A Nanostructural Study of Mixed Carbon and Boron Nitride Nanotube Solutions in Superacid using Cryogenic Electron Microscopy

We study the nanostructure of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) mixed in chlorosulfonic acid (CSA), a superacid that is a true solvent for both nanotube types. Cryogenic transmission electron microscopy (cryo-TEM) and cryogenic scanning electron microscopy (cryo-SEM) were used to analyze the phase behavior and morphological characteristics of the nanotube mixtures at various concentrations and proportions. We find that, surprisingly, CNTs and BNNTs mix well at all length scales. We image different phases, including isotropic and nematic liquid crystal, and find that the mixture composition influences the phase behavior and morphology. The consistent admixture of BNNTs and CNTs at small length scales observed in the isotropic and the nematic phases emphasizes the potential for developing hybrid materials that combine the unique properties of each nanotube type.