Strontium carbonate (SrCO3) is one of the most important strontium compounds that have been used in a variety of technological and industrial applications. In the present investigation, nano-structured strontium carbonate was synthesized... more
Strontium carbonate (SrCO3) is one of the most important strontium compounds that have been used in a variety of technological and industrial applications. In the present investigation, nano-structured strontium carbonate was synthesized by mechano-chemical reaction of celestite ore (SrSO4) collected from Dasht-e kavir, Iran and sodium carbonate during high energy mechanical milling.The milling were performed for different durations of time up to 16 hours in a high-energy planetary ball mill with the rotational speed and ball to powder weight ratio of 300 rpm and 30, respectively. X-Ray diffraction (XRD), X-ray fluorescence spectrometer (XRF) and scanning electron microscope (SEM) were used to characterize the obtained samples. XRD results showed that at a Na2CO3:SrSO4 molar ratio of 1.05:1, mechano-chemical reaction started after 1 hour of milling. Although the longer milling times gives a more conversion of SrSO4 to SrCO3 but it has not been completed even after 16 hours of millin...
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Silicon nanoparticles are the focus of attention thanks to their potentialities in advanced applications such as new batteries, photovoltaic cells and so on. The need to porous silicon is thus rising and will follow the same trend. In... more
Silicon nanoparticles are the focus of attention thanks to their potentialities in advanced applications such as new batteries, photovoltaic cells and so on. The need to porous silicon is thus rising and will follow the same trend. In this work, highly porous nanostructured silicon is synthesized via Self-propagating high-temperature synthesis (SHS) route. Microstructural and phase analyses show that the employed technique is capable of producing a three-dimensional porous silicon which can act as a skeleton for embedding lithium ions and therefore, resisting large volume expansions arising during lithiation phase. Considering the fact that the wave front experiences high temperatures (above 1900°C) which can result in nanoparticles’ sintering, and in order to improve the porosity level, ammonium nitrate is used as a neutral additive at Mg/SiO2/NH4NO3 (2.4:1:0.1) molar ratio. The influence of nitrate addition on the final microstructure is studied through comparing salt-added sample...
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Although Cu and Fe are immiscible under equilibrium conditions, they can form supersaturated solid solutions by mechanical alloying. In this paper, nano-structured of the metastable Cu-Fe phase containing 10, 15, 20 and 25% wt Fe were... more
Although Cu and Fe are immiscible under equilibrium conditions, they can form supersaturated solid solutions by mechanical alloying. In this paper, nano-structured of the metastable Cu-Fe phase containing 10, 15, 20 and 25% wt Fe were synthesized by intensive ball milling for 15h, in order to achieve a solid solution of Fe in Cu. The phase composition, dissolution of the Fe atoms into the Cu matrix, and the morphology of the milling products were studied by X-ray Diffraction (XRD), Energy Dispersive Spectrometer (EDS), and Field Emission Scanning Electron Microscope (FESEM) techniques, respectively. The mean crystallite size of the milled samples was determined by XRD peak broadening using the Williamson-Hall approximation. The XRD analysis results showed that the solid solubility of the Fe in the Cu was extended to 20%wt after milling for 15 h, and a homogeneous solid solution of Cu80Fe20 with a mean crystallite size of 19nm was obtained. The mean crystallite size decreased with in...
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Abstract Production of Cu–Cr/carbon nanotube (CNT) hybrid nano-composite by wet and dry milling processes at three different levels of milling energy was investigated in order to study the effect of milling energy in two different media... more
Abstract Production of Cu–Cr/carbon nanotube (CNT) hybrid nano-composite by wet and dry milling processes at three different levels of milling energy was investigated in order to study the effect of milling energy in two different media on dispersion of CNTs, and preparation of the nano-composite. The structural evolution and solid solution formation were evaluated by X-ray diffraction technique. The microstructure was characterized by scanning electron microscopy and transmission electron microscopy. Also, the mechanical properties were measured by microhardness test. The mean crystallite size was in the range of 20–63 nm depending on milling medium and energy. CNTs dispersion is a function of milling energy. According to FESEM images and microhardness results, it can be concluded that wet milling is more applicable in dispersing CNTs homogeneously in comparison to dry milling. It was also found that wet milling at higher milling energies can be a beneficial method of producing the homogeneous hybrid nano-composite with the least damages introducing on CNTs because of the higher microhardness which can be attributed to better dispersion of less damaged CNTs. Compared with crystallite size changes, CNTs dispersion and damages were considerably more effective on hardness.
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Cobalt ferrite nanopowders with an average particle size of 50 nm were synthesized by a modified Pechini type sol–gel method. Obtained powder was subjected for fabrication of magnetic foams by using microwave and conventional sintering... more
Cobalt ferrite nanopowders with an average particle size of 50 nm were synthesized by a modified Pechini type sol–gel method. Obtained powder was subjected for fabrication of magnetic foams by using microwave and conventional sintering approaches coupled by space holder method. Carbamide was used as space holder material. Samples were characterized by X-ray diffraction, stereomicroscope, scanning and transmission electron microscope, nitrogen gas adsorption–desorption, and vibration sample magnetometer analyses. The results revealed that microwave sintering offered magnetic foams with surface area of 5.21 m2/g which is four times greater than the samples obtained by conventional sintering. Such a mesoporous nanostructure was achieved only after 5 min of microwave sintering which yielded monolith foams with sufficient strength and grain growth suppression of nanostructure. Moreover, magnetic studies indicated that magnetic parameter of squareness ratio for microwave sintered foams is twice greater than that of conventionally sintered foams.
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Nanostructured Cu-20Fe alloy was synthesized by mechanical alloying process and the effects of process control agents (PCA) on the phase formation, crystallite refinement and morphology of powder particles were studied. The dissolution of... more
Nanostructured Cu-20Fe alloy was synthesized by mechanical alloying process and the effects of process control agents (PCA) on the phase formation, crystallite refinement and morphology of powder particles were studied. The dissolution of Fe into Cu matrix and the morphology of powder particles were analyzed by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), respectively. The mean crystallite size was approximated by the method developed by Williamson and Hall. It was found that in the absence of PCA (Toluene in the present work), the iron peaks vanish after 5 h of mechanical alloying process and the mean crystallite size of the matrix decreases to 35 nm and large agglomerated particles are formed during milling. In this regard, it was found that the addition of PCA decreases the rate of crystallite refinement and formation of solid solution but does not affect the final mean crystallite size. It was also found that the addition of PCA during milling decrea...
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Titanium diboride (TiB 2) is a refractory ceramic which has excellent properties such as high melting point, high hardness, good thermal and electrical conductivity, high wear resistance and considerable chemical stability[1, 2]. A... more
Titanium diboride (TiB 2) is a refractory ceramic which has excellent properties such as high melting point, high hardness, good thermal and electrical conductivity, high wear resistance and considerable chemical stability[1, 2]. A mixture of TiO 2 , H 3 BO 3 and Mg with a stoichiometric ratio has been mechanically activated in a planetary high energy ball mill for 5, 10, 15 and 20 h and then compacted. Nano-size particles of TiB 2 were synthesized by self propagating high temperature synthesis route through putting a hot filament on top of the compact mixture. Effects of the milling time and addition of NaCl as process diluents on the phase composition and morphology of the products were investigated. The X-ray diffraction patterns indicated the formation of TiB 2 together with MgO and some minor intermediate phases like Mg 3 B 2 O 6 and Mg 2 TiO 4 in the un-milled sample. Nano-crystalline TiB 2 with mean crystallite size of 36 nm became the major phase in the leached sample by HCl...
Silica exists in Rice husk, an agriculture waste, as a naturally occurring phase. In first step, acidic pre-treatment and calcination of the rice husk were performed to obtain nano-silica, in which various sizes of the nano-silica,... more
Silica exists in Rice husk, an agriculture waste, as a naturally occurring phase. In first step, acidic pre-treatment and calcination of the rice husk were performed to obtain nano-silica, in which various sizes of the nano-silica, totally with sizes under 80 nm, were achieved. Second, to reduce nano-silica to elemental Si and subsequently formation of the composite, Mg used as the reducing agent. In this work, the as-obtained composite mainly is the product of magnesiothermic reduction reaction of the nano-silica, which finally resulted in formation of elemental Si (silicon), MgO (magnesia) and Mg2SiO4 (magnesium silicate). The as-synthesized composite can be used as anode in lithium ion batteries. The products in each step were characterized using X-ray powder diffraction (XRD) and scanning electron microscopy (FESEM and HRSEM) techniques. X-ray powder diffraction patterns confirmed the formation of almost amorphous silica while the FE-SEM images were representing the spherical si...
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In this research, the effect of different biopolymers such as polyethylene glycol (PEG) and polyvinylalcohol (PVA) on synthesis and characterization of polymer/cobalt ferrite (CF) nano-composites bymechanical alloying method has been... more
In this research, the effect of different biopolymers such as polyethylene glycol (PEG) and polyvinylalcohol (PVA) on synthesis and characterization of polymer/cobalt ferrite (CF) nano-composites bymechanical alloying method has been systematically investigated. The structural, morphological andmagnetic properties changes during mechanical milling were investigated by X-ray diffraction (XRD),Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), fieldemission scanning electron microscopy (FESEM), and vibrating sample magnetometer techniques(VSM), respectively. The polymeric cobalt ferrite nano-composites were obtained by employing atwo-step procedure: the cobalt ferrite of 20 nm mean particle size was first synthesized by mechanicalalloying route and then was embedded in PEG or PVA biopolymer matrix by milling process. Theresults revealed that PEG melted due to the local temperature raise during milling. Despite thisphenomenon, cobalt ferrite nano-pa...
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In this study the characteristics of two different kinds of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one in-house synthesized powder by a co-precipitation method and another one purchased from Fuel Cell Materials Co. (FCM Co., USA), were... more
In this study the characteristics of two different kinds of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one in-house synthesized powder by a co-precipitation method and another one purchased from Fuel Cell Materials Co. (FCM Co., USA), were compared. The co-precipitated powder was prepared by using ammonium carbonate as precipitant with a NH4+/NO3- molar ratio of 2 and calcination at 1000C for 1 h. Phase composition, morphology and particle size distribution of powders were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and laser particle size analysis (LPSA), respectively. The synthesized and commercial LSCF powders were overlaid on Yttria-stabilized zirconia (YSZ) electrolyte having a gadolinium-doped ceria (GDC) interlayer. Electrochemical Impedance Spectroscopy (EIS) measurement was carried out at various operating temperatures in the range of 600-850C. XRD and FESEM analysis revealed that single phase nano-crystalline LSCF...
Research Interests: Chemical Engineering, Materials Science, Solid Oxide Fuel Cells, Fuel Cells, Scanning Electron Microscopy, and 15 moreNanostructured materials, Perovskites, Electrochemical Impedance Spectroscopy, SOFC, Nanostructures, Solid oxide fuel cell, XRD, Oxide, materials synthesis for SOFC, Nanostructured Electrodes, Coprecipitation, IT SOFC, Cathode, Co Precipitation, and Simple Particle Size Measurement by Laser
Nano-structured lanthanum strontium cobalt ferrite, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), was successfully synthesized via co-precipitation method using metal nitrates as starting materials. Effects of precipitating agent and calcination... more
Nano-structured lanthanum strontium cobalt ferrite, La0.6Sr0.4Co0.2Fe0.8O3 (LSCF), was successfully synthesized via co-precipitation method using metal nitrates as starting materials. Effects of precipitating agent and calcination temperature on the phase composition and morphology of synthesized powders were systematically studied using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. XRD analysis revealed that a single phase La0.6Sr0.4Co0.2Fe0.8O3 perovskite was obtained in the processed sample using ammonium carbonate as precipitating agent with a NH4+/NO3-molar ratio of 2 after calcination at 1000C for 1 h. The phase composition of products was also affected by changing pH values. Moreover, using sodium hydroxide as a precipitant resulted in a mixture of La0.6Sr0.4Co0.2Fe0.8O3 and cobalt ferrite (CoFe2O4) phases. Careless washing of the precursors can also led to the formation of mixed phase after calcination of final powders. Mean ...
Research Interests: Chemical Engineering, Materials Science, Synthesis of nanoparticles, Solid Oxide Fuel Cells, Fuel Cells, and 9 morePerovskites, Synthesis and Characterization of nanomaterials, SOFC, University of Tehran, materials synthesis for SOFC, Precipitants, SOFC- Ceramics Fabrication-Modeling, IT SOFC, and Co Precipitaion
Abstract This study aims at recovering manganese from a low-grade mining waste and valorizing it through the synthesis of manganese ferrite (MnFe2O4). Full recovery of manganese from the low-grade waste was obtained by heat treatment... more
Abstract This study aims at recovering manganese from a low-grade mining waste and valorizing it through the synthesis of manganese ferrite (MnFe2O4). Full recovery of manganese from the low-grade waste was obtained by heat treatment (700 °C), and leaching optimization of the waste in a reductively promoted sulfuric acid medium. Subsequently, the Fe: Mn molar ratio (2:1) of the leachate was adjusted to prepare the precursors for the MnFe2O4 synthesis through co-precipitation. The optimization of the synthesis parameters including temperature (15–90 °C), aging time (0–120 min), and calcination temperature (800–1200 °C) was investigated. The optimum condition suggested by the response surface method (RSM) led to the synthesis of pure plate-like MnFe2O4. Additionally, nano-sized particles (45 nm) were obtained at the 90 °C synthesis temperature, 120 min aging time, and without any calcination. Both nano-sized and plate-like MnFe2O4 particles with the saturation magnetization of 34.47 and 51.03 emu g−1 presented superior magnetic properties.
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Abstract N i 0.5 Z n 0.5 F e 2 O 4 Ferrite (NZF) and N i 0.5 Z n 0.5 F e 2 O 4 /CNTs nanocomposite (CNZF) were prepared by inverse co-precipitation method as novel magnetic adsorbents. The characteristic consequences of XRD, FTIR, FESEM... more
Abstract N i 0.5 Z n 0.5 F e 2 O 4 Ferrite (NZF) and N i 0.5 Z n 0.5 F e 2 O 4 /CNTs nanocomposite (CNZF) were prepared by inverse co-precipitation method as novel magnetic adsorbents. The characteristic consequences of XRD, FTIR, FESEM and XPS analysis indicated that the adsorbents were favorably produced. The results revealed that the saturated magnetization ( M s ) of the NZF and CNZF powders was 35 and 15 emu/g, respectively. The reason of this decrease for the CNZF nanocomposite was the existence of CNT with a weak magnetic property in the complex of CNZF compared to the NZF. However, the both adsorbents have a fast-magnetic response that can be effective for separation of adsorbents from the solution by an external magnetic field. The adsorbents were then assessed for removal of arsenic(V) contaminated anions from simulated industrial wastewater. Batch reactor model was utilized to investigate the performance of adsorption and modifying efficient parameters like pH, adsorbent dosage and contact time to enhance the maximum adsorption capacity ( q m ). The maximum adsorption capacities of NZF and CNZF were found to be 56 mg/g and 66 mg/g, respectively at contact time of 30 min, adsorbent dosage of 6 g/l and pH of 2. The adsorption isotherm as a function of adsorbent dosage was assessed. It was shown that Langmuir isotherm had the highest consistency with the experimental data for both adsorbents. The kinetic behavior of adsorption over the time was evaluated. The pseudo-second order model provided the finest agreement to the experimental data. The dominant mechanism of adsorption was estimated to be surface complexation.
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Research Interests: Materials Engineering, Mechanical Engineering, Materials Science, Microstructural Evolution, Rietveld refinement, and 12 moreMultiferroics, Ceramics, Porosity, Manufacturing Engineering, Optical microscopy, Pore Formers, Mercury Porosimetry, XRD analysis, Porous ceramics, Science and Technology of Heterogeneous Materials, Bismuth Ferrite, and Elsevier
Abstract Nanostructured manganese cobaltite spinel oxide (MnCo 2 O 4 ) was successfully synthesized by co-precipitation method. X-ray diffraction (XRD) results revealed that the molar ratio of OH − / NO 3 − = 1.5 in the precipitation... more
Abstract Nanostructured manganese cobaltite spinel oxide (MnCo 2 O 4 ) was successfully synthesized by co-precipitation method. X-ray diffraction (XRD) results revealed that the molar ratio of OH − / NO 3 − = 1.5 in the precipitation stage is more appropriate for achieving MnCo 2 O 4 phase. The results of thermal analysis (TGA/DTA) along with the XRD results revealed that the MnCo 2 O 4 phase remains stable up to 1050 °C. Morphological studies show that by increasing the calcination temperature from 350 to 550 and 1000 °C, morphology of the particles varies from plate-like to quasi spherical and polyhedral shape, respectively. Density and porosity measurement of cold pressed and sintered samples showed that by employing un-calcined powder, a dense sample with 98% of the theoretical density could be obtained at the sintering temperature of 1000 °C. Selected synthesized powders were coated on the AISI 430 ferritic stainless steel coupons and the results demonstrated that using un-calcined powder, leads to the formation of a highly dense and adhesive coating layer due to the very high tendency of un-calcined powder for densification.
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Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium... more
Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium hexaferrite nano- particles to remove Cr (VI) ions from aqueous solutions was examined. Structural, magnetic, and adsorption properties of the powders are investigated by different techniques. X-ray diffraction analysis revealed that barium hexaferrite formed at a relatively low temperature of 700˚C in the sample prepared with a mixture of water/alcohol as a solvent. The FESEM and VSM studies confirmed that all samples had a plate like structure with a particle size in the range of 87-145 nm and high magnetic properties. It was demonstrated that nanometer barium hexaferrite was produced to be an operative adsorbent for removal of Cr (VI) ions from solutions. Different Cr (VI) adsorption experiments were carried out by controlling effective adsorption factors. It was revealed that the sample calcined at a temperature of 700°C and then milled for 5 h (owing themaximum surface area 13 m 2 /g) showed the highest removal efficiency of 99.5% at pH 3.0, amount of nano adsorbent 1.5 g, initial chromium concentration 133 mg/l, and contact time 1 h. FTIR analysis showed that due to the existence of Cr-O stretching band on the surface of nano-particles, the electrostatic reaction between Cr (VI) ions and nano-adsorbent is possible. The adsorption data were best fitted with the pseudo-second-order kinetic model. Also, the equilibrium adsorption capacity of Cr (VI) calculated from adsorption experiments was found to be 13.25 mg/g. Adsorption studies indicated that the potential use of barium hexaferrite nano-adsorbents for the removal of the other heavy metal ions without sacrificing adsorption capacity can be practical. Copyright © 2016 VBRI Press.
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Nano-structured manganese cobalt oxide (MnCo2O4) was successfully synthesized by co-precipitation method using metal nitrates as starting materials. The phase formation and morphology of the products were characterized by means of X-ray... more
Nano-structured manganese cobalt oxide (MnCo2O4) was successfully synthesized by co-precipitation method using metal nitrates as starting materials. The phase formation and morphology of the products were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The effects of pH and calcination temperature were investigated on the characteristics of MnCo2O4 powders. The results revealed that the MnCo2O4 phase was obtained easier at relatively higher pH values. XRD results showed that at the temperature of 450˚C the phase formation was not completed, while with increasing the calcination temperature to 1000˚C the desired phase was fully achieved. Furthermore, by increasing the calcination temperature from 550 to 1000˚C, the mean crystallite size of the powders increases from 30 to 140 nm. FESEM investigation shows that in the sample processed with OH-/NO3- =1.5 and calcined at 550˚C completely uniform particles with mean...
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Research Interests: Materials Engineering, Materials Science, Synthesis of nanoparticles, Nanotechnology, Electrical and Magnetic Properties of Composites, and 11 moreNanostructured materials, Multiferroics, Ceramics, Synthesis and Characterization of nanomaterials, Magnetic Nanostructures, Nanoscience, Magnetic Properties, Electrical Properties, Dopant, Bismuth Ferrite, and Elsevier
Nano-crystalline barium hexaferrite powders have been prepared by mechanical alloying of nFe2O3+Ba(CH3COO)2 with Fe/Ba molar ratios of 10-12 and subsequent heat treatment. Thermal behavior, phase composition, morphology and magnetic... more
Nano-crystalline barium hexaferrite powders have been prepared by mechanical alloying of nFe2O3+Ba(CH3COO)2 with Fe/Ba molar ratios of 10-12 and subsequent heat treatment. Thermal behavior, phase composition, morphology and magnetic properties of samples were studied using DTA/TGA, XRD, SEM and VSM, respectively. Nano-crystalline Ba-hexaferrite with a mean crystallite size of 46 nm and magnetic properties as high as Ms = 73.9 A.m2/kg and Hci = 334.2 kA/m was formed for mixture of 5.5Fe2O3+Ba(CH3COO)2 which was milled for 48 h and then annealed at 1100 °C.
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Multiferroic bismuth ferrite, BiFeO3, was synthesized via conventional solid-state reaction method using Bi2O3, Fe2O3 as starting materials. Effects of Bi2O3/Fe2O3 molar ratio and calcination temperature on the phase composition,... more
Multiferroic bismuth ferrite, BiFeO3, was synthesized via conventional solid-state reaction method using Bi2O3, Fe2O3 as starting materials. Effects of Bi2O3/Fe2O3 molar ratio and calcination temperature on the phase composition, morphology and magnetic properties of produced powders were systematically studied using XRD, FESEM/EDS and VSM techniques, respectively. The results revealed that BiFeO3 phase with rhombohedral R3c structure with a mean particle size of 40 nm was formed in the sample processed with a Bi2O3/Fe2O3 molar ratio of 1:1 after calcination at 800 °C. Rietveld analysis which was applied to the x-ray diffraction data via MAUD software indicated high purity of 95%wt for the above sample. Deviation from the stoichiometric molar ratio (Bi2O3/Fe2O3: 0.9, 1.1, 1.2) yielded higher content of the intermediate phases of Bi2Fe4O9 and Bi25FeO40. FESEM studies showed that the mean particle size was increased from 40 to 62 nm by increasing calcination temperature from 800 to 85...
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In this paper, the effects of infiltration of La2NiO4 (LNO) as a mixed ionic and electronic conductor (MIEC) on the electrochemical performance of porous strontium doped lanthanum manganite (LSM) oxygen electrode of solid oxide cells, in... more
In this paper, the effects of infiltration of La2NiO4 (LNO) as a mixed ionic and electronic conductor (MIEC) on the electrochemical performance of porous strontium doped lanthanum manganite (LSM) oxygen electrode of solid oxide cells, in the temperature ranges of 650-850 °C, is reported. XRD and FE-SEM results of the LNO sample calcined at 900 °C confirmed the formation of single phase LNO nanoparticles and uniform distribution of LNO into the porous LSM backbone with a mean particle size of 40 nm, respectively. To characterize the electrochemical behavior of half-cells, electrochemical impedance spectroscopy (EIS) measurement at temperature intervals of 50 °C was carried out. The LNO infiltrated LSM electrodes showed a noticeably decreased activation energy (from 130 to 103 kJ mol-1) and polarization resistance (from 26.2 to 2.5 Ωcm2 at 650 °C) under open circuit voltage (OCV) condition. Besides, the equivalent circuit (EC) modeling revealed that LNO addition has a major effect on ...
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The principles and magnetic properties of nanostructured high-entropy alloys (HEAs) processed by mechanical alloying are overviewed. Firstly, the general concepts of HEAs (multi-principal element alloys with ≥5 elements) and phase... more
The principles and magnetic properties of nanostructured high-entropy alloys (HEAs) processed by mechanical alloying are overviewed. Firstly, the general concepts of HEAs (multi-principal element alloys with ≥5 elements) and phase formation rules are briefly reviewed. Subsequently, the processing of nanocrystalline and amorphous HEAs by mechanical alloying and the effect of high-energy ball milling parameters are summarized. Finally, the magnetic properties of nanostructured HEAs are critically discussed to infer some general rules. In summary, a higher content of ferromagnetic elements (e.g. Fe, Co, and Ni) normally results in a higher saturation magnetization. The as-milled products with solid solution phases show better soft-magnetic properties compared to the fully amorphous phases, and increasing the amount of the amorphous phase decreases the saturation magnetization. The magnetic properties are also influenced by processing (such as sintering) and thermal history through the ...
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Abstract The possibility to control the structural parameters of nanostructured spinel cobalt ferrite paves the way to prepare the ferrite with the anticipated magnetic properties for broad applications. This study is aimed at elucidating... more
Abstract The possibility to control the structural parameters of nanostructured spinel cobalt ferrite paves the way to prepare the ferrite with the anticipated magnetic properties for broad applications. This study is aimed at elucidating the correlation between structural parameters and magnetic properties of cobalt ferrite nanoparticles subjected to post-calcination high-energy ball milling. The milling energy was predicted at four different levels, using the standard collision model. The samples produced were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometry (VSM). Both FTIR studies and Rietveld refinement of the XRD data shows re-distribution of cations in the spinel structure, induced by a critical level of milling energy. Also, the presence of the three ionization peaks, Co−2p, Fe−2p and O−1s, revealed by XPS confirms the formation of spinel ferrite structure in the cobalt ferrite nanoparticle. The maximum energy products (BH)max of the sample milled under high level ball milling energy was 2.18 MGOe which is almost 5 times higher than that of the un-milled calcined sample. Additionally, the magnetic anisotropy constant was calculated by the Law of Approach to Saturation (LAS) method and indicates a direct correlation between lattice strain and coercivity of samples.
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Mechanical activation processes on ilmenite concentrate were performed in three different energy levels. Iron powder as a reducing agent was added to ilmenite in the milling stage and the mechanically activated mixture was subjected to... more
Mechanical activation processes on ilmenite concentrate were performed in three different energy levels. Iron powder as a reducing agent was added to ilmenite in the milling stage and the mechanically activated mixture was subjected to acid leaching. The leaching experiments were designed using the Taguchi method, and the optimum ranges were obtained. Furthermore, response surface methodology (RSM) was used to optimize the critical parameters in the leaching system to achieve the highest titanium (Ti) leachability. Based on the inductively coupled plasma-optical emission spectrometry (ICP-OES) results, maximum leaching recovery of Ti (80%) was obtained using activated Ti concentrates at a medium activation energy level, which is calculated to be 25.38 kJ/g, using 15vol% hydrochloric acid (HCl), a temperature of 70°C, leaching time of 3 h, and a solid-to-liquid ratio of 0.05 g·mL–1. Intensifying the milling energy from a low to high level led to a decrease in the mean crystallite size and also structure homogenization at the high energy level. According to the transmission electron microscopy (TEM) images, the mean grain size of the ilmenite/Fe nanocomposite was about 30 nm at the medium energy level sample. Finally, solvent extraction by tributyl phosphate (TBP) was performed on the leach liquor to separate dissolved Fe (the major impurity) from Ti, which led to 83% extraction recovery of Ti.
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LaFe1−x−yCoxPdyO3 [(x, y) = (0, 0), (0.40, 0), (0.38, 0.05)] nanoparticles were synthesized via a co-precipitation route using ammonium hydroxide, sodium hydroxide and ammonium carbonate as the precipitant and calcination at different... more
LaFe1−x−yCoxPdyO3 [(x, y) = (0, 0), (0.40, 0), (0.38, 0.05)] nanoparticles were synthesized via a co-precipitation route using ammonium hydroxide, sodium hydroxide and ammonium carbonate as the precipitant and calcination at different temperatures to study the compositional driven structural changes in lanthanum ferrites. Analysis of X-ray diffraction (XRD) patterns confirms the formation of single-phase perovskite structure and existence of orthorhombic Pnma symmetry for calcined powders. Field emission scanning electron microscope (FESEM) observations show that Pd-doped powders yield finer particles along with narrower particle size distribution compared with LaFeO3 and LaFe0.6Co0.4O3. Moreover, using ammonia as the precipitant leads to a smaller mean particle size of powders compared to NaOH, as well as significant difference in morphology of the particles. Raman analysis reveals that both Co and Pd atoms substitute Fe site in perovskite structure with shifting of phonon modes. Comparing Raman spectra demonstrates the presence of more oxygen vacancies in Pd-doped perovskites. It can be concluded from the results that Pd is successfully incorporated into the perovskite structure by co-precipitation method.
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In this study the characteristics of two La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one obtained from an in-house synthesized by co-precipitation method and a commercial one from Fuel Cell Materials Co. (USA), were compared. The... more
In this study the characteristics of two La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one obtained from an in-house synthesized by co-precipitation method and a commercial one from Fuel Cell Materials Co. (USA), were compared. The co-precipitated powder was processed by using ammonium carbonate as precipitating agent with a NH4+/NO3- molar ratio of 2 and calcination at 1000C for 1 h. Phase composition, morphology and particle size distribution of powders were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and laser particle size analysis (LPSA), respectively. The synthesized and commercial LSCF powders were overlaid on Yttria-stabilized zirconia (YSZ) electrolyte having a gadolinium-doped ceria (GDC) interlayer. Electrochemical Impedance Spectroscopy (EIS) measurement was carried out at various operating temperatures in the range of 600-850C. XRD and FESEM analysis revealed that single phase nano-crystalline LSCF powder with a m...
Research Interests: Materials Science, Solid Oxide Fuel Cells, Fuel Cells, Scanning Electron Microscopy, Nanostructured materials, and 13 morePerovskites, Electrochemical Impedance Spectroscopy, SOFC, Nanostructures, XRD, materials synthesis for SOFC, Nanostructured Electrodes, Coprecipitation, Electrochemical Impedance Spectroscopy (EIS), SOFC- Ceramics Fabrication-Modeling, IT SOFC, Co Precipitation, and Simple Particle Size Measurement by Laser
Exchange bias which accompanies a magnetic hysteresis loop shift along field axis or increase in coercivity, occurs due to exchange interactions between ferromagnetic (FM) and antiferromagnetic (AFM) or in ferrimagnetic... more
Exchange bias which accompanies a magnetic hysteresis loop shift along field axis or increase in coercivity, occurs due to exchange interactions between ferromagnetic (FM) and antiferromagnetic (AFM) or in ferrimagnetic nanoparticles/nanolayers systems. Mixture of barium ferrite (BaFe12O19) and graphite was mechanically milled for different times. Phase analysis, particles morphology, magnetic properties at room temperature and magnetic properties after field cooling at 4 k were measured via XRD, HRTEM, VSM and SQUID, respectively. A nanocomposite of BaFe12O19/Fe3O4 forms after 20 and 40 h of milling. HRTEM images revealed that the nanocomposite consists of crystallites of both phases in intimate contact with crystallite sizes below 20 nm after 20 h milling. Field cooling of the 20- and 40-h milled samples up to 4 k resulted in exchange bias phenomenon. The shift in hysteresis loop for 20- and 40-h milled samples was 204 and 254 Oe, respectively. In spite of the mostly observed exchange coupling systems being ferromagnetic/antiferromagnetic systems, in this research the exchange coupling occurred between ferrimagnetic phases. The large difference between coercivity values at 300 and 4 k revealed that superparamagnetic particles constitute a large volume fraction of the milled nanocomposites.
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In this research, mixtures of barium ferrite and graphite were milled in a high-energy mechanical milling machine. The effect of recalcination on the magnetic properties of the milled samples was studied. Phase analysis, phase... more
In this research, mixtures of barium ferrite and graphite were milled in a high-energy mechanical milling machine. The effect of recalcination on the magnetic properties of the milled samples was studied. Phase analysis, phase transformations at high temperatures, particle size distribution, magnetic properties, and particle morphology were characterized by means of X-ray diffraction, hot stage X-ray diffraction, dynamic light scattering, vibrating sample magnetometry, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy, respectively. A magnetic nanocomposite of BaFe12O19/Fe3O4 formed after 20 and 40 h milling. The average particle size for the 20 and 40 h milled samples reached 106 and 68 nm, respectively. Recalcination of the milled samples resulted in barium ferrite structure recovery. The decreased particle size due to the milling and subsequent recalcination results in increased coercivity values. The coercivity for the milled and c...
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In this study, cobalt ferrite, CoFe2O4, was synthesized via mechanical activation of CoCO3 and Fe2O3 powder (1:1 molar ratio) using a planetary high energy ball mill in air and subsequent heat treatment. Effects of milling time and... more
In this study, cobalt ferrite, CoFe2O4, was synthesized via mechanical activation of CoCO3 and Fe2O3 powder (1:1 molar ratio) using a planetary high energy ball mill in air and subsequent heat treatment. Effects of milling time and calcination temperature on the structural evolution, morphology and magnetic properties of the powders were evaluated using XRD, FESEM and VSM techniques, respectively. XRD results indicated that the reaction between the starting materials has not occurred up to 20 hours of milling. Cobalt ferrite magnetic phase started to form in the 20 hours milled sample and becomes the major phase in the sample milled for 30 hours. FESEM images showed that the mean particle size of the milling products was decreased from 75 to 50 nm by increasing the milling time from 30 to 50 hours. Single phase cobalt ferrite was obtained in the 30 hours milled sample after heat treatment at 800°C. VSM measurement revealed that the magnetic properties were improved with controlling ...
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Nano-structured manganese cobalt oxide (MnCo2O4) was successfully synthesized by co-precipitation method using metal nitrates as starting materials. The phase formation and morphology of the products were characterized by means of X-ray... more
Nano-structured manganese cobalt oxide (MnCo2O4) was successfully synthesized by co-precipitation method using metal nitrates as starting materials. The phase formation and morphology of the products were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The effects of pH and calcination temperature were investigated on the characteristics of MnCo2O4 powders. The results revealed that the MnCo2O4 phase was obtained easier at relatively higher pH values. XRD results showed that at the temperature of 450˚C the phase formation was not completed, while with increasing the calcination temperature to 1000˚C the desired phase was fully achieved. Furthermore, by increasing the calcination temperature from 550 to 1000˚C, the mean crystallite size of the powders increases from 30 to 140 nm. FESEM investigation shows that in the sample processed with OH-/NO3- =1.5 and calcined at 550˚C completely uniform particles with mean size of 45nm can be obtained.
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In this study, multiferroic BiFeO3 (BFO) powders were synthesized via mechanical activation of Bi2O3 and Fe2O3 with the molar ratio of 1:1, using a planetary high energy ball mill and subsequent heat treatment. All samples were milled for... more
In this study, multiferroic BiFeO3 (BFO) powders were synthesized via mechanical activation of Bi2O3 and Fe2O3 with the molar ratio of 1:1, using a planetary high energy ball mill and subsequent heat treatment. All samples were milled for 20 h and heat treated at various temperatures. XRD, FESEM, LPSA, and VSM techniques were used to evaluate the powder particle characteristics. FESEM images of 20 h milled sample indicated plate-like particles with a mean thickness of 45 nm and its LPSA results showed the mean agglomerate size of about 2.0 μm. XRD results of calcined samples showed that the BFO phase began to form at 650 °C and fully formed at 750 °C. In comparison to the conventionally processed samples, BFO phase formation temperature decreases by ∼100 °C in the samples produced by mechanical activation assisted process. VSM measurements of the sample heat treated at 750°C revealed a saturation magnetization (Ms) of 0.054 emu/g and coercivity (Hc) of 412 Oe.
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Nano-structured Bi1−xBaxFeO3(x = 0, 0.2) were synthesized by solid-state reaction.Ferromagnetic, ferroelectric and dielectric properties enhanced with Ba doping.The best properties obtained in calcined doped sample at 850 °C.20wt.%... more
Nano-structured Bi1−xBaxFeO3(x = 0, 0.2) were synthesized by solid-state reaction.Ferromagnetic, ferroelectric and dielectric properties enhanced with Ba doping.The best properties obtained in calcined doped sample at 850 °C.20wt.% Ba-dopant change the structure of BFO from rhombohedral to pseudo-cubic.Bi1−xBaxFeO3(x = 0, 0.2) compounds were synthesized by conventional solid-state reaction method. Structural, morphological, magnetic and ferroelectric properties of the products were investigated systematically by employing X-ray diffraction, field emission scanning electron microscope, vibrating sample magnetometer as well as electrical evaluation techniques, respectively. The XRD results demonstrated distorted rhombohedral BiFeO3 crystal structure with the space group of R3c. However, 20wt% Ba doped sample underwent a structural phase transition from rhombohedral to distorted pseudo-cubic structure. FESEM images of the BiFeO3 sample calcined at 850 °C showed agglomerated nano-particles with a mean particle size of 60 nm, while Bi0.8Ba0.2FeO3 sample showed uniform cubic particles with a mean particle size of 220 nm. For Bi0.8Ba0.2FeO3 sample calcined at 850 °C, an anomaly in permittivity was observed in the vicinity of 370 °C which is around the Neel temperature of bismuth ferrite and is in agreement with the recent reports.
Research Interests: Synthesis of nanoparticles, Nanotechnology, Electrical and Magnetic Properties of Composites, Nanostructured materials, Multiferroics, and 8 moreCeramics, Synthesis and Characterization of nanomaterials, Magnetic Nanostructures, Nanoscience, Magnetic Properties, Electrical Properties, Dopant, and Bismuth Ferrite
Nano-sized barium hexaferrite particles were synthesized by mechanical activation of BaCO3 and Fe2O3 powders mixture as starting materials. The effects of mechanical milling energy on the phase composition, morphology, thermal behavior... more
Nano-sized barium hexaferrite particles were synthesized by mechanical activation of BaCO3 and Fe2O3 powders mixture as starting materials. The effects of mechanical milling energy on the phase composition, morphology, thermal behavior and magnetic properties of the samples were systematically investigated by employing X-ray diffractometer, field emission scanning electron microscopy, differential thermal/thermo gravimetery analysis and vibrating sample magnetometer, respectively. The milling energy was calculated at five different levels using collision model. It was found that there is an optimum milling energy value for obtaining barium hexaferrite phase. The results revealed that applying a minimum total milling energy of 93.7 kJ/g was necessary for formation of almost single barium hexaferrite at a relatively low calcination temperature of 800C. FESEM micrograph of the above sample exhibited nano-size particles with a mean particle size of 80 nm. Further increase in milling energy leads to dramatic decrease in phase purity as well as magnetic characteristics of the samples. By increasing the milling energy from 93.7 to 671.9 kJ/g, saturation magnetization (Ms) decreased from 22.5 to 0.39 emu/g, and also coercivity (Hc) decreased from 4.28 to 1.46 kOe.
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In this study, porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, urea and... more
In this study, porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, urea and graphite was intensively milled for 10 h in a planetary ball mill, uniaxially cold pressed and then subjected to the multi-stage heat treatment. The results revealed that urea and polyvinyl alcohol are appropriate candidates for maintaining the strength of the final porous structure. Density and porosity measurements showed that by employing 20wt% of high density polyethylene and graphite, a porous sample with a maximum porosity of nearly 40% could be obtained. Mercury porosimetry results showed that using urea as a pore former gives porous bismuth ferrite with a mean pore diameter of 7μm, uniform pore distribution as well as interconnected pores. Moreover, reactions between BiFeO3 matrix phase and thermal decomposition products of pore formers can lead to degradation of the BiFeO3 phase in the final porous samples. Analysis of X-ray diffraction patterns illustrated that in the samples processed with graphite, high density polyethylene and polyvinyl alcohol as pore former, BiFeO3 matrix phase partially or completely decomposes to intermediate phases of Bi2Fe4O9 and Bi25FeO40. While, using of urea does not damage the matrix phase and porous BiFeO3 within the original pervoskite structure could be prepared. Furthermore, thermodynamic investigation was carried out for prediction of possible interactions between matrix phase and pore former at elevated temperatures.