Masatsugu Fujishige

High electrical conductivity of double-walled carbon nanotube fibers by hydrogen peroxide treatments

Double-walled carbon nanotube (DWNT) fibers are of great interest due to their electrical properties and light weight, making them attractive for industrial applications including their potential use in power transmission lines. We present here a detailed study of the mechanism by which hydrogen peroxide (H2O2) treatment improves the electrical transport of DWNT fibers. These fibers were immersed and sonicated in H2O2 for several hours. Experimental results suggest that residual H2O2 could be intercalated within intertube channels inside the bundles of DWNTs, and the oxidation treatment could also result in the removal of small diameter carbon nanotubes (CNTs). In addition, an increase in the fiber density resulted in a decrease of the electrical resistivity. The H2O2 treatment of the DWNT fibers resulted in a metallic-like temperature dependent resistivity behavior with a transition to a semiconducting-like behavior below 30 K. We compared the effects of H2O2 with other well-known solvents and additives commonly used to reduce the carbon nanotube fiber electrical resistivity and found that the electrical conductivity values observed in our study are as good as those obtained with thionyl chloride and iodine additives. The H2O2 method was also used to treat other forms of carbon, where only the multi-walled carbon nanotubes doped with nitrogen exhibited a decrease in electrical resistivity. The fabrication method presented here is simple, efficient and low cost, thus making it an ideal process to be applied in the fabrication of electrically conducting carbon nanotube fibers.

Microwave plasma-induced graphene-sheet fibers from waste coffee grounds

Graphene-sheet fiber, a novel structure of graphitic carbon, grew from coffee grounds under the condition of microwave plasma irradiation. The resulting fiber consisted of only few-layer graphene without a hollow structure inside while possessing a large amount of graphene edges and high conductivity. Due to these advantages, graphene-sheet fibers may find applications in electrochemical energy conversion and storage.

Gold–Carbon Nanotube Composite Plating Film Deposited Using Non-Cyanide Bath

We developed a gold–carbon nanotube (Au–CNT) composite plating film by electrodeposition. An effective additive was added into a non-cyanide CNT plating solution, affording an environmentally friendly method for fabricating an Au–CNT composite plating film using a basic solvent. The fabricated Au–CNT composite film was harder than the Au film by 1.4 times and showed a low friction coefficient. Thus, the Au–CNT composite film could be considered as a promising material for next-generation electrical contact applications.

Electric Contact Characteristic under Low Load of Silver?Carbon Nanotube Composite Plating Film Corroded Using H2S Gas

We fabricated silver–carbon nanotube (Ag–CNT) composite plating films and prepared samples after a H2S gas corrosion test. After corrosion, although the elastic modulus of Ag film increased 1.9 times, there was no marked difference in the mechanical characteristic of Ag–CNT film. At a low load, for the Ag–CNT film after corrosion, there was no polarity and the contact resistance was low and ohmic, although the contact resistance of Ag film after corrosion was high and polar. Therefore, Ag–CNT film can be considered as a promising material for next-generation electrical contact applications.

Nitrogen-rich green leaves of papaya and Coccinia grandis as precursors of activated carbon and their electrochemical properties

Activated carbon (AC) was synthesized from papaya and Coccinia grandis leaves (PL-AC and CL-AC, respectively) which are nitrogen-rich precursors and their electrochemical properties were investigated. The synthesis process included carbonization at 400 °C, impurity removal by H2SO4 cleaning, and post activation by NaOH at 720 °C. Surpassing the conventional bamboo-derived AC (B-AC), PL- and CL-ACs show relatively high surface areas of 2664 and 2576 m2 g−1, respectively. Moreover, the nitrogen contents in the PL- and CL-ACs were approximately 2.3 and 1.8 at%, respectively. Furthermore, the electrochemical properties of the synthesized PL- and CL-ACs were investigated using both aqueous and organic electrolytes. The specific capacitances of the PL- and CL-ACs were 98.47 and 89.91 F g−1, respectively, in Na2SO4 electrolyte. Especially, compared to the B-AC, the PL-AC shows a dramatic decrease in series resistances (RS) from 1.33 to 0.53 Ω and charge transfer resistances (RCT) from 25.83 to 9.00 Ω. The decrease of RS and RCT is attributed to the existence of nitrogen in the PL-AC, resulting in a higher conductivity of electrode material and an enhancement of the charge transfer between electrode material and electrolyte. The large surface area of the PL- and CL-ACs was successfully achieved without detriment to the electrical conductivity. These results suggest that nitrogen-rich PL and CL are potential precursors for the synthesis of nitrogen-doped AC in a one-step process, which can be used as an alternative electrode material for electrochemical capacitors and can potentially be applied for large-scale industrial production with low cost.