Continuous Carbon Nanotube-Based Fibers and Films for Applications Requiring Enhanced Heat Dissipation

Abstract

The production of continuous carbon nanotube (CNT) fibers and films has paved the way to leverage the superior properties of individual carbon nanotubes for novel macroscale applications such as electronic cables and multifunctional composites. In this manuscript, we synthesize fibers and films from CNT aerogels that are continuously grown by floating catalyst chemical vapor deposition (FCCVD) and measure thermal conductivity and natural convective heat transfer coefficient from the fiber and film. To probe the mechanisms of heat transfer, we develop a new, robust, steady-state thermal characterization technique that enables measurement of the intrinsic fiber thermal conductivity and the convective heat transfer coefficient from the fiber to the surrounding air. The thermal conductivity of the as-prepared fiber ranges from 4.7 ± 0.3 to 28.0 ± 2.4 W m(-1) K(-1) and depends on fiber volume fraction and diameter. A simple nitric acid treatment increases the thermal conductivity by as much as a factor of ∼3 for the fibers and ∼6.7 for the thin films. These acid-treated CNT materials demonstrate specific thermal conductivities significantly higher than common metals with the same absolute thermal conductivity, which means they are comparatively lightweight, thermally conductive fibers and films. Beyond thermal conductivity, the acid treatment enhances electrical conductivity by a factor of ∼2.3. Further, the measured convective heat transfer coefficients range from 25 to 200 W m(-2) K(-1) for all fibers, which is higher than expected for macroscale materials and demonstrates the impact of the nanoscale CNT features on convective heat losses from the fibers. The measured thermal and electrical performance demonstrates the promise for using these fibers and films in macroscale applications requiring effective heat dissipation.

Thermal conductivity of carbon nanotube networks: a review

“…Another variant of the steady-state method differs from the original one with the manner of recording the sample temperature distribution while alternating current of specific amperage flows through the sample. Instead of the classic thermocouples to measure the value of DT, the changes in temperature of the sample as a function of its length may be recorded using an IR thermometer [47,48] or IR microscope [49]. Then, proper calculations are made on the basis of the results obtained, and the value of thermal conductivity is determined.…”

“…Then, proper calculations are made on the basis of the results obtained, and the value of thermal conductivity is determined. The method was applied by Zhang [47], Wang [48] and Liu [49]. Figure 7 provides a schematic presentation of the measurement setup.…”

“…A CNT bundle or cut film is placed, using silver paste, on the electrodes (copper [48,49] or aluminum [47]). The whole measurement setup is placed on an insulating substrate (wooden [47], plastic [49] or glass [48]). The measurements are taken in a vacuum chamber in order to reduce the impact of the ambient environment.…”

Convenient but powerful method to dope single-walled carbon nanotube films with iodonium salts

“…The results were averaged and statistical error was calculated. Thermal conductivity was measured using steady-state method with infrared thermography (Wang et al 2008;Zhang et al 2012;Liu et al 2016a). The measurement consisted in recording the temperature profile along the whole length of the sample, while direct current of specific parameters flows through it.…”

Stretchable and Energy‐Efficient Heating Carbon Nanotube Fiber by Designing a Hierarchically Helical Structure

“…The HHFs also showed ultrafast thermal response (Figure S7, Supporting Information), and the maximal heating rate rose with increasing voltages and reached up to 1030 °C s −1 at a low voltage of 8 V. This remarkably fast responding behavior was attributed to their high thermal conductivity, ultrasmall heat capacity per unit volume, and large specific surface area . The cooling rate represented the thermal insulation property of a material, so the SNF, SSF, and HHF with the same length (2 cm) and diameter (220 µm) were heated to 80 °C and then the input voltages were turned off at the same time to compare their cooling curves (Figure d).…”