Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH 3 SiO 1.5 ) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercrit...

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Bibliographic Details
Published in:Journal of sol-gel science and technology 2008-11, Vol.48 (1-2), p.172-181
Main Authors: Kanamori, Kazuyoshi, Aizawa, Mamoru, Nakanishi, Kazuki, Hanada, Teiichi
Format: Article
Language:English
Subjects:
Capillary pressure
Ceramics
Chemistry
Chemistry and Materials Science
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Composites
Compressive strength
Exact sciences and technology
General and physical chemistry
Glass
Inorganic Chemistry
Materials Science
Mechanical properties
Nanotechnology
Natural Materials
Optical and Electronic Materials
Original Paper
Porosity
Porous materials
Pressure
Shrinkage
Silica aerogels
Silicon dioxide
Sol-gel processes
Xerogels
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Summary:Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH 3 SiO 1.5 ) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.
ISSN:0928-0707
1573-4846
DOI:10.1007/s10971-008-1756-6