WO2006095564A1

WO2006095564A1 - Porous body composed of silicon carbide sintered body and method for manufacturing same

Info

Publication number: WO2006095564A1
Application number: PCT/JP2006/302994
Authority: WO
Inventors: Fumio Odaka
Original assignee: Bridgestone Corporation
Priority date: 2005-03-08
Filing date: 2006-02-21
Publication date: 2006-09-14
Also published as: JP2006282496A

Abstract

A porous body composed of a silicon carbide sintered body is characterized in that a surface layer having a pore diameter of 10-50μm is arranged on one side surface in a thickness direction on the silicon carbide sintered body having a pore diameter of 50-200μm.

Description

Porous body made of sintered carbide and method for producing the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to a porous body having a strength of sintered carbonized carbide and a method for producing the same. More particularly, the present invention relates to a porous body having a sintered carbon carbide strength for exhaust gas filters and a method for producing the same.

Background art

[0002] Since exhaust gas filters are required to have strength and heat resistance, a porous body having a ceramic force is used as one mode (for example, see Patent Documents 1 and 2). For example, Patent Document 1 includes a first layer that has a fiber reinforced ceramic porous body force with a porosity of 60 to 92%, and a plurality of layers that have the same matrix porous body force with a porosity of 70 to 95%. A light-weight ceramic sound-absorbing material having a multilayer structure in which the pore diameter is reduced by the force on the surface and the density of each layer differs is disclosed. Patent Document 2 discloses a ceramic porous body in which a ceramic layer having a large pore diameter is sequentially laminated in a thickness direction from a ceramic layer having a small pore diameter.

[0003] However, since the manufacturing of the porous body according to Patent Documents 1 and 2 requires a complicated process, there has been a demand for simplification of the manufacturing process. In the invention according to Patent Document 1, the components of the first layer and the other layers are different from each other, and there is a possibility that cracks may occur during firing. Furthermore, in the invention according to Patent Document 2, since the pore gradient structure is formed using the difference in the sedimentation rate caused by the difference in the particle size of the slurry powder, the shrinkage rate is different between the large and small parts, so that the dimensional accuracy is improved. There was a need for improvement.

Patent Document 1: Japanese Patent Laid-Open No. 11-291403

Patent Document 2: Japanese Patent Laid-Open No. 4-209772

Disclosure of the invention

Means for solving the problem

[0004] That is, the present invention relates to the following description items.

(1) On one side surface in the thickness direction of the sintered carbide carbide body having a pore diameter of 50 to 200 m, A porous body having a diameter of 10 to 50 and a surface layer of ζ ΐη and also having a sintered carbon carbide strength.

(2) One-side surface force in the thickness direction Equipped with a slanted pore structure in which the pore diameter increases toward the other side surface, the pore diameter of the first layer is 10-50 μm, and the pore diameter of the second layer or more A porous body made of sintered carbonized carbide having a size of 50 to 200 μm.

(3) A porous body comprising the sintered carbide body according to the above (1) or (2) having a bending strength of 30 MPa or more.

(4) a step of producing aggregates comprising a carbide carbide powder, aluminum boride and a binder, a step of compressing the aggregates into a mold to obtain a temporary molded body, and the temporary molded body as a carbon sheet. And a step of obtaining a sintered carbide body by firing at 2100 ° C. to 2300 ° C. and producing a porous body having a sintered carbon carbide strength.

(5) The method for producing a porous body comprising the silicon carbide sintered body according to (4), wherein the binder is carboxymethylcellulose.

(6) The method for producing a porous body having the strength of sintered carbonized carbide according to (4), wherein the temporary molded body is heated in an argon atmosphere during the step of obtaining the sintered carbide carbide.

(7) The method for producing a porous body having the strength of sintered carbonized carbide according to any one of the above (4) to (6), wherein the obtained porous body having the strength of sintered carbonized carbide has a bending strength of 30 MPa or more. .

(8) Production of a porous body comprising the sintered carbonized body according to (5) above, wherein the amount of the carboxymethylcellulose added is 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the carbonized carbide powder. Method.

Brief Description of Drawings

FIG. 1 shows a SEM photograph of a cross section of Example 1. FIG.

[FIG. 2] FIGS. 2 (a) to 2 (e) are partially enlarged views of SEM photographs of the cross section of Example 1. FIG. BEST MODE FOR CARRYING OUT THE INVENTION

[0006] There has been a demand for a porous body having a strength of sintered carbonized carbide that can be easily manufactured and a method for manufacturing the same. The ability to explain the present invention with reference to the embodiments below It goes without saying that the present invention is not limited to the following embodiments.

[Ingredients used in the method for producing a sintered carbide body]

First, components used in a method for producing a sintered carbide carbide according to an embodiment of the present invention Explain about:

(Carbon carbide powder)

Examples of the silicon carbide powder include α-type, ι8-type, amorphous, and a mixture thereof. Moreover, in order to obtain a high-purity silicon carbide sintered body, it is preferable to use a high-purity silicon carbide powder as a raw material carbide carbide powder.

There is no particular limitation on the grade of this ι8 type carbide powder, for example, commercially available ι8 type carbide can be used. The particle size of the carbide powder is preferably small from the viewpoint of high density. Specifically, it is about 0.01 / ζ πι to 20 / ζ πι, and more preferably 0.05 μm. m to 10 μm. When the particle size force is less than 0.01 μm, handling in processing steps such as weighing and mixing becomes difficult, and when it exceeds 20 / zm, the specific surface area is small, that is, the contact area with the adjacent powder is small. This is not preferable because it is difficult to increase the density.

[0007] The high-purity silicon carbide powder is produced by, for example, polymerizing a carbon source containing at least one or more types of silicon compounds, a carbon source containing at least one or more organic compounds that generate carbon by heating. Or it can obtain by the process of baking the powder obtained after melt | dissolving a crosslinking catalyst in a solvent, and drying in non-acidic atmosphere.

[0008] As a key source containing the above key compound (hereinafter referred to as a "key source"), a force capable of using both a liquid and a solid one is selected. Must-have. As the liquid form, alkoxysilane (mono-, G-, tree, tetra-) and tetraalkoxysilane polymers are used. Among the alkoxysilanes, tetraoxysilane is preferably used. Specifically, methoxysilane, ethoxysilane, propoxysilane, butoxysilane and the like are preferable from the viewpoint of force handling. Examples of the tetraalkoxysilane polymer include a low molecular weight polymer (oligomer) having a degree of polymerization of about 2 to 15, and a polymer having a high degree of polymerization and a liquid of a carboxylic acid polymer. Solid oxides that can be used in combination with these include silicon oxide. In the above reaction sintering method, the acid silicate is silica, silica gel (liquid containing colloidal ultrafine silica, containing OH group or alkoxyl group), diacid silicate (silica gel, fine Silica, quartz powder) and the like. These key sources may be used alone or in combination of two or more Use together.

Among these key sources, tetraethoxysilane oligomers and mixtures of tetraethoxysilane oligomers and finely divided silica are preferred from the viewpoint of good homogeneity and ringing properties. Further, these key sources are high-purity substances, and the initial impurity content is preferably 20 ppm or less, more preferably 5 ppm or less.

[0010] The substance used as the carbon source is preferably a high-purity organic compound that contains oxygen in the molecule and retains carbon by heating. Specific examples include monosaccharides such as phenol resin, furan resin, epoxy resin, phenoxy resin and glucose, oligosaccharides such as sucrose, polysaccharides such as cellulose and starch, and the like. . For the purpose of homogeneously mixing with the key source, these may be liquid at room temperature, those that dissolve in a solvent, those that soften or become liquid when heated, such as thermoplastic or heat-melting properties. Used mainly. Of these, resol type phenol resin and novolak type resin resin are preferable. In particular, a resol type phenolic resin is preferably used.

[0011] The polymerization and cross-linking catalyst used in the production of high-purity silicon carbide powder can be appropriately selected according to the carbon source. When the carbon source is phenol resin or furan resin, toluenesulfonic acid, toluene Acids such as carboxylic acid, acetic acid, oxalic acid and sulfuric acid can be mentioned. Of these, toluenesulfonic acid is preferably used.

[0012] The ratio of carbon to silicon (hereinafter abbreviated as CZSi ratio) in the process of producing high purity carbide powder is the elemental analysis of the carbide intermediate obtained by carbonizing the mixture at 1000 ° C. It is defined by Stoichiometrically, the force that free carbon in the generated carbide should be 0% when the CZSi ratio is 3.0. Actually, it is released at a low CZSi ratio due to volatilization of the SiO gas generated at the same time. Carbon is generated. It is important to determine the blending in advance so that the amount of free carbon in the generated carbon carbide powder does not become an amount that is not suitable for the purpose of manufacturing a sintered body or the like. Usually, in firing at 1600 ° C or higher near 1 atm, free carbon can be suppressed by setting the CZSi ratio to 2.0 to 2.5, and this range can be suitably used. When the CZSi ratio is 2.55 or more, free carbon increases remarkably, but this free carbon has the effect of suppressing crystal growth, so the CZSi ratio may be selected appropriately according to the crystal growth size to be obtained. . However, if the atmospheric pressure is low or high, pure carbonization Since the czsi ratio for obtaining the key fluctuates, this is not necessarily limited to the above range of czsi ratio.

[0013] (auxiliary and binder)

As an auxiliary agent, it is preferable to add boron aluminum (A1B 2). The reason is not particularly clear! /, But the addition of aluminum boride promotes vitrification of the porous body and improves the density of the porous body. In addition, by covering aluminum boride, liquid phase formation and grain growth can be performed at the same time, and the surface of the sintered carbonized carbide on the side where the carbon sheet (carbon source) is arranged becomes dense. That's it. The amount of aluminum boride added is preferably 0.1 to 5 parts by weight and more preferably 0.2 to 0.5 parts by weight with respect to 100 parts by weight of the silicon carbide powder.

[0014] It is preferable to use carboxymethyl cellulose (CMC) as the binder. This is because by adding CMC, the strength of the molded body is increased by heating and drying becomes easier. Moreover, by covering the CMC, it can have a binder function as a liquid and formability can be given by drying. The amount of CMC added is preferably 3 to 20 parts by weight and more preferably 5 to 10 parts by weight with respect to 100 parts by weight of the carbide carbide powder.

[0015] Further, a dispersant may be appropriately provided. Examples of the dispersant include lower alcohols such as ethanol and methanol. This is because silicon carbide and aluminum boride can be uniformly dispersed. When adding a dispersant, it is preferable to leave the mixture for several hours until the alcohol has evaporated.

[Porous body made of sintered carbonized carbide]

As an embodiment of the present invention, a sintered carbide carbide in which a surface layer having a pore diameter of 10 to 50 m is provided on one surface in the thickness direction of a sintered carbide carbide body having a pore diameter of 50 to 200 m. A porous body comprising a body is provided.

As a modification of the embodiment of the present invention, a one-side surface force in the thickness direction is provided with a pore inclination structure in which the pore diameter increases toward the other surface, and the first layer has a pore diameter of 10 to 50 111, A porous body having a carbon carbide sintered body strength in which the pore diameter of two or more layers is 50 to 200 μm is provided.

[0017] The porous body made of sintered carbonized carbide that is effective in the embodiment of the present invention has a bending strength of 30. MPa or more, and in a preferred embodiment, 50 MPa or more. The porosity is 1% to 32%, preferably 5% to 29%. Furthermore, the porous body made of the sintered carbonized carbide that is effective in the embodiment of the present invention has characteristics of high purity, high density, and high toughness. Since the porous body made of sintered carbonized carbide according to the embodiment of the present invention has the above characteristics, it can be suitably used as an exhaust gas filter, for example.

[0018] [Method for producing sintered carbide body]

(Ii) First, agglomerates containing silicon carbide powder, aluminum boride (A1B) and binder

2

To manufacture. In that case, it is preferable to produce by the direct granulation method using an Eirich granulator. If desired, a dispersant may be added in addition to the above components.

(Mouth) The obtained aggregate is put into a mold and compressed to obtain a temporary molded body. In this case, it is preferable to obtain a temporary molded body by compressing it with a surface pressure of 100 to 300 kgZcm ² using a uniaxial press machine or the like. If the pressure is lower than the above lower limit value, it will be difficult to maintain the shape as a temporary molded body in a later step, and if the pressure is higher than the upper limit value, the obtained effect is the same, so it is not efficient. .

(C) Next, the obtained temporary molded body is placed on a carbon sheet. This is the force that densifies the surface by contacting the carbon source in the carbon sheet with the surface of the temporary molded body. Any commercially available carbon sheet can be used as long as it functions as a hearth plate. Then, heating is performed at 2100 ° C or higher, preferably 2200 ° C to 2300 ° C. The reason why the temperature is set to 2100 ° C or higher is because V is a sintered carbonized carbide body having an inclined pore structure. In other words, the liquefaction phenomenon and grain growth do not occur, and the force of the scattering of the carbon by the thermal decomposition of the carbide. The upper limit of the heating temperature is set to 2300 ° C because the heating furnace may be destroyed at temperatures above 2300 ° C. Also, if the heating temperature is out of the range of 2100 ° C to 2300 ° C, the strength decreases, so it is preferable to heat to a certain temperature within this temperature range. At that time, from the viewpoint of increasing the strength, it is preferable that the temperature is maintained for 0.5 to 8 hours in an argon (Ar) gas atmosphere after reaching a certain temperature. The reason for heating in an argon gas atmosphere is that Si N is formed when heated in a nitrogen (N) gas atmosphere.

3 4

This is because there is a possibility that the atmosphere is an argon gas atmosphere.

Through the above process, a fine surface layer is formed on the surface on one side, and internal force A porous body made of a sintered carbide carbide having an inclined structure is obtained.

[0021] Although the embodiments have been described above, the present invention is not limited to the above embodiments. Therefore, as long as the heating conditions of the present invention can be satisfied, a known heating furnace reactor can be used, with no particular restrictions on the production apparatus.

Example

Examples of the present invention are shown below, but the present invention is not limited to these examples.

(Example 1)

Aggregate production process: high purity carbon carbide powder with a central particle size of 5 μm as the carbide carbide powder (impurity content of 5 p pm or less produced according to the production method described in JP-A-9-48605 Carbohydrate Zr. 5% by weight silica) 100 parts by weight, 0.3 parts by weight boron boride (A1B), 5 parts by weight carboxymethylcellulose (CMC)

2

Further, 100 parts by weight of polybulal alcohol (PVA) as a dispersing agent was charged into an Eirich granulator and subjected to vibration granulation to produce aggregates. After standing for 3 hours, the alcohol was evaporated and granulated to obtain aggregates. The aggregate was put into a mold having a diameter of 210 mm, and compressed with a surface press of 200 kgZcm ² by a shaft press to obtain a temporary molded body.

Step of obtaining a sintered body: The obtained temporary molded body was placed on a carbon sheet in a graphite crucible. The temperature was raised to 600 ° C over 5 hours under an argon atmosphere, and then heated to 2200 ° C at 150 ° C Z for 1 hour and held at 2200 ° C for 6 hours.

Molding process: Using a milling machine, surface processing was performed to form a disk with a diameter of 200 mm and a thickness of 10 mm.

The cut surface of the obtained porous carbide body was analyzed with a scanning electron microscope (SEM). The results obtained are shown in FIGS. Further, the obtained porous carbide body was examined for bending strength, force density, thermal conductivity, surface pore diameter, and internal pore diameter according to the criteria described later. The experimental results obtained are shown in Table 1. In the table, “PVA” indicates polyvinyl alcohol.

[table 1]

[0023] (Evaluation)

The items listed in Table 1 were evaluated based on the following criteria:

The bending strength was determined by cutting a 50mm x 8mm x 6mm sample and conducting a three-point bending strength test under the conditions of 30 and a crosshead speed of 0.5mmZmin.

As for the pore diameter, the minimum value and the maximum value of the surface layer and the inner layer were measured.

The force density was measured by Archimedes method according to JIS R1634.

The thermal conductivity was measured using a milling force machine to form a disk with a diameter of 10 mm and a thickness of 2 mm. After the surface treatment was performed on the porous carbon carbide body, the laser-flash method was applied to the porous carbon carbide body. Then, the thermal diffusivity and specific heat were measured and calculated from the formula of thermal diffusivity X specific heat X density. For measurement, a laser flash heat measuring device manufactured by ULVAC-RIKO Inc. was used.

(Examples 2 to 7) (Comparative Examples 1 to 3)

The experiment was performed in the same manner as in Example 1 except that the experimental conditions were set as shown in Table 1. The experimental results obtained are shown in Table 1.

As shown in FIGS. 1 and 2 and Table 1, Example 1 has a surface layer with a pore diameter of 12 to 28 / ζ πι on one side surface, and has a pore gradient structure from the inside to the surface. It was done. In addition, Example 1 had good bending strength, bulk density and thermal conductivity. In Example 2, as in Example 1, a dense surface layer and a pore gradient structure were formed, and it was confirmed that they had good bending strength, bulk density, and thermal conductivity. In Examples 3 and 4, a dense surface layer and an inclined pore structure were formed, but the bending strength and thermal conductivity were lower than in Example 1.

On the other hand, the pore gradient structure was not observed for Comparative Examples 1 to 3, and all items of bending strength, strength density and thermal conductivity were inferior to Examples 1 to 4. From the above results, heating the aggregates containing aluminum boride and CMC in an argon atmosphere results in a sintered body of silicon carbide having a dense surface layer and pore gradient structure and good bending strength. It was confirmed that a porous body was obtained.

[0025] This application is a Japanese patent application filed earlier by the same applicant, ie, Japanese Patent Application 2005-6 4503 (filing date March 8, 2005) and Japanese Patent Application 2006- 27331 (filing date 2006). February 3 With the priority claim based on (Japan), and these specifications are incorporated herein by reference.

Industrial applicability

A porous body having a sintered carbon carbide strength that can be easily produced and a method for producing the same are provided.

Claims

The scope of the claims

[1] A carbonized cage characterized in that a surface layer having a pore diameter of 10 to 50 111 is provided on one side surface in the thickness direction of a sintered carbide carbide body having a pore diameter of 50 to 200 / ζ m. A porous material that also has a sintered body strength.

[2] One-side surface force in the thickness direction Equipped with an inclined pore structure in which the pore diameter increases as the force is applied to the other-side surface, the pore diameter of the first layer is 10-50 μm, and the pore diameter of the second layer or more A porous body having a strength of sintered carbonized carbide, characterized by being 50 to 200 μm.

[3] The porous body comprising the sintered carbonized carbide according to claim 1 or 2, wherein the bending strength is 30 MPa or more.

[4] A step of producing aggregates containing a carbonized carbide powder, aluminum boride and a binder, a step of putting the aggregates into a mold and compressing to obtain a temporary molded body,

Placing the temporary molded body on a carbon sheet and firing at 2100 ° C to 2300 ° C to obtain a silicon carbide sintered body;

A method for producing a porous body comprising a sintered carbonized carbide, comprising:

[5] The method for producing a porous body according to claim 4, wherein the binder is carboxymethylcellulose.

6. The method for producing a porous body made of a sintered carbide body according to claim 4, wherein in the step of obtaining the sintered carbide body, the temporary molded body is heated in an argon atmosphere.

7. The method for producing a porous body having a sintered body of sintered carbonized carbide according to any one of claims 4 to 6, wherein the obtained porous body having a sintered body of sintered carbonized carbide has a bending strength of 30 MPa or more.

[8] The sintered body of silicon carbide according to claim 5, wherein the amount of added carboxymethyl cellulose is 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the carbonized carbide powder. A method for producing a porous body comprising: