JPS6340765A - Isotropic carbon material - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to dense isotropic carbon materials (including graphite materials), and particularly to isotropic materials such as crucibles, cylinders, and rocket nozzles for semiconductor manufacturing. The present invention relates to a carbon material suitable for a member requiring thermal shock resistance.

Compared to other materials, carbon materials have high thermal conductivity, low thermal expansion, and are resistant to thermal shock.However, in recent years, the usage conditions for various applications have become harsher, and carbon materials have become more homogeneous, isotropic, high strength, and resistant to thermal shock. carbon materials are in demand.

BACKGROUND TECHNOLOGY The most common method for producing carbon materials is to add a binder such as pitch or resin to powder such as coke or graphite, and then form the powder, sinter it, and graphitize it if necessary. When molding is done by extrusion, the molded product becomes anisotropic, so when isotropy is particularly required, rubber press molding is also used. However, the above manufacturing method does not have sufficient strength and also has problems with thermal shock resistance. So in recent years, carbon m! Composite materials using I have been in the spotlight, and some are in practical use.

Problems to be Solved by the Invention Although composite materials using carbon fibers have high strength, they usually have anisotropy due to the orientation of the fibers. There is also a method in which this composite material is bonded to a carbon fiber woven or nonwoven fabric, and if necessary, carbon powder is added thereto and kneaded to disperse the carbon fibers in the kneaded material. In this case, the carbon iaB is made of relatively short fibers such as chopped yarn,
Fibers tend to aggregate, and it is difficult to disperse them nondirectionally and as uniformly as possible in a kneaded material. This makes it difficult to produce homogeneous products. Since molding in this case is generally performed by extrusion or molding, anisotropy is unavoidable.

An object of the present invention is to provide a carbon material that is homogeneous and isotropic and has high strength and excellent thermal shock resistance.

Means for Solving the Problems In order to achieve the above object, the present invention basically consists of carbon fibers, carbon powder, and carbonized carbon binders (carbide). The carbon fibers are uniformly and non-directionally dispersed by using a rubber press or the like. That is, carbon fibers having a size of 30 ILm to 2 mm and an aspect ratio of 5 or more are used, and the particle size of the carbon powder is 100 g or less, and these are dispersed non-directionally in the carbide matrix of the carbon binder. In the present invention, "carbon" includes "graphite", and "carbide" includes "graphitized material". Therefore, for example, when referring to carbon powder, it also means graphite powder.

As carbon fibers, in addition to PAN-based, pitch-based, etc. carbon fibers, those produced by the vapor phase method can also be used. The length needs to be at least 304 m in order to take advantage of its properties as a fiber, but on the other hand, if it is long, it has poor dispersibility, and is particularly likely to get entangled and become lumpy during kneading, so it must be 2+
It is necessary to keep it below ++m.

Carbon fiber is PAN type, and pitch type usually has a thickness of 7 to 1.
2JLm, and the ma of the gas phase method is extremely thin, for example 0
．． There are sizes ranging from 05JI 11th to the considerably thicker 10JLffi, all of which can be used. The thicker the fiber, the longer it is within the above range.

That is, in terms of aspect ratio (length/thickness), an aspect ratio of 5 or more is suitable, and an aspect ratio of 10 or more is desirable.

The carbon material of the present invention contains carbon fine powder. The reason why carbon fine powder is included in addition to carbon fibers is that if only short carbon fibers are used, it is difficult to disperse the TA fibers during mixing, so a homogeneous material cannot be obtained, and in order to obtain a more isotropic material. .

For these purposes, the carbon fine powder must be 1001L11 or less.

As the carbon binding material, pitch or synthetic resins such as phenol resin and furan resin are used, and these become carbides and constitute a matrix in the carbon material of the present invention. The above-mentioned carbon fibers are non-directionally, ie, three-dimensionally, randomly dispersed in this matrix, and carbon fine powder is also uniformly dispersed in the matrix. and carbon ta
Male, carbon fine powder is bonded together in a matrix to form a carbon material.

The carbon fibers dispersed in the carbon material are 5 to 60% by weight (
It is preferable that the following percentages are based on weight). If it is less than 5%, the effect of carbon short fibers will be reduced, and properties such as thermal shock resistance will be equivalent to ordinary isotropic materials, and if it exceeds 80%, it will be difficult for carbon short fibers to be randomly dispersed, resulting in differences in properties. This is because the square ratio tends to increase.

The carbon fiber content is preferably 10 to 60% by weight.

If it is less than 10, the material will not be homogeneous and the density will tend to decrease. This is because if it exceeds 60%, it becomes close to a normal isotropic material and the thermal shock resistance tends to decrease.

The carbon material of the present invention preferably has a bending strength of 300 kg/
crn' or more. And the anisotropy is small. For example, if anisotropy is expressed in terms of bending strength, the strength ratio falls within the range of 0.9 to 1 even if the difference is greatest in the direction of the carbon material.

To produce the carbon material of the present invention, the above-described carbon powder, carbon ram, and binder are mixed and kneaded using a mixer. When the binder is pitch, kneading is usually carried out at a temperature of 130 DEG to 200 DEG C. A suitable mixing time is 45 minutes to 1.5 hours.

After mixing is completed, the next step is molding, and a rubber press is suitable for molding to reduce anisotropy. Rubber press molding is usually carried out by crushing the solidified mass after mixing and filling the powder into a rubber mold. Depending on the particle size during pulverization, carbon m
It is best to avoid grinding too finely as some of the fibers will be cut off.

The shape of the molded body can be various as desired, but it is difficult to make it too complicated, so the molded body is fired to form a carbon material and then machined. Molding pressure is 50
Approximately 0 to 1500Kg/crn2 is suitable.

Firing of the molded body is the same as in the case of ordinary carbon materials. After firing, it can be impregnated with pitch or the like and fired again. Furthermore, if necessary, heat at a high temperature of 2800°C or higher,
It can also be graphitized.

Next, examples of the present invention will be described.

Example 1 Pitch coke was pulverized to 74 cm or less, and a binder (
coal tar pitch), carbonaceous staple fiber (pitch type diameter 7
The blending ratio of 60% by weight of pitch coke, 10% by weight of short fibers, and 30% by weight of binder was kneaded at 160°C for 1 hour, and then cooled to reduce the particle size to 150p, m or less. Crush it, fill it into a rubber mold, mold it with a rubber press at 1000Kg/Cm',
A molded article having a size of about 250 layers and a diameter of 500 mm was obtained. This molded body was fired at 1000°C by a known method, impregnated with pitch, fired a second time, and further graphitized at 2800°C. Its composition is shown in Table 1, and its bulk density, bending strength, rippability, and thermal shock resistance are shown in Table 2.

Example 2 Using the same raw materials as Example 1, the blend was pitch coke.
50% by weight, short fibers 20% by weight, and binder 30% by weight. Further, it was molded in the same manner and heat treated in the same manner. Its composition is shown in Table 1, and its various properties are shown in Table 2.

Example 3 Using the same raw materials as in Example 1.2, the composition was 40% by weight of pitch coke, 30% by weight of short m fiber, and 3 binders.
It was set to 0% by weight. The heat treatment was also the same. Its composition is shown in Table 1.
The properties are shown in Table 2.

Comparative Example 1 Pitch coke (74 pm or less), carbonaceous short fiber (pitch type diameter 7 to 10 μm, length 3000 to 5000 pi),
Binder (coal tar pitch) 40% by weight each
, #F#/FIIi 30% by weight, two; 130% by weight
And so. Molding and heat treatment were the same.

Its composition is shown in Table 1, and its various properties are shown in Table 2.

Comparative Example 2 A binder (coal tar pitch) was added to 70% pitch coke (744 m below) and 30% by weight, and molding and heat treatment were performed in the same manner. Its composition is shown in Table 1, and its various properties are shown in Table 2.

Table 2 Various Properties [Average value of n=20 excluding River] 10 disk-shaped samples of Bowsφ×5×1 were collected for each graphite material. A 2000 ampere intake current was passed through the center (17mmφ) of these samples, and a thermal stress fracture test was conducted using the resistance heat generation. 4. The presence or absence of fracture was determined using a soft X-ray transmission device. .

The anisotropy ratio was expressed as a value in the longitudinal direction/radial direction for each average value of 10 pieces in the radial direction and 10 pieces in the longitudinal direction, based on electrical resistivity.

Effects of the Invention As is clear from Tables 1 and 2, the graphite material provided by the present invention is more isotropic and has superior thermal shock resistance compared to conventional homogeneous graphite materials, so it can withstand high temperatures. It is extremely useful as a required member.

Claims (2)

[Claims] (1) An isotropic carbon material in which non-directionally dispersed carbon fibers with a length of 30 μm to 2 mm and an aspect ratio of 5 or more and carbon powder with a particle size of 100 μm or less are bonded together by a carbide of a carbon binder. (2) The isotropic carbon material according to claim 1, wherein the carbon fiber content is 5 to 60% by weight, and the carbon powder content is 10 to 60% by weight.