KR100198153B1 - A vacuum pressure impregnation carbonization for densifying c/c composite - Google Patents

Abstract

The present invention relates to a vacuum pressurized impregnated carbonization furnace (VPIC) for increasing the density of a carbon / carbon composite material. In order to increase the density of the carbon fiber preform or the carbonized body 10, And the impregnated carbonization is carried out by heating and pressurization. In a state where the reaction furnace 2 is vacuumed, a large amount of volatile substances are generated from the pitch 11, the lower becomes the temperature performing a first heating step which heats the temperature was raised to (T ₁₎ which is then kept at a certain time the temperature (T ₂₎ the temperature was raised pressure at a predetermined pressure (P ₂₎ and continued heating of the melt viscosity is the cheapest And a third heating step of coking the impregnated pitch by pressurizing with a higher forward force (P ₃ ) and heating up the mixture, followed by cooling the mixture By performing the densification process under relatively low pressure, the energy consumption can be reduced, and the cost can be easily and economically achieved by the low-cost equipment. Nevertheless, the impregnation efficiency is increased to be higher than that of the conventional high temperature static impregnation carbonization method You can.

Description

Vacuum pressure impregnation carbonization for high density of carbon / carbon composites

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pressure impregnation carbonization (VPIC) for densifying a carbon / carbon composite material, and more particularly, to a vacuum pressure impregnation carbonization (VPIC) To a vacuum pressurized impregnated carbonization method which can be carried out at a relatively low pressure when the carbon / carbon composite material is produced at a high density by impregnating a pitch into a carbonized carbon / carbon composite material, thereby increasing the impregnation efficiency.

Generally, a carbon / carbon composite material manufacturing method can be roughly classified into liquid impregnation and chemical vapor deposition (CVD) according to a method of forming a carbon-based material on a preform woven with carbon fiber, The dual liquid impregnation method is a method of producing a carbon / carbon composite material by impregnating a preform with a resin such as pitch or phenol resin, and then carbonizing the resin by a pyrolysis reaction. As compared with the chemical vapor infiltration method, Manufacturing costs are economically advantageous, and a lot of electricity is being used.

In this liquid impregnated carbonization method, conventionally used are pressure impregnation carbonization (PIC) and high isostatic pressure impregnation carbonization (HIPIC), both of which are classified by reaction temperature and pressure , And the latter has the advantage that the impregnation efficiency is somewhat higher than that of the former.

However, since the high-temperature static-pressure impregnated carbonization process is performed at a high pressure of about 1000 atm, it requires a very expensive equipment as compared with the pressure-impregnated carbonization process performed at about 100 atm, and also has a disadvantage of high energy consumption.

Therefore, the present invention improves the conventional pressurized impregnated carbonization method, and provides a high-density impregnated carbon fiber preform or a carbonized body at a comparatively low pressure by a relatively low-cost equipment at a relatively low impregnation efficiency as compared with the high- The present invention provides a vacuum pressurized impregnated carbonization method capable of producing a carbon / carbon composite material.

In order to achieve the above-mentioned object, the vacuum pressurized impregnated carbonization method of the present invention is characterized in that the preform or the carbonized body is put into a reaction vessel together with the pitch in order to densify the carbon fiber preform or the carbonized body to produce the carbon / (T _{1) at} which a large amount of volatile matter starts to be generated from the pitch in a vacuum state of the reaction furnace and the viscosity of the pitch is lowered, (T ₂ ) at which the melt viscosity is kept at a lowest temperature for a predetermined time, and after the first heating step is performed again A third heating step for heating the heated mixture to coke the impregnated pitch, and cooling the mixture .

The vacuum pressurized impregnation method of the present invention has an effect of achieving a high impregnation efficiency while being economically advantageous in terms of cost by performing the process at a relatively low pressure. Especially, a high impregnation efficiency It is possible to manufacture a high-density carbon / carbon composite material.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic structural view of an apparatus for carrying out the vacuum pressurized impregnation method of the present invention,

2 is a graph showing process conditions according to the present invention,

FIG. 3 is a graph showing a density change according to the number of times of impregnation of a carbon / carbon composite material made into a density according to the present invention.

Description of the Related Art [0002]

1: heater 2: reactor

3: thermocouple 4: pressure gauge

5: Nitrogen gas cylinder 6: Flow rate regulator

7: Vacuum pump 10: Carbon fiber preform or carbonizing agent

11: pitch 12: reaction vessel

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

Fig. 1 is a schematic view showing an apparatus for carrying out the vacuum pressurized impregnation method of the present invention. This apparatus comprises a reactor 2 having a heater 1, a thermocouple 3 for temperature measurement, A nitrogen gas cylinder 5 is connected to the reactor 2 through a flow rate control device 6 so that nitrogen gas can be regulated and injected into the reactor 2, , And a vacuum pump (7) is connected to exhaust the reaction furnace (2).

In order to carry out the vacuum pressurized impregnation method of the present invention in such an apparatus, a carbon fiber preform or a carbon body 10 is put into a reaction vessel 12 together with a pitch 11, and the reaction vessel 12 is placed in a reactor 2, the inside of the reaction furnace 2 is evacuated by using a vacuum pump 7 and heated by the heater 1. When pressurization is required, nitrogen gas is supplied to the flow rate regulator 6, As shown in FIG.

At this time, the heating and pressurizing conditions characteristic of the present invention can be classified into three process steps as shown in the graph of FIG.

The first is a first heating step (0 to t ₁ ) in which the viscosity is lowered while the pitch is softened. The pressure (P ₁ ) of the reactor is maintained at a vacuum of 400 torr or less, (T ₁ ) at which the temperature is lowered.

At this time, the temperature of T ₁ is a temperature at which a large amount of volatile substances starts to be generated, and a range of 150 - 250 ° C is suitable.

The second is a second heating step (t _{1 to} t ₃ ) in which the pitch is sufficiently impregnated into the freerode, in which nitrogen gas is injected into the reaction furnace and the pressure is pressurized to 10 - 50 atm, and the melt viscosity of the pitch is lowest the temperature (T ₂₎ and heating continued to be heated to a stage that keeps for at least 1 hour at this temperature condition. The preferred temperature range for T ₂ is 250-350 ° C.

The third is a third heating step (t _{3 to} t ₅ ) in which the impregnated pitch is coked, is heated again to a temperature of 550 - 700 ° C (T ₃ ), maintained at this temperature for at least 1 hour , Wherein the pressure is preferably maintained at a pressure (P ₃ ) of 50 - 100 atm.

It is preferable that the heating temperature is set in the range of 10 to 150 ° C / hr in heating, and the coal pitch is preferably used as the impregnation material. The coal pitch has a softening point of 110 ° C or less, Can be easily changed to a carbonized or graphitized structure, and the carbon yield is relatively high.

During the above steps, the pitch composed of many kinds of hydrocarbons is released through the softening and melting states and a part is discharged out of the system (the first heating step), and the remaining components are cyclized and aromatized by the polycondensation reaction, (The second heating step), and the impregnated pitch is coked by being heated to a higher temperature and then finally cooled (third heating step).

Meanwhile, the vacuum pressurized impregnation method of the present invention can be used in combination with the "heat gradient vapor phase method" (filed on October 29, 1996), another inventor of the present invention, to form a uniform carbon- Economically and efficiently. In this thermal gradient chemical vapor deposition method, pyrolytic carbon is deposited on the preform by injecting hydrocarbon gas into a reaction tube or reactor equipped with a carbon fiber preform and thermally decomposing the carbon fiber preform as described in detail in the specification, It is a new chemical vapor infiltration method which induces the temperature gradient in the thickness direction of the preform by attaching a heating element to the center of the preform and heating it through this heating element.

In the vacuum pressurized impregnated carbonization method of the present invention as described above, the carbon / carbon composite material was manufactured according to the following specific examples and the properties thereof were tested. As a result, the carbon / carbon composite material having a high density of carbon / carbon It was confirmed that the composite material can be efficiently produced.

That is, carbon fiber preforms were formed by three-dimensionally woven with a corbon rod to produce graphitized carbonaceous material having a density of 1.70 g / cc (diameter: 115 mm, length: 100 mm) by the above thermal gradient chemical vapor deposition method This was put in a tin-iron reaction vessel 12 with a finely crushed pitch of 10 mm in diameter and heated and pressed under the conditions of pressure and temperature as shown in the graph of FIG. 2. The number of times of impregnation was repeated three times .

The density change of the carbon / carbon composite material thus produced is shown in FIG. 3. It can be seen that the density of 1.70 g / cc was changed to a high density of 1.90 g / cc by the number of times of impregnation three times.

As described in detail above, the vacuum pressurized impregnation method of the present invention can be carried out economically with low-cost equipment while reducing energy consumption by performing the densification process under a relatively low pressure. Nevertheless, the impregnation efficiency Can be increased to a level higher than that of the conventional high-temperature static pressure impregnated carbonization process.

Claims (10)

The preform or the carbonized body 10 is put into the reaction vessel 12 together with the pitch 11 to prepare the carbon fiber composite material or the carbon fiber preform or the carbonized body 10 by increasing the density of the carbon fiber preform or the carbonized body 10, (2) is vacuumed, and a temperature at which the viscosity of the pitch decreases as a large amount of volatile substances starts to be generated from the pitch (11) in the reaction furnace (2) 2 that maintains the first and then performing the heating step, the predetermined temperature (T ₂₎ the temperature was raised pressure at a predetermined pressure (P ₂₎ and continued heating of the melt viscosity is the cheapest time that heated the temperature was raised to (T ₁₎ And a third heating step of coking the impregnated pitch by performing a heating step, heating the same again, and cooling the impregnated carbonaceous material. The vacuum pressurized impregnated carbonization method according to claim 1, wherein the pitch (11) is a coal-based pitch. The vacuum pressurized impregnated carbonization method according to claim 1, wherein the degree of vacuum (P ₁ ) in the first heating step is 400 Torr or less. The vacuum pressurized impregnated carbonization method according to claim 1, wherein the heating temperature (T ₁ ) in the first heating step is 150 to 250 ° C. The vacuum pressure impregnated carbonization method according to claim 1, wherein the pressure (P ₂ ) in the second heating step is 10-50 atm. The vacuum pressurized impregnated carbonization method according to claim 1, wherein the heating temperature (T2) in the second heating step is 250-350 占 폚 and maintained at this temperature for 1 hour or more. The vacuum pressurized impregnated carbonization method according to claim 1, wherein the pressure (P ₃ ) is further increased to 50 - 100 atm in the third heating step. The vacuum pressure impregnated carbonization method according to claim 1, wherein the heating temperature (T ₃ ) in the third heating step is set to 550-700 ° C and maintained at this temperature for 1 hour or more. The vacuum pressurized impregnated carbonization method according to claim 1, wherein a heating rate is 10 to 150 ° C / hr in each heating step. The method of claim 1, wherein the carbon fiber preform or the carbonized material (10) to be densified is injected with a hydrocarbon gas into a reaction tube or a reactor equipped with a carbon fiber preform and pyrolyzed to deposit pyrolytic carbon on the preform The first density treatment is performed by a thermal gradient chemical vapor deposition method in which a heating element is mounted on a central portion of the preform and heated through the heating element to induce a temperature gradient in the thickness direction of the preform ≪ / RTI >