JPH08295565A - Production of silicon carbide material - Google Patents

Abstract

PURPOSE: To obtain a silicon carbide material having superior strength and suitable for use as the reinforcing fibers of a composite material, a heat insulator, a filter material, etc., and to especially obtain a silicon carbide material having a fibrous, sheetlike or three-dimensional structure. CONSTITUTION: This silicon carbide material is made of a fibrous, sheetlike or three-dimensional structure having 100-3,000m<2> /g specific surface area. A porous carbon material contg. at least one kind of metal selected from among B, Al, Si, Ti, Y and Mg or at least one kind of metallic compd. selected from among oxides, hydrides, hydroxides, alkoxides, nitrides and halides of the metals is allowed to react with gaseous SiO at 800-2,000 deg.C and the resultant metal- or metallic compd.-contg. silicon carbide material is heated at 800-2,200 deg.C in an atmosphere not practically contg. oxygen or in a gaseous atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a reinforcing fiber of a composite material,
The present invention relates to a method for producing a silicon carbide material having excellent strength, which is suitable as a heat insulating material, a filter material, and the like, and in particular, a silicon carbide material having excellent fibrous, sheet-like and three-dimensional structures.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 1-131016 discloses a pole.
It consists of aggregates of fine particles and has a specific surface area of at least 100.
m²/ G of silicon carbide fine particles, especially for petrochemical catalysts
Carrier and high temperature catalytic reaction that can reach 1000 ° C
For the purpose of manufacturing as a body, the gas of silicon monoxide SiO is carbonized.
SiO in the first reaction zone, including the step of reacting with SiO.
₂+ Si mixture under pressure of 0.1-1.5 hPa 1
By heating to 100 to 1400 ° C, SiO gas is removed.
And has a specific surface area of at least 2 in the second reaction zone.
00m²/ G of the divided reactive carbon and the SiO
Since the gas is contacted at a temperature of 1100 to 1400 ° C
A method for producing silicon carbide is disclosed. like this
Silicon carbide has not been used as a carrier for catalysis of chemical reactions.
Therefore, increase the specific surface area as much as possible and
It is intended to last for a while.

Further, Japanese Patent Application Laid-Open No. 60-231820 discloses a method in which carbon fibers are heated and reacted with silicon monoxide (SiO) gas to coat the surfaces of the carbon fibers with silicon carbide. However, this method has a problem that silicon carbide adheres only to the very surface of the carbon fiber, and thus a fiber completely siliconized to the inside cannot be obtained, and the oxidation resistance is poor at high temperature. In order to solve this problem, the present inventors have found that the inside of the fiber contains uniform pores having a pore size of several angstroms to several hundred angstroms, a specific surface area of 100 to 2500 m ² / g, and a fiber diameter of 5 to 10 m ^2.
800 μm of 0 μm porous carbon fiber and silicon monoxide gas
A method of reacting at a temperature of 2000 ° C. was proposed (Japanese Patent Laid-Open No. 6-192917).

One of the above-mentioned porous carbon fibers is activated carbon fiber. As a method for producing this activated carbon fiber, a method using a cellulosic fiber such as rayon as a raw material (Japanese Patent Publication No. 61-58567). , A method using an acrylic fiber as a raw material (JP-A-61-28430), a method using a fiber obtained by spinning petroleum pitch as a raw material (JP-A-60-199922), a phenolic resin fiber A method of using as a raw material (Japanese Patent Publication No. 57-43647, etc.)
And the like, both of which, while contacting the carbon fiber obtained by heating the dehydration carbonization temperature of 200 to 400 ° C. in an inert gas atmosphere with steam, oxygen, carbon dioxide gas, and other oxidizing gas, 4 higher than the dehydration carbonization temperature
Activated carbon fibers are obtained by performing activation treatment of heating at 50 to 1000 ° C. However, the fiber obtained by the reaction between the porous carbon fiber and silicon monoxide gas is
Although it is a silicon carbide fiber consisting essentially of silicon carbide,
The strength was low and it was difficult for practical use.

Therefore, the inventors of the present invention have made diligent efforts to solve this problem, and heat-treat the silicon carbide fiber obtained by the above method in a gas atmosphere such as oxygen gas or nitrogen gas to obtain strength. Although it has been found that the above-mentioned characteristics are improved (Japanese Patent Application Laid-Open No. 7-18520, Japanese Patent Application No. 6-73425).
No.), the strength was not sufficient for practical use. On the other hand, conventionally, when a metal such as Fe, Al, Cr, or B, particularly B (boron) and C (carbon), is added in a trace amount when the silicon carbide powder is sintered by hot pressing, the silicon carbide particles are It is known that the sinterability of slag is increased and a sintered body having high strength can be obtained at high temperature (silicon carbide ceramics, 1
55-173, 1988, issued by Uchida Otsuruho Co., Ltd.). However, this method has a problem in dispersibility and cannot be applied to a delicate material.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, the inventors of the present invention have been keen on a method of improving the strength of silicon carbide materials, particularly silicon carbide materials having fibrous, sheet-like and three-dimensional structures. As a result of examination, when a porous carbon material used as a raw material of a silicon carbide material is made to contain silicon or a metal compound in advance and then siliconized, the obtained silicon carbide material is substantially free of oxygen. When heated in an atmosphere, an inert gas, or a nitrogen gas atmosphere, the above-mentioned problems regarding the strength of the conventional silicon carbide material in the fibrous, sheet-shaped and three-dimensional structures are solved, and it is superior to the conventional level. It was found that tensile strength was developed, and the present invention was completed. It is an object of the present invention to provide a method for producing a silicon carbide material using a porous carbon material, the method providing a silicon carbide material having more excellent strength than ever before.

[0007]

The first aspect of the present invention is obtained by reacting a porous carbon material having a specific surface area of 100 to 3000 m ² / g with a silicon monoxide gas at a temperature of 800 to 2000 ° C. In the method for producing a silicon carbide material, the porous carbon material is preliminarily contained with a metal or a metal compound, and the second aspect of the present invention provides the method for producing a silicon carbide material. The method for producing a silicon carbide material according to the first aspect of the present invention is characterized in that heating is performed at a temperature of 800 to 2200 ° C. in an atmosphere or a gas atmosphere that does not substantially contain oxygen. In a third aspect of the present invention, the porous carbon material is selected from a porous carbon fiber, a sheet made of porous carbon fiber, a three-dimensional structure made of the sheet, and a three-dimensional structure made of porous carbon fiber. The method for producing a silicon carbide material according to the first or second aspect of the present invention is characterized in that it is one kind. A fourth aspect of the present invention is that the metal is at least one selected from boron (B), aluminum (Al), silicon (Si), titanium (Ti), yttrium (Y), and magnesium (Mg). The method for producing a silicon carbide material according to the first, second or third aspect of the present invention is characterized by: A fifth aspect of the present invention is characterized in that the metal compound is at least one selected from the oxides, hydrides, hydroxides, alkoxides, nitrides and halides of the metals described in the fourth aspect of the present invention. The method for producing a silicon carbide material according to the first, second or third aspect of the present invention.

The fiber or fibrous substance in the present invention means a continuous long fiber (filament or yarn) having a fiber diameter of 5 to 100 μm or a short fiber of 1 to 100 mm,
Fiber diameters other than those mentioned above can be used,
Fiber diameter is 0.5-1 μm and aspect ratio is 20-100
It does not contain fine fibrous substances such as whiskers characterized by. The sheet in the present invention means a sheet made of the above-mentioned fibrous substance and having a planar spread, and for example, it is obtained by arranging continuous long fibers (filaments, yarns) in the warp and weft directions. Included is a cloth-like material or a short fiber having an appropriate length formed into a sheet by a dry method or a wet method (felt, sheet, mat, etc.). Further, when they are made into sheets, it is possible to add granular and powdery ones. In addition, Tokuhei 2-2
As disclosed in Japanese Patent No. 3505, a sheet obtained by mixing organic fiber and pulp for producing carbon fiber and making paper is impregnated with an organic polymer solution in which carbonaceous powder is suspended. A porous carbon plate obtained by baking after drying and firing at a temperature of 800 ° C. or higher in an inert gas atmosphere can also be used in the present invention.

Further, the three-dimensional structure in the present invention is
A granular or powdery substance, a fibrous substance, or a sheet made of a fibrous substance, having a three-dimensional shape is meant, and for example, the sheet-like substance is pasted and processed. It includes three-dimensionalized ones and three-dimensionally three-dimensionally processed ones of granular, powdery and fibrous substances. The porous carbon material having a sheet-like or three-dimensional structure used in the present invention preferably contains the activated carbon fiber at least 10% by weight of the sheet or the three-dimensional structure when the material is composed of activated carbon fiber. When the content of the activated carbon fibers is less than 10%, the amount of silicon carbide fibers contained in the obtained silicon carbide material becomes insufficient when silicon carbide is formed, and the expected performance cannot be obtained. The porous carbon fiber, sheet and three-dimensional structure used in the present invention can be obtained by directly applying the known method disclosed in JP-A-6-192917.

The silicon carbide material of the present invention is obtained by preliminarily containing a metal or a metal compound in the porous carbon material as a raw material thereof, and then reacting it with silicon monoxide (SiO). Further, the obtained silicon carbide material containing a metal or a metal compound is optionally heated in an atmosphere containing substantially no oxygen, an inert gas atmosphere or a nitrogen gas atmosphere. That is, in the present invention, a porous activated carbon material as a starting material is made to contain a metal or a metal compound uniformly as a third component in advance, and the porous carbon material is reacted with silicon monoxide to form silicon carbide. During the process, the metal or metal oxide is bonded to silicon carbide, which improves the strength of the silicon carbide material. Further, the obtained silicon carbide material is subjected to a heat treatment in a reduced pressure atmosphere containing substantially no oxygen, a gas atmosphere containing no oxygen and nitrogen, or a nitrogen gas atmosphere containing no oxygen to burn silicon carbide. By assisting or further promoting the binding, the strength of the finally obtained silicon carbide material is further improved.

In the present invention, the porous carbon material containing a metal or a metal compound has a specific surface area of 100 to 3000 m ² / g, and the metal or the metal compound is contained inside the porous carbon. It is a material. Porous carbon material, as long as it has the specific surface area, may be an activated carbon material by any production method by known activation treatment, or may be produced by another method not by activation treatment, fiber The sheet or the three-dimensional structure containing fibers or fibers is preferably made of acrylic fiber as a raw material or phenolic resin fiber as a raw material. Further, if the porous carbon material contains the above-mentioned metal or metal compound, the metal or metal compound is either on the surface of the porous carbon, inside the pores or inside the pore walls, or two of them. It may be contained over the above parts. That is, in the present invention, the metal or the metal compound may be contained in any part of the porous carbon and is not particularly limited.

The content of the metal or metal compound contained in the porous carbon material having the fibrous, sheet-like or three-dimensional structure used in the present invention is 10 weight% of the total carbon material weight when the metal is a simple substance. %, And in the case of a metal compound, the metal compound is 20% by weight or less based on the total weight of the carbon material. If the amount of metal or metal compound exceeds the above range, the obtained silicon carbide material loses its properties as silicon carbide or significant grain growth of silicon carbide occurs, and the strength of the obtained silicon carbide material is reversed. It may decrease to. The lower limit of the content of such metal or metal compound varies depending on the form and type of metal, but is 0.01
% By weight. The metal contained in the porous carbon material used in the present invention includes boron (B), aluminum (A
l), silicon (Si), titanium (Ti), yttrium (Y), magnesium (Mg),
At least one of these is selected and used.
Further, examples of the metal compound contained in the porous carbon material used in the present invention include oxides, hydrides, hydroxides, alkoxides, nitrides, and halides of the above metals. Similarly, at least one selected from these metal compounds is used. Further, the metal and the metal compound may be combined and used together.

When a metal or metal compound is contained in the porous pores of the porous carbon material used in the present invention or on the surface of the material, for example, after the porous carbon material is immersed in an aqueous solution containing the target metal or metal compound. , A method of removing the excess solution by removing the liquid and drying it, a method of bringing the gas containing the target metal or metal compound into contact with the porous carbon material, and adsorbing it in the pores of the porous carbon material. However, the method of incorporating the metal or the metal compound is not particularly limited to the above method. The metal or metal compound contained in the porous carbon material is hydrolyzed, oxidized, or
It may be subjected to chemical changes such as reduction. In particular, as a method of containing a metal or a metal compound only inside the pores of a porous carbon material, porous carbon (activated carbon) and a metal alkoxide are separately placed in a closed container or in a dry air stream, and the metal alkoxide Porous carbon containing metal oxides is generated by generating steam, adsorbing the steam on the porous carbon, and then contacting it with water vapor to hydrolyze the adsorbed metal alkoxide to form a metal oxide. The method (Japanese Patent Application No. 7-49716) can be preferably used.

The method of incorporating a metal or metal compound into the inside of the pore walls of the porous carbon material is, for example, at the stage of a polymer consisting of an organic compound before carbonization, in which the target metal is added to the polymer. It is contained as a simple substance, or mixed in the form of a metal compound, and then converted to the target metal simple substance or another metal compound by hydrolysis, neutralization, thermal decomposition, oxidation, reduction, etc., or a polymer of an organic compound is fibrous. , In the form of a sheet or a three-dimensional structure,
After the metal compound containing the target metal is allowed to act on the molded product in a liquid state or in a gaseous state and contained therein, the metal compound may be contained in the porous carbon through the steps of carbonization and activation. Alternatively, a method may be used in which the target metal or metal compound is contained in the carbon by further carrying out the chemical reaction as described above after containing the metal compound in this way. For example, if metallic boron is added to a novolac resin, mixed well, spun, carbonized and activated, a porous carbon fiber containing boron inside the pore walls can be obtained. The method of incorporating the metal or the metal compound into the pores of the porous carbon material, the material surface or the pore wall of the present invention is not limited to the above method.

The above-mentioned porous carbon material containing a metal or a metal compound is converted into silicon carbide by a known method disclosed in JP-A-6-192917. That is, the porous carbon material is composed of silicon monoxide gas and a temperature of 80%.
A silicon carbide material is obtained by reacting at 0 to 2000 ° C.
As the silicon monoxide gas used in this case, a mass or powder of silicon monoxide or silicon dioxide, or a mixture of silicon and silicon monoxide or fine particles of silicon and silicon dioxide well mixed, is used as a supply source and is 10 ⁻⁶ to 10 Pa. Under reduced pressure of (Pascal),
Helium (He), Neon (Ne), Argon (Ar)
What is generated by heating to 500 to 2000 ° C. in an inert gas atmosphere such as or in a nitrogen (N ₂ ) gas stream is introduced into the reaction furnace and used for the reaction. On the other hand, a certain amount of the mixture serving as a supply source of silicon monoxide gas and a specific amount of the porous carbon material may be placed in the same heating furnace and heated to simultaneously generate gas and silicon carbide. In that case, the weight of the substance that generates silicon monoxide is used in an amount of 1.5 to 30 times the mass of the porous carbon material, and it is desirable that the distance between the two in the heating furnace be as small as possible.

That is, when a supply source of silicon monoxide gas and a porous carbon material are placed in the same furnace and heated, in order to react with the carbon while maintaining a high concentration of the generated silicon monoxide gas, It is effective to increase the reaction rate by bringing both of them close to each other and by covering them with some kind of cover so that the generated silicon monoxide gas is in contact with the porous carbon material as much as possible so as not to escape. is there. In this case, it is preferable that the material of the cover be heat-resistant, dense, and non-permeable, such as alumina. In the method of the present invention, the silicidation reaction is an internal heating type, an external heating type, or an induction heating type heating furnace capable of firing in a gas atmosphere or gas stream under reduced pressure or normal pressure, and the furnace material is alumina, Materials made of materials such as magnesia, zirconia, mullite, carbon and refractory metals can be preferably used. The silicon carbide conversion reaction is carried out under reduced pressure without using gas in the furnace, or He, N
e, under reduced pressure using an inert gas such as Ar, or N ₂ performed and kept under reduced pressure using a gas, 10 ^-3 to 10 ² Pa and vacuum here, preferably 10 ^over 2 10 Pa Is the pressure of.

The temperature of the furnace at which silicon carbide is formed is 80
The temperature is 0 to 2000 ° C, preferably 1000 to 1800 ° C. If the temperature of the furnace is as low as less than 800 ° C., the reaction between the carbon of the porous carbon material and silicon monoxide is insufficient and the inside of the porous carbon material is not completely converted to silicon carbide, and the temperature is 200 ° C.
If the temperature is higher than 0 ° C., the generated silicon carbide grains grow, the strength decreases, and the silicon carbide material is easily damaged, which is not suitable. The heating rate in the heating furnace is not particularly limited, but is performed at 50 to 1500 ° C./hour, and the holding time at the maximum temperature is 1 minute to 20 hours, preferably 30 minutes to
It is appropriately selected and used within a range of 10 hours. If the holding time is short such as less than 1 minute, the reaction becomes insufficient and the inside of the carbon material is not completely converted to silicon carbide. If the holding time is longer than 20 hours, the generated silicon carbide is generated as in the case of high temperature. Are not suitable because the grains grow and the strength decreases and the silicon carbide material is easily broken. Further, unnecessarily lengthening the reaction time is wasteful of energy and is uneconomical. Further, in order to obtain a silicon carbide material having higher strength, it is desirable to keep the material in a tension state when reacting the porous carbon material and silicon monoxide. In particular, when the material is a fiber, a sheet containing fibers, or a three-dimensional structure, the effect of improving strength by tensioning is high. For example, in the case of long fibers, it is preferable to tension the porous carbon fibers and fix both ends with an adhesive or a weight, or fix one end and attach a weight to the other end to tension the fibers.

The silicon carbide material obtained by reacting the porous carbon material containing the metal or the metal compound with silicon monoxide as described above is higher than the silicon carbide material containing no metal or the metal compound. By subjecting the silicon carbide material, which has strength, but further contains a metal or a metal compound, to heat treatment in an atmosphere that does not substantially contain oxygen, it is possible to exhibit even higher strength. The temperature for this heat treatment is 800-2200.
C., preferably 1000 to 2100.degree. Temperature is 8
If the temperature is lower than 00 ° C., the sintering of the metal or metal compound and silicon carbide does not proceed, and the strength of the silicon carbide material does not improve. If the temperature exceeds 2200 ° C., the crystals or particles constituting the silicon carbide material become coarse. Grains grow into particles, and the silicon carbide is thermally decomposed to cause a weight reduction, resulting in a significant decrease in the strength of the silicon carbide material, which is not suitable. As the furnace used for the heat treatment, the same furnace as in the case of performing the silicidation can be used.

The atmosphere containing substantially no oxygen during the heat treatment is an atmosphere decompressed by a vacuum pump to an extremely low pressure of 10 ² Pa or less, an inert gas such as He, Ne, Ar or the like under atmospheric pressure or under pressure. In a stream of air or in a stream of N ₂ gas, the oxygen content in that case is 0.1.
Volume% or less. When a silicon carbide material containing no metal or metal compound is subjected to a heat treatment in an atmosphere or a gas atmosphere which does not substantially contain oxygen and nitrogen, silicon carbide crystals and fine particles grow and the strength decreases conspicuously. However, in the case of the present invention, crystals and fine particles do not grow by heating even in an atmosphere substantially containing oxygen and nitrogen, and a marked improvement in strength can be obtained. The gas is placed in a silicon carbide material containing a metal or a metal compound in a heating furnace that maintains a heating temperature, introduced into the furnace under atmospheric pressure or under pressure, and passed through the silicon carbide material. When the above gas is introduced into the furnace under atmospheric pressure or under pressure, the flow rate of the gas used varies depending on the volume of the furnace, but the flow rate of the gas in the furnace changes from several times to several hundred times per hour. Preferably. If the flow rate of this gas is too low,
Sintering of silicon carbide with metal or metal compound does not proceed,
The effect of the heat treatment is not sufficiently exhibited, and even if the flow rate of the gas is too high, the effect of the treatment reaches the ceiling and is uneconomical. The time for performing the heat treatment in the atmosphere or in the gas stream cannot be unconditionally limited because it varies depending on the combination of conditions such as treatment temperature, gas flow rate, and pressure, but after reaching the treatment temperature,
It is several seconds to several tens of hours, preferably 5 to 600 minutes. If the treatment time is short, heat is not sufficiently transmitted to the silicon carbide material, and the temperature of the silicon carbide material does not rise sufficiently, so that the heat treatment effect is not sufficiently exhibited, and a long treatment time decreases the productivity or is obtained. It is not suitable because it grows silicon carbide crystals and fine particles, and conversely reduces the strength of the silicon carbide material.

The heating rate in the heating furnace is not particularly limited, but it is selected from the range of 10 to 12000 ° C./hour and used. It is effective to perform the heat treatment in two steps within the above temperature range. That is, the temperature is 10
In the range of 00 to 1500 ° C., if the temperature rising rate is slowed or the treatment time is set to be slightly longer in the above temperature range and a treatment temperature of 1500 to 2200 ° C. is applied in the latter half of the reaction, the metal or metal compound Sintering of silicon carbide can be efficiently performed with a smaller content. Heat treatment temperature is 10
When the temperature is less than 00 ° C. and exceeds 1500 ° C., it is preferable that the temperature is as high as possible within the range in which the thermal expansion of the furnace material used in the heating furnace does not cause impact, and if the rate of temperature rise is too slow,
If the temperature is lower than 1000 ° C, the efficiency is poor and the productivity does not rise. If the temperature is 1500 ° C, it takes time to reach the predetermined temperature, and the silicon carbide material is kept at a high temperature close to the predetermined temperature for a long time. Since it is exposed, the desired effect cannot be obtained, and the efficiency becomes poor, so it is necessary to avoid it.
Further, as another method, a furnace preheated to a desired temperature in the range of 1000 to 1500 ° C. and 1500 to 2200 are used.
It is also possible to prepare two types of heating furnaces that are heated to a desired temperature in the range of ° C and heat at each temperature for a necessary time. Further, in order to obtain a silicon carbide material having higher strength, it is desirable to keep the silicon carbide material in a tension state even when the heat treatment is performed, as in the case of reacting the porous carbon material and silicon monoxide. . In particular, when the material is silicon carbide fiber, a sheet made of the same, or a three-dimensional structure, the effect of improving strength by tensioning is high.

As described in detail above, according to the present invention, by pre-containing the elemental metal or the metal compound in the porous carbon material, during the silicon carbide conversion or in the atmosphere containing substantially no oxygen. During the heating, certain bonds are uniformly generated between the silicon carbide and the metal or the metal compound, and this bond further increases the strength, and a practically excellent silicon carbide material can be manufactured.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples and comparative examples,% means
Unless otherwise specified, it represents% by weight.

Example 1 Long fiber bundle 0.5 of phenolic activated carbon fiber having a specific surface area of 1000 m ² / g (fiber diameter 10 μm, length 100 mm, trade name: Kynol activated carbon fiber, manufactured by Nippon Kynol Co., Ltd.)
g was dried in a hot air circulation dryer at a temperature of 105 ° C. for 12 hours. Next, a wire net having a 150-mesh support was placed at a position 20 mm from the bottom of a separable flask capable of opening and closing a 200-ml glass lid, and triethoxyborane (B (OC ₂ H ₅ ) ₃ ) (made by Aldrich) 5g was put, and the above-mentioned dried activated carbon fiber put in another glass container was placed on the wire net without the lid of the glass container so as not to come into direct contact with triethoxyborane. Then, the separable flask was immediately capped. Then, the inside of the separable flask was depressurized by an aspirator to the extent that triethoxyborane did not boil, and the flask was allowed to stand in a thermostatic chamber at 20 ° C. for 3 hours.

Then, 10 m of pure water was added to the bottom of another 200 ml separable flask equipped with a wire net in the same manner as above.
1 was prepared, and the activated carbon fiber adsorbed with triethoxyborane was taken out of the separable flask together with the glass container so as not to come into direct contact with water on the wire mesh of the prepared separable flask. placed. Immediately thereafter, the lid was closed, and this separable flask was allowed to stand in a thermostatic chamber at 20 ° C. for 2 hours for hydrolysis. After the reaction, the fiber had no change in appearance from that before the reaction and no fusion of the fibers was observed, but the weight of the fiber after heating in an electric furnace at a temperature of 350 ° C. for 3 hours was measured. When measured, it was increased by 3% compared to the dry weight before the reaction. This fiber was heated in air at 900 ° C. for 1 hour to be ashed, and the infrared absorption spectrum (I
As a result of measuring R), it was found that the substance supported on the fiber was an oxide of boron. From the weight increase, it was found that the content of boron oxide based on the total weight of activated carbon was 3.0%.

Next, 0.1 g of this activated carbon fiber containing boron oxide was placed on an alumina plate and fixed by placing 5 g of weight on each end. At the bottom of the alumina Tamman tube, granular silicon monoxide (reagent,
1 g of a product having a purity of 99.9% and manufactured by Wako Pure Chemical Industries, Ltd. was added to the activated carbon fiber near the opening, and a molybdenum sheet was covered on the opening. This Tammann tube is 60φ
1 Pa in a tubular furnace equipped with a core tube made of alumina
After that, the temperature was reduced to 1,300 ° C. at a heating rate of 400 ° C./hr, the temperature was maintained for 2 hours to perform silicon carbide conversion, and then naturally cooled to room temperature. When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ⁻¹ , and the diffraction angle of the crystal was examined using an X-ray diffractometer.
Since a peak was observed at CuKα2θ = 35.7 degrees, it was found that this fiber was made of crystalline silicon carbide.

Further, the obtained fiber is treated with 1000 in air.
After heating at ℃ for 1 hour, no weight loss was observed, so it was revealed that there was no unreacted carbon. When the tensile strength of the obtained fiber was measured, it was 1500 MPa. A part of the obtained silicon carbide fiber was placed on a graphite plate and fixed with 5 g of weight on each end, and then placed in a graphite furnace having a core tube of 50φ and 500 ml / min. While flowing argon gas (purity 99.999% by volume) at a flow rate, up to 1200 ° C. 3
The temperature was raised in 0 minutes (2400 ° C / hour) and the temperature was raised to 300
After holding for 1 minute, the temperature is raised to 1800 ° C in 30 minutes (12
The temperature was held for 60 minutes, and then cooled to room temperature. The total flow rate of the argon gas used was 200 times the volume of the heating furnace. When the tensile strength of the obtained fiber was measured, it was 2000 MPa.

The test methods used to measure the specific surface area and tensile strength used in the present invention are as follows. Test Method (1) Specific Surface Area of Porous Carbon Material The specific surface area was measured by the low temperature nitrogen adsorption method using the BET multipoint method. (2) Tensile Strength According to the method of JIS R-7601, the tensile strength was measured at room temperature using a tensile tester (Tensilon; manufactured by Toyo Baldwin).

Comparative Example 1 The same specific surface area as used in Example 1 is 1000 m ² / g
0.1g long fiber bundle of dried phenol-based activated carbon fiber
Was used, and silicon carbide was formed in the same manner as in Example 1 except that triethoxyborane was not used. When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ⁻¹ , and the diffraction angle of the crystal was examined using an X-ray diffractometer. Since a peak was observed at CuKα2θ = 35.7 degrees, it was found that this fiber was made of crystalline silicon carbide. Further, the obtained fiber is heated to 1000 in air.
After heating for 1 hour at 0 ° C., no weight loss was observed and it was found that there was no unreacted carbon. When the tensile strength of the obtained fiber was measured, it was 800 MPa. Then, the silicon carbide fiber was heated in an argon gas (purity 99.999% by volume) in the same manner as in Example 1, and the obtained fiber was slightly coarsened as compared with the fiber before the heat treatment. It was observed that the tensile strength of the fiber had dropped to 400 MPa.

Example 2 Example 1 was repeated except that an activated carbon fiber made of a polyacrylonitrile resin having a specific surface area of 700 m ² / g was used as a raw material.
It was put in a hot air circulation type dryer in the same manner as above and dried at a temperature of 105 ° C. for 12 hours. Triethoxyborane was adsorbed and hydrolyzed on the activated carbon fiber in the same manner as in Example 1 except that 0.1 g of this activated carbon fiber was used. The fibers after the reaction did not change in appearance as compared with those before the reaction, and fusion between the fibers was not observed. This fiber in an electric furnace 350
When the weight after heating for 3 hours at ℃ was measured, it was increased by 2.5% compared to the dry weight before the reaction. Infrared absorption spectrum (IR) of the fiber which had been ashed by heating this fiber at 900 ° C. for 1 hour in air was measured by the potassium bromide tablet method. As a result, the substance supported on this felt was a boron oxide. I found out. The content of boron oxide based on the total weight of activated carbon was 2.5%. Next, silicon carbide was formed in the same manner as in Example 1 except that 0.1 g of activated carbon fiber containing boron oxide and 1 g of silicon monoxide were used.

When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ^-1 , and the diffraction angle of the crystal was examined by using an X-ray diffractometer. CuKα2θ = 3
Since the peak was observed at 5.7 degrees, it was found that this fiber was composed of crystalline silicon carbide. Furthermore, the obtained fiber was heated in air at 1000 ° C. for 1 hour, but no weight loss was observed. The tensile strength of the obtained fiber was measured and found to be 1600 MPa. Furthermore, a heat treatment was performed in the same manner as in Example 1 except that this silicon carbide fiber was used. X of the obtained fiber
When the line diffraction analysis was carried out in the same manner as in Example 1, it was found that this fiber was composed of silicon carbide. The tensile strength of this fiber was measured and found to be 2100 MPa.

Comparative Example 2 Activated carbon fibers were carbonized in the same manner as in Example 1 except that activated carbon fibers made of polyacrylonitrile resin having a specific surface area of 700 m ² / g were used as raw materials and triethoxyborane was not used. Siliconized. The fiber obtained was made of silicon carbide and had a tensile strength of 1000 MPa. Further, a portion of this silicon carbide fiber was placed on a graphite plate, and a weight of 5 g was placed on each end of the graphite plate, and the fiber was placed in a graphite furnace having a 50φ core tube. While flowing nitrogen gas (purity 99.999% by volume) at a flow rate of, the temperature was raised to 1200 ° C. in 30 minutes (2400 ° C./hour), and the temperature was raised to 30
After holding for 0 minutes, the temperature was raised to 1600 ° C in 20 minutes (12
(00 ° C./hour), the temperature was maintained for 60 minutes, and then cooled to room temperature. The total flow rate of nitrogen gas used was 200 times the volume of the heating furnace. When the tensile strength of the obtained fiber was measured, it was 1300 MPa.

Example 3 In the same manner as in Example 1 except that tetraethoxysilane (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal alkoxide, the metal alkoxide was adsorbed on the activated carbon fiber and hydrolyzed to obtain silicon. A metal oxide was included in the activated carbon fiber. After the reaction, the fibers had no change in appearance from those before the reaction and no fusion of the fibers was observed, but the fibers were dried with a hot air circulation dryer at a temperature of 105 ° C. for 12 hours. When the rear weight was measured, it was increased by 30% as compared with the weight when first dried. An infrared absorption spectrum (IR) was measured by the potassium bromide tablet method for a portion of this fiber which had been heated in air at 900 ° C. for 1 hour to be incinerated. As a result, the substance supported on the fiber was silicon. It was found to be an oxide. From the weight of the remaining ashed material, it was found that the content of silicon oxide based on the total weight of activated carbon was equivalent to 4.0%. Next, the fibers were siliconized in the same manner as in Example 1 except that the activated carbon fibers supporting the silicon oxide were used.

When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was found at around 900 cm ^-1 , and the diffraction angle of the crystal was examined by using an X-ray diffractometer. CuKα2θ = 3
Since the peak was observed at 5.7 degrees, it was found that this fiber was composed of crystalline silicon carbide. Furthermore, the obtained fiber was heated in air at 1000 ° C. for 1 hour, but no weight loss was observed. The tensile strength of the obtained fiber was measured and found to be 1600 MPa. Subsequently, 0.07 g of the obtained fiber was placed on a graphite plate, and 5 g of weight was placed on each end of the graphite plate and fixed, and then placed in a graphite furnace having a 50φ core tube.
While flowing nitrogen gas (purity 99.999% by volume) at a flow rate of 00 ml / min, the temperature was raised to 1200 ° C. in 30 minutes (2
400 ° C./hour), after holding that temperature for 300 minutes,
After raising the temperature to 1600 ° C. in 20 minutes (1200 ° C./hour) (1200 ° C./hour) and maintaining the temperature for 3 hours,
Cooled to room temperature. The total flow rate of nitrogen gas used was 250 times the volume of the graphite furnace. When the tensile strength of the fiber after this heat treatment was measured, it was 2000 MPa.

Example 4 In the same manner as in Example 1 except that titanium isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal alkoxide, the metal alkoxide was adsorbed on the activated carbon fiber and hydrolyzed, An oxide of titanium metal was included in the activated carbon fiber. The appearance of the fiber after the reaction was the same as that before the reaction and the fusion of the fibers was not observed, but the weight was measured after heating the fiber in an electric furnace at a temperature of 500 ° C for 1 hour. When compared, 3.5% compared to the dry weight before reaction
Was increasing. This fiber was heated in air at 900 ° C. for 1 hour to be incinerated, and the result of analysis by a fluorescent X-ray method and an X-ray diffraction method revealed that the substance contained in the fiber was an oxide of titanium. It was From the weight increase, it was found that the content of titanium oxide based on the total weight of activated carbon was 3.5%. Next, the fibers were siliconized in the same manner as in Example 1 except that the activated carbon fibers containing the oxide of titanium were used.

When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ^-1 , and the diffraction angle of the crystal was examined using an X-ray diffractometer. CuKα2θ = 3
Since the peak was observed at 5.7 degrees, it was found that this fiber was composed of crystalline silicon carbide. Furthermore, the obtained fiber was heated in air at 1000 ° C. for 1 hour, but no weight loss was observed. The tensile strength of the obtained fiber was measured and found to be 1600 MPa. Furthermore, the silicon carbide fiber containing the oxide of titanium was used, and the heat treatment condition was 1200 ° C. for 300 minutes, 1900
The heat treatment was performed in the same manner as in Example 1 except that the temperature was 60 minutes. When the tensile strength of the obtained fiber was measured, it was 2100 MPa.

Example 5 In a horizontal tubular reaction vessel, 0.5 g of the activated carbon fiber used in Example 1 and 5 g of solid aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) as a metal alkoxide were placed in dry nitrogen. When introducing (purity 99.9% by volume) into the reaction vessel, aluminum isopropoxide is upstream,
The activated carbon fibers were placed so that they were on the downstream side and they were not mixed. 50m of the dry nitrogen in a cylindrical reaction vessel
While flowing at a flow rate of 1 / min, aluminum isopropoxide and activated carbon fibers were heated to 150 ° C. by a heater wound on the outside of the reaction vessel and held for 3 hours. It was carried by a stream of air and adsorbed on activated carbon downstream. After cooling, the activated carbon fiber was taken out and the metal alkoxide adsorbed on the activated carbon fiber was hydrolyzed in the same manner as in Example 1 to contain an oxide of aluminum in the activated carbon. After the reaction, the fibers had no change in appearance from those before the reaction and no fusion of the fibers was observed, but after heating the fibers at a temperature of 105 ° C. for 12 hours with a hot air circulation dryer. When the weight was measured, it was increased by 20% compared to the dry weight before the reaction. A part of this fiber was heated in air at 1200 ° C. for 1 hour to be incinerated, and the result was measured by infrared absorption spectrum by potassium bromide tablet method and analysis result by X-ray diffraction method. The substance that was identified was found to be an oxide of aluminum. From the weight of the remaining ashed material, the content of aluminum oxide per total activated carbon weight was found to correspond to 3.0%.

Then, the fibers were siliconized in the same manner as in Example 1 except that the activated carbon fibers carrying the aluminum oxide were used. When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ⁻¹ , and the diffraction angle of the crystal was examined using an X-ray diffractometer.
Since a peak was observed at CuKα2θ = 35.7 degrees, it was found that this fiber was made of crystalline silicon carbide. Furthermore, the obtained fiber was heated in air at 1000 ° C. for 1 hour, but no weight loss was observed. Also,
The tensile strength of the obtained fiber was measured to be 1700.
It was MPa. Furthermore, the heat treatment was performed in the same manner as in Example 3 except that silicon carbide fibers containing an oxide of aluminum were used. When the tensile strength of the obtained fiber was measured, it was 2100 MPa.

Example 6 6.5 kg of phenol, 3.4 kg of formalin having a solid content of 44% and 20 g of oxalic acid were placed in a separable flask having a capacity of 10 liter, and stirred at 20 ° C. to 1 ° C.
The temperature was raised to 00 ° C. in 5 hours, and this temperature was maintained for 1 hour. Then, it heated under reduced pressure of 20 mmHg and heated up to 180 degreeC in 3 hours, and removed water, an unreacted substance, and a low boiling point compound. The melt softening temperature of the obtained novolak resin was 125 ° C. After 2 kg of the obtained resin was heated and melted at 150 ° C., 4 g of metal boron powder was added and mixed well, and then spun at 145 ° C. using a spinneret having a number of holes of 120 and a hole diameter of 0.20 mmφ at 700 m / min. It was wound up at a speed of to obtain an uncured novolac fiber. The uncured novolac fiber obtained is immersed in a mixed aqueous solution of 18% hydrochloric acid and 13% formaldehyde at 20 ° C.
After gradually raising the temperature to 7 ° C, the temperature was maintained at 95 to 98 ° C for 5 hours. The fibers thus obtained were immersed in a 5% aqueous ammonia solution and treated at a temperature of 75 ° C. for 3 hours to be cured.

10 g of the obtained cured novolac fiber was added to 60 g.
The tube was placed in a tubular furnace equipped with a φ-made alumina core tube, and nitrogen gas (purity 9
(9.9% by volume) and then heated up to 150 ° C.,
A mixed gas consisting of 76.5% by volume of nitrogen and 23.5% by volume of water vapor, which was obtained by passing nitrogen gas whose flow rate was reduced to 390 ml / min, through hot water previously heated to 70 ° C. was added to nitrogen. Instead, the temperature was raised to 700 ° C. in 1 hour while flowing into the core tube, and then the flow rate was changed to only 500 ml / min of nitrogen gas again, and the temperature was raised to 800 ° C. in 12 minutes to raise the temperature to 3
After holding for 0 minutes, it was cooled. The specific surface area of the obtained porous carbon fiber was 1000 m ² / g, and the yield of the porous fiber obtained by activating the novolak resin containing no metal boron in the same manner as above was 40%. Therefore, the content ratio of metal boron contained in the activated carbon fiber was 0.5% based on the total weight of the activated carbon. Then, the fibers were siliconized in the same manner as in Example 1 except that the porous carbon fibers containing the metal boron were used.

When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ⁻¹ , and the diffraction angle of the crystal was examined by using an X-ray diffractometer. CuKα2θ = 3
Since the peak was observed at 5.7 degrees, it was found that this fiber was composed of crystalline silicon carbide. Furthermore, when the obtained fiber was heated in air at 1000 ° C. for 1 hour, no weight loss was observed. When the tensile strength of the obtained fiber was measured, it was 1600 MPa. next,
0.07 g of the obtained silicon carbide fiber containing boron metal
The heat treatment was performed in the same manner as in Example 1 except that the above was used. When the tensile strength of the fiber after this heat treatment was measured, it was 2000 MPa.

Example 7 2 kg of novolak resin was heated and melted at 150 ° C.
To 2.4g of metallic boron powder and alumina (aluminum
Oxide, manufactured by Aldrich) except that 8 g of powder was added,
In the same manner as in Example 6, spun into fibers, cured, and
After carbonization and porosification (activation) are performed, metal boron and
1000m specific surface area containing Lumina ²/ G porous
Carbon fiber was obtained. Novolac resin as in Example 6
Since the yield of porous carbon fiber from is 40%,
Content of boron metal and alumina in the obtained porous fiber
Are 0.3% and 1.0% based on the total carbon fiber weight, respectively.
there were. Next, Example 1 except that this fiber was used.
The fibers were siliconized in the same manner as in. Obtained fiber
Infrared absorption spectrum of fiber was measured by potassium bromide tablet method.
When examined, 900 cm^-1Absorption of silicon carbide
And the diffraction angle of the crystal was investigated using an X-ray diffractometer.
As a result, a peak was observed at CuKα2θ = 35.7 degrees.
Therefore, this fiber is made of crystalline silicon carbide.
I understood. Further, the obtained fiber is heated to 1000 in air.
After heating at ℃ for 1 hour, no weight loss was observed.
Was. The tensile strength of the obtained fiber was measured to be 16
It was 00 MPa. Next, include metal boron and alumina.
Using the silicon carbide fiber having
Other than that it was 300 minutes at 0 ° C and 60 minutes at 1700 ° C
Was heat-treated in the same manner as in Example 1. This heating
When the tensile strength of the treated fiber was measured, it was 2100M.
It was Pa.

Example 8 Example 2 was conducted except that 2 kg of novolac resin was heated and melted at 150 ° C., and 8 g of alumina powder, 3.2 g of yttria (yttrium oxide) powder and 4 g of magnesia (magnesium oxide) powder were added. In the same manner as in Example 6, the fiber was spun into a fiber, cured, and then carbonized and made porous to obtain a porous carbon fiber containing alumina, yttria and magnesia and having a specific surface area of 1000 m ² / g. The content of alumina, yttria and magnesia in the obtained fiber was 1.0 based on the total carbon fiber weight,
0.4 and 0.5%. Then, the fibers were siliconized in the same manner as in Example 1 except that this fiber was used. When the infrared absorption spectrum of the obtained fiber was examined by the potassium bromide tablet method, absorption of silicon carbide was observed at around 900 cm ⁻¹ , and the diffraction angle of the crystal was examined using an X-ray diffractometer. CuKα2θ = 35.7
It was found that this fiber was composed of crystalline silicon carbide, because peaks were observed every time. Furthermore, the obtained fiber was heated in air at 1000 ° C. for 1 hour, but no weight loss was observed. When the tensile strength of the fiber was measured, it was 1800 MPa. Next, heat treatment was performed in the same manner as in Example 3 except that silicon carbide fibers containing alumina, yttria, and magnesia were used.
When the tensile strength of the fiber after this heat treatment was measured, it was 2
It was 100 MPa.

Example 9 A felt (a unit weight of 120 g / m ² by Kuraray Chemical Co., Ltd.) made of activated carbon fibers made of a phenol resin having a specific surface area of 1000 m ² / g as a raw material was put in a hot air circulation dryer,
It was dried at a temperature of 105 ° C. for 12 hours. Triethoxyborane was adsorbed as a metal alkoxide on the felt made of activated carbon fibers in the same manner as in Example 1 except that the activated carbon fiber felt (size: 5 cm × 5 cm) was used, and then hydrolysis was performed. The felt in this state is
There was no change in appearance as compared with before the reaction, and no aggregation of fibers or particles was observed. After heating this felt in an electric furnace at 350 ° C. for 3 hours, the weight was measured and found to be 3.0% greater than the dry weight before the reaction. Infrared absorption spectrum (IR) of the fiber which had been ashed by heating this fiber at 900 ° C. for 1 hour in air was measured by the potassium bromide tablet method. As a result, the substance supported on this felt was a boron oxide. From the increase in weight, it was found that the content of boron oxide based on the total weight of activated carbon was 3.0%. Next, except that the felt of activated carbon fiber containing the oxide of boron was used, silicon carbide was formed in the same manner as in Example 1, and the felt made of silicon carbide was used. The heat treatment was performed in the same manner as in Example 1. Although the strength was not measured, the felt had a firm feel.

Example 10 A carbon sheet containing activated carbon fibers made of a phenol resin having a specific surface area of 700 m ² / g (manufactured by Nippon Kynol Co., Ltd., basis weight 50 g / m ² , activated carbon fiber content 50%, carbon content rate). 50%) using a phenolic resin adhesive, size 20 cm x 20 cm, thickness 2 cm, side length 10 m
The hexagonal honeycomb-shaped three-dimensional structure made of m was processed.
Then, put this in a hot-air circulation type dryer, and keep the temperature at 105 ° C.
And dried for 12 hours. After that, the upper lid can be opened and closed 18
A 150-mesh wire net having columns was installed so that a height of 50 mm could be secured from the bottom of the metal closed vessel of liter volume, and triethoxyborane (B (OC ₂ H ₂ H ₅ ) ₃ ) 100 g (manufactured by Aldrich Co.) was placed, and 2 g of the dried honeycomb structure placed in another glass container was placed on the wire net together with the glass container without a lid, and directly with triethoxyborane. Avoid contact and immediately cap the container. Then, the inside of the container was depressurized with an aspirator to the extent that triethoxyborane did not boil, and the container was allowed to stand in a thermostatic chamber at 20 ° C. for 3 hours.

Then, this structure is taken out and purified water 30 is used.
Water and the structure are directly mixed and contacted in the same manner as in the case of adsorbing triethoxyborane on the three-dimensional structure in an 18 liter metal closed container with an upper lid that can be opened and closed with 0 ml in the bottom. The structure was placed on a wire net without doing so, the upper lid was closed, and the mixture was allowed to stand in a thermostatic chamber at a temperature of 20 ° C. for 2 hours for hydrolysis. The structure after the reaction is
There was no change in appearance from before the reaction. This structure was placed in an electric furnace, heated at a temperature of 350 ° C. for 3 hours, and then weighed. As a result, 3.0% of the dry weight before reaction was measured.
Was increasing. 1 part of this structure at 900 ° C in air
Infrared absorption spectrum (IR) was measured by the potassium bromide tablet method for the ashed product that had been heated for a period of time, and as a result, the substance supported by the structure was an oxide of boron, and due to the increase in weight, boron oxidation was observed. Content of the total activated carbon weight of the product,
Next, it was found that the amount corresponds to 3.0%. Then, the structure was obtained in the same manner as in Example 1 except that 0.5 g of the honeycomb structure containing the oxide of boron and 5 g of silicon monoxide were used. Was converted to silicon carbide. Further, heat treatment was performed in the same manner as in Example 1 except that this silicon carbide-made honeycomb structure was used. Although the strength could not be measured, a very solid honeycomb three-dimensional structure was obtained.

Table 1 shows the measurement results obtained in the examples and comparative examples.

[0047]

[Table 1]

The silicon carbide fiber produced from the porous carbon fiber containing the metal or the metal compound of the present invention is composed of the porous carbon fiber substantially consisting of silicon carbide and containing no metal or metal compound. In comparison, the tensile strength is improved. The strength is further improved by heat treating a silicon carbide fiber produced from a porous carbon fiber containing a metal or a metal compound in an inert gas atmosphere containing substantially no oxygen (Examples). 1 and 2 and Comparative Examples 1 and 2). The strength of silicon carbide fibers containing no metal or metal compound was impaired when heat-treated in an atmosphere containing no nitrogen gas (Comparative Example 1). In the present invention, the metal or metal compound contained in the porous carbon material may be any of boron, silicon, titanium, aluminum, yttrium, magnesium and their compounds, or any combination thereof. ,
The strength improving effect of the silicon carbide material as described above was obtained (Examples 1 to 8). By using a porous carbon material containing a metal or a metal compound, it can be applied as a silicon carbide material having excellent strength regardless of the shape such as a fibrous, sheet-shaped or three-dimensional structure ( Examples 9-10).

[0049]

INDUSTRIAL APPLICABILITY The present invention has the effect of providing a method for producing a silicon carbide material having higher strength by preliminarily containing a metal or a metal compound in the porous carbon material when producing the silicon carbide material. Play.

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Claims (5)

[Claims] 1. A porous carbon material having a specific surface area of 100 to 3000 m ² / g and a silicon monoxide gas of 800 to 20.
A method for producing a silicon carbide material obtained by reacting at a temperature of 00 ° C., wherein the porous carbon material contains a metal or a metal compound in advance. 2. The method for producing a silicon carbide material according to claim 1, wherein the silicon carbide material is heated at a temperature of 800 to 2200 ° C. in an atmosphere or a gas atmosphere that does not substantially contain oxygen. . 3. One kind of porous carbon material selected from a porous carbon fiber, a sheet made of porous carbon fiber, a three-dimensional structure made of the sheet, and a three-dimensional structure made of porous carbon fiber. The method for manufacturing a silicon carbide material according to claim 1, wherein 4. The metal is at least one selected from boron (B), aluminum (Al), silicon (Si), titanium (Ti), yttrium (Y), and magnesium (Mg). The method for producing a silicon carbide material according to claim 1, 2, or 3. 5. The metal compound is at least one selected from the oxides, hydrides, hydroxides, alkoxides, nitrides, and halides of the metal according to claim 4. 4. A method for manufacturing a silicon carbide material according to 1, 2 or 3.