The Significance of Bundling Effects on Carbon Nanotubes' Response to Hydrostatic Compression

TL;DR

This study demonstrates that bundling significantly affects the G-mode pressure coefficients of carbon nanotubes, providing crucial experimental evidence to clarify discrepancies in previous literature and enhance understanding of their mechanical properties.

Contribution

It offers the first unambiguous experimental comparison of pressure coefficients for individual and bundled carbon nanotubes, highlighting bundling as a key factor influencing their mechanical response.

Findings

Bundling reduces G-mode pressure coefficients by about half in certain solvents.

G-minus pressure coefficient is significantly affected by bundling in different solvents.

Experimental evidence clarifies the impact of bundling on nanotube mechanical properties.

Abstract

The study of the G-mode pressure coefficients of carbon nanotubes, reflecting the stiff sp2 bond pressure dependence, is essential to the understanding of their extraordinary mechanical properties as well as fundamental mechanics. However, it is hindered by the availability of carbon nanotubes samples only as bundles or isolated with surfactants. Octadecylamine functionalized carbon nanotubes are mostly of a single diameter and can be stably dispersed in 1, 2-dichloroethane and chloroform without surfactants. Here we perform high pressure Raman spectroscopy on these tubes and obtain their experimental G-mode pressure coefficients for individual tubes and bundles. The G-plus pressure coefficient for bundles is only about half of that for individual tubes in 1, 2-dichloroethane and is about two-thirds in chloroform. The G-minus pressure coefficient for bundles is about one-third of G-plus in 1, 2-dichloroethane and about the same in chloroform. These results for the first time provide unambiguous experimental evidence of the significant effect of bundling on carbon nanotubes' G-mode pressure coefficients, identifying it as one of the major reasons for the lack of consensus on what the values should be in the literature.