JP5612149B2 - Silicon nitride-based porous body, silicon nitride-based porous body manufacturing method, honeycomb structure, and honeycomb filter - Google Patents

Description

  The present invention relates to a silicon nitride-based porous body used for exhaust gas treatment, a method for manufacturing the same, a honeycomb structure using the same, and a honeycomb filter.

Ceramic porous bodies are used in exhaust gas treatment members of internal combustion engines. In particular, it is used as a DPF (Diesel Particulate Filter) for collecting and purifying particulate matter contained in exhaust gas. As such a porous material, cordierite, aluminum titanate, silicon carbide, etc. have already been put into practical use from the viewpoint of heat resistance and thermal shock resistance of the material, and silicon nitride (Si ₃ N ₄ ) has also been put into practical use. It is being considered.

  Such a ceramic porous body is first made into a clay that can be extruded by adding a binder material (such as methylcellulose or an organic binder resin) to an inorganic raw material. A pore-forming material for adjusting the amount of pores is also added to the clay. Next, the formed clay is extruded to obtain a desired shape, which is dried, degreased and sintered. Degreasing is a process of removing organic components such as a binder substance, and sintering is a process of baking and solidifying an inorganic raw material. By passing through these steps, a porous body having a desired shape can be obtained.

  By the way, in the degreasing process, it is generally performed that the degreasing is not completed but all the organic components are removed. This is because if the organic component is completely removed, the substance that binds the inorganic raw materials disappears, and the molded product collapses before sintering.

  Conventionally, a silicon nitride based porous material containing silicon carbide (SiC) has also been proposed. For example, Patent Document 1 discloses that silicon carbide (SiC) is formed at the manufacturing stage in a silicon nitride-based porous body manufactured by heat-treating raw materials composed of silicon oxide particles, carbon particles, and metal silicon particles in a nitrogen atmosphere. It is described that it is contained in a porous body. According to Patent Document 1, it is described that silicon carbide is not preferable in the silicon nitride based porous body.

JP 2001-206775 A (released July 31, 2001)

  However, in the case of a silicon nitride-based porous body in which silicon nitride particles are used as raw materials and silicon nitride particles are bonded to each other by glass, there is a problem in that the mechanical strength of the porous body decreases due to the organic component remaining in the degreasing process. I understood.

This will be described in detail. In the case of a silicon nitride-based porous body, since the sintering process is performed in a nitrogen atmosphere, carbon, which is the remaining organic component, does not react with oxygen and disappear by gasification. It reacts with the oxide film (SiO ₂ ) and disappears by gasification (SiO ₂ + C → SiO + CO).

In a silicon nitride-based porous body using silicon nitride particles as a raw material, an oxide film (SiO ₂ ) on the surface of the silicon nitride particles reacts with magnesia spinel or the like added to the raw material as an auxiliary agent to form glass. Acts as an adhesive to bond the silicon nitride particles together. Therefore, when the oxide film on the surface of the silicon nitride particles changes from SiO ₂ to SiO by reacting with the remaining carbon, it does not react with the auxiliary agent, and the amount of glass formed is insufficient. As a result, the bonding between the silicon nitride particles becomes brittle, and the mechanical strength of the porous body is reduced. Patent Document 1 does not use silicon nitride particles as a raw material, and does not describe any of the above problems.

  The present invention has been made in view of the above problems, and its purpose is a silicon nitride based porous body in which silicon nitride particles are joined together by glass using silicon nitride particles as a raw material, and obstructs ease of production. Accordingly, an object of the present invention is to provide a silicon nitride-based porous body having excellent mechanical strength and high thermal conductivity, a method for manufacturing the same, a honeycomb structure, and a honeycomb filter.

  The inventors of the present application focused on effective use of organic substances that must be left in the degreasing process, and conducted intensive studies. As a result, in the state of silicon carbide, which has conventionally been considered unfavorable to be included in the silicon nitride-based porous body, by making it exist within a predetermined amount range, The present inventors have found that it is excellent in mechanical strength and can be increased to thermal conductivity, and have come to carry out the present invention.

  The silicon nitride based porous material of the present invention is a silicon nitride based porous material in which silicon nitride particles and silicon particles are used as raw materials, and the silicon nitride particles are bonded to each other by glass. It is characterized by being included in a range of 5 to 22 wt% and having a porosity of 40 to 70%.

According to the above configuration, carbon, which is an organic component that must be left in the degreasing process, is reacted with the silicon particles of the raw material and included as silicon carbide in the silicon nitride-based porous body, so that the remaining organic component is silicon nitride. It does not occur that the amount of glass produced is insufficient due to reaction with SiO ₂ which is an oxide film on the surface of the particles, and the mechanical strength of the porous body can be maintained.

  However, even if the amount of glass produced can be secured, it has been confirmed that when the content of silicon carbide particles exceeds 22 wt%, the mechanical strength of the porous body decreases. On the other hand, when the content of the silicon carbide particles is less than 5 wt%, the molded product before sintering is easily collapsed and is difficult to manufacture. Therefore, the silicon carbide particles to be included are in the range of 5 to 22 wt%.

  Silicon carbide is a substance having higher thermal conductivity than silicon nitride. Therefore, the thermal conductivity of the silicon nitride based porous body mainly composed of silicon nitride can be increased by containing silicon carbide particles.

  As a result, the silicon nitride porous body is made of silicon nitride particles and the silicon nitride particles are bonded to each other by glass, and has excellent mechanical strength and high thermal conductivity while ensuring ease of manufacture. It is possible to obtain a silicon nitride-based porous body having

In order to solve the above problems, the method for producing a silicon nitride based porous material of the present invention is a method of producing glass by reacting raw material silicon nitride particles, silicon particles, and SiO _{2 on} the surface of the silicon nitride particles. A mixing step of mixing a binder, an organic binder substance, and a pore former, a molding step of molding the mixture obtained in the mixing step, and a molding obtained in the molding step are mixed in an atmosphere. A degreasing step of adjusting the amount of oxygen and degreasing to leave a part of the organic component, and a sintering step of sintering the degreased molding obtained in the degreasing step in a nitrogen atmosphere, the degreasing step Then, the amount of oxygen to be mixed in the atmosphere is adjusted so that the silicon carbide particles produced by the reaction between the organic component contained after degreasing and the silicon particles in the sintering step are 5 to 22 wt% (wt%). Adjusting, in the sintering step, the silicon While the particles are converted to silicon carbide particles with organic components contained after degreasing, the silicon particles are nitrided to form silicon nitride particles, and then the raw silicon nitride particles and the nitrided silicon nitride particles formed on the respective surfaces of SiO ₂ and a sintering aid are reacted to produce glass, and the silicon nitride particles are bonded together by glass.

According to the above method, since silicon particles to be reacted with carbon, which is an organic component that must be left in the degreasing step, are mixed with the raw material in advance, the remaining organic component reacts with the silicon particles in the sintering step. As a result, silicon carbide particles are produced. As a result, the remaining organic component does not react with SiO ₂ that is the oxide film on the surface of the silicon nitride particles to cause a shortage of the amount of glass produced, and the mechanical strength of the porous body can be maintained.

  However, even if the amount of glass produced can be secured, it has been confirmed that when the content of silicon carbide particles exceeds 22 wt%, the mechanical strength of the porous body decreases. On the other hand, when the content of the silicon carbide particles is less than 5 wt%, the molded product before sintering is easily collapsed and is difficult to manufacture. Therefore, in the degreasing step, the amount of oxygen to be mixed in the atmosphere is adjusted, and the amount of organic components remaining after degreasing reacts with silicon in the sintering step so that 5 to 22 wt% silicon carbide particles are generated. It is adjusted to. Silicon particles that have not reacted with carbon are nitrided into silicon nitride particles in the sintering process, mixed with the original silicon nitride particles, and bonded with glass.

  Silicon carbide is a substance having higher thermal conductivity than silicon nitride. Therefore, the thermal conductivity of the silicon nitride based porous body mainly composed of silicon nitride can be increased by containing silicon carbide particles.

  Thereby, it is possible to obtain a silicon nitride based porous body having excellent mechanical strength and high thermal conductivity while ensuring ease of manufacture.

  In the method for producing a silicon nitride-based porous body of the present invention, the degreasing step may be performed in a temperature range of 200 to 350 ° C. with oxygen of 10% or less. According to this, it is possible to easily adjust the remaining amount of the organic component in the degreasing step.

  The silicon nitride based porous material of the present invention is produced by the method for producing a silicon nitride based porous material of the present invention, and has a porosity of 40 to 70%.

  As described above, the silicon nitride-based porous body produced by the production method of the present invention is excellent in mechanical strength and has high thermal conductivity. In addition to these characteristics, the silicon nitride based porous body of the present invention has the above porosity, and can function stably as a DPF. When the porosity is less than 40%, the porosity is in the above range, and the performance of collecting the particulate matter cannot be guaranteed, and the pressure loss also increases. Conversely, if the porosity exceeds 70%, it is not possible to obtain a strength that can withstand use.

  Further, the present invention comprises a honeycomb structure having a plurality of cells extending in one direction formed by the silicon nitride based porous body of the present invention and partitioned by cell walls, and the honeycomb structure, The honeycomb filter in which the end portions on one side in the extending direction of the plurality of cells in the honeycomb structure are alternately sealed by the sealing portions is also included in the category.

  According to the present invention, there is an effect that it is possible to provide a silicon nitride-based porous body having excellent mechanical strength and high thermal conductivity, a manufacturing method thereof, a honeycomb structure, and a honeycomb filter without hindering the ease of manufacturing. .

1 is a perspective view showing an overview of a honeycomb filter according to an embodiment of the present invention. It is a schematic cross section of a plane parallel to the axial direction of the honeycomb filter.

[Embodiment 1]
Hereinafter, the present invention will be described with reference to embodiments. The silicon nitride based porous body according to the present embodiment can be used, for example, as an exhaust gas processing member of an internal combustion engine. It can be used as an exhaust gas catalyst support for gasoline engines, as an oxidation catalyst support for exhaust gas treatment for diesel engines, or as a DPF (Diesel Particulate Filter) for collecting and purifying particulate matter contained in exhaust gas.

The silicon nitride based porous material according to the present embodiment is mainly composed of silicon nitride particles (Si ₃ N ₄ ), and the silicon nitride particles are bonded to each other by glass existing between them. Further, between silicon nitride particles, silicon carbide particles (SiC) are contained in an amount of 5 to 22 wt%, and Al, Mg, as a sintering aid that reacts with SiO _{2 on} the surface of the silicon nitride particles to generate glass. At least one of the group consisting of Fe, Zr, or rare earth may be included. The silicon nitride based porous material also includes sialon in which a part of silicon and nitrogen of silicon nitride is replaced with aluminum and oxygen, respectively.

As described above, in the degreasing step, in order to prevent the molded body from collapsing, not all the organic components (organic components) such as the organic binder are removed, but the degreasing is finished with a little left. Therefore, carbon (C) which is an organic component remaining in the subsequent sintering process is brought in, and when this reacts with the oxide film (SiO ₂ ) on the surface of the silicon nitride particles in the sintering process, gasification disappears. The amount of glass that bonds silicon nitride particles is reduced, and the mechanical strength of the silicon nitride porous body is reduced.

  Therefore, in the silicon nitride based porous material according to the present embodiment, silicon (Si) particles are included in the raw material together with the silicon nitride particles, and the organic components remaining after the degreasing step are reacted with the silicon particles in the sintering step. Thus, silicon carbide particles are produced.

Thus, the less the amount of carbon lost gasified by reaction with the oxide film on the surface of silicon nitride particles (SiO _2), the oxide film on the surface of the silicon nitride particles (SiO ₂₎ is reacted with sintering aids A sufficient amount of glass can be produced, and the silicon nitride particles can be firmly bonded to each other.

  However, even if the amount of glass produced can be secured, it has been confirmed that when the content of silicon carbide particles exceeds 22 wt%, the mechanical strength of the porous body decreases. On the other hand, when the content of the silicon carbide particles is less than 5 wt%, the molded product before sintering is easily collapsed and is difficult to manufacture. Therefore, in the degreasing step, the amount of oxygen mixed in the atmosphere is adjusted, and the amount of organic components remaining after degreasing reacts with the silicon particles in the sintering step to produce 5 to 22 wt% silicon carbide particles. Adjust as follows.

  Silicon carbide is a substance having higher thermal conductivity than silicon nitride. Therefore, the thermal conductivity of the silicon nitride-based porous body mainly composed of silicon nitride can be increased by positively containing an organic component that must be left in the degreasing step in the form of silicon carbide.

  When the silicon nitride based porous body of the present embodiment is used as a DPF filter, the porosity is preferably 40 to 70%. By setting it as such a porosity, it can be functioned stably as DPF. The porosity is in the above range because if the porosity is less than 40%, the performance of collecting the particulate matter cannot be guaranteed and the pressure loss becomes large. On the contrary, if the porosity exceeds 70%, it is used. This is because it is impossible to obtain a strength that can withstand the above.

  As the raw material silicon nitride particles, those having a particle diameter of 60 to 90 μm are used. The reason why the particle diameter is in such a range is that when the particle diameter is less than 60 μm, the pressure loss increases, and conversely, when the particle diameter is greater than 90 μm, the collection performance decreases.

As the raw material silicon particles, those having the same particle size as the silicon nitride particles are used. The silicon particles react with carbon to produce silicon carbide particles, but in the sintering process under a nitrogen atmosphere, the silicon particles also react with nitrogen to produce silicon nitride particles. Therefore, it is preferable that the particle diameter of the silicon particles is equal to that of the silicon nitride particles. The amount of silicon particles is 10 to 50 wt% with respect to the total weight of silicon nitride particles + silicon particles. The reason why the amount of silicon is within such a range is that when the amount is less than 10 wt%, the amount of the remaining organic component reacts with carbon and reacts with the oxide film (SiO ₂ ) on the surface of the silicon nitride particles. Conversely, if it exceeds 50 wt%, low-speed sintering is required to avoid abnormal heat generation during nitriding in the sintering process, and productivity is reduced.

  For example, a combination of methylcellulose and water can be used as a binder material (organic binder material) for making an inorganic raw material into a clay that can be extruded. When methylcellulose is used, the addition amount is 10 to 20 wt% with respect to the total weight of the silicon nitride particles, the silicon particles, and the pore former. The reason why the amount of addition is in such a range is that when the amount of addition is less than 10 wt%, extrusion molding cannot be performed, and conversely, when it exceeds 20 wt%, it is difficult to degrease the next step.

  In addition, in order to stably obtain a porous sintered body having a porosity of 40 to 70%, a pore former is added to the raw material, and as the pore former, for example, starch can be used. The addition amount of the pore former is 20 to 40 wt% with respect to the total weight of the silicon nitride particles, the silicon particles, and the pore former. By setting the addition amount in such a range, the porosity can be stably controlled. The pore diameter of the pore former is preferably 70 to 100 μm, which is substantially the same as the particle diameter of silicon.

Any sintering aid may be used as long as it generates glass by reacting with SiO _{2 on} the surface of the silicon nitride particles. For example, Al, Mg, Fe, Zr, or rare earth can be used. At this time, some of the silicon nitride particles may be dissolved in the glass.

  Next, a method for producing a silicon nitride based porous material according to the present embodiment will be described. First, silicon nitride particles, silicon particles, a pore former and a sintering aid are mixed with a binder substance to obtain a mixture (mixing step). Next, extrusion is performed using an extrusion die, and the honeycomb structure or the like is molded into a desired shape (molding process), and then the molded product is dried.

  Next, the amount of oxygen mixed in the dried molding is adjusted in a nitrogen atmosphere, and the organic matter such as the binder substance and pore former remaining in the degreasing process reacts with the silicon particles in the sintering process. And degreasing so that 5 to 22 wt% of silicon carbide is produced (degreasing step). As a guideline of the amount of carbon remaining in the degreasing step, 1.5 to 6.6 wt. %.

Specifically, degreasing is performed in a state where oxygen is added to a nitrogen atmosphere, and at that time, the amount of oxygen (O ₂ ) to be added to nitrogen (N ₂ ) is adjusted, thereby remaining carbon that is an organic component. Adjust the amount. When the amount of oxygen added is increased, the amount of carbon that reacts with oxygen and disappears by gasification increases, and the amount of remaining carbon decreases. Conversely, when the amount of oxygen added is reduced, the amount of carbon that reacts with oxygen and disappears by gasification decreases, and the amount of remaining carbon increases. More specifically, it is preferably performed at 200 to 350 ° C. and oxygen of 10% or less.

Next, the degreased product is post-reaction sintered in a nitrogen atmosphere. Specifically, silicon particles are nitrided at 1200 to 1400 ° C., and finally fired and sintered at 1700 to 1800 ° C. In the final sintering step, the oxide film (SiO ₂ ) on the surface of the silicon nitride particles reacts with the auxiliary agent to generate glass, and the silicon nitride particles are bonded to each other by the glass.

[Embodiment 2]
Hereinafter, the present invention will be described with reference to embodiments. FIG. 1 is a perspective view showing an overview of a honeycomb filter according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a plane parallel to the axial direction of the honeycomb filter.

  As shown in FIGS. 1 and 2, the honeycomb filter 1 has a columnar honeycomb structure 10 made of a silicon nitride porous body according to the present invention. A plurality of cells 11 extending in one direction are formed inside the cylindrical main body of the honeycomb structure 10. Each cell 11 has a cross-sectional shape that is substantially square in a direction perpendicular to the axial direction (cell extending direction) and is defined by a porous cell wall 12. The porous cell wall 12 serves as a particulate matter (hereinafter, PM) collecting member.

  Each cell 11 provided in the honeycomb structure 10 is sealed (sealed) by sealing a filler at one end in the axial direction (stretching direction), and a sealing portion 21 is formed. ing. The sealing part 21 is provided with a plurality of cells 11 alternately at both ends in the axial direction of the honeycomb structure 10.

  The outer peripheral portion of the honeycomb structure 10 is covered with an outer peripheral coating layer 15. The outer periphery covering layer 15 is made of a ceramic layer, and is formed by firing an outer periphery covering material applied to the outer periphery of the honeycomb structure 10. The outer peripheral coating layer 15 is not necessarily required. In addition, in FIG. 2, description of the outer periphery coating layer 15 is abbreviate | omitted.

  As shown in FIG. 2, the honeycomb filter 1 having such a configuration is arranged such that the axial direction, which is also the extending direction of the cells 11, is parallel to the flow of exhaust gas. The exhaust gas flows in from a cell (inflow side cell) 11 that is located upstream of the flow and whose cell end is not sealed. The exhaust gas that has flowed into the cell 11 passes through the micropores of the porous cell wall 12 and is located on the downstream side of the flow to the adjacent cell (outflow side cell) 11 where the cell end is not sealed. And move out of it.

  As the exhaust gas passes through the fine holes in the cell wall 12, PM contained in the exhaust gas is collected in the cell wall 12. The collected PM is removed from the cell wall 12 by regenerating and heating the honeycomb filter 1, thereby regenerating the honeycomb filter 1.

  In FIG. 1, the honeycomb structure 10 is exemplified as a columnar shape in which the cross-sectional shape of the surface perpendicular to the axial direction of the honeycomb filter 1 is circular, but the cross-sectional shape is not particularly limited. For example, it may be oval, square, rectangular, or polygonal. Such a honeycomb structure 10 can be molded in advance into a desired shape by using an extruder. Further, the optimum value of the cross-sectional size of the plane perpendicular to the axial direction of the honeycomb filter 1 is determined by the engine displacement.

  On the other hand, the cross-sectional shape of the cell 11 is preferably substantially square. However, it is not necessarily limited to this, and other shapes may be used. The thickness of the cell wall 12 is not particularly limited, and may be 0.2 to 0.4 mm, for example. Further, the number of cells in the unit area is not particularly limited, and may be, for example, 200 to 300 cpsi. Although the thickness of the outer peripheral coating layer 15 is not particularly limited, it is generally set to 0.3 mm to 1.0 mm.

  As the material of each part in the honeycomb filter 1, existing conventional materials can be used except for the honeycomb structure 10 using the silicon nitride porous body according to the present invention.

  For example, as a filler for sealing the cell end, ceramic clay such as aluminum oxide (alumina), aluminum titanate, silicon carbide, silicon nitride, cordierite, mullite, apatite, or cement material should be used. Can do. These may be used alone or in combination. Among these, aluminum oxide is particularly preferable from the viewpoint of versatility as a cement material.

  The outer peripheral coating layer 15 is made of a ceramic layer, and a material obtained by blending inorganic particles such as inorganic balloon, colloidal silica, bentonite, an inorganic binder, or the like with the material of the honeycomb structure 10 described above is used.

  The honeycomb filter 1 is a so-called integral type in which the honeycomb structure 10 is formed of one porous ceramic fired body. However, a divided type in which a honeycomb segment body, which is a plurality of porous ceramic fired bodies formed in a prismatic shape, is bonded to each other through a joint portion may be used.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention will be described in more detail with reference to examples.

  # 200 under silicon powder 37 parts by weight, magnesia spinel 3 parts by weight, # 200 under β silicon nitride particles 34 parts by weight, pore forming material starch 26 parts by weight, methyl cellulose 15 parts by weight as binder material 30 parts by weight of water and 30 parts by weight of water were added and mixed to prepare an extruded goblet (mixture). Extruded goblet was extruded using an extrusion die to form a honeycomb structure of 35 mm × 35 mm × 100 mm as a molded product.

The honeycomb structure thus formed was dried and then degreased by heating to 300 ° C. in a stream of N ₂ + 5% O ₂ to remove a part of methylcellulose. Next, the degreased molded product (degreasing molded product) is put in a sintering furnace, and baked at a temperature of 1200 to 1400 ° C. in a nitrogen atmosphere to nitride silicon, and finally fired at 1700 ° C. for 6 hours. A sample of Example 1 was obtained.

  In addition, only the oxygen amount added to the nitrogen atmosphere in the degreasing process was adjusted using the same raw materials as in Example 1, and samples of Examples 2 to 5 and Comparative Examples 1 to 3 were obtained.

  The honeycomb structure of the example manufactured as described above was measured for compressive strength, thermal conductivity, and porosity.

  The porosity was measured using an Archimedes density meter. The compressive strength was measured by compressing a 35 mm square honeycomb molded body in a direction parallel to the through hole. The thermal conductivity was measured using a hot disk method thermal conductivity measuring device manufactured by Kyoto Electronics Industry Co., Ltd. The sample size was set to 35 mm × 35 mm × 10 mmt.

  Table 1 shows the measurement results.

  As can be seen from Table 1, when degreasing so that the SiC content is 5 wt% or more of carbon (C) content, the material does not collapse and a material exceeding the use strength level of 5 MPa can be produced (Examples 1 to 5). ), When the SiC content was less than 5 wt% (Comparative Examples 1 and 3), the molded product collapsed during degreasing. Moreover, although there exists a merit which the heat conductivity of the material which SiC content increases improves, when SiC content exceeds 22 wt% (comparative example 2), the compressive strength cut | disconnected 5 Mpa.

  The present invention can be suitably used as an exhaust gas purification filter for collecting particulate matter contained in exhaust gas of a diesel engine.

DESCRIPTION OF SYMBOLS 1 Honeycomb filter 10 Honeycomb structure 11 Cell 12 Cell wall 15 Perimeter coating layer 21 Sealing part

Claims (5)

  A silicon nitride-based porous body in which silicon nitride particles and silicon particles are used as raw materials and the silicon nitride particles are bonded to each other by glass, the silicon carbide particles obtained by carbonizing the silicon particles are included in the range of 5 to 22 wt%, and the pores A silicon nitride-based porous body having a rate of 40 to 70%.   A honeycomb structure comprising a plurality of cells extending in one direction formed by being divided by cell walls, comprising the silicon nitride based porous body according to claim 1.   A honeycomb filter comprising the honeycomb structure according to claim 2, wherein one end in the extending direction of the plurality of cells in the honeycomb structure is alternately sealed by adjacent cells. Mixing step of mixing main material silicon nitride particles, silicon particles, a sintering aid that reacts with SiO _{2 on} the surface of the silicon nitride particles to produce glass, an organic binder material, and a pore former. ,
A molding step of molding the mixture obtained in the mixing step;
A degreasing step of adjusting the amount of oxygen to be mixed in the atmosphere of the molding obtained in the molding step, leaving a part of the organic component, and degreasing;
A sintering step of sintering the degreased molding obtained in the degreasing step in a nitrogen atmosphere,
In the degreasing step, the amount of oxygen to be mixed in the atmosphere is adjusted so that the silicon carbide particles produced by the reaction between the organic component and the silicon particles contained in the degreasing step are 5 to 22 wt%. And
In the sintering step, the silicon particles are carbonized with organic components contained after degreasing to form silicon carbide particles, while the silicon particles are nitrided to form silicon nitride particles, and then the silicon nitride particles and the raw material are nitrided A method for producing a silicon nitride-based porous body, characterized in that SiO _{2 on} each surface of the formed silicon nitride particles reacts with a sintering aid to produce glass, and the silicon nitride particles are bonded to each other with glass. .   5. The method for producing a silicon nitride based porous material according to claim 4, wherein the degreasing step is performed in a temperature range of 200 to 350 ° C. with oxygen of 10% or less.

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