Super Thermal Insulating SiO2 Cryogels Prepared by Vacuum Freeze Drying

2010 ◽  
Vol 105-106 ◽  
pp. 851-854 ◽  
Author(s):  
Li Fen Su ◽  
Lei Miao ◽  
Gang Xu ◽  
Sakae Tanemura
Keyword(s):  
Freeze Drying ◽  
Ambient Pressure ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
Base Catalysis ◽  
Low Density ◽  
Solvent Exchange ◽  
Acid Base ◽  
Thermal Insulating ◽  
Silica Precursor

Traditionally, silica aerogels with low thermal conductivity are prepared by supercritical drying, however, the process is expensive and hazardous due to it run in autoclaves. In order to overcome these disadvantages, a cheaper and safer process, drying at ambient pressure has been developed for decades, but tedious repetitive gel washing and solvent exchange steps are involved. Therefore, in the present study, a novel vacuum freeze-drying was utilized to prepare the super thermal insulating SiO2 cryogels. The wet gels were synthesized via acid-base catalysis using tetraethoxysilane (TEOS) as a silica precursor and ethanol as a solvent. After vacuum freeze drying, nanoporous SiO2 cryogels with low density in the range of 0.08-0.15 g/cm3 were obtained.

Hydrophobic and low density silica aerogels dried at ambient pressure using TEOS precursor

2009 ◽  
Vol 471 (1-2) ◽  
pp. 296-302 ◽  
Author(s):  
Jyoti L. Gurav ◽  
A. Venkateswara Rao ◽  
Uzma K.H. Bangi
Keyword(s):  
Ambient Pressure ◽  
Silica Aerogels ◽  
Low Density

Preparation Of Low-Density Xerogels At Ambient Pressure For Low K Dielectrics

1995 ◽  
Vol 381 ◽  
Author(s):  
D. M. Smith ◽  
J. Anderson ◽  
C. C. Cho ◽  
G. P. Johnston ◽  
S. P. Jeng
Keyword(s):  
Dielectric Constant ◽  
Ambient Pressure ◽  
Supercritical Drying ◽  
Temperature Limit ◽  
Ambient Pressure Drying ◽  
Low Dielectric Constant ◽  
Low Density ◽  
Silica Xerogels ◽  
High Temperature Limit ◽  
Low Dielectric

AbstractLow density silica xerogels have many properties which suggest their use as a low dielectric constant material. Recent process improvements to control capillary pressure and strength by employing aging and pore chemistry modification, such that shrinkage is minimal during ambient pressure drying, have eliminated the need for supercritical drying. Although xerogels offer advantages for intermetal dielectric (IMD) applications because of their low dielectric constant (<2), high temperature limit, and compatibility with existing microelectronics precursors and processes, they suffer from unanswered questions. These include: 1) are all pores smaller than microelectronics features, 2) what are their mechanical properties (for processing and particle generation), and 3) what is their thermal stability. We have produced bulk xerogels under similar conditions to those used for films and studied the effect of density on the pore size distribution and bulk modulus.

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

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.

Synthesis of Silica Aerogel Thin Film from Waterglass

2007 ◽  
Vol 124-126 ◽  
pp. 671-674 ◽  
Author(s):  
Young Chul Cha ◽  
Chul Eui Kim ◽  
Seung Hun Lee ◽  
Hae Jin Hwang ◽  
Ji Woong Moon ◽  
...  
Keyword(s):  
Thin Film ◽  
Water Glass ◽  
Ph Value ◽  
Ambient Pressure ◽  
Silica Aerogels ◽  
Dip Coating ◽  
Ambient Pressure Drying ◽  
Drying Method ◽  
Silica Precursor ◽  
Dip Coating Technique

Hydrophobic thin film silica aerogels were synthesized by ambient pressure drying method from silicic acid which was prepared from sodium silicate (water glass) solution. The pH value of the silica precursor sol was adjusted to make a spinable sol, and gel films were coated on a glass substrate by dip coating technique. Aerogel-like thin films with the thickness of about 1 μm could be successfully fabricated by repeating the dip coating process three times.

An economic and environmentally benign approach for the preparation of monolithic silica aerogels

RSC Advances ◽  
2016 ◽  
Vol 6 (96) ◽  
pp. 93374-93383 ◽  
Author(s):  
Yuanyuan Zhang ◽  
Junxia Peng ◽  
Guanqun Du ◽  
Hongxia Zhang ◽  
Yu Fang
Keyword(s):  
Ambient Pressure ◽  
Sol Gel ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Environmentally Benign ◽  
Solvent Exchange ◽  
Monolithic Silica ◽  
One Step ◽  
Thermal Conductivities

One step sol–gel reaction, followed by solvent exchange free ambient pressure drying resulted in various monolithic silica aerogels from super-hydrophobic to hydrophilic with densities as low as 0.026 g cm−3 and thermal conductivities lower than air.

Highly flexible silica aerogels derived from methyltriethoxysilane and polydimethylsiloxane

2015 ◽  
Vol 39 (10) ◽  
pp. 7832-7838 ◽  
Author(s):  
Liang Zhong ◽  
Xiaohong Chen ◽  
Huaihe Song ◽  
Kang Guo ◽  
Zijun Hu
Keyword(s):  
Ambient Pressure ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Low Density ◽  
Rapid Synthesis ◽  
Hydrophobic Silica ◽  
Highly Hydrophobic

The rapid synthesis of low-density, highly hydrophobic silica aerogels was performedviaambient pressure drying.

Preparation of Silica Aerogels Modified Foamed Polypropylene for Thermal Insulating Applications

2015 ◽  
Vol 1090 ◽  
pp. 50-54 ◽  
Author(s):  
Li Fen Su ◽  
Wei Zhang ◽  
Ru Xia ◽  
Bin Yang ◽  
Ji Bin Miao ◽  
...  
Keyword(s):  
Weight Ratio ◽  
Silica Aerogels ◽  
Low Density ◽  
Cross Link ◽  
Thermal Insulating ◽  
Insulating Properties ◽  
Thermal Conductivities

The foamed polypropylene (PP) with excellent thermal insulating property was prepared by using the nanosilica (SiO2) aerogels as nucleators, followed by mould pressing foam in cross-link. The weight ratio of SiO2/ PP, which was at the range of 0~ 2%, significantly affected the morphology and thermal insulating properties of the foamed PP. The results showed that the foamed PP can get excellent properties when the weight contents of SiO2aerogels was 1 %. The foamed PP with low density as 0.43 g/cm3and thermal conductivities at the range of 0.046~0.507 W.(m.K-1) was obtained by using this method.

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