Patent Application
20130011602
The present invention relates to a C/C composite material and a method of manufacturing the same. More particularly, the invention relates to a C/C composite material and a method of manufacturing the same that can improve the thermal conductivity in a stacking direction at room temperature without degrading the flexural strength or the interlaminar shear strength.
C/C composite materials are allowed to have high strength and high toughness due to combination with carbon fiber, in addition to the corrosion resistance and heat resistance that are inherent to carbon. Another feature of the C/C composite materials is that they are lighter in weight than metal, because carbon has a small specific gravity. Because of such features, it has been studied to use a C/C composite material for various applications such as the materials for aerospace applications, for semiconductor and solar battery panel manufacturing applications, and for nuclear power applications, as well as metal heat-treatment jig applications. When used for these applications, the C/C composite material is required to have a high heat conduction capability in addition to high strength. In particular, when the material needs to support an object having a large area, it is often necessary to improve the thermal conductivity coefficient in the stacking direction of the C/C composite material.
Here, a proposal has been made in order to increase the strength and heat conduction capability of a C/C composite material. For example, the thermal conductivity coefficient is improved by impregnating pyrocarbon into a carbon felt, and the strength is improved by restricting the bulk density (see Patent Document 1 below).
In addition, another proposal of restricting the flexural strength and the thermal conductivity coefficient in the stacking direction has been made in order to optimize the strength characteristics and thermal conductivity coefficient of a C/C composite material, although the object is different (see Patent Document 2 below).
[Patent Document 1]
JP H05(1993)-306168 A
[Patent Document 2]
JP 2002-255664 A
However, although the technique disclosed in Patent Document 1 can improve the thermal conductivity in a direction perpendicular to the stacking direction, it is difficult to improve the thermal conductivity in the stacking direction. In addition, merely restricting the bulk density cannot enhance the strength of the C/C composite material sufficiently.
Moreover, the technique disclosed in Patent Document 2 cannot improve the thermal conductivity coefficient at a low temperature (room temperature) to a desired value.
In view of the foregoing circumstances, it is an object of the present invention to provide a C/C composite material and a method of manufacturing the same that can improve the thermal conductivity in the stacking direction at room temperature while at the same time improving the flexural strength and the interlaminar shear strength.
In order to accomplish the foregoing object, the present invention provides a
C/C composite material comprising a laminated material having at least two raw materials laminated on one another, the at least two raw materials each containing carbon fiber and selected from the group consisting of a layered material using continuous fiber, a layered material using chopped fiber, a 2D fabric, and a layered material using felt, the laminated material containing therein a matrix component, the C/C composite material having, at room temperature, a flexural strength of 100 MPa or higher, and a thermal conductivity of 30 W/(m·K) or higher in a stacking direction.
The above-described configuration makes it possible to improve the thermal conductivity in the stacking direction at room temperature while at the same time improving the flexural strength.
Herein, the layered material using continuous fiber refers to, for example, a layered material formed by arranging integral-type long carbon fibers disposed in one direction to both ends of a plane direction so as to be parallel to each other. The layered material using chopped fiber refers to, for example, a layered material formed by laying short carbon fibers two-dimensionally randomly in a thin sheet form without leaving gaps, and pressing them into the layered material. The 2D fabric refers to, for example, a fabric formed by disposing tows, each having long carbon fibers disposed parallel to each other into a strip-like shape, longitudinally and transversely, and causing the tows to intersect each other so as to form them into a woven fabric form. The layered material using felt refers to, for example, a layered material formed by causing short carbon fibers to aggregate three-dimensionally randomly and pressing them at a certain level of pressure into the layered material.
In order to accomplish the foregoing object, the present invention also provides a C/C composite material comprising a laminated material having at least two raw materials laminated on one another, the at least two raw materials each containing carbon fiber and selected from the group consisting of a layered material using continuous fiber, a layered material using chopped fiber, a 2D fabric, and a layered material using felt, the laminated material containing therein a matrix component, the C/C composite material having, at room temperature, an interlaminar shear strength of 10 MPa or higher, and a thermal conductivity of 30 W/(m·K) or higher in a stacking direction.
The above-described configuration makes it possible to improve the thermal conductivity in the stacking direction at room temperature while at the same time improving the interlaminar shear strength.
It is desirable that a portion or the entirety of the matrix component comprise vapor-phase pyrolytic carbon or pitch-based carbon.
The just-described configuration makes it possible to produce a matrix easily. Thus, the flexural strength and the interlaminar shear strength can be further improved. In addition, the thermal conductivity in the stacking direction at room temperature can be further improved.
It is desirable that the carbon fibers be arranged in the stacking direction of the laminated material.
With the just-described configuration, heat conduction is effected by the carbon fibers. As a result, the thermal conductivity in the stacking direction at room temperature can be further improved.
In order to accomplish the foregoing object, the present invention also provides a C/C composite material comprising: a laminated material comprising two or more layered materials laminated on one another, each of the layered materials containing carbon fiber and having a felt and two or more cloths each comprising continuous fiber, the laminated material containing therein a matrix component, wherein: the fibers of each of the cloths are extended in one direction within a plane perpendicular to a stacking direction; the fibers in at least one of the cloths in the layered materials are extended in a different direction from the extending direction in the other cloth(s); and a portion of the fibers of the felt pierces through the cloths in the stacking direction.
With the just-described configuration, the cloths comprising continuous fiber, which has high flexural strength and high interlaminar shear strength (hereinafter also referred to as both of the strengths) exist. Therefore, it is possible to increase both of the strengths of the C/C composite material. In addition, since a portion of the fibers of the felt, which has high thermal conductivity, penetrates the cloths in the stacking direction, the thermal conductivity in the stacking direction at room temperature can be improved in the C/C composite material. Furthermore, since the fibers of the felt penetrate the cloths in the stacking direction, each of the layers is firmly bonded together, so that both of the strengths of the C/C composite material can be further increased. In addition, since the fibers in at least one of the cloths in the layered material is extended in a direction different from that in the other cloth(s), both of the strengths of the C/C composite material can be increased in, not one direction, but a plurality of directions. Moreover, since the matrix component is contained in the laminated material, both of the strengths of the C/C composite material can be further increased.
It is desirable that the extending direction of the fibers in the one of the cloths and the extending direction of the fibers in the other cloth(s) be configured to be at right angles.
When the extending direction of the one of the fibers is configured to be at a right angle to the extending direction of the other fibers, both of the strengths of the C/C composite material can be increased in both of the directions.
It is desirable that a portion or the entirety of the matrix component comprise vapor-phase pyrolytic carbon or pitch-based carbon.
Such a configuration is desirable for the same reason as described above.
In order to accomplish the foregoing object, the present invention also provides a method of manufacturing a C/C composite material, comprising the steps of: preparing a laminated material comprising at least two raw materials laminated on one another, the at least two raw materials selected from the group consisting of a layered material using continuous fiber, a layered material using chopped fiber, a 2D fabric, and a layered material using felt; arranging carbon fibers in a stacking direction of the laminated material using needle punching; and disposing a matrix component inside the laminated material.
Such a method makes it possible to manufacture the above-described C/C composite material easily. Moreover, the use of the needle punching enables to arrange the carbon fibers in the stacking direction of the laminated material easily. Therefore, the thermal conductivity in the stacking direction at room temperature can be improved at low cost. Furthermore, each of the layers can be firmly bonded together, so the strength of the C/C composite material is enhanced.
The present invention achieves the significant advantageous effect of improving the thermal conductivity in the stacking direction at room temperature while at the same time improving the flexural strength and the interlaminar shear strength.
Hereinbelow, embodiments of the present invention will be described.
First, a PAN-based carbon fiber tow (single fiber diameter: about 7 μm, tensile strength: about 5 GPa, number of filaments: about 12000) was prepared. Thereafter, using nylon fiber, a plurality of the PAN-based carbon fiber tows were tied in a bundle-like form to thereby prepare carbon fiber unidirectional cloths. The carbon fiber unidirectional cloths have high flexural strength, and the PAN-based carbon fiber tows have a high thermal conductivity coefficient in the extending direction. However, when the carbon fiber unidirectional cloths are laminated, the thermal conductivity of the carbon fiber unidirectional cloths that are adjacent to each other in the stacking direction becomes low.
At the same time, the same PAN-based carbon fibers as described above were cut into about 25 mm, and a felt (bulk density: about 0.1 g/cm3) in which the carbon fibers were oriented randomly was prepared. A C/C composite in which this felt is impregnated with a matrix component is poor in, for example, flexural strength, but it shows high thermal conductivity in any direction.
Next, as illustrated in
Next, as illustrated in
Thereafter, the above-described 2.5D preform was CVI-processed. Specifically, under the conditions of a temperature of about 1000° C. and a pressure of 10 Torr, the above-described 2.5D preform was retained for about 1000 hours in a mixed gas flow of hydrogen and propane (the volume ratio of hydrogen and propane being about 90:10), whereby a vapor-phase pyrolytic carbon, i.e., the matrix component, was deposited inside the 2.5D preform. Thereby, a C/C composite material in which the bulk density was increased to about 1.7 g/cm3 was obtained. Lastly, the C/C composite material was heat-treated at about 2000° C. Note that the thickness of the C/C composite material was about 10 mm.
In the above-described embodiment, needles are allowed to pierce through all the layers by the needle punching because the carbon fiber preform has a relatively small thickness, about 10 mm. However, when using a carbon fiber preform having a large thickness such that the needles are difficult to pierce through all the layers, it is possible to repeat the step of performing the needle punching for a certain number of the layered materials that have been stacked, and further performing the needle punching for additional layered materials stacked thereon, so that the fibers of the felt can pierce through the carbon fiber preform in the stacking direction.
A C/C composite material prepared in the manner described in the above-described embodiment was used for Example 1.
The C/C composite material fabricated in this manner is hereinafter referred to as a present invention material A1.
A C/C composite material was fabricated in the same manner as described in Example 1 above, except that, in order to remove the nylon fiber in the 2.5D preform, a heat treatment was carried out under a nitrogen atmosphere at about 1000° C. for about 1 hour, after the preparation of the 2.5D preform and before the CVI process.
The C/C composite material fabricated in this manner is hereinafter referred to as a present invention material A2.
A C/C composite material was fabricated in the same manner as described in Example 1 above, except that the C/C composite material was further subjected to a heat treatment (at about 3000° C. for about 24 hours) using an Acheson graphitization furnace.
The C/C composite material fabricated in this manner is hereinafter referred to as a present invention material A3.
A C/C composite material was fabricated in the same manner as described in Example 2 above, except that the C/C composite material was further subjected to a heat treatment (at about 3000° C. for about 24 hours) using an Acheson graphitization furnace.
The C/C composite material fabricated in this manner is hereinafter referred to as a present invention material A4.
A C/C composite material was fabricated in the same manner as described in Example 1 above, except that, when forming a matrix in the 2.5D preform, pitch-based carbon was used in place of using the vapor-phase pyrolytic carbon.
Specifically, the same 2.5D preform as used in Example 1 was impregnated with a phenolic resin and was baked in a nitrogen atmosphere at about 1000° C. for about 1 hour, to obtain a low density C/C composite material. Next, this low density C/C composite material was impregnated with coal-tar pitch and was baked at about 1000° C. for about 1 hour, followed by repeating this process 5 times, whereby a C/C composite material in which the bulk density was increased to about 1.6 g/cm3 was obtained. Lastly, this was heat-treated at about 2000° C. for about 1 hour. It should be noted that since the process of impregnating the 2.5D preform with coal-tar pitch and then baking was repeated, the resulting matrix component was mainly composed of pitch-based carbon.
The C/C composite material fabricated in this manner is hereinafter referred to as a present invention material A5.
First, plain weave cloths were prepared using tows each comprising about 12000 carbon fiber filaments and were impregnated with a phenolic resin. Then, the resulting cloths were laminated together and thereafter shaped using a heated platen press, to thereby obtain a laminated material (a low density C/C composite material, hereinafter also referred to as a “2D-cloth laminated material”). Next, this laminated material was baked in a nitrogen atmosphere at about 1000° C. for about 1 hour. Thereafter, the resultant material was impregnated with petroleum pitch and was baked at about 1000° C. for about 1 hour, followed by repeating this process 5 times, whereby a C/C composite material in which the bulk density was increased to about 1.6 g/cm3 was obtained. Lastly, this was heat-treated at about 2000° C. for about 1 hour.
The C/C composite material fabricated in this manner is hereinafter referred to as a comparative material Z1.
A C/C composite material was fabricated in the same manner as described in Comparative Example 1 above, except that the C/C composite material was further subjected to a heat treatment (at about 3000° C. for about 1 hour) using an Acheson graphitization furnace.
The C/C composite material fabricated in this manner is hereinafter referred to as a comparative material Z2.
A laminated material was formed by laminating 40 sheets of the same layered material as used in Example 1. The resulting laminated material was not subjected to needle punching, but was sandwiched between two metal plates with a gap of about 10 mm. Thereafter, the laminated material was impregnated with a phenolic resin and then hardened, to obtain a laminated material having a thickness of about 10 mm. This laminated material was baked in a nitrogen atmosphere at about 1000° C. for about 1 hour, to prepare a low density C/C composite. This was impregnated with coal-tar pitch and was baked at about 1000° C. for about 1 hour, followed by repeating this process 5 times, whereby a C/C composite material in which the bulk density was increased to about 1.6 g/cm3 was obtained. Lastly, this was heat-treated at about 2000° C. for about 1 hour.
The C/C composite material fabricated in this manner is hereinafter referred to as a comparative material Z3.
The bulk density, the flexural strength, the interlaminar shear strength (ILSS), the thermal conductivity coefficient in the stacking direction (hereinafter also represented as “thermal conductivity coefficient ⊥”), the thermal conductivity coefficient in the plane direction (the thermal conductivity coefficient in a direction perpendicular to the stacking direction, hereinafter also represented as “thermal conductivity coefficient //”) were determined for the present invention materials A1 through A5 and the comparative materials Z1 through Z3 by the following methods. The results are shown in Table 1 below. The experiment was conducted at room temperature (23° C.). Also, for these materials, the relationship between flexural strength and thermal conductivity coefficient ⊥, and the relationship between thermal conductivity coefficient ⊥ and interlaminar shear strength are shown in
Test pieces each having a rectangular parallelepiped shape with a length of 60 mm, a width of 10 mm, and a height of 3 mm (the height being in the stacking direction) were prepared, and a three-point bending test was conducted with a span distance of 40 mm and a crosshead speed of 0.5 mm/min. From the maximum load, the flexural strength was calculated using the following equation (1).
Flexural strength=3PL/(2wh2) (1)
In equation (1), P is the load, L is the span distance, w is the width, and h is the height.
Test pieces each having a rectangular parallelepiped shape with a length of 50 mm, a width of 10 mm, and a height of 6 mm (the height being in the stacking direction) were prepared, and a three-point bending test was conducted with a span distance of 30 mm and a crosshead speed of 0.5 mm/min. From the maximum load, the interlaminar shear strength was calculated using the following equation (2).
ILSS=3P/(4wh) (2)
In equation (2), P is the load, w is the width, and h is the height.
Test pieces each having a diameter of about 10 mm and a thickness of 3 mm (the measurement direction is in the thickness-wise direction) were prepared, and the thermal diffusivity was determined using laser flash photolysis. This was multiplied by the bulk density and the specific heat (the values for graphite was used. The source is, for example, JANAF Thermochemical Tables, 3rd edition) to thereby obtain the thermal conductivity coefficient.
It was observed that each of the present invention materials A1 and A2, in which the 2.5D preform was densified by a CVI process, exhibited a flexural strength of 100 MPa or higher, an interlaminar shear strength of 10 MPa or higher, and a thermal conductivity coefficient ⊥ of 30 W/(m·K) or higher.
Each of the present invention materials A3 and A4, which are different from the present invention materials A1 and A2 in the respect that they were subjected to a heat treatment at about 3000° C. (graphitization process), showed a slightly lower flexural strength and a slightly lower interlaminar shear strength than the present invention materials A1 and A2 (note, however, that the flexural strength was 100 MPa or higher and the interlaminar shear strength was 10 1MPa or higher). However, they were significantly better in both of the two thermal conductivities (thermal conductivity coefficient ⊥ and thermal conductivity coefficient //) than the present invention materials A1 and A2.
Moreover, the present invention material A5, which is different from the present invention material A1 in the respect that the matrix component was composed of pitch-based carbon, showed slightly lower in both of the two thermal conductivities than those of the present invention material A1 (note, however, that the thermal conductivity coefficient ⊥ was 30 W/(m·K) or higher) but exhibited substantially the same flexural strength and interlaminar shear strength as those of the present invention material A1.
Thus, it is demonstrated that all of the present invention materials A1 through A5 have a flexural strength of 100 MPa or higher, an interlaminar shear strength of 10 MPa or higher, and a thermal conductivity coefficient ⊥ of 30 W/(m·K) or higher.
In contrast, each of the comparative materials Z1 and Z2, which are different from the present invention material A1 in the respect that they used the 2D-cloth laminated material in place of the 2.5D preform, showed a flexural strength of 100 MPa or higher, but both of them showed a thermal conductivity coefficient ⊥ of less than 30 W/(m·K). Moreover, the comparative material Z2 also showed an interlaminar shear strength of less than 10 MPa.
Furthermore, the comparative material Z3, which is different from the present invention material A5 in the respect that needle punching was not performed when forming the preform, showed a flexural strength of 100 MPa or higher, but showed a thermal conductivity coefficient ⊥ of less than 30 W/(m·K) and an interlaminar shear strength of less than 10 MPa.
From the foregoing, it will be appreciated that it is desirable to employ the structure of the present invention, in order to ensure a flexural strength of 100 MPa or higher and a thermal conductivity of 30 W/(m·K) or higher in the stacking direction, or to ensure an interlaminar shear strength of 10 MPa or higher and a thermal conductivity of 30 W/(m·K) or higher in the stacking direction. This is also clear from
(1) The layered material 1 is not limited to the above-described structure. For example, as illustrated in
In addition, as illustrated in
Furthermore, as illustrated in
In addition, the number of the felt 10 in the layered material 1 is not limited to one as described above but may be two or more. Also, it is possible to employ an embodiment as shown in
(2) The laminated material 2 is not limited to the one having the above-described structure. For example, it is also possible to employ the structure as illustrated in
(3) The diameter of the single fiber that makes up the carbon fiber tow and the carbon fiber felt is not limited to that described above, but may preferably be from about 5 to about 20 μm. If the diameter of the single fiber is less than 5 μm, the strength per each single fiber is too low, and the resulting material may have the problem of low strength. On the other hand, if the diameter of the single fiber exceeds 20 μm, the problem may arise that the fibers tend to break easily in handling and in needle punching.
Moreover, it is preferable that the carbon fiber length of the carbon fiber felt be from about 10 to about 100 mm. If the carbon fiber length is less than 10 mm, the problem may rise that the fibers are difficult to be entangled with each other and the shape of the felt as a fiber aggregate is difficult to be formed. On the other hand, if the carbon fiber length exceeds 100 mm, the problem may arise that the fibers are entangled with each other excessively and the production of the felt becomes difficult.
(4) The size of the holes formed by the needle punching is not limited to that described above, but it is preferable that the diameter be from about 0.1 mm to about 1.0 mm. If the diameter of the holes is less than 0.1 mm, the amount of the fibers of the felt that penetrate the cloths in the stacking direction will be so small that the thermal conductivity in a stacking direction at room temperature may not be improved sufficiently. On the other hand, if the diameter of the holes exceeds 1.0 mm, the area of the holes will be so large that the strength of the C/C composite material may be degraded.
The C/C composite material according to the present invention may be used for various applications including various materials for aerospace applications, for semiconductor and solar battery panel manufacturing applications, and for nuclear power applications, as well as metal heat-treatment jig applications.
1—Layered material
10—Felt
11—Carbon fiber unidirectional cloth
12—Carbon fiber unidirectional cloth
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-072849 | Mar 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/057309 | 3/25/2011 | WO | 00 | 9/19/2012 |
