Assessment of near Pr2/3Sr1/3MnO3 oxide in magnetic cooling

International audienc

Magnetic properties of tin ferrites nanostructures doped with transition metal

International audienc

Efficient synthesis of pure bulk black phosphorus and high-quality exfoliation of phosphorene

Black phosphorus (BP) is the most promising material among the two-dimensional (2D) materials thanks to its layered structure and excellent semiconducting properties. Currently, bulk BP flakes are synthesized under high pressure and high-temperature conditions by chemical vapor deposition using high-cost Au-catalyst. Consequently, its applications as a crystalline semiconductor material in electronic devices are limited due to the low quality and purity of BP. In this work, we demonstrate an efficient and low-cost synthesis of highly crystalline BP by rapid low-pressure reaction of red phosphorus (RP) in the presence of a small amount of silver (Ag) in a vacuum-sealed quartz tube. The phosphorene layers were prepared by liquid-phase exfoliation (LPE) of high-quality BP crystals using various solvents such as isopropanol (IPA), N-methyl pyrrolidone (NMP) and Dimethylformamide (DMF). The resulting materials are investigated in detail including structural and morphological characterization along with thermal properties. We have obtained BP flakes which are uniform in size and morphology. The lateral sizes of the stable BP range from 50.7 nm after exfoliation in IPA to 204 nm after exfoliation in NMP. The most effective phosphorene layer separation was achieved by using the IPA solvent and centrifugation at 15000 rpm with a monolayer thickness of 0.5 - 0.6 nm. Phosphorene layer thicknesses of 1.0 - 2.0 nm and 1.7 – 2.6 nm are obtained when using NMP and DMF as solvents, respectively. We demonstrate the fine tuning of the optical bandgap by controlling the number of phosphorene layers

Coexistence of blocked, metamagnetic and canted ferrimagntic phases at high temperature in Co–Nd ferrite nanorods

International audienc

Magnetocaloric Properties of Zinc-Nickel Ferrites Around Room Temperature

International audienc

Effect of zinc concentration on the structural and magnetic properties of mixed Co–Zn ferrites nanoparticles synthesized by sol/gel method

International audienc

La cimenterie de Temara : besoins d’un nouveau gisement de calcaires (cas du gisement de l’oued Cherrat)

Au cours de ces dernières années, Asment Temara a eu recourt uniquement aux calcaires de l’ancienne carrière (Asment) pour la fabrication de son ciment, dont elle utilise environ 80 %. Cependant, avec l’évolution de l’exploitation de la carrière, la teneur moyenne en CaO a chuté, en outre l’usage du crible au niveau du concasseur primaire a conduit à une consommation accrue de calcaire. Cette situation a obligé Asment Temara de lancer une campagne de prospection pour la recherche d’une nouvelle carrière de calcaire dans la banlieue du site principal. Cette quête s’est montrée fructueuse par la découverte d’un nouveau gisement qui est celui de l’oued Cherrat. l’étude de ce gisement nous a permis de distinguer trois lithologies : calcaires francs, calcaires dolomitiques et faciès de transition (calcaires à interlits schisteux). Les données de sondages et la cartographie de surface nous ont permis d’estimer les réserves de ce gisement, qui sont de l’ordre de 22712213 millions de tonnes. Les mélanges réalisés au cours de ce travail nous amène à déduire qu’il s’avère nécessaire d’utiliser le calcaire de l’oued Cherrat pour prolonger la durée de vie de la carrière d’Asment, et de là, satisfaire les besoins du marché

From amorphous red phosphorus to black phosphorus crystal: An optimization, controllable and highest yield synthesis process

Understanding the growth mechanism of large crystals and high-quality of black phosphorus (BP) is a fundamental challenge to further study its physical properties. The BP was prepared from amorphous red phosphorus (RP), by short-way chemical vapor transport (CVT) reaction using the addition of small quantities of copper, tin, and tin(IV) iodide as reaction promoters. The method used in this present work is currently developed by our research laboratory for preparation of BP. In fact, a series of experiments was designed to understand and optimize the preparation conditions (the catalyst's choice (Cu), temperature, time, dimensions of quartz tube ...) of this surprisingly easy and effective method and to ensure a high BP conversion ratio (wt%) from RP with high purity, high crystallinity, and large size of orthorhombic BP (flakes size ∼1 cm), It’s the main goal of this work. The products recovered in the hot and cold zones of the tube are analyzed by X-ray diffraction (XRD) to give an idea of the role of mineralizers (Cu,Sn, and SnI4) allowing the synthesis of BP. Decomposition of reaction system (RP/Cu/Sn) with the tin(IV) iodide should lead to the formation of the condensed phases represented by Cu4SnP10,Sn4P3, CuSn,Cu2P7, SnI4 and P2O5could be detected at a hot zone of the tube. The characterizations of the prepared BP were carried out also using Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and Raman spectroscopy

Synthesis and magnetic properties of tin spinel ferrites doped manganese

International audienc

Magnetocaloric Properties of Zinc-Nickel Ferrites Around Room Temperature

In this paper, structural, magnetic, and magnetocaloric properties of zinc-doped nickel ferrite, Zn1−xNixFe2O4 (x = 0.3 and 0.4) were investigated. The samples were prepared using solid-state reaction. X-ray diffraction (XRD) and magnetization measurements were performed to study crystallographic structure and magnetic properties. For a magnetic field changing from 0 to 5 T, the corresponding isothermal entropy change was found to be near 1.4 J/kg K for both samples. The decreasing of Ni content from x = 0.4 to 0.3, enables to shift the Curie temperature of Zn1−xNixFe2O4 from 450 K toward (325 K). As main results, it was found that the relative cooling power (RCP) could be significantly enhanced by changing Ni concentration in Zn1−xNixFe2O4 (505 J/kg (for x = 0.3) and 670 J/kg (for x = 0.4)), which is considered as a recommended parameter for a wide temperature range in magnetic refrigeration application. Our finding should inspire and open new ways for the enhancement of the magnetocaloric effect in spinel ferrite-based materials