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silicon-dioxide
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The Effect of Nano-TiO2 and CaF2 Additives on Formulation and Properties of SiO2-Li2O Glass-Ceramics
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor)
Abstract
The goal of the present study is to analyze the effect of CaF2 and nano-TiO2 as additives on formulation and properties of common dental glass-ceramics. To achieve the goal, a glass system based on SiO2-Al2O3-Li2O-K2O-P2O5-ZnO-ZrO2 was considered to produce glass-ceramic samples and the additives, nano-TiO2 and CaF2, with the 0.5, 1, and 1.5 %Wt was added to the system. After the melting process, the glass samples poured in the water and ferrite was produced. In the next step, the ferrite was milled and pressed. In the heat treatment step, the samples were treated in the temperature range of 650-850°C in order to gain lithium disilicate glass-ceramics. In the last step, the chemical...
Synthesis of Super Hydrophobic and Anti-Wear Coating with SiO2 and SiC Nano Particles on Glass Surface )
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
In this research we developed a superhydrophobic and anti-wear coating on a glass substrate using SiO2 nanoparticles to form a transparent superhydrophobic thin film and SiC nanoparticles to improve the wear resistance of coating.
Silica nanoparticles were produced via a simple sol gel method from Tetraethylorthosilicate (TEOS) as precursor. Hexamethyldisilazane (HMDS) and Tetramethylclourosilane (TMCS) were used as hydrophobic inducing agents and at last SiC nanoparticles were dispersed in the solution in order to provide wear resistance. The final results indicate the contact angle (CA) of water droplet on the surface was about 158° and sliding angle (SA) lower than 9°. Studying the...
Silica nanoparticles were produced via a simple sol gel method from Tetraethylorthosilicate (TEOS) as precursor. Hexamethyldisilazane (HMDS) and Tetramethylclourosilane (TMCS) were used as hydrophobic inducing agents and at last SiC nanoparticles were dispersed in the solution in order to provide wear resistance. The final results indicate the contact angle (CA) of water droplet on the surface was about 158° and sliding angle (SA) lower than 9°. Studying the...
Surface and Interface Effects on the Elastic Fields of an Edge Dislocation Inside a Silicon Nanotube with Thin Siox Coating
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
The exact analytical elastic fields within a double-walled silicon nano-tube with a thin layer of SiOx coating associated with surface/ interface effects as well as the classical theory of elasticity due to the presence of an edge dislocation with an arbitrary Burger’s vector and position inside of the silicon is determined via complex potential function method. Stress contours within surface elasticity and classical theory are given, and both theory results are compared. Then, the effects of surface Lamé Constants, magnitude and direction of Burger’s vector, shear modulus, nano-tube size, and position of the edge dislocation on the distribution of stress components are illustrated, and the...
Investigating The Mechanical Properties Of Two-Dimensional Silicon Dioxide With Inherent Negative Poisson's Ratio by Molecular Dynamics Method
,
M.Sc. Thesis
Sharif University of Technology
;
Tavakoli, Ruholah
(Supervisor)
Abstract
Silicon dioxide or silica with the chemical formula SiO2 is the basic component of many minerals. SiO2 films and sheets are widely used in mechanics, optics and electronics due to their outstanding mechanical and electronic performance. The main reason for research in the field of materials with negative Poisson's ratio is their unusual properties, which arise due to the inherent property of negative Poisson's ratio. In this research, the mechanical properties of four two-dimensional silica structures at a temperature of one Kelvin were investigated with the help of molecular dynamics simulation. Also, the sensitivity of the results to the system size and strain rate was studied, and the...
Molybdenum liquid salts immobilized on ionic liquid-modified silica as efficient heterogeneous catalysts for sulfoxide reduction
, Article Tetrahedron Letters ; Volume 54, Issue 29 , 2013 , Pages 3765-3768 ; 00404039 (ISSN) ; Ghazali Esfahani, S ; Sharif University of Technology
2013
Abstract
Two room temperature liquid salts containing molybdenum(VI), [BMIM] 2[MoO2(NCS)4] (1) and [DMIM] 2[MoO2(NCS)4] (2), were immobilized on ionic liquid-modified silica leading to materials which showed notable catalytic activity for the reduction of sulfoxides into sulfides with triphenylphosphine (PPh3). The molybdenum liquid salts immobilized on the supported ionic liquid phase could be reused at least for three catalytic cycles without significant loss of activity
Green synthesis of silica nanoparticles from olive residue and investigation of their anticancer potential
, Article Nanomedicine ; Volume 16, Issue 18 , 2021 , Pages 1581-1593 ; 17435889 (ISSN) ; Afjoul, H ; Shamloo, A ; Maleki, A ; Afjoul, N ; Sharif University of Technology
Future Medicine Ltd
2021
Abstract
Graphical abstract
Enhanced Superhydrophobic and Photocatalytic Characteristics of Tio2 Hybrid Nanocoating for Self-cleaning Applications
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Many researches have been made on super hydrophobic and photocatalyst nano coatings in the last decades as a solution to some environmental issues. Among all semiconductors chosen for this property, titanium dioxide is often used because of it's low cost, ease of accessibility and stability in different chemical circumstances to break up organic pollutions. Mixing this property of TiO2 with hydrophobic manner of SiO2 causes a superhydrophobe & photocatalyst nano coating. Doping TiO2 with another semiconductor may also improve photocatalytic behavior of coating by increasing surface area of reaction or decreasing the band-gap.In this research TiO2-SiO2 hybrid nano coating is made via...
Physiological temperature has a crucial role in amyloid beta in the absence and presence of hydrophobic and hydrophilic nanoparticles
, Article ACS Chemical Neuroscience ; Volume 4, Issue 3 , December , 2013 , Pages 375-378 ; 19487193 (ISSN) ; Rezaei, M ; Ejtehadi, R ; Lotfi, M ; Shokrgozar, M. A ; Abd Emamy, B ; Raush, J ; Mahmoudi, M ; Sharif University of Technology
2013
Abstract
Amyloid beta fibrillation can lead to major disorder of neurons processes and is associated with several neuronal diseases (e.g., Alzheimer's disease). We report here an importance of slight temperature changes, in the physiological range (35-42 °C), on the amyloid fibrillation process in the presence and absence of hydrophilic (silica) and hydrophobic (polystyrene) nanoparticles (NPs). The results highlight the fact that slight increases in temperature can induce inhibitory and acceleratory effects of hydrophobic and hydrophilic NPs on the fibrillation process, respectively. Using further in vivo considerations, the outcomes of this study can be used for considerable modifications on the...
New grafted nanosilica-based sorbent for needle trap extraction of polycyclic aromatic hydrocarbons from water samples followed by GC/MS
, Article Chromatographia ; Volume 74, Issue 5-6 , September , 2011 , Pages 429-436 ; 00095893 (ISSN) ; Roostaie, A ; Babanezhad, E ; Sharif University of Technology
2011
Abstract
In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes...
Immobilization of a molybdenum complex on the surface of magnetic nanoparticles for the catalytic epoxidation of olefins
, Article New Journal of Chemistry ; Volume 40, Issue 2 , 2016 , Pages 1580-1586 ; 11440546 (ISSN) ; Moradi Shoeili, Z ; Bagher Zadeh, M ; Akbayrak, S ; Özkar, S ; Sharif University of Technology
Royal Society of Chemistry
Abstract
Novel organic-inorganic hybrid heterogeneous nanocatalysts were obtained by covalent anchoring of a molybdenum(vi) complex of salicylidene 2-picoloyl hydrazine, MoO2(sal-phz)(CH3OH), (1) on the surface of magnetic nanoparticles functionalized by one of two routes: in the first method, the surface of magnetic nanoparticles is directly modified with 3-chloropropyltrimethoxysilane yielding 1A. In the second method, magnetic nanoparticles were silica-coated with tetraethoxysilane and then with 3-chloropropyltrimethoxysilane yielding the intermediate 2B. Then complex 1 was grafted on the surface of 1A or 2B through covalent interaction yielding 2A or 3B, respectively. The nanocatalysts 2A and 3B...
Imprinted silica nanofiber formation via sol-gel-electrospinning for selective micro solid phase extraction
, Article New Journal of Chemistry ; Volume 42, Issue 16 , 2018 , Pages 13864-13872 ; 11440546 (ISSN) ; Bagheri, H ; Es Haghi, A ; Sharif University of Technology
Royal Society of Chemistry
2018
Abstract
Sol composition and ripening conditions are two important parameters in silica fiber production through the conventional sol-gel process. In the current study, silica nanofibers were successfully obtained via the electrospinning technique, and sol-gel formation occurred during this process. Based on previous reports, with the aim of increasing the selectivity, we used the molecular imprinted methodology to produce a selective medium via sol-gel electrospinning. In this process, sol-gel was formed during electrospinning and then, the backbone polymer was removed by heating. To obtain a thin layer of silica nanofibers, the influencing parameters such as backbone polymer types, imprinting time...
Highly efficient Michael addition reaction of amines catalyzed by silica-supported aluminum chloride
, Article Synthetic Communications ; Volume 39, Issue 6 , 2009 , Pages 1109-1119 ; 00397911 (ISSN) ; Pourshojaei, Y ; Aryanasab, F ; Sharif University of Technology
2009
Abstract
Aliphatic and aromatic amines undergo smooth nucleophilic addition to α,β-unsaturated compounds in the presence of a catalytic amount of silica-supported aluminum chloride at 60°C and under solvent-free conditions to produce the corresponding β-amino compounds in excellent yields. This method is simple and convenient and works efficiently under mild conditions. This catalyst can used again without losing its activity three times. Copyright © Taylor & Francis Group, LLC
Grafted CMC/silica gel superabsorbent composite: Synthesis and investigation of swelling behavior in various media
, Article Journal of Applied Polymer Science ; Volume 108, Issue 5 , 2008 , Pages 3281-3290 ; 00218995 (ISSN) ; Seidi, F ; Salimi, H ; Soleyman, R ; Sharif University of Technology
2008
Abstract
In the present study, we attempt to synthesize and characterize novel CMC-g-poly (acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid)/silica gel composite. Infrared spectroscopy and TGA thermal analysis were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy. The effect of reaction variables affecting on water absorbency of the composite and swelling behavior in various solvents, salt, and pH solutions was investigated. Maximum water absorbency of the optimized final product was found to be 4000 g/g in distilled water. The absorbency under load (AUL) of the hydrogel was also determined by...
Evaluation of bio-compatible poly(ethylene glycol)-based solid-phase microextraction fiber for in vivo pharmacokinetic studies of diazepam in dogs
, Article Analyst ; Volume 132, Issue 7 , 2007 , Pages 672-678 ; 00032654 (ISSN) ; Zhang, X ; Musteata, F. M ; Bagheri, H ; Pawliszyn, J ; Sharif University of Technology
Royal Society of Chemistry
2007
Abstract
Solid-phase microextraction probes based on poly(ethylene glycol)/C18-bonded silica were used for in vivo monitoring of drugs from circulating blood of beagles, over a period of 8 h. After sampling, the extracted drugs were subsequently quantified by liquid chromatography coupled with tandem mass spectrometry. External calibrations in whole blood and phosphate-buffered saline were used to correlate the amount of analytes extracted in regard to the total and free concentrations in blood respectively. The probe provided sufficient sensitivity for the drugs in the blood matrix, while the need for drawing blood was eliminated. The limit of detections of the method from whole blood were 1.7, 1.4...
Solid state oxidation of phenols to quinones with ammonium persulfate/wet SiO2
, Article Journal of Chemical Research ; Issue 3 , 2005 , Pages 160-161 ; 03082342 (ISSN) ; Karimi Jaberi, Z ; Eftekhari Sis, B ; Sharif University of Technology
Scientific Reviews Ltd
2005
Abstract
A solid state method for the oxidation of phenols to quinones is described using ammonium persulfate/wet silica gel as oxidant
Efficient aerobic oxidation of alcohols using a novel combination N-hydroxy phthalimide (NHPI) and a recyclable heterogeneous cobalt complex
, Article Journal of Molecular Catalysis A: Chemical ; Volume 232, Issue 1-2 , 2005 , Pages 95-99 ; 13811169 (ISSN) ; Karimi, B ; Sharif University of Technology
2005
Abstract
A novel combination between N-hydroxy phthalimide (NHPI) and a silica based cobalt (II) interphase catalyst (1) efficiently catalyzes the aerobic oxidation of various types of alcohols to the corresponding carbonyl compounds. The catalyst 1 shows high thermal stability and also could be recovered and reused in combination with NHPI for at least five reaction cycles without considerable loss of reactivity. © 2005 Elsevier B.V. All rights reserved
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....
Photoactive and self-cleaning TiO 2-SiO 2 thin films on 316L stainless steel
, Article Thin Solid Films ; Volume 520, Issue 20 , 2012 , Pages 6355-6360 ; 00406090 (ISSN) ; Afshar, A ; Dolati, A ; Sharif University of Technology
Abstract
In this study, TiO 2-SiO 2 nanocomposite films with different amounts of SiO 2 were prepared by sol-gel process and were coated onto stainless steel 316L. The effect of addition of various amount of SiO 2 in the precursor solution on the photocatalysis, photo-generated hydrophilicity and self-cleaning property of TiO 2 thin films was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements and UV spectroscopy. In the tested ranges of SiO 2 content and sintering temperature, the highest photocatalytic activity and self-cleaning property were observed in the 15 mol% SiO 2 sample sintered at 750 °C. Addition of less than 30 mol% SiO 2 had a...
Study on modification of colloidal silica surface with magnesium ions
, Article Journal of Colloid and Interface Science ; 2009 , Pages 379-383 ; 00219797 (ISSN) ; Sharif University of Technology
2009
Abstract
The prepared colloidal silica via ion exchange was modified by adding Mg+2 ions in the surface growth process of colloidal silica. The particle size of the modified colloidal silica was decreased by increasing the seed concentration, whereas that of colloidal silica was slightly increased as the seeds concentration exceed 15 wt%. But the trend of changes in surface area was completely reversed. Magnesium ions on surface of the modified colloidal silica were identified by the measurement of energy-dispersive X-ray spectrometry (EDS). After modifying with Mg+2 ions, the iso-electric point (IEP) of colloidal silica in pH ∼ 2 without modification, disappears over the whole pH range. © 2008...
Remediation of trapped DNAPL enhanced by SDS surfactant and silica nanoparticles in heterogeneous porous media: experimental data and empirical models
, Article Environmental Science and Pollution Research ; Volume 27, Issue 3 , 2020 , Pages 2658-2669 ; Khasi, S ; Fatemi, M ; Ghazanfari, M. H ; Sharif University of Technology
Springer
2020
Abstract
The remediation of nonaqueous phase liquids (NAPLs) enhanced by surfactant and nanoparticles (NP) has been investigated in numerous studies. However, the role of NP-assisted surfactants in the dissolution process is still not well discussed. Besides, there is a lack of empirical dissolution models considering the effects of initial residual saturation Strap, NAPL distribution, and surfactant concentration in NAPL-aqueous phase systems. In this work, micromodel experiments are conducted to quantify mass transfer coefficients for different injected aqueous phases including deionized water, SDS surfactant solutions, and NP-assisted solutions with different levels of concentrations and flow...