Zhenzhong Yong

Ultrastrong, Foldable, and Highly Conductive Carbon Nanotube Film

Preparation of strong, flexible, and multifunctional carbon-based films has attracted considerable interest not only in fundamental research areas but also for industrial applications. We report a binder-free, ultrastrong, and foldable carbon nanotube (CNT) film using aligned few-walled nanotube sheets drawn from spinnable nanotube arrays. The film exhibits tensile strengths up to ∼2 GPa and a Youngs modulus up to ∼90 GPa, which is markedly superior to other types of carbon-based films reported, including commercial graphite foils, buckypapers, and graphene-related papers. The film can bear severe bending (even being folded) and shows good structure integrity and negligible change in electric conductivity. The unique structure of the CNT film (good nanotube alignment, high packing density) provides the film with direct and efficient transport paths for electricity. As a flexible charge collector, it favors a magnesium oxide coating to exhibit high charge/discharge rate stability and an excellent electrochemical capacitance close to its theoretical value.

Ultrastrong, Stiff and Multifunctional Carbon Nanotube Composites

Carbon nanotubes (CNTs) are an order of magnitude stronger than any other current engineering fiber. However, for the past two decades, it has been a challenge to utilize their reinforcement potential in composites. Here, we report CNT composites with unprecedented multifunctionalities, including record high strength (3.8 GPa), high Youngs modulus (293 GPa), electrical conductivity (1230 S·cm −1), and thermal conductivity (41 W m −1 K −1). These superior properties are derived from the long length, high volume fraction, good alignment and reduced waviness of the CNTs, which were produced by a novel-processing approach that can be easily scaled up for industrial production.

Carbon‐Nanotube Fibers for Wearable Devices and Smart Textiles

Carbon-nanotube (CNT) fibers integrate such properties as high mechanical strength, extraordinary structural flexibility, high thermal and electrical conductivities, novel corrosion and oxidation resistivities, and high surface area, which makes them a very promising candidate for next-generation smart textiles and wearable devices. A brief review of the preparation of CNT fibers and recently developed CNT-fiber-based flexible and functional devices, which include artificial muscles, electrochemical double-layer capacitors, lithium-ion batteries, solar cells, and memristors, is presented.

Continuous electrodeposition for lightweight, highly conducting and strong carbon nanotube-copper composite fibers

Carbon nanotube (CNT) fiber is a promising candidate for lightweight cables. The introduction of metal particles on a CNT fiber can effectively improve its electrical conductivity. However, the decrease in strength is observed in CNT-metal composite fibers. Here we demonstrate a continuous process, which combines fiber spinning, CNT anodization and metal deposition, to fabricate lightweight and high-strength CNT-Cu fibers with metal-like conductivities. The composite fiber with anodized CNTs exhibits a conductivity of 4.08 × 10(4)-1.84 × 10(5) S cm(-1) and a mass density of 1.87-3.08 g cm(-3), as the Cu thickness is changed from 1 to 3 μm. It can be 600-811 MPa in strength, as strong as the un-anodized pure CNT fiber (656 MPa). We also find that during the tensile tests there are slips between the inner CNTs and the outer Cu layer, leading to the drops in electrical conductivity. Therefore, there is an effective fiber strength before which the Cu layer is robust. Due to the improved interfacial bonding between the Cu layer and the anodized CNT surfaces, such effective strength is still high, up to 490-570 MPa.

Carbon nanotube composite films with switchable transparency.

A composite film with switchable transparency is fabricated by sandwiching a carbon nanotube (CNT) sheet within polyurethane (PU) films. The introduction of CNTs not only makes the composite film electrically conductive but also induces a rapid crystal melting of soft segments in the PU. As a result, the film can be switched from opaque to transparent in just several seconds after turning on voltage, and reversed back to opaque after turning off voltage. The film also possesses several other attractive properties, including excellent flexibility, low energy consumption, switching speed insensitivity to ambient temperature, and easy coloration, which make the film promising for a wide variety of practical applications.

Aligned Carbon Nanotubes for High-Efficiency Schottky Solar Cells

The development of low-cost and high-efficiency silicon Schottky solar cells has drawn considerable interest in recent years. A facial approach for the fabrication of carbon nanotube-silicon (CNT-Si) Schottky solar cells by using aligned double-walled CNTs drawn from a CNT array is demonstrated. The aligned CNTs help to form high CNT-Si junction density and provide efficient charge-transport paths. The power conversion efficiency (PCE) reaches 10.5%, which is higher than that of solar cells fabricated using pristine and random CNT networks. Furthermore, the cell fabrication is scalable, and the solar cells fabricated in one batch show very small PCE fluctuations.

Polymethylmethacrylate coating on aligned carbon nanotube-silicon solar cells for performance improvement

Polymethylmethacrylate (PMMA) coating has been spin-coated onto aligned carbon nanotube–silicon (CNT–Si) solar cells and the efficiency increased from 7.1% to 11.5%, and was further increased to 13.1% when doped with nitric acid (HNO3) under air mass (AM 1.5) conditions. The antireflection of PMMA coating and the decreased resistance at the CNT–Si interface during PMMA drying process together contributed to the performance improvement.

Robust and aligned carbon nanotube/titania core/shell films for flexible TCO-free photoelectrodes.

Carbon nanotube (CNT)/semiconducting oxide hybrids are an ideal architecture for light-harvesting devices, in which the CNTs are expected to not only act as a scaffold but also provide fast transport paths for photogenerated charges in the oxide. However, the current potential of CNTs for charge transport is largely suppressed due to the nanotubes not being interconnected but isolated by the low conductive oxide coatings. Herein, a flexible and conductive CNT/TiO(2) core/shell heterostructure film is reported, with aligned and interconnected CNTs wrapped in a continuous TiO(2) coating. Without using additional transparent conducting oxide (TCO) substrates, this unique feature of the film boosts the incident photon-to-electron conversion efficiency to 32%, outperforming TiO(2) nanoparticle electrodes fabricated on TCO substrates. Moreover, the film shows high structural stability and can generate a stable photocurrent even after being bent hundreds of times.

One-dimensional carbon nanotube-FexCy nanocrystal composite

Ferromagnetic material–carbon nanotube composites are promising magnetic nanowires that have recently been prepared, with many possible applications. In this paper, using carbon nanotubes as a nucleate template, one-dimensional carbon nanotube–FexCy nanocrystal composites were successfully synthesized by the chemical combination of sputtered Fe atoms and carbon nanotubes at high temperature. The structural characterization, by scanning electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy, reveals that FexCy nanocrystal particles (5–20 nm diameter) were uniformly embedded in the walls of the carbon nanotubes with a high density. In addition, the formation mechanism of the composite is discussed.

Broadband laser polarization control with aligned carbon nanotubes.

We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 μm) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ∼12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary.