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    , M.Sc. Thesis Sharif University of Technology Ali Abadi, Azar (Author) ; Akhavan, Mohammad (Supervisor)
    The most important researchers’ purposes in superconductivity are achievement of the room temperature superconductivity and to understand the high temperature superconductivity mechanism. Researchers’ goal in to increase the transition temperature by applying pressure, changing oxygen content, different doping, and changing stoichiometry in the families of the high temperature superconductors. In this research, which has been carried out in the Magnet Research Laboratary of Sharif University of Technology, samples of Y3Ba5Cu8O18, Gd3Ba5Cu8O18, and Pr3Ba5Cu8O18 have been synthesized by the standard solid-state reaction technique, the structure, electrical and magnetic properties of the... 

    Study Effects of Nucleating Agent and Nano Reinforecment on Crystalline Structure and Mechanical Properties of Polypropylene Block Copolymer

    , M.Sc. Thesis Sharif University of Technology Shahsavan, Shakiba (Author) ; Bagheri, Reza (Supervisor)
    Polypropylene block copolymer is used in different industries like pipe productions. This copolymer has proper mechanical properties, specially it has good impact strength, but in some applications it’s elastic modulus (stiffness) is not enough and that leads to some problemes in servise. Nucleating agents influence crystalline structure and properties and also the mechanical properties by controlling the crystallization process. Nanoparticles also have a beneficial effects on physical and mechanical properties. In this study, the effect of adding two types of α-phase nucleating agents (commercial names NA11 and DMDBS) in the form of masterbatch wt 5% with a carrier of polypropylene block... 

    Atomistic Study of Iinterface Properties and Structure of Nickel-Silicon and Polyethelene-Ghraphene by Molecular Dynamics Simulation

    , M.Sc. Thesis Sharif University of Technology Amini, Hamed (Author) ; Kokabi, Amir Hossein (Supervisor) ; Simchi, Abdolreza (Supervisor)
    First atomistic simulation was used to study the deformation and fracture mechanisms of Ni-Si interfaces under tensile and shear loads dependent on the crystal structure of interface zone. Modified embedded atom method (MEAM) potential was utilized for molecular dynamics (MD) modeling. The simulation includes analysis of common neighbors, coordination number, least-square atomic local strain, and radial distribution function. The profound effect of interface crystallography on the tensile and shear deformation is shown. The highest tensile strength is obtained for interfaces with high plane density due to lowest atomic disorder while under shear loading planes with low density exhibit a high... 

    Effect of Co Doping on Crystal and Electronic Structure of BaFe2-xCoxAs2

    , M.Sc. Thesis Sharif University of Technology Shafiei, Manouchehr (Author) ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Supervisor)
    The discovery of the iron-based superconductors attracted much experimental and theoretical attention in the recent years. BaFe2As2 is one of the highlighted materials which is the antiferromagnetic metal (below Neel temperature) and undergoes to superconducting and non-magnetic state by variety of doping, usually accompanied by a structural phase transition. Superconductivity is appeared in this system by doping Co and Ni at the Fe sites which is one of the excited situations in the physics of superconductors, where the magnetic doping suppresses the superconducting state. So, the study of Co doping of the electronic structure of this system, might lead us to better understanding of the... 

    Effect of Doping of La in Pr Site and Cu/Fe in Ni site on Crystal Structure, Oxygen Non-stoichiometry level and Electrical Conductivity of Pr2NiO4 as Intermediate Temperature Solid Oxide Fuel Cell Cathode

    , M.Sc. Thesis Sharif University of Technology Farhat, Pooneh (Author) ; Faghihi Sani, Mohammad Ali (Supervisor)
    Nowadays, one of the most important research goals is to develop intermediate-temperature solid oxide fuel cells (IT-SOFC) operated at 500–800 °C. However, the large cathode polarization resistance caused by the reduced temperature is a major barrier against such an urgent demand for commercialization. In this regard, it is necessary to select a proper material as a cathode working efficiently at reduced temperatures without losing its desired performance. Various mixed ionic electron conductors (MIECs), especially Ruddlesden–Popper-type oxides, are used to improve the cathode performance at intermediate temperatures. Among these layered oxides, Pr2NiO4 has been reported to possess the... 

    Protein-directed synthesis of γ-Fe2O3 nanoparticles and their magnetic properties investigation

    , Article Bulletin of the Korean Chemical Society ; Vol. 35, issue. 5 , May , 2014 , pp. 1375-1378 ; ISSN: 02532964 Soleyman, R ; Pourjavadi, A ; Masoud, N ; Varamesh, A ; Sattari, A ; Sharif University of Technology
    In this study, maghemite (γ-Fe2O3) nanoparticles were produced using gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe2O3 nanoparticles were characterized using XRD, FT-IR, TEM, SEM and VSM data. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced gelatin-Fe3O4 nanocomposite were examined to prove the fundamental effect of gelatin; both as a capping agent in the nanoscale synthesis and as the director of the spinel γ-Fe2O3 synthesis among possible Fe 2O3 crystalline structures  

    Investigation of the effect of nanosilica on rheological, thermal, mechanical, structural, and piezoelectric properties of poly(vinylidene fluoride) nanofibers fabricated using an electrospinning technique

    , Article Industrial and Engineering Chemistry Research ; Volume 56, Issue 44 , 2017 , Pages 12596-12607 ; 08885885 (ISSN) Haddadi, S. A ; Ahmad Ramazani, S. A ; Talebi, S ; Fattahpour, S ; Hasany, M ; Sharif University of Technology
    The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline... 

    The formation and dissociation energy of vacancies in cementite: A first-principles study

    , Article Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ; Volume 502 , 2021 , Pages 157-163 ; 0168583X (ISSN) Mehrdad Zamzamian, S ; Amirhossein Feghhi, S ; Samadfam, M ; Sharif University of Technology
    Elsevier B.V  2021
    Because of the possibility of various types of vacancies in cementite due to its crystalline structure, the focus of this paper was only on vacancies. In this regard, the formation energies of single, two, three and four vacancies of over than 120 different cases were calculated using first-principles method. For the case of single vacancy, the results were in three values of ~1.63, 1.39 and 0.78 eV according to iron vacancies at general positions, iron vacancies located on mirror planes and carbon vacancies in the interstitial positions, respectively. The results for the case of two, three and four vacancies were between from 2.10 to 3.34 eV, from 3.92 to 5.10 eV and from 4.77 to 6.33 eV,... 

    Study of Crystalline Structure in Random Co-polypropylene and Its Influence on Melting Behavior

    , M.Sc. Thesis Sharif University of Technology Khedri, Faezeh (Author) ; Bagheri, Reza (Supervisor) ; Asgari, Sirus (Supervisor)
    In today’s world the growth in population make food production and also the packaging industry increase. Finding new ways to enhance the efficiency of packaging is become so important beyond researchers. As the randomized co-polypropylene is the most suitable materials for this industry many attempts have been made to control its melting behavior with the aim of expanding their application in the packaging industry. The study in this field indicate the dependence of the melting behavior on the structural characteristics of the material such as molecular mass, chain structure, type of crystalline structure, and the amount of dispersion of the crystals thickness. Due to the lack of proper... 

    Determination of Stable Crystal Structure of Y358 New Superconductor and its Phonon and Electronic Structure using Density Functional Theory

    , M.Sc. Thesis Sharif University of Technology Rasti, Mohammad (Author) ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Co-Advisor)
    Y-based Superconducting compounds (YBCO) with different stoichiometry have been considered by researchers for its transition temperature above the boiling temperature of liquid nitrogen, preparation of high quality samples, simple crystal and electronic structure and other advantages relative to the other high-Tc copper oxide superconductors. Reaching to higher transition temperature has been considered in the recent years. In 2009, new compound of this family with different stoichiometry Y3Ba5Cu8O18(Y358) and transition temperature above 100 K was synthesized which is 10 K higher than maximum transition temperature in this family. Confirming this transition temperature can be help us for... 

    Application of Dynamics Multi-scale Modeling of Dislocation in Nano-Crystalline Materials

    , M.Sc. Thesis Sharif University of Technology Karimi, Hossein (Author) ; Khoei, Amir Reza (Supervisor)
    Dislocations are one of the most important classes of defects in crystals. They have significant effects on the physical properties of crystals. They could be primarily created during the formation of a crystal or during the loading on specimen. Dislocation’s movement due to stress is the main cause of crystal plasticity. Since dislocation is a change in perfect crystal structure it is possible to identify it in the molecular level. However, the high computational cost of the MD level, has led researchers to using the multi-scale methods. Researchers have used many various multi-scale methods to study dislocations. The method used in this paper is based on energy. Total energy of system for... 

    Simulation of the Effect of Cooling Rate and Chemical Composition on the Atomic Structure of Bulk Metallic Glass Iron-Phosphorus and Nickel-Phosphorus

    , M.Sc. Thesis Sharif University of Technology Hosseinzadeh, Danial (Author) ; Tavakoli, Rouhollah (Supervisor)
    bulk metallic glass Unlike metal materials that have a crystalline structure, amorphous glass is an amorphous material with an irregular atomic structure that simultaneously has the same physical properties as metals. Due to the absence of crystal defects such as dislocation and grain boundaries, these materials show unique mechanical properties such as high strength and elastic strain, abrasion resistance and proper corrosion. However, their plastic deformation is heterogeneous, concentrated, and accompanied by sudden failure. Unlike metals, these materials do not have a long-range crystalline order, and their atomic structure includes short-range and mid-range order. The short-range order... 

    Synthesis and Characterization of Transition Metal Complexes with Carboxamide Ligands and Nanostructures for Catalytic and Antibacterial Activites Application

    , Ph.D. Dissertation Sharif University of Technology Kiani, Mahsa (Author) ; Bagherzadeh, Mojtaba (Supervisor)
    Carboxamide ligands have been part of the growing research in the field of coordination chemistry of transition metal complexes. The solvent used in the classical method of synthesis of these compounds is pyridine, a solvent which is extremely toxic. In this project, we have developed a new method of synthesis using ionic liquids as the reaction media and have prepared Hqcq (1), Htp(2) under optimum conditions for Pd(II) and Pt(II) complexes of Hqcq and Co(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes of Htp with the formula:[Pd(qcq)(OAc)] (1a), [Pt(qcq)(Cl)] (1b), [Co(Htp)2(H2O)2].C2H5OH (2a), Co3O4 (2b), [Cu(tp)2(H2O)].CHCl3 (2c), CuO (2d), [Zn(tp)2(H2O)2] (2e), [Cd(tp)2(H2O)2].CH3OH... 

    Preparation of PVDF/PMMA/PZT Nanocomposites and Studying of Its Crystal Structure, Morphology and Electrical Properties

    , M.Sc. Thesis Sharif University of Technology Omoomi, Ali (Author) ; Frounchi, Masoud (Supervisor)
    Polyvinylidene fluoride is highly regarded by researchers due to its piezoelectric properties, mechanical properties, chemical and thermal stability and biocompatibility. This thermoplastic polymer has a semi-crystalline structure and, depending on the crystallization conditions, has five distinct crystalline phases α, β, γ, δ and ε. The β, γ and δ phases are electroactive, and among them, the β phase has high piezoelectric activity due to its high dipole moment. This study focuses on increasing the amount of β phase in polyvinylidene fluoride and increasing its piezoelectric property. Polyvinylidene fluoride is highly miscible with oxygen containing polymers such as polymethyl... 

    A coupling atomistic-continuum approach for modeling mechanical behavior of nano-crystalline structures

    , Article Computational Mechanics ; Volume 54, Issue 2 , August , 2014 , Pages 269-286 ; ISSN: 01787675 Khoei, A. R ; Aramoon, A ; Jahanbakhshi, F ; Dormohammadi, H ; Sharif University of Technology
    In this article, a novel approach is presented for the concurrent coupling of continuum-atomistic model in the nano-mechanical behavior of atomic structures. The study is focused on the static concurrent multi-scale simulation, which is able to effectively capture the surface effects intrinsic in the molecular mechanics modeling. The Hamiltonian approach is applied to combine the continuum and molecular models with the same weight in the overlapping domain. A Lagrange-multiplier method is employed over the overlapping domain for coupling the continuum nodal displacement with the atomic lattice deformation. A multiple-step algorithm is developed to decouple the solution process in the atomic... 

    Electron beam induced modifications in crystalline structure of polyvinylidene fluoride/nanoclay composites

    , Article Radiation Measurements ; Vol. 60 , January , 2014 , pp. 1-6 ; ISSN: 13504487 Rahmani, P ; Dadbin, S ; Frounchi, M ; Sharif University of Technology
    PVDF/nanoclay nanocomposites were prepared via melt mixing method. The intercalated dispersion of the nanoclay in PVDF matrix was confirmed by XRD. According to FTIR, DSC and XRD results, the presence of nanoclay facilitated transition from α-to-β crystalline phase. Electron beam irradiation decreased the melting point of the nanocomposites. The decrease in melting point of the nanocomposites was about 11 C at 500 kGy. The crystallinity of nanocomposites increased at an irradiation dose of 100 kGy and decreased at higher irradiation doses. The extent of crosslinking of the nanocomposites increased significantly with irradiation up to 300 kGy. The nanoclay intensified the increase in yield... 

    A concurrent multi-scale modeling for dynamic behavior of nano-crystalline structures

    , Article Computational Materials Science ; Volume 79 , 2013 , Pages 841-856 ; 09270256 (ISSN) Khoei, A. R ; Aramoon, A ; Jahanbakhshi, F ; Dormohammadi, H ; Sharif University of Technology
    In this paper, a new multi-scale technique is developed for concurrent coupling of atomistic-continuum domains in modeling nano-mechanical behavior of atomic structures. A Lagrange multiplier method is employed over an overlapping domain to coupling the continuum nodal velocities with atomic lattice velocities. The Hamiltonian method is applied to combine the continuum and molecular Hamiltonians with the same weight in the overlapping domain. The mass and stiffness matrices of the continuum domain are obtained using a linear bridging map of the atomic lattice displacement laid underneath the continuum grid to the element displacements. Numerical examples are performed by presenting the... 

    Immobilization of α -chymotrypsin on the surface of magnetic/gold core/shell nanoparticles

    , Article Journal of Nanotechnology ; Volume 2013 , 2013 ; 16879503 (ISSN) Kamal Ahmadi, M ; Vossoughi, M ; Sharif University of Technology
    Hindawi Publishing Corporation  2013
    Over the last decade, nanoparticles used as protein carriers have opened new avenues for a variety of biomedical applications. The main concern for these applications is changes in biological activity of immobilized proteins due to conformational changes on the surface of the carrier. To evaluate this concern, the preparation and biocatalyst activity of α-chymotrypsin-Fe 3O4 @ Au core/shell nanoparticles were investigated. First, Fe3O4 @ Au core/shell nanoparticles were synthesized by coprecipitation method and citrate reduction of HAuCl 4. TEM imaging revealed a core size of 13 ± 3 nm and a shell thickness of 4 ± 1 nm for synthesized nanoparticles. X-ray diffraction (XRD) was used to study... 

    TPU/graphene nanocomposites: effect of graphene functionality on the morphology of separated hard domains in thermoplastic polyurethane

    , Article Polymer ; Volume 148 , 18 July , 2018 , Pages 169-180 ; 00323861 (ISSN) Razeghi, M ; Pircheraghi, G ; Sharif University of Technology
    Elsevier Ltd  2018
    Graphene nanoplatelets with different surface functional groups and polarity were prepared by Hummer's method and electrochemical exfoliation of graphite in two aqueous acids. The XRD, FTIR and sedimentation tests performed to characterize the polarity of the prepared graphenes. The highest polarity was associated with the sample prepared by Hummer's method and the sample synthesized by electrochemical exfoliation in nitric acid medium showed the moderate polarity. Meanwhile, the sample prepared in sulfuric acid medium showed the lowest polarity. Then thermoplastic polyurethane (TPU)/graphene nanocomposite films were fabricated with solvent exchange method. While the dispersion state and... 

    K4Nb6O17/Fe3N/α-Fe2O3/C3N4 as an enhanced visible light-driven quaternary photocatalyst for acetamiprid photodegradation, CO2 reduction, and cancer cells treatment

    , Article Applied Surface Science ; Volume 544 , 2021 ; 01694332 (ISSN) Padervand, M ; Ghasemi, S ; Hajiahmadi, S ; Wang, C ; Sharif University of Technology
    Elsevier B.V  2021
    A new magnetic quaternary photocatalyst, K4Nb6O17/α-Fe2O3/Fe3N/g-C3N4, was synthesized via a simple one-step thermal pyrolysis process. The prepared photocatalyst was well characterized, and its photocatalytic activity was evaluated towards acetamiprid pesticide degradation, CO2 reduction reaction, and U87-MG cell eradication. The coexistence of four different crystalline structures in the prepared photocatalyst could simultaneously facilitate photoelectron transport and suppress charge recombination through their coupled heterogeneous interfaces. Because of the coexistence of various photosensitive compounds, the prepared photocatalyst showed the excellent capability to harvest the visible...