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

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.

Download Full-text

Effect of protic solvents on the physical properties of the ambient pressure dried hydrophobic silica aerogels using sodium silicate precursor

Journal of Porous Materials ◽

10.1007/s10934-007-9104-8 ◽

2007 ◽

Vol 15 (5) ◽

pp. 507-512 ◽

Cited By ~ 33

Author(s):

A. Parvathy Rao ◽

A. Venkateswara Rao ◽

Jyoti L. Gurav

Keyword(s):

Physical Properties ◽

Sodium Silicate ◽

Ambient Pressure ◽

Silica Aerogels ◽

Hydrophobic Silica ◽

Protic Solvents

Download Full-text

The influence of various pH values on the aerogel physical properties by sol-gel technique

Iraqi Journal of Physics (IJP) ◽

10.30723/ijp.v17i41.461 ◽

2019 ◽

Vol 17 (41) ◽

pp. 75-81

Author(s):

Baha Fakhry Shehab

Keyword(s):

Physical Properties ◽

Ph Value ◽

Ambient Pressure ◽

Sol Gel ◽

Silica Aerogels ◽

Spectroscopic Studies ◽

Ambient Pressure Drying ◽

Ph Values ◽

Bet Method ◽

The Fourier Transform

Hydrophobic silica aerogels were successfully preparation by an ambient pressure drying method from sodium silicate (Na2SiO3) with different pH values (5, 6, 7, 8, 9 and 10). In this study, acidic HCl (1M), a basic NH4OH (1M) were selected as a catalyst to perform the surface modification in a TMCS (trimethylchlorosilane) solution. The surface chemical modification of the aerogels was assured by the Fourier transform infrared (FTIR) spectroscopic studies. Other physical properties, such as pore volume and pore size and specific surface area were determined by Brunauer-Emmett- Teller (BET) method. The effect of pH values on the bulk density of aerogel. The sol–gel parameter pH value in the sol, have marked effects on the physical properties of the silica aerogels produced by this technique. The density and the hydrophobic tendency of the aerogels were significantly influenced.

Download Full-text

Hydrophobic and physical properties of the ambient pressure dried silica aerogels with sodium silicate precursor using various surface modification agents

Applied Surface Science ◽

10.1016/j.apsusc.2006.12.117 ◽

2007 ◽

Vol 253 (14) ◽

pp. 6032-6040 ◽

Cited By ~ 183

Author(s):

A. Parvathy Rao ◽

A. Venkateswara Rao ◽

G.M. Pajonk

Keyword(s):

Surface Modification ◽

Physical Properties ◽

Sodium Silicate ◽

Ambient Pressure ◽

Silica Aerogels

Download Full-text

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.

Download Full-text