JP2721557B2 - Coiled carbon fiber and carbon composite - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coiled fiber consisting essentially of carbon and a carbon composite material using the same.

Carbon fiber is useful as a raw material for reinforcement of high-temperature high-strength composite materials, and various applications have been made. In particular, the present invention has a coil-like shape having a spring property, and has a micromechanical element, a cushioning material, a switching element, The present invention relates to a completely new carbon fiber applicable as such, and a composite material of the carbon fiber and carbon.

[Prior art] Carbon fibers are generally obtained by carbonizing or graphitizing organic fibers (precursors) such as PAN-based or pitch-based organic fibers, but the fibers are formed directly by gas phase pyrolysis of hydrocarbons. A method has been proposed, and attention has been paid to functional materials utilizing various functions such as conductivity, thermal conductivity, and adsorptivity other than the conventionally required strength. As a method for producing carbon fiber by this gas phase pyrolysis method, Japanese Patent Publication No. 51-33210 discloses a mixed gas of hydrocarbon and carrier gas at 1030 to 1300 ° C.
Into the core tube held at a flow rate of 100 to 1500 cm / min to form nuclei for fiber growth, and then increase the flow rate to 10 to 30 cm / min.
A method for growing fibers as a fraction is disclosed. In addition, various proposals have been made, such as those characterized by a catalyst for efficiently producing carbon fibers, or those characterized by a method for dispersing the catalyst, but examples in which coiled carbon fibers were obtained There is no.

[Specific Means for Solving the Problems] In the course of studying a method for obtaining carbon fibers by gas phase pyrolysis of hydrocarbons, the present inventors have found that a coiled shape which has never been known before under specific reaction conditions. The present inventors have found that a carbon fiber exhibiting the following formula is obtained, and have reached the present invention. That is, the present invention is a coil-shaped fiber obtained as a result of a gas phase pyrolysis reaction consisting of substantially amorphous carbon having a fiber diameter of 0.05 to 5 μm, wherein the outer diameter of the coil is 2 to 10 times the fiber diameter. , Turns 10μ
A coiled carbon fiber characterized by being in the range of 5 to 50 times the reciprocal of the coil outer diameter (μm) per m, and a carbon composite material composed of carbon containing the coiled carbon fiber, Ni metal In a system where is present, a carbon fiber is deposited by causing a gas phase pyrolysis reaction of a mixed gas containing hydrogen gas or a diluent gas in a molar ratio of 1 to 5 times with an acetylene gas in a range of 400 to 900 ° C. An object of the present invention is to provide a method for producing the coiled carbon fiber and a method for producing a carbon composite material in which a molded body in which the coiled carbon fiber is dispersed in a resin is subjected to a densification treatment for filling pores.

As the hydrocarbon used in the present invention, acetylene,
Examples thereof include unsaturated hydrocarbons such as ethylene and propylene, and saturated hydrocarbons such as ethane, propane and butane. Among them, acetylene is most preferable from the viewpoint of the catalytic action of Ni metal. In the case of a low-molecular substance such as methane, 1200 to 1300 ° C. is required for gas phase pyrolysis, and benzene also requires a temperature exceeding 1000 ° C., so that coiled carbon fibers cannot be obtained.

A mixture of acetylene gas and hydrogen is used, and the molar ratio is preferably up to 10 times, more preferably 1 to 5 times. By adding hydrogen, the pyrolysis reaction temperature can be controlled, and as a result, the shape of the coil can be controlled. If it exceeds this range, the thermal decomposition reaction of acetylene gas will be excessively suppressed. In addition, it is of course possible to use a diluting gas such as argon, nitrogen or helium, which is useful for controlling the coil shape. The amount of diluent gas is a molar ratio to acetylene gas.
The range is preferably up to 10 times, more preferably 1 to 5 times.

The reaction temperature is in the range of 300 to 1000 ° C., more preferably 400 to
It is in the range of 900 ° C. If the temperature is lower than this, no thermal decomposition reaction occurs. On the other hand, when the temperature exceeds this temperature, the obtained fiber becomes linear, and a coiled fiber cannot be obtained.

The reaction pressure is preferably in the range of 200 mmHg to atmospheric pressure, and if it is out of this range, it becomes difficult to control the reaction.

In the present invention, it is necessary that a Ni metal catalyst be present, and an alloy thereof may be used. In the absence of a Ni metal catalyst, coiling is difficult.

This Ni metal catalyst itself can be used as a substrate. In this case, it is preferable to polish the surface. In addition, fine particles of Ni metal or its alloy are sprayed on the substrate or in the reaction system. An organic compound of Ni metal is introduced into the reaction system together with acetylene gas, and a thermal decomposition reaction is performed in a high temperature part. Means such as applying or spraying a solution of a Ni metal salt on the substrate or in the reaction system can be used.

On the lower temperature side even within the reaction temperature range of the present invention, it is necessary that the Ni metal catalyst be present in the reaction system in powder form. By such means, coiled carbon fibers can be produced at lower temperatures, although the reason for this is not always clear, but powdered Ni catalysts are extremely active, and due to this activity, they are efficient even at lower temperatures. It is presumed that the thermal decomposition proceeds and turns into a coil.

In the present invention, a boron source, a nitrogen source, and various gases serving as a silicon source are mixed and added as raw material gases, so that 0 to 10 wt% of B,
N and Si can be contained.

Although the coiled carbon fiber of the present invention can be applied to various uses in which carbon fiber is conventionally used, in particular, micromechanical elements, cushioning materials, switching elements, etc., utilizing the spring characteristics derived from the shape. Useful as Further, it is useful as a raw material for a composite material of carbon fiber and carbon, which has attracted attention as a material having excellent strength, friction, and sliding characteristics. The composite material will be described below.

The carbon fiber / carbon composite material is a material in which the interfiber space of the carbon fiber layer is filled with carbon, and is generally obtained by impregnating carbon fiber with a resin or tar pitch and carbonizing. The process is performed by thermal CVD of a carbon source gas such as ethylene in order to fill and densify.

The coiled carbon fiber of the present invention has excellent spring properties derived from its shape, and in such a carbon fiber / carbon composite material, the grip properties are improved, and the composite material has excellent mechanical strength such as bending strength and tensile modulus. Material can be provided.

 Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 A 500 mm × 20 mm × 3 mmt Ni substrate was placed at the center of a thermal CVD apparatus consisting of a quartz tube having an inner diameter of 40 mm and a length of 1000 mm, and the center of the reaction tube was heated to 750 ° C. using acetylene and hydrogen as raw materials and argon gas as a carrier gas. Was introduced into the furnace. The respective gas flow rates are as follows.

Acetylene; 40 cc / min Hydrogen; 140 cc / min Argon; 225 cc / min The furnace pressure was set at atmospheric pressure.

When the Ni substrate was taken out after the reaction for 5 hours, 3.7 g of a product was obtained in the front part of the electric furnace (520 to 750 ° C. during the reaction). The product was fibrous, of which about 10% was coiled. FIG. 2 shows an SEM photograph showing the fiber shape of the coiled fiber.

The diameter of this coiled carbon fiber is 0.1-1 μm and the length is about 3
00μm, aspect ratio 30-3000, coil diameter 0.2-10
μm, the coil outer diameter was in the range of 2 to 10 times the fiber diameter in each case. The number of turns of the coil was in the range of 5 to 30 times the reciprocal of the coil outer diameter (μm) per 10 μm.

X measured by crushing this coiled fiber in an agate mortar
The X-ray diffraction pattern is shown in FIG. The peak position of the 002 diffraction line is 24.9 ° at 2θ, and is a fairly amorphous carbon fiber having a half width of 7 °.

Example 2 Using the same apparatus as in Example 1, 5 g of Ni powder was placed between 150 mm in the center of the reaction tube, and acetylene was used as a raw material, and argon gas was used as a carrier gas. Introduced. The respective gas flow rates are as follows.

Acetylene: 50 cc / min Argon: 50 cc / min The furnace pressure was set at atmospheric pressure.

After 1 hour of reaction, 0.8 g of product was obtained at the front of the electric furnace (650-700 ° C). Most of the products were coiled carbon fibers.

The diameter of this coiled carbon fiber is 0.5-1 μm and the length is about 1
000 μm, aspect ratio 1000-2000, coil diameter 2-1
At 0 μm, the coil outer diameter was in the range of 2 to 10 times the fiber diameter in each case. The number of turns of the coil was in the range of 5 to 30 times the reciprocal of the coil outer diameter (μm) per 10 μm.

It was confirmed by X-ray diffraction that the coiled fiber was a considerably amorphous carbon fiber.

Example 3 A reaction was performed under the same conditions as in Example 2 except that the center of the reaction tube was heated to 400 ° C.

After reacting for 1 hour, 1.7 g of product was obtained at the front of the electric furnace (350 to 400 ° C.). The product is fibrous, of which about 5%
Was coiled.

The diameter of this coiled carbon fiber is 0.2 to 2.6 μm and the length is
10-1000μm, aspect ratio 50-1000, coil outer diameter is
Although it was considerably non-uniform at 0.8 to 10 μm, each range was 2 to 10 times the fiber diameter. The number of turns of the coil is
The range was 5 to 50 times the reciprocal of the coil outer diameter (μm) per 10 μm. X-ray diffraction confirmed that the coiled carbon fiber was a considerably amorphous carbon fiber.

Example 4 100 g of the synthesized coiled carbon fiber was uniformly dispersed in a phenol resin-alcohol solution 3 to form a slurry, and the slurry was passed through a 250-mesh (62 μm) screen to remove the solution. As a result, a preform in which the coiled carbon fibers were uniformly dispersed was obtained. The preform was dried to obtain a molded body having a fiber content of 40%.

After firing this molded body at 2000 ° C, it is heated to 1000 ° C,
Ethylene gas was introduced, and the pores were densified by CVD. Further, heat treatment at 2000 ° C. was performed to obtain a carbon fiber / carbon composite material having a porosity of 15%. Its bending strength is 15 kg / mm ² and its tensile modulus is 6 × 10 ³ kg / mm
² and strength characteristics were excellent.

[Effect of the Invention] The carbon fiber of the present invention has a coil shape, and is useful as a high-temperature high-strength composite material, a micromechanical element or a cushion material that requires spring characteristics under a high-temperature and corrosive atmosphere, and It can also be applied as a switching element or the like that controls the value of a current flowing by changing the contact cross-sectional area during expansion and contraction by utilizing the conductivity of carbon fibers. Also, the composite material with carbon has excellent grip characteristics due to its spring performance, and can improve various physical properties.

[Brief description of the drawings]

1 and 2 are SEM photographs showing the shape of the coiled carbon fiber of the present invention. FIG. 3 shows an X-ray diffraction diagram of the coiled carbon fiber of the present invention.

Claims (4)

(57) [Claims] 1. A coiled fiber as obtained by a gas phase pyrolysis reaction of substantially amorphous carbon having a fiber diameter of 0.05 to 5 μm, wherein the outer diameter of the coil is 2 to 10 times the fiber diameter. The coiled carbon fiber, wherein the number of turns is in the range of 5 to 50 times the reciprocal of the coil outer diameter (μm) per 10 μm. 2. A carbon composite material comprising carbon containing the coiled carbon fiber according to claim 1. 3. A gas-phase pyrolysis reaction of a mixed gas containing a hydrogen gas or a diluent gas in a molar ratio of 1 to 5 times with an acetylene gas in a system in which Ni metal is present at a temperature of 400 to 900 ° C. The method for producing coiled carbon fibers according to claim 1, wherein the carbon fibers are precipitated by the method. 4. The method for producing a carbon composite material according to claim 2, wherein the molded body in which the coiled carbon fibers are dispersed in the resin is baked to perform a densification treatment for filling pores.