JPH05201763A - Production of carbon/carbon composite material - Google Patents

Abstract

PURPOSE:To produce a carbon/carbon composite material without using an expensive fabric of carbon fibers or carrying out a complex forming process before a densifying process. CONSTITUTION:Carbon pitch is spun and made infusible. The resulting infusible fibers are carbonized and compacted under a uniaxial pressurization to form a primary compact having 5-70vol.% void volume and 0.1-1.8g/cm<3> bulk density. This primary compact is densified with a carbonaceous matrix. Since the primary compact can be produced without using a binder, a carbon/carbon composite material is produced with considerably increased efficiency.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a carbon / carbon composite material.

[0002]

2. Description of the Related Art Carbon / carbon composite materials are materials having unique properties such as high strength and high elastic modulus even at a high temperature of 1000 ° C. or higher and a small coefficient of thermal expansion. It is expected to be used for parts, brakes, furnace materials, etc.

The shape of the aggregate of carbon fibers used in these carbon / carbon composite materials is mainly a two-dimensional woven fabric,
Three-dimensional fabrics are also used depending on the application. Although high strength carbon / carbon composite materials are obtained using these fabrics, the structure and manufacturing method of the fabrics are complicated and expensive.

On the other hand, when a short fiber carbon fiber such as so-called chopped fiber is used, a sufficient reinforcing effect is usually not obtained. In addition, when performing the densification step of producing a carbon / carbon composite material from the above-mentioned woven fabric or short fiber carbon fiber,
It is necessary to separately perform the process of fixing the carbon fibers with pitch or thermosetting resin (binder).
This is one of the causes for lowering the productivity in the carbon composite material manufacturing process.

[0005]

An object of the present invention is to provide a method for producing a carbon / carbon composite material without using an expensive carbon fiber woven fabric.

[0006]

According to the present invention, the infusibilized fiber obtained by spinning carbonaceous pitch and further infusibilizing it is carbonized and molded under uniaxial pressure to obtain a porosity of 5 to 70.
vol%, bulk density 0.1 to 1.8 g / cm ² of a primary compact, and the primary compact is densified with a carbonaceous matrix, and a method for producing a carbon / carbon composite material, and a carbonaceous pitch Is spun, and the infusible fibers obtained by further infusibilizing treatment are filled into the container by forced shaking or free fall, carbonization and molding are performed under uniaxial pressure, porosity 5 to 70 vol%, bulk density 0. 1 to 1.8 g / cm ²
The present invention relates to a method for producing a carbon / carbon composite material, which comprises densifying the primary molded body with a matrix formed by chemical vapor deposition and / or a matrix using carbonaceous pitch as a starting material.

The method for producing the carbon / carbon composite material according to the present invention will be described in detail below.

The infusible fiber in the present invention is a fiber obtained by infusibilizing pitch fiber. The pitch fiber here is a fiber having an average diameter of usually 5 to 100 μm, preferably 7 to 30 μm, which is obtained by melt spinning carbonaceous pitch by a known method.

The carbonaceous pitch is not particularly limited, and known ones can be used, and the softening point is usually 100-40.
It is desirable to use coal-based or petroleum-based pitch having a temperature of 0 ° C, preferably 150 to 350 ° C. Also,
As the carbonaceous pitch, either an optically isotropic pitch or an anisotropic pitch can be used, but an optically anisotropic pitch having an optically anisotropic phase content of 60 to 100% is particularly preferable. Used.

The infusibilizing treatment can be carried out in an oxidizing gas atmosphere at usually 50 to 400 ° C., preferably 100 to 350 ° C. As the oxidizing gas, air, oxygen, nitrogen oxide, sulfur oxide, halogen, or a mixture thereof can be appropriately used. The treatment time is such a time that the fibers do not show heat-welding property, and is usually 10 minutes to 20 hours, preferably 30 minutes to 10 hours.

In the present invention, the infusible fiber is carbonized and molded under uniaxial pressure to obtain a primary molded product having a porosity of 5 to 70 vol% and a bulk density of 0.1 to 1.8 g / cm ² .
Preferably, the infusibilized fiber is forcibly dropped or free-falled into the container and stacked or spontaneously deposited in the container or the like to be filled. At this time, the infusible fibers are continuous fibers or 1 to 10
It is laminated or deposited in the form of 0 cm short fibers.

As a method for filling the continuous fiber into a container or the like, for example, a fiber infusible in a container such as a basket is dropped as it is into a container for uniaxial pressing, or the infusible fiber is once sent to a pulley and uniaxially applied. Examples thereof include a method of uniformly filling the container for pressure, a method of forcibly transferring and filling the infusible fiber into the container via an air ejector, and the like.

As a method for filling short fibers into a container or the like, for example, a method of freely dropping infusibilized fibers made into short fibers into a container for uniaxial pressurization and depositing and filling them, continuous fibers on the container Examples include a method of supplying, cutting with a cutter or the like, and dropping.

In any of the above filling methods,
It is desirable to fill evenly, for which purpose it is also preferred to move the filling device and / or the filling container such that the dropping position or the filling position moves during filling, for example. Further, it is preferable to use a die for uniaxial pressurization as the container for uniaxial pressurization because the process is simplified. Before or after carbonization / molding under uniaxial pressure, needle punching may be performed in a direction perpendicular to the fiber laminating surface direction.

The method of carbonizing and forming under uniaxial pressure is as follows:
Usually 1-100kg / c by hot press machine
m ^2, preferably to 50 kg / cm ^2, more preferably under a pressure of 2~20kg / cm ^2, usually from 400 to 200
At 0 ° C, preferably 500 to 1000 ° C, usually 1
It is carried out by treating for 0 minutes to 10 hours, preferably for 30 minutes to 4 hours. The atmosphere at this time is preferably a non-oxidizing atmosphere such as nitrogen, helium, neon, argon, xenon, or radon. Further, if the treatment is performed at a relatively low temperature, for example, at a temperature of about 400 to 600 ° C. for a short time, it can be performed even in an oxidizing atmosphere.

The porosity of the obtained primary molded body is usually 5 to
70 vol%, preferably 10 to 60%, more preferably 15 to 50%. When the porosity exceeds the above range, the shape retention of the primary molded article is deteriorated and the molded article may be lost or deformed in the subsequent densification step, which is not preferable. Further, when the porosity is less than the above range, the primary molded body causes brittle fracture and behaves like a monolithic material, so that the carbon / carbon composite material has the original characteristics after densification. Is not shown, which is not preferable.

The bulk density of the obtained primary molded body is
Usually 0.1 to 1.8 g / cm ² , preferably 0.2 to
1.7 g / cm ² , more preferably 0.5 to 1.6
It is g / cm ² . If the bulk density is less than the above range, the shape retention of the primary molded article is deteriorated, and the molded article may be lost or deformed in the subsequent densification step, which is not preferable. When the bulk density exceeds the above range, the carbon / carbon composite material after densification becomes brittle and behaves like a monolithic material. Is not preferable because it cannot be used.

Carbonization under uniaxial pressure may be followed by carbonization or graphitization under normal pressure. In this case, under a non-oxidizing atmosphere, the temperature is usually 400 to 3000 ° C., preferably 500 to 2500 ° C. It can be carried out below.

In the present invention, the carbon / carbon composite material is manufactured by densifying the primary compact. The method of densification is not particularly limited as long as it is a method of forming a carbonaceous matrix, and a known method can be used. In particular, a densification matrix and / or a matrix using pitch as a starting material can be used for densification. A preferred method is to use

In the case of densification by chemical vapor deposition, for example, hydrocarbons such as methane, ethane, acetylene, propane, benzene and natural gas, or at least one or more of them diluted with an inert gas or hydrogen. Pyrolytic carbon is deposited in the primary compact by thermal decomposition using the material as a raw material. As the inert gas, for example, helium, neon, argon, xenon, radon or the like can be used.

The thermal decomposition temperature is usually 700 to 3000 ° C.,
It is preferably 800 to 2500 ° C. Pyrolysis pressure is
Although it can be carried out at normal pressure, reduced pressure is preferable, and specifically, it is usually 0.5 to 100 Torr, preferably 0.5.
~ 50 Torr.

An inert gas or a diluting gas such as hydrogen can be used for the purpose of controlling the reaction rate. In that case, these diluting gases are used for the above hydrocarbon gas.
Usually, it is desirable to use a volume of 0.1 to 1000 times, preferably 1 to 100 times. When the proportion of the diluent gas is less than the above range, a sufficient dilution effect cannot be obtained, and when the proportion of the diluent gas is more than the above range, the reaction rate decreases unnecessarily, Not preferable.

In the case of densifying with a matrix having pitch as a starting material, a method of impregnating a primary molding with carbonaceous pitch and then carbonizing is usually used. The carbonaceous pitch is not particularly limited, and known ones can be used. Particularly, it is desirable to use coal-based or petroleum-based pitch having a softening point of usually 100 to 400 ° C, preferably 150 to 350 ° C. As the carbonaceous pitch, either an optically isotropic pitch or an anisotropic pitch can be used, but the content of the optically anisotropic phase is 60 to 100.
% Optically anisotropic pitch is particularly preferably used. The impregnation method is not particularly limited and may be a known method, for example, by sealing the primary compact and the carbonaceous pitch in a vacuum container and heating and melting under reduced pressure. The pressure reduction in this case is, for example, 1 × 10 ^{−2 to} 3
It can be performed at about 00 Torr. The heating temperature is usually the softening point temperature of the carbonaceous pitch or higher and lower than the decomposition start temperature, preferably 30 ° C. or higher and lower than the decomposition start temperature, and more preferably 180 to 450 ° C. higher than the softening point temperature.

Carbonization is preferably carried out under pressure or by pressing. The carbonization under pressure is carried out, for example, by applying a vacuum to a container containing the impregnated primary molded body, and then, for example, with a non-oxidizing gas such as argon, helium, radon, neon, and optionally N ₂ , preferably argon, usually at 50 to 1000
0 kg / cm ² , preferably 100 to 2000 kg / c
pressurized to m ^2, 400~2000 ℃, preferably 500
It is carried out by heating to ˜1500 ° C.

The carbonization under the press is usually 10 to 500 kg / cm ² , preferably 20 to 500 by hot pressing.
Uniaxially pressurized to 200 kg / cm ² , usually 400-200
It is carried out by heating to 0 ° C, preferably 500 to 1500 ° C.

[0026]

According to the present invention, a primary molded body can be manufactured by a simple process, and a carbon / carbon composite material can be manufactured by a simple method.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 An optically anisotropic petroleum pitch having a softening point of 280 ° C. was melt-spun and an average diameter of 13 μm was obtained.
m pitch fibers were obtained. This tow of 2000 pitch fibers was infusibilized in air to obtain an infusibilized fiber tow.
Pass this infusible fiber tow through the pulley as it is as continuous fiber,
The hot press die was continuously fed into the die from above. The die was moved so that the infusible fibers were evenly deposited inside the die. (Fig. 1) 5kg / cm by hot pressing after filling the infusible fiber in the die
Under pressure of ² , at 700 ° C., press carbonization was carried out for 1 hour to obtain a primary compact having a porosity of 25% and a bulk density of 1.1 g / cm ² . The shape did not change even when the primary molded body was taken out from the die.

The primary compact was subjected to chemical vapor deposition using methane as a raw material gas at 1200 ° C. and 1.5 Torr.
Was densified for 120 hours to produce a carbon / carbon composite material. The porosity of the obtained carbon / carbon composite material was about 4%, and no crack was observed. The obtained carbon / carbon composite material retained the shape of the primary molded body.

Example 2 An optically anisotropic petroleum pitch having a softening point of 280 ° C. was melt-spun and the average diameter was 13 μm.
Fiber having a pitch of. This tow of 2000 pitch fibers was infusibilized in air at 300 ° C. for 1 hour. The obtained infusible fiber tow was passed through a pulley as it was as a continuous fiber, and continuously fed into the die from above the hot pressing die. The die was moved so that the infusible fibers were evenly deposited inside the die. After filling the infusible fiber into the die, it is press carbonized for 1 hour at 600 ° C. under a pressure of 10 kg / cm ² by hot pressing to obtain a porosity of 3
The primary molding was 0% and the bulk density was 1.1 g / cm ² .
The primary compact was fired in nitrogen at 1000 ° C. under atmospheric pressure to obtain a compact having a porosity of 30% and a density of 1.2 g / cm ² . The molded body retained the shape of the primary molded body.

The molded body was subjected to chemical vapor deposition using methane as a raw material gas at 1100 ° C. and 1 Torr.
A densification treatment was performed for 20 hours to produce a carbon / carbon composite material. The obtained carbon / carbon composite material had a porosity of about 4% and no cracks were observed. The obtained carbon / carbon composite material retained the shape of the primary molded body.

(Comparative Example 1) Carbon fiber tow was passed through a pulley as it was as a continuous fiber, and continuously fed into the die from above the hot pressing die. The die was moved so that the carbon fibers were evenly deposited inside the die. After filling the die with carbon fiber, hot press 10k
It was pressed at 600 ° C. for 1 hour under a pressure of g / cm ² , and further baked at 1000 ° C. in nitrogen under atmospheric pressure. In the obtained fired body, fibers were not fixed and the porosity was large. When this was densified by chemical vapor deposition using methane as a raw material gas at 1100 ° C. and 1 Torr for 120 hours, the compact was swollen and deformed, and the dispersion of the fibers became nonuniform.

[0033]

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus used in Examples.

[Explanation of symbols]

 1. Infusible fiber 2. Die for hot press 3. pulley

Claims (2)

[Claims] 1. An infusible fiber obtained by spinning carbonaceous pitch and further infusibilizing treatment is carbonized and molded under uniaxial pressure to obtain a porosity of 5 to 70 vol% and a bulk density of 0.1 to 10.
A method for producing a carbon / carbon composite material, which comprises forming a primary compact of 1.8 g / cm ² and densifying the primary compact with a carbonaceous matrix. 2. An infusible fiber obtained by spinning carbonaceous pitch and further infusibilizing treatment is forcibly shaken or free-falling and filled in a container, carbonized and molded under uniaxial pressure, and porosity 5 ~ 70 vol%, bulk density 0.1-1.8
Production of a carbon / carbon composite material, characterized in that it is a g / cm ² primary compact, and the primary compact is densified with a matrix by chemical vapor deposition and / or a matrix using carbonaceous pitch as a starting material. Law.