The formation of carbon nanotube dispersions by high pressure homogenization and their rapid characterization by analytical centrifuge

Dispersion of carbon nanotubes (CNTs) in a liquid medium requires separation of the bundles, a process which is usually achieved by sonication for prolonged time, and is suitable for low sample volumes. A rapid and simple process for producing dispersions of multi-wall carbon nanotubes (MWCNTs) was developed, by using a high pressure homogenization process (HPH). Dispersions of MWCNTs were prepared in aqueous solutions containing ethoxylated octyl phenol, and were compared to dispersions prepared by the conventional sonication method. They were evaluated by rapid measurement of sedimentation rate during centrifugation, and results compared to other evaluation methods. It was found that samples processed by HPH for a short time yielded similar dispersions to those obtained by sonication for prolonged time, and that the first pass through the homogenizer, which takes less than a minute, is the most significant in breaking up the bundle. The process can be used in a continuous mode for large volumes, and is very suitable for large-scale industrial production. Evaluation of the CNT dispersions by centrifugal sedimentation analysis correlates well with other time-consuming methods.