Sharif Digital Repository

Nanotechnology is an efficient method suitable for fabrication and production of minimal single dimensional nanometric structures. Such materials and systems can be logically designed that lead to new and optimized biological, chemical and physical properties and characteristics due to their size. Nucleation and growth –appearance of a new phase out of an old phase – is a ubiquitous phenomenon in nature. Fundamental understanding of nanoparticles nucleation and growth mechanism allows more control on form, size and composition and allows tuning of the above said properties easily with use of different reactive conditions as a result of this ability . Nanoparticles of titania are one of... 

Thermoacoustics deals with the conversion of heat energy into sound energy and vice versa. This new and emerging technology has a strong potential towards the development of sustainable and renewable energy systems by utilizing waste heat or solar energy. Although thermoacoustic devices are simple to fabricate; however, the design process is very challenging. The thermoacoustic phenomenon is discovered over a century ago; nevertheless, the rapid advancement in this field occurred during the past three decades when the theoretical understanding of the phenomenon is developed along with the prototype devices. There are several advantages of heat engines and refrigerators based on... 

Nowadays, too much attention has been paid to Solid Oxide Fuel Cells (SOFC). One of the key components in SOFC is interconnect which plays an important role in SOFC performance. Interconnect can be either a metallic or ceramic layer that sits between each individual cell. The reduction in operating temperature of SOFC resulted in interests in using metallic interconnectors. However, the oxidation of these metallic materials is big challenge. Chromium (Cr), Nickel (Ni) and Iron (Fe) alloys have been employed to overcome this deficiency. However, these alloys bring another difficulty which is the presence of active elements such as Cr which reduces the performance of interconnects by forming... 

In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy... 

In this study, leaching of Sarcheshmeh Reverberatory Furnace Dust was investigated in the H2SO4-O3 media. Response surface methodology based on central composite face-centered design (RSM-CCF), was applied to optimize the operating parameters. The optimum conditions to obtain the main goal of maximum copper and minimum iron dissolution from dust were identified to be temperature of 30˚C, leaching time of 3hr, initial pH of 0.5, pulp density of 20% and ozone flow rate of 1g/h. The copper and iron concentrations of leaching solution were found to be 27.11 and 0.89983 g/L under the optimum conditions, respectively. The results showed that selective copper extraction from the dust could be... 

Li-ion batteries have been widely applied as power sources for portable electronic devices. Recently, Li-ion batteries are considered as the most promising energy storage technology for electric vehicle applications however, fundamental improvements are needed. TiO2 (B) is attractive candidate for anodes in rechargeable Li-ion batteries, due to their low cost, non-toxicity and favorable channel structure for fast lithium mobility. It is predicted that synthesis of doped nanostructure of this material, through reducing the diffusion pathway and formation of crystal defects, will increase the capacity of TiO2(B). In this investigation, Co and V doped TiO2(B) nanowires are synthesized by... 

In Iran, titanium dioxide is still not produced and imports of titanium dioxide are required by various industries, including dyeing, electrodeposition, plastics and Therefore, according to the Ministry of Industries and Mines objectives, to obtain the technology of extraction Ti and TiO2, a research was carried out on titanomagnetite concentrate, extracted from the minerals of the plancher titanumitent and low-grade kahnoj. In this research, titanium dioxide is produced by sulfate method. Solid state recovery and magnetic separation were used to isolate titanium and iron. The dissolution process was then performed to achieve maximum dissolution. At this stage, the effects of temperature,... 

The primary objective of this thesis is comprehensive treatment of epistemic uncertainties in probabilistic seismic hazard analysis based on structural reliability methods. The classical methods of probabilistic seismic hazard analysis, i.e., PSHA, traditionally consider a limited number of uncertainties. The ones that they do consider comprise the aleatory uncertainty in the magnitude, the distance, and the residuals of ground motion prediction equations and the epistemic uncertainty in the intensity measures predicted by different such equations. However, there are many sources of epistemic uncertainty that, according to past studies, have a significant impact on the upper tail of the... 

The most common form of communication on the internet and social network websites is text messages. normally communication on social media or even on the web is by posting some sort of text. usually, these messages or posts are short and text used in them may not follow any language standards, this makes it very difficult to process them. Different age groups use a certain language differently and this is shown in the way, each of them writes texts. The advancements made in the field of natural language processing and computational linguistics makes it possible to predict, text authors age groups by analyzing the way they write. This study focuses on ways to automatically recognize the age... 

Some of the low-grade titanium resources which are located in the country are titanomagnetite placer deposits. In current study, beneficiation of titanium-bearing concentrate of a placer deposit containing 6.13wt.% TiO2 was investigated by acidic leaching in order to remove impurities. To beneficiate the concentrate, based on the optimum conditions obtained in previous studies, solid-state reduction, magnetic separation, and calcination of non-magnetic product were performed. Afterwards, by studying temperature, time, acid concentration and L:S ratio, the final product was leached under optimal conditions were as follows: H2SO4 concentration of 15wt.%, L:S ratio of 20:1 (mL:g), reaction... 

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 involving salt-lake brines and sea water. The ion exchange process is a promising method for lithium extraction from brine and seawater having low concentrations of this element. 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... 

Titanomagnetites are resources of iron and titanium. high level of titanium in titanomagnetites makes using them in iron making processes very difficult. In this work an attempt was made to produce an iron bearing and a titanium bearing product using solid state reduction of Fanouj mine titanomagnetite concentrate. For this purpose, the concentrate was reduced using coal and then was subjected to magnetic separation. In this work, effect of temperature, time, added coal amount, and additive amount on reduction was studied. The result showed that the optimum conditions are 1325 celsius degree, 2.5 hours, 25 percent added coal and 2 percent additive. In optimum conditions a magnetic product... 

Midrex sponge iron is an active product and there are several problems with store and export it.Cold briquetting sponge iron method is a new method to protect sponge iron from oxidation and provides the possibility of its storage and transportation. Iran as one of the biggest countries that produce sponge iron, has a lot of sponge iron pilots that equipped with cold briquetted machines,but their production capacity is limited and is about 5 percent of their production capacity. With regard to no need for country to these amount of sponge iron, most of these pilots have to store and transport large volumes of sponge iron and the risk of oxidation and fire threatens these units.By using cold... 

Today, recycling lithium as a valuable metal from brine plays an important role in various applications such as battery manufacturing, computers, aerospace and automobiles. Among the aqueous methods available for the extraction of the lithium element in brines, ion exchange by TiO2 nanosorbents is one of the most efficient methods. In this study, first the titanium dioxide nanotubes were well synthesized by anodizing method and the nanograss created after the anodizing process were completely eliminated. Then, the effect of three cathodes of aluminum, graphite and stainless steel in order to select the best cathode and achieve a regular morphology as well as their replacement with platinum... 

One of the lesser-known issues in the modeling literature of assortment optimization issues is the assortment optimization for reusable products, which is an issue in various areas, including offering parking space, renting cloud computing systems resources, and rental of fashion products, etc.In this issue, we are faced with a high diversity product rental store that has a customer in each period. The seller offers a limited set of products depending on the customer demand and the inventory in hand. He can decide to rent the product or leave the system without renting the product. In case of renting the products by the customer, he may return them until the end of this period or keep them... 

Metal foams are considered as a group of new materials and are applied widely in various areas due to their particular properties such as low density, high strength-to-weight ratio and appropriate mechanical, thermal, physical, electrical and magnetic properties. The aim of the present study is acquiring the technical knowledge of Zinc foam production by melting route and also optimizing the effective parameters on the foam stability. For this reason, 4 Zinc foams were produced at different times and temperatures. The amount of Calcium as the melt fluidity reducing agent and Titanium hydride and Zinc carbonate as the blowing agent were the same in all the specimens. The effect of heat... 

Iron is a common impurity in copper minerals. The presence of iron in hydrometallurgical copper PLS causes continuous reactions between Fe(II) and Fe(III) ions. In order to improve energy efficiency and product quality iron removal shall be done. In this study separation of iron from Sarcheshme copper leaching liquor containing 6 g/L Fe, was conducted by solvent extraction using D2EHPA in kerosene. Chloric acid solution was used to strip the loaded iron from organic phase. Results of extraction experiments designed by taguchi method showed 92.49% iron recovery and 2.44% copper extraction under optimum condition. Using same method for stripping experiments, it was found that variation of time... 

In this study, Lithium recovery process from lithium-ion battery was investigated by electrodialysis method. First, the cathode of the battery was leached in NMP to separate cathode from aluminum foil. Then, the cathode was leached in sulfuric acid with concentration 3.25 M and 10 volume percent hydrogen peroxide that pulp density was 55 g/L at 60°C for 100 minutes. in the next step, an electrodialysis cell was designed and created to recover lithium. And the influence of time, voltage, flow rate of feed solution, concentration of electrode solution and concentration of feed solution on process was investigated. Purpose of this project were investigated lithium ion recovery rate, lithium... 

Solvent extraction of vanadium (V) from sulfated leaching solution of the converter slag of the Isfahan steel company followed by stripping of this element from the organic solvent were examined in this study. In the experimental section, 2-ethyl-1-hexanol extractor was utilized for selective separation of V(V) from the acidic medium containing Si, Na, Fe, Al, Ca, and P ions. Ammonium chloride solution was also used for stripping V from the organic phase. Under optimal condition (pH=1.9, T=65℃, extractor concentration of 68% and organic phase volume fraction of 0.66), 91% was extracted in solvent extraction stage. Under optimal stripping conditions (pH=7.5, T=25℃, organic phase volume...