KR940006433B1 - Process for the preparation of carbon/carbon composite - Google Patents

Abstract

The carbon/carbon composite material using rayon based or polyacrylonitrile based stabilized carbon fiber as a reinforcing agent is prepared by (a) impregnating thermosetting resin, i.e. furfuryl alcohol into stabilized fiber and curing them, (b) molding the impregnated body and heating it at 900-1,500 deg.C with raising temp. speed, 5 deg.C/min, (c) depositing it by chemical vapor deposition, flowing the mixed gas including 2-100 vol% hydrocarbon gas with hydrocarbon and inert gas into a reactor, and cooling.

Description

Manufacturing Method of Carbon / Carbon Composite Using Stabilized Fiber

1 (a), (b) and (c) are scanning electron microscopy (SEM) photographs of the cross-sectional structure of the carbon / carbon composite material prepared using stabilizing fibers according to the present invention, respectively.

The present invention relates to a method for producing a carbon material reinforced with carbon fibers, i.e., a carbon / carbon composite material, and more particularly, using a stabilized (or insoluble) fiber as a reinforcing fiber and forming a carbon matrix by chemical vapor deposition. To a carbon / carbon composite material.

Carbon / carbon composite materials are widely used in aircraft brakes, rocket nozzles, space shuttles, and other heat-resistant structural materials because they have light weight, high mechanical strength, and excellent heat resistance, as well as excellent mechanical properties and thermal shock resistance at high temperatures.

Conventional methods for producing a carbon / carbon composite material can be largely divided into two.

First, the method is made of short or long fibers of carbon fiber, and then a hydrocarbon gas such as propane or methane is added to the space between the carbon fibers. It is a gas phase incorporation method that fills a carbon matrix by chemical vapor deposition at high temperature (1000-1500 ° C. (eg Carbon, vol. 23, p. 691, 1985; 炭素 Mo. 115, pp. 106-208, 1983).

The second method is to heat and mold thermosetting resins or pitches such as phenol resins and furan resins, which are raw materials of carbon fibers and carbon matrices, and heat them, and carbonize them at 1000-2000 ° C. in an inert atmosphere. It is a liquid phase impregnation method that repeats the cycle of impregnation and carbonization treatment, etc., or graphitizes it at a high temperature of 2000-3000 ° C. in the intermediate process (for example, Japanese Patent No. 62-212262; Japanese Patent 62-241871). .

In general, carbon fiber is made of fiber by melting and spinning rayon, polyacrylonitrile, pitch, etc. It is prepared by carbonization at a temperature of 1000-3000 ° C. in an inert atmosphere. In this process, the infusible fibers before carbonization are called stabilizing fibers or infusible fibers, and the carbonized fibers are called carbon fibers.

All of the conventional carbon / carbon composite materials manufacturing methods described above use coarse carbon fiber as a raw material for reinforcing materials until the final carbonization process. However, in either case, carbon fiber, which is a reinforcing material, undergoes a carbonization process because carbon fiber, which is a reinforcing material, is inevitably required to be carbonized at or near 1000 ° C. in order to fill the carbon matrix in the manufacturing process of the carbon fiber / carbon composite material. do. Conventional carbonization process is not only very time-consuming but also energy consuming process, the conventional method of carbonizing the fibers used as reinforcing material before and during the manufacturing process of the composite material is a significant economic loss There is this.

Accordingly, an object of the present invention is to produce a carbon / carbon composite material having low physical cost and excellent physical properties by using stabilized (insoluble) fibers that have not undergone a carbonization process as reinforcing materials.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention relates to a method for producing a carbon / carbon composite material using carbon fiber as a reinforcing material, wherein a molded article formed by using a purifying fiber as the carbon fiber and incorporating a thermosetting resin into the stabilizing fiber in a reaction tube in an inert atmosphere. Heated to a temperature of 900-1500 ° C. at a heating rate of 5 ° C./min or less, followed by chemical vapor deposition by introducing a mixture of hydrocarbon gas / inert gas containing 2-100 vol% of hydrocarbon gas into the reaction tube The present invention relates to a method for producing a carbon / carbon composite material.

Hereinafter, the present invention will be described in more detail.

Stabilizing fibers used in the present invention can be any fiber made from any known raw materials such as rayon, polyacrylonitrile, pitch, etc., and the stabilizing fibers in the form of yarn, cloth, tape ( Long fibers such as tape and short fibers such as chopped fibers, mats and felts are possible. The stabilized fiber bundle is impregnated with a thermosetting resin such as furfuryl alcohol and then cured to form a molded article having a fixed shape. At this time, if the stabilizing fiber is not hardened by thermosetting resin and the shape is not fixed, it is difficult to handle it in the subsequent treatment process, and a problem arises in that the arrangement of fibers is dispersed by the flow of inert gas or hydrocarbon gas in the reaction tube. .

As described above, the stabilized fiber molded article impregnated with the thermosetting resin was charged into a tubular reaction tube made of alumina or quartz, and heated at a rate of 5 ° C./min or lower while flowing inert gas such as nitrogen, argon, and helium, thereby increasing the temperature to 900-1500. Heat to a temperature of ° C. After confirming that the temperature is kept stable, hydrocarbon gas, such as propane, methane, ethane, or the like is added to the inert gas and introduced into the reaction tube, using a flowmeter, in a total gas, that is, a mixture of inert gas and hydrocarbon gas. The concentration of hydrocarbon gas is adjusted to 2-100 vol%.

The chemical vapor deposition process described above causes two reactions in the reaction zone. One is to maintain the reaction temperature at 900 ℃ or more by allowing the heterogeneous elements other than carbon, ie nitrogen, hydrogen, oxygen, etc. of the molecules constituting the stabilizing fiber to escape and almost carbon atoms remain. It is to convert the stabilized fibers into carbon fibers. Another reaction is to pyrolyze the hydrocarbon gas introduced into the reaction zone to attach the pyrolytic carbon, which is a solid carbonaceous material, to the surface of the fiber, so that the empty spaces between the fibers are filled with the carbon matrix.

The thermal decomposition rate of the hydrocarbon gas, that is, the filling rate of the carbon matrix in the chemical vapor deposition process increases as the reaction rate increases and the concentration of the hydrocarbon gas increases, so that the reaction temperature is 900 ° C. or less, or the hydrocarbon concentration is 2 vol% or less. It is not desirable because it takes too long to produce the / carbon composite. In addition, when the reaction temperature rises to 1500 ° C. or higher, or the temperature increase rate is 5 ° C./min or more, the stabilizing fibers are deformed due to heat shrinkage, distortion, warpage, and the like.

In producing a carbon / carbon composite material according to the present invention, the reaction time for the chemical vapor deposition process depends on the production conditions. In other words, the larger the size of the stabilized fiber molded article, the smaller the fiber content in the molded article, the lower the reaction temperature, the lower the concentration of the hydrocarbon, and the higher the thermal stability of the used hydrocarbon, the longer it takes.

Hereinafter, the present invention will be described in detail through examples.

Example 1

Furfuryl alcohol was impregnated into the bundle of pitch-based stabilizing fibers, placed in an oven, and cured at 200 ° C. for 1 hour. The cured stabilized fiber molded body was charged into a tubular reaction tube of a heating furnace and heated at a rate of 5 ° C./min while introducing nitrogen gas. When the temperature of the reaction tube reached 900 ° C., the propane gas was maintained at a concentration of 80 vol% for 10 hours, and then the inflow of propane gas was stopped and slowly cooled at a normal cooling rate.

The apparent density was calculated by measuring the weight and volume of the carbon / carbon composite material prepared by the reaction, and the structure of the cross section is shown in FIG. The preparation conditions and apparent density are shown in Table 1.

Example 2

After stabilizing the fiber in the same manner as in Example 1, it was heated at a rate of 5 ℃ / min and maintained for 8 hours while introducing a propane gas at a concentration of 10 vol% at 1100 ℃ to prepare a carbon / carbon composite material. The structure of the cross section is shown in Figure 1 (b), and the manufacturing conditions and the apparent density are shown in Table 1.

Example 3

After curing the stabilizing fibers in the same manner as in Example 1, and heated to a rate of 5 ℃ / min up to 1000 ℃ and then heated to 2 ℃ / min 2 hours while introducing propane gas at a concentration of 5 vol% at 1400 ℃ To prepare a carbon / carbon composite. The structure of the cross section is shown in Fig. 1 (c), and the manufacturing conditions and the apparent density are shown in Table 1.

[Comparative Example]

Polyacrylonitrile-based carbon fiber was treated in the same reaction tube as in Example 2 in the same manner and conditions to prepare a carbon / carbon composite material. The apparent density of the obtained carbon / carbon composite material was calculated in the same manner as in the above example. The manufacturing conditions and results are shown in Table 1.

TABLE 1

As shown in Table 1, it can be seen that it is possible to produce a high-density carbon / carbon composite material by using the stabilizing fibers not subjected to the carbonization process as a reinforcing material according to the present invention. In addition, in the present invention, the stabilizing fibers are slightly shrinked while carbonizing, and the spacing between the fibers is narrowed. Thus, a carbon / carbon composite material having a higher density is manufactured under the same conditions than when carbon fibers are used according to a conventional method. can do.

Claims (1)

In the method for producing a carbon / carbon composite material using carbon fiber as a reinforcing material, stabilizing fiber is used as the carbon fiber, the stabilizing fiber is impregnated with a thermosetting resin and then cured, and the resultant formed body is reacted with an inert atmosphere. After heating at a temperature of 900-1500 ° C. at a temperature increase rate of 5 ° C./min or less, the mixture gas of hydrocarbon gas / inert gas containing 2-100 vol% of hydrocarbon gas was introduced into the reaction tube, followed by chemical vapor deposition. Method for producing a carbon / carbon composite material using a stabilized fiber, characterized in that the cooling.