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Effect of rotational speed and copper interlayer on the mechanical and fracture behaviour of friction stir spot welds of 5754 aluminium alloy

Ramzi Gassaa, Larbi Hemmouche, Riad BADJI, Lionel Gilson, Luc Rabet, Oussama Mimouni  (2023)

The application of joining processes requires advanced mechanical tests to control the joints quality. Generally, welded sheets are verified using tensile shear tests. However, few studies also recommend conducting tension peel and cross-tension tests. The present work evaluates the mechanical behaviour of 5754 aluminium sheets jointed by friction stir spot welding (FSSW). The influence of the rotational speed on joint strength was first compared to riveted assemblies. Then, sheets welded with pure copper interlayers were compared to the precedents. The results indicated that, without an interlayer, lower and intermediate rotational speeds lead to higher mechanical strength under tensile shear tests compared to riveted assembly. However, it performed worse under tension peel and cross-tension tests at all studied rotational speeds. By adding copper, the strength of welded sheets is globally improved under tensile shear tests. Nevertheless, under tension peel and cross-tension tests, it performed worse, although a slight improvement was observed for increasing rotational speeds. Two different failure morphologies and four fracture modes were observed regarding the different tested samples. Microhardness tests were also conducted, to relate the influence of the studied parameters on the joint s strength. Voir les détails

Mots clés : 5754 aluminium alloy, Failure and fracture modes, Friction stir spot welding, Mechanical testing, Microhardness

Solar still productivity improvement using nanofluids: a comprehensive review

Tawfiq Chekifi, Moustafa BOUKRAA  (2023)

The production of drinking water is a critical issue due to the lack of access to clean water and the increasing demands of the environment. One of the main technologies for water purification is solar still. Solar distillation is an economical and ecological alternative for the production of quality distilled water. Many recent researches on the use of nanofluids in solar still have focused on its performance, which subsequently implies an increase in the productivity of the solar still, whereas thermophysical and evaporation properties of the base fluid are changed by suspended metallic or non-metallic nanoparticles. According to some reports, the use of nanofluids can raise the distillate productivity up to 100%, other works revealed an improvement up to 20% in terms of thermal efficiency compared to the Conventional solar still. The current review summarizes previous works that studied the improvement of solar still productivity using nanofluids, a significant portion of analysis and discussion is devoted to how different factors affecting the global performance of these devices including nanofluids proprieties, radiation absorption, evaporation and condensation. Finally, propositions for future numerical and experimental research and application guidance are also presented. Voir les détails

Mots clés : nanofluids and nanoparticles, Solar still, water desalination

Integration of reconfigurable fault-tolerant three-level inverter in photovoltaic power system

Omar Fethi BENAOUDA, Sami KAHLA, Mohamed Bouchakour, Azzedine Bendiabdellah  (2023)

A lot of previous studies have shown a great interest in connecting photovoltaic (PV) arrays to electric power grids. A Maximum Power Point Tracker (MPPT) controlled 100 kW PV array to boost its power that feeds the grid with the help of a three-level inverter. This paper investigated the effects of open-circuit faults of three-level inverter IGBT switches on the performance of the PV array system. This paper proposes a new diagnostic method called the Double Threshold-Trigonometric Coordinates (DT-TC) that relies on the double threshold technique and the trigonometric coordinates, respectively, for early detection and the precise location of open-circuit faults. To the best knowledge of the authors, two simultaneous open-circuit faults were not considered in the previous studies. The obtained simulation results prove the great success of the proposed diagnosis method even under noticeable changes in irradiation, temperature, and the number of PV array connected in series and in parallel. In this study, the reconfigurable fault-tolerant inverter was included to ensure the perfect continuity of the PV array system and its recovery in an extremely very short time up to 7 ms. Voir les détails

Mots clés : diagnosis, DT-TC, fault-tolerant, IGBT, Multi-level Inverter, Open-circuit faults, PV array, reconfigurable

Effect of CaF2 addition on the densification behavior and mechanical properties of resistant anorthite and its bioactivity

S. Zaiou, O. Beldjebli, D. Belfennache, M. Tayeb, F. Zenikheri, A. Harabi  (2023)

In the current study, anorthite ceramic (CaO, Al2O3, 2SiO2) was synthesized by a simple solid-state reaction method, using local Algerian raw materials. The effect of sintering temperature at 800, 850, 900, 950, 1000, and 1100 °C for 1h under atmosphere, and 0.5, 1.5, and 3 wt % calcium fluoride (CaF2) addition on the densification and mechanical properties of anorthite were studied. The correlation between these properties and the bioactivity of samples was investigated. The results showed that samples with 1.5 wt.% CaF2 sintered at 900 °C has the highest bulk density (2.7, lowest apparent porosity (3%), outstanding micro-hardness (8.7 GPa), and high flexural strength (222 MPa) of anorthite. The in vitro bioactivity test was assessed by determining the changes in surface composition and morphology after immersion in a simulated body fluid (SBF) for 8 h to 21 days. The results of the bioactivity test determined the formation of hydroxyapatite (Ca5(PO4)3OH) on the sample surface after 3 days, suggesting it is a bioactive ceramic. Voir les détails

Mots clés : anorthite, CaF2 addition amount, bioactive properties Mechanical, sintering temperature

Theoretical study of structural and optical properties of ZnO in wurtzite phase

Y. Benkrima, S. Benhamida, D. Belfennache  (2023)

Our calculations are done with the help of density functional theory (DFT). Actually, we could find the structural and optical properties of the wurtzite-type ZnO compound. The pseudo-potential linearised augmented plane wave (PP-LAPW) method is applied to solve the Kuhn-Sham equations. The results are obtained using Both Generalized Gradient Approximation according to the scheme described by Perdew-Burke-Ernzerhof(GGA-PBE) and Local Density Approximation according to the scheme described by Ceperly-Alder (LDA-CA) approximations as two types of exchange-correlation. The convergence of energy and charge has been checked. This is in order to study the properties of the ground state. It was found that the primary cell constants calculated in the equilibrium state are very close to the previous theoretical works. The general results of optical properties including the imaginary part of the dielectric constant, reflectivity, absorption coefficient, refractive index, optical conductivity, and extinction coefficient of wurtzite-phase ZnO under the imposed conditions are discussed and compared with previous works. Our results show new and important optical properties. Besides, we predicted the behavior of transparent conductive oxides in the direction of light. Voir les détails

Mots clés : ZnO, Structural properties, reflectivity, absorption, Refractive index, Optical conductivity

Investigation of Structural, Morphological, and Photoluminescence Properties of Zn1_xMgxS Nanoparticles Prepared by Solvothermal Method: Insight from Experimental and DFT Study

Messai Youcef, Bezzi Hamza, Bourzami Riadh, Chetoui Abdelmounai, Bouarroudj Tayeb, Samira TLILI, Tairi Latifa, Ahmed Belghidoum, Ouksel Louiza  (2023)

Various concentrations of Mg2+ substitutional doped ZnS nanoparticles (Zn1-xMgxS,x = 0, 0.02, 0.07, and 0.1) were prepared by adopting the solvothermal method, using ethanol as the solvent at 135°C. The obtained micro/nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and room temperature photoluminescence (PL) spectroscopy. XRD revealed the conservation of the host ZnS crystal phase after the substitution of Zn2+ by Mg2+ but was accompanied by a weak decrease of the lattice parameter. SEM analysis showed the formation of aggregated particles that were evenly distributed. PL spectra exhibited a near-band-edge (NBE) emission centered at 430 nm, and another band at 585 nm, related to sulfur defects; moreover, no shift occurred when x increased. To explain this finding, computational density functional theory (DFT) calculations were performed, revealing constant gap energy after substitution was maintained at the point G, whereas the density of stats of both CV and BV were reinforced near the band gap Voir les détails

Mots clés : solvothermal preparation, Zn1-xMgxS substitution doped, structural study, Photoluminescence (LP), DFT calculations

Synthesis, characterization, DFT/M06 studies, NBO, QTAIM and RDG analyses of new copper (II) complexes with bis-phosphonamide obtained under microwave irradiation

Fouzia Bouchareb, Malika Berredjem, Djenet Amel Dehmchi, Rayene Kadri, Mekki Kadri, Hana Ferkous, Achraf Mansouri, Saida Bouyegh, Saleh A. Ahmed, Taibi Ben Hadda, Rania Bahadi  (2023)

We have devised a novel one-step approach for synthesizing bis-phosphonamides utilizing primary amines and phenylphosphonic dichloride (PPDC) under ultrasound irradiation. The bis-phosphonamides obtained were used as organophosphorus ligands for the synthesis of new copper (II) complexes with metal ions. The synthesis of these complexes was accomplished via a novel eco-friendly method employing microwave irradiation. The desired complex obtained, as a green powder in 65% yield, which were fully characterized by spectroscopic methods (FT-IR, UV–vis, XDR). To gain and further insights into structure and properties of studied complexes, several calculations such as Natural Atomic Orbitals (NAO), Natural Bond orbitals(NBO), Quantum Theory of Atoms in Molecules (QTAIM) analysis were performed at M06/6-311++g(d, p) level. Using the Reduced electron Density Gradient (RDG) approach, the non-covalent interactions were explored and visualized in two and three-dimensional spaces. Voir les détails

Mots clés : Phenylphosphonicdichloride, Bis-phosphonamide, Organometallic complexes, Green chemistry, Ultrasound Microwave

Economic Evaluation of Degradation by Corrosion of an On-Grid Battery Energy Storage System: A Case Study in Algeria Territory

Fouzia BRIHMAT  (2023)

Economic planning models, which are used to build microgrids and Distributed Energy Resources (DER), are the current norm for expressing such confidence. These models often decide both short-term DER dispatch and long-term DER investments. This research investigates the most cost-effective hybrid (photovoltaicdiesel) renewable energy system (HRES) based on Total Net Present Cost (TNPC) in an Algerian Saharan area, which has a high potential for solar irradiation and has a production capacity of 1 GW/h. Leadacid batteries have been around much longer and are easier to understand, but have limited storage capacity. Lithium-ion batteries last longer, are lighter, but generally more expensive. By combining the advantages of each chemistry, we produce cost-effective highcapacity battery banks that operate solely on AC coupling. The financial implications of this research describe the corrosion process that occurs at the interface between the active material and grid material of the positive plate of a lead-acid battery. The best cost study for the HRES is completed with the assistance of the HOMER Pro MATLAB Link. Additionally, during the course of the project's 20 years, the system is simulated for each time step. In this model, which takes into consideration decline in solar efficiency, changes in battery storage levels over time, and rises in fuel prices above the rate of inflation, the trade-off is that the model is more accurate, but the computation takes longer. We initially utilized the optimizer to run the model without multi-year in order to discover the best system architecture. The optimal system for the single-year scenario is the Danvest generator, which has 760 kW, 200 kWh of the necessary quantity of lead-acid storage, and a somewhat lower Cost Of Energy (COE) of $0.309/kWh. Different scenarios that account for fluctuations in the gasified biomass generator's production of electricity have been simulated, and various strategies to guarantee the balance between generation and consumption have been investigated. Voir les détails

Mots clés : Battery, corrosion, Diesel, Economic planning optimization, Hybrid energy system, HES, Lead-acid battery, Li-ion battery, Multi-year planning, Microgrid, price forecast, total net present cost, Wind

Multiyear Load Growth Based Techno-Financial Li-ion Discharge and Corrosion Behaviors in a Microgrid Located in Algeria

Fouzia BRIHMAT  (2023)

The primary current-collector materials used in lithium-ion cells, aluminum and copper, are both susceptible to environmental degradation. Localized corrosion occurred on bare aluminum electrodes during simulated ambient-temperature cycling in an excess of electrolyte. The highly oxidizing potential associated with the positive electrode charge condition was the most important factor. In contrast to typical aqueous electrolyte pitting, each site was filled with a mixed metal/metal-oxide product, forming surface mounds or nodules. The status quo for relaying such confidence is economic and technical planning models, which are used to design microgrids and distributed energy resources DER. Long-term DER investments and short-term DER dispatch are typically determined by these models. This paper investigates the optimal cost analysis of a hybrid (photovoltaic-diesel) renewable energy system (HRES) in the Adrar region based on the Total Net Present Cost (TNPC). The Hybrid Optimization Model for Electric Renewable is used to perform the optimal cost analysis of HRES. Furthermore, the system is simulated for each time step for each year of the project's 20-year lifespan. The trade-off for this model, which captures battery storage levels from year to year, photovoltaic performance degradation, and diesel cost escalation above the inflation rate, is that the model is more precise, but the calculation takes longer. To begin, we ran the model without MultiYear and used the Optimizer to find the best system design. The optimal system for the single-year model includes a Danvest generator with 760 kW, 200 kWh of recommended Li-ion storage, and a slightly lower COE of $0.309/kWh. Various scenarios have been simulated, taking into account variations in the power production of the gasified biomass generator, and various solutions to ensure the balance generation/consumption have been analyzed. Voir les détails

Mots clés : corrosion, Diesel, Financial planning optimization, Hybrid energy system (HES), Li-ion battery, Multi-year planning, Microgrid, Photovoltaic, Technical planning optimization, total net present cost

Synthesis, Characterization, and Photocatalytic Activity ofBa-Doped BiFeO3 Thin Films.

KHIAT Abdelmadjid, Felicia Gheorghiu Boughelout Abderrahmane.  (2022)

Abstract: In the present paper, Bi1-xBaxFeO3 (BBFO) thin films (where x = 0, 0.02 and 0.05) wereprepared by a combined sol-gel and spin-coating method. The influence of Ba substitutions on thestructural, microstructural, optical properties, and photocatalytic activity of BiFeO3 thin films hasbeen studied. X-ray diffraction pattern correlated with FTIR analysis results confirms that all thefilms have a perovskite structure of rhombohedral symmetry with an R3m space group. Atomicforce microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate thesurface morphology and reveals microstructural modifications with the increase in Ba concentration.The optical properties show that the band gap is narrowed after doping with Ba ions and decreasesgradually with the increase of doping content. The photocatalytic investigations of depositedfilms revealed that Ba doping of BFO material leads to the enhancement of photocatalytic response.The present data demonstrates that Bi1-xBaxFeO3 (BBFO) thin films can be used in photocatalyticapplications. Voir les détails

Mots clés : perovskites; films; optical properties; doped BaTiO3; photocatalytic activity