Dispersion State and Damage of Carbon Nanotubes and Carbon Nanofibers by Ultrasonic Dispersion: A Review.

Harald Rennhofer,Benjamin Zanghellini

doi:10.3390/nano11061469

Abstract

Dispersion of carbon nanotubes and carbon nanofibers is a crucial processing step in the production of polymer-based nanocomposites and poses a great challenge due to the tendency of these nanofillers to agglomerate. Besides the well-established three-roll mill, the ultrasonic dispersion process is one of the most often used methods. It is fast, easy to implement, and obtains considerably good results. Nevertheless, damage to the nanofibers due to cavitation may lead to shortening and changes in the surface of the nanofillers. The proper application of the sonicator to limit damage and at the same time enable high dispersion quality needs dedicated knowledge of the damage mechanisms and characterization methods for monitoring nano-particles during and after sonication. This study gives an overview of these methods and indicates parameters to be considered in this respect. Sonication energy rather than sonication time is a key factor to control shortening. It seems likely that lower powers that are induced by a broader tip or plate sonicators at a longer running time would allow for proper dispersions, while minimizing damage.

Highlights

Carbon-fiber-reinforced polymers (CFRP) are advanced light-weight materials for high-end applications like aeronautics or the automotive industry [1,2,3]
We present the basic concept of cavitation, damage mechanisms during ultrasonication treatment, and methods to estimate damage; measure the dispersion state; and give an overview of relevant publications that investigated damage to carbon nanotubes (CNT) by sonication
A lot of publications report on the effects that ultrasound amplitude, frequency, and sonication time have on the dispersion quality, and subsequently on the products’

Summary

Introduction

Carbon-fiber-reinforced polymers (CFRP) are advanced light-weight materials for high-end applications like aeronautics or the automotive industry [1,2,3]. Different nano-fillers are used in research and industry, but most often ceramics and carbon-based filler materials are applied [5,6,7]. The latter would be graphene, carbon nanotubes (CNT)—single walled or multi walled (SWCNT/MWCNT)—and carbon nano-fibers (CNF). CFRP, and the polymer alone might show enhanced fracture characteristics due to application of nanofillers in the matrix [10,11]. This is due to the influence that nanofillers have on the crack initiation and crack propagation in the composite. Fibrous fillers with a high aspect ratio allow, for example, crack bridging or fiber pull-out, depending on the interaction with the resin [12,13,14]

Methods

Discussion

Conclusion