Search for: nanostructured-materials
0.009 seconds
Total 249 records

    Development of Nanostructural Al-Mg-Si Alloys using ECAE and Ageing Processes

    , Ph.D. Dissertation Sharif University of Technology Vaseghi, Majid (Author) ; Karimi Taheri, Ali (Supervisor)
    The manufacture of ultra high strength materials has always been a target for aerospace and transportation industries. Currently, the limitation of energy resources even makes this goal more serious. Nowadays, more than 50% of total extrusion products are made from Al alloys and around 90% of them are the 6000 series alloys. Therefore, regarding to high strength, low weight, and hardening aluminum AA6000 alloys capabilities can play a major role in fulfilling this task. Over the last decade, a number of techniques collectively referred to as severe plastic deformation (SPD), have emerged as a promising approach for the production of bulk ultrafine-grained (UFG) nano-structured materials.... 

    Multiscale Nonlinear Finite Element Analysis of Nanostructured Materials Based on Equivalent Continuum Mechanics

    , Ph.D. Dissertation Sharif University of Technology Ghanbari, Jaafar (Author) ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor)
    Nanostructured materials are a new kind of engineering materials which attracted researchers’ interest because of their interesting mechanical /physical properties, as well as controllable microstructural design ability for desired applications. These new materials are homogeneous at the macroscale but at the microstructural level, may have heterogeneities including common nanostructures. Because of multiscale nature of these materials, new multiscale methods should be developed and used for better understanding the behavior of them. Multiscale methods could be categorized into concurrent and hierarchical methods. In concurrent methods, the domain under study is explicitly divided into... 

    Investigation of the Performance of Microbial Fuel Cell Based on Shewanella Bacteria with the Aim of Nanostructured Materials

    , M.Sc. Thesis Sharif University of Technology Davoudi, Omid (Author) ; Yaghmaei, Soheila (Supervisor) ; Sanaee, Zeinab (Co-Supervisor)
    The development of clean, renewable and alternative sources of fossil fuels has increased in recent years due to various factors such as environmental pollution, reduced fossil fuel resources and increased energy consumption. The application of microbial fuel cells is one of the clean energy production methods using renewable sources such as municipal sewage. The microbial fuel cell converts the chemical energy stored in organic materials into electrical energy and simultaneously purifies the sewage. Increasing current density and power density are the most important challenges for microbial fuel cells. In this study, the two biocatalysts of Shewanella Oneidensis MR1 and Escherichia coli... 

    Design and Synthesis of Novel Polyglycerol Hybrid Nanomaterials for Potential Applications in Drug Delivery Systems

    , Article Macromolecular Bioscience ; Volume 11, Issue 3 , NOV , 2011 , Pages 383-390 ; 16165187 (ISSN) Zarrabi, A ; Adeli, M ; Vossoughi, M ; Shokrgozar, M. A ; Sharif University of Technology
    The synthesis of a new drug delivery system based on hybrid nanomaterials containing a β-CD core and hyperbranched PG is described. Conjugating PG branches onto β-CD not only increases its water solubility but also affects its host/guest properties deeply. It can form molecular inclusion complexes with small hydrophobic guest molecules such as ferrocene or FITC with reasonable release. In addition, the achievable payloads are significantly higher as for carriers such as hyperbranched PGs. Short-term in vitro cytotoxicity and hemocompatibility tests on L929 cell lines show that the hybrid nanomaterial is highly biocompatible. Due to their outstanding properties, β-CD-g-PG hybrid nanomaterials... 

    Heterogeneous SBA-15-supported oxoperoxomolybdenum(VI) complex for enhanced olefin epoxidation

    , Article Catalysis Communications ; Volume 88 , 2017 , Pages 9-12 ; 15667367 (ISSN) Zare, M ; Moradi Shoeili, Z ; Ashouri, F ; Bagherzadeh, M ; Sharif University of Technology
    Heterogeneous nanoscale catalyst was successfully synthesized via anchoring of oxoperoxo molybdenum(VI) complex on the chloro-functionalized SBA-15. The mesoporous nanomaterials, MoO3(sal-phz)/SBA-15 (where sal-phz is salicylidene 2-picoloyl hydrazine) were identified by several characterization techniques. MoO3(sal-phz)/SBA-15 and MoO3(sal-phz) were also treated as catalysts in the olefins epoxidation reactions. Both homogenous and heterogeneous catalysts exhibit outstanding activity and selectivity for epoxide with tert-BuOOH in decane as oxidant at 95 °C. In addition, the heterogeneous nanocatalyst was chemically stable and can be efficiently reused for at least six cycles without a... 

    Hydrothermal synthesis and characterization of TiO 2 nanostructures using LiOH as a solvent

    , Article Advanced Powder Technology ; Volume 22, Issue 3 , 2011 , Pages 336-339 ; 09218831 (ISSN) Zanganeh, S ; Kajbafvala, A ; Zanganeh, N ; Molaei, R ; Bayati, M. R ; Zargar, H. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    In the present study, we performed hydrothermal method as a simple and efficient route for the synthesis of rutile TiO 2 nanostructures in various concentrations of lithium hydroxide solutions. TiO 2 nanopowders with average sizes of 15 and 23 nm were prepared using 4 M and 7 M LiOH solutions. X-ray diffraction analysis (XRD), transmission electron microscope (FEG-STEM), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses were used in order to characterize the obtained products and comparison of the morphology of the powders obtained in different concentrations of LiOH solvent. It was shown that alkali solution concentration has affected the crystallinity,... 

    Nano-crystalline growth of electrochemically deposited apatite coating on pure titanium

    , Article Journal of Electroanalytical Chemistry ; Volume 589, Issue 1 , 2006 , Pages 96-105 ; 15726657 (ISSN) Yousefpour, M ; Afshar, A ; Yang, X ; Li, X ; Yang, B ; Wu, Y ; Chen, J ; Zhang, X ; Sharif University of Technology
    Elsevier  2006
    Hydroxyapatite (HA) coatings were deposited on commercially pure titanium plates using a hydrothermal-electrochemical deposition method in an electrolyte containing calcium and phosphate ions. The deposition conditions used in this study were the followings: electrolyte temperature (33-80 °C), current density (1-8 mA/cm2), and deposition time (10-120 min). Needle-like and granular crystals of apatite coating were created with different concentrations of calcium (0.0021-0.042 M) and phosphate (0.00125-0.025 M) salts. The size of HA crystals of the coating was considerably changed with different concentration of calcium and phosphate salts, temperature of the electrolyte, and deposition time.... 

    Oxidized graphitic carbon nitride nanosheets as an effective adsorbent for organic dyes and tetracycline for water remediation

    , Article Journal of Alloys and Compounds ; Volume 809 , 2019 ; 09258388 (ISSN) Yousefi, M ; Villar Rodil, S ; Paredes, J. I ; Zaker Moshfegh, A. R ; Sharif University of Technology
    Elsevier Ltd  2019
    Graphitic carbon nitride (g-C3N4) is promising as adsorbent for water remediation as its chemical structure allows a variety of mechanisms to interact with wastewater pollutants. However, several issues, such as low specific surface area and insufficient dispersibility in water, have to be tackled to achieve a competitive performance in such use. Previous attempts to improve the features of g-C3N4as an adsorbent have relied on carbon doping and exfoliation in the solid phase by thermal expansion. Here, we demonstrate that exfoliation in the liquid phase by a combination of oxidation and sonication allows preparing g–C3N4–based materials with improved dispersibility in water, increased... 

    Carbon nanoparticles in high-performance perovskite solar cells

    , Article Advanced Energy Materials ; Volume 8, Issue 12 , 2018 ; 16146832 (ISSN) Yavari, M ; Mazloum Ardakani, M ; Gholipour, S ; Marinova, N ; Delgado, J. L ; Turren Cruz, S. H ; Domanski, K ; Taghavinia, N ; Saliba, M ; Gratzel, M ; Hagfeldt, A ; Tress, W ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    In the past few years, organic–inorganic metal halide ABX3 perovskites (A = Rb, Cs, methylammonium, formamidinium (FA); B = Pb, Sn; X = Cl, Br, I) have rapidly emerged as promising materials for photovoltaic applications. Tuning the film morphology by various deposition techniques and additives is crucial to achieve solar cells with high performance and long-term stability. In this work, carbon nanoparticles (CNPs) containing functional groups are added to the perovskite precursor solution for fabrication of fluorine-doped tin oxide/TiO2/perovskite/spiro-OMeTAD/gold devices. With the addition of CNPs, the perovskite films are thermally more stable, contain larger grains, and become more... 

    An electron back-scattered diffraction study on the microstructure evolution of severely deformed aluminum AI6061 alloy

    , Article IOP Conference Series: Materials Science and Engineering ; Vol. 63, Issue. 1 , 30 June- 4 July , 2014 ; ISSN: 17578981 Vaseghi, M ; Taheri, A. K ; Kim, H. S ; Sharif University of Technology
    In this paper dynamic strain ageing behavior in an Al-Mg-Si alloy related to equal channel angular pressing (ECAP) was investigated. In order to examine the combined plastic deformation and ageing effects on microstructure evolutions and strengthening characteristics, the Al6061 alloy were subjected to φ=90° ECAP die for up to 4 passes via route Bc at high temperatures. For investigating the effects of ageing temperature and strain rate in ECAP, Vickers hardness tests were performed. The combination of the ECAP process with dynamic ageing at higher temperatures resulted in a significant increase in hardness. The microstructural evolution of the samples was studied using electron... 

    Inhomogeneity through warm equal channel angular pressing

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 6 , 2013 , Pages 1666-1671 ; 10599495 (ISSN) Vaseghi, M ; Kim, H. S ; Karimi Taheri, A ; Momeni, A ; Sharif University of Technology
    In this study, the hardness inhomogeneity of billets during multi-passes of equal channel angular pressing (ECAP) at elevated temperatures is investigated and the effect of large strain deformation during ECAP on the hardness inhomogeneity characteristics due to dynamic aging of aluminum 6061 under a variety of temperatures and ram speed was studied by TEM and hardness measurements. The hardness results showed that the hardness distribution is more homogenous after four passes using the pressing route Bc. However, when the deformation temperature was considered, performing ECAP at 100 C may provide the most homogeneous microstructure after multi-pressing as long as the total number of... 

    Nanopowder synthesis of zinc oxide via solochemical processing

    , Article Materials and Design ; Volume 28, Issue 2 , 2007 , Pages 515-519 ; 02613069 (ISSN) Vaezi, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier Ltd  2007
    Zinc oxide is used in functional devices, catalysts, pigments, optical materials and many other important applications. ZnO nanopowders can be produced mechanochemically or solochemically. The synthesis of ZnO nanopowder has been carried out via solochemical processing from an aqueous solution of a zinc containing complex in this research. This is the newest economic method for synthesis of ZnO nanopowder. The results obtained from XRD and TEM show that the nanoparticles are single crystals and the mean particle size is 45.3 nm. TEM micrographs of ZnO nanopowder reveal that the particles have elongated particulate shape with a narrow size distribution. Solochemical processing can thus be an... 

    Electrochemical deposition of flower-like nickel nanostructures on well-defined n-si(111):h

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 21, Issue 2 , 2008 , Pages 177-182 ; 1728-144X (ISSN) Torabi, M ; Khalifehzadeh, R ; Arami, H ; Sadrnezhaad, S. K ; Sharif University of Technology
    Materials and Energy Research Center  2008
    In this paper the electrodeposition of nickel on n-Si(111):H substrate, in the presence of sulphuric acid, was studied. Cyclic voltammetry has been used to characterize the electrochemical behavior of the system. The nickel deposits had a flower-like morphology with the spherical nanostructure nucleus, distributed uniformly on the surfaces of the prepared n-Si(111) substrate  

    Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media

    , Article Applied Physics A: Materials Science and Processing ; Volume 84, Issue 1-2 , 2006 , Pages 215-219 ; 09478396 (ISSN) Tilaki, R. M ; Irajizad, A ; Mahdavi, S. M ; Sharif University of Technology
    We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1.064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano silver in acetone showed a narrow size distribution with a mean size of 5 nm and the colloidal solution was stable. In deionised water a rather narrow size distribution with a mean size of 13 nm was observed and nanoparticles were precipitated slowly after about two weeks. In ethanol, a broadening... 

    Supercritical synthesis and in situ deposition of PbS nanocrystals with oleic acid passivation for quantum dot solar cells

    , Article Materials Chemistry and Physics ; Volume 156 , 2015 , Pages 163-169 ; 02540584 (ISSN) Tavakoli, M. M ; Simchi, A ; Aashuri, H ; Sharif University of Technology
    Elsevier Ltd  2015
    Colloidal quantum dot solar cells have recently attracted significant attention due to their low-processing cost and surging photovoltaic performance. In this paper, a novel, reproducible, and simple solution-based process based on supercritical fluid toluene is presented for in situ growth and deposition PbS nanocrystals with oleic-acid passivation. A lead precursor containing sulfur was mixed with oleic acid in toluene and processed in a supercritical fluid condition at different temperatures of 140, 270 and 330 °C for 20 min. The quantum dots were deposited on a fluorine-doped tin oxide glass substrate inside the supercritical reactor. Transmission electron microscopy, X-ray diffraction,... 

    Amine functionalized TiO2 coated on carbon nanotube as a nanomaterial for direct electrochemistry of glucose oxidase and glucose biosensing

    , Article Journal of Molecular Catalysis B: Enzymatic ; Volume 68, Issue 2 , 2011 , Pages 206-210 ; 13811177 (ISSN) Tasviri, M ; Rafiee Pour, H. A ; Ghourchian, H ; Gholami, M. R ; Sharif University of Technology
    A nano-composite material consisting of amine functionalized TiO 2-coated carbon nanotubes was prepared and used for glucose oxidase (GOx) absorption. The GOx bearing nanomaterial was fixed on a glassy carbon electrode to construct a novel biosensor for glucose determination. The direct electrochemistry of immobilized GOx and its electron transfer parameters at the modified glassy carbon electrode were reported. The apparent heterogeneous electron transfer rate constant (ks) of GOx was estimated to be 3.5 s-1, which is higher than those reported previously. Amperometric detection of glucose resulted in a rapid (3 s) and stable response in the linear concentration range from 1.8 to 266 μM.... 

    Fluidity enhancement of hard-to-fluidize nanoparticles by mixing with hydrophilic nanosilica and fluid catalytic cracking particles: Experimental and theoretical study

    , Article Physics of Fluids ; Volume 31, Issue 7 , 2019 ; 10706631 (ISSN) Tahmasebpoor, M ; Rahimvandi Noupoor, Y ; Badamchizadeh, P ; Sharif University of Technology
    American Institute of Physics Inc  2019
    As a low-cost method, hydrophilic SiO2 nanoparticles (NPs) and fluid catalytic cracking (FCC) coarse particles were used as assistant materials to improve the fluidity of Al2O3 and TiO2 hard-to-fluidize nanopowders. To decrease the strong electrostatic forces between the hydrophilic nanopowders, prepared samples were fluidized in the presence of methanol vapor. Results revealed that the amount of SiO2 NPs, increased from 5 to 50 wt. %, has a beneficial effect on the fluidization quality of the binary (hard-to-fluidize NPs + SiO2) and ternary (hard-to-fluidize NPs + SiO2 + FCC) mixtures. However, the amount of FCC particles when it varied from 15 to 30 wt. % in the ternary mixtures should... 

    Blue- and red-emitting phosphor nanoparticles embedded in a porous matrix

    , Article Thin Solid Films ; Volume 503, Issue 1-2 , 2006 , Pages 190-195 ; 00406090 (ISSN) Taghavinia, N ; Lerondel, G ; Makino, H ; Yao, T ; Sharif University of Technology
    Eu3+- and Ce3+-doped yttrium silicate, as well as Eu2+-doped zinc silicate nanoparticles, were grown in a porous SiO2 matrix using an impregnation method. For Y2Si 2O7:Eu3+, particles of about 50 nm size were obtained that exhibited several photoluminescence (PL) peaks in red. Different peaks showed slightly different decay times; however, their excitation mechanism was found the same. Increasing the Eu concentration increased the PL intensity while reducing the decay time. Y2Si2O7:Ce 3+ nanoparticles in the porous matrix showed bright blue emission, consisting of two peaks at 358 nm and 378 nm. Re-impregnation process was found effective in changing the relative intensity of the two peaks.... 

    Photo-induced CdS nanoparticles growth

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 30, Issue 1-2 , 2005 , Pages 114-119 ; 13869477 (ISSN) Taghavinia, N ; Azam Iraji Zad ; Mahdavi, S. M ; Reza-Esmaili, M ; Sharif University of Technology
    A photochemical approach on the size control of CdS nanoparticles is presented. CdS nanoparticles were grown using the photo-induced reaction of sodium thiosulfate with Cadmium sulfate, in the absence of any surfactant. Particles of 5.5-11 nm were obtained by changing the illumination time. The dark growth of nanoparticles was negligible, however we found by optical scattering measurements that a ripening phenomenon occurs and the size of nanoparticles slightly increases with time. © 2005 Elsevier B.V. All rights reserved  

    Evolution of roughness and photo-crystallization effect in ZnS-SiO 2 nanocomposite films

    , Article Nanotechnology ; Volume 16, Issue 6 , 2005 , Pages 944-948 ; 09574484 (ISSN) Taghavinia, N ; Lee, H. Y ; Makino, H ; Yao, T ; Sharif University of Technology
    Amorphous chalcogenides in the form of bulk or thin films are known as photosensitive materials that undergo changes in optical or structural properties upon irradiation. Here we study the optical properties of nanocomposite films of ZnS-SiO2 illuminated with ultraviolet (UV) light and relate them to the photo-induced evolution of roughness, as well as photo-crystallization effects in these films. We observe that upon UV irradiation a new crystalline phase of ZnSiO3 is formed in the nanocomposite film. This is accompanied by the evolution of surface roughness on the film. © 2005 IOP Publishing Ltd