How is CNT prepared?
CNTs have been prepared in various ways such as arc discharge [2-7], laser ablation [8-9], and chemical vapor deposition (CVD) [10-18]. CVD has proved to be the most suitable synthesis process for the production of CNTs with controlled characteristics, such as diameter, length and number of walls.
How is CNT prepared by arc-discharge?
Classically, carbon nanotubes are synthesized by arc-discharge method, in which an arc is generated in between two graphitic rods kept at a certain distance of few mm (Bethune et al., 1993. Cobalt-catalysed growth of carbon nanotubes with single-atomic-layer walls.
How is CNT prepared by laser ablation?
In laser ablation, a pulsed laser vaporizes a graphite target in a high-temperature reactor while an inert gas is led into the chamber. Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon condenses. A water-cooled surface may be included in the system to collect the nanotubes.
Who first used the word carbon nanotubes CNT and when?
Carbon nanotubes having nanoscale dimension (1-D) have been well-known over the past 15 years. The molecules were first discovered by Iijima in 1991 [1] when he was studying the synthesis of fullerenes by using electric arc discharge technique.
Which gas is used in electric arc discharge method?
In the arc discharge method, a DC bias of 20–30 V is applied between two carbon electrodes in a helium atmosphere. Carbon atoms are ejected from the anode, and accumulate in the form of nanotubes on the cathode. The electrodes are typically 5–20 mm in diameter.
How many types of carbon nanotubes are there?
In addition to the two different basic structures, there are three different possible types of carbon nanotubes. These three types of CNTs are armchair carbon nanotubes, zigzag carbon nanotubes, and chiral carbon nanotubes.
What is arc discharge?
An electric arc, or arc discharge, is an electrical breakdown of a gas that produces a prolonged electrical discharge. The current through a normally nonconductive medium such as air produces a plasma; the plasma may produce visible light.
Is an electric arc plasma?
An electric arc is an electrical breakdown of a gas, which produces an ongoing plasma discharge, resulting from a current through normally non-conductive media such as air.
What are the different types of carbon nanotubes?
Do carbon nanotubes occur naturally?
Carbon nanotubes (CNTs) have a broad range of applications and are generally considered human-engineered nanomaterials. Here, we show evidence of naturally occurring multiwalled carbon nanotubes (MWCNTs) produced from Pinus oocarpa and Pinus pseudostrobus, following a forest wildfire.
How does arc discharge work?
In an arc-discharge method, carbon atoms are evaporated by an energetic plasma of helium gas that is ignited by passing high currents through opposing carbon anode and cathode electrodes.
What can arc discharge be used for in science?
Arc discharge method is used to generate metal or metal oxide nanoparticles, CNTs, fullerenes, or graphene films (26,29,39). This method typically produces small quantities of metal ENM (milligram level) but is an important method for the synthesis of CNT and fullerenes, core–shell, and encapsulated structures.
How are electrodes held apart in arc discharge?
In arc discharge method, two high purity graphite electrodes as anode and cathode are held at short distance apart under a helium atmosphere. Under these conditions, some of the carbon evaporated from the anode, re-condensed as a hard cylindrical deposit on the cathodic rod.
What is the arc discharge method for carbon nanotubes?
ARC DISCHARGE METHOD FOR CARBON NANOTUBES The principle of this technique is to vaporize carbon in the presence of catalysts (iron, nickel, cobalt, yttrium, boron, gadolinium, and so forth) under reduced atmosphere of inert gas (argon or helium).
How is arc discharge used in multiwalled CNTs?
Arc discharge was the method used to prepare multiwalled CNTs (MWCNTs) by Iijima in 1991. In this method, an AC plasma arc is generated between two electrodes maintained in an inert atmosphere as described in Figure 4.1. The high temperature between the electrodes (3000–4000 °C) causes sublimation of the carbon.
