Manufacturing method of ceramic with coating and firing furnace for execution of manufacturing method thereof

Abstract

To provide a manufacturing method of a ceramic with coating, capable of firing a coating material in an energy saving manner while suppressing crack formation.SOLUTION: A manufacturing method of a ceramic with coating includes the steps of: (A) preparing a ceramic applied with a coating material on at least a part of one or both of a first bottom face and a second bottom face; (B) preparing an assembly of the ceramic and a pyrogenic member with the whole body covered with a heat insulation material under a condition that at least one pyrogenic member is arranged opposed to the one or both having been applied with the coating material, of the first bottom face and the second bottom face and a heat insulation material rotates around a side face of the ceramic while coming into contact with the side face; and (C) firing the coating material applied on at least a part of the one or both of the first bottom face and the second bottom face opposed to the at least one pyrogenic member by heat evolution of the at least one pyrogenic member of the assembly.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing ceramics with a coating. The present invention also relates to a firing furnace for implementing the method for manufacturing ceramics with a coating.

Background Art

[0002] Regarding heating technology using electromagnetic waves, the following prior art documents exist.

[0003] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2020-053118) discloses a heating method in which a heating element including a heat-generating material containing carbon that absorbs microwaves and generates heat, and a container that transmits microwaves and houses the heat-generating material is irradiated with microwaves. The method measures the temperature of the heating element, raises the temperature of the heating element at a heating rate of 30 (°C / sec) or more, adjusts the temperature of the heating element to a target temperature, and irradiates the heating element with microwaves based on the measured temperature so as to maintain the temperature of the heating element at the target temperature. According to this heating method, the heating element can be heated to a desired temperature in a short time, and the object to be heated can be heated.

[0004] Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2006-024502) aims to provide a microwave heating element that can be used at high temperatures. It describes a manufacturing method of a microwave heating element, which includes applying a coating liquid obtained by kneading one or more ceramic powders selected from the group consisting of graphite, carbon black, silicon carbide (SiC), titanium carbide (TiC), zirconium carbide (ZrC), tungsten carbide (WC), calcium oxide (CaO), CaO·6Al 2 O 3 , zirconium boride (ZrB 2 ), titanium boride (TiB 2 ), molybdenum boride (MoB), and calcium fluoride (CaF 2 ) and one or more selected from the group consisting of SiO 2 sol, water glass, and metal alkoxide onto a ceramic substrate to form a heat-generating layer on the substrate.

[0005] Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2011-025313) describes a method for joining materials in which materials of the same type or different types are joined by heating the vicinity of the joint surface by electromagnetic wave irradiation. In this method, a self-heating material having electromagnetic wave absorption characteristics greater than those of the material to be joined is disposed in the vicinity of the joint surface, and the vicinity of the joint surface is heated by the self-heating material. The self-heating material is in a state of an aggregate of solid-phase powder particles or massive bodies in its arrangement, and the entire aggregate state has fluidity. According to this joining method, by using a self-heating body having high electromagnetic wave absorption efficiency and fluidity and disposing the self-heating body in the vicinity of the joint surface, it is possible to locally heat the joint surface of the material to be joined, and it is said that energy-saving, highly efficient, and highly reliable joining can be performed in a short time.

[0006] Patent Document 4 (International Publication No. 2016 / 021173) describes an invention related to a microwave composite heating furnace for heating an object to be heated by using a combination of microwave and external heating such as a burner. This microwave composite heating furnace includes a housing made of a heat insulating material, a heating container disposed inside the housing for accommodating and heating the object to be heated, a microwave irradiation device that generates microwaves by a microwave generating device and irradiates the object to be heated accommodated in the heating container with microwaves without passing through the outer wall of the heating container by microwave transmission means for transmitting the microwaves, and a heating means for heating the heating container from the outside. The heating container is formed mainly of a carbon-based material having conductivity, is formed so as to be able to reflect microwaves inside, and is configured to be able to heat the object to be heated by microwaves and the heating means.

[0007] Patent Document 5 (Japanese Patent Application Laid-Open No. 2023-095923) describes an invention aimed at providing a microwave processing apparatus or the like that can appropriately process an object to be processed using microwaves. Specifically, it includes a container in which the object to be processed moves, microwave irradiation means having an irradiation unit that irradiates microwaves into the container, a heat generating member that is partially provided in the container so as to cover the object to be processed along the movement path of the object to be processed and is not provided in other parts along the movement path, and that absorbs the microwaves irradiated from the microwave irradiation means and generates heat. The microwave processing apparatus is configured such that the microwave irradiation means irradiates microwaves to the part of the movement path where the heat generating member is provided to heat the heat generating member, and irradiates microwaves to the part of the movement path where the heat generating member is not provided to heat the object to be processed.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] Some ceramic products are partially coated. As a method for forming the coating, for example, there is a method of applying a coating material to a predetermined surface of the ceramic and then firing it. In this case, it was common to put the ceramic coated with the coating material into a heating furnace and heat the entire ceramic to fire the coating material. However, in this method, although only the coating material needs to be fired at the location where firing is required, the entire ceramic is heated, so long-time firing is required, and there is a problem that the power consumption increases. In addition, if the temperature of the entire ceramic is rapidly increased to improve production efficiency, the temperature difference between the inside and the vicinity of the surface of the ceramic becomes large, stress due to the thermal expansion difference is generated, and there is a problem that cracking is likely to occur. Patent Documents 1 to 5 do not describe a heating method for partially providing a coating on the surface of the ceramic and cannot provide a method for solving the problem.

[0010] The present invention has been created in view of the above circumstances, and in one embodiment, an object is to provide a method for manufacturing a coated ceramic that enables the coating material to be fired with energy savings while suppressing the occurrence of cracks. Further, in another embodiment of the present invention, an object is to provide a firing furnace suitable for carrying out such a manufacturing method.

Means for Solving the Problems

[0011] The present inventor has intensively studied to solve the above problems and completed the present invention exemplified below. [1] Step A of preparing a columnar ceramic having a first bottom surface, a second bottom surface, and a side surface, wherein a coating material is applied to at least a part of one or both of the first bottom surface and the second bottom surface; Step B of preparing an assembly in which at least one heat-generating member is disposed so as to face one or both of the first bottom surface and the second bottom surface on which the coating material is applied, and the heat insulating material covers the entire ceramics and the heat-generating member on the condition that the heat insulating material circulates along the side surface while contacting the side surface; Step C of firing the coating material applied to at least a part of one or both of the first bottom surface and the second bottom surface facing the at least one heat-generating member by generating heat in the at least one heat-generating member of the assembly; A method for manufacturing a coated ceramic including the above. [2] The method for manufacturing according to Mode 1, wherein the ceramics prepared in Step A further has a coating material applied to at least a part of one or both of the portion near the first bottom surface of the side surface and the portion near the second bottom surface of the side surface. [3] The method for manufacturing according to Mode 2, wherein the heat insulating material in the assembly prepared in Step B does not contact the portion of the side surface where the coating material is applied, among the portion near the first bottom surface of the side surface and the portion near the second bottom surface of the side surface. [4] The method for manufacturing according to any one of Modes 1 to 3, wherein the heat insulating material in the assembly prepared in Step B contacts a portion of 60% or more of the total area of the side surface. [5] The method for manufacturing according to any one of Modes 1 to 4, wherein the at least one heat-generating member in the assembly prepared in Step B faces one or both of the first bottom surface and the second bottom surface on which the coating material is applied and has parallel surfaces. [6] The method for manufacturing according to any one of Modes 1 to 4, wherein the at least one heat-generating member in the assembly prepared in Step B has a surface facing the entire surface of one or both of the first bottom surface and the second bottom surface on which the coating material is applied. [7] In the assembly prepared in Project B, the at least one heat-generating member has a surface facing one or both entire surfaces of the first bottom surface and the second bottom surface on which the coating material is applied, and also has a surface facing the portion of the first bottom surface vicinity and the second bottom surface vicinity of the side surface on which the coating material is applied. The manufacturing method according to any one of Embodiment 2 or Embodiments 3 to 6 subordinate to Embodiment 2. [8] The heat-generating member contains a material that absorbs microwaves, and Step C includes irradiating the heat-generating member with microwaves. The manufacturing method according to any one of Embodiments 1 to 7. [9] When the length from the first bottom surface to the second bottom surface is H and the equivalent circle diameter of the first bottom surface and the second bottom surface is D, 1.0 ≤ H / D holds. The manufacturing method according to any one of Embodiments 1 to 8.

[10] The ceramics have a plurality of flow paths extending from the first bottom surface to the second bottom surface. The manufacturing method according to any one of Embodiments 1 to 9.

[11] A firing furnace for implementing the manufacturing method according to any one of Embodiments 1 to 10, A furnace body having a space for accommodating the assembly, An electric energy supply source for generating heat in the at least one heat-generating member in the assembly, A firing furnace comprising

[12] The firing furnace according to Embodiment 11, comprising a microwave oscillator as the electric energy supply source.

Advantages of the Invention

[0012] By implementing the manufacturing method of the coated ceramics according to one embodiment of the present invention, it becomes possible to bake the coating material partially applied to one or both bottom surfaces of the ceramics with energy savings while suppressing the generation of cracks.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and modifications, improvements, etc. may be appropriately added to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention, and such modifications and improvements also fall within the scope of the present invention.

[0015] [1. Manufacturing Method of Coated Ceramics] The manufacturing method of coated ceramics according to an embodiment of the present invention is as follows. Step A of preparing a columnar ceramic having a first bottom surface, a second bottom surface, and a side surface, and having a coating material applied to at least a part of one or both of the first bottom surface and the second bottom surface. Step B of preparing an assembly in which at least one heat-generating member is disposed opposite to one or both of the first bottom surface and the second bottom surface on which the coating material is applied, and the entire ceramic and the heat-generating member are covered with the heat insulating material on the condition that the heat insulating material circulates around the side surface while contacting the side surface; Step C of firing the coating material applied to at least a part of one or both of the first bottom surface and the second bottom surface facing the at least one heat-generating member by generating heat in the at least one heat-generating member of the assembly; including.

[0016] <Step A> In Step A, a columnar ceramic 10 having a first bottom surface 12, a second bottom surface 13, and a side surface 14 is prepared, and a coating material 16 is applied to at least a part of one or both of the first bottom surface 12 and the second bottom surface 13 (see FIG. 1).

[0017] The shapes of the first bottom surface and the second bottom surface of the columnar ceramic are not limited, but for example, round shapes such as circular, elliptical, racetrack-shaped, and oval-shaped, polygonal shapes such as triangular and quadrangular (rectangular, square), and other irregular shapes can be used. When the first bottom surface and the second bottom surface are polygonal, the corners may be chamfered. The ceramic shown in FIG. 1 has a circular first bottom surface and a circular second bottom surface, and has a cylindrical outer shape as a whole.

[0018] Referring to FIG. 2, the columnar ceramic 10 may have one or a plurality of flow paths 15 extending from the first bottom surface 12 to the second bottom surface 13. The flow path may penetrate the inside of the ceramic from the first bottom surface to the second bottom surface to form openings at both ends, and a plugging portion may be formed at one or both ends.

[0019] The height of the columnar ceramics (the length from the first bottom surface to the second bottom surface) is not particularly limited and may be appropriately set according to the use and required performance. There is also no particular limitation on the relationship between the height of the columnar ceramics and the maximum diameter of each bottom surface (the maximum length among the diameters passing through the centroid of each bottom surface of the columnar ceramics). Therefore, the height of the columnar ceramics may be longer than the maximum diameter of each bottom surface, or the height of the columnar ceramics may be shorter than the maximum diameter of each bottom surface.

[0020] However, if the height of the columnar ceramics is denoted as H and the equivalent circular diameter of the first bottom surface and the second bottom surface (the diameter of a circle having an area equal to the area of the first bottom surface and the second bottom surface) is denoted as D, it is preferably that 1.0 ≦ H / D holds, more preferably that 3.0 ≦ H / D holds, and even more preferably that 5.0 ≦ H / D holds. This is because the coating material partially applied to one or both bottom surfaces of the columnar ceramics can enhance the effect of firing in a short time and with low power consumption while suppressing the occurrence of cracks. The upper limit of H / D is not particularly set, but usually H / D ≦ 100 holds, typically H / D ≦ 75 holds, and more typically H / D ≦ 50 holds. Therefore, in a preferred embodiment, 1.0 ≦ H / D ≦ 100 holds, in a more preferred embodiment, 3.0 ≦ H / D ≦ 75 holds, and in still another preferred embodiment, 5.0 ≦ H / D ≦ 50 holds.

[0021] The specific dimensions of the columnar ceramics may be appropriately set according to the application, and there is no particular limitation. However, from the perspective of enhancing the effect of firing in a short time and saving power while suppressing crack generation, the height H of the columnar ceramics is preferably 5 cm or more, more preferably 50 cm or more, and even more preferably 100 cm or more. The upper limit of the height H of the columnar ceramics is not particularly set, but from the perspective of ease of handling, it is preferably 250 cm or less, more preferably 200 cm or less, and even more preferably 150 cm or less. Therefore, the height H of the columnar ceramics is preferably, for example, 5 to 250 cm, more preferably 50 to 200 cm, and even more preferably 100 to 150 cm.

[0022] The material of the columnar ceramics may be appropriately selected according to the application and is not limited. For example, oxide-based ceramics such as alumina, silica, mullite, zirconia, spinel, indialite, sapphirine, corundum, titania, yttria, and cordierite, and non-oxide-based ceramics such as silicon carbide, silicon nitride, and aluminum nitride can be mentioned. Composite materials such as silicon-silicon carbide composites (e.g., Si-bonded SiC) and cordierite-silicon carbide composites may also be used. These may be used alone or in combination of two or more. The columnar ceramics may further contain one or more other components such as glass and clay minerals. The columnar ceramics may be porous or dense. Note that dense means a porosity of 5% or less. The porosity is a value measured by a mercury porosimeter.

[0023] When the columnar ceramics have one or more flow paths extending from the first bottom surface to the second bottom surface, a functional film for exerting a predetermined function may be provided on the surface of each flow path. The functional film may be porous. The predetermined function is not limited, but for example, the target gas, liquid (e.g., CO 2 , H 2 , N 2, functions such as selectively separating substances (e.g., particles such as soot, moisture) and adsorbing target substances (e.g., particles such as soot, moisture). Further, a catalyst may be supported on the surface of each flow path. Examples of the catalyst include catalysts for exhaust gas purification (oxidation catalysts, LNT catalysts, SCR catalysts, etc.), catalysts for decomposing ammonia into hydrogen, catalysts for promoting the reverse shift reaction of reducing CO 2 to CO, and FT synthesis catalysts for synthesizing hydrocarbons from carbon monoxide and hydrogen.

[0024] The method for manufacturing the columnar ceramics is not particularly limited and can be manufactured by any known method. Exemplarily, a method includes a step of kneading a raw material composition containing a desired ceramic raw material, a dispersion medium, a pore-forming material, etc. to form a clay, then extruding the clay through a predetermined die to obtain a molded body, and a step of drying and firing the molded body. When performing extrusion molding, it is also possible to form a plurality of flow paths extending from the first bottom surface to the second bottom surface by using a die having a shape corresponding to the cross-sectional shape, number, and position of the plurality of desired flow paths. A dispersant or other additives may be blended in the raw material composition as necessary.

[0025] The columnar ceramics 10 prepared in Step A has a coating material 16-1 applied to at least a part of one or both of the first bottom surface 12 and the second bottom surface 13 (see FIG. 2). The location where the coating material should be applied on one or both of the first bottom surface and the second bottom surface may be appropriately selected according to the purpose, and there is no particular limitation. For example, the coating material may be applied to the entire surface of one or both of the first bottom surface and the second bottom surface. Further, when the columnar ceramics has a flow path penetrating the inside of the ceramics from the first bottom surface to the second bottom surface, and the first bottom surface and the second bottom surface have openings forming the ends of the flow path, the coating material may be applied to the portion excluding the openings on one or both of the first bottom surface and the second bottom surface.

[0026] The coating material applied to one bottom surface may continuously extend to the vicinity of the bottom surface on the side surface. Therefore, in one embodiment, the columnar ceramic 10 prepared in step A has the coating material 16-2 further applied to at least a part of one or both of the vicinity of the first bottom surface portion and the vicinity of the second bottom surface portion of the side surface 14 (see Fig. 2). The vicinity of the first bottom surface portion (vicinity of the second bottom surface portion) of the side surface refers to, for example, a side surface portion within 1 / 5 of the height H of the columnar ceramic, typically within 1 / 10, and more typically within 1 / 20 in the height direction of the columnar ceramic from the first bottom surface (second bottom surface).

[0027] The material of the coating material may be appropriately selected according to the application, and there are no particular restrictions as long as the properties of the coating material can be changed by firing. For example, heating the coating material above the melting point to form a film, or heating the coating material at a temperature below the melting point and sintering it to form a film is included in the firing referred to here. The coating material may, by way of example, contain glass frit or the like. The glass frit can be provided in a powder form, for example, SiO 2 , ZrO 2 , Li 2 O, K 2 O, Cs 2 O, MgO, CaO, SrO, and BaO can be contained. Further, the coating material can contain a thickener, a dispersant, a metal, clay, and other additives as necessary.

[0028] The coating material may be applied as it is to at least a part of one or both of the first bottom surface and the second bottom surface. Further, the coating material may be applied in a state of being mixed with a dispersion medium to form a coating composition. Examples of the dispersion medium include, but are not limited to, water-soluble dispersion media such as water and alcohol, and water is preferred from the perspective of the working environment. There are no particular restrictions on the method of applying the coating material, and examples include methods using a spray coater, a roll coater, a dip coater, a spin coater, a screen printing machine, an inkjet coater, etc. Further, a brush coating method and a stamp method can be mentioned.

[0029] <Project B> In Project B, at least one heat-generating member 20 is arranged so as to face one or both of the first bottom surface 12 and the second bottom surface 13 on which the coating material 16 is applied, and the heat insulating material 30 is arranged while contacting the side surface 14 of the columnar ceramic 10 and surrounding the side surface 14. On the condition that, an assembly 70 in which the entire columnar ceramic 10 and the heat-generating member 20 are covered with the heat insulating material 30 is prepared (see FIGS. 1 and 2). When the coating material is applied to both the first bottom surface and the second bottom surface, it is preferable from the viewpoint of production efficiency to arrange the heat-generating member facing the first bottom surface and the heat-generating member facing the second bottom surface, respectively.

[0030] By arranging the heat-generating member so as to face one or both of the first bottom surface and the second bottom surface on which the coating material is applied, it becomes possible to locally heat the coating material. As a result, the coating material can be fired without heating the entire columnar ceramic, so that it is possible to fire in a short time and with power saving. Further, since the heat-generating member is arranged only on the first bottom surface and / or the second bottom surface, the temperature difference of the columnar ceramic mainly occurs in the height direction of the ceramic and is unlikely to occur in the direction orthogonal to the height direction. Therefore, the thermal expansion that occurs acts in the height direction and is unlikely to occur in the direction from the central axis to the side surface (outer peripheral surface). Further, since the heat insulating material surrounds the side surface while contacting the side surface of the columnar ceramic, the side surface that does not require heating is covered with the heat insulating material, so that it becomes possible to suppress thermal expansion. Furthermore, the heat insulating material can also be expected to serve as a correction type for suppressing thermal strain. Due to the above mechanism, even when the temperature is raised at a higher speed than when the entire ceramic is heated, the generation of cracks can be suppressed.

[0031] From the perspective of enhancing the effect of suppressing thermal expansion on the side surface of the columnar ceramics, it is desirable that the area ratio of the surface area of the side surface in contact with the heat insulating material is larger. Therefore, the heat insulating material in the assembly preferably contacts 60% or more of the total surface area of the side surface of the columnar ceramics, more preferably 80% or more, and even more preferably 90% or more. The area ratio of the surface area of the side surface of the columnar ceramics in contact with the heat insulating material may be 100%.

[0032] However, as described above, there may be a case where a coating material is applied to the vicinity of the first bottom surface and / or the vicinity of the second bottom surface of the side surface of the columnar ceramics. In such a case, it is preferable that the heat insulating material in the assembly does not contact the portion where the coating material is applied among the vicinity of the first bottom surface of the side surface of the columnar ceramics and the vicinity of the second bottom surface of the side surface. This is because the firing of the coating material is hindered by the heat insulating material. Therefore, when a coating material is applied to the vicinity of the first bottom surface of the side surface of the columnar ceramics and the vicinity of the second bottom surface of the side surface, the heat insulating material in the assembly preferably contacts 60% or more of the total surface area of the portion of the side surface of the columnar ceramics where the coating material is not applied, more preferably 80% or more, and even more preferably 90% or more.

[0033] There is no particular limitation on the material of the heat insulating material, but it usually contains ceramics such as silica, alumina, and calcium silicate. In addition, for example, the heat insulating material in the form of fibers or porous can be used. In particular, from the perspective of heat insulation, it is preferable to use a porous form, and from the perspective of adhesion, it is preferable to use a fibrous form.

[0034] At least one heat-generating member 20 in the assembly 70 preferably has a plane 21 that faces and is parallel to one or both of the first bottom surface 12 and the second bottom surface 13 on which the coating material 16 is applied (see FIG. 2). This is because the heat generated from the heat-generating member can be easily and evenly transmitted to the coating material, making it possible to enhance the homogeneity of the coating. A heat-generating member having such a function can have, for example, a flat outer shape, and it is preferable to arrange it such that the plate surface faces the bottom surface (the first bottom surface or the second bottom surface) of the columnar ceramics.

[0035] Further, at least one heat-generating member 20 in the assembly 70 preferably has a plane 21 that faces the entire surface of one or both of the first bottom surface 12 and the second bottom surface 13 on which the coating material 16 is applied (see FIG. 2). This is because by enhancing the uniformity of the heat history received by the coating material from the heat-generating member, the homogeneity of the coating can be enhanced. That the heat-generating member has a plane facing the entire surface of the first bottom surface (the second bottom surface) means that any normal line extending outward from the first bottom surface (the second bottom surface) has an intersection point with the heat-generating member. A heat-generating member having such a function can have, for example, a flat outer shape, and it is preferable to make the area of the plate surface equal to or larger than the area of the opposing bottom surface (the first bottom surface or the second bottom surface), and arrange it such that the plate surface faces the bottom surface (the first bottom surface or the second bottom surface) of the columnar ceramics.

[0036] The heat-generating member may be brought into contact with the coating material applied to the opposing first bottom surface (second bottom surface). However, since there is a risk of the two adhering during firing, it is preferable to leave a space. Exemplarily, the shortest distance d1 between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) is preferably 1 mm or more, and more preferably 2 mm or more. On the other hand, if the distance between the heat-generating member and the coating material is too large, the heating efficiency of the coating material will decrease. Therefore, the shortest distance d1 between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) is preferably 100 mm or less, and more preferably 50 mm or less. Accordingly, the shortest distance d1 between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) is preferably, for example, 1 to 100 mm, and more preferably 2 to 50 mm.

[0037] Furthermore, the distance between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) is preferably constant regardless of the location. Therefore, the coefficient of variation (= standard deviation ÷ arithmetic mean) of the distance between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. Note that the distance between the heat-generating member and the coating material applied to the first bottom surface (second bottom surface) means the length between the heat-generating member and the normal line extending outward from the surface of the coating material of the portion of the bottom surface where the coating material is applied.

[0038] In addition, when the coating material 16-2 is applied to the vicinity of the first bottom surface and / or the vicinity of the second bottom surface of the side surface 14 of the columnar ceramic 10, at least one heat-generating member 20 in the assembly 70 has a surface 21 facing one or both entire surfaces of the first bottom surface 12 and the second bottom surface 13 on which the coating material 16 is applied, and preferably has a surface 22 facing the portion of the vicinity of the first bottom surface and the vicinity of the second bottom surface of the side surface 14 where the coating material 16-2 is applied. More preferably, it has a surface 22 facing all the portions of the vicinity of the first bottom surface and the vicinity of the second bottom surface of the side surface 14 where the coating material 16-2 is applied (see FIG. 2). This is because by enhancing the uniformity of the heat history received by the coating material from the heat-generating member, the homogeneity of the coating can be enhanced.

[0039] The fact that the heat-generating member has a surface facing all the portions of the vicinity of the first bottom surface (vicinity of the second bottom surface) of the side surface of the columnar ceramic where the coating material is applied means that any normal line extended outward from the portion of the side surface where the coating material is applied has an intersection with the heat-generating member. A heat-generating member having such a function can have, for example, a bottomed cylindrical outer shape, and it is preferable that its bottom surface faces the bottom surface (first bottom surface or second bottom surface) of the columnar ceramic, and the inner peripheral surface of its cylindrical portion faces the vicinity of the first bottom surface (vicinity of the second bottom surface) of the side surface of the columnar ceramic.

[0040] The heat-generating member may be in contact with the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) on the side surface of the columnar ceramic. However, for the same reason as above, it is preferable to leave a space. Exemplarily, the shortest distance d2 between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) is preferably 1 mm or more, and more preferably 2 mm or more. On the other hand, if the distance between the heat-generating member and the coating material is too large, the heating efficiency of the coating material will decrease. Therefore, the shortest distance d2 between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) is preferably 100 mm or less, and more preferably 50 mm or less. Therefore, the shortest distance d2 between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) is preferably, for example, 1 to 100 mm, and more preferably 2 to 50 mm.

[0041] Furthermore, the distance between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) on the side surface of the columnar ceramic is preferably constant regardless of the location. Therefore, the coefficient of variation of the distance between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. Note that the distance between the heat-generating member and the coating material applied to the vicinity of the first bottom surface (vicinity of the second bottom surface) means the length between the heat-generating member and the normal line extending outward from the surface of the coating material of the portion where the coating material is applied on the side surface.

[0042] The material of the heat-generating member may be selected appropriately according to the method of heating the heat-generating member. The methods of heating the heat-generating member include, but are not limited to, an induction heating method in which eddy currents are passed through a conductive substance (heat-generating member) using a coil for heating, a dielectric heating method in which a dielectric (heat-generating member) is placed between electrodes and heated by applying a high-frequency voltage, an electromagnetic wave heating method in which an electromagnetic wave such as a microwave is irradiated onto a dielectric (heat-generating member) for heating, and a resistance heating method in which an electric current is passed through a metal heating element or a non-metal heating element (heat-generating member) to generate Joule heat. One of these may be used, or two or more of them may be used in combination.

[0043] Among them, the microwave heating method is preferable because the structure around the heat-generating member can be simplified. When the microwave heating method is adopted, the heat-generating member is required to contain a material that absorbs microwaves, and known substances having such properties can be used without limitation. As the material constituting the heat-generating member, for example, carbon, silicon carbide, iron oxide, etc. can be used.

[0044] <Process C> In Process C, by heating at least one heat-generating member of the assembly, the coating material applied to at least a part of one or both of the first bottom surface and the second bottom surface facing the at least one heat-generating member is baked. When the coating material is applied to both the first bottom surface and the second bottom surface, it is preferable from the viewpoint of production efficiency to arrange the heat-generating member facing the first bottom surface and the heat-generating member facing the second bottom surface respectively and heat them simultaneously.

[0045] The firing conditions may be appropriately set according to the type of the coating material, and there is no particular limitation. Exemplarily, when the coating material contains glass frit, it is usually heated to 800 °C or higher, typically heated to 900 °C or higher, and can be heated to, for example, 920 to 980 °C. Further, the heating rate of the coating material can be 100 °C / Hr or higher, can also be 300 °C / Hr or higher, can be, for example, 100 to 3000 °C / Hr, and typically can be 300 to 3000 °C / Hr. Here, the heating rate of the coating material means the rate from when the temperature of the coating material starts to rise until it first reaches the holding temperature from 25 °C.

[0046] [2. Firing Furnace] According to an embodiment of the present invention, there is provided a firing furnace suitable for implementing the above-described method for manufacturing the coated ceramics. Referring to FIG. 1, in one embodiment, the firing furnace includes a furnace body 50 having an accommodation space 54 for accommodating an assembly 70 in which the above-described ceramics 10 and the heat-generating member 20 are entirely covered with a heat insulating material 30, and an electric energy supply source 40 for generating heat in at least one heat-generating member 20 in the assembly 70. The furnace body 50 can include, for example, a furnace floor 51, an inner wall 52, and a ceiling 53.

[0047] For the specific configuration around the heat-generating member, a suitable configuration may be adopted according to the method of heating the heat-generating member. In the case of the induction heating method in which eddy currents are passed through a conductive substance (heat-generating member) using a coil to generate Joule heat, an AC power source, conducting wires, and a coil are required as the electrical energy supply source. In the case of the dielectric heating method in which a dielectric (heat-generating member) is placed between electrodes and heated by applying a high-frequency voltage, an AC power source, conducting wires, and electrodes are required as the electrical energy supply source. In the case of the electromagnetic wave heating method in which electromagnetic waves such as microwaves are irradiated onto a dielectric (heat-generating member) for heating, an electromagnetic wave oscillator such as a microwave oscillator is required as the electrical energy supply source. When irradiating microwaves, the frequency can be, for example, 0.3 to 300 GHz, and preferably 2.4 to 2.5 GHz. In the case of the resistance heating method in which an electric current is passed through a metal heating element or a non-metal heating element (heat-generating member) to generate Joule heat, a DC or AC power source and conducting wires are required as the electrical energy supply source.

[0048] Regarding the material constituting the inner wall of the furnace body, a suitable one may be appropriately selected according to the method of heating the heat-generating member. For example, when adopting the electromagnetic wave heating method, the inner wall of the furnace body is preferably composed of a metal such as stainless steel that has high conductivity and reflects electromagnetic waves such as microwaves to confine them inside. Also, instead of metal, it is also preferable to be composed of a material with high heat resistance, for example, a sintered body in which silicon carbide powder is bonded by carbon.

[0049] The firing furnace may be a continuous furnace or a batch furnace. Further, the firing furnace can have a gas inlet for introducing a gas (such as air, nitrogen, oxygen, inert gas, etc.) for adjusting the furnace atmosphere and a gas outlet for discharging the gas inside the furnace as required. Also, an openable and closable entrance such as a door or a lid of the assembly can be provided.

Example

[0050] [Test Example 1] <1-1. Preparation of Cylindrical Ceramics> The porous columnar ceramics having the following materials, outer dimensions and structures were manufactured by conventional means including the preparation of clay, extrusion molding, drying and firing. Material: A mixture of alumina and glass Outer dimensions: Φ30mm × 160mmL Multiple flow paths extending from the first bottom surface to the second bottom surface: Yes

[0051] A coating material containing glass frit and water was applied to the entire bottom surface of one side of the columnar ceramics prepared above and the portion near the bottom surface on the side surface (specifically, 30 mm in the height direction of the columnar ceramics from the bottom surface) by means of a brushing method to a thickness of about 30 μm, and then naturally dried. In this way, the required number of columnar ceramics coated with the coating material was prepared for the following tests.

[0052] <1-2. Firing of the coating material> (Comparative Examples 1-1 to 1-2) As shown in FIG. 3, a batch furnace having a housing space 54 surrounded by a furnace floor 51 (material: SS), four inner walls 52 (material: SS) and a ceiling 53 (material: SS) was prepared inside the furnace body 50. Heat insulating materials 30 containing ceramics such as silica, alumina, and calcium silicate were arranged on the furnace floor 51, the four inner walls 52, and the ceiling 53, respectively, and heaters 60 of a resistance heating method were installed on the inner surfaces of the heat insulating materials 30 arranged on the four inner walls 52 and the heat insulating materials 30 arranged on the ceiling 53. One columnar ceramic 10 coated with the coating material 16 prepared above was placed in this batch furnace, and the coating material 16 was fired at the heating rate, holding temperature, holding time, and cooling rate shown in Table 1 by heating the heater 60. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the furnace atmosphere an air atmosphere. The heating rate means the rate at which the temperature of the thermocouple installed near the center of the furnace (≒ the temperature of the coating material) first reaches the holding temperature from 25°C after the start of heating. The holding temperature means the holding temperature of the thermocouple installed near the center of the furnace (≒ the holding temperature of the coating material). The holding time means the time at the holding temperature of the thermocouple installed near the center of the furnace (≈ the holding temperature of the coating material). The temperature decrease rate means the rate from the holding temperature to the first reaching of 25°C of the temperature of the thermocouple installed near the center of the furnace (≈ the temperature of the coating material) after the start of cooling. In Comparative Examples 1-1 to 1-2, the temperature decrease rate was controlled by adjusting the heater output.

[0053] (Comparative Examples 1-3 to 1-4) As shown in FIG. 4, a batch furnace was prepared which had an accommodation space 54 surrounded by a furnace floor 51 (material: SUS), four inner walls 52 (material: SUS) and a ceiling 53 (material: SUS) inside the furnace body 50, and a microwave oscillator as an electric energy supply source 40 was installed on the ceiling 53. One cylindrical ceramic 10 coated with the above coating material 16 was accommodated in this batch furnace. At this time, the cylindrical ceramic 10 was placed on the heat insulating material 30 laid on the furnace floor 51. Further, a disk-shaped heat generating member (material: silicon carbide) 20 with a diameter of φ80 mm and a thickness of 3 mm was arranged on the bottom surface side where the coating material 16 of the ceramic 10 was applied. Specifically, a 5 mm gap (= shortest distance) was provided between the coating material 16 and the heat generating member 20 so that the plate surface of the heat generating member 20 faced the entire bottom surface where the coating material 16 was applied and the plate surface of the heat generating member 20 was parallel to the bottom surface. At this time, in order to maintain the positional relationship between the heat generating member 20 and the cylindrical ceramic 10, the outer peripheral portion of the heat generating member 20 was fitted into the recess provided in the heat insulating material 30. In this state, microwave irradiation was performed, and the coating material 16 was fired at the heating rate, holding temperature, holding time and temperature decrease rate shown in Table 1, respectively. The heating rate means the rate from 25°C to the first reaching of the holding temperature of the temperature of the thermocouple installed near the bottom surface where the coating material 16 was applied (≈ the temperature of the coating material) after the start of heating. The holding temperature means the holding temperature of the thermocouple installed near the bottom surface where the coating material 16 was applied (≈ the holding temperature of the coating material). The holding time means the holding time at the holding temperature (≈ the holding temperature of the coating material) of the thermocouple installed near the bottom surface where the coating material 16 is applied. The temperature drop rate means the rate from the holding temperature to the first reaching of 25°C of the temperature of the thermocouple (≈ the temperature of the coating material) installed near the bottom surface where the coating material 16 is applied after the start of cooling. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the atmosphere inside the furnace an air atmosphere. In Comparative Examples 1-3 to 1-4, during temperature drop, furnace cooling (natural cooling by leaving it in the furnace) was performed, and no special control was carried out for the temperature drop rate.

[0054] (Examples 1-1 to 1-3) As shown in Fig. 1, a batch furnace was prepared which had an accommodation space 54 surrounded by a furnace floor 51 (material: SUS), four inner walls 52 (material: SUS) on the sides, and a ceiling 53 (material: SUS) inside the furnace body 50, and a microwave oscillator as an electric energy supply source 40 was installed on the ceiling 53. Also, a bottomed cylindrical heat-generating member (material: silicon carbide) 20 as shown in Fig. 2 with an outer diameter of 80 mm × an inner diameter of 40 mm × a cylindrical part height of 38 mm × a cylindrical part bottom depth of 35 mm was arranged on the bottom surface 12 side where the coating material 16 of the above-mentioned cylindrical ceramics 10 was applied. Specifically, the inner bottom surface of the heat-generating member 20 was arranged to face the entire bottom surface 12 where the coating material 16 was applied with a parallel positional relationship and a 5-mm gap (= the shortest distance), and the inner peripheral surface of the cylindrical part of the heat-generating member 20 was arranged to face the side surface 14 where the coating material 16 was applied with a 5-mm gap (= the shortest distance). Next, a flexible heat insulating material (material: SiO 2 , form: fibrous) 30 was wound around the side surface 14 while being in contact with the entire side surface 14, and further, the entire ceramics 10 and the heat-generating member 20 were covered with a heat insulating material (material: SiO 2)By coating with 30, an assembly 70 composed of a columnar ceramic 10 coated with a coating material 16, a heat-generating member 20, and a heat insulating material 30 was produced. At this time, in order to maintain the positional relationship between the heat-generating member 20 and the columnar ceramic 10, the outer peripheral portion of the heat-generating member 20 was fitted into a recess provided in the heat insulating material 30. One of the assemblies 70 was accommodated in the above batch furnace, and the coating material 16 was fired at the heating rate, holding temperature, holding time, and cooling rate shown in Table 1 by irradiating microwaves. The heating rate means the rate at which the temperature of the thermocouple (≈ the temperature of the coating material) installed near the bottom surface 12 coated with the coating material 16 first reaches the holding temperature from 25°C after the start of temperature rise. The holding temperature means the holding temperature of the thermocouple (≈ the holding temperature of the coating material) installed near the bottom surface 12 coated with the coating material 16. The holding time means the holding time at the holding temperature of the thermocouple (≈ the holding temperature of the coating material) installed near the bottom surface 12 coated with the coating material 16. The cooling rate means the rate at which the temperature of the thermocouple (≈ the temperature of the coating material) installed near the bottom surface 12 coated with the coating material 16 first reaches 25°C from the holding temperature after the start of cooling. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the atmosphere in the furnace an air atmosphere. In Examples 1-1 to 1-3, during cooling, it was furnace-cooled (naturally cooled by leaving the assembly in the furnace) in the state of the assembly, and no special control was performed on the cooling rate.

[0055] [Test Example 2] [2-1. Preparation of Columnar Ceramics] A porous columnar ceramic having the following material, outer dimensions, and structure was manufactured by conventional means including the preparation of clay, extrusion molding, drying, and firing. Material: A mixture of alumina and glass Outer dimensions: Φ180 mm × 1000 mm L Multiple flow paths extending from the first bottom surface to the second bottom surface: Yes

[0056] On the entire bottom surface of one side of the columnar ceramics prepared above, and on the portion of the side surface near the bottom surface (specifically, 30 mm in the height direction of the columnar ceramics from the bottom surface), a coating material containing glass frit and water was applied with a thickness of about 30 μm by a coating method using a stamp and a brush, and then dried with warm air. In this way, the required number of ceramics coated with the coating material was prepared for the following tests.

[0057] <2-2. Firing of Coating Material> (Comparative Examples 2-1 to 2-2) As shown in FIG. 3, a batch furnace having an accommodation space 54 surrounded by a furnace floor 51 (material: SS), four inner walls 52 (material: SS), and a ceiling 53 (material: SS) inside the furnace body 50 was prepared. Heat insulating materials 30 containing ceramics such as silica, alumina, and calcium silicate were arranged on the furnace floor 51, the four inner walls 52, and the ceiling 53, respectively, and heaters 60 of a resistance heating type were installed on the inner surfaces of the heat insulating materials 30 arranged on the four inner walls 52 and the heat insulating materials 30 arranged on the ceiling 53. One columnar ceramic 10 coated with the coating material 16 prepared above was accommodated in this batch furnace, and by heating the heater 60, the coating material 16 was fired at the heating rate, holding temperature, holding time, and cooling rate shown in Table 2, respectively. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the furnace atmosphere an air atmosphere. The heating rate means the rate at which the temperature of the thermocouple installed near the center of the furnace (≒ the temperature of the coating material) first reaches the holding temperature from 25°C after the start of temperature rise. The holding temperature means the holding temperature of the thermocouple installed near the center of the furnace (≒ the holding temperature of the coating material). The holding time means the holding time at the holding temperature of the thermocouple installed near the center of the furnace (≒ the holding temperature of the coating material). The cooling rate means the rate at which the temperature of the thermocouple installed near the center of the furnace (≒ the temperature of the coating material) first reaches 25°C from the holding temperature after the start of cooling. In Comparative Examples 2-1 to 2-2, the rate of temperature decrease was controlled by adjusting the heater output.

[0058] (Comparative Examples 2-3 to 2-4) As shown in FIG. 4, a batch furnace was prepared that had an accommodation space 54 inside the furnace body 50 surrounded by a furnace floor 51 (material: SUS), four inner walls 52 (material: SUS), and a ceiling 53 (material: SUS), and a microwave oscillator as an electric energy supply source 40 was installed on the ceiling 53. One cylindrical ceramic 10 coated with the coating material 16 described above was accommodated in this batch furnace. At this time, the cylindrical ceramic 10 was placed on the heat insulating material 30 laid on the furnace floor 51. Further, a disk-shaped heat generating member (material: silicon carbide) 20 with a diameter of φ190 mm and a thickness of 3 mm was arranged on the bottom surface side of the ceramic 10 where the coating material 16 was applied. Specifically, a 5-mm gap (= shortest distance) was provided between the coating material 16 and the heat generating member 20 so that the plate surface of the heat generating member 20 faced the entire bottom surface where the coating material was applied and the plate surface of the heat generating member 20 was parallel to the bottom surface. At this time, in order to maintain the positional relationship between the heat generating member 20 and the cylindrical ceramic 10, the outer peripheral portion of the heat generating member 20 was fitted into a recess provided in the heat insulating material 30. In this state, microwave irradiation was performed, and the coating material 16 was fired at the heating rate, holding temperature, holding time, and cooling rate shown in Table 2, respectively. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the furnace atmosphere an air atmosphere. The heating rate means the rate at which the temperature of the thermocouple installed near the bottom surface where the coating material 16 is applied (≈ the temperature of the coating material) first reaches the holding temperature from 25°C after the start of temperature increase. The holding temperature means the holding temperature of the thermocouple installed near the bottom surface where the coating material 16 is applied (≈ the holding temperature of the coating material). The holding time means the holding time at the holding temperature of the thermocouple installed near the bottom surface where the coating material 16 is applied (≈ the holding temperature of the coating material). The cooling rate means the rate at which the temperature of the thermocouple (≈ the temperature of the coating material) installed near the bottom surface where the coating material 16 is applied first reaches 25°C from the holding temperature after the start of cooling. In Comparative Examples 2-3 to 2-4, during cooling, furnace cooling (natural cooling by leaving it in the furnace) was performed, and no special control was carried out on the cooling rate.

[0059] (Examples 2-1 to 2-3) As shown in Fig. 1, a batch furnace was prepared which had an accommodation space 54 surrounded by a furnace floor 51 (material: SUS), four inner walls 52 (material: SUS) on the sides, and a ceiling 53 (material: SUS) inside the furnace body 50, and a microwave oscillator as an electric energy supply source 40 was installed on the ceiling 53. Also, a bottomed cylindrical heat-generating member (material: silicon carbide) 20 with an outer diameter of 196 mm × an inner diameter of 190 mm × a cylindrical part height of 38 mm × a cylindrical part bottom depth of 35 mm as shown in Fig. 2 was arranged on the bottom surface 12 side where the coating material 16 of the above-mentioned cylindrical ceramics 10 was applied. Specifically, the inner bottom surface of the heat-generating member 20 was arranged to face the entire bottom surface 12 where the coating material 16 was applied in a parallel positional relationship with a 5-mm gap (= shortest distance), and the inner peripheral surface of the cylindrical part of the heat-generating member 20 was arranged to face the side surface 14 where the coating material 16 was applied with a 5-mm gap (= shortest distance). Next, a flexible heat insulating material (material: SiO 2 , form: fibrous) 30 was wound around the entire side surface 14 of the cylindrical ceramics 10 while being in contact with the side surface 14, and further, the entire cylindrical ceramics 10 and the heat-generating member 20 were covered with a heat insulating material (material: SiO 2 ) 30 to produce an assembly 70 composed of the cylindrical ceramics 10 with the coating material 16 applied, the heat-generating member 20, and the heat insulating material 30. At this time, in order to maintain the positional relationship between the heat-generating member 20 and the cylindrical ceramics 10, the outer peripheral portion of the heat-generating member 20 was fitted into a recess provided in the heat insulating material 30. One of the above-described assembly 70 was placed in the batch furnace, and the coating material 16 was fired at the heating rate, holding temperature, holding time, and cooling rate shown in Table 2 by irradiating microwaves. During firing, air was naturally introduced from the opening of the furnace and exhausted from the exhaust port to make the atmosphere inside the furnace an air atmosphere. The heating rate means the rate at which the temperature of the thermocouple installed near the bottom surface 12 where the coating material 16 is applied (≈ the temperature of the coating material) first reaches the holding temperature from 25°C after the start of heating. The holding temperature means the holding temperature of the thermocouple installed near the bottom surface 12 where the coating material 16 is applied (≈ the holding temperature of the coating material). The holding time means the holding time at the holding temperature of the thermocouple installed near the bottom surface 12 where the coating material 16 is applied (≈ the holding temperature of the coating material). The cooling rate means the rate at which the temperature of the thermocouple installed near the bottom surface 12 where the coating material 16 is applied (≈ the temperature of the coating material) first reaches 25°C from the holding temperature after the start of cooling. In Examples 2-1 to 2-3, during cooling, the assembly was furnace-cooled (naturally cooled by leaving the assembly in the furnace), and no special control was performed on the cooling rate.

[0060] [3. Evaluation of Power Consumption] Regarding the examples and comparative examples of Test Examples 1 and 2 above, the power consumption when firing the coating material was evaluated. The power consumption was obtained by measuring the amount of power consumed using a wattmeter placed in the power supply. The results are shown in Table 1 and Table 2.

[0061] [4. Evaluation of Cracks and Defects] Regarding the examples and comparative examples of Test Examples 1 and 2 above, the presence or absence of cracks and defects on the bottom and side surfaces of the cylindrical ceramics after firing the coating material was investigated by visual appearance inspection and SEM microstructure observation. Here, cracks refer to cracks and fissures on the coating surface, and defects refer to peeling and missing of the coating. The evaluation was performed according to the following criteria. The results are shown in Table 1 and Table 2. ○: No cracks or defects were found. ×: At least one of cracks and defects was found.

[0062]

Table 1

[0063]

Table 2

[0064] [5. Discussion] (Test Example 1) First, compare between Comparative Example 1-1, Comparative Example 1-3, and Example 1-1 with a heating rate of 100 °C / hr. For Comparative Example 1-1 where the entire ceramics was heated by resistance heating, Comparative Example 1-3 and Example 1-1 performed local heating of the coating material. However, in Comparative Example 1-3, since the entire ceramics and the exothermic member were not covered with a heat insulating material, the power consumption increased instead. On the other hand, in Example 1-1, since the entire ceramics and the exothermic member were covered with a heat insulating material, efficient firing of the coating material could be performed, and the power consumption could be reduced. The same can be said when comparing between Comparative Example 1-2, Comparative Example 1-4, and Example 1-2 with a heating rate of 300 °C / hr. Also, in Comparative Example 1-2 and Comparative Example 1-4, cracks and / or defects occurred in the coating due to the high heating rate of 300 °C / hr. However, as can be seen from the results of Example 1-3, no cracks and / or defects occurred in the coating even when the heating rate was extremely high at 3000 °C / hr. Also, as can be seen from the results of Example 1-1, Example 1-2, and Example 1-3, it can be understood that the higher the heating rate, the more the power consumption can be reduced.

[0065] (Test Example 2) In Test Example 2, a sample larger than that in Test Example 1 was used, but the same can be said as in Test Example 1.

Explanation of Symbols

[0066] 10 Cylindrical ceramics 12 First bottom surface 13 Second bottom surface 14 Side surface 15 Flow path 16 Coating material 16-1 Coating material applied to the first bottom surface (or second bottom surface) of the cylindrical ceramics 16-2 Coating material applied to the portion near the first bottom surface (or second bottom surface) of the side surface of the cylindrical ceramics 20 Heat-generating member 21 Surface of the heat-generating member facing the first bottom surface (or second bottom surface) of the cylindrical ceramics 22 Surface of the heat-generating member facing the portion near the first bottom surface (or second bottom surface) of the cylindrical ceramics 30 Heat insulating material 40 Electric energy supply source 50 Furnace body 51 Furnace floor 52 Inner wall 53 Ceiling 54 Accommodation space 60 Resistance heating type heater 70 Assembly

Claims

1. Step A of preparing a columnar ceramic having a first bottom surface, a second bottom surface, and side surfaces, wherein a coating material is applied to at least a part of one or both of the first bottom surface and the second bottom surface; Step B of preparing an assembly in which at least one heat-generating member is disposed facing one or both of the first bottom surface and the second bottom surface to which the coating material is applied, and the entire ceramic and the heat-generating member are covered with the heat insulating material on the condition that the heat insulating material circulates around the side surfaces while contacting the side surfaces; Step C of firing the coating material applied to at least a part of one or both of the first bottom surface and the second bottom surface facing the at least one heat-generating member by generating heat in the at least one heat-generating member of the assembly; A method for manufacturing a coated ceramic including the above steps.

2. The manufacturing method according to claim 1, wherein in the ceramic prepared in step A, the coating material is further applied to at least a part of one or both of the portion of the side surface near the first bottom surface and the portion of the side surface near the second bottom surface.

3. The manufacturing method according to claim 2, wherein in the heat insulating material in the assembly prepared in step B, the heat insulating material does not contact the portions of the side surface near the first bottom surface and the portion of the side surface near the second bottom surface to which the coating material is applied.

4. The manufacturing method according to claim 1 or 2, wherein in the heat insulating material in the assembly prepared in step B, the heat insulating material contacts a portion of 60% or more of the total area of the side surface.

5. The manufacturing method according to claim 1 or 2, wherein the at least one heat-generating member in the assembly prepared in step B faces one or both of the first bottom surface and the second bottom surface to which the coating material is applied and has parallel surfaces.

6. The manufacturing method according to claim 1 or 2, wherein the at least one heat-generating member in the assembly prepared in step B has a surface facing the entire surface of one or both of the first bottom surface and the second bottom surface to which the coating material is applied.

7. The manufacturing method according to claim 2 or 3, wherein the at least one heat-generating member in the assembly prepared in step B has a surface facing the entire surface of one or both of the first bottom surface and the second bottom surface to which the coating material is applied, and also has a surface facing the portion of the side surface near the first bottom surface and the portion of the side surface near the second bottom surface to which the coating material is applied.

8. The heat-generating member contains a material that absorbs microwaves, and step C includes irradiating the heat-generating member with microwaves. The manufacturing method according to claim 1 or 2.

9. The manufacturing method according to claim 1 or 2, wherein when the length from the first bottom surface to the second bottom surface is H and the equivalent diameter of the circle of the first bottom surface and the second bottom surface is D, 1.0 ≤ H / D holds.

10. The manufacturing method according to claim 1 or 2, wherein the ceramics has a plurality of flow paths extending from the first bottom surface to the second bottom surface.

11. A firing furnace for implementing the manufacturing method according to claim 1 or 2, a furnace body having a space for accommodating the assembly, and an electric energy supply source for generating heat in the at least one heat-generating member in the assembly. A firing furnace comprising the above.

12. The firing furnace according to claim 11, comprising a microwave oscillator as the electric energy supply source.

Images