JP5712142B2 - Porous ceramic sintered body and method for producing porous ceramic sintered body - Google Patents

Description

  The present invention relates to a porous ceramic sintered body and a method for producing the same, and more particularly to a porous ceramic sintered body mainly composed of a composite oxide containing silicon and a method for producing the same.

  Ceramic sintered bodies have features such as high heat resistance and high chemical stability, and are used in various applications such as ceramic setters (tables used during heat treatment of ceramic capacitors) or ceramic filters. Widely used. However, generally, a ceramic sintered body has a characteristic that it is vulnerable to thermal shock. Therefore, there has been a great demand for a ceramic sintered body having good thermal shock resistance.

  In order to improve the thermal shock resistance of the ceramic sintered body, it is significant to form a large number of pores in the ceramic matrix, thereby reducing the heat capacity of the ceramic sintered body.

  As a method for producing such a porous ceramic sintered body, mixed particles obtained by adding a pore former in advance to ceramic raw material particles are prepared, and after forming the mixed particles to produce a molded body, A method of firing is known (for example, Patent Document 1).

JP 2007-21484 A

  In the conventional method for producing a porous ceramic sintered body as described above, an organic and / or inorganic pore former is used to form pores in the ceramic matrix.

  However, the pore former is decomposed during the production process of the porous ceramic sintered body and does not remain in the finally obtained sintered body. In other words, such a pore former is a completely unnecessary component for the finally obtained porous ceramic sintered body, and the use of such a component increases the manufacturing cost of the porous ceramic sintered body. Cause.

  Further, in the production process of the porous ceramic sintered body, the pore-forming agent is decomposed and released as a gas, but such gas discharge in the production process is not environmentally preferable. In particular, when an organic pore former is used, organic component gases are discharged into the atmosphere during the production of the porous ceramic sintered body. In such organic component gas, there is a possibility that a gas having a safety problem may be contained, and the use of an organic pore former has a problem not only in the environment but also in safety.

  In addition, for example, when a pore-forming agent having a relatively large diameter is used for the purpose of forming large pores in the ceramic sintered body, a large amount of gas is discharged during the decomposition and release process of the pore-forming agent. End up. Furthermore, due to the sudden increase in internal pressure or volume reduction during the generation of such gas, the strength of the molded body is lowered, and cracks are generated in the skeleton of the porous ceramic sintered body finally obtained. The problem arises that will be crushed. Therefore, the conventional method using a pore-forming agent has a problem that it is difficult to produce a porous ceramic sintered body having pores having a relatively large pore diameter of 50 μm or more.

  The present invention has been made in view of such a background, and in the present invention, even if no pore forming agent is used or the amount of the pore forming agent is significantly reduced, the thermal shock resistance is excellent. Another object of the present invention is to provide a method capable of producing a porous ceramic sintered body having pores having a desired pore diameter. It is another object of the present invention to provide a porous ceramic sintered body that has excellent thermal shock resistance and has a plurality of pores having a pore diameter of 50 μm or more.

In the present invention, a method for producing a porous ceramic sintered body having a composite oxide containing silicon (Si),
(A) mixing first raw material particles having a compound containing silicon and second raw material particles having a melting point higher than that of the first raw material particles to prepare mixed particles;
(B) molding the mixed particles to form a molded body;
(C) firing the molded body to form a porous ceramic sintered body, the molded body being higher than the melting point of the first raw material particles, and the melting point of the second raw material particles Firing at a lower temperature, whereby at least a part of the first raw material particles and the second raw material particles react to produce a composite oxide, and a substantially spherical pore is obtained. When,
There is provided a method characterized by comprising:

  Here, in the method, the mixed particles may not contain a pore-forming agent.

  In the method, the spherical pores may have an average pore diameter in the range of 50 μm to 100 μm. In the present application, the “average pore diameter” means an average value of the diameters of 20 substantially spherical pores selected at random in a micrograph (magnification: 100 times) of the porous ceramic sintered body. To do.

  In the method, the first raw material particles may have an average particle size in the range of 50 μm to 100 μm. In the present application, the “average particle size” of the raw material particles means a nominal value by the manufacturer when the raw material particles are commercially available, and when the raw material particles are not commercially available, It means the average value of two times of the average particle diameter obtained using the measuring device.

Further, in the method, the ratio _r 1 / _{r 2} of the average particle diameter _{r 1} of the first raw material particles to the average particle diameter _{r 2} of the second raw material particles is in a range of 0.1 to 500 Also good.

In the method, the first raw material particles may include silica (SiO ₂ ).

In the method, the second raw material particles may include alumina (Al ₂ O ₃ ).

  In the method, the complex oxide may be mullite.

  In the method, in the step (a), third raw material particles having a melting point higher than that of the first raw material particles may be further mixed.

In this case, in particular, the third raw material particles include magnesia (MgO),
The composite oxide may be cordierite.

In the method, the mixed particles may further contain zirconia (ZrO ₂ ).

In this case, the zirconia (ZrO ₂ ) may be included in the range of 1 wt% to 10 wt% with respect to the total amount of other raw material particles.

  Moreover, in the said method, the range of 1550 degreeC-1650 degreeC may be sufficient as the calcination temperature of the said step (c).

  In the method, the porosity of the porous ceramic sintered body may be in the range of 20% to 30%.

Furthermore, in the present invention, a porous ceramic sintered body having a composite oxide containing silicon (Si),
A porous ceramic sintered body having a plurality of substantially spherical pores having an average pore diameter of 50 μm to 100 μm is provided.

  Here, the composite oxide containing silicon (Si) may be mullite or cordierite.

The porous ceramic sintered body may further contain zirconia (ZrO ₂ ).

  The porosity of the porous ceramic sintered body may be in the range of 20% to 30%.

In the porous ceramic sintered body, the initial strength in a four-point bending test is X, and the porous ceramic sintered body is subjected to a thermal shock with a temperature difference (ΔT) of 400 ° C. or more. When the strength in the four-point bending test of the porous ceramic sintered body is Y,
The initial strength X exceeds 30 MPa,
The ratio Y / X may exceed 0.6.

  In the present invention, a porous ceramic sintered body having excellent thermal shock resistance and having pores having a desired pore diameter can be obtained without using a pore-forming agent or significantly reducing the amount of pore-forming agent used. A method that can be manufactured can be provided. In the present invention, a porous ceramic sintered body having excellent thermal shock resistance and having a plurality of pores having a pore diameter of 50 μm or more can be provided.

It is the flowchart which showed roughly an example of the manufacturing method of the porous ceramics sintered compact by this invention. It is a SEM photograph (low magnification) of the porous ceramic sintered compact (sample which concerns on Example 1) by this invention. It is a SEM photograph (high magnification) of the porous ceramic sintered compact (sample which concerns on Example 1) by this invention. It is the figure which showed collectively the initial intensity | strength X obtained in each sample. It is the figure which put together and showed the residual rate (strength Y after thermal shock / initial strength X) obtained in each sample. It is the Weibull plot obtained about the intensity | strength before and behind the thermal shock test of each sample.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In FIG. 1, an example of the flow of the manufacturing method of the porous ceramics sintered compact by this invention is shown roughly. In addition, in the example of FIG. 1, although the manufacturing flow in the case of manufacturing the porous ceramics sintered compact which has complex oxide containing silicon (Si) is shown as an example, this invention is limited to this. is not.

As shown in FIG. 1, the method for producing a porous ceramic sintered body according to the present invention is roughly divided into (a) first raw material particles having a compound containing silicon (Si), and the first raw material particles. Mixing the second raw material particles having a higher melting point to prepare mixed particles (step S110);
(B) molding the mixed particles to form a molded body (step S120);
(C) firing the molded body to form a porous ceramic sintered body, the molded body being higher than the melting point of the first raw material particles, and the melting point of the second raw material particles Firing at a lower temperature, whereby at least a part of the first raw material particles and the second raw material particles react to produce a composite oxide, and a substantially spherical pore is obtained. (Step S130),
It is characterized by having.

  In the method of the present invention, in step S130, the compact is fired at a firing temperature higher than the melting point of the first raw material particles and lower than the melting point of the second raw material particles. In this case, only the first raw material particles in the molded body start to melt during the firing treatment. In addition, the unmelted second raw material particles react when they come into contact with the molten component of the first raw material particles to generate a composite oxide. Since the molten component of the first raw material particles is liquid and has high permeability, the molten component of the first raw material particles moves in a wide range within the molded body due to a capillary phenomenon or the like. As a result, the molten component of the first raw material particles comes into contact with the unreacted second raw material particles one after another, and a composite oxide is continuously generated at the position where the second raw material particles are present. By progressing such a reaction, a skeleton portion composed of a composite oxide is finally formed.

  On the other hand, the position where the first raw material particles originally existed becomes a substantially spherical void due to melting and movement of the first raw material particles. Therefore, in the method of the present invention, a porous ceramic sintered body including a skeleton made of a complex oxide and a large number of substantially spherical pores is manufactured at the completion of the sintering process in step S130.

For example, when the first raw material particles are silica (SiO ₂ ) and the second raw material particles are alumina (Al ₂ O ₃ ), the fused silica, (SiO ₂ ), and alumina (Al ₂ O ₃ ) are In reaction, mullite is formed. “Mullite” is a complex oxide in which alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) are mixed in a ratio (weight ratio) of 80:20 to 75:25.

  Here, in the conventional method for producing a porous ceramic sintered body using an organic and / or inorganic pore former, the pore former is a process for producing the porous ceramic sintered body. It does not remain in the sintered body finally obtained. In other words, such a pore-forming agent is a completely unnecessary component for the finally obtained porous ceramic sintered body, and the use of such a pore-forming agent results in the production cost of the porous ceramic sintered body. Cause an increase.

  Further, in the production process of the porous ceramic sintered body, the pore-forming agent is decomposed and released as a gas, but such gas discharge in the production process is not environmentally preferable. In particular, when an organic pore former is used, organic component gases are discharged into the atmosphere during the production of the porous ceramic sintered body. In such organic component gas, there is a possibility that a gas having a safety problem may be contained, and the use of an organic pore former has a problem not only in the environment but also in safety.

  In addition, for example, when a pore forming agent having a relatively large particle size is used for the purpose of forming large pores in the ceramic sintered body, a large amount of gas is discharged during the decomposition and release process of the pore forming agent. End up. Furthermore, due to the sudden increase in internal pressure or volume reduction during the generation of such gas, the strength of the molded body is lowered, and cracks are generated in the skeleton of the porous ceramic sintered body finally obtained. The problem arises that will be crushed. Therefore, the conventional method using a pore-forming agent has a problem that it is difficult to produce a porous ceramic sintered body having pores having a relatively large pore diameter of 50 μm or more.

  On the other hand, in the method for producing a porous ceramic sintered body according to the present invention, it is basically unnecessary to use a pore forming agent (or the amount of the pore forming agent used is significantly suppressed). For this reason, an increase in manufacturing cost due to the addition of the pore forming agent can be significantly suppressed.

  Also, since no pore-forming agent is used (or because the amount of pore-forming agent used is significantly suppressed), when the pore-forming agent such as organic component gas is decomposed in the manufacturing process of the porous ceramic sintered body. Release of the generated gas can be significantly suppressed. Therefore, according to the present invention, it is possible to provide an environment-friendly and safe manufacturing method.

  Further, in the present invention, pores having a desired pore diameter can be formed in the porous ceramic sintered body by appropriately adjusting the particle diameter of the first raw material particles. For this reason, pores having a large pore diameter can be easily formed. Therefore, problems that occur in the conventional method of using a pore-forming agent, that is, problems such as cracking in the ceramic skeleton and crushing of pores due to the generation of a large amount of gas due to decomposition of the pore-forming agent are significant. It is suppressed.

  Furthermore, the porous ceramic sintered body obtained by the production method of the present invention has a feature of having substantially spherical pores. In the present invention, due to this feature, when the porous ceramic sintered body is subjected to thermal shock, the sites that are the starting points of crack generation are significantly reduced, and the porous ceramic sintered body has good thermal shock resistance. Can be provided.

  Hereinafter, each step (step S110), (step S120), and (step S130) of the manufacturing method according to the present invention shown in FIG. 1 will be described in detail. In the following description, the description will be made assuming that a porous ceramic sintered body containing mullite as a complex oxide is manufactured.

(Step S110)
In this step, the first raw material particles having a compound containing silicon and the second raw material particles having a melting point higher than that of the first raw material particles are mixed to prepare mixed particles.

For example, when a porous ceramic sintered body finally containing mullite is manufactured, the first raw material particles are silica (SiO ₂ ) and the second raw material particles are alumina (Al ₂ O ₃ ). May be.

However, the first and second raw material particles are not necessarily oxides. For example, as the first raw material particles, a compound containing silicon, for example, silicon nitride (Si _x N _y ), silicon carbide (SiC), or the like may be used. Similarly, nitride, carbide, carbonate or the like may be used as the second raw material particles.

  The average particle diameter of the first raw material particles is a factor that determines the pore diameter (diameter) of the spherical pores finally formed. Therefore, the average particle diameter of the first raw material particles is selected based on the required average pore diameter (diameter) of the spherical pores. For example, the average particle diameter of the first raw material particles may be in the range of 50 μm to 100 μm (for example, 60 μm or 80 μm). In this case, spherical pores having an average pore diameter (diameter) of about 50 μm to about 100 μm (for example, about 60 μm or about 80 μm, etc.) are finally generated (however, in actuality, some (several μm) is obtained by firing. Shrinkage).

On the other hand, the average particle diameter of the second raw material particles is not particularly limited. However, when the average particle diameter of the second raw material particles is significantly larger than the average particle diameter of the first raw material particles, the molten first raw material particles are sufficiently combined with the second raw material particles in the firing process. It becomes difficult to come into contact, and a skeletal part having a non-uniform material composition is formed (that is, a composite oxide part and an unreacted part made of a component of the second raw material are generated in the ceramic skeleton part). . Therefore, when it is necessary to obtain a uniform skeleton, the average particle diameter of the second raw material particles is preferably equal to or less than the average particle diameter of the first raw material particles. For example, when the average particle diameters of the first and second raw material particles are r ₁ and r ₂ , respectively, the ratio r ₁ / r ₂ is preferably in the range of 0.1 to 500, Is more preferably in the range of 2 to 200. For example, the average particle diameter of the second raw material particles is in the range of 0.5 μm to 2 μm (for example, 1 μm).

  However, when it is desired to form a ceramic skeleton having an intentionally non-uniform composition distribution, there is no such restriction, and the average particle diameter of the second raw material particles may be significantly larger than that of the first raw material particles. good.

  It should be noted that the shape of the first raw material particles needs to be substantially spherical, but the shape of the second raw material particles is not particularly limited.

  Here, the mixed particles may further contain an “additive”.

  In the present application, the term “additive” refers to (i) a component that remains in the ceramic sintered body after the firing step (hereinafter referred to as “first additive”), and (ii) basically. It should be noted that the component does not remain in the ceramic sintered body after the firing step (hereinafter referred to as “second additive”). Unlike the “raw material particles”, the “additive” does not directly participate in the complex oxide formation reaction (that is, is not consumed by the complex oxide formation reaction).

  The “first additive” includes, for example, a reaction accelerator for promoting the reaction and / or sintering of the first raw material particles and the second raw material particles.

For example, when the first raw material particles are silica (SiO ₂ ), the second raw material particles are alumina (Al ₂ O ₃ ), and mullite is produced as a composite oxide, zirconia ( ZrO ₂ ) particles may be added. By adding zirconia (ZrO ₂ ) particles, the formation reaction and sintering reaction of the composite oxide are promoted, and a porous ceramic sintered body containing mullite can be manufactured in a shorter time. In this case, the zirconia (ZrO ₂ ) particles remain in the skeleton part of the finally obtained ceramic sintered body (mullite).

When adding zirconia (ZrO ₂ ) particles as the “first additive”, the average particle diameter of the zirconia (ZrO ₂ ) particles is not particularly limited, but is preferably about the same as the second raw material particles, For example, it is 0.5 μm to 2 μm (for example, 1 μm). The amount of zirconia (ZrO ₂ ) particles added is not particularly limited, but is the sum of the first and second raw material particles (when three or more raw material particles are included, the sum of the raw material particles excluding zirconia) ) Is preferably in the range of 1 wt% to 10 wt%. Addition of a large amount of zirconia (ZrO ₂ ) exceeding 10 wt% has a problem in that the thermal expansion coefficient of the skeleton portion increases and the thermal shock resistance decreases. As the types of zirconia (ZrO _2), yttria _(Y 2 _{O 3)} stabilized zirconia _(ZrO 2), scandia _(Sc 2 _{O 3)} stabilized zirconia (ZrO ₂₎ or the like, various zirconia (ZrO ₂₎ Can be used equally.

  On the other hand, the “second additive” is a general binder (organic binder / inorganic binder), dispersant, solvent (water, alcohol, etc.) used in the manufacturing process of a conventional ceramic sintered body. ) And / or a pore-forming agent. However, as described above, in the present invention, it is basically unnecessary to add a pore forming agent. Therefore, even if a pore forming agent is added, the amount added is suppressed to a minimum.

  The method for mixing the raw material particles is not particularly limited, and various methods such as ball milling can be used. In addition, since the shape of the first raw material particles determines the shape of the pores finally generated, it is preferable that the first raw material particles are not mixed for a long time after the first raw material particles are added. Thereby, the change of the shape of the first raw material particles can be minimized.

(Step S120)
Next, a molded body is formed using the mixed powder prepared by the above-described method.

  The molding method is not particularly limited, and various conventionally known methods are applied. For example, when the mixed powder is used as it is (as it is in a solid state), a CIP method (cold isostatic pressing method), a normal powder pressing method, or the like is used as a forming method. Moreover, when obtaining a molded object from mixed powder via a paste, a slurry, etc., you may obtain a molded object by implementing extrusion molding or injection molding using such paste.

  In the latter case, after the molded body is obtained, the molded body is dried.

(Step S130)
Next, the obtained molded body is fired.

Calcination is performed at a temperature higher than the melting point of the first raw material particles and lower than the melting point of the second raw material particles (and, if “the first additive” is present). For example, silica (SiO ₂ ) (melting point 1414 ° C.) is used as the first raw material particles, alumina (Al ₂ O ₃ ) (melting point 2020 ° C.) is used as the second raw material particles, and zirconia is used as the first additive. When using (ZrO ₂ ) (melting point 2680 ° C.), a range of 1450 ° C. to 1700 ° C. is selected as the firing temperature. The firing temperature is, for example, 1550 ° C., 1600 ° C., or 1650 ° C.

  The firing time depends on the firing temperature, but in the case of the above-mentioned example, it may be in the range of 1 hour to 24 hours (for example, 1 hour, 2 hours, 4 hours, 6 hours, etc.).

  Usually, the baking treatment is performed in the air.

As described above, by firing the molded body, the first raw material particles are melted, and the second raw material particles react with the melted first raw material to form a composite oxide. For example, mullite is generated by a reaction between alumina (Al ₂ O ₃ ) and fused silica (SiO ₂ ). In the molded body, the position occupied by the first raw material particles remains as pores, and finally a porous ceramic sintered body having a large number of spherical pores and a skeleton portion containing a composite oxide. can get.

  By the way, in the above description, it demonstrated centering on the method of manufacturing a porous ceramic sintered compact using the two types of particle | grains of 1st and 2nd raw material particles as a starting material. However, it should be noted that the present invention may use three or more kinds of raw material particles as starting materials.

For example, when the first raw material particle is silica (SiO ₂ ), the second raw material particle is alumina (Al ₂ O ₃ ), and the third raw material particle is magnesia (MgO), the porous material has cordierite. A ceramic sintered body can be manufactured. Here, it should be noted that the melting point of the third raw material particles is higher than the melting point of the first raw material particles. In this case, in the firing step, molten silica, (SiO ₂ ), solid alumina (Al ₂ O ₃ ), and solid magnesia (MgO) react to generate cordierite. “Cordierite” refers to a composite oxidation in which alumina (Al ₂ O ₃ ), magnesia (MgO), and silica (SiO ₂ ) are mixed at a ratio (chemical composition ratio) of 2: 2: 5. A general term for things.

  Examples of the present invention will be described below.

Example 1
A sample of a porous mullite sintered body was produced by the following method.

80 g of alumina (Al ₂ O ₃ ) particles (purity 99% or more) having an average particle diameter of about 1 μm and zirconia (ZrO ₂ ) particles (purity 99% or more (3 mol yttria (Y ₂ O ₃ )) having an average particle diameter of about 1 μm. 1), 60 g of water, and a small amount of an organic dispersant were mixed and mixed in a ball mill for more than half a day. Next, silica (SiO ₂ ) particles (purity 99% or more) having an average particle diameter of 60 μm were added to this mixed solution, and further mixed for 1 hour using a stirrer. The silica particles were added so that the weight ratio of alumina: silica was 80:20. The addition amount of the zirconia particles of the above, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), a 1 wt%.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Furthermore, this molded body was fired at 1650 ° C. for 2 hours in the air to obtain a sintered body sample (hereinafter referred to as “sample according to Example 1”).

  2 and 3 show SEM photographs of the sample according to Example 1. FIG. FIG. 2 is a low-magnification photograph, and FIG. 3 is a high-magnification photograph. As shown in FIGS. 2 and 3, it can be seen that a large number of substantially spherical pores are formed in the sintered body. The average pore diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 1, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

  Furthermore, when the porosity of the sample according to Example 1 was measured, the porosity was 27.0%. The porosity was measured by an underwater substitution method.

Further, the density (bulk density) of the sample according to Example 1 was 2.27 g / cm ³ . The density was calculated based on the measurement results of the sample dimensions and weight.

(Example 2)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 2”) was produced in the same manner as in Example 1.

  However, in Example 2, the firing time was 4 hours. The firing temperature was 1650 ° C. as in Example 1.

  When the sample according to Example 2 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 2, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 2 were measured, the porosity was 23.5% and the density was 2.20 g / cm ³ .

(Example 3)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 3”) was produced in the same manner as in Example 1.

However, in Example 3, zirconia particles were added to 3 wt% with respect to the total amount of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). In Example 3, the firing time was 4 hours. The firing temperature was 1650 ° C. as in Example 1.

  When the sample according to Example 3 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  As a result of the X-ray diffraction analysis of the sample according to Example 3, a mullite peak was recognized in addition to the zirconia peak, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 3 were measured, the porosity was 25.2% and the density was 2.19 g / cm ³ .

Example 4
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 4”) was produced in the same manner as in Example 1.

However, in Example 4, the zirconia particles were added so as to be 5 wt% with respect to the total amount of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). In Example 4, the firing time was 4 hours. The firing temperature was 1650 ° C. as in Example 1.

  When the sample according to Example 4 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  As a result of the X-ray diffraction analysis of the sample according to Example 4, a mullite peak was observed in addition to the zirconia peak, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 4 were measured, the porosity was 24.6% and the density was 2.24 g / cm ³ .

(Example 5)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 5”) was produced in the same manner as in Example 1.

However, in Example 5, the zirconia particles that do not contain yttria (Y ₂ O ₃ ) as a stabilizing material were used. The diameter of the zirconia particles is 1 μm or less, which is the same as in Example 1. Further, the zirconia particles, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), was added to a 10 wt%. In Example 5, the firing time was 4 hours. The firing temperature was 1650 ° C. as in Example 1.

  When the sample according to Example 5 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of the X-ray diffraction analysis of the sample according to Example 5, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 5 were measured, the porosity was 27.1% and the density was 2.35 g / cm ³ .

(Example 6)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 6”) was produced in the same manner as in Example 1.

However, in Example 6, the zirconia particles that do not contain yttria (Y ₂ O ₃ ) as a stabilizing material were used. The diameter of the zirconia particles is 1 μm or less, which is the same as in Example 1. Further, the zirconia particles, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), was added to a 1 wt%. In Example 6, the firing temperature was 1600 ° C. and the firing time was 6 hours.

  When the sample according to Example 6 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 6, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 6 were measured, the porosity was 28.4% and the density was 2.31 g / cm ³ .

(Example 7)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 7”) was produced in the same manner as in Example 1.

In Example 7, however, zirconia particles containing 6 mol% of yttria (Y ₂ O ₃ ) as a stabilizer were used. The diameter of the zirconia particles is 1 μm or less, which is the same as in Example 1. Further, the zirconia particles, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), was added to a 10 wt%. In Example 7, the firing temperature was 1600 ° C. and the firing time was 2 hours.

  When the sample according to Example 7 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 7, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 7 were measured, the porosity was 25.7% and the density was 2.35 g / cm ³ .

(Example 8)
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 8”) was produced in the same manner as in Example 1.

However, in Example 8, as zirconia particles, those containing 6 mol% of yttria (Y ₂ O ₃ ) as a stabilizing material were used. The diameter of the zirconia particles is 1 μm or less, which is the same as in Example 1. Further, the zirconia particles, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), was added to a 1 wt%. In Example 8 , the firing temperature was 1550 ° C. and the firing time was 4 hours.

  When the sample according to Example 8 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 8, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 8 were measured, the porosity was 26.5% and the density was 2.29 g / cm ³ .

Example 9
A sample of a porous mullite sintered body (hereinafter referred to as “sample according to Example 9”) was produced in the same manner as in Example 1.

However, in Example 9, the zirconia particles were added to 10 wt% with respect to the total amount of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). In Example 9, the firing temperature was 1550 ° C., and the firing time was 6 hours.

  When the sample according to Example 9 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Example 9, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

Furthermore, when the porosity and density of the sample concerning Example 9 were measured, the porosity was 28.7% and the density was 2.30 g / cm ³ .

  Table 1 summarizes the production conditions, porosity, and density of each sample.

(Comparative Example 1)
80 g of alumina (Al ₂ O ₃ ) particles (purity 99% or more) having an average particle diameter of about 1 μm and zirconia (ZrO ₂ ) particles (purity 99% or more, yttria (Y ₂ O ₃ )) having an average particle diameter of about 1 μm 3 g), 60 g of water, 5 g of a pore-forming agent, and a small amount of an organic dispersant were mixed and mixed with a ball mill for half a day or more. Next, silica (SiO ₂ ) particles (purity 99% or more) having an average particle diameter of 5 μm were added to the mixed solution, and further mixed for 1 hour using a stirrer. The silica particles were added so that the weight ratio of alumina: silica was 80:20. The addition amount of the zirconia particles of the above, the total amount of alumina _(Al 2 _{O 3)} and silica (SiO _2), is 3 wt%.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Furthermore, this molded body was fired at 1650 ° C. for 2 hours in the air to obtain a sintered body sample (hereinafter referred to as “sample according to Comparative Example 1”).

  When the sample according to Comparative Example 1 was observed by SEM, it was confirmed that a large number of non-spherical and deformed pores were formed in the sintered body. The average diameter of the pores was about 25 μm.

  As a result of the X-ray diffraction analysis of the sample according to Comparative Example 1, in addition to the zirconia peak, a mullite peak was observed, and it was confirmed that mullite was generated by the above method.

When the porosity of the sample according to Comparative Example 1 was measured, the porosity was about 17.8%. Moreover, the density of the sample according to Comparative Example 1 was 2.64 g / cm ³ .

(Comparative Example 2)
80 g of alumina (Al ₂ O ₃ ) particles (purity 99% or more) having an average particle diameter of about 1 μm, 60 g of water, and a small amount of an organic dispersant were mixed and mixed by a ball mill for half a day or more. Next, silica (SiO ₂ ) particles (purity 99% or more) having an average particle diameter of 60 μm were added to this mixed solution, and further mixed for 1 hour using a stirrer. The silica particles were added so that the weight ratio of alumina: silica was 80:20.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Furthermore, this molded body was fired at 1400 ° C. for 6 hours in the atmosphere to obtain a sintered body sample (hereinafter referred to as “sample according to Comparative Example 2”). It should be noted that this firing temperature is lower than the melting point of silica (1414 ° C.).

  When the sample according to Comparative Example 2 was observed by SEM, spherical pores were not confirmed in the sintered body. The average diameter of the pores was about 15 μm.

  Moreover, as a result of the X-ray diffraction analysis of the sample according to Comparative Example 2, a peak of sillimanite was observed, and in the above method, it was confirmed that sillimanite was generated instead of mullite.

Furthermore, when the porosity of the sample according to Comparative Example 2 was measured, the porosity was about 18.9%. Further, the density of the sample according to Comparative Example 2 was 2.58 g / cm ³ .

(Comparative Example 3)
A sintered body sample (hereinafter referred to as “sample according to Comparative Example 3”) was produced in the same manner as in Comparative Example 1.

However, in Comparative Example 3, silica (SiO ₂ ) particles (purity 99% or more) having an average particle diameter of 60 μm were used. In Comparative Example 3, the zirconia particles were added so as to be 15 wt% with respect to the total amount of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). In Comparative Example 3, the firing temperature was 1550 ° C. and the firing time was 4 hours.

  When the sample according to Comparative Example 3 was observed by SEM, it was confirmed that a large number of substantially spherical pores similar to the pores shown in FIGS. 2 and 3 were formed in the sintered body. The average diameter of the spherical pores was about 50 μm.

  Moreover, as a result of the X-ray diffraction analysis of the sample according to Comparative Example 3, the peaks of zircon and mullite were recognized, and it was confirmed that not only mullite but also zircon was generated in the above method.

Further, when the porosity and density of the sample according to Comparative Example 3 were measured, the porosity was 21.3% and the density was 2.61 g / cm ³ .

(Comparative Example 4)
80 g of alumina (Al ₂ O ₃ ) particles (purity 99% or more) having an average particle size of about 0.5 μm, 60 g of water, and a small amount of an organic dispersant were mixed and mixed for more than half a day with a ball mill. Next, silica (SiO ₂ ) particles (purity 99% or more) having an average particle diameter of 280 μm were added to this mixed solution, and further mixed for 1 hour using a stirrer. The silica particles were added so that the weight ratio of alumina: silica was 80:20.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Furthermore, this molded body was fired at 1550 ° C. for 4 hours in the air to obtain a sintered body sample (hereinafter referred to as “sample according to Comparative Example 4”).

  When the sample according to Comparative Example 4 was observed by SEM, it was confirmed that a large number of substantially spherical pores were formed in the sintered body, but the average diameter of the spherical pores was about 250 μm.

  Further, as a result of the X-ray diffraction analysis of the sample according to Comparative Example 4, the peak of Anderusite was recognized, and it was confirmed that in the above method, Anderusite was generated instead of mullite.

Furthermore, when the porosity of the sample according to Comparative Example 4 was measured, the porosity was about 31.7%. Moreover, the density of the sample according to Comparative Example 4 was 2.01 g / cm ³ .

(Comparative Example 5)
100 g of mullite having an average particle size of about 5 μm, 60 g of water, and a small amount of an organic dispersant were mixed and mixed by a ball mill for half a day or more. Furthermore, this mixed solution was further mixed for 1 hour using a stirring device.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Furthermore, this molded body was fired at 1600 ° C. for 8 hours in the air to obtain a sintered body sample (hereinafter referred to as “sample according to Comparative Example 5”).

  When the sample according to Comparative Example 5 was observed by SEM, spherical pores were not confirmed in the sintered body, and the average diameter of the pores was about 15 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Comparative Example 5, only the peak of mullite was observed.

Furthermore, when the porosity of the sample according to Comparative Example 5 was measured, the porosity was about 14.2%. Moreover, the density of the sample according to Comparative Example 5 was 2.66 g / cm ³ .

(Comparative Example 6)
100 g of mullite having an average particle size of about 5 μm, 60 g of water, 10 g of a pore-forming agent, and a small amount of an organic dispersant were mixed and mixed by a ball mill for half a day or more. Furthermore, this mixed solution was further mixed for 1 hour using a stirring device.

  Next, the obtained mixed solution was dried in the air at room temperature, water and the like were evaporated, and mixed particles were obtained.

  Next, the obtained mixed particles were subjected to pressure molding by the CIP method (cold isostatic pressing method) to produce a molded body having dimensions of about 50 mm in length, about 50 mm in width, and about 5 mm in thickness.

  Further, this molded body was fired at 1600 ° C. for 8 hours in the air to obtain a sintered body sample (hereinafter referred to as “sample according to Comparative Example 6”).

  When the sample according to Comparative Example 6 was observed by SEM, it was confirmed that a large number of substantially spherical pores were formed in the sintered body. However, the average diameter of the spherical pores was about 10 μm.

  Further, as a result of X-ray diffraction analysis of the sample according to Comparative Example 6, only the peak of mullite was observed.

Furthermore, when the porosity of the sample according to Comparative Example 6 was measured, the porosity was about 45.0%. Moreover, the density of the sample according to Comparative Example 6 was 1.73 g / cm ³ .

  In Table 2, the production conditions, average pore diameter, porosity, and density of each sample of Comparative Examples 1 to 6 are collectively shown.

(Strength evaluation)
Using each sample according to Examples 1 to 9 and Comparative Examples 1 to 6 manufactured by the above-described method, a thermal shock test is performed by the following method, and the thermal shock resistance of each sample is evaluated. It was.

  First, each sample was cut into a bar shape having a size of about 3 mm × about 4 mm × about 40 mm to prepare a test piece. A four-point bending test was performed using this test piece, and the initial strength X of each sample was measured. The 4-point bending test was performed based on Japanese Industrial Standard JISR1601 (room temperature bending strength test method for fine ceramics). The distance L1 between the two lower fulcrums was 30 mm, and each fulcrum was provided at a position 15 mm from the center in the longitudinal direction of the test piece toward the outside in the longitudinal direction. The distance L2 between the upper two load points was 10 mm, and each load point was provided at a position 5 mm from the center in the longitudinal direction of the test piece toward the outside in the longitudinal direction. In this state, the load was added to the two load points, and the load when the test piece was broken was defined as the initial strength X.

  Next, the test piece cut out to the above-mentioned dimensions was put in an electric furnace and heated to 425 ° C. in the atmosphere. Next, the heated test piece was dropped into water having a water temperature of 25 ° C. (thus, temperature difference ΔT = 400 ° C.). Thereafter, a four-point bending test was performed again using the test piece cooled to room temperature. Thereby, the strength Y after thermal shock was measured.

  The ratio of the strength Y after thermal shock to the initial strength X of each sample (that is, Y / X) was determined, and this value was defined as the “residual rate”. This “residual rate” can be used as an index of the thermal shock resistance of each sample. The closer to 1, the better the thermal shock resistance of the sample.

  Table 1 above shows the values of the initial strength X, the strength Y after thermal shock, and the residual rate Y / X obtained in each sample of Examples 1 to 9. 4 and 5 are graphs showing the initial intensity X and the residual ratio Y / X of the samples according to the respective examples.

  When a mullite sintered body having a porosity of about 20% to 30% is manufactured using a conventional organic pore former, its initial strength X and residual rate Y / X are about 30 MPa and about 30 MPa, respectively. It is expected to be about 0.6.

  On the other hand, as shown in FIGS. 4 and 5, in the samples according to Examples 1 to 9, it was found that the initial strength exceeded 30 MPa and the residual rate Y / X exceeded 0.6 at the minimum. . In particular, the sample according to Example 7 was found to have an initial strength exceeding 70 MPa. Moreover, in the sample which concerns on Example 1, residual ratio Y / X was set to about 1, and it turned out that it has the very favorable thermal shock resistance.

  In FIG. 6, the Weibull plot obtained about the intensity | strength before and behind the thermal shock test of each sample of Example 1- Example 9 is shown. From this result, it can be seen that the initial strength of each sample and the strength variation after the thermal shock test are small and the strength is stable.

  In addition, within the range of experiment, the influence of the addition amount of zirconia on the initial strength and thermal shock resistance of the sample was not remarkable. Further, the influence of the amount of yttria contained in zirconia was not significant.

  Thus, it was confirmed that the porous ceramic sintered body manufactured by the method according to the present invention has a good initial strength and an excellent thermal shock resistance.

  Table 2 above shows the values of the initial strength X, the strength Y after thermal shock, and the residual rate Y / X obtained in the samples of Comparative Examples 1 to 6.

  From this result, it can be seen that in Comparative Example 2, Comparative Example 4, and Comparative Example 6, the initial strength X of the sample is below 30 MPa. Further, in Comparative Examples 1 to 4 and Comparative Examples 5 to 6, the residual ratio Y / X is less than 0.6, and these samples are porous materials produced by the method according to the present invention. It was found that the thermal shock resistance was inferior compared with the ceramic sintered body.

  The present invention can be applied to a ceramic setter or a ceramic filter.

  In addition, this application claims the priority based on the Japan patent application 2009-278647 for which it applied on December 8, 2009, and uses all the content of the Japan application as reference of this application.

Claims (10)

A method for producing a porous mullite-zirconia sintered body,
The zirconia is included in the range of 1 wt% to 10 wt% with respect to the total amount of other raw material particles,
(A) a step of preparing mixed particles by mixing first raw material particles having a compound containing silica, and second raw material particles having a melting point higher than that of the first raw material particles and containing alumina and zirconia; The mixed particles do not contain a pore-forming agent;
(B) molding the mixed particles to form a molded body;
(C) firing the molded body to form a porous ceramic sintered body, the molded body being higher than the melting point of the first raw material particles, and the melting point of the second raw material particles Firing at a lower temperature, whereby at least a part of the first raw material particles and the second raw material particles react to produce a composite oxide, and a substantially spherical pore is obtained. When,
A method characterized by comprising:   The method of claim 1, wherein the spherical pores have an average pore diameter in the range of 50 μm to 100 μm.   The method according to claim 1 or 2, wherein the first raw material particles have an average particle diameter in the range of 50 µm to 100 µm.   The ratio r1 / r2 of the average particle diameter r1 of the first raw material particles to the average particle diameter r2 of the second raw material particles is in the range of 0.1 to 500. The method according to any one of the above.   The method according to claim 1, wherein the complex oxide includes mullite.   The method according to any one of claims 1 to 5, wherein in the step (a), third raw material particles having a melting point higher than that of the first raw material particles are further mixed. The third raw material particles include magnesia (MgO),
The method according to claim 6, wherein the composite oxide includes cordierite.   The method according to any one of claims 1 to 7, wherein the firing temperature in the step (c) is in the range of 1550 ° C to 1650 ° C.   The method according to any one of claims 1 to 8, wherein the porosity of the porous ceramic sintered body is in a range of 20% to 30%. A porous mullite-zirconia sintered body,
The zirconia is included in the range of 1 wt% to 10 wt% with respect to the total amount of other raw materials,
The average pore diameter is more than have a substantially pores of spherical 50 .mu.m to 100 .mu.m,
The porosity of the porous mullite-zirconia sintered body is in the range of 20% to 30%,
The initial strength in a four-point bending test of a porous mullite-zirconia sintered body is X, and the porous mullite-zirconia sintered body is subjected to a thermal shock with a temperature difference (ΔT) of 400 ° C. or more. When the strength in the four-point bending test of the mullite-zirconia sintered body is Y,
The initial strength X exceeds 30 MPa,
A porous mullite-zirconia sintered body characterized in that the ratio Y / X exceeds 0.6 .