Loading...
Search for:
thermal-analysis
0.008 seconds
Total 71 records
Effects of chemical composition on nanocrystallization kinetics, microstructure and magnetic properties of finemet-type amorphous alloys
, Article Metals and Materials International ; Volume 19, Issue 4 , 2013 , Pages 643-649 ; 15989623 (ISSN) ; Castellero, A ; Rizzi, P ; Tiberto, P ; Hosseini, H. R. M ; Baricco, M ; Sharif University of Technology
2013
Abstract
In this study, the kinetics of nanocrystallization of amorphous Fe 73.5Si13.5B9Nb3Cu1 (F1) and Fe77Si11B9Nb2.4Cu0.6 (F2) alloys is investigated. The microstructure and magnetic properties of the nanocrystalline alloys are compared. The crystallization temperature of F2 alloy is shifted towards lower temperatures with respect to F1. Thus, the crystalline volume fraction and the crystalline grain size at specific annealing temperature for the F2 alloy are higher than for the F1 alloy, accounting for the higher coercive force of F2 alloy with respect to the one of F1 alloy. According to isoconversional methods, the activation energy for crystallization is variable as a function of transformed...
Kinetic of Partial Reduction of Hematite to Magnetite
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
This research has studied the kinetic and mechanism of partial reduction of hematite to magnetite via carbon monoxide gas. In addition, temperature and partial pressure of CO gas as two main parameters which influence the rate of the reduction process has been studied. In order to investigate the change in mass during the reaction, thermogravimetric analysis (TGA) has been applied and in order to evaluate the effect of the temperature and partial pressure of CO on the rate of the reduction, three different temperatures and two different ratios of CO/CO2 has been experimented. Three isothermal analysis in 390°C, 440°C, and 490°C in pure CO atmosphere and two isothermal analysis in 550°C with...
Thermal Behavior of Concrete Arch Dams Including Water Level Fluctuations
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor)
Abstract
One of the major reasons causing cracks in external surfaces of concrete arch dams are thermal loads. Therofore, in order to avoid instabilities due to function of thermal loads in association with hydrostatic and hydrodynamic pressures, a precise evaluation of temperature distribution through dam body is indispensable. In this study, effects of thermal loads mostly on upstream surface of Karun-3 concrete arch dam in Iran were examined using a 3-D finite element method considering water level fluctuations. Also the influence of operatvie boundry conditions in our problem which are water temperature, air temperature and solar radiation was precisely taken into account. Moreover, nonlinear...
Thermal Analysis of Concrete arch Dams Using Real Reservoir Data and Comparing the Results with Stucky-derron Method
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor)
Abstract
Thermal analysis of concrete arch dams is always an important issue in designig these enormous concrete structures. The reason this issue mainly concerns arch dams and not gravity dams is because of little thickness of arch dams which makes them prone to cracking due to thermal loading. To solve any thermal problem we need boundary conditions. In arch dam case, these boundaries are the temperature of the upstream and downstream face of the dam which, depending on circumstances, can be in touch with water or air. Estimating air temperature is a fairly easy task when you have monthly mean temperatures. The challenging part is defining water temperature in any depth of the reservoir whenever we...
Feasibility Study and Conceptual Design of A Radioisotope Thermoelectric Generator
,
M.Sc. Thesis
Sharif University of Technology
;
Vosoughi, Naser
(Supervisor)
;
Feghhi, Amir Hosain
(Supervisor)
Abstract
Radioisotope thermoelectric generator (RTG) is a kind of nuclear batteries, in which thermal energy resulting from the discharge of charged particles decayed of radioisotope, using thermoelectric arrays, can be converted to electrical energy. In this study, the different kinds of RTGs introduced and applications of them have been expressed. All types of radioisotopes used in RTGs have been reviewed and the most suitable of them in terms of maximum thermal power density and minimum dose rate have been selected. All types of thermoelectrics used in RTGs have been reviewed and the most suitable of them in terms of the range of temperature and maximum efficiency have been selected.
In this...
In this...
Fabrication and Thermal Analysis of Superhydrophobic Nano-textured Condensation Substrates
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor) ; Asghari, Mohsen (Supervisor)
Abstract
This thesis is a research corresponding to Super-Hydrophobic condensation substrates with Nanometer texture. In this study, the foresaid surfaces are fabricated by two methods that are Nano-composite paint and Electrophoretic coating. As a summary for the first method (the Super-Hydrophobic Nano-composite paint), the hybrid coating contains two mineral and organic phases; The organic phase is a two-part clear-coat polyurethane and plays the role as a polymer matrix in Nano-composite structure. Silica Nano-particles are the mineral phase and the two phases of Nano-composite have made connection with silane compounds. Also, surface-modification in Nano-particles for giving hydrophobicity...
Transient growth of a micro-void in an infinite medium under thermal load with modified Zerilli–Armstrong model
, Article Acta Mechanica ; Volume 227, Issue 4 , 2016 , Pages 943-953 ; 00015970 (ISSN) ; Eskandari, A. H ; Zakerzadeh, M. R ; Sharif University of Technology
Abstract
In this paper, the transient growth of a spherical micro-void under remote thermal load in an infinite medium is investigated. After developing the governing equations in the problem domain, the coupled nonlinear set of equations is solved through a numerical scheme. It is shown that a small cavity can grow rapidly as the temperature increases in a remote distance and may damage the material containing preexisting micro-voids. Conducting a transient thermal analysis simultaneously with a structural one reveals that the material may experience a peak in the radial stress distribution, which is five times larger compared to the steady-state one, and shows the importance of employing a...
Investigation of thermal behavior of α-PbO and β-PbO IN O2 atmosphere
, Article Metalurgija ; Volume 57, Issue 4 , 2018 , Pages 287-290 ; 05435846 (ISSN) ; Nazari Alavi, A ; Mirzai, M ; Sharif University of Technology
Faculty of Metallurgy
2018
Abstract
The compounds α-lead oxide (α-PbO) and β-lead oxide (β-PbO) were purchased from Merck co. and used for thermal investigations in laboratory. The compound was heated in a thermogravimeter at different temperature, from 25 to 400 °C. The used gas atmosphere was O2. The received products were investigated by X-ray diffraction (XRD) technique. The received product Pb3O4 was confirmed by XRD. The textures of two different morphologies of α-PbO, β-PbO and the product Pb3O4 is investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. © 2018, Faculty of Metallurgy. All rights reserved
Preparation and characterization of yttrium iron garnet (YIG) nanocrystalline powders by auto-combustion of nitrate-citrate gel
, Article Journal of Alloys and Compounds ; Volume 430, Issue 1-2 , 2007 , Pages 339-343 ; 09258388 (ISSN) ; Madaah Hosseini, H. R ; Nemati, Z. A ; Sharif University of Technology
2007
Abstract
The nitrate-citrate gel exhibits auto-catalytic behavior, which can be used to synthesize nanocrystalline YIG powders. In this study, yttrium iron garnet (Y3Fe5O12) nanocrystalline powders were prepared by a sol-gel auto-combustion process. The influence of metal nitrates to citric acid molar ratio (MN/CA) of the precursor solution on the combustion behavior and crystallite size of synthesized powders was investigated by scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and X-ray diffraction (XRD). The results show that with increasing MN/CA value, the combustion rate increases and the single-phase YIG forms at a higher temperature. The crystallite size of the single phase YIG...
Alumina nanopowder production from synthetic bayer liquor
, Article Journal of the American Ceramic Society ; Volume 89, Issue 12 , 2006 , Pages 3654-3657 ; 00027820 (ISSN) ; Khalifehzadeh, R ; Sadrnezhaad, Kh ; Arami, H ; Sharif University of Technology
2006
Abstract
Alkoxides are the most common precursors used for the production of alumina nanopowders. These materials are, however, expensive and corrosive. This paper introduces a new method for the production of alumina nanopowders by rapid cooling of a synthetic caustic sodium aluminate solution (Bayer liquor), followed by calcination in the presence of a surface-stabilizing agent like 1,2-dihydroxy-3,5-benzene disulfonic acid disodium salt (Tiron). The powders produced are characterized by differential thermal analysis, XRD, transmission electron microscopy, scanning electron microscope, and Brunauer-Emmet-Teller. A nanopowder of α-alumina with an average crystallite size of 27.7 nm and an average...
Thermal Analysis of Regenerative Cooling in Liquid Rocket Engines
, M.Sc. Thesis Sharif University of Technology ; Kebriaei, Azadeh (Supervisor)
Abstract
In this thesis to simulate the behavior of liquid engine Thrust chamber of hot gas from a quasi one dimensional code used when the effects of the heat transfer and friction in those terma. As well as during the regenerative channel is simulated by considering the equation’s of continuity, momentum and energy for one dimensional, effects of increase temperature, pressure drop, change the density of coolant flow resulting from the warming which is visible along the way to increase the accuracy of calculation of the thermal flux output of the engine, use a suitable model for unclear boiling in consideration of heat transfer coefficient used coolant flow it has been. As well as coupling of heat...
Investigation on the Effect of Cooling Rate on the Solidification Behavior and Microstructure of Al 713 alloy using Thermal Analysis Technique
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor)
Abstract
Considering the limited number of works on investigation of solidification characteristics of Al-Zn-Mg-Cu cast alloys as well as the applications of this alloy system in aerospace industries, the solidification conditions of Al 713 alloy were investigated in this study. In order to achieve this goal, a number of experiments were designed and conducted including quantometry, thermal analysis, metallography and hardness measurements. In this thesis, effects of cooling rate on secondary dendritic arms spacing as well as solidification parameters including nucleation temperature, solidification time and temperature range, dendrite coherency point and formation temperature of intermetallic...
Thermal Analysis of RCC Dams During Construction and Operation
, M.Sc. Thesis Sharif University of Technology ; Ghaemian, Mohsen (Supervisor)
Abstract
The most important issues in massive concrete structures such as concrete dams are the increase in temperature due to heat generated by the dam Hydration of cement in concrete. Internal restrains are created from thermal gradient between the surface and the interior of the structure. External restrains are created from connections between structures and foundation for obstruct the movement of concrete structures due to temperature change. External restrains and internal creates tensile stresses in the concrete considerable, which can lead to thermal cracks in the structure. To prevent or minimize the possibility of cracks are examined thermal studies for the design of reinforced concrete...
Thermal Analysis of Dry Spent Fuel Transportation System of BNPP
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor)
Abstract
Spent fuel assemblies are kept in spent fuel maintenance pools, designed at the vicinity of the reactor, after consuming. As capacity of these pools are limited, fuel assemblies should be transported to outside of the reactor building for maintenance. Transportation cask is used for this reason which is Russian type, named TUK-13, at Bushehr Nuclear Power Plant. The aim of this project is to ensure proper removal of heat from the transportation cask(TUK-13). For this purpose, numerical computational fluid dynamics method is used. The software used in this study is the Comsol. The temperature range suitable for any part of the chamber is different; but the most sensitive and the most...
Kinetic of Zinc Sulfide Roasting of
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
In this study, the effect of two main parameters, time and temperature, were investigated in the roasting process of zinc sulfide of Bafgh’s mine, and kinetics and the mechanism of the roasting reaction were examined, too. The oxidation process was performed in a muffle furnace in the presence of the oxygen of air atmosphere. The raw powder material (with the particle size of 74-250 micron) was poured in Alumina crucibles. The roasting process was run in eight temperatures of 650, 700, 750, 800, 850, 900, 950 and 1000 ◦C. Oxidation percent was calculated in six times of 5, 10, 15, 30, 45 and 60 minutes. The experiments were designed in a way that the effect of each parameter could be...
Investigation into the Effects of Using Various Thermal Insulators on the Behaviour of Structural Connections During Fire
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Steel is a non-combustible material, but at high temperatures, steel structures, due to their diminishing yield strength, undergo a considerable visco-plastic deflection, which results in a reduction in their load bearing capacity. Thus, to increase safety against fire must be considered as an important objective in the design and construction of steel structures. One of the safety measures which can be taken against fire is to increase the resistance of the structure against heat by using heat-resistant coatings. This decreases the rate of transfer of heat to the structure, and must include the ‘structural members’ and ‘structural joints’. Due to the role of structural connections in...
Modeling of coke formation and catalyst deactivation in propane dehydrogenation over a commercial Pt-Sn/γ-Al2O3 catalyst
, Article Petroleum Science and Technology ; Volume 31, Issue 23 , 2013 , Pages 2451-2462 ; 10916466 (ISSN) ; Soltani, M ; Farjoo, A ; Khorasheh, F ; Sharif University of Technology
2013
Abstract
Propane dehydrogenation was carried over a commercial Pt-Sn/γ-Al 2O3 catalyst at atmospheric pressure and reaction temperatures of 580, 600, and 620°C and WHSV of 11 h-1 in an experimental tubular quartz reactor. Propane conversions were measured for catalyst time on stream of up to nine days. The amounts of coke deposited on the catalyst were measured after one, three, six, and nine days on stream using a thermogravimetric differential thermal analyzer (TG-DTA) for each reaction temperature. The coke formation kinetics was successfully described by a coke formation model based on a monolayer-multilayer mechanism. In addition, catalyst deactivation was presented by a time-dependant...
Influence of autogenous seeding on densification and microstructure in processing of γ-alumina nanopowders
, Article Phase Transitions ; Volume 84, Issue 1 , 2011 , Pages 1-14 ; 01411594 (ISSN) ; Maleksaeedi, S ; Paydar, M. H ; Saadat, S ; Sharif University of Technology
2011
Abstract
The effect of α-Al 2O 3 seeds and MgO on the densification behavior and microstructure of the nanocrystalline γ-Al 2O 3 powder was investigated. The required α-Al 2O 3 seeds were produced by 'autogenous seeding' where the seeds were obtained by calcination of the initial nanosized γ-Al 2O 3 powders above its transformation temperature and incorporated into γ-Al 2O 3 matrix. The seeds were characterized by means of laser particle size analyzer, X-ray diffraction, and Brunauer-Emmett-Teller surface analyzer. The simultaneous influence of α-Al 2O 3 seeds and MgO on γ-Al 2O 3 behavior was evaluated by differential thermal analysis, densitometry, and electron microscopy. The results showed that...
Improvement in mechanical performance of anionic hydrogels using full-interpenetrating polymer network reinforced with graphene oxide nanosheets
, Article Advances in Polymer Technology ; Volume 35, Issue 4 , 2016 , Pages 386-395 ; 07306679 (ISSN) ; Bagheri, R ; Kabiri, K ; Ossipov, D. A ; Jokar, E ; Asadian, E ; Sharif University of Technology
John Wiley and Sons Inc
Abstract
Weak mechanical possession is one of the limiting factors in application of hydrogels. To modify this inherent disadvantage, different approaches have been studied including synthesizing interpenetrating polymer network (IPN) and nanocomposite hydrogels. So, this study has focused on preparation of a novel full-IPN structure based on anionic monomers of 2-acrylamido-2-methylpropane sulfonic acid/acrylic acid–sodium acrylate via facile solution polymerization technique in an aqueous media with incorporation of graphene oxide (GO) nanosheets. Mechanical performance of materials in the “as-prepared condition” and “swollen state” was characterized via tensile, compression, and rheology tests,...
Thermal analysis of laser hardening for different moving patterns
, Article International Journal of Engineering, Transactions A: Basics ; Volume 22, Issue 2 , 2009 , Pages 169-180 ; 17281431 (ISSN) ; Sistaninia, M ; Sharif University of Technology
Materials and Energy Research Center
2009
Abstract
Transient thermal field in laser surface hardening treatment of medium carbon steel was analyzed by employing both three-dimensional analytical model and finite element model. In finite element model the laser beam was considered as a moving plane heat flux to establish the temperature rise distribution in the work-piece, while in analytical model laser beam was considered as an internal heat source. The numerical results were compared with the analytical results. In laser heat treatment of steel some methods are used to produce a wider and nearly uniform average irradiance profile. It may be achieved by rotating the beam optically, thereby producing an overlapping spiral track, or by...