Ceramic structures, catalyst composites, and catalyst supports for electric field application

Abstract

This invention provides a technology for ceramic structures that improves gas flowability while maintaining a certain level of strength, and also increases the specific surface area. [Solution] The ceramic structure comprises a ceramic foam having pores and formed of a plurality of first ceramic particles, and a covering portion covering the ceramic foam, which is formed of a plurality of second ceramic particles, wherein the average particle size of the plurality of second ceramic particles is smaller than the average particle size of the plurality of first ceramic particles.

Description

Technical Field

[0001] The present invention relates to a ceramic structure, a catalyst composite, and a catalyst carrier for applying an electric field.

Background Art

[0002] Conventionally, a ceramic structure having pores has been known (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even with prior art such as Patent Document 1, there is still room for improvement in the technology of increasing the specific surface area and improving the gas flowability while having a certain degree or more of strength in the ceramic structure.

[0005] An object of the present invention is to provide a technology that increases the specific surface area and improves the gas flowability while having a certain degree or more of strength in a ceramic structure.

Means for Solving the Problems

[0006] The present invention has been made to solve at least a part of the above problems and can be realized in the following forms.

[0007] (1) According to one embodiment of the present invention, a ceramic structure is provided. This ceramic structure comprises a ceramic foam having pores and formed of a plurality of first ceramic particles, and a covering portion covering the ceramic foam, the covering portion being formed of a plurality of second ceramic particles, wherein the average particle size of the plurality of second ceramic particles is smaller than the average particle size of the plurality of first ceramic particles.

[0008] In this configuration, the porous ceramic foam is formed from multiple first ceramic particles, thus possessing a three-dimensional network structure, resulting in a certain level of strength while maintaining relatively high gas flowability. The coating portion covering the ceramic foam is formed from multiple second ceramic particles, each with an average particle size smaller than the average particle size of the multiple first ceramic particles. This allows the specific surface area of ​​the ceramic structure to be larger than that of the ceramic foam alone. Therefore, it is possible to increase the specific surface area and improve gas flowability while maintaining a certain level of strength.

[0009] (2) In the ceramic structure of the above form, the coating portion may have cracks. With this configuration, the presence of cracks in the coating portion can relieve the stress generated in the coating portion. This makes it possible to suppress the detachment of the coating portion from the ceramic foam.

[0010] (3) In the ceramic structure of the above form, the coating portion may have a plurality of coating layers that are stacked on top of each other. With this configuration, since the coating portion has a plurality of coating layers, even if some of the coating layers fall off, the remaining coating layers can maintain the specific surface area of ​​the ceramic structure.

[0011] (4) In the ceramic structure of the above form, the ratio of the thickness of the ceramic foam to the thickness of the coating portion in a cross-section passing through the ceramic foam and the coating portion may be 0.5 or more and 4 or less. With this configuration, since the ratio of the thickness of the ceramic foam to the thickness of the coating portion is 0.5 or more and 4 or less, it is possible to increase the specific surface area of ​​the ceramic structure while suppressing the increase in pressure loss due to clogging of pores.

[0012] (5) In the ceramic structure of the above form, the first ceramic particles may contain cerium oxide as the main component. With this configuration, since the first ceramic particles contain cerium oxide as the main component, the ionic conductivity of the ceramic foam can be improved.

[0013] (6) In the ceramic structure of the above form, the second ceramic particles may contain cerium oxide as the main component. With this configuration, since the second ceramic particles contain cerium oxide as the main component, the ionic conductivity of the coated portion can be improved.

[0014] (7) In the ceramic structure of the above form, the average of the porosity of the ceramic foam and the porosity of the coating may be 60% or more and 93% or less. With this configuration, the average of the porosity of the ceramic foam and the porosity of the coating is 60% or more and 93% or less. This makes it possible to reduce pressure loss relatively small.

[0015] (8) According to another embodiment of the present invention, a catalyst composite is provided. This catalyst composite comprises the above-described ceramic structure and a catalyst supported on the coating portion and formed of a metal. In this configuration, the catalyst composite has a ceramic foam with a relatively small specific surface area formed by first ceramic particles with a relatively large average particle size, and the catalyst is supported on the ceramic foam, while the coating portion with a relatively large specific surface area formed by second ceramic particles with a relatively small average particle size also supports the catalyst. As a result, the catalyst composite can contain a larger amount of catalyst than when the ceramic foam alone supports the catalyst, and has a structure that allows gas in contact with the catalyst to flow easily, thereby improving the performance of the catalyst.

[0016] (9) According to yet another embodiment of the present invention, a catalyst support for electric field application is provided. This catalyst support for electric field application comprises the ceramic structure described above. With this configuration, because the catalyst support for electric field application comprises the ceramic structure described above, it can support a large amount of catalyst and the gas in contact with the catalyst flows easily. As a result, the catalyst support for application makes it easier to bring out the performance of the supported catalyst.

[0017] Furthermore, the present invention can be realized in various forms, for example, as a method for manufacturing a ceramic structure, a method for manufacturing a catalyst composite, a method for manufacturing a catalyst support for electric field application, an apparatus equipped with a ceramic structure, a method for controlling an apparatus equipped with a ceramic structure, a computer program that causes a computer to manufacture a ceramic structure, a server device for distributing the computer program, a non-temporary storage medium storing the computer program, and so on. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram showing the overall structure of the ceramic structure according to the first embodiment. [Figure 2] This is a first enlarged view of the ceramic structure of the first embodiment. [Figure 3]It is a second enlarged view of the ceramic structure of the first embodiment. [Figure 4] It is a first figure showing the result of image processing for the sample for boundary setting. [Figure 5] It is a second figure showing the result of image processing for the sample for boundary setting. [Figure 6] It is a third enlarged view of the ceramic structure of the first embodiment. [Figure 7] It is a figure explaining the schematic configuration of the reaction apparatus provided with the catalyst complex of the first embodiment. [Figure 8] It is a flowchart showing the manufacturing method of the ceramic structure of the first embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0019] <First Embodiment> FIG. 1 is a view showing the whole of the ceramic structure of the first embodiment. As shown in FIG. 1, the ceramic structure 1 of the present embodiment is a porous body having a three-dimensional network structure formed of ceramics.

[0020] FIG. 2 is a first enlarged view of the ceramic structure 1 of the present embodiment. FIG. 2 is an image obtained by imaging a part of the cross section of the ceramic structure 1 at a magnification of 25 times. The ceramic structure 1 of the present embodiment includes a ceramic foam 10 and a coating portion 20.

[0021] The ceramic foam 10 has pores and is formed of a plurality of first ceramic particles. The ceramic foam 10 corresponds to the skeleton of the ceramic structure 1. As shown in FIG. 2, which is an image taken using a scanning electron microscope (SEM), the ceramic foam 10 has a plurality of pores 11 on the order of several hundred micrometers and has a structure in which a network-like skeleton on the order of several micrometers is connected. It has better gas flowability than a so-called monolith molded body, and the pressure loss when gas is circulated can be reduced.

[0022] The first ceramic particles forming the ceramic foam 10 mainly contain cerium oxide (CeO2). Here, "the first ceramic particles mainly contain cerium oxide" means that the molar concentration of cerium oxide in the first ceramic particles is 50 mol% or more. The first ceramic particles in this embodiment are doped with alkaline earth metals and rare earth elements. Calcium is an example of an alkaline earth metal doped into the first ceramic particles. Gadolinium (Gd), lanthanum (La), yttrium (Y), and the like are examples of rare earth elements doped into the first ceramic particles. In the first ceramic particles of this embodiment, the total amount of alkaline earth metal doping and rare earth element doping is between 5 mol% and 30 mol%. The elements contained in the first ceramic particles and their molar concentrations are identified and measured using inductively coupled plasma mass spectrometry (ICP-MS).

[0023] The coating portion 20 is formed of a plurality of second ceramic particles and coats the ceramic foam 10. The average particle size of the second ceramic particles forming the coating portion 20 is smaller than the average particle size of the plurality of first ceramic particles forming the ceramic foam 10. The average particle size of the plurality of first ceramic particles forming the ceramic foam 10 and the average particle size of the second ceramic particles forming the coating portion 20 are measured by observing the cross-section formed by cutting a ceramic structure (hereinafter referred to as "resin-embedded ceramic structure") 1 impregnated with a two-component curing resin or the like. Specifically, the cross-section of the ceramic structure 1 is polished, and the average particle size of the ceramic particles is calculated using the intercept method on the image of the cross-section captured using a scanning electron microscope or the like. If the grain boundary phase is difficult to observe even after cross-sectional polishing of the cross-section, the cross-section may be treated by chemical etching or the like.

[0024] The second ceramic particles forming the coating portion 20 mainly contain cerium oxide. Here, "the second ceramic particles mainly contain cerium oxide" means that the molar concentration of cerium oxide in the second ceramic particles is 50 mol% or more. The second ceramic particles in this embodiment are doped with alkaline earth metals and rare earth elements. Calcium is an example of an alkaline earth metal doped into the second ceramic particles. Gadolinium (Gd), lanthanum (La), yttrium (Y), and the like are examples of rare earth elements doped into the second ceramic particles. In the second ceramic particles of this embodiment, the total amount of alkaline earth metal doping and rare earth element doping is between 5 mol% and 30 mol%. The identification of elements contained in the second ceramic particles and the measurement of their molar concentrations are performed using inductively coupled plasma mass spectrometry (ICP-MS), similar to the first ceramic particles.

[0025] In the ceramic structure 1 of this embodiment, the average of the porosity of the ceramic foam 10 and the porosity of the coating portion 20 is 60% to 93%. The porosity of the ceramic foam 10 is 5% to 65%. In the ceramic foam 10 of the ceramic structure 1 of this embodiment, the number of cells is 5 to 50 (5 to 50 cells / 25.4 mm). The number of cells is calculated by acquiring an image of the cross-section of the ceramic structure 1 in which the resin is embedded, setting a line segment of unit length (25.4 mm) at an arbitrary position in the acquired image, and measuring the number of pores (cells) on this line segment.

[0026] Figure 3 is a second enlarged view of the ceramic structure 1 of this embodiment. Figure 3 is an enlarged view of part A in Figure 2, and is an image of a part of the cross-section of the ceramic structure 1 taken at a magnification of 300 times.

[0027] In the ceramic structure 1 of this embodiment, the ratio of the thickness of the ceramic foam 10 to the thickness of the coating portion 20 in a cross-section passing through the ceramic foam 10 and the coating portion 20 is 0.5 or more and 4 or less. Here, the method for calculating the ratio of the thickness of the ceramic foam 10 to the thickness of the coating portion 20 will be specifically explained. First, in an image including the ceramic foam 10 and two coating portions 20a and 20b arranged so as to sandwich the ceramic foam 10, as shown in Figure 3, boundaries BLa and BLb between the ceramic foam 10 and the coating portions 20a and 20b are set.

[0028] In setting the boundaries BLa and BLb in this embodiment, first, a cross-section of the resin-embedded ceramic structure 1 is polished to create a boundary setting sample. Next, a backscattered electron image is captured of the polished surface of the boundary setting sample using a scanning electron microscope (SEM). In the backscattered electron image obtained by the SEM, the degree of unevenness on the polished surface appears as contrast in the image, making it easy to see the differences in unevenness due to differences in the particle size of the ceramic particles. Next, image processing is performed on the backscattered electron image of the polished surface to determine the portion corresponding to the ceramic foam 10 and the portions corresponding to the coatings 20a and 20b on the polished surface. In this embodiment, the image processing software ImageJ is used to perform binarization on the backscattered electron image obtained by the SEM.

[0029] Figure 4 is the first figure showing the results of image processing on a boundary setting sample. Figure 5 is the second figure showing the results of image processing on a boundary setting sample. Figures 4 and 5 show the results of image processing applied to the cross-section included in the image shown in Figure 3. In Figure 4, which shows the results of image processing focusing on the ceramic foam 10, the portion 10p corresponding to the first ceramic particles forming the ceramic foam 10 is displayed relatively black, and the portion 20p corresponding to the coating portion 20 is relatively lighter than portion 10p. In Figure 5, which shows the results of image processing focusing on the coating portion 20, the portion 20p corresponding to the coating portion 20 is displayed relatively black, and the portion 10p corresponding to the first ceramic particles forming the ceramic foam 10 is whitish compared to portion 10p. In this embodiment, the results of image processing on boundary setting samples as shown in Figures 4 and 5 are used to determine the portion of the polished surface corresponding to the ceramic foam 10 and the portions corresponding to the coatings 20a and 20b, and the boundaries BLa and BLb between the ceramic foam 10 and the coatings 20a and 20b are set. In setting the boundaries BLa and BLb, either the results of image processing focusing on the ceramic foam 10 (Figure 4) or the results of image processing focusing on the coatings 20 (Figure 5) may be used.

[0030] After setting the boundaries BLa and BLb between the ceramic foam 10 and the covering portions 20a and 20b, a virtual line VL1 is set passing through the ceramic foam 10 and the two covering portions 20a and 20b. The intersection point P1 is defined as the intersection point between the virtual line VL1 and boundary BLa, the intersection point P2 is defined as the intersection point between the virtual line VL1 and boundary BLb, and the intersection points P3 and P4 are defined as the intersection points between the virtual line VL1 and the respective outer surfaces 201a and 201b of the two covering portions 20a and 20b. For each of the intersection points P1, P2, P3, and P4 on the virtual line VL1, the distance between intersection point P1 and intersection point P2 is the thickness d10 of the ceramic foam 10, the distance between intersection point P1 and intersection point P3 is the thickness d20a of the covering portion 20a, and the distance between intersection point P2 and intersection point P4 is the thickness d20b of the covering portion 20b. The ceramic structure 1 of this embodiment satisfies the following equation (1). 0.5≦d10 / (d20a+d20b)≦4 (1)

[0031] Figure 6 is a third enlarged view of the ceramic structure of this embodiment. Figure 6 is an enlarged view of part B in Figure 3, and is an image of a part of the cross-section of the ceramic structure 1 taken at a magnification of 1000 times.

[0032] In the ceramic structure 1 of this embodiment, the coating portion 20 has multiple coating layers stacked on top of each other. As shown in Figure 6, the coating portion 20 of this embodiment has three coating layers 21, 22, and 23 stacked on top of each other. For convenience, Figure 6 shows a dashed line BL12 indicating the boundary between coating layer 21 and coating layer 22, and a dashed line BL23 indicating the boundary between coating layer 22 and coating layer 23.

[0033] In the ceramic structure 1 of this embodiment, the coating portion 20 has cracks C20. As shown in Figure 6, multiple cracks C20 are formed in the coating portion 20. Specifically, within a 100 μm length range of the boundary BLc between the ceramic foam 10 and the coating portion 20, one to twenty cracks C20 are formed in the coating portion 20 (the length of the solid line L100 shown in Figure 6 corresponds to the 100 μm length of the boundary BLc). In the image shown in Figure 6, at least four cracks C20 can be seen within a 100 μm length range of the boundary BLc. The cracks C20 are formed along a direction substantially perpendicular to the boundary BLc. Of the four visible cracks C20, crack C20a is formed continuously from the surface 201 of the coating portion 20 to the boundary BLc. In the ceramic structure 1 of this embodiment, the length (length in the direction from the surface 201 of the coating portion 20 toward the boundary BLc) of all four cracks C20 is 10 μm or more. In the ceramic structure 1 of this embodiment, each of the four cracks C20 has a width (length in the direction along the boundary BLc) of 2 μm or more and 20 μm or less.

[0034] Figure 7 is a diagram illustrating the schematic configuration of a reactor equipped with the catalyst complex of this embodiment. In this embodiment, the ceramic structure 1 becomes a catalyst complex 1a by supporting a catalyst made of metal. Examples of catalysts supported on the ceramic structure 1 include nickel (Ni), platinum (Pt), palladium (Pd), and ruthenium (Ru). The catalyst complex 1a of this embodiment is used as a catalyst in a methanation reaction that produces methane gas from carbon dioxide and hydrogen. In the methanation reactor 5 shown in Figure 7, the catalyst complex 1a is set inside the methanation reactor 5 and an electric field is applied by power supplied from an external power source 6. This makes it possible for the catalyst complex 1a to carry out the methanation reaction at a relatively low temperature.

[0035] In this embodiment, the catalyst composite 1a has a three-dimensional network structure in the ceramic foam 10 of the ceramic structure 1 on which the metal is supported, resulting in superior gas flow compared to catalysts with metal supported on a monolithic molded body. Furthermore, the first and second ceramic particles forming the ceramic structure 1 of the catalyst composite 1a each contain cerium oxide as the main component, thereby enhancing ionic conductivity and contributing to improved catalyst performance. In this embodiment, since the ceramic structure 1 on which the catalyst is supported is formed from ceramic particles with relatively high ionic conductivity and is a single molded body, the stability of the current when an electric field is applied is improved and the interfacial resistance is reduced compared to when the catalyst is in particle form. In addition, because the specific surface area of ​​the coating portion 20 on which the catalyst is supported is relatively large, the performance of the supported catalyst can be improved. Therefore, the ceramic structure 1 is suitable for use as a catalyst support for electric field application in methanation reactions. Furthermore, the technical field to which the ceramic structure for electric field application catalyst support of this embodiment is applicable is not limited to methanation reactions, but can be applied to technical fields including reaction processes using catalysts that utilize electric fields formed by the supply of electricity.

[0036] Figure 8 is a flowchart illustrating the manufacturing method of the ceramic structure 1 according to this embodiment. Next, the manufacturing method of the ceramic structure 1 according to this embodiment will be described.

[0037] In the method for manufacturing the ceramic structure 1 of this embodiment, first, an inorganic binder is added to ceria (CeO2) powder to prepare a slurry for ceramic foam (step S1). In step S1, the molar amounts of alkaline earth metals and rare earth elements doped into the first ceramic particles that form the ceramic foam 10 are adjusted. The alkaline earth metals and rare earth elements doped into the first ceramic particles can be added to the slurry as ceria powder, an inorganic binder, or an additive. The inorganic binder only needs to have enough heat resistance to maintain its function as a binder at the firing temperature in the firing process described later. A glass-based binder can be used as the inorganic binder. Using a glass-based binder allows firing at a lower temperature. However, when a glass-based binder is used, the heat resistance temperature of the resulting ceramic structure 1 tends to decrease. Therefore, when the ceramic structure 1 is to be used in a relatively high temperature range, it is desirable to use a metal oxide-based inorganic binder.

[0038] In the manufacturing method of the ceramic structure 1 of this embodiment, following step S1, a resin foam is coated using the prepared ceramic foam slurry (step S2). The resin foam used in step S2 is a porous body having a mesh structure with three-dimensionally interconnected pores, and is formed from resin material that is burned off during the firing of the ceramic foam slurry. For example, polyurethane foam can be used as the resin foam. The number of cells in the three-dimensional mesh structure of the ceramic foam 10 can be adjusted by the number of cells in the resin foam to be coated with the slurry.

[0039] In the manufacturing method of the ceramic structure 1 of this embodiment, the slurry coated on the resin foam is then fired to burn off the resin foam, thereby producing a ceramic foam 10 (step S3). The firing in step S3 is carried out at a temperature of about 1600°C, which produces a ceramic foam 10 with a three-dimensional network structure formed by first ceramic particles with relatively large particle sizes.

[0040] In the manufacturing method of the ceramic structure 1 of this embodiment, ceria powder and a solvent, such as ethanol, are mixed to prepare a slurry for the coating portion (step S4). In step S4, the molar amounts of alkaline earth metal and rare earth element to be doped into the second ceramic particles that form the coating portion 20 are adjusted. The alkaline earth metal and rare earth element to be doped into the second ceramic particles can be added to the slurry as ceria powder, an inorganic binder, or an additive. The preparation of the slurry for the coating portion may be done at the same time as the preparation of the slurry for the ceramic foam.

[0041] In the manufacturing method of the ceramic structure 1 of this embodiment, the ceramic foam 10 prepared in step S3 is then coated with a coating slurry and dried (step S5). In step S5, the coating of the ceramic foam 10 with the coating slurry is performed using, for example, a dipping method. This allows fine ceria powder to be coated onto the relatively dense ceramic foam 10. The thickness of the coating portion 20 in the ceramic structure 1 can be changed by the concentration of the coating slurry prepared in step S4 and the number of times the coating slurry is applied in step S5.

[0042] In the manufacturing method of the ceramic structure 1 of this embodiment, the ceramic foam 10 coated with the coating slurry produced in step S5 is then fired (step S6). The firing in step S6 is carried out at a relatively low temperature, causing the ceria powder contained in the coating slurry to form necking. This produces the ceramic structure 1.

[0043] In this embodiment, the catalyst composite 1a uses a ceramic structure 1 to support a metal, for example, by impregnation. Specifically, the ceramic structure 1 is immersed in a solution containing the catalyst metal, and then dried to disperse and fix the metal on the surface of the coating portion 20 of the ceramic structure 1.

[0044] As described above, the ceramic structure 1 of this embodiment has a three-dimensional network structure because the ceramic foam 10 having pores 11 is formed of a plurality of first ceramic particles, and therefore has a certain level of strength while having relatively high gas flowability. The coating portion 20 covering the ceramic foam 10 is formed of a plurality of second ceramic particles whose average particle size is smaller than the average particle size of the plurality of first ceramic particles, so the specific surface area of ​​the ceramic structure 1 can be made larger than the specific surface area of ​​the ceramic foam 10 alone. Therefore, it is possible to increase the specific surface area and improve gas flowability while having a certain level of strength.

[0045] Furthermore, according to the ceramic structure 1 of this embodiment, the presence of cracks C20 in the coating portion 20 can alleviate the stress generated in the coating portion 20. This prevents the coating portion 20 from falling off the ceramic foam 10.

[0046] Furthermore, according to the ceramic structure 1 of this embodiment, the coating portion 20 has a plurality of coating layers 21, 22, and 23 that are stacked on top of each other. As a result, even if a part of the coating layer falls off, the remaining coating layers can maintain the specific surface area of ​​the ceramic structure 1.

[0047] Furthermore, according to the ceramic structure 1 of this embodiment, in a cross-section passing through the ceramic foam 10 and the coating portion 20, the ratio of the thickness of the ceramic foam 10 to the thickness of the coating portion 20 is 0.5 or more and 4 or less. This makes it possible to increase the specific surface area of ​​the ceramic structure 1 while suppressing the increase in pressure loss due to clogging of the pores 11.

[0048] Furthermore, according to the ceramic structure 1 of this embodiment, the first ceramic particles forming the ceramic foam 10 mainly contain cerium oxide. As a result, the ionic conductivity of the ceramic foam 10 is improved, and when the ceramic structure 1 is used as a catalyst support for applying an electric field in catalytic reactions involving hydrogen ions, such as methanation reactions, the performance of the catalyst can be improved.

[0049] Furthermore, according to the ceramic structure 1 of this embodiment, the second ceramic particles forming the coating portion 20 mainly contain cerium oxide. As a result, the ionic conductivity of the coating portion 20 is improved, and when the ceramic structure 1 is used as a catalyst support for applying an electric field in catalytic reactions involving hydrogen ions, such as methanation reactions, the performance of the catalyst can be improved.

[0050] Furthermore, according to the ceramic structure 1 of this embodiment, the average porosity of the ceramic foam 10 and the porosity of the coating portion 20 is between 60% and 93%. This makes it possible to keep pressure loss relatively low.

[0051] Furthermore, according to the catalyst composite 1a of this embodiment, the catalyst is supported by a ceramic foam 10 formed of first ceramic particles with a relatively large average particle size, which has a relatively small specific surface area, and a coating portion 20 formed of second ceramic particles with a relatively small average particle size, which has a relatively large specific surface area. As a result, the catalyst composite 1a can contain a larger amount of catalyst than when the ceramic foam alone supports the catalyst, and has a structure that allows gas in contact with the catalyst to flow easily, thereby improving the performance of the catalyst.

[0052] Furthermore, the ceramic structure 1 of this embodiment can be used as a catalyst support for electric field application. As a result, the ceramic structure 1 can support a large amount of catalyst, and the gas in contact with the catalyst flows easily. Therefore, the ceramic structure 1 can easily bring out the performance of the supported catalyst.

[0053] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0054] [Example 1] In the above-described embodiment, the coating portion 20 is assumed to have a crack C20. The coating portion does not necessarily have to have a crack, but for example, if stress is generated due to thermal expansion, the stress is relieved by the crack, which can suppress the detachment of the coating portion from the ceramic foam.

[0055] [Differentiation 2] In the above-described embodiment, the coating portion 20 is assumed to have a plurality of coating layers 21, 22, and 23 that are stacked on top of each other. The coating portion may be formed from a single layer, but for example, if stress is generated due to thermal expansion, even if a part of the coating layer falls off, the remaining coating layer can maintain the specific surface area of ​​the ceramic structure.

[0056] [Difference 3] In the above-described embodiment, the ratio of the thickness of the ceramic foam 10 to the thickness of the coating portion 20 was set to 0.5 or more and 4 or less. However, the ratio of the thickness of the ceramic foam to the thickness of the coating portion is not limited to this. When the ratio of the thickness of the ceramic foam to the thickness of the coating portion is 0.5 or more and 4 or less, it is possible to balance increasing the specific surface area of ​​the ceramic structure with suppressing the increase in pressure loss due to clogging of pores.

[0057] [Differentiation Example 4] In the above-described embodiment, the first ceramic particles forming the ceramic foam 10 and the second ceramic particles forming the coating portion 20 each contain cerium oxide as the main component and are doped with alkaline earth metals and rare earth elements. The compositions of the first ceramic particles and the second ceramic particles are not limited to these.

[0058] [Difference 5] In the above embodiment, the average porosity of the ceramic foam 10 and the coating portion 20 was set to 60% or more and 93% or less, and the porosity of the ceramic foam 10 was set to 5% or more and 65% or less. Furthermore, the number of cells in the ceramic foam 10 was set to 5 or more and 50 or less (5 to 50 cells / 25.4 mm). The porosity and number of cells of the ceramic foam 10 and the coating portion 20 are not limited to these.

[0059] [Modification 6] In the above-described embodiment, the ceramic structure 1 is used as a catalyst support for electric field application in the catalyst composite 1a. The technical field to which the ceramic structure is applied is not limited thereto. It may also be applied to technical fields where a ceramic structure having a certain level of strength, a large specific surface area, and high gas flowability is applicable.

[0060] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0061] <Application Example 1> A ceramic structure, A ceramic foam having pores and formed by a plurality of first ceramic particles, A covering portion for covering the ceramic foam, comprising a covering portion formed of a plurality of second ceramic particles, The average particle size of the plurality of second ceramic particles is smaller than the average particle size of the plurality of first ceramic particles. Ceramic structure. <Application Example 2> A ceramic structure as described in Application Example 1, The covering portion is characterized by having cracks. Ceramic structure. <Application Example 3> A ceramic structure as described in Application Example 1 or Application Example 2, The covering portion is characterized by having a plurality of covering layers that are stacked on top of each other. Ceramic structure. <Application Example 4> A ceramic structure described in any one of the three application examples, In a cross-section passing through the ceramic foam and the coating portion, The ratio of the thickness of the ceramic foam to the thickness of the coating portion is characterized in that it is 0.5 or more and 4 or less. Ceramic structure. <Application Example 5> A ceramic structure according to any one example from Application Example 1 to Application Example 4, The first ceramic particle is characterized by containing cerium oxide as its main component. Ceramic structure. <Application Example 6> A ceramic structure described in any one of Application Examples 1 to 5, The second ceramic particle is characterized by containing cerium oxide as its main component. Ceramic structure. <Application Example 7> A ceramic structure described in any one of the examples from Application Example 1 to Application Example 6, The average of the porosity of the ceramic foam and the porosity of the coating is 60% or more and 93% or less. Ceramic structure. <Application Example 8> A catalyst complex, A ceramic structure described in any one of Application Examples 1 to 7, The coating portion is supported and comprises a catalyst made of metal, Catalyst complex. <Application Example 9> A catalyst support for electric field application, A ceramic structure comprising one of the examples from Application Example 1 to Application Example 7, Catalyst support for electric field application. [Explanation of Symbols]

[0062] 1…Ceramic structure (catalyst support for electric field application) 1a... Catalyst complex 10…Ceramic foam 11…Pore 20, 20a, 20b... Covered parts 21,22,23…covering layer C20... Crack

Claims

1. A ceramic structure, A ceramic foam having pores and formed by a plurality of first ceramic particles, A covering portion for covering the ceramic foam, comprising a covering portion formed of a plurality of second ceramic particles, The average particle size of the plurality of second ceramic particles is smaller than the average particle size of the plurality of first ceramic particles. Ceramic structure.

2. A ceramic structure according to claim 1, The covering portion is characterized by having cracks. Ceramic structure.

3. A ceramic structure according to claim 1 or claim 2, The covering portion is characterized by having a plurality of covering layers that are stacked on top of each other. Ceramic structure.

4. A ceramic structure according to claim 1 or claim 2, In a cross-section passing through the ceramic foam and the coating portion, The ratio of the thickness of the ceramic foam to the thickness of the coating portion is characterized in that it is 0.5 or more and 4 or less. Ceramic structure.

5. A ceramic structure according to claim 1 or claim 2, The first ceramic particle is characterized by containing cerium oxide as its main component. Ceramic structure.

6. A ceramic structure according to claim 1 or claim 2, The second ceramic particle is characterized by containing cerium oxide as its main component. Ceramic structure.

7. A ceramic structure according to claim 1 or claim 2, The average of the porosity of the ceramic foam and the porosity of the coating is 60% or more and 93% or less. Ceramic structure.

8. A catalyst complex, A ceramic structure according to claim 1 or claim 2, The coating portion is supported and comprises a catalyst made of metal, Catalyst complex.

9. A catalyst support for electric field application, A ceramic structure comprising the ceramic structure described in claim 1 or claim 2, Catalyst support for electric field application.

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