Thermal Gelation for Synthesis of Surface-Modified Silica Aerogel Powders

A spherical silica aerogel powder with hydrophobic surfaces displaying a water contact angle of 147° was synthesized from a water glass-in-hexane emulsion through ambient pressure drying. Water glass droplets containing acetic acid and ethyl alcohol were stabilized in n-hexane with a surfactant. Gelation was performed by heating the droplets, followed by solvent exchange and surface modification using a hexamethyldisilazane (HMDS)/n-hexane solution. The pH of the silicic acid solution was crucial in obtaining a highly porous silica aerogel powder with a spherical morphology. The thermal conductivity, tapped density, pore volume, and BET surface area of the silica aerogel powder were 22.4 mW·m−1K−1, 0.07 g·cm−3, 4.64 cm3·g−1, and 989 m2·g−1, respectively. Fourier transform infrared (FT–IR) spectroscopy analysis showed that the silica granule surface was modified by Si-CH3 groups, producing a hydrophobic aerogel.

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Highly transparent silica aerogel thick films with hierarchical porosity from water glass via ambient pressure drying

Materials Chemistry and Physics ◽

10.1016/j.matchemphys.2014.04.007 ◽

2014 ◽

Vol 147 (1-2) ◽

pp. 65-74 ◽

Cited By ~ 11

Author(s):

Peng He ◽

Xiang-dong Gao ◽

Xiao-min Li ◽

Zheng-wu Jiang ◽

Zheng-hong Yang ◽

...

Keyword(s):

Silica Aerogel ◽

Water Glass ◽

Ambient Pressure ◽

Thick Films ◽

Ambient Pressure Drying ◽

Hierarchical Porosity

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Fabrication of Spherical Silica Aerogel Granules from Water Glass by Ambient Pressure Drying

Journal of the American Ceramic Society ◽

10.1111/j.1551-2916.2011.04765.x ◽

2011 ◽

Vol 94 (10) ◽

pp. 3198-3201 ◽

Cited By ~ 24

Author(s):

Sun Ki Hong ◽

Mi Young Yoon ◽

Hae Jin Hwang

Keyword(s):

Silica Aerogel ◽

Water Glass ◽

Ambient Pressure ◽

Ambient Pressure Drying ◽

Spherical Silica

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Preparation and Characterization of Nanoporous Silica Aerogel Granules on The Basis of Water Glass Via Ambient Pressure Drying Method

Jurnal Teknologi ◽

10.11113/jt.v59.2598 ◽

2012 ◽

Vol 59 (2) ◽

Author(s):

Ehsan Amirjan ◽

Omid Mirzaee ◽

Mohammad Reza Soleimani Dorcheh ◽

Ali Soleimani Dorcheh

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Silica Aerogel ◽

Water Glass ◽

Ambient Pressure ◽

Nanostructured Material ◽

Ambient Pressure Drying ◽

High Porosity ◽

Hydrophobic Silica

A crack-free silica aerogel monolith is a nanostructured material with so many surprising properties such as high specific surface area, high porosity, low dielectric constant, low density and outstanding heat insulation properties that were fabricated from a cheap water glass derived silicic acid solution.In this research , the OH surfaces of the wet gel were modified using a HMDZ/n-hexane or TMCS/n-hexane mixture followed by solvent exchange from water to n-hexane. The obtained surface modified wet gel was dried at different temperature under ambient pressure.The properties of hydrophobic silica aerogels synthesized by this new route were investigated by scanning electron microscopy (SEM), differential temperature analysis (DTA) and Fourier-transform infrared spectroscopy (FT-IR).The results showed that 20 wt% HMDZ as surface modifier and 75 °C as drying temperature resulted an acceptable hydrophobic silica aerogel with the density of 0.15 gr/cm³ and specific surface area of about 520 m²/gr.

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Carbon Fiber—Silica Aerogel Composite with Enhanced Structural and Mechanical Properties Based on Water Glass and Ambient Pressure Drying

Nanomaterials ◽

10.3390/nano11020258 ◽

2021 ◽

Vol 11 (2) ◽

pp. 258

Author(s):

Agnieszka Ślosarczyk

Keyword(s):

Carbon Fiber ◽

Carbon Fibers ◽

Silica Aerogel ◽

Water Glass ◽

Structural Parameters ◽

Ambient Pressure ◽

Ambient Pressure Drying ◽

Physical Parameters ◽

Synthesis Time ◽

Aerogel Composite

The article presents the synthesis of silica aerogel from a much cheaper precursor of water glass that was reinforced with short pitch carbon fiber by way of ambient pressure drying. Before being added to the silica gel, the carbon fibers were surface modified to increase adhesion at the interfacial border. We were able to obtain stable structures of the composite with the amount of fibers above 10% by volume. The presence of fibers in the silica matrix resulted in lower synthesis time of the composite, improved adhesion of fibers to the aerogel nanostructure, and increased mechanical and structural parameters. An additional effect of the presence of fibers in excess of 10% by volume was a new function of the nanocomposite—the ability to conduct electric current. The most optimal parameters of the composite, however, were obtained for silica aerogel reinforced with 10 vol.% of carbon fibers. This material indicated relatively low density and good physical parameters. The paper also analyzes the results on the synthesis of fiber-reinforced silica aerogels that have appeared in recent years and compares these to the results gained in presented work.

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Silica Aerogel Monoliths Derived from Silica Hydrosol with Various Surfactants

Molecules ◽

10.3390/molecules23123192 ◽

2018 ◽

Vol 23 (12) ◽

pp. 3192 ◽

Cited By ~ 3

Author(s):

Dong Chen ◽

Xiaodong Wang ◽

Wenhui Ding ◽

Wenbing Zou ◽

Qiong Zhu ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermal Stability ◽

Silica Aerogel ◽

Low Cost ◽

Ambient Pressure ◽

Silica Aerogels ◽

Ambient Pressure Drying ◽

Low Thermal Conductivity ◽

Silica Hydrosol ◽

High Production Cost

Owing to their ultra-low thermal conductivity, silica aerogels are promising thermal insulators; however, their extensive application is limited by their high production cost. Thus, scientists have started to explore low-cost and easy preparation processes of silica aerogels. In this work, a low-cost method was proposed to prepare silica aerogels with industrial silica hydrosol and a subsequent ambient pressure drying (APD) process. Various surfactants (cationic, amphoteric, or anionic) were added to avoid solvent exchange and surface modification during the APD process. The effects of various surfactants on the microstructure, thermal conductivity, and thermal stability of the silica aerogels were studied. The results showed that the silica aerogels prepared with a cationic or anionic surfactant have better thermal stability than that prepared with an amphoteric surfactant. After being heated at 600 °C, the silica aerogel prepared with a cationic surfactant showed the highest specific surface area of 131 m2∙g−1 and the lowest thermal conductivity of 0.038 W∙m−1∙K−1. The obtained low-cost silica aerogel with low thermal conductivity could be widely applied as a thermal insulator for building and industrial energy-saving applications.

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