JP2012153596A - Method for manufacturing inorganic porous body which has one-dimensional structure body arranged, the inorganic porous body and member made using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment method for a surface treatment member capable of forming a microstructure to a desired position regardless of the quality of the material and the shape of the surface treatment member.SOLUTION: The surface treatment method for a surface treatment member includes (a) a step of preparing a surface treatment member, (b) a step of preparing a surface treatment agent including a silicon-based polymer, (c) a step of setting up the surface treatment agent at least at a part of the surface treatment member, and (d) a step of firing the surface treatment member to which the surface treatment agent is set at a temperature of 800°C or more under an environment in which a catalyst is included and gas flow is present, and the gas flow is supplied at a flow rate of 0.01 L/min or more per surface area 50 mof the surface treatment member, to thereby form a fibrous structure of a silicide.

Description

  The present invention relates to a method for producing an inorganic porous body in which a one-dimensional structure is arranged, the inorganic porous body, and a member using the inorganic porous body.

  Porous members made of metal, carbon, ceramics, and the like are widely applied to filters, reactors, catalyst carriers, electrodes, and the like. In these fields, the porous member is often required to have a high porosity, and for this reason, a porous member such as a honeycomb structure or a foam (sponge-like) structure is used.

  In applications such as filters, reactors, catalyst carriers, and electrodes, it is desirable to increase the specific surface area of the porous member in order to efficiently perform adsorption, separation, permeation, chemical reaction, and the like of substances. For this purpose, it is necessary to improve the porosity of the porous member or to reduce the pore diameter.

  For example, in the filter, the collection efficiency of the filter can be increased by making the pore diameter smaller than the size of the substance to be removed. However, when the pore size of the filter is extremely reduced, there arises a problem that an object to be filtered such as a gas or a liquid containing a substance to be removed does not easily pass through the filter. This leads to a decrease in the amount of filtration per unit time due to an increase in the pressure loss of the filter, and further to the problem of clogging of the filter, and also results in a shortened filter life.

  Thus, normally, in a porous member such as a filter, the problem of the collection effect and the pressure loss is in a trade-off relationship.

  Therefore, instead of increasing the porosity of the porous member or reducing the pore diameter, the specific surface area of the porous member can be reduced by forming a microstructure on the surface of the porous member or inside the pores. It is possible to enlarge it. This is because such a method can be expected to improve the collection efficiency of the substance to be removed by the fine structure, and can suppress an increase in pressure loss.

  For example, Patent Document 1 discloses that a plurality of sintered porous members having silicon carbide (SiC) ceramics as a parent phase and having open pores are stacked, and SiC whiskers are disposed in the gaps.

  Further, in Patent Document 2, a carbon-containing substance is blended with a ceramic raw material blended so as to have a cordierite composition, and a molded body formed into a predetermined shape is fired, whereby the diameter of the sintered body surface is reduced. It is disclosed that granular aggregates in which fibrous ceramics of 100 nm or less are entangled with each other are formed.

JP 7-291756 A JP 2007-244993 A

  As described above, various methods have been conventionally proposed for increasing the specific surface area of a porous member by forming a fine structure on the surface of the porous member or inside the pores.

  However, in the conventional method, the material combination of the porous member and the fine structure is limited to a specific one, the shape of the porous member is limited to a predetermined shape, or the formation position of the fine structure is a specific position. There is a problem that it is limited to. For this reason, in the conventional method, the material set of the porous member and the fine structure, the shape of the porous member cannot be freely selected, and the fine structure cannot be formed at a desired position. There is a big problem with the versatility of the process.

  The present invention has been made in view of such a background, and in the present invention, a surface-treated member capable of forming a fine structure at a desired position regardless of the material and shape of the surface-treated member. An object of the present invention is to provide a surface treatment method. Another object of the present invention is to provide a porous member obtained by such a surface treatment method.

In the first invention of the present application,
A surface treatment method for a surface-treated member,
(A) preparing a surface-treated member;
(B) preparing a surface treating agent containing a silicon-based polymer;
(C) installing the surface treatment agent on at least a part of the surface treatment member;
(D) A silicide-like fibrous structure is formed by firing the surface-treated member on which the surface treatment agent is placed at a temperature of 800 ° C. or higher in an environment containing a catalyst and containing a gas flow. A step of supplying the gas flow at a flow rate of 0.01 L / min or more per 50 m ² of a surface area of the surface treatment member;
A surface treatment method is provided.

Here, in the surface treatment method according to the present invention, the gas flow is at least selected from the group consisting of argon, helium, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas. Including one or more types,
The silicide fibrous structure may include silicon carbide (SiC) and / or silicon oxycarbide (SiOC).

Alternatively, in the surface treatment method according to the present invention, the gas stream includes nitrogen and / or ammonia, and further includes a group consisting of water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas. Including at least one selected from
The silicide fibrous structure may include silicon nitride (SiN) and / or silicon oxynitride (SiON).

  In the surface treatment method according to the present invention, the gas flow may further include a free catalyst air flow.

  In the surface treatment method according to the present invention, the catalyst may be added to the surface treatment agent in the step (b).

  In the surface treatment method according to the present invention, the surface treatment agent may further include an organic polymer and / or a carbon-containing material.

  In this case, the organic polymer may be one or more selected from the group consisting of polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, phenol, polyimide, and nylon.

  In the surface treatment method according to the present invention, the catalyst may include at least one selected from the group consisting of cobalt, copper, platinum, silver, gold, iron, and nickel.

  In the surface treatment method according to the present invention, the silicon polymer is a group consisting of siloxane, silazane, polycarbosilane, borazine, borosilazane, polyorganoborosilazane, polyborosiloxane, polyorganosiloxane, alkoxysilane, and alkoxide. 1 type or 2 types or more selected from may be sufficient.

  In the surface treatment method according to the present invention, the surface treatment member may include at least one material selected from the group consisting of ceramics, glass, metal, cement, and carbon.

  In the surface treatment method according to the present invention, the surface-treated member is formed of a honeycomb-like porous member, a lattice-like porous member, a foam-like porous member, a fiber-like porous member, a dense bead, or a porous bead. It may be at least one selected from the group consisting of a bead-shaped porous member, a three-dimensional cellular porous member, a molded body, and a dense or porous powder.

Furthermore, in the second invention of the present application,
(A) a raw material comprising any one or more of talc, kaolin, silicon carbide, silicon nitride, alumina, silica, mullite, cordierite, graphite, carbon fiber, iron, iron alloy, aluminum, and aluminum alloy; Preparing a porous molded body including a silicon-based polymer and a catalyst;
(B) a step of forming a fibrous structure of silicide by firing the porous molded body at a temperature of 800 ° C. or higher in an environment where a gas flow exists, A step of being supplied at a flow rate of 0.01 L / min or more per 50 m ² of a surface area of the porous molded body;
A surface treatment method is provided.

Here, in the surface treatment method according to the second invention of the present application,
The gas stream includes at least one selected from the group consisting of argon, helium, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas;
The silicide fibrous structure may include silicon carbide (SiC) and / or silicon oxycarbide (SiOC).

Alternatively, in the surface treatment method according to the second invention of the present application, the gas stream contains nitrogen and / or ammonia, and further, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas Including at least one selected from the group consisting of
The silicide fibrous structure may include silicon nitride (SiN) and / or silicon oxynitride (SiON).

  In the surface treatment method according to the second invention of the present application, the fibrous structure may have an average diameter of 10 μm or less and an aspect ratio of 2 or more.

  In the surface treatment method according to the second invention of the present application, the fibrous structure may have a substantially spherical silicon or silicide at a fiber tip.

  Furthermore, the present invention provides a porous member that has been surface-treated by any one of the surface treatment methods having the characteristics described above.

Further, in the present invention, an apparatus comprising such a porous member and selected from the following group:
Catalyst, catalyst carrier, diesel particulate filter, dust filter, molten metal filter, heavy metal recovery filter, VOC purification filter, air purification filter, water purification filter, bacteria separation filter, virus separation filter, gas or droplet size control member , Gas or droplet diffusers, sound insulation, insulation, shock absorbers, and reactors:
Is provided.

  In the present invention, it is possible to provide a surface treatment method for a surface treatment member that can form a fine structure at a desired position regardless of the material and shape of the surface treatment member. Moreover, the porous member obtained by such a surface treatment method can be provided.

It is the flowchart which showed roughly an example of the surface treatment method by 1st invention of this application. It is the flowchart which showed roughly an example of the surface treatment method by 2nd invention of this application. 1 is a diagram showing an example of an SEM photograph of a porous member according to Example 1. FIG. 6 is a diagram showing an example of an SEM photograph of a porous member according to Example 2. FIG. 6 is a diagram showing an example of an SEM photograph of a porous member according to Example 3. FIG. 6 is a diagram showing an example of an SEM photograph of a porous member according to Example 4. FIG. 6 is a diagram showing an example of an SEM photograph of a porous member according to Example 6. FIG. 6 is a diagram showing an example of an SEM photograph of a porous member according to Example 7. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 8. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 9. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 10. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 11. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 12. FIG. 10 is a diagram showing an example of another SEM photograph of a porous member according to Example 12. FIG. FIG. 10 is a view showing an example of still another SEM photograph of a porous member according to Example 12. 14 is a diagram showing an example of an SEM photograph of a porous member according to Example 13. FIG. It is the figure which showed an example of the SEM photograph of the porous member which concerns on Example 14. FIG. FIG. 16 is a diagram showing an example of an SEM photograph of a porous member according to Example 15. 14 is a diagram showing an example of an SEM photograph of a porous member according to Example 16. FIG. FIG. 14 is a view showing an example of an SEM photograph of a porous member according to Example 17; FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 18. FIG. 10 is a diagram showing an example of an SEM photograph of a porous member according to Example 19. It is the figure which showed the schematic structure of the apparatus used for the ultrafine particle collection test in Example 20. FIG. It is the figure which showed the relationship of the ultrafine particle density | concentration (number density | concentration) with respect to the particle diameter of the ultrafine particle in the ultrafine particle collection test of the various porous members in Example 20. FIG. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which showed the relationship of the density | concentration (volume concentration) of the ultrafine particle with respect to the particle diameter of the ultrafine particle in the ultrafine particle collection test of the various porous members in Example 20. FIG. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which showed the relationship of the ultrafine particle density | concentration (weight concentration) with respect to the particle diameter of the ultrafine particle in the ultrafine particle collection test of the various porous members in Example 20. FIG. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which showed the schematic structure of the apparatus used for the pressure loss test in Example 21.

  The present invention will be described below.

  The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, when the surface treatment method for the porous member satisfies a specific condition, the surface of the porous member and / or the pores. A fibrous structure containing silicon carbide (SiC), silicon oxycarbide (SiOC), silicon nitride (SiN), and / or silicon oxynitride (SiON) at a desired position such as inside (hereinafter collectively referred to as these) The present invention was completed by finding that a “silicide fibrous structure” was formed.

  For example, a surface treatment agent containing a predetermined raw material is placed on at least a part of the porous member and then fired under predetermined conditions to form a “silicide fibrous structure” at a desired position. be able to.

  Further, in the present invention, the object to be treated is not necessarily limited to the sintered porous member. For example, the intermediate (and the like such as a molded body, a granular body, a granular body, and a green compact) Even if it is a semi-finished product (the same applies hereinafter), a “silicide fibrous structure” can be formed at a desired position after the firing treatment. In this case, a predetermined raw material contained in the surface treatment agent installed on the porous member may be added to the intermediate in advance. Therefore, in the present invention, even when a member having a “silicide fibrous structure” is obtained from an intermediate, the raw material added to the intermediate to form such a “silicide fibrous structure” is “surface”. It will be referred to as “the raw material of the treatment agent”.

  In the present application, “(silicide) fibrous structure” means a structure having an average diameter of 0.1 μm to 10 μm and an aspect ratio of 2 or more. The “(silicide) fibrous structure” includes various forms such as a needle shape, a rod shape, a whisker shape, a coil shape, a nanotube shape, a belt shape, and a wire shape.

  Further, in the “(silicide) fibrous structure” in the present invention, a substantially spherical silicide or silicon (spherical material) is often observed at the tip of the fiber (however, the diameter of the spherical material and In some cases, such spheres may not be recognized, such as when the fiber diameters are approximately equal). As will be described later, this is considered to indicate that the “(silicide) fibrous structure” grows by a VLS (Vapor Liquid Solid) reaction mechanism in the method of the present invention.

  As described above, the object to be treated to which the method according to the present invention is applied is not limited to the porous member after firing, but may be various types such as a compact, a powder, a granule, and an intermediate such as a green compact. The member can be used as an object to be processed. Moreover, there is no restriction | limiting in particular also in the shape of a to-be-processed object, a dimension, a pore diameter, a cell diameter, and a porosity.

  For example, when the object to be processed is a honeycomb-shaped porous member, the cell diameter may be in the range of 10 μm to 50 mm, for example, in the range of 100 μm to 30 mm. When the cell diameter is less than 10 μm, it may be difficult to sufficiently permeate the surface treatment agent solution into the cell. Further, when the porous member is used as a dedusting filter, the fine particles must be captured by the silicide fibrous structure, and the coarse particles must be captured by the pores in the porous member. Therefore, in this case, the pore diameter of the porous member is desirably 100 μm or less. On the other hand, when a foam is used as the object to be treated, the pore diameter is preferably in the range of 10 μm to 20 mm, and more preferably in the range of 50 μm to 2 mm.

  Moreover, when using a granular material as a to-be-processed object, granular material characteristics, such as the kind, shape, particle diameter, particle diameter distribution, and density, are not restricted in particular. In addition, the molding method for molding such a granular material is not limited at all.

  For example, the molding method may be a press molding method, a cold isostatic pressing method, a warm isostatic pressing method, or the like, which is a general molding method for molding powder particles.

  Further, an organic binder is further added to the surface treatment agent, and a molded body to be processed is molded by each powder metallurgy method such as an extrusion molding method, an injection molding method, a casting molding method, or a gel cast molding method. Also good.

  Thus, in the surface treatment method of the present application, the material of the porous member is not particularly limited, and for example, a fibrous structure can be formed on various porous members such as oxide, non-oxide, metal, carbon, and / or ceramics. The body can be formed. Further, in this surface treatment method, the shape of the porous member is not particularly limited, and for example, an intermediate body having various shapes such as a honeycomb shape, a lattice shape, a foam shape, a fiber shape, a particle shape, and a granular shape is used. A fibrous structure can be formed after the firing. Furthermore, in this surface treatment method, the physical properties of the porous member and the intermediate are not particularly limited. For example, values such as porosity, pore diameter, and / or cell size of the porous member and the intermediate are: There is no particular limitation.

  Therefore, in the present invention, it is possible to provide a highly versatile surface treatment method for obtaining a fibrous structure.

  Here, the raw material of the surface treatment agent used in the present invention contains at least a silicon-based polymer. Moreover, the raw material of the surface treatment agent may further contain an organic polymer and / or a carbon-containing material.

  In the present application, “silicon-based polymer” means a general term for polymers in which silicon (Si) or a compound containing Si is generated by firing. Therefore, the “silicon-based polymer” includes all polymers having a function of causing a thermal carbon reduction reaction and / or a nitridation reaction of a silica component at a high temperature, or alkoxides thereof. In addition to alkoxides, chlorosilane, nitrite nitrate, and the like can be given. By adding carbon powder to these compounds and carrying out hydrolysis, the thermal carbon reduction reaction can proceed, so these are also included in the “silicon polymer”.

  Usually, the “silicon polymer” is a polymer having a silicon-oxygen bond or a silicon-hydrocarbon bond as a skeleton. The “silicon polymer” may have an organic functional group such as a hydrocarbon chain bonded to silicon. The “silicon-based polymer” may be called by various names such as a preceramic polymer, a precursor, an alkoxide, a polymer, silicone, siloxane, silane, an inorganic polymer, or an organic-inorganic hybrid. In addition, English names include names such as prepolymeric polymer, precursor, siloxane, silane, silazane, carbosilane, alkoxide, and organic organic hybrid.

  As the “silicon-based polymer”, for example, siloxane-based, carbosilane-based, and silazane-based polymers may be used alone or in combination of two or more. Alternatively, it may be a silica-based or organically modified silica-based alkoxide.

  The organic polymer is not particularly limited, and includes, for example, carbon material precursors polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, phenol, polyimide, and nylon.

  The carbon-containing material is not particularly limited, but may be a pitch, for example.

  The organic polymer and / or carbon-containing material may be selected in consideration of the Si / C ratio in the raw material, the residual carbon ratio after processing, the cost, and the like.

  The raw material for the surface treatment agent may further contain a catalyst. Thereby, the growth of the silicide fibrous structure can be promoted. The catalyst may be, for example, a metal or a metal compound. The catalyst may be, for example, Co, Fe, Cu, Ni, and compounds thereof. As the compound, for example, chloride, acetylacetonate salt, acetate salt, nitrate salt, oxide, silicide and the like can be used.

  The addition amount of the catalyst may be in the range of 0.01 wt% to 10 wt% with respect to the silicon-based polymer, and is preferably in the range of 0.5 wt% to 5 wt% with respect to the silicon-based polymer. When the addition amount of the catalyst is less than 0.01 wt%, the growth of the silicide fibrous structure is not promoted so much. Even if the catalyst is added in an amount of more than 10 wt%, the effect of promoting the growth of the silicide fibrous structure by the addition of the catalyst does not change so much.

  The catalyst may be supplied not as a raw material for the surface treatment agent but as a gas component (free catalyst airflow) in the atmosphere during the firing treatment.

  The surface treatment agent may be prepared as a solution in which the raw materials as described above are dissolved or dispersed. In the solution state, it becomes easy to install the surface treatment agent on the porous member or the intermediate. For example, the surface treatment agent can be placed on the porous member by immersing the porous member in the solution or applying the solution to the porous member. Even when the surface-treated member is an intermediate, the surface treatment agent can be easily placed on the intermediate by applying the solution to the intermediate.

  Alternatively, a known method such as spray coating, spin coating, vapor deposition coating, spraying with an air brush, brush coating, or the like can be used for installing the surface treatment agent. Moreover, partial application | coating can also be performed according to a use. In that case, an inkjet method can also be applied.

  Although it does not restrict | limit especially as a solvent, You may use 1 or more types among water, methanol, ethanol, isopropanol, acetone, diethyl ether, chloroform, hexane, benzene, xylene, toluene, tetrahydrofuran, etc. The solvent may be selected in consideration of cost, solubility, dispersibility, concentration and the like.

  When the surface treatment agent is a solution, the content of the silicon-based polymer may be in the range of 10 wt% to 30 wt%. However, the content of the silicon-based polymer in the solution is adjusted according to the solubility of the silicon-based polymer in the solution and / or the coating amount of the surface treatment agent.

  When the surface treatment agent is a solution, operations such as decompression with a vacuum pump, ultrasonic irradiation, and vibration may be performed so that the porous member or the intermediate is sufficiently impregnated with the surface treatment agent.

  When the surface treatment agent is a solution, a drying process is performed next. The conditions for the drying treatment are not particularly limited, but may be performed in a temperature range of room temperature to 250 ° C. for about 10 minutes to 100 hours. For example, the drying process may be performed in the range of room temperature to 80 ° C. for 24 hours. A drying treatment at a temperature exceeding 250 ° C. is not preferable because outgassing of low molecular weight components contained in the silicon-based polymer may occur. In addition, depending on the type of silicon polymer and / or organic polymer, a polymerization reaction (curing) may proceed during drying. Such curing may be caused in consideration of handling properties and the like.

  The drying treatment can be performed by a known method such as standing at room temperature, evaporator, vacuum drying, freeze drying, hot air dryer, hot air blowing, or microwave irradiation alone or in combination of two or more.

  As described above, when the surface treatment agent is a solution, the silicon polymer and the catalyst are usually contained in the same solution. However, in consideration of reactivity such as hydrolyzability of the catalyst, it is also possible to first apply the catalyst only to the porous member or intermediate and then apply the silicon polymer. Alternatively, conversely, it is also possible to first apply the silicon-based polymer to the porous member or intermediate and then apply the catalyst.

  In addition, when the raw material powder of the surface treatment agent is added directly to an intermediate such as a molded body, the silicon-based polymer is 1 wt% to 30 wt%, more preferably 5 wt% to 20 wt% with respect to the raw material powder. You may add so that it may become. This is because when the silicon-based polymer is less than 1 wt%, the amount of silicide fibrous structures produced is reduced, and conversely, when the silicon-based polymer exceeds 20 wt%, the amount of released gas increases and the final product is cracked. This is because there is a risk of occurrence.

  Next, a porous member having a silicide fibrous structure is prepared by firing a porous member provided with a surface treatment agent containing a silicon-based polymer (and catalyst) under predetermined conditions. Can do. Or the member which has a silicide fibrous structure can be prepared by baking the intermediate body containing a silicon type polymer (and catalyst) on predetermined conditions.

  Firing is performed at a temperature of 800 ° C. or higher. This is because at a temperature lower than 800 ° C., the reaction for producing the silicide fibrous structure does not proceed sufficiently. Although the upper limit of the firing temperature is not particularly limited, it has been confirmed by experiments of the present inventors that an appropriate silicide fibrous structure can be obtained, for example, up to about 1800 ° C. The firing temperature is, for example, in the range of 1200 ° C to 1500 ° C.

  The firing time is not particularly limited. For example, a silicide fibrous structure can be sufficiently obtained even by firing for about 30 minutes to 1 hour. The firing time is, for example, 2 hours.

  The firing temperature and firing time are determined based on the amount and dimensions of the target silicide fibrous structure.

  The firing atmosphere is preferably performed in a non-oxidizing atmosphere in order to prevent disappearance of the carbon component due to oxidation of the silicon-based polymer.

  The firing atmosphere may include, for example, one or more gases selected from the group consisting of argon, helium, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas. In this case, a silicide fibrous structure made of silicon carbide, silicon oxycarbide, and / or silica can be formed after firing.

  Alternatively, the firing atmosphere is, for example, nitrogen and / or ammonia, and one or more gases selected from the group consisting of water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas May be used in combination. In this case, a silicide fibrous structure made of silicon nitride, silicon oxynitride, and / or silica is formed.

  When no catalyst is added to the raw material of the surface treatment agent, a free catalyst air stream may be supplied to the firing atmosphere. The components of the free catalyst air stream may be Co, Fe, Cu, Ni, and their compounds as described above. As the compound, for example, chloride, acetylacetonate salt, acetate salt, nitrate salt, oxide, silicide and the like can be used.

  In addition, the firing treatment is generally performed only once for the sake of simplicity. However, the firing treatment is performed a plurality of times for the purpose of promoting the growth of the silicide fibrous structure and the expression of the catalytic function. Also good.

  Next, the reaction mechanism in the firing step of the surface treatment method according to the present invention will be briefly discussed.

When the temperature is higher than 1100 ° C., silicon dioxide (SiO ₂ ) is decomposed according to the formulas (1) to (3), and silicon monoxide (SiO) gas is released.

  Further, according to the formula (4), the silica component is reduced by carbon to form silicon carbide (SiC).

Thereafter, in a nitrogen atmosphere, silicon nitride (Si ₃ N ₄ ) or silicon oxynitride (Si ₂ N ₂ O) is formed from silicon monoxide (SiO) gas in accordance with formulas (6) to (9). .

At higher temperatures, silicon oxynitride (Si ₂ N ₂ O) changes to silicon nitride (Si ₃ N ₄ ) according to the equation (10).

SiO ₂ (s) + SiC (s) = 3SiO (g) + CO (g) (1) Formula SiO ₂ (s) + C (s) = SiO (g) + CO (g) (2) Formula SiO ₂ (s) + CO (G) = SiO (g) + CO ₂ (g) (3) Formula SiO ₂ (s) + 3C (s) = SiC (s) + 2CO (g) (4) Formula CO ₂ (g) + C (s) = 2CO (G) (5) Formula 3SiO (g) + 3C (s) + 2N ₂ (g)
= Si ₃ N ₄ (s) + 3CO (g) (6) Formula 3SiO (g) + 3CO (g) + 2N ₂ (g)
= Si ₃ N ₄ (s) + 3CO ₂ (g) (7) Formula 2SiO (g) + C (s) + N ₂ (g)
= Si ₂ N ₂ O (s) + CO (g) (8) Formula 2SiO (g) + CO (g) + N ₂ (g)
= Si ₂ N ₂ O (s) + CO ₂ (g) (9) Formula 3Si ₂ N ₂ O (s)
_{= Si 3 N 4 (s)} + 3SiO (g) + N 2 (g) (10) Equation

In an atmosphere containing nitrogen, silicon nitride (Si ₃ N ₄ ) or silicon oxynitride (Si ₂ N ₂ O) is formed according to the formulas (6) to (9). When these reactions proceed, if metal silicide exists as droplets, a VLS (Vapor Liquid Solid) reaction occurs. That is, when SiO gas is deposited on the metal silicide droplet, a reaction occurs between free carbon and / or nitrogen gas existing around the droplet. Thereby, the silicon nitride grows so as to push up the droplet, and it is considered that the fibrous structure is formed by the progress.

  In an atmosphere containing carbon monoxide, silicon monoxide, or silicon dioxide, the chemical equilibrium moves in the direction in which the fibrous structure is generated. For this reason, the growth of the fibrous structure is promoted by firing in such an atmosphere.

On the other hand, in an argon atmosphere, silicon carbide (SiC) is formed by a reduction reaction between silicon dioxide (SiO ₂ ) and free carbon (C) according to the equation (4). In this case, it is considered that gas phase reactions such as the formulas (11) and (12) are involved.

SiO (g) + 3CO (g) = SiC (s) + 2CO ₂ (g) (11) Formula 3SiO (g) + CO (g) = SiC (s) + 2SiO ₂ (g) (12) Formula

Also in this case, if the metal silicide exists as droplets, SiO gas is deposited there. Moreover, since the silicon carbide fiber formed in the lower part of the droplet grows so as to push up the droplet, a fibrous structure is finally formed.

  In an atmosphere containing carbon monoxide or silicon monoxide, the chemical equilibrium moves in the direction in which the fibrous structure is generated. For this reason, the growth of the fibrous structure is promoted by firing in such an atmosphere.

  From the above, it is expected that the gas atmosphere at the time of firing the porous member containing the surface treatment agent (raw material) and the intermediate body has a great influence on the formation behavior of the silicide fibrous structure.

  For example, from the formulas (6) and (7), when a fibrous structure made of silicon nitride is grown inside the porous member, it is important to sufficiently flow nitrogen gas to the inside of the porous member. Become.

Therefore, in the present invention, the gas is supplied into the gas atmosphere at a flow rate of 0.01 L / min or more per 50 m ² of the surface area of the surface-treated member such as the porous member and the intermediate during the firing process. Yes. Thereby, it becomes possible to supply gas sufficiently to the inside of the surface treatment member, and the fibrous structure can be grown also inside the surface treatment member. The surface area of the surface-treated member can be obtained by multiplying the specific surface area (m ² / g) obtained by the BET method and the weight (g) of the surface-treated member.

  Next, the first invention and the second invention of the present application will be described in detail with reference to the drawings.

(First invention)
FIG. 1 schematically shows an example of the surface treatment method according to the first invention of the present application.

This surface treatment method is
A surface treatment method for a surface-treated member,
(A) preparing a surface-treated member;
(B) preparing a surface treating agent containing a silicon-based polymer;
(C) installing the surface treatment agent on at least a part of the surface treatment member;
(D) A silicide-like fibrous structure is formed by firing the surface-treated member on which the surface treatment agent is placed at a temperature of 800 ° C. or higher in an environment containing a catalyst and containing a gas flow. A step of supplying the gas flow at a flow rate of 0.01 L / min or more per 50 m ² of a surface area of the surface treatment member;
Have

  Hereinafter, each step will be described.

(Step S110)
First, a surface-treated member for surface treatment is prepared. As described above, in the present invention, the material of the multi-surface treated member is not particularly limited. The surface-treated member may be, for example, metal, carbon, ceramics, or the like.

  However, in the subsequent steps (step S140), the surface-treated member is exposed to a temperature of 800 ° C. or higher. Therefore, a material that does not have heat resistance at this temperature cannot be used.

  The surface-treated member may be, for example, a fired porous member. Alternatively, the surface-treated member is not in a completed state like a porous member, but in an intermediate stage such as a molded body, a powder body, a granule body, and a green compact, that is, an intermediate body (semi-finished product). There may be.

  The shape of the surface treatment member is not particularly limited. The shape of the surface-treated member may be, for example, a honeycomb shape, a lattice shape, a foam shape, a fiber shape, a particle shape, or a granule shape.

(Step S120)
Next, a surface treating agent containing a silicon polymer is prepared.

  As described above, the surface treatment agent may further include an organic polymer and / or a carbon-containing material. The surface treatment agent may further contain a catalyst.

  The surface treatment agent may be a solution in which a silicon-based polymer is dissolved or dispersed.

  Further, carbon powder, silica, silicon monoxide powder and the like may be added to the surface treatment agent. This is because these components promote the thermal decomposition reaction and promote the growth of the silicide fibrous structure. That is, from the above-mentioned formulas (2), (4), (6), and (8), the thermal carbon reduction reaction of silica easily proceeds in a reducing atmosphere, and silicon monoxide and carbon monoxide content Pressure rises. This also facilitates the progression of formulas (3), (7), (9), (11), and (12) and promotes the formation of a fibrous structure of silicon carbide or silicon nitride. Is done.

  In the case where silica and / or carbon is contained in the surface treatment agent, the content thereof may be in the range of 1 wt% to 20 wt% with respect to the silicon-based polymer. When adding silica and / or carbon to the surface treatment agent, first, the silicon-based polymer and the catalyst are dissolved in an organic solvent, and silica and / or carbon is added to and mixed with the solution, and the slurry is prepared. adjust. In order to ensure the dispersibility of the slurry, a magnetic stirrer, ball mill, planetary mill, kneader, mixer, or planetary stirring mixer may be used. At the same time, a dispersant may be used. Moreover, when applying a slurry to a porous member, in order to prevent sedimentation of silica and / or carbon powder, impregnation may be performed while performing ultrasonic irradiation.

(Step S130)
Next, the surface treatment agent containing the silicon-based polymer prepared in step S120 is installed on at least a part of the surface-treated member prepared in step S110.

  The method for installing the surface treatment agent on the surface treatment member is not particularly limited. When the surface treatment agent is a solution, the surface treatment agent may be installed by immersing the surface treatment member in the solution or applying the solution to the surface treatment member.

  Further, for example, after a solution containing a silicon-based polymer is first placed on the surface-treated member, carbon and / or silica may be placed later.

  Carbon and / or silica may be sprayed onto the surface-treated member by, for example, an air brush, or may be dispersed in a solvent and applied to the surface-treated member. In that case, it is preferable to use a solvent that does not melt the silicon-based polymer in advance by heat-treating the silicon-based polymer in advance.

  When the surface-treated member is an intermediate (semi-finished product) such as a molded body, as described above, the surface-treated member may be prepared with a surface treatment agent added in advance.

(Step S140)
Next, the surface-treated member provided with the surface treatment agent obtained in step S130 is fired at a temperature of 800 ° C. or higher.

  The firing atmosphere varies depending on the type of silicide fibrous structure to be grown. For example, when a fibrous structure made of silicon carbide (SiC) and / or silicon oxycarbide (SiOC) is grown on the surface-treated member, the firing atmosphere is argon, helium, water vapor, hydrogen, silicon, carbon monoxide, It includes at least one selected from the group consisting of silicon monoxide, silicon dioxide, and oxynitride gas. On the other hand, when a fibrous structure made of silicon nitride (SiN) and / or silicon oxynitride (SiON) is grown on the porous member, the firing atmosphere contains nitrogen and / or ammonia, and further includes water vapor, hydrogen, It includes at least one selected from the group consisting of silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas.

  Further, the firing atmosphere may include a free catalyst air stream.

However, in any case, the gas supply rate is 0.01 L / min or more per 50 m ² of the surface area of the surface-treated member.

  Through the above steps, the silicide fibrous structure can be formed at a desired position of the surface treatment member.

(Second invention)
Next, a surface treatment method according to the second invention of the present application will be described with reference to FIG.

  FIG. 2 schematically shows an example of the surface treatment method according to the second invention of the present application.

This surface treatment method is
A raw material composed of at least one of talc, kaolin, silicon carbide, silicon nitride, alumina, silica, mullite, cordierite, graphite, carbon fiber, iron, iron alloy, aluminum, and aluminum alloy, and silicon-based high Preparing a porous molded body containing molecules and a catalyst (S210);
A step of forming a fibrous structure of silicide by firing the porous molded body at a temperature of 800 ° C. or higher in an environment in which a gas flow exists, wherein the gas flow is the porous molding. A step (S220) of supplying at a flow rate of 0.01 L / min or more per 50 m ² of the surface area of the body;
Have

  Hereinafter, each step will be described.

(Step S210)
First, a porous molded body to be a surface treated member is prepared.

  The porous molded body is composed of at least one of talc, kaolin, silicon carbide, silicon nitride, alumina, silica, mullite, cordierite, graphite, carbon fiber, iron, iron alloy, aluminum, and aluminum alloy. A raw material, a silicon-based polymer, and a catalyst are included.

  The method for preparing the porous molded body is not particularly limited.

  For example, the porous molded body is prepared by sufficiently stirring the raw material, the silicon polymer, and the catalyst to obtain a mixed powder, and then pressure-molding it with a general molding method. Also good. The pressure molding method may be, for example, a press molding method, a cold isostatic pressing method, a warm isostatic pressing method, or the like.

  Alternatively, a slurry may be prepared by adding an organic binder or the like to such a mixed powder. Thereafter, the slurry is molded by various powder metallurgy methods such as an extrusion molding method, an injection molding method, a cast molding method, or a gel cast molding method, thereby preparing a porous molded body.

(Step S220)
Next, the porous molded body obtained in step S210 is fired at a temperature of 800 ° C. or higher.

The firing conditions are the same as those shown in step S140 of the first invention. It should be noted that the gas supply rate is 0.01 L / min or more per 50 m ² of the surface area of the porous molded body.

  After firing in step S220, the porous molded body becomes a porous member. The porous member has a large number of silicide fibrous structures in the pores and on the surface.

  In general, in the field of catalyst carriers composed of honeycomb-shaped substrates having pore walls, in order to improve the capture performance for the substance to be removed, the contact probability with the substance to be removed is increased, that is, the specific surface area of the reaction site is increased. It is important to increase it. Further, in order to increase the specific surface area of the reaction site, a method is used in which a coating member such as γ-alumina is installed on the pore wall and a catalyst is supported on the coating member.

  However, installation of such a coating member on the pore wall may lead to problems such as a delay in catalyst activation due to an increase in the heat capacity of the catalyst carrier, and an increase in pressure loss due to a decrease in the opening area. Furthermore, γ-alumina transitions to α-alumina at a temperature range of 1000 ° C. or higher, and sintering proceeds. For this reason, the coating member of γ-alumina is sintered at a high temperature, and there is a problem that a high specific surface area cannot be maintained.

  In contrast, in the present invention, a fibrous structure of silicide can be formed inside the pores of the porous member, and therefore the specific surface area of the porous member can be easily increased. Further, the fibrous structure of silicide obtained by the surface treatment method according to the present invention has a very fine structure. For this reason, in the porous member to which the surface treatment method according to the present invention is applied, an increase in pressure loss can be significantly suppressed as compared with a conventional method of installing a coating member.

  Furthermore, since the silicide fibrous structure obtained by the surface treatment method according to the present invention may have a certain amount of space between the fibers, it is difficult to sinter even if kept at a high temperature. For this reason, the porous member to which the surface treatment method according to the present invention is applied can maintain a high specific surface area even when exposed to high temperatures.

  Thus, the porous member surface-treated by the surface treatment method according to the present invention can be significantly applied to a catalyst carrier composed of a honeycomb-like substrate having pore walls.

  In general, in a fiber-containing member such as a heat insulating material, a soundproofing material, and an impact absorbing material, the fiber is made of silica. That is, these fiber-containing members are often produced by melting silica-based ceramics and preparing the melt into fibers by a centrifugal method.

  However, since a silica-based fiber generally has relatively poor heat resistance, a fiber-containing member including such a silica-based fiber has a limit in usable temperature. Further, in such a fiber-containing member, the ceramic fiber is often not firmly bonded to the base material, and in that case, the ceramic fiber is easily scattered to the outside by dropping or the like. Such scattering of ceramic fibers also has an effect on the human body.

  In contrast, the silicide fibrous structure obtained by the surface treatment method according to the present invention is stable even at high temperatures, and is significant in terms of heat resistance compared to silica-based fibers. Further, the silicide fibrous structure is properly bonded to the porous member. For this reason, in the porous member surface-treated by the surface treatment method according to the present invention, the detachment of the fibrous structure of silicide can be significantly suppressed, and the problem of fiber scattering can be significantly suppressed. .

  Next, examples of the present invention will be described. It should be noted that the present invention is not limited to the following examples.

Example 1
Polymethylphenylsilsesquioxane (type H44, manufactured by Wacker) was used as the silicon polymer, and cobalt chloride (produced by Aldrich) was used as a catalyst for the growth of the fibrous structure. Polymethylphenylsilsesquioxane and cobalt chloride were mixed at a weight ratio of 97/3, and this mixture was dissolved in acetone at a weight ratio of 1/4 to obtain a solution of a surface treatment agent.

  A commercially available silicon carbide foam (manufactured by Lanic, 86% porosity, cell size 40 CPSI) was used as the surface treatment member, and this was immersed in a solution of the surface treatment agent. The silicon carbide foam had a diameter of 30 mm and a thickness of 14 mm.

Next, after this surface-treated member was dried at room temperature, it was placed in an atmosphere-controlled electric furnace and baked. Firing was performed at 1250 ° C. for 2 hours in a nitrogen flow atmosphere. Nitrogen was supplied at a flow rate of 0.1 L / min. Since the surface area of the silicon carbide foam obtained by the BET method is 2 m ² , the current flow rate of nitrogen sufficiently satisfies the condition of 0.01 L / min per 50 m ² of the surface area of the surface-treated member (silicon carbide foam Per surface area of 50 m ² , the nitrogen flow rate corresponds to 2.5 L / min).

  Thereby, the porous member which concerns on Example 1 was obtained.

  Table 1 summarizes the conditions for producing the porous member according to Example 1.

FIG. 3 shows an SEM photograph of the porous member according to Example 1. As is apparent from FIG. 3, it was observed that a large number of fibrous structures were formed on the surface and pores of the porous member.

(Example 2)
A porous member according to Example 2 was obtained in the same manner as in Example 1. However, in Example 2, the firing temperature of the surface-treated member was 1450 ° C. Other conditions are the same as in the first embodiment.

  Table 1 above summarizes the conditions for producing the porous member according to Example 2.

  FIG. 4 shows an SEM photograph of the porous member according to Example 2. As is clear from FIG. 4, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 3)
A porous member according to Example 3 was obtained in the same manner as in Example 2. However, in Example 3, polymethylsilsesquioxane (type ML, manufactured by Wacker) was used as the silicon-based polymer. Other conditions are the same as in Example 2.

  Table 1 described above collectively shows the conditions for producing the porous member according to Example 3.

  FIG. 5 shows an SEM photograph of the porous member according to Example 3. As is clear from FIG. 5, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

Example 4
A porous member according to Example 4 was obtained in the same manner as in Example 2. However, in Example 4, polyphenylsilsesquioxane (type Silres 601 manufactured by Wacker) was used as the silicon polymer. Other conditions are the same as in Example 2.

  Table 1 above summarizes the conditions for producing the porous member according to Example 4.

  FIG. 6 shows an SEM photograph of the porous member according to Example 4. As is clear from FIG. 6, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 5)
A porous member according to Example 5 was obtained in the same manner as in Example 2. However, in Example 5, polycarbosilane (type S, manufactured by Nippon Carbon Co., Ltd.) was used as the silicon polymer. Other conditions are the same as in Example 2.

  Table 1 above summarizes the conditions for producing the porous member according to Example 5.

  As a result of SEM observation of the porous member according to Example 5, it was observed that a large number of fibrous structures were formed in the pores of the porous member according to Example 5.

(Example 6)
A porous member according to Example 6 was obtained in the same manner as in Example 2. However, in Example 6, a commercially available alumina foam (manufactured by Lanic, porosity 86%, cell size 20 or 40 CPSI) was used as the surface-treated member. Other conditions are the same as in Example 2.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 6.

  FIG. 7 shows an SEM photograph of the porous member according to Example 6. As is clear from FIG. 7, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 7)
A porous member according to Example 7 was obtained in the same manner as in Example 2. However, in Example 7, a commercially available zirconia foam (porosity 82%, cell size 60 CPSI) was used as the surface-treated member. Other conditions are the same as in Example 2.

  Table 1 above summarizes the conditions for producing the porous member according to Example 7.

  FIG. 8 shows an SEM photograph of the porous member according to Example 7. As is clear from FIG. 8, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 8)
A porous member according to Example 8 was obtained in the same manner as in Example 1. However, in Example 8, a commercially available cordierite honeycomb was used as the surface-treated member. Other conditions are the same as in the first embodiment.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 8.

  FIG. 9 shows an SEM photograph of the porous member according to Example 8. As is clear from FIG. 9, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

Example 9
Polymethylphenylsilsesquioxane (type H44, manufactured by Wacker) was used as the silicon-based polymer, and cobalt chloride (produced by Aldrich) was used as a catalyst for fiber growth. Polymethylphenylsilsesquioxane and cobalt chloride were mixed at a weight ratio of 97/3. Further, 10 wt% of this mixture was mixed with 86 wt% silicon carbide powder, 2.4 wt% alumina powder, and 1.6 wt% yttria powder to obtain a mixed powder.

  Furthermore, 5 wt% of methylcellulose (Yuken Industries) was added to this mixed powder, and mixed with a kneader to prepare a molding clay.

  By the above kneading, ceramic powder particles coated with the silicon polymer and the metal compound were obtained. A honeycomb formed body was manufactured by extruding this.

The honeycomb formed body was degreased at 600 ° C. in nitrogen, and then placed in an atmosphere-controlled electric furnace and fired. Firing was performed at 1700 ° C. for 2 hours in a nitrogen flow atmosphere. Nitrogen was supplied at a flow rate of 2.5 L / min per 50 m ² of the surface area of the honeycomb formed body.

  Thereby, a porous member according to Example 9 was obtained.

  Table 1 above summarizes the conditions for producing the porous member according to Example 9.

  FIG. 10 shows an optical micrograph of the porous member according to Example 9. As is clear from FIG. 10, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 10)
Polymethylsilsesquioxane (type MK, manufactured by Wacker) was used as the silicon-based polymer, and cobalt chloride (Aldrich) was used as a catalyst for fiber growth. Polymethylsilsesquioxane and cobalt chloride were mixed at a weight ratio of 97/3, and this mixture and carbon black were mixed at a weight ratio of 99.9 / 0.1. Moreover, this and acetone were dissolved in the ratio of 1/4 weight ratio, and it was set as the solution of a surface treating agent.

  A commercially available silicon carbide foam (manufactured by Lanic, 86% porosity, cell size 40 CPSI) was used as the surface treatment member, and this was immersed in a solution of the surface treatment agent.

Next, after this surface-treated member was dried at room temperature, it was placed in an atmosphere-controlled electric furnace and baked. Firing was performed at 1450 ° C. for 2 hours in a nitrogen flow atmosphere. Nitrogen was supplied at a flow rate of 2.5 L / min per 50 m ² of surface area of the silicon carbide foam. Since the surface area of the silicon carbide foam obtained by the BET method is 2 m ² , the current nitrogen flow rate sufficiently satisfies the condition of 0.01 L / min per 50 m ² surface area of the surface-treated member.

  Through the above steps, the porous member according to Example 10 was obtained.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 10.

  FIG. 11 shows an SEM photograph of the porous member according to Example 10. As is clear from FIG. 10, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 11)
A porous member according to Example 11 was obtained in the same manner as in Example 10. However, in Example 11, polymethylsilsesquioxane and cobalt chloride were mixed at a weight ratio of 97/3, and this mixture and carbon black were mixed at a weight ratio of 99.5 / 0.5. Other conditions are the same as in the first embodiment.

  Table 1 above summarizes the conditions for producing the porous member according to Example 11.

  FIG. 12 shows an SEM photograph of the porous member according to Example 11. As is clear from FIG. 12, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 12)
A phenol resin was used as the organic polymer, colloidal silica was used as the silica particles, and cobalt chloride (manufactured by Aldrich) was used as a catalyst for fiber growth. Phenol resin and silica particles are mixed at a weight ratio of 0/100, 20/30, or 40/60, and for each mixture, cobalt chloride is mixed / cobalt chloride is mixed at a weight ratio of 97/3. did. Moreover, this and acetone were dissolved in the ratio of 1/4 weight ratio, and it was set as the solution of a surface treating agent.

  A commercially available silicon carbide foam (manufactured by Lanic, porosity 86%, cell size 40 cpsi) was used as the surface treatment member, and this was immersed in a solution of the surface treatment agent.

Next, after this surface-treated member was dried at room temperature, it was placed in an atmosphere-controlled electric furnace and baked. Firing was performed at 1450 ° C. for 2 hours in a nitrogen flow atmosphere. Nitrogen was supplied at a flow rate of 2.5 L / min per 50 m ² of surface area of the silicon carbide foam. Since the surface area of the silicon carbide foam obtained by the BET method is 2 m ² , the current nitrogen flow rate sufficiently satisfies the condition of 0.01 L / min per 50 m ² surface area of the surface-treated member.

  Thereby, a porous member according to Example 12 was obtained.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 12.

  13 to 15 show SEM photographs of the porous member according to Example 12. As is clear from FIGS. 13 to 15, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 13)
A porous member according to Example 13 was obtained in the same manner as in Example 2. However, in Example 13, the firing atmosphere was a nitrogen and silicon monoxide atmosphere, and silicon monoxide powder (manufactured by Aldrich) was placed in the electric furnace. Other conditions are the same as in Example 2.

  Table 1 above summarizes the conditions for producing the porous member according to Example 13.

  FIG. 16 shows an SEM photograph of the porous member according to Example 13. As apparent from FIG. 16, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 14)
A porous member according to Example 14 was obtained in the same manner as in Example 2. However, in Example 14, the firing atmosphere was an argon circulation atmosphere. Other conditions are the same as in Example 2.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 14.

  Moreover, in FIG. 17, the SEM photograph of the porous member which concerns on Example 14 is shown. As is clear from FIG. 17, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 15)
A porous member according to Example 15 was obtained in the same manner as in Example 2. However, in Example 15, copper chloride (manufactured by Aldrich) was used as a catalyst for fiber growth. Other conditions are the same as in Example 2.

  Table 1 above summarizes the conditions for producing the porous member according to Example 15.

  FIG. 18 shows an SEM photograph of the porous member according to Example 15. As is clear from FIG. 18, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 16)
A porous member according to Example 16 was obtained in the same manner as in Example 2. However, in Example 16, iron chloride (manufactured by Aldrich) was used as a catalyst for fiber growth. The firing temperature was 1400 ° C. Other conditions are the same as in Example 2.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 16.

  Moreover, in FIG. 19, the SEM photograph of the porous member which concerns on Example 16 is shown. As is clear from FIG. 19, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 17)
A porous member according to Example 17 was obtained in the same manner as in Example 2. However, in Example 17, nickel acetylacetonate (manufactured by Aldrich) was used as a catalyst for fiber growth. The firing temperature was 1400 ° C. Other conditions are the same as in Example 2.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 17.

  FIG. 20 shows an SEM photograph of the porous member according to Example 17. As is clear from FIG. 20, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 18)
A porous member according to Example 18 was obtained in the same manner as in Example 2. However, in Example 18, platinum chloride (manufactured by Aldrich) was used as a catalyst for fiber growth. Other conditions are the same as in Example 2.

  Table 1 above collectively shows the conditions for producing the porous member according to Example 18.

  FIG. 21 shows an SEM photograph of the porous member according to Example 18. As is clear from FIG. 21, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Example 19)
Polymethylphenylsilsesquioxane (type H44, manufactured by Wacker) was used as the silicon-based polymer, and iron chloride (produced by Aldrich) was used as a catalyst for fiber growth. Polymethylphenylsilsesquioxane and iron chloride were mixed at a weight ratio of 97/3, and the mixture was dissolved in acetone at a weight ratio of 1/4 to obtain a solution of a surface treatment agent.

  A commercially available alumina ceramic particle was prepared as a surface-treated member.

A surface treatment agent was applied to the alumina ceramic powder and dried, and then placed in an atmosphere-controlled electric furnace and fired. Firing was performed at 1450 ° C. for 2 hours in a nitrogen flow atmosphere. Nitrogen was supplied at a flow rate of 2.5 L / min per 50 m ² of the surface area of the alumina ceramic powder. Therefore, the current flow rate of nitrogen sufficiently satisfies the condition of 0.01 L / min per 50 m ² of the surface area of the surface treatment member.

  Thereby, a porous member according to Example 19 was obtained.

  Table 1 summarizes the conditions for producing the porous member according to Example 19.

  FIG. 22 shows an SEM photograph of the porous member according to Example 19. As apparent from FIG. 22, it was observed that a large number of fibrous structures were formed in the pores of the porous member.

(Comparative Example 1)
By the same method as in Example 2, a porous member according to Comparative Example 1 was obtained. However, in this Comparative Example 1, during firing, nitrogen was supplied at a flow rate of less than 0.01 L / min per 50 m ² of the surface area of the silicon carbide foam. Other conditions are the same as in Example 2.

  Table 1 described above collectively shows the conditions for producing the porous member according to Comparative Example 1.

  As a result of SEM observation of the porous member according to Comparative Example 1, it was observed that a fibrous structure was not formed on the surface and pores of the porous member.

  As shown in Example 1 to Example 19, the type of gas used for firing and the firing temperature are greatly increased in the growth of the fibrous structure formed inside the porous member, the cell wall, the surface of the granular material, and the like. It turns out that it affects.

On the other hand, in the porous member according to Comparative Example 1, the fibrous structure was not formed. This is because the method as in Comparative Example 1, that is, when the gas supply amount is less than 0.01 L / min per 50 m ² of the surface area of the surface-treated member, the supply gas is sufficient to the inside of the pores of the porous member. It is thought that it is because it cannot invade.

  Further, as is clear from comparison between FIG. 4 (Example 2) and FIG. 5 (Example 3), the silicon polymer contains more carbon, that is, polymethylphenylsilsesquioxane is used. It was found that many fibrous structures tend to form.

  4 and 9, it was observed that a spherical substance was formed at the tip of the fibrous structure. From the results of composition analysis and X-ray diffraction by EDS observation, this spherical substance was cobalt silicide.

  Further, from FIG. 10, in the method of Example 8, a honeycomb member having a fibrous structure was obtained.

  Further, from the comparison between FIG. 11 (Example 10) and FIG. 12 (Example 11), when carbon is added as a raw material for the surface treatment agent, the thermal carbon reduction reaction of the silicon-based polymer is promoted, and the fibrous structure It was found that the growth of was promoted.

  Further, as shown in FIG. 13 (Example 12), it was found that a fibrous structure could be obtained using only silica and a metal catalyst.

  The fibrous structure produced in the atmosphere containing silicon monoxide in FIG. 16 (Example 13) was found to be silicon nitride from the results of composition analysis by X-ray diffraction and EDS. On the other hand, in Example 14, the fibrous structure was composed of silicon carbide.

  Furthermore, from the results of Examples 15 to 18, it was found that fibrous structures can be formed using various metal catalysts.

  In Example 19, it was also possible to form a fibrous structure on the ceramic powder.

(Example 20)
Using the porous member having the fibrous structure according to the present invention, applicability as a filter was evaluated from the viewpoint of collection efficiency.

  The porous member for the evaluation test was manufactured as follows.

  First, a porous member having a fibrous structure was produced by the same method as in Example 15. At this time, the diameter of silicon carbide foam (manufactured by Lanic, porosity 86%, cell size 40 CPSI) used as the surface-treated member is 30 mm, and the thicknesses are 14 mm, 28 mm, 42 mm, and 56 mm. 4 types.

  The porous members having the fibrous structures thus obtained were sample 1 (thickness of the surface-treated member being 14 mm), sample 2 (thickness of the surface-treated member being 28 mm), and sample 3, respectively. They are referred to as (surface treated member having a thickness of 42 mm) and sample 4 (surface treated member having a thickness of 56 mm).

  Next, the ultrafine particle collection test was implemented using the porous member which concerns on the obtained samples 1 to 4.

(Ultrafine particle collection test)
FIG. 23 shows a schematic configuration of an apparatus used for the ultrafine particle collection test.

  As shown in FIG. 23, the apparatus 100 includes a compressor 110, an aerosol generator 120, a charge neutralizer 130, a dryer 140, a first particle counter 150, and a second particle counter 170. Between the first particle counter 150 and the second particle counter 170, any one of the porous members 160 of the samples 1 to 4 is installed.

  The aerosol generator (Atomizer Aerosol generator model 3079, manufactured by TSI, USA) 120 has a function of generating ultrafine NaCl particles. The ultrafine particles generated by the aerosol generator 120 are conveyed to the charge neutralizer 130 by the compressed air from the compressor 110.

  The charge neutralizer (manufactured by TSI, USA: Model KR85) 130 has a role of neutralizing the charge of ultrafine particles conveyed by compressed air and preventing the charged ultrafine particles from adhering to a pipe or the like.

  Thereafter, the ultrafine particles neutralized by the charge neutralizer 130 are conveyed to the dryer 140 by compressed air. Silica gel is disposed in the dryer 140. The ultrafine particles generated by the aerosol generator 120 may contain moisture, but such moisture is sufficiently removed by passing through the dryer 140.

  Thereafter, the dried ultrafine particles are introduced into the porous member 160 through the first particle counter 150. A first particle counter (manufactured by TSI, USA: Electrostatic Particle Size Classifier 3080) 150 measures the number of ultrafine particles (particle concentration) contained in compressed air. That is, the number of ultrafine particles (particle concentration) measured by the first particle counter 150 is introduced into the porous member 160. The porous member 160 collects ultrafine particles.

  Thereafter, the compressed air that has passed through the porous member 160 is introduced into the second particle counter 170. A second particle counter (manufactured by TSI, USA: Electrostatic Particle Size Classifier 3080) 170 measures the number (particle concentration) of ultrafine particles contained in the compressed air after being processed by the porous member 160. Hereinafter, the number of ultrafine particles (particle concentration) included in the compressed air measured by the first particle counter 150 is referred to as the number (particle concentration) of ultrafine particles on the “porous member inlet side”, and the second The number of ultrafine particles (particle concentration) contained in the compressed air measured by the particle counter 170 is referred to as the number (particle concentration) of ultrafine particles on the “porous member outlet side”.

  Using such an apparatus 100, the number (concentration) of ultrafine particles contained in the compressed air on the porous member inlet side and outlet side was measured.

  Table 2 summarizes the test conditions.

The temperature of the aerosol generator 120 was 25 ° C. The filtration speed in the porous member 160 was 0.57 m / sec, and the filtration flow rate (volume) was 6 L (liter) / min. The effective filtration area of the porous member 160 is 1.77 cm ² . The concentration of the ultrafine particles in the first particle counter 150 is 2.32 × 10 ⁷ particles / cm ³ (number concentration), 4.97 × 10 ¹⁰ nm ³ / cm ³ (volume concentration), and 107.5 μg. / M ³ (weight concentration).

  Prior to the measurement, it was confirmed that in the configuration of the apparatus 100 in which the porous member 160 is not installed, a decrease in the amount (concentration) of ultrafine particles due to the influence of ultrafine particles adhering to the pipe or the like can be ignored.

  The measurement result obtained in the porous member 160 concerning each sample 1 to sample 4 is shown in FIGS. For comparison, a porous member having no fibrous structure, that is, a sample (referred to as sample 5) made of only silicon carbide foam (thickness 56 mm) was used in FIGS. The results of the case are shown simultaneously.

  24 to 25, the horizontal axis indicates the particle size of the ultrafine particles, and the vertical axis indicates the concentration (number concentration) of the ultrafine particles. 24 to 25 simultaneously show the number concentration of ultrafine particles on the porous member inlet side and the number concentration of ultrafine particles on the porous member outlet side in each of samples 1 to 5. Note that FIG. 25 is a graph in which the value on the vertical axis in FIG. 24 is enlarged, but for the sake of clarification of the graph, the data of the sample 5 having greatly different density orders is not shown.

  In FIG. 26 to FIG. 27, the horizontal axis indicates the particle size of the ultrafine particles, and the vertical axis indicates the concentration (volume concentration) of the ultrafine particles. 26 to 27 show simultaneously the volume concentration of the ultrafine particles on the porous member inlet side and the volume concentration of the ultrafine particles on the porous member outlet side in each of the samples 1 to 5. Note that FIG. 27 is a graph obtained by enlarging the value on the vertical axis in FIG.

  Similarly, in FIGS. 28 to 29, the horizontal axis indicates the particle size of the ultrafine particles, and the vertical axis indicates the concentration (weight concentration) of the ultrafine particles. 28 to 29 simultaneously show the weight concentration of the ultrafine particles on the porous member inlet side and the weight concentration of the ultrafine particles on the porous member outlet side in each of samples 1 to 5. Note that FIG. 29 is a graph in which the value of the vertical axis is enlarged in FIG.

  From the results shown in FIGS. 24 to 28, it can be seen that in Sample 5, the collection performance of ultrafine particles is not so good, and many ultrafine particles remain without being collected on the porous member outlet side. . On the other hand, in Samples 1 to 4, it can be seen that many ultrafine particles are collected by the porous member 160, and the concentration of the ultrafine particles is significantly reduced on the porous member outlet side. In particular, it can be seen that the collection performance of the ultrafine particles tends to improve as the thickness of the porous member 160 increases in the order of the samples 1 to 4.

  In addition, from the particle size distribution of the ultrafine particles obtained on the porous member outlet side in Samples 1 to 4, it is expected that the fibrous structures from Sample 1 to Sample 4 have not dropped out. When each sample after the ultrafine particle collection test was observed by SEM, the fibrous structure was bonded to the inside or the surface of the porous member without dropping off in any sample. In addition, it was observed that the collected ultrafine particles were trapped by the fibrous structure. This result suggests that the fibrous structure is not dropped in Samples 1 to 4.

Next, based on these results, the collection efficiency η (%) of samples 1 to 5 was calculated. The collection efficiency η (%) was obtained from the following equation (13).

η (%) = {1− (C _E −C _S ) / C _E } × 100 (13) Formula

Here, C _S represents the concentration of the ultrafine particles in the porous member outlet, C _E represents the concentration of the ultrafine particles in the porous member inlet side.

  Table 3 shows the calculation results of the collection efficiency η (%) of Samples 1 to 5.

From Table 3, in any concentration display, in the case of the porous member according to Sample 1 to Sample 4, the collection efficiency η (%) is significantly improved as compared with the porous member according to Sample 5. I understand. In particular, in the porous member according to sample 3 (surface treated member thickness 42 mm) and sample 4 (surface treated member thickness 56 mm), the collection efficiency η (%) is 100%, It was found that it showed very good collection characteristics.

  Thus, it was confirmed that Samples 1 to 4 have a significantly high ultrafine particle collection efficiency η (%) and can be sufficiently applied as a filter.

(Example 21)
Using the porous member having the fibrous structure according to the present invention, applicability as a filter was evaluated from the viewpoint of pressure loss.

  The porous member for the evaluation test was manufactured as follows.

  First, the porous member which has a fibrous structure was produced by the method similar to Example 2, Example 11, and Example 15. FIG. The obtained porous members having a fibrous structure were respectively sample 6 (porous member according to Example 2), sample 7 (porous member according to Example 11), and sample 8 (in Example 15). Such a porous member).

  In addition, a porous member having no fibrous structure, that is, a sample (referred to as sample 9) made only of silicon carbide foam (thickness 56 mm) was prepared. Furthermore, a commercially available hepa filter (cellulose type: manufactured by Becod Brasil Co., Ltd.) having a thickness of 0.4 mm was prepared. The hepa filter has a trapping efficiency of 99.97% or more with respect to ultrafine particles having a particle size of 0.3 μm and an initial pressure loss of 245 Pa or less in the JISZ8122 standard. Hereinafter, this hepa filter is referred to as sample 10.

  Next, the following pressure loss tests were performed using Sample 6 to Sample 10.

(Pressure loss test)
FIG. 30 shows a schematic configuration of the apparatus used for the pressure loss test.

  As shown in FIG. 30, the apparatus 200 includes a compressor 210, a first pressure and flow rate measuring device 220, and a second pressure and flow rate measuring device 240. Between the first pressure and flow rate measuring device 220 (hereinafter referred to as “first measuring device” 220) and the second pressure and flow rate measuring device 240 (hereinafter referred to as “second measuring device” 240). The sample 230 of any one of the sample 6 to the sample 10 is installed.

  When performing a pressure loss test using such an apparatus 200, the compressor 210 is first operated. As a result, compressed air is supplied from the compressor 210 to the sample 230 via the first measuring device 220. Thereafter, the compressed air passes through the sample 230 and is discharged through the second measuring device 240.

  In this state, the first measuring device 220 measures the pressure of the compressed air (hereinafter referred to as “inlet side pressure”), and the second pressure gauge 240 measures the pressure of the compressed air (hereinafter referred to as “outlet side pressure”). Measured). The first measuring device 220 measures the air flow rate (hereinafter referred to as “inlet side flow rate”), and the second pressure gauge 240 measures the flow rate (hereinafter referred to as “outlet side flow rate”). Such a measurement was performed by changing the pressure of the compressed air supplied from the compressor 210.

  From the difference between the obtained inlet side pressure and the outlet side pressure, and the difference between the inlet side flow rate and the outlet side flow rate, the Darcy permeability k1 and the non-Darcy permeability k2 were calculated using the Forchheimer equation.

  Note that the Darcy permeability k1 and the non-Darcy permeability k2 are indices representing the fluid permeability, and the pressure loss in the sample 230 can be evaluated from these values.

  Table 4 summarizes the Darcy transmittance k1 and the non-Darcy transmittance k2 in each of Sample 6 to Sample 10.

From Table 4, it can be seen that Samples 6 to 8 are somewhat inferior to Sample 9, but have high Darcy transmittance k1 and non-Darcy transmittance k2, and show relatively high transmittance. In particular, Sample 6 to Sample 8 showed values of Darcy transmittance k1 and non-Darcy transmittance k2 that were approximately two orders of magnitude greater than Sample 10, respectively. This is notable, considering that the thickness of Sample 6 to Sample 8 is 140 times that of Sample 10.

  As described above, it was confirmed that Sample 6 to Sample 8 had significantly low pressure loss and could be sufficiently applied as a filter.

  As described above, the porous member according to the present invention is characterized by high collection efficiency and low pressure loss. Therefore, the porous member according to the present invention can be applied to a dedusting filter, a catalyst carrier and the like.

  For example, fine particles contained in exhaust gas discharged from combustion engines such as automobiles and gas turbines have a relatively wide particle size distribution and a distribution from the micron order to the nano order. In particular, fine particles having a size of several hundred nanometers or less (so-called ultrafine particles) may have a high number concentration of 90% or more even if the weight concentration is low. Conventional dedusting filters and catalyst carriers have a problem that it is difficult to sufficiently treat exhaust gas containing fine particles having such a particle size distribution.

  However, it seems that the porous member according to the present invention can be significantly applied to the treatment of exhaust gas containing such ultrafine particles.

  In the porous member according to the present invention, a fibrous structure of silicide can be formed inside the pores, and therefore, the specific surface area of the porous member can be easily increased. Further, the fibrous structure of silicide obtained by the surface treatment method according to the present invention has a very fine structure. For this reason, in the porous member to which the surface treatment method according to the present invention is applied, an increase in pressure loss can be significantly suppressed as compared with the conventional method of installing a coating member such as γ-alumina.

  Furthermore, in the porous member according to the present invention, the silicide fibrous structure is in good contact with the porous member, and there is little possibility of the fibrous structure dropping off. For this reason, the porous member according to the present invention can be applied as a heat insulating material, a sound absorbing material, and a shock absorber with less scattering of fibers.

  The present invention can be applied to, for example, various porous member products and molded articles for porous members. For example, filters, adsorbents, deodorants, reactors, diffusers, shock absorbers, processing members, lightweight It can be applied to materials, solid catalysts, heat insulating materials, biomaterials, and the like.

DESCRIPTION OF SYMBOLS 100 apparatus 110 compressor 120 aerosol generator 130 charge neutralizer 140 dryer 150 first particle counter 160 porous member 170 second particle counter 200 apparatus 210 compressor 220 first pressure and flow rate measuring device 230 sample 240 Second pressure and flow meter

Claims (18)

A surface treatment method for a surface-treated member,
(A) preparing a surface-treated member;
(B) preparing a surface treating agent containing a silicon-based polymer;
(C) installing the surface treatment agent on at least a part of the surface treatment member;
(D) A silicide-like fibrous structure is formed by firing the surface-treated member on which the surface treatment agent is placed at a temperature of 800 ° C. or higher in an environment containing a catalyst and containing a gas flow. A step of supplying the gas flow at a flow rate of 0.01 L / min or more per 50 m ² of a surface area of the surface treatment member;
A surface treatment method comprising: The gas stream includes at least one selected from the group consisting of argon, helium, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas;
The surface treatment method according to claim 1, wherein the silicide fibrous structure includes silicon carbide (SiC) and / or silicon oxycarbide (SiOC). The gas stream includes nitrogen and / or ammonia, and further includes at least one selected from the group consisting of water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas. ,
The surface treatment method according to claim 1, wherein the silicide fibrous structure includes silicon nitride (SiN) and / or silicon oxynitride (SiON).   The surface treatment method according to claim 1, wherein the gas flow further includes a free catalyst air flow.   The surface treatment method according to any one of claims 1 to 4, wherein the catalyst is added to the surface treatment agent in the step (b).   The surface treatment method according to claim 1, wherein the surface treatment agent further contains an organic polymer and / or a carbon-containing material.   The surface according to claim 6, wherein the organic polymer is one or more selected from the group consisting of polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, phenol, polyimide, and nylon. Processing method.   The surface treatment method according to any one of claims 1 to 7, wherein the catalyst includes at least one selected from the group consisting of cobalt, copper, platinum, silver, gold, iron, and nickel. .   The silicon polymer is one or more selected from the group consisting of siloxane, silazane, polycarbosilane, borazine, borosilazane, polyorganoborosilazane, polyborosiloxane, polyorganosiloxane, alkoxysilane, and alkoxide. The surface treatment method according to claim 1, wherein the method is a surface treatment method.   The surface treatment according to any one of claims 1 to 9, wherein the surface treatment member includes at least one material selected from the group consisting of ceramics, glass, metal, cement, and carbon. Method.   The surface-treated member is a honeycomb-like porous member, a lattice-like porous member, a foam-like porous member, a fiber-like porous member, a bead-like porous member made of dense beads or porous beads, and a three-dimensional cellular shape The surface treatment method according to any one of claims 1 to 10, wherein the surface treatment method is at least one selected from the group consisting of a porous member, a molded body, and a dense or porous granular material. . (A) a raw material comprising any one or more of talc, kaolin, silicon carbide, silicon nitride, alumina, silica, mullite, cordierite, graphite, carbon fiber, iron, iron alloy, aluminum, and aluminum alloy; Preparing a porous molded body including a silicon-based polymer and a catalyst;
(B) a step of forming a fibrous structure of silicide by firing the porous molded body at a temperature of 800 ° C. or higher in an environment where a gas flow exists, A step of being supplied at a flow rate of 0.01 L / min or more per 50 m ² of a surface area of the porous molded body;
A surface treatment method comprising: The gas stream includes at least one selected from the group consisting of argon, helium, water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas;
The surface treatment method according to claim 12, wherein the silicide fibrous structure includes silicon carbide (SiC) and / or silicon oxycarbide (SiOC). The gas stream includes nitrogen and / or ammonia, and further includes at least one selected from the group consisting of water vapor, hydrogen, silicon, carbon monoxide, silicon monoxide, silicon dioxide, and oxynitride gas. ,
The surface treatment method according to claim 12, wherein the silicide fibrous structure includes silicon nitride (SiN) and / or silicon oxynitride (SiON).   The surface treatment method according to claim 1, wherein the fibrous structure has an average diameter of 10 μm or less and an aspect ratio of 2 or more.   The surface treatment method according to claim 1, wherein the fibrous structure has a substantially spherical silicon or silicide at a fiber tip.   The porous member surface-treated by the surface treatment method as described in any one of Claims 1 thru | or 16. An apparatus comprising the porous member according to claim 17 and selected from the following group:
Catalyst, catalyst carrier, diesel particulate filter, dust filter, molten metal filter, heavy metal recovery filter, VOC purification filter, air purification filter, water purification filter, bacteria separation filter, virus separation filter, gas or droplet size control member , Gas or droplet diffusers, sound insulation, insulation, shock absorbers, and reactors.