U.S. patent application number 12/384979 was filed with the patent office on 2009-10-22 for method for making carbon nanotubes.
This patent application is currently assigned to Tsinghua University. Invention is credited to Chang-Shen Chang, Feng-Wei Dai, Shou-Shan Fan, Kai-Li Jiang, Hsien-Sheng Pei, Yuan Yao.
Application Number | 20090263310 12/384979 |
Document ID | / |
Family ID | 41201267 |
Filed Date | 2009-10-22 |
United States Patent
Application |
20090263310 |
Kind Code |
A1 |
Dai; Feng-Wei ; et
al. |
October 22, 2009 |
Method for making carbon nanotubes
Abstract
A method for making carbon nanotubes that includes the following
steps. A metal substrate is provided. The surface of the metal
substrate is polished. The polished metal substrate is put into a
reaction device. A protecting gas is introduced to the reaction
device while the environment inside of the reaction device is
heated to about 400 to 800 degrees. A mixture of carbon source gas
and protecting gas is introduced to the reaction device, whereby
the carbon nanotubes are grown on the metal substrate on the
polished metal substrate.
Inventors: |
Dai; Feng-Wei; (Beijing,
CN) ; Yao; Yuan; (Beijing, CN) ; Chang;
Chang-Shen; (Tu-Cheng, TW) ; Pei; Hsien-Sheng;
(Tu-Cheng, TW) ; Jiang; Kai-Li; (Bejing, CN)
; Fan; Shou-Shan; (Beijing, CH) |
Correspondence
Address: |
PCE INDUSTRY, INC.;ATT. Steven Reiss
288 SOUTH MAYO AVENUE
CITY OF INDUSTRY
CA
91789
US
|
Assignee: |
Tsinghua University
Beijing City
CN
HON HAI Precision Industry CO., LTD.
Tu-Cheng City
TW
|
Family ID: |
41201267 |
Appl. No.: |
12/384979 |
Filed: |
April 9, 2009 |
Current U.S.
Class: |
423/447.3 ;
977/742 |
Current CPC
Class: |
C01B 32/162 20170801;
B82Y 40/00 20130101; B82Y 30/00 20130101 |
Class at
Publication: |
423/447.3 ;
977/742 |
International
Class: |
D01F 9/12 20060101
D01F009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2008 |
CN |
200810066744.8 |
Claims
1. A method for making carbon nanotubes, the method comprising the
following steps: providing a metal substrate; polishing a surface
of the metal substrate; putting the polished metal substrate into a
reaction device; introducing a first protecting gas while heating
the environment inside of the reaction device to about 400 to 800
degrees; and introducing a mixture of a carbon source gas and a
second protecting gas, whereby the carbon nanotubes are grown
directly on the polished metal substrate.
2. The method as claimed in claim 1, wherein the step of polishing
the surface of the metal substrate comprising the following steps:
rubbing the surface of the metal substrate along a first direction;
then rubbing the surface of the metal substrate along a second
direction; and then repeatedly rubbing the surface of the metal
substrate along the first direction.
3. The method as claimed in claim 2, wherein the surface of the
metal substrate is first rubbed along the first direction for about
3 to 5 minutes, then is rubbed along the second direction for about
5 to 8 minutes, and then is rubbed along the first direction for
about 10 to 15 minutes.
4. The method as claimed in claim 2, wherein the surface of the
metal substrate is first rubbed along the first direction with an
abrasive paper of about 600 to 800 grit, then is rubbed along the
second direction with an abrasive paper of about 1000 to 1300 grit,
and then is rubbed along the first direction with an abrasive paper
of about 1500 to 2000 grit.
5. The method as claimed in claim 2, wherein an angle between the
first direction and the second direction is larger than 0 degrees
and less than or equal to 90 degrees.
6. The method as claimed in claim 1, further comprising a step of
removing powder generated from polishing the surface of the metal
substrate.
7. The method as claimed in claim 6, wherein the powder is removed
by the application of air flow.
8. The method as claimed in claim 1, wherein the metal substrate
comprises of copper.
9. The method as claimed in claim 1, wherein the metal substrate is
a rectangular.
10. The method as claimed in claim 1, wherein a thickness of the
metal substrate is in a range from about 0.5 centimeters to about 5
centimeters.
11. The method as claimed in claim 1, wherein the reaction device
is a box furnace or a tube furnace.
12. The method as claimed in claim 1, wherein the first or second
protecting gas is inert gas or nitrogen.
13. The method as claimed in claim 1, wherein the carbon source gas
is acetylene or ethylene.
14. The method as claimed in claim 1, wherein a growth time for the
carbon nanotubes is in a range from about 5 minutes to 30
minutes.
15. The method as claimed in claim 1, wherein the first protecting
gas and the second protecting gas comprise of the same gas.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present disclosure relates to methods for making carbon
nanotubes and, particularly, to a method for making carbon
nanotubes on a metal substrate.
[0003] 2. Discussion of Related Art
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Many aspects of the present method for making carbon
nanotubes can be better understood with reference to the following
drawings. The components in the drawings are not necessarily to
scale, the emphasis instead being placed upon clearly illustrating
the principles of the present method for making carbon
nanotubes.
[0009] FIG. 1 is a flowchart of a method for making carbon
nanotubes, in accordance with a present embodiment.
[0010] FIG. 2 is a scanning electron microscope (SEM) image of
carbon nanotubes formed using the method in accordance with the
present embodiment.
[0011] FIG. 3 is a transmission electron microscopy (TEM) image of
carbon nanotubes formed using the method in accordance with the
present embodiment.
[0012] 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.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0013] 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:
[0014] 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 cm.sup.2 to 100
cm.sup.2.
[0015] Step 2, polishing a surface of the metal substrate, S2, is
detailed below. In the present embodiment, the surface of the metal
substrate is rubbed along a first direction with an abrasive paper
for about 3-5 minutes. The abrasive paper is about 600-800 grit.
After that, powder generated by the sanding during the polishing
process is removed by an application of air flow, e.g. blowing. The
treated surface of the metal substrate is then rubbed along a
second direction with an abrasive paper for about 5-8 minutes. The
abrasive paper employed in such step is about 1000-1300 grit. The
powder generated due to sanding in this step is also removed. After
rubbing the surface of the metal substrate along the second
direction, the surface of the metal substrate is rubbed along the
first direction with an abrasive paper for about 10-15 minutes. In
this case, the abrasive paper is about 1500-2000 grit. Finally,
powder generated by this is removed. An angle .alpha. between the
first direction and the second direction is in a range of
0.degree.<.alpha..ltoreq.90.degree.. Particularly, in the
present embodiment, the angle .alpha. is about 90.degree..
[0016] As a result, the surface of the metal substrate is
substantially flat and smooth by way of the polishing in step 2
that will facilitate the growth of the carbon nanotubes on the
metal substrate. However, it is understood that there are micro
variations in the form of notches or fine grooves that can be
observed on the surface of the metal substrate. Particularly, such
the notches or fine grooves are formed on a nanometer scale and in
a net-like pattern due to repeatedly rubbing steps.
[0017] Step 3, putting the polished metal substrate into a reaction
device, S3. In the present embodiment, the reaction device is a
furnace, e.g. a box furnace or a tube furnace. Particularly, the
polished metal substrate is put into a quartz boat, which is
subsequently inserted into the center of the tube furnace.
[0018] Step 4, introducing a first protecting gas while heating the
environment inside of the reaction device, S4. The first protecting
gas can be nitrogen. In the present embodiment, the environment
inside of the reaction device is heated to about 400-800 degrees
(C). For example, the environment inside of the reaction device is
heated to about 700 C. In step 4, during the heating process, a
plurality of metal particles, e.g. copper particles, forms around
the notches or fine grooves formed on the surface of the metal
substrate, and can serve as seeds for facilitating the growth of
carbon nanotubes. In the present embodiment, diameters of the metal
particles range from about 1-10 nanometers (nm). In addition, the
density of the metal particles is closely related to the number of
times of rubbing and the angle of the rubbing directions between
different rubbing steps. It is understood that the higher density
of metal particles is obtained by the greater number of times of
rubbing and the smaller angle of rubbing directions between
different rubbing steps.
[0019] Step 5, introducing a mixture of a carbon source gas and a
second protecting gas, S5. In the present embodiment, the carbon
source gas can be hydrocarbon, such as acetylene or ethylene while
the protecting gas can be inert gas or nitrogen. Particularly,
acetylene is chosen as the carbon source gas by virtue of its low
decomposition temperature and nitrogen is used as the second
protecting gas. In addition, the first protecting gas and the
second protecting gas can be the same gas. In step 5, S5, once the
mixture of carbon source gas and second protecting gas is
introduced into the reaction device, the carbon nanotubes are grown
in a temperature range from about 400-800 C for about 5-30 minutes.
The reaction device is then cooled down and the metal substrate is
taken out from the reaction device.
[0020] Referring to FIG. 2 and FIG. 3, the carbon nanotubes
fabricated by the method, in accordance with the present
embodiment, are disorderly arranged on the metal substrate. One end
of each carbon nanotube is connected with the surface of the metal
substrate. In addition, a diameter of each carbon nanotube is in a
range from about 5 nm to 20 nm.
[0021] In conclusion, the carbon nanotubes fabricated by the method
of the present embodiment can be directly formed on the metal
substrate. There is no need to coat a catalyst layer on the metal
substrate in advance for growth of the carbon nanotubes. Therefore,
the manufacturing procedure is simplified and the manufacturing
cost is decreased that is suitable for mass production.
[0022] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
invention. Variations may be made to the embodiments without
departing from the spirit of the invention as claimed. The
above-described embodiments illustrate the scope of the invention
but do not restrict the scope of the invention.
[0023] It is also to be understood that above description and the
claims drawn to a method may include some indication in reference
to certain steps. However, the indication used is only to be viewed
for identification purposes and not as a suggestion as to an order
for the steps.
* * * * *