Tuning electric field aligned CNT architectures via chemistry, morphology, and sonication from micro to macroscopic scale

Abstract

Electric-field alignment of carbon nanotubes (CNT) is widely used to produce composite materials with anisotropic mechanical, electrical, and optical properties. Nevertheless, consistent results are difficult to achieve, and even under identical electric field conditions the resulting aligned morphologies can vary over μm to cm length scales. In order to improve reproducibility, this study addresses (1) how solution processing steps (oxidation, sonication) affect CNT properties, and (2) how CNT chemistry, morphology, and dispersion influence alignment. Aligned CNT were deposited onto PVDF membranes using a combination of electric-field alignment and vacuum-filtration. At each step in solution processing, the CNT chemistry (oxygen content) and morphology (length/diameter) were characterized and compared to the final aligned morphology. Well-dispersed CNT with high oxygen content (>8.5%O) yielded uniform membrane coatings and microscopically aligned CNT, whereas CNT with low oxygen CNT (<2.2%O) produced aligned bundles visible at a macroscopic level, but microscopically the individual CNT remained disordered. Based on regression analysis, CNT with larger mean length and diameter, smaller length and diameter variation, and higher oxygen content yielded increased electrical anisotropy, and bath sonication was slightly preferable to probe sonication for initial dispersion.

Airflow-assisted dielectrophoresis to reduce the resistance mismatch in carbon nanotube-based temperature sensors

“…The minimum resistance variation was observed at a concentration of 0.005%, and the worst resistance mismatch was observed at a deposition time of 3 minutes (resistance variation in basic alignment setups could exceed 10%). 42 Fig. 1 The setup of the AA-DEP.…”

Sampling‐based Randomised Designs for Causal Inference under the Potential Outcomes Framework

“…To assess how the findings from Theorems and are informative for real experiments, we now conduct a simulation study based on a real experiment in nanomaterials (Remillard et al , ). One purpose of this experiment was to assess how the dimensions of carbon nanotubes change as they undergo different processing procedures.…”

“…In summary, the aforementioned simulation study confirms that Theorems and correctly establish the behaviour of the ATE estimators and under Design 2. However, for these data that are based on the experiment from Remillard et al (), in order for to be more precise than , we would have had to obtain two or three times as many pre‐treatment measurements than was actually feasible in this experiment, and these measurements would need to be at least moderately associated with the post‐treatment measurements. As noted in Remark , may also be more precise than if the post‐treatment measurements are substantially more variable than the pre‐treatment measurements, but this was not the case for the Remillard et al () experiment.…”

Ultrahigh‐Areal‐Capacitance Flexible Supercapacitor Electrodes Enabled by Conformal P3MT on Horizontally Aligned Carbon‐Nanotube Arrays

“…All the CV curves exhibit quasi‐rectangular and symmetric shapes, indicating an ideal capacitive behavior and high conductivity due to the horizontal alignment of the nanotubes in the flexible electrodes. The higher sheet conductance (lower sheet resistance) can also be found for composite electrode shown in Table S1 (Supporting Information), which can be attributed to the combined effect including the reduction of electron hopping between CNTs . To evaluate the capacitive performance of the cell, GCD curves at different current densities from 5 to 500 mA cm −2 were investigated.…”