Insight into the structural changes upon ultrasonic fragmentation and dispersion of carbon nanomaterials of different dimensions and bulk moduli

Stable dispersions of carbon and graphene nanomaterials are becoming key precursors for composite carbon electrodes in energy storage and harvesting applications such as batteries, supercapacitors, and solar cells. One promising top-down approach for producing stable dispersions of these materials is ultrasonic irradiation, a cost-effective method capable of operating across micron to nanoscale dimensions. The degree of structural damage during ultrasonic treatment depends heavily on the composition and physicochemical properties of the parent materials. In this study, the extent of structural damage to carbon/graphene materials with varying dimensions and type of carbon backbone was investigated. High-performance ultrasonication with short sonication times was used to obtain nanoparticle dispersions in N-methylpyrrolidone. One-dimensional carbon nanotubes, two-dimensional graphite, and three-dimensional porous carbons including graphene mesosponge and activated carbon were studied. These materials were thoroughly characterized using X-ray diffractometry, Infrared spectroscopy, Raman spectroscopy, dynamic light scattering, scanning electron microscopy, small angle X-ray scattering and X-ray photoelectron spectroscopy. The results showed that ultrasonic fragmentation effectively fractures graphene-based and carbon materials on a sub-micrometre scale, facilitating dispersion into the solvent, while causing minimal damage to their nanometer-scale structure. The extent of degradation was found to depend on the dimension of material, with lower-dimensional materials suffering less damage. Interestingly, the extent of degradation is also related to the bulk modulus of the materials, suggesting that the more compressible the material is, the more resistant to the effect of ultrasound it becomes. 1) Carbon materials exhibit highly distinct degradability upon ultrasound irradiation 2) Damage caused to pores and surfaces highly depend on the dimension and crystallinity 3) Fracture efficiency of 3D nanocarbons correlates very well with their bulk moduli