Carbon fiber-reinforced carbon composite materials processes for their production, and first walls of nuclear fusion reactors employing them

A carbon fiber-reinforced carbon composite material, wherein carbon fibers are oriented substantially in the thickness direction, the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in a direction perpendicular to the thickness direction is at least 2, and the thermal conductivity in the thickness direction is at least 3 W/cm.multidot..degree.C.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to carbon fiber-reinforced carbon composite 
materials, processes for their production and first walls of nuclear 
fusion reactors made of such carbon composite materials. 
2. Discussion of the Background 
Carbon fiber-reinforced carbon composite materials (hereinafter referred to 
simply as C/C composite materials) are light in weight and highly strong 
and have a feature that they are excellent in the heat resistance and 
corrosion resistance. Therefore, they are used, for example, for aerospace 
materials such as rocket nozzles, nose cones or disk brakes of air planes, 
for heater elements, for hot pressing molds, for other mechanical parts, 
and for parts of nuclear reactors. 
Such C/C composite materials are usually prepared by impregnating or mixing 
a matrix material such as a thermosetting resin such as a phenol resin or 
a furan resin, or a thermoplastic resin such as pitch, to long or short 
carbon fibers of e.g. polyacrylonitrile or pitch type, followed by heating 
and molding, then baking the molded product in a non-oxidizing atmosphere 
such as an inert gas atmosphere at a temperature of from 600.degree. to 
1,000.degree. C., and further densifying-the product by impregnating pitch 
or a resin thereto, followed by baking, or by a chemical vapor deposition 
method, or a combination of such methods, followed, if necessary, by 
graphitization. 
However, the resulting C/C composite materials were not necessarily 
satisfactory when they were used for the purposes of conducting or 
removing heat in one direction i.e. in the thickness direction, and they 
had problems in their practical application. 
For example, a first wall of a nuclear fusion reactor represents the entire 
structure in the nuclear fusion reactor, which is disposed to face the 
plasma, and includes e.g. limiters, diverters, blankets, and parts 
thereof. Such first wall is disposed close to the plasma and thus is under 
a severe environmental condition such that it is subjected to heat from 
plasma and bombernment of plasma particles. Particularly, the limiters and 
diverters receive high temperature loads, whereby the heat load conditions 
are particularly severe. As one of materials used for the first wall under 
such severe conditions, graphite may be mentioned. Graphite is an 
excellent low atomic number material from the viewpoint of plasma 
impurities and also has high thermal shock resistance. 
FIG. 4 in the drawings illustrates the most typical conventional first wall 
wherein graphite is used. In the illustrated first wall, a graphite tile 
11 is secured to a metal substrate 3 by means of a fixing plate 8 and a 
connector 9. When heat from the plasma enters the graphite tile 11 facing 
the plasma, the heat is conducted to the substrate by the contact thermal 
conduction and also dissipated by thermal radiation. In such system, the 
graphite tile 11 and the substrate 3 are in contact with each other merely 
by the mechanical connection, and the thermal conductivity at the contact 
portion is not adequate, and cooling tends to be inadequate when the heat 
load is high or lasts for a long period of time. The conventional first 
wall has the following problems. 
When a high heat load (for example, 2 km/cm.sup.2 for 3 seconds, or 4 
km/cm.sup.2 for at least one second) is exerted to the first wall, the 
surface temperature will be as high as at least about 2,800.degree. C. and 
the vapor pressure of the graphite tile will be at least about 10.sup.-3 
atm, whereby the loss in thickness by sublimation from the surface of the 
graphite tile will be as large as about a few tends .mu.m/sec. As a 
result, inclusion of carbon atoms in the plasma increases, which brings 
about a problem that the control of plasma impurities will be thereby 
seriously adversely affected. Further, the loss of the graphite surface is 
substantial, whereby there is a problem that the useful life of the first 
wall is short. 
In conventional nuclear fusion reactors, it is rare that such high heat 
load is exerted to the first wall, and the conventional first wall may 
sufficiently provide its function against the above-mentioned problems. 
However, in order to further improve the level of safety, or for a future 
nuclear fusion reactor for which it is expected that a heat load higher 
than ever will be exerted to the first wall constantly over a long period 
of time, it is desired to develop a first wall having the above problems 
adequately solved. 
Under these circumstances, the present inventors have conducted various 
studies to overcome the above-mentioned drawbacks and to obtain a C/C 
composite material useful for the above-mentioned first wall or the like, 
and have finally arrived at the present invention. 
SUMMARY OF THE INVENTION 
The present invention provides: 
1. A carbon fiber-reinforced carbon composite material, wherein carbon 
fibers are oriented substantially in the thickness direction, the ratio of 
the thermal conductivity in the thickness direction to the thermal 
conductivity in a direction perpendicular to the thickness direction is at 
least 2, and the thermal conductivity in the thickness direction is at 
least 3 W/cm.multidot..degree.C. 
2. A process for producing a carbon fiber-reinforced carbon composite 
material, which comprises impregnating long carbon fibers with a 
thermosetting resin, followed by heating to obtain a fiber/resin 
composite, cutting the fiber/resin composite into pieces having a length 
longer than the thickness of the desired composite material, aligning the 
composite pieces in one direction substantially in parallel to one 
another, exerting a pressure to the aligned composite pieces in a 
direction perpendicular to the longitudinal direction of the fibers, 
molding them to cure the resin, followed by carbonization, and 
impregnating the carbonized product with pitch or with a thermosetting 
resin, followed by carbonization and, if necessary, by graphitization. 
3. A carbon fiber-reinforced carbon composite material having a metal 
bonded thereto, wherein: 
(i) the carbon composite material comprises carbon fibers which are 
oriented substantially in the thickness direction, wherein the ratio of 
the thermal conductivity in the thickness direction to the thermal 
conductivity in a direction perpendicular to the thickness direction is at 
least 2, and the thermal conductivity in the thickness direction is at 
least 3 W/cm.multidot..degree.C., and 
(ii) the metal is bonded to one side of the carbon composite material which 
is substantially perpendicular to the thickness direction of the carbon 
composite material. 
4. A method for producing a carbon fiber-reinforced carbon composite 
material having a metal bonded thereto, which comprises impregnating long 
carbon fibers with a thermosetting resin, followed by heating to obtain a 
fiber-resin composite, cutting the fiber/resin composite into pieces 
having a length longer than the thickness of the desired composite 
material, aligning the composite pieces in one direction substantially in 
parallel to one another, exerting a pressure to the aligned composite 
pieces in a direction perpendicular to the longitudinal direction of the 
fibers, molding them to cure the resin, followed by carbonization, 
impregnating the carbonized product with pitch or with a thermosetting 
resin, followed by carbonization and, if necessary, by graphitization, to 
obtain a carbon fiber-reinforced carbon composite material, and then 
bonding a metal to one side of the carbon composite material which is 
substantially perpendicular to the thickness direction of the carbon 
composite material. 
5. A first wall of a nuclear fusion reactor to be disposed to face a plasma 
of the nuclear fusion reactor, which is composed essentially of a carbon 
fiber-reinforced carbon composite material wherein carbon fibers are 
oriented substantially in the thickness direction, the ratio of the 
thermal conductivity in the thickness direction to the thermal 
conductivity in a direction perpendicular to the thickness direction is at 
least 2, and the thermal conductivity in the thickness direction is at 
least 3 W/cm.multidot..degree.C., and which is to be disposed so that one 
side which is substantially perpendicular to the thickness direction, 
faces the plasma. 
6. A carbon fiber-reinforced carbon composite material, wherein at least 
about 50% of carbon fibers are oriented substantially in the thickness 
direction, the ratio of the thermal conductivity in the thickness 
direction to the thermal conductivity in a direction perpendicular to the 
thickness direction and to the plane of orientation of the fibers in the 
thickness direction is at least 1.2, and the thermal conductivity in the 
thickness direction is at least 1.5 W/cm.multidot..degree.C. 
7. A process for producing a carbon fiber-reinforced carbon composite 
material, which comprises impregnating a woven fabric of carbon fiber with 
a thermosetting resin to obtain a fiber/resin composite, cutting the 
fiber/resin composite into pieces having a desired size, overlaying the 
composite pieces one on another so that the plane of each woven fabric is 
in the thickness direction, followed by molding, curing and carbonization, 
and impregnating the carbonized product with pitch or with a thermosetting 
resin, followed by carbonization and, if necessary, graphitization. 
8. A process for producing a carbon fiber-reinforced carbon composite 
material, which comprises overlaying woven fabrics of carbon fiber 
impregnated with a thermosetting resin one on another, followed by 
molding, curing and carbonization, and impregnating the carbonized product 
with pitch or with a thermosetting resin, followed by carbonization and, 
if necessary, graphitization to obtain a carbon fiber-reinforced carbon. 
composite material, cutting the carbon composite material into pieces 
having a desired size, overlaying the pieces one on another so that the 
plane of each woven fabric is in the thickness direction and binding or 
bonding them integrally. 
9. A process for producing a carbon fiber-reinforced carbon composite 
material, which comprises fibrillating short carbon fibers to form webs, 
overlaying webs one on another so that the plane of each web is in the 
thickness direction, impregnating the webs with pitch or with a 
thermosetting resin before or after the overlaying, followed by molding, 
curing and carbonization, and impregnating the carbonized product with 
pitch or with a thermosetting resin, followed by carbonization and, if 
necessary, graphitization. 
10. A process for producing a carbon fiber-reinforced carbon composite 
material, which comprises fibrillating short carbon fibers to form webs, 
needling the webs in the thickness direction to obtain felts, overlaying 
the felts one on another so that the plane of each felt is in the 
thickness direction of the desired carbon composite material, impregnating 
the felts with pitch or with thermosetting resin before or after the 
overlaying, followed by molding, curing and carbonization, and 
impregnating the carbonized product with pitch or with a thermosetting 
resin, followed by carbonization and, if necessary, graphitization. 
11. A carbon fiber-reinforced carbon composite material obtained by the 
method of the above 9 or 10, wherein the thermal conductivity in the 
thickness direction and the thermal conductivity in a direction 
perpendicular to the thickness direction and parallel to the plane of each 
web or felt, are at least 3 W/cm.multidot..degree.C. 
12. A first wall of a nuclear fusion reactor to be disposed to face a 
plasma of the nuclear fusion reactor, which is composed essentially of a 
carbon fiber-reinforced carbon composite material wherein at least 50% of 
carbon fibers are oriented substantially in the thickness direction, the 
ratio of the thermal conductivity in the thickness direction to the 
thermal conductivity in a direction perpendicular to the thickness 
direction and to the plane of orientation of the fibers in the thickness 
direction, is at least 1.2, and the thermal conductivity in the thickness 
direction is at least 1.5 W/cm.multidot..degree.C., and which is to be 
disposed so that one side which is substantially perpendicular to the 
thickness direction, faces the plasma. 
13. A first wall of a nuclear fusion reactor to be disposed to face a 
plasma of the nuclear fusion reactor, which is composed essentially of a 
carbon fiber-reinforced carbon composite material obtained by the method 
of the above 9 or 10, wherein the thermal conductivity in the thickness 
direction and the thermal conductivity of a direction perpendicular to the 
thickness direction and parallel to the plane of each web or felt, are at 
least 3 W/cm.multidot..degree.C., and which is to be disposed so that one 
side which is substantially perpendicular to the thickness direction, 
faces the plasma.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, the present invention will be described in detail. 
The carbon fibers useful for the present invention may be of any type, such 
as polyacrylonitrile (PAN) type or pitch type carbon fibers or carbon 
fibers prepared by a gas phase growing method. However, high performance 
pitch-type carbon fibers having high thermal conductivity in the axial 
direction of fibers, are particularly preferred. 
The C/C composite materials of the present invention are obtainable by 
using such carbon fibers. 
(I) In a case where carbon fibers are oriented substantially in the 
thickness direction, the ratio of the thermal coductivity in the thickness 
direction to the thermal conductivity in a direction perpendicular to the 
thickness direction is at least 2, and the thermal conductivity in the 
thickness direction is at least 3 W/cm.multidot..degree.C., such C/C 
composite material can be prepared by the following method. 
Firstly, long carbon fibers are impregnated with a thermosetting resin, 
followed by heating to partially cure the thermosetting resin. 
Such thermosetting resin includes, for example, a phenol resin, a furan 
resin, an epoxy resin and an unsaturated polyester resin. A phenol resin, 
particularly a resol-type phenol resin, is preferred. Such thermosetting 
resin is used usually as dissolved and diluted with a solvent, for 
example, an alcohol such as ethanol, a hydrocarbon such as hexane, or 
acetone. 
The concentration of the thermosetting resin solution is usually within a 
range of from 10 to 70% by weight, preferably from 20 to 60% by weight. 
When a curing agent is required as in the case of a furan resin or an epoxy 
resin, such curing agent is also added to the solution. Such curing agent 
is added in an amount suitable for the particular resin used. As a method 
for impregnating long carbon fibers to such thermosetting resin solution, 
a simple method of dipping the carbon fibers in the solution, may be 
employed. However, in the case of a long fiber robing, a method of 
continuously passing it through a tank filled with the solution, is 
preferred from the viewpoint of the efficiency of the treatment. Further, 
in this case, it is preferred to apply supersonic waves of a level of from 
10 to 50 KHz to the tank filled with the solution, whereby an adverse 
effect of irregular treatment due to e.g. air bubbles among monofilaments 
or among weave openings, can be prevented. The carbon fibers impregnated 
with the thermosetting resin solution is, for instance, passed through 
rollers to remove an excess solution and then subjected to heat treatment. 
By the heat treatment, the thermosetting resin is thermally cured. The 
conditions for the heat treatment vary depending upon the type of the 
thermosetting resin used. However, the heat treatment is conducted usually 
at a temperature of from 50.degree. to 300.degree. C., preferably from 
80.degree. to 200.degree. C. for from 0.2 to 5 hours, preferably from 0.2 
to 2 hours. In such a case, it is preferred to gradually raise the 
temperature to the prescribed temperature in order to avoid abrupt release 
of the solvent from the thermosetting resin solution coated on the carbon 
fibers. The heat treatment is preferably conducted by continuously passing 
the carbon fibers through a heating furnace, from the viewpoint of the 
efficiency of the treatment. 
Then, the obtained fiber/resin composite is cut into pieces having a length 
longer than the thickness of the desired C/C composite material. 
The length is selected usually within a range slightly longer than the 
thickness of the desired product and may, for example, be selected within 
a range of from 15 to 100 mm. The composite pieces are then aligned in one 
direction so that they will be substantially parallel to one another. 
Then, a pressure is exerted to the aligned pieces in a direction 
perpendicular to the longitudinal direction of the fibers, followed by 
heating and molding. 
For example, by supplying the composite pieces to a mold by means of a 
funnel-form feader, the composite pieces are aligned substantially in 
parallel to one another in the mold, then a pressure is exerted in a 
direction perpendicular to the longitudinal direction of the fibers under 
heating at a temperature required for the curing of the resin, to cure the 
resin and obtain a molded product. 
Then, the molded product is introduced into a container so that it is 
surrounded by coke breeze. Then, the container is introduced into an 
electric furnace, and the temperature is raised to a level of 100.degree. 
C., if necessary, under a nitrogen gas stream, for carbonization. 
If necessary, the carbonized product is introduced into a graphitization 
furnace and subjected to heat treatment at a temperature of at least 
2,000.degree. C. under an inert atmosphere. 
Then, obtained carbonized product or graphitized product is impregnated 
with a petroleum-type or coal-type pitch or with a thermosetting resin 
such as a phenol resin or a furan resin, followed by carbonization, after 
curing the resin in the case where the thermosetting resin is employed. 
In such case, the thermosetting resin is used usually as dissolved in a 
solvent such as an alcohol, acetone or anthracene oil to have a proper 
viscosity. 
Further, in such case, it is preferred to employ an impregnation method 
under pressure. 
For example, a molded carbonized or graphitized product and pitch are 
introduced into a low pressure reactor (autoclave), which is then heated 
under vacuum to dissolve the pitch. After the carbonized or graphitized 
product is immersed in the molten pitch, nitrogen gas is introduced, and 
the temperature is raised under a low pressure to a level of from 
550.degree. to 600.degree. C. 
Then, the reactor is cooled, and the densified product of the carbonized or 
graphitized product is withdrawn, and it is carbonized at a temperature of 
up to 100.degree. C. in the same manner as described above and, if 
necessary, graphitized. 
The above-mentioned so-called densification is repeated to obtain a high 
density C/C composite material having a specific gravity of at least 1.6. 
If the densification or the resin content in the fiber/resin composite is 
inadequate, or if the temperature raising rate for carbonization or 
graphitization is too high, the strength of the fibers in a direction 
perpendicular to the longitudinal direction of the fibers, tends to be 
low. In some cases, the fibers are likely to break. Therefore, it is 
necessary to select proper conditions. 
The C/C composite material thus obtained is an anisotropic material having 
high heat conductivity and electrical conductivity in the direction of the 
thickness. In order to improve the strength in a direction perpendicular 
to the thickness direction, the obtained C/C composite material may be 
wound by long carbon fibers or by a carbon material such as a C/C 
composite material, depending upon the particular purpose. Further, a 
plurality of composite materials may be bonded by means of e.g. a resin 
composed essentially of a phenol resin, and the bonded product is again 
heated to a temperature range at which the C/C composite materials were 
finally treated, to firmly bond the plurality of pieces of the C/C 
composite materials to obtain a composite material having a desired size. 
In the present invention, this C/C composite material may be reinforced in 
both the thickness direction and the direction perpendicular thereto, by 
bonding a metal to one side of the C/C composite material, which is 
substantially perpendicular to the thickness direction of the composite 
material. 
Various metals may be employed depending upon the particular purposes of 
application of the resulting C/C composite materials. However, it is usual 
to select the metal from, for example, Ti, Cu, Fe, Ni, Cr and alloys 
thereof. When heat resistance is required, Ti or an alloy of Ti is 
preferred. For example, in the case of Ti, such an alloy preferably 
contains A1 or V. Such metal is employed usually in the form of a thin 
plate having a thickness of at most about 5 mm, preferably from 0.1 to 1 
mm. The bonding may be conducted by a usual method such as vacuum 
soldering, diffusion bonding or HIP (hot isostastic press). 
(II) In a case where at least 50% of carbon fibers are oriented 
substantially in the thickness direction, the ratio of the thermal 
conductivity in the thickness direction to the thermal conductivity in a 
direction perpendicular to the thickness direction and to the plane of 
orientation of the fibers in the thickness direction, is at least 1.2, 
preferably at least 1.5, and the thermal conductivity in the thickness 
direction is at least 1.5 W/cm.multidot..degree.C., preferably at least 
1.8 W/cm.multidot..degree.C., such C/C composite material can be obtained 
by the following method using woven fabrics, short fibers, webs or 
non-woven fabrics. 
(A) A case where woven fabric is used: 
As the woven fabric, a plain weave fabric, a satin fabric or a twill fabric 
may be employed. 
Firstly, such woven fabric is impregnated with a thermosetting resin. 
The type and the concentration of the thermosetting resin may be selected 
in the same manner as described above with respect to (I). 
The method of impregnating the woven fabric of carbon fibers to such 
thermosetting resin solution may also be the same as described above with 
respect to (I). 
After the impregnation, the woven fabric is dried in a drier to remove the 
solvent. The fiber/resin composite thus obtained, is then cut into pieces 
having a desired size. 
For example, the woven fabric is passed through rolls to impregnate an 
alcohol solution of a phenol resin, and the impregnated fabric is then 
passed through rolls to remove an excess resin and then introduced in a 
drier kept at a temperature lower by 10.degree. C. than the boiling point 
of the alcohol to remove the alcohol. Then, the fabric is cut by a cutter 
into pieces having a size slightly larger than the cross section in the 
thickness direction of the desired product. 
The cut pieces of the composite are overlayed one on another in a mold 
frame having a size slightly larger than the desired product, to fill the 
mold, and molded. For example, the cut pieces of the composite are piled 
one on another, and a pressure is exerted in the direction of piling, and 
the temperature is raised for molding and curing the resin to obtain a 
molded product. 
The conditions for the heat curing treatment vary depending upon the type 
of the thermosetting resin used. Usually, however, the heat treatment is 
conducted at a temperature of from 50.degree. to 300.degree. C., 
preferably from 80.degree. to 200.degree. C. for from 0.2 to 5 hours, 
preferably from 0.2 to 2 hours. 
Then, the molded product is introduced into a container, followed by 
carbonization and, if necessary, graphitization, in the same manner as in 
the case of the above-mentioned (I). 
Then, by repeating the so-called densification in the same manner as in the 
case of the above (I), a high density C/C composite material having a 
specific gravity of at least 1.6 can be obtained. 
The C/C composite material thus obtained is an anisotropic material having 
a thermal conductivity of at least 1.5 W/cm.multidot..degree.C. (usually 
less than 3.0 W/cm.multidot..degree.C.) and excellent electrical 
conductivity, in the thickness direction. 
(B) Another embodiment in which woven fabric is used: 
Woven fabrics of carbon fibers impregnated with a thermosetting resin were 
overlayed one on another, followed by molding, curing and carbonization, 
and the carbonized product is impregnated with pitch or a thermosetting 
resin, followed by carbonization and, if necessary, graphitization, to 
obtain the desired C/C composite material. 
This material is then cut into pieces having a size, in the plane of the 
woven fabric of this C/C composite material, larger than the cross section 
in the thickness direction of the desired product. 
The cut pieces of the composite material are bound or bonded in such a form 
wherein the plane direction agrees i.e. the plane of each woven fabric is 
in the thickness direction of the desired product. 
They may be bound by winding long fibers made of carbon fibers thereon. 
Otherwise, they may be bound by a C/C composite material or a usual carbon 
material, so that there will be no space between the overlayed pieces. 
Further, the pieces may be bonded by means of e.g. a resin composed 
essentially of a phenol resin, and they are heated to a temperature level 
at which the C/C composite material was finally treated, to bond the 
plurality of the cut pieces of the C/C composite material to one another. 
(C) A case where short fibers or non-woven fabric is used: 
(i) Short carbon fibers are fibrillated to form a web by a conventional 
method. This web is used instead of the woven fabric of (A) and treated in 
the same manner as in (A) to obtain a C/C composite material wherein the 
direction of the majority of fibers of the web (the direction of the plane 
of the web) is in the same direction as the thickness direction of the 
desired product. 
(ii) A non-woven fabric of carbon fiber prepared from long carbon fibers by 
a usual method is used instead of the woven fabric of (A) and treated in 
the same manner as in (A) to obtain a C/C composite material wherein the 
direction of the plane of the non-woven fabric is in the same direction as 
the thickness direction of the desired product. 
(D) A case where a web formed from short fibers and subjected to needling 
is used: 
A product obtained by needling the web obtained in (C) in the thickness 
direction of the web, is used instead of the web, and it is treated in the 
same manner as in (C) to obtain a C/C composite material wherein the 
direction of the plane of the web is in the same direction as the 
thickness direction of the desired C/C composite material. 
Further, in the present invention, in the above method (C) (i) or (D) 
(preferably (D)), it is possible to obtain a product wherein the thermal 
conductivity in the thickness direction and the thermal conductivity in a 
direction perpendicular to the thickness direction and parallel to the 
plane of each web or felt, are at least 3 W/cm.multidot..degree.C., by 
increasing the number of densification operation (at least about 6 or 7 
times) or needling operation, or by conducting graphitization at a 
relatively high temperature (at least about 2,900.degree. C.)) for 
applications wherein heat is effectively conducted in two directions i.e. 
in the thickness direction and one direction perpendicular to the 
thickness direction. 
In the present invention, such C/C composite material is used as the main 
constituting material for the first wall to be disposed to face a plasma 
of a nuclear fusion reactor, and it is disposed so that one side which is 
substantially perpendicular to the thickness direction, faces the plasma. 
The C/C composite material is positioned to extend, in its thickness 
direction between the high temperature plasma region and the external low 
temperature region. 
Further, in the present invention, it is preferred to bond or bind, by 
metallurgical bonding or by mechanical binding, a metal to one side of the 
C/C composite material which is substantially perpendicular to the 
thickness direction of the C/C composite material. Particularly preferred 
is the metallurgically bonding. The metal is usually selected from, for 
example, Ti, Cu, Fe, Ni, Mo, Cr and alloys thereof. As an alloy system, 
for example in the case of Ti, it is preferred that the alloy contains A1 
or V. 
Such metal is used usually in the form of a thin plate having a thickness 
of at most about 5 mm, preferably from 0.1 to 0.3 mm. However, a stainless 
steel plate having a thickness of not more than about 50 mm, may be 
employed as the substrate directly or with inter-position of the above 
thin plate. The bonding may be made by a conventional method such as 
vacuum soldering, diffusion bonding or HIP (hot isotactic press). 
The C/C composite material of the present invention has high heat 
conductivity and electrical conductivity in at least one direction 
including the thickness direction and thus is capable of effectively 
removing or conducting heat. Further, when a metal is bonded as mentioned 
above, the thermal shock resistance in both the thickness direction and 
the direction perpendicular thereto is high. 
Now, the present invention will be described in further detail with 
reference to Examples. However, it should be understood that the present 
invention is by no means restricted to such specific Examples. 
EXAMPLE 1 
Long fibers of pitch-originated carbon fiber ("Dialead" manufactured by 
Mitsubishi Kasei Corporation, 4,000 filaments, fiber diameter: 10 .mu.m) 
were immersed in an ethanol solution of a phenol resin, and then they were 
introduced into a drier to remove ethanol at 70.degree. C. and then heated 
to a temperature of at least 100.degree. C. to half-cure the phenol resin. 
The fiber/resin composite thus obtained (tow prepreg) (carbon 
fiber/resin=56/44 in weight ratio) was cut into pieces having a length of 
40 mm. The pieces were rod-like and rigid with the fibers fixed with the 
resin. The cut pieces of the composite were aligned in one direction in a 
mold so that they were in parallel to one another, so as to fill the mold 
in the form larger than the size of the desired C/C composite material. 
Then, a low pressure is exerted at 150.degree. C., and the temperature was 
raised to 250.degree. C. over a period of one hour and held at 250.degree. 
C. for one hour for molding and curing. 
The size after the molding was 101.9.times.102.5.times.40.1 
Then, this molded product was introduced into a container packed with coke 
breeze and heated to 1,000.degree. C. over a period of about 50 hours in a 
state covered with the-coke breeze, for carbonization of the resin. 
Then, this carbonized composite and solid pitch were introduced into an 
autoclave, and the temperature was raised to 250.degree. C. under a 
reduced pressure condition. Then, nitrogen was permitted to bring the 
atmosphere to a positive pressure. Then, the temperature was raised to 
500.degree. C. in 8 hours and then held at 500.degree. C. for 5 hours. 
The pressure during the temperature raising, was maintained at a constant 
level by adjusting the valve attached to the autoclave. 
The autoclave was cooled, and the composite material was taken out and 
carbonized to a temperature of 1,000.degree. C. in the same manner as the 
carbonization of the molded product. The above autoclave treatment and the 
subsequent carbonization treatment were repeated in a total of three 
times. Then, the product was introduced into a graphitization furnace and 
heated to 2,800.degree. C. in an argon atmosphere and then cooled to 
obtain a C/C composite material. The C/C composite material thus obtained 
had a bulk density of 1.8 g/cm.sup.3, and the thermal conductivities in 
the thickness direction (the same direction as the fiber axis) and in a 
direction perpendicular thereto, were measured by a laser flash method 
thermal coefficient measuring device (manufactured by Shinkuriko). 
The thermal conductivity in the thickness direction was 3.70 
W/cm.multidot..degree.C., and the thermal conductivity in the direction 
perpendicular to the thickness direction was 0.31 W/cm.multidot..degree.C. 
The ratio was 12.0. 
This product did not break even when rapidly introduced into the 
graphitization furnace heated at a temperature of 2,500.degree. C., and 
was superior also in the thermal shock resistance. 
EXAMPLE 2 
A C/C composite material was prepared in the same manner as in Example 1 
except that the size after the molding was 122.times.137.times.44 mm, and 
the autoclave treatment and the subsequent carbonization treatment were 
repeated in a total of 4 times. 
The bulk density of the C/C composite material thus obtained, was 1.83 
g/cm.sup.3. The thermal conductivity in the thickness direction was 3.61, 
and the thermal conductivity in the direction perpendicular to the 
thickness direction was 0.51. The ratio was 7.08. 
This C/C composite material did not break even when rapidly introduced into 
a graphitization furnace heated at a temperature of 2,500.degree. C., and 
it was excellent also in the thermal shock resistance. 
EXAMPLE 3 
Eight satin fabric sheets (260 g/m.sup.2) of pitch fibers ("Dialead", 3,000 
filaments, fiber diameter: 10 .mu.m) were impregnated in an ethanol 
solution of a phenol resin (phenol resin/ethanol=1/4 ) and then introduced 
into a drier maintained at a temperature of 70.degree. C. to remove 
ethanol. Then, the obtained composite was cut into pieces of 22.times.105 
mm. The pieces of the composite were overlayed one on another in a 
thickness of about 95 mm in a direction perpendicular to the plane of 
22.times.105 mm to obtain a size larger than the size of the desired C/C 
composite material. 
Then, a low pressure was exerted at 150.degree. C., and the temperature was 
raised to 250.degree. C. over a period of one hour, and maintained at 
250.degree. C. for one hour for molding and curing. The size of the molded 
product thus obtained was 103.2.times.93.4.times.21.9 mm. 
Then, this molded product was introduced into a container packed with coke 
breeze and heated to 1,000.degree. C. over a period of about 50 hours in a 
state covered with coke breeze, for carbonization. Then, the carbonized 
composite material and solid pitch were introduced into an autoclave, and 
the temperature was raised to 250.degree. C. under a reduced pressure 
condition. Then, nitrogen gas was introduced to bring the atmosphere in a 
positive pressure, and the temperature was raised to 500.degree. C. over a 
period of 8 hours and then maintained at 500.degree. C. for 5 hours. 
The pressure during the temperature raise, was maintained at a constant 
level by means of a valve attached to the autoclave. 
The autoclave was cooled, and the composite material was taken out and 
carbonized to a temperature of 1,000.degree. C. in the same manner as in 
carbonization of the molded product. The above-mentioned autoclave 
treatment and the subsequent carbonization treatment were conducted in a 
total number of three times, and the product was introduced into a 
graphitization furnace and heated to a temperature of 2,800.degree. C. in 
an argon atmosphere and then cooled to obtain a C/C composite material. 
The bulk density of the C/C composite material thus obtained was 1.62 
g/cm.sup.3. The thermal conductivity in the thickness direction was 1.63 
W/cm.multidot..degree.C., and the thermal conductivity in a direction 
perpendicular thereto and perpendicular to the plane of the woven fabric, 
was 0.23 W/cm.multidot..degree.C. The ratio of the thermal conductivities 
was 7.0. (The orientation in the thickness direction of the carbon fibers 
was about 50%.) 
EXAMPLE 4 
The same satin fabric of pitch-originated carbon fibers as used in Example 
3 was impregnated in an ethanol solution of a phenol resin in the same 
manner as in Example 3, dried, molded into a flat plate and cured. Then, 
this product was heated at 1,000.degree. C., and then usual pitch 
impregnation method was repeated to densify the product. Finally, 
graphitization was conducted at 2,800.degree. C. Then, this flat plate C/C 
composite material having a thickness of 10 mm was cut into pieces having 
a width of 20 mm and a length of 100 mm. Twenty pieces thus obtained were 
overlayed one on another so that their flat surfaces were in contact one 
another, and they were bonded by a phenol resin. Further, they were wound 
by carbon fibers to obtain C/C composite material having a width of 100 
mm, a length of 200 mm and a thickness of 20 mm. The thermal conductivity 
in the thickness direction of this product was 1.64 
W/cm.multidot..degree.C., and the ratio of the thermal conductivity in the 
thickness direction to the thermal conductivity in a direction 
perpendicular to the thickness direction and perpendicular to the bonding 
surfaces, was 7.5. (The orientation in the thickness direction was about 
50%.) 
EXAMPLE 5 
Pitch-originated fibers ("Dialead", 3,000 filaments, fiber diameter: 10 
.mu.m) were cut to obtain short fibers, which were then fibrillated to 
obtain a web. The web was cut into pieces of 30 mm.times.150 mm. The 
pieces were impregnated in an ethanol solution of a phenol resin. Then, 
these pieces were overlayed one on another to obtain a thickness of about 
100 mm, and a C/C composite material was prepared in the same manner as in 
Example 3. 
The thermal conductivity in the thickness direction of the C/C composite 
material thus obtained was 1.64. The ratio of the thermal conductivity in 
the thickness direction to the thermal conductivity in a direction 
perpendicular to the thickness direction and parallel to the laminating 
direction, was about 6.5. (The orientation of the planes of webs in the 
thickness direction was about 100%.) 
EXAMPLE 6 
The same web as obtained in Example 5 was subjected to needling, to obtain 
a felt in which fibers were oriented in the thickness direction of the 
web. 
By using this felt, a C/C composite material was obtained in the same 
manner as in Example 5, and the thermal conductivity was measured in the 
same manner as in Example 5. The thermal conductivity in the thickness 
direction was 1.64, and the ratio was 6.0. (The orientation of the planes 
of webs in the thickness direction was about 93%.) 
EXAMPLE 7 
A C/C composite material was prepared in the same manner as in Example 3 
except that since the desired size for the C/C composite material was 
large, the composite was cut into pieces having a size of 45.times.110 mm, 
and the size of the molded product obtained by overlaying to increase the 
carbon fiber content in the finally obtainable C/C composite material, was 
changed to 112.times.105.times.46 mm, and the autoclave treatment and the 
subsequent carbonization treatment were conducted four times in total. 
The bulk density of the composite material thus obtained was 1.82 
g/cm.sup.3. The thermal conductivity in the thickness direction was 2.14 
W/cm.multidot..degree.C., and the thermal conductivity in a direction 
perpendicular to the thickness direction and to the plane of each woven 
fabric, was 0.34 W/cm.multidot..degree.C. The ratio of the thermal 
conductivities was 6.0. (The orientation of the carbon fibers in the 
thickness direction was about 50%.) 
EXAMPLE 8 
A C/C composite material was prepared in the same manner as in Example 7 
except that the temperature for heat treatment was changed to 
3,000.degree. C. in Example 7. 
The bulk density of the composite material thus obtained was 1.84 
g/cm.sup.3. The thermal conductivity in the thickness direction was 2.95 
W/cm.multidot..degree.C., and the thermal conductivity in a direction 
perpendicular to the thickness direction and to the plane of each woven 
fabric, was 0.37 W/cm.multidot..degree.C. The ratio of the thermal 
conductivities was about 8.0. 
EXAMPLE 9 
A C/C composite material was obtained in the same manner as in Example 5 
except that in Example 5, the thickness of lamination was increased to 
increase the carbon fiber content in the finally obtainable C/C composite 
material. 
The bulk density of the composite material was 1.85 g/cm.sup.3. The thermal 
conductivity in the thickness direction was 1.72 W/cm.multidot..degree.C., 
and its ratio to the thermal conductivity (0.39) in a direction 
perpendicular to the thickness direction and to the bonding surface, was 
about 
EXAMPLE 10 
A C/C composite material was obtained in the same manmer as in Example 9 
except that in Example 9, the temperature for heat treatment was changed 
to 3,000.degree. C. 
The bulk density of the composite material thus obtained was 1.83 
g/cm.sup.3, and the ratio of the heat conductivities was about 4.9 
(2.19/0.45). 
EXAMPLE 11 
A C/C composite material was prepared in the same manner as in Example 6 
except that in Example 6, the number of needling was increased to increase 
the proportion of fibers oriented in the thickness direction of the webs, 
and the autoclave treatment and the subsequent carbonization treatment 
were conducted five times in total. 
The bulk density of the composite material thus obtained was 1.72 
g/cm.sup.3. The thermal conductivity in the thickness direction was 1.66, 
and its ratio to the thermal conductivity (1.17) in a direction 
perpendicular to the thickness direction and to the direction of 
lamination was about 1.4. 
EXAMPLE 12 
A C/C composite material was prepared in the same manner as in Example 11 
except that in Example 11, the temperature for heat treatment was changed 
to at least about 2,900.degree. C. 
The bulk density of the composite material thus obtained was 1.73 
g/cm.sup.3, and the ratio of the heat conductivities was about 1.2 
(1.84/1.53). 
EXAMPLE 13 
A C/C composite material was prepared in the same manner as in Example 6 
except that in Example 6, the densification treatment was conducted 8 
times, and the temperature of graphitization was changed to at least about 
2,900.degree. C. 
The thermal conductivity in the thickness direction and the thermal 
conductivity in a direction perpendicular to the thickness direction and 
to the direction of lamination, were 3.3 W/cm.multidot..degree.C. and 3.1 
W/cm.multidot..degree.C., respectively. Further, the thermal conductivity 
in a direction perpendicular to the thickness direction and parallel to 
the direction of lamination, was 0.57 W/cm.multidot..degree.C. 
EXAMPLE 14 
By using the C/C composite material obtained in Example 1, a pure Ti plate 
was bonded to one side of the composite material which is substantially 
perpendicular to the thickness direction of the composite material. 
Namely, on a pure Ti plate (melting point: about 1,675.degree. C. having a 
thickness of about 0.3 mm, a Cu solder was placed, and the above C/C 
composite material was placed thereon. Then, a weight of about 1 kg was 
placed thereon. In a vacuum furnace, the temperature was raised over a 
period of about one hour and maintained at about 1,050.degree. C. for 5 
hours to obtain a desired C/C composite material having Ti bonded thereto. 
The obtained C/C composite material had adequate reinforcing effects also 
in a direction perpendicular to the thickness direction. 
EXAMPLE 15 
A C/C composite material was prepared in the same manner as in Example 14 
except that in Example 14, the size after the molding was 
122.times.137.times.44 mm and the autoclave treatment and the subsequent 
carbonization treatment were conducted four times in total. 
The bulk density of the C/C composite material thus obtained was 1.83 
g/cm.sup.3. The thermal conductivity in the thickness direction was 3.61, 
and the thermal conductivity in the direction perpendicular to the 
thickness direction was 0.51. The ratio of the thermal conductivities was 
7.08. 
This C/C composite material did not break even when introduced rapidly into 
a graphitization furnace heated to a temperature of 2,500.degree. C., and 
it was excellent in the thermal shock resistance. 
Then, a pure Ti plate was bonded to one side of this C/C composite material 
in the same manner as in Example 14. The C/C composite material thus 
obtained had adequate reinforcing effects also in a direction 
perpendicular to the thickness direction. 
EXAMPLE 16 
FIG. 1 illustrates a first embodiment of the first wall of a nuclear fusion 
reactor according to the present invention. The first wall 1 comprises the 
C/C composite material 2 prepared in Example 1, which is vacuum-soldered 
to a substrate 3. 
Namely, the composite material 2 is bonded to a stainless steel substrate 3 
having a thickness of 10 mm by a copper solder with interposition of a Ti 
plate 7 having a thickness of 1 mm and a solder portion 4. 
The substrate 3 is provided with cooling tubes 5 to improve the cooling 
effects. 
In this Figure, the plasma-facing side 6 is disposed to face the plasma of 
the nuclear fusion reactor. In this manner, the composite material of the 
present invention is used as the first wall. 
FIG. 2 illustrates a second embodiment of the first wall of the present 
invention. In this embodiment, the C/C composite material 2 obtained in 
Example 1 was used, and a thin metal plate 7' (pure Ti plate) was bonded 
to one side which is substantially perpendicular to the thickness 
direction. 
Namely, on a pure Ti plate (melting point: 1,675.degree. C.) 7 having a 
thickness of about 1 mm, a copper solder was placed, and the above C/C 
composite material was placed thereon. A weight of about 1 kg was placed 
thereon. In a vacuum furnace, the temperature was raised over a period of 
1 hour and maintained at about 1,050.degree. C. for 5 hours to obtain a 
C/C composite material having Ti bonded thereto with the solder portion 4 
interposed therebetween. 
Then, the thin metal plate 7 of this C/C composite material was 
mechanically connected to the substrate 3 by e.g. a bolt. Reference 
numeral 8 indicates a fixing plate, and numeral 9 indicates a connector. 
The substrate 3 may be provided with cooling tubes as in the first 
embodiment. Reference numeral 6 indicates the plasma-facing side. 
FIG. 3 illustrates a third embodiment of the first wall of the present 
invention. In this embodiment, the C/C composite materials 2 and 2' are 
bonded around a cooling tube 5 with a solder portion 4 interposed 
therebetween. The plasma-facing side is disposed to face the plasma of the 
nuclear fusion reactor. Thus, the composite materials of the present 
invention are used as the first wall. 
EXAMPLE 17 
A C/C composite material having a metal bonded thereto was prepared in the 
same manner as in Example 16 except that in the first embodiment of 
Example 16, the C/C composite material obtained in Example 3 was used, and 
a Mo plate having a thickness of 2 mm was used as the material for 
interposition. It was used as the first wall. 
Further, a C/C composite material for the first wall was prepared in the 
same manner as in Example 16 except that in the second embodiment of 
Example 16, the C/C composite material obtained in Example 3 was bonded to 
a Mo plate (melting point: about 2,620.degree. C.) having a thickness of 2 
mm to obtain a C/C composite material having Mo bonded thereto. 
The C/C composite material of the present invention has large heat 
conductivity and electrical conductivity in the thickness direction and 
thus is useful for application where heat or electrical conductivity in 
one direction is required. 
For example, it is useful as a material for a heat exchanger whereby heat 
removal or heat conduction is carried out by contacting one flat surface 
with a cooling jacket, or as a material for a switch. 
Further, the first wall made of the C/C composite material of the present 
invention has particularly excellent properties as the first wall, since 
the surface temperature, the vapor pressure and the sublimation loss are 
maintained at low levels even when exposed to a high heat load for a long 
period of time.