Sharif Digital Repository

In this study the effect of nanoparticles on the mass transfer of dispersed phase in the liquid-liquid extraction systems, containing toluene with acetic acid as dispersed phase and saturated water of toluene as continues phase was investigated. For the ease of dispersion of nanoparticles in nonpolar organic dispersed phase, with the use of a novel method, hydrophobic tiania nanoparticles were synthesized and during producing with the sole-gel method were modified by adding Tetraethyl Ortho titanate as modifying agent, also the smallest hydrophobic nanoparticles of magnetite were synthesized by co-precipitating method and then, under optimum thermal condition were coated by adding Oleic... 

Smart materials are able to change their physical properties under various environmental conditions. Shape memory alloys (SMA) are relatively new smart materials that can respond to environmental stimuli e.g., heat, electricity, etc. Unique behaviors of SMAs, called shape memory effect and superelasticity, have motivated many applications in various fields of study (aerospace, medical, civil engineering, etc.). Although the behavior of SMAs is complicated, modeling and utilizing these materials have been receiving much attention in the past 20 years. Since a cable tolerate more tension than a wire or rod, the shape memory alloy cables could have a broad range of potential applications.... 

By increasing growth of the composite materials and achieving nano-materials and understanding the unique and specific properties, using materials for production with ideal specifications widely spread. So far nano-materials were used for strengthening materials and producing composite and then nano composites were produced.
Regarding to widespread use of polymer matrix composites, nano particles for reinforcement polymers were used. Thus desirable and unexpected properties were observed in polymer matrix nano composites.
In this project, due to the unique properties of carbon nano tubes such as high strength and modulus, low density, and high ratio of length to diameter. They are... 

In this study in-situ Al/Al3Ti was fabricated by mechanical alloying, hot extrusion and subsequent heat treatment. First, initial pure powders of Al and Ti were mechanically alloyed with 5 weight percentages of Ti for 40 hours. The as-hot extruded samples containing 5 wt% of initial Ti particles, were exposed to heating at 600 oC for various time intervals up to 10 hours. Microstructure analysis by OM and SEM proved that in-situ Al3Ti phase was formed as a layer around Ti particles by solid reactive diffusion between Al and Ti particles. After 10 hours of heating, all the Ti particles were consumed and transformed to Al3Ti. Mechanical properties of samples were investigated by Brinell... 

In this work the effect of recycling process and nanometric CaCO3 on the rheological and heat-sealing properties of co-polymer Polypropylene (R40) was studied. Nanocomposites with recycled and neat matrix were prepared with twin extruder. Complex viscosity, dynamic modulus, flexural and tensile properties, impact strength and sealing ability of nanocomposites of neat Co-PP (R40) and Recycled Co-PP (RPP) determined according to the relevant standard specifications.Rheological analysis revealed that incorporation of nanofiller enhances values of Complex viscosity and dynamic modulus, broadening molecular weight distribution (MWD) and decrease cross over point (ωc, GC) for RPP. In this study,... 

Melt blending of polymers is a rather cheap and easy approach for obtaining new set of properties compared to synthesizing new polymeric materials. For the same reason, binary and ternary polyethylene blends are made to provide added value for different applications. Polyethylene blends are commonly composed of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). Although the Mechanical and physical properties of polyethylene binary blends have been studied extensively, microstructure and mechanical properties of polyethylene ternary blends have been the subject of very few studies. In this work, samples with 40-60 Wt. % HDPE and... 

During the last few years researchers have drawn much attention to HSLA steels because of the application of these steels in many industries. Ferrite-martensite dual phase(DP) steels are one of the most common HSLA steels which are currently used. Combination of these two phases provides good strength along with good ductility. Joining and welding of these steels has always been an important challenge. The aim of this study is to examine applicability of TLP method for joining and dual phase processing of this steels at the same time. Microstructural and mechanical examination of the bonded specimens showed that isothermal solidification occurred during holding for 50 min at the... 

In the present work preparation of Ni-TiO2 films and their microstructural and mechanical properties were studied. For film preparation, DC current mode of electrochemical deposition method was used in Watts Nickel bath with different concentrations of transparent TiO2 sol up to 30 mL/L. It presents a new generation of nano Ni-TiO2 coating as a composite film for corrosion and erosion resistance applications. The best wear volume of 0.0046 mm3 was achieved for 30 mL/L Ni-TiO2 nanocomposite in comparison to 0.0071 mm3 for pure Ni film. Moreover, the coating hardness increased to ~345 HV50 for Ni-TiO2 nanocomposite. Corrosion rate of the coatings improved down to 1.10E-05 mm/year with addition... 

The austenitic heat resistant stainless steels have been widely used in petrochemical industry as furnace tubes which are exposed to extremely high temperatures. In this study, the quench aging process of a HP modified heat resistant stainless steel is assessed and the kinetics of aging is evaluated by the JMAK model. The microstructure of steel in as cast and aged conditions was characterized by optical microscope and scanning electron microscope equipped with EDS. The effects of aging time and temperature on the microstructure, tensile propertices, shear strength, hardness, and ductility of the aged steel were determinded. The results of tensile and shear punch tests show a linear... 

Demand to structural and industrial materials with unique properties lead to produce unorthodox combination of metals. One of the most useful combinations is composites of Aluminum-Steel and this composites is mostly used as a sheet. Due to differences in melting point of two metals, preferred method for welding of this two metals is Cold Roll Bonding. For enhance of mechanical properties of this two metals, preferred methods is Severe Plastic Deformation. By the way, in SPD methods, two method was established for sheets. Accumulative Roll Bonding and Constrained Groove Pressing but ARB method produce multi-layer composites so preferred method to produce bilayer sheets is CGP. In this study,... 

In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as... 

Recently, due to the increase of environmental concerns, a significant raise in applying films and packaging containers, pollution produced from petroleum-based plastics packaging and problems arising from the various methods of waste disposal, the researchers have concentrate to replace these materials with biodegradable ones. In this study, a nanocomposite based on alloy matrix of thermoplastic starch and polyethylene which is reinforced with different amounts of Montmorillonitenanoclay has been constructed by the extrusion process. Furthermore, in order to increase the compatibility between the polar and non-polar components in the group of samples, compatibilizer was used and its... 

A novel reduced mechanism is introduced which aimed to predicts NOx and CO generation in advanced industrial gas turbine combustors. The survey is initially conducted by considering 25 species in GRI-3 mechanism of Methane oxidation and continued to choose nine of the most important species based on the quasi-steady state analysis. Finally, a new skeletal reduced mechanism with 35 reactions and 20 species is derived using sensitivity analysis, reaction path analysis, and some physical reasons. The overall validity of this mechanism is clearly confirmed by comparing the present predicted results with GRI-3 full mechanism in a PSR reactor. The adiabatic flame temperature and all of the main... 

Models wih extra dimensions have been among the most important models built for solving the problems of the standard model. In the standard model, Higgs mechanism is used to ex-plain electroweak symmetry breaking. One of the theoretical problems of the standard model,the hierchy problem, is about the Higgs mass being unnaturally small and models with extra dimensions have provided solutions to solve the problem. Moreover, extra dimensions pro-vide tools using which several models have been developed to explain electroweak symmetry breaking. In this thesis, acher reviewing the electroweak symmetry breaking sector of the stan-dard model, and the hierarchy problem, some models of electroweak... 

Preparation of binary polyamide 6 (PA6) / carbon nano tube (CNT) and ternary PA6 / EPR-g-MA / CNT has been carried out using melt mixing. Four PA6s were selected with different viscosities (and molecular weights) and molecular structures (linear or branched). Effect of CNT content (up to 2 wt%) and mechanical mixing conditions (rotor speed, temperature and time of mixing) have been investigated. Ethylene- propylene rubber grafted maleic anhydride (EPR-g-MA) was selected at 20 wt% as toughening agent for ternary nanocomposites and mixing sequence of PA6 , EPR-g-MA and CNT has been investigated. Morphological observations showed that dispersion of CNT is done by erosion mechanism at low melt... 

Dual Phase ferritic-martensitic steels are kind of high strength low alloy steels (HASLA) which are widely used in industry because of their strength and formability. Since welding of dual phase steels in conventional welding methods causes structural change and Subsequently alters mechanical properties of both weld zone and heat affected zone(HAZ), additional operations which are not commercially viable is needed to achieve a dual phase structure in structurally changed regions. In this study, transient liquid phase (TLP) bonding method is used during dual phasing process in order to preserve dual phase ferritic-martensitic structure and avoid extra heat treatment. Applied pressure during... 

Gravity drainage is known as one of the major mechanisms of oil recovery in naturally fractured reservoirs which petroleum engineers conducted research in this realm. Block to block interaction such as capillary continuity and reinfiltration mainly control the efficiency of this mechanism. In this study, first of all, free fall and forced gravity drainage experiments have been conducted in a single block apparatus and effect of some parameters like, density viscosity relation, matrix permeability, vertical fracture aperture, presence of viscose force and type of injected gas were investigated, in the second step, three stack block apparatus were designed and constructed. This apparatus were... 

The trailing edge brakes are the conventional controller mechanisms for autonomous precision delivery parafoil systems. Asymetric braking creates differential drag on the left and right sides of canopy leading to generation of turn rate, whereas symmetric deflection changes the aangle of attack which in turn affects airspeed and limit the glide slope. In the current work , in addition to the conventional controller , the canopy is considered to have the ability of changing its longitudinal and lateral incidence angles. This can be achieved by changing the length of sidelong suspension lines.Unlike brakes, the lateral incidence angle creates heavily coupling in lateral dynamics.The results... 

Interlayer composition as one of the most important factors of TLP bonding could affect bonding region composition and microstructure that both of them govern the mechanical properties of the joint. Due to the risk of substrate microstructure degradation , welding of dual phase steel needs more cautions. TLP bonding ideally acquires joints having more similar microstructure to substrate. Moreover , using this method could avoid the change of base metal microstructure when heat treatment of carbon steel is postponed until after bonding. Fe-based , Ni-based and commercially pure Cu are three different composition has been studied in this work. The bonded samples were investigated by optic and... 

In recent decades, nano-structured materials have been allocated specific position for wide use in various fields. The nano-diamonds has attracted the attention of many researchers. The inherent characteristics of a diamond like spherical structure of nanoparticles and carbon atoms which have used their full capacity in the chemical bonds,also the same surface as the radiography particles which have empty orbital, provides an ability to perform a variety of surface modification on the particle . This article introduces the nanocomposites based on polymer, constituents specification and discuss properties of nanocomposites after mixing components together. Lots of studies was on...