In the present research, Fe3O4/TiO2 magnetic photo-catalytic nanocomposites with a core/shell str... more In the present research, Fe3O4/TiO2 magnetic photo-catalytic nanocomposites with a core/shell structure were successfully synthesized using two techniques of ultrasonic and St?ber. In this way, iron oxide (II, III) nanoparticles as soft magnetic cores of this composite were prepared by utilizing a chemical method assisted by ultrasound with a Fe+3/Fe+2 molar ratio of 1.5 under the nitrogen atmosphere. Thereafter, titanium oxide coating was performed on Fe3O4 nanoparticles by using tetrabutyl orthotitanate (TBOT) and titanium isopropoxide (TTIP) precursors. The resultant nanostructures were characterized by means of X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Through findings obtained from TEM examinations, the formation of core/shell nanostructure was confirmed in the prepared Fe3O4/TiO2 compo...
ذرات نانوکریستالی هگزافریت باریم به�وسیله روش هم�رسوبی با استفاده از محلول کلریدهای آهن و باریم ت... more ذرات نانوکریستالی هگزافریت باریم به�وسیله روش هم�رسوبی با استفاده از محلول کلریدهای آهن و باریم تهیه شدند. در این فرآیند از آب و مخلوطی از دی اتیلن گلیکول و آب با نسبت حجمی 1:3 به عنوان حلال استفاده شد و پودرهای حاصل از هم�رسوبی در دماهای مختلف برای 1 ساعت کلسینه شدند. نتایج حاصل از XRD نمونه?های کلسینه شده نشان داد که تشکیل تک فاز هگزافریت باریم برای نمونه سنتز شده در محلول آبی با نسبت مولی Fe+3/Ba+2 برابر 11 در دمای 900 درجه سانتیگراد اتفاق می?افتد و تشکیل آن ناشی از واکنش فازهای عمدتا کریستالی است؛ درحالی�که این دما برای نمونه سنتز شده در محلول مخلوط دی اتیلن گلیکول/آب با نسبت مولی Fe+3/Ba+2 برابر 12 تا 700 درجه سانتیگراد کاهش یافته و تشکیل هگزافریت باریم شامل واکنش فازهای آمورف با فازهای کریستالی است. کریستالیتهای تک فاز هگزافریت باریم با اندازه متوسط nm 35 در تصویر TEM نمونه سنتز�شده در محلول دی اتیلن گلیکول/آب بعد از کلسیناسیون در 700 درجه سانتیگراد قابل مشاهده بودند و در این سیستم استفاده از نسبت مولی Fe+3/Ba+2 برابر 11 منجر به تشکیل تک فاز هگزافریت باریم نشد.
Severe plastic deformation is a technical method to produce functional material with special prop... more Severe plastic deformation is a technical method to produce functional material with special properties such as high strength and specific physical properties. Selection of an efficient severe plastic deformation for grain refinement is a challenging field of study and using a modeling technique to predict the refinement efficiency has gained a lot of attentions. A comparative study was carried out on the grain refinement ability of two severe plastic deformation techniques. Accordingly, beta-tin samples were processed for almost the same strain level by the equal channel angular extrusion (ECAE) and the newly developed multi-axial incremental forging and shearing (MAIFS). Optical microscope and tensile tests were used to investigate the microstructure and mechanical properties. It was found that the MAIFS process is more efficient in grain refinement than ECAE by help of crystal plasticity analysis and experimental observation. This was ascribed to the more activated slip systems i...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
Multi-axial incremental forging and shearing (MAIFS), as a new severe plastic deformation techniq... more Multi-axial incremental forging and shearing (MAIFS), as a new severe plastic deformation technique, was successfully applied up to eight passes on the workpieces of commercially pure Al (AA1100). The microstructure evolutions and mechanisms of the grain refinement in the billets deformed through various passes of process were studied using the electron backscatter diffraction (EBSD) analysis. Microhardness measurements and tensile tests were carried out to evaluate the mechanical properties and deformation behavior of the material after successive passes of the MAIFS process. Measured microhardness evolution indicated that while the distribution of hardness was non-uniform after odd-numbered passes up to four passes, but thereafter outstanding deformation homogeneity was achieved when the consecutive MAIFS passes were applied. Tensile tests indicated that yield stress and ultimate tensile strength increased rapidly during the primary pass of process but thereafter there was only a ...
Pure anatase powders of titanium dioxide with a homogeneous nanosized particles distribution were... more Pure anatase powders of titanium dioxide with a homogeneous nanosized particles distribution were prepared by a facile hydrothermal route using solution of acetic acid and tetraisopropyl orthotitanate as the precursors with a molar ratio of 1:1. The modified hydrolyzed alkoxide was treated at various temperatures under different autogenic pressures. Two different reactors were employed as autoclaves for heating and generation of high pressures during the synthesis and crystallization of TiO2 nanoparticles. The characteristics of TiO2 powders obtained under various synthesis conditions were verified using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). The results indicated that particles size of the formed TiO2 could be finely tuned by varying the experimental parameters of temperature, pressure and the amount of nitric acid in the peptization step. TiO2 nanoparticles with good dispersion and mean size of about 9 nm could be seen in FE-SEM image of ...
The evolution of flow stress with imposed strain for an aluminum alloy (AA1100) processed by seve... more The evolution of flow stress with imposed strain for an aluminum alloy (AA1100) processed by severe plastic deformation (SPD) has been described by utilizing three different models. The applied constitutive laws include a generalized three-dimensional dislocation density based model, a formulation based on the combination of the Estrin and Mecking model with an Avrami-type equation (EMA), and finally a relationship based upon the dimensional analysis using Pi-theorem. To verify the predicted flow stress, newly developed SPD process called multi-axial incremental forging and shearing (MAIFS) were performed from one to eight passes on the aluminum alloy workpieces. It was shown that the predictions of the EMA and Pi-theorem based models agreed well with the experimental trend of flow stress variations over a wide range of strain, and these models were able to address both hardening and softening observed at high strains. But, some modifications should be carried out on the disloca-tion density based model to give results with a reasonable agreement with the experimental data in the range of strain softening. The correct true stress-strain curves of each of eight passes after tensile test flow localization were firstly calculated according to a neck evolution model proposed by Segal et al. (2006). Then, a general descriptive constitutive equation for tensile flow behavior of the material after each pass of SPD process was developed based on an extension of the model originated from Pi-theorem. Furthermore, the severely deformed specimens kept fairly large total tensile elongation and for proving ductility, scanning electron microscopy observations of fracture surfaces were carried out. These observations indicated that the fracture surfaces were characterized by a dimple-like structure, which implied the existence of a ductile failure mode.
A novel experimental technique called "Multi-Axial Incremental Shearing" (MAIS) is prop... more A novel experimental technique called "Multi-Axial Incremental Shearing" (MAIS) is proposed to impose plastic shear strain to the bulk metallic materials. The evolution of strain during MAIS processing of AA1100 alloy has been studied by employing 3D finite element modeling. The commercial code DEFORM was used to analyze the deformation and evolution of the working load with rams displacement as the material passes through the die. Simulation results showed that a large amount of accumulative strain can be applied to the sample without change of its dimensions. In order to verify the metal flow and microstructure characteristics, Sn-1wt.% Bi alloy specimens as the representative of the soft metals have been deformed by MAIS process.
Nanocrystalline particles of barium ferrite magnetic material have been prepared by co-precipitat... more Nanocrystalline particles of barium ferrite magnetic material have been prepared by co-precipitation route using aqueous and non-aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11 and subsequent drying-annealing treatment. Water and ethanol/water mixture with volume ratio of 3:1 were used as solvents in the process. Coprecipitated powders were annealed at various temperatures for 1 h. FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), DTA/TGA (differential thermal analy-sis/thermogravimetric analysis) and SEM (scanning electron microscopy) techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium ferrite occurs in sample synthesized in ethanol/water solution at a relatively low temper-ature of 631 • C. Nano-size particles of barium ferrite with mean particle size of almost 75 and 100 nm were observed in the SEM micrographs of the samples synthesized in ethanol/water solution after annealing at 700 and 800◦C for 1 h, respectively.
Nano-crystalline particles of barium hexaferrite have been prepared by co-precipitation route usi... more Nano-crystalline particles of barium hexaferrite have been prepared by co-precipitation route using solution of iron and barium chlorides with a Fe/Ba molar ratio of 12 by addition of NaOH with OH-/Cl- molar ratio of 2. A mixture of water and diethylene glycol with volume ratio of 1:3 was used as a solvent in the process. Dried co-precipitated powder was annealed at various temperatures for 1 h. FTIR, XRD, DTA/TGA, SEM, and TEM techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium hexaferrite occurs at relatively low temperature of 614 degC for precursor synthesized in diethylene glycol/water solution. The corresponding mean crystallite size measured by TEM for sample annealed at 700degC was 35 nm.
In the present research, Fe3O4/TiO2 magnetic photo-catalytic nanocomposites with a core/shell str... more In the present research, Fe3O4/TiO2 magnetic photo-catalytic nanocomposites with a core/shell structure were successfully synthesized using two techniques of ultrasonic and St?ber. In this way, iron oxide (II, III) nanoparticles as soft magnetic cores of this composite were prepared by utilizing a chemical method assisted by ultrasound with a Fe+3/Fe+2 molar ratio of 1.5 under the nitrogen atmosphere. Thereafter, titanium oxide coating was performed on Fe3O4 nanoparticles by using tetrabutyl orthotitanate (TBOT) and titanium isopropoxide (TTIP) precursors. The resultant nanostructures were characterized by means of X-ray powder diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, vibrating sample magnetometer (VSM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Through findings obtained from TEM examinations, the formation of core/shell nanostructure was confirmed in the prepared Fe3O4/TiO2 compo...
ذرات نانوکریستالی هگزافریت باریم به�وسیله روش هم�رسوبی با استفاده از محلول کلریدهای آهن و باریم ت... more ذرات نانوکریستالی هگزافریت باریم به�وسیله روش هم�رسوبی با استفاده از محلول کلریدهای آهن و باریم تهیه شدند. در این فرآیند از آب و مخلوطی از دی اتیلن گلیکول و آب با نسبت حجمی 1:3 به عنوان حلال استفاده شد و پودرهای حاصل از هم�رسوبی در دماهای مختلف برای 1 ساعت کلسینه شدند. نتایج حاصل از XRD نمونه?های کلسینه شده نشان داد که تشکیل تک فاز هگزافریت باریم برای نمونه سنتز شده در محلول آبی با نسبت مولی Fe+3/Ba+2 برابر 11 در دمای 900 درجه سانتیگراد اتفاق می?افتد و تشکیل آن ناشی از واکنش فازهای عمدتا کریستالی است؛ درحالی�که این دما برای نمونه سنتز شده در محلول مخلوط دی اتیلن گلیکول/آب با نسبت مولی Fe+3/Ba+2 برابر 12 تا 700 درجه سانتیگراد کاهش یافته و تشکیل هگزافریت باریم شامل واکنش فازهای آمورف با فازهای کریستالی است. کریستالیتهای تک فاز هگزافریت باریم با اندازه متوسط nm 35 در تصویر TEM نمونه سنتز�شده در محلول دی اتیلن گلیکول/آب بعد از کلسیناسیون در 700 درجه سانتیگراد قابل مشاهده بودند و در این سیستم استفاده از نسبت مولی Fe+3/Ba+2 برابر 11 منجر به تشکیل تک فاز هگزافریت باریم نشد.
Severe plastic deformation is a technical method to produce functional material with special prop... more Severe plastic deformation is a technical method to produce functional material with special properties such as high strength and specific physical properties. Selection of an efficient severe plastic deformation for grain refinement is a challenging field of study and using a modeling technique to predict the refinement efficiency has gained a lot of attentions. A comparative study was carried out on the grain refinement ability of two severe plastic deformation techniques. Accordingly, beta-tin samples were processed for almost the same strain level by the equal channel angular extrusion (ECAE) and the newly developed multi-axial incremental forging and shearing (MAIFS). Optical microscope and tensile tests were used to investigate the microstructure and mechanical properties. It was found that the MAIFS process is more efficient in grain refinement than ECAE by help of crystal plasticity analysis and experimental observation. This was ascribed to the more activated slip systems i...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
Multi-axial incremental forging and shearing (MAIFS), as a new severe plastic deformation techniq... more Multi-axial incremental forging and shearing (MAIFS), as a new severe plastic deformation technique, was successfully applied up to eight passes on the workpieces of commercially pure Al (AA1100). The microstructure evolutions and mechanisms of the grain refinement in the billets deformed through various passes of process were studied using the electron backscatter diffraction (EBSD) analysis. Microhardness measurements and tensile tests were carried out to evaluate the mechanical properties and deformation behavior of the material after successive passes of the MAIFS process. Measured microhardness evolution indicated that while the distribution of hardness was non-uniform after odd-numbered passes up to four passes, but thereafter outstanding deformation homogeneity was achieved when the consecutive MAIFS passes were applied. Tensile tests indicated that yield stress and ultimate tensile strength increased rapidly during the primary pass of process but thereafter there was only a ...
Pure anatase powders of titanium dioxide with a homogeneous nanosized particles distribution were... more Pure anatase powders of titanium dioxide with a homogeneous nanosized particles distribution were prepared by a facile hydrothermal route using solution of acetic acid and tetraisopropyl orthotitanate as the precursors with a molar ratio of 1:1. The modified hydrolyzed alkoxide was treated at various temperatures under different autogenic pressures. Two different reactors were employed as autoclaves for heating and generation of high pressures during the synthesis and crystallization of TiO2 nanoparticles. The characteristics of TiO2 powders obtained under various synthesis conditions were verified using X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM). The results indicated that particles size of the formed TiO2 could be finely tuned by varying the experimental parameters of temperature, pressure and the amount of nitric acid in the peptization step. TiO2 nanoparticles with good dispersion and mean size of about 9 nm could be seen in FE-SEM image of ...
The evolution of flow stress with imposed strain for an aluminum alloy (AA1100) processed by seve... more The evolution of flow stress with imposed strain for an aluminum alloy (AA1100) processed by severe plastic deformation (SPD) has been described by utilizing three different models. The applied constitutive laws include a generalized three-dimensional dislocation density based model, a formulation based on the combination of the Estrin and Mecking model with an Avrami-type equation (EMA), and finally a relationship based upon the dimensional analysis using Pi-theorem. To verify the predicted flow stress, newly developed SPD process called multi-axial incremental forging and shearing (MAIFS) were performed from one to eight passes on the aluminum alloy workpieces. It was shown that the predictions of the EMA and Pi-theorem based models agreed well with the experimental trend of flow stress variations over a wide range of strain, and these models were able to address both hardening and softening observed at high strains. But, some modifications should be carried out on the disloca-tion density based model to give results with a reasonable agreement with the experimental data in the range of strain softening. The correct true stress-strain curves of each of eight passes after tensile test flow localization were firstly calculated according to a neck evolution model proposed by Segal et al. (2006). Then, a general descriptive constitutive equation for tensile flow behavior of the material after each pass of SPD process was developed based on an extension of the model originated from Pi-theorem. Furthermore, the severely deformed specimens kept fairly large total tensile elongation and for proving ductility, scanning electron microscopy observations of fracture surfaces were carried out. These observations indicated that the fracture surfaces were characterized by a dimple-like structure, which implied the existence of a ductile failure mode.
A novel experimental technique called "Multi-Axial Incremental Shearing" (MAIS) is prop... more A novel experimental technique called "Multi-Axial Incremental Shearing" (MAIS) is proposed to impose plastic shear strain to the bulk metallic materials. The evolution of strain during MAIS processing of AA1100 alloy has been studied by employing 3D finite element modeling. The commercial code DEFORM was used to analyze the deformation and evolution of the working load with rams displacement as the material passes through the die. Simulation results showed that a large amount of accumulative strain can be applied to the sample without change of its dimensions. In order to verify the metal flow and microstructure characteristics, Sn-1wt.% Bi alloy specimens as the representative of the soft metals have been deformed by MAIS process.
Nanocrystalline particles of barium ferrite magnetic material have been prepared by co-precipitat... more Nanocrystalline particles of barium ferrite magnetic material have been prepared by co-precipitation route using aqueous and non-aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11 and subsequent drying-annealing treatment. Water and ethanol/water mixture with volume ratio of 3:1 were used as solvents in the process. Coprecipitated powders were annealed at various temperatures for 1 h. FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), DTA/TGA (differential thermal analy-sis/thermogravimetric analysis) and SEM (scanning electron microscopy) techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium ferrite occurs in sample synthesized in ethanol/water solution at a relatively low temper-ature of 631 • C. Nano-size particles of barium ferrite with mean particle size of almost 75 and 100 nm were observed in the SEM micrographs of the samples synthesized in ethanol/water solution after annealing at 700 and 800◦C for 1 h, respectively.
Nano-crystalline particles of barium hexaferrite have been prepared by co-precipitation route usi... more Nano-crystalline particles of barium hexaferrite have been prepared by co-precipitation route using solution of iron and barium chlorides with a Fe/Ba molar ratio of 12 by addition of NaOH with OH-/Cl- molar ratio of 2. A mixture of water and diethylene glycol with volume ratio of 1:3 was used as a solvent in the process. Dried co-precipitated powder was annealed at various temperatures for 1 h. FTIR, XRD, DTA/TGA, SEM, and TEM techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium hexaferrite occurs at relatively low temperature of 614 degC for precursor synthesized in diethylene glycol/water solution. The corresponding mean crystallite size measured by TEM for sample annealed at 700degC was 35 nm.
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