Molecular Architecture and its role in Silica Sol-Gel Polymerization

1990 ◽  
Vol 180 ◽  
Author(s):  
P. C. Cagle ◽  
W. G. Klemperer ◽  
C. A. Simmons
Keyword(s):  
Molecular Level ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Sol ◽  
Molecular Architecture ◽  
Model Studies ◽  
Large Size ◽  
Neutral Conditions ◽  
Very High

ABSTRACTSol-gel polymerization of [Si8O12](OCH3)8 in CH3CN under neutral conditions yields very high surface area (SBET > 900 m2/g) xerogels. This property is seen to result from the structure of the gel on the molecular level. According to N2 adsorption studies, model studies, and TEM studies, the large size and rigidity of the cubic [Si8O12] core structure leads to polymers whose rigidity inhibits extensive crosslinking of the type observed in orthosilicate derived xerogels.

Tailored Silica Based Xerogels and Aerogels for Insulation in Space Environments

2010 ◽  
Vol 63 ◽  
pp. 41-46 ◽  
Author(s):  
Luisa Durães ◽  
Marta Ochoa ◽  
António Portugal ◽  
Nelson Duarte ◽  
João Paulo Dias ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Acid Base ◽  
Highly Porous Materials ◽  
Small Pore ◽  
Space Environments ◽  
Highly Porous ◽  
Very High

In this work, the sol-gel technology is used to produce silica based xerogels and aerogels suitable for insulation applications in Space. The properties of the obtained materials are tailored varying the precursor – Methyltrimethoxysilane (MTMS) or Methyltriethoxysilane (MTES), and the solvent – methanol or ethanol. A two-step acid-base catalyzed synthesis is used, being the obtained gels dried at atmospheric pressure, in the case of xerogels, and in supercritical conditions, for aerogels. Density and thermal conductivity must be made as low as possible for the sought application and only highly porous materials can fulfill this requirement. The obtained xerogels and aerogels, either with MTMS or MTES, show very promising properties for thermal insulation in Space, when methanol is used as solvent. The more suitable materials are obtained with MTMS and exhibit very low density (80-100 kg/m3), very high surface area (~ 400 m2/g) and small pore size (~ 30-40 Å). They also show moderate flexibility and a remarkable hydrophobic character (~ 150º).

Platinum Supported Mesoporous Silica Spheres by Optimized Microfluidic Sol-Gel Synthesis Scheme

2010 ◽  
Author(s):  
Venkatachalam Chokkalingam ◽  
Boris Weidenhof ◽  
Wilhelm F. Maier ◽  
Stephan Herminghaus ◽  
Ralf Seemann
Keyword(s):  
Mesoporous Silica ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Processing Parameters ◽  
Pore Radius Distribution ◽  
Sol Gel Synthesis ◽  
Long Operation ◽  
Very High ◽  
Mesoporous Silica Spheres

Droplet based microfluidics is used to perform sol-gel reactions. The chemicals are dispensed, mixed, and pre-processed inside a microfluidic device allowing for long operation times without any clogging. Using this approach and optimizing all reaction and processing parameters we generate mesoporous silica particles with a very high surface area of 820 m2g−1 and a narrow pore radius distribution of around 2.4 nm. To take full advantage of the possibilities offered by this microfluidic synthesis route, we produced platinum supported silica microspheres (as high as 7 mol. %) for heterogeneous catalysis.

High-Surface-Area Alumina-Silica Nanocatalysts Prepared by a Hybrid Sol-Gel Route Using a Boehmite Precursor

2010 ◽  
Vol 93 (12) ◽  
pp. 4047-4052 ◽  
Author(s):  
Padmaja Parameswaran Nampi ◽  
Padmanabhan Moothetty ◽  
Wilfried Wunderlich ◽  
Frank John Berry ◽  
Michael Mortimer ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area

Synthesis and structural characteristics of high surface area TiO2 aerogels by ultrasonic-assisted sol–gel method

2018 ◽  
Vol 29 (7) ◽  
pp. 075702 ◽  
Author(s):  
Feng Qingge ◽  
Cai Huidong ◽  
Lin Haiying ◽  
Qin Siying ◽  
Liu Zheng ◽  
...  
Keyword(s):  
Surface Area ◽  
Structural Characteristics ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Gel Method ◽  
Sol Gel Method ◽  
Ultrasonic Assisted

Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

2013 ◽  
Vol 284-287 ◽  
pp. 230-234
Author(s):  
Yu Jen Chou ◽  
Chi Jen Shih ◽  
Shao Ju Shih
Keyword(s):  
Surface Area ◽  
Calcination Temperature ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Bioactive Glasses ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

scholarly journals Recent Advances in Applications of Ceramic Nanofibers

2021 ◽  
Author(s):  
Nuray Kizildag
Keyword(s):  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Ceramic Materials ◽  
Water Remediation ◽  
Mechanical And Thermal Properties ◽  
Chemical Erosion ◽  
Recent Advances ◽  
Wide Range ◽  
Ceramic Nanofibers

Ceramic materials are well known for their hardness, inertness, superior mechanical and thermal properties, resistance against chemical erosion and corrosion. Ceramic nanofibers were first manufactured through a combination of electrospinning with sol–gel method in 2002. The electrospun ceramic nanofibers display unprecedented properties such as high surface area, length, thermo-mechanical properties, and hierarchically porous structure which make them candidates for a wide range of applications such as tissue engineering, sensors, water remediation, energy storage, electromagnetic shielding, thermal insulation materials, etc. This chapter focuses on the most recent advances in the applications of ceramic nanofibers.

Aqueous colloidal sol–gel route to synthesize nanosized ceria-doped titania having high surface area and increased anatase phase stability

2007 ◽  
Vol 43 (3) ◽  
pp. 299-304 ◽  
Author(s):  
Pradeepan Periyat ◽  
K. V. Baiju ◽  
P. Mukundan ◽  
P. Krishna Pillai ◽  
K. G. K. Warrier
Keyword(s):  
Surface Area ◽  
Phase Stability ◽  
Anatase Phase ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Doped Titania

scholarly journals Enhancement of Photocatalytic Oxidation of Glucose to Value-Added Chemicals on TiO2 Photocatalysts by A Zeolite (Type Y) Support and Metal Loading

Catalysts ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 423 ◽  
Author(s):  
Kamonchanok Roongraung ◽  
Surawut Chuangchote ◽  
Navadol Laosiripojana
Keyword(s):  
Formic Acid ◽  
Surface Area ◽  
Gluconic Acid ◽  
Photocatalytic Oxidation ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Value Added ◽  
Incipient Wetness Impregnation ◽  
Microwave Assisted

TiO2-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO2 with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO2 nanoparticles and increasing the photocatalytic activity. Effects of the TiO2 dosage to zeolite ratio (i.e., TiO2/ZeY of 10, 20, 40, and 50 mol %) and the silica to alumina ratio in ZeY (i.e., SiO2:Al2O3 of 10, 100, and 500) were firstly studied. It was found that the specific surface area of TiO2/ZeY was 400–590 m2g−1, which was higher than that of pristine TiO2 (34.38 m2g−1). The good properties of 20%TiO2/ZeY photocatalyst, including smaller particles (13.27 nm) and high surface area, could achieve the highest photocatalytic glucose conversion (75%). Yields of gluconic acid, arabinose, xylitol, and formic acid obtained from 20%TiO2/ZeY were 9%, 26%, 4%, and 35%, respectively. For the effect of the silica to alumina ratio, the highest glucose conversion was obtained from SiO2:Al2O3 ratio of 100. Interestingly, it was found that the SiO2:Al2O3 ratio affected the selectivity of carboxylic products (gluconic acid and formic acid). At a low ratio of silica to alumina (SiO2:Al2O3 = 10), higher selectivity of the carboxylic products (gluconic acid = 29% and formic acid = 32%) was obtained (compared with other higher ratios). TiO2/ZeY was further loaded by metals using the microwave-assisted incipient wetness impregnation technique. The highest glucose conversion of 96.9 % was obtained from 1 wt. % Ag-TiO2 (40%)/ZeY. Furthermore, the bimetallic Ag-Cu-loaded TiO2/ZeY presented the highest xylitol yield of 12.93%.

A silica aerogel as an extractive coating for in-tube solid-phase microextraction to determine polycyclic aromatic hydrocarbons in water samples

2019 ◽  
Vol 11 (45) ◽  
pp. 5784-5792 ◽  
Author(s):  
Xiangping Ji ◽  
Juanjuan Feng ◽  
Chunying Li ◽  
Sen Han ◽  
Jiaqing Feng ◽  
...  
Keyword(s):  
Silica Aerogel ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Ambient Pressure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Ambient Pressure Drying ◽  
Acid Base ◽  
Polycyclic Aromatic

A silica aerogel with high surface area was prepared by an acid–base two-step catalytic sol–gel method under ambient pressure drying.

Sign in / Sign up

Export Citation Format

Share Document