Papers by Mehdi Montazeri-Pour
Processing and Application of Ceramics 16 [3] (2022) 291–301, 2022
In this research, three magnetically separable photocatalysts, Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/Ti... more In this research, three magnetically separable photocatalysts, Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO, with core/shell/shell structures were successfully prepared. In the first step, soft magnetic and hard magnetic Fe3O4 and SrFe12O19 powders were synthesized using carbon reduction and co-precipitation routes, respectively. In the second step, silica coating was performed by controlling the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) precursor on the magnetic cores. In the third step, a layer of TiO2 or ZnO photocatalytic shells was made on the as-prepared composites using titanium n-butoxide (TNBT) or zinc nitrate hexahydrate, respectively. The formation of the core/shell/shell structures was confirmed by FESEM and TEM analyses. The saturation magnetizations of the Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO photocatalytic materials were 41.5, 33 and 49 emu/g, respectively. Photocatalytic activity was evaluated by degradation percentages of methylene blue (MB) under UV illumination, which were 88%, 83% and 62%, for the Fe3O4/SiO2/TiO2, SrFe12O19//TiO2 and Fe3O4/SiO2/ZnO composites, respectively. The first-, and second-order reaction kinetics were used to find out the suitable MB removal kinetics.
Processing and Application of Ceramics 16 [3] (2022) 291–301, 2022
In this research, three magnetically separable photocatalysts, Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/Ti... more In this research, three magnetically separable photocatalysts, Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO, with core/shell/shell structures were successfully prepared. In the first step, soft magnetic and hard magnetic Fe3O4 and SrFe12O19 powders were synthesized using carbon reduction and co-precipitation routes, respectively. In the second step, silica coating was performed by controlling the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) precursor on the magnetic cores. In the third step, a layer of TiO2 or ZnO photocatalytic shells was made on the as-prepared composites using titanium n-butoxide (TNBT) or zinc nitrate hexahydrate, respectively. The formation of the core/shell/shell structures was confirmed by FESEM and TEM analyses. The saturation magnetizations of the Fe3O4/SiO2/TiO2, SrFe12O19/SiO2/TiO2 and Fe3O4/SiO2/ZnO photocatalytic materials were 41.5, 33 and 49 emu/g, respectively. Photocatalytic activity was evaluated by degradation percentages of methylene blue (MB) under UV illumination, which were 88%, 83% and 62%, for the Fe3O4/SiO2/TiO2, SrFe12O19//TiO2 and Fe3O4/SiO2/ZnO composites, respectively. The first-, and second-order reaction kinetics were used to find out the suitable MB removal kinetics.
Physica scripta, May 30, 2024
Science of Sintering, 2020
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.
Journal of Inorganic and Organometallic Polymers and Materials, Jan 2, 2020
The strontium ferrite nano-crystals were prepared via co-precipitation method in different synthe... more The strontium ferrite nano-crystals were prepared via co-precipitation method in different synthesis media including a mixture of ethanol and water (with a volume ratio equal to 3:1) and water. In this way, the iron and strontium chlorides with various molar ratios were utilized as sources for Fe 3+ and Sr 2+ ions, respectively. Phase analyses, structural properties and morphology of the SrFe 12 O 19 powders were characterized by various techniques including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer and Fourier transform infrared spectra. Thermal decomposition behaviors of the as-synthesized precursors were monitored by DTA/TGA (differential thermal analysis/thermo-gravimetric analysis). The effects of molar ratio, calcination temperature and co-precipitation media of the strontium ferrite powder were investigated. The results of DTA indicated that the strontium hexaferrite prepared by co-precipitation in ethanol/water media was formed at a lower temperature. The maximum saturation magnetization of the strontium ferrite powder with the value of 58 emu/g was achieved at a temperature of 950 °C by a Fe 3+ /Sr 2+ molar ratio of 12. Wide coercivity in the range of 1512-5764 Oe was observed by tuning calcination temperatures. Furthermore, the photocatalytic properties of the resultant optimum SrFe 12 O 19 particles were assessed. The destruction of methylene blue dye was about 46% in the presence of the strontium ferrite under UV light irradiation for 120 min.
Journal of Materials Science: Materials in Electronics, Oct 2, 2014
TiO 2-SiO 2 nano-composites with the core/shell structure have been prepared by means of a techni... more TiO 2-SiO 2 nano-composites with the core/shell structure have been prepared by means of a technique based on an extension of well-known Stöber process. In this way, the silica coating of TiO 2 nano-particles in the presence of various commercially available surfactants of cationic, anionic and nonionic has been conducted with the aim to increase barrier properties against UV (UV blocking) radiation, in order to optimize photo-killing ability of the TiO 2 nano-particles and decline of the high photocatalytic property of titania. The influences of varying coating parameters such as time and temperature on the silica content of nano-composites have been studied and optimum conditions for attaining a thick layer of SiO 2 have been determined. Electro-phoretic mobility measurements indicated that the silica coating shifted the iso-electric point of titania toward that of a typical pure colloidal silica. Surface elemental composition of core/shell structured TiO 2-SiO 2 nano-composites was verified by using energy dispersive X-ray analysis. It was found that maximum silica shell thickness can be obtained in the presence of polyethylene glycol as a nonionic surfactant at 80°C for 360 min. The photo-catalytic activities were evaluated by the degradation of an aqueous solution of methylene blue under UV light irradiation. In addition, the resultant optimum nano-composites have been characterized by FE-SEM, TEM, BET, FTIR and UV-Vis spectroscopy.
Journal of Materials Science: Materials in Electronics, 2017
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...
Journal of Inorganic and Organometallic Polymers and Materials, 2020
The strontium ferrite nano-crystals were prepared via co-precipitation method in different synthe... more The strontium ferrite nano-crystals were prepared via co-precipitation method in different synthesis media including a mixture of ethanol and water (with a volume ratio equal to 3:1) and water. In this way, the iron and strontium chlorides with various molar ratios were utilized as sources for Fe 3+ and Sr 2+ ions, respectively. Phase analyses, structural properties and morphology of the SrFe 12 O 19 powders were characterized by various techniques including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer and Fourier transform infrared spectra. Thermal decomposition behaviors of the as-synthesized precursors were monitored by DTA/TGA (differential thermal analysis/thermo-gravimetric analysis). The effects of molar ratio, calcination temperature and co-precipitation media of the strontium ferrite powder were investigated. The results of DTA indicated that the strontium hexaferrite prepared by co-precipitation in ethanol/water media was formed at a lower temperature. The maximum saturation magnetization of the strontium ferrite powder with the value of 58 emu/g was achieved at a temperature of 950 °C by a Fe 3+ /Sr 2+ molar ratio of 12. Wide coercivity in the range of 1512-5764 Oe was observed by tuning calcination temperatures. Furthermore, the photocatalytic properties of the resultant optimum SrFe 12 O 19 particles were assessed. The destruction of methylene blue dye was about 46% in the presence of the strontium ferrite under UV light irradiation for 120 min.
Journal of the Australian Ceramic Society, 2018
In the present research, CoAl 2 O 4 nano-pigment powder was synthesized by a combination of citra... more In the present research, CoAl 2 O 4 nano-pigment powder was synthesized by a combination of citrate-gel processing and microwave-assisted heating route. Blue CoAl 2 O 4 ceramic nano-pigment was rapidly obtained after calcination in microwave oven. Thermal decomposition behavior of the as-synthesized precursor was monitored by DTA/TGA (differential thermal analysis/thermo-gravimetric analysis). The effects of various microwave exposure times (8-15 min) on the phase composition and difference in color were evaluated through X-ray diffraction (XRD) and CIE Lab color space system, respectively. The mean crystallite size of blue nano-pigment powders was determined by the X-ray line broadening technique. The optimum time of pigment processing by utilizing microwave oven was obtained at 15 min to get a sufficiently intense blue color. Scanning electron microscopy (SEM) and field emission SEM (FE-SEM) characterizations were employed to observe the size and morphology of optimum powder particles. Particles size analysis by SEM indicated that the majority of quasi-spherical particles have a small size in the range of nano which was in agreement with XRD results, while FE-SEM studies confirmed flower-like morphology of asprepared powder.
Advanced Engineering Materials, 2015
A novel severe plastic deformation (SPD) technique entitled Multi-Axial Incremental Forging and S... more A novel severe plastic deformation (SPD) technique entitled Multi-Axial Incremental Forging and Shearing (MAIFS) has been introduced and the preliminary evaluation of this technique by characterizing the material flow has been described in this paper. The MAIFS process is the combination of incremental forging (or incremental back extrusion) followed by angular pressing. The streamline visualized data of a tin-based alloy as the representative of the soft deformable metals was utilized to predict the strain distribution experienced by material during deformation induced by MAIFS process. It was demonstrated that acceptable deformation homogeneity can be achieved after pass two of the process, and the workpieces were deformed up to four passes of MAIFS without any crack or discontinuity. The first results of numerical simulations of proposed process after four consecutive passes proved its general feasibility, and comparison of acquired data with the simulation results of same specimen processed by four passes ECAP through route B c confirmed the capability of MAIFS process. An attempt has also been made to primarily investigate the potential of the process for grain refinement.
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.
Materials Science and Technology, 2014
A constitutive equation for description of mechanical behaviour of metals at large strains was pr... more A constitutive equation for description of mechanical behaviour of metals at large strains was proposed to relate the important process variables associated with severe plastic deformation. Dimensional analysis based on the so called p-theorem was used for this purpose; in which the obtained dimensionless groups were related and rewritten to achieve the constitutive equation. The validity of the proposed relationship was investigated using the flow stress data of an aluminium alloy processed by accumulative roll bonding (ARB), copper processed by equal channel angular pressing (ECAP) and low carbon steel processed by constrained groove pressing (CGP) technique. It was shown that the predictions of the proposed model agree well with the experimental observations over a wide range of strain for different materials. Moreover, this model was able to address both hardening and softening at high strains. These prove the applicability of the p-theorem as an alternative approach to derive the constitutive relationships of heavily deformed metals with emphasis on the microstructure evolution.
Mechanics of Materials, 2016
International Journal of Nanoscience, 2011
Nanosize particles of barium hexaferrite were prepared by co-precipitation route using solution o... more Nanosize particles of barium hexaferrite were prepared by co-precipitation route using solution of iron and barium chlorides with a Fe þ3 /Ba þ2 molar ratio of 11. Water and a mixture of water/ ethanol with volume ratio of 1:3 were used as solvents. Co-precipitated powders were calcined at various temperatures. XRD results showed that single phase barium hexaferrite forms at 900 C for sample synthesized in aqueous solution and its formation is resulted from the reaction between mainly crystalline phases, while this temperature decreased to 700 C for sample synthesized in water/ethanol solution and the formation of barium hexaferrite consists of reactions between amorphous phases with crystalline phases. SEM micrographs of the calcined samples at 800 C indicated that the morphology of particles was a®ected by the type of solvent. Nano size particles of barium hexaferrite with mean particle size of almost 80 nm were observed in the SEM micrograph of sample synthesized in water/ethanol solution after calcination at 800 C. Barium hexaferrite crystallites with mean size of 35 nm, which was approximately consistent with size obtained from XRD line broadening technique, could be seen in TEM image of this sample after calcination at 700 C.
Advanced Materials Research, 2013
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.
Journal of Materials Science: Materials in Electronics, 2014
TiO 2 -SiO 2 nano-composites with the core/shell structure have been prepared by means of a techn... more TiO 2 -SiO 2 nano-composites with the core/shell structure have been prepared by means of a technique based on an extension of well-known Stöber process. In this way, the silica coating of TiO 2 nano-particles in the presence of various commercially available surfactants of cationic, anionic and nonionic has been conducted with the aim to increase barrier properties against UV (UV blocking) radiation, in order to optimize photo-killing ability of the TiO 2 nano-particles and decline of the high photocatalytic property of titania. The influences of varying coating parameters such as time and temperature on the silica content of nano-composites have been studied and optimum conditions for attaining a thick layer of SiO 2 have been determined. Electro-phoretic mobility measurements indicated that the silica coating shifted the iso-electric point of titania toward that of a typical pure colloidal silica. Surface elemental composition of core/shell structured TiO 2 -SiO 2 nano-composites was verified by using energy dispersive X-ray analysis. It was found that maximum silica shell thickness can be obtained in the presence of polyethylene glycol as a nonionic surfactant at 80°C for 360 min. The photo-catalytic activities were evaluated by the degradation of an aqueous solution of methylene blue under UV light irradiation. In addition, the resultant optimum nano-composites have been characterized by FE-SEM, TEM, BET, FTIR and UV-Vis spectroscopy.
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Papers by Mehdi Montazeri-Pour