shahram Raygan | University of Tehran (original) (raw)
Papers by shahram Raygan
Journal of Environmental Chemical Engineering, 2017
Abstract In the present study, leaching of tailing containing 29.6 wt.% Ni in sulfuric acid was i... more Abstract In the present study, leaching of tailing containing 29.6 wt.% Ni in sulfuric acid was investigated. Tailing was characterized by X-ray powder diffraction (XRD), X-ray fluorescence (XRF) and inductively coupled plasma (ICP-OES) methods. Rinsing process for the separation of tungsten from tailing was conducted in distilled water at 80 °C for 240 min. After the filtration of solid residue from tungsten solution by vacuum filtration, batch leaching tests were carried out on solid residue at atmospheric pressure in stirred acid solution. The effects of sulfuric acid concentration (1–4 mol), pulp density (1/10–1/20 gmL −1 ), particle size (−600 +420 to −180 +125 mm) and temperature (25–80 °C) on the nickel dissolution were studied. The results showed that leaching of about 99% of nickel content of the washed tailing could be achieved using 4.0 mol sulfuric acid, pulp density of 1/20 gmL −1 and particle size of −180 +250 mm at 80 °C after 240 min. Kinetic analysis of the leaching data properly followed the shrinking core model, and the dissolution rate of nickel was found to be controlled by diffusion through the product layer for 25 and 40 °C and chemical reaction for 80 °C. Leaching rate of nickel at 60 °C at the first stage (0–60 min) was controlled by diffusion through the product; then, at the second stage, it was controlled by the chemical reaction (60–240 min).
Powder Technology, 2013
W–Cu nanocomposites were prepared by reactive milling of tungsten trioxide (WO3) and copper oxide... more W–Cu nanocomposites were prepared by reactive milling of tungsten trioxide (WO3) and copper oxide (CuO) with pure magnesium and subsequent elimination of the undesired byproduct. In-situ reduction of the oxides primarily resulted in the formation of W–Cu–MgO composite. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were employed to study the structural evolution of the milled samples. The XRD patterns indicated that, in the experiments with 10 and 20% over-stoichiometric magnesium, the reactions completed after about 16 min. The crystallite size obtained from XRD data analysis was estimated to be 23 nm for W and 37 nm for Cu, while the powder particle size measured by SEM was in the range of 40–500 nm after 2 h. Based on the thermodynamic properties of the reactants, XRD investigation, and temperature monitoring of the vial outside wall, a mechanism was proposed for the kinetics of the reactions. Finally, selective acid leaching was applied to remove the MgO, leav...
Applied Physics A
Exchange bias which accompanies a magnetic hysteresis loop shift along field axis or increase in ... 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.
Powder Metallurgy, 2017
The aim of this work is to identify relationships between the input variables and the process res... more The aim of this work is to identify relationships between the input variables and the process responses and to develop predictive models that could be used in the design of coating AISI D2 steel substrate with TiC powder by a ball milling process. A ‘one-factor design’ combining a response surface methodology with a modified cubic model was employed to modelling and optimisation of key operating factors involved in the ball milling procedure. The mentioned experiment was performed by changing these three variables, milling duration in the range of 10–50 h, fine and coarse powder particle size and as-received and hardened substrate. Coating thickness, microhardness and scratch hardness number were defined as process responses. Predicted values of responses obtained by using this model were in good agreement with experimental values. Optimum condition (24 h milling, hardened substrate and fine powder particle) supported the respective experimental test.
Surface and Coatings Technology
International Journal of Minerals, Metallurgy and Materials
Materials for Renewable and Sustainable Energy
Mechanical milling and a gas-selective polymer were used to protect MgH 2 from oxidation and impr... more Mechanical milling and a gas-selective polymer were used to protect MgH 2 from oxidation and improve its dehydrogenation properties. MgH 2 and poly(methyl methacrylate) (PMMA) were simultaneously ball-milled for 5 and 20 h, respectively, to prepare an air-resistant nanostructured composite. The properties of the nanostructured composite were studied by XRD, SEM, and FTIR methods. The dehydrogenation performance of all samples was investigated by TGA analysis. The hydrogen desorption performance of ball-milled samples was also evaluated after exposure to air for 4 weeks. Results showed that MgH 2 desorbed about 0.79 wt.% of hydrogen after heating up to 300 ˚C and holding for 15 min at this temperature. The ball-milling of MgH 2 and PMMA for 5 and 20 h led to hydrogen desorption of 6.21 and 6.10 wt.% after heating up to 300 ˚C and holding for 15 min at this temperature, respectively, which proved the surface protection of MgH 2 from oxidation by PMMA. After 4 weeks of exposing the ball-milled MgH 2-PMMA samples to air, their hydrogen desorption percentage at the same condition changed to 5.80 and 5.72 wt.% for 5 and 20 h milled samples, respectively. A slight reduction in the dehydrogenation percentage of air-exposed samples proved that the air stability of MgH 2 had been significantly enhanced by its confinement with PMMA.
Metals and Materials International
Materials Science and Engineering: A
Materials Science and Engineering: A
International Journal of Hydrogen Energy
Metals
The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of ... more The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al 2 O 3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix-MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 • C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.
Materials and Manufacturing Processes
Publication details, including instructions for authors and subscription information: The publish... more Publication details, including instructions for authors and subscription information: The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Abstract One of the most important methods to produce sponge iron is coal based reduction of iron... more Abstract One of the most important methods to produce sponge iron is coal based reduction of iron ore. Direct reduction methods based on coal are being improved due to the abundance of coal sources and its lower cost in comparison with natural gas. Volatile materials in coal play an important role in the reduction of iron oxides. In this study, noncoking coal with high volatile materials from Iran and commercial hematite with the purity of 98% were used to investigate the effect of volatile materials on the reduction process. The effects of reduction time (0 to 75 minutes), temperature of reduction (700 to 1000 oC), particle size of coal (53 to 250 micron), and the ratio of carbon content of coal to hematite (0.9 to 1.2) were investigated. The results indicated that volatile materials could reduce 56% of iron oxide. The XRD results of reduced materials implied the stepwise reduction process. Furthermore, activation energy was increased with increasing the degree of reduction.
International Journal of Engineering, 2013
Journal of Environmental Chemical Engineering, 2017
Abstract In the present study, leaching of tailing containing 29.6 wt.% Ni in sulfuric acid was i... more Abstract In the present study, leaching of tailing containing 29.6 wt.% Ni in sulfuric acid was investigated. Tailing was characterized by X-ray powder diffraction (XRD), X-ray fluorescence (XRF) and inductively coupled plasma (ICP-OES) methods. Rinsing process for the separation of tungsten from tailing was conducted in distilled water at 80 °C for 240 min. After the filtration of solid residue from tungsten solution by vacuum filtration, batch leaching tests were carried out on solid residue at atmospheric pressure in stirred acid solution. The effects of sulfuric acid concentration (1–4 mol), pulp density (1/10–1/20 gmL −1 ), particle size (−600 +420 to −180 +125 mm) and temperature (25–80 °C) on the nickel dissolution were studied. The results showed that leaching of about 99% of nickel content of the washed tailing could be achieved using 4.0 mol sulfuric acid, pulp density of 1/20 gmL −1 and particle size of −180 +250 mm at 80 °C after 240 min. Kinetic analysis of the leaching data properly followed the shrinking core model, and the dissolution rate of nickel was found to be controlled by diffusion through the product layer for 25 and 40 °C and chemical reaction for 80 °C. Leaching rate of nickel at 60 °C at the first stage (0–60 min) was controlled by diffusion through the product; then, at the second stage, it was controlled by the chemical reaction (60–240 min).
Powder Technology, 2013
W–Cu nanocomposites were prepared by reactive milling of tungsten trioxide (WO3) and copper oxide... more W–Cu nanocomposites were prepared by reactive milling of tungsten trioxide (WO3) and copper oxide (CuO) with pure magnesium and subsequent elimination of the undesired byproduct. In-situ reduction of the oxides primarily resulted in the formation of W–Cu–MgO composite. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were employed to study the structural evolution of the milled samples. The XRD patterns indicated that, in the experiments with 10 and 20% over-stoichiometric magnesium, the reactions completed after about 16 min. The crystallite size obtained from XRD data analysis was estimated to be 23 nm for W and 37 nm for Cu, while the powder particle size measured by SEM was in the range of 40–500 nm after 2 h. Based on the thermodynamic properties of the reactants, XRD investigation, and temperature monitoring of the vial outside wall, a mechanism was proposed for the kinetics of the reactions. Finally, selective acid leaching was applied to remove the MgO, leav...
Applied Physics A
Exchange bias which accompanies a magnetic hysteresis loop shift along field axis or increase in ... 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.
Powder Metallurgy, 2017
The aim of this work is to identify relationships between the input variables and the process res... more The aim of this work is to identify relationships between the input variables and the process responses and to develop predictive models that could be used in the design of coating AISI D2 steel substrate with TiC powder by a ball milling process. A ‘one-factor design’ combining a response surface methodology with a modified cubic model was employed to modelling and optimisation of key operating factors involved in the ball milling procedure. The mentioned experiment was performed by changing these three variables, milling duration in the range of 10–50 h, fine and coarse powder particle size and as-received and hardened substrate. Coating thickness, microhardness and scratch hardness number were defined as process responses. Predicted values of responses obtained by using this model were in good agreement with experimental values. Optimum condition (24 h milling, hardened substrate and fine powder particle) supported the respective experimental test.
Surface and Coatings Technology
International Journal of Minerals, Metallurgy and Materials
Materials for Renewable and Sustainable Energy
Mechanical milling and a gas-selective polymer were used to protect MgH 2 from oxidation and impr... more Mechanical milling and a gas-selective polymer were used to protect MgH 2 from oxidation and improve its dehydrogenation properties. MgH 2 and poly(methyl methacrylate) (PMMA) were simultaneously ball-milled for 5 and 20 h, respectively, to prepare an air-resistant nanostructured composite. The properties of the nanostructured composite were studied by XRD, SEM, and FTIR methods. The dehydrogenation performance of all samples was investigated by TGA analysis. The hydrogen desorption performance of ball-milled samples was also evaluated after exposure to air for 4 weeks. Results showed that MgH 2 desorbed about 0.79 wt.% of hydrogen after heating up to 300 ˚C and holding for 15 min at this temperature. The ball-milling of MgH 2 and PMMA for 5 and 20 h led to hydrogen desorption of 6.21 and 6.10 wt.% after heating up to 300 ˚C and holding for 15 min at this temperature, respectively, which proved the surface protection of MgH 2 from oxidation by PMMA. After 4 weeks of exposing the ball-milled MgH 2-PMMA samples to air, their hydrogen desorption percentage at the same condition changed to 5.80 and 5.72 wt.% for 5 and 20 h milled samples, respectively. A slight reduction in the dehydrogenation percentage of air-exposed samples proved that the air stability of MgH 2 had been significantly enhanced by its confinement with PMMA.
Metals and Materials International
Materials Science and Engineering: A
Materials Science and Engineering: A
International Journal of Hydrogen Energy
Metals
The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of ... more The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al 2 O 3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix-MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 • C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.
Materials and Manufacturing Processes
Publication details, including instructions for authors and subscription information: The publish... more Publication details, including instructions for authors and subscription information: The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Abstract One of the most important methods to produce sponge iron is coal based reduction of iron... more Abstract One of the most important methods to produce sponge iron is coal based reduction of iron ore. Direct reduction methods based on coal are being improved due to the abundance of coal sources and its lower cost in comparison with natural gas. Volatile materials in coal play an important role in the reduction of iron oxides. In this study, noncoking coal with high volatile materials from Iran and commercial hematite with the purity of 98% were used to investigate the effect of volatile materials on the reduction process. The effects of reduction time (0 to 75 minutes), temperature of reduction (700 to 1000 oC), particle size of coal (53 to 250 micron), and the ratio of carbon content of coal to hematite (0.9 to 1.2) were investigated. The results indicated that volatile materials could reduce 56% of iron oxide. The XRD results of reduced materials implied the stepwise reduction process. Furthermore, activation energy was increased with increasing the degree of reduction.
International Journal of Engineering, 2013