Loading...
Search for:
nanomaterial
0.009 seconds
Total 124 records
Immobilized polyoxomolybdate nanoclusters on functionalized sba-15: green access to efficient and recyclable nanocatalyst for the epoxidation of alkenes
, Article ChemistrySelect ; Volume 4, Issue 19 , 2019 , Pages 5911-5917 ; 23656549 (ISSN) ; Hosseini, H ; Akbayrak, S ; Özkar, S ; Sharif University of Technology
Wiley-Blackwell
2019
Abstract
A heterogeneous nanocatalyst containing polyoxomolybdate immobilized on the internal surface of amino-functionalized SBA-15 pores was prepared and fully characterized by several analytical techniques. The textural property of supported material was found to retain important mesoporous features, compatible with its potential use as heterogeneous catalysts. The catalyst SBA-15-NH3+•{Mo36}–shows excellent catalytic activity for the epoxidation of alkenes as compared to POM, which is attributed to the large specific surface area and highly ordered pore structure of SBA-15, allowing for easy access of reactants to the active sites and removal of products. The prepared catalyst has high...
ZnS nanocrystals embedded in SiO2 matrix
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 21, Issue 1 , 2004 , Pages 96-102 ; 13869477 (ISSN) ; Yao, T ; Sharif University of Technology
2004
Abstract
Growing nanocrystals in a matrix is a way to have separate, non-agglomerated nanoparticles, which are surface passivated and stabilized against environmental attacks. To create nanocrystals of the desired size and properties in a matrix, it is required that the growth parameters are properly tuned. In this work, we study the growth parameters for ZnS nanocrystals in an SiO2 matrix. Samples were prepared by cosputtering of SiO 2 and ZnS on a silica substrate, followed by annealing at different temperatures. Two categories of samples with low-content ZnS (4 mol%) and high-content ZnS (15 mol%) were examined. In the low-content samples, ZnS nanocrystals are not formed below 900°C annealing...
The wet precipitation process of hydroxyapatite
, Article Materials Letters ; Volume 57, Issue 24-25 , 2003 , Pages 4064-4069 ; 0167577X (ISSN) ; Afshar, A ; Ghorbani, M ; Ehsani, N ; Sorrell, C. C ; Sharif University of Technology
2003
Abstract
Stoichiometric hydroxyapatite (HA) powder was synthesized by wet method using orthophosphoric acid and calcium hydroxide, as raw materials. In this regard, the time-depending changes of the precipitated particles and effects of heating on them were investigated. The as-precipitated and heated powder samples were examined using field emission electron microscopy (FESEM), XRD and Raman spectroscopy methods. The results revealed that the morphology and size of the precipitated particles change in each stage of the process. After drying, these nanoparticles tend to form small agglomerates. © 2003 Elsevier Science B.V. All rights reserved
Formation of carbon nanotubes in Iron-catalyzed arcing method: Effect of iron-ion charge in the aqueous medium [electronic resource]
, Article International Journal of Modern Physics B Condensed Matter Physics; Statistical Physics; Atomic, Molecular and Optical Physics ; 30 December 2011, Volume 25, Issue 32, PP. 4411-4417 ; Gheytani, S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
Abstract
Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe2+]/[Fe3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism
Cytotoxicity of carbon nanotube/polycitric acid hybrid nanomaterials
, Article Iranian Polymer Journal (English Edition) ; Vol. 23, issue. 3 , 2014 , pp. 195-201 ; ISSN: 10261265 ; Alavidjeh, M. S ; Mohammadifar, E ; Sharif University of Technology
Abstract
Polycitric acid was conjugated onto the surface of carbon nanotubes (CNTs), and hybrid nanomaterials containing CNT axis and polycitric acid branches that were highly soluble in aqueous solutions were synthesized. In this work, pristine MWCNTs were opened and functionalized through treatment with acid, then polycitric acid was covalently grafted onto their surface by the "grafting from" approach based on polycondensation of citric acid in the melting state. The chemical structure, morphology, thermal properties and size of MWCNT-g-PCA hybrid materials were investigated by IR, 13C NMR, 1H NMR, TEM, TGA, DSC and DLS. To investigate the biocompatibility of the synthesized hybrid nanomaterials...
Formation of carbon nanotubes in iron-catalyzed liquid arcing method: Effect of iron-ion charge in the aqueous medium
, Article International Journal of Modern Physics B ; Volume 25, Issue 32 , 2011 , Pages 4411-4417 ; 02179792 (ISSN) ; Gheytani, S ; Simchi, A ; Sharif University of Technology
2011
Abstract
Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe 2+]/[Fe 3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism
Supramolecular hybrid nanomaterials as drug delivery systems
, Article Supramolecular Chemistry ; Volume 23, Issue 6 , Apr , 2011 , Pages 411-418 ; 10610278 (ISSN) ; Hakimpour, F ; Sagvand, M ; Jaafari, M. R ; Kabiri, R ; Moshari, Z ; Sharif University of Technology
2011
Abstract
Highly fluorescent and water-soluble cadmium selenide quantum dots (QDs) functionalised by thio-cyclodextrin (HS-CD) and mercaptoacetic acid (MAA) as surface coating agents (QDs-CD-MAA) were synthesised successfully. The synthesised hybrid nanomaterials, QDs-CD-MAA, were able to form water-soluble complexes with paclitaxel and folic acid. QDs and their complexes were characterised by usual spectroscopy and microscopy methods. Size and morphology of functionalised QDs were dependent on their capping agents and guest molecules. Short-term in vitro cytotoxicity tests on mouse tissue connective fibroblast adhesive cells (L929) showed that conjugation of CD molecules onto the surface of QDs...
A novel nanocomposite with superior antibacterial activity: a silver-based metal organic framework embellished with graphene oxide
, Article Advanced Materials Interfaces ; Volume 5, Issue 11 , 3 April , 2018 ; 21967350 (ISSN) ; Arabi Shamsabadi, A ; Sharifian Gh, M ; Rahimpour, A ; Soroush, M ; Sharif University of Technology
Wiley-VCH Verlag
2018
Abstract
Silver-based nanomaterials have attracted considerable attention due to their antimicrobial activities. In this work, a silver (Ag)-based metal organic framework (Ag-MOF) is embellished with graphene-oxide (GO), leading to the fabrication of a novel Ag-based nanocomposite (GO-Ag-MOF) whose biocidal activity is higher than those of Ag-MOF and GO nanomaterials. The nanocomposite is characterized using X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectra, ultraviolet−visible absorption spectra, X-ray powder diffraction, dynamic light scattering, and nitrogen gas adsorption/desorption. The characterization shows that...
Single-layer MoS2-MoO3-x heterojunction nanosheets with simultaneous photoluminescence and co-photocatalytic features
, Article Catalysts ; Volume 11, Issue 12 , 2021 ; 20734344 (ISSN) ; Akhavan, O ; Fazli, H ; Sharif University of Technology
MDPI
2021
Abstract
Single-layer MoS2-MoO3-x heterojunction nanosheets with visible-light-sensitive band gap energy and average lateral dimensions of ~70 nm were synthesized by using a two-step combined exfoliation method. The exfoliation was initiated from pristine MoS2, while some sulfur sites in expanded MoS2 sheets during exfoliating were substituted by ambient non-thermal oxygen, resulting in formation of α-MoO3-x crystalline domains. The morphological features, crystalline structure, phase formation, number of layers, and optical properties of the MoS2-MoO3-x nanosheets were determined by atomic force microscopy; X-ray diffraction; field emission electron microscopy; transmission electron microscopy; and...
Stabilization of Collapsible Soil with Nano-Material and Injection using Electrokinetic Procedure .Case Study: Gorgan Loess
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohsen (Supervisor)
Abstract
Collapsible soils, a kind of which is Loess, are mainly in silt size in the nature, and are present in many part of Iran, such as Golestan, Semnan, Khorasan, Yazd, Kerman, Hormozgan, Sistan and Balouchestan provinces. when the water content of the soil is lower than a critical water content, the soil shows high shear strength. However, increase in water content due to leakage of water, wastewater or heavy rains in the presence of enough induced pressure, when a certain coupled hydro-mechanical condition is reached, will result in a sudden collapse or excessive deformation. Hence, improvement or stabilization of this kind of soil is of high importance. In this research, specimens are prepared...
Evaluation of using different nanomaterials to stabilize the collapsible loessial soil
, Article International Journal of Civil Engineering ; 2020 ; Valishzadeh, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
Construction over problematic soils is a common problem in many parts of the world, and one of the effective procedures to tackle this problem is soil stabilization. Accordingly, the current study provides the finding of a laboratory investigation into the effect of three kinds of nanomaterials, including nano-silica (NS), nano-clay (NC) and nano-calcium carbonate (NCC) on the properties of a loessial collapsible soil. To accomplish this issue, reconstituted samples of the stabilized loessial soil were prepared for unconfined compression and consolidation tests. The results illustrated that an insignificant amount of nanomaterials (less than 1% of the total dry weight of the soil when is...
Ab initio study of AMBO3 (A = Li, Na and M = Mn, Fe, Co, Ni) as cathode materials for Li-ion and Na-Ion batteries
, Article ACS Omega ; Volume 5, Issue 15 , April , 2020 , Pages 8952-8961 ; Hafizi Barjini, M ; Momeni, M ; Sharif University of Technology
American Chemical Society
2020
Abstract
According to the importance of polyanion cathode materials in intercalation batteries, they may play a significant role in energy-storage systems. Here, evaluations of LiMBO3 and NaMBO3 (M = Mn, Fe, Co, Ni) as cathode materials of Li-ion and Na-ion batteries, respectively, are performed in the density functional theory (DFT) framework. The structural properties, structural stability after deintercalation, cell voltage, electrical conductivity, and rate capability of the cathodes are assessed. As a result, Li compounds have more structural stability and energy density than Na compounds in the C2/c frame structure. Cell voltage is increased by increasing the atomic number of the transition...
Evaluation of using different nanomaterials to stabilize the collapsible loessial soil
, Article International Journal of Civil Engineering ; Volume 19, Issue 5 , 2021 , Pages 583-594 ; 17350522 (ISSN) ; Valishzadeh, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Construction over problematic soils is a common problem in many parts of the world, and one of the effective procedures to tackle this problem is soil stabilization. Accordingly, the current study provides the finding of a laboratory investigation into the effect of three kinds of nanomaterials, including nano-silica (NS), nano-clay (NC) and nano-calcium carbonate (NCC) on the properties of a loessial collapsible soil. To accomplish this issue, reconstituted samples of the stabilized loessial soil were prepared for unconfined compression and consolidation tests. The results illustrated that an insignificant amount of nanomaterials (less than 1% of the total dry weight of the soil when is...
Investigating the rheological properties of nanofluids of water/hybrid nanostructure of spherical silica/MWCNT
, Article Thermochimica Acta ; Volume 578 , 20 February , 2014 , Pages 53-58 ; ISSN: 00406031 ; Rashidi, A ; Soleimanisalim, A. H ; Rashtchian, D ; Sharif University of Technology
Abstract
Regarding the importance of rheological properties of water based drilling fluids, the effects of silica nanospheres, multiwall carbon nanotubes (MWCNTs) and two types of their hybrid, i.e. H1 (80 wt.% silica nanosphere/20 wt.% MWCNT) and H2 (50 wt.% silica nanosphere/50 wt.% MWCNT) on the viscosity and density of distilled water were investigated. According to the results, viscosity and density of the nanofluids increased with the concentration, while they were reduced by increasing the temperature. At high concentrations, the least increase in the viscosity of distilled water by adding the nanomaterials is related to H2 (8.2% increase at 1.0 wt.%). Likewise, the optimum operating...
Coating of Sewage Pipes with Appropriate Nanomaterials Aimed at Preventing Biological Growth (Algae+Biofilm)
, M.Sc. Thesis Sharif University of Technology ; Borghei, Mehdi (Supervisor) ; Ghasemi, Shahnaz (Co-Supervisor)
Abstract
Biological layers are one of the main problems related to water transfer with pipe lines which are formed through time in the inner surface of the pipes by the water nutrients. Hence, the inner surfaces in the pipe lines and water refineries should be made in order not to let these biological layers to be made. The reason is that when the biofilm is formed on these surfaces, the traversing water is polluted. Dredging of these pipes is not only necessary in most of the countries in the world and needs huge amounts of water but is also very complex and expensive.In this research, nanomaterials, namely ZnO, T〖iO〗_2،S〖iO〗_2 have been used to cover the surface of concrete and steel pipes (The...
Studying the Interaction Between Dislocation Sandin Homogeneities in Nano-Scale, by Incorporating Surface Effect
,
M.Sc. Thesis
Sharif University of Technology
;
Mohammadi Shodja, Hossein
(Supervisor)
Abstract
By considering the effect of surface/interface stress, classical problems of the interaction between dislocations and inhomogeneities are addressed. Especifically two distinct problems are solved, the first one is consisted of an edge dislocation located near an elliptical nano-inhomogeneity and the second one hasa screw dislocation laid in the core-shell nanowire. The stress field as well as the image force on the dislocation are calculated and discussed in detail. Results show that by decreasing the dimension of the problem to nano-scale, the differences between classical elasticity and surface approachincrease rapidly. By considering the effect of the surface/interface stress, new...
Study of Lithium-transition Metals-orthosilicates as Cathode Materials for Li-ion Batteries
, Ph.D. Dissertation Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
In this study, orthosilicate materials with chemical formula of Li2MSiO4 (M one or two transition metal/metals) were investigated experimentally and theoretically as cathode material of Li-ion batteries. The most important material in this category i.e. Li2FeSiO4 was synthesized by three methods including nitrate-based sol-gel, oxalate-based solid state reaction and oxide-based solid state reaction. Based on XRD and SEM evaluations, grain size of synthesized powders was estimated to be between 15 to 100 nanometers. Of these three methods, oxide-based solid state reaction was employed in this study for the first time. This syntheses method is very important due to the significant lower...
A Temperature Dependant Multiscale Modeling of Crack Growth in Nano Materials
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
The fact that materials and crack behave differently under different temperatures, brings a need for further investigation in this field. Recent studies regarding this behavior are mainly based on molecular dynamic method. While this method garuntee a highpercicion, the computational costs of this method can be high when dealing with crack propagation problem. Taking advantage of multiscale methods allows us to overcome this challenge by reducing the calculation time while providing acceptable results. In this research a multi-scale method capable of considering thermal effects has been developed. A concurrent model is created by using theory of elasticity for continuum part and taking...
Synthesis and Characterization of TiO2 Nanoparticles for Enhanced Oil Recovery Applications
, Ph.D. Dissertation Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Ahadian, Mohammad Mahdi (Supervisor) ; Vosoughi, Manouchehr (Co-Advisor)
Abstract
Enhanced oil recovery (EOR) techniques are gaining more attention worldwide as the proved oil is declining and the oil price is hiking. Although many giant oil reservoirs around the world were already screened for EOR processes, the main challenges such as low sweep efficiency, costly techniques, possible formation damages, transportation of huge amounts of EOR agents to the fields especially for offshore cases and the lack of analyzing tools in traditional experimental works, hinder the proposed EOR process.It has been shown that recently, nanoparticles are attractive agents to enhance the oil recovery at the laboratory scale.
In this study TiO2 nanoparticles were used to improve...
In this study TiO2 nanoparticles were used to improve...
On the growth sequence of highly ordered nanoporous anodic aluminium oxide
, Article Materials and Design ; Volume 27, Issue 10 , 2006 , Pages 983-988 ; 02613069 (ISSN) ; Nasirpouri, F ; Iraji zad, A ; Saedi, A ; Sharif University of Technology
Elsevier Ltd
2006
Abstract
Anodic aluminium oxide films were fabricated by well known two-step anodizing process in oxalic acid electrolyte. The ordering characteristics (ordered pore domains, average pore diameter size and through-pore arrangement) of anodic aluminium oxide films, obtained in different growth sequences, were identified by microscopic analysis such as ex situ contact-mode atomic force microcopy and scanning electron microscopy. Flattened areas in which some pits are seen mostly cover the electropolished surface of aluminium. Single anodizing of aluminium produces a broad distribution of nanopore size, whereas induces a highly ordered hemispherical pattern, which plays the ordered nucleation sites for...