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    The Investigation of PTC Effects of Barium Titanate Prepared from Nano-Structural BaTiO3 by Two Step Sintering Method

    , M.Sc. Thesis Sharif University of Technology Esmaeili Rad, Ahmad (Author) ; Nemati, Ali (Supervisor)
    The PTC effect which is one of the most important properties of electroceramics is being used in lots of electrical devices. This effect is observed in ceramics based on Barium Titanate. In the present study, the effects of grain size and two-step sintering method on PTC effect of Barium Titanate were investigated and La2O3 was used as an additive to improve the PTC effect and sintering behaviors of BaTiO3. Characterization analysis showed that the BaTiO3 powders had Cubic structure up to 700°C and Tetragonal structure at 1150°C. The FE-SEM analysis and density analysis showed that the samples which were two-step sintered at T1 less than 1200°C only reached 90% of relative density. Under... 

    Effects of Ce-Co Substitution on Magnetic and Dielectric Properties of Barium Hexaferrite Nanoparticles Synthetized by Sol-Gel Auto-Combustion Route

    , M.Sc. Thesis Sharif University of Technology Lellahgani, Zahra (Author) ; Nemati, Ali (Supervisor)
    In this study, the substituted barium hexaferrite nanoparticles with general formula Ba1-xCexFe12-xCoxO19 (x = 0, 0.1, 0.2 and 0.3) were prepared by the sol-gel auto combustion method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), Mossbauer spectroscopy (MS), vibrating sample magnetometer (VSM) and performing network analyzer (PNA) were employed to investigation of structural, magnetic, dielectric and microwave properties of barium hexaferrite nanoparticles. Moreover, differential scanning calorimetry (DSC) were performed to observe the formation mechanism of barium hexaferrite. DSC studies showed that barium... 

    An Investigation on Photocatalytic Behavior of Heavily Doped Titania

    , M.Sc. Thesis Sharif University of Technology Hoseinian, Farideh (Author) ; Nemati, Ali (Supervisor)
    TiO2 has been considered the most promising photocatalyst for the degradation of pollutants in air or water; however, it shows poor absorption of visible light and requires ultraviolet (UV) light for activation. We have successfully synthesized a visible-light-active carbon and nitrogen and yttrium tridoped TiO2 catalyst. In this study, Nanocrystalline photocatalysts of TiO2 doped with yttrium, codoped with carbon and nitrogen and tridoped with carbon and nitrogen and yttrium were prepared by the sol–gel method and investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy ( DRS), Scanning electron microscopy (SEM/EDS) and... 

    Preparation and Characterization of a Lithium Ion Conducting Electrolyte

    , M.Sc. Thesis Sharif University of Technology Toofan, Samin (Author) ; Nemati, Ali (Supervisor)
    In recent years lithium-air batteries captured worldwide attention because of their high energy density. Solid state electrolytes is one of the main components of lithium-air batteries. Lithium almunium titanium phosphate(LATP) is a nasicon type ion conduction which may be of great potential as solid electrolyte. The object of this thesis was the preparation of LATP solid electrolyte which can be used in a lithium-air battery. To reach this goal LATP powder was synthesized using a solution-based method and an appropriate crystallization temperature was selected based on obtained results of X-ray diffraction analysis. In the next step solid electrolytes was prepared under different pressing... 

    Electrical and Optical Properties of Doped (Ba, Sr)TiO3 Layers Prepared Via Sol-gel Method

    , M.Sc. Thesis Sharif University of Technology Emadi, Fahimeh (Author) ; Nemati, Ali (Supervisor)
    The main purpose of this research was simultaneous doping of carbon and nickel in the structure of barium strontium titanate, in order to investigate its dielectric and optical properties. Powders and films of BST, was synthesized by the sol-gel method in six different compositions: without any dopant, 0.04mol nickel dopant, 0.04mol nickel dopant accompanied by different amounts of carbon (0.01, 0.02, 0.03 and 0.04 mol). Suspensions were dip coated on alumina and quartz substrates. Structural features and chemical bonds, were studied through thermal analysis, XRD, FT-IR, FESEM and AFM. For electrical and optical properties, LCR-meter and UV-Vis were used. XRD and FESEM proved that nickel... 

    A Comparison of the Effects of Additives Alumina Nanoparticles and Microparticles on Microstructure and Properties of Magnesia-Doloma Refractory

    , M.Sc. Thesis Sharif University of Technology Shahraki, Aziz (Author) ; Nemati, Ali (Supervisor)
    Magnesia-Doloma refractories has advantages such as stability in alkaline environments, clean steel production, resistance to acid slag, good cement kiln coating flexibility, low production cost. It also has some weaknesses such as low resistance to thermal shock and quick hydration. In the present study using Birjand Mines Magnesite powders and Dolomites from Zefreh, Esfahan, Magnesia-Doloma clinkers were pressed under the pressure 90 MP and prepared at 1650⁰C in furnace under air atmosphere. The effect of adding 0, 2, 4, 6, and 8% of the Microparticles and Nanoparticles of α-Alumina on microstructure, physical properties, hydration resistance and Thermal shock resistance was studied. Phase... 

    Investigation Effect of Nano- sized Additives on Microstructure and properties of MgO-CaO Refracrories

    , M.Sc. Thesis Sharif University of Technology Ghasemi Kahrizsangi, Salman (Author) ; Nemati, Ali (Supervisor)
    Magnesia–Doloma refractories are considered as a mixed product of alkali products i.e. sintered (fused) magnesia and doloma in which 50-80 wt% magnesia is contained. These refractories enjoy some advantages such as high slag resistance corrosion, high-temperature performance, potential for production of pure molten iron and low cost due to abundance of magnesia and doloma resources in access. However, there exist some problems with these refractories that render them unsuitable for some applications. Among these cases, poor resistance of hydration can be cited that may constrain the amount of this refractory in various industrial applications. In the present work, the addition effect of... 

    Synthesis and Microstructure of Multi Valent Heavily Doped TiO2 Ceramics

    , M.Sc. Thesis Sharif University of Technology Motahari, Majid (Author) ; Nemati, Ali (Supervisor)
    In this project, the nanostructured titanium oxide with heaily doping of oxides of cerium and tin was synthesized using the sol-gel process and its properties were studied. To synthesize TiO2, titanium tetraisopropoxide precursor was used. Cerium nitrate and aqueous tin chloride precursors were utilized for cerium and tin synthesis. Then, they were mixed with Titania precursor causing a severe doping. After that, a gel was produced and it was aged and eventually, it was dried and calcined. XRD and SEM were used to determine the phase and particle size SEM and XRD results showed that doping had great impact on TiO2 crystals. The approximate size of nanoparticles was calculated using... 

    Synthesis of Magnesium Aluminate Spinel Nanoparticles Using Chemical Method and Investigation of the Effect of Zirconia on Spinel Composites Properties

    , M.Sc. Thesis Sharif University of Technology Maddahi, Vahid (Author) ; Nemati, Ali (Supervisor)
    In this research, a powder containing magnesium-aluminate spinel particles is prepared based on co-precipitation method and 5% , 10%, 15% and 20% zirconia-contained composites are produced as second phase from the synthesized powder. The raw materials used in the synthesis comprise hexa-hydrated magnesium nitrate, nona-hydrated aluminum nitrate, ammonium bicarbonate, 28% ammonium solution and distilled water. The properties of the powder is then investigated using STA, XRD and SEM tests. Also, XRD and SEM analyses as well as triple point flexural strength and Vickers hardness tests are carried out in order to investigate the effect of adding zirconia to the powders. The variations of the... 

    Optical Properties of Gel Cast and Sintered Alumina Ceramics

    , M.Sc. Thesis Sharif University of Technology Ghorbani, Mohammad (Author) ; Nemati, Ali (Supervisor)
    In this process transparent polycrystalline alumina ceramic was provided by submicron alumina gel casting and spark plasma sintering. The monomer system in this process including met acrylamide and methylene bis acrylamide was chosen as a monomer and cross linker. These two agents comprise 5%wt of the precursor with the ratio of 3 to 1 respectively. With the optimization of Dolapix CE64 as a dispersant and providing the suspension with 76%wt, a greenware with the density of 56.3% wt was obtained. Differential thermal analysis of green body showed that the existing monomers are removed by the time the body reaches 550°C. In order to access high real in-line transmittance, the microstructure... 

    The Effect of Nano-TiO2 and CaF2 Additives on Formulation and Properties of SiO2-Li2O Glass-Ceramics

    , M.Sc. Thesis Sharif University of Technology Gol, Saba (Author) ; Nemati, Ali (Supervisor)
    The goal of the present study is to analyze the effect of CaF2 and nano-TiO2 as additives on formulation and properties of common dental glass-ceramics. To achieve the goal, a glass system based on SiO2-Al2O3-Li2O-K2O-P2O5-ZnO-ZrO2 was considered to produce glass-ceramic samples and the additives, nano-TiO2 and CaF2, with the 0.5, 1, and 1.5 %Wt was added to the system. After the melting process, the glass samples poured in the water and ferrite was produced. In the next step, the ferrite was milled and pressed. In the heat treatment step, the samples were treated in the temperature range of 650-850°C in order to gain lithium disilicate glass-ceramics. In the last step, the chemical... 

    Formulation and Prodution of Organometal-halide Provskite Cells to Increase Solar Cells Efficieny

    , M.Sc. Thesis Sharif University of Technology Attari Navab, Arvin (Author) ; Nemati, Ali (Supervisor)
    Today organometallic perovskites are very important in fabrication of solar cells. This materials have advantages like high mobility of charge carriers, changing in range of light aborption with changing in structures atoms, having longer charge carrier diffusion lengths than other materials, high stability and efficiency, Low-cost fabrication process, having capability of studying and processing in low temperatures and having flexibility because of Weak chemical bond in perovskite structure. Due to the low stability and rapid decomposition of this material with the presence of light and moisture, in this study has tried to use PbS quantum dots which is used in sensitive dye solar cells as... 

    The Effects of Composition on Hardness and Toughness of ZrO2-Based Ceramics

    , M.Sc. Thesis Sharif University of Technology Farooghi, Mohammad (Author) ; Nemati, Ali (Supervisor)
    The purpose of this thesis is the construction of hard and tough Zirconia bodies from economical raw materials using minimum sintering time and temperature.
    Stabilizers cause tetragonal particles to be remained in cubic phase. Most additives are Ca, Ce, Mg and Y ions the whole of which are rare earth elements and make solid solutions with Zirconia.
    In this project different percents of CaO, MgO, CeO2, and Y2O3 were mixed with ZrO2 and they were sintered after granulation, cold pressing and Cold Isostatic Pressing. Using jar milling and fast milling, the particle size of purchased ZrO2 was reduced to 0.7 um. The whole needed additives were purchased with particle size below 300 nm.... 

    Formulation and Properties of Scaffolds based on Hydroxyapatite Composites Containing Titanium Dioxide and Magnesium Oxide

    , M.Sc. Thesis Sharif University of Technology Arab, Mehdi (Author) ; Nemati, Ali (Supervisor)
    This study investigates the effect of titanium dioxide and magnesium oxide additives on hydroxyapatite synthesized by sol-gel and composite with the predominant phase of hydroxyapatite by in situ method to improve mechanical properties. Scaffold samples were synthesized with nanometer-sized hydroxyapatite and composite powder particles by gel casting and sintered at 1200 ° C. Then, to evaluate the synthesized powders, simultaneous thermal analysis (STA), X-ray diffraction test, FTIR test, FESEM, EDS, and MAP analysis were used. Also, to evaluate the mechanical properties of the scaffolds, a compressive test was used, and to evaluate the scaffolds' density, the Archimedes method was used.... 

    Synthesis of Fe3O4@ SiO2 Core-shell Magnetic Nanoparticles with Porous SiO2 Shell Extracted from Rice Husk Ash

    , M.Sc. Thesis Sharif University of Technology Aharipour, Nazli (Author) ; Nemati, Ali (Supervisor)
    Magnetic nanoparticles, especially magnetic nanoparticles with silicate coatings, have attracted the attention of many researchers; Mainly because the silica shell can be functionalized with different molecules and functional groups and used in biological applications as targeted drug carriers. This study aimed to synthesize Fe3O4 core-shell nanoparticles with continuous and porous SiO2 shells on the surface of Fe3O4 particles. So that the coating is done evenly and with a strong connection. The procedure was as follows: core nanoparticle individual nanoparticles were made by the single-step method. To extract silica from rice husk, rice husk was subjected to heat treatment to obtain rice... 

    Investigating the Joining between Silicon Carbide and Aluminum Oxide Using Separate Metal Layers

    , M.Sc. Thesis Sharif University of Technology Ahadi Dolatsara, Reza (Author) ; Nemati, Ali (Supervisor)
    Sometimes, some ceramics and metals cannot be produced in an integrated manner; In addition, ceramics, like metals, do not fully benefit from the properties of melting and casting; Therefore, it is necessary to produce this group of parts with other methods such as joining to each other. By using joining methods and technologies, it is possible to make composite materials; Therefore, in this way, the applications of ceramic or metal composites have been increasingly expanded. In many researches, bonding of oxide ceramics such as aluminum oxide to itself as well as carbide ceramics such as silicon carbide to itself have been investigated. In this research, the bonding mechanisms of two types... 

    Characterization of Nanohydroxyapatite-Carbon Nanotube on Stainless Steel 316L Produced by Sol-Gel Method

    , M.Sc. Thesis Sharif University of Technology Mohamadi, Pouya (Author) ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor)
    In this investigation, hydroxyapatite-carbon nanotube nano composite coatings were applied on the 316L stainless steel implants. After polishing with 1200 sand paper, stainless steel implants were coated via dip coating method. The specimens were heat treated at 350˚C after being coated with HAP and HAP-CNTs composite. In vitro test was done in simulated body fluid (SBF) in 1 to 4 weeks periods. XRD evaluation of powder obtained from sol-gel process, showed the presence of HAP and CNTs in the powders. Comparison of XRD results of HAP and HAP-CNTs powders showed the better crystalinity of composite hydroxyapatite. After in vitro tests, specimens were studied with atomic force microscope (AFM)... 

    Investigation on Synthesis and Properties of TiO2-CNT Nanocomposites Coating on Al Substrate

    , M.Sc. Thesis Sharif University of Technology Shadravan, Aysan (Author) ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor)
    The aim of this project is investigation on synthesis and characterization of the TiO2-CNT nanocomposite films on aluminum substrate by sol-gel dip coating method. The pure TiO2 and TiO2-CNT nanocomposite layers were coated on aluminum substrate and heat treated in 400 C. In this work Ti-tetra isopropxide and different amounts of CNTs (5,10,15 %wt), were used for obtain the composites. The coatings were characterized by X-Ray diffraction (XRD) and the crystallite size of TiO2 was calculated by Scherrer formula. The corrosion properties of coating were examined by polarization test, and corrosion resistance of pure TiO2 was compared with TiO2-CNT coatings, and It showed that the composite... 

    Evaluation of Magnetic and Microwave Absorption Properties of Sr-Hexaferrite Nano Particles Doped With Zn and Ti

    , M.Sc. Thesis Sharif University of Technology Baniasadi, Amin Reza (Author) ; Nemati, Ali (Supervisor) ; Ghasemi, Ali (Supervisor)
    In this study, the micro and nano particles of substituted strontium hexaferrites with nominal composition of SrFe12-xTix/2Znx/2O19 (x=0, 0.5, 1, 1.5, 2 and 2.5) were prepared by a co-precipitaion method. Ferrite-PVA composites (70:30) with thickness of 1.8mm were prepared at 220°C and 50Mpa. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) were employed for characterization of synthesized powders and composites. XRD and FTIR results showed that single phase hexaferrite were obtained for almost all of the... 

    BiFeO3 Thin Films Deposition by Sol-Gel and Dip Coating Process

    , M.Sc. Thesis Sharif University of Technology Kianinia, Mehran (Author) ; Nemati, Ali (Supervisor) ; Alizadeh, Masoud (Supervisor)
    Dark and light conductivity has been investigated in Ca-doped bismuth ferrite thin films. Higher conductivity in the order of 105 magnitude of pure Bismuth ferrite has been observed for Bi0.85Ca0.15FeO3-δ. Structural analysis using Rietveld refinement showed a deviation from volume reduction for Bi0.85Ca0.15FeO3-δ that could be the reason of the abnormally high conductivity for this compound. Although higher calcium doping reduced conductivity but photoresponse could be revived. Atomic Forec Microscopy investigations showed that surface roughness decreases with increasing calcium concentration. Enhanced photoconductivity is reported for Bi0.7Ca0.3FeO3-δ with ~2.9 eV direct optical band gap...