The Rheology of Carbon Nanotube (CNT) Suspensions: Experiments and Modelling

Anson W K Ma,Ralph H Colby,Gary L Leal,Albert Co,A Jeffrey Giacomin,Malcolm R Mackley,Francisco Chinesta

doi:10.1063/1.2964834

Abstract

This paper reports the latest experimental results and rheological modelling for semi‐dilute Carbon Nanotube (CNT) suspensions. CNTs belong to a relatively new class of nano‐scale fibres having fascinating physical properties. In terms of experimental rheology, there are some similarities between CNT suspensions and classical carbon, glass, or polymeric fibre suspensions. Suspensions of CNTs with a Newtonian matrix were found to be shear‐thinning in simple shear. The extent of shear‐thinning, however, varies significantly depending on the type of CNTs used. As‐produced untreated CNTs tended to give a much higher low‐shear viscosity coupled with optically resolvable CNT aggregates, whereas CNTs that have been chemically treated showed little optical microstructure with less pronounced shear‐thinning. Treated CNTs have been successfully modelled as short and rigid fibres that can align in the flow, but there are also randomising events due to Brownian rotary diffusion and tube‐tube interactions. In the case of untreated CNTs, CNT orientation consideration alone was inadequate in explaining the experimentally observed shear thinning and a new model taking into account both elements of CNT orientation and aggregation kinetics has been formulated to describe the experimental data.

Highlights

This paper highlights some of our recent findings in relation to the steady shear rheology of Carbon Nanotubes (CNTs) suspended in a Newtonian matrix, whilst further experimental and modelling details will be reported in future papers [1,2]
Reasonable agreement between experimental results and theAO model was obtained with D';'ax = 0.001 s-1 and fJ = 0.004, further supporting the belief that the more pronounced shear-thinning in untreated CNT suspensions was due to the orientation as well as the aggregation ofCNTs
Untreated CNT suspensions were found to exhibit a more pronounced shear-thinning effect compared with treated CNT suspensions

Summary

Introduction

This paper highlights some of our recent findings in relation to the steady shear rheology of Carbon Nanotubes (CNTs) suspended in a Newtonian matrix, whilst further experimental and modelling details will be reported in future papers [1,2]. It is clear from these results that chemically treated suspensions with little optical microstructure showed less pronounced shear-thinning effect compared with untreatedCNT suspensions where clear network ofCNT (aggregate) was observed. The rheological responses of treated CNTs can be explained by considering treated CNTs as rigid, short fibres that can align in flow, and subject to Brownian rotary diffusion.

Results

Conclusion