Correlation between Pitch Impregnation Pressure and Pore Sizes of Graphite Block.

This study aimed to investigate the effect of impregnation pressure on the decrease in porosity of impregnated bulk graphite. The correlation between pitch impregnation behavior and the pore sizes of the bulk graphite block was studied to determine the optimal impregnation pressure. The densities and porosities of the bulk graphite before and after pitch impregnation under various pressures between 10 and 50 bar were evaluated based on the Archimedes method and a mercury porosimeter. The density increased rates increased by 1.93-2.44%, whereas the impregnation rate calculated from the rate of open porosity decreased by 15.15-24.48%. The density increase rate and impregnation rate were significantly high when the impregnation pressures were 40 and 50 bar. Compared with impregnation pressures of 10, 20, and 30 bar, the minimum impregnatable pore sizes with impregnation pressures of 40 and 50 bar were 30-39 and 24-31 nm, respectively. The mercury intrusion porosimeter analysis results demonstrated that the pressure-sensitive pore sizes of the graphite blocks were in the range of 100-4500 nm. Furthermore, the ink-bottle-type pores in this range contributed predominantly to the effect of impregnation under pressure, given that the pitch-impregnated-into-ink-bottle-type pores were difficult to elute during carbonization.

Publisher Correction: Synthesis of nanobelt-like 1-dimensional silver/nanocarbon hybrid materials for flexible and wearable electronics.

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Flexible carbonized cellulose/single-walled carbon nanotube films with high conductivity.

A carbonized cellulose/single-walled carbon nanotube composite film (cell/SWCNTcarbon) was prepared with well-dispersed cellulose/SWCNT doped in N-methylmorpholine N-oxide (NMMO) monohydrate. After carbonization at 400 °C, the SWCNT content at electrical threshold of the cell/SWCNTcarbon nanocomposite decreased from 2 wt% to 1 wt%, and the electrical conductivity of the cell/SWCNT(1 wt%)carbon nanocomposite (0.6 S cm-1) increased by more than 6 orders of magnitude compared to that of pure carbonized cellulose (1.1 × 10-7 S cm-1). Further, it continuously increased as the carbonization temperature increased and reached 100 S cm-1 when the cell/SWCNT(1 wt%) nanocomposite was carbonized at 1400 °C. This drastic increase in the electrical conductivity at low carbonization temperatures (e.g. 400 °C) was due to the percolation of small carbon clusters with conducting SWCNTs. The incorporated SWCNTs improved flexibility and mechanical stability during carbonization so that the cell/SWCNT(1 wt%)carbon nanocomposite could be bent even after carbonization at 1400 °C; however, the carbonized cellulose prepared using the same method was too brittle. This cell/SWCNTcarbon nanocomposite may render the eco-friendly production of flexible electrodes for various applications, including heat sink parts, electromagnetic interference shielding materials, and electronic devices, feasible.

Synthesis of nanobelt-like 1-dimensional silver/nanocarbon hybrid materials for flexible and wearable electroncs.

Most synthetic processes of metallic nanostructures were assisted by organic/inorganic or polymeric materials to control their shapes to one-dimension or two-dimension. However, these additives have to be removed after synthesis of metal nanostructures for applications. Here we report a straightforward method for the low-temperature and additive-free synthesis of nanobelt-like silver nanostructures templated by nanocarbon (NC) materials via bio-inspired shape control by introducing supramolecular 2-ureido-4[1H]pyrimidinone (UPy) groups into the NC surface. The growth of the Ag nanobelt structure was found to be induced by these UPy groups through observation of the selective formation of Ag nanobelts on UPy-modified carbon nanotubes and graphene surfaces. The synthesized NC/Ag nanobelt hybrid materials were subsequently used to fabricate the highly conductive fibres (>1000S/cm) that can function as a conformable electrode and highly tolerant strain sensor, as well as a highly conductive and robust paper (>10000S/cm after thermal treatment).

Bioinspired Multifunctional Superhydrophobic Surfaces with Carbon-Nanotube-Based Conducting Pastes by Facile and Scalable Printing.

Directly printed superhydrophobic surfaces containing conducting nanomaterials can be used for a wide range of applications in terms of nonwetting, anisotropic wetting, and electrical conductivity. Here, we demonstrated that direct-printable and flexible superhydrophobic surfaces were fabricated on flexible substrates via with an ultrafacile and scalable screen printing with carbon nanotube (CNT)-based conducting pastes. A polydimethylsiloxane (PDMS)-polyethylene glycol (PEG) copolymer was used as an additive for conducting pastes to realize the printability of the conducting paste as well as the hydrophobicity of the printed surface. The screen-printed conducting surfaces showed a high water contact angle (WCA) (>150°) and low contact angle hysteresis (WCA < 5°) at 25 wt % PDMS-PEG copolymer in the paste, and they have an electrical conductivity of over 1000 S m-1. Patterned superhydrophobic surfaces also showed sticky superhydrophobic characteristics and were used to transport water droplets. Moreover, fabricated films on metal meshes were used for an oil/water separation filter, and liquid evaporation behavior was investigated on the superhydrophobic and conductive thin-film heaters by applying direct current voltage to the film.

Enhanced transparent conducting networks on plastic substrates modified with highly oxidized graphene oxide nanosheets.

Atomically thin and two-dimensional graphene oxide (GO) is a very fascinating material because of its functional groups, high transparency, and solution processability. Here we show that highly oxidized GO (HOGO) nanosheets serve as an effective interfacial modifier of transparent conducting films with one-dimensional (1D) silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs). Optically transparent and small-sized GO nanosheets, with minimal sp(2) domains, were successfully fabricated by step-wise oxidation and exfoliation of graphite. We demonstrated that under-coated HOGO further decreases the sheet resistance of the SWCNT film top-coated with HOGO by increasing the contact area between the SWCNTs and HOGO nanosheets by generating hole carriers in the SWCNT as a result of charge transfer. Moreover, HOGO nanosheets with AgNWs contribute to the efficient thermal joining of AgNW networks on plastic substrates by limiting the thermal embedding of AgNWs into the plastic surface, resulting in efficient decrease of the sheet resistance. Furthermore, flexible organic photovoltaic cells with GO-modified AgNW anodes on a flexible substrate were successfully demonstrated.

Sub-second carbon-nanotube-mediated microwave sintering for high-conductivity silver patterns on plastic substrates.

A method of microwave sintering that is mediated by carbon nanotubes (CNTs) has been developed to obtain high-conductivity Ag patterns on the top of heat-sensitive plastic substrates within a short time. The Ag patterns are printed on CNTs formed on plastic substrates and rapidly heated to a great extent by the heat transferred from the microwave-heated CNTs. The conductivity of the microwave-sintered Ag patterns reaches ∼39% that of bulk Ag within 1 s without substrate deformation. Furthermore, microwave sintering enhances the adhesion of Ag patterns to the thermoplastic substrates because the sintering causes interfacial fusion between the Ag patterns and the substrates, and CNTs physically connect the patterns with the substrates.

Rearrangement of 1D conducting nanomaterials towards highly electrically conducting nanocomposite fibres for electronic textiles.

Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 × 10(5) S m(-1)) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors.

Extremely efficient liquid exfoliation and dispersion of layered materials by unusual acoustic cavitation.

Layered materials must be exfoliated and dispersed in solvents for diverse applications. Usually, highly energetic probe sonication may be considered to be an unfavourable method for the less defective exfoliation and dispersion of layered materials. Here we show that judicious use of ultrasonic cavitation can produce exfoliated transition metal dichalcogenide nanosheets extraordinarily dispersed in non-toxic solvent by minimising the sonolysis of solvent molecules. Our method can also lead to produce less defective, large graphene oxide nanosheets from graphite oxide in a short time (within 10 min), which show high electrical conductivity (>20,000 S m(-1)) of the printed film. This was achieved by adjusting the ultrasonic probe depth to the liquid surface to generate less energetic cavitation (delivered power ~6 W), while maintaining sufficient acoustic shearing (0.73 m s(-1)) and generating additional microbubbling by aeration at the liquid surface.

Electrically robust metal nanowire network formation by in-situ interconnection with single-walled carbon nanotubes.

Modulation of the junction resistance between metallic nanowires is a crucial factor for high performance of the network-structured conducting film. Here, we show that under current flow, silver nanowire (AgNW) network films can be stabilised by minimizing the Joule heating at the NW-NW junction assisted by in-situ interconnection with a small amount (less than 3 wt%) of single-walled carbon nanotubes (SWCNTs). This was achieved by direct deposition of AgNW suspension containing SWCNTs functionalised with quadruple hydrogen bonding moieties excluding dispersant molecules. The electrical stabilisation mechanism of AgNW networks involves the modulation of the electrical transportation pathway by the SWCNTs through the SWCNT-AgNW junctions, which results in a relatively lower junction resistance than the NW-NW junction in the network film. In addition, we propose that good contact and Fermi level matching between AgNWs and modified SWCNTs lead to the modulation of the current pathway. The SWCNT-induced stabilisation of the AgNW networks was also demonstrated by irradiating the film with microwaves. The development of the high-throughput fabrication technology provides a robust and scalable strategy for realizing high-performance flexible transparent conductor films.

Microwave flash annealing for stability of chemically doped single-walled carbon nanotube films on plastic substrates.

Microwave flash annealing dramatically enhances the environmental stability of AuCl3-doped single-walled carbon nanotube (SWCNT) films on plastic substrates using fast microwave nanoheating to produce a large temperature difference between the films and the substrates. Within one second, the microwave nanoheating rapidly caused thermal decomposition of AuCl3 dopants as well as simultaneous embedding of SWCNTs in the substrate, without deforming it. The hygroscopic Cl atoms were partially desorbed from the SWCNTs by rapid thermal decomposition, and the embedded substrate surface acted as a passivation layer, which synergistically contributed to the stability of the doped and annealed SWCNTs.

Dispersant-free conducting pastes for flexible and printed nanocarbon electrodes.

The dispersant-free fabrication of highly conducting pastes based on organic solvents with nanocarbon materials such as carbon nanotubes and graphene nanoplatelets has been hindered by severe agglomeration. Here we report a straightforward method for fabricating nanocarbon suspensions with >10% weight concentrations in absence of organic dispersants. The method involves introducing supramolecular quadruple hydrogen-bonding motifs into the nanocarbon materials without sacrificing the electrical conductivity. Printed films of these materials show high electrical conductivity of ~500,000 S m(-1) by hybridization with 5 vol% silver nanowires. In addition, the printed nanocarbon electrodes provide high-performance alternatives to the platinum catalytic electrodes commonly used in dye-sensitized solar cells and electrochemical electrodes in supercapacitors. The judicious use of supramolecular interactions allows fabrication of printable, spinnable and chemically compatible conducting pastes with high-quality nanocarbon materials, useful in flexible electronics and textile electronics.