JPH059812A - Porous carbon fiber, its production, production of porous graphite fiber and treatment of porous carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the subject carbon fiber useful as a reinforcing filler for various composite materials or the host material for its interlaminar compound from a carbon fiber grown in vapor phase by heating the carbon fiber in an inert gas atmosphere containing steam, air, oxygen, etc., until the specific surface area ratio of the fiber reaches a specific level. CONSTITUTION:A carbon fiber grown in vapor phase is heated in an inert gas such as nitrogen or argon containing steam or steam and air or oxygen until the specific area ratio of formula B/A (B is specific surface area measured by BET method; A is specific surface area calculated from the average diameter and the average length) reaches 1.5-20. The objective carbon fiber can be produced by the above simple process. A porous graphite fiber can be produced by heating the obtained carbon fiber at >=1500 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous carbon fiber, a method for producing the same, a method for producing a porous graphite fiber and a method for treating a porous carbon fiber, and more specifically, as a filling material for reinforcing various composite materials. , A porous carbon fiber useful as a host material for an intercalation compound by utilizing its ability to form an intercalation compound, a simple method for producing the same, a method for producing a porous graphite fiber from the porous carbon fiber, and a porous fiber Regarding processing method.

[0002]

2. Description of the Related Art Vapor-grown carbon fibers have a structure in which a condensed annular carbon surface is parallel to the fiber axis and has a ring-shaped structure centered on the fiber axis. , Has high mechanical strength, high elasticity.
Therefore, this vapor grown carbon fiber is
It is expected that the mechanical properties of these various matrix materials can be greatly improved by combining them with ceramics, rubber, metals, etc., and various studies have been made so far.

However, the improving effect of the vapor-grown carbon fiber on the matrix material was not so large as expected from its high mechanical properties. The reason is that the stress transmission (or propagation) between the matrix material and the vapor grown carbon fiber is poor. That is, when observing a composite material in which vapor grown carbon fibers are dispersed in various matrix materials with an electron microscope, a minute gap is generated between the vapor grown carbon fibers in the matrix and the matrix material, or such a gap is generated. Since there was a state in which it was simply in contact even without it,
The above reason is presumed. As a result, while it is said that the vapor-grown carbon fibers are dispersed in the matrix to reinforce the matrix material, a large number of voids containing the vapor-grown carbon fibers in the matrix rather reduce the strength of the matrix. It became

For the purpose of better improving the transfer of stress between the vapor grown carbon fiber and the matrix material,
Attempts have been made to improve the affinity of the vapor grown carbon fiber for the matrix material by introducing a functional group into the surface of the vapor grown carbon fiber by an oxidation reaction or by performing graft polymerization. However, PA
Compared with conventional carbon fibers obtained by carbonizing N-based fibers, cellulose-based fibers or pitch-based fibers, the surface of vapor-grown carbon fibers has few defects and the surface is chemically stable. Attempts such as have not been successful enough to be considered industrial.

Attempts have also been made to partially remove or corrode the surface of the vapor-grown carbon fiber by rubbing or the like, but unlike ordinary carbon fiber, defects are formed inside the surface of the vapor-grown carbon fiber. Since few crystals are oriented, the improvement was not sufficient to achieve good stress transfer in the matrix material of vapor grown carbon fibers.

The present invention has been made based on the above circumstances. That is, an object of the present invention is to provide a porous carbon fiber having a novel physical structure capable of achieving improvement in physical properties such as mechanical strength of a composite material by being dispersed in a matrix material, An object of the present invention is to provide a simple method for producing carbon fibers, and provide a method for producing porous graphite fibers, which is a further improvement of the porous carbon fibers, and a method for treating the porous fibers.

Another object of the present invention is to provide a porous carbon fiber having a novel structure, which is suitable as a host material for an intercalation compound. Another object of the present invention is to provide a suitable porous carbon fiber having improved film strength and releasability as a filler for paints.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied the improvement of good stress transmissibility of a vapor grown carbon fiber to a matrix material by a physical method. During the research, we focused on steam treatment of carbon in the activated carbon manufacturing technology, which belongs to a technical field that has nothing to do with new material-related technology or composite material-related technology. In order to activate carbon to produce activated carbon, the specific surface area is 2
00~400m ² / g also oxidized carbon in, opening the following hole 500 Å, a specific surface is intended to be about 1,000 m ² / g. It is believed that this oxidation reaction oxidizes the edges of carbon microcrystals and lattice defects to form pores.

It is considered that pores are not easily formed in the vapor-grown carbon fiber having few crystal edges and lattice defects, and in fact, depending on the oxidation reaction that has been performed so far, the matrix-reinforcing effect of the vapor-grown carbon fiber. Could hardly be improved. However, while conducting various experiments, the inventors of the present invention were able to perforate the vapor-grown carbon fiber by a specific oxidation condition, that is, steam treatment, although the amount was small, and the specific surface area was reduced. It was found to increase and significantly improve the reinforcing effect on the matrix. If vapor-grown carbon fibers and a large number of pores are formed by this method, it is presumed that the strength of the fiber itself is decreased and the reinforcing effect is lost. This invention was completed under such circumstances.

That is, according to the invention described in claim 1 for solving the above-mentioned problems, the condensed annular carbon surface is laminated in an annual ring shape around the fiber axis, the center of the fiber axis becomes hollow, and the formula B / A (where B represents the specific surface area by the BET method,
A represents a specific surface area that can be calculated by the average diameter and the average length. ) Specific surface area ratio C is 1.5
The porous carbon fiber according to claim 2, wherein the porous carbon fiber has a porosity of 600 Å or less and a pore volume of 600 Å or less measured by a mercury intrusion method.
^-2 cc / g or more, which is the porous carbon fiber according to claim 1, wherein the invention according to claim 3 is vapor grown carbon fiber containing steam or steam and steam or air or oxygen. A method for producing a porous carbon fiber, which comprises heating in an active gas until the specific surface area ratio according to claim 1 becomes 1.5 to 20, and the invention according to claim 4 The method for producing a porous carbon fiber according to claim 3, wherein the content of water vapor in the inert gas is 10 to 90% by volume, and the heating temperature is 500 to 1,500 ° C.
The invention according to claim 5 is the above claim 3 or claim 4.
The porous carbon fiber obtained by the method described in 1.
A method for producing a porous graphite fiber, which comprises heating to 00 ° C. or higher to graphitize, and the invention according to claim 6 is obtained by the method according to claim 3 or claim 4. Porous carbon fiber in an inert gas 500-1,5
It is a method for treating porous carbon fibers, which comprises heating to 00 ° C.

The porous vapor-grown fiber of the present invention, the method for producing the same, and the graphite fiber produced from the porous carbon fiber will be described in more detail. The porous carbon fiber of the present invention has a structure in which condensed annular carbon surfaces are laminated in an annual ring shape around the fiber axis, and the center of the fiber axis is hollow, that is, a tubular shape in which both ends are closed or opened. And has a specific surface area ratio and is porous.

The specific surface area ratio C is expressed by the formula B / A (where
B represents the specific surface area by the BET method, and A represents the specific surface area that can be calculated by the average diameter and the average length. ), And in the present invention, 1.5
~ 20. On the other hand, the specific surface area A is obtained from the outer shape ignoring the existence of pores. That is, the diameter and length of the porous carbon fiber are obtained by microscopic observation, and the surface area per unit weight is calculated from them and the specific gravity. Since the diameter and the length vary depending on the measurement, an average value of values obtained by observing 100 or more porous carbon fibers under a microscope is used.

The specific gravity can be determined by the Archimedes method using alcohol. When immersing the porous carbon fibers in alcohol, it is necessary to sufficiently permeate the alcohol into the pores of the porous carbon fibers by reducing the pressure of the atmosphere. Other specific surface area B
Is a specific surface area considering the existence of pores in the porous carbon fiber, and can be calculated from the amount of nitrogen adsorbed by the BET method.

When the specific surface area ratio C is 1, it means that there are no pores. Further, the specific surface area ratio C increases as the amount of pores increases. In the present invention, when the specific surface area ratio C is less than 1.5, the effect of improving the stress transmissibility of the porous carbon fiber with respect to the matrix material is small.
When it exceeds 0, the mechanical strength of the porous carbon fiber is lowered and the function as a reinforcing material cannot be exhibited.

The specific range of the specific surface area ratio C varies depending on the intended use of the porous carbon fiber. For example, when this porous carbon fiber is used as a reinforcing material, the preferable range of the specific surface area ratio C is 2-1.
5, especially 3 to 12, and when used as an intercalation compound, the preferable range of the specific surface area ratio C is 3 to 18, particularly 5 to 15.

The porous carbon fiber of the present invention is characterized by having the specific surface area ratio C and being porous.
Further, regarding the above-mentioned porosity, in the porous fiber of the present invention, the pore volume having a pore diameter of 600 Å or less is 2 × 10 ^-2 cc /
It is preferably g or more, and more preferably 3 × 10 ^-2 cc / g or more.

The pore volume for each pore diameter can be measured by a low temperature gas adsorption / desorption method (for example, OMRON Corporation, fully automatic precision gas adsorption device Omnisorb 100) or a mercury injection method. When the value of the pore volume is less than the above, the strength of the composite material is not sufficiently improved, and the production rate of the intercalation compound and the reaction amount with the guest substance are low.

The porous carbon fiber of the present invention forms a composite material by using the porous carbon fiber as a reinforcing material due to the two factors of having the specific surface area ratio C as described above and being porous. Sometimes it has an excellent stress transfer function. Furthermore, when focusing solely on the specific surface area, for example, a fiber having a diameter of 0.2 μm and a length of 4 μm,
The calculated specific surface area of a fiber having a diameter of 2 μm and a length of 40 μm is 10 when the density is 2 g / cm ^2.
m ² / g and 1 m ² / g, which are greatly different, but when both are used as the reinforcing material in the composite material, there is no substantial difference between the two. The latter is subjected to the treatment of the present invention, that is, the treatment of heating in steam or an inert gas containing steam and air or oxygen to give a specific surface area of 10 m ² /
When it is set to g, a big difference occurs. Further, the vapor-grown carbon fiber is sliced into slices to have an aspect ratio L / D of about 1
When set to, the surface area increases due to the cross-sectional area of both ends of the fiber,
The specific surface area ratio C may become larger than 1 in combination with the exposure of the annual ring structure at both ends, but since it is not porous, there is no stress transmission effect and no reinforcement effect on the matrix resin. Absent.

This porous carbon fiber is preferably used as a reinforcing material which can be compounded with plastics, ceramics, rubber, metals and the like. Among these matrix materials, the matrix material suitable for combination with the porous carbon fiber of the present invention is plastic, and thermosetting resins and thermoplastic resins can be used.
Since the surface condition of this porous carbon fiber is improved and the wettability with respect to the matrix material is remarkably improved, the mechanical strength of the matrix material can be greatly improved.

Since this porous carbon fiber is porous, it can intercalate various substances,
Various new physical properties can be imparted depending on the type of intercalating substance. For example, as intercalating substances, NaH, AsF ₅ , K,
KHG, mention may be made of _{FeCl 3, CuCl 3, Br 2} , HNO 3 or the like. It is possible to provide a novel material having high conductivity, superconductivity, hydrogen storage effect, and catalytic effect by properly selecting these intercalating substances and intercalating the porous carbon fibers. it can.

The porous carbon fiber having the above characteristics can be manufactured by the method of the present invention. That is, the vapor-grown carbon fiber is heated in water vapor or an inert gas containing water vapor and air or oxygen until the specific surface area ratio C becomes 1.5 to 20, whereby the porosity of the present invention is improved. Carbon fiber can be manufactured. However, as for the porous carbon fiber, the raw material is limited to the above-mentioned vapor-grown carbon fiber as long as the condensed annular carbon surface is laminated in an annual ring shape around the fiber axis and the center of the fiber axis is hollow. There is no such thing. In the method for producing a porous fiber of the present invention,
Condensed ring-shaped carbon surfaces are laminated in an annual ring shape around the fiber axis, and the center of the fiber axis has a hollow structure. It is a suitable manufacturing method since it can be opened.

Here, the vapor grown carbon fiber can be produced by a vapor growth method. There are a so-called substrate method and a fluidized vapor phase method as a method for producing the vapor grown carbon fiber by the vapor phase growth method. In the substrate method, a catalyst metal such as a transition metal or a transition metal compound is supported on the substrate, and while heating to a high temperature, a hydrocarbon gas that is a carbon source gas is circulated on the substrate to form carbon fibers on the substrate surface. It is a method to generate, the fluidized vapor phase method does not use a substrate,
In this method, a metal compound that can be a catalyst metal and a carbon compound that is a carbon source are vaporized and passed through a high-temperature reaction tube to generate carbon fibers in a space.

Specifically, Japanese Patent Laid-Open No. 52-107320
No. 57-176622 and 58-156.
512, JP-A-58-180615, JP-A-60-
185818, JP-A-60-224815, JP-A-60-231821, JP-A-61-132630,
JP-A-61-132600, JP-A-61-132666
3, JP-A-61-225319, JP-A-61-222.
5322, JP-A-61-225325, JP-A-61
-225327, JP-A-61-225328, JP-A-61-2275425, and JP-A-61-282427.
The vapor-grown carbon fibers produced by the method described in each of the publications can be used as a raw material in the method of the present invention.

Among these, the diameter is 0.1 to 5 μm, and the length is usually 0.5 although it varies depending on the manufacturing method.
The dimension ranges from μm to 1,000 μm, d ₀₀₂ measured by X-ray diffractometry is 3.45 to 3.6 Å, and d
The thickness Lc of the crystals in which the ₀₀₂ planes overlap is less than 50Å,
A vapor-grown carbon fiber having a length La of d ₀₀₂ surface of 140 Å or less is preferable. In particular, vapor grown carbon fiber obtained by the fluidization method is preferable.

As the above-mentioned inert gas when the vapor-grown carbon fiber is heat-treated, nitrogen and rare gases such as argon and helium can be used. The water vapor concentration in the inert gas is 10 to 95% by volume, preferably 5
It is 0 to 90% by volume. The oxygen concentration is preferably 10% by volume or less. The heating temperature is usually 500-1,
It is 500 ° C., preferably 800 to 1,200 ° C.

As the treatment operation, for example, a predetermined amount of vapor-grown carbon fiber is accommodated in a reaction tube, and then the reaction tube is heated to the heating temperature while the inert gas and steam or steam and air or Oxygen is passed through the reaction tube. Porous carbon fibers are produced by such an operation. As a treatment operation other than this, while continuously supplying vapor-grown carbon fibers into the reaction tube heated to the heating temperature at a constant rate, the inert gas and water vapor or water vapor and air or oxygen are reacted. It is also possible to employ a so-called continuous method in which the vapor-grown carbon fibers retained in the reaction tube for a predetermined period of time are continuously fed into the tube at a constant rate and continuously taken out of the reaction tube. When using this continuous method,
The vapor grown carbon fiber as a raw material and the steam or an inert gas containing steam and air or oxygen may be in countercurrent contact or cocurrent contact.

What is interesting in this operation is that in the above operation process, the number of pores observed by an electron microscope increases and the pore diameter also increases as the reaction progresses. The surface area increases once, but then begins to decrease. The tendency of increase and decrease of the specific surface area is significantly different from the case where activated carbon is produced by steaming carbon powder. That is,
When the carbon powder is steam-treated, the specific surface area measured by the BET method unilaterally increases as the steam treatment progresses. From this point, steam treatment of carbon powder,
The action and effect are completely different from the treatment of the vapor grown carbon fiber of the present invention.

The treatment with the steam or the inert gas containing the steam and the air or oxygen in the present invention does not impair the mechanical properties of the vapor grown carbon fiber,
Pores are formed in the vapor grown carbon fiber. Therefore, the steam treatment in the present invention is completely different from the mere oxidation treatment of oxidizing the surface of the fiber by using various oxidizing agents or utilizing an electrolytic reaction, as described below.

For example, by using various oxidizing agents or by utilizing an electrolytic reaction to oxidize the surface of the fiber, oxygen-containing functional groups are introduced into the surface of the fiber to improve the affinity with the matrix material. Improvements have been made in the past. In that case, the oxidation reaction is usually carried out at a low temperature of less than 800 ° C. so as not to decompose the introduced functional group. And the treatment by such an oxidation reaction was effective for general carbon fibers. However, in this oxidation treatment, if the carbon fiber is oxidized under extreme conditions in order to increase the introduction amount of the functional group, the introduction amount of the functional group will surely increase, but the carbon fiber itself will be oxidatively decomposed. As a result, the mechanical properties of the composite material deteriorated, and the strength of the composite material decreased.

The same oxidation treatment as that for general carbon fiber was examined for vapor grown carbon fiber, but the orientation of the carbon ring plane is good and there are few surface defects.
The introduction amount of the functional group did not increase, and even if the introduction amount was increased depending on the reaction conditions, the reinforcing effect by the carbon fiber was not as expected. Moreover, when the oxidizing conditions are made extreme, the inner wall of the hollow portion of the fiber shaft essentially possessed by the vapor-grown carbon fiber is corroded to increase the diameter of the hollow, and finally the surface layer only becomes a thin-skinned fiber. It even happened.

As described above, the conventional oxidation treatment for carbon fibers and vapor-grown carbon fibers is greatly different from the treatment method of the present invention. When the compound is an intercalation compound, the presence of a functional group capable of reacting with the guest substance or its solvent is not preferable. Judging from the fact that the wettability and the like have not been improved so much in the porous carbon fiber obtained in the present application, it is considered that the functional groups are less formed.
It is preferable to reheat at 00 to 1,500 ° C. in an inert atmosphere.

The porous fiber should be further heated to 1,500 ° C. or higher, preferably 2,000 ° C. or higher in an inert atmosphere such as argon, helium or other rare gas, nitrogen gas, or hydrogen gas in some cases. Thus, porous graphite fiber can be obtained. This porous graphite fiber has a diameter of 0.1 to 5 μm, a length of 0.5 to 1,000 μm, and a d ₀₀₂ measured by an X-ray diffraction method of 3.35-.
3.40Å, and the thickness Lc of the crystal with the d ₀₀₂ planes overlapping
Is 550Å or more, and the length La of the d ₀₀₂ surface is 140 to
It is 1,200Å. Moreover, the formula B '/ A' (however,
B'represents a specific surface area by the BET method, and A'represents a specific surface area that can be calculated by the average diameter and the average length. ), The specific surface area ratio C'is 1.5 to 20, and the volume of pores having a pore diameter of 600 Å or less measured by mercury porosimetry is 2 × 10 ^-2 cc / g or more.

This porous graphite fiber is also suitably used as a reinforcing material which can be compounded with plastics, ceramics, rubber, metals and the like. In particular, since the surface condition of the porous graphite fiber is improved and the stress transmission to the matrix material is remarkably improved, the mechanical strength of the matrix material can be greatly improved.

[0034]

Embodiments of the present invention will be described below. The present invention is not limited to the examples below. It goes without saying that the invention can be appropriately modified and implemented within the scope of the gist of the present invention.

Example 1 Vapor grown carbon having a diameter of 0.8 μm, an aspect ratio of 46, a true specific gravity of 1.96, and a specific surface area calculated from this of 2.58 m ² / g. Prepared the fiber. This vapor grown carbon fiber is 1,0
While heating to 00 ° C., a mixed gas of nitrogen and water vapor having a water vapor concentration of 80% by volume was added to the vapor grown carbon fiber,
The contact was made for 3 minutes at a total flow rate of 5 l / min.

After the contact treatment, the specific surface area of the obtained fiber was measured by the BET method to be 20.6 m ² / g and the specific surface area ratio C was 7.98. In addition, the obtained fiber has a pore size of 600Å measured with an omni soap.
The following pore volumes were as shown in Table 1. as a result,
This fiber was the porous carbon fiber defined in this invention.

[0037]

[Table 1]

Epoxy resin (manufactured by Ciba Geigy, "LY
-556 ") 100 parts by weight, a curing agent (manufactured by Ciba Geigy," HY-917J ") 90 parts by weight and an accelerator (manufactured by Ciba Geigy," DY-062 ") 1 part by weight as a matrix. Mixing the porous carbon fiber in the matrix so that the volume ratio of the porous carbon fiber in the matrix is 20%,
A cured composite material was obtained by curing at 100 ° C. for 1 hour and then at 150 ° C. for 2 hours. This cured composite material was subjected to a bending test according to JIS K7203. As a result, the bending strength is 20.4 kg / mm
² , the flexural modulus was 631 kg / mm ² .

(Comparative Example 1) Using the vapor-grown carbon fiber used in the above-mentioned Example 1, the resin composition similar to that in Example 1 was used as a matrix and cured under the same conditions as in Example 1 to obtain a composite. Got the material. The flexural strength and flexural modulus of this cured composite material were measured in the same manner as in Example 1. As a result, the bending strength was 14.2 kg / mm ² ,
The flexural modulus was 513 kg / mm ² .

(Examples 2 to 7) Gas phase having a diameter of 0.8 μm, a specific gravity of 1.96 g / m ² , an aspect ratio of 46, and a specific surface area calculated from this of 2.58 m ² / g A grown carbon fiber was prepared. This vapor grown carbon fiber is
While heating at 100 ° C., a mixed gas of nitrogen having a water vapor concentration of 70% by volume and oxygen of 5% by volume, water vapor and oxygen was brought into contact with the vapor grown carbon fiber at a total flow rate of 5 liters / minute. At this time, the contact time was changed to obtain porous carbon fibers having different specific surface area ratios.

Then, as in the case of Example 1, using epoxy resin as a matrix, a composite material was formed so that the volume ratio of the porous carbon fibers was 20%.
A bending test was performed according to SK7203. The results are shown in Table 2.

[0042]

[Table 2]

Example 8 The same vapor-grown carbon fiber prepared in Example 7 was heated to 1,000 ° C. and a mixed gas of nitrogen and water vapor having a water vapor concentration of 80% by volume was added. 5 liters / total flow rate for vapor grown carbon fiber
For 10 minutes to obtain a porous carbon fiber. This porous vapor-grown carbon fiber is used in an argon gas atmosphere for 2,
It was treated at 900 ° C. for 30 minutes to obtain a porous graphite fiber. The specific gravity of this porous graphite fiber measured by the Archimedes method was 2.25 g / cm ² , and the specific surface area measured by the BET method was 25.1 m ² / g. The specific surface area calculated was 2.52 m ² / g, and the specific surface area ratio C was 0.96. A composite material was formed from this porous graphite fiber in the same manner as in Example 1, and JIS K72 was used.
Bending test was performed according to No. 03. As a result, the bending strength was 23.1 kg / mm ² , and the bending elastic modulus was 661 kg.
/ Mm ² .

Comparative Example 2 A composite material was obtained in the same manner as in Example 8 except that the treatment with steam was not performed.
This composite material was subjected to a bending test according to JIS K7203. As a result, bending strength is 13.5 kg / m
m ² and the flexural modulus was 551 kg / mm ² .

(Example 9) The vapor-grown carbon fiber obtained in Example 1 was graphitized in a nitrogen atmosphere at 2850 ° C for 10 minutes in one space of a Pyrex glass tube having a constricted central portion. 0.05 g of graphite fiber obtained by treatment
While containing 0.03 g of purified potassium in the other space.
5g was stored. Then, both spaces in the glass tube were sealed under vacuum to obtain a Pyrex tube having a length of 12 cm, an inner diameter of 10 mm, and a necked portion inner diameter of 4 mm. This Pyrex tube was loaded into an electric furnace and heat-treated at 250 ° C. for 1 day.

As a result, the graphite fiber changed from black to yellowish brown, and the first stage graphite-potassium intercalation compound KC ₈
It was shown that it became. Put the yellow-brown fiber into a 200cc glass container filled with hydrogen,
When the state of hydrogen gas absorption was observed, it reached parallel in about 8 days. In addition, a similar experiment was conducted using the vapor-grown carbon fiber before the oxidation treatment. It took 2 days for the whole to turn yellowish brown, and it took 24 hours for the hydrogen gas absorption to reach parallel.
Needed more than time.

[0047]

Since the porous carbon fiber of the present invention has a specific surface area ratio within a specific range and is porous, it can be used as a reinforcing filling material for various composite materials and can utilize its ability to form intercalation compounds. And is useful as a host material for the intercalation compound. Particularly, when the porous carbon fiber is dispersed in the matrix material, the stress transmissibility between the porous carbon fiber and the matrix material is improved, and the mechanical strength of the composite material can be improved. Further, according to the method of the present invention, the porous carbon fiber having the above-mentioned excellent properties can be produced by a simple treatment process. Moreover, according to the present invention, porous graphite fibers can be easily produced from such excellent porous carbon fibers.

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[Procedure amendment]

[Submission date] July 8, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

As a result, the graphite fiber changed from black to yellowish brown, and the first stage graphite-potassium intercalation compound KC ₈
It was shown that it became. Put the yellow-brown fiber into a 200cc glass container filled with hydrogen,
Observation of hydrogen gas absorption showed equilibrium in about 8 hours.
It reached. In addition, when the same experiment was conducted using the vapor-grown carbon fiber before the oxidation treatment, it took two days for the whole to turn yellowish brown, and it took 24 hours for the hydrogen gas absorption to reach equilibrium.
Needed more than time.

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Claims (6)

[Claims] 1. A condensed ring-shaped carbon surface is laminated in an annual ring shape around a fiber axis, and the center of the fiber axis is hollow, and the formula B / A is used.
(However, B represents the specific surface area by the BET method, and A represents the specific surface area that can be calculated by the average diameter and the average length.) The specific surface area ratio C is 1.5 to 20.
And a porous carbon fiber characterized by being porous. 2. The porous carbon fiber according to claim 1, which has a pore volume of 2 × 10 ⁻² cc / g or more with a pore diameter of 600 Å or less as measured by mercury porosimetry. 3. The vapor grown carbon fiber in steam or an inert gas containing steam and air or oxygen until the specific surface area ratio C according to claim 1 becomes 1.5 to 20, A method for producing a porous carbon fiber, which comprises heating. 4. The content of water vapor in the inert gas is 1
0 to 90% by volume, and the heating temperature is 500 to 1,500
The method for producing a porous carbon fiber according to claim 3, wherein the method is at ° C. 5. A method for producing a porous graphite fiber, which comprises heating the porous carbon fiber obtained by the method according to claim 3 or 4 to 1,500 ° C. or higher to graphitize it. Method. 6. The porous carbon fiber obtained by the method according to claim 3 or 4 is added to 50% in an inert gas.
A method for treating a porous carbon fiber, which comprises heating to 0 to 1,500 ° C.