JPH04114981A - Sintered multilayer composite ceramics and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject sintered material having improved mechanical strength without causing cracking, etc., by introducing inorganic colloid particles into open pores of a laminated and sintered material composed of a porous ceramic layer having open pores and a ceramic layer having dense texture and integrally sintering the layers. CONSTITUTION:A green sheet (A) for forming a dense layer is produced by drying a formed layer of a slurry for dense layer composed of (a) an inorganic colloid liquid containing water as dispersion medium, (b) a sintering assistant and (c) a water-soluble binder. Separately, a green sheet (B) for porous layer is produced by drying the formed layer of a slurry for porous layer composed of the component (a), the component (b) and the component (c), wherein the content of the component (b) is smaller than the content in the sheet A or the component (b) is absent in the sheet B. The green sheet A is bonded to one or both surfaces of the sheet B with an adhesive and the laminate is baked at 1000-1600 deg.C to obtain a sintered laminate of a porous ceramic layer and a dense ceramic layer. An inorganic colloid liquid (d) different from the component (a) is introduced into the porous ceramic layer of the sintered product, subjected to hydrothermal treatment and cooled to deposit the inorganic colloid particle (C) in the open pores of the porous ceramic layer. The product is baked again to obtain the objective sintered material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is manufactured by a green sheet multilayer lamination method.
This invention relates to a multilayer ceramic composite sintered body made of different ceramic raw materials. More specifically, the present invention relates to a multilayer ceramic composite sintered body useful as a catalyst carrier or filter, and a method for manufacturing the same.

[Prior Art] Conventionally, when manufacturing a multilayered ceramic composite sintered body made of different types of ceramic raw materials, different types of ceramic molded bodies are manufactured separately, and then these different types of ceramic molded bodies are hot-pressed or laminated. After laminating them to form a composite body, they are fired to obtain a multilayer ceramic composite sintered body.

[Problems to be Solved by the Invention] However, the sintering temperature, thermal expansion coefficient, firing shrinkage, etc. of ceramic molded bodies differ depending on the raw materials, and when fired in a laminated state, cracks may occur between the layers of the sintered body. There was a problem that defects such as warping and peeling were likely to occur.

The purpose of the present invention is to prevent defects such as cracks, warping, and peeling between the layers of the sintered body when fired in a laminated state.
Moreover, it is an object of the present invention to provide a multilayer ceramic composite sintered body having high mechanical strength and a method for manufacturing the same.

[Means for Solving the Problems] In order to achieve the second object, the multilayer ceramic composite sintered body of the present invention has a porous ceramic layer made of the same type of ceramic raw material as the porous ceramic layer on both or one side of the porous ceramic layer. A multilayer ceramic sintered body is a multilayered ceramic sintered body in which dense ceramic layers are laminated and integrally sintered, and the porous ceramic layer has open pores formed therein as a support. It is characterized in that inorganic colloidal particles made of different types of ceramic raw materials are introduced into the open pores and sintered integrally with the porous ceramic layer.

In addition, in the method for manufacturing a multilayer ceramic composite sintered body of the present invention, first, a first sintering aid and a first water-soluble binder are added and mixed to a first inorganic colloid liquid using water as a dispersion medium to form a slurry for a dense layer. This slurry for dense layer is formed into a film and dried to form a green sheet for dense layer. Next, water is used as a dispersion medium, and a second inorganic colloid liquid of the same type as the first inorganic colloid liquid is mixed with no sintering aid or a second sintering aid in a smaller amount than the first sintering aid. 2 A water-soluble binder is added and mixed to prepare a slurry for a porous layer, and this slurry for a porous layer is formed into a film and dried to form a green sheet for a porous layer. Next, the dense layer green sheet is adhered to both sides or one side of the porous layer green sheet with an adhesive, and the adhered green molded body is
A laminated sintered body is formed by firing at 0°C. Next, using water as a dispersion medium, a third inorganic colloid liquid different from the first and second inorganic colloid liquids is added.
After introducing an inorganic colloid liquid into the porous ceramic layer of the laminated sintered body and hydrothermally treating the third inorganic colloid liquid,
By cooling, inorganic colloid particles are precipitated in the open pores of the porous ceramic layer. Furthermore, the laminated sintered body in which the inorganic colloid particles have been precipitated is fired again.

The first inorganic colloid liquid, which is the main component of the slurry for the dense layer, the second inorganic colloid liquid, which is the main component of the slurry for the porous layer, and the eighth inorganic colloid liquid, which is introduced into the porous ceramic layer, are all metal alkoxides. The particle size obtained by hydrolyzing and peptizing the hydrolyzed product is several 10 to 1.
Inorganic colloidal liquids with 0,000 microscopic colloidal particles are preferred.

Examples of the inorganic colloid liquid include alumina sol, silica sol, TiO□ sol, ZrO□ sol, and the like.

The difference between the preparation methods of the slurry for dense layers and the slurry for porous layers is that the former contains 0.5 to 10% by weight of the sintering aid based on 100% by weight of the inorganic colloid liquid, while the latter In order to increase the porosity of the ceramic layer, either no sintering aid is included or a smaller amount of sintering aid is included. Examples of the sintering aid include silicon dioxide, magnesium oxide, calcium oxide, magnesium acetate, and titanium dioxide. In the addition system of magnesium oxide and silicon dioxide, it is preferable to add at least 0.1% by weight of calcium oxide.

The water-soluble binder is added in an amount of 10 to 80% by weight based on the solid content of the inorganic colloid liquid in both the dense layer slurry and the porous layer slurry.

Since this binder tends to generate pores in the ceramic layer due to removal of the binder during sintering, in order to reduce the porosity, it is added to the inorganic colloid liquid in a small amount within the above range. Examples of water-soluble binders include polyvinyl alcohol and water-soluble acrylic. The binder contained in the slurry for the dense layer may be different from the binder contained in the slurry for the porous layer.

Methods for forming dense layer slurry and porous layer slurry include the doctor blade method, extrusion molding method, roll rolling method, and slurry casting method, but these methods have low molding distortion and smoothness of the molded product. A good doctor blade method is preferred. When forming a slurry for a porous layer, ammonia or an alkaline substance such as amines may be added to the slurry to form a gel in the slurry, thereby increasing the porosity.

After forming the slurry for the dense layer and the slurry for the porous layer, they are dried at 30 to 95°C, respectively, to form a green sheet for the dense layer and a green sheet for the porous layer. The green sheet for the dense layer has pores with a diameter of 6 to facilitate the introduction of the inorganic colloid liquid into the porous ceramic layer, which will be described later.
A through hole of 0 to 100 μm may be provided.

Next, an adhesive is applied to both sides or one side of the green sheet for the porous layer, and the adhesive is applied at a temperature of 0 to 70°C at a rate of 5 to 200 kg/c.
The green sheet for the porous layer and the green sheet for the dense layer are adhered and laminated under a pressure of m2.

If necessary, both green sheets can be rolled up while being adhered to each other using a laminating device with a winding mechanism.

As this adhesive, an aqueous adhesive such as a cellulose derivative, an acrylic emulsion, or a vinyl acetate emulsion, or a non-aqueous adhesive such as an acrylic resin, a butyral resin, or a vinyl resin can be used.

In addition to the two layers in which one green sheet for a dense layer is laminated on one side of one green sheet for a porous layer, the number of laminated layers varies depending on the use, size, etc. of the composite sintered body. It is also possible to have three or more layers in which a solid layer and a porous layer are alternately stacked.

After the green sheets are laminated, they are cut into predetermined dimensions, placed in a firing furnace, and fired. The green compact that was wound up and formed into a cylindrical shape was cut into a predetermined length, the central hole created by removing the winding core was filled with a slurry for a dense layer, and the material was heated at 30 to 95°C. After drying this slurry, it is placed in a kiln and fired.

Firing is performed at a temperature of 1000 to 160 to obtain the desired porosity.
It is carried out at a temperature range of 0° C. for 1 to 2 hours under atmospheric pressure.

The higher the firing temperature and the longer the firing time, the lower the porosity. If the temperature is less than 1,000°C, the porosity of the dense ceramic layer increases, and if it exceeds 1,600°C, the porosity of the porous ceramic layer decreases, making it impossible to achieve the object of the present invention.

In the multilayer ceramic composite sintered body of the present invention, the porosity of the porous ceramic layer is in the range of 20 to 60%, and the porosity of the dense ceramic layer is 0%, depending on the amount of sintering aid added or the firing temperature. The content is controlled within the range of .01 to 5%.

Open pores are formed in the porous ceramic layer of the laminated sintered body obtained by the above firing. Here, open pores are different from closed pores and refer to fine pores that are continuous from one end of the sintered body to the other and allow fluid to pass through.

Next, using the laminated sintered body as a support, a third inorganic colloid liquid containing water as a dispersion medium is introduced into the porous ceramic layer.

The following two methods are typical for this introduction method. That is, the first introduction method is to hydrolyze a metal alkoxide,
In this method, an inorganic colloid liquid obtained by peptizing this hydrolyzed product is placed in a container, and then the laminated sintered body is immersed in this liquid to introduce the inorganic colloid liquid into the porous ceramic layer. .

The second introduction method is to immerse the laminated sintered body in water in a container, then add metal alkoxide, hydrolyze the metal alkoxide with this water, and then peptize the hydrolysis product to form an inorganic colloid. This method involves introducing a liquid into a porous ceramic layer.

By the above method, fine inorganic colloid particles having a particle size of several tens to a thousand are introduced into the open pores of the porous ceramic layer of the laminated sintered body. By adjusting the colloid particle size, the open pores can have a desired pore size. A method for adjusting the colloid particle size includes, for example, a method of hydrothermally treating a peptized inorganic colloid liquid. If carboxylic acid is further added to the colloidal liquid before this hydrothermal treatment,
Particle size can be adjusted even more easily. After the hydrothermal treatment, inorganic colloid particles are precipitated in the open pores by cooling. As the inorganic colloid particles, alumina (A
03), titanium dioxide (T102), zirconia (Z
rO2), magnesium oxide (Mg0), barium titanate (BaTi0s), and the like.

The precipitated inorganic colloid particles reduce the pore size of the open pores of the porous ceramic layer according to their particle size. Hydrothermal treatment and cooling treatment of the inorganic colloidal liquid in an autoclave is preferred because it can speed up the growth and precipitation of colloidal particles.

The laminated sintered body is taken out from the container and the water content of the inorganic colloid liquid is removed. This moisture removal is performed by air drying or hot air drying the laminated sintered body under atmospheric pressure or reduced pressure. The colloidal liquid is gelled by drying, and in this state, the laminated sintered body is fired again at 900-1300'C for 13-5 hours under atmospheric pressure. As a result, the inorganic colloid particles deposited in the open pores are supported and integrated into the laminated sintered body.

FIG. 1 shows a manufacturing process diagram of the multilayer ceramic composite sintered body of the present invention. FIG. 2 shows a five-layer ceramic composite sintered body 10 sintered into a plate shape, and FIG. 3 shows a multilayer ceramic composite sintered body 20 sintered into a columnar shape. 10a and 20a are porous ceramic layers serving as fluid passages, 10b and 20b are dense ceramic layers, and 11 is a dense ceramic layer 10b.
It is a through hole formed in.

[Effects of the Invention] As described above, the multilayer ceramic composite sintered body of the present invention is produced by laminating dense ceramic layers on both sides or one side of a porous ceramic layer by the green sheet multilayer lamination method and sintering them integrally. After that, inorganic colloid particles of a different kind from the ceramic layer are introduced into the open pores of the porous ceramic layer and sintered integrally with the porous ceramic layer. No defects such as cracks, warping, or peeling occur.

In particular, the dense ceramic layer acts as a reinforcing material to increase mechanical strength, and the porous ceramic layer increases the specific surface area and pore volume.

Further, the pore size of the laminated sintered body serving as the support is arbitrarily adjusted according to the particle size of the inorganic colloid particles introduced into the open pores of the porous ceramic layer and sintered integrally with the porous ceramic layer. be able to.

Furthermore, the physical properties of the inorganic colloid particles and the physical properties of the porous ceramic layer of the laminated sintered body serving as the support can be combined. Therefore, by selecting the inorganic colloid particles to be introduced into the porous ceramic layer, the multilayer ceramic composite sintered body of the present invention can be used as a catalyst carrier or a filter.

[Example] Next, embodiments of the present invention will be described in detail.

<Example 1> Aluminum isopropoxide [A Q (C3H70
) 3] to produce boehmite [A Q OOH]
was produced and peptized by adding water adjusted to pH 2 to 4 to obtain a stable pseudo-boehmite sol with an alumina concentration of 5% by weight in which fine colloidal particles with a particle size of several 10 to 1000 were dispersed. .

In order to prepare a slurry for a dense layer, silica colloid, magnesium acetate, and calcium acetate were added as sintering aids to this sol, and polyvinyl alcohol was further added as a water-soluble binder. These sintering aids have a composition ratio of A, Q208:5iOz:MgO:Ca0=92:7 when sintered into a dense alumina layer.
: 2:1. The binder was added in an amount of 40% by weight based on the solid content. As a result, a slurry having a solid content of 4% by weight was prepared.

This slurry is coated onto a high-density polyethylene tape, which is a moving carrier, to a thickness of approximately 0.4 mm using a doctor blade method, and then dried to remove water, which is a dispersion medium of the slurry, to a thickness of approximately 20 μm. A green sheet for dense layer was obtained. Nine holes with a diameter of 100 μm were bored per 1 square cm in the green sheet for the dense layer.

On the other hand, a green sheet for a porous layer having a thickness of about 60 μm was obtained in the same manner as above except that no sintering aid was added to facilitate porosity.

As shown in FIG. 2, green sheets for a porous layer are adhered to both sides of green sheets for a dense layer, and green sheets for a dense layer are further adhered to the outer surfaces of these green sheets for a porous layer. A 5-layer green molded body was obtained. An isopropyl alcohol solution of polyvinyl butyral with a concentration of 1% was used as the adhesive.

Next, this 5-layer green molded body was placed in a firing furnace for 1300
It was fired for 1 hour at C. under atmospheric pressure to obtain a 5-layer laminated sintered body. In order to investigate the pore size distribution and porosity of the porous alumina layer, only the green sheet for the porous layer was heated at 1000°C.
1200°C, 1300°C, 14000°C, 1500°
C. for 1 hour each under atmospheric pressure. The results are shown in FIGS. 4 and 5. From Figure 4, the firing temperature is 130
At temperatures above 0°C, the pore volume becomes 0,1 c+r+37
In addition, the pore diameter is 250 Å or more, and 150 Å or more.
It was found that at 0°C, the pore volume was 0.2 cm'/g or more, and the pore diameters were extremely distributed in the range of 750 to 1250 cm'/g. Also, from Figure 5, the pore volume of the porous alumina layer is in the range of 0.2 to 0.4 cm37g,
It was found that the porosity was in the range of 40 to 60%, and the pore volume and porosity decreased as the firing temperature increased.

On the other hand, the five-layered laminated sintered body was placed in an autoclave containing water and immersed in water. Next, titanium alkoxide was added to this water to hydrolyze the titanium alkoxide to produce a sol.

Nitric acid was added and mixed as a deflocculant to this sol. The molar ratio of water/alkoxide was 100, and the molar ratio of nitric acid/alkoxide was 0.1. This introduced the sol into the open pores of the porous alumina layer.

Hydrothermally treat the sol at room temperature in an autoclave at a temperature of 1
The temperature was increased to 50'C at a rate of 5°C per minute.

Heating was stopped when the temperature reached 150°C and maintained for 3 hours. Subsequently, the temperature was lowered from 150°C to 100'C at a rate of 5°C per minute to precipitate titanium colloid particles within the open pores.

The laminated sintered body was removed from the autoclave, air-dried to gel the sol, and then the laminated sintered body was heated again at 900°C for 3 hours.
Fired under atmospheric pressure. A five-layer ceramic composite sintered body in which titanium dioxide was supported on a porous alumina layer was obtained.

FIG. 6 is an electron micrograph enlarged 350 times to mainly show the grain structure of the cross section of this porous ceramic layer. From FIG. 6, no defects such as cracks or peeling were observed between the porous ceramic layer and the dense ceramic layer. The bending strength of this sintered body was 40 kgf/mm2.

The porosity of the single-layer dense sintered sheet and the single-layer porous sintered sheet supporting titanium dioxide was examined and found to be 0.5% and 50%, respectively.

From this, the porosity of the dense ceramic layer of the five-layer ceramic composite sintered body is estimated to be 0.5%, and the porosity of the porous ceramic layer is also estimated to be 50%. The porosity of the entire five-layer ceramic composite sintered body was 33%.

<Example 2> A highly concentrated aqueous magnesium acetate solution was prepared by dissolving 7 g of reagent magnesium acetate in 10 g of water, and the five-layer sintered body obtained in Example 1 was immersed in this solution. The laminated sintered body was taken out from the aqueous solution, air-dried, and then fired at 900°C for 3 hours under atmospheric pressure, resulting in a 5-layer ceramic composite sintered body in which magnesium oxide was supported on the porous ceramic layer. .

FIG. 7 is an electron micrograph enlarged 3500 times to mainly show the grain structure of the cross section of this porous ceramic layer.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of the multilayer ceramic composite sintered body of the present invention. FIG. 2 is a perspective view of a sintered five-layer ceramic composite sintered body. FIG. 3 is a perspective view of a sintered cylindrical ceramic composite sintered body. FIG. 4 is a diagram showing changes in pore size distribution and pore volume depending on the firing temperature of the porous sintered sheet before inorganic colloid particles are introduced into the open pores. FIG. 5 is a diagram showing changes in pore volume and porosity depending on the firing temperature of a porous sintered sheet. FIGS. 6 and 7 are electron micrographs mainly showing the particle structure of the cross section of the porous alumina layer of the multilayer ceramic composite sintered body. 10.20: Ceramic composite sintered body, 10a, 20a: Porous alumina layer, 10b, 20b: Dense alumina layer, 11: Through hole.

Claims (1)

[Claims] 1) A dense ceramic layer made of the same type of ceramic raw material as the porous ceramic layer is laminated on both sides or one side of the porous ceramic layer and is integrally sintered, and the porous ceramic layer A multilayer ceramic sintered body using a laminated sintered body in which open pores are formed as a support, wherein inorganic colloid particles made of a ceramic raw material different from the ceramic layer are introduced into the open pores, and the porous ceramic layer A multilayer ceramic composite sintered body characterized by being integrally sintered with. 2) The porosity of the porous ceramic layer is in the range of 20 to 60%, and the porosity of the dense ceramic layer is 0.01 to 5%.
The multilayer ceramic composite sintered body according to claim 1, which falls within the range of . 3) The multilayer ceramic composite sintered body according to claim 1 or 2, wherein the dense ceramic layer is provided with through holes communicating with the open pores of the porous ceramic layer. 4) Prepare a slurry for a dense layer by adding and mixing a first sintering aid and a first water-soluble binder to a first inorganic colloid liquid using water as a dispersion medium, and form and dry this slurry for a dense layer. A green sheet for a dense layer is formed using water as a dispersion medium, and a second inorganic colloid liquid of the same type as the first inorganic colloid liquid is formed.
No sintering aid is added to the inorganic colloid liquid, or the first
A slurry for the porous layer is prepared by adding and mixing a second sintering aid and a second water-soluble binder in a smaller amount than the sintering aid, and this slurry for the porous layer is formed and dried to form a green for the porous layer. A sheet is formed, the dense layer green sheet is adhered to both sides or one side of the porous layer green sheet with an adhesive, and the adhered green molded body is fired at 1000 to 1600°C to obtain a laminated sintered body. and introducing a third inorganic colloid liquid different from the first and second inorganic colloid liquids into the porous ceramic layer of the laminated sintered body, using water as a dispersion medium, and introducing the third inorganic colloid liquid into the porous ceramic layer of the laminated sintered body. A method for producing a multilayer ceramic composite sintered body, which comprises heat-treating, cooling, precipitating inorganic colloid particles in the open pores of the porous ceramic layer, and firing the laminated sintered body in which the inorganic colloid particles have been precipitated again. 5) A claim that any one or more of the first, second, or third inorganic colloid liquid is an inorganic colloid liquid obtained by hydrolyzing a metal alkoxide and then peptizing the hydrolysis product. Item 4. A method for producing a multilayer ceramic composite sintered body according to Item 4. 6) The method for producing a multilayer ceramic composite sintered body according to claim 4, wherein the hydrothermal treatment of the third inorganic colloid liquid is performed in an autoclave.