Discharge flocking, a new method to disperse nano-particles

One of the big challenges in the nano-field is how to effectively disperse nano-scale particles, especially CNTs and carbon blacks, which are strongly agglomerated by intermolecular van der Waals forces. Solution-based dispersion methods such as sonication and three-roll milling require lots of dispersion time and have re-agglomeration problems after processing. This study suggests a new method, i.e. discharge flocking, to disperse the particles effectively. Firstly nano-scale particles located between two electrodes, a negative electrode and a ground electrode, are charged by Townsend discharge. Next the negatively charged particles flow toward a target substrate by electric field generated by a positive electrode behind the substrate, and they are finally attached on the substrate. In contrast with the solution-based methods, this process makes nano-scale particles disperse in the air and repel each others because of their negative charges. Therefore, the re-agglomeration problem of processed particles could be prevented. In this study, carbon fiber reinforced epoxy composites including CNTs and carbon blacks were fabricated by the discharge flocking and the solution-based dispersion methods, respectively, and then their mechanical and electrical properties were compared with each other.