Dynamic Compressive Response of Bi-continuous Mesoporous Silica Aerogel
Aerogels are low-density mesoporous materials with exceptionally low dielectric constants, low thermal conductivities (up to 40 times better thermal insulators than the best fiberglass) and high acoustic impedance. Their practical applications of native aerogel, however, have been slow due to their hydrophilicity and brittleness. The fragility problem was resolved by nanocasting a ∼2-4 nm thick polymer layer on the fractal network of nanoparticles without clogging the pores, which strengthens the weak inter-nanopartical necks. With a density increase by only three times, crosslinking aerogels have the flexural strength increased by 300 times. The method has been applied for crosslinking aerogels consisting of oxides of more than 30 different elements from the periodic table. The network morphology of aerogel skeleton is key to improve the mechanical properties further such as incorporating 5% (w/w) carbon nanofibers into native silica aerogels, and 2-D fiber or worm-like of vanadia aerogel which can dissipate applied forces more efficiently. Certain micelle-templated aerogels were known to have a worm-like microstructure with a macro/mesoporous (bi-continuous) skeletal framework. Crosslinked, surfactant-templated macro/mesoporous silica aerogels, X-MP4-T045, was made by encapsulating the native 3D skeletal framework with polymers derived from di-isocyanate (N3200). Through an acid-catalyzed sol-gel process from tetramethoxysilane (TMOS) using a triblock co-polymer (Pluronic P123: PEO 20PPO70PEO20) as structure-directing agent and 1,3,5-trimethylbenzene (TMB) as micelle-swelling reagent, macroporous monolithic silica aerogels have been synthesized, consisting of both random and ordered mesoporous walls. Those monoliths are more robust than base-catalyzed silica aerogels of similar density, and the mechanical properties can be improved dramatically by letting di-isocyanate react with the silanols on the mesoporous surfaces. ©2009 Society for Experimental Mechanics Inc.
H. Luo et al., "Dynamic Compressive Response of Bi-continuous Mesoporous Silica Aerogel," Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2009, Society for Experimental Mechanics, Inc, Jan 2009.
Article - Conference proceedings
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