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    Heterogeneities in polymer structural and dynamic properties in graphene and graphene oxide nanocomposites: molecular dynamics simulations

    , Article Macromolecular Theory and Simulations ; Volume 26, Issue 2 , 2017 ; 10221344 (ISSN) Azimi, M ; Mirjavadi, S. S ; Salem Hamouda, A. M ; Makki, H ; Sharif University of Technology
    Wiley-VCH Verlag  2017
    The effect of graphene (G) and graphene oxide (GO), used as the nanofiller in polymer nanocomposites (NC), on the structural and dynamic properties of polymer chains, has been studied by means of molecular dynamics (MD) simulations. Two polymers, i.e., poly(propylene) and poly(vinyl alcohol), are employed as matrices to cover a wider range of polymer–filler interactions. The local structural properties, e.g., density profile, average Rg, and end-to-end distance as well as dynamic properties, e.g., estimated translational and orientational relaxation times, of polymer chains are studied. In addition, the interaction energies are estimated between polymers and nanofillers for different hybrid... 

    Calculation of the density and activity of water in ATPS systems for separation of biomolecules

    , Article Journal of Solution Chemistry ; Volume 42, Issue 7 , 2013 , Pages 1423-1437 ; 00959782 (ISSN) Valavi, M ; Shirazian, S ; Pour, A. F ; Ziary, M ; Sharif University of Technology
    In this study, the perturbed hard sphere chain equation of state is utilized to calculate the activity of water in binary and ternary solutions of polyethylene glycol (PEG), salt and water. The liquid density of the binary and ternary solutions is also predicted. To estimate the water activity in PEG-water binary systems, a linear correlation is obtained for the binary interaction parameter between water and PEG. Then, using this correlation and without introducing any additional binary parameters, the water activities are predicted in ternary solutions of water, salt and PEG with different molecular weights (MW). Our results show that the mean absolute average relative deviation (AARD %) of... 

    Design and modeling of a semiconductor laser by employing silicon carbide polymers (6H-SiC, 3C-SiC and 4H-SiC)

    , Article Asian Journal of Chemistry ; Volume 24, Issue 5 , May , 2012 , Pages 2177-2179 ; 09707077 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    We present an edge emitting laser structure employing silicon carbide polymers only. In this structure, 3C-SiC well embedded in 6H-SiC barriers are used as the active region, which is sandwiched between the 6H-SiC mirror at the top and bottom of structure. The basic design goal is to use only silicon carbide polymers and decrease the threshold current and stable optical wavelength of the lasers with silicon carbide polymers. This paper provides key results of the device characteristics, including the light power versus electrical current and the optical wavelength versus current  

    Analysis and design of semiconductor laser with silicon carbide polymers (6H-SiC and 3C-SiC)

    , Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 1060-1063 ; 19918178 (ISSN) Marjani, S ; Faez, R ; Marjani, H ; Sharif University of Technology
    In the present work, a new structure of the strained quantum-well (QW) laser diode is designed and simulated. In this structure, the active region consists of tow 6H-SiC barrier and 3C-SiC quantum well (QW)which is sandwiched between two layers of 6H-SiC that can be interpreted in terms of a type-II heterostructure character and a built-in electric field due to the pyroel ectricity of 6H using an industrial-based numerical simulator. The basic design goal was to decrease the threshold current by using only silicon carbide polymers. We could obtain a working model at stable optical wavelength of 0.83μm. This paper provides key results of the device characteristics, including the light power... 

    The study on microbial polymers: Pullulan and PHB

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 28, Issue 1 , 2009 , Pages 13-21 ; 10219986 (ISSN) Iran, A ; Sharif University of Technology
    Microbial cells are producers of natural polymers present in plant cells. Production of pullulan (an extracellular microbial polysaccharide) by Aureobasidium pullularia pullulans (P. pullulans) was studied under fermentation conditions, and kinetic parameters were determined. Pullulan formation obeyed a growth and non-growth associated term. PHB (polyhydroxybutyrates) an intracellular biopolymer production by Rastonia eutropha (Alcaligen eutrophus), R. eutropha was studied under different culture media, including synthetic and natural carbon sources. Molasses as a natural carbon source in the culture media presented high efficiency in cell and biopolymer accumulation  

    Preparation, crystal structure, and characterization of a polymeric phenol-bridged potassium compound with 2-bromo-4,6-dinitrophenolate

    , Article Main Group Chemistry ; Volume 8, Issue 1 , 2009 , Pages 11-19 ; 10241221 (ISSN) Najafpour, M. M ; Boghaei, D.M ; McKee, V ; Sharif University of Technology
    A polymeric phenolato-bridged potassium compound, K(2-bromo-4,6 dinitrophenolate) (H2O), was obtained by reaction of methylammonium 2-bromo-4,6-dinitrophenolate and potassium chloride in water. 2-bromo-4,6 dinitrophenolate co-ordinates to the metal ion by phenolic O atom, Br, and O atoms of the nitro groups. K+ ion is eleven-coordinate in the compound. Single-crystal X-ray diffraction for methylammonium 2-bromo-4,6-dinitrophenolate and single-crystal X-ray diffraction, elemental analysis, IR, UV-Vis spectra, and fluorescence emission spectra for the complex have also been determined. Methylammonium 2-bromo-4,6-dinitrophenolate was solved in the monoclinic system, space group P21/c, with the... 

    Preparation of polyaniline/graphene coated wearable thermoelectric fabric using ultrasonic-assisted dip-coating method

    , Article Materials for Renewable and Sustainable Energy ; Volume 9, Issue 4 , 2020 Amirabad, R ; Ramazani Saadatabadi, A ; Siadati, M. H ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2020
    Abstract: The use of thermoelectric fabrics for powering wearable devices is expected to become widespread soon. A thermoelectric fabric was prepared by coating nanocomposite of polyaniline/graphene nanosheets (PANI/GNS) on a fabric. Four samples of the fabric containing different wt% of GNS (0.5, 2.5, 5, and 10) were prepared. To characterize the samples, Fourier transform infrared (FTIR) spectra, attenuated total reflectance-Fourier transform infrared (AT-FTIR) spectra, field-emission scanning electron microscopy (FE-SEM), electrical conductivity and Seebeck coefficient measurements were used. The electrical conductivity increased from 0.0188 to 0.277 S cm−1 (from 0.5 to 10 wt% of the GNS... 

    Optimization of synthetic conditions CMC-g-poly (acrylic acid)/celite composite superabsorbent by taguchi method and determination of its absorbency under load

    , Article Express Polymer Letters ; Volume 1, Issue 8 , 2007 , Pages 488-494 ; 1788618X (ISSN) Pourjavadi, A ; Amini Fazl, M. S ; Ayyari, M ; Sharif University of Technology
    A novel biopolymer-based composite hydrogel was synthesized through chemical crosslinking by graft copolymerization of partially neutralized acrylic acid onto the carboxymethyl cellulose (CMC). The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis based on the swelling capacity of the hydrogels. This method was applied for the experiments and standard L16 orthogonal array with five factors and four levels. In the synthesis of the composite superabsorbent, N,N'-methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, acrylic acid (AA) as monomer, CMC/Celite weight ratio and neutralization percent (NU) were used as... 

    Manufacturing and structural evaluation of polymer derived sioc/tic and SiOC/TiC/mullite nanocomposites

    , Article Iranian Journal of Materials Science and Engineering ; Volume 18, Issue 3 , 2021 ; 17350808 (ISSN) Paryab, A ; Godary, T ; Abdollahi, S ; Anousheh, M ; Khachatourian, A. M ; Sharif University of Technology
    Iran University of Science and Technology  2021
    Silicon oxycarbide (SiOC) materials derived from silicone attracted great attention for their superior high-temperature behavior. In the present study, Si (Ti)OC and Si (Ti,Al)OC nanocomposites, in which alkoxide precursors were used with the main silicone precursor, have been compared with SiOC material. Although in SiOC, C was bonded with Si in a carbon-rich SiOC phase, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that TiC was the preferred state for C atoms upon adding Ti into the system. This claim was also substantiated by Raman spectroscopy, where adding Ti into the system lowered the intensity of the D band, indicating the high affinity of C to... 

    The UNIQUAC-NRF segmental interaction model for vapor-liquid equilibrium calculations for polymer solutions

    , Article Polimeri (Zagreb) ; Volume 26, Issue 3 , 2005 , Pages 115-120 ; 03511871 (ISSN) Radfarnia, H. R ; Bogdanić, G ; Taghikhnai, V ; Ghotbi, C ; Sharif University of Technology
    This paper presents a new segment-based thermodynamic model containing the combinatorial and energetic contributions to the excess Gibbs energy for correlating/predicting of the vapor-liquid equilibrium (VLE) of polymer solutions. The model is derived from the UNIQUAC-NRF model, recently proposed by Haghtalab and Asadollahi, following the idea to associate the nonideality of polymer-solvent mixture with polymer segment-solvent interaction parameters, Segment activity coefficients are calculated by means of the UNIQUAC-NRF model. At the present state of development, 16 binary segmental interaction parameters have been estimated, The capability of the model is demonstrated with successful... 

    Phase morphology of polyblends of amorphous polycarbonate and semi-crystalline polyethylene terephthalate

    , Article Iranian Polymer Journal (English Edition) ; Volume 11, Issue 3 , 2002 , Pages 151-157+209 ; 10261265 (ISSN) Frounchi, M ; Mehrabzadeh, M ; Mohseni, S. S ; Sharif University of Technology
    Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 μm for PC20/FPET80 up to about 5 μm for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. Tg of PC-rich phase decreased from 153 deg;C for pure PC down... 

    Polymeric reservoirs for controlled release of iodine in drinking water

    , Article Scientia Iranica ; Volume 6, Issue 5 , 2000 , Pages 143-146 ; 10263098 (ISSN) Abdekhodaie, M. J ; Mohseni, A. R ; Sharif University of Technology
    Sharif University of Technology  2000
    In this paper, different polymers are utilized for controlling the release rate of iodine in drinking water to counteract iodine deficiency. Polyethylene, polyvinyl chloride and ethylene vinyl acetate copolymer are used to fabricate polymeric reservoirs of Nal. Zero-order release kinetics with different release rates has been achieved through choosing different materials and various formulation factors. The experimental results are consistent with the expectation that by using a polymer with a greater permeability or a device with a large release area, higher release rate could be achieved  

    Synthesis, structural characterization and application of a 2D coordination polymer of Mn-terephthalate as a heterogeneous catalyst for olefin oxidation

    , Article Polyhedron ; Volume 69 , 17 February , 2014 , Pages 167-173 ; ISSN: 02775387 Bagherzadeh, M ; Ashouri, F ; Crossed D Signakovic, M ; Sharif University of Technology
    A metal-organic coordination polymer of [Mn3(1,4- benzenedicarboxylate)3(DMF)4] ([Mn3(BDC) 3(DMF)4]n) was synthesized and characterized by IR spectra, elemental analysis (CHN), thermal gravimetric analysis (TGA) and single crystal X-ray diffraction analysis. The structure of [Mn 3(BDC)3(DMF)4]n is a 2D-periodic framework based on Mn(II)-terephthalate secondary building units (SBUs). The catalytic oxidation of various olefins was effectively carried out with [Mn 3(BDC)3(DMF)4]n. Moreover, the influence of key reaction parameters, including the solvents, reaction temperatures and nature of oxidant were studied. The optimized conditions were achieved by TBHP as the efficient oxidant in... 

    Numerical approach to unbiased and driven generalized elastic model

    , Article The Journal of chemical physics ; Vol. 140, Issue. 2 , 2014 , pp. 24106- ; ISSN: 0021-9606 Ghasemi Nezhadhaghighi, M ; Chechkin, A ; Metzler, R ; Sharif University of Technology
    From scaling arguments and numerical simulations, we investigate the properties of the generalized elastic model (GEM) that is used to describe various physical systems such as polymers, membranes, single-file systems, or rough interfaces. We compare analytical and numerical results for the subdiffusion exponent β characterizing the growth of the mean squared displacement 〈 (δh)(2)〉 of the field h described by the GEM dynamic equation. We study the scaling properties of the qth order moments 〈 {divides}δh{divides}(q)〉 with time, finding that the interface fluctuations show no intermittent behavior. We also investigate the ergodic properties of the process h in terms of the ergodicity... 

    Electro-mechanical bending analysis of ionic polymer metal nanocomposites (IPMNCs)

    , Article Mechanics Research Communications ; Vol. 62 , December , 2014 , pp. 77-82 ; ISSN: 00936413 Ozmaian, M ; Baghani, M ; Naghdabadi, R ; Sharif University of Technology
    A nonlinear electro-elasticity formulation for a cantilever beam made of IPMNC is used to obtain constitutive equations. Using the measured experimental data, the constitutive parameters connecting the free energy to the beam characteristics are calibrated. The results show that the constitutive equations are able to include the softening behavior of the material under applied voltages as well as the shift of the bending neutral axis from the geometrical midline of the beam by a closed-form solution which bridges between macroscopic and microscopic scales. The equations consider large deformations of thin and thick beams  

    Rapid start-up and improvement of granulation in SBR

    , Article Journal of Environmental Health Science and Engineering ; Volume 13, Issue 1 , 2015 ; 2052336X (ISSN) Jalali, S ; Shayegan, J ; Rezasoltani, S ; Sharif University of Technology
    BioMed Central Ltd  2015
    Abstract Background: The aim of this study is to accelerate and improve aerobic granulation within a Sequencing Batch Reactor (SBR) by cationic polymer addition. Methods: To identify whether the polymer additive is capable of enhancing granule formation, two SBRs (R1 and R2, each 0.15 m in diameter and 2 m in height) are used by feeding synthetic wastewater. The cationic polymer with concentration of 30 to 2 ppm is added to R2, while no cationic polymer is added to R1. Results: Results show that the cationic polymer addition causes faster granule formation and consequently shorter reactor start-up period. The polymer-amended reactor contains higher concentration of biomass with better... 

    Polymer matrix nanocomposites for heavy metal adsorption: a review

    , Article Journal of the Iranian Chemical Society ; Volume 17, Issue 6 , 31 January , 2020 , Pages 1259-1281 Mohammadnezhad, G ; Keikavousi Behbahan, A ; Sharif University of Technology
    Springer  2020
    Heavy metals belong to a group of lethal environmental pollutants. Ongoing efforts targeted at safeguarding public health have led to considerable attention being focused on methods that allow efficient extraction of these toxic substances. Polymer nanocomposites (PNCs) with their special characteristics are a class of adsorbents that demonstrate high potential for use in heavy metal extraction. As this process of removal is predominantly governed by adsorption, various parameters in PNCs’ chemical structure, as well as the metal solutions, can have a significant effect on the adsorption process. Herein, this review undertakes a survey of recently developed PNCs and their metal adsorption... 

    Experimental investigation of flooding hydrolyzed-sulfonated polymers for EOR process in a carbonate reservoir

    , Article Petroleum Science and Technology ; Vol. 32, issue. 9 , Mar , 2014 , p. 1114-1122 ; ISSN: 10916466 Bamzad, S ; Nourani, M ; Ramazani, A ; Masihi, M ; Sharif University of Technology
    The main purposes of this study were to scrutinize experimentally effects of polymer and rock types on the oil recovery using water and polymer flooding processes. Four dynamic flooding experiments were carried out at simulated reservoir condition of temperature and pressure. According to the obtained results, the ultimate oil recovery by water flooding in highly fractured reservoirs was less than reservoirs with the microfractures. The results of polymer flooding showed that in addition the polymer molecular weight, the sulfonation of polymers also affects the oil recovery  

    Thermal conductivity of polyamide-6,6 in the vicinity of charged and uncharged graphene layers: A molecular dynamics analysis

    , Article Journal of Physical Chemistry C ; Volume 116, Issue 26 , May , 2012 , Pages 14115-14122 ; 19327447 (ISSN) Alaghemandi, M ; Gharib-Zahedi, M. R ; Spohr, E ; Böhm, M. C ; Sharif University of Technology
    The thermal conductivity (λ) of nanoconfined polyamide-6,6 (PA) oligomers in polymer-graphene nanocomposites has been investigated by reverse nonequilibrium molecular dynamics (RNEMD) simulations. The preferential alignment of the PA chains parallel to the graphene plane as well as their elongation implies that λ of the polymer in nanocomposites is larger than that in the neat polymer system. The ordering of the polymer phase is enhanced in an arrangement of charged graphene surfaces made of one layer with a charge deficit and one with a charge excess. The consequence of the enhanced polymer ordering as well as the denser packing is an increase in λ in the polymer network. Differences in the... 

    Efficient inductively heated shape memory polyurethane acrylate network with silane modified nanodiamond@Fe3O4 superparamagnetic nanohybrid

    , Article European Polymer Journal ; Volume 159 , 2021 ; 00143057 (ISSN) Salkhi Khasraghi, S ; Shojaei, A ; Janmaleki, M ; Sundararaj, U ; Sharif University of Technology
    Elsevier Ltd  2021
    Multifunctional magnetic shape memory polymer (SMP) nanocomposites with high sensitivity was synthesized through inclusion of silane functionalized nanodiamond@Fe3O4 (S-NDF) hybrid nanoparticle into polycaprolactone (PCL) based polyurethane acrylate (PUA) matrix followed by in situ crosslinking of the matrix. Highly biocompatible and superparamagnetic nanodiamond(ND)@Fe3O4 nanohybrids were synthesized through in situ co-precipitation method. The morphological analysis suggested that S-NDFs filled PUAs (2 to 9 wt% loadings) well interacted with both soft and hard domains of the matrix. The base polymer and the nanocomposites presented excellent shape fixity ratio (above 97%) and shape...