JP2995583B2 - Composite carbon fiber used for carbon bonded carbon fiber composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite carbon fiber,
For more information, Carbon-bonded carbon fiber composites for space, aviation and defense
The present invention relates to a composite carbon fiber used for a carbon-bonded carbon fiber composite material such as a material and an automobile part.

[0002]

2. Description of the Related Art It is well known that carbon-bonded carbon fiber composite materials (C / C composites) are commonly used as high-strength lightweight structures, especially at high temperatures. However, the carbon-bonded carbon fiber composite material (C / C composite) is a matrix carbon base material.
Abrasion resistance, oxidation resistance and elasticity
There was a limit in every respect.

[0003] Therefore, conventionally, the surface of carbon fiber is subjected to CVD processing, PVD processing, plating, and thermal spraying to obtain SiC, WC,
Attempts have been made to deposit TiC, W, Mo, Cu and the like to suppress the reaction with oxidizing gas and improve the sliding characteristics .

[0004]

However, the conventional deposition, coating, or the like of a metal or the like on a carbon fiber surface by a CVD process, a PVD process, a plating process, a thermal spraying process, etc. , as shown in FIG. Since the surface of the carbon fiber 19 and the coating material 21 are bonded to each other by physical adhesion such as van der Waals force,
When the composite with matrix carbon is repeatedly used under a high temperature under a high load due to insufficient interfacial adhesion with No. 1 , not only the problem of rapid deterioration of strength but also the wear resistance
Wear, oxidation resistance and elasticity were also limited.

[0005]

The present invention SUMMARY OF THE INVENTION, which has been made with respect to the above-mentioned problems, not only is no Succoth to put the composite material produced strength degradation at high temperatures,
Carbon bonded carbon fiber with excellent wear resistance, oxidation resistance and elasticity
An object of the present invention is to find carbon fibers used as a raw material of a composite material . That is, the present invention provides a carbon-bonded carbon fiber composite material.
(C / C composite)
A composite carbon fiber obtained by converting a surface layer of carbon fiber into silicon carbide, wherein the crystal structure of the silicon carbide is mainly composed of a polytype of 2H or 3C, or a mixture of a polytype of 2H and 3C. The gist of the present invention is a composite carbon fiber.

As a method of converting the carbon fiber surface layer into silicon carbide, there is a method of reacting with silicon vapor or various silicon compounds, or a method of applying pack cementation. The most preferable method is a method of converting silicon monoxide gas. There is a method of reacting carbon fibers according to the following formula. SiO (g) + 2C = SiC + CO (g) By using this method, the crystal structure of 2H, 3C, 4H, 15R, 6H or the like by Ramsdale notation while maintaining the shape and dimensions of the carbon fiber 19 as shown in FIG. The silicide layer 20 having (polytype) can be formed.

This reaction proceeds by heating in a temperature range of 1200 ° C. to 2000 ° C. Here, in order to generate silicon monoxide gas, a mixture of silicon powder and silicon dioxide powder, a mixture of silicon carbide powder and silicon dioxide powder, a mixture of carbon powder and silicon dioxide powder, and other various silicon It can be carried out by heating the compound to 1200 ° C to 2000 ° C.

When the surface of carbon fiber is converted into silicon carbide by reacting carbon fiber with silicon monoxide, the treatment temperature is set at 12
By selecting in the range of 00 ° C to 1650 ° C, unreacted carbon remains in the silicide layer on the surface of the carbon fiber, and silicon carbide having a crystal structure of 2H as a main component can be generated, It is possible to produce a material in which the silicidation rate, which is the weight ratio of silicon carbide, is variously changed. The thickness of the silicide layer on the carbon fiber surface can also be controlled by adjusting the processing time in addition to the processing temperature. In addition, the silicidation rate and the thickness of the silicide layer can be controlled by adjusting the concentration of silicon monoxide.

Similarly, by selecting the reaction temperature between carbon fiber and silicon monoxide in the range of 1650 ° C. to 2000 ° C., unreacted carbon remains in the silicide layer on the surface of carbon fiber, and the crystal structure becomes 2H. And 3C polytype, or silicon carbide mainly containing 3C polytype.

At least 10% by weight of unreacted carbon in the entire composite carbon fiber in which the carbon fiber surface layer has been converted to silicon carbide.
It is desirable to keep the above. Thereby, the flexibility of the carbon fiber due to the sea-island structure of carbon and silicon carbide can be ensured.

Next, a method of continuously firing and producing carbon fibers will be described with reference to the drawings. FIG. 1 is a schematic view of an apparatus for producing a composite carbon fiber of the present invention. In FIG. 1, reference numeral 1 denotes a pre-carbonized fiber or a carbon fiber, which is treated at 150 ° C. to 300 ° C. using a preheater 2. Atmosphere gas in the furnace is introduced from the gas supply port 3, and exhaust gas is taken out from the exhaust gas ports 7 and 13 in the furnace.

Further, a sealing gas flows from a supply port 15 from a water seal portion provided with a sealing water bath 17 in the furnace, and is taken out from exhaust gas ports 7 and 13 in the furnace.

The fiber subjected to the preheat treatment is heated at 1000 ° C. to 3000 ° C. by the carbonizing heater 5 and carbonized. The carbon fiber that has been subjected to the above processing moves to the silicidation zone divided by the slits 12 and 14, and the surface layer is converted into silicon carbide. Here, the silicidation zone is adjusted to 1200 ° C. to 2000 ° C. using the heater 6 for silicification. Further, the silicon monoxide gas can be generated by heating the silicon monoxide gas generation source 10 in the graphite crucible 9 to 1200 ° C. to 2000 ° C. React with fiber. 1
Induction heating coil 8 for heating to 200 ℃ ~ 2000 ℃
Can be used to heat the graphite crucible 9. The residual silicon monoxide gas is exhausted from an exhaust gas port 13 in the furnace.

The carbon fiber whose surface layer has been converted into silicon carbide is cooled through a cooling zone defined by slits 14 and 18 and emerges from a water seal portion provided with slits 16.

The carbon fibers used here are not particularly limited, but pitch-based carbon fibers are suitable from the viewpoint of easy conversion to silicon carbide.

[0016]

The present invention is characterized in that silicon monoxide gas permeates and diffuses through the carbon fiber surface layer and reacts with the carbon fiber itself to convert it to silicon carbide. Or, it is fundamentally different from the one in which the same substance or another substance is deposited and coated on the carbon fiber surface such as plating, thermal spraying, and coating.

That is, the surface of the carbon fiber obtained by the CVD method, the PVD method, or plating, thermal spraying, coating, or the like is formed by bonding the deposited film material and the carbon fiber surface only by physical adhesion by van der Waals force or the like. When used as a fiber filler of a composite material, when repeatedly used at a high temperature, the deposited coating material is peeled off due to a difference in thermal expansion and the like, and the deterioration of strength is stopped.

However, the silicon carbide layer on the surface of the carbon fiber of the present invention has a completely continuous structure at its boundary since the fiber itself has been changed by reacting with silicon monoxide. The silicide layer does not peel off.

Further, since the silicon carbide layer on the surface of the carbon fiber of the present invention has the same porosity as that of the carbon fiber, the silicon carbide layer has a lower thermal shock resistance than those having almost no pores such as a deposited film formed by a CVD method or a PVD method. Since the matrix is high and penetrates into the micropores of the silicon carbide layer, a so-called anchor effect works, so that the matrix is more firmly bonded to the matrix.

On the other hand, it was found that the function of the crystal structure is to increase the flexibility of the composite carbon fiber by making the crystal structure of silicon carbide on the surface of the carbon fiber of the present invention a 2H polytype as a main component. did. Although the reason is not clear, it can be presumed that the contribution of the ionic cohesion energy of the silicon carbide crystal component of 2H is large.

Further, by making the crystal structure of silicon carbide on the surface of the carbon fiber a 3C polytype as a main component, the characteristic of increasing the strength at 1200 ° C. or more inherent in the 3C silicon carbide crystal component is exhibited, and High temperature strength can be increased.

Similarly, a composite carbon fiber having both flexibility and high-temperature and high-strength characteristics can be obtained by making the crystal structure of silicon carbide on the surface of the carbon fiber mainly a mixture of polytypes of 2H and 3C. Can be.

In addition, the composite carbon fiber filler of the present invention has a large 3D polycrystalline structure due to the action of a silicon carbide component having a 3C polytype crystal structure, in comparison with the ordinary carbon fiber filler in terms of the wear resistance of the composite material. It was found to improve.

The present invention includes not only single carbon fibers but also various mats or cloths assembled in one-dimensional or higher dimensions, or various non-woven fabrics or yarns. It is extremely effective as well. Next, the present invention will be specifically described with reference to examples.

[0025]

EXAMPLE A pitch-based fiber (2 denier, number of filaments 10,000) was calcined by carbonization and silicidation using the apparatus shown in FIG. A nitrogen gas containing a predetermined amount of oxygen was sent from the gas supply port 3, and a nitrogen gas was sent from the gas supply port 15.

The silicon monoxide gas generating source 10 puts 300 g (molar ratio 1: 1) of a mixture of silicon powder and silicon dioxide powder into a graphite crucible 9 and heats it to 1600 ° C. by induction heating.
Silicon monoxide was generated. The temperature in the furnace was adjusted as shown in FIG. 2 using a preheater 2, a calcination heater 5, and a silicification heater 6. The thus obtained composite carbon fiber having a surface layer made of silicon carbide having a 2H polytype as a main component was rich in flexibility .

[0027]

As described above, the carbon bond of the present invention
Composite carbon used for carbon fiber composite material (C / C composite)
The elementary fiber converts the surface layer of carbon fiber into silicon carbide,
Polytypes of crystal structure 2H or 3C, or 2
Since a mixture of H and 3C polytype is converted into silicon carbide having a main component, wear resistance, oxidation resistance and elasticity are improved.
It is possible to produce carbon-bonded carbon fiber composites
Wear.

Also, utilizing the flexibility characteristic of the 2H polytype and the mechanical strength increasing effect at 1200 ° C. or higher, which is a characteristic of the 3C polytype, carbon-bonded carbon which does not undergo strength deterioration up to high temperatures. A fiber composite can be obtained.

In the production of the composite carbon bicomponent fiber of the present invention,
By freely adjusting the silicidation temperature, treatment time, silicon monoxide gas concentration, etc., it is possible to obtain carbon fibers with various silicidation rates, and to slide mechanical seals made of carbon-bonded carbon fiber composites. Characteristics can also be easily controlled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus for producing a composite carbon fiber of the present invention.

FIG. 2 is a graph showing an example of a temperature distribution in the composite carbon fiber manufacturing apparatus shown in FIG.

FIG. 3 is a cross-sectional view of a carbon fiber and a composite carbon fiber of the present invention.

FIG. 4 is a cross-sectional view of a carbon fiber and a composite carbon fiber whose surface is coated by CVD, PVD, coating, or the like.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fiber 2 Preheater 3,15 Gas supply port 4,12,14,16,18 Slit 5 Heater for firing carbonization 6 Heater for silicification 7,13 Exhaust gas port 8 Induction heating coil 9 Graphite crucible 10 Silicon monoxide gas source 11 Silicon Monoxide Gas Supply Port 17 Water Bath for Sealing 19 Carbon Fiber 20 Silicide Layer 21 Coating Material

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI D06M 11/00 C04B 35/52 G

Claims (1)

(57) [Claims] 1. A carbon-bonded carbon fiber composite material (C / C composite)
The carbon fibers used in the body)
A composite carbon fiber in which a face layer is converted into silicon carbide, wherein the silicon carbide has a polytype of 2H or 3C crystal structure,
Alternatively, a composite carbon fiber comprising a mixture of a polytype of 2H and 3C as a main component.