Optically transparent silica aerogels based on sodium silicate by a two step sol–gel process and ambient pressure drying

In this research, aerogels were synthesized by a two-step sol-gel process without supercritical conditions. During the process, tetraethoxysilane (TEOS) was used as precursor, and different surfactants, i.e. cetyltrimethyl ammonium bromide (CTAB) and polyethylene glycol–600 (PEG–600), were used as dopants respectively. In order to minimize the drying shrinkage and preserve the high porosity structure, the surface of the gels was modified by trimethylchlorosilane (TMCS) before the ambient pressure drying (APD). The effect of surfactent on the structure of the resulting aerogels was investigated. The aerogels which involved surfactants exhibited resistance to cracking during the APD of the alcogels. The modification by TMCS has been confirmed using Infrared (IR) spectroscopy. The porous structure of aerogels was investigated by Brunauer-Emmett- Teller (BET) instrument, differential scanning calorimeter (DSC) and scanning electron micrograph (SEM). The results indicated that surfactants as dopants could significantly affect the structure and optical property of aerogels and be beneficial for obtaining crack-free silica aerogels via ambient pressure drying process.

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Physical properties of sodium silicate based silica aerogels prepared by single step sol–gel process dried at ambient pressure

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2008.09.029 ◽

2009 ◽

Vol 476 (1-2) ◽

pp. 397-402 ◽

Cited By ~ 62

Author(s):

Jyoti L. Gurav ◽

A. Venkateswara Rao ◽

A. Parvathy Rao ◽

D.Y. Nadargi ◽

S.D. Bhagat

Keyword(s):

Physical Properties ◽

Sodium Silicate ◽

Ambient Pressure ◽

Sol Gel ◽

Silica Aerogels ◽

Single Step ◽

Sol Gel Process

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Hydrophobic Flexible Silica Aerogels Felts Fabricated by Ambient Pressure Drying

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.709.32 ◽

2013 ◽

Vol 709 ◽

pp. 32-35

Author(s):

Xiao Yun Wu ◽

Yu Xi Yu ◽

De Qian Guo ◽

Yong Chen

Keyword(s):

Aqueous Ammonia ◽

Ambient Pressure ◽

Sol Gel ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Ethanol Solution ◽

Hydrophobic Properties ◽

Ph Values ◽

Sol Gel Process ◽

Hexane Solution

Hydrophobic flexible silica aerogels felts were fabricated successfully by two-steps sol-gel process via ambient pressure drying. First of all, the sol with various pH values was obtained from tetraethylorthosilicate (TEOS) as silicon source, hydrochloric acid/aqueous ammonia ethanol solution as catalysts. Then glass fiber felts was incorporated into the sol to increase the mechanical properties of silica aerogel. After the completion of solvent exchange and surface modification by using trimethylchlorosilane (TMCS)/n-hexane solution, the gel felts were dried under ambient pressure. The samples show excellent hydrophobic properties.

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Hydrophobic Silica Aerogels by Ambient Pressure Drying

Materials Science Forum ◽

10.4028/www.scientific.net/msf.830-831.476 ◽

2015 ◽

Vol 830-831 ◽

pp. 476-479

Author(s):

Srinivasan Nagapriya ◽

M.R. Ajith ◽

H. Sreemoolanadhan ◽

Mariamma Mathew ◽

S.C. Sharma

Keyword(s):

Surface Area ◽

Atmospheric Pressure ◽

Polar Solvent ◽

Ambient Pressure ◽

High Surface ◽

Sol Gel ◽

High Surface Area ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Sol Gel Process

Silica aerogels have been prepared through sol-gel process by polymerization of TEOS in the presence of NH4F and NH4OH as catalysts. The solvent present in the gel is replaced by ethanol followed by a non-polar solvent such as n-hexane prior to solvent modification step. Gels are made hydrophobic by treating them with HMDZ to prevent rupture during drying, which has been confirmed by FTIR. Gels are then washed and dried carefully in a PID controlled oven at atmospheric pressure. The ageing duration and solvent exchange combinations are optimized to yield crack-free gels prior to drying. Aerogels are characterized for density, specific surface area, pore volume, pore size, thermal stability and contact angle. Hydrophobic, high surface area (570 m2/g), low density (0.07 g/cm3) silica aerogels are synthesized by using optimized mole ratio of precursors and catalysts. Silica aerogel granules (1-3 mm) as well as monoliths (Ф~35 mm) could be produced through ambient pressure drying of gels.

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Effect of solvent exchanging process on the preparation of the hydrophobic silica aerogels by ambient pressure drying method using sodium silicate precursor

Journal of Materials Science ◽

10.1007/s10853-007-1788-2 ◽

2007 ◽

Vol 42 (20) ◽

pp. 8418-8425 ◽

Cited By ~ 31

Author(s):

A. Parvathy Rao ◽

A. Venkateswara Rao ◽

G. M. Pajonk ◽

Poonam M. Shewale

Keyword(s):

Sodium Silicate ◽

Ambient Pressure ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Drying Method ◽

Effect Of Solvent ◽

Hydrophobic Silica

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A Novel Route for Preparation of Transparent and Superhydrophobic Silica Aerogels

MRS Proceedings ◽

10.1557/proc-1234-qq06-12 ◽

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°.

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Preparation of monolithic titania aerogels with high surface area by a sol–gel process combined surface modification

RSC Advances ◽

10.1039/c4ra03812f ◽

2014 ◽

Vol 4 (62) ◽

pp. 32934-32940 ◽

Cited By ~ 16

Author(s):

Hui Yang ◽

Wenjun Zhu ◽

Sai Sun ◽

Xingzhong Guo

Keyword(s):

Surface Modification ◽

Surface Area ◽

Ambient Pressure ◽

High Surface ◽

Sol Gel ◽

High Surface Area ◽

Ambient Pressure Drying ◽

Sol Gel Process

Monolithic titania (TiO2) aerogels with high surface area were successfully synthesized by the sol–gel process combined surface modification, followed by ambient pressure drying.

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Study on Preparation of Mesoporous Silica Aerogels with Low Density and High Properties via Ambient Pressure Drying

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.148-149.1491 ◽

2010 ◽

Vol 148-149 ◽

pp. 1491-1496

Author(s):

Gang Qiang Geng ◽

Wei Tao Bi ◽

Yu Zhang ◽

Deng Ke Sun

Keyword(s):

Mesoporous Silica ◽

Ambient Pressure ◽

Sol Gel ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Ethanol Solution ◽

Low Density ◽

Micro Structure ◽

Gel Time

The SiO2 aerogels of low density was fabricated by ion exchange and sol-gel method on the basis of sodium silicate. The effect of pH, aging，addition of DCCA and annealed temperature on the gel time, aerogel density, porosity and the micro-structure was systemly studied. The results showed that when the pH is 5, aging was 30%Vol .of TEOS/ethanol solution ,the addition of DCCA was 1.5ml, the gel system was annealed at 50 for 84 h, 60 for 72h, the best quality of silica aerogels with low density (0.14g/cm3), higher specific surface(610.643 m2/g) and pore size of 20~40 nm can be obtained.

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Synthesis of sodium silicate-based silica aerogels with graphene oxide by ambient pressure drying

Journal of Porous Materials ◽

10.1007/s10934-021-01103-2 ◽

2021 ◽

Author(s):

Oznur Kaya Cakmak ◽

Khalil T. Hassan ◽

Jiabin Wang ◽

Xiao Han ◽

Lidija Šiller

Keyword(s):

Graphene Oxide ◽

Surface Area ◽

Sodium Silicate ◽

Ambient Pressure ◽

Physical And Mechanical Properties ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Silica Matrix ◽

X Ray Diffraction ◽

Composite Aerogels

AbstractHere we study how graphene oxide affects silica aerogels and their physical and mechanical properties by examining volume shrinkage, pore volume, surface area and compressive strength of these composite aerogels. Composite aerogels were made through adding different amount of graphene oxide (GO) to sodium silicate precursor by using ambient pressure drying method. Additionally, the chemical composition of the composite aerogels was determined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. A rougher structure was observed when the GO loading increased and the characteristic peak of GO in XRD disappeared due to the random distribution of GO within the silica matrix. FTIR spectrum of composite aerogels shows that the relative intensity of silanol groups on the silica matrix have downward tendency with the addition of GO. The specific surface area had maxima with the addition of 0.01 wt% GO surface area to 578 m2 /g. The mechanical strength of aerogels was increased, with the loading of GO from 0.0 wt% to 0.2 wt%, and the compressive modulus increased from 0.02 MPa to 0.22 MPa.

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