Crust removal and effective modulus of aligned multi-walled carbon nanotube films

Carbon nanotubes (CNTs) have been attractive materials because of the unique combination of their small size and physical properties, such as high thermal conductivity and mechanical compliance. This paper extracts in-plane modulus of 100-220 μm-thick vertically aligned multi-walled carbon nanotube (VA-MWCNT) films. The films have low modulus in the range of 0.5-2 MPa, consistent with expectations due to the direction of CNT alignment. We study the effect of a top crust of entangled CNTs on the modulus by etching the surface of the VA-MWCNT films using O₂ plasma. Scanning electron micrographs reveal that the surface etching removes the entanglements of the crust layer. The modulus values of the etched samples indicate that there is no significant effect of this crust on the modulus of thick films (>;100 μm). This is in contrast to previous work that showed that the crust layer had a very strong effect in thinner films.