Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Summary

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

Abstract

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices^1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.

To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT ⁵, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes ⁶, and change the ratio of metallic and semiconducting carbon nanotubes ⁷, as well as lead to graphene synthesis ⁸.

Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J×B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Protocol

1. Anode preparation

1. Scale nickel powder (99.8%, 300 mesh) and yttrium powder (99.9%, 40 mesh) according to the molar radio of 4.2:1 as catalyst powder.
2. Mix the catalyst powder with graphite powder (99.9995%, 200 mesh) very well. Fill the mixed powder into hollow graphite rod (5 mm outer diameter, 2.5 mm inner diameter and 75 mm length) firmly. Make sure the total molar radio of C:Ni:Y in anode rod is 94.8:4.2:1, which is optimum ratio to synthesize SWCNT ⁹.
3. Install cathode rod (pure graphite, 13 mm diameter) and the stuffed anode rod inside cylindrical chamber (stainless steel, 152 mm diameter and 254 mm length). Adjust the ....

Discussion

In the video snapshots shown in Figure 1b and 1d, for the case that the interelectrode gap was placed at the distance of about h=75 mm from the bottom of permanent magnet, it should be noted that change of magnet position (we tested magnet shift along z-axis and turning the magnet over) results in deviation of arc jet flow in x-direction corresponding to direction of J×B force illustrated in Figure 1c. It was also observed that the geometry of arc plasma column did.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Table of specific reagents and equipment:
Methanol	Acros Organics	423950010
Nickel powder	Alfa Aesar	10581
Yttrium powder	Acros Organics	318060050
Graphite powder	Alfa Aesar	40799
Hollow graphite rod	Saturn Industries	POCO EDM 3
Permanent magnet	McMaster-Carr	57315K51
Molybdenum sheet	Dingqi Sci. and Tech.	080504-11
Ultrasonic dismembrator	Fisher Scientific	Model 150T
Hall-effect gaussmeter	AI	Model 100
Welding power supply	Miller	Gold Star 600SS
Vacuum pump	J/B	DV-85N
SEM	Carl Zeiss, Inc.	LEO 1430VP
TEM	JEOL	1200 EX
Raman	Horiba Instruments Inc	HR800