ACS Nano – Ultralight Multiwalled Carbon Nanotube Aerogel Carbon nanotube aerogel is the lightest solid material. It can be used in sensors to detect pollutants and toxic substances, chemical reactors, and electronics components. Aerogels made from silicon dioxide (the main ingredient in sand) and other material already are used as thermal insulation in windows and buildings, tennis rackets, sponges to clean up oil spills, and other products. MCNT aerogels mixed with plastic material are flexible like a spring that can be stretched thousands of times. MCNT aerogels also are excellent conductors of electricity.
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/cm3 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 m2/g which is much higher than that of pristine MWCNTs (241 m2/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.