U.S. patent application number 14/026809 was filed with the patent office on 2014-01-09 for continuous vapor grown carbon fiber mat and the producing method thereof.
This patent application is currently assigned to National Cheng Kung University. The applicant listed for this patent is National Cheng Kung University. Invention is credited to Hsiao Ping CHUNG, Dillip Kumar MISHRA, Jyh Ming TING.
Application Number | 20140011920 14/026809 |
Document ID | / |
Family ID | 43030592 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140011920 |
Kind Code |
A1 |
TING; Jyh Ming ; et
al. |
January 9, 2014 |
CONTINUOUS VAPOR GROWN CARBON FIBER MAT AND THE PRODUCING METHOD
THEREOF
Abstract
A method for fabricating a continuous vapor grown carbon fiber
mat including: (a) providing a substrate which has a catalyst on
its surface; (b) placing the substrate in a furnace; (c)
introducing hydrogen, ammonia, or combinations thereof into the
furnace; (d) adjusting a temperature of the furnace to 400.degree.
C. to 900.degree. C. to proceed heat treatment for 15 to 90
minutes; (e) adding a carbon-containing compound into the furnace
and adjusting the ratio of the carbon-containing compound and the
hydrogen, ammonia, or combinations thereof; (f) adjusting the
temperature of the furnace to 600.degree. C. to 1200.degree. C. to
crack the carbon-containing compound, and thereby forming a carbon
fiber mat, where time for reaction is 1 to 3 hours. A continuous
vapor grown carbon fiber mat and a graphitized carbon fiber mat are
also provided.
Inventors: |
TING; Jyh Ming; (Taipei
City, TW) ; MISHRA; Dillip Kumar; (Tainan City,
TW) ; CHUNG; Hsiao Ping; (Bade City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Cheng Kung University |
Tainan City |
|
TW |
|
|
Assignee: |
National Cheng Kung
University
Tainan City
TW
|
Family ID: |
43030592 |
Appl. No.: |
14/026809 |
Filed: |
September 13, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12771380 |
Apr 30, 2010 |
|
|
|
14026809 |
|
|
|
|
Current U.S.
Class: |
524/1 ;
427/249.1; 428/221 |
Current CPC
Class: |
D01F 9/127 20130101;
Y10T 428/249921 20150401; Y10T 428/249924 20150401; B82Y 30/00
20130101; C08K 3/04 20130101 |
Class at
Publication: |
524/1 ; 428/221;
427/249.1 |
International
Class: |
C08K 3/04 20060101
C08K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 4, 2009 |
TW |
98114687 |
Claims
1. A carbon fiber mat, which is fabricated by the following steps:
(a) providing a substrate with a catalyst on its surface;
(b)placing said substrate in a furnace; (c) introducing hydrogen,
ammonia, or a combination thereof into said furnace; (d) adjusting
the temperature of said furnace to 400.degree. C. to 900.degree. C.
to proceed a heat treatment for 15 to 90 minutes, thereby obtaining
nucleation points on said substrate, in which the density of said
nucleation points distributes between 1.about.50 sites/.mu.m.sup.2,
and the size of said nucleation points distributes between
10.about.2000 nm; (e) adding a carbon-containing compound into said
furnace and adjusting the ratio of said carbon-containing compound
and said hydrogen, ammonia, or a combination thereof; and (f)
adjusting the temperature of said furnace to 600.degree. C. to
1200.degree. C. to crack said carbon-containing compound and
reacting for 1 to 3 hours, and thereby forming a carbon fiber
mat.
2. A graphitized carbon fiber mat, which is obtained by heating the
carbon fiber mat according to claim 1 in inert gases at
2400.degree. C. to 2800.degree. C.; wherein said carbon fiber mat
has a graphitization degree of 99.about.100%.
3. The graphitized carbon fiber mat according to claim 2, which has
a room temperature thermal conductivity of up to 1950 W/m-k.
4. A polymer matrix composite material, characterized by comprising
the graphitized carbon fiber mat according to claim 2, which has a
thermal conductivity of 400 W/m-K to 600 W/m-K.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application No.
12/771,380, filed on Apr. 30, 2010, which claims priority under 35
U.S.C. .sctn.119(a) on Patent Application No. 98114687, filed in
Taiwan on May 4, 2009, the contents of each are hereby expressly
incorporated by reference into the present application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is related to a vapor grown carbon
fiber mat and a method for fabricating the same, especially, to a
vapor grown carbon fiber mat having a continuous structure.
[0004] 2. Description of the Related Art
[0005] During the past decades, traditional mechanical products
have been quietly substituted by 3C electronic products in our
daily life. Scientists must dedicate themselves to develop products
with more powerful functions, higher efficiency and faster
processing velocity for satisfying the needs of speed and
convenience.
[0006] All electronic products with high efficiency have to face
the issues of power conversion. Powerful products need a better
electronic efficiency, and accordingly, more waste heat is
produced. Therefore, how to dissipate heat to maintain operating
system stability is a more and more important issue.
[0007] Furthermore, lots of traditional heat-dissipating materials
are gradually eliminated from the market because of the customers'
critical demands for small, light and portable products.
[0008] In other words, the development of novel heat-dissipating
materials is an urgent and essential issu for scientists. The basic
requirements of novel heat-dissipating materials include a higher
thermal conductivity and smaller size.
[0009] Some composite materials with high conductivity have been
available in the market. Among those composite materials, the
heat-dissipating composite material using vapor grown carbon fibers
as a reinforcing material is the most potential one.
[0010] That is because the room temperature thermal conductivity of
a graphitized vapor grown carbon fiber is up to 1950 W/m-K, which
is approximately five times higher than that of copper, and the
density of the vapor grown carbon fiber is 1/4 or less than that of
copper. Moreover, the room temperature resistance of the vapor
grown carbon fiber is extremely low, i.e. about 0.6 .OMEGA..m,
which is similar to that of titanium.
[0011] Among all carbon fibers, the vapor grown carbon fiber has
the best thermal conductivity and resistance, and it also has good
tensile stress and tension coefficient; therefore, the vapor grown
carbon fiber is the best choice for developing composite materials
with high thermal conductivity.
[0012] However, the length of traditional vapor grown carbon fibers
is at most hundreds of microns, so that the composite materials
fabricated by the traditional vapor grown carbon fibers have a lot
of discontinuous scission points, which significantly restrict heat
conduction and therefore reduce the thermal conductivity of the
composite materials to be similar to or even lower than that of
aluminum.
[0013] In view of the disadvantages of conventional technology, we
provide a novel method for producing a vapor grown carbon fiber mat
to fabricate carbon fiber mats having a continuous structure, which
can be used for improving thermal conductivity of composite
materials.
SUMMARY OF THE INVENTION
[0014] In view of foregoing, one object of the present invention is
to provide a method for fabricating a carbon fiber mat. The method
of present invention fabricates a vapor grown carbon fiber mat with
a continuous structure by vapor deposition, wherein the mat has a
continuous length of longer than 10 centimeter. In contrast with
the carbon fiber mats fabricated by traditional methods (which has
a length of tens to hundreds of microns), the carbon fiber mats
fabricated by the method of present invention have a high thermal
conductivity, which results in high heat-dissipating efficiency.
The continuous carbon fiber mats of the present invention
successfully overcome the disadvantage of thermal resistance caused
by scission points that form a discontinuities structure in carbon
fibers used for traditional vapor grown carbon fiber composite
materials. Therefore, it dramatically improves the thermal
conductivity of the composite materials. In addition, it has a low
density, so it is more suitable for fabricating composite
materials.
[0015] Another object of the present invention is to provide a
carbon fiber mat with a continuous structure and a continuous
length of longer than 10 centimeter. The carbon fiber mat of the
present invention has a higher thermal conductivity because of the
advantage in structure. The continuous carbon fiber mats of the
present invention successfully overcome the disadvantage of thermal
resistance caused by scission points that form a discontinuities
structure in carbon fibers used for traditional vapor grown carbon
fiber composite materials. Therefore, it dramatically improves the
thermal conductivity of the composite materials. In addition, it
has a low density, so it is more suitable for fabricating composite
materials.
[0016] Yet another object of the present invention is to provide a
graphitized carbon fiber mat, which comprises a continuous carbon
fiber structure. Therefore, the disadvantage of thermal resistance
caused by scission points that form a discontinuities structure in
carbon fibers is overcome, and the thermal conductivity of the
composite materials is significantly improved.
[0017] To achieve the above objects, the present invention provides
a method for fabricating a carbon fiber mat, comprising the
following steps: (a) providing a substrate with a catalyst on its
surface; (b) placing said substrate in a furnace; (c) introducing
hydrogen, ammonia, or a combination thereof into said furnace; (d)
adjusting the temperature of said furnace to 400.degree. C. to
900.degree. C. to proceed a heat treatment for 15 to 90 minutes;
(e) adding a carbon-containing compound into said furnace and
adjusting the ratio of said carbon-containing compound and said
hydrogen, ammonia, or a combination thereof; (f) adjusting the
temperature of said furnace to 600.degree. C. to 1200.degree. C. to
crack said carbon-containing compound and reacting for 1 to 3
hours, and thereby forming a carbon fiber mat.
[0018] Preferably, nucleation points are obtained after processing
said catalyst through said step (a) to said step (d), wherein the
density of said nucleation points distributes between 1.about.50
sites/.mu.m.sup.2, and the size of said nucleation points
distributes between 10.about.2000 nm.
[0019] Preferably, said catalyst is a transition metal, an alloy
comprising one or more transition metals, or a compound comprising
one or more transition metals. Said catalyst is in form of powder,
solution, or film.
[0020] More preferably, said transition metal is iron.
[0021] Preferably, said substrate in said step (a) is a
plane-surface structure made by any material resistant to the high
temperatures determined in the following experiments (for instance,
said substrate includes but not limited to a quartz substrate, a
graphite substrate, a silicon substrate, a ceramic substrate, a
carbon/carbon composite substrate and a bamboo carbon plate).
[0022] Preferably, said furnace is a horizontal high temperature
furnace or a vertical high temperature furnace.
[0023] Preferably, the temperature of said heat treatment in said
step (d) is 500.degree. C. to 850.degree. C.; the time of said heat
treatment is 25 to 60 minutes.
[0024] Preferably, said carbon-containing compound in said step (e)
comprises a hydrocarbon (for instance, including but not limited to
methane, ethane, propane, butane, pentane, hexane, ethene, ethyne,
and benzene) or other carbon-containing organic compound (for
instance, including but not limited to methanol, ethanol, propanol,
formic acid, acetic acid, propionic acid, native gas and
petroleum). The molar ratio of said carbon-containing compound and
said hydrogen, ammonia, or a combination thereof in said step (e)
is 1:100 to 200:100; more preferably, is 5:100 to 150:100.
[0025] Preferably, the cracking temperature in said step (f) is
700.degree. C. to 1100.degree. C. In this step (f), said
carbon-containing compound is cracked to carbon element. Said
carbon element is diffused into said catalyst on the substrate and
then formed carbon fibers at 600.degree. C. to 1200.degree. C.
Because nucleation points are formed with appropriate density and
size, said carbon fibers cross and interact with each other, they
slightly bend due to gravity and specific gas flow and grow on said
substrate to form a carbon fiber mat along the direction of the gas
flow in said furnace.
[0026] Preferably, said hydrogen, ammonia, or a combination thereof
is introduced into said furnace at a flow velocity of 0.5.about.10%
of volume of said furnace per minute.
[0027] To achieve the above objects, the present invention provides
a carbon fiber mat, which is fabricated by the method of the
present invention. The carbon fiber mat provided by the present
invention has a carbon fiber structure with a continuous length of
1.about.50 centimeter.
[0028] To achieve the above objects, the present invention provides
a graphitized carbon fiber mat, which is obtained by heating the
carbon fiber mat of the present invention in inert gases at
2400.degree. C. to 2800.degree. C., wherein the graphitization
degree is 99.about.400%.
[0029] To sum up, the method provided by the present invention can
fabricate a carbon fiber mat with a continuous structure. The
graphitized continuous vapor grown carbon fiber mat of the present
invention can be used to produce a composite material. Because it
has a continuous structure, the produced composite material
successfully overcomes the disadvantage of thermal resistance
caused by scission points that form a discontinuities structure in
carbon fibers used for traditional vapor grown carbon fiber
composite materials.
[0030] The polymer-based composite material fabricated by using the
aforementioned graphitized carbon fiber mat as a reinforced
material has a thermal conductivity of 400 W/m-K to 600 W/m-K.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 shows the growth process of the carbon fiber mat of
the present invention.
[0032] FIG. 2 displays the graphitized carbon fibers of the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0033] As mentioned above, the present invention provides a method
for fabricating a carbon fiber mat, comprising the following steps:
(a) providing a substrate with a catalyst on its surface; (b)
placing said substrate in a furnace; (c) introducing hydrogen,
ammonia, or a combination thereof into said furnace; (d) adjusting
the temperature of said furnace to 400.degree. C..about.900.degree.
C. to proceed a heat treatment for 15 to 90 minutes; (e) adding a
carbon-containing compound into said furnace and adjusting the
ratio of said carbon-containing compound and said hydrogen,
ammonia, or a combination thereof; (f) adjusting the temperature of
said furnace to 600.degree. C. to 1200.degree. C. to crack said
carbon-containing compound and reacting for 1 to 3 hours, and
thereby forming a carbon fiber mat.
[0034] Please refer to FIG. 1, which shows the growth process of
the carbon fiber mat of the present invention. Catalyst particles
(20) or catalyst thin-films are evenly coated onto a substrate (10)
with appropriate density. Then, said substrate is placed into a
high temperature furnace tube (30), which is able to adjust the
atmosphere therein. Said high temperature furnace can be a
horizontal furnace or a vertical furnace, wherein a horizontal
furnace is preferred. Said catalyst preferably is a transition
metal, an alloy comprising one or more transition metals, or a
compound comprising one or more transition metals. After that, 1
atm of hydrogen or ammonia (40), or a mixed gas containing hydrogen
and ammonia in an appropriate ratio (40) is introduced into the
furnace tube (30). By adjusting the temperature of the furnace, the
catalyst is proceed heat treatment inside a reaction area with an
appropriate temperature for an appropriate period of time to form
nucleation points, wherein the density of said nucleation points
distributes between 1.about.50 sites/.mu.m.sup.2, and the size of
said nucleation points distributes between 10.about.2000 nm. The
length of said substrate is equal to that of said reaction area;
the temperature for said heat treatment is 400.about.900.degree.
C., wherein 500.about.850.degree. C. is preferred; and the time for
said heat treatment is 15.about.90 minutes, wherein 25.about.60
minutes is preferred. Then, a hydrocarbon or a carbon-containing
organic compound (50) is added into the furnace tube (30), and the
volume ratio of said hydrocarbon or said carbon-containing organic
compound (50) and said hydrogen or ammonia is adjusted
appropriately for the fabrication of vapor grown carbon fiber mats.
Said hydrocarbon is a gas such as methane, ethane, propane, butane,
pentane, hexane, ethene, ethyne, or benzene, said carbon-containing
organic compound is an alcohol (such as methanol, ethanol, or
propanol), an acid (such as formic acid, acetic acid, or propionic
acid), native gas, petroleum or combinations thereof, wherein
methane, ethyne, native gas or a combination thereof is preferred.
The molar ratio of said hydrocarbon and said hydrogen or ammonia is
1:100 to 200:100, wherein 5:100 to 150:100 is preferred. At the
same time, by adjusting the temperature of said furnace, said
hydrocarbon is cracked in a reaction area with an appropriate
temperature and diffused into the heat-treated catalyst to form
carbon fibers (60). The temperature for cracking is
600.about.1200.degree. C., wherein 700.about.1100.degree. C. is
preferred. In this condition, the length and diameter of said
carbon fibers can be varied in accordance with temperature, types
of hydrocarbon, concentration of hydrocarbon and time. Moreover,
because said nucleation points have appropriate density and size,
said carbon fibers intend to grow and cross with adjacent carbon
fibers successively during growth. As said carbon fibers grow to a
certain length, gravity and specific gas flow (70) inside the
furnace tube will make said carbon fibers to bend and grow on said
substrate, thereby forming a carbon fiber mat.
[0035] Then, the temperature of said furnace and the volume ratio
of said hydrocarbon and said hydrogen or ammonia can be adjusted
optionally to make the gradually formed carbon fiber mat keep
growing successively until the top (80) of said carbon fiber mat
protrudes the reaction area. The range of adjustment of the
temperature and the volume ratio of said hydrocarbon and said
hydrogen or ammonia are the same as the aforementioned cracking
step. The structure, the length and diameter of carbon fibers of
said continuous vapor grown carbon fiber mat cannot be achieved by
traditional method for fabricating vapor grown carbon fibers.
[0036] It is noted that the continuous vapor grown carbon fiber
mats can be graphitized simply by heat treatment in inert gases at
2600.degree. C., and the obtained graphitized mats have a room
temperature thermal conductivity of up to 1950 W/m-k. The
graphitized continuous vapor grown carbon fiber mats (as shown in
FIG. 2) are capable to be used for fabricating composite materials.
Because the mats of the present invention have continuous
structure, the fabricated composite materials successfully overcome
the disadvantage of thermal resistance caused by scission points
that form a discontinuities structure in carbon fibers used for
traditional vapor grown carbon fiber composite materials, and have
significantly improved thermal conductivity, wherein the thermal
conductivity is much higher than that of the composite materials
fabricated by traditional vapor grown carbon fibers. A
polymer-based composite material fabricated by the aforementioned
graphitized carbon fiber mat used as a reinforced material has
thermal conductivity of 400 W/m-K to 600 W/m-K.
[0037] The following examples are used to clearly demonstrate the
technical features and advantages of the present invention. It
shall be understood that the technical features of the present
invention have already described herein, those skilled in the art
can easily accomplish the present invention in accordance with the
description of the present invention. The following examples are
only used as examples but not used to limit the technical features
of the present invention.
Example 1
Preparation of the Continuous Vapor Grown Carbon Fiber Mat of the
Present Invention
[0038] Iron catalyst was sprayed evenly onto a ceramic substrate
with a length of 8 cm and a width of 6 cm, and then the substrate
was placed into a horizontal high temperature furnace tube. 1 atm
and 800 sccm of argon was introduced into the high temperature
furnace, and the temperature of the furnace was adjusted to
600.degree. C. After that, 1 atm and 100 sccm of hydrogen was
introduced immediately to substitute the argon and the catalyst was
processed heat treatment. Then, the temperature of the furnace was
raised to 1100.degree. C., and 50 sccm of methane was introduced
therein. At this time, the molar ratio of said methane and said
hydrogen is 50:100. After maintaining the temperature (1100.degree.
C.) for 2 hours, a continuous vapor grown carbon fiber mat with a
length of 8 cm and a width of 6 cm was obtained and the average
diameter of carbon fiber thereof was about 5 .mu.m.
Example 2
Preparation of the Continuous Vapor Grown Carbon Fiber Mat of the
Present Invention
[0039] The preparation procedures were the same as Example 1 except
that the substrate was replaced with a carbon/carbon composite
substrate with a length of 8 cm and a width of 6 cm. Eventually, a
continuous vapor grown carbon fiber mat with a length of 8 cm and a
width of 6 cm was obtained and the average diameter of the carbon
fibers thereof was about 5 .mu.m.
Example 3
Preparation of the Continuous Vapor Grown Carbon Fiber Mat of the
Present Invention
[0040] Iron catalyst was sprayed evenly onto a ceramic substrate
with a length of 35 cm and a width of 10 cm, and then the substrate
was placed into a horizontal high temperature furnace tube. 1 atm
and 1000 sccm of argon was introduced into the high temperature
furnace, and the temperature of furnace was adjusted to 600.degree.
C. After that, 1 atm and 600 sccm of hydrogen was introduced
immediately to substitute the argon and the catalyst was processed
heat treatment. Then, the temperature of the furnace was raised to
1100.degree. C., and 300 sccm of methane was introduced therein. At
this time, the molar ratio of said methane and said hydrogen is
50:100. After maintaining the temperature (1100.degree. C.) for 2
hours, a continuous vapor grown carbon fiber mat with a length of
35 cm and a width of 10 cm was obtained and the average diameter of
the carbon fibers thereof was about 6 .mu.m.
Example 4
Preparation of the Continuous Vapor Grown Carbon Fiber Mat of the
Present Invention
[0041] Iron catalyst was sprayed evenly onto a carbon/carbon
composite substrate with a length of 50 cm and a width of 12 cm,
and then the substrate was placed into a horizontal high
temperature furnace. 1 atm and 800 sccm of argon was introduced
into the high temperature furnace, and the temperature of furnace
was adjusted to 600.degree. C. After that, 1 atm and 600 sccm of
hydrogen was introduced immediately to substitute the argon and the
catalyst was processed heat treatment. Then, the temperature of the
furnace was raised to 1100.degree. C., and 700 sccm of methane was
introduced therein. At this time, the molar ratio of said methane
and said hydrogen is 116.67:100. After maintaining the temperature
(1100.degree. C.) for 2 hours, a continuous vapor grown carbon
fiber mat with a length of 50 cm and a width of 12 cm was obtained
and the average diameter of the carbon fibers thereof was about 8
.mu.m. The obtained carbon fiber mat was graphitized at
2600.degree. C. to fabricate a polymer-based composite material,
wherein the thermal conductivity of the polymer-based composite
material was 530 W/m-K.
[0042] To sum up, the continuous vapor grown carbon fiber mat with
high thermal conductivity of the present invention is fabricated by
a chemical vapor deposition method. The size of said mat depends on
the substrate used; that is, the size of said mat can be varied
easily. The continuous vapor grown carbon fiber mats not only have
the advantages of the traditional vapor grown carbon fiber mats,
such as high thermal conductivity, but also overcome the
disadvantage of great thermal resistance and low heat-dissipating
capacity caused by scission points that form a discontinuities
structure in carbon fibers used for traditional vapor grown carbon
fiber composite materials.
[0043] Therefore, the thermal conductivity of the composite
materials is significantly improved to much higher than that of
composite materials fabricated by traditional vapor grown carbon
fibers. Moreover, the structure of the mats of the present
invention is also beneficial for the fabrication of composite
materials. The embodiments and the technical principles used are
described above. All variations and modifications of the present
invention and the uses thereof are included in the scope of the
present invention if they do not depart from the spirit of the
disclosure of this specification and drawings.
Other Embodiments
[0044] All characteristics disclosed herein can be combined in a
variety of ways. And the characteristics disclosed herein can be
replaced by any characteristics to be used for the same, equal, or
similar purpose. Thus, unless otherwise specified, any
characteristic disclosed herein is just an example of a series of
equal or similar characteristics.
[0045] In addition, based on the disclosure herein, appropriate
changes and modifications may be made by those skilled in the art
according to different uses and situations without departing from
the spirit and scope of the invention. Therefore, other embodiments
are included in the claims of the present invention.
* * * * *