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Development of a continuous kinetic model for catalytic hydrodenitrogenation of bitumen
, Article Scientia Iranica ; Volume 14, Issue 2 , 2007 , Pages 152-160 ; 10263098 (ISSN) ; Khorasheh, F ; Gray, M. R ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
Catalytic hydrocracking of topped Athabasca bitumen was investigated in a continuous stirred-basket 0reactor, using a fresh and spent commercial catalyst, as well as in the presence of no catalyst. A continuous lumping model was developed for kinetic analysis of hydrodenitrogenation and hydrocracking reactions. The normalized boiling point was used to describe the reactant mixture as a continuous mixture. The continuous model, with five adjustable parameters, was used to describe hydrocracking reactions. Reactions of nitrogen compounds were described by series reactions, involving cracking to lower molecular weight products, as well as direct denitrogenation. The model was able to accurately...
Al-doped Li7La3Zr2O12 garnet-type solid electrolytes for solid-state Li-Ion batteries
, Article Journal of Materials Science: Materials in Electronics ; Volume 32, Issue 5 , 2021 , Pages 6369-6378 ; 09574522 (ISSN) ; Golmohammad, M ; Soleimany Mehranjani, A. R ; Faghihi Sani, M ; Sharif University of Technology
Springer
2021
Abstract
Cubic phase Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for next-generation Li-ion batteries. In this work, the combustion sol–gel technique is used to prepare an Al-doped LLZO solid electrolyte. The crystal structure is investigated, and the cubic phase is confirmed. Densification properties were investigated using SEM and optical dilatometry. The densification of the Al-doped sample takes place in two stages through two different shrinkage rates. Using 0.25 mol Al-dopant 94% relative density is achieved at 1100 °C. The effect of Al-doping on electrochemical properties is investigated in detail using AC impedance spectroscopy. The result indicates that the optimum concentration of...
Semisolid Stir Joining of AZ91 Alloy to A356 Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Today, Mg and Al as the widely used metals, make a special contribution to automotive, electronics and aerospace industries. Increasing the application of alloys of these metals, has extended the demand for reliable joint between alloys of these two metals. The main problem with the dissimilar joining of A356 alloy and AZ91 alloy is hard and brittle intermetallic compounds formation such as Mg17Al12 and Mg2Si which brings about welding strength reduction. By far, a large number of researches about dissimilar joining of AZ91 alloy and A356 alloy in semi-solid condition have not accomplished. In this method two fragments, one from AZ91 alloy and another from A356 alloy among which was a 2...
Investigation of Semisolid Microstructure of Aluminum A356 Alloy Prepared by Electromagnetic Stirring and Gas Induction
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Diverse methods of producing semi-solid metal have been the subject of extensive study for the past 40 years. Among all these methods, electromagnetic stirring (EMS) and gas induced semi solid (GISS) have been used on a commercial scale. Considering the fact that in previous studies the intensity of electromagnetic field in the central part of the stirring chamber was negligible, a hollow cylinder with an almost pure iron core was utilized in the central part of the chamber in order to intensify the electromagnetic field in the center and to introduce gas bubbles into the melt. Aluminum A356 alloy was stirred by a three phase electromagnetic stirrer and introduction of gas bubbles under...
Semi Solid Rheocasting of A356 Aluminum Alloy by High Speed Injection
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Aluminum is the lightest industrial element after magnesium. As a result, aluminum alloys have many industrial usages because of their high specific strength. Semisolid casting is one of the processes that is capable of producing aluminum alloys with high mechanical properties. In this process, there are a wide variety of methods to prepare semisolid slurry, one of the best ways of which to produce globular structure is electromagnetic stirrer. In this research, the semisolid slurry of A356 aluminum alloy is fabricated by electromagnetic stirrer under different conditions of stirrer intensity current, stirring time and pouring temperature. Then the fabricated semisolid slurry is injected...
Effect of Alternative Electromagnetic Vibration on Joining of 2024 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
2024 Aluminum alloy has an abundant application in the aerospace and automobile industries. One of the most important problems of the alloy is hot cracking during the fusion welding process. It is stated that the solidified grains can be refined by a static magnetic field and an alternative electric field applied simultaneously during solidification. To make the alternative electric field, an alternative current was passed through the specimen. In order to prevent hot cracking, electromagnetic vibration was used. Then the effect of intensity of the static magnetic field and alternative electric current on joint was examined. Joining was carried out at electric currents of 40, 60, and 80A and...
Microstructural Study Of Inconel 718 Alloy Produced by VAR and Comparing it with Other Rapid Solidification Methods
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
The purpose of this investigation was to study the microstructure of the Inconel718 alloy wich was produced by VAR and suction casting method, and study the effect of cooling rate on the solidification structure of Inconel718 alloy. In the first a labratoary scale VAR furnace was made. After producing some sample's with this furnace, a suction casting sample was produced using a 3mm diameter copper mold. Metallography, SEM, EDS, and microhardness analysis was carried away. Cooling rate evaluation was done by using a equation between secondary dendrite arm spacing and solidification time. Results showed that by increasing cooling rate from 63 c/s to around 2000 c/s, columnar and equiaxed...
Effect of Electromagnetic Vibration and Alternative current on A356 Microstructure
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
A356 Aluminium alloy has an abundant application in the aerospace and automobile industries. One of the most important problems of the alloy is in it’s microstructure after solidification with long dendrite grain of Aluminium.It is stated that solidied grains can be refined by electromagnetic vibration and an alternative electric feild applied simultaneously. To make electric field, electric current passed through the specimen. In order to change in microstructure, electromagnetic vibration was used. Then the effect of intensity of electromagnetic field and alternative electric current on microstructure was examined.Grain refining carried out at electric current 80A and magnetic flux of 13,...
Evaluation of Structure of Powder-thixoformed A390 Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Hypereutectic A390 alloy has some exclusive specification among aluminum alloys because of its' excellent properties such as high wear resistance and low thermal expansion. In this research powder-thixoforming method, a compilation of powder and thixoforming methods is used for production of parts. In this method gas atomized powder of pre-fabricated alloy was consolidated by hot pressing under argon atmosphere and converted to an acceptable feedstock for thixoforming stage. The feedstock is reheated to semi solid region and rapidly transferred to a injection sleeve with central runner. The semi-solid feedstock is injected in a step die by a hydraulic press of 1 m/s ram speed. According to...
Spherical Graphite Cast iron Production from Sponge Iron
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Due to the increasing spread of metal industries and the need for raw material as feed for electric furnaces in order to produce cast iron and steel, as well as scrap deficiency and rising prices, the use of sponge iron as a substitute for scrap was considered in this project Therefore, in order to achieve the chemical analysis of the sorel ingot that is special for spherical graphite cast iron production with low manganese and chromium content, the direct reduction process was carried out using tunnel kiln method on low-manganese iron ore concentrate.After the investigation on direct reduction parameters including the saggers and coal grading,the produced sponge iron has melted in...
Study on the Kinetics of Enzymatic Biodiesel Production Using Castor Oil
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor) ; Ashuri, Hossein (Supervisor)
Abstract
Increasing emissions of greenhouse gases from one hand and decline in the fossile resources of energy on the other hand has raised the motivation of searching for renewable sources. Biodiesel, because of having perfect feature for replacing with petroleum diesel, has been considered as candidate for this purpose. Using enzymatic reaction is one of the methods for biodiesel production. Understanding the kinetics of this reaction is important to achieve higher production rates. In present work, the kinetic of transesterification of castor oil with use of Novozyme 435 (as enzyme) was investigated. Enzymatic biodiesel production is a bi-substrate (oil and alcohol) reaction. Genetic algorithm was...
A356 Aluminum Alloy Joining By Local Semisolid Method
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Semisolid joining is a relatively new method that is started since 2002. So far, Aluminum alloys semisolid joining is not studied in details. In this research, by obtaining local semisolid region in the vicinity of the joining seam, two A356 Aluminum part were welded. Hot Nitrogen gas was used to prepare local semisolid region. Since the hot gas was not capable to produce the region by itself, samples were preheated. In experimental procedure, preheating plane type, hot gas temperature, gas flow, sample dimensions, and welding speed were investigated. Effects of each parameter were determined by microstructure studies and measuring the mechanical properties of welding seam. Results showed...
Halo Distribution Inside Cosmic Voids in the Excursion Set Theory
, M.Sc. Thesis Sharif University of Technology ; Baghram, Shant (Supervisor)
Abstract
The purpose of this research is to provide a model to explain the dependence of the galaxy distribution within voids on redshift and the density of the environment. The study of the formation of large-scale structures in the universe, as one of the most important observables in cosmology, is of great importance. Investigating the formation of these structures is possible by going beyond the linear regime and using theories such as the Press-Schechter and the excursion set. Also, by developing this type of approach, theories have been made possible to study the statistics of halos in environments such as voids, which can be useful for a better understanding of the formation and evolution of...
Effect of Electromagnetic Stirring on GTAW Weld Solidification Structure of AA5052
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Conventional defects in GTAW welding of Aluminum 5052 alloy are the decrease in weld zone strength because of grain growth, formation of columnar grains in the fusion line, solidification cracks and porosities. In this work, effect of strong field electromagnetic stirring on solidification structure of 5052 alloy and elimination of GTAW defects have been investigated. For arc welding processes (especially tungsten inert gas welding), a process called magnetic stirring was proposed, patented, and investigated in the 1970s. The essential aim was to improve weld quality and they indicated that the the Lurentz force is cause of weld stirring. In the earlier researches, alternating magnetic field...
Formation of Globular Microstructure by Electromagnetic Stirring and Rheocasting of Semi-Solid A356 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
The study on new rheoforming technologies of semi-solid alloys has recently been one main subject interesting many researchers and industrials, and so many new methods about preparing semi-solid alloy slurry and rheoforming process have been suggested. Among more than 20 proposed methods, only MHD (Magneto Hydro Dynamics) and EMS (electromagnetic stirring) methods has been industrialized. In this research, the semi-solid slurry of A356 aluminum alloy was fabricated by electromagnetic stirrer under different conditions of stirring current, stirring time and pouring temperatures. Then the semi-solid slurry prepared in optimum conditions was injected into a step-die cavity by a drop device and...
Investigating the Effect of Heat Treatment and Incorporation of Y on the Microstructure, Mechanical Properties and Corrosion Behavior of Biodegradable Mg-3Sn Alloys
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor) ; Ashuri, Hossein (Supervisor)
Abstract
Magnesium metal has attracted attention as a base material for the fabrication of temporary implants due to its biocompatibility and mechanical properties similar to human bone. However, its rapid degradation and mechanical integrity loss in physiological environments have limited its applications. To enhance the overall properties of magnesium-based implants, alloying and heat treatment are considered effective metallurgical approaches. To enhance the characteristics of Mg-3Sn, 1% yttrium (by weight) was added, followed by solution heat treatment and ageing heat treatment. The microstructure analyses revealed that in the as-cast state of both alloys, the matrix consists of the...
Advanced gel polymer electrolyte for lithium-ion polymer batteries
, Article ASME 2013 7th Int. Conf. on Energy Sustainability Collocated with the ASME 2013 Heat Transfer Summer Conf. and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology ; July , 2013 ; 9780791855515 (ISBN) ; Hashemi, N ; Ashuri, M ; Montazami, R ; Advanced Energy Systems Division, Solar Energy Division ; Sharif University of Technology
2013
Abstract
We report improved performance of Li-ion polymer batteries through advanced gel polymer electrolytes (GPEs). Compared to solid and liquid electrolytes, GPEs are advantageous as they can be fabricated in different shapes and geometries; also ionic properties are significantly superior to that of solid and liquid electrolytes. We have synthetized GPE in form of membranes by trapping ethylene carbonate and propylene carbonate in a composite of polyvinylidene fluoride and N-methylpyrrolidinore. By applying phase-transfer method, we synthetized membranes with micro-pores, which led to higher ionic conductivity. The proposed membrane is to be modified further to have higher capacity, stronger...
Effect of Alloying Elements and Heat Treatment on Microstructure and Mechanical Properties of Austempered Ductile Iron by Modulus above 2 Cm
, M.Sc. Thesis Sharif University of Technology ; Varahram, Nasser (Supervisor) ; Ashuri, Hossein (Supervisor)
Abstract
Since its discovery in 1943, the use of ductile iron is increasing continuously, this is due to the combination of various excellent mechanical properties. Excessive amount of research has being carried out to improve the properties. Austempererd ductile iron is the most recent development in this field. The application of this material included to automobile, railway, military, agricultural, mining & construction industries. The newly developed austempered ductile iron is now replacing steel in many fields so it has become very important to various aspects of this material. In this thesis, the effect of alloying elements (copper & nickel) and the austempering process variables on the...
Semisolid Stir Joining of As-Cast Silicon-Aluminum Bronze
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Ashuri, Hossein (Supervisor)
Abstract
Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C...
Investigation of Mechanical Properties of Thixoformed Melt-Spin Al-30Si-5Fe Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor) ; Varahram, Naser (Supervisor)
Abstract
Aluminum alloys are one of the most economical light alloys that are used in automobile and aerospace industries. Application of Al-Si alloys are considerably used more than other Al alloys. Hypereutectic Al-Si alloys are well developed among Al-Si alloys due to their excellent properties such as high wear resistance and low thermal expansion coefficient. In these alloys formation of the primary silicon particles and hard intermetallic compounds in a ductile matrix provides a desirable wear properties. Coarsening of these particles in the structure of castings will reduce their mechanical properties. Moreover, oxidation of powders and difficulty in manufacturing complex parts in powder...