Journal of Renewable Energies

Physico-chemical characterization of Al2O3/Ti6A4V type thermal barrier systems

Tue, 04 Feb 2025 00:00:00 +0000

Al₂O₃ alumina deposits were deposited on Ti6A4V titanium alloy substrates by rf-PVD at different substrate polarizations 0V, -50V, -100V and without polarization (wp). SEM images, at the surface of the deposits, showed a very good substrate coverage with a dense morphology. Quantitative EDS analysis of these deposits revealed the presence of the elements Al and O in these deposits. The mass percentage of these elements, at different polarizations of the substrate, varies between 51.72% and 56.19% for Al and between 43.80% and 48.27% for O. The images, revealed by AFM, showed well-spread deposits on the surface of the substrates with relatively uniform grooves. The values of the arithmetic roughness R_a, ranging from 3.45 to 4.75 nm, testify to the low crystallinity of these deposits and an appreciable density. The DRX of these deposits in mode showed a weak crystallization of the Al₂O₃ phase and characteristic peaks of the partially crystallized phases Al_0.3Ti_1.7, and Ti_0.7V_0.3, resulting from the interaction of the elements of the Ti6A4V substrate and those of the Al₂O₃ deposit.

Impact of using corrugated wall and nanofluid on the performance improvement of thermoelectric generator mounted channels

Hessem Djeddou , Brahim Fersadou , Henda Kahalerras , Mohamed Benelhaoues — Tue, 04 Feb 2025 00:00:00 +0000

The influence of using a corrugated wall as a passive heat transfer enhancement technique for the sake of improving the power generation of thermoelectric generator (TEG) located in between two corrugated channels flowing nanofluid has been numerically examined. The upper and the lower channels carry hot and cold water-based single-walled carbon nanotube nanofluid (SWCNT), respectively. Finite element method, FEM, is chosen to tackle the 3D steady-state equations governing the TEG with associated boundary conditions. Several parameters related to the performance of thermoelectric generator such as Reynolds number (between 50 and 1000) and the number of corrugations (between 1 and 5) were in depth assessed. The findings indicate that the Reynolds number plays a significant role in improving thermoelectric power generation. When the Reynolds number increases, TEG produces a higher electric power value. However, the results also reveal that the number of corrugations has a limited impact on the performance of TEG.

Towards a more powerful hydrogen engine

Hassina Ghodbane , Fouad Khaldi , Bahloul Derradji — Tue, 04 Feb 2025 00:00:00 +0000

This research examines the operational efficiency of a single-cylinder hydrogen engine through simulations conducted in OpenModelica. The research focuses on analyzing the combustion characteristics, heat release, temperature, and pressure at varying engine speeds of 1700, 2000, and 2500 rpm. The combustion process is modeled Applying the Wiebe function to represent the proportion of fuel mass that is burned, while the heat released by combustion is calculated using a formula incorporating the fuel mass, lower heating value, and combustion efficiency. The study presents detailed simulations of in-cylinder temperature, heat release rate, and pressure profiles, and examines how these parameters vary with engine speed. Results reveal that peak temperatures and heat release rates increase with engine speed, indicating more intensive combustion at higher speeds. The pressure curves and power output also show significant changes with speed, with higher engine speeds leading to increased power output and improved engine efficiency. This study provides insights into the hydrogen engine's behavior under different operating conditions, highlighting the impact of engine speed on performance metrics.

Prediction Cell Parameter of A2MX6 Cubic Perovskites

Hadda Krarcha , Abdelhak Ferroudj — Tue, 04 Feb 2025 00:00:00 +0000

A₂MX₆ perovskites materials have shown impressive advances in the last 50 years due on their photovoltaic application, made them one of the most-promising technologies for next-generation solar cells. We present in this work a semi empirical model for prediction of cell parameter of cubic A₂MX₆ perovskites. It is useful for providing the predicted structural information for estimating the physical properties of materials for which accurate structural data are not available. We propose a linear formula according to the factors: Interatomic distance R_A+ R_X and R_M + R_X and electronegativity difference . The interatomic distances d_X-_X and d_M-Xd can be estimated from the crystalline structure of the compounds studied. A new prediction of cell parameter is estimated for 90 perovskites and the results are compared with the experimental one whose error is of the order of 1.13%.

Photocatalytic properties of Mn2O3 nanoparticles synthesized via green chemistry method

Nadjah Sobti, samiha Chaguetmi , Leila Amiour , Youcef Aouabdia , lynda Saci — Tue, 04 Feb 2025 00:00:00 +0000

The objective of this work is to synthesize Mn₂O₃ nanoparticles (NPs) using green method based on olive leaf extract (OLE). These nanoparticles are intended for photocatalytic applications, specifically the degradation of pollutants and dyes using methylene blue (MB) as a test substance. The synthesized material, initially described as manganese oxide (Mn₂O₃), was characterized using various techniques: thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), FT-IR, Raman and UV-visible spectroscopies. Additionally, the photocatalytic tests were performed. XRD analysis revealed the formation of Bixbyite (Mn₂O₃) phases. Raman and FT-IR spectroscopy confirmed the presence of Mn-O bonds within the synthesized material. The TGA results supported the decomposition of organic compounds and the formation of the Mn₂O₃. The photocatalytic degradation tests with methylene blue yielded promising results. The addition of the synthesized material (Mn₂O₃) significantly enhanced the degradation of methylene blue, achieving an efficiency of 87.8%.

Biological properties study of bioactive diopside prepared from local raw materials

Tue, 04 Feb 2025 00:00:00 +0000

In this study, it was synthesized of ultrafine-structured diopside granules using the sintering method from solid raw materials (Dolomite) at a temperature of 1300 °C for 2 hours. Following the preparation, the pawders were homogenized within the [200-400 um] range and then immersed in simulated body fluid (SBF) at 37°C for 2, 7, 14 and 21 days. Following different soaking durations, the samples were carefully extracted from the fluids using deionized water. Subsequently, they were air-dried at room temperature prior to examine the impact of immersion on their crystalline properties. This involved monitoring the variation in ion concentration and pH during the immersion periods, as well as using X-ray diffraction (XRD), characterization through scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. The findings revealed the partial dissolution of ultrafine Structured diopside granules and the development of a layer of carbonate-hydroxyapatite (Ca_10.00P_6.00O₂₆.₁₄H_2.60C_0.02) on the surface of the samples after seven days of immersion, with a granular size estimated at D_nm=102.96 nm. This volume continued to increase with longer dipping durations, reaching D_nm=205.94 nm for samples immersed for 21 days. Finally, the results obtained suggest that ultrafine-structured diopside granules are promising candidates for bone regeneration.