Publications internationales
Résumé: To examine the structural, optoelectronic, thermodynamic, and thermoelectric properties of KBaTh (Th = Sb, Bi) half-Heuslers, we used the full potential, linearized augmented plane wave (FP_LAPW) approach as in the Wien2K simulator. Generalized gradient approximation (GGA), technique, was used for the structural optimization. Mechanical stability and ductility were inherent characteristics of the studied KBaTh (Th = Sb, Bi). Having band gaps of 1.31 eV and 1.20 eV for the KBaTh (Th = Sb, Bi) compounds, they have a semiconducting character. The KBaTh (Th = Sb, Bi) compounds are suggested for use in optoelectronic devices based on studies of their optical characteristics. Thermoelectric properties were investigated using the Boltzmann transport provided by the BoltzTraP software. Since the acquired figures of merit (ZT) values for the KBaTh (Th = Sb, Bi) compounds are all almost equal to one at room temperature, this demonstrates that these substances can be used in thermoelectric devices. Additionally, we used the Slack method to determine the lattice thermal conductivity of KBaTh (Th = Sb, Bi). Our research shows that the half-Heusler compounds under investigation increase actuator response time and hence can be considered as good materials for actuators.
Résumé: In this research work, first-principles computational study is performed on the structural, elastic,thermal, magnetic, electronic, and thermoelectric properties of the ternary Heusler compound Co2MnGe inits cubic phase. For this purpose, the “full potential linearized augmented plane-wave FP-L(APW + lo)” approach realized in the WIEN2k code is employed. To determine total energy, the exchange–correlation energy/potential part is treated within the “Perdew–Burke–Ernzerhof (PBE)” parameterized approach of “generalized gradient approximation (GGA) and modified Becke–Johnson (mBJ)” schemes. The magnetic phase stability was predicted via quantum mechanically total energy calculations for both non-magnetic and magnetic phases. Our obtained results for total energy show that the title material is stable in the ferromagnetic phase. The analysis of the profile of density of states (DOS), band structure plots, and the calculations of spin magnetic moment endorse the semi-metallic nature of the title compound. Calculations of the elastic constants, Cij , and results of the elastic moduli, such as bulk modulus (B), shear modulus (G), Young modulus (E), Poisson ratio (ν), and ratio B/G, are reported and analyzed as well. Gibbs computational code based on the “quasi-harmonic Debye model” is used to explore thermal properties, whereas parameters to understand the thermoelectric behavior, BoltzTrap code based on Boltzmann theory for transport properties is applied. Besides that, the chemical potential effect on the Seebeck coefficient and power factor is also analyzed at temperatures 300, 600, and 900 K. The results of thermoelectric parameters of the title Heusler compound, for the spin-down channel, are found good; hence, the obtained results highlight the title compound as a potential candidate for thermoelectric devices.
Résumé: The Density Functional Theory (DFT) with an approximation of generalised gradient is used for the study of elastic, thermodynamic and transport properties and for that of structural stability of ternary Half-Heuslers compounds X(X=Co, Rh and Ir)MnAs. This first predictive study of this compounds determines the mechanical properties such that the compression, shearing, Young modulla and Poisson coefficient without omitting the checking parameters of the nature of these compounds such that hardness, Zener anisotropic facto rand Cauchy pressure. The Pugh ratio and Poisson coefficient have allowed the identification of ductile nature of these compounds. The speed of sound and Debye temperature of these compounds has also been estimated from the elastic constants. The thermodynamic properties have been calculated as well for a pressure interval from zero to 25 GPa. The effect of chemical potential variation on Seebeck coefficient, electric, thermal and electronic conductivities, the power and merit factors have also been studied for different temperatures (300, 600, 900°K), so that these alloys can be better potential candidates for thermoelectric applications.
Résumé: The first principles calculations of structural and magnetic properties of the Heusler material Mn2NiAl, have been studied using a full potential linearized augmented plane wave (FP-LAPW) within the density-functional theory (DFT). The phase stability of the cubic austenitic (L21) structure for Mn2NiAl in both Cu2MnAl (Fm3 m space group) and Hg2CuTi (F43 m space group) type of structures with ferromagnetic and antiferromagnetic states, has been treated by applying the generalized gradient approximation proposed by Wu and Cohen (WC-GGA) alongside with the martensitic structure of Mn2NiAl. The analysis of phase stability, cohesive energy and the calculated formation enthalpy of Mn2NiAl reveal that the ferromagnetic MnMnNiAl is the most stable type of structure. Moreover, the calculated lattice parameters are found to be in good agreement with theoretical data. The variation of total magnetic moments MT(μB), MMn (μB), MNi (μB) and MAl (μB) in Mn2NiAl with pressure at varying temperature (0, 273 and 344 K), have been calculated.
Résumé: The human body has been the subject of thorough researches—not only from medical perspective but from a technical one as well—are very rich, amongst them we find blood circulation system comprising: the heart, the arteries and the veins. The overriding role of these researches is to explain some cardiovascular pathology and provide an aid tool for the endoprothesis positioning in blood vessels while treating them. In this study we have developed a digital pattern using the common (engineering technique of the) finite element method (FEM) to simulate the mechanical behavior of the thoracic aorta and the abdominal aorta below the kidney under blood pressure effect. This pattern calculates the displacements, the stresses (constraints) and the deformations of the two arteries’ walls enabling us to know their experimentally determined mechanical and geometric properties. This pattern could be applied to detect the aneurysm and dissection phenomena.
Résumé: An accretion dalliance is accorded by biotechnology, in general, and biomaterials, in particular, in determining the mechanical properties of different biological tissues comprising or composing the living creatures’ bodies. Their microscopic and macroscopic structures are complex and mechanical tests can be of a major in studying their mechanical properties [1] [8] [7]. During operation, any blood circulation system is subject to an alternating blood pressure and the constituent organs behave differently. Amongst the rudimentary mechanical tests to characterize thoracic and abdominal arteries, and soft tissues as well - vital components of the blood circulatory system – we find the traction test. This work focuses on the characterization of thoracic and abdominal arteries, located on the same trunk of a sheep, precisely determining Young’s modulus, elasticity constraints, and deformations and break strain.