https://dspace.univ-guelma.dz/jspui/handle/123456789/677 2026-04-23T22:08:04Z 2026-04-23T22:08:04Z KOUARTA, AYA https://dspace.univ-guelma.dz/jspui/handle/123456789/18984 2026-04-08T21:22:58Z 2025-01-01T00:00:00Z

Titre: " Évaluation théorique des effets inhibiteurs de corrosion des composés organiques " Auteur(s): KOUARTA, AYA Résumé: Including The capacity of a series of derivatives of the thiadiazole molecule 2-amino-1,3,4-thiadiazole (ATD), 5-amino-1,3,4-thiadiazole-2-thiol (ATDT), 2-amino-5-ethyl-1,3,4 thiadiazole (AETD) and 2-amino-5-tert-butyl-1,3,4-thiadiazole (ATBTD), to inhibit the corrosion of an iron substrate in 1 M HCl was investigated. An extensive theoretical study was carried out to examine adsorption modes and electronic structures, and to identify and quantify the nature of interactions at the inhibitor/substrate interface, using density functional theory (DFT/B3LYP) calculations based on Grimme's method for DFT-D correction, in combination with a dual digital plus polarisation (DNP) basis set, and Monte Carlo simulations based on the simulated annealing algorithm via automated temperature control using the DMol3 and Adsorption Locator modules implemented in Material studio 17 software. 0. The effect of the solvent was represented by the implicit solvation model COSMO. The inhibitors studied show spontaneous and favorable adsorption, but the expected order of effectiveness is: ATDT > ATBTD > AETD > ATD. ATDT was the most effective of the inhibitors studied.

2025-01-01T00:00:00Z Seridi Abir, Benhamdi Naima https://dspace.univ-guelma.dz/jspui/handle/123456789/18602 2025-11-06T14:50:43Z 2025-01-01T00:00:00Z

Titre: Protection contre la corrosion de l’acier A9 en milieu acide par des inhibiteurs verts Auteur(s): Seridi Abir, Benhamdi Naima Résumé: This work is dedicated to the study of the effect of olive leaf extract (OL), marjoram oregano (MO), and their mixture (OL, MO) as green inhibitors on the corrosion of A9 steel in an acidic medium (1M HCl), using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and gravimetric measurements. To better understand how the inhibitor acts against corrosion, a thermodynamic study was conducted, along with the analysis of different adsorption isotherms. The results from the weight loss method and electrochemical techniques show that both extracts effectively inhibit steel corrosion, especially their mixture, which can reach up to 90% efficiency at a concentration of 50 ppm. This inhibitor behaves as an anodic inhibitor. The inhibitor molecules adhere to the steel surface according to the Langmuir isotherm, indicating the formation of a monolayer. Moreover, the activation energy values suggest that the adsorption is of the physisorption type. FTIR and UV-Vis spectra confirm the simultaneous presence of functional groups such as O-H, C-O, and C=O. The steel surface morphology was examined using optical microscopy. The findings show that olive leaf extract, marjoram oregano extract, and their mixture effectively inhibit the corrosion of A9 steel, form a protective film, and thus act as a good barrier against the penetration of the corrosive medium to the metallic surface.

2025-01-01T00:00:00Z HADDAD, CHAIMA https://dspace.univ-guelma.dz/jspui/handle/123456789/18561 2025-10-29T13:47:18Z 2025-01-01T00:00:00Z

Titre: Propriétés électroniques et optiques du GaN dopé : Une analyse par WIEN2k Auteur(s): HADDAD, CHAIMA Résumé: The analysis of the structural, electronic, and optical properties of pure gallium nitride (GaN) and GaN doped with aluminium (Al) and tallium (Tl) was carried out using the FP-LAPW method. The generalized gradient approximation (GGA-PBEsol) combined with the TB-mBJ potential, implemented in the WIEN2k code, was used for the calculations of the different properties. It was observed that doping GaN with Al at a concentration of 12.5% leads to the formation of wide-bandgap semiconductors, while the incorporation of Tl of the same concentration induces a reduction in the bandgap. The results also show that doping modifies the properties of GaN, particularly by shifting the absorption peaks toward blue and a red for Al and Tl dopants, respectively. This modification enhances light absorption, which could be beneficial for optoelectronic applications.

2025-01-01T00:00:00Z ELBEKRI, MERIEM https://dspace.univ-guelma.dz/jspui/handle/123456789/18560 2025-10-29T13:32:38Z 2025-01-01T00:00:00Z

Titre: Transitions de phase et propriétés vibrationnelles du matériau LiBeP : Étude ab initio Auteur(s): ELBEKRI, MERIEM Résumé: A comprehensive study was conducted on the structural, electronic, vibrational and dielectric properties of the semiconductor compound LiBeP within the framework of density functional theory (DFT). We employed the pseudopotential method, implemented in the ABINIT code. The analysis examined five distinct candidate structural phases (polymorphs): included the cubic phase (AgMgAs), two hexagonal phases (LiGaGe) and (Ni2In), tetragonal phase (Cu2Sb), and orthorhombic phase (MgSrSi). The results of the equation of state showed a very good agreement with the experimental values and confirmed that the tetragonal (Cu2Sb) structure is the most stable. Under pressure, the compound transitions from the tetragonal structure to the orthorhombic structure at 11.43 GPa, and then to the hexagonal structure at 12 GPa. Electrically, in all three phases, the energy gap is indirect. To investigate the vibrational properties, density functional perturbation theory (DFPT) was used in conjunction with the previously mentioned computational method, confirming the dynamical stability of these phases by the absence of imaginary frequencies in the phonon spectra - a finding that was conclusively verified. The dielectric properties revealed that the hexagonal (LiGaGe) structure exhibits the highest dielectric polarization among the studied phases

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