Ultralight Multiwalled Carbon Nanotube Aerogel

Abstract

Ultralight multiwalled carbon nanotube (MWCNT) aerogel is fabricated from a wet gel of well-dispersed pristine MWCNTs. On the basis of a theoretical prediction that increasing interaction potential between CNTs lowers their critical concentration to form an infinite percolation network, poly(3-(trimethoxysilyl) propyl methacrylate) (PTMSPMA) is used to disperse and functionalize MWCNTs where the subsequent hydrolysis and condensation of PTMSPMA introduces strong and permanent chemical bonding between MWCNTs. The interaction is both experimentally and theoretically proven to facilitate the formation of a MWCNT percolation network, which leads to the gelation of MWCNT dispersion at ultralow MWCNT concentration. After removing the liquid component from the MWCNT wet gel, the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm(3) is obtained. The MWCNT aerogel has an ordered macroporous honeycomb structure with straight and parallel voids in 50-150 μm separated by less than 100 nm thick walls. The entangled MWCNTs generate mesoporous structures on the honeycomb walls, creating aerogels with a surface area of 580 m(2)/g which is much higher than that of pristine MWCNTs (241 m(2)/g). Despite the ultralow density, the MWCNT aerogels have an excellent compression recoverable property as demonstrated by the compression test. The aerogels have an electrical conductivity of 3.2 × 10(-2) S·cm(-1) that can be further increased to 0.67 S·cm(-1) by a high-current pulse method without degrading their structures. The excellent compression recoverable property, hierarchically porous structure with large surface area, and high conductivity grant the MWCNT aerogels exceptional pressure and chemical vapor sensing capabilities.

Biomimetic superelastic graphene-based cellular monoliths

“…The compressive stress is B8 kPa at the plateau, and is 18 kPa at 80% strain for the monolith with density of 5.10 mg cm À 3 . These compressive stress values are 2-9 times higher than those of other carbon-based foams with a similar or twice the density 18,19 and are comparable to that of metallic lattice 24 with a density of 14 mg cm À 3 . At 80% strain, the When a well-dispersed pr-GO dispersion (the first scheme) is frozen, pr-GO sheets are concentrated at the boundary of ice crystals and then aligned along the growth direction of ice due to the squeezing effect (the second scheme, side-view).…”

“…Subsequent sublimation of ice results in the formation of a porous solid material. Freeze casting has been successfully adopted to synthesize a variety of porous ceramic, metallic, polymeric and composite materials, including carbon nanotubes or graphene-based polymer composites 18,[30][31][32][33] . Although previous research on freeze casting has been centred on polymers and spherical particles 28,29 , we were particularly interested in studying how 2D graphene sheets interact with anisotropic ice crystal growth without the interference of other polymer or surfactant additives.…”

“…However, as with most of the existing porous carbon materials 13 , the resulting graphene monoliths are generally brittle and have small recoverable deformation before failure unless they are infiltrated with an elastomeric polymer 5 or grown on pre-formed carbon nanotube aerogels 14 . Superelasticity that has been observed in foams made of carbon-based tubular or fibrillar nanostructures [15][16][17][18][19][20][21] has not been achieved in foams solely based on graphene sheets. Indeed, as the specific elastic bending stiffness of a sheet-like structure is known to be intrinsically inferior to that of its tubular or fibrillar counterparts 22 , previous analysis 13 suggests that it would be highly challenging to realize superelasticity in graphene foams.…”

Lightweight nanoporous metal hydroxide-rich zeotypes

“…For example, the BOT framework with purely beryllium-based tetrahedral as a Be(OH) 2 polymorph would have a density of only 0.88 g cm − 3 ; while replacing As by P at the levels found in BET-P would decrease its density to near 1 g cm − 3 . Although such values are significantly higher than many large pore MOFs and meso-structured, ultralightweight materials [16][17][18][19] , a key feature of these beryllium hydroxide-based frameworks is that the high internal surface area is likely to be available for the strong physisorption of gases. Even within the larger cage sizes, such as bet, the maximum wall-to-wall separation is 10.2 Å, and allowing for partial decoration of these walls by OH groups reduces these distances further.…”

“…16). Ultra-lightweight materials include carbon nanotube aerogels 17 , metallic microlattices 18 and silica xerogels 19 , all with densities < 10 mg cm − 3 ; however, these structured materials do not grow in crystalline forms and their internal surface areas for strong physisorption are relatively low.…”