Search for: apparent-activation-energy
0.006 seconds

    Synthesis and Evaluation of A Catalyst for Selective Oxidation of H2S to Elemental Sulfur as A Desulfurization Method for Gaseous Streams

    , M.Sc. Thesis Sharif University of Technology Alemi, Faezeh (Author) ; Hamzehlouyan, Tayebeh (Supervisor) ; Rashidi, Alimorad (Supervisor) ; Zamani, Yahya (Supervisor)
    The selective oxidation of H2S into elemental sulfur is a complementary desulfurization method for reducing H2S emissions from gas streams. Several studies have been conducted in recent years to develop active, selective, and stable catalysts. The purpose of this research is to develop a catalyst with high activity and selectivity that is suitable for the gas output of one of the country's refineries. For this purpose, three supports of mixed metal oxide (solid solution), Ce-Al, Ce-Si, and Ce-Zr with a molar ratio of 1:2 (ceria: metal) were made by the co-precipitation method. In the following, three samples named 10V-CeAl, 10V-CeSi, and 10V-CeZr were prepared by impregnating 10% wt vanadium... 

    Hot ductility of a Fe-Ni-Co alloy in cast and wrought conditions

    , Article Materials and Design ; Volume 32, Issue 5 , 2011 , Pages 2956-2962 ; 02641275 (ISSN) Yazdani, M ; Abbasi, S. M ; Momeni, A ; Karimi Taheri, A ; Sharif University of Technology
    The hot ductility of Fe-29Ni-17Co alloy was studied in both cast and wrought conditions by hot tensile tests over temperature range of 900-1250°C and at strain rates of 0.001-1s-1. Over the studied temperature range, the wrought alloy represented higher elongation and reduction in area as compared to the cast alloy. Dynamic recrystallization was found responsible for the higher hot ductility of the wrought alloy and the improvement of hot ductility of the cast alloy at high temperatures. At temperature range of 1000-1150°C the wrought alloy exhibited a hot ductility drop while a similar trough was not observed in case of the cast alloy. It was also found that at temperatures of 1150-1250°C... 

    Deformation behavior of AA2017-SiCp in warm and hot deformation regions

    , Article Materials and Design ; Volume 67 , February , 2015 , Pages 318-323 ; 02613069 (ISSN) Serajzadeh, S ; Ranjbar Motlagh, S ; Mirbagheri, S. M. H ; Akhgar, J. M ; Sharif University of Technology
    Elsevier Ltd  2015
    In this work, the flow stress behavior of a metal matrix composite AA2017-10% SiCp was studied by means of the uni-axial compression test. The composite was first produced by stir casting technique and then, hot extrusion with the ratio of 18:1 was carried out to achieve a microstructure with a homogeneous distribution of SiC particles. In the next stage, the isothermal compression tests were conducted on the cylindrical specimens up to the true strain of 0.6. The experiments were performed at temperatures between room temperature to 400°C and strain rates of 0.003, 0.03 and 0.3s-1. Negative strain rate sensitivity was observed in the temperatures less than 250°C indicating the occurrence of... 

    Investigation into dynamic strain aging behaviour in high carbon steel

    , Article Ironmaking and Steelmaking ; Volume 37, Issue 2 , Jul , 2010 , Pages 155-160 ; 03019233 (ISSN) Kohandehghan, A. R ; Sadeghi, A. R ; Akhgar, J. M ; Serajzadeh, S ; Sharif University of Technology
    In this work, the phenomenon of dynamic strain aging in a high carbon steel is studied and different initial microstructures including fine and coarse pearlite structures are considered. Tensile tests at different temperatures and strain rates are performed to evaluate the occurrence of dynamic strain aging and mechanical properties as well as to calculate apparent activation energies for onset and termination of dynamic strain aging. The results show that dynamic strain aging occurs for both microstructures while the initial microstructures alters the activation energies for appearance and termination of this phenomenon. The microstructural studies illustrate that a combination of cementite... 

    Microstructural evolution in creep aged of directionally solidified heat resistant HP-Nb steel alloyed with tungsten and nitrogen

    , Article Materials Science and Engineering A ; Volume 659 , 2016 , Pages 104-118 ; 09215093 (ISSN) Attarian, M ; Karimi Taheri, A ; Sharif University of Technology
    Elsevier Ltd 
    The effect of tungsten and nitrogen on the as cast and the creep aged microstructures of heat resistant HP-Nb steel was studied. The steel was directionally solidified under two cooling rates of 31.2 and 7.6 K sec-1. Creep rupture tests were performed at temperatures of 1150-1255 K on the specimens prepared from the cast ingots in transverse and longitudinal directions. It is shown that the addition of nitrogen significantly increases the eutectic temperature and thus refines the dendrites and alters the morphology of M7C3 eutectic carbide. Also, it is found that due to short time aging, nitrogen addition decreases the M7C3 carbide fragmentation, increases the secondary M23C6 precipitation... 

    Synergistic cobalt–nickel co-catalyst for enhanced visible light-induced photocatalytic water oxidation

    , Article Journal of Chemical Sciences ; Volume 132, Issue 1 , 2020 Nazari, P ; Nouri, O ; Rahman Setayesh, S ; Sharif University of Technology
    Springer  2020
    Abstract: The loading of co-catalyst is an efficient way to increase the activity of synthesized carbon-based photocatalysts in the energy and environmental applications. Herein, Co and Ni decorated on g-C3N4 was synthesized as a visible light active photocatalyst and characterized with XRD, FT-IR, BET, DRS, TGA, FE-SEM, EDX, and EIS techniques. From the characterization results, it was demonstrated that cobalt and nickel which were present in the structure of the nanocatalyst, were in the metallic form. The decoration of Ni and Co reduced bandgap energy of g-C3N4 and made the synthesized nanocomposite active under visible light. The operating condition of O2 photocatalytic generation was... 

    Beneficial Role of oxygen in co and propylene oxidation over a pt-pd-based wiremesh catalyst as a retrofit emission control device for four-stroke gasoline spark-ignited motorcycles

    , Article Energy and Fuels ; Volume 35, Issue 12 , 2021 , Pages 10122-10133 ; 08870624 (ISSN) Lotfollahzade Moghaddam, A ; Hamzehlouyan, T ; Hosseini, V ; Mayer, A ; Sharif University of Technology
    American Chemical Society  2021
    Over 200 million motorcycles in use worldwide account for a substantial portion of global mobile source total hydrocarbons (THC) and carbon monoxide (CO) emissions. In Tehran, capital of Iran, ultrarich inefficient combustion in gasoline-fueled motorcycles results in significantly high CO and THC emissions. Motorcycle catalysts can reduce CO and C3H6(as a representative hydrocarbon) emission factors by 60-80%. In the present work, CO and propylene oxidation over a commercial Pt-Pd-based wiremesh catalyst is studied in a flow reactor setup under simulated conditions relevant to 125 cc four-stroke gasoline carburetor motorcycles. Steady-state individual and co-oxidation tests for CO and... 

    Reductive leaching of indium from the neutral leaching residue using oxalic acid in sulfuric acid solution

    , Article International Journal of Minerals, Metallurgy and Materials ; Volume 28, Issue 3 , 2021 , Pages 373-379 ; 16744799 (ISSN) Maddah, F ; Alitabar, M ; Yoozbashizadeh, H ; Sharif University of Technology
    University of Science and Technology Beijing  2021
    The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution. The effect of main factors affecting the process rate, including the oxalic-acid-to-sulfuric-acid ratio, stirring rate, grain size, temperature, and the initial concentration of synergic acid, was precisely evaluated. The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid. The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution. On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the... 

    Hot deformation behavior of Fe-29Ni-17Co alloy

    , Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 23, Issue 11 , 2013 , Pages 3271-3279 ; 10036326 (ISSN) Yazdani, M ; Abbasi, S. M ; Taheri, A. K ; Momeni, A ; Sharif University of Technology
    Hot compression tests were carried out on a Fe-29Ni-17Co alloy in the temperature range of 900 °C to 1200 °C and at strain rates of 0.001-1 s-1. Dynamic recrystallization was found responsible for flow softening during hot compression. The flow behavior was successfully analyzed by the hyperbolic sine equation and the corresponding material constants A, n and α were determined. The value of apparent activation energy was determined as 423 kJ/mol. The peak and steady state strains showed simple power-law dependence on the Zener-Hollomon parameter. The dynamic recrystallization kinetics was analyzed using Avrami equation and the corresponding exponent was determined to be about 2.7. This... 

    Process optimization and kinetics for leaching of cerium, lanthanum and neodymium elements from iron ore waste's apatite by nitric acid

    , Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 27, Issue 2 , 2017 , Pages 420-428 ; 10036326 (ISSN) Ferdowsi, A ; Yoozbashizadeh, H ; Sharif University of Technology
    Nonferrous Metals Society of China  2017
    The leaching of rare earth elements (REEs) including cerium, lanthanum and neodymium from apatite concentrate obtained from iron ore wastes by nitric acid was studied. The effects of nitric acid concentration, solid to liquid ratio and leaching time on the recoveries of Ce, La and Nd were investigated using response surface methodology. The results showed that the acid concentration and solid to liquid ratio have significant effect on the leaching recoveries while the time has a little effect. The maximum REE leaching recoveries of 66.1%, 56.8% and 51.7% for Ce, La and Nd, respectively were achieved at the optimum leaching condition with 18% nitric acid concentration, 0.06 solid to liquid... 

    An investigation of crystallization kinetics of the Na3MnCO3PO4 cathode material, synthesized by the hydrothermal method

    , Article Materials Chemistry and Physics ; Volume 214 , 2018 , Pages 73-79 ; 02540584 (ISSN) Hassanzadeh, N ; Sadrnezhaad, S. K ; Ghorbanzadeh, M ; Sharif University of Technology
    Elsevier Ltd  2018
    Na3MnCO3PO4 (NMCP) is produced by hydrothermal synthesis for rechargeable sodium-ion battery (SIB) cathode. Mechanism of formation of NMCP was investigated by measuring the influence of time and temperature on the rate of production of the NMCP crystallites. X-ray diffraction analysis of the synthesized samples showed that MnCO3 first formed as an intermediate phase. Na3MnCO3PO4 was, however, the last phase retained after 24 h of the hydrothermal process at 120 °C. Sigmoidal shape of the crystallization curves followed the Avrami–Erofeev model which described the chemical kinetics of the Na3MnCO3PO4 formation. Respective apparent activation energies of 29.10 for nucleation and 73.91 kJ/mol... 

    A study on the hot workability of wrought NiTi shape memory alloy

    , Article Materials Science and Engineering A ; Volume 528, Issue 18 , July , 2011 , Pages 5656-5663 ; 09215093 (ISSN) Morakabati, M ; Kheirandish, S ; Aboutalebi, M ; Taheri, A. K ; Abbasi, S. M ; Sharif University of Technology
    The hot workability of a wrought 49.8 Ni-50.2 Ti (at pct) alloy was assessed using the hot compression tests in temperature range of 700-1000°C, strain rate of 0.001-1s-1, and the total strain of 0.7. The constitutive equations of Arrhenius-type hyperbolic-sine function was used to describe the flow stress as a function of strain rate and temperature. The preferable regions for hot workability of the alloy were achieved at Z (Zener-Holloman parameter) values of about 109-1013 corresponding to the peak efficiency of 20-30% in the processing map. However, a narrow area in the processing map including the deformation temperature of 1000°C and strain rate of 1s-1 is inconsistent with the related... 

    Hot deformation behavior of an aluminum-matrix hybrid nanocomposite fabricated by friction stir processing

    , Article Materials Science and Engineering A ; Volume 626 , 2015 , Pages 458-466 ; 09215093 (ISSN) Khodabakhshi, F ; Gerlich, A. P ; Simchi, A ; Kokabi, A. H ; Sharif University of Technology
    A fine-grained aluminum-matrix hybrid nanocomposite reinforced with TiO2, MgO and Al3Ti nanoparticles was prepared via reactive friction stir processing (FSP) of an Al-Mg sheet with pre-placed TiO2 particles (50nm; 3.1vol%). The microstructure of the hybrid nanocomposite comprises high-angle grain boundaries (~90%) with an average size of 2μm and hard inclusions with sizes in the range of 30-50nm. Evaluation of the hot deformation behavior of the nanocomposite by uniaxial tensile testing at different temperatures (300-450°C) and strain rates (0.001-0.1s-1) shows that the deformation apparent activation energy of the nanocomposite is 137kJmol-1 at ≤300°C. The values of the activation energy... 

    Effect of copper on the thermal stability and non-isothermal crystallization behavior of Al 86 Ni 10-x Cu x RE 4 (x = 0.5–2.5) amorphous alloys prepared by melt spinning

    , Article Journal of Non-Crystalline Solids ; Volume 506 , 2019 , Pages 46-50 ; 00223093 (ISSN) Mansouri, M ; Varahram, N ; Simchi, A ; Sharif University of Technology
    Elsevier B.V  2019
    Microstructural features, thermal stability and crystallization kinetics of various melt spun Al-based alloys containing transition metals (TM = Ni, Cu) and Ce-based rare earth metals (MM: Misch Metal) were investigated via X-ray diffractometry (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). It is shown that the extended topological instability of Egami-Waseda model (λ criterion) is a useful tool to predict the crystallization behavior of the prepared alloys. FCC-Al nanoparticles are formed during the initial crystallization process. Calculation of the apparent activation energy using the Kissinger method indicates that partial replacement of...