The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Alireza Badiei - One of the best experts on this subject based on the ideXlab platform.
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the role of surfactant in synthesis of magnetic Nanocrystalline Powder of nife2o4 by sol gel auto combustion method
Journal of Non-crystalline Solids, 2008Co-Authors: Mohammad Barati, S Seyyed A Ebrahimi, Alireza BadieiAbstract:Abstract In this work, a new sol–gel auto-combustion method has been performed to synthesize single phase nickel ferrite Nanocrystalline Powders by using n-cetyltrimethylammonium bromide, as a cationic surfactant. The gels were prepared from ferric and nickel nitrates and citric acid. Ammonia was used as pH adjusting agent as well. The effects of the surfactant on the after combustion calcination process and the reduction of the resulting Powder crystallite size which affects the magnetic properties of the material were investigated by XRD and DTA/TGA techniques. The results showed that the ignition of the gels in air have a self-propagating behavior. Addition of surfactant to the starting solution affected the crystallite size of the synthesized Powders and their phase constitution. The crystallite size of nickel ferrite Powder in sample with surfactant was obtained 31.2 nm. The other important result of this study was production of single phase nickel ferrite directly after combustion while without surfactant the nickel ferrite single phase was obtained only after a post-calcination process at 1000 °C.
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INFLUENCE OF pH ON PHYSICAL PROPERTIES OF NICKEL-ZINC Nanocrystalline PowderS SYNTHESIZED BY A SOL-GEL AUTO-COMBUSTION METHOD
International Journal of Modern Physics B, 2008Co-Authors: Mohammad Barati, S.a. Seyyed Ebrahimi, Alireza BadieiAbstract:In this research a sol-gel auto-combustion route has been proposed to synthesize nickel-zinc ferrite Nanocrystalline Powder, using metal nitrates, citric acid as fuel and ammonia as pH adjusting agent. The influence of pH value of the solution on phase evolution, crystallite size and morphology of as-burnt Powders were investigated by XRD, SEM and TEM techniques. The results revealed that with pH=7 the single phase nickel-zinc ferrite Nanocrystalline Powders with crystallite size of about 27nm were formed directly after auto combustion process.
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an investigation on physical properties of strontium hexaferrite nanoPowder synthesized by a sol gel auto combustion process with addition of cationic surfactant
Journal of The European Ceramic Society, 2007Co-Authors: Ghobeiti M Hasab, S Seyyed A Ebrahimi, Alireza BadieiAbstract:Abstract In this study a novel sol–gel auto-combustion method, using n -decyltrimethylammonium bromide as a cationic surfactant, has been used to synthesize strontium hexaferrite Nanocrystalline Powder. The dried nitrate–citrate gel, prepared from a solution of ferric nitrate, strontium nitrate, citric acid, trimethylamine and cationic surfactant, exhibited an auto-combustion behavior after ignition in air. The formation reaction temperature, phase identification, crystallites size, particles size distribution and morphology of resultant strontium hexaferrite Powder were investigated by DTA/TGA, FTIR, XRD, LPSA, TEM and SEM techniques. The results showed that in presence of the cationic surfactant, the combustion intensity increases and the crystallite size decreases. The crystallite size of strontium hexaferrite Powder in sample with surfactant calcined at 800 °C was 27.2 nm.
S Seyyed A Ebrahimi - One of the best experts on this subject based on the ideXlab platform.
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optimization of hydrogen dynamic heat treatment and re calcination for preparation of strontium hexaferrite Nanocrystalline Powder
Journal of Alloys and Compounds, 2009Co-Authors: H R Koohdar, S Seyyed A Ebrahimi, Amin Yourdkhani, R Dehghan, F ZajkanihaAbstract:Abstract Strontium hexaferrite is a hard magnetic material which under hydrogen treatment and re-calcination, its phase composition and also particles size and morphology change completely. Strontium hexaferrite was prepared by conventional route with calcination of strontium carbonate and hematite at 1100 °C for 1 h. Then strontium hexaferrite was heat treated in hydrogen dynamic atmosphere at various temperatures and gas flows for different times. Optimum conditions of hydrogen treatment were obtained at 850 °C with 60 cm 3 /min flow for 1 h. Subsequent re-calcination was carried out at various temperatures for the optimum hydrogen treated Powder and its optimum conditions were obtained at 1000 °C for 1 h. The effect of dynamic hydrogen treatment and re-calcination on the phase composition and particles size and morphology characterized by X-ray diffraction (XRD) and scanning and transmission electron microscopes (SEM and TEM). The results showed decomposition of strontium hexaferrite and reduction of the resultant hematite mainly to iron during hydrogen treatment. Nanocrystalline Powder of strontium hexaferrite was also reformed after the re-calcination. The magnetic properties of the initial and final strontium hexaferrite Powder were measured by a vibration sample magnetometer (VSM). The results showed about 30% increase in the coercivity by application of this process on the strontium hexaferrite Powder.
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Influences of Precursors Molar Ratio and Basic Agent on Processing of Nickel–Zinc Ferrite NanoPowders by a Sol-Gel Auto-Combustion Method
IEEE Transactions on Magnetics, 2009Co-Authors: Mohammad Barati, S Seyyed A Ebrahimi, R DehghanAbstract:In the present investigation, nickel-zinc ferrite Nanocrystalline Powder has been prepared by a sol-gel auto-combustion technique using a gel including citric acid as a reductant and nitrates as oxidants. The results showed that the nitrate citrate gels exhibit a self- propagating behavior after ignition in air. The effects of Fe/(Ni, Zn) molar ratio and the kind of the basic agent on the thermal decomposition of the gels, and phase constitution, crystallite size, and morphology of the resultant Powders were investigated by differential thermal analysis, thermo gravimetric analysis, X-ray diffraction, and transmission electron microscopy techniques. The results also revealed that in the presence of ammonia as a pH adjusting agent and Fe/(Ni, Zn) molar ratio of 2, the smallest crystallite size of nickel-zinc ferrite as 27 nm could be obtained directly after auto-combustion without the postcalcination process.
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Conversion of Conventionally Synthesized Strontium Hexaferrite Powder Into a Nano Size Powder With Enhanced Coercivity Using GTMR Method
IEEE Transactions on Magnetics, 2009Co-Authors: S Seyyed A Ebrahimi, H R Koohdar, R Dehghan, Amin YourdkhaniAbstract:Strontium hexaferrite Nanocrystalline Powder was prepared by H2, CO and CH4 gas heat treatment and recalcination of the conventionally synthesized Powder. The conventionally synthesized strontium hexaferrite was heated in hydrogen, carbon monoxide and methane dynamic atmospheres. This resulted in a change in magnetic nature of the material from hard to soft by decomposition of hexaferrite and reduction of the resultant iron oxide to the ultraflne grains of iron. Then the resultant Powders calcined at 1000degC for 1 hour to form the single phase strontium hexaferrite again but with a Nanocrystalline structure due to the formation of hexaferrite crystallites on the ultraflne grains of iron. In this work, the comparative effects of these processes on the phase evolution, morphology and size of the crystallites and magnetic properties were investigated by X-Ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (SEM and TEM) and Vibration Sample Magnetometery (VSM) techniques. The results show a good enhancement in the magnetic properties particularly coercivity by applying this new method on the hexaferrite Powder. Finally, the effect of milling process before recalcination on the magnetic properties has been investigated which shows a more significant improvement in the intrinsic coercivity of the initial material.
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the role of surfactant in synthesis of magnetic Nanocrystalline Powder of nife2o4 by sol gel auto combustion method
Journal of Non-crystalline Solids, 2008Co-Authors: Mohammad Barati, S Seyyed A Ebrahimi, Alireza BadieiAbstract:Abstract In this work, a new sol–gel auto-combustion method has been performed to synthesize single phase nickel ferrite Nanocrystalline Powders by using n-cetyltrimethylammonium bromide, as a cationic surfactant. The gels were prepared from ferric and nickel nitrates and citric acid. Ammonia was used as pH adjusting agent as well. The effects of the surfactant on the after combustion calcination process and the reduction of the resulting Powder crystallite size which affects the magnetic properties of the material were investigated by XRD and DTA/TGA techniques. The results showed that the ignition of the gels in air have a self-propagating behavior. Addition of surfactant to the starting solution affected the crystallite size of the synthesized Powders and their phase constitution. The crystallite size of nickel ferrite Powder in sample with surfactant was obtained 31.2 nm. The other important result of this study was production of single phase nickel ferrite directly after combustion while without surfactant the nickel ferrite single phase was obtained only after a post-calcination process at 1000 °C.
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evaluation of nife2o4 ferrite Nanocrystalline Powder synthesized by a sol gel auto combustion method
Journal of Non-crystalline Solids, 2007Co-Authors: S Seyyed A Ebrahimi, Jalal AzadmanjiriAbstract:Nanocrystalline NiFe 2 O 4 ferrite Powder was prepared by a sol-gel auto-combustion method from metal nitrates and citric acid. The combustion process is an oxidation-reduction reaction in which the NO - 3 ion is oxidant and the carboxyl group is reductant. The thermal analysis of nitrate-citrate gels and the phase evolution of as-burnt Powder with the different ratios of Fe/Ni and calcined Powder were investigated by DTA/TG and XRD techniques respectively. SEM and Hysteresigraph were also used to characterize the microstructure and magnetic properties of the products. The results revealed that the nitrate-citrate gel exhibits a self-propagating combustion behavior. By using this novel auto-combustion method, NiFe 2 O 4 ferrite Powder was obtained with crystallite size of 20-40 nm and suitable soft magnetic properties.
C D Stanciu - One of the best experts on this subject based on the ideXlab platform.
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structural magnetic and mossbauer spectroscopy characterisation of the fe 15 wt si Nanocrystalline Powder obtained by mechanical alloying and annealing
Journal of Alloys and Compounds, 2019Co-Authors: C D Stanciu, I Chicinas, J Marimon B Da Cunha, O IsnardAbstract:Abstract Fe-Si alloy with a large content of 15 wt % Si has been obtained in Nanocrystalline state by mechanical alloying. The influence of the milling duration and heat treatment on the formation of the alloy, its structure and magnetic properties was investigated. The Fe-Si alloy is obtained after 4 hours of mechanical alloying as shown by X-ray diffraction measurements. Annealing of the as-milled Powders leads to the formation of the Fe3Si intermetallic compound with a DO3-type superstructure. The progressive formation of the Fe-Si alloy during mechanical alloying and annealing was investigated by 57Fe Mossbauer spectrometry. Thermal stability of the Fe-15 wt % Si Powders was studied by differential scanning calorimetry (DSC). The alloy formation is also shown by the decrease of the saturation magnetisation in the first hours of mechanical milling. A difference in the saturation magnetisation of the as-milled and the milled and subsequently annealed samples is due to the magnetic moment of the iron atoms which is different in the Fe3Si structure. The Curie temperature decreases during the formation of the Fe-Si alloy.
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characterisation of the fe 10 wt si Nanocrystalline Powder obtained by mechanical alloying and annealing
Journal of Magnetism and Magnetic Materials, 2017Co-Authors: C D Stanciu, T F Marinca, I Chicinas, O IsnardAbstract:Abstract Nanocrystalline Fe-10 wt% Si Powders has been obtained by mechanical alloying. The synthesis conditions as well as their influence on the structural and magnetic properties of this soft magnetic alloy have been investigated in the light of several experimental techniques (X-ray diffraction, neutron diffraction, DSC, magnetic measurement, SEM). By X-ray diffraction (XRD) investigations have been highlighted that Fe-Si alloy is formed after 4 h of mechanical milling and the mean crystallite size is down to 14 nm (8 h milled sample). The heat treatment leads to the formation of the Fe 3 Si compound with DO3-type superstructure for low milling times. The saturation magnetisation of the as-milled Powders decreases in the first 4 h of milling due to the formation of the Fe-Si alloy. The behaviour of the saturation magnetisation versus milling time and annealing was explained by the different magnetic moment of iron atoms in Fe 3 Si structure. The Curie temperature decreases from 770 °C (the Curie temperature for pure iron) to about 650 °C after 8 h of milling.
O Isnard - One of the best experts on this subject based on the ideXlab platform.
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structural magnetic and mossbauer spectroscopy characterisation of the fe 15 wt si Nanocrystalline Powder obtained by mechanical alloying and annealing
Journal of Alloys and Compounds, 2019Co-Authors: C D Stanciu, I Chicinas, J Marimon B Da Cunha, O IsnardAbstract:Abstract Fe-Si alloy with a large content of 15 wt % Si has been obtained in Nanocrystalline state by mechanical alloying. The influence of the milling duration and heat treatment on the formation of the alloy, its structure and magnetic properties was investigated. The Fe-Si alloy is obtained after 4 hours of mechanical alloying as shown by X-ray diffraction measurements. Annealing of the as-milled Powders leads to the formation of the Fe3Si intermetallic compound with a DO3-type superstructure. The progressive formation of the Fe-Si alloy during mechanical alloying and annealing was investigated by 57Fe Mossbauer spectrometry. Thermal stability of the Fe-15 wt % Si Powders was studied by differential scanning calorimetry (DSC). The alloy formation is also shown by the decrease of the saturation magnetisation in the first hours of mechanical milling. A difference in the saturation magnetisation of the as-milled and the milled and subsequently annealed samples is due to the magnetic moment of the iron atoms which is different in the Fe3Si structure. The Curie temperature decreases during the formation of the Fe-Si alloy.
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characterisation of the fe 10 wt si Nanocrystalline Powder obtained by mechanical alloying and annealing
Journal of Magnetism and Magnetic Materials, 2017Co-Authors: C D Stanciu, T F Marinca, I Chicinas, O IsnardAbstract:Abstract Nanocrystalline Fe-10 wt% Si Powders has been obtained by mechanical alloying. The synthesis conditions as well as their influence on the structural and magnetic properties of this soft magnetic alloy have been investigated in the light of several experimental techniques (X-ray diffraction, neutron diffraction, DSC, magnetic measurement, SEM). By X-ray diffraction (XRD) investigations have been highlighted that Fe-Si alloy is formed after 4 h of mechanical milling and the mean crystallite size is down to 14 nm (8 h milled sample). The heat treatment leads to the formation of the Fe 3 Si compound with DO3-type superstructure for low milling times. The saturation magnetisation of the as-milled Powders decreases in the first 4 h of milling due to the formation of the Fe-Si alloy. The behaviour of the saturation magnetisation versus milling time and annealing was explained by the different magnetic moment of iron atoms in Fe 3 Si structure. The Curie temperature decreases from 770 °C (the Curie temperature for pure iron) to about 650 °C after 8 h of milling.
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ac magnetic properties of the soft magnetic composites based on supermalloy Nanocrystalline Powder prepared by mechanical alloying
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2012Co-Authors: I Chicinas, B V Neamţu, O Geoffroy, O IsnardAbstract:Abstract The preparation and characterization of the Nanocrystalline soft magnetic composite core based on Supermalloy Powder obtained via mechanical alloying route are presented. The AC magnetic properties of the compacts were determined in frequency range from 100 Hz to 100 kHz for flux densities of 0.05 and 0.1 T. Composite materials were obtained by covering the Supermalloy particles with a polymer binder, then compacted into toroidal shape and finally polymerized. It is found that an increase of the compacting pressure from 600 MPa to 800 MPa leads to an increase of the compacts permeability by more than 8%. Also, reducing the polymer content from 2 wt.% to 0.5 wt.% leads to an increase of the magnetic losses (at 100 kHz and 0.1 T) by 380%. The removal of the stresses induced during compaction has been accomplished by a heat treatment at 170 °C for 120 h. This leads to a significant increase (12%) of the relative initial permeability of the compacts.
Ghobeiti M Hasab - One of the best experts on this subject based on the ideXlab platform.
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an investigation on physical properties of strontium hexaferrite nanoPowder synthesized by a sol gel auto combustion process with addition of cationic surfactant
Journal of The European Ceramic Society, 2007Co-Authors: Ghobeiti M Hasab, S Seyyed A Ebrahimi, Alireza BadieiAbstract:Abstract In this study a novel sol–gel auto-combustion method, using n -decyltrimethylammonium bromide as a cationic surfactant, has been used to synthesize strontium hexaferrite Nanocrystalline Powder. The dried nitrate–citrate gel, prepared from a solution of ferric nitrate, strontium nitrate, citric acid, trimethylamine and cationic surfactant, exhibited an auto-combustion behavior after ignition in air. The formation reaction temperature, phase identification, crystallites size, particles size distribution and morphology of resultant strontium hexaferrite Powder were investigated by DTA/TGA, FTIR, XRD, LPSA, TEM and SEM techniques. The results showed that in presence of the cationic surfactant, the combustion intensity increases and the crystallite size decreases. The crystallite size of strontium hexaferrite Powder in sample with surfactant calcined at 800 °C was 27.2 nm.
