Ultra-flexible spiked-shell microparticles of aerographite

Abstract

Aerographite is an ultralight porous material with a three-dimensional interconnected network structure consisting of hollow carbon fibers. The unique morphology is derived from using tetrapod-type zinc oxide (ZnO) as a template in fabrication process, demonstrating that aerographite's architecture can be designed through the choice of templates with the desired morphologies. Here we synthesized aerographite microparticles by utilizing the morphology of ZnO nanorods-microspheres as a template. The microparticles exhibited spiked-shell structures consisting of radially aligned hollow nanorods. Experimental results for single-particle-level compressive tests indicated excellent flexibility under large deformation for the microparticles, with elastic recovery after 73% compression. The structure-dependent large elastic limit is a unique characteristic that differentiates this material from other microparticles. Both normalized load–displacement curves and in situ observations suggested that two-step compressive mechanism occurred: local deformation at the contact region and whole-particle deformation. The Young's modulus of the aerographite particles is comparable to that of silicone rubber despite the density being <3% of silicone. The probability of cracking during the compression likely increased above 40% strain; however, even then, the particles almost recovered its spherical shapes after unloading. Repetitive tests also indicated less accumulation of residual strain for the particles annealed at higher temperature.