Preparation of Spherical Silica with Controllable Size

2018 ◽  
Vol 281 ◽  
pp. 65-70
Author(s):  
Shu Lin Wang ◽  
Zhao Wang ◽  
Bing Hao Li ◽  
Man Xu
Keyword(s):  
Particle Size ◽  
Silica Particle ◽  
Sol Gel ◽  
Silica Particles ◽  
Spherical Particles ◽  
Alkali Content ◽  
Spherical Silica ◽  
Hydrolysis Temperature ◽  
Spherical Silica Particles ◽  
Size And Morphology

The spherical silica particles were prepared by sol-gel method with TEOS as precursor, ethanol as solvent in the presence of ammonia. The effects of reaction temperature and the amount of ammonia and TEOS on the size and morphology of silica particles were investigated. The hydrolysis temperature , alkali and TEOS content does not affect the morphology of silica, the silica particles were spherical; With the increase of hydrolysis temperature, particle size of silica showed first increased and then decreased, when the hydrolysis temperature is 30 °C, the silica particle size up to 0.6 μm, when the hydrolysis temperature is 60 °C, the silica particle size is 0.15 μm; With the increase of the content of alkali, silica particle size showed first increased and then decreased, when the alkali content is 20 ml, the silica particle size up to 0.6 μm and when the alkali content is 10 ml, the silica particle size is 0.2 μm; With the increase of TEOS dosage, the amount of spherical silica increased and the particle size of silica spherical particles first increased and then decreased.

Synthesis of TEOS-Based Silica Spherical Particles by Sol-Gel Process

2013 ◽  
Vol 773 ◽  
pp. 606-610
Author(s):  
Jing Li ◽  
Hong Qi Zhang ◽  
Wei Xue
Keyword(s):  
Sol Gel ◽  
Silica Particles ◽  
Electron Cloud ◽  
Polymerization Rate ◽  
Spherical Particles ◽  
Condensation Polymerization ◽  
Spherical Silica ◽  
Sol Gel Process ◽  
Spherical Silica Particles

Spherical silica particles, with mean sizes about 1.2 μm, were prepared through TEOS sol-gel process catalyzed by ammonia. The silica particles have a smooth surface and a small specific surface area, 3.4 m2/g. The sol-gel process was monitored by React IRTMusing an in-situ technique. Based on the measurements, mechanism of TEOS hydrolyzation and succedent condensation polymerization was inferred. With the adding of ammonia, OH-anion attacks Si atomic nucleus directly and makes it showing negative electricity. Therefore the electron cloud shifts to the OR group on the other side. This weakens the Si-O bond and results in the removal of the OR group. Furthermore, silanol, generated from TEOS hydrolyzation, attracts Si-OR or other Si-OH around; thereby resulting rapid dehydration or dealcohol between molecular. So the condensation polymerization rate is elevated, and Si-O-Si bond comes into being. Lastly, cross-linking reaction among Si-O-Si bonds forms the particle.

Synthesis of spherical silica particles by sol-gel method and application

2008 ◽  
Vol 19 (8) ◽  
pp. 977-983 ◽  
Author(s):  
Kiyomi Fuchigami ◽  
Yoshinari Taguchi ◽  
Masato Tanaka
Keyword(s):  
Sol Gel ◽  
Silica Particles ◽  
Gel Method ◽  
Sol Gel Method ◽  
Spherical Silica ◽  
Spherical Silica Particles

Controlling Factors of the Particle Size of Spherical Silica Synthesized by Wet and Dry Processes

2021 ◽  
Vol 6 (7) ◽  
pp. 118-121
Author(s):  
Keiji Saiki ◽  
Toshihiro Ishikawa
Keyword(s):  
Particle Size ◽  
Reaction Time ◽  
Silica Particles ◽  
Controlling Factors ◽  
Dry Process ◽  
Wet Process ◽  
Spherical Silica ◽  
Wide Range ◽  
Spherical Silica Particles ◽  
Trimethoxy Silane

We clarified the controlling factors of the particle size of the amorphous silica synthesized by wet and dry processes. In the wet process using methyl-trimethoxy-silane as a starting monomer, the obtained particle size can be easily controlled by changing the reaction time appropriately. However, to obtain larger particles, a relatively long time is needed. After the condensation reaction was conducted for 50h, the silica particles (D50: 3μm) were synthesized by calcination at 550oC in air. To synthesize larger silica particles, we used silica-seed particles (8μm) to obtain very large spherical silica particles (D50: 20μm). Thus, although the wet process needs a relatively long reaction time, it is very useful for synthesizing spherical silica particles with a wide range of particle size. In the dry process, we used methyl-trimethoxy-silane (MTMS), tetra-ethoxy-silane (TEOS), and octamethyl-cyclotetrasiloxane (OMCTSO) as the starting materials. In this process, the size of the silica particles was dominated by the molecular structure of the monomer, in particular, the number of silicon atoms contained in the monomer and the bulkiness of the substituent group. The largest silica particles were synthesized from OMCTSO, which contains the largest number of silicon atoms.

Effect of Sodium Chloride on the Sol-Gel Synthesized Silica Colloidal Particles

2011 ◽  
Vol 181-182 ◽  
pp. 417-421 ◽  
Author(s):  
Yun Gao Cai ◽  
Qing Lan Ma ◽  
Yuan Ming Huang
Keyword(s):  
Sodium Chloride ◽  
Colloidal Particles ◽  
Size Range ◽  
Sol Gel ◽  
Silica Particles ◽  
Tetraethyl Orthosilicate ◽  
Silica Spheres ◽  
Spherical Silica ◽  
Spherical Silica Particles ◽  
Wide Size Distribution

The effect of sodium chloride on the sol-gel synthesized silica colloidal particles has been investigated. The silica colloidal particles in the size range of 420-800 nm were synthesized from the hydrolysis and condensation of tetraethyl orthosilicate by varying the amount of sodium chloride from 15 to 30 mg while keeping the tetraethyl orthosilicate (20 ml), ethanol (125 ml), ammonia (6 ml) and distilled water (18 ml) fixed. Scanning electron microscopy (SEM) was employed to analyze the morphology of the synthesized silica particles. Our results demonstrated that: (1) sticky and spongy silica spheroids were resulted if the amount of sodium chloride was less than 15 mg; (2) spherical silica particles were resulted with good monodispersity when the amount of sodium chloride was in the range of 22-24 mg; and (3) silica spheres were obtained but with a wide size distribution when the amount of sodium chloride was more than 26 mg.

Enhanced Thermal and Mechanical Properties of Epoxy Composites by Spherical Silica with Different Size

2017 ◽  
Vol 727 ◽  
pp. 519-526 ◽  
Author(s):  
Li Ya Chen ◽  
Ji Fang Fu ◽  
Wen Qi Yu ◽  
Lei Huang ◽  
Jing Tao Yin ◽  
...  
Keyword(s):  
Particle Size ◽  
Dielectric Properties ◽  
Impact Strength ◽  
Flexural Modulus ◽  
Silica Particles ◽  
Epoxy Composites ◽  
Pure Epoxy ◽  
Spherical Silica ◽  
Spherical Silica Particles ◽  
The Impact

Spherical silica particles with mean diameter 350 nm, 500 nm and 1000 nm were used to modify o-cresol-novolac epoxy resin (ECN) at a ranging constant weight fraction from 0 to 20 wt%. The effects of particle size and fillers content on the impact strength, flexural modulus, dynamic mechanical analysis (DMA), coefficient of thermal expansion (CTE), dielectric properties and bulk resistivities of epoxy composites filled with spherical silica particles were investigated. The results revealed that the impact strength and flexural modulus showed significant improvements with the addition of spherical silica particles. The glass transition temperature (Tg) of composites was higher than that of pure epoxy. The maximum increment of Tg was 34 °C by the addition of 2 wt% D500. The CTE of the composites with different size silica exhibit much lower dimension changes than that of pure epoxy. The dielectric constant was decreased with the addition of spherical silica particles. However, the particle size exhibited weakly effect on the dielectric properties. The bulk resistivities of the composites have greatly improved compared to the pure epoxy and increase with decreasing the particle size.

scholarly journals Preparation of Gd Complex-Immobilized Silica Particles and Their Application to MRI

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yoshio Kobayashi ◽  
Hikaru Morimoto ◽  
Tomohiko Nakagawa ◽  
Yohsuke Kubota ◽  
Kohsuke Gonda ◽  
...  
Keyword(s):  
Ethylenediaminetetraacetic Acid ◽  
Sol Gel ◽  
Silica Particles ◽  
Disodium Salt ◽  
Colloid Solution ◽  
Amino Groups ◽  
Spherical Silica ◽  
Spherical Silica Particles ◽  
Average Size ◽  
Ethylenediaminetetraacetic Acid Disodium Salt

A preparation method for Gd-ethylenediaminetetraacetic acid disodium salt dihydrate (ETDA) complex-immobilized silica particles (Gd-EDTA/SiO2) is proposed. Preparation of spherical silica particles was performed by a sol-gel method at 35°C using 0.2 M tetraethylorthosilicate, 25 M H2O, and 0.01 M NaOH in ethanol, which produced silica particles with an average size of  nm. Immobilization of Gd-EDTA on the silica particles was conducted at 35°C by introducing amino groups on the silica particles with (3-aminopropyl)trimethoxysilane at pH 3 (NH2/SiO2) and then making Gd-EDTA act on the NH2/SiO2 particles at pH 5. The as-prepared Gd-EDTA/SiO2 particle colloid solution was concentrated up to a Gd concentration of 0.347 mM by centrifugation. The sphere structure of Gd-EDTA/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated Gd-EDTA/SiO2 colloid solution revealed good MRI properties. A relaxivity value for T1-weighted imaging was as high as 5.15 mM−1 s−1, that was comparable to that for a commercial Gd complex contrast agent.

scholarly journals Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

RSC Advances ◽  
2021 ◽  
Vol 11 (28) ◽  
pp. 17108-17115
Author(s):  
Mahnaz Mirheidari ◽  
Javad Safaei-Ghomi
Keyword(s):  
Graphene Oxide ◽  
Cobalt Complex ◽  
Catalytic Performance ◽  
Silica Particles ◽  
Design Synthesis ◽  
Spherical Silica ◽  
Modified Graphene Oxide ◽  
Spherical Silica Particles ◽  
Heterogenous Catalyst ◽  
Modified Graphene

GO@f-SiO2@Co is a heterogenous catalyst composed of spherical silica particles grafted on the surface of graphene oxide with ethylenediamine ligands and coordination with Co(ii). We assessed the activity of the catalyst for the synthesis of aminonaphthoquinones.

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