Sharif Digital Repository

Highly active unsupported MoO3 and (Co) MoO3 catalysts were synthesized utilizing the solution combustion method where the Ammonium molybdate powder and an organic additive were used as precursors. Different organic materials including Ethylene Diamin Tetra-acetic acid (EDTA), Polyethylene Glycol 200 (PEG 200), Sorbitol and Urea were used as additive in order to investigate the effect of additive structure on morphology and particle size of products. Also various reaction parameters such as the additive/Mo molar ratio, concentration of metal ion in solution, pH of the reaction and temperature of the synthesis media were changed to study effects on product morphology and size. Outcomes were... 

Different molybdenum oxide nano/micro structure thin films were synthesized by thermal evaporation method under various growth conditions such as deposition time, temperature and evaporation source-substrate distance. Molybdenum oxide nanostructures grown on Si(100) such as nanowalls, nanostars and nanowires were characterized with scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). Shape and type of nanostructures were determined with SEM, AFM and HRTEM analysis. XPS analysis showed that the synthesized nanostructures contained Mo6+, Mo5+, Mo4+ and... 

Physical and chemical properties of tungsten oxide thin films change reversibly while exposure to hydrogen gas. This property is called gasochromic. To enhance optical properties of such films, nanostructured, amorphous and porous thin films of (WO3)1-x(MeO)x (MeO= TiO2, MoO3, NiO; x=0.09, 0.17, 0.23, 0.29, 0.33) were fabricated by Pulsed Laser Deposition. Molar percentage of Me/W (Me= Ti, Mo and Ni) was changed in films with respect to targets; for Ti and Ni always a reduction, but for Mo an enhancement for low percentages was observed. The reason is the existence of thermal ablation mechanism during deposition, in the other word is different vapor pressure effect. An increment in x for... 

Adding solid lubricant particles such as PTFE, Graphite and MoS2, has major influence on electroless composite nickel coatings in order to make low friction surfaces. Among these lubricants, MoS2 has attracted great attention due to its highest stability under wearing condition. In this work Ni-P-MoS2 composite coatings using MoS2 nano-particles have been made and in the next step, we evaluated tribological properties of these coatings. For exploring these coatings different experiments were utilized, like Scanning Electron Microscope study (SEM), chemical composition analysis exploiting AAS and XRF method, and thickness measurements. Two kinds of surfactants, CTAB and PVP, have been applied... 

In this study solid lubricants MoS2 nanoparticles with average size 50 nm and hard ZrO2 nanoparticles with average size 51 nm were used in watts bath and Ni/ZrO2-MoS2 composite coatings were prepared by pulse plating technique. Effect of current density, frequency, duty cycle, surfactant type and concentration of particles in the electrolyte on the amount of particles in the coatings were investigated and optimum conditions were determined to create composite coatings. Scanning Electron Microscopy (SEM) and x-ray diffraction (XRD) analysis were performed to study the morphology, structure, chemical composition of coatings. Corrosion testing of coatings by potentiodynamic polarization in... 

Quite a few methods have been reported to synthesize monolayer MoS2, which has recently attracted scientist attentions. Fully controlled conditions, however, have not been achieved in these methods. In this research, two-dimensional MoS2 nanofilms have been synthesized by Chemical Vaper Deposition (CVD). Layer thickness of synthesized layer and effects of various parameters of used method have been investigated. Although every scientist synthesizes 2D MoS2 at 650°C in the CVD method by using seeds, in this research, it has been proved that MoS2 nanofilms can be produced at 575°C without using any seeds, which leads to lower consumption of time and price and increases the quality of... 

Ultra high molecular weight polyethylene has attracted the attention of numerous researchers and industries. This polymer due to its strong properties can be used in advanced military industries, medical engineering and cases in which high strength and high abrasion resistance is required. Present study aims to fabricate UHMWPE/Molybdenum disulfide composites, using in-situ polymerization. Before carrying out the polymerization process, nanoparticles of molybdenum disulfide underwent various processes such as oxidation, pickling, ultrasonic and thermal shock, in order to increase the interlayer distance and creating functional groups on the surface, then various analyzes, such as XRD, FESEM,... 

In this research Feasibility of application of oxide compounds of bismuth, molybdenum and tin as biocide was studied. So some epoxy paints with different ratio of these compounds were formulated. Afterward some tests were performed to assessment paints properties such as leaching rate, antifouling activity, adhesion, corrosion resistance and impact resistance. Results of leaching rate test showed that increase in the ratio of bismuth oxide from 10% to 60%, led to increase leaching rate from 0.029mg.day-1.cm-2 to 0.126mg.day-1.cm-2. beside that Microscopic results showed proved that the ratio of bismuth oxide in the cured coating is 25% of the paint formulate. In similar ratio of biocides,... 

Today, the process of corrosion and compensation of minor injuries, without the need for tracing or any other physical interference, has become one of the subjects of interest to researchers. Inhibitors have been considered as one of the anti-corrosion agents. In this research, safflower extract as a green inhibitor in sodium chloride corrosive environment was used to evaluate the rate of corrosion of mild steel. Also the MoS2 nanoparticles were used as carrier of this green inhibitore in the epoxy coating to allow the activation of the coating in a scratched state in sodium chloride solution of 3.5%. In the first step, the extract of the safflower was prepared to reach the best part of this... 

Organic light emitting diodes (OLEDs) are one of the main subjects of research in the organic electronic advanced technology. There are many advantages for OLEDs like self-emitting, high efficiency, wide vision angle, high contrast, and rapid response time. The main challenge in this area is the long-time stability of performance in air ambiance. Although the encapsulation process could overcome the instability problem, it increases the final cost. In this project, metal oxides have been utilized for the injection of electrons and holes in hybrid light emitting diodes (HyLEDs). In the first stage, inverted structure of HyLEDs with ZnO and MgxZn1-xO layers was fabricated and characterized.... 

In this study, to synthesize molybdenum disilicide nano powder, mixed powder of Mo and Si were ball milled for 15, 30, 45 and 55 hours. By the results of the analyses, milled powders for time intervals of 55 hours were heat treated to release the stresses. This process was carried out in an argon vacuum tube furnace at 1000˚C for 1 hour. XRD analysis was carried for sample. Finally, MoSi2 powder with 86.62 nm crystallite size was used as reinforcement. Cu-MoSi2 composite powder with 2, 3, 5wt% were produced. Cu-MoSi2 with 2wt% reinforcement was milled for 60 hours. Powder composite was compacted by Spark Plasma Sintering . Microstructure of composite was investigated by scanning electron... 

Molybdenum disilicide is an intermetallic compound in Mo-Si binary system that has very applications because of its individual properties. High melting point of MoSi2 limits the fabrication of this compound by conventional methods. Nowadays modern techniques such as Mechanical Alloying are used for synthesis of Molybdenum disilicide. In this investigation the MoSi2 has been synthesized from the elemental powders by Mechanically activated Self propagating Reaction method and the effect of milling atmosphere on synthesis efficiency is discussed  

Molybdenum disilicide is an intermetallic compound in Mo-Si binary system that is appropriate to use at high temperatures. Because of its special properties such as high melting point, oxidation resistance, good electrical resistivity and thermal conductivity, this material can be used in high temperatures applications such as gas turbines, heat shield and tiles. High melting point of MoSi2 limits the fabrication of this compound by conventional methods. Nowadays modern techniques such as mechanical alloying are being used for synthesis of Molybdenum disilicide. The objective of this study is to investigate the effects of sintering time and temperature on the mechanical and electrical... 

In the first part of this thesis, the application of core-shell magnetic nanoparticles supported V(V), Mo(VI) and Mn(III) complexes in the catalytic oxidation and reduction reactions was discussed. A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica coated Fe3O4 nanoparticles. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles. A manganese(III) complex was immobilized on... 

In the first part of this thesis, the application of metal oxide nanoparticles in oxidative degradation of methylene blue is discussed. Nanoparticles of manganese tungstate (MnWO4) were prepared via an impregnation method using Mn(NO3)2.4H2O and WO3 as a source of Mn and W, respectively. The morphology of the manganese tungstate nanoparticles was studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MnWO4 nanoparticles showed severe catalytic performance for the degradation of organic dye (methylene blue) in the presence of tertiary-butyl hydrogen peroxide, TBHP, as the oxidant at room temperature in water. Mn doped ZnO... 

A new dioxomolybdenum(VI) complex, (Cis-[MoO2(L)])n, has been synthesized by reacting 4-bromo-2-((2-hydroxy-5-methylphenylimino)methyl)phenol as a ligand and [MoO2(acac)2] in methanolic solution. For characterization and structure determination of the synthesized complex, different techniques were performed such as elemental analyses, 1H NMR, IR, UV-Vis and X-ray crystallography. The complex was tested as a catalyst for the homogeneous epoxidation of olefins, using tert-butyl hydperoxide (TBHP) as an oxidant. The catalytic system showed high yield, selectivity and turnover number in olefin epoxidation reactions under atmospheric conditions. For example, when the molar ratio of catalyst,... 

In this study, linear polarization resistance (LPR) of cathodic pulse electrodeposited graphene- Nickel-Molybdenum coating is optimized by design of experiments approach (central composite design). Applied current density (i), cathodic pulse durations (Ton) and total electrodeposition time (Ttotal) are selected as the substantial factors. The best prediction model proposes a definitive linear relation without any significant interaction of the LPR by analysis of variance. The best value of LPR is achieved equal to 1406KΩ.cm2, obtaining at i of 137.5 A/cm2, Ton of 45.5 ms and Ttotal equal to 315 s. Polarization test is carried out to determine corrosion behavior of the coating. It shows... 

The extraction of molybdenum and rhenium from acidic solution produced by pressure leaching of molybdenite concentrate, using organophosphorus solvents has been investigated. First, extraction of molybdenum by Di-2-EthyHexyl Phosphoric Acid (D2EHPA) extractant dissolved in kerosene diluents was done. Extraction experiments were designed using Taguchi L16b orthogonal array. The effects of four factors: Shaking time, Organic solvent concentration, Organic to aqueous phase ratio, pH were studied in four levels. Optimum conditions occur at: shaking time: 35 min, organic solvent concentration: 30 volumetric percent, organic to aqueous phase ratio: 3, pH: 7 and molybdenum is completely extracted.... 

In this work, the recovery of rhenium from ferromolybdenum furnace outgoing dust in semi industrial scale was conducted. The ferromolybdenum furnace outgoing dust contains rhenium as major part and large amounts of molybdenum plus Iron and copper as impurities. An overall flow sheet, consist of leaching, solvent extraction and precipitation methods, was design to recovery and purification of rhenium. Firstly, ferromolybdenum furnace outgoing dust was subjected to leaching treatment by 10 g/L sulfuric as solvent at 85 C. Secondly, solvent extraction method was employed, using LIX984N 10 %vol, to separate copper from rhenium containing solution. The results of MacCab thiele diagram for... 

The present work investigates joining of two MoSi2 parts through Cusil/Zr/Cusil interlayer with Cusil being a commercial eutectic of Ag-Cu alloy. The joining operation was implemented in an inert gas tube furnace by brazing. The brazing temperature ranged at 800-930°C while the operation lasted for 1hr. Interfacial microstructure was studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) techniques. Applying the temperature of 830°C was led to uniform dense joint consisting of various reaction phases with excellent bonding within interfaces. Diffusion of Si to the liquid phase will transform MoSi2 to Mo5Si3 which bears Ag to some...