Mohamed Rashad | Faculty of Organized Science (original) (raw)

Papers by Mohamed Rashad

Crystal Research and Technology, 2004

Free Sulfate is a major parameter affecting gypsum crystallization during phosphoric acid product... more Free Sulfate is a major parameter affecting gypsum crystallization during phosphoric acid production. Gypsum crystal size, shape and filtration rate are significantly affected by the concentration of free sulfate. It is, therefore, important to evaluate the effectiveness of different sulfate levels from 1.5% to 3.5% on induction time and gypsum morphology. The crystallization of gypsum was carried out under simulated conditions of phosphoric acid production by the dihydrate process. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 °C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation. With increasing free sulfate concentration, the induction time was significantly decreased. Chemical processing of Central and South Florida phosphate concentrates under different concentrations of free sulfate from 1.5% to 5.5% was carried out. The change on crystal size distribution and filtration rate were traced with free sulfate concentrations. The results show that, filtration rate of phosphogypsum was correlated to the mean diameter of crystals. In addition, induction time and co-crystallized (lattice) P2O5 % in gypsum are decreased with increasing free sulfate content from 1.5% to 3.5%. Morphology of formed gypsum crystals at different sulfate contents and different supersaturation ratios are investigated. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cubic copper ferrite CuFe 2 O 4 nanopowders have been synthesized via a hydrothermal route using ... more Cubic copper ferrite CuFe 2 O 4 nanopowders have been synthesized via a hydrothermal route using industrial wastes. The synthesis conditions were systematically studied using statistical design (Box-Behnken Program) and the optimum conditions were determined. The results revealed that single phase of cubic copper ferrite powders can be obtained at different temperatures from 100 to 200°C for times from 12 to 36 h with pH values 8-12. The crystallite size of the produced powders was in the range between 24.6 and 51.5 nm. The produced copper ferrite powders were appeared as a homogeneous pseudo-cubic-like structure. A high saturation magnetization (M s 83.7 emu/g) was achieved at hydrothermal temperature 200°C for 24 h and pH 8. Photocatalytic degradation of the methylene blue dye using copper ferrite powders produced at different conditions was investigated. A good catalytic efficiency was 95.9% at hydrothermal temperature 200°C for hydrothermal time 24 h at pH 12 due to high surface area (118.4 m 2 /g).

Materials, 2021

Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe2O4/SrFe12−2xSmxLaxO19; x = 0.2, 0.5,... more Spinel cobalt ferrite/hexagonal strontium hexaferrite (2CoFe2O4/SrFe12−2xSmxLaxO19; x = 0.2, 0.5, 1.0, 1.5) nanocomposites were fabricated using the tartaric acid precursor pathway, and the effects of La3+–Sm3+ double substitution on the formation, structure, and magnetic properties of CoFe2O4/SrFe12−2xSmxLaxO19 nanocomposite at different annealing temperatures were assayed through X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. A pure 2CoFe2O4/SrFe12O19 nanocomposite was obtained from the tartrate precursor complex annealed at 1100 °C for 2 h. The substitution of Fe3+ ion by Sm3–+La3+ions promoted the formation of pure 2CoFe2O4/SrFe12O19 nanocomposite at 1100 °C. The positions and intensities of the strongest peaks of hexagonal ferrite changed after Sm3+–La3+ substitution at ≤1100 °C. In addition, samples with an Sm3+–La3+ ratio of ≥1.0 annealed at 1200 °C for 2 h showed diffraction peaks for lanthanum cobalt oxide (La3Co3O8; dominant phase) and ...

Particulate Science and Technology, 2017

Generally, the efficiency of solid oxide fuel cells (SOFCs) is heavily dependent on the electroca... more Generally, the efficiency of solid oxide fuel cells (SOFCs) is heavily dependent on the electrocatalytic activity of the cathode toward the oxygen reduction reaction (ORR). In order to achieve a better cathode performance, LaxSr1-xMnO3 (LSM) nanopowders with different Sr 2+ ion contents varying from 0.2 to 0.8 have been synthesized using the co-precipitation method. The obtained nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (EIS). It is found that the LSM nanoparticles were seemed to exhibit the high polarization resistance with the increase of the Sr 2+ ion molar ratios. The crystallite size was found to increase from 16.4 to 24.3 nm with increasing the Sr 2+ content from 0.2 to 0.8. The lattice parameters were decreased with Sr 2+ ion content which may be caused by an increase in internal stress with increasing the grain size of LSM. Meanwhile, the real part impedance (Z') was increased from 10(Ω) at 0.2 Sr 2+ to be 24(Ω) at 0.8 Sr 2+ ion ratio. Alternatively, |Z| of prepared sample was increased from 12 to 26 (Ω) by increasing Sr 2+ ion molar ratios from 0.2 to 0.8.

RSC Advances, 2016

We report on the synthesis and characterization of lanthanum strontium manganite with tunable opt... more We report on the synthesis and characterization of lanthanum strontium manganite with tunable optical, magnetic and electrical properties.

Journal of Magnetism and Magnetic Materials, 2015

Magnesium ferrite (MgFe 2 O 4) nanoparticles have been prepared, for the first time, by ethylene ... more Magnesium ferrite (MgFe 2 O 4) nanoparticles have been prepared, for the first time, by ethylene diamine tetraacetic acid (EDTA)-based sol-gel combustion method. The prepared ferrite system is calcined at 400, 500 and 600°C. Thermo-gravimetric and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM) were applied for elucidating the structural and magnetic properties of the prepared system. XRD patterns revealed that the prepared system have two spinel MgFe 2 O 4 structures, namely cubic and tetragonal phases that are dependent on calcination temperature (T c). The crystallite sizes varied from 8.933 to 41.583 nm, and from 1.379 to 292.565 nm for the cubic and tetragonal phases respectively depending on T c. The deduced lattice parameters for the cubic and (tetragonal) systems are a¼ 8.368, 8.365 and 8.377 and (a ¼7.011, 5.922, 5.908 and c ¼6.622, 8.456, 8.364) Å at T c ¼ 400, 500 and 600°C respectively. While the cation distribution of the cubic phase is found to be mixed spinel and T c-dependent, it is an inverse spinel in the tetragonal phase where the Fe 3 þ ions occupy both the tetrahedral A-and octahedral B-sites in almost equal amount; the Mg 2 þ ions are found to occupy only the B-sites. The HRTEM and selected-area electron diffraction (SAED) revealed the detailed morphology of the nanoparticles, and confirmed their crystalline spinel structure. VSM indicated the existence of an appreciable fraction of superparamagnetic particles at room temperature, with pure superparamagnetic behavior observed for samples calcined at 400°C. Besides, the magnetic properties are found to change by thermal treatment as a result of the varied phase concentration, cation distribution and lattice parameters. Thus, the new synthesis route used in this study by applying EDTA as an organic precursor for preparing MgFe 2 O 4 nanoparticles at rather low temperatures proved to be efficient in obtaining nanoparticles with favorable structural and magnetic properties. Such properties would qualify them for several potential applications including e.g. in hyperthermia treatment, as contrast agents in magnetic resonance imaging (MRI), and in ferroelastomers technology.

Journal of Cluster Science, 2014

Nanocrystalline cobalt nickel tungstate powders (CO 1-X Ni X WO 4 where X = 0, 0.5 and 1) have be... more Nanocrystalline cobalt nickel tungstate powders (CO 1-X Ni X WO 4 where X = 0, 0.5 and 1) have been synthesized by a microemulsion method. The results indicate that pure monoclinic wolframite tungstate structure was obtained from the precipitated precursors at pH 10 calcined at a temperature 600°C for 6 and 10 h. Meanwhile, the average particle sizes of the formed tungstate powders were about 12-35 nm. The specific surface areas of the produced materials were about 33.8-42.8 cm 3 /g and the average pore diameters were 4.5-6.3 nm. The NiWO 4 material indicated band gap energy E g value of 3.2 eV whereas that of CoW-O 4 revealed a value of 2.7 eV. TEM images investigated that the formed particles were nearly nanoclusters. Furthermore, HRTEM results revealed that NiWO 4 powders have (0 1 0) and (1 0 0) planes which led to the highest photocatalytic activity. Photocatalytic decomposition of methylene blue (MB) as a model pollutant was used to evaluate the photocatalytic activity of CO 1-X Ni X WO 4 catalysts under UV irradiations. The MB degradation rate with the irradiation time using NiWO 4 , CoWO 4 and Co 0.5 Ni 0.5 WO 4 catalysts was estimated apparent first kinetic rate constants of 0.013, 0.012 and 0.010 min-1 , respectively.

Journal of Magnetism and Magnetic Materials, 2009

Yttrium iron garnet (YIG) (Y3Fe5O12) powders have been synthesized through a co-precipitation met... more Yttrium iron garnet (YIG) (Y3Fe5O12) powders have been synthesized through a co-precipitation method in the presence of sodium bis(2-ethylhexylsulfosuccinate), AOT as an anionic surfactant. The garnet precursors produced were obtained from aqueous iron and yttrium nitrates mixtures using 5M sodium hydroxide at pH 10. A statistical Box–Behnken experimental design was used to investigate the effect of the main parameters (i.e.

Ceramics International, 2014

The pure titania (TiO 2) and the heterogeneous ternary magnetic nanocomposite of copper ferrite/f... more The pure titania (TiO 2) and the heterogeneous ternary magnetic nanocomposite of copper ferrite/ferrite oxide (CuFe 2 O 4 / Fe 2 O 3) deposited by titanium dioxide (TiO 2) were fabricated using a facile one-pot hydrothermal synthesis for the photocatalytic decomposition of methylene blue (MB) dye, under visible light. The nanocomposite was encoded as TCF in this work, where T stands for TiO 2 , C for CuFe 2 O 4 and F for Fe 2 O 3. Various techniques such as powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, diffuse reflectance spectroscopy, nitrogen physisorption, and vibrational sample magnetometry (VSM) were used to characterize the prepared samples. The PXRD data showed that the samples had pure anatase structure and the average crystal size of anatase TiO 2 in the pure titania and ternary nanocomposite were calculated 147 Å and 135 Å, respectively. The nitrogen physisorption analysis data showed that the pore diameter was increased from 10.6 nm in pure titania to 16.0 nm in TCF. The pore volume was also increased from 0.316 in titania to 0.383 cm 3 /g in TCF sample. It also increased the typical magnitude of the mesopores' diameter and volume per weight but it reduced the specific surface area of the samples. The VSM analysis of the ternary nanocomposite showed a considerable magnetic property of the sample (1.99 emu/g), qualifying it as a paramagnetic material. The photocatalytic decomposition efficiency of MB reached 77% and 68% in the presence of pure titania and TCF ternary nanocomposite, after 240-min exposure by the visible light. Active species trapping experiments showed that the major active species responsible for the photodecomposition of MB in the presence of TCF are O ⋅− 2 radicals and holes (h +).

Advanced Powder Technology, 2012

ACS applied materials & interfaces, Jan 16, 2018

Toxicity as well as chemical instability issues of halide perovskites based on organic-inorganic ... more Toxicity as well as chemical instability issues of halide perovskites based on organic-inorganic lead-containing materials still remains the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with non-toxic Cu metal for lead free perovskite solar cells; investigate of its potential towards solar cells applications based on experimental and theoretical studies. The formation of (CH3NH3)2CuX4 [(CH3NH3)2CuCl4, (CH3NH3)2CuCl2I2, and (CH3NH3)2CuCl2Br2] were discussed in details. Furthermore, founding chlorine (Cl-) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials illustrated attractive absorbance features extended to the near-infrared, with appropriate band gaps. Green photoluminescence of these materials obtained due to Cu+ ions. The power conversion efficiency (PCE) measured experimentally and estimated theoretically for diffe...

Journal, 2019

Typically, low cost as well as stability factors of the organo-metal halide perovskite solar cell... more Typically, low cost as well as stability factors of the organo-metal halide perovskite solar cells based on inorganic hole transport layers (HTLs) have been the focus of intense research over the past few years. Accordingly, the power conversion efficiencies have rapidly been improved to ~ 20% with high stabilities. Therefore, this review covers the major advances of inorganic HTLs in perovskite solar cells that have contributed to the recent efficiencies and stabilities, including the evolution of device architecture, the development of hole transport material deposition processes, synthesis, morphology and the interface properties between inorganic HTLs and perovskite layers. Eventually, the challenges and future directions for inorganic HTLs-based perovskite solar cells are also discussed.