U.S. patent application number 11/579445 was filed with the patent office on 2008-06-19 for method of producing carbon fiber reinforced ceramic matrix composites.
This patent application is currently assigned to DACC CO., Ltd.. Invention is credited to Dae Hyun Cho, Dong Won Lim, Hong Sik Park, Hyun Kyu Shin.
Application Number | 20080143005 11/579445 |
Document ID | / |
Family ID | 35450796 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080143005 |
Kind Code |
A1 |
Lim; Dong Won ; et
al. |
June 19, 2008 |
Method of Producing Carbon Fiber Reinforced Ceramic Matrix
Composites
Abstract
The present invention relates to a method of producing carbon
fiber reinforced ceramic matrix composites, the method of producing
carbon fiber reinforced ceramic matrix composites according to the
present invention is characterized in that the method comprises the
steps of: producing a carbon fiber reinforced resin composite that
is molded with a mixture in which carbon fibers and polymer
precursors containing carbon are mixed; producing a carbon fiber
reinforced carbon composite by depositing pyrolytic carbon during a
rapid thermal gradient chemical vapor infiltration process while
increasing the deposition speed in a direction from the inside to
the outside by performing a thermal treatment on said carbon fiber
reinforced resin composite at high temperature; and infiltrating
liquid-phase silicon into the pores of said carbon fiber reinforced
carbon composite. The method of producing carbon fiber reinforced
ceramic matrix composites according to the present invention as
described above has the effect of improving the properties of
carbon fiber reinforced ceramic matrix composites, and it is
possible to deposit a pyrolytic carbon layer at a deposition speed
5-10 times faster than other conventional chemical vapor
infiltration processes, thereby showing a remarkably improved
effect in terms of manufacturing process, time, and cost.
Inventors: |
Lim; Dong Won;
(Gyeongsangnam-do, KR) ; Park; Hong Sik;
(Gyeongsangnam-do, KR) ; Cho; Dae Hyun;
(Gyeongsangnam-do, KR) ; Shin; Hyun Kyu;
(Gyeongsangnam-do, KR) |
Correspondence
Address: |
DAVID S. RESNICK
100 SUMMER STREET, NIXON PEABODY LLP
BOSTON
MA
02110-2131
US
|
Assignee: |
DACC CO., Ltd.
Changwon-si
KR
|
Family ID: |
35450796 |
Appl. No.: |
11/579445 |
Filed: |
May 27, 2005 |
PCT Filed: |
May 27, 2005 |
PCT NO: |
PCT/KR05/01581 |
371 Date: |
August 27, 2007 |
Current U.S.
Class: |
264/29.2 |
Current CPC
Class: |
F16D 69/023 20130101;
F16D 2200/0047 20130101; C04B 2235/48 20130101; C04B 38/0032
20130101; C04B 38/0058 20130101; C04B 35/83 20130101; C04B 38/068
20130101; C04B 35/83 20130101; C04B 38/0067 20130101; C04B 2235/614
20130101; C04B 35/83 20130101; C04B 35/573 20130101; C04B 35/565
20130101; C04B 38/0032 20130101; C04B 35/806 20130101; C04B 38/0032
20130101; C04B 2111/26 20130101; C04B 2111/00362 20130101; C04B
2111/28 20130101; C04B 2235/5248 20130101 |
Class at
Publication: |
264/29.2 |
International
Class: |
D01F 9/12 20060101
D01F009/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2004 |
KR |
10-2004-0038589 |
Claims
1. A method of producing carbon fiber reinforced ceramic matrix
composites comprising the steps of: producing a carbon fiber
reinforced resin composite that is molded with a mixture in which
carbon fibers and polymer precursors containing carbon are mixed;
producing a carbon fiber reinforced carbon composite by depositing
pyrolytic carbon during a rapid thermal gradient chemical vapor
infiltration process while increasing the deposition speed in a
direction from the inside to the outside by performing a thermal
treatment on said carbon fiber reinforced resin composite at high
temperature; and infiltrating liquid-phase silicon into the pores
of said carbon fiber reinforced carbon composite.
2. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein said mixture includes
10-60 wt % of said carbon fibers, and 30-60 wt % of said polymer
precursors containing carbon.
3. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 2, wherein said mixture includes less
than 30 wt % silicon carbide powder, and less than 30 wt % carbon
powder.
4. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 2 or 3, wherein said carbon fiber
reinforced resin composite is stacked with said mixture and carbon
fabrics alternately.
5. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 4, wherein said green body is formed
with a first surface layer for preventing carbon fibers from
reacting with silicon by means of said mixture that has been mixed
during the mixing process, and said first surface layer is formed
with a ceramic matrix layer including silicon carbide and silicon
by chemically reacting with said liquid-phase silicon in the step
of infiltrating said liquid-phase silicon.
6. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein said green body undergoes
a thermal treatment in a range of 900-2,200.degree. C. in inert gas
atmosphere, and then a pyrolytic carbon matrix layer as a second
surface layer is deposited on the first surface layer in a
deposition step through said rapid thermal gradient chemical vapor
infiltration process.
7. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein the deposition step by
said rapid thermal gradient chemical vapor infiltration process is
performed in a range of pyrolytic reaction temperatures
700-1,200.degree. C. and reaction pressures 188-1,130 torr using
hydro-carbon gas.
8. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein a deposition region is
divided into a plurality of regions from the inside to the outside,
and individual regions are deposited at different speeds from one
another in a deposition step through said rapid thermal gradient
chemical vapor infiltration process.
9. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein said deposition region is
deposited from the inside to the outside at a deposition speed in a
range of 0.5-3.0 mm/hr.
10. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein said carbon fiber
reinforced carbon composite has 1.0-1.7 g/cm.sup.3 apparent
density, and 5-30% of open pores that are used for in-filtrating
paths of said liquid-phase silicon.
11. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 1, wherein the step of infiltrating
liquid-phase silicon is performed by stacking said carbon fiber
reinforced carbon composite on silicon powder, maintaining a
pressure less than 100 torr within a reactor, and then heating it
at the silicon melting point more than 1,410.degree. C., thereby
infiltrating liquid-phase silicon into a preform while chemically
reacting with a plurality of carbon layers.
12. A method of producing carbon fiber reinforced ceramic matrix
composites comprising the steps of: producing a carbon felt
preform; producing a carbon fiber reinforced carbon composite by
depositing said carbon felt preform through a rapid thermal
gradient chemical vapor infiltration process while increasing the
deposition speed from the inside to the outside; and infiltrating
liquid-phase silicon into the pores of said carbon fiber reinforced
carbon composite.
13. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein said carbon felt preform
is any one of carbon-based fibers, such as oxyphene, phene, rayon,
pitch-based, etc.
14. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein said carbon felt preform
has mat laminates with quasi-isotropic orientations, such as
0/+60/-60.degree., and it is reinforced with carbon fibers less
than 10 mm in the Z-direction.
15. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein said carbon felt preform
is deposited with a pyrolytic layer having 5-100 in thickness by
means of a deposition step through said rapid thermal gradient
chemical vapor infiltration process.
16. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein carbon fibers are
reinforced in the three X, Y and Z axes by impregnating
liquid-phase silicon into said carbon fiber reinforced carbon
composite in the step of infiltrating liquid-phase silicon.
17. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein the deposition step by
said rapid thermal gradient chemical vapor infiltration process is
performed in a range of pyrolytic reaction temperatures
700-1,200.degree. C. and reaction pressures 188-1,130 torr using
hydro-carbon gas.
18. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein a deposition region is
divided into a plurality of regions from the inside to the outside,
and individual regions are deposited at different speeds from one
another in a deposition step through said rapid thermal gradient
chemical vapor infiltration process.
19. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein said deposition region is
deposited from the inside to the outside at a deposition speed in a
range of 0.5-3.0 mm/hr.
20. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein said carbon fiber
reinforced carbon composite has 1.0-1.7 g/cm.sup.3 apparent
density, and 5-30% of open pores that are used for infiltrating
paths of said liquid-phase silicon.
21. The method of producing carbon fiber reinforced ceramic matrix
composites according to claim 12, wherein the step of infiltrating
liquid-phase silicon is performed by stacking said carbon fiber
reinforced carbon composite on silicon powder, maintaining a
pressure less than 100 torr within a reactor, and then heating it
at the silicon melting point more than 1,410.degree. C., thereby
infiltrating liquid-phase silicon into a carbon felt preform while
chemically reacting with a plurality of carbon layers.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of producing
carbon fiber reinforced ceramic matrix composites, maintaining
excellent mechanical strength at high temperature as well as having
excellent properties in corrosion resistance, thermal resistance,
friction and abrasion under a severe environment, such as heat,
chemical erosion, etc.
BACKGROUND ART
[0002] Fiber reinforced ceramic matrix composites are lightweight
materials having excellent mechanical and thermal properties at
high temperature. With these properties, fiber reinforced ceramic
matrix composites are applicable to friction and abrasion
materials, such as brake disks, and pads for aircraft or ground
transport means, and also to ultrahigh thermal resistant materials,
such as ceramic engines, and rocket nozzle parts, which require
mechanical strength, corrosion resistance, and thermal resistance.
Fiber reinforced ceramic matrix composites have been studied to
overcome the drawbacks to monolithic ceramics, such as brittle
failure, or the like, and they can be produced by filling the pores
of a preform made of carbon fibers or silicon carbide fibers with
thermal resistant materials, such as pyrolytic carbon, silicon
carbide, or boron nitride.
[0003] Up to now, fiber reinforced ceramic matrix composites have
been produced with a variety of manufacturing processes, however,
in most cases, they cause mechanical and/or chemical impact damages
to fibers during the manufacturing processes. To solve such a
problem, ceramic matrix composites are produced by injecting
precursors in a gas state into a porous fiber preform having low
density, and then pyrolyzing it for the deposition of ceramic
matrix-phase. Such a process is called chemical vapor
in-filtration, and the matrix-phase is infiltrated under a low
temperature and pressure condition during this manufacturing
process to solve the problem causing damage to fibers, which has
been created when producing conventional ceramic matrix
composites.
[0004] In this process, however, high-priced raw materials and
manufacturing equipment are employed, its manufacturing process is
complicated, and lots of process time more than several hundred
hours is required, and therefore its application is extremely
restricted to high-tech industries, such as aerospace, or the
like.
[0005] Rather than the chemical vapor infiltration process using
raw materials in a gas state, a process of producing carbon fiber
reinforced ceramic matrix composites by in-filtrating liquid-phase
silicon into a porous carbon preform has been developed.
[0006] As described in U.S. Pat. No. 6,308,808, U.S. Pat. No.
6,358,565, and U.S. Pat. No. 5,942,064 owned by Walter Krenkel et
al., a mixture including carbon fibers that have been cut out,
liquid-phase phenol, and carbon powder, is molded under a high
temperature and pressure condition, and then a thermal treatment
process at high temperature is performed to produce a carbon fiber
reinforced carbon composite. The produced carbon fiber reinforced
carbon composite is infiltrated with liquid-phase silicon to
produce a carbon fiber reinforced ceramic matrix composite, and it
is applicable to brake disks for ground vehicles and thermal
resistance materials in the field of aerospace.
[0007] As described above, however, the carbon fiber reinforced
resin composite produced by mixing with liquid-phase carbon
precursors is more effective than existing chemical vapor
infiltration processes in terms of manufacturing cost, but it is
difficult to prevent the reaction of liquid-phase silicon against
carbon fibers due to some difficulties in forming a uniform carbon
fiber protective layer, and thereby rapidly reducing mechanical
properties of carbon fiber reinforced ceramic matrix composites. To
solve such a problem, as disclosed in Korean Patent Application No.
1999-7008146, as well as U.S. Pat. No. 6,079,525, U.S. Pat. No.
6,030,913, and U.S. Pat. No. 6,231,791, the carbon fiber reinforced
ceramic matrix composite is produced by iterative impregnation of
liquid organic binders or by changing the composition of the
mixture, but it is impossible to prevent the reduction in
mechanical properties caused by carbon fiber erosion and to improve
friction and abrasion characteristics at high temperature.
[0008] As a different process from the above, as disclosed in U.S.
Pat. No. 6,221,475 and Korean Patent Application No. 1999-7003211,
a preform made of weaved carbon fibers is deposited with pyrolytic
carbon by means of an isothermal/isobaric chemical vapor
infiltration (ICVI) process, and then a densification process is
performed on carbon precursors by means of a liquid-phase
infiltration method to produce a carbon fiber reinforced ceramic
matrix composite. This process has remarkably improved an aspect of
fiber protection, but it is difficult to produce carbon fiber
reinforced ceramic matrix composites having a complicated shape due
to difficulty in combining different carbon fiber reinforced
ceramic matrix composites into a structured body. In particular,
the manufacturing process is complicated and required more than
several hundred hours for the manufacturing time, and therefore it
caused an increase in the manufacturing cost.
[0009] Examining the overall problems related to the production
technologies of carbon fiber reinforced ceramic matrix composites
in most cases a process of producing a carbon fiber reinforced
carbon composite that is employed for producing carbon fiber
reinforced ceramic matrix composites still has some difficulties in
terms of its production cost and technologies. For example,
conventional chemical vapor in-filtration process has excellent
characteristics as a fiber protective layer; but it is not adequate
for producing carbon fiber reinforced carbon composites due to its
high-cost raw materials and manufacturing process difficulties.
Furthermore, when carbon fiber reinforced resin composites are
produced by performing an infiltration process of organic binders
containing carbon component, it is known that iterative
infiltration processes are required, and the effect is reduced in
an aspect of fiber protection.
DISCLOSURE OF INVENTION
Technical Problem
[0010] The present invention is devised to solve the aforementioned
problems, and it is an object of the invention to provide a method
of producing carbon fiber reinforced ceramic matrix composites for
improving thermal and mechanical properties of the carbon fiber
reinforced ceramic matrix composites and for providing a solution
to the problems due to its high manufacturing cost and processes as
described above, by improving the method of producing starting
material and a carbon fiber reinforced carbon composite, which are
required for producing the carbon fiber reinforced ceramic matrix
composites.
[0011] To solve the above problems, a method of producing carbon
fiber reinforced ceramic matrix composites is provided by the
inventors to simplify the manufacturing process by employing a
carbon felt preform having a sandwich structure or a carbon fiber
mixture as starting material, and to produce carbon fiber
reinforced carbon composites having a uniform fiber protective
layer with a rapid and low cost process by applying a rapid thermal
gradient chemical vapor infiltration process as well as employing a
liquid-phase silicon infiltration process.
Technical Solution
[0012] To achieve the aforementioned object, a method of producing
carbon fiber reinforced ceramic matrix (C/C--SiC) composites
according to the present invention comprises the steps of:
producing a carbon fiber reinforced resin composite that is molded
with a mixture in which carbon fibers and polymer precursors
containing carbon are mixed; producing a carbon fiber reinforced
carbon composite by depositing pyrolytic carbon during a rapid
thermal gradient chemical vapor infiltration process while
increasing the deposition speed in a direction from the inside to
the outside by performing a thermal treatment on said carbon fiber
reinforced resin composite at high temperature; and infiltrating
liquid-phase silicon into the pores of said carbon fiber reinforced
carbon composite.
[0013] Moreover, it is preferable that the mixture includes 10-60
wt % of the carbon fibers, and 30-60 wt % of the polymer precursors
containing carbon.
[0014] Further, it is preferable that the mixture includes less
than 30 wt % silicon carbide powder, and less than 30 wt % carbon
powder.
[0015] Further, it is preferable that the carbon fiber reinforced
resin composite is stacked with the mixture and carbon fabrics
alternately.
[0016] Further, it is preferable that the green body is formed with
a first surface layer for preventing carbon fibers from reacting
with silicon by means of the mixture that has been mixed during the
mixing process, and the first surface layer is formed with a
ceramic matrix layer including silicon carbide and silicon by
chemically reacting with the liquid-phase silicon in the step of
infiltrating the liquid-phase silicon.
[0017] Further, it is preferable that the green body undergoes a
thermal treatment in a range of 900-2,200.degree. C. under inert
gas atmosphere, and then a pyrolytic carbon matrix layer as a
second surface layer is deposited on the first surface layer in a
deposition step through the rapid thermal gradient chemical vapor
infiltration process.
[0018] Further, it is preferable that the deposition step by the
rapid thermal gradient chemical vapor infiltration process is
performed in a range of pyrolytic reaction temperatures
700-1,200.degree. C. and reaction pressures 188-1,130 torr using
hydro-carbon gas.
[0019] Further, it is preferable that a deposition region is
divided into a plurality of regions from the inside to the outside,
and individual regions are deposited at different speeds one
another in a deposition step through the rapid thermal gradient
chemical vapor in-filtration process.
[0020] Further, it is preferable that the deposition region is
deposited from the inside to the outside at a deposition speed in a
range of 0.5-3.0 mm/hr.
[0021] Further, it is preferable that the carbon fiber reinforced
carbon composite has 1.0-1.7 g/cm.sup.3 apparent density, and 5-30%
of open pores that are used for infiltrating paths of the
liquid-phase silicon.
[0022] Further, it is preferable that the step of infiltrating
liquid-phase silicon is performed by stacking the carbon fiber
reinforced carbon composite on silicon powder, maintaining a
pressure less than 100 torr within a reactor, and then heating it
at the silicon melting point more than 1,410.degree. C., thereby
infiltrating liquid-phase silicon into a preform while chemically
reacting with a plurality of carbon layers.
[0023] To achieve the aforementioned object, a method of producing
carbon fiber reinforced ceramic matrix composites according to the
present invention is characterized in that the method comprises the
steps of: producing a carbon felt preform; producing a carbon fiber
reinforced carbon composite by depositing the carbon felt preform
through a rapid thermal gradient chemical vapor infiltration
process while increasing the deposition speed from the inside to
the outside; and infiltrating liquid-phase silicon into the pores
of the carbon fiber reinforced carbon composite.
[0024] Moreover, it is preferable that the carbon felt preform is
any one of carbon-based fibers, such as oxyphene, phene, rayon,
pitch-based, etc.
[0025] Further, it is preferable that the carbon felt preform has
mat laminates with quasi-isotropic orientations, such as
0/+60/-60.degree., and it is reinforced with carbon fibers less
than 10 mm in the Z-direction.
[0026] Further, it is preferable that the carbon felt preform is
deposited with a pyrolytic layer having 5-100 in thickness by means
of a deposition step through the rapid thermal gradient chemical
vapor infiltration process.
[0027] Further, it is preferable that carbon fibers are reinforced
in the three X, Y and Z axes by impregnating liquid-phase silicon
into the carbon fiber reinforced carbon composite in the step of
infiltrating liquid-phase silicon.
[0028] Further, it is preferable that the deposition step by the
rapid thermal gradient chemical vapor infiltration process is
performed in a range of pyrolytic reaction temperatures
700-1,200.degree. C. and reaction pressures 188-1,130 torr using
hydro-carbon gas.
[0029] Further, it is preferable that a deposition region is
divided into a plurality of regions from the inside to the outside,
and individual regions are deposited at different speeds one
another in a deposition step through the rapid thermal gradient
chemical vapor in-filtration process.
[0030] Further, it is preferable that the deposition region is
deposited from the inside to the outside at a deposition speed in a
range of 0.5-3.0 mm/hr.
[0031] Further, it is preferable that the carbon fiber reinforced
carbon composite has 1.0-1.7 g/cm.sup.3 apparent density, and 5-30%
of open pores that are used for infiltrating paths of the
liquid-phase silicon.
[0032] Further, it is preferable that the step of infiltrating
liquid-phase silicon is performed by stacking the carbon fiber
reinforced carbon composite on silicon powder, maintaining a
pressure less than 100 torr within a reactor, and then heating it
at the silicon melting point more than 1,410.degree. C., thereby
infiltrating liquid-phase silicon into the carbon felt preform
while chemically reacting with a plurality of carbon layers.
ADVANTAGEOUS EFFECTS
[0033] The method of producing carbon fiber reinforced ceramic
matrix composites according to the present invention as shown above
has the effect of improving the properties of carbon fiber
reinforced ceramic matrix composites, and it is possible to deposit
a pyrolytic carbon layer at a deposition speed 5-10 times faster
than other conventional chemical vapor infiltration processes,
thereby providing a remarkably improved effect in terms of
manufacturing process, time, and cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a block diagram illustrating a method of producing
carbon fiber reinforced ceramic matrix composites using carbon
fabrics and a carbon fiber mixture according to the present
invention.
[0035] FIG. 2 is a block diagram illustrating a method of producing
carbon fiber reinforced ceramic matrix composites using a carbon
felt preform according to the present invention.
[0036] FIG. 3 is a microscopic structural view of a carbon fiber
reinforced ceramic matrix composite according to the present
invention.
[0037] FIG. 4 is a conceptual view illustrating a rapid thermal
gradient chemical vapor in-filtration process according to the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0038] Hereinafter, a method of producing carbon fiber reinforced
ceramic matrix composites will be described. The method of forming
and producing each of mixture in the following embodiments can be
implemented in a variety of ways by modifying a part of the
composition. However, if any technical elements claimed by the
present invention are basically included in the modified
embodiments, they should be considered to be within the technical
scope of the invention.
[0039] First, in view of starting material, a carbon felt preform
reinforced with carbon fibers in the direction of three X, Y, and Z
axes may be employed, or a sandwich structure that is produced by
stacking a mixture comprising carbon fibers 0.3-150 mm in length,
polymer precursors containing carbon, silicon carbide powder, and
graphite powder with carbon fabrics alternately may be applied, or
a carbon fiber reinforced resin composite (CFRP) comprising only
the aforementioned mixture may be employed.
[0040] Moreover, pyrolytic carbon is deposited on the produced
starting material by means of a rapid thermal gradient chemical
vapor infiltration process to produce a porous carbon fiber
reinforced carbon composite, and then liquid-phase silicon is
infiltrated into the pores of the carbon fiber reinforced carbon
composite to produce a carbon fiber reinforced ceramic matrix
composite. The carbon fiber reinforced ceramic matrix composites
has physical properties of more than 2.2 g/cm.sup.2 apparent
density, less than 1% apparent porosity, more than 100 MPa bending
strength, and more than 35 W/mk thermal conductivity.
[0041] The method of producing carbon fiber reinforced ceramic
matrix composites can be divided into two types of processes based
upon its starting material as shown in FIG. 1 and FIG. 2.
[0042] First, FIG. 1 illustrates a process for producing a carbon
fiber reinforced resin composite using a mixture comprising carbon
fibers cut in the size of 0.3-150 mm, polymer precursors containing
carbon, silicon carbide powder, and graphite powder with carbon
fabrics.
[0043] In the step of producing a carbon fiber reinforced resin
composite, carbon fibers cut in the size of 0.3-150 mm is added to
distilled water together with polymer precursors containing carbon,
silicon carbide powder, graphite powder, and carbon fabrics to
produce a uniform mixture through dispersion and mixing
processes.
[0044] Furthermore, this mixture will be formed with a first
surface layer comprising polymer precursors containing carbon,
silicon carbide powder, and graphite powder on a carbon fiber
surface, whose mixture ratio is 10-60 wt % carbon fibers, 30-60 wt
% polymer precursors containing carbon. In addition, silicon
carbide powder and carbon powder will be included selectively. In
other words, it may be composed of 0-30 wt % silicon carbide
powder, and 0-30 wt % carbon powder (S101 and S102).
[0045] The mixture produced in this way is alternately stacked with
carbon fabrics to form a green body having a sandwich structure
(S110). The carbon fabrics may be formed with plain, satin, and
twill weaves. Here, for another method, the green body, may be
produced by stacking only the mixture, without stacking carbon
fabrics alternately.
[0046] Subsequently, the produced green body is placed in a mold,
and then heated and pressurized simultaneously in a range of
80-250.degree. C. and 1-20 MPa to produce a carbon fiber reinforced
resin composite. At this time, the produced carbon fiber reinforced
resin composite has physical properties of apparent density 1.2-1.6
g/cm.sup.2, and apparent porosity 1-20% (S110, S120 and S130).
[0047] For the aforementioned method of producing carbon fiber
reinforced ceramic matrix composites, technical specifications
disclosed in Korean Patent Application Nos. 1995-0069130 and
1997-0023344 filed by this applicant, may be employed for applying
to other embodiments.
[0048] Subsequently, in the deposition step by means of a rapid
thermal gradient chemical vapor infiltration process (S140), the
produced carbon fiber reinforced resin composite is subjected to
thermal treatment in a range of 700-2,200.degree. C. under inert
gas atmosphere, and then a rapid thermal gradient chemical vapor
infiltration process is performed to produce a carbon fiber
reinforced carbon composite.
[0049] More specifically, the rapid thermal gradient chemical vapor
infiltration process according to the present invention is provided
to produce a carbon fiber reinforced carbon composite having high
density greater than 1.3 g/cm.sup.3, and this rapid thermal
gradient chemical vapor infiltration process performs a rapid
deposition by dividing a region to be deposited into three or more
portions to control its deposition speed for each portion. Here,
deposition speed is controllable by moving a thermocouple that has
been installed in a chemical vapor deposition apparatus to increase
the speed gradually in the green body from the inside to the
outside.
[0050] In other words, as illustrated in FIG. 4, a carbon fiber
reinforced resin composite 500 is installed in a reactor, and a
heating element 400 is installed in the center. Furthermore, it may
be implemented by supplying hydrocarbon gas as a process gas. In
addition, deposition speed is controllable by using a thermocouple
(not shown) as described above, and the deposition process may be
performed from the inside to the outside.
[0051] Moreover, for deposition speed arrows as illustrated in the
drawing, a shorter one indicates a low deposition speed, and a
longer one indicates a high deposition speed. Furthermore, the T1
and T2 portions denote a high temperature and a low temperature
respectively, and thereby a thermal gradient will be induced.
[0052] Here, deposition speed will be within a range of 0.5-3.0
mm/hr, and it will be deposited from the inside to the outside. For
example, a region can be divided into three portions, such as the
inside, the middle, and the outside, and then they may be deposited
at 1.0 mm/hr, 1.5 mm/hr, and 2.0 mm/hr respectively to perform a
deposition process more rapidly. Here, deposition speed is set to
be low in the inside portion, because the deposition in the inside
will be relatively slower than the outside.
[0053] When deposition speed is controlled in this manner, its
manufacturing process and cost may be greatly improved and cut
down, compared to all other existing chemical vapor infiltration
processes, such as isothermal/isobaric chemical vapor infiltration
process, pressure gradient chemical vapor infiltration process, and
existing isokinetic thermal gradient chemical vapor infiltration
process, which require lots of manufacturing cost due to their
complicated process and long manufacturing time.
[0054] This rapid thermal gradient chemical vapor infiltration
process may be performed at a deposition speed 10 times faster and
more densely than the thermal gradient chemical vapor infiltration
process disclosed in Korean Patent No. 0198154 owned by this
applicant to form a pyrolytic carbon layer approximately 5-100 in
thickness.
[0055] Additionally, the pyrolytic carbon layer that has been
formed at this time will act as a reaction layer to form silicon
carbide matrix-phase by reacting with liquid-phase silicon during
the liquid-phase silicon impregnation process.
[0056] The carbon fiber reinforced resin composite that has been
produced by the rapid thermal gradient chemical vapor infiltration
process according to the present invention has physical properties
of apparent density 1.0-1.7 g/cm.sup.3, and apparent porosity
5-30%.
[0057] Then, the carbon fiber reinforced carbon composite produced
by the rapid thermal gradient chemical vapor infiltration process
is placed on silicon powder having particles in a range of 1 -10 mm
in size during a liquid-phase silicon infiltration process.
[0058] Here, as a process condition, it is heated at a silicon
melting point greater than 1,410.degree. C. under vacuum
atmosphere. Most of pores existing within the carbon fiber
reinforced carbon composite will be filled with the silicon that
has been melted at high temperature above 1,410.degree. C. by
capillary action of the pores in a few minutes, and at the same
time it will be reacted with a carbon reaction layer on carbon
fibers to form a silicon carbide. In this way, the finally produced
carbon fiber reinforced ceramic matrix composite is composed of
30-60 wt % carbon, 35-60 wt % silicon carbide, and less than 5 wt %
non-reaction silicon.
[0059] Next, the carbon fiber reinforced ceramic matrix composite
can be produced using a green body made of a carbon felt preform as
starting material as illustrated in FIG. 2.
[0060] First, a carbon felt preform reinforced in the three X, Y
and Z axes is produced (S200); more specifically, carbon-based
fibers, such as oxyphene, phene, rayon, pitch-based, or the like
are wound around a mandrel to produce unidirectional carbon mats,
and the carbon mats produced by this method are stacked together.
For its stacking method, they are alternately stacked with
quasi-isotropic orientation at 0/+60/-60.degree..
[0061] Furthermore, at least two layers may be stacked, and then
punched using a needle to reinforce all layers in the z-direction,
and the above process will be reiterated to produce a felt preform
greater than 30 mm in thickness.
[0062] This felt preform is made by a fiber volume ratio
approximately 10-55%, where the thickness of one layer is
approximately less than 0.1 mm, the length of fabrics in length is
less than 10 mm, and the fabric ratio is approximately 10%.
Furthermore, a needle having density of 15 penetration/cm.sup.3 may
be used for the Z-direction.
[0063] Then, in order to remove impurities of the carbon felt
preform, a thermal treatment process is performed at a temperature
greater than 1,700.degree. C. under vacuum atmosphere. The method
of producing such a carbon felt preform is disclosed in the
embodiments of U.S. patent application Ser. No. 10/180,778 and the
Korean Patent No. 27788, filed by this applicant.
[0064] Subsequently, a carbon fiber reinforced carbon composite is
produced by means of a rapid thermal gradient chemical vapor
infiltration process (S210). The same rapid thermal gradient
chemical vapor infiltration process as in the embodiment of the
aforementioned first process will be applied to this.
[0065] In addition, a carbon fiber reinforced ceramic matrix
composite is produced by means of a liquid-phase silicon
infiltration process (S220). The same liquid-phase silicon
infiltration process as in the embodiment of the aforementioned
first process will be applied to this.
MODE FOR THE INVENTION
First Embodiment
[0066] A mixture comprising 30 wt % carbon fibers that have been
cut out in the size of 30 mm, 40 wt % phenol resin, 5 wt % carbon
powder, and 5 wt % silicon carbide powder is prepared and stacked
alternately with carbon fabrics in the form of 20 wt % satin weave
to produce a green body. The produced green body is placed in a
mold, and then cured while being pressurized at a pressure 2 MPa
for 10 minutes to produce a carbon fiber reinforced resin
composite.
[0067] The carbon fiber reinforced resin composite is subjected to
thermal treatment in inert gas atmosphere. Furthermore, pyrolytic
carbon is deposited in a condition of rapid thermal gradient
chemical vapor infiltration process to produce a carbon fiber
reinforced carbon composite.
[0068] The produced carbon fiber reinforced carbon composite is
stacked on silicon powder, and heated at 1,550.degree. C. in vacuum
atmosphere, and infiltrated with liquid-phase silicon to produce a
carbon fiber reinforced ceramic matrix composite. Here, physical
properties of the produced carbon fiber reinforced ceramic matrix
composite are shown in Table 1.
Second Embodiment
[0069] A mixture comprising 55 wt % carbon fibers that have been
cut out in the size of 30 mm, 35 wt % phenol resin, 5 wt % carbon
powder, and 5 wt % silicon carbide powder is prepared to produce a
green body. Stacking alternately with carbon fabrics is not
implemented in the second embodiment. The produced green body is
placed in the mold, and then cured while being pressurized at a
pressure 2 MPa for 10 minutes to produce a carbon fiber reinforced
resin composite.
[0070] The carbon fiber reinforced resin composite is subjected to
thermal treatment in inert gas atmosphere. Furthermore, pyrolytic
carbon is deposited in a condition of rapid thermal gradient
chemical vapor infiltration process to produce a carbon fiber
reinforced carbon composite.
[0071] The produced carbon fiber reinforced carbon composite is
stacked on silicon powder, and heated at 1,550.degree. C. in vacuum
atmosphere, and infiltrated with liquid-phase silicon to produce a
carbon fiber reinforced ceramic matrix composite. Here, physical
properties of the produced carbon fiber reinforced ceramic matrix
composite are shown in Table 1.
Third Embodiment
[0072] 320K oxyphene carbon fiber is wound around a mandrel to
produce unidirectional carbon mats, and the carbon mats produced by
this method are stacked together. For stacking method, they are
stacked alternately by a method of 0/+60/-60.degree..
[0073] At least two layers are stacked together, and then punched
using a needle to reinforce every layer in the z-direction, and the
process is reiterated to produce a felt preform having 30 mm in
thickness. This felt preform is produced at approximately 45% of
oxyphene fiber volume ratio, where the thickness of a layer is
approximately 0.9 mm, and the fiber ratio in the z-direction is
approximately 10%.
[0074] The produced preform is subjected to thermal treatment at
1,700.degree. C. in vacuum atmosphere to remove the impurities of
the preform.
[0075] Pyrolytic carbon is deposited on the produced carbon felt
preform in a condition of rapid thermal gradient chemical vapor
infiltration process to produce a carbon fiber reinforced carbon
composite.
[0076] The produced carbon fiber reinforced carbon composite is
stacked on silicon powder and heated at 1,550.degree. C. in vacuum
atmosphere, and infiltrated with liquid-phase silicon to produce a
carbon fiber reinforced ceramic matrix composite. Here, the
physical properties of the produced carbon fiber reinforced ceramic
matrix composite are shown in Table 1.
Comparative Example 1
[0077] A mixture is prepared by mixing 54 wt % of carbon fibers
that have been cut out in the size of 130 mm, 36 wt % of phenol
resin, and 10 wt % of carbon powder, and is placed in a mold, and
then cured while being pressurized at 3 MPa of pressure to produce
a carbon fiber reinforced resin composite.
[0078] The carbon fiber reinforced resin composite is subjected to
thermal treatment at 900.degree. C. in inert gas atmosphere to
produce a carbon fiber reinforced carbon composite. The produced
carbon fiber reinforced carbon composite is stacked on silicon
powder and heated at 1,600.degree. C. in vacuum atmosphere, and
infiltrated with liquid-phase silicon to produce a carbon fiber
reinforced ceramic matrix composite. Here, the physical properties
of the produced carbon fiber reinforced ceramic matrix composite
are shown in Table 1.
TABLE-US-00001 TABLE 1 Apparent Apparent Porosity Bending Thermal
Density (%) Strength Conductivity Friction Specimen g/cm.sup.3 %
MPa W/mK Factor First 2.3 0.5 125 40 0.45 Embodiment Second 2.4 0.3
120 42 0.45 Embodiment Third 2.3 0.7 140 40 0.43 Embodiment
Comparative 2.1 0.9 80 35 0.40 Example 1
[0079] As described above, for a method of producing carbon fiber
reinforced ceramic matrix composites according to the present
invention, carbon fibers in the carbon fiber reinforced carbon
composites, which have been produced by the rapid thermal gradient
chemical vapor infiltration process, have a uniformly deposited
pyrolytic carbon layer, and such a pyrolytic carbon layer is
reacted with silicon to form silicon carbide during the
liquid-phase silicon impregnation process. The pyrolytic carbon
layer has excellent properties for a fiber protection layer to
prevent carbon fiber erosion, which is a most difficult problem
during the liquid-phase silicon permeation process, as well as for
a reaction layer to form silicon carbide; moreover, it improves
physical properties of carbon fiber reinforced ceramic matrix
composites by forming a new interface between carbon fibers and
silicon carbide matrix-phase.
[0080] The microstructure of carbon fiber reinforced ceramic matrix
composites that have been produced by the production method
according to the present invention comprises a pyrolytic carbon
layer 102 as shown in a dark gray portion, a silicon carbide layer
103 as shown in a light gray portion, and a residual silicon layer
104 as shown in the lightest color portion. It is known that carbon
fiber erosion is hardly created by the pyrolytic carbon layer
around carbon fibers, and silicon carbide is formed around the
pyrolytic carbon layer.
[0081] Furthermore, for a rapid thermal gradient chemical vapor
infiltration process according to the present invention in terms of
the time of producing carbon fiber reinforced ceramic matrix
composites, pyrolytic carbon layer can be deposited at a deposition
speed 10 times faster or more than conventional chemical vapor
infiltration processes, or 5 times faster or more than conventional
thermal gradient chemical permeation processes, thereby remarkably
reducing the cost of producing carbon fiber reinforced carbon
composites.
[0082] Moreover, carbon fiber reinforced resin composites can be
simply produced by one-time process without performing iterative
densification processes that are typically employed in the process
of producing carbon fiber reinforced resin composites using
liquid-phase precursors containing carbon. In addition, in
combination with the rapid thermal gradient chemical vapor
infiltration process and the liquid-phase silicon impregnation
process, it is possible to simplify the process of producing carbon
fiber reinforced ceramic matrix composites, thus reducing its
manufacturing cost remarkably, and therefore application of carbon
fiber reinforced ceramic matrix composites to a variety of industry
fields is possible.
[0083] Furthermore, for a green body that has been produced by
mixing carbon fibers in the size of 0.3-150 mm with polymer
precursors containing carbon, silicon carbide powder, and graphite
powder, and then alternatively stacking with carbon fabrics, or
that has been produced by the mixture only, its dispersion and
mixture is uniform, and also it has excellent properties for
forming a first surface layer of carbon fibers and carbon fabrics.
Additionally, as contraction is hardly generated when it is
subjected to thermal treatment at a high temperature greater than
1,000.degree. C., there are no dimensional changes, thus reducing
the cost of processing its dimension and shape remarkably.
INDUSTRIAL APPLICABILITY
[0084] The present invention is applicable to the transportation
industry, such as aerospace, or ground vehicles.
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