JPH03150276A - Ceramic multilayer body and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applied to piping parts that require heat resistance, heat insulation, and thermal shock resistance, or to porous ceramics used as chemical reaction media. The present invention relates to a ceramic multilayer body characterized in that the porosity of the ceramic sintered body made of a single material differs in each layer, and a method for manufacturing the same.

[Prior art] In recent years, ceramics have been used for molten metal pouring vibes, piping parts exposed to high temperatures such as high-temperature and high-pressure gas, and chemical reactions for exhaust gas purification, taking advantage of their unique characteristics of low thermal conductivity and high heat resistance. It has begun to be widely used as a catalytic WpA body.

As a result, thermal efficiency was improved. But fli#l
From the viewpoint of improving the TK rate, the current situation is that there is still a desire for a material with high heat insulation properties. To improve insulation, 1) Select a ceramic material with low thermal conductivity.

2) Increase porosity.

There is. However, there is a strong view that there is almost no limit to the ability to increase insulation performance by selecting ceramic raw materials.Although it is possible to improve insulation performance by increasing the porosity of ceramics, it is not possible to increase the insulation performance by simply increasing the porosity. , a new problem arises in that the strength is reduced and the fluid flowing inside the vibrator may leak. Therefore, from the viewpoint of making ceramics share both of its heat insulating properties and its strength as a structural material, it has been proposed to use a multilayer structure ceramic #11tI body in which the porosity of the ceramic sintered body differs in each layer. The 11 manufacturing method is 0. A method of sintering a ceramic molded body with a multilayer structure in which each layer has a different average particle size.

0 A method of applying a mortar-like material containing ceramic fibers to a ceramic sintered body.

0 A method of attaching a layer made of a ceramic sintered body to a ceramic sintered body using an inorganic adhesive.

0 A method described in US Pat. No. 3,568,723, in which a porous ceramic is formed on a ceramic sintered body by applying a mixture of water glass and cellulose and sintering it again.

0 Method of spraying ceramics onto the surface of a ceramic sintered body [Problem to be solved by the invention] Each of the above-described conventional proposals had the following drawbacks.

According to the proposal of 0, cracks may occur during sintering because the temperatures at which grain growth and shrinkage start are different in each layer, and in order to prevent cracks during sintering, ceramic M material It is necessary to select the composition and particle size distribution.

According to the proposal of No. 0, it is difficult to control the thickness of the applied ceramic fiber.

According to the proposal of No. 0, the ceramic must be fired to match the shape of the ceramic sintered body, and such firing becomes more difficult as the shape becomes more complex.

According to the proposal of No. 0, it is necessary to perform a step of firing again after coating the ceramic sintered body.

According to the proposal of No. 0, it is difficult to form a layer formed by thermal spraying to a thickness of several mm.

[Means to solve the problem 1 The present invention has been made in view of the above circumstances.

To be more specific, a ceramic sintered body with a multilayer structure having different porosity contains particles with a particle size of 30 μm or less that decompose and/or sublimate and combine and vaporize at a temperature below the temperature at which the sintered ceramic starts sintering. It is manufactured by sintering a ceramic molded body that has a multilayer structure in which each layer has a different content of the vaporized particles by sequentially applying slurry with different ratios to G4. , each layer of the sintered body has a different porosity.

[Function] When a ceramic molded body is sintered in which each layer of the ceramic molded body has a different content of particles that are vaporized by decomposition and/gB-sublimation unit and/or, the vaporized particles are decomposed and/or. As they combine and vaporize, pores are formed.

As the temperature rises further, the ceramic begins to sinter.

At this time, regardless of the content of the vaporized particles mentioned above, the shrinkage rate of each scrap is almost the same because the same ceramic raw material powder is used for each layer, and each layer remains in close contact without cracking or distortion. It is sintered in this state.

〔Example〕

The chemical composition is AI20.99.54wt%. Na20
0.02vt%.

Fe, 030. OIvt%, Si02G, 02wt
%, Mg00.05vt%LOI (0-3100℃)
The mixing ratio of alumina powder with an average particle size of 0.67 zm and 1F-shaped graphite with a particle size of 15 to 307 zm at a weight ratio of 0.36 wt%, alumina powder nibroughite = lO
:0.8:2.624.5:5.4:6.3.5:6゜5, and 100 parts of each mixed powder was used as a dispersant, Cerna 0305 (product). name)'s 10vt
% water soluble? &5 parts, isopropanol 1 part, ■2020
of the mixture was added and kneaded for 20 hours using a ball mill. Next, 1 part of a 10vt% aqueous solution of polyvinyl alcohol and 0.0% of Antix (trade name), which is an antifoaming agent, were added. 5th part,
After adding 205 parts of n, the mixture was kneaded for 1 hour and degassed using a vacuum bomb to obtain slurries with different graphite contents.

The combinations of each layer of the multilayered ceramic molded body were prepared using the lli types a to k in Table 1. These slurries were warmed into 11 plaster molds each having the structure shown in Fig. 1, and the slurry was deposited and removed. I did it. The inked slurry was allowed to dry for several minutes until it was no longer fluid. Next, slurries with different graphite contents were poured into the plaster mold to which the slurry had been deposited, and a molded product with a two-layer integral structure was obtained. Molding with three or more layers with different graphite content at each end is
In the same manner as the manufacturing method of the two-layer integrated structure described above, if
4. This was done by repeating sludge removal and 12 drying steps.

After demolding and drying, heating rate 120”c/hr,
Sintering was carried out by holding at 1600" Ct-S. Table 1 shows the thickness of each layer of the compact, the graphite content, and the presence or absence of cracks during sintering.

Alumina powder nigeraphite = 3.6:6.5 by weight
In other words, a graphite-containing slurry having a graphite content of 65% exhibits remarkable thixotropic behavior, making it difficult to control the wall thickness.

Therefore, it was found that a good slurry could be obtained if the wall thickness of Example e using this material varied widely, that is, if the graphite content was preferably 60 vt% (72.2 vol%) or less.

Shaping and sintering was performed using the graphite-containing slurry, and the relationship between the graphite content and the porosity and linear shrinkage rate of the sintered body was obtained (FIG. 2). A linear correlation was obtained between the graphite content and the porosity of the sintered body in the range of 0 to 65 wt%.

Moreover, the linear shrinkage rate was almost constant regardless of the graphite content.

In addition, although a slurry was manufactured using a graphite-containing slurry with an average particle diameter of 40 μm, the graphite sedimented, making it difficult to control the wall thickness, so the average particle diameter of graphite should be smaller than that. If it is preferably 30 μm or less, a good slurry can be obtained.

Although we have described the method for manufacturing alumina sintered bodies with different porosity in each layer, it is also possible to sinter ceramic materials such as zirconia, mullite, and cordierite powder in a large gas atmosphere furnace. It is natural that something is true.

[Effects] As described above, the present invention's ceramic sintered body with a multilayer structure in which each layer has a different porosity and its manufacturing method are as follows: (1) Even if the target shape is a KN shape, graphite-containing A ceramic sintered body having a multilayer structure in which each layer has a different porosity can be manufactured by a simple method of forming a slurry using the slurry removal method.

0 You can freely select the porosity and wall thickness according to your purpose. 0 You can create a ceramic sintered body with a multilayer structure with different porosity in each layer with just one sintering process! ! Can be built.

0 The ceramic powder used has a porous layer and a pasture [71
There is no need to change between the two, just use the same one.

It is very effective.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a stone mold for slip forming. , FIG. 2 is a graph showing the relationship between the graphite content in the slurry and the porosity and linear shrinkage rate of the dense aggregates.

Claims (1)

[Claims] (1) The ceramic sintered body has a porosity in the range of 0 to 65%, and the ceramic sintered body is made of a single material with a different porosity for each layer. (2) Decomposition and/or sublimation and/or sublimation at a temperature below the temperature at which the ceramic to be sintered starts sintering.
/or The porosity of each layer is characterized by sintering ceramic particles having a multilayer structure and a ceramic molded body made of the particles, in which the content of particles with a particle size of 30 μm or less that are combined and vaporized is different in each layer. (3) A method for manufacturing a ceramic multilayer body with different porosity as described in item 2, characterized in that the vaporized particles are especially graphite (4) In particular, the ceramic powder is an oxide-based ceramic powder. The method for producing a ceramic multilayer body having different porosities according to item 2, characterized in that a powder is used (5) In particular, the ceramic powder is any one of alumina powder, zirconia, mullite, and cordierite. (6) A method for producing a ceramic multilayer body having different porosity as described in item 4 (6) A method for manufacturing a ceramic multilayer body as described in item 2, characterized in that it is formed by a slurry removal method.