WO2008026789A1

WO2008026789A1 - Whiskered porous body and method for manufacturing the same

Info

Publication number: WO2008026789A1
Application number: PCT/KR2006/003479
Authority: WO
Inventors: Jae Hyung Lee; Hyun Wook Ahn; Sun Hee Cho
Original assignee: Industry-Academic Cooperation Foundation, Yeungnam University
Priority date: 2006-09-01
Filing date: 2006-09-01
Publication date: 2008-03-06

Abstract

The present invention relates to a whiskered porous body, wherein whiskers are grown in the pores of the porous body, and a method of manufacturing the same. Whiskers of a prior art whiskered porous body were not sufficiently formed at the deeper places of the ceramic porous body. The present invention is directed to solving such a problem. The whiskered porous body of the present invention is manufactured by infiltrating slurry containing a whisker source into a porous body and growing whiskers inside the porous body under a non-oxidizing gas atmosphere by means of carbothermal reduction. According to the present invention, the whiskers are grown uniformly up to the interior of the porous body.

Description

WHISKERED POROUS BODYAND METHOD FORMANUFACTURING

THE SAME

TECHNICAL FIELD The present invention generally relates to a porous body, and more particularly to a whiskered porous body, wherein whiskers are grown in the pores to maintain high porosity as well as to reduce substantial sizes of the pores. The present invention further relates to a method of manufacturing such a porous body.

BACKGROUND ART

Porous bodies with variously sized open pores have been applied to numerous fields. In particular, they are used as filters for filtering gas or liquid. For example, a vehicular catalyst filter, which is used to remove carbon monoxide or nitric oxide from exhaust gas, is manufactured by extruding a ceramic substrate with a large number of linearly arranged holes of several millimeters and then coating a catalyst on the surfaces of the holes. Another carbon-removing filter for use in a diesel vehicle is composed of a great deal of ceramic particles of several tens μm size. In such a filter, carbon particles are filtered in such a manner so that fine carbon particles among exhaust gas are attached to the surfaces of the pores while the exhaust gas passes through relatively large pores formed between the ceramic particles.

In the case of the filters having the porous bodies with opened pores, particles larger than the sizes of the pores are filtered. Accordingly, smaller pores are advantageous for filtering finer particles. However, smaller pores and lower porosity increase flow resistance to thereby reduce breathability. Therefore, porous bodies with smaller pores and high porosity are desirable.

Ceramic porous bodies are fabricated by forming ceramic powders through extrusion, uniaxial compression, etc, and then burning the same at a relatively low temperature to bond the same without any contraction. The pore sizes of such a ceramic porous body can be controlled in a range of nano to several tens μm according to the sizes of the ceramic source particles. The porosity ranges from approximately 20% to approximately 60%. As the size of the pore is smaller, the breathability becomes lower. Said ceramic porous body with the small sized pores is advantageous for filtering the fine particles, but is disadvantageous in terms of high flow resistance.

Other ceramic porous body with low flow resistance and large breathability i can be fabricated using a sponge. When a sponge is wet by ceramic slurry and is dried and then burned, the sponge is burned up and only the ceramic is sintered, thereby fabricating a sponge-structured ceramic porous body. Such a porous body generally has a porosity of 75% or more and has a very high breathability. As used herein, "a sponge-micro structured porous body" means a porous body having a spongy structure with a porosity of 75% or more. It is discriminated from the porous bodies fabricated by compressing and sintering the powder. Since the sponge-mi crostructured porous bodies are fabricated using a sponge, the sizes of their pores are as large as hundreds μm to several mm. They are widely used as filters for filtering molten metal in metal casting, but are not appropriate for use as filters for fine particles.

Another ceramic filter with higher breathability can be fabricated from ceramic fibers. Such a ceramic filter is similar to an air filter or a water purifier filter composed of organic or chemical fibers. Since most ceramic fibers are expensive and make large pores dues to their relatively large diameters and are compressed by back pressure, it is difficult to maintain high breathability and constant pore sizes.

In order to fabricate a porous body with high breathability and small-sized pores, there have been recently suggested methods for growing whiskers in the pores by chemical vapor infiltration. Such methods are disclosed in Korean Laid-Open Patent Publications Nos. 2001-0013300 and 2004-0082529. They use growing silicon carbide whiskers on the surfaces of a substrate or an object by well-known chemical vapor deposition. That is, they grow silicon carbide whiskers in the pores by infiltrating vapor into the interior of the porous body and then by chemical vapor infiltration. However, there are problems with chemical vapor infiltration. Specifically, since vapor flows from the surface of the porous body toward its inside, an amount of whiskers grown in the vicinity of the surface and an amount of whiskers grown at the interior of the porous body are considerably different from each other. Further, silicon carbide whiskers are slightly grown at only the pores in close proximity of the surface of the porous body and are not nearly grown at the deeper places of the porous body, as taught in the following documents: "Microstructure and Growth Mechanism of SiC Whiskers on Carbon-carnon Composites Prepared by CVD" (Fu Qiangang, Li Hejun, Shi Xiaohong, Li Kezhi, Hu Zhibiao, Wei Jian) published in Materials Letters, vol. 59, No.19/20, pp. 2593-2597, 2005; "The Microstructural Effect of Chemically Vapor Infiltrated SiC Whiskered Thin Film on the Green Body of SiC/C Composites" (Young Jin Lee, Sang Min Hwang, Doo Jin Choi, Sang Hwan Park, Hae Doo Kim) published in Thin Solid

Films, pp. 402-421 and pp. 354-359, 2002; "hi Situ Growth of /3-SiC Nanowires in

Porous SiC Ceramics" (Sumin Zhu, Hong-An Xi, Qin Li, Ruoding Wang) published in J. Am. Ceram. Soc, 88[9], pp. 2619-2621, 2005; and "Pore Structure Modification and Characterization of Porous Alumina Filter with Chemical Vapor Infiltration

(CVI) SiC Whisker" (Park et al.) published in Journal of the Korean Ceramic

Society, vol. 41, No. 7, pp. 518-527, 2004. Further, the chemical vapor infiltration is disadvantageous since expensive organic gases must be used and is difficult to be applied to mass production.

DISCLOSURE

TECHNICAL PROBLEM

The present invention is directed to solving the foregoing problems of the prior art. It is an object of the present invention to provide a whiskered porous body and a method of manufacturing the same, wherein porosity is high and pores are small sized by making whiskers grown even at deeper places of the interior of the porous body.

It is a further object of the present invention to provide a method of manufacturing a whiskered porous body at low costs and by using a simple process. It is another object of the present invention to provide a whiskered porous body catalyst filter, which does not require additionally coating a chemical catalyst, and a method of manufacturing the same.

TECHNICAL SOLUTION In order to achieve the above objects, according to the present invention, whiskers are grown at the interior of a porous body by carbothermal reduction and, in particular, a whisker source is fed in the form of slurry.

A method of manufacturing whiskers using carbothermal reduction comprises creating whiskers by high-temperature heat treating source powders containing a whisker source (mainly, oxide powder and carbon compound) under a non-oxidizing gas atmosphere, if necessary, together with a catalyst. For example, when carbon- containing source powder and silicon-containing source powder or a material containing both of them (e.g., rice bran) are loaded in a graphite crucible and they are heat-treated under an argon gas atmosphere or an argon gas atmosphere mixed with hydrogen gas, Si ingredient and C ingredient among the source react together to thereby create silicon carbide whiskers. A method of growing silicon carbide whiskers on a substrate or an object using carbothermal reduction is disclosed in U.S. Patent Nos. 3,754,076, 4,284,612, 4,637,924 and 4,975,392.

The present invention will now be described by means of concrete embodiments thereof.

According to one embodiment of the present invention, slurry, which comprises a whisker source and a catalyst for promoting the growth of the whiskers, if necessary, solved together with water or alcohol solvent are infiltrated to the interior of a porous substrate. Thereafter, preventing a whisker source vapor from leaking out of the porous substrate is carried out. Then, whiskers are grown on the surfaces of the pores inside the porous substrate by high-temperature heat treatment under a non-oxidizing gas atmosphere and by carbothermal reduction, thereby manufacturing the whiskered porous body.

According to another embodiment of the present invention, the surfaces of the pores may be coated with a carbon layer by infiltrating a carbon precursor to the interior of the porous substrate before infiltrating the slurry to the porous substrate.

According to yet another embodiment of the present invention, the carbon precursor for coating the surfaces of the pores with the carbon layer may be infiltrated to the interior of the porous substrate as contained in the slurry comprising the whisker source.

As the porous substrate in which the whiskers are grown, oxide and non- oxide ceramics such as silicon carbide, silicon nitride, alumina, zirconia, cordierite or the like, or carbon or graphite may be used. Any metal capable of withstanding a whisker-creating temperature can be used. As the carbon precursor for coating the surfaces of the pores of the interior of the porous substrate with the carbon layer on which the whiskers are readily grown, for example, organic substance such as liquid phenol resin, which has a great deal of residual carbon after being burned, may be used. When burned, 40 ~ 50% of the liquid phenol resin leaves as carbon. The liquid phenol resin is primarily used to coat the surfaces of the pores of the interior of the porous substrate with the carbon layer on which the whiskers are readily grown. However, it can serve as a carbon source for creating the whiskers.

In case of creating the silicon carbide whiskers in the interior of the porous substrate, silicon dioxide (SiO₂), silicon, silica gel, silicon nitride (Si₃N₄) or the like may be used as a Si source and carbon black, pitch, tar or the like may be used as a C source. Further, silicon carbide and silicon dioxide may be used together. Rice bran or rice hulls containing both Si and C may be used as a source of the silicon carbide whiskers. A catalyst may not be needed for causing the creation of the whiskers by means of carbothermal reduction using rice bran or rice hulls. Those sources may be used as a source as properly mixed together. Whiskers of titanium carbide (TiC), titanium nitride (TiN), boron carbide (B₄C), boron nitride (BN) or mixtures thereof may be grown by substituting the whisker sources with the above- mentioned substances according to types of whiskers to be grown. Further, a fluoride may be fed in order to assist reaction gases of such sources to be created.

As the catalyst for causing or promoting the growth of the whiskers composed of silicon carbide, one or more of metallic powder of iron, nickel, cobalt, tungsten, platinum, magnesium, chrome, titanium, stainless steel, etc., compounds thereof, or glass based on SiO₂ may be used. Such a catalyst may be fed after feeding the whisker sources or may be fed together with the whisker sources as mixed therewith. Further, they may be used as mixed with the carbon precursor for coating the carbon layer.

With regard to infiltrating the slurry containing the whisker sources deeply and uniformly into the porous substrate, the pores of the porous substrate can be filled with the source slurry by distributing the slurry into the pores of the porous substrate by an ultrasonic homogeniger when the porous substrate is placed in the source slurry. In case of small-sized pores, a pressure can be applied so that the slurry can be uniformly distributed up to the interior.

As for growing the whiskers uniformly up to the inward deeper places of the porous body, it is important to prevent a vapor of the whisker sources from leaking out of the porous body during heat treatment. When the porous substrate is covered up with the whisker sources during heat treatment, the leak of the vapor of the whisker sources out of the porous body can be prevented. Also, when vapor pressures of the whisker sources are set equally throughout inside and outside of the porous body, the leak of the vapor of the whisker sources can be prevented. According to the experiment conducted by the present inventors, when the whisker sources were not disposed sufficiently enough around the porous body, it was found that the very little whiskers were created in the interior of the porous body and were not created nearly in the vicinity of the surface thereof.

For non-oxidizing gas used for growing the whiskers by carbothermal reduction, argon gas, helium gas, hydrogen gas or mixture thereof is used for growing the silicon carbide whiskers. On the other hand, in case such non- oxidizing gas is substituted with nitrogen gas or nitrogen-containing gas such as ammonia gas and other conditions are maintained equally with the case of growing the silicon carbide whiskers, silicon nitride whiskers are created instead of the silicon carbide whiskers or both the silicon carbide whiskers and the silicon nitride whiskers can be created. Heat treatment of the porous substrate with the whisker sources infiltrated thereto is carried out in a container, which is composed of a refractory material such as graphite, ceramics or molybdenum metal, for example, at 125O⁰C to 1800°C (preferably at approximately 1400⁰C). While heat treatment time can vary according to the types and amounts of the sources, the growth of the whiskers is generally completed within 1 hour. By regulating the lengths and diameters of the created whiskers based on the types and amounts of the sources or the time and temperature of the heat treatment, the whiskers may be fully filled in the pores. On the other hand, the whiskers may be created at suitable length on the surfaces of the pores and may not be created in the middle of the pores. Meanwhile, the whiskered porous body with the whiskers grown therein can be heat-treated under an inert gas atmosphere such as argon gas, nitrogen gas or the like at a suitable temperature according to the substrate (in case of the SiC substrate, at more than 2000⁰C; and in case of the alumina substrate, at more than 1300°C) to enhance the strength of the porous body or the bonding strength between the substrate and the whiskers. Further, the residual carbon can be burned and removed by heat treatment at about 500⁰C under air or oxygen atmosphere. Also, residual silicon oxide source or a catalyst in the whiskered porous body can be removed by acid treatment of fluoric acid or by heat treatment using chloric gas.

The whiskered porous body manufactured by the present invention may be used as a catalyst filter or a catalyst material for gas sensors by coating the interiors of the whiskered pores with a catalyst source for a chemical catalyst filter such as platinum, palladium and the like. Further, in case of using the catalyst source for a chemical catalyst filter such as platinum, palladium and the like as the catalyst for creating the whiskers of the present invention and then growing the whiskers, the whiskered porous body can be directly used as a catalyst material without any other additional coating since it already contains a catalyst for filters such as platinum, palladium and the like.

DESCRIPTION OF DRAWINGS Figs. 1 and 2 are photographs taken through an electron microscope, which show a section of a sponge-structured silicon carbide porous substrate before growing whiskers.

Figs. 3 and 4 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with one embodiment of the present invention. Figs. 5 and 6 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with a further embodiment of the present invention.

Figs. 7 and 8 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with another embodiment of the present invention.

Figs. 9 and 10 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with yet another embodiment of the present invention.

Figs. 11 and 12 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with still yet another embodiment of the present invention.

Figs. 13 and 14 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered honeycomb porous body constructed in accordance with still yet another embodiment of the present invention. Figs. 15 and 16 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered porous body constructed in accordance with still yet another embodiment of the present invention.

Figs. 17 and 18 are photographs taken through an electron microscope, which show a section of a silicon carbide whiskered codierite honeycomb porous body constructed in accordance with still yet another embodiment of the present invention.

BEST MODE

The examples, wherein the silicon carbide whiskers are grown in the interior of the porous substrate under various process conditions according to the present invention, will now be described with reference to the accompanying drawings.

[EXAMPLE 1]

Figs. 1 and 2 are photographs of a sponge-structured porous substrate (silicon carbide), which are taken through an electron microscope at 20 magnifications and

100 magnifications, respectively. Each numerical value (1.5mm, 300μm), which is seen at a lower right side of each photograph, represents a length corresponding to summed up 10 scales, which are seen above each numerical value. Further, the magnification of the electron microscope (X20.0, XlOO) is seen at a left side of the numerical value. The above-mentioned matters are equally applied to other drawings. In the sponge-structured porous substrate of this example, the sizes of the pores were approximately 300μm and the porosity was 97%. Rice bran heat-treated for 1 hour at 800⁰C under an argon gas atmosphere, silicon dioxide powder having mean grain sizes of approximately O.Oόμm and iron trichloride hydrate (FeCl₃.6H₂O) serving as an iron catalyst were mixed into ethyl alcohol in a weight ratio of 58:42:0.5 (i.e., rice bran : silicon carbide : iron). They were made into slurry by ball-milling for 24 hours with silicon nitride balls. Thereafter, they were dried. The dried mixed powder, liquid phenol resin for coating the carbon layer and ethyl alcohol were mixed by means of an ultrasonic homigenizer in a weight ratio of 1.7:1.5:2.0, thereby making slurry that is infiltrated into a porous substrate. Subsequently, the sponge-structured silicon carbide porous body was placed in the slurry containing the sources and the source slurry was distributed for 2 minutes by means of the ultrasonic homigenizer so that the source slurry was sufficiently infiltrated into the pores of the porous body. Thereafter, the silicon carbide porous body was taken out from the slurry and was dried. The dried porous body was put in a graphite crucible with non-heat-treated rice bran laid on a bottom thereof and was covered up sufficiently with the rice bran and a lid is then closed. Thereafter, heat treatment was carried out in a high-temperature electric furnace, which is heated by graphite heating elements, for 1 hour at 1400⁰C under an argon gas atmosphere.

Figs. 3 and 4 are photographs of a section of the silicon carbide whisker porous body, which was manufactured in accordance with the above. Those photographs were taken through an electron microscope at 100 magnifications and 5000 magnifications, respectively. By comparing Figs. 2 and 3 showing the states before and after the creation of the silicon carbide whiskers at the same magnifications, it could be found that the silicon carbide whiskers were fully grown in the interiors of all the pores of the porous body after being processed like this example. The lengths and diameters of the grown whiskers were approximately 1 OOμm and 0.2μm, respectively. The porosity of the sponge-structured whiskered porous body, wherein the whiskers were grown, was 91%. [EXAMPLE 2] A silicon carbide whiskered porous body was fabricated using the same method as in example 1 except that a sponge-structured porous substrate with lmm- sized pores was used, and that nickel chloride that could produce the same amount of nickel as an amount of iron in example 1 was used as a catalyst, and that powder of SiO₂ and carbon black were filled around the porous body instead of the rice bran.

Figs. 5 and 6 are photographs of a section of the silicon carbide whisker porous body, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 40 magnifications and 5000 magnifications, respectively. The whiskers were grown fully and uniformly in the interiors of all the pores of the porous body. The lengths of the whiskers were approximately 500μm and the diameters of the whiskers were approximately 0.1 μm.

[EXAMPLE 3] A silicon carbide whiskered porous body was fabricated using the same method as in example 2 except that SiO₂ and carbon black were used in the weight ratio of 65:35 as a whisker source, and that rice bran was filled around the porous body.

Figs. 7 and 8 are photographs of a section of the silicon carbide whisker porous body, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 80 magnifications and 5000 magnifications, respectively. The whiskers were grown fully and uniformly in the interiors of all the pores of the porous body. A great number of catalyst droplets were observed at the stems of the whiskers. The lengths of the whiskers were approximately 500μm and the diameters of the whiskers were approximately 0.1 μm. [EXAMPLE 4]

A silicon carbide whiskered porous body was fabricated using the same method as in example 3 except that nickel chloride was used as a catalyst, and that powder of SiO₂ and carbon black was filled around the porous body. Figs. 9 and 10 are photographs of a section of the silicon carbide whisker porous body, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 60 magnifications and 5000 magnifications respectively. The whiskers were grown uniformly in the interiors of all the pores of the porous body. The lengths of the whiskers were approximately 500μm and the diameters of the whiskers were approximately 0. lμm. [EXAMPLE 5]

A silicon carbide whiskered porous body was fabricated using the same method as in example 1 except that a sponge-structured porous substrate with 0.5mm-sized pores was used, and that powder of SiO₂, SiC and Si was used as a whisker source in a mole ratio of 1 :2: 1 , and that cobalt was used as a catalyst.

Figs. 11 and 12 are photographs of a section of the silicon carbide whisker porous body, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 40 magnifications and 5000 magnifications, respectively. The whiskers were grown fully and uniformly in the interiors of all the pores of the porous body. Further, the whiskers were grown straight. The lengths of the whiskers were approximately 200μm and the diameters of the whiskers were approximately 0.2μm. [EXAMPLE 6]

Silicon carbide whiskers were made grown in the pores of a silicon carbide honeycomb using the same method as in example 5 except that a silicon carbide honeycomb for diesel particulate filters, wherein a great number of 1.2 x 1.2mm- sized square pores are linearly arranged, was used as a porous substrate, and that cobalt chloride was used as a catalyst, and that the surfaces of the honeycomb pores were coated with a mixture of liquid phenol resin and ethanol (mixed in a weight ratio of 3:4) before infiltrating a slurry containing both a whisker source and a catalyst .

Figs. 13 and 14 are photographs of a section of the honeycomb with the silicon carbide whiskers grown therein, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 60 magnifications and 5000 magnifications, respectively. The created whiskers were straight. The diameters of the whiskers were approximately 0.2μm. [EXAMPLE 7]

Silicon carbide whiskers were made grown in the pores of a cordierite honeycomb using the same method as in example 6 except that a cordierite honeycomb for vehicular exhaust gas purifying filters, wherein a great number of 1.0 x 1.Omm-sized square pores are linearly arranged, was used as a porous substrate.

Figs. 15 and 16 are photographs of a section of the honeycomb with the silicon carbide whiskers grown therein, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 60 magnifications and 5000 magnifications respectively. The created whiskers were straight. The diameters of the whiskers were 0.1 μm or less. [EXAMPLE 8]

A silicon carbide whiskered porous body was fabricated using the same method as in example 5 except that palladium, which is used as a catalyst source in catalyst filters, was used as a catalyst for growing whiskers. Figs. 17 and 18 are photographs of a section of the silicon carbide whisker porous body, which was fabricated in the above-described manner. Those photographs were taken through an electron microscope at 40 magnifications and 5000 magnifications, respectively. The whiskers were grown uniformly in the interiors of all the pores of the porous body. Further, the whiskers were grown straight. The lengths of the whiskers were approximately 150μm and the diameters of the whiskers were approximately 0.5μm. Droplets containing the palladium catalyst were formed not only at the distal ends of the silicon carbide whiskers but also at the stems thereof.

The above-described embodiments and examples should not be construed as limiting the scope of the present invention. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention as defined by the following claims.

INDUSTRIAL APPLICABILITY As described above in detail, according to the present invention, there is provided a whiskered porous body, wherein whiskers are grown fully uniformly or by an appropriate amount even at the deeper places of the porous body. Further, in case whiskers are made grown inside a porous substrate with high porosity such as a sponge-structured porous body as taught by the present invention, a porous body, wherein high porosity is preserved and a specific surface area is large and substantial sizes of the pores become small due to the whiskers, can be manufactured.

Further, in case such whiskered porous body is used as a filter, since flow resistance becomes lower due to high porosity and pores are small sized, even fine particles can be effectively filtered off. Also, since carbothermal reduction, which can grow whiskers from inexpensive sources and through simple process compared to conventional chemical vapor infiltration, is employed in manufacturing the whiskered porous body of the present invention, the entire process costs can be reduced and processes can be simplified with regard to manufacturing the whiskered porous body. Moreover, in case a catalyst source of a chemical catalyst filter is used as a catalyst for causing or promoting the growth of the whiskers as taught by the present invention, since a catalyst for a catalyst filter is already contained in the manufactured whiskered porous body, such whiskered porous body can be utilized as a catalyst material without the need for additionally coating a catalyst for a chemical filter.

Claims

1. A method of manufacturing a whiskered porous body, comprising: infiltrating a slurry containing a whisker source into a porous substrate; and growing whiskers on an interior surface of the porous substrate by heat treatment at a whisker growth temperature under a non-oxidizing gas atmosphere and by carbothermal reduction.

2. The method of Claim 1, wherein the method further comprises preventing a vapor of the whisker source from leaking out of the porous substrate between infiltrating the slurry and growing the whiskers.

3. The method of Claim 2, wherein preventing the vapor of the whisker source from leaking includes covering up the porous substrate with the whisker source.

4. The method of Claim 1 , wherein the slurry further contains a catalyst for promoting growth of the whiskers.

5. The method of Claim 4, wherein the catalyst is a catalyst source used for a chemical catalyst filter.

6. The method of Claim 1, wherein the method further comprises infiltrating a carbon precursor into the porous substrate prior to infiltrating the slurry.

7. The method of Claim 1, wherein the slurry further contains a carbon precursor.

8. The method of Claim 1, wherein the slurry is made by mixing a mixed powder, a carbon precursor and a solvent of water or alcohol in a ratio of 1.7:1.5:2.0, and wherein the mixed powder is made by heat-treating the whisker source and a catalyst for promoting growth of the whiskers under an argon gas atmosphere.

9. The method of Claim 8, wherein the slurry is infiltrated into the porous body by placing the porous substrate in the slurry.

10. The method of any one of Claims 6 to 9, wherein the carbon precursor is phenol resin.

11. The method of any one of Claims 1 to 9, wherein the porous substrate has a spongy microstructure with a porosity of 75% or more.

12. The method of any one of Claims 1 to 9, wherein the non-oxidizing gas is one of argon gas, helium gas, hydrogen gas and mixtures thereof.

13. The method of any one of Claims 1 to 9, wherein the non-oxidizing gas is a nitrogen-containing gas.

14. A whiskered porous body manufactured by the method of any one of Claims 1 to 9.

15. A whiskered porous body, wherein whiskers are grown on surfaces of pores of a porous substrate, wherein the porous substrate has a spongy microstructure with a porosity of 75% or more, and wherein the whiskers are uniformly distributed inside the porous substrate.