Preparation of high-strength silica aerogels by two-step surface modification via ambient pressure drying

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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Surface modification of silica aerogels with trimethylchlorosilane in the ambient pressure drying

Inorganic Materials ◽

10.1134/s0020168508090148 ◽

2008 ◽

Vol 44 (9) ◽

pp. 976-979 ◽

Cited By ~ 28

Author(s):

XiaoChun Zhou ◽

LuPing Zhong ◽

YaPing Xu

Keyword(s):

Surface Modification ◽

Ambient Pressure ◽

Silica Aerogels ◽

Ambient Pressure Drying

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Facile Preparation of High Strength Silica Aerogel Composites via a Water Solvent System and Ambient Pressure Drying without Surface Modification or Solvent Replacement

Materials ◽

10.3390/ma14143983 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3983

Author(s):

Dongxuan Du ◽

Fengqi Liu ◽

Yonggang Jiang ◽

Junzong Feng ◽

Liangjun Li ◽

...

Keyword(s):

Thermal Conductivity ◽

Surface Modification ◽

Silica Aerogel ◽

Ambient Pressure ◽

High Strength ◽

Ambient Pressure Drying ◽

Synthesis Process ◽

Insulation Material ◽

Fiber Density ◽

Solvent Replacement

To further reduce the manufacturing cost and improve safety, silica aerogel composites (SAC) with low density and low thermal conductivity synthesized via ambient pressure drying (APD) technology have gradually become one of the most focused research areas. As a solvent, ethanol is flammable and needs to be replaced by other low surface tension solvents, which is dangerous and time-consuming. Therefore, the key steps of solvent replacement and surface modification in the APD process need to be simplified. Here, we demonstrate a facile strategy for preparing high strength mullite fiber reinforced SAC, which is synthesized by APD using water as a solvent, rather than using surface modification or solvent replacement. The effects of the fiber density on the physical properties, mechanical properties, and thermal conductivities of SAC are discussed in detail. The results show that when the fiber density of SAC is 0.24 g/cm3, the thermal conductivity at 1100 °C is 0.127 W/m·K, and the compressive strength at 10% strain is 1.348 MPa. Because of the simple synthesis process and excellent thermal-mechanical performance, the SAC is expected to be used as an efficient and economical insulation material.

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Preparation and surface modification mechanism of silica aerogels via ambient pressure drying

Materials Chemistry and Physics ◽

10.1016/j.matchemphys.2011.04.003 ◽

2011 ◽

Vol 129 (1-2) ◽

pp. 308-314 ◽

Cited By ~ 49

Author(s):

Guoyou Wu ◽

Yuxi Yu ◽

Xuan Cheng ◽

Ying Zhang

Keyword(s):

Surface Modification ◽

Ambient Pressure ◽

Silica Aerogels ◽

Ambient Pressure Drying

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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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