Sharif Digital Repository

Graphene is a one layer atom thickness and zero energy gap so for using it in nano electronic and transistors baised on graphene it's energy gap should be opened.one of the methods for opening graphene band gap is creating nano scale boundaries or synthesize graphene nanoribbons. One of the new methods for graphene nanoribbon synthesize is longitudinal opening of carbon nanotube. In this thesis graphene nanoribbons synthesize with this method and analyze with AFM and Raman spectroscopy. Carbon nanotubes also have energy gap and IR absorption recently they used for living cell destruction. In this thesis we synthesize graphene nanoribbons and analyzing their optical absorption and use it for... 

TiO2 is known as a photocatalyst in near UV-Visible light region with better efficiency compared to other semiconductor photocatalysts. Many attempts have been done to increase the efficiency of this photocatalyst. also, application of 2D carbon nanostructures namely graphene for increasing the photocatalytic activity of TiO2 has shown positive results.
In this research, we first synthesized Graphene Oxide (GO) suspension by exfolation of graphite oxide suspension. then we fabricated TiO2 thin films on glass substrates by so-called sol-gel method. finally we fabricate Graphene Oxide/TiO2 nanowalls composite films as a photocatalyst in visible light. X-ray photoelectron spectroscopy... 

WO3 is known as a photocatalyst in the visible light region, but with lower efficiency compared to more interesting semiconductor photocatalysts such as TiO2 and ZnO. Many attempts have been done to increase the efficiency of this photocatalyst by incorporating metal and metal oxide nanoparticles or recently carbon nanotubes.On the other hand, application of graphene, as an unrolled carbon nanotube, for increasing the photocatalytic activity of TiO2 and ZnO has shown positive results. Furthermore, it was reported that such semiconductor photocatalysts (and very recently WO3) can photocatalytically reduce the chemically exfoliated graphene oxide sheets under UV-vis irradiation.
In this... 

Graphene nanogrids fabricated by graphene nanoribbons obtained through oxidative unzipping of multi-walled carbon nanotubes, used as two-dimensional selective templates for accelerated differentiation of human mesenchymal stem cells (hMSCs), isolated from umbilical cord blood, into osteogenic lineage. The biocompatible and hydrophilic graphene nanogrids showed high actin cytoskeleton proliferations that coinciding with patterns of the nanogrids. The amounts of proliferations found are slightly better than proliferation on hydrophilic graphene oxide (GO) sheets, and significantly higher than non-uniform proliferations on hydrophobic reduced graphene oxide (rGO) sheets and polydimethylsiloxane... 

Knowledge Based Firms are considered to be important for the economic development of a country in regards to both employment growth and innovative activity. The latter is believed to contribute significantly to the increase in productivity and therefore the competitiveness of Iran’s economy. This study contributes to the above literature by investigating the factors that are believed to treat the growth of such firms in Iran. The purpose of this study is to identify functional risks of vital signs monitors via Fault Tree Analysis (FTA) method to use as a guide for manufacturers to identify and control hazards. Therefore, 30 knowledge based firms were selected as sample. Then, based on a... 

One atom thick layer of pure carbon in bonded and hexagonal lattice is named graphene. graphene has unique mechanical, optical, thermal and electrical properties and because of these properties has grabbed attention. graphene has been made from high pure graphite by different methods such as CVD(chemical vapor deposition) , chemical exfoliation , micromechanical cleavage and colloidal suspension. through these methods, green methods for synthesis of graphene, using eco-friendly reductants during synthesis of graphene instead of hydrazine and recently using waste(not graphite) are attractive for synthesis of graphene. Following this idea , a group has produced graphene from wastes such as... 

Graphene is a two dimensional lattice which is created from carbon atoms. Having special feature, it has such various medical usage, for example in diagnosing and treating cancer. Adding a particular factor to graphene could improve their efficiency. In comparis on with graphene itself, graphene oxide and reduced graphene oxide are much more successful in diagnosing and treating than others because of their higher hygroscopic. Recent studies state that hydrogenized combinations including hydrogenized graphene show desired results. Due to its higher hygroscopic and the possibility of adherence to the cells, hydrogenized graphene could be very effective in diagnosing and treating the sarcomas.... 

This study discusses about mass customization and optimization of supply network in which both goal considering to set the flow of raw material and final product to satisfy the customer demand. The mass customization is more important concept in this study, so that this goal is placed to the first objective. In this research, the model which contained both goal is presented. The model focus on mass customization and try to satisfy various products demand, which constitute 3 kind of speed demands. Each product can satisfy in 3 way: fast, normal, slow.In the first model the new approach present in which the speed affects all of supplying, manufacturing and distributing system. The system try... 

Graphene oxide is a single sheet of Carbon atoms which has been arranged on a two-dimensional honeycomb lattice. Functional groups such as epoxy, carboxyl and carbonyl are located on basal plane and at the edges of graphene oxide and they localize electrons on the surface of graphene oxide and open band gap in its band structure. Pure graphene has zero band gap, so existence of fluorescence properties is unlikely; but graphene oxide has fluorescence properties due to band gap in its band structure. Fluorescence properties of graphene have been used in live cell imaging and drug delivery, so study and increasing of fluorescence properties is significantly important. The purpose of this... 

The Internet is often used for communication-based applications such as online banking, stock trading, and shopping where service interruption is unacceptable. Thus, analysis of the impact of the failures of hardware, software, and related services’ performance quality of the service provided to users is of importance to designers and managers in these functions. In this study, we developed a strategy to the design of a dynamic combination of file servers with the aim of providing reliability and SLA. At first, we examine the reasons for the violation of service level in file host services and datacenters, and then we introduce the criteria to measure the violation of service level on the... 

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... 

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... 

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... 

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... 

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... 

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...