The critical role of the forest morphology for dry drawability of few-walled carbon nanotubes

Inoue, Hirokazu; Hada, Masaki; Nakagawa, Toshio; Marui, Tatsuki; Nishikawa, Takeshi; Yamashita, Yoshifumi; Inoue, Yasuo; Takahashi, Kazuhiko; Hayashi, Yûji

doi:10.1016/j.carbon.2019.11.038

Cited by 18 publications

(12 citation statements)

References 63 publications

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“…24 In our study, we developed a dry spinning method using drawable CNT forests grown by CVD with precise control of growth conditions, such as growth time, growth temperature, and morphology of the catalyst, providing the tunability of density and height, thereby resulting in the drawability of CNT forests. 25 Based on this technique, we produced drawered CNT sheets and spun CNT yarns.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Despite using the floating chemical vapor deposition (CVD) method, one of the dry processes, the large number of residual metal catalysts is also a critical issue for the cleanliness of the surface . In our study, we developed a dry spinning method using drawable CNT forests grown by CVD with precise control of growth conditions, such as growth time, growth temperature, and morphology of the catalyst, providing the tunability of density and height, thereby resulting in the drawability of CNT forests . Based on this technique, we produced drawered CNT sheets and spun CNT yarns.…”

Section: Introductionmentioning

confidence: 99%

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Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies

Suzuki

Kishibuchi

Shimogami

et al. 2021

ACS Appl. Electron. Mater.

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The van der Waals (VdW) heterostructure has attracted significant attention owing to its potential as a platform for unique physics and electronic device applications. Recently, a one-dimensional VdW (1D-VdW) heterostructure was achieved by the direct growth of two-dimensional materials, such as hexagonal boron nitride (hBN) and transition-metal dichalcogenide on carbon nanotubes (CNTs). Despite its attractive configuration in terms of the possible high integration density of VdW heterojunctions, scaling up from individual nanostructures to bulk structures for actual applications remains unachieved. One possible strategy to fabricate the bulk-scale 1D-VdW heterostructure is the direct growth of heterogeneous materials on CNT assemblies. In the past decade, significant developments have been made in the dry spinning method to scale up CNTs to bulk structures while maintaining the clean surface of CNTs without any mixture. By combining the dry spinning technique and direct heterogeneous growth of hBN, we successfully achieved the bulk-scale integration of the hBN/CNT heterostructures with high controllability of crystallinity of the hBN layer. Through electric transport investigations, we found memristive behavior in hBN/CNT heterostructure assemblies. Through systematic experiments and structural observations, we propose a possible model for the mechanism of memristive behavior that originates from the one-dimensional growth of the hBN layer on the CNTs and functionalized amorphous carbon (a-C). The imperfect crystallinity of hBN with turbostratic layers and grain boundaries prepared by well-controlled growth may function as an appropriate barrier for the formation of a conductive filament channel, enhancing the memristive behavior. The hBN/ CNT heterostructure assemblies with memristive functions and high mechanical degrees of freedom are extremely valuable for future neuromorphic computing and conventional nonvolatile memory devices.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies

Suzuki

Kishibuchi

Shimogami

et al. 2021

ACS Appl. Electron. Mater.

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“…We synthesized high-density CNT forests using the chemical vapor deposition (CVD) method. , The CNT forests were drawable and produced a CNT sheet (Figure a, b). The atomic structure of the CNTs was characterized using a transmission electron microscope (TEM) (Figure c).…”

Section: Resultsmentioning

confidence: 99%

Highly Oriented Carbon Nanotube Supercapacitors

Komatsubara

Suzuki

Inoue

et al. 2022

ACS Appl. Nano Mater.

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The demand for supercapacitors (SCs) with high capacitance, high charge–discharge rate, and long lifespan has been increasing because of the rapid development of wearable devices. In particular, flexible and durable SCs are essential for applications in wearable devices. A reasonable strategy to achieve such SCs involves the design and fabrication of SCs with flexible materials. In this study, we present a flexible SC with highly oriented carbon nanotube (CNT) sheets, which exhibit all the component functions of SCs: activated materials, conductive materials, and current collectors. Repeated bending tests validated the robustness of the flexible SCs. The SCs demonstrated extremely high durability with >99.9% capacitance retention after 50 000 bending cycles. Furthermore, we observed that the orientation angle of the CNT sheets with respect to the current flow direction (θ) was crucial for determining the performance of SCs. The SCs with CNT sheets oriented in the current flow direction (θ = 0°) showed a higher scan rate and robustness than those with other CNT sheet orientations (θ = 45 or 90°), because of the ease of access of charge carriers to the electrodes of the entire CNT sheet. Well-designed flexible and durable CNT-SCs can drastically improve the performance of future flexible devices.

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“…The use of densely packed carbon nanotube (CNT) forests (10 9 to 10 13 cm –2 ) is expected to be a candidate for thermal interface materials (TIMs), which rapidly transfer heat from the heat-generating parts of semiconductors to metal coolers. , The high-density CNT forests with large current transport capacity are also suitable for interconnects in multilayer structures of semiconductor devices. , Furthermore, the large-surface area of high-density CNT forests can be effectively used for energy devices such as capacitance and rechargeable batteries. , On the other hand, when the CNTs are strongly bundled together on the substrate, such a CNT forest shows the dry spinning phenomenon where the drawn CNTs continuously pull out the neighboring CNT bundles with van der Waals interactions. The densification of the forest is essential for the dry spinning techniques. , …”

Section: Introductionmentioning

confidence: 99%

Catalyst Dynamics in the Growth of High-Density CNT Forests; Fine Control of the Mass Density of Forest by Colloidal Catalyst Nanoparticles

et al. 2022

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In the growth of carbon nanotube (CNT) forests, the catalytic activity decreases due to structural changes of the catalytic nanoparticles, and the mass density becomes lower at the root of the forest in the case of the base-growth mechanism, which is an obstacle to the application of high-density forests. In this study, colloidal nanoparticles were used as catalyst precursors to grow CNT forests with independently controlled CNT diameter, length, and mass density to elucidate the catalytic dynamics in the CNT growth process. By optimizing the chemical vapor deposition process, high catalytic activity was maintained during the growth. A mass density of 46 mg/ cm 3 was achieved with CNT forests grown to 1.2 mm length, a very high mass density compared to previously reported CNT forests over 1 mm. From a downward linear relationship between the mass density and length of the CNT forests in the double logarithmic plot, we proposed a transition model for the active catalyst survival rate, which changes dynamically with the growth of CNTs. It was found that the catalysts of CNT forests grown over several hundred microns are significantly deactivated and reduced to less than a few percent of their initial density.

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The critical role of the forest morphology for dry drawability of few-walled carbon nanotubes

Cited by 18 publications

References 63 publications

Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies

Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies

Highly Oriented Carbon Nanotube Supercapacitors

Catalyst Dynamics in the Growth of High-Density CNT Forests; Fine Control of the Mass Density of Forest by Colloidal Catalyst Nanoparticles

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