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This paper presents a study of the complex permittivity of n-type copper indium selenide semiconductor compound at low temperatures down to −175 °C. Alternating current with frequency varying between 20 Hz and 1 MHz is applied to the... more
This paper presents a study of the complex permittivity of n-type copper indium selenide semiconductor compound at low temperatures down to −175 °C. Alternating current with frequency varying between 20 Hz and 1 MHz is applied to the material in order to measure the dielectric constant ɛ′ and dielectric loss D = ɛ″/ɛ′. ɛ′ is found to decrease with temperature and frequency, whereas D decreases with frequency and increases with temperature. The experimental data of ɛ″ agree with the expression ε ″ = A ω m ω , T ${\varepsilon }^{{\prime\prime}}=A{\omega }^{m\left(\omega ,T\right)}$ , where the frequency exponent m(ω, T), calculated through the relation m ω , T = ∂ ln ε ″ / ∂ ln ω T $m\left(\omega ,T\right)={\left.\left(\partial \mathrm{ln}{\varepsilon }^{{\prime\prime}}/\partial \mathrm{ln}\omega \right.\right)}_{T}$ , shows a frequency and temperature dependence. The data are analyzed in light of existing theoretical models.
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Abstract In the present study we report on the synthesis and crystal structure studies of NaCryFe1−yP2O7 sodium diphosphate solid solution (0 ≤ y ≤ 1). The X-ray diffraction shows that these compounds are isostructural with NaFeP2O7 and... more
Abstract In the present study we report on the synthesis and crystal structure studies of NaCryFe1−yP2O7 sodium diphosphate solid solution (0 ≤ y ≤ 1). The X-ray diffraction shows that these compounds are isostructural with NaFeP2O7 and NaCrP2O7 (space group P21/c ( C 2 h 5 ) Z = 4). The Rietveld refinements based on the XRD patterns show the existence of a continuous solid solution over the whole composition range (0 ≤ y ≤ 1). A continuous evolution of the monoclinic unit cell parameters was obtained. The transition metal ions (Cr3+ and/or Fe3+) connect the diphosphate anions forming a three-dimensional network with cages filled by Na+ cations. IR and Raman spectra have been interpreted using factor group analysis. A small shift of the band frequencies is observed when Fe is substituted by Cr. The POP bridge angles are determined from Lazarev's relation and agree well with those deduced from the crystal structure refinement.
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In this work, we present a study of two NaSICON families of general formula Na2.800M1.775Si0.900P2.100O12 with M=Zr or Hf. The synthesis was carried out using sol-gel process and the synthesized precursors were characterized using coupled... more
In this work, we present a study of two NaSICON families of general formula Na2.800M1.775Si0.900P2.100O12 with M=Zr or Hf. The synthesis was carried out using sol-gel process and the synthesized precursors were characterized using coupled DTA-TG. The obtained oxides after pyrolysis of precursors were identified by X-ray diffraction. The electric properties of the sintered oxides were carried out by impedance spectroscopy (SIC). The obtained results at this conditions highlight a good improvement of electrical conductivity ( σ tot around 10 -4 S.cm -1 ). This value is comparable to total electrical conductivity at 300K given in the literature.
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Superconductivity, Superconductors, and 15 moreElectrical Resistance, Magnetic Susceptibility, Potassium, Bismuth, Oxide, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Thermogravimetric Analysis, Low Temperature, Aqueous Solution, High Tc Superconductivity, Physical Properties, Electrical And Electronic Engineering, Oxalic acid, and Volume Fraction
Abstract In the present work, the magnetocaloric effect of La1-xNaxMn1-yFeyO3 (x = 0.1, 0.2 and y = 0, 0.1) was investigated using magnetic characterization data. The X-ray diffraction confirms that all samples synthesized by flash... more
Abstract In the present work, the magnetocaloric effect of La1-xNaxMn1-yFeyO3 (x = 0.1, 0.2 and y = 0, 0.1) was investigated using magnetic characterization data. The X-ray diffraction confirms that all samples synthesized by flash combustion and calcined at 1000 °C have been crystallized in a rhombohedral structure with an R 3 - c space group. According to the magnetization versus temperature results, LaMnO3 is a ferromagnetic material with a Curie temperature TC = 95 K. The substitution of the rare earth La by alkali magnetic metal Na leads to an increase of TC to 265 and 330 K accompanied with large magnetic entropy change / - Δ S M max / of 2.88 and 4.88 J.Kg-1K-1 for x = 0.1, 0.2, respectively. The addition of 10% of Fe in La1-xNaxMn1-yFeyO3 decreases the Curie temperature and the magnetic entropy change, while, the relative cooling efficiency increases. The Mossbauer spectrum recorded at room temperature represents a paramagnetic character of the manganites and proves the distribution of Fe3+ in the samples.
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Research Interests: Engineering, Materials Engineering, Condensed Matter Physics, Chemistry, Raman Spectroscopy, and 12 moreScanning Electron Microscopy, Cyclic Voltammetry, Physical sciences, Lithium Ion Battery, Nickel, CHEMICAL SCIENCES, Polyethylene Glycol, X ray diffraction, Microstructures, Electrochemical Properties, D structure, and Carbon Source
Research Interests: Chemistry, Inorganic Chemistry, Electrochemistry, Solid State Chemistry, Impedance Spectroscopy, and 11 moreDielectric Spectroscopy, Gas Sensor, Ceramic, Conductivity, Ionic Conductivity, Electrical Properties, Potentiometric Titration, Sol Gel Method, Electric Conductivity, Electrolyte, and Solid electrolyte
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Research Interests: Engineering, Materials Science, Electrochemistry, Carbon, Medicine, and 15 moreCrystal structure, X Rays, Lithium Ion Battery, Structural Change, Lancet, CHEMICAL SCIENCES, X ray diffraction, Electrochemical Properties, Carbon Fibers, Electrode, Anode, Carbon Source, Lithium Iron Phosphate, Power Sources, and The Lancet
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Nowadays, increasing demands for energy sources are stimulating the development of electrical storage, in which Li-ion batteries have become one of the most successful technologies due to their high energy density, high rate, good cycle... more
Nowadays, increasing demands for energy sources are stimulating the development of electrical storage, in which Li-ion batteries have become one of the most successful technologies due to their high energy density, high rate, good cycle stability and little contamination. Liion batteries have been widely used for mobile phones, laptops, electric vehicles, military special devices and so on. Commercial Lithium-ion batteries employ a mixed oxide LiCoO2 or LiMnO4, as the positive (cathode) electrode and graphite or carbonaceous materials as the negatives (anode) electrodes [1]. In a search for new negative electrode materials for lithium-ion (Li-ion) batteries to replace graphite or carbonaceous materials, we have investigated in our previous study the electrochemical properties of Li0.5Ni0.25TiOPO4/C titanium oxyphosphate. The Li0.5Ni0.25TiOPO4/C [2] was prepared from a stoichiometric mixture between an aqueous solution of Ni(NO3)2.6H2O and (NH4)2HPO4 with a solution of TiCl4 diluted in ethanol. After evaporation at 45C under vacuum, the resulting powder was heated up to 400°C for 5h to remove ammonia and water. Finally, the powder was fired up to 900o C for 12h. This obtained powder was dispersed with 10% in mass of polyethylene glycol (PEG) powder in acetone, and heated to 500C for 6 h in a flow of CO/CO2 gas (50:50). XRD diffraction shows that the studied compound crystallizes in the monoclinic system with P21/c space group. The diffraction peaks indicate a high degree of crystallinity of the material, with two peaks labeled by asterisk (*) which corresponds to TiO2 impurity (Fig.1). Thermogravimetric analysis (TG) of the C-coated oxyphosphate evidenced that only 0.22% of residual carbon is present in the studied composite. The electrochemical behavior of Li0.5Ni0.25TiOPO4/C was tested in galvanostatic mode between 0.5V and 3V at C/20 (Fig. 2). The first discharge capacity was 307 mAh/g. On charge, the capacity decreased to 200 mAh/g losing about one third of its discharge capacity. This capacity loss is probably due to the above mentioned irreversible electrochemical processes during the first discharge. During the following cycles, good reversible capacity retention and better cycleability were obtained. Fig. 3 shows the capacity vs. cycle number plots for Li0.5Ni0.25TiOPO4/C at different rates. Stable capacities of ca. 200 mAh/g are obtained when the compound is cycled at C/10, C/5 and C/2 rates. In contrast the capacity decreased gradually with further cycling at C, 2C and 4C rates. The good capacity retention during cycling is favorable to consider this titanium oxyphosphate as a candidate for the negative electrode.
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Abstract Because of the physical, chemical and environmental risks related to industrial wastes and the high consumption of finite natural resources in the construction industry, this paper presents an ecological and sustainable way to... more
Abstract Because of the physical, chemical and environmental risks related to industrial wastes and the high consumption of finite natural resources in the construction industry, this paper presents an ecological and sustainable way to manufacture ceramic products using calamine hydrometallurgical processing wastes. This process generates a by-product called herein calamine process tailings (CPMT). Moreover, a sample of treated calamine process tailings (TCPMT) with low amounts of lead was also studied. The aim of this study is to characterize both wastes in order to assess the feasibility of their reuse potential as ceramic alternative materials. The effect of firing temperature on the chemical, mineralogical, environmental behaviors and the physical and mechanical properties of ceramic samples as well as the characterization of the fumes released during firing process are assessed. The results showed that increasing firing temperature enhances the flexural strength of ceramic samples and decreases their open porosity and water absorption. The TCPMT ceramic samples showed very different physical and mechanical properties in comparison with those made with CPMT. These latter samples present high flexural strength values and very low level of water absorption when fired at 1050 °C. This difference might be attributed to high amounts of glassy phase produced in CPMT fired samples. Moreover, the amount of leached metals is reduced significantly after the thermal treatment. However, arsenic, which was in a non-leachable form in the green samples, was found to be leached when tailings are fired. The scanning electron microscopy analysis (SEM-EDS) of condensed fumes evolved during the thermal treatment shows that lead is slightly volatilized.
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Superconducting single crystal of Bi2Sr2CaCu2Oz was grown from stoichiometric melt composition. The effect of Pb-doping on the superconducting properties was studied. The superconducting transition temperature (Tc0) for Pb-free and... more
Superconducting single crystal of Bi2Sr2CaCu2Oz was grown from stoichiometric melt composition. The effect of Pb-doping on the superconducting properties was studied. The superconducting transition temperature (Tc0) for Pb-free and Pb-doped Bi-2212 crystals was determined to be in the range of 90–95 K and 80–90 K respectively from resistivity and dc susceptibility measurements. We found that the electrical transport along the c-axis of Bi-2212 is changed from semiconductor-like to metallic by lead doping. In the Pb-doped crystal, the measurement of magnetic response reveals a high volume fraction compared with Pb-free crystal.
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ABSTRACT Many studies on various methods for growing crystals by methods including flux, self-flux, Bridgman, and floating zone growth have been carried out. Recently the micro-pulling down (μ-PD) method has been used to grow high-quality... more
ABSTRACT Many studies on various methods for growing crystals by methods including flux, self-flux, Bridgman, and floating zone growth have been carried out. Recently the micro-pulling down (μ-PD) method has been used to grow high-quality oxide fibers with minimal residual stresses, even incongruently melting compounds or high melting temperature materials. Thus, we thought to extend this technique to superconducting materials.In this work, the (Bi,Pb)2Sr2Can−1CunOz superconductors fibers were successfully grown by the micro-pulling-down using a seeding technique and were of reasonable quality, as was proved by X-ray diffraction, scanning electron microscopy and SQUID measurements.The grown fibers had a regular shape with uniform diameter and different length which was limited only by the crucible size and quantities of starting materials. The fibers were composed of plate-like crystals, oriented along the pulling direction and were superconducting. Nearly pure-phase (more than 90%) Bi-2201 and Bi-2212 fibers could be obtained at pulling rates 0.08 mm/min, exhibit superconducting behaviour with critical temperature Tc = 21 K and 90 K respectively with transition width (10–90% level) between 5 and 10 K.For (Bi,Pb)-2223 fiber obtained displays two superconducting transitions around 107 and 85 K, corresponding to 2223 and 2212 phases, respectively. Therefore the 2212 phase is the dominant phase in fiber grown.
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Superconductivity, Scanning Electron Microscopy, and 9 moreFiber, Superconductors, Composite Material, X ray diffraction, Scanning Electron Microscope, Residual Stress, Electrical And Electronic Engineering, Critical Temperature, and Melting Temperature
ABSTRACT Synthesis by soft chemistry and characterization of hafnyle (IV) nitrate hydrate HfO(NO3)2, xH2O. This paper deals with the synthesis and characterization of hafnyle (IV) nitrate hydrate from HfCl4. The elaboration method is a... more
ABSTRACT Synthesis by soft chemistry and characterization of hafnyle (IV) nitrate hydrate HfO(NO3)2, xH2O. This paper deals with the synthesis and characterization of hafnyle (IV) nitrate hydrate from HfCl4. The elaboration method is a soft chemistry one which allows to obtain a pure product. The nitrate was characterized by FTIR spectra, X ray diffraction and thermal analysis data (TDA-TGA). The degree of hydration was determined to be 2.
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Research Interests: Chemistry, Analytical Chemistry, Space Science, Medicine, Environmental Analytical Chemistry, and 11 moreAdsorption, Chemisorption, Calcination, Fourier transform infrared spectroscopy, Thermogravimetric Analysis, Langmuir, Congo Red, ENVIRONMENTAL SCIENCE AND MANAGEMENT, Alginate beads, Adsorption kinetic, and Layered double hydroxides (LDH)
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Superconducting single crystal of Bi2Sr2CaCu2Oz was grown from stoichiometric melt composition. The effect of Pb-doping on the superconducting properties was studied. The superconducting transition temperature (Tc0) for Pb-free and... more
Superconducting single crystal of Bi2Sr2CaCu2Oz was grown from stoichiometric melt composition. The effect of Pb-doping on the superconducting properties was studied. The superconducting transition temperature (Tc0) for Pb-free and Pb-doped Bi-2212 crystals was determined to be in the range of 90–95 K and 80–90 K respectively from resistivity and dc susceptibility measurements. We found that the electrical transport along the c-axis of Bi-2212 is changed from semiconductor-like to metallic by lead doping. In the Pb-doped crystal, the measurement of magnetic response reveals a high volume fraction compared with Pb-free crystal.