Sol-Gel Process from Heterobimetallic Alkoxides to Incorporate Lanthanides in an Alumina Matrix

1992 ◽  
Vol 271 ◽  
Author(s):  
Chaitanya K. Narula
Keyword(s):  
Acetic Acid ◽  
Structural Changes ◽  
Sol Gel ◽  
Alumina Matrix ◽  
Slow Evaporation ◽  
Thermally Induced ◽  
Excess Water ◽  
Sol Gel Process ◽  
Amorphous Powders ◽  
Hydrolysis Of

ABSTRACTGels form on addition of seven or more moles of water diluted withi-PrOH to one mole of M[Al(O-i-Pr)4]3, M = La, Ce dissolved in i-PrOH. Thermal treatment of xerogels derived from La[AI(O-i-Pr)4]3gives amorphous powders below 900°C. LaAIO3crystallizes out at 900°C and residual alumina remains amorphous. CeO2starts to separate out above 600°C from the xerogels prepared from Ce[M(O-i-Pr)4]3. Thermally induced structural changes in xerogels prepared from the mixtures of La[AI(O-i-Pr)4]3and Ce[AI(0-i-Pr)4]3in 1:1 or 1:3 ratio are different from those prepared from individual precursors. These xerogels remain amorphous below 700°C. Crystalline CeO2forms on heating at 900°C but alumina remains amorphous. Sols are formed on hydrolysis of M[AI(0-/-Pr)4]3in excess water and acidifying the reaction mixture with acetic acid. Sols can be converted to gels by slow evaporation of volatiles. This method is useful in preparing coatings.

Synthesis, Structure and Applications of TiO2 Gels

1986 ◽  
Vol 72 ◽  
Author(s):  
J. Livage
Keyword(s):  
Acetic Acid ◽  
Molecular Level ◽  
Sol Gel ◽  
Titanium Alkoxides ◽  
Chemical Additives ◽  
Display Devices ◽  
Sol Gel Process ◽  
Infra Red ◽  
Tio2 Gels ◽  
Hydrolysis Of

AbstractTiO2 gels are usually obtained through hydrolysis of titanium alkoxides. Chemical additives can however react with the precursor at a molecular level and therefore modify the hydrolysis-condensation reactions. Several examples will be described :acetic acid, acetylacetone or Cr(acac)3. The whole sol-gel process is followed all the way from the precursors to the gel and each step is characterized by spectroscopic experiments (Infra-red, N.M.R, E.S.R.). Some electronic properties of TiO2 gels are then described. Chemical addi-tives allow an optimization of thý sol-gel process according to each speci-fic applications : electrochromic display devices, photoanodes or photoche-mical reactions.

Synthesis of Hollow Titania Photocatalytic Particles Using Yeast as Templates

2013 ◽  
Vol 699 ◽  
pp. 126-132 ◽  
Author(s):  
Toshiyuki Nomura ◽  
Syota Tanii ◽  
Hayato Tokumoto ◽  
Yasuhiro Konishi
Keyword(s):  
Pore Diameter ◽  
Sol Gel ◽  
Solid Particles ◽  
Core Shell ◽  
Average Pore ◽  
Inorganic Particles ◽  
Sol Gel Process ◽  
Yeast Powder ◽  
Titania Precursor ◽  
Hydrolysis Of

Hollow inorganic particles have attracted considerable interest for a variety of applications. In this work, yeast powder was used as a bio-template to fabricate yeast/titania core-shell spheres. A titania precursor was deposited via the hydrolysis of tetraisopropyl titanate. Triethanolamine was employed to control the reaction rate of the sol-gel process. The hollow titania particles with a diameter of approximately 4 m and a thickness of approximately 54 nm were successfully obtained after calcination of the core-shell spheres at 700 °C. The crystal structure of the particles was anatase. The specific surface area and the average pore diameter were 21.4 m2/g and 1.6 nm, respectively. The photocatalytic activity of the hollow particles was higher compared with that of solid particles.

Homogeneous phase synthesis of chitosan silica hybrid materials in ionic liquid medium and adsorption of Fe(III) from aqueous solutions

2019 ◽  
Vol 38 (9) ◽  
pp. 586-597 ◽  
Author(s):  
Ananda S. Amarasekara ◽  
Deping Wang
Keyword(s):  
Ionic Liquid ◽  
Hybrid Materials ◽  
Sol Gel ◽  
Phase Reaction ◽  
Phase Synthesis ◽  
Homogeneous Phase ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Silica Hybrid ◽  
Ionic Liquid Medium

Two chitosan silica hybrid materials were prepared by a two-step process in 78–84% yields using the homogeneous phase reaction of 3-(triethoxysilyl)propyl isocyanate with chitosan dissolved in 1-n-butyl-3-methylimidazolium chloride ionic liquid (∼10% w/w), which was followed by NH4OH catalyzed hydrolysis of triethoxysilyl groups and then sol-gel process. These new hybrid materials were shown to adsorb up to about 95% of Fe3+ from 5 × 10−4 M aqueous solution at room temperature in 24 h.

Preparation and Electrophoretic Deposition of an Yttrium Silicate Precursor Sol

2009 ◽  
Vol 412 ◽  
pp. 267-272 ◽  
Author(s):  
Jana Grosse-Brauckmann ◽  
Günter Borchardt ◽  
Christos Argirusis
Keyword(s):  
Electrophoretic Deposition ◽  
Sol Gel ◽  
Constant Current ◽  
Particle Charge ◽  
Yttrium Silicate ◽  
Micro Cracks ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Controlled Hydrolysis

. In the present work we used the sol-gel process to prepare Y2SiO5 precursor sols suitable for electrophoretic deposition (EPD). The sol synthesis was performed through the controlled hydrolysis of alkoxide solutions of tetraethoxysilane and yttriumoxoisopropoxide. During sol development emphasis was put on characterization of particles size and zeta potential of the formed aggregates. We succeeded in synthesizing a clear sol containing polymeric aggregates with acceptable particle charge. The electrophoretic deposition on glassy carbon or C/C-SiC slabs led to homogenous layers. At low sol concentrations micro cracks in the deposited layers were observed whereas higher concentrations led to thin and dense layers. During constant current EPD a constant voltage was recorded indicating that the deposited layer does not lead to an increase in resistivity in this kind of EPD system.

Leaching Behavior of Edta In A Silica Sol-Gel Matrix

1994 ◽  
Vol 346 ◽  
Author(s):  
Kris S. Oka ◽  
J.D. Mackenzie
Keyword(s):  
Pore Volume ◽  
Sol Gel ◽  
Silica Matrix ◽  
Silica Gels ◽  
Volume Distribution ◽  
Leaching Behavior ◽  
Sol Gel Process ◽  
The Matrix ◽  
Physical Changes ◽  
Hydrolysis Of

ABSTRACTEthylene diamine tetra-acetic acid (EDTA) doped silica gels were made by the sol-gel process for the potential application as a filter for heavy metal ions in wastewater. The behavior of the organic molecule in the matrix was studied by investigating the percentage of EDTA leached out with a variation in the timing of addition of the EDTA molecule into the starting silica gel solution. Leach tests using water as the medium were performed for 2, 12 and 24 hours in order to determine the amount of EDTA trapped in the pores or in the matrix. A minimum amount of EDTA leached from the gels was detected in the samples to which EDTA was added 4 hours after initial hydrolysis of TEOS. This result was correlated to having a greater percentage of pore volume in the range of 15–20 Å, which was further substantiated with density measurements. The physical changes in the silica matrix altering the pore volume distribution were attributed to the addition of the water into which the EDTA molecule was initially dissolved.

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%).

scholarly journals Injectability of Thermosensitive, Low-Concentrated Chitosan Colloids as Flow Phenomenon through the Capillary under High Shear Rate Conditions

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2260
Author(s):  
Anna Rył ◽  
Piotr Owczarz
Keyword(s):  
Shear Rate ◽  
Structural Changes ◽  
Sol Gel ◽  
Thermally Induced ◽  
Flow Phenomenon ◽  
Injectable Scaffolds ◽  
Gel Phase ◽  
Injection Force ◽  
Needle Diameter ◽  
Injection Forces

Low-concentrated colloidal chitosan systems undergoing a thermally induced sol–gel phase transition are willingly studied due to their potential use as minimally invasive injectable scaffolds. Nevertheless, instrumental injectability tests to determine their clinical utility are rarely performed. The aim of this work was to analyze the flow phenomenon of thermosensitive chitosan systems with the addition of disodium β-glycerophosphate through hypodermic needles. Injectability tests were performed using a texture analyzer and hypodermic needles in the sizes 14G–25G. The rheological properties were determined by the flow curve, three-interval thixotropy test (3ITT), and Cox–Merz rule. It was found that reducing the needle diameter and increasing its length and the crosshead speed increased the injection forces. It was claimed that under the considered flow conditions, there was no need to take into account the viscoelastic properties of the medium, and the model used to predict the injection force, based solely on the shear-thinning nature of the experimental material, showed very good agreement with the experimental data in the shear rate range of 200–55,000 s−1. It was observed that the increase in the shear rate value led to macroscopic structural changes of the chitosan sol caused by the disentangling and ordering of the polysaccharide chains along the shear field.

The Effects of Aluminum Alkoxides on the Synthesis of Composite Powders of Alumina and Titania

1989 ◽  
Vol 155 ◽  
Author(s):  
Michael T. Harris ◽  
Charles H. Byers ◽  
Ronald R. Brunson
Keyword(s):  
Sol Gel ◽  
Particle Morphology ◽  
Ceramic Materials ◽  
Metal Alkoxide ◽  
Oxide Ceramic ◽  
Powder Synthesis ◽  
Composite Powders ◽  
Sol Gel Process ◽  
Hydrolysis Of ◽  
Uniform Composition

ABSTRACTThe synthesis of mixed oxide ceramic powders that consist of very fine (submicron)-monodisperse particles with uniform composition is desirable in the improvement of existing ceramics and the development of new ceramic materials. Metal alkoxide hydrolysis is a very attractive method for the synthesis of ultrapure composite powders at low temperatures by the sol-gel process.The present study investigates the effects of the hydrolysis of aluminum alkoxides and the condensation products on the growth kinetics and morphology of composite particles containing alumina and titania. Alkoxides of titanium and aluminum are employed; therefore, powders of high purity are produced. Since various solvents are used as media for powder synthesis, the effect of the solvent on particle morphology will also be discussed.

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