scholarly journals Synthesis of High-Purity Silica Nanoparticles by Sol-Gel Method

2017 ◽  
Vol 19 (4) ◽  
pp. 295 ◽  
Author(s):  
S.V. Lazareva ◽  
N.V. Shikina ◽  
L.E. Tatarova ◽  
Z.R. Ismagilov
Keyword(s):  
Particle Size ◽  
Sol Gel ◽  
Sio2 Content ◽  
Reaction Conditions ◽  
Minimum Particle Size ◽  
Size Stability ◽  
Different Temperatures ◽  
Acid Catalyzed ◽  
Silica Sols ◽  
Hydrolysis Of

Colloidal silica (silica sol) nanoparticles were synthesized by ammonia- and hydrochloric acid-catalyzed hydrolysis of tetraethoxysilane with subsequent condensation and polymerization. Silica particles with the size of 12‒160 nm were obtained at different temperatures and ratios of the initial reactants and studied by means of TEM, AFM, IR spectroscopy and zeta-potential measurements. The reaction conditions providing the minimum particle size in the final product of the most complete hydrolysis were determined. At pH above 8.5, an increase in the SiO2 content of the sol to 23 wt.% did not change the particle size. At a low (~ 1.8 wt.%) SiO2 content of the sol, a wide variation in pH also did not exert a significant effect on the particle size. Stability of the silica sols synthesized in an alkaline medium was enhanced by the replacement of alcohol with water during evaporation at pH 8.5‒9.5. The possibility to produce silica sols with the required characteristics (particle size, pH, stability, purity, and SiO2 content in an aqueous or alcohol medium) makes them applicable in various industries.

scholarly journals Cross-Condensation Reactions in an Organically Modified Silica Sol-Gel

1994 ◽  
Vol 346 ◽  
Author(s):  
S. Prabakar ◽  
R. A. Assink ◽  
N. K. Raman ◽  
C. J. Brinker
Keyword(s):  
Experimental Error ◽  
Molecular Level ◽  
Sol Gel ◽  
Resonance Assignments ◽  
Silica Sol ◽  
Modified Silica ◽  
Organically Modified ◽  
Organically Modified Silica ◽  
Acid Catalyzed ◽  
Hydrolysis Of

ABSTRACTHigh resolution 29Si NMR has been used to study the extent of cross condensation taking place in a hybrid organic/inorganic sol-gel system. Tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) sol-gels were chosen for this purpose. The sols were prepared by acid catalyzed hydrolysis of TEOS and MTEOS with a H2O/Si ratio of 0.3. 29Si NMR shows signals due to both self-condensation and cross-condensation between TEOS and MTEOS. Resonance assignments were made by comparing the positions and intensities of peaks in the spectra of single and multicomponent systems. It was found that, within experimental error, the self- and cross-condensation rates are equal and that extensive molecular level mixing takes place during the early stages of the reaction.

XRD Study of the Influence of Heat Treatment on the Microstructure of Sol-Gel Processed ZrO2-Y2O3 Ceramics

1995 ◽  
Vol 398 ◽  
Author(s):  
C. Barrera-Solano ◽  
M. PiÑero ◽  
C. Jiménez-Solís ◽  
L. Gago-Duport
Keyword(s):  
Heat Treatment ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Profile Function ◽  
Xrd Study ◽  
Different Temperatures ◽  
Hydrolysis Of Metal Alkoxides ◽  
Induced Changes ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

ABSTRACTYSZ samples containing 5 and 10 mol% of Y203 were prepared by controlled hydrolysis of metal alkoxides. The dried powders were calcined at 800°C and then they were uniaxially pressed and sintered at different temperatures and next heated at 1400°C (∼ 5 MPa) or annealed at 1600°C for 24 h. The quantitative analysis of the experimental X-ray diffraction (XRD) spectra was performed by Whole Pattern Fitting (WPF). A Pseudo-Voigt (Thompson-Cox-Hastings) was used as shape profile function. The respective phase fractions (wt %) were fitted for both solid state solutions using the scale factor. The heat treatment induced changes are discussed.

Preparation of SiO2 Antireflective Film by a Base/Acid Two-Step Catalyzed Sol-Gel Process

2013 ◽  
Vol 860-863 ◽  
pp. 845-848 ◽  
Author(s):  
De Yi Li ◽  
Kun Peng ◽  
Ling Ping Zhou ◽  
Jia Jun Zhu
Keyword(s):  
Raw Materials ◽  
Salt Spray ◽  
Sol Gel ◽  
Acid Base ◽  
Gel Method ◽  
Antireflective Film ◽  
Sol Gel Process ◽  
Acid Catalyzed ◽  
Antireflective Films ◽  
Silica Sols

SiO2 antireflective films were prepared by two-step catalyzed sol-gel method with TEOS as the raw materials, acid and ammonia as catalyst. Effects of the ratio of acid-catalyzed and base-catalyzed silica sols on the transmittance and stability of SiO2 film were investigated. The transmittance can be adjusted by change the ratio of base-catalyzed sols, and a higher transmittance can be obtained in the higher ratio of base-catalyzed coatings. A higher stability of SiO2 film in salt spray can be obtained in higher ratio of acid-catalyzed AR coatings. AR coatings with excellent transmittance and stability can be obtained by adjusting the ratio of acid/base catalyzed silica sols.

scholarly journals Characterization and photocatalytic study of tantalum oxide nanoparticles prepared by the hydrolysis of tantalum oxo-ethoxide Ta8(μ3-O)2(μ-O)8(μ-OEt)6(OEt)14

2014 ◽  
Vol 5 ◽  
pp. 1082-1090 ◽  
Author(s):  
Subia Ambreen ◽  
N D Pandey ◽  
Peter Mayer ◽  
Ashutosh Pandey
Keyword(s):  
Particle Size ◽  
Sol Gel ◽  
Tantalum Oxide ◽  
Organic Dye ◽  
Oxide Nanoparticles ◽  
Tauc Plot ◽  
Particle Size Analyzer ◽  
Bet Method ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

Ta8(μ3-O)2(μ-O)8(μ-OEt)6(OEt)14 (1) was obtained by the controlled hydrolysis of tantalum ethoxide Ta(OEt)5 in the presence of ammonia. Compound 1 is considered as the intermediate building block in the sol–gel polymerization of Ta(OEt)5. Further hydrolysis of compound 1 yielded nanoparticles of Ta2O5, which were characterized by various techniques such as TGA-DTA-DSC, UV–vis DRS, XRD, SEM, TEM, particle size analyzer (DLS) and the Brunauer–Emmett–Teller (BET) method. The band gap of the particles was calculated by using the Tauc plot. The photocatalytic activity of Ta2O5 nanoparticles was tested by the degradation of the organic dye rhodamine B.

Preparation of TiO2 Thin Films and its Superhydrophilic Properties

2009 ◽  
Vol 620-622 ◽  
pp. 695-698
Author(s):  
Jing Ma ◽  
Wen Xiu Liu ◽  
Xiao Guang Qu ◽  
Dan Ni Yu ◽  
Wen Bin Cao
Keyword(s):  
Thin Film ◽  
Tio2 Thin Film ◽  
Annealing Temperature ◽  
Sol Gel ◽  
Soda Lime ◽  
Contact Angles ◽  
Soda Lime Glass ◽  
Water Contact ◽  
Different Temperatures ◽  
Hydrolysis Of

TiO2 thin film was prepared on soda lime glass by hydrolysis of Ti(OC4H9)4 in alcoholic solutions by sol-gel method combined with spin-coating and calcination different temperatures. Prepared samples were characterized by XRD, FESEM, and measurement of contact angles and transmittance. XRD identification reveals that the films are composed of anatase TiO2 when the annealing temperature was set at 450~550 oC. SiO2 layer was coated on the surface of the glass firstly to barrier the diffusing of sodium ions from the substrate. Light-induced superhydrophilicity of the TiO2 thin film has been investigated. To increase the illumination light intensity will decrease the water contact angle. The superhydrophilicity of the TiO2 thin film will disappear more slowly in the dark than that in the field of ultrasound.

A novel bulk sol-gel process to prepare monolithic silica materials

1999 ◽  
Vol 14 (10) ◽  
pp. 4098-4102 ◽  
Author(s):  
Ce Wang ◽  
Yahong Zhang ◽  
Yunfeng Lu ◽  
Yen Wei
Keyword(s):  
Sol Gel ◽  
Silica Content ◽  
Monolithic Silica ◽  
Nonpolar Solvents ◽  
Sol Gel Process ◽  
Silica Materials ◽  
High Silica ◽  
Acid Catalyzed ◽  
Carbonate Salts ◽  
Hydrolysis Of

A bulk sol-gel process has been developed to prepare monolithic silica materials at room temperature. The process involves an acid-catalyzed hydrolysis of tetraethyl orthosilicate in tetrahydrofuran containing aqueous HC1 catalyst, followed by neutralization with carbonate salts, extraction with aliphatic nonpolar solvents, molding, gelation, and drying. This method shortens the processing time from weeks for the conventional sol-gel process to several days. The silica objects prepared from the process are transparent, crack-free, and of relatively low volume shrinkage (e.g., 52%) and high silica content (e.g., 82%).

Influence of Colloidal Silica on Final Properties of no Cement Castables

2021 ◽  
Vol 321 ◽  
pp. 125-130
Author(s):  
David Zemánek ◽  
Lenka Nevřivová
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Bulk Density ◽  
Colloidal Silica ◽  
Sol Gel ◽  
Setting Times ◽  
Sol Gel Process ◽  
Initial Setting ◽  
Basic Parameters ◽  
Silica Sols

This paper deals with sol-gel process and application in no cement castables based on andalusite. The use of calcium free binder increases the refractory parameters of material and allows its faster drying. Six colloidal sols from CWK Bad Köstritz based on SiO2 were tested, which differed not only in concentration and particle size, but also in pH. The influence of silica sols on the consistency of fresh castable, initial setting and final setting times were investigated. Furthermore, basic parameters after firing, such as bulk density, apparent porosity, flexural and compressive strength, were tested.

Effects of different sintering temperature on structural and magnetic properties of Ni–Cu–Co ferrite nanoparticles

2018 ◽  
Vol 32 (27) ◽  
pp. 1850321 ◽  
Author(s):  
Xiaoguang Pan ◽  
Aimin Sun ◽  
Yingqiang Han ◽  
Wei Zhang ◽  
Xiqian Zhao
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Spinel Structure ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Stable State ◽  
Precursor Solution ◽  
Auto Combustion ◽  
Different Temperatures ◽  
Ft Ir

In this work, sol–gel auto-combustion technology is used to synthesize nanocrystalline Ni[Formula: see text]Cu[Formula: see text]Co[Formula: see text]Fe2O4 with high purity metal nitrate and citric acid as precursor solution. The prepared samples are sintered at different temperatures (400[Formula: see text]C, 500[Formula: see text]C, 600[Formula: see text]C, 700[Formula: see text]C, 800[Formula: see text]C, 900[Formula: see text]C, 1000[Formula: see text]C and 1100[Formula: see text]C) for 3.5 h. The structure and magnetic properties of the samples are characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and vibrating sample magnetometer (VSM). The analysis of the XRD patterns confirms that all the samples have a single-phase cubic spinel structure. The particle size of the prepared samples (between 23 nm and 36 nm) is determined by the Scherrer equation. The effect of particle size is through observation of samples sintered at different temperatures. FT-IR spectroscopy shows the characteristic peak is near 588 cm[Formula: see text]. And the measurement also confirms the formation of spinel structure. The magnetic parameters of the samples are measured by VSM at room temperature with a maximum magnetic field of 1 T. Coercivity, remanent magnetization and saturation magnetization change with the changing sintering temperature. It can be clearly observed that the magnetic properties increase significantly with the temperature increasing from 600[Formula: see text]C to 700[Formula: see text]C. The dM/dH versus H curves are obtained by differentiating the hysteresis loop. The increasing peak height of dM/dH at [Formula: see text], indicates a magnetically stable state for the samples with good crystalline cubic spinel structure.

Synthesis and Characterization of Li-Ti-O Nano-Composites and Their Doped BaTiO3 Based X7R-Type Ceramics

2010 ◽  
Vol 148-149 ◽  
pp. 1575-1579
Author(s):  
Qing Zhang ◽  
Rui Yuan Niu ◽  
Min Wang ◽  
Bin Cui ◽  
Zhu Guo Chang
Keyword(s):  
Particle Size ◽  
Dielectric Properties ◽  
Ph Value ◽  
Sol Gel ◽  
Nano Composites ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Minimum Particle Size ◽  
Sol Gel Process

Li-Ti-O (abbreviated as LTO) nano-composites were synthesized via sol-gel process, and then doped BaTiO3 based X7R type ceramics. The LTO nano-composites and their ceramics were characterized by means of thermaogravimetric, Fourier-transform infrared, X-ray diffraction methods, transmission electron microscopy. We also characterized the dielectric properties of the LTO doped BaTiO3 based ceramics of X7R type. The results indicated that LTO nano-composites were nanometer scale powders. The pH value and calcining temperature had an influence on particle size of LTO sintering aids. At pH about 3 and with calcining at 600 °C, the nano-composites attained minimum particle size (about 10 nm). By adding 0.10 wt% of the LTO nano-composites, the temperature permittivity achieved about 4200 when sintered at 1240 °C for 4 h, and the dielectric properties met X7R standard.

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