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An atmospheric‐pressure plasma system is developed and is used to treat carbon nanotube assemblies, producing a hybrid carbon‐zinc structure. This system is integrated into a floating‐catalyst chemical vapor deposition furnace used for the synthesis of macroscopic assemblies of carbon nanotubes to allow for the in‐line, continuous, and single‐step production of nano‐composite materials. Material is deposited from a sacrificial zinc wire in the form of nanoparticles and can coat the surface of the individual carbon nanotubes as they form. Additionally, it is found that the deposited materials penetrate further into the carbon nanotube matrix than a comparable post‐synthesis deposition, improving the uniformity of the material through the thickness. Thus, a single‐step metal‐based coating and carbon nanotube synthesis process which can form the basis of production scale manufacturing of metal‐carbon nanotube composite materials with an atmospheric‐pressure plasma system are demonstrated. [ABSTRACT FROM AUTHOR]

Macroscopic ribbon-like assemblies of carbon nanotubes (CNTs) are functionalised using a simple direct-current-based plasma–liquid system, with oxygen and nitrogen functional groups being added. These modifications have been shown to reduce the contact angle of the ribbons, with the greatest reduction being from 84° to 35°. The ability to improve the wettability of the CNTs is of paramount importance for producing nanofluids, with relevance for a number of applications. Here, in particular, we investigate the efficacy of these samples as nanofluid additives for solar–thermal harvesting. Surface treatments by plasma-induced non-equilibrium electrochemistry are shown to enhance the stability of the nanofluids, allowing for full redispersion under simulated operating conditions. Furthermore, the enhanced dispersibility results in both a larger absorption coefficient and an improved thermal profile under solar simulation. [ABSTRACT FROM AUTHOR]

Nitrogen doping of carbon nanomaterials has emerged as a method to develop novel material properties, though limitations in the form of extended treatment times, harsh chemical usage and limited total nitrogen content exist. Here, macroscopic ribbon-like assemblies of carbon nanotubes are functionalized with nitrogen using a simple direct current-based plasma–liquid system. This system utilizes the plasma-generated species in an ethanol:water solution with ethylenediamine as a nitrogen precursor for the nitrogen functionalization of the carbon nanotube assembly. These unique, plasma-generated species and pathways enable rapid and high levels of functionalization with the atomic concentration of nitrogen reaching 22.5%, with amine groups, pyrrolic groups and graphitic nitrogen observed in the X-ray photoelectron spectra, the highest ever achieved. This nitrogen content is demonstrated to be significantly higher than a comparative electrolysis process. This demonstrates that this plasma process enhances the availability of nitrogen from the ethylenediamine precursor, facilitating greater functionalization. [ABSTRACT FROM AUTHOR]

Alkali‐activated functionalized carbon nanotubes (AFCNTs) and 2D nanostructured MoS2 are investigated as a novel hybrid material for energy‐storage applications. The nanoflower‐like 2D MoS2 is grown on the surface of AFCNT using the controlled one‐step hydrothermal technique. The activation of functionalized carbon nanotubes results in greater performance due to the improved surface area. The Brunauer–Emmett–Teller (BET) surface area of the AFCNTs is found to be 594.7 m2 g−1 which is almost 30 times of the as‐prepared carbon nanotubes (CNTs). The improved surface area with attached hydroxyl and carboxylic functional groups helps in the attachment of MoS2 nanoflowers onto the AFCNT, thus reducing the interfacial resistance and providing an easy path for electron transfer. The electrochemical analysis shows a high specific capacitance of 516 F g−1 at 0.5 A g−1 with a corresponding energy density of 71.76 Wh kg−1, which is an encouraging reported value from AFCNT and MoS2 hybrid material. To the best of our knowledge, herein, the first report on AFCNTs and 2D MoS2 nanostructured hybrid electrode material for supercapacitor applications is provided, and promising results in terms of specific capacitance, energy density, and power density by boosting the properties of individual material are explained. [ABSTRACT FROM AUTHOR]

Spinning carbon nanotube (CNT) thread directly from 4-6 mm long aligned carbon nanotube arrays is reported here. The strength of carbon nanotube thread was improved by optimizing the chemical vapor deposition parameters for growing long aligned carbon nanotube arrays. The morphological and structural characterization of CNT arrays and threads were studied by Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. After optimization of growth parameters threads were spun with diameters between 10 and 70 µm. We have achieved thread strength of about 280 MPa. [ABSTRACT FROM AUTHOR]

Abstract: The effect of substrate positions inside the chemical vapor deposition reactor on the length and quality of the grown carbon nanotube (CNT) arrays is reported. It was found that longer CNT arrays are grown when located downstream on the platform in the reactor. This effect becomes more pronounced for increased growth time. Related factors such as temperature of the gas mixture and its flow velocity seem to be responsible for the behavior. The quality of the CNTs is not affected by the position of the substrates inside the reactor. [Copyright &y& Elsevier]

Field emission properties of a stand-alone MgO-coated carbon nanotube (CNT) have been investigated by a field emission microscopy. A finite element method is used to analyze the electric field distribution on the surface of a CNT and in the layer of MgO. It is found that the dielectric MgO layer decreases the strength of electric field on the CNT surface and then increases the tunnel barrier of field emission. However, it is observed that the MgO coating largely decreases the fluctuation of the emission current from a CNT especially in the current of over 10-7 A. [ABSTRACT FROM AUTHOR]

Successful growth of vertically aligned carbon nanotube (CNT) arrays on copper substrate by thermal chemical vapor deposition is reported in this paper. The effects of Ti, Ni, and Ni-Cr intermediate layers have been studied to eliminate cracking of the copper surface during the synthesis of CNTs. It was found that these intermediate layers play a critical role in achieving vertical alignment of CNTs on copper substrates. The effects of other reaction parameters such as flow rate of ethylene, concentration of water vapor, and deposition temperature have also been studied. Scanning electron microscopy, transmission electron microscopy, and micro-Raman spectroscopy were used to evaluate the quality and nature of the CNT formed. [ABSTRACT FROM AUTHOR]

Abstract: We successfully prepared a vertically aligned double-walled carbon nanotube (DWCNT) sheet by a transfer procedure from a silicon substrate as a DWCNT seedbed that was covered with catalyst grains to an aluminum sheet as a current collector for application to a high-performance electrode for an electric double layer capacitor (EDLC). The charge–discharge characteristics and EDLC performances of the aligned DWCNT electrode were evaluated and compared with those of a vertically aligned multi-walled CNT (MWCNT) electrode. The gravimetric capacitance of the DWCNT electrode was ca. four times larger than that of the MWCNT electrode. The rate capability of the DWCNT electrode was found to be excellent. This is mainly ascribed to our transfer technique. [Copyright &y& Elsevier]