Sharif Digital Repository

The purpose of this project is to investigate the production of nano-micro metallic particles—of different elements—with different characteristics in size and optical property by employing a pulsed laser ablation processes in liquid medium. In this study, the means by which we build the laser, the experimental arrangement of the pulsed laser ablation process, the measurement of the absorption spectrum of generated nano-micro particles as well as the size of the particles are discussed.
To satiate this aim, we have expressed the manner of constructing the Nd:YAG laser, the power supply circuits, along with its optics. This laser has some advantages such as high energy ~700mj, good... 

The Ni-base superalloy CM88Y has good hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of gas turbine hot components. In most applications, heat treatment is required in order to achieve the desired mechanical properties and corrosion resistance of the working conditions; often three stages of heat treatment is designed for precipitation hardening nickel-base superalloy. In general, the effective parameters of heat treatment cycles includes temperature, time, heating rate and the cooling rate. In this study, the effect of cooling rate from partial solution temperature (second stage of heat treatment) on the... 

The development of new wrought magnesium alloys for automotive industry has increased in recent years due to their high potential as structuralmaterials for low density and high strength/weight ratio demands. However, the poor mechanical properties of the magnesium alloys have led tosearch a new kind of magnesium alloys for better strength and ductility.In this research,a new type of magnesium alloy based on Mg-Zn-Si-Ca system has been developed using the permanent gravity casting process. For comparison, an alloy without Siby the same method was also produced. The effects of trace Si addition on the microstructure and mechanical properties in magnesium alloy with composition of... 

In the present study, nanocomposite of Ce-TZP/Al2O3 was synthesized via aqueous combustion synthesis. In order to investigate the effects of alumina on the morphology and the mechanical properties of this nanocomposite, four sample with 20, 40, 60 and 80 mole percent of alumina were prepared. At first, the synthesized powders were characterized with scanning electron microscope and X-ray diffraction technique. Then, in order to determine the effects of alumina mole percent on the mechanical properties of the nanocomposite, the powders were uniaxailly compacted with the press of 250 MPa followed by sintering at the temperature of 1400 °C for 4 hours. The density of the compacted powders was... 

Hydrogen gas is considered as a clean fuel and energy carrier that its storage for future uses is a challenging issue. One of the methods to store it, is adsorption on a group of adsorbents called metal-organic frameworks. In this research, one of these frameworks called ZIF-8, has been selected to study hydrogen storage capability. To evaluate the effect of having two metals, a mixture of two metals was used in the synthesis process. To characterize the structure of the synthesized adsorbents, X-ray powder diffraction (XRD),adsorption and desorption of nitrogen at temperature of 77 K, Field Emission Scanning Electron Microscopy (FESEM), energy-dispersive X-ray Spectroscopy (EDS) and... 

A large number of metals and alloys show an irregular plastic behavior called serrated flow when being deformed in a certain temperature and strain rate range. The occurrence of this phenomenon affects the mechanical properties of the material, such as work hardening rate and ductility; consequently, it exerts limitations on the service conditions in which the alloy can be used.
IN600, IN625 and MP35N are wrought Ni based and Ni-Co based alloys which are thermo-mechanically processed. When these alloys are deformed in temperatures between 300-700 ˚C, serrated plastic flow occurs. In order to investigate the mechanisms responsible for irregularities, hot compression tests were conducted... 

Concrete has long been one of the most widely used materials in the world. Cement, as a major component of concrete, due to the use of fossil fuels in its production process, emitting greenhouse gases such as carbon dioxide, which cause air pollution and environmental issues such as climate change. On the other hand, the wastes of industrial factories such as slag of the Blast furnace, due to their large volume and lack of sufficient space for storage of these wastes, lead to the release of these wastes that have alkaline structures into enviroment, causing environmental pollution Such as embankment pollution. Alkali-activated concrete has prevented the release of these pollutant into the... 

In this work, multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) were synthesized in an aqueous solution of iron chloride and solfate via arc discharge. Thermogravimetric (TG) analysis showed that the multi layer structures including carbon nanotubes (CNTs) and multi-shell graphite particles were formed when DI-water was used. SWCNTs were synthezied in the presence of the iron ions. The effect of [Fe3+]/[Fe2+] ratio on the CNTs yield were investigated. Raman spectroscopy investigations showed that the highest yield was obtained when the ferric to ferro ratio was one. When the concentration of Fe3+ ion was higher than that of Fe2+, many short tubes were... 

In this study, nano-powders of copper-cobalt spinel (CuCo2O4) were fabricated by solution combustion synthesis (SCS) of Cu and Co nitrates with urea, glycine,acid citric and alanine. The method involved exothermic decomposition of viscous liquid nitrates and the fuel. Products which were synthesized by using this fuels contained less impurity constituents. Duo to low purity, other factors which have influence on synthesis process investigated and observed that pH have key role on process. X-ray diffraction (XRD) patterns gave crystal structure and the existing phases. Particle size distribution and morphology changes were studied by dynamic light scattering (DLS) and field emission scanning... 

Polymer concrete is well-known for the quick repair of concrete structures and pavement. Many concrete structures such as bridges, offshore, and pavements are under cyclic loads when they are exposed to different environmental conditions during their lifespan. However, there are relatively few studies on the durability of Polymer concrete. The durability and fatigue performance of these structures are significant issues that should be considered. This study aims to investigate the long-term environmental effects on the mechanical properties of Polymer concrete. Therefore, polymer and ordinary cement concrete specimens were prepared and exposed to four chemical solutions with pH values of... 

A broad range of plain carbon steels have ferrite-pearlite microstructures, which are used in many industrial applications due to the good strength and formability provided by the typical combination of ferrite grains and pearlite colonies. The mechanical behavior of ferrite-pearlite steels inherently originates from the configurations of ferrite grains and pearlite colonies, which comprised alternating lamellae of cementite with randomly distributed orientations in a ferrite matrix. In this thesis, three different experimental-numerical approaches were employed to investigate the deformation behavior, damage mechanisms, and formability of the ferrite-pearlite steels. At the first step, two... 

The purpose of this study was to create a three-cationic electro phosphate coating of zinc-nickel-manganese by cathodic method and to investigate the effect of operating variables on the properties of zinc-nickel-manganese tri-cationic electro phosphate coating. Hence, the effects of variables such as coating acidity, coating thickness, coating temperature, coating time and concentration of manganese were studied in the bath on the properties such as coating morphology, corrosion resistance, coating thickness. Coating morphology was characterized by scanning electron microscopy and corrosion resistance by polarization test. The pH values of 1.4, 1.8, 2 and 2.2 were selected, and the results... 

In this project alumina-zirconia-ceria nanocomposite with 80% mol alumina (0.2Ce0.1Zr0.9O2-0.8Al2O3) was produced by solution combustion synthesis method. In the mentioned method, optimal fuel with composition of 75% urea, 25% ammonium acetate, and stoichiometric amount of glycine (0.75U-0.25AA-1G) was used. Moreover, ammonium nitrate as aid combustion was added to optimal fuel. In order to calcinations, nanopowder obtained from combustion synthesis was heated to 500°C for 1 hour and kept at this temperature for 2 hours. To complete heat treatment, the nanopowder was heated to 1150°C for 2 hours and 10 min and kept at this temperature for 2 hours. Then the specimens were pressed at pressure... 

The feasibility to fabricate Al/SiCp nano-composite with functionally graded structure (FG-Al/SiCp) via friction stir processing was studied successfully in this paper. The distribution of well-dispersed nano-SiCp got a range of 6mm×3mm on the cross-section of nano-composite. A compositionally graded structure of nano-SiCp in thickness direction of the 5083Al plate was obtained via four passes of FSP. The percentage of nano-SiCp over 15%, 9% and 5% was found at the depth of 1.0mm, 2.0mm and 3.0mm, under processed surface of 5083Al rolled plate, respectively. Results show that the microhardness of FG-Al/SiCp nano-composite can reach steady 46%, 34% and 15% higher than the one of the base... 

Sharif University of Technology Plasma Focus (SUT-PF) is a Mather Type DPF device which has a 39 μF capacitor bank with 14 KV charging ability at its ultimate limit corresponding to 7 KJ stored energy. In the first step of this experiment, a test has been done at three distances 5, 7, 10 cm from anode tip with the different number of shots 20, 30, and 40 at 0 constant angles.In the following, a test is done at 5 and 10 degrees with 40 shots, and PF chamber has been filled up with nitrogen gas. Various tests have carried out for survey of this experiment, the result of which are as follow:The X-ray diffraction (XRD) analysis are used in order to reveal if the Nickel or Nickel nitride have... 

In this research, a nanocomposite blend of polyamide 6/polystyrene containing polyaniline-coated carbon nanotubes was fabricated via melt blending method, aiming to achieve electrical conductivity in the range of static dissipation. The effect of weight percentage of nanofillers and surface modification of carbon nanotubes with polyaniline on the electrical properties and microstructure of the nanocomposite was investigated. To promote compatibility between the immiscible polyamide 6 and polystyrene polymers, PS-g-MA compatibilizer was utilized, and its effect on the morphology of the nanocomposite blend was examined. Additionally, the influence of weight percentage of nanofillers and the... 

Nowadays, composites have wide applications in different industries especially in aerospace industry because of their high strength to weight ratio. Epoxy 5052 for its relatively good mechanical properties and high thermal resistance has vaidly use for manufacturing of large composite components. However; fracture toghness of epoxy resins is not good in comparison to their other exceptional properties. Therefore, researchers have endeavored to improve this characteristic with different approaches. One of these methods is nanotechnology. Since the components in aerospace industry are often under impact loads and impact strength of these materials has been less studied, effect of carbon... 

Capturing the atmospheric CO2 and turning it into value added products is a topic that has been extensively studied in recent years. One of the methods through which CO2 is valorized is via converting it into carbon nanofiber, CNFs. CNFs can be an important material in future human activities due to its valuable properties such as wide range of electrical conductivity, their superior flexibility and strength, But it is currently obstructed in use due to the high cost of manufacturing and the complexity of the synthesis. Furthermore, in today's world, human life is heavily influenced by greenhouse gases, and avoiding emitting gases like CO2, is almost infeasible. This thesis provides an... 

In order to prevent electrostatic attraction on non-conductive surfaces, the most practical solution is to put antistatic coatings to reduce surface resistance. Nano tin oxide coatings are designed to produce surfaces with antistatic properties in the resistance range of 108-1012 Ω/cm. In this project, using a simple method, low temperature, without heat treatment and without the use of additive (dopant), tin oxide films with antistatic property were placed on the glass. Further, in order to obtain a coating with a suitable morphology and structure to increase the surface conductivity, the synthesis of tin oxide using the sol-gel method at ambient temperature was used. And to place the... 

Understanding many issues related to environmental geotechnics and soil sciences such as: instability and collapse of soil slopes, sinkholes, leakage from landfills and isolation of nuclear landfills, and optimization Agricultural processing depends on our knowledge of the behavior of unsaturated soils and their volume changes. To better understand the behavior of unsaturated soils, it is important to study the soil-water retention curve (SWRC) and the factors affecting it. These include factors such as porosity, grain size distribution, soil minerals, pore size distribution, and pore water chemistry, which affect soil-water retention curves and volume changes. Since the simultaneous effect...