thermoelastic damping is the main energy dissipation mechanism.

Abstract: Metal dopants are commonly used to improve the transport properties of semiconducting iron silicide (β-FeSi₂). However, the formation of metallic phases is sensitive to the addition of dopants, especially when they reach their solubility limits. Those secondary phases negatively impact on the transport properties of the materials. In this study, the strategy to investigate the metal solubility in β-FeSi₂ matrix based on crystal structure transition, phase fraction, and microstructural evolution was established. The X-ray diffraction results show that the peak intensity of the metallic phases (ε-FeSi and α-Fe₂Si₅) increases with increasing doping level. For Mn-doped β-Fe_1−xMn_xSi₂, phase fraction analysis shows that the semiconducting β phase remains the dominant phase (>95%) up to x = 0.08, whereas metallic phases become dominant for x > 0.08. Although the β-phase persists up to x = 0.08, local compositional analysis reveals that the solubility of Mn within the β-phase decreases with increasing formation of secondary phases. The local elemental distribution analysis shows that Mn and Co, respectively, have a solid solution limit of ~6.3±0.1 % and ~8.8±0.7 % in β-FeSi₂. It is found that Mn and Co have higher solubility than Ni. Our study provides insights into the strategy to probe the solubility of dopants, which could be beneficial for performance enhancement in semiconducting iron silicide systems.

Abstract: This work aims to investigate efficient ZnO-NiO (zinc oxide-nickel oxide) nanocomposite/nanocrystalline silicon µc-Si solar cells. The µc-Si film was fabricated by annealing hydrogenated amorphous silicon α-Si: H deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD), and the nanocomposite ZnO-NiO thin film was manufactured using the sol-gel spin coating technique. The experimental study highlights the physical properties of the device’s thin films. The enhancement of structural properties is confirmed by Raman spectroscopy. The crystalline fraction is estimated to be 60% for µc-Si. The XRD results show sharp peaks for ZnO-NiO and µc-Si, indicating good crystallinity, which is crucial for solar cell efficiency. The association of µc-Si/ZnO-NiO considerably enhances the optical properties, reducing the reflectivity to 5% when compared with the amorphous silicon/ZnO-NiO association. The conductivity is also improved from 50 to 1 (Ω cm)^-1. The solar cell is then theoretically investigated using the Solar Cell Capacitance Simulator (SCAPS-1D). The parameters used in the simulation, including the effective density of states, electron and hole mobilities, and the band gap energy, and their impact on device performance were analyzed. The amorphous silicon/ZnO-NiO device was also theoretically investigated for comparison purposes. The simulated nanocrystalline solar cell displayed a theoretical efficiency of 28% using SCAPS-1D, an open-circuit voltage (Voc) of 0.8 V, and a short-circuit current density (Jsc) of 42 mA/cm². The theoretical electrochemical study reveals improved charge transport and a high effective lifetime, in agreement with the high-power conversion efficiency. The simulation of external quantum efficiency yields good results in the UV-vis-NIR range, surpassing those of the amorphous silicon/ZnO-NiO solar cell, particularly for wavelengths exceeding 600 nm. The SCAPS-1D investigation significantly reduces manufacturing costs and energy losses by optimizing the solar cell design and validates these results with theoretical findings that highlight the potential of this solar cell as a highly efficient and cost-effective device.

Abstract: Sloshing, characterized by free-surface wave formation in partially filled tanks under forced excitation, remains a major challenge in aerospace engineering, particularly for propellant tanks in launch vehicles. Laboratory studies have demonstrated that a granular layer placed at the liquid surface can significantly attenuate sloshing waves, provided that the granular medium remains compact. However, the performance of this mitigation strategy under real flight conditions has yet to be assessed. In this work, we investigate sloshing mitigation using a granular surface layer through an in-flight experiment conducted aboard a supersonic sounding rocket. The results show that granular surface damping is effective under realistic launch conditions as long as sufficient apparent gravity preserves the cohesion of the granular layer. Conversely, under near-microgravity conditions, loss of granular compactness leads to a breakdown of the damping mechanism. These findings indicate that granular-based sloshing mitigation is well suited for first-stage launch vehicles and sounding rockets, but is unlikely to remain effective during extended microgravity phases.

Abstract: In social housing are commonly used panels made with wood particles like partitioning walls, because of its low cost and ease of assembly, dry way. One problem with these panels is their low acoustic insulation. In the Experimental Economical Housing Center of Cordoba, Argentina, a research team has developed panels for housing made from recycled plastics and polyester resin, more ecological than the traditional ones made with wood particles, and with technical advantages. They are manufactured with recycled various plastics from food, perfumery or cleaning packaging, waste production from factories due to failures in sheet thickness or ink application. These panels contribute to the environmental decontamination, because they are made from plastic residues. Most of this waste is buried, accumulated or burned in municipal garbage dumps without any use, causing environmental degradation. The technical advantages of these panels are that they have higher acoustic insulation than conventional panels made with wood chips or fibers. They are also water resistant, and they have higher flexural resistance. This paper presents the study about the acoustic insulation property of this panel, comparatively with other conventional panels made with wood particles. Besides, different designs of multilayer panels for housing enclosures are presented, with steel frame structure, and the corresponding Sound Reduction Index of each alternative was calculated. The results were compared with the regulations in force in our country (IRAM Standard 4044 - 2014) regarding acoustic requirements, to verify its compliance.

Abstract: Using Eulerian coordinates to describe solid lattice deformations, it has been shown that the set of equations known as Maxwell’s equations—typically applied to electromagnetic phenomena in vacuum or matter—can also describe the elastic, anelastic, and plastic deformations of isotropic solid lattices containing topological defects such as dislocations and disclinations, under conditions of constant and homogeneous expansion. The analogy between the two physical systems is complete: it extends beyond one of the two Maxwell equation pairs in vacuum to both pairs, and includes analogues to dielectric polarization, magnetization, electric charges, and currents. In the Eulerian approach, Maxwell’s equations emerge as a special case derived from a tensor theory of lattice deformation, reducible to a vector formulation only for constant and homogeneous expansion. When dynamic and non-homogeneous expansions are considered, the tensorial nature of the theory becomes essential. This generalization naturally leads to a new conceptual framework for the Universe based on the existence of a crystalline ether. This framework offers a simple, unified, and coherent description of all major theories of modern physics—including electromagnetism, relativity, gravitation, quantum physics, cosmology, and the Standard Model of particle physics.

Abstract: We investigate the dynamics of full skyrmions in chiral liquid crystals using an Eulerian formalism originally developed for topological defects in crystals. We show how this approach can be extended to liquid crystals and related to the Frank–Oseen description. Within this framework, skyrmions are characterised by their associated distortion charges, and their dynamics are derived from a generalised Peach–Koehler force combined with Newton’s second law. We demonstrate that the resulting equations of motion recover the behaviour reported in previous studies, in particular those of Alvim et al., while providing a purely analytical perspective. This approach offers a unified and conceptually transparent description of skyrmion dynamics and suggests possible extensions to interacting skyrmions and other topological defects.

Abstract: Increasing demand for improving the strength of Aluminium Alloy (AMCs), which are widely used in the aerospace, automobile, and defence industries, has been seen in recent years. Aluminum 7075 (Al-7075) is a widely used aluminium alloy because of its high wear opposition and process-ability. By dispersing a suitable combination of Boron Nitride in the aluminium alloy, new techniques are being developed to im-prove the hardenability, strength and hardness of the composite. However, these hard-reinforced composites pose a number of difficulties during the machining process using WEDM process. The performance measures and surface topography acquired and input process parameters are also need to be observed and explained with aid of Taguchi-DEAR methodology. The material removal rate and kerf width have been checked and evaluated using Taguchi-DEAR methodology. The proposed method can efficiently enhance the cutting process with les tool wear and heat affected zone. 32 µs (Ton), 36 µs (Toff), 3.5 A (I), and 4.74 m/min (WF) were discovered to be the optimal arrangement of input factors in the WEDM process, with an error accuracy of 1.6%.