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    Pr at Gd or Ba site in GdBa2Cu3O7: Appearance of superconductivity

    , Article Physical Review B - Condensed Matter and Materials Physics ; Volume 68, Issue 10 , 2003 ; 10980121 (ISSN) Mohammadizadeh, R ; Akhavan, M ; Sharif University of Technology
    2003
    Abstract
    Gd(Ba2-xPrx)Cu3O7+δ single phase polycrystalline samples with 0.0 < − x < − 1.0 were investigated for their structural and electronic properties. Due to the solubility limit, the 123 structure forms in the 0.0 < − x < −0.50 range; for x > −0.6, a decomposition of the perovskite-type phases occurs. For x=0.2, there is an orthorhombic-tetragonal phase transition, concurrent with a metal-insulator transition, which is evident in the normal state resistivity. For xc=0.35, the superconductor-insulator transition occurs. An unusual hump has been observed on the resistivity vs temperature curve of the samples for particular values of Pr doping. Based on the Rietveld refinement of the x-ray... 

    Efficient and practical solvent-free oxidation of alcohols using microwave irradiation

    , Article Journal of Chemical Research - Part S ; Issue 6 , 2002 , Pages 286-287 ; 03082342 (ISSN) Mojtahedi, M. M ; Sharifi, A ; Kaamyabi, S ; Saidi, M. R ; Sharif University of Technology
    Scientific Reviews Ltd  2002
    Abstract
    Alcohols are oxidised rapidly to the corresponding carbonyl compounds by montmorillonite KSF or silica supported barium manganate, under solvent-free conditions and microwave irradiation  

    Piezoelectric conductive electrospun nanocomposite PCL/Polyaniline/Barium Titanate scaffold for tissue engineering applications

    , Article Scientific Reports ; Volume 12, Issue 1 , 2022 ; 20452322 (ISSN) Peidavosi, N ; Azami, M ; Beheshtizadeh, N ; Ramazani Saadatabadi, A ; Sharif University of Technology
    Nature Research  2022
    Abstract
    Recent trends in tissue engineering technology have switched to electrical potentials generated through bioactive scaffolds regarding their appropriate effects on cell behaviors. Preparing a piezo-electrical stimuli scaffold with high electrical conductivity for bone and cartilage tissue regeneration is the ultimate goal of the present study. Here, Barium Titanate nanoparticles (BaTiO3 NPs) were used as piezoelectric material and highly conductive binary doped Polyaniline nanoparticles (PANI NPs) were synthesized by oxidative polymerization. Polycaprolactone (PCL) was applied as carrier substrate polymer and conductive spun nanofibrous scaffolds of PCL/PANI composites were prepared in two... 

    Reactive Crystallization in an Impinging Jets Reactor

    , M.Sc. Thesis Sharif University of Technology Raoufi, Farzan (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    Abstract
    Reactive crystallization or precipitation is an important industrial process. Many chemicals and biochemicals such as catalysts and pigments are produced by precipitation. Because of the advantages of impinging jets in chemical engineering processes, the main aim of this research was to investigate the application of this method in precipitation and to study the effects of different operating and design parameters on the product’s quality and properties. Two chemical models of barium sulfate and copper oxalate were used as main products. Each of these chemicals was produced by a liquid-liquid reaction of two aqueous solutions, which were fed to an impinging-jets reactor. Effects of... 

    Prediction of the aqueous solubility of BaSO4 using pitzer ion interaction model and LSSVM algorithm

    , Article Fluid Phase Equilibria ; Vol. 374, issue , July , 2014 , p. 48-62 ; ISSN: 03783812 Safari, H ; Shokrollahi, A ; Jamialahmadi, M ; Ghazanfari, M. H ; Bahadori, A ; Zendehboudi, S ; Sharif University of Technology
    Abstract
    Deposition of barium sulfate (or BaSO4) has already been recognized as a devastating problem facing process industries and oilfield operations, mainly owing to its low solubility in aqueous solutions. Predicting and also preventing the overall damage caused by BaSO4 precipitation requires a profound knowledge of its solubility under different thermodynamic conditions. The main aim of this study is to develop a solubility prediction model based on a hybrid of least squares support vector nachines (LSSVM) and coupled simulated annealing (CSA) aiming to predict the solubility of barium sulfate over wide ranges of temperature, pressure and ionic compositions. Results indicate that predictions of... 

    Nanothickness films, nanostructured films, and nanocrystals of barium titanate obtained directly by a newly developed sol–gel synthesis pathway

    , Article Journal of Materials Science: Materials in Electronics ; Vol. 25, issue. 12 , 2014 , p. 5345-5355 Ashiri, R ; Nemati, A ; Sasani Ghamsari, M ; Dastgahi, M. M ; Sharif University of Technology
    Abstract
    This work aims to develop a chemically modified sol–gel synthesis pathway for obtaining various barium titanate nanostructures. The method is able to prepare different BaTiO3 nanostructures such as highly stable nanoparticle embedded colloids, highly transparent amorphous nanolayers, nanocrystalline BaTiO3 powders and ultrathin BaTiO3 nanostructured films directly from a precursor solution. All the products have been prepared at a lower temperature and in a more cost-effective way in contrast to other established sol–gel methods. The results show that the optical transparency of the thin films has been significantly improved in contrast to the similar researches. The deposited thin film is... 

    A modified method for barium titanate nanoparticles synthesis

    , Article Materials Research Bulletin ; Volume 46, Issue 12 , 2011 , Pages 2291-2295 ; 00255408 (ISSN) Ashiri, R ; Nemati, A ; Sasani Ghamsari, M ; Sanjabi, S ; Aalipour, M ; Sharif University of Technology
    2011
    Abstract
    In this research, a modified, cost effective sol-gel procedure applied to synthesize BaTiO3 nanoparticles. XRD and electron microscopy (SEM and TEM) applied for microstructural characterization of powders. The obtained results showed that the type of precursors, their ratio and the hydrolysis conditions had a great effect on time, temperature and therefore the costs of the synthesis process. By selection, utilization of optimized precursor's type, hydrolysis conditions, fine cubic BaTiO3 nanoparticles were synthesized at low temperature and in short time span (1 h calcination at 800 °C). The proposed procedure seems to be more preferable for mass production. The result indicated that the... 

    Effects of Ce–Co substitution on structural, magnetic and dielectric properties of M-type barium hexaferrite nanoparticles synthetized by sol–gel auto-combustion route

    , Article Journal of Materials Science: Materials in Electronics ; Volume 26, Issue 4 , 2015 , Pages 2134-2144 ; 09574522 (ISSN) Lalegani, Z ; Nemati, A ; Sharif University of Technology
    Springer New York LLC  2015
    Abstract
    M-type Ce–Co substituted barium hexaferrite nanoparticles were synthesized by sol–gel auto-combustion route. The general formula of ferrites was Ba1−xCexFe12−xCoxO19 in which the x was considered to be: x = 0, 0.1, 0.2, and 0.3. The formed phases in the samples were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometer. The results indicated that an increase in substitutional ion amount caused to decrease vibration frequencies of Fe–O band in the tetrahedral site due to the substitution of heavier Co2+ ion for Fe3+ ion in the tetrahedral site. Moreover, some of Ce3+ ions was transformed to Ce4+ and... 

    Characterization of optical properties of amorphous BaTiO3 nanothin films

    , Article Journal of Non-Crystalline Solids ; Volume 355, Issue 50-51 , 2009 , Pages 2480-2484 ; 00223093 (ISSN) Ashiri, R ; Nemati, A ; Sasani Ghamsari, M ; Aadelkhani, H ; Sharif University of Technology
    Abstract
    Amorphous barium titanate nanothin films were prepared by sol-gel dip-coating method. According to transmission spectrum, the refractive index and optical band gap of nanothin films have been determined. High transmission spectrum without any fluctuation in visible wavelength region was recorded. Experimental results indicated that the surface morphology of prepared nanothin films were improved and as a result of that, a better optical properties, less optical losses and higher band gap width were obtained in contrast with other reported data. It was found that optical propagation loss of BaTiO3 nanothin film was much lower than normal polycrystalline BaTiO3 thin film. It seems to us that,... 

    Experimental investigation and process intensification of barium sulfate nanoparticles synthesis via a new double coaxial spinning disks reactor

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 115 , 2017 , Pages 11-22 ; 02552701 (ISSN) Bagheri Farahani, H ; Shahrokhi, M ; Molaei Dehkordi, A ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    In this article, a new double spinning disks reactor (DSDR) has been proposed and tested successfully for the synthesis of barium sulfate nanoparticles by means of the reactive precipitation. The proposed DSDR consists of two coaxial rotating disks placed horizontally in a cylindrical chamber. Continuous precipitation of barium sulfate nanoparticles as a chemical test system was carried out using this new contacting device and the effects of operating and design parameters such as the disk rotational speed, distance between the disks, feed concentration, feed flow rate, free ion ratio, feed location, and feed distribution pattern on the mean size, size distribution, and morphology of the... 

    Influence of synthesis variables on the properties of barium hexaferrite nanoparticles

    , Article Journal of Materials Science: Materials in Electronics ; Volume 28, Issue 6 , 2017 , Pages 4606-4612 ; 09574522 (ISSN) Lalegani, Z ; Nemati, A ; Sharif University of Technology
    Abstract
    Barium hexaferrite (BaFe12O19) nanoparticles were synthesized by sol–gel auto-combustion route. Prepared samples were sintered at 950 and 1100 °C with Fe3+/Ba2+ = 12 and 20 mol ratio. The formation mechanism of barium hexaferrite was investigated by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. In addition, the effect of temperature and Fe3+/Ba2+ mole ratio on BaFe12O19 formation and magnetic properties, and the effect of increasing the Fe3+/Ba2+ upon gel ignition and subsequent phase development were investigated. Finally the magnetic behavior was monitored with VSM. DSC studies showed that pure barium hexaferrite phase was formed from maghemite... 

    Synthesis and characterization of YBaCu2O5-δ compound

    , Article Physica C: Superconductivity and its Applications ; Volume 548 , 15 May , 2018 , Pages 112-115 ; 09214534 (ISSN) Ehsandoust, A ; Sandoghchi, M ; Mokhtari, P ; Akhavan, M ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    YBaCu2O5 compound as one of the possible microstructures of Y3Ba5Cu8O19 has been synthesized. The X-ray diffraction analysis of this compound indicates that its formation is accompanied with the formation of YBa2Cu3O7-δ. The observed superconductivity around ∼92 K supports this. So, it seems that YBa2Cu3O7-δ is responsible for the observed superconductivity in YBaCu2O5, and this phase is not an independent superconducting phase. Consequently, the overall effect of the YBaCu2O5 formation during the Y3Ba5Cu8O19 fabrication process could be a reduction in Tc. © 2018 Elsevier B.V  

    Synthesis of barium sulfate nanoparticles using a spinning disk reactor: Effects of supersaturation, disk rotation speed, free ion ratio, and disk diameter

    , Article Industrial and Engineering Chemistry Research ; Volume 48, Issue 16 , 2009 , Pages 7574-7580 ; 08885885 (ISSN) Dehkordi, A. M ; Vafaeimanesh, A ; Sharif University of Technology
    2009
    Abstract
    The aim of this research was to synthesize barium sulfate nanoparticles using a spinning disk reactor. Barium sulfate was produced by continuously pumping two aqueous solutions of BaCl2 and Na2SO 4, respectively, into the chamber of spinning disk reactor, where a liquid-liquid reaction took place to form BaSO4. The influences of various operating and design parameters such as the initial supersaturation, disk rotation speed, free ion ratio, and the disk diameter on the size of barium sulfate nanoparticles were carefully investigated. By varying the supersaturation and disk rotation speed, a broad range of particle size ranging from micrometer sizes down to nanoparticles smaller than 100 nm... 

    Doping of Sm3Ba5Cu8O19 compound with praseodymium

    , Article Journal of Low Temperature Physics ; Volume 198, Issue 5-6 , 2020 , Pages 252-268 Sandoghchi, M ; Akhavan, M ; Sharif University of Technology
    Springer  2020
    Abstract
    An investigation has been carried out on the effects of praseodymium doping in Sm3−xPrxBa5Cu8O19 for different values of x. Results indicate that the transition temperature reduces almost linearly with x. Based on the Abrikosov–Gor’kov pair-breaking theory, it has been concluded that the exchange interaction constant is large (Jex = 110 meV) in the Sm3Ba5Cu8O19 compound. In addition, it seems that the hybridization of Pr4f states with O2p–Cu3d states has an important role in the depression of transition temperature of Sm3−xPrxBa5Cu8O19 for the Pr content < 10%. However, for the higher values of Pr, the two observed plateaus at the transition temperatures of ~ 60 K and ~ 17 K, respectively,... 

    Oxidative coupling of methane on BaTiO3 perovskites partially substituted with germanium

    , Article Catalysis and Reaction Engineering Division Conference, Presentations at the 2008 AIChE Spring National Meeting, 6 April 2008 through 10 April 2008 ; 2008 , Pages 89-94 ; 9781605602233 (ISBN) Boghaee, D. M ; Hamidzadeh, M ; Negin, S ; Sharif University of Technology
    AIChE  2008
    Abstract
    The perovskite oxide BaTiO3, doped with Ge oxides oxidized methane to C2 coupled hydrocarbons. The ultraviolet-visible spectra of pure barium titanate and Ge doped BaTi(1-x)GexO3(x=0.05,0.1) were compared. The pure barium titanate exhibited an ultraviolet absorption effect. The addition of GeO2 resulted in an increase in absorption of wavelength. Therefore, small amount of Ge decreased band gap energy. Oxygen is inserted by nucleophilic attack which may be considered as an acid-base process. For promoted BaTiO3catalysts with stable cation valance, electron donation ability of lattice oxygen is parallels to its ability of adsorb and active oxygen, and decrease the chance of deep oxidation of... 

    Investigation of Sintering Behavior of BaTiO3 Nanoparticles Synthesized Via Hydrothermal Method

    , M.Sc. Thesis Sharif University of Technology Soroush, Soheil (Author) ; Nemati, Ali (Supervisor) ; Simchi, Abdolreza (Supervisor)
    Abstract
    In the present work, Barium Titanate nanoparticles were synthesized by a facile hydrothermal method at 180oC for 4 hours and their sintering behavior was studied. The characterization tests illustrated that the obtained powder was BaTiO3 single phase with excess Ti content from stoichiometric composition. The average particle size of about 50 nm and a narrow particle size distribution was noticed. SEM investigations showed that the samples sintered at temperatures less than 1250oC had plate-like grains. This behavior resulted from twin plates existed in the grains and facetted grain boundaries. At the temperatures more than 1250oC, the grains became polygonal due to the formation of trace... 

    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)
    Abstract
    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... 

    Water-based sol-gel nanocrystalline barium titanate: Controlling the crystal structure and phase transformation by Ba:Ti atomic ratio

    , Article Journal of Materials Science ; Volume 44, Issue 18 , 2009 , Pages 4959-4968 ; 00222461 (ISSN) Mohammadi, M. R ; Esmaeili Rad, A ; Fray, D. J ; Sharif University of Technology
    2009
    Abstract
    Highly stable, water-based barium titanate (BaTiO3) sols were developed by a low cost and straightforward sol-gel process. Nanocrystalline barium titanate thin films and powders with various Ba:Ti atomic ratios were produced from the aqueous sols. The prepared sols had a narrow particle size distribution in the range 21-23 nm and they were stable over 5 months. X-ray diffraction pattern revealed that powders contained mixture of hexagonal- or perovskite-BaTiO3 as well as a trace of Ba2Ti 13O22 and Ba4Ti2O27 phases, depending on annealing temperature and Ba:Ti atomic ratio. Highly pure barium titanate with cubic perovskite structure achieved with Ba:Ti = 50:50 atomic ratio at the high... 

    Electrothermal simulation of barium titanate based PTCR thermistor

    , Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 133, Issue 1-3 , 2006 , Pages 157-166 ; 09215107 (ISSN) Moetakef, P ; Nemati, Z. A ; Sharif University of Technology
    2006
    Abstract
    PTCR thermistors are thermally sensitive resistors that show positive temperature coefficient of resistance and are good candidates for applications as self-regulating heating elements and thermal control switches. For these applications, the current-time behavior of thermistors is of primary importance. In this work, heat transfer models were developed to simulate the electrothermal behavior of BaTiO3 thermistors. Also, using simulated temperature profiles, thermal stress distributions of the specimen were calculated to predict crack formation at different conditions. At high voltages, the effects of thermal conductivity and heat transfer coefficient were negligible. At low voltages, the... 

    Synthesis and characterization of nanocrystalline barium strontium titanate

    , Article Materials Science- Poland ; Volume 28, Issue 2 , 2010 , Pages 421-426 ; 01371339 (ISSN) Golmohammad, M ; Nemati, Z. A ; Faghihi Sani, M. A ; Sharif University of Technology
    2010
    Abstract
    Barium strontium titanate (BST) was prepared via the simple sol-gel method by using tetrabutyl ti-tanate, ethanol, citric acid and ethylene glycol as starting materials. Thermogravimetry and differential thermal analysis were used to examine the behaviour of the xerogel. The particle size of BST was approximately 21 nm, as calculated by the X-ray diffraction and confirmed by transition electron microscopy for the calcination temperature of 750 °C. It was found that the particles of BST powders calcined at 750 °C were smaller and more homogeneous and uniform than those obtained at 800 °C