JPH05306180A - Production of carbon fiber reinforced carbon-inorganic compound composite material - Google Patents

Abstract

PURPOSE:To obtain a composite material excellent in resistance to oxidation and thermal shock by impregnating and depositing pyrolytic carbon in felt of carbon fibers with a supported specified compd. CONSTITUTION:At least one among boron, a boron compd. and a silicon compd. is supported on felt of carbon fibers. After the felt is compressed if necessary, pyrolytic carbon is impregnated and deposited in the felt and heat treatment is carried out to obtain the objective composite material. The carbon fibers of the felt as starting material may be made from pitch, polyacrylonitrile or rayon fibers. Carbon fibers not subjected to carbonization treatment, carbon fibers after carbonization or carbon fibers subjected to graphitization treatment may be used as the carbon fibers of the felt in accordance with the purpose for which the composite material is used. The heat treatment is carried out at 2,000-3,000 deg.C in an inert atmosphere or in vacuum. By this heat treatment, powder of the inorg. compd. is softened, melted and decomposed and the component of the powder is more uniformly dispersed in the composite material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon fiber reinforced carbon-inorganic compound composite material, which is extremely suitable as a material required to have thermal shock resistance and oxidation wear resistance.

[0002]

2. Description of the Related Art Carbon fiber reinforced carbon composite materials have been used for a long time and are characterized by excellent thermal shock resistance in a non-oxidizing atmosphere and mechanical strength like metal even in an ultrahigh temperature range of 2000 ° C. or higher. It does not show a decrease in the electric field and is lighter than aluminum. For this reason, this composite material has become an indispensable material for materials in fusion reactors and aerospace equipment.

However, since it also has the drawback of being weak against oxidation peculiar to carbon materials, various measures have been considered. For example

A) A method of depositing boron having an antioxidant function on the surface of voids of a carbon composite material by using a chemical vapor deposition method (JP-A-61-2222977).

B) A method of selectively converting matrix carbon of a carbon fiber reinforced carbon composite material into boron carbide (Japanese Patent Laid-Open No. 3-252360).

C) A method of sintering carbon fibers with a binder such as a resin containing boron (JP-A-60-200860).
issue).

D) A method of sintering raw coke in which short carbon fibers and ceramic powder are dispersed. Etc.

[0008]

However, in the so-called coating method of the above a) or b), the coating layer peels off, wears, or breaks due to mechanical shock, thermal shock, or long-term use, and the coating layer is rapidly abraded. Oxidation progresses.

Further, in the method of dispersing a substance for preventing oxidation in the whole material as in c), since a binder such as a resin is used, gas generated by decomposition of the binder during firing and matrix carbon itself. Contraction occurs. As a result, the material is very porous and of insufficient strength. Furthermore, there is a limit to the amount of boron that can be contained in the binder, and sufficient oxidation resistance has not been achieved. Further, when the binder resin is carbonized by firing, a temperature gradient is formed inside the felt molded body, which is originally a heat insulating material, which causes peeling. Of course, there was a limit to the thickness of the molded body.

Further, a material such as d) which is excellent in oxidation resistance and strong against mechanical shock has been proposed, but there is a problem that the matrix is coke and thus lacks in thermal shock resistance. The present invention is to overcome the above-mentioned conventional drawbacks, in other words, to provide a method for producing a carbon fiber-reinforced carbon-inorganic compound composite material having excellent oxidation resistance and also excellent thermal shock resistance. is there.

[0011]

Means for Solving the Problems As a result of intensive studies by the present inventors, a carbon fiber in which a powder of a boron or silicon compound exhibiting oxidation resistance is uniformly adhered to the surface of the carbon fiber forming the felt. Felt is used as a material, and pyrolytic carbon (hereinafter referred to as PyC) is impregnated and deposited on it.
It was found that it can be solved by further heat treatment.

[0012]

The carbon fiber forming the felt as a raw material may be any of pitch type, PAN type and rayon type. Furthermore, carbon fibers that have not been carbonized,
There is no particular limitation as long as it has been carbonized or has been graphitized, and it may be used properly. Further, these impurities may be highly purified to the order of ppm of impurities. However, in order to minimize fiber shrinkage and decomposition gas generation during high-temperature treatment of carbon fiber-reinforced carbon-inorganic compound composites, and to obtain good quality materials, graphitized and highly purified felt is used as a starting material. It is preferable to use as.

The thickness of the felt is not particularly limited, but it is preferably 1 to 20 mm, more preferably 3 to 15 mm.
mm. At this time, if the thickness of the carbon fiber felt is less than 1 mm, many layers must be laminated to obtain a desired thickness, and the work increases and the work becomes complicated. It becomes difficult to adhere uniformly.

The inorganic compound powder adhered to the felt is mainly an inorganic compound of boron or silicon, which is widely known to form a glassy antioxidative coating to enhance the oxidation resistance of the carbon material. For example B ₄ C, SiC, Ti
Examples include B ₂ , ZrB ₂ , BN, and B alone.
Further, the powder of the above-mentioned inorganic compound can be used alone or in combination of two or more kinds. In addition, the particle size of these powders should be 5 in order to achieve uniform dispersion.
It is preferably 0 μm or less.

The carbon fiber reinforced carbon-inorganic compound composite material of the present invention is manufactured by using the above raw materials and following the steps shown in FIG.

First, the inorganic compound powder is mixed with water, alcohol,
Mix with a dispersion medium such as an organic solvent to obtain a slurry. The concentration of the slurry is usually 1 to 3000 (g / liter).
The slurry thus obtained is permeated into the felt, and then the dispersion medium is evaporated by a vacuum dryer or the like to obtain a felt in which the powder of the inorganic compound is attached to the fiber surface. The powder amount at this time is preferably 10 wt% or more of the felt weight, and particularly preferably about 50 to 500 wt%.

Next, the felts are laminated as needed,
For example, it is compressed by the jig shown in FIG. For this lamination, the number of layers may be appropriately selected according to the thickness of the target object, and usually 10
It is about 150 mm. If the felt is thick enough, it may not be necessary to stack it.

The laminate is compressed as necessary. This compression is performed by adjusting the porosity of the felt and pressure bonding between the felt layers (if the felt is compressed to a certain degree, the adhesive force between the felts when the pyrolytic carbon is deposited). However, the compression means itself is not limited in any way. For example, a means for compression with a jig shown in FIG. 2 can be exemplified. However, in FIG. 2, (1) is a restraining plate, (2) is a bolt-shaped support,
(3) shows a nut. A surface view of the restraining plate (1) is shown in FIG. However, (4) in FIG. 3 is a hole for inserting the bolt-like support (2).

The jig shown in FIG. 2 is an example, and a material that does not deform or deteriorate at a temperature of 2000 ° C. or higher is used as a material for forming the jig. For example, a graphite material, a silicon carbide material, or a carbonized material. A graphite material coated with silicon, a carbon composite material using carbon fibers, a boron nitride material, or the like can be used.

As the structure of the restraining plate (1), a flat plate having a large number of circular holes, a flat plate having a net-like shape, a honeycomb-like shape, a lattice-like shape, or the like having a large number of gas diffusion holes is used. be able to.

The restraining plates can adjust the porosity of the felt by means of bolt-shaped columns or compression means by a load.

Incidentally, FIG. 4 shows a pressing plate having a honeycomb pattern. Compressed felt (hereinafter sometimes referred to as precursor)
It is preferable that the porosity is 0.5 or more. Here, the porosity means the following [Chemical formula 1].

[0023]

[Chemical 1]

V: Volume of felt molded body (cm ³ ) A: Volume occupied by carbon fibers in molded body (cm ³ ) B: Volume occupied by powder of inorganic compound in molded body (cm ³ ) C: Heat in molded body Calculated by the formula of volume occupied by decomposed carbon (cm ³ ). Expressing this in words, it indicates the ratio of the space in the precursor (where pyrolytic carbon can be deposited) to the volume (bulk) of the precursor.

If this value is smaller than 0.5, the space for precipitation of PyC, which acts as a substantial binder, becomes small,
There is a risk of insufficient adhesion between the compressed fibers. By depositing pyrolytic carbon to the inside of the precursor, this precursor firmly bonds the carbon fibers to each other, the carbon fibers and the powder of the inorganic compound, and obtains sufficient strength.

In the present invention, the method of infiltrating and precipitating pyrolytic carbon may be in accordance with a conventional method. In a general embodiment, a hydrocarbon having about 1 to 8 carbon atoms such as methane or propane is thermally decomposed, and the thermally decomposed carbon is permeated and deposited on the base material. At this time, the hydrocarbon concentration is adjusted to 3 to 30%, preferably 5 to 1 by using H ₂ or Ar gas for adjusting the concentration.
It is preferable to operate at a total pressure of 5 Torr and a total pressure of 100 Torr, preferably 50 Torr or less. The temperature range for precipitation is generally a wide range of about 800 to 2500 ° C., but in order to impregnate as much as possible, it is preferable to precipitate pyrolytic carbon in a relatively low temperature range of 1300 ° C. or less. The impregnated amount of pyrolytic carbon has a porosity of usually 0.4 or less, preferably 0.1.
Impregnate until it becomes about 3 to 0.1.

The felt compact containing the powder of the inorganic compound thus obtained has a greater risk of peeling than the method of adhering several layers of felt using a resin, and a thick compact can be obtained. it can.

Next, under an inert atmosphere or vacuum, 2000
The target carbon fiber reinforced carbon-inorganic compound composite material is obtained by performing heat treatment at ˜3000 ° C. That is, the heat treatment at a high temperature softens, melts, and decomposes the powder of the inorganic compound, and the carbon fiber-reinforced carbon-inorganic powder composite material in which the powder components are more uniformly dispersed can be obtained. Further, if necessary, a degassing process may be added in a vacuum furnace under the conditions of 10 Torr or less and 2000 ° C. or more.

According to the present invention, a carbon fiber-reinforced carbon-inorganic compound composite material having excellent oxidation resistance can be obtained without using a conventional binding material method or a hot pressing method. Furthermore, unlike the short carbon fiber dispersion type, since a felt is used, a long continuous carbon fiber is entangled in the material, and pyrolytic carbon is deposited to surround it to form a matrix. As a result, the carbon fiber felt, the inorganic powder and the pyrolytic carbon are firmly adhered to each other, and cracks, peeling, cracking and the like can be prevented by the excellent thermal shock resistance of the pyrolytic carbon. Further, the desired carbon fiber reinforced carbon-inorganic powder composite material can be obtained by changing the concentration of the slurry obtained by dispersing the powder of the inorganic compound in the solvent during the manufacturing process or by changing the type of the powder to be dispersed.

In summary, in the method of the present invention,

(A) A carbon fiber felt having a large porosity is impregnated deeply with at least one powder of boron, a compound thereof and a silicon compound having an effect of suppressing an oxidation reaction, and the fiber surface is impregnated with the powder. Finely dispersed and deposited,

(B) Further, pyrolytic carbon having a hardly-oxidizing property is deposited in the voids, and the surfaces of the fiber and the powder of the inorganic compound are covered with pyrolytic carbon,

(C) A carbon composite material having extremely high oxidation resistance can be obtained by further baking at a high temperature of 2000 ° C. or higher to further uniformly finely disperse the boron and silicon components.

The carbon-inorganic composite material obtained by such a combination of steps has a significantly higher oxidation resistance and thermal shock resistance than the conventional oxidation resistant carbon composite material due to the synergistic effect.

[0035]

The present invention will be described in detail below with reference to examples.

[0036]

Example 1 A graphitized rayon felt (fiber diameter 10 μm, density 0.05 / cm ³ ) was prepared. Boron carbide (manufactured by Kyoritsu Kiln Raw Materials Co., Ltd .: average particle size: 10 μm) was used as an inorganic compound powder in an amount of 2 k per 1 liter of methanol.
A slurry was prepared by dispersing at a ratio of g. While applying ultrasonic vibration to this slurry, 100 × 100 × 10
The felt having a shape of (mm) was infiltrated. Next, methanol was evaporated in a vacuum dryer at 50 ° C. for 5 hours to obtain a felt containing 70 wt% of boron carbide. This felt was overlaid and compressed with a graphite jig shown in FIG. 2 to a porosity of 0.8 to obtain a precursor. Put this together with the jig into the vacuum furnace,
A raw material gas was supplied at a ratio of methane: hydrogen = 1: 6 at 1200 ° C. and 30 Torr to impregnate the inside of the precursor with pyrolytic carbon.
When the porosity was taken out at the time of 0.3, the felt was firmly bonded by the pyrolytic carbon. Next, in a non-oxidizing atmosphere, it is heated to 2500 ° C. at a rate of 500 ° C./hr, kept for 30 minutes and subjected to high temperature treatment.
An inorganic compound composite material (100 × 100 × 50 (mm)) was obtained.

[0037]

Example 2 As an inorganic compound powder, 1 kg of silicon carbide powder having a particle size of 10 μm (manufactured by Kyoritsu Kiln Raw Materials Co., Ltd.) and 1 kg of titanium boride (TiB ₂ ) powder were mixed and dispersed in 1 liter of methanol. A carbon fiber-reinforced carbon-inorganic compound composite was obtained by the same method as in Example 1 except that the slurry thus obtained was used.

[0038]

Comparative Example 1 The same procedure as in Example 1 was carried out except that no inorganic compound powder was used.

[0039]

Comparative Example 2 A SiC layer having a film thickness of 100 μm was formed on the material obtained in Comparative Example 1 by a chemical vapor deposition method.

[0040]

[Comparative Example 3] As the temperature for high temperature treatment, the maximum temperature is 1
A composite was obtained in the same manner as in Example 1 except that the temperature was 800 ° C.

[0041]

[Experimental Example 1] The bulk specific gravity, bending strength, thermal conductivity and coefficient of thermal expansion of each material of Examples 1 and 2 and Comparative Examples 1, 2 and 3 were measured. The results are shown in Table 1.

[0042]

[Table 1]

[0043]

[Experimental Example 2] The materials of Examples 1 and 2 and Comparative Examples 1, 2 and 3 were heated at a predetermined temperature in advance, and this was heated to 20 ° C.
It was put into water and rapidly cooled, and it was examined whether cracks occurred. The sample shape was φ30 × 3 mm, and an isotropic graphite material (“IG-11” manufactured by Toyo Tanso Co., Ltd.) was used as a reference material. As a result, cracks did not occur at all even when the sample heated to a maximum temperature of 1500 ° C. was rapidly cooled in water. However, isotropic graphite materials (I
G-11) had fine cracks at 500 ° C.

[0044]

[Experimental Example 3] 20, 40, 60, 80, 10 for the materials of Examples 1 and 2 and Comparative Examples 1 and 2 at 800 ° C in air.
Oxidation consumption experiment was performed for 0 hours (sample shape 10 × 20 × 3
0 mm; rectangular parallelepiped shape). The oxidation consumption rate (Y) was obtained from [Chemical Formula 2].

[0045]

[Chemical 2]

M: sample weight before experiment (g) Nx: sample weight after X hours (g) The results are shown in Table 2.

Both Examples 1 and 2 show stable oxidation and wear resistance, and it can be seen that even after 100 hours have elapsed, the material is much less oxidative than the materials of Comparative Examples 1 and 2. In Comparative Example 2, when the sample was taken out of the furnace at the time of weighing 20 hours after the start of the experiment, the temperature was 800 ° C → 20 ° C.
Due to the thermal shock, a crack was generated in the SiC coating layer. After that, as in Comparative Example 1, oxidation consumption rapidly progressed.

[0048]

[Table 2]

[0049]

[Experimental Example 4] The materials of Example 1 and Comparative Example 3 were subjected to scanning electron microscope photographs of fracture surfaces and boron mapping with an X-ray microanalyzer. The results are shown in FIG. 5 (Example 1) and FIG. 6 (Comparative Example 3). However, FIGS.
Is a schematic diagram of each of them. It can be seen that the boron component in the material of Example 1 is uniformly dispersed in the fiber and matrix. It is considered that in Comparative Example 3, the boron component was localized, and therefore the effect of suppressing the oxidation was low.

[0050]

The carbon fiber-reinforced carbon-inorganic compound composite material produced in this manner is excellent in thermal shock resistance, and the weight loss rate due to oxidation after 100 hours in air at 800 ° C. is 10 wt% or less, which is stable for an extremely long time Shows sex. It is extremely suitable as a material for a fusion reactor, for example, a first wall, a neutron absorber, a spacecraft material, a jig for a metal melting device, for example, a material for a crucible, a boat, a nozzle for continuous casting.

[0051]

[Brief description of drawings]

[0052]

[Figure 1]

FIG. 1 is a flow sheet of an example of the method of the present invention.

[0054]

[Fig. 2]

FIG. 2 shows an example of a jig used for carrying out the method of the present invention.

[0056]

[Figure 3]

FIG. 3 is an explanatory view of the surface of a holding plate which is one of the constituent elements of the jig.

[0058]

[Figure 4]

FIG. 4 is an explanatory view of the surface of the holding plate which is one of the components of the above jig.

[0060]

[Figure 5]

FIG. 5 is a schematic diagram of a scanning electron microscope photograph (No. 1) of the material of the present invention and a photograph of boron mapping by an X-ray microanalyzer (No. 2).

[0062]

[Figure 6]

FIG. 6 is a schematic diagram of a scanning electron microscope photograph (No. 1) of the material of the comparative example and a photograph of boron mapping by an X-ray microanalyzer (No. 2).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhide Nagaoka 2181 Nakahime, Onohara Town, Mitoyo-gun, Kagawa Toyo Carbon Co., Ltd. Onohara Plant (72) Inventor Toshiharu Hiraoka 2181 Nakahime, Onohara Town, Mitoyo-gun, Kagawa Prefecture -2 Toyo Tanso Co., Ltd. Onohara factory

Claims (2)

[Claims] 1. A carbon fiber characterized in that a carbon fiber felt is loaded with at least one of boron, a compound thereof and a silicon compound, compressed if necessary, impregnated and precipitated with pyrolytic carbon, and then heat treated. A method for producing a reinforced carbon-inorganic compound composite material. 2. The manufacturing method according to claim 1, wherein the heat treatment temperature is 2000 ° C. or higher.