Publications Internationales

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Author: search.filters.author.Djafar, RabahHas files: Yes

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    The Synergistic Effect of Algerian Na-Bentonite/Potato Starch/Grass Powder on the Enhancement of Aged Water-based Drilling Fluids
    (Springer, 2022) Sid, Asma Nour El Houda; Benalia, Kouin; hazourli, Abdelkrim; Djafar, Rabah; Gherraf, Noureddine; Bououdina, Mohamed
    Nowadays, the use of eco-friendly additives in drilling fluids to improve rheological properties is widespread. This work aims to examine and assess the rheological characteristics and fluid loss of drilling fluid suspensions containing Algerian Na-Bentonite (NaB) and potato starch (PS) as viscosifier upon the addition of grass powder (GP). The obtained results indicate that the aging tests applied on different drilling fluid suspensions during 192 h at (20 °C) reduce the values of apparent viscosity by an average of (14.3%), plastic viscosity (22.2%), yield point (6.7%), and shear stress (47.3%) when varying the (PS) concentration in the suspensions (0.6, 1.2, 2%) as well as the values of fluid loss (9.5%); meanwhile, the values of initial and final gel strength are increased (32.6% and 19.6%, respectively). Subsequently, the possibility to further improve the rheological properties of drilling fluid suspensions using an environment eco-friendly additive (GP) has been studied. The introduction of (3, 6, 9 g) GP in the aged suspensions increases the values of rheological properties, i.e., the highest efficiency of 18.4% has been achieved by adding 9 g of GP to 2% (PS) aged suspension. The fluid loss test indicates that increasing the (GP) concentration in the (NaB+PS) suspension reduces the fluid loss volume by 36.42%. This study demonstrates the synergy of combining cost-effective GP to (NaB+PS) in aged drilling fluids by enhancing significantly its rheological properties besides a better environmental protection.
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    Preparation and characterization of biocomposites based on chitosan and biomimetic hydroxyapatite derived from natural phosphate rocks
    (Elsevier, 2021) Brahimi, Salim; Ressler, Antonia; Boumchedda, Khaled; Hamidouche, Mohamed; Kenzour, Abdeghani; Djafar, Rabah; Antunović, Antunovic; Bauer, Leonard; Hvizdoš, Pavol; Ivanković, Hrvoje
    Highly porous chitosan/hydroxyapatite (CS/HA) biocomposite scaffolds were prepared using the freeze-gelation method. A starting biomimetic HA powder was synthesized by a wet precipitation method using an abundant natural phosphate (NP) ore as raw material. Then, CS/HA scaffolds with different weight ratios (100/0; 90/10; 80/20; 70/30) have been prepared. The used powders and synthesized scaffolds were characterized by XRF, ICP-MS, FTIR, TG-DSC, XRD, SEM, and cell viability. The results showed that the precipitated raw powder was mainly composed of HA and amorphous calcium phosphate (ACP) with some traces of Mg2+, SiO42−, Sr2+, Na+ and Fe2+ ions which were usually found in such mineral NP precursors. The heat treatment of the raw powder at more than 750 °C leads to the formation of Mg-substituted β-tricalcium phosphate (β-TCMP). Moreover, the culture of human embryonic kidney cells indicated the non-cytotoxicity of the as-prepared powder. On the other hand, the elaborated CS/HA scaffolds exhibited a highly porous structure with well-interconnected pores and homogeneously dispersed HA particles. The measurement of swelling capacity under physiological conditions revealed that the addition of HA to the CS matrix effectively decreased the swelling percentage. The obtained results suggest that the elaborated CS/HA composites may have effective potential as biocompatible scaffolding materials for bone tissue engineering
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    Cu2O addition and sintering temperature dependence of structural, microstructural and dielectric properties of CaCu3Ti4O12 ceramics
    (Elsevier, 2020) Djafar, Rabah; Boumchedda, K.; Chaouchi, A.; Fasquelle, D.; Sedda, K.; Brahimi, S.; Khalfaoui, K.; Bououdina, M.
    This study is aimed in the replacement of commonly used (CuO) by Cu2O in the synthesis of perovskite CaCu3Ti4O12 (CCTO) phase by the solid-state reaction method. The XRD analysis of powder calcined at 1100 °C and ceramics sintered at different temperatures show that the CCTO phase was well crystallized with the presence of small quantities of additional phases. The SEM/EDS analysis of prepared pellets show that the formation of Cu2O/CuO phase occurs above 950 °C, resulting in enhanced densification at 1050 °C (>96%). However, it is found that the Cu2O-based CCTO begins to degrade around 1090 °C. The densification after sintering at 1050 °C reaches 96%, meanwhile dielectric constant and loss tangent values are optimum in the low frequency range (<103 Hz); i.e. 13378 and 0.177, respectively. This favors the use of Cu2O instead of CuO in CCTO ceramics for applications at low frequencies