Method for making carbon nanotubes

1. Technical Field

The present disclosure relates to methods for making carbon nanotubes and, particularly, to a method for making carbon nanotubes on a metal substrate.

2. Discussion of Related Art

Carbon nanotubes (CNTs) are a novel carbonaceous material discovered by Iijima, a researcher of NEC Corporation, in 1991. Typically, carbon nanotubes have tube-shaped structures with small diameters (less than 100 nanometers) and large aspect ratios (length/diameter). They have excellent electrical properties as well as excellent mechanical properties. The electronic conductance of carbon nanotubes is related to their structures. Because the carbon nanotubes can transmit extremely high electrical current and emit electrons easily, at less than 100 volts, they are considered to be promising for use in a variety of electrical devices.

Generally, a number of electronic devices, such as field emission devices, traveling-wave tubes or electron guns, employ the carbon nanotubes as electron emitters. In order to achieve high power requirements, a substrate for supporting carbon nanotubes should have an ability to endure large amounts of electrical current to pass through. Therefore, it is understood that a substrate made of metal with high conductivity is considered to be a good option for use.

Currently, a method of chemical vapor deposition (CVD) is mainly adopted for forming the carbon nanotubes on the substrate. CVD is performed by coating metal catalysts, such as transition metal or transition metal complex, on the substrate and directly synthesizing the carbon nanotubes on the substrate. In principle, a carbon source gas is thermally decomposed at a predetermined temperature in the presence of the metal catalyst, thereby forming the carbon nanotubes.

However, once the transition metal is used as a catalyst and coated on the metal substrate, it is easy for the transition metal reacting on the metal of the metal substrate to form an alloy. Thus, the transition metal has become an inactive catalyst, and the catalytic reaction for growing carbon nanotubes will be affected. What is needed, therefore, is to provide a method for making carbon nanotubes, which is able to be performed easily on a metal substrate and is suitable to be employed in mass production.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one embodiment of the present method for making carbon nanotubes, in at least one form, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.

Reference will now be made to the drawings to describe, in detail, embodiments of the present method for making carbon nanotubes. Referring to FIG. 1, a method for making carbon nanotubes, according to a present embodiment, includes the following steps:

Step 1, providing a metal substrate, S1. In the present embodiment, the metal substrate is a copper substrate. The metal substrate can vary in shape and thickness according to practical requirements. For example, the metal substrate can be a solid rectangular piece. A thickness of the metal substrate can be in a range of about 0.5 centimeters (cm) to about 5 centimeters. An area of the metal substrate can be in a range of about 4 cm² to 100 cm².