Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Synthesis and characterization of magnetic nanoparticles coated with silica through a sol-gel approach
Andrade, A. L.;Souza, D. M.;Pereira, M. C.;Fabris, J. D.;Domingues, R. Z.;
Ceramica , 2009, DOI: 10.1590/S0366-69132009000400013
Abstract: this paper investigates the influence of reaction medium ph on silica-coating of magnetite nanoparticles. magnetite nanoparticles were prepared by means of a reduction-precipitation method using ferric chloride as a starting material, which was partially reduced to ferrous salts by na2so3 before alkalinizing with ammonia. the particles were coated by sol-gel method with either ammonia or hcl aqueous solutions for either base- or acid-catalyzed hydrolysis, respectively. powder x-ray diffraction, fourier-transform infrared, and zeta potential were used for the characterization of oxides and of the coated magnetic nanoparticles. the observed difference of phiep in kcl solution for pure silica (2.0), magnetite (5.0), and silica-coated magnetite (2.3) samples confirms that the coating process was effective since the charge surface properties of coated magnetic nanoparticles are close to that of pure silica, even though the fourier-transform infrared spectra did not evidence the formation of fe-o-si bonds.
Synthesis of Silica Nanoparticles by Sol-Gel: Size-Dependent Properties, Surface Modification, and Applications in Silica-Polymer Nanocomposites—A Review
Ismail Ab Rahman,Vejayakumaran Padavettan
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/132424
Abstract: Application of silica nanoparticles as fillers in the preparation of nanocomposite of polymers has drawn much attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nanocomposites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique. The effect of nanosilica on the properties of various types of silica-polymer composites is also summarized.
Preparation And Characterization Of Magnetite Nanoparticles By Sol-Gel Method For Water Treatment
International Journal of Innovative Research in Science, Engineering and Technology , 2013,
Abstract: Environmental Pollution Such As Dyes Has Been Excessively Released Into The Environment And Has Created A Major Global Concern. Congo Red Is A Benzidine-Based Anionic Diazo Dye With Two Azo Groups. It Is Toxic To Many Organisms And Is A Suspected Carcinogen And Mutagen. The Presence Of Congo Red (CR) In Water Even At Very Low Concentration Is Highly Visible And Undesirable. Present Work Is Focused On Synthesis Of Magnetite Nanoparticles Which Showed A High Adsorption Capacity Of Congo Red And Is Useful In Removal Of CR From Wastewater. Magnetite (Fe3O4) Nanoparticles Have Been Successfully Synthesized By Sol–Gel Method By Using Ferric Nitrate (Fe (NO3)3.9H2O) And Ethylene Glycol (C2H6O2) As Precursors In Different Annealing Temperatures. The Obtained Nanoparticles Have Been Characterized By X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), X-Ray Energy Dispersive Spectrometer (EDS) And Particle Size Analyzer. XRD Measurements Indicate That The Obtained Nanoparticles Are Single Phase And The Particle Size Increased By Increasing The Temperature.
Characterization and Modification of Mesoporous Silica Nanoparticles Prepared by Sol-Gel  [PDF]
Meysam Keshavarz,Norhayati Ahmad
Journal of Nanoparticles , 2013, DOI: 10.1155/2013/102823
Abstract: Mesoporous silica nanoparticles (MSNs) were synthesized by sol-gel reaction at normal pressure by using TEOS as a silica source and CTAB as a directing agent in ammonia solution at 323?K subsequently calcined at 823?K. Then inorganic pores were modified with metal-supported MSN with attention to the acidity, surface area, pore size, and ability of ion exchange. Crystalline size was shown to decrease up to 20 molar ratios of Si/Al followed by increasing while further adding nanoparticles-aluminium. Moreover, the XRD patterns revealed the mesostructured material for all with 2D hexagonal structure. The obtained results from the XRD patterns were confirmed by using BET and EDX. The BET surface areas revealed the spherical shape for all samples with a decrease in the pore volume and surface area for various AlMSNs which emphasized that the loading of Al and was compatible with XRD results. MSN was prepared by sol-gel methods followed by loading of Al in order to prepare AlMSN which possess strong Lewis acidic sites. This modification occurred by using various molar ratios of 0, 5, 10, 20, 50, and 100 Si/Al, respectively. The XRD patterns of various ratios of Si/Al were interpreted in terms of strain, nanocrystalline size, and distribution of the particle size by deriving Wiliamson Hall equation. 1. Introduction More than 10 years passed since the discovery of the so-called M41S mesoporous silica materials, and the synthesis of the mesoporous materials with different characterizes has been gaining increasing attention. This study attempts to reveal the dependence effect of various ratios of Si/Al additive on nanocrystalline size, residual stress and physicochemical property of mesostructure siliceous nanoparticles (MSN) which can give a better insight of its application on petroleum refinery and petrochemical industries. Moreover, the nobility of this research might be the utilization of XRD pattern to find out nanocrystalline size, residual stress, and microstructure. The surfactant-templating method has been extended to the synthesis of nonsilica oxide mesoporous materials [1–3]. Potential application of mesoporous transition metal oxides has been found in the fields of electromagnetic, photoelectronics, catalysis, and separation [4]. By using cationic surfactants with quaternary ammonium derivatives and then nonionic alkoxysilanes, a series of ordered mesoporous silicas had been synthesized [5–7] and the various alkaline or acidic [8–10] conditions were used. These experiments have shown better condensation of the silanol groups in mesoporous silica
Formation and structural characterization of silver nanoparticles in ormosil sol–gel films  [PDF]
Renata Reisfeld,Tsiala Saraidarov,Victoria Levchenko
Optica Applicata , 2008,
Abstract: Silver nanoparticles were obtained in situ in ormosil sol–gel films with attached urethane groups. Optical spectra of the silver nanoparticles in the films show red shift of absorption maximum with increasing silver concentration from 2% to 10%. In the solutions λmax is shifted from 390 nm till 425 nm; in the films λmax is shifted from 438 nm till 456 nm. Structural characterizations of the composite sol–gel films incorporated by silver nanocrystals have been studied by: scanning electron microscopy (SEM), atomic force microscope (AFM), energy dispersion X-rays analysis (EDAX), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and scanning transmission electron microscopy (STEM). Two types of silver nanoparticles with sizes of 1–2 nm and 20–40 nm were observed. The crystal grow process and particle sizes depend on the starting concentrations of silver ions, reaction temperature and time. The small silver particles are arranged in micro pores of the matrix, as shown from STEM images. SAED confirms the silver face-centered cubic crystal lattice.
Preparation and Characterization of CuO Nanoparticles by Novel Sol-Gel Technique  [PDF]
Y.?Aparna,K.?Venkateswara Rao,P.?Srinivasa Subbarao
Journal of Nano- and Electronic Physics , 2012,
Abstract: Recent developments of nanosize materials of metal and metal oxide particles are intensively pursued because of their prominence in different fields of applications. Among all the transition metal oxides, CuO is a potential candidate for the application of magnetic storage devices, solar energy transfer, sensors, and super capacitors etc. Moreover CuO nanoparticles act as a good catalyst in some of the chemical reactions. CuO nanoparticles were prepared by novel sol-gel method. In this technique CuCl2.6H2O is added with acetic acid and heated to 100 °C with continuous stirring. To control the ph of the above solution, NaOH is added to the solution till ph reached desired value. The color of the solution changed from blue to black with precipitation. The black precipitation was washed 3 – 4 times with distilled water. Finally the solution was centrifuged and dried in air for one day. The CuO nanoparticles were characterized by studying their structure with X-ray diffraction and composition by energy dispersive X-ray analysis. The size of the nanoparticles is estimated by particle size analyzer and transmission electron microscopy. The optical studies were carried out with Uv-Vis spectrophotometer.
Synthesis, Characterization and Catalytic Performance of Prepared by Sol-Gel Technique  [PDF]
W. N. R. W. Isahak,M. Ismail,N. M. Nordin,J. M. Jahim,M. A. Yarmo
Journal of Nanotechnology , 2011, DOI: 10.1155/2011/507692
Abstract: The purpose of this work is to study the synthesis, characterization, and catalytic performance of two types of solid heteropoly acid catalysts, namely, silicotungstic acid bulk (STAB) and STA-silica sol-gel (STA-SG) compared with sulfuric acid. From the XPS analyses, there was a significant formation of W-O-Si, W-O-W, and Si-O-Si bonding in STA-SG compared to that in STAB. The main spectra of O1s (90.74%, 531.5?eV) followed by other O1s peak (9.26%, 532.8?eV) were due to the presence of W-O-W and W-O-Si bonds, respectively. The STA-SG catalyst was found to be the more environmentally benign solid acid catalyst for the esterification reaction between oleic acid and glycerol due to its lower toxicity supported by silica via sol-gel technique. In addition, the ease of separation for STA-SG catalyst was attributed to its insoluble state in the product phase. The esterification products were then analysed by FTIR and HPLC. Both the H2SO4 and the STAB gave high conversion of 100% and 98% but at a lower selectivity of GME with 81.6% and 89.9%, respectively. On the contrary, the STA-SG enabled a conversion of 94% but with a significantly higher GME selectivity of 95%, rendering it the more efficient solid acid catalyst. 1. Introduction During the recent years, glycerol has been used as combustion materials around the world. The glycerol usage was expanded into many other high-quality products such as pharmaceutical, foods, and engine lubricant. To date, glycerol modification into glycerol monoester (GME) as lubrication materials that was based on the biosources was not really practised in the industry. The nature of the polar head group and the structure of the hydrocarbon tail of GME gave the strong impact as a friction reducer [1]. The GME is synthesized at present by acid catalyzed esterification of glycerol and fatty acids [2, 3]. Recently, list of studies involving alternative heterogeneous catalytic routes have been reported such as the glycerol esterification with lauric acid (LA) and oleic acid (OA) by using functionalized mesoporous materials [4], zeolitic molecular sieves [5, 6], and solid cationic resins [7, 8] as catalysts. In another work, the beta-zeolite catalyst gave the conversion of fatty acids above 20% at optimum condition of glycerol?:?LA molar ratio of 1?:?1 at 100°C for 24 hours [9]. In this work, the usage and activities of the silicotungstic acid bulk (STAB) and the silicotungstic acid-silica sol-gel (STA-SG) have been studied. The STAB consists of two molecular structures, namely, Keggin and Dawson structures with four protons. The
Characterization and comparison of PZT powder synthesis by solid state and sol gel methods  [cached]
E Pakizeh,GM Khorrami,M Ghasemifard,SM Hosseini
Iranian Journal of Physics Research , 2012,
Abstract: This paper describes the synthesis of Pb(Zr0.95Ti0.05)O3 powder by sol gel and solid state methods. PZT powders were fabricated by solid-state reaction process using metal oxides and in sol gel method salts and organic compounds were employed. The powders were calcined at 700 and 950 oC in sol gel and solid state methods, respectively. The synthesized powders were analyzed by FTIR and XRD. The average crystal grain size of PZT powders determined by X-ray diffraction method using the Scherrer equation, and in sol gel and solid state methods measured 42 and 330 nm, respectively. The optical constants of powders were evaluated and compaed using FTIR transmittance spectroscopy and Kramers-Kronig analysis.
A Simple Sol Gel Protocol Towards Synthesis of Semiconducting Oxide Nanomaterial  [PDF]
G.S. Devi,H.Z.R. Hamoon,A. Nanaji,K.R. Reddy
Journal of Nano- and Electronic Physics , 2011,
Abstract: Nanostructured Tin oxide (SnO2), powders was synthesized by employing a novel Sol-gel protocol at RT. A wide variety of techniques such as energy – dispersive spectroscopy(EDX), N2 sorption, X-ray diffraction (XRD), have been used to study the formation process and characterization of the nanoparticles obtained. Transmission electron microscopy (TEM) has been applied to find out about the shape and size distribution of the particles. The nanoparticles thus synthesized were monodispersed, with an average particle size of ~ 10 nm and spherical in shape. The EDX analysis revealed the presence of Sn, O signal in the synthesized nanoparticles confirming the purity of the synthesized samples. This protocol appears promising for application in large-scale synthesis of nanoparticles.
Synthesis and Characterization of Hydroxyapatite Powder by Sol-Gel Method for Biomedical Application  [PDF]
Khelendra Agrawal, Gurbhinder Singh, Devendra Puri, Satya Prakash
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.108057
Abstract: Hydroxyapatite (HA) is effectively used as a bioimplant material because it closely resembles bone apatite and exhibits good biocompatibility. This paper describe synthesis technique of HA powder by sol-gel method. The product was sintered twice at two different temperatures 400°C to 750°C to improve its crystallinity. The final powder sintered at two temperatures was characterized by X-ray analysis, Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR) to reveal its phase content, morphology and types of bond present within it. Thermal analysis (TG–DTA) was carried out to investigate the thermal stability of the powder.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.