Synthesis of Monolithic Macroporous Carbon Xerogels from Phenol, m-Cresol, Furfural and Phosphoric Acid by Sol-Gel Approach

2013 ◽  
Vol 750-752 ◽  
pp. 1804-1811
Author(s):  
Rui Zhang ◽  
Zi Jun Hu ◽  
Shuang Ling Jin ◽  
Xia Shao ◽  
Ming Lin Jin
Keyword(s):  
Phosphoric Acid ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Nitrogen Atmosphere ◽  
Molar Ratio ◽  
Surface Areas ◽  
Carbon Xerogels ◽  
Porous Properties ◽  
Macroporous Carbon

Mixtures of phenol and m-cresol in 1-propanol were first reacted with phosphoric acid and then with furfural to form gels, which were dried under ambient pressure and pyrolyzed under nitrogen atmosphere to form monolithic macroporous carbon xerogels. The molar ratio of m-cresol to phenol (m-C/P), phenol and m-cresol to furfural ((m-C+P)/F), phenol and m-cresol to phosphoric acid ((m-C+P)/H3PO4) was fixed at 1:5, 1:2 and 4.0 respectively while the m-C+P+F in 1-propanol was changed from 18 to 30 g/100ml to investigate the effect of the m-C+P+F concentrations on the porous properties of the monolithic carbon xerogels. It is found that the surface areas of the monolithic carbon xerogels are mainly contributed by micropores and their mesopore volumes are negligible. The monolithic carbon xerogels are rich in macropores whose sizes decrease from 4 to 0.22μm with increasing m-C+P+F concentrations. Moreover, the yields of the monolithic carbon xerogels are around 60%, which is higher than previous ones without phosphoric acid.

Synthesis and Characterization of Pd/Ag/SiO2 Nano-Composite Materials

2017 ◽  
Vol 726 ◽  
pp. 204-209 ◽  
Author(s):  
Jing Yang ◽  
Bao Song Li ◽  
Zhi Tong ◽  
Rui Hua Mu
Keyword(s):  
Zeta Potential ◽  
Size Distribution ◽  
Sol Gel ◽  
Linear Structure ◽  
Nitrogen Atmosphere ◽  
Molar Ratio ◽  
Powder Materials ◽  
X Ray Diffraction ◽  
Silica Network

Pd/Ag/SiO2 sols and powder materials were prepared by adding AgNO3 and Pd (NO3)2·2H2O into a methyl-modified silica sol. Tetraethylorthosilicate and methyltriethoxysilane were used as the silica precursor for the sol-gel reaction. The obtained SiO2 sols and powder materials were characterized by sol particle size distribution, zeta potential analysis, UV-Vis spectra, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurement. It was found that most of the particle sizes of the prepared Pd/Ag/SiO2 sols are about 2~10 nm with narrow size distribution. The zeta potential of Pd/Ag/SiO2 sol with Pd/Ag molar ratio of 7.5/2.5 presents the highest value. The FTIR analysis substantiates that the Si-CH3 groups exist in the silica network and the formed Pd/Ag/SiO2 sol particles possess linear structure. XRD characterization indicates that the Pd2+ and Ag+ in the Pd/Ag/SiO2 materials had be reduced to Pd0 and Ag0, respectively, after annealed in a nitrogen atmosphere at 350°C.

A Novel Route for Preparation of Transparent and Superhydrophobic Silica Aerogels

2009 ◽  
Vol 1234 ◽  
Author(s):  
Guo-you Wu ◽  
Xuan Cheng ◽  
Yu-xi Yu ◽  
Ying Zhang
Keyword(s):  
Surface Modification ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Three Dimensional ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Nanoporous Structure ◽  
Surface Areas ◽  
Superhydrophobic Silica ◽  
Dta Curve

AbstractSilica aerogels were synthesized via sol-gel processing followed by a two-step surface modification and ambient pressure drying, using methyltrimethoxysilane (MTMS) and trimethylchlorosilane (TMCS)/ethanol/n-hexane as surface modification agents. The transparent silica aerogels possessed the porosities, densities and specific surface areas in the range of 87.7–92.3%, 0.27–0.17 g·cm-3 and 852–1005 m2·g-1, respectively. The SEM and HRTEM analysis revealed the three-dimensional nanoporous structure of the silica aerogels. The presence of –CH3 functional groups on the surface of silica particles as indicated by the FTIR spectra was further confirmed by two visible exothermic peaks at 310 and 450–500 °C from the DTA curve. In addition, the silica aerogels were superhydrophobic with the contact angle as high as 160°.

scholarly journals Coesite Formation at Ambient Pressure and Low Temperatures

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
J. R. Martínez ◽  
A. Vázquez-Durán ◽  
G. Martínez-Castañón ◽  
G. Ortega-Zarzosa ◽  
S. A. Palomares-Sánchez ◽  
...  
Keyword(s):  
Glass Matrix ◽  
Colloidal Particles ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Molar Ratio ◽  
Silica Xerogel ◽  
Thermal Treatments ◽  
Refinement Method ◽  
Partial Crystallization ◽  
Starting Solutions

Partial crystallization of silica xerogel in the form of coesite has been obtained at low-pressure conditions and temperatures of∼565∘C, in samples containing chlorophyll aggregates dispersed in amorphous silica. Silica xerogel samples were prepared by the sol-gel method using an ethanol:H2O:TEOS molar ratio of 4:11.6:1 and loaded with extracts from frozen spinach leaves. The silica xerogel microstructure of the powders was studied as a function of annealing temperature. It was found that partial crystallization of the glass matrix in the form of coestite was obtained at lower pressure than those specified by the phase diagram. Chlorophyll aggregates were added to the starting solutions which, upon thermal treatments, form small colloidal particles in the glass matrix. The presence of coesite is corroborated by the Rietveld refinement method.

scholarly journals Chitosan-GPTMS-Silica Hybrid Mesoporous Aerogels for Bone Tissue Engineering

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2723
Author(s):  
María V. Reyes-Peces ◽  
A. Pérez-Moreno ◽  
Deseada María de-los-Santos ◽  
María del Mar Mesa-Díaz ◽  
Gonzalo Pinaglia-Tobaruela ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Sol Gel ◽  
Polymer Networks ◽  
Supercritical Drying ◽  
Hybrid Structure ◽  
Stress Fibers ◽  
Molar Ratio ◽  
Surface Areas ◽  
Silica Hybrid

This study introduces a new synthesis route for obtaining homogeneous chitosan (CS)-silica hybrid aerogels with CS contents up to 10 wt%, using 3-glycidoxypropyl trimethoxysilane (GPTMS) as coupling agent, for tissue engineering applications. Aerogels were obtained using the sol-gel process followed by CO2 supercritical drying, resulting in samples with bulk densities ranging from 0.17 g/cm3 to 0.38 g/cm3. The textural analysis by N2-physisorption revealed an interconnected mesopore network with decreasing specific surface areas (1230–700 m2/g) and pore sizes (11.1–8.7 nm) by increasing GPTMS content (2–4 molar ratio GPTMS:CS monomer). In addition, samples exhibited extremely fast swelling by spontaneous capillary imbibition in PBS solution, presenting swelling capacities from 1.75 to 3.75. The formation of a covalent crosslinked hybrid structure was suggested by FTIR and confirmed by an increase of four hundred fold or more in the compressive strength up to 96 MPa. Instead, samples synthesized without GPTMS fractured at only 0.10–0.26 MPa, revealing a week structure consisted in interpenetrated polymer networks. The aerogels presented bioactivity in simulated body fluid (SBF), as confirmed by the in vitro formation of hydroxyapatite (HAp) layer with crystal size of approximately 2 µm size in diameter. In vitro studies revealed also non cytotoxic effect on HOB® osteoblasts and also a mechanosensitive response. Additionally, control cells grown on glass developed scarce or no stress fibers, while cells grown on hybrid samples showed a significant (p < 0.05) increase in well-developed stress fibers and mature focal adhesion complexes.

CHARACTERIZATION OF TITANIUM PHOSPHATE AS ELECTROLYTES IN FUEL CELLS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4147-4152 ◽  
Author(s):  
A. T. T. TRAN ◽  
M. C. DUKE ◽  
P. G. GRAY ◽  
J. C. DINIZ DA COSTA
Keyword(s):  
Fuel Cells ◽  
Relative Humidity ◽  
Proton Conductivity ◽  
Proton Exchange Membrane ◽  
Sol Gel ◽  
Proton Exchange ◽  
Titanium Phosphate ◽  
Molar Ratio ◽  
Oh Groups ◽  
Surface Areas

Titanium phosphate is currently a promising material for proton exchange membrane fuel cells applications (PEMFC) allowing for operation at high temperature conditions. In this work, titanium phosphate was synthesized from tetra iso-propoxide (TTIP) and orthophosphoric acid ( H 3 PO 4) in different ratios by a sol gel method. High BET surface areas of 271 m2.g-1 were obtained for equimolar Ti:P samples whilst reduced surface areas were observed by varying the molar ratio either way. Highest proton conductivity of 5.4×10-2 S . cm -1 was measured at 20°C and 93% relative humidity (RH). However, no correlation was observed between surface area and proton conductivity. High proton conductivity was directly attributed to hydrogen bonding in P - OH groups and the water molecules retained in the sample structure. The proton conductivity increased with relative humidity, indicating that the Grotthuss mechanism governed proton transport. Further, sample Ti/P with 1:9 molar ratio showed proton conductivity in the order of 10-1 S.cm-1 (5% RH) and ~1.6×10-2 S . cm -1 (anhydrous condition) at 200°C. These proton conductivities were mainly attributed to excess acid locked into the functionalized TiP structure, thus forming ionisable protons.

scholarly journals Formation of Silicon Carbide Whiskers from Organic Precursors Via Sol-Gel Method

2010 ◽  
Vol 13 (1-2) ◽  
pp. 27 ◽  
Author(s):  
S. Manocha ◽  
Ankur Darji ◽  
L.M. Manocha
Keyword(s):  
Silicon Carbide ◽  
Sol Gel ◽  
Nitrogen Atmosphere ◽  
Molar Ratio ◽  
Carbon Precursor ◽  
Silica Network ◽  
Black Glass ◽  
Sic Whiskers ◽  
Water Ph ◽  
Silica Precursor

<p>Silicon Carbide (SiC) was synthesized by carbothermal reduction of silica precursor and carbon precursor. The silica precursor was obtained from tetraethoxysilane. Sucrose was used as carbon source. Tetraethoxysilane (TEOS) was hydrolyzed in acidic water (pH= 2). The molar ratio of TEOS-H<sub>2</sub>O-EtOH was taken as 1:8:2 in the sol-gel processing. Hydrolysed silica sol was polymerized with sucrose to incorporate carbon precursor into the silica network. The gel thus obtained was dried in an oven at 70 °C and at 100 °C. The solid mass obtained on drying was heat treated at 1000 °C in nitrogen atmosphere to obtain the black glass. It was characterized by FTIR, SEM and TGA. The black glass was further heated to 1500 °C in argon to yield silicon carbide. This resulted in formation of β-SiC whiskers.</p>

Nanoporous TiO2/SiO2 Composite Prepared by a Combined Sol-Gel and Hybrid Method

2008 ◽  
Vol 368-372 ◽  
pp. 1497-1499 ◽  
Author(s):  
Wen Yuan Xu ◽  
Lu Bin Wei ◽  
Ming Biao Luo
Keyword(s):  
Phase Composition ◽  
Pore Size ◽  
Hybrid Method ◽  
Average Pore Size ◽  
Sol Gel ◽  
Molar Ratio ◽  
Tetrabutyl Titanate ◽  
Average Pore ◽  
Silica Nanocomposites ◽  
Surface Areas

Titania-silica nanocomposites with different TiO2/SiO2 compositions have been prepared by a sol-gel and hybrid method from tetraethylorthosilicate (TEOS) and tetrabutyl titanate(TBT) and β-Cyclodextrin as a pore-forming template. Drying and calcining of the hybrid xerogel can lead to the formation of nanoporous particles with surface areas in the range of 298-418 m2/g. The effect of the β-cyclodextrin concentration, the molar ratio of TiO2/SiO2 and the calcining temperature on the phase composition and structural properties of TiO2/SiO2 composites were also investigated. The results show that an increase in β-cyclodextrin concentration can lead to a decrease of the surface area and an increase of average pore size, which can be controlled by the amount of β- cyclodextrin in the hybrid sol.

scholarly journals Preparation of Silica Aerogels by Ambient Pressure Drying without Causing Equipment Corrosion

Molecules ◽  
2018 ◽  
Vol 23 (8) ◽  
pp. 1935 ◽  
Author(s):  
Lixiao Zhu ◽  
Yali Wang ◽  
Suping Cui ◽  
Feihua Yang ◽  
Zuoren Nie ◽  
...  
Keyword(s):  
Pore Structure ◽  
Raw Materials ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Molar Ratio ◽  
Insulation Property ◽  
Water Contact ◽  
Thermal Insulation Property

The silica aerogels were prepared via a sol-gel technique and ambient pressure drying by using industrial solid wastes, dislodged sludges, as raw materials. A strategy was put forward to reduce the corrosion of equipment during the drying procedure. The pore structure, hydrophobicity, and thermal insulation property of the obtained samples were investigated in detail. The results show that the corrosion can be effectively avoided by using an equimolar mixture of trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) as silylation agents. At a Si:TMCS:HMDS molar ratio of 1:0.375:0.375, the silica aerogels possess a desirable pore structure with a pore volume of 3.3 ± 0.1 cm3/g and a most probable pore size of 18.5 nm, a high hydrophobicity with a water contact angle of 144.2 ± 1.1°, and a low thermal conductivity of 0.031 ± 0.001 W/(m∙K).

The Orthogonal Optimization of Process Parameters of Silica Xerogels

2007 ◽  
Vol 121-123 ◽  
pp. 235-238
Author(s):  
Xiao Dong He ◽  
Fei He ◽  
Yao Li
Keyword(s):  
Process Parameters ◽  
Ambient Pressure ◽  
Sol Gel ◽  
Ambient Pressure Drying ◽  
Molar Ratio ◽  
Process Conditions ◽  
Silica Xerogels ◽  
Optimization Of Process Parameters ◽  
Acid Catalyzed ◽  
Orthogonal Optimization

Two-step acid-base catalyzed silica xerogels were prepared through sol-gel and ambient pressure drying. Various additive components were main fators which influenced the porosity of silica xerogles. An orthogonal array (OA) design OA9(34) was applied to select the optimum conditions of additives. The effects of the molar ratio of H2O, alcohol, HCl, and ammonia were evaluated on the basis of the other same process parameters. Every experiment was conducted several times under different process conditions which included reactive temperature, the acid catalyzed time, aging, exchanging solvent and drying for assuring gels formed. The porosity was an index which was used to appraise the characteristic of silica xerogels. Two kinds of silica xerogels, prepared by the most optimal molar ratio (OMR) and the best OA experiment respectively, were compared by means of SEM. The results showed that the most OMR of TEOS, H2O, alcohol, HCl and ammonia was 1:4:10:7.5× 10-4:0.0375.

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