JPH11116359A - Carbon-boron carbide composite material, its production, protecting part for measuring instrument in nuclear fusion reactor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon-boron carbide composite material that is suitable as a protective material for a variety of instruments arranged in a nuclear fusion reactor, its production and a protective material for instruments in the nuclear fusion reactor using the same. SOLUTION: The objective carbon-boron carbide composite material is prepared by impregnating boron carbide with either thermally decomposed carbon or glassy carbon and has a thermal conductivity of 30 W/mK at room temperature. The carbon-boron carbide composite material is produced by impregnating a body formed by binding carbon fiber with a slurry of boron carbide powder, then impregnating it with thermally decomposed carbon at a temperature of <=1,600 deg.C, or the molded body is impregnated with a slurry of boron carbide powder and with glassy carbon, then treated with heat at a temperature of <=1,600 deg.C thereby giving the objective carbon-boron carbide composite material with a thermal conductivity of <=30 W/mK.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon composite material, particularly a carbon-boron carbide composite material, which is suitable for a protective member of various devices disposed in a nuclear fusion reactor, a method for producing the same, and a use thereof. .

[0002]

2. Description of the Related Art In a nuclear fusion reactor, various instruments such as various measuring instruments (including attached parts) for examining the state of plasma generation and the like are arranged. Since a member for covering and protecting the substrate comes into direct contact with the plasma, it is not preferable to use a member that inhibits not only heat resistance but also plasma stabilization. Therefore, generally, an excellent carbon material is used as it is as a material for furnace wall lining.

That is, conventionally, carbon materials have properties such as heat resistance (infusibility at atmospheric pressure or less), thermal stability, corrosion resistance, high strength and high toughness while being lightweight, and the atomic number of carbon. Attention has been paid to advantages such as a small size and a small decrease in plasma temperature, and this carbon material, particularly a carbon fiber felt or a carbon fiber reinforced carbon composite material having a relatively large thermal conductivity (hereinafter referred to as a “C / C material”). ) Is used.

Furthermore, when boron is mixed into a carbon material, an effect of gettering impurities such as oxygen in plasma and an effect of suppressing chemical sputtering by hydrogen plasma appear, which is advantageous in that plasma is stabilized. Attention has been paid to a carbon-boron carbide composite material obtained by impregnating and immobilizing boron in a carbon fiber-bonded molded body as a so-called improved material of the carbon molded body.
Such a carbon-boron carbide composite material was originally developed for a material having a higher thermal conductivity as a material for lining the walls of a fusion reactor as described above. That is, even a generally obtained carbon-boron carbide composite material has reached about 80 to 100 W / mK even at a low thermal conductivity, and more recently a carbon-boron carbide composite material having a thermal conductivity of 200 W / mK or more has been developed (Japanese Unexamined Patent Publication No. -198691).

[0005]

However, since the protective member of various equipment is intended to protect the equipment by cutting off as much heat as possible from the high temperature atmosphere in the furnace in order to make the equipment function properly, It is preferable that only the thermal conductivity be as low as possible. However, the conventional carbon-boron carbide composite material has a low thermal conductivity of 80 W / mK.
Since it is at the level before and after, the function as a protection member of the equipment is small, and erosion accidents etc. occur relatively early, so that the number of replacement work of the equipment increases, and the maintenance becomes complicated accordingly. was there.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a carbon-boron carbide composite material and a carbon-boron carbide composite material which are most suitable as protection members for various devices arranged in a fusion reactor. It is an object of the present invention to provide a manufacturing method thereof and a protective member for a fusion reactor measuring instrument using the composite material.

[0007]

The carbon-boron carbide composite material according to the first aspect of the present invention, which has achieved the above object, comprises boron carbide and either one of pyrolytic carbon or glassy carbon. Is a carbon-boron carbide composite material impregnated with a material having a thermal conductivity (room temperature) of 3
0 W / mK or less. This allows
A carbon composite material suitable for protection members of various devices arranged in a fusion reactor can be provided.

[0008] The manufacturing method according to the second aspect of the present invention is characterized in that:
Bulk density of 0.6 to 1.3 Mg / m ³ , thermal conductivity (room temperature)
Is impregnated with a slurry of boron carbide powder into a compact having a carbon fiber of 35 W / mK or less,
A carbon-boron carbide composite material having a thermal conductivity (room temperature) of 30 W / mK or less is obtained by impregnating pyrolytic carbon at a temperature of not more than ℃. Thereby, it is possible to provide a carbon composite material suitable for a protection member of various devices arranged in the nuclear fusion reactor.

[0009] The manufacturing method according to the third aspect of the present invention is characterized in that:
Bulk density of 0.6 to 1.3 Mg / m ³ , thermal conductivity (room temperature)
Is impregnated with a slurry of boron carbide powder, and then further impregnated with vitreous carbon, and then heat-treated at 1600 ° C. or less to obtain a heat conductivity ( (Room temperature) of 30 W / mK or less. Thereby, it is possible to provide a carbon composite material optimal for protection members of various devices disposed in the fusion reactor at a lower cost.

[0010] Further, the invention according to claim 4 is the invention according to claim 1.
A protection member for a nuclear fusion reactor measuring device, characterized by using the carbon-boron carbide composite material described above. This allows
It is possible to extend the life of the fusion reactor measuring instrument, thereby reducing the number of replacements of the measuring instrument and facilitating maintenance.

Hereinafter, the present invention will be described in detail, but a representative example of a measuring instrument as an example of equipment installed in a fusion reactor will be described. (1) As described above, in order to make the conventional carbon-boron carbide composite material suitable for a protection member for a fusion reactor measuring instrument, the present inventors have found that the heat resistance required for a member arranged in a fusion reactor is required. From the standpoint of improving the carbon-boron carbide composite material, while maintaining the essential and essential properties of high-temperature strength and plasma stability, but having only a low thermal conductivity. Various studies were conducted to find such a carbon-boron carbide composite material and a method for producing the same.
As a result, as a base material such as a C / C material, a material having a bulk density and a thermal conductivity (room temperature) within a specific range is used, and the base material is impregnated with boron carbide. It has been found that a satisfactory carbon-boron carbide composite material can be obtained by impregnating a carbon material capable of exerting an effect of densifying the surface layer of the base material while fixing the same under predetermined high-temperature conditions. is there.

That is, the carbon-boron carbide composite of the present invention (the invention according to claim 1) is a carbon-boron carbide composite impregnated with boron carbide and either pyrolytic carbon or glassy carbon. And the thermal conductivity (room temperature) of the carbon-boron carbide composite material is 30 W / mK or less. "

As a method for producing the carbon-boron carbide composite material, a bulk density of 0.6 to 1.3 Mg / m ³ ,
A slurry of boron carbide powder is impregnated into a carbon fiber-bonded compact having a thermal conductivity (room temperature) of 35 W / mK or less,
Then, impregnated with pyrolytic carbon at 1600 ° C. or lower ”, a configuration unique to the present invention (the invention according to claim 2) can be adopted.

Further, when glassy carbon capable of performing a similar function is used as a substitute for pyrolytic carbon, more desirable characteristics are obtained than a carbon-boron carbide composite material obtained using pyrolytic carbon. It has been found that the carbon-boron carbide composite material can be obtained at a lower cost, and as an invention according to another manufacturing method (an invention according to claim 3), of the configuration of the manufacturing method according to the invention according to claim 2, It is possible to adopt a configuration in which the impregnating step of decomposed carbon is changed to the impregnating step of glassy carbon.

(2) A molded article as a substrate used in the present invention will be described. As the base material, a molded body to which carbon fibers are bonded is used. That is, carbon fibers such as pitch-based, PAN (polyacrylonitrile) -based, rayon-based carbon fibers are bonded, laminated as necessary, and, if necessary, pyrolytic carbon or carbides of various resins are used as a matrix. A felt, a one-dimensional, two-dimensional, three-dimensional or other C / C material can be used as the molded body. From the viewpoint of lowering the thermal conductivity, a pitch type is preferable.

In the present invention, the bulk density is 0.6 to 1.3 Mg.
/ M ³ must be used, but the reason for limiting to this range is as follows. In general, the level of the thermal conductivity of the final product corresponds to the level of the thermal conductivity of the raw material substrate, and the degree of the level of the thermal conductivity of the substrate tends to be determined according to the magnitude of the bulk density. Therefore, conventional carbon-
To reduce the thermal conductivity of the boron carbide composite, C / C
First, a solution guide is given that a material having a low bulk density may be selected as a base material such as a material. However, if the bulk density of the base material is too low, the mechanical strength of the base material is reduced in proportion thereto, so that cracks or the like are easily generated during processing, and it is difficult to obtain a protective member having a predetermined shape. Therefore, the range in which the bulk density can be reduced under the limited condition that good workability can be maintained to some extent is limited to 0.6 to 1.3 Mg / m ³ . From the viewpoint of ensuring reliability, 0.7 to 1.2 Mg / m ³ is a desirable range.

Furthermore, it is necessary to use a molded product having a thermal conductivity (room temperature) of 35 W / mK or less. The reason for limiting the range is to measure the carbon-boron carbide composite material as the final product. This is because it is effective as a protective member of the container. That is, in order to achieve the effect, it is necessary to reduce the thermal conductivity of the carbon-boron carbide composite material to 30 W / mK or less, and the thermal conductivity of the base material corresponding to this level is 35 W / mK or less. Because it must be. Further, the average pore radius of the molded body is 1 to 50 μm.
Are preferred. When the thickness is less than 1 μm, the impregnation efficiency of boron carbide, pyrolytic carbon, or the like becomes low, and when it exceeds 50 μm, the boron carbide tends to be unevenly distributed. Incidentally, the average pore radius is from 0.01 to the pore radius measured by the mercury intrusion method.
The pore radius corresponds to 1/2 of the cumulative pore volume at 100 μm.

(3) The boron carbide to be impregnated into the molded product is
Commercially available boron carbide powder or the like can be used. As a method for impregnating the boron carbide powder, for example, a slurry is prepared by dispersing the boron carbide powder using an organic solvent such as water or alcohol as a dispersion medium, and the formed body may be impregnated. In this case, the average particle size of the boron carbide powder is preferably 20 μm or less, and the boron carbide powder is easily dispersed uniformly in the dispersion medium.
Particularly, boron carbide powder having a size of 5 μm or less is most suitable because it easily impregnates into the open pores of the molded body. On the other hand, those having a diameter of more than 20 μm are hardly impregnated into pores and may remain on the substrate surface. This residual boron carbide powder is not suitable in the present invention because it is not only wasted but also the wiping operation becomes complicated.

When the slurry is impregnated into the compact, the concentration of the slurry is preferably 1000 g or less of boron carbide powder per liter of the dispersion medium. If it is higher than 1000 g / liter, the viscosity of the slurry becomes too high and impregnation becomes difficult. The impregnation method may be performed by a known method such as a method using a brush or a spray, a method of dipping the molded body in a slurry, and a vacuum impregnation method. Here, by appropriately selecting the impregnation conditions, the slurry concentration, and the average pore radius of the molded product, not only the surface layer of the molded product but also the entire surface can be impregnated with boron carbide. After the impregnation with boron carbide, the dispersion medium is evaporated by heating or evacuation.

(4) After that, the operation of impregnating the molded body impregnated with boron carbide with either pyrolytic carbon or glassy carbon is started. explain. This impregnation is carried out based on a conventional method, by thermally decomposing a hydrocarbon gas or a hydrocarbon compound having 1 to 8 carbon atoms as a carbon generation source (raw material gas), so that pyrolytic carbon is formed in voids and pores of the boron carbide powder. A carbon-boron carbide composite material (product) having a thermal conductivity (room temperature) of 30 W / mK or less and suitable for a protective member for a measuring instrument by completing the impregnation operation of the pyrolytic carbon. Is obtained.

According to the conventional method, the temperature range for impregnating the pyrolytic carbon can be in a wide range from about 800 to 2500 ° C., but the present invention impregnates the pyrolytic carbon at 1600 ° C. or less. There is a need. The reason is 1600
If the temperature exceeds ℃, the graphitization proceeds too much, and it is difficult to suppress the thermal conductivity of the carbon-boron carbide composite material to be obtained to 30 W / mK or less. That is, as the carbon-boron carbide composite material, it is sufficient that graphitization has progressed to such an extent that sufficient heat resistance can be exhibited as a protective member for equipment placed in a nuclear fusion reactor, and further graphitization is rather graphite. This is because the thermal conductivity increases as the process progresses, which leads to a decrease in the performance as a protective member.

(5) Next, a series of operations after the impregnation of glassy carbon according to another production method will be described. There is no particular limitation on the vitreous carbon used in the present invention. As the thermosetting resin, for example, polycarbodiimide, phenol, furfuryl alcohol, polyamide, polyamideimide, or polyimide can be used. The molded article impregnated with boron carbide in the manner described in (3) above is further impregnated with polycarbodiimide or the like. Heat treatment (carbonization) may be performed.

The conditions for the impregnation may be basically the same as those of the above (4) for the impregnation with the pyrolytic carbon. The molded body after the impregnation of the thermosetting resin is sufficiently dried at 80 to 300 ° C., and this temperature range is desirable. If the temperature is lower than 80 ° C., the carbonization ratio after the heat treatment is small, and if the temperature exceeds 300 ° C., the resin reacts with oxygen and is easily decomposed. The dried compact is further subjected to a heat treatment at 1600 ° C. or lower. The reason why the heat treatment temperature is set to 1600 ° C. or lower is the same as the reason for setting the ambient temperature to 1600 ° C. or lower when impregnating with pyrolytic carbon. The thermal conductivity of the carbon-boron carbide composite is 30
This is because it is difficult to suppress the W / mK or less. As the pressure during the heat treatment, the total pressure is set to 0.01 to 100 Torr from the viewpoint of improving the carbonization rate and suppressing the evaporation of boron carbide.
It is desirable to set to. Completion of the heat treatment operation, the carbon-boron carbide composite material (product) with a thermal conductivity (room temperature) of 30 W / mK or less, which is optimal for a protective member for a measuring instrument
Is obtained.

[0024]

The present invention will be described more specifically with reference to the following examples. Example 1 Boron carbide powder (manufactured by Kyoritsu Ceramics Ind. Co., Ltd., average particle size: 3 μm) was dispersed in methanol (dispersion medium) 1
The slurry was dispersed at a rate of 200 g per liter to prepare a slurry. As a molded body, dimensions 100 × 100 × 10
mm C / C material (bulk density: 1.2 Mg / m ³ , thermal conductivity (room temperature): 31.32 W / mK) was used. After the slurry was impregnated into the whole of the formed body by a vacuum impregnation method, it was kept at 50 ° C. for 5 hours during vacuum drying to spatter methanol. Then, methane gas (raw material gas) 3 l / min, hydrogen gas (carrier gas) 12 l / min.
The whole molded body was impregnated with pyrolytic carbon by a treatment for 1 hour under the condition of min to obtain a carbon-boron carbide composite material (product).

Example 2 In the same manner as in Example 1, the same boron carbide powder-adjusted slurry was applied to the entire surface of a C / C material compact having the same dimensions by brushing, and the solvent was removed in the same manner as in Example 1. Splashed. Next, polycarbodiimide was impregnated into the entire molded body. Thereafter, the temperature was raised to 100 ° C. in the atmosphere, dried for 1 hour, introduced into a heating furnace, and then heated for 0.01 T.
A final heat treatment at 1500 ° C. was performed over 1 hour under orr to obtain a carbon-boron carbide composite material (product). (Example 3) As a C / C material of a molded body, a bulk density of 0.7 M was used.
g / m ³ , thermal conductivity (room temperature) of 19.72 W / mK, and an average pore radius of 25 μm, except that carbon-boron carbide impregnated with boron carbide and pyrolytic carbon was used in exactly the same manner as in Example 1. A composite material (product) was obtained. (Example 4) As a C / C material of a molded body, a bulk density of 0.7 M was used.
g-m ³ , thermal conductivity (room temperature) 19.72 W / mK, and carbon-boron carbide impregnated with boron carbide and glassy carbon in exactly the same manner as in Example 2 except that a material having an average pore radius of 25 μm was used. A composite material (product) was obtained.

(Comparative Example 1) As in Example 1, the same C /
Boron carbide powder was impregnated using the C material compact. Then, at about 1700 ° C. in a vacuum heating furnace, methane gas 3 l / mi
n, the entire molded body was impregnated with pyrolytic carbon by a treatment for one hour under the conditions of hydrogen gas 12 l / min to obtain a carbon-boron carbide composite material (product). (Comparative Example 2) In the same manner as in Example 2, using the same C / C material compact, impregnated with boron carbide and polycarbodiimide, dried, introduced into a heating furnace, and heated to 1700 ° C under 0.01 Torr. Was performed over 1 hour to obtain a carbon-boron carbide composite material (product). (Comparative Example 3) As a C / C material of a molded body, a bulk density of 1.4 M
g / m ³ , a thermal conductivity (room temperature) of 39.18 W / mK, and an average pore radius of about 13 μm, except that carbon-carbonized carbon fiber impregnated with boron carbide and glassy carbon was used in the same manner as in Example 1. A boron composite material (product) was obtained.

The thermal conductivity (room temperature) of the carbon-boron carbide composite (product) obtained in Examples 1 to 4 and Comparative Examples 1 to 3,
The oxidation resistance and thermal shock resistance were examined, and the results are shown in Table 1 together with the physical properties of each base material used. However, the bending strength and the compressive strength were measured in the direction of the fiber orientation and the value in the direction perpendicular thereto.
"Parallel" in the figure indicates the strength parallel to the fiber orientation direction, "Vertical"
Indicates the strength in the direction perpendicular to the fiber orientation direction. The thermal conductivity is a value measured by a laser flash method in a shape of diameter 10 mm × thickness 4 mm.
The thermal conductivity of the / C material in the fiber orientation direction was measured. The oxidation resistance test is performed to determine the degree of the gettering effect of oxygen impurities by examining the weight increase due to oxidation.
Evaluation was made based on a change in weight when 0 l / min of air was flowed for 1 to 3 hours. Furthermore, the thermal shock resistance is such that the electron beam
It was examined whether the product cracked when irradiated at MW / m ³ 50 times for 10 seconds.

[0028]

[Table 1]

As is clear from Table 1, Examples 1-4
The carbon-boron carbide composite (product) obtained in the above was compared with a comparative example showing a conventional carbon-boron carbide composite in terms of oxidation resistance which is also an index of the gettering effect and thermal shock resistance which directly relates to the life. Although excellent, the thermal conductivity of the product is low, indicating that the product is very effective as a material for a protective member for a measuring instrument. On the other hand, in Comparative Examples 1 to 3, the requirements of the present invention, that is, the thermal conductivity of the molded body as the base material was 35%.
Since either the requirement that the bulk density is 0.7 to 1.3 Mg / m ³ at W / mK or less or the requirement that the heat treatment temperature is 1600 ° C. or less is deviated, the obtained carbon-carbonized Each of the boron composite materials (products) has a higher thermal conductivity than that of the product of the present invention, indicating that it is unsuitable as a material for a protective member for a measuring instrument.

Also, from Table 1, it can be seen that, even when the molded bodies having the same physical properties are used, the case where glassy carbon is used (Examples 2 and 4) is the case where pyrolytic carbon is used (Example 1). It can be seen that a carbon-boron carbide composite material (product) having more preferable characteristics than that of (3) is obtained. That is, in the oxidation resistance test, since the degree of weight increase due to oxidation is large, it can be said that the gettering effect of oxygen impurities is excellent. Also, carbon-boron carbide composite (product)
Has a lower thermal conductivity, indicating that the carbon composite material has more favorable characteristics as a protective member for equipment placed in a fusion reactor.

[0031]

As described above, the first aspect of the present invention is a carbon-boron carbide composite material impregnated with boron carbide and either pyrolytic carbon or glassy carbon. And a thermal conductivity (room temperature) of 30 W / mK or less. Therefore, it is possible to provide a carbon composite material suitable for a protection member of various devices arranged in a fusion reactor.

Further, the manufacturing method according to the second aspect of the present invention
Bulk density of 0.6 to 1.3 Mg / m ³ , thermal conductivity (room temperature)
Is impregnated with a slurry of boron carbide powder into a compact having a carbon fiber of 35 W / mK or less,
The carbon-boron composite material having a thermal conductivity (room temperature) of 30 W / mK or less is obtained by impregnating pyrolytic carbon at a temperature of not more than ° C. Therefore, according to this method, it is possible to provide a carbon composite material suitable for a protection member of various devices arranged in a fusion reactor.

Further, the manufacturing method according to the third aspect of the present invention
Bulk density of 0.6 to 1.3 Mg / m ³ , thermal conductivity (room temperature)
Is impregnated with a slurry of boron carbide powder, and then further impregnated with vitreous carbon, and then heat-treated at 1600 ° C. or less to obtain a heat conductivity ( (Room temperature) of 30 W / mK or less. Glassy carbon is a carbon material that is expected to produce carbon-boron carbide composites (products) that are more excellent in plasma stabilizing ability than pyrolytic carbon and have lower thermal conductivity than in the case of pyrolytic carbon impregnation. is there. Moreover, there is an advantage that the impregnation cost of glassy carbon is about one tenth of the impregnation cost of pyrolytic carbon. Therefore, according to the present production method, it is possible to provide a carbon composite material having more desirable characteristics as a protective member for various devices disposed in a nuclear fusion reactor at a lower cost.

Further, the invention described in claim 4 is the same as the claim 1.
It is a protection member for a fusion reactor measuring instrument using the carbon-boron carbide composite material described in the above. Therefore, it is possible to extend the life of the fusion reactor measuring instrument, thereby reducing the number of replacements of the measuring instrument and facilitating maintenance.

Claims (4)

[Claims] 1. A method of impregnating boron carbide with one of pyrolytic carbon and glassy carbon and having a thermal conductivity (room temperature) of 30
A carbon-boron carbide composite material having a W / mK or less. 2. A carbon fiber-bonded compact having a bulk density of 0.6 to 1.3 Mg / m ³ and a thermal conductivity (room temperature) of 35 W / mK or less is impregnated with a boron carbide powder slurry. A carbon-boron carbide composite material having a thermal conductivity (room temperature) of 30 W / mK or less by impregnating with pyrolytic carbon at 1600 ° C. or less. . 3. A slurry of boron carbide powder was impregnated into a carbon fiber-bound compact having a bulk density of 0.6 to 1.3 Mg / m ³ and a thermal conductivity (room temperature) of 35 W / mK or less. Thereafter, the glass is further impregnated with glassy carbon, and then heat-treated at 1600 ° C. or lower, so that the thermal conductivity (room temperature) is 30 W.
A method for producing a carbon-boron carbide composite material, which comprises obtaining a carbon-boron carbide composite material having a viscosity of not more than / mK. 4. A protective member for a nuclear fusion reactor measuring instrument, comprising the carbon-boron carbide composite material according to claim 1.