Multiscale Metrologies for Process Optimization of Carbon Nanotube Polymer Composites

Published

July 18, 2016

Author(s)

Bharath N. Natarajan, Nate Orloff, Rana N. Ashkar, Sagar Doshi, Kevin A. Twedt, Ajay Krishnamurthy, Chelsea S. Davis, Aaron M. Forster, Erik Thostenson, Jan Obrzut, Renu Sharma, James Alexander Liddle

Abstract

Carbon nanotube (CNT) polymer composites are materials with attractive multifunctional properties that are becoming used in a growing range of commercial applications. With the increasing demand for these materials, it is imperative to develop methods for on-line quality control and process monitoring during production. In this work, we utilize a suite of characterization techniques that facilitates the non-invasive assessment of the CNT dispersion produced by the scalable process of calendering, and validate these tools against more conventional, high-resolution methods. Epoxy composites with varying CNT dispersion states and mass fractions are prepared by tuning the gap size in a three-roll calendering mill. The structural parameters of the nanocomposites are evaluated across multiple length scales using scanning gallium-ion microscopy, transmission electron microscopy and small-angle neutron scattering (10-10 m to 10-3 m). The impact of dispersion on conductivity, an important parameter for many CNT applications, is quantified using a non-contact AC resonant cavity perturbation (RCP) technique. The conductivity is found to monotonically increase with increased CNT loading and improved CNT dispersion. Quantitative correlations between conductivity and dispersion indicate that the AC electrical properties vary strongly with CNT mass fraction, up to a critical point, after which the dispersion state of CNTs dominates. The sensitivity to the processing parameters, the non-contact nature, and speed of RCP measurements makes this technique ideally suited for quality control of CNT composites in an industrial setting. We postulate that, by identifying the optimal processing parameters, RCP could be used to indirectly evaluate CNT dispersion in a nanomanufacturing environment. When validated by multiscale characterization, RCP may be broadly applicable in the production of hybrid functional materials, such as graphene, gold nanorod and carbon black nanocomposites.

Citation

Carbon

Volume

108

Pub Type

Journals

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DOI Link

Keywords

Carbon Nanotubes, Nanocomposites, Metrology, Dispersion, Dielectric Properties, Characterization, Structure-Property Relationships

Citation

Natarajan, B. , Orloff, N. , Ashkar, R. , Doshi, S. , Twedt, K. , Krishnamurthy, A. , Davis, C. , Forster, A. , Thostenson, E. , Obrzut, J. , Sharma, R. and Liddle, J. (2016), Multiscale Metrologies for Process Optimization of Carbon Nanotube Polymer Composites, Carbon, [online], https://doi.org/10.1016/j.carbon.2016.07.028 (Accessed October 15, 2024)