Search for: silicones
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    Hot filament CVD of Fe-Cr catalyst for thermal CVD carbon nanotube growth from liquid petroleum gas

    , Article Applied Surface Science ; Volume 256, Issue 5 , 2009 , Pages 1365-1371 ; 01694332 (ISSN) Akbarzadeh Pasha, M ; Shafiekhani, A ; Vesaghi, M. A ; Sharif University of Technology
    A hot filament chemical vapor deposition (HFCVD) method was used to prepare Fe-Cr thin film on Si substrate. The produced layers were used as catalysts for growing carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 825 °C by thermal CVD (TCVD) method. To characterize the obtained catalysts or CNTs, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy were used. CNTs were grown on HFCVD derived Fe-Cr catalyst with the LPG as carbon source successfully. It was found that an annealing process on catalysts enhances the surface concentration of Cr atoms and reduces the sizes of catalyst particles. The... 

    Pulsed-laser annealing of NiTi shape memory alloy thin film

    , Article Journal of Materials Science and Technology ; Volume 25, Issue 1 , 2009 , Pages 135-140 ; 10050302 (ISSN) Sadrnezhaad, S. K ; Rezvani, E ; Sanjabi, S ; Ziaei Moayed, A. A ; Sharif University of Technology
    Local annealing of amorphous NiTi thin films was performed by using an Nd:YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si (100) and Silica (111) substrates were used for annealing. Delicate treatment with 15.92 W/mm2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns  

    High-performance enzyme-free glucose sensor with Co-Cu nanorod arrays on Si substrates

    , Article Recent Patents on Biotechnology ; Volume 12, Issue 2 , 2018 , Pages 126-133 ; 18722083 (ISSN) Shirinzadeh, H ; Yazdanpanah, A ; Karponis, D ; Aghabarari, B ; Tahmasbi, M ; Seifalian, A ; Mozafari, M ; Sharif University of Technology
    Bentham Science Publishers B.V  2018
    Background: Glucose sensors have been extensively researched in patent studies and manufactured a tool for clinical diabetes diagnosis. Although some kinds of electrochemical enzymatic glucose sensors have been commercially successful, there is still room for improvement, in selectivity and reliability of these sensors. Because of the intrinsic disadvantages of enzymes, such as high fabrication cost and poor stability, non-enzymatic glucose sensors have recently been promoted as next generation diagnostic tool due to their relatively low cost, high stability, prompt response, and accuracy. Objective: In this research, a novel free standing and binder free non-enzymatic electrochemical sensor... 

    Effects of physicochemical characteristics of magnetically recoverable biocatalysts upon fatty acid methyl esters synthesis from oils

    , Article Renewable Energy ; Volume 116 , 2018 , Pages 613-622 ; 09601481 (ISSN) Esmaeilnejad Ahranjani, P ; Kazemeini, M ; Singh, G ; Arpanaei, A ; Sharif University of Technology
    Elsevier Ltd  2018
    This study reports the importance of physicochemical characteristics of the core-shell structured polymer-coated Fe3O4 cluster@SiO2 nanocomposite particles for designing the biocatalysts used for transesterification of soybean oil. To demonstrate this issue, two different types of polymer molecules such as polyethylenimine (PEI) and polyacrylic acid (PAA) each with two different molecular weights are employed. The highest fatty acid methyl esters (FAMEs) synthesis yield values are achieved by the lipases immobilized onto the low- and high-molecular-weight PEI-coated particles as compared to those of the low- and high-molecular-weight PAA-coated particles (i.e., ∼64.8% and ∼73.1% versus... 

    Grand canonical Monte Carlo and molecular dynamics simulations of the structural properties, diffusion and adsorption of hydrogen molecules through poly(benzimidazoles)/nanoparticle oxides composites

    , Article International Journal of Hydrogen Energy ; Volume 43, Issue 5 , 2018 , Pages 2803-2816 ; 03603199 (ISSN) Khosravanian, A ; Dehghani, M ; Pazirofteh, M ; Asghari, M ; Mohammadi, A. H ; Shahsavari, D ; Sharif University of Technology
    Elsevier Ltd  2018
    Comprehensive structural/molecular simulations have been undertaken to study the poly(benzimidazoles) (PBI) membrane combined with four different nano-oxide materials (ZnO, Al2O3, SiO2 and TiO2) for purification and production of hydrogen from natural gases. Composite membranes were built with different amounts of nano-oxide materials to investigate the influence of nano-oxide content on the PBI membrane performance. Several structural characterizations such as FFV, WAXD and also a thermal one (glass transition temperature) were done to study the structural properties of all simulated membrane cells. Moreover, MSD and adsorption isotherms tasks were used to estimate the diffusivity and... 

    Growth and field emission study of molybdenum oxide nanostars

    , Article Journal of Physical Chemistry C ; Volume 113, Issue 44 , 2009 , Pages 19298-19304 ; 19327447 (ISSN) Khademi, A ; Azimirad, R ; Zavarian, A. A ; Zaker Moshfegh, A. R ; Sharif University of Technology
    The field emission properties of MoO2 nanostars grown on a silicon substrate and their emission performance in various vacuum gaps are reported in this article. A new structure of molybdenum oxides, named a nanostar, is grown by thermal vapor deposition with a length of ̃1 μm, a thickness of ̃50 nm, and its width in the range of 500-700 nm. The morphology, structure, composition, and chemical states of the prepared nanostars were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to XRD analysis, the grown nanostructures are composed of both crystalline Mo4O11 and... 

    Synthesis of titania/carbon nanotube heterojunction arrays for photoinactivation of E. coli in visible light irradiation

    , Article Carbon ; Volume 47, Issue 14 , 2009 , Pages 3280-3287 ; 00086223 (ISSN) Akhavan, O ; Abdolahad, M ; Abdi, Y ; Mohajerzadeh, S ; Sharif University of Technology
    TiO2/multi-wall carbon nanotube (MWNT) heterojunction arrays were synthesized and immobilized on Si(0 0 1) substrate as photocatalysts for inactivation of Escherichia coli bacteria. The vertically aligned MWNT arrays were grown on ∼5 nm Ni thin film deposited on the Si by using plasma enhanced chemical vapor deposition at 650 °C. Then, the MWNTs were coated by TiO2 using dip-coating sol-gel method. Post annealing of the TiO2/MWNTs at 400 °C resulted in crystallization of the TiO2 coating and formation of Ti-C and Ti-O-C carbonaceous bonds at the heterojunction. The visible light-induced photoinactivation of the bacteria increased from MWNTs to TiO2 to TiO2/MWNTs, in which the bacteria could... 

    Synthesis and characterization of diopside glass-ceramic matrix composite reinforced with aluminum titanate

    , Article Ceramics International ; Volume 35, Issue 4 , 2009 , Pages 1447-1452 ; 02728842 (ISSN) Yousefi, M ; Alizadeh, P ; Eftekhari Yekta, B ; Molaie, F ; Ghafoorian, N ; Montazerian, M ; Sharif University of Technology
    Glass-ceramic composites in the SiO2-CaO-MgO-(Na2O) system, reinforced with 5, 10 and 20 wt.% aluminum titanate were synthesized by pressureless sintering. Optimum sintering temperatures with maximum relative density were determined for each composition. The composites were fired above the crystallization peak temperature of glass-ceramic. Mechanical properties of glass-ceramic and sintered composites, such as fracture toughness, flexural strength and Vickers microhardness, were investigated. The sintered composites were characterized by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that the composite containing 10... 

    Hydrolysis kinetics of lead silicate glass in acid solution

    , Article Journal of Nuclear Materials ; Volume 389, Issue 3 , 2009 , Pages 427-431 ; 00223115 (ISSN) Rahimi, R. A ; Sadrnezhaad, Kh ; Raisali, G ; Hamidi, A ; Sharif University of Technology
    Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy... 

    Mass transfer through PDMS/zeolite 4A MMMs for hydrogen separation: Molecular dynamics and grand canonical Monte Carlo simulations

    , Article International Communications in Heat and Mass Transfer ; Volume 108 , 2019 ; 07351933 (ISSN) Riasat Harami, H ; Amirkhani, F ; Khadem, S. A ; Rezakazemi, M ; Asghari, M ; Shirazian, S ; Sharif University of Technology
    Elsevier Ltd  2019
    In industry, utilizing membrane separation technology to purify natural gas streams is of remarkable significance. Molecular Simulation was used in the current article to study the structural and gas separation properties of polydimethylsiloxane (PDMS)/zeolite 4A Mixed Matrix Membranes (MMMs). To explore the optimal performance of MMMs, several structural analyses, namely Fractional Free Volume (FFV), Radial Distribution Function (RDF), X-Ray Diffraction (XRD) and also Glass Transition Temperature (Tg) as one of the most important properties of membranes have been evaluated. Also, the solubilities and diffusivities of periodic cells were respectively measured using MSD and adsorption... 

    Fabrication of a form-stable phase change material with green fatty acid and recycled silica nanoparticles from spent lead-acid battery separators with enhanced thermal conductivity

    , Article Thermochimica Acta ; Volume 693 , November , 2020 Nemati, S ; Pircheraghi, G ; Sharif University of Technology
    Elsevier B.V  2020
    Massive amounts of spent lead-acid battery separators with 50 wt % silica nanoparticles (SiNPs) can be recycled for further use. One compelling application is form-stable phase change materials (FSPCMs). This study proposes a novel tertiary eutectic mixture of green and non-toxic lauric acid, palmitic acid, and paraffin, and recycled SiNPs to find a sustainable approach to deal with industrial wastes and energy consumption. Fatty acids and paraffin are promising for thermal energy storage in buildings. However, they lack sufficient thermal conductivity, mechanical strength, and suffer from leakage. To give mechanical strength, high-density polyethylene (HDPE) was added and sintered.... 

    Phenomenological investigation of drop manipulation using surface acoustic waves

    , Article Microgravity Science and Technology ; Volume 32, Issue 6 , 2020 , Pages 1147-1158 Sheikholeslam Noori, M ; Shams Taleghani, A ; Taeibi Rahni, M ; Sharif University of Technology
    Springer Science and Business Media B.V  2020
    This paper aims at the investigation of acoustic streaming produced by surface acoustic waves (SAWs) in a drop. Computational simulation of acoustofluidic phenomenon, using lattice Boltzmann method (LBM), presenting acoustic applications in flow control, and a relatively complete parametric study are the motivations of this work. For this purpose, a computational fluid dynamics modeling based on multi-relaxation time multi-component multiphase color gradient lattice Boltzmann method was used. The simulations were carried out at wave frequencies ranging from 20 MHz to 271 MHz and wave amplitudes ranging from 0.5 nm to about 350 nm. First, the non-dimensional form of Navier-Stokes equations... 

    Quantitative in vivo microsampling for pharmacokinetic studies based on an integrated solid-phase microextraction system

    , Article Analytical Chemistry ; Volume 79, Issue 12 , 2007 , Pages 4507-4513 ; 00032700 (ISSN) Zhang, X ; Eshaghi, A ; Musteata, F. M ; Ouyang, G ; Pawliszyn, J ; Sharif University of Technology
    An integrated microsampling approach based on solid-phase microextraction (SPME) was developed to provide a complete solution to highly efficient and accurate pharmacokinetic studies. The microsampling system included SPME probes that are made of poly(ethylene glycol) (PEG) and C18-bonded silica, a fast and efficient sampling strategy with accurate kinetic calibration, and a high-throughput desorption device based on a modified 96-well plate. The sampling system greatly improved the quantitative capability of SPME in two ways. First, the use of the C18-bonded silica/PEG fibers minimized the competition effect from analogues of the target analytes in a complicated sample matrix such as blood... 

    Effect of material and population on the delivery of nanoparticles to an atherosclerotic plaque: a patient-specific in silico study

    , Article Langmuir ; Volume 37, Issue 4 , 2021 , Pages 1551-1562 ; 07437463 (ISSN) Amani, A ; Shamloo, A ; Barzegar, S ; Forouzandehmehr, M ; Sharif University of Technology
    American Chemical Society  2021
    Coronary artery disease (CAD) is the prevalent reason of mortality all around the world. Targeting CAD, specifically atherosclerosis, with controlled delivery of micro and nanoparticles, as drug carriers, is a very proficient approach. In this work, a patient-specific and realistic model of an atherosclerotic plaque in the left anterior descending (LAD) artery was created by image-processing of CT-scan images and implementing a finite-element mesh. Next, a fluid-solid interaction simulation considering the physiological boundary conditions was conducted. By considering the simulated force fields and particle-particle interactions, the correlation between injected particles at each cardiac... 

    Sol-gel-based solid-phase microextraction and gas chromatography-mass spectrometry determination of dextromethorphan and dextrorphan in human plasma

    , Article Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences ; Volume 818, Issue 2 , 2005 , Pages 147-157 ; 15700232 (ISSN) Bagheri, H ; Eshaghi, A ; Rouini, M. R ; Sharif University of Technology
    A novel solid-phase microextraction (SPME) method was developed for isolation of dextromethorphan (DM) and its main metabolite dextrorphan (DP) from human plasma followed by GC-MS determination. Three different polymers, poly(dimethylsiloxane) (PDMS), poly(ethylenepropyleneglycol) monobutyl ether (Ucon) and polyethylene glycol (PEG) were synthesized as coated fibers using sol-gel methodologies. DP was converted to its acetyl-derivative prior to extraction and subsequent determination. The porosity of coated fibers was examined by SEM technique. Effects of different parameters such as fiber coating type, extraction mode, agitation method, sample volume, extraction time, and desorption... 

    Plasma-enhanced chemical vapor deposition for fabrication of yolk-shell SnO2@Void@C nanowires, as an efficient carbon coating technique for improving lithium-ion battery performance

    , Article Materials Science in Semiconductor Processing ; Volume 149 , 2022 ; 13698001 (ISSN) Habibi, A ; Mousavi, M. R ; Yasoubi, M ; Sanaee, Z ; Ghasemi, S ; Sharif University of Technology
    Elsevier Ltd  2022
    This manuscript describes the implementation of plasma-enhanced chemical vapor deposition (DC-PECVD) and vapor-liquid-solid (VLS) techniques to fabricate a yolk-shell SnO2@Void@C nanowire (NW) structure. SnO2 nanowires have been synthesized on the stainless steel mesh substrate through the VLS method. The PECVD-assisted growth of carbon nanolayer on the SnO2 and SiO2 coated SnO2 NWs has been performed to fabricate SnO2@C core-shell and SnO2@SiO2@C yolk-shell structures, respectively. A consequent silica etching process converted the SnO2@SiO2@C into SnO2@Void@C structure. The electrochemical performance of bare SnO2 NWs, SnO2 NWs @ C, and SnO2 @Void @ C coaxial NWs structures have been... 

    Label-Free real-time detection of HBsAg using a QCM immunosensor

    , Article Clinical Laboratory ; Volume 68, Issue 4 , 2022 , Pages 707-720 ; 14336510 (ISSN) Saffari, Z ; Ghavidel, A ; Ahangari Cohan, R ; Hamidi Fard, M ; Khoobi, M ; Aghasadeghi, M ; Norouzian, D ; Sharif University of Technology
    Verlag Klinisches Labor GmbH  2022
    Background: Hepatitis B virus surface antigen (HBsAg) is an important protein in both diagnosis and prevention of hepatitis B infection. In the current study, a piezoelectric immunosensor based on antibody-antigen interaction was designed to detect HBsAg. A quartz crystal microbalance system was employed to detect antibody-antigen interaction. Methods: At first, an oscillator was designed to measure the resonant frequency affected by the reactants using IC 74LVC1GX04. Antibody against HBsAg was immobilized on 10 MHz AT-cut quartz crystal. The surface modifications were monitored by atomic force microscopy (AFM) and contact angle measurements. Different concentrations of antibody were used... 

    Molecularly imprinted polydopamine nano-layer on the pore surface of porous particles for protein capture in HPLC column

    , Article Journal of Colloid and Interface Science ; Volume 404 , 2013 , Pages 117-126 ; 00219797 (ISSN) Nematollahzadeh, A ; Shojaei, A ; Abdekhodaie, M. J ; Sellergren, B ; Sharif University of Technology
    Bio-inspired Human Serum Albumin (HSA) imprinted polydopamine nano-layer was produced through oxidative polymerization of dopamine on the pore surface of HSA modified porous silica particles. The coating thickness was controlled by the reaction time and thereby varied within 0-12. nm. The samples were characterized by elemental analysis, FT-IR, DSC, SEM, TEM, TGA, physisorption and thermoporometry. The characterization confirmed the success of evolution and deposition of polydopamine layer on the silica pore surface. Batch rebinding experiment showed that the molecularly imprinted polymer (MIP) with 8.7. nm coating thickness, in comparison with the thinner and thicker coatings, displays the... 

    Effect of CVD parameters on hydrogen permeation properties in a nano-composite SiO 2-Al 2O 3 membrane

    , Article Journal of Membrane Science ; Volume 423-424 , 2012 , Pages 530-535 ; 03767388 (ISSN) Amanipour, M ; Ganji Babakhani, E ; Safekordi, A ; Zamaniyan, A ; Heidari, M ; Sharif University of Technology
    Tubular ceramic membranes were synthesized by depositing a dense layer of silica-alumina on top of a multilayer substrate using co-current chemical vapor deposition (CVD) method. The multilayer substrate was prepared by coating with a series of bohemite sols with certain particle sizes. Cross-sectional and surface images obtained from high resolution FESEM showed that the intermediate layer had a thickness of about 1μm and the top selective layer was uniform and dense with a thickness of less than 100nm. Permeance tests, which were carried out with H 2, CO 2, N 2 and CH 4 at a high temperature range of 923-1073K, indicated that gas permeation took place via different mechanisms through... 

    Towards greater mechanical, thermal and chemical stability in solid-phase microextraction

    , Article TrAC - Trends in Analytical Chemistry ; Volume 34 , 2012 , Pages 126-138 ; 01659936 (ISSN) Bagheri, H ; Piri-Moghadam, H ; Naderi, M ; Sharif University of Technology
    Solid-phase microextraction (SPME) is a fast, solvent-free technique, which, since its introduction in the 1990s, has been increasingly applied to sample preparation in analytical chemistry. Conventional SPME fibers are fabricated by making a physical bond between the usual silica substrate and the polymeric coatings. However, some applications are limited, as the lifetime and the stability of conventional SPME fibers cannot meet the demands of analyzing relatively non-volatile compounds with more polar moieties. There have been attempts to analyze less volatile compounds by increasing the thermal, physical and chemical stability of the fibers. In this review, we present some new...