Search for: silica
0.007 seconds
Total 382 records

    Influence of surface-modified nanoparticles on the hydrodynamics of rising bubbles

    , Article Chemical Engineering and Technology ; Volume 44, Issue 3 , 2021 , Pages 513-520 ; 09307516 (ISSN) Fayzi, P ; Bastani, D ; Lotfi, M ; Miller, R ; Sharif University of Technology
    Wiley-VCH Verlag  2021
    Local velocities of bubbles rising in four different nanosilica solutions were investigated experimentally. Also, the density, viscosity, and surface tension of fumed nanosilica and modified nanosilica solutions were measured. Heat treatment and chemical functionalization were used to modify the properties of silica nanoparticles. It was found that the addition of nanosilica affected the hydrodynamics of the rising bubble by increasing the drag friction at the interface. However, environmentally responsive nanosilica particles behaved like surfactant molecules, due to the interfacial activity of hydrophilic and hydrophobic chains. Silica nanoparticles coated with both hydrophilic and... 

    , M.Sc. Thesis Sharif University of Technology khazaei Nezhad Gharatekan, Mehdi (Author) ; Bahrampour, Alireza (Supervisor)
    By employing the image theory the Er doped microsphere coupled to an external cavity made by a metallic mirror is simulated by a bimicrosphere laser. The symmetric structure causes the formation of odd and even modes corresponding to the TE and TM mode of the microsphere and splitting the oscillation frequencies. The oscillation frequencies are dependent on the coupling coefficient. The coupling coefficient is obtained near the mirror-microsphere distance. The ohmic mirror loss also is determined as a function of the mirror distance. The total optical loss experienced in these resonators is exceptionally low. In fact,quality factor as high as 108 − 1011 have already been demonstrated for... 

    Preparation and Investigation of Behavior of Silica Nano Composites with TPU/PP

    , M.Sc. Thesis Sharif University of Technology Meshkati, Erfan (Author) ; Ramazani Saadatabadi, Ahmand (Supervisor)
    Blending can be used as one of the ways of producing materials with appropriate properties, which have many relative advantages in comparison with other methods like polymerization. Among the existing blends in the market and scientific areas, blends of polyurethane thermoplastic and polypropylene have been also studied because of its commercial importance and scientific interest. This blending can improve the mechanical properties, friction resistance, improvement of impact strength at low temperatures and improvement of plasticity properties. In this research, blends with different ratios of TPU/PP is produced by melt mixing, and for improving properties of blends, two kinds of nano fumed ... 

    Manufacturing and Investigation the Properties of Polyethylene/ Fumed Silica Nanocomposites Via in situ Polymerization

    , M.Sc. Thesis Sharif University of Technology Ghahri Saremi, Maysam (Author) ; Ramazani Saadatabadi, Ahmad (Supervisor)
    In this research UHMWPE/FUMED SILICA nanocomposites with different concentrations of nano fumed silica (0.5, 1.5, 2.5, 4.5 wt %) were prepared via in situ polymerization using a novel Bi-supported Ziegler-Natta catalytic systems. Magnesium etoxide and Fumed Silica functionalized by hydroxyl groups were used as supports of catalyst. TiCl4 accompanied by triethylaluminum constituted Ziegler-Natta catalytic system. Preparation of catalyst and polymerization were done in slurry phase under the argon atmosphere. Scanning Electron Microscopy (SEM) images also certified very good dispersion of fumed silica throughout PE matrix. Intrinsic viscosity measurements showed high molecular weight for... 

    ZnO Coating, Containing SiO2 Nano Particles, Prepared by Sol-gel Process and Investigation of Surface Properties

    , M.Sc. Thesis Sharif University of Technology Rostami, Rahman (Author) ; Ghorbani, Mohammad (Supervisor) ; Askari, Masoud (Co-Advisor)
    Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to... 

    Characterization of Elecroless Ni-P-Al2O3-SiO2 Nano-composite Coating on Aluminium

    , M.Sc. Thesis Sharif University of Technology Rahemi Ardekani, Saeed (Author) ; Afshar, Abdollah (Supervisor) ; Dolati, Abolghasem (Supervisor)
    In this study Ni-P-Al2O3-SiO2 nano composite coating developed on aluminium alloy 6061 using electroless method. Due to oxidation of aluminium, a double zincate pretreatment performed to obtain proper adhesion of coating on substrate. Effect of solution temperature and heat treatment on thickness and property of nano composite coating was studied. Furthermore, effect of concentration of nano particles in electroless solution on thickness, morphology, micro hardness, wear behavior, corrosion resistance and particle content in coating were investigated. Field emission scanning electron microscopy (FESEM, Hitachi S-4160) with energy dispersive spectroscopy (EDS) was used to evaluate morphology... 

    Synthesis and Investigation on the Properties of Silica-Graphene Oxide Nanocomposite Coating

    , M.Sc. Thesis Sharif University of Technology Afzali, Neda (Author) ; Dolati, Abolghasem (Supervisor)
    The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with... 

    The Effect of Surfactant Agents on the Superhydrophobic Properties of Silica Coatings Synthesis by Sol-gel

    , M.Sc. Thesis Sharif University of Technology Ziaee, Hamed (Author) ; Dolati, Abolghasem (Supervisor)
    The purpose of this research is producing one phase silica superhydrophobic coating by sol-gel method and drying temperature less than 200 degrees. For preparing micrometer and nanometer scaled hierarchical structure based on silica, TEOS precursor and Fumed Silica nanoparticles were used by density of 43/30 cc/lit and 6/52 gr/lit in order to provide desired roughness in the range of 40 nm. Moreover, HMDS surface modifying agent was used for reducing the surface energy of coating, which is not a danger to the environment in comparison to the same substances. The best Contact Angle is 155 degree and the best Sliding Angle is less than 5 degree. For instance, it was created with the... 

    Study of Micropollutants Adsorption from Water by Nanoporous Silica Aerogels

    , M.Sc. Thesis Sharif University of Technology Abdoli, Majid (Author) ; Bastani, Daruoosh (Supervisor) ; Bargozin, Hassan (Co-Advisor)
    Phenolic compounds are important environmental pollutants that the removal and separation of them from the water and industrial wastewater especially in the oil industry is essential before entering the environment. In the present study, the removal efficiency of the adsorbent silica aerogel 4-Chlorophenol and 4-Bromophenol as phenolic compounds from aqueous solution was surveyed. In this research, the effects of various factors such as contact time, pH, and initial concentration of the pollutant and the adsorbent on the adsorption were studied. It was observed that there is a large amount of adsorption in acidic pH and this amount increases by incrementing the concentration of the... 

    Synthesis of Silica Nanoparticles Modified with Alumina and Its Performance in Compressive Strength of Concrete

    , M.Sc. Thesis Sharif University of Technology Karbalaee, Omid (Author) ; Sajadi, Ali Akbar (Supervisor) ; Ghanbari, Bahram (Supervisor)
    Silica nanoparticles is one of the most important mineral particles. In this study, Sodium silicate, Sulfuric acid and Sodium aluminate is used in order to synthesis of the modified Silica nanoparticles. The effects of temperature, reaction time and the molar ratio of regents were tested and optimized. Synthesized nanoparticles were characterized by use of XRD, FT-IR and SEM techniques. The results show that by controlling the reaction conditions, nanoparticles with an average size of 26.2 nm is obtained. The increase of temperature and reaction time alters the structure of the particles of amorphous state to a crystalline needles. The particle surface modification process was performed by... 

    Efficient and practical protocol for silylation of hydroxyl groups using reusable lithium perchlorate dispread in silica gel under neutral condition [electronic resource]

    , Article Journal of Organometallic Chemistry ; 2006, Volume 691, Issue 5, Pages 817–820 Azizi, N. (Najmodin) ; Yousefi, R ; Saidi, M. R ; Sharif University of Technology
    A very efficient and mild procedure for the trimethylsilylation of a wide variety of alcohols, including primary, allylic, benzylic, secondary, hindered secondary, tertiary, and phenols with hexamethyldisilazane on the surface of silica gel dispersed with LiClO4 in room temperature at few minutes in excellent yields under neutral conditions is reported. This procedure also allows the excellent selectivity under LP-SiO2 system for silylation of alcohols in the presence of amine and phenolic hydroxy groups  

    Immobilized palladium nanoparticles on silica functionalized N-propylpiperazine sodium N-propionate (SBPPSP): Catalytic activity evaluation in copper-free Sonogashira reaction

    , Article Journal of the Iranian Chemical Society ; Volume 10, Issue 6 , 2013 , Pages 1291-1296 ; 1735207X (ISSN) Niknam, K ; Deris, A ; Panahi, F ; Hormozi Nezhad, M. R ; Sharif University of Technology
    An efficient heterogeneous palladium catalyst system has been developed based on immobilization of Pd nanoparticles on silica-bonded N-propylpiperazine sodium N-propionate (SBPPSP) substrate. SBPPSP substrate can stabilize the Pd nanoparticles effectively so that it can improve their stability against aggregation. In addition, grafted piperazine species on to the silica backbone prevent the removing of Pd nanoparticles from the substrate surface. Transmission electron microscopy (TEM) of catalyst is shown the size of Pd nanoparticles, also it confirmed by particle size analyzer which shown the average size of 21 nm for Pd. The catalytic activity of these catalysts was investigated in the... 

    Modification of silica using piperazine for immobilization of palladium nanoparticles: A study of its catalytic activity as an efficient heterogeneous catalyst for Heck and Suzuki reactions

    , Article Journal of the Iranian Chemical Society ; Volume 10, Issue 3 , 2013 , Pages 527-534 ; 1735207X (ISSN) Niknam, K ; Habibabad, M. S ; Deris, A ; Panahi, F ; Reza Hormozi Nezhad, M ; Sharif University of Technology
    An efficient heterogeneous palladium catalyst system has been developed based on immobilization of Pd nanoparticles on silica-bonded N-propylpiperazine (SBNPP) substrate. SBNPP substrate can stabilize the Pd nanoparticles effectively so that it can improve their stability against aggregation. Also, grafted piperazine species onto the silica backbone prevents the removing of Pd nanoparticles from the substrate surface. It seems that the high recyclable capability of Pd-SBNPP catalysts is resulted from these two characteristics. Transmission electron microscopy (TEM) of catalyst is shown the size of Pd nanoparticles in Pd-SBNPP average of 20 nm. Furthermore, X-ray photoelectron spectroscopy... 

    Synthesis of spherical silica/multiwall carbon nanotubes hybrid nanostructures and investigation of thermal conductivity of related nanofluids

    , Article Thermochimica Acta ; Volume 549 , 2012 , Pages 87-94 ; 00406031 (ISSN) Baghbanzadeh, M ; Rashidi, A ; Rashtchian, D ; Lotfi, R ; Amrollahi, A ; Sharif University of Technology
    In this study, a hybrid of silica nanosphere/multiwall carbon nanotube (MWCNT) has been synthesized by wet chemical method at room temperature. The effect of MWCNTs, silica nanospheres and hybrid nanostructures (80% silica nanosphere/20% MWCNT and 50% silica nanosphere/50% MWCNT) on the thermal conductivity of distilled water has been investigated. SDBS was used as the dispersant to stabilize nanomaterials in the aqueous suspension and its concentration was 1.5 times of the concentration of nanomaterials. As results show, by increasing the concentration of nanomaterials, effective thermal conductivity of nanofluids increased. The most and the least enhancement in the effective thermal... 

    The effect of water-cement ratio in compressive and abrasion strength of the nano silica concretes

    , Article World Applied Sciences Journal ; Volume 17, Issue 4 , 2012 , Pages 540-545 ; 18184952 (ISSN) Shamsai, A ; Rahmani, K ; Peroti, S ; Rahemi, L ; Sharif University of Technology
    Development and construction of hydraulic structures like dams, the concrete durability in these kinds of structures has gained special attention. One of the crucial factor in concrete technology is it durability in hydraulic structures. Concrete has to resist against abrasion due to the crash of particles carried by water. To enhance the abrasion resistance of concrete different methods have been offered. In the present stud, the role of water-cement ratio in compressive and abrasion strength of nano silica concrete was investigated. The constructed concrete samples with 3% nano silica and water-cement ratios of 0.33, 0.36, 0.40, 0.44 and 0.50 were experimented. Other design features... 

    Investigations for gas-phase deprotonation of the silica-propyl-SO3H catalyst using cage-like nanocluster modeling technique

    , Article Journal of the Iranian Chemical Society ; Volume 12, Issue 11 , November , 2015 , Pages 1991-1997 ; 1735207X (ISSN) Vafaeezadeh, M ; Hashemi, M. M ; Sharif University of Technology
    Springer Verlag  2015
    Exploring deprotonation properties of silica-functionalized propylsulfonic acid catalyst (silica-propyl-SO3H) is the subject of various experimental and theoretical researches. In the current study, the structure of the silica-propyl-SO3H has been simulated using density functional theory (DFT) methods by mimicking the surface of the silica in the form of cubic cage-like nanoclusters of silicon and oxygen. The values of ΔHacidity for gas-phase deprotonation are calculated considering various possible interactions of the propylsulfonic acid on the surface of the silica. Our investigations indicate that interactions of sulfonic acid (-SO3H) head... 

    The effect of protein corona on doxorubicin release from the magnetic mesoporous silica nanoparticles with polyethylene glycol coating

    , Article Journal of Nanoparticle Research ; Volume 17, Issue 4 , April , 2015 ; 13880764 (ISSN) Pourjavadi, A ; Tehrani, Z. M ; Mahmoudi, N ; Sharif University of Technology
    Kluwer Academic Publishers  2015
    In the present work, biocompatible superparamagnetic iron oxide nanoparticles coated by mesoporous silica were used as drug nanocarriers for doxorubicin (Dox; an anticancer drug) delivery. In biological media, the interaction of protein corona layer with the surface of nanoparticles is inevitable. For this reason, we studied the effect of protein corona on drug release from magnetic mesoporous silica nanoparticles (MMSNs) in human plasma medium. Besides, we used hydrophilic and biocompatible polymer, polyethylene glycol (PEG), to decrease protein corona effects. The results showed the increased Dox release from PEGylated MMSNs compared with bare MMSNs. This result indicated that the coating... 

    Design and calibration procedure of a proposed V-band antenna array on fused silica technology intended for MIMO applications

    , Article International Journal of Microwave and Optical Technology ; Volume 13, Issue 4 , 2018 , Pages 317-329 ; 15530396 (ISSN) Salarpour, M ; Farzaneh, F ; Staszewski, R. B ; Sharif University of Technology
    International Academy of Microwave and Optical Technology (IAMOT)  2018
    A coplanar-fed wideband antenna array system to characterize MIMO channels in the 60 GHz band is proposed. The array consists of six U-slot patch elements with half-wavelength separation and is fed independently by individual transceivers. The system is designed and simulated on fused silica substrate to be integrated easily with RFICs and to achieve fine fabrication resolution (1um) for accurate mm-wave measurements. It can provide 11dBi peak gain at broadside and beam steering up to ±40° tilted from broadside over 57-63 GHz band. A new on-wafer calibration technique is developed to balance the amplitude and phase of all transceivers at the input of the array system which realizes high... 

    Analysis of the effect of kevlar fibers on abrasion resistance, flexural strength and hydraulic conductivity coefficient of silica fume concretes

    , Article Iranian Journal of Science and Technology - Transactions of Civil Engineering ; Volume 44, Issue 2 , 2020 , Pages 669-674 Rahmani, K ; Piroti, S ; Ghameian, M ; Sharif University of Technology
    Springer  2020
    Reinforcing fiber and silica fume of concrete can be considered as one of the most widely used additives. In this study, with a review of the history and advantages of using silica fume and polypropylene fibers in concrete, 380 concrete laboratory samples were constructed, of which 25 mixing designs with water–cement ratio of 0.35 and fiber content of 0.2, 0.3, 0.4 and 0.5 of concrete volume and 7% silica fume were prepared according to the ACI standard in their manufacturing. In the present research, samples of Kevlar fiber containing silica fume were tested under flexural strength, abrasion resistance and hydraulic conductivity coefficient. According to achieved results, the optimum amount... 

    BF3.SiO2: An efficient heterogeneous alternative for regio-chemo and stereoselective Claisen-Schmidt condensation

    , Article Journal of the Iranian Chemical Society ; Volume 5, Issue 4 , 2008 , Pages 694-698 ; 1735207X (ISSN) Sadeghi, B ; Mirjalili, B. F ; Hashemi, M. M ; Sharif University of Technology
    Iranian Chemical Society  2008
    Under solvent free conditions between 40-50 °C, BF3.SiO 2, a mild solid acid catalyst, is applied to regio-chemo and stereoselective Claisen-Schmidt condensation. The procedure is very simple and the products are isolated with an easy workup in good to excellent yields