Nanoengineering Strong Silica Aerogels

Abstract

In the quest for strong lightweight materials, silica aerogels would be very attractive, if they were not fragile. The strength of silica aerogel monoliths has been improved by a factor of over 100 through cross-linking the nanoparticle building blocks of preformed silica hydrogels with poly(hexamethylene diisocyanate). Composite monoliths are much less hygroscopic than native silica, and they do not collapse when in contact with liquids.

Reversibly Assembled Cellular Composite Materials

“…Their response is characterized as displaying either stretch-dominated or transverse beam bending-dominated microstructural behavior, based on periodic mechanical models (7,11). For the Young's modulus E, ideal stretch-dominated scaling with density r follows a proportional law, E º r (12); common stochastic foams follow a quadratic law, E º r 2 (7), associated with transverse beam bending-dominated behavior; and at ultralight densities, a further reduced cubic scaling law, E º r 3 , is commonly observed, such as with aerogels and aerogel composites (7,11,13,14).…”

Flexible and Transparent Silica Aerogels: An Overview

“…Liquid-phase cross-linking, vapor-phase cross-linking, fibre reinforcing, and reduced bonding can enhance the mechanical properties of aerogel as well [80,91,92]. X-aerogels have been proven to improve considerably the fractal properties of native aerogels under both quasi-static [43,[93][94][95][96][97] and highimpact loading conditions [98,99]. While their strength is superior to silica aerogels, their elasticity and flexibility properties are yet to be tailored for advanced aerospace applications such as structural components and thermal protection for small satellites, spacecraft, planetary vehicles, and habitats.…”

“…One year later, Leventis et al developed the ultralight mechanically modified aerogels, called X-aerogels by cross-linking diisocyanates into the microstructure of silica aerogels. The strength of the latter was multiplied by 300 whilst its specific compressive strength is approximately ten times that of steel [43]. His work was extended with the assistance of other researchers to investigate the polymer cross-linking with other types of aerogel such as transition metal oxides and organics which would further broaden the applications of aerogels [44].…”

Carbon aerogel evolution: Allotrope, graphene-inspired, and 3D-printed aerogels

“…In fact, at a density of 100 mg/cm 3 , aerogels with high CNT loadings (over 16 wt%) are ;12 and ;3 times stiffer than conventional silica and CAs, respectively. [43][44][45] These CNT-based aerogels are also ;3 times stiffer than the "super-stiff" alumina nanofoams whose struts have the morphology of curled nanoleaflets. 46 The inset in Fig.…”