Materials Science Forum Vol. 1199

Abstract: This work focuses on the modeling and prediction of the optical absorption coefficient in GaAs 2D nanostructure subjected to hydrostatic pressure. The database is generated from numerical calculations describing the optical absorption of exciton confined in GaAs 2D nanostructure. The obtained data are exploited to develop predictive models based on machine learning such as Decision Tree and Gradient Boosting techniques, in order to establish an accurate relationship between the incident photon energies and the optical absorption coefficient. The quality of the proposed approaches is examined using standard statistical metrics, considering the mean absolute, squared errors, and root mean squared error, as well as the coefficient of determination. The obtained results demonstrate an excellent agreement between the predicted and numerical values, with very low errors and strong generalization capability. these approaches therefore represent an efficient alternative to conventional numerical methods for the rapid prediction of the optical properties of discoidal quantum dots and offers promising perspectives for the optimization of optoelectronic devices.

Abstract: The generation of entangled photon pairs through spontaneous parametric down conversion (SPDC) is widely used and considered one of the key entanglement generation techniques in quantum optics. The quality of the entanglement produced depends significantly on the physical properties of the nonlinear crystal employed in the SPDC process. In this study, we investigate the influence of the crystal parameters such as phase matching configurations on the degree of entanglement. Our results demonstrate the importance of crystal selection for achieving highly entangled photon sources, which are essential for applications in quantum communication and quantum information.

Abstract: In this work, the structural and electronic properties of the ternary phosphide SrLiP, which crystallizes in the hexagonal space group P6 ̅2m (N°.187), were investigated using Density Functional Theory (DFT). To optimize the equilibrium geometry, we used the Generalized Gradient Approximation (GGA) with the Full-Potential Linearized Augmented Plane-Wave approach (FP-LAPW) method. The optimized structure is found to be mechanically stable. The calculated electronic band structure of SrLiP, within GGA approach shows that it exhibits a semiconducting behavior with an estimated band gap of about 0.85 eV. The projected density of states (PDOS) indicates that the top of the valence band is mainly dominated by P-p states, while Sr and Li orbitals contribute significantly to the bottom of the conduction band, indicating hybridization effects governing the electronic transitions. Owing to its structural stability and moderate band gap, SrLiP may represent a promising candidate for potential optoelectronic applications.

Abstract: Semiconducting silicon carbide (SiC) has been developed and characterized as an anode electrode for lithium (Li), sodium (Na), potassium (K), beryllium (Be), magnesium (Mg), boron (B), aluminum (Al), and gallium (Ga) ion batteries. This is due to the formation of Si(Li₂)C, Si(Na₂)C, Si(K₂)C, Si(Be₂)C, Si(Mg₂)C, Si(B₂)C, Si(Al₂)C, and Si(Ga₂)C nanoclusters. A comprehensive study on energy savings using Si(Li₂)C, Si(Na₂)C, Si(K₂)C, Si(Be₂)C, Si(Mg₂)C, Si(B₂)C, Si(Al₂)C, and Si(Ga₂)C complexes was conducted using computational approaches, including density of state analysis, charge density differences (CDD), total density of state (TDOS), and electron localization function analysis (ELF) for hybrid clusters of Si(Li₂)C, Si(Na₂)C, Si(K₂)C, Si(Be₂)C, Si(Mg₂)C, Si(B₂)C, Si(Al₂)C, and Si(Ga₂)C. Functionalizing lithium, sodium, beryllium, and magnesium elements can enhance the negative charge distribution of carbon elements as electron acceptors in Si(Li₂)C, Si(Na₂)C, Si(K₂)C, Si(Be₂)C, Si(Mg₂)C, Si(B₂)C, Si(Al₂)C, and Si(Ga₂)C nanoclusters. Increased Si/C content can boost battery capacity through Si(Li₂)C, Si(Na₂)C, Si(K₂)C, Si(Be₂)C, Si(Mg₂)C, Si(B₂)C, Si(Al₂)C, and Si(Ga₂)C nanoclusters for energy storage processes and improve rate performance by enhancing electrical conductivity. Additionally, the SiC anode material may improve cycling consistency by reducing electrode degradation and increasing capacity due to higher surface capacitive effects.

Abstract: Thermodynamic behavior and phase stability of binary and ternary alloy systems containing Fe, Al, and Ni are systematically investigated. Formation enthalpies (ΔH) of solid solutions and intermetallic compounds in the Fe–Al, Fe–Ni, Al–Ni, and Fe–Al–Ni systems were calculated using Miedema’s semi-empirical model implemented in the Materials Analysis Applying Thermodynamics (MAAT) software. Overall, the results indicate that solid solutions in the binary systems are thermally stable, and when the concentration of alloying elements is increased, solids solutions demonstrate a low change in thermal behavior while compounds exhibit more complex thermodynamic behavior and require higher energy for formation. The ternary Fe–Al–Ni system also exhibits exothermic and endothermic reactions according to the molar ratio of elements. The electronic and vibrational properties of the Fe₈₀Al₁₅Ni₅ alloys are theoretically simulated using DFT and TD-DFT for UV–Visible calculations, and the spectroscopic features are interpreted in correlation with the thermodynamic stability predicted by Miedema’s semi-empirical model. No experimental spectroscopic measurements were performed in this study.

Abstract: This work presents an experimental investigation for the failure mechanisms and shunt effect phenomenon in resistance spot welded high-strength low-alloy (HSLA) steel sheets with single-and double-nugget configurations. Welded joints were produced under controlled conditions following to ISO/DIS 14273:2016 standard, and their performance was assessed through tensile-shear testing, microhardness measurements, and microstructural analysis. The results revealed a clear influence of nugget configuration on both mechanical strength and fracture behavior. Single-nugget welds primarily exhibited interfacial and partial pull-out failures, whereas double-nugget welds demonstrated combined pull-out and sheet-tearing modes, indicating improved energy absorption and joint integrity. Microstructural observations showed refined martensitic zones in the fusion region, with hardness values significantly higher than those of the base metal. The shunt effect phenomenon observed in double-nugget welds led to noticeable variations in nugget diameter and hardness symmetry, influencing current distribution and local heat input.

Abstract: The impact of periodic mechanical vibration on the phase transitional property of VO₂ based thermal sensing thin film synthesized on AT-cut quartz has been investigated in this paper. VO₂ were found to go through phase transition due to effect of heat, and display reduction of film resistivity and transmitted infrared power at a specific transition temperature, typically around 60-70°C. But sometimes the transmitted infrared power has been observed to decrease at a significantly lower temperature compared to the similar phenomenon for resistivity reduction. In order to correctly validate the transition temperature, the derivative of the transmitted optical power signal is measured, and it has been found that this measurement is experimentally possible when the VO₂ film is subjected to a moderate to high frequency periodic mechanical vibration. It has also been observed that the variation of the mechanical vibration frequency has a direct effect on the derivative signal, which indicates the sharpness of the phase transition and magnitude of change of the transmitted infrared power depending on the width of the extrema lobe of the derivative.

Abstract: This study investigates the dual solution existence and the associated temporal stability of magnetohydrodynamic hybrid nanofluid (HNF) flow over a bidirectional shrinking sheet. The working fluid consists of an Al₂O₃–Cu/water HNF subjected to suction, magnetic field effects, and porous medium resistance. The reduced coupled ordinary differential governing equations are solved using the Galerkin weighted residual method. A temporal stability analysis based on eigenvalue formulation is conducted to distinguish physically realizable solutions from unstable ones. The effects of emerging parameters on the skin friction coefficients and the Nusselt number are examined with the concentration given on magnetic effect. The results reveal the dual solution existence in a critical range of suction values, beyond which no solutions exist, indicating boundary-layer separation. Stability analysis confirms that only the upper-branch solution is stable and physically admissible. Enhanced magnetic field strength, delay boundary-layer separation and improve thermal performance. The present results show excellent agreement with previously reported limiting cases, demonstrating the accuracy and robustness of the proposed method.

Abstract: In recent years, thermoelectric materials based on noble metal chalcogenides are attracting considerable interest due to their high figure of merit. On the other hand, it is well known that noble metal chalcogenides exhibit high ionic conductivity. By looking the reported experimental data, there are wide evidences that the thermoelectric and high ionic conduction behavior are interrelated. In the present study, the viscoelastic theory of superionic conductors which was used previously to study the properties of Ag_2+δSe is reconsidered. The model predicts that the composition dependence of the sound velocity and diffusion coefficient near the stoichiometric composition exhibit a minimum and maximum respectively, when the value of the Thomas-Fermi screening parameter is decreased. Such a behavior provides an insight to exploit the alloying effect in the development of thermoelectric materials. In addition to the results from the viscoelastic theory, the electronic transport properties provided by the bond fluctuation model of superionic conductors is also discussed shortly.