JP2003073179A - Calcium zirconate/spinel compound multi porous compact and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calcium zirconate/spinel compound multi-porous copact which is impoved in mechanical strength, acid resistance, the corrosion resistance and its manufacturing method. SOLUTION: The calcium zirconate/spinel compound multi-porous compact which is thermally and chemically stable, is obtained by crushing and mixing a raw material powder, the main ingredient of which is calcite, magnesia, zirconia, and alumina or dolomite, zirconia, and alumina. By reaction firing it in the atmosphere after properly molding it, wherein the same mole calcium zirconia [CaZrO3 ] and spinel [MgAl2 O4 ] are mutually dispersed homogeneously while suppressing the growth of grain. Therefore, the fired compact has fine structure, high strength and stable structure under high temperatures. And its manufacturing method is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a calcium zirconate / spinel composite porous body and a method for producing the same, more specifically, equimolar amounts of calcium zirconate [CaZrO ₃ ] and spinel [MgAl ₂ ]. O
_[4 ] has a fine composite structure formed by uniformly dispersing each other and suppressing grain growth, and comprises a calcined body having a thermally and chemically stable porous structure, calcium zirconate / spinel System composite porous body and a method for producing the same. INDUSTRIAL APPLICABILITY The composite porous body of the present invention is useful, for example, as a highly corrosion-resistant fluid permeation filter functional material, an ultrahigh temperature lightweight member, a catalyst carrier, a heat insulating material, or a sound absorbing material.

[0002]

2. Description of the Related Art Oxide ceramics porous bodies having a high porosity are used, for example, as fluid permeation filters. The conventional products are a method of dispersing pores in a sintered body by lowering the molding density or the sintering temperature (sintering control method), a method of forming pores by burning an organic binder (organic binder removal method), This was due to a method of forming uniform pores at a relatively low temperature (sol-gel method) by using a chemical method such as decomposition / reaction of alkoxide. In addition, most of the porous body materials produced by any of the manufacturing methods were single-phase porous bodies made of a single ceramic.

However, these porous materials include
It had the following drawbacks. That is, in the conventional porous body material, for example, in the porous body produced by the sintering control method, the bonding strength between the crystal particles constituting the porous body is insufficient, and the material strength of the entire porous body is also insufficient. Moreover, since the pore size distribution is wide, the fluid selectivity was not sufficient. In the porous material produced by the organic binder removal method, NO is generated depending on its component due to the combustion of the polymer.
There is a problem that harmful gas such as _x is generated.
There is a problem that it is difficult to control the fine structure of the porous structure due to the heat generated by the combustion of the polymer. Also,
The porous material produced by using a chemical method such as the sol-gel method allows relatively high degree of structure control, but has a high cost and has a problem in mass production. Furthermore, in any porous material produced by any of the manufacturing methods, when used at a high temperature of 1000 ° C. or higher, the performance of the porous material deteriorates because sintering of the porous material progresses, the structure coarsens with time, and the pore size changes. There was a drawback.

Based on these prior arts, recently, the present inventors (Suzuki, Daiji) et al. Have found that equimolar amounts of calcium zirconate [CaZrO ₃ ] and magnesia [MgO] are evenly dispersed in each other to cause grain growth. It was reported that a calcium zirconate / magnesia-based composite porous body was developed, which is a fired body having a fine composite structure by suppressing and maintaining a stable structure at high temperature [JP 2001-2001 1226
75, Journal of American Society
Ceramic Society), Volume 83, Volume 2
091, 2000]. Although this porous body material could solve many of the drawbacks of the conventional porous body materials, depending on its application, there was a need for further improvement in mechanical strength and acid / corrosion resistance. More specifically, for example, regarding bending strength, when the porosity is 47%, it is about 35 MPa, which is sufficient as a filter material, but when viewed as a structural member, higher strength is desirable, and Since it contains magnesia as a constituent phase, it was necessary to improve the stability against acid vapor and high temperature steam.

[0005]

Under these circumstances, the present inventors, in view of the above-mentioned prior art, develop a new porous material capable of surely solving the above-mentioned problems of the prior art. As a result of earnestly researching with the aim of achieving the above, we succeeded in developing a calcium zirconate / spinel composite porous body having more excellent properties, and completed the present invention. That is, the present invention has been made in order to eliminate the drawbacks of the prior art as described above, highly controlled structure, further heat resistance, calcium zirconate / spinel-based composite porous body excellent in mechanical properties, Another object of the present invention is to provide a method for efficiently producing the porous body material by applying a simple and cost-effective process.

[0006]

[Means for Solving the Problems] To solve the above problems
The present invention comprises the following technical means. (1) Calcite, magnesia, zirconia, alumina
As the main raw material, or dolomite, zirconia,
Mina as the main raw material, this raw material powder is uniformly crushed and mixed,
After appropriately molding this, it was decided to carry out reaction firing in the atmosphere.
Thermally and chemically stable porous structure produced by
With a calcium zirconate / spinel composite porous body
There is an equimolar amount of calcium zirconate [CaZrO
₃ ] And spinel [MgAl₂ O_Four ] Evenly distributed with each other
And a fine composite formed by suppressing grain growth
It has a structure, has high strength, and keeps a stable structure at high temperature.
Calcium zirconate characterized by comprising a fired body
Mu / spinel composite porous body. (2) Equimolar amount of calcite [CaCO₃], Magnesi
A [MgO], zirconia [ZrO₂ ], Alumina [A
l₂ O₃] As the main raw material,
Manufactured according to the above (1), characterized in that
The described calcium zirconate / spinel composite porous body. (3) An equimolar amount of dolomite [CaMg (CO₃ )
₂ ], Zirconia [ZrO₂ ], Alumina [Al₂ O
₃ ] As the main raw material, and produced by a single-step reaction firing
The above-mentioned (1), characterized in that
Calcium zirconate / spinel composite porous body. (4) Alkali fluoride is mainly used as a low melting point liquid phase forming material.
By adding a small amount to the raw material, the porosity is
Characterized by controlling the specific surface area without changing
Zirconic acid according to the above (1), (2) or (3)
Calcium / spinel composite porous body. (5) The complex poly according to any one of (1) to (4) above.
A method for producing a pore body, which comprises an equimolar amount of calcite,
Magnesia, zirconia, alumina or equimolar amount
The main raw material is dolomite, zirconia, and alumina.
The raw material powder was uniformly crushed and mixed, and this was appropriately molded.
Zircon, characterized by reactive firing in air
A method for producing a calcium acid / spinel composite porous body. (6) The low-melting-point liquid phase-forming material was added to the total amount of the main raw materials in an amount of 0.
2 to 0.5% by weight is mixed uniformly and the
Specific surface is promoted by promoting the diffusion of raw material on the particle surface.
CO produced by controlling the product₂ By releasing
Form uniform open pores and open at 1100 to 1300 ℃
A high porosity of 40 to 60% can be obtained by firing in
It has a small dimensional change before and after firing and has high strength.
The porous body according to (5) above,
Method for producing calcium zirconate / spinel composite porous body
Law.

The calcium zirconate / spinel composite porous material of the present invention is an equimolar amount of calcium zirconate [C
aZrO ₃ ] and magnesia [MgAl ₂ O ₄ ] are evenly dispersed in each other and have a fine composite structure formed by suppressing grain growth, and are composed of a fired body that maintains a stable structure at high temperatures. Is characterized by. Compared with the existing calcium zirconate / magnesia-based composite porous body, the calcium zirconate / spinel-based composite porous body has been converted into a double oxide by using magnesia as a spinel.
It has improved mechanical properties and chemical stability. Further, by adding alumina as a main component, even if the low melting point liquid phase forming agent is not added, the solid phase reaction sufficiently proceeds at the firing temperature of 1100 to 1300 ° C., and the low melting point liquid phase forming agent was added. In this case, the surfaces of the calcium zirconate crystal particles and the spinel crystal particles become smoother, and the specific surface area can be controlled without significantly changing the porosity.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail. The calcium zirconate / spinel-based composite porous body of the present invention has an equimolar amount of calcium zirconate and spinel uniformly dispersed in each other, has a fine composite structure by suppressing grain growth, and can be stored at high temperature for a long time. Even when used, calcium zirconate and spinel mutually suppress grain growth, thus maintaining a stable structure. The crystal grain sizes of calcium zirconate and spinel change slightly depending on the sintering temperature, but since they have a three-dimensional network structure, they do not easily cause mass transfer like a bulk body, and have fine crystal grains of several microns or less. Becomes In this composite porous body, almost all pores are through open pores, and the porosity is 4
0 to 60%, having a porosity sufficient to selectively permeate a fluid. In this porous material, necking of the constituent ceramic particles occurs at a relatively low temperature, so that the mechanical strength is excellent and the fluid can be selectively permeated efficiently. Further, as other uses as a porous body, the porous body material according to the present invention is very useful, for example, in the fields of a lightweight member for ultra-high temperature, a catalyst carrier, a heat insulating material, a sound absorbing material and the like.

In addition, in the porous body of the present invention, when alkali fluoride is added as a low temperature liquid phase forming material, most of it goes out of the system through open pores, so that the amount remaining in the porous body is reduced. However, the high temperature characteristics are hardly deteriorated. In this case, the surfaces of the calcium zirconate crystal particles and the spinel crystal particles become smoother, and it becomes possible to control the specific surface area without significantly changing the porosity. It is useful for controlling the flow rate in the case of using the catalyst and controlling the amount of the catalyst carried when used as the catalyst carrier.

In the present invention, as a raw material of the porous body,
Using calcite [CaCO ₃ ] and magnesia [MgO] individually as a calcium source and a magnesium source,
Or dolomite [CaMg containing each of them in an equimolar amount
(CO ₃ ) ₂ ] can both be used. Similar materials can be obtained by replacing magnesia [MgO] with magnesite [MgCO ₃ ] and, in the present invention, these are considered to be equivalent, but in general, the magnesium source is different from the calcium source. Since excellent oxide powders are available as commercial products, it is not always necessary to stick to carbonates. For calcite and dolomite, it is possible to reduce costs by using natural raw materials. As for the zirconium source, natural baddelite can be used, but it cannot be said that the output is abundant, and high-performance oxide commercial powder is available at a relatively low price,
Synthetic products are desirable.

As the aluminum source, high-performance commercially available oxide powders are available at low cost. When a low melting point liquid phase forming material is added for the purpose of controlling the specific surface area, LiF or NaF which is an alkali metal fluoride is added.
However, similar effects can be expected with fluorides of alkaline earth metals such as CaF ₂ , SrF ₂ and BaF ₂ . In the present invention, the alkali fluoride is defined to include these. If the amount of the low melting point liquid phase forming material remaining in the porous body is large, the characteristics at high temperature are deteriorated and the sintering furnace is adversely affected. In the present invention, the specific surface area can be sufficiently controlled with a small amount of 0.2 to 0.5%.

Next, a method for producing the calcium zirconate / spinel composite porous body of the present invention will be described. The composite porous material of the present invention is preferably an equimolar amount of calcite,
Main components are magnesia, zirconia, alumina or equimolar amounts of dolomite, zirconia, and alumina, and a low melting point liquid phase forming material is used in order to control the specific surface area of the porous body. % Evenly mixed, and appropriately molded by a molding method such as uniaxial mold molding, cold isostatic molding, sludge casting molding, tape molding, etc. The specific surface area is controlled by promoting diffusion, and uniform open pores are formed by liberating CO _2.
It is manufactured by firing in air at 300 ° C. Here, the equivalent molar amounts of calcite, magnesia, zirconia, and alumina are CaCO ₃ : MgO: ZrO ₂ : Al ₂ O ₃ = 1: 1 in terms of molar ratio when expressed by chemical formulas.
1: 1: 1 and equimolar amount of dolomite,
Zirconia and alumina, when expressed by chemical formula,
The molar ratio of CaMg (CO ₃ ) ₂ : ZrO ₂ : Al ₂ O ₃
= 1: 1: 1. In the present invention,
Substantially, it is converted into a double oxide by using magnesia as a spinel and equimolar amount of calcium zirconate [CaZrO ₃ ].
The above main raw materials may be appropriately used so as to obtain a composite in which and spinel [MgAl ₂ O ₄ ] are uniformly dispersed.

The reason for the above temperature conditions is that when the temperature is lower than 1100 ° C., for example, when the temperature is 1000 ° C., the solid phase reaction proceeds but the mechanical strength is insufficient. This is because the porosity becomes smaller than the value suitable for the filter application when the firing is performed at a temperature higher than 1300 ° C, for example, when the firing is performed at 1400 ° C. During this calcination process, pyrolysis of carbonate, ie, calcite or dolomite, formation of pores by generated CO ₂ , formation of calcium zirconate phase and spinel phase occurs. Further, when the low melting point liquid phase forming material is added, further diffusion promotion on the surface of the main raw material particles and evaporation of the low melting point liquid phase forming material occur. In the present invention, such a complicated process can be realized by a simple heat treatment of only one step, which is very effective for high efficiency and low cost. The firing can be performed in a general atmospheric furnace. Further, by providing an appropriate CO ₂ trap, it is possible to recover the generated gas, which does not have an adverse effect on the environment.

The calcium zirconate / spinel composite porous body of the present invention produced by the above method is formed by uniformly dispersing calcium zirconate and spinel in equimolar amounts and suppressing grain growth. It has a fine composite structure with high strength and maintains a stable porous structure at high temperature, and as shown in the examples below, the problems of the prior art are reliably solved and its characteristics are improved. To realize the characteristics of the excellent porous body.

[0015]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to the examples. Example 1 In this example, a porous body was manufactured using calcite, magnesia, zirconia, and alumina as raw materials. (1) Preparation of Raw Material of Porous Body In this example, as starting powder, an equimolar amount of calcite CaCO ₃ (manufactured by Kojundo Chemical Laboratory, 99 mass%),
Magnesia MgO (Ube Industries, 50 nm grade),
Zirconia ZrO ₂ (Sumitomo Osaka Cement Co., 99 ma
ss%), alumina Al ₂ O ₃ (Taimei Chemical Co., Ltd., T
(MD grade) was used. Alcohol was added to these powders as a dispersion medium, and the mixture was subjected to planetary ball mill pulverization and mixing under 6 G for 6 hours using a zirconia container and zirconia balls. The obtained mixed powder was dried, treated with a dry ball mill, and then classified to obtain a starting material.

(2) A uniaxial compact was obtained by compacting the green compact and preforming it with a heat treatment die. This was sealed under reduced pressure in a plastic film bag, and then cold isostatic molding (pressurization: 200 MPa) was performed to obtain a molded body. The green compact is charged into a firing furnace, and 1100 to 100
The heat treatment was carried out at 1,300 ° C. for 2 hours under normal pressure. A test porous body was obtained through the above steps.

(3) Properties of Porous Body The porosity of the porous body (test material 1) obtained by firing at 1300 ° C. was about 49%, showing a good porosity. The dimensional change before and after firing was suppressed to 5% or less, and it had a good bulk shape with no warp or crack.
Moreover, the specific surface area of the test material 1 was 4.6 m ² / g. The X-ray diffraction pattern of Sample 1 is shown in FIG. It was confirmed that the constituent phases of the test material 1 were calcium zirconate and a spinel phase. A similar X-ray diffraction pattern is 11
It was also obtained when firing was performed at 00 ° C. (porosity about 52%). Specimen 1 showed a three-point bending strength of about 65 MPa (span 30 mm) and was shown to have excellent mechanical strength. It was revealed that the structure of the present porous body hardly changed even after a long-term heat treatment at 1200 ° C., and that it was extremely excellent in heat resistance. Also, because it is an oxide,
It has excellent oxidation resistance, and because it is composed of calcium zirconate and spinel alone, it has excellent acid resistance and alkali resistance.

Example 2 In this example, dolomite, zirconia, alumina
A porous body was manufactured as a raw material. (1) Preparation of porous material In this example, as the starting powder, an equimolar amount of dolomite was used.
CaMg (CO₃ )₂ (Thailand origin, 200 mesh),
Zirconia ZrO₂ (Sumitomo Osaka Cement Co., 99 ma
ss%), alumina Al₂ O₃ (Taimei Chemical Co., Ltd., T
(MD grade) was used. These powders were used in Example 1
The starting material was pulverized and mixed by the same method as described above.

(2) Molding of green compact and heat treatment A green compact was molded by the same method as in Example 1 and heat treated to obtain a test porous body.

(3) Properties of Porous Material The porosity of the porous material (test material 2) obtained by firing at 1300 ° C. was about 51%, which was as good as the test material 1. . The increase in porosity of about 2 points is due to the fact that the amount of CO ₂ generated during decomposition is larger in the test material 2. Moreover, the specific surface area of the sample material 2 was 8.1 m ² / g. This value corresponds to 1.8 times that of Sample 1, and is due to the large amount of CO ₂ produced during decomposition in Sample 2 and the extremely fine crystals produced by the thermal decomposition of dolomite. is doing. In addition, the dimensional change before and after firing was suppressed to 5% or less as in the case of the sample material 1, and it had a good bulk shape with no warp or crack. The X-ray diffraction pattern of the sample material 2 is shown in FIG. It was confirmed that the constituent phases of this porous body were calcium zirconate and a spinel phase as well. Also, a similar X-ray diffraction pattern is 1100
It was also obtained when firing was performed at ℃ (porosity about 58%). Specimen 2 showed a three-point bending strength (span of 30 mm) of about 50 MPa, and although it was slightly inferior to Specimen 1, it was shown to have relatively excellent mechanical strength. Specimen 2
Shows excellent heat resistance, acid resistance, and alkali resistance equivalent to those of Specimen 1.

Example 3 In this example, a porous body was manufactured by adding 0.2 to 0.5% by weight of a low melting point liquid phase forming material to a main raw material. In order to further clarify the effect on the specific surface area, production was carried out based on the composition of Example 2 in which a high specific surface area was obtained. (1) Preparation of Porous Body Raw Material In this example, the same starting material dolomite as in Example 2 was used.
Using zirconia and alumina, for the total amount of this,
0.2-0.5 wt% LiF was added. In addition, NaF
Since almost the same effect was seen even when using, LiF will be described here. These powders were pulverized and mixed by the same method as in Example 1 to obtain starting materials.

(2) Molding of green compact and heat treatment A green compact was molded by the same method as in Example 1 and heat treated to obtain a test porous body.

(3) Properties of Porous Material 0.5% by weight of LiF was added, and the porosity of the porous material (test material 3) obtained by firing at 1300 ° C. was about 48%. Good porosity similar to materials 1 and 2 was exhibited.
The change in porosity was slight compared to Sample 2, and this decrease in porosity of about 3 points is considered to be due to the fact that the addition of LiF slightly promotes the firing.
Further, the specific surface area of the sample material 3 is 1.0 m ² / g, which is 1/8 of that of the sample material 2. By adding a trace amount of the low melting point liquid phase forming material, the structure of the crystal grain surface is significantly increased. It turns out that it can be changed. In addition, 0.2% LiF
When added, the specific surface area is 1.1 m ² / g,
The same effect as when 0.5% was added was observed. Similar to Samples 1 and 2, the dimensional change before and after firing of Sample 3 was suppressed to 5% or less, and it had a good bulk shape with no warp or crack. The X-ray diffraction pattern of Sample 3 is shown in FIG. It was confirmed that the constituent phases of this porous body were calcium zirconate and a spinel phase. Also, the same X-ray diffraction pattern was obtained when firing was performed at 1100 ° C. (porosity about 61%). Specimen 3 exhibited excellent heat resistance, acid resistance, and alkali resistance equivalent to those of Specimens 1 and 2.

COMPARATIVE EXAMPLE In this comparative example, the commercially available calcium zirconate powder [CaZrO ₃ ] and the commercially available spinel powder [MgAl ₂ O were used without using the reaction sintering method involving pyrolysis of the carbonate shown in the present invention.
₄ ] was used to produce a porous body. (1) Preparation of Raw Material for Porous Body In this comparative example, a commercially available powder having a final intended constituent phase was used as a starting material. Equimolar amounts of calcium zirconate CaZrO ₃ (manufactured by Kojundo Chemical Laboratory, 98 mass%) and spinel MgAl ₂ O ₄ (manufactured by Kojundo Chemical Laboratory, 99.9 mass%) were used as starting powders. These powders were pulverized by the same method as in Examples 1 to 3.
It was mixed and used as a starting material.

(2) Molding of green compact and heat treatment A green compact was molded by the same method as in Examples 1 to 3, and a test porous body was obtained by heat treatment.

(3) Properties of Porous Material The porosity of the porous material (test material 4) obtained by firing at 1300 ° C. is about 26%, which is different from the test materials 1 to 3 and is a porous material for filters. As a result, the porosity was insufficient. This is because unlike the test materials 1 to 3, CO2, which acts as a pore-forming material, is not released during firing. The specific surface area of the test material 4 was 1.6 m ² / g, which was larger than the test material 3 using the low-melting point liquid phase forming material, but was much smaller than the test materials 1 and 2. Further, the dimensional change before and after firing was different from those of the test materials 1 to 3 and was as large as about 15%. Although no cracks were observed, there was some warpage. The X-ray diffraction pattern of the sample material 4 is shown in FIG. In addition to calcium zirconate and spinel phase, cubic zirconia solid solution, which is thought to have been decomposed and formed, was observed as the constituent phase of the porous body, suggesting the influence of impurities in the raw material and compositional shift. When fired at 1100 ° C (test material 5), the porosity was 43%, which was close to a practical value for filter use, but the bending strength was about 17%.
It became MPa and it was shown that mechanical properties were inferior. The X-ray diffraction pattern of the sample material 5 is shown in FIG. In the sample material 5, almost no cubic zirconia solid solution was observed.
It was suggested that the cubic zirconia solid solution phase-separated between 100 and 1300 ° C.

Table 1 collectively shows the characteristics of the test materials 1 to 3 of Examples 1 to 3 and the test materials 4 to 5 of Comparative Examples.

[0028]

[Table 1]

[0029]

As described in detail above, the present invention is
A calcium zirconate / spinel composite porous body having a chemically stable porous structure, which comprises equimolar amounts of calcium zirconate [CaZrO ₃ ] and spinel [MgAl].
₂ O ₄ ] are uniformly dispersed in each other and have a fine composite structure formed by suppressing grain growth, and are composed of a fired body having high strength and maintaining a stable structure at high temperature. Calcium zirconate / spinel composite porous body,
And a method for manufacturing the same, according to the present invention,
1) It is possible to provide a calcium zirconate / spinel-based composite porous body having improved mechanical strength and acid / corrosion resistance. 2) The method of the present invention is extremely effective regardless of using a simple process. Highly tissue controlled, thermal,
It is possible to realize a chemically stable porous body structure. 3) The obtained composite porous body is, for example, a highly corrosion-resistant fluid permeation filter functional material, an ultrahigh temperature lightweight member, a catalyst carrier, a heat insulating material, or It is useful as a sound absorbing material, etc. 4)
Further, the present invention is particularly advantageous in terms of equipment and cost as compared with the conventional method, and enables a variety of engineering applications, which is a particular effect.

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction pattern of a porous body.

[Explanation of symbols]

(A): Specimen 1 (B): Sample material 2 (C): Sample material 3 (D): Sample material 4 (E): Test material 5

Claims (6)

[Claims] 1. Calcite, magnesia, zirconia,
Alumina as the main raw material, or dolomite, zirconia, and alumina as the main raw material, this raw material powder is uniformly pulverized and mixed, and after appropriately molding this, produced by reaction firing in the atmosphere, thermal, A calcium zirconate / spinel composite porous body having a chemically stable porous structure, in which an equimolar amount of calcium zirconate [C
aZrO ₃ ] and spinel [MgAl ₂ O ₄ ] are evenly dispersed in each other, and has a fine composite structure formed by suppressing grain growth, and has a high strength and maintains a stable structure at high temperatures. A calcium zirconate / spinel composite porous body characterized by comprising a body. 2. An equimolar amount of calcite [CaCO ₃ ],
_2. Calcium zirconate according to claim 1, characterized in that it is produced by a single-step reaction firing using magnesia [MgO], zirconia [ZrO ₂ ] and alumina [Al ₂ O ₃ ] as main raw materials. / Spinel-based composite porous material. 3. An equimolar amount of dolomite [CaMg (CO
₃ ) ₂ ], zirconia [ZrO ₂ ], alumina [Al ₂
[ ₃ ] The calcium zirconate / spinel-based composite porous body according to claim 1, which is produced by a single step reaction firing using O3] as a main raw material. 4. The specific surface area is controlled by adding a small amount of an alkali fluoride as a low melting point liquid phase forming material to the main raw material so that the porosity is hardly changed. The calcium zirconate / spinel-based composite porous body according to 1, 2 or 3. 5. A method for producing the composite porous body according to claim 1, wherein equimolar amounts of calcite, magnesia, zirconia, alumina or equimolar amounts of dolomite, zirconia and alumina are used. As the main raw material,
A method for producing a calcium zirconate / spinel-based composite porous body, which comprises uniformly pulverizing and mixing this raw material powder, appropriately shaping the raw material powder, and then subjecting it to reaction firing in the atmosphere. 6. The low melting point liquid phase forming material is uniformly mixed in an amount of 0.2 to 0.5% by weight with respect to the total amount of the main raw material to promote diffusion of the main raw material on the particle surface in the temperature rising process. By controlling the specific surface area and liberating the generated CO ₂ to form uniform open pores.
The porous body having a high porosity of 40 to 60%, a small dimensional change before and after firing, and a high strength, is obtained by firing in the air at ℃. 1. A method for producing a calcium zirconate / spinel composite porous body according to.