Investigation of the effect of the structure of large-area carbon nanotube/fuel composites on energy generation from thermopower waves

Abstract

Thermopower waves are a recently developed energy conversion concept utilizing dynamic temperature and chemical potential gradients to harvest electrical energy while the combustion wave propagates along the hybrid layers of nanomaterials and chemical fuels. The intrinsic properties of the core nanomaterials and chemical fuels in the hybrid composites can broadly affect the energy generation, as well as the combustion process, of thermopower waves. So far, most research has focused on the application of new core nanomaterials to enhance energy generation. In this study, we demonstrate that the alignment of core nanomaterials can significantly influence a number of aspects of the thermopower waves, while the nanomaterials involved are identical carbon nanotubes (CNTs). Diversely structured, large-area CNT/fuel composites of one-dimensional aligned CNT arrays (1D CNT arrays), randomly oriented CNT films (2D CNT films), and randomly aggregated bulk CNT clusters (3D CNT clusters) were fabricated to evaluate the energy generation, as well as the propagation of the thermal wave, from thermopower waves. The more the core nanostructures were aligned, the less inversion of temperature gradients and the less cross-propagation of multiple thermopower waves occurred. These characteristics of the aligned structures prevented the cancellation of charge carrier movements among the core nanomaterials and produced the relative enhancement of the energy generation and the specific power with a single-polarity voltage signal. Understanding this effect of structure on energy generation from thermopower waves can help in the design of optimized hybrid composites of nanomaterials and fuels, especially designs based on the internal alignment of the materials. More generally, we believe that this work provides clues to the process of chemical to thermal to electrical energy conversion inside/outside hybrid nanostructured materials.

Giant Peak Voltage of Thermopower Waves Driven by the Chemical Potential Gradient of Single‐Crystalline Bi2Te3

“…We carried out additional 30 experiments using the square‐shaped SC‐BT specimen (5 × 5 mm 2 , anisotropy: 1), otherwise the identical experimental condition, and the peak voltage was significantly smaller (maximum: 0.88 V; average: 0.3 V) than that of the 1D specimen as shown in Figure S8 (Supporting Information). Hwang et al also observed the greater peak voltage for 1D substrate, compared with 2D or 3D substrates, although the materials and experimental conditions were different from this work …”

“…Finally, electrodes were connected at both ends of the specimen using copper tapes and silver paste (DOTITE, D‐550). An exothermic chemical reaction was initiated by a hot nickel–chromium wire . The wire was Joule‐heated and immediately came into contact with the fuel mixture on one end of the specimen after turning off the power supply.…”

“…The SC‐BT flake was cut into rectangular shape (1 × 10 mm 2 ), and fuel was coated on the top surface. The exothermic chemical reaction was initiated at the right end of the device using a hot nickel–chromium wire, and the induced electrical potential was monitored using an oscilloscope. Figure e shows a self‐propagating heat wave, toward the left end, recorded by a high‐speed camera.…”

Scalable Synthesis of Triple‐Core–Shell Nanostructures of TiO2@MnO2@C for High Performance Supercapacitors Using Structure‐Guided Combustion Waves

“…The triple‐core–shell nanostructures of TiO 2 @MnO 2 @C are designed as electrode materials for supercapacitors, and synthesized via SGCWs, which appear in the combustion of the hybrid composites, comprised of micro‐nanostructured materials and chemical fuels. As the ignition of fuels, the entire micro‐nanostructures are instantaneously exposed to a self‐propagating reaction waves along the interfaces of the materials and fuels . These interface‐driven combustion waves simultaneously induce the formation of carbon shells around the core structures for a few seconds, in an open‐air atmosphere .…”

Ultrahigh thermopower waves in carbon nanotube‐antimony telluride composites enabled by thermal decomposition of formaldehyde

“…When the TW was subjected to an inverse temperature gradient, the direction of charge transport oppositely changed, which resulted in negative voltage signals. Thus, various voltage signals that corresponded to the rear‐inverse peak, no inverse peak, or front‐inverse peak scenarios could be obtained, as shown in Figure S2, depending on the ignition and propagation during the combustion process 31,34 …”