Sharif Digital Repository

Stress whitening is a type of discoloration that can occur in variety of polymers used in automotive and household industries. The current research tries to investigate the effective microstructural parameters such as strain rate, rubber second phase, and branched polypropylene (PP) on the stress whitening in polypropylene in order to propose toughed PP blends with limited stress whitening. It is shown that increasing the strain rate in tensile test results in formation of more visible whitened area within the plastically deformed zone. This is the consequence of further growth of micro-voids at higher strain rates. The results are in accordance with the Mie scattering concepts. Besides, the... 

Fossil fuels provide the most needs of the world's energy, however, continues to lead to two key problems. The first problem is their limitation, and the second problem is the creation of serious environmental issues. Therefore, the need for renewable energy sources is felt more than ever.As an energy source, hydrogen is the lightest, most efficient and cleanest fuel. One of its unique properties is efficiency, the production of electricity by fuel cells through the electrochemical process, has far greater efficiency than of mechanical energy production from fossil fuels in internal combustion engines or energy production in thermal power plants. A fuel cell is a device that converts... 

The nickel-based superalloys play a key role in the development of aircraft and power-generation turbines due to their exceptional properties of high temperature strength, toughness, crack growth resistance and resistance to degradation corrosive and oxidisation environment.In this thesis, the role of base metal composition in isothermal solidification time during diffusion brazing of Nickel-based super alloys was investigated. To achieve this aim, four different super alloys Hynes230, Hastalloy X, Nimonic 263 and Monel were used in similar joining systems. Systems of H230/H230, HX/HX, C263/C263, and Monel/Monel were joined by BNi2 interlayer at 1323K and for different times, until the... 

Polypropylene (PP) is one of the most widely used commercial plastics in various industrial applications due to its desirable physical and mechanical properties and low cost. Engineering properties of this polymer depend very much on its crystalline structure. It is a common practice in polymer industry to modify crystalline structure by means of nucleating agents. Since nucleating agents are added in a rather low level to polymers, some investigators have tried this task in modifying crystalline structure of polypropylene by incorporating nucleating agent masterbatches. However, none have looked at the possible influence of the carrier resin in such masterbatches on the performance of... 

Due to the technology advancement and the large-scale application of lithium-ion batteries in recent years, the market demand for lithium is growing rapidly and the availability of land lithium resources is decreasing significantly. As such, the focus of lithium extraction technologies has shifted to water lithium resources. Among various aqueous recovery technologies, the lithium ion-sieve (LIS) technology is considered the most promising one. This is because LISs are excellent adsorbents with high lithium uptake capacity, superior lithium selectivity, and good cycle performance. TiO2-based nanotubes are an appropriate option for adsorbing lithium from solution due to their high specific... 

In this thesis, macrostructural evolutions in dissimilar TLP bonding of as-cast nickel based supperalloy IN792 to wrought HX was investigated. In the first step of this study solidification behavior of Ni-Cr-Fe-Si-B (MBF-15) interlayer in presence of HX as base metal at 1120 °C was surveyed. In second step, bonding of HX/HX, IN792/IN792 and HX/IN792 systems with MBF-15 interlayer at 1120 °C and different times were studied and isothermal solidification time and factors that affect this stage were discussed. In third step, synchronization of dissimilar bonding with standard heat treatment cycle of IN792 was investigated and effect of this cycle on aging response of different zones, isothermal... 

In this study, static softening kinetics and microstructural evolution during isothermal and non-isothermal annealing of aluminum-magnesium alloy and low carbon steel after cold plastic deformation was investigated. It is known that in industrial cold forming processes, the material properties and microstructure changes during the annealing depends on the inhomogeneous initial microstructure and the deformation history of the cold worked material. To predict the microstructural changes during the annealing of cold worked alloys, a multiscale model based on probabilistic cellular automata (at mesoscale), and the finite element method (at macroscale), was used. To do so, a two-dimensional... 

Softening behavior containing static recovery and static recrystallization in isothermal and non-isothermal conditions in aluminum 1050 after cold rolling has been simulated using Cellular Automata(CA). The effect of strain pass on recrystallization process has been investigated. The finite element method was employed to simulate 1,2 and 3 pass rolling processes and compute the stored energy distribution and transferred to the CA model. For the initial microstructure the topologic deformation and site-saturated nucleation has been considered. For non-isothermal conditions the thermal model has been utilized to compute temperature distribution and decreasing in stored energy due to... 

The thesis is focused on the process-microstructure-properties relationships in transient liquid phase (TLP) bonded IN718 nickel based superalloy. The bonding was carried out using Ni-B-(Si)-(Cr) interlayers at temperatures of 1273-1448 K with various bonding time to ensure completion of isothermal solidification. Microstructure development mechanism, kinetics of isothermal solidification during bonding process, influence of microstructure gradient induced by bonding process on the aging behavior of the joint and the response of joint region to post-bonded heat treatment were considered. It was shown that the isothermal solidification rate depends on the (1) diffusion flux of B into the... 

This research aims to extract lithium from brines with low concentrations. Aluminum hydroxide has been chosen as a suitable and selective adsorbent. This absorbent is made by combining one of the aluminum salts in an alkaline environment. Due to the high cost of providing the raw materials for making the absorbent and sensitivity to the pH value and environmental harm, it is suggested that the absorbent be made by hydrolysis of water by aluminum particles. The manufacturing method has shown promising results in such a way that with the combination of NaCl+CaO and aluminum and activation by ball mill, the amount of extraction is 97% at a temperature of 40 ˚C; in two days, the molar ratio of... 

During fuel combustion, aromatic sulfur compounds in energy fuels convert into sulfur oxides, which cause major environmental problems such as acidic rain, global warming, and air pollution. Absorption desulfurization is one of the promising and economical methods to remove these sulfur compounds from fuels. Metal-organic frameworks (MOFs) are a class of nanoporous materials that are of interest for use as adsorbents due to their high specific surface area, unique surface adsorption properties, high adsorption capacity, tunable porosity, flexible dynamic behavior, and diversity in functional and metal groups. In this research, we first synthesized five metal-organic frameworks, namely... 

Sulfur dioxide is known as an acidic gas and one of the standard pollutants in determining air quality. This gas mostly enters into the atmosphere by flue gas causing many environmental problems. In order to remove this gas, various methods are used. One of the suitable methods to reduce the emission of this pollutant in low concentrations is the use of Metal-Organic Frameworks (MOF) as an adsorbent. One of these Metal-Organic Frameworks is NH2-MIL-53(Al) that owing to its relatively good stability under wet and acidic conditions, has been chosen to adsorb sulfur dioxide in this research. In most studies on SO2 adsorption, often MOFs with a long synthesis time, high synthesis cost, and/or... 

In this study, ZIF-8 was synthesized at room temperature and Then ZIF-8/PEGDA mixed matrix membranes with 5 and 10% of ZIF-8 were prepared by UV photopolymerization to analyze the separation CO2 from natural gas for the first time. The permeation results of gases in mixed matrix membranes in the temperature range of 35-75 degrees centigrade and in pressure ranging from 4-15 bar show the permeability of gases in mixed matrix membranes with 5 and 10% increase more than a pure polymer nearly 14.3 and 31%, respectively, But, CO2=CH4 selectivity decreases. The gas sorption in ZIF-8 was measured in the temperature range up to 75 ◦C and pressure ranging from 2-5 bar. The adsorption isotherm follows... 

During the recent years, shortage of drinking water is one of the concerns of the society and necessity of purification of contaminated water are taken into consideration. Different methods to be developed to prevent problematic pollutions. Among these different methods the most common one is adsorption. In this thesis, the copper oxide nanoparticle was synthesized and its surface was modified using N-(2-aminoethyl)-3-(trimethoxysilyl)propylamine. The bi-amino surface functionalized nanoparticle was used to remove anionic dyes from single and binary systems. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy-dispersive X-ray spectroscopy (EDAX)... 

In this thesis, the copper oxide - zinc oxide nanocomposite was synthesized and functionalized using 3-aminopropyltrimethoxysilane. The functionalized nanocomposite was characterized using X-ray Diffraction spectroscopy (XRD), Fourier Transform Infrared (FT-IR), X-ray Fluorescence Spectroscopy (XRF), Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (BET). Dye removal from synthetic wastewater was done in a batch system using functionalized copper oxide - zinc oxide nanocomposite as adsorbent. Direct red 23, direct red 80 and direct red 81 were used for preparation of synthetic wastewaters. The effects of operational parameters such as adsorbent dosage, initial dye concentration,... 

It is necessary to monitor pollutants in aquatic samples, because many of these compounds can pose threats to human health and the ecosystem. Separation technology based on magnetic materials has received considerable attention in recent years. The magnetic extraction method is not only convenient, economical and highly efficient, but it also overcomes problems with conventional solid-phase extraction. In order to remove anionic dyes from single and ternary systems, zinc ferrite nanoparticle was synthesized using co-precipitation method and its surface was modified by Cetyltrimethyl ammonium bromide (CTAB) cationic surfactant. Surface characteristics of ZFN-CTAB was studied using Fourier... 

Xylene isomers have similar boiling points and, therefore, their separation by conventional distillation is not practical. The industrial separation of these isomers is generally performed by adsorption or crystallization processes, which are very energy consuming. In this work, the various methods of the separation of these isomers have been reviewed and the equilibrium adsorption of these components in liquid phase using two commercial types of zeolite including Z-700 and Na-BETA as adsorbent at 15, 25, and 35 oC and an initial concentration range of up to 50 wt% as well as in single and binary solutions was investigated. It was found that Z-700 adsorbent has no selectivity for the binary... 

This project surveys bioregeneration of granular activated carbons contaminated with phenolic compounds. To carry out this survey, the procedure of phenol absorption on the surface of activated carbon was studied and their adsorption isotherms were calculated. In the first step, newly activated carbon was contaminated with phenol solution and optimum amount of carbon in phenol elimination was 0.5g. Then, the effect of time contact on phenol elimination was studied and eventually 1 hour of time contact was determined as the equilibrium time of phenol adsorption. In the second step, kinetics of adsorption of phenol and different stages of adsorption were studied. The results of this study... 

In this work, biosorption of Zirconium from aqueous solution by A.niger as a biosorbent was investigated. For this goal, both of live and dried biomasses were used. The effect of factors pH, temperature, contact time, initial concentration of metal and biomass dosage were investigated on biosorption. To preparing dried biomass,the live biomass was dried at 60-80 º C for 24 hr and then this dried cell was crushed by mortar and pestle and the drying biomass was ground through a set of sieve with 100 mesh. Also, effect of the pretreatment of biomass by NaOH 0.5 M on biosorption was studied. Optimization of factors was performed by Response Surface Methodology (RSM). The experiments were... 

Adsorption of acetone vapors on mixture of silica gel and activated carbon was studied. Adsorption is defined as the attraction adsorbate (liquid or gas) particles onto the surface of a solid (porous solid). Most of the experimental works are adsorption of a one or more component on an adsorbent. Presence of two or more adsorbents together may effect on adsorption rate, uptake and thermodynamic conditions. When we have limitation in using a kind of adsorbent, these results can be helpful. There are several motivating reasons for the study of adsorption on adsorbent mixtures. During the adsorbent manufacturing process, multiple batches may differ slightly from each other(and from the customer...