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silica
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Bactericidal effects of Ag nanoparticles immobilized on surface of SiO2 thin film with high concentration
, Article Current Applied Physics ; Volume 9, Issue 6 , 2009 , Pages 1381-1385 ; 15671739 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2009
Abstract
Bactericidal activity of high concentration Ag nanoparticles immobilized on surface of an aqueous sol-gel silica thin film was investigated against Escherichia coli and Staphylococcus aureus bacteria. Size of the surface nanoparticles was estimated in the range of 35-80 nm by using atomic force microscopy. Due to accumulation of the silver nanoparticles at near the surface (at depth of 6 nm and about 40 times greater than the silver concentration in the sol), the synthesized Ag-SiO2 thin film (with area of 10 mm2) presented strong antibacterial activities against E. coli and S. aureus bacteria with relative rate of reduction of the viable bacteria of 1.05 and 0.73 h-1 for initial...
Persistent superhydrophilicity of sol-gel derived nanoporous silica thin films
, Article Journal of Physics D: Applied Physics ; Volume 42, Issue 2 , 2009 ; 00223727 (ISSN) ; Azimirad, R ; Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
2009
Abstract
In this investigation, sol-gel synthesized nanoporous silica thin films, annealed at different temperatures, with long time superhydrophilic property have been studied. Two kinds of sol-gel silica thin films were fabricated by dip-coating of glass substrates in two different solutions; with low and high water. The transparent coated films were dried at 100 °C and then annealed in a temperature range of 200-500 °C. The average water contact angle of the silica films prepared with low water content and annealed at 300 °C measured about 5° for a long time (6 months) without any UV irradiation. Instead, adding water into the sol resulted in silica films with an average water contact angle...
Experimental and numerical study of low frequency pulsed Nd:YAG laser heating of slip cast fused silica ceramics for laser assisted turning process considering laser beam overlapping
, Article Scientia Iranica ; Volume 26, Issue 1B , 2019 , Pages 394-407 ; 10263098 (ISSN) ; Movahhedy, M. R ; Shoja Razavi, R ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low-thermal conductivity. Laser Assisted Machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on Slip Cast Fused Silica (SCFS) ceramics is investigated by conducting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for Laser Assisted Turning (LAT) of SCFS is performed using finite-element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters, such as...
Experimental and numerical study of low frequency pulsed Nd:YAG laser heating of slip cast fused silica ceramics for laser assisted turning process considering laser beam overlapping
, Article Scientia Iranica ; Volume 26, Issue 1B , 2019 , Pages 394-407 ; 10263098 (ISSN) ; Movahhedy, M. R ; Shoja Razavi, R ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low-thermal conductivity. Laser Assisted Machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, the effect of laser heating in the LAM process on Slip Cast Fused Silica (SCFS) ceramics is investigated by conducting a numerical thermal analysis of laser effects on material behavior. A transient three-dimensional heat transfer analysis for Laser Assisted Turning (LAT) of SCFS is performed using finite-element method. Temperature distributions in SCFS cylindrical specimens are obtained. Moreover, the influence of laser parameters, such as...
Efficient method for oxidation of ketones to esters with 4-aminoperoxybenzoic acid supported on silica gel
, Article Synthetic Communications ; Volume 38, Issue 12 , 2008 , Pages 2037-2042 ; 00397911 (ISSN) ; Hashemi, M. M ; Shahidi Zandi, M ; Sharif University of Technology
2008
Abstract
4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright © Taylor & Francis Group, LLC
Comparison between electron-beam and chemical crosslinking of silicone rubber
, Article Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ; Volume 243, Issue 2 , 2006 , Pages 354-358 ; 0168583X (ISSN) ; Dadbin, S ; Panahinia, F ; Sharif University of Technology
2006
Abstract
Silicone rubber (SR) was irradiated by electron beam over a dose range of 50-300 kGy in the absence of chemical reagents. Molecular weight between crosslinks (Mc) in the network of SB was determined by two methods of solvent swelling and modulus of elasticity. The network structure of the elastomer crosslinked by electron beam irradiation and chemical vulcanization was compared. Mechanical tests were performed to determine shore hardness, tensile elongation, strength and modulus of the samples. It was found that SR is effectively crosslinked by electron beam irradiation. The tensile strength, hardness, modulus and elongation of irradiated SR were higher than peroxide-crosslinked SR. The...
Hydrometallurgical treatment of tailings with high zinc content
, Article Hydrometallurgy ; Volume 82, Issue 1-2 , 2006 , Pages 54-62 ; 0304386X (ISSN) ; Rashchi, F ; Sadrnezhaad, S. K ; Sharif University of Technology
2006
Abstract
Zinc exists as smithsonite and hemimorphite in the lead flotation tailings from the Dandi mineral processing plant in north western Iran. In this research, zinc-rich tailings produced in the Dandi plant were characterized mineralogically and a leaching study was carried out to assess the effect of several parameters on the kinetics of zinc dissolution. Parameters studied included: sulfuric acid concentration, reaction time, temperature and slurry density. It was found that leaching is controlled by a single rate-controlling step with an activation energy of 23.5 kJ/mol. To overcome some of the filtration problems associated with polymerization of silicic acid, lime was added as a coagulant....
Removal of naphthalene from aqueous solutions by phosphorus doped-titanium dioxide coated on silica phosphoric acid under visible light
, Article Desalination and Water Treatment ; Volume 224 , 2021 , Pages 187-196 ; 19443994 (ISSN) ; Hassani, A. H ; Tirgir, F ; Fadaei, A ; Borghaei, S. M ; Sharif University of Technology
Desalination Publications
2021
Abstract
In this research, titanium dioxide-phosphorus (TiO2-P) immobilized on silica phosphoric acid (SPA) was prepared by a simple modified sol–gel method with SPA as a precursor instead of phosphoric acid. TiO2-P thin film photocatalyst immobilized on SPA as a novel high-efficiency photocatalyst was investigated to remove naphthalene as a toxic compound from wastewater. The novel resulting photocatalyst were characterized by energy-dispersive X-ray (EDX) and X-ray diffraction pattern revealed nano-photocatalyst TiO2-P with the average size of 15–20 nm. EDX analysis showed the presence of phosphorus elements in the crystalline structure of TiO2 and diffuse reflectance spectroscopy showed the energy...
Evolution of quantum electronic features with the size of silicon nanoparticles embedded in a SiO2 layer obtained by low energy ion implantation
, Article 11th International Autumn Meeting on Gettering and Defect Engineering in Semiconductor Technlogy, GADEST 2005, Giens, 25 September 2005 through 30 September 2005 ; Volume 108-109 , 2005 , Pages 71-76 ; 10120394 (ISSN); 3908451132 (ISBN); 9783908451136 (ISBN) ; Shalchian, M ; BenAssayag, G ; Coffin, H ; Bonafos, C ; Dumas, C ; Atarodi, S. M ; Claverie, A ; Sharif University of Technology
Trans Tech Publications Ltd
2005
Abstract
In this paper, we have studied the evolution of quantum electronic features with the size of silicon nanoparticles embedded in an ultra-thin SiO 2 layer. These nanoparticles were synthesized by ultralow energy (1 KeV) ion implantation and annealing. Their size was modified using the effect of annealing under slightly oxidizing ambient (N2+O2). Material characterization techniques including transmission electron microscopy (TEM) Fresnel imaging and spatially resolved electron energy loss spectroscopy (EELS) have been used to evaluate the effects of oxidation on structural characteristics of nanocrystal layer. Electrical transport characteristics have been measured on few (less than two...
Monitoring the influence of dispersed nano-particles on oil-water relative permeability hysteresis
, Article Journal of Petroleum Science and Engineering ; Vol. 124, issue , December , 2014 , p. 222-231 ; ISSN: 09204105 ; Masihi, M ; Ghazanfari, M. H ; Sharif University of Technology
Abstract
In recent years, polysilicon nanoparticles are used to enhance the oil recovery through the water injection process in oilfields. The contributing mechanisms are the reduction of interfacial tension and wettability alteration which lead to improving or decreasing the oil phase relative permeability and can be traced by change of relative permeability curves. However, profound understanding of the effect of dispersed nano-silica particles on the hysteretic behavior of relative permeability curves remains a controversy topic in the literature.The current study illustrates the influence of dispersed silica particles on hysteretic trend of two-phase curves of oil-water relative permeability....
Efficient fatty acid esterification using silica supported Brønsted acidic ionic liquid catalyst: Experimental study and DFT modeling
, Article Chemical Engineering Journal ; Vol. 250 , 2014 , Pages 35-41 ; ISSN: 13858947 ; Hashemi, M. M ; Sharif University of Technology
Abstract
A task-specific Brønsted acidic ionic liquid (BAIL), 1-benzyl-3-methylimidazolium hydrogensulfate ([BnMIm]HSO4), was prepared and confined onto the high surface area silica gel. The catalyst has shown extraordinary activity in comparison of homogeneous ionic liquid (IL) system for Fischer esterification of fatty acid with ethanol. The ester derivatives were synthesized in high yields and catalyst was easily separated from the reaction mixture by simple filtration. The structure of the catalyst is theoretically modelized to investigate the unusual catalytic activity. Hence, a hydroxylated cage-like nano-cluster, H6Si8O12(OH)2, was selected to mimic the surface of silica gel. The interactions...
Evaluation of biodiesel production using lipase immobilized on magnetic silica nanocomposite particles of various structures
, Article Biochemical Engineering Journal ; Volume 79 , 2013 , Pages 267-273 ; 1369703X (ISSN) ; Kazemeini, M ; Arpanaei, A ; Sharif University of Technology
2013
Abstract
Nonporous and mesoporous silica-coated magnetite cluster nanocomposites particles were fabricated with various silica structures in order to develop a desired carrier for the lipase immobilization and subsequent biodiesel production. Lipase from Pseudomonas cepacia was covalently bound to the amino-functionalized particles using glutaraldehyde as a coupling agent. The hybrid systems that were obtained exhibited high stability and easy recovery regardless of the silica structure, following the application of an external magnetic field. The immobilized lipases were then used as the recoverable biocatalyst in a transesterification reaction to convert the soybean oil to biodiesel with methanol....
Interactions between superabsorbent polymers and cement-based composites incorporating colloidal silica nanoparticles
, Article Cement and Concrete Composites ; Volume 37, Issue 1 , March , 2013 , Pages 196-204 ; 09589465 (ISSN) ; Fakoorpoor, S. M ; Hosseini, P ; Khaloo, A ; Sharif University of Technology
2013
Abstract
The relatively new applications of superabsorbent polymers (SAPs) in cement based materials call for investigations regarding their behaviors in relation to other constituents in the system. Colloidal silica nanoparticles (CS) are becoming increasingly important for the improvement of strength and durability of cement based materials. In this study, a poly (AA-co-AM) SAP was synthesized by free radical polymerization, and its behaviors in cement based composites incorporating CS were investigated. These included swelling behavior, setting time, mechanical performance in different curing conditions, and rheological properties of fresh pastes. The observation of an unusual reduction in...
Theoretical analysis of polymeric and crystalline thick films melting with a single gold nanoparticle embedded in a transparent matrix under nanosecond pulsed laser excitation
, Article Journal of Physics D: Applied Physics ; Volume 45, Issue 47 , 2012 ; 00223727 (ISSN) ; Bahrampour, A. R ; Pepe, G. P ; Sharif University of Technology
2012
Abstract
Optothermal properties of noble metal nanoparticles can be used in a wide range of applications. This paper presents the results of a theoretical study on the utilization of laser-induced heating of a gold nanoparticle (GNP) to melt a region of a transparent material with sub-wavelength spatial resolution. The considered system consists of a 10 or 15nm diameter GNP fixed inside a silica substrate. The silica surface is covered with a thick film of the transparent polymeric or crystalline material. The heating and melting processes are studied under a 7.5ns pulsed laser illumination. Calculations are conducted under three temperature limits, on the maximum temperature of the free electrons,...
Production and characterization of UHMWPE/fumed silica nanocomposites
, Article Polymer Composites ; Volume 33, Issue 10 , 2012 , Pages 1858-1864 ; 02728397 (ISSN) ; Saremi, M. G ; Amoli, B. N ; Izadi, H ; Sharif University of Technology
Wiley
2012
Abstract
Ultrahigh-molecular-weight polyethylene (UHMWPE)/fumed silica nanocomposites were prepared via in situ polymerization using a bi-supported Ziegler-Natta catalytic system. Nanocomposites with different nanoparticle weight fractions were produced in order to investigate the effect of fumed silica on thermal and mechanical properties of UHMWPE/fumed silica nanocomposites. The viscosity average molecular weight (M) of all samples including pure UHMWPE as the reference sample and nanocomposites were measured. Scanning electron microscope (SEM) images showed the homogenous dispersion of nanoparticles throughout the UHMWPE matrix while no nanoparticle cluster has been formed. Crystallization...
Reduction of cement consumption by the aid of silica nano-particles (investigation on concrete properties)
, Article Journal of Civil Engineering and Management ; Volume 18, Issue 3 , 2012 , Pages 416-425 ; 13923730 (ISSN) ; Hosseini, P ; Sharif University of Technology
2012
Abstract
In this study, effects of replacing cement with colloidal amorphous silica nano-particles have been experimentally investigated on the physical and mechanical properties, durability and microstructure of concrete. Experimental results include workability, fresh concrete density, and hardened concrete properties like compressive strength at different ages of 3, 7, and 28-days, and also 28-days splitting tensile strength. Furthermore, influence of silica nano-particles on durability and microstructure of concrete for 28-days specimens was tested by conducting water absorption test, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Analysis (EDAX), respectively. In order to study...
Evaluation of interfacial layer properties in the polystyrene/silica nanocomposite
, Article Journal of Applied Polymer Science ; Volume 119, Issue 4 , August , 2011 , Pages 2039-2047 ; 00218995 (ISSN) ; Farzi, G ; Kalaee, M. R ; Zabihpoor, M ; Sharif University of Technology
2011
Abstract
Processing conditions and final mechanical properties of polymer nanocomposites are affected by their interfacial layers behavior. However, it is impossible to determine directly the properties of these layers by dynamic rheometry tests. In this work, the interfacial layers properties are evaluated for polystyrene containing silica nanoparticles by the concept of glass-transition temperature shift. The samples were prepared via solution-mixing method and dynamic rheometry was used to determine the viscoelastic behavior of filled polymers in the melt state. This initial step showed that addition of silica particles increased the glass-transition temperature. By preference, decrease in the...
High-capacity hierarchically imprinted polymer beads for protein recognition and capture
, Article Angewandte Chemie - International Edition ; Volume 50, Issue 2 , December , 2011 , Pages 495-498 ; 14337851 (ISSN) ; Sun, W ; Aureliano, C. S. A ; Lütkemeyer, D ; Stute, J ; Abdekhodaie, M. J ; Shojaei, A ; Sellergren, B ; Sharif University of Technology
2011
Abstract
Leaving an imprint: Hierarchical protein imprinting starting from wide-pore silica modified with a submonolayer of adsorbed protein (IgG or HSA) leads to an inverse polymeric replica of the silica template that features highly accessible protein-complementary binding sites (see picture). The resulting poly(acrylamide) beads (PIgG or PHSA) feature high binding capacities and can be used to selectively capture the proteins HSA and IgG from blood serum
Magnetic graphene oxide mesoporous silica hybrid nanoparticles with dendritic pH sensitive moieties coated by PEGylated alginate-co-poly (acrylic acid) for targeted and controlled drug delivery purposes
, Article Journal of Polymer Research ; Volume 22, Issue 8 , 2015 ; 10229760 (ISSN) ; Shakerpoor, A ; Tehrani, Z. M ; Bumajdad, A ; Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
In this study synthesis of a drug delivery system (DDS) is described which has several merits over its counterparts. In order to synthesize this nano-carrier, graphene oxide nano-sheets are used to accommodate MCM-41 nanoparticles. Furthermore Fe3 O4 nanoparticles are introduced to this nano-material to produce a traceable nanoparticle. Since cancerous tissues have lower pH than healthy tissues, pH-sensitive oligomers are attached to this nano-material. Finally the nano-carrier is wrapped by a biocompatible shell (PEGylated sodium alginate); this polymeric shell makes the DDS capable of a more controllable drug release. By measuring in vitro situation, ‘loading content%’...
The simultaneous effect of silica nanoparticles and rubber particles on the toughness of epoxy polymer
, Article International Journal of Nanomanufacturing ; Volume 5, Issue 3-4 , 2010 , Pages 232-244 ; 17469392 (ISSN) ; Bagheri, R ; Sharif University of Technology
2010
Abstract
The objective of this study is to investigate the effects of both rubbery phase and nanosilica on mechanical properties of epoxy. Three series of formulations based on epoxy including nanosilica, rubber and rubber/nanosilica were prepared. Transmission electron microscopy showed that nanoparticles were homogeneously dispersed throughout the epoxy matrix. Compression and fracture toughness tests along with scanning electron microscopy and transmission optical microscopy were also done to evaluate the properties of the compounds. Although the results of compression tests indicate that addition of nanosilica could not change elastic modulus and yield strength of neat resin significantly,...