Crack-Induced Superelastic, Strength-Tunable Carbon Nanotube Sponges

Abstract

Lightweight strong aerogels have many applications, but they suffer from the trade-off between key mechanical properties, and it remains challenging to realize superelastic aerogels simultaneously possessing high strength and excellent structural recovery. Herein, a strategy to overcome such a problem by designing a carbon nanotube (CNT)-based aerogel consisting of flexible-rigid core-shell structure, which achieve a combination of excellent properties including superelasticity (complete recovery at 90%), high strength (over 12 MPa at 90%) and wide tunability (from 101 kPa to 4.5 MPa at 50% strain), is presented. It is found that the outer rigid but brittle amorphous carbon shells crosslink the CNT cores and crack into orderly distributed segments during the first compression cycle, while the flexible CNT cores ensure the integrity of the overall skeleton and tolerance to large deformation. This designed CNT composite sponges exhibit overall superior mechanical properties than previously reported foams/aerogels, and due to such unique crack-induced superelasticity mechanism, potential applications such as pressure sensors with wide-range tailored sensitivity and high-performance energy absorbers have been developed. This flexible-rigid core-shell synergia may provide further insight for tunable high-strength aerogel design and innovative applications.