Sharif Digital Repository

It is well known that poly(ethylene terephthalate) (PET) is a high melting compound which has exceptional value as a fiber and film-making material, and which currently dominates the whole field of linear polyester substances. However, the high viscosity and limited solubility in liquid solvents restrict its processing to powders and hence the range of applications of such a polymer. Traditionally, crushing, mechanical grinding, ball milling and precipitation from solution are methods for producing powders. The first three ones inevitably change the property of materials. The last one is carried out on the basis of the application of an anti-solvent to decrease the solubility of a... 

In this study, an alkaline bath for co-deposition of Fe and Pd was selected. In order to investigate the mechanism of deposition, each of the metals iron and palladium electrodeposited from selected bath separately; and the kinetics of electrodeposition by electrochemical techniques such as linear voltammetry, cyclic voltammetry, chronoamperometry and chronopotentiometry were evaluated. Electrodeposition processes of Fe, Pd and their alloy were irreversible and under diffusion of reducing agents are controlled. Moreover the electroreduction of palladium from utilized bath was performed in two steps. At following, the mechanism of iron– palladium alloy electrocrystallization was discussed and... 

Nickel oxide is used in the manufacture of ceramic, magnetic materials, battery cathodes, electrochromic films, heterogeneous catalytic materials and gas sensors. NiO nano-powder can be produced with many different methods. The synthesis of NiO nanopowder has been carried out via solochemical processing from an aqueous solution of a Ni containing complex in this research. Another name for this method is two-stage solochemical (TSSC) method. This is the newest economic method for synthesis of NiO nanopowder. NiCl2 anhydrous and NH3-H2O used as the raw materials and H2O used as solvent. The results obtained from XRD and TEM show that the nanoparticles have cubic crystal structure and the mean... 

I-131 isotope is one of the most significant radio medicines for treatments of the thyroid cancer and nuclear tomography of thyroid. As for purification of this radioisotope several methods have been developed among which adsorption-desorption on metallic copper is the most promising. The current study is aimed at elaboration of the kinetics behavior of the different types of metallic copper for adsorption of iodine vapor. The used copper samples included plain and silica-supported Cu nanoparticles as well as micronized copper. The silica-supported Cu nanoparticles were prepared by impregnation of highly porous silica (≈500 m2/g) in Cu(NO3)2 solution, heating of the solution to above... 

In this study, the recovery mechanism of nickel oxide by carbon dissolved in molten iron with the study of reaction kinetics were investigated. Nickel oxide pellets into molten iron containing graphite were added in the neutral atmosphere and the release of CO gas as a function of reaction time was measured until the end. The volume of gas produced at different times shows the number of moles of Ni metal was revived. Reaction by a) the following decomposition reaction under 1475 °C ; and b) carbon diffusion rate at temperatures over ° C1475 is controlled. The main reaction mechanism in order to a) decomposition of NiO; b) penetration of oxygen atoms in the melt, and c) reaction between... 

Platinum is one of the most used catalysts in refining and petrochemical industries. Also, Platinum uses in other industries like automobile catalytic convertor. As respect to importance of Platinum in these industries, growth of its consumption in recent decades and its very high price, recovery of Platinum is essential. Hence, many of various methods including hydro-metallurgy are applied. In despite of these wide spreading experimental investigations, due to low information about the reactions and the nature of reaction products, a few investigations were done on kinetics of Platinum recovery. A new method that used iodine solution to extract Platinum from spent reforming catalysts was... 

N, N′, N″-triethylenethiophosphoramide (Thiotepa) and its oxo analogue (Tepa) as the major metabolite are trifunctional alkylating agents with a broad spectrum of antitumor activity. In vivo and vitro studies show alkylation of DNA by Thiotepa and Tepa can follow two pathways, but it remains unclear which pathway represents the precise mechanism of action. In pathway 1, these agents are capable of forming cross-links with DNA molecules which can be carried out via two different mechanisms. In the first mechanism, the ring opening reaction is initiated by protonating the aziridine, which then becomes the primary target of nucleophilic attack by the N7-Guanine of DNA. The second one is the... 

Every year, an enormous amount of catalysts are consumed in oil refineries during refining processes. After some regeneration cycles in order to recover their activity, they are not anymore effective and must be disposed. These spent catalysts are regarded as dangerous solid wastes as they significantly include some contaminations like vanadium, nickel, arsenic, sodium. From another point of view, the metals present in spent catalysts are highly valuable and are used extensively in steel industry and manufacture of special alloys. So, it sounds profitable to extract and recover these metals from such a cheap source instead of minerals and ores. Basically, there are two main processes, hydro-... 

High advantages of hydrometallurgy have led to its recent development in metal extraction. Many investigations are being carried out on applying hydrometallurgy processes on copper extraction. In this study, the chloride leaching of chalcopyrite in a concentrated sodium chloride solution (4M) –which is a novel process–, using CuCl2 as leachant is investigated. Main effects and interactions of temperature (50–90°C), time (2–6 hr), CuCl2 concentration (0.1–0.5M), pulp density and HCl concentration (0.1–1M) at constant stirring rate (600 rpm) on leaching is studied using 2k factorial design and applying Design–Expert 7.0.0 software. While the effect of pulp density is almost negligible,... 

In the present work, primary crystallization mechanism, glass forming ability, thermal stability and formation of nano Al crystals and their effects on the mechanical behavior were investigated in various Al amorphous alloy containing misch metal including Al90-xNi10-yFeyMMx (x=2-10%at, y=0-10 %at) alloys. In order to elaborate the Cu effect on the primary crystallization mechanism Al86Ni10-xCuxMM4(x=0-2/5) alloy were prepared. The results showed that in Al90-xNi10MMx (x=2-10 %at) alloying system variation of the misch metal from 2 to 10 atomic present results in increase in glass forming ability. The crystallization onset temperature also increases from 405 K in Al88Ni10MM2 to 630 K in... 

Catalytic esterification of acetic acid with 1-hexanol was investigated over polyoxometalates. H3PW12O40 and H3PMo6W6O40 polyoxometalates with keggin structures were synthesized. Catalytic activity and recyclability of them were improved by loading on the γ-Al2O3 with impregnation method and Cs, K and NH4 salts preparing.Catalysts were characterized by XRD, SEM, FT-IR, BET, DRS and NMR techniques. According to XRD's results, catalysts have ace-centered cubic crystal systems. Loading on supports and preparing the salts do not destroy the structures of polyoxometalates. SEM images show the uniformity of catalysts' surface and catalysts' fixing on the support. It was seen that the keggin... 

In this study, the effect of two main parameters, time and temperature, were investigated in the roasting process of zinc sulfide of Bafgh’s mine, and kinetics and the mechanism of the roasting reaction were examined, too. The oxidation process was performed in a muffle furnace in the presence of the oxygen of air atmosphere. The raw powder material (with the particle size of 74-250 micron) was poured in Alumina crucibles. The roasting process was run in eight temperatures of 650, 700, 750, 800, 850, 900, 950 and 1000 ◦C. Oxidation percent was calculated in six times of 5, 10, 15, 30, 45 and 60 minutes. The experiments were designed in a way that the effect of each parameter could be... 

Real fuels contain hundreds of hydrocarbons such as linear and chain paraffins, naphthenes, olefins and aromatics.Behavior of this real fuels are represented by mixtures with simple compounds. Since engine with homogeneous charge compression ignition (HCCI) is a promising combustion concept able to provide very low NOx and PM diesel engine emissions while keeping good fuel economy, for use in vehicles requires kinetic reaction mechanism to simulate the hydrocarbons oxidation and it’s rules.combustion control is facing with basic problem in this engine.unlike conventional methods, . HCCI combustion is a kinetically controlled process and start of combustion will be controlled and dominanted... 

In this project the effect of rolling temperature on mechanical properties and microstructure evolution of a low carbon steel was studied. The steel was rolled up to a nominal strain of 67% at three different temperatures consisted of room, blue brittleness, and subzero temperature. Micreohardnessand tensile tests were used to characterize the recrystallization kinetics. Optical and scanning electron microscopic examinations were carried out to evaluate the mechanical, grain size, and the kinetics of static recrystallization by the Avrami equation. The results indicated that the volume fraction of static recrystallization increases with the increase in annealing period. The Avrami exponent... 

The recycling of the secondary resources for the extraction of their metallic contents is undoubtedly environmentally friendly and can be economic. One of the most important secondary resources is the electronic wastes (E-wastes) which has been widely produced as the discarded electrical/electronic devices. The usual physical/chemical treatments of E-wastes not only result in an increase in human health risks and environmental pollution but also lead to the missing of their valuable metallic contents. An alternative method for the recycling of E-wastes is bioleaching which has recently attracted more attention. The advantages of this process are low energy consumption and environment... 

This research has studied the kinetic and mechanism of partial reduction of hematite to magnetite via carbon monoxide gas. In addition, temperature and partial pressure of CO gas as two main parameters which influence the rate of the reduction process has been studied. In order to investigate the change in mass during the reaction, thermogravimetric analysis (TGA) has been applied and in order to evaluate the effect of the temperature and partial pressure of CO on the rate of the reduction, three different temperatures and two different ratios of CO/CO2 has been experimented. Three isothermal analysis in 390°C, 440°C, and 490°C in pure CO atmosphere and two isothermal analysis in 550°C with... 

In present study, various cocatalysts were used to improve catalytic properties of metal oxides and oxy-acids. Ag3VO4/Ag3PO4/Ag and Cu2O/MoS2/rGO photocatalysts were synthesized. The photocatalytic activities of the prepared nanocomposites were evaluated by the photodegradation of dye in the heterogenous systems as a series of advanced oxidation reactions. The results revealed that heterojunction between two semiconductors may prevent fast electron-hole pair recombination and then improve efficiency and rate of dye photodegradation. Mechanism and kinetics of dye degradation were studied in the presence of new photocatalysts by using of different scavengers. In the other works, Pt-NiO/G and... 

Based on the new standards, less than 10 ppm sulfur is allowed for the automotive fuels. This has led researchers to try improving the present conventional methods as well as seeking alternative routes for refinement of the petroleum products so much to comply with the requirements. Since thiophenic fragments such as dibenzothiophene (DBT) are the most durable sulfur compounds in the current hydrodisulfurization method, many studies have been conducted over recent years on how to remove these compounds. In this thesis, the desulfurization of dibenzothiophene from gasoline via adsorption method was studied. In order to carry out the adsorption process, a nanocomposite of graphitic-carbon... 

Bimetallic nanoparticles with unique structure, synergistic effect between two metals, and the tunable physical/chemical properties have been used for catalysis. Various methods exist for the staibility, and improvement of the catalytic performance of nanoparticles. In this thesis, different co-catalysts were applied to increase tha staibility, and activity of nanoparticles and metal oxides. In this way, Ni-based bimetallic nanoparticles including CuNi, CoNi, and AgNi, and AgPt with different concentrations were synthesized on the cerium oxide nanorods derived from cerium metal-organic frameworks and magnetic graphene oxide nanosheets, respectively and characterized. The catalytic... 

Direct Reduction of magnetite concentrate with thermal coal in concentric cylindrical arrangement has been investigated. At first, thermal behavior and physical and chemical properties of 3 type of coals from different coal mines of Iran in a thermal treatment similar to pre heating section of tunnel kiln direct reduction of Iron were investigated.Study of changes in reactivity and calorific values of coal in addition to providing a fundamental understanding of coal performance in the thermal process of reduction set a base for investigation of recycling of unburnt coal in the reduction process. Thermogravimetric data for coal devolatilization in three heating rates yielded an activation...