FIRING JIG AND METHOD FOR MANUFACTURING METAL-IMPREGNATED CERAMIC FIRED BODY

- NGK INSULATORS, LTD.

A firing jig for impregnating a metal into a ceramic formed body including a first mounting surface for mounting the ceramic formed body directly, or via the metal in a form of granules, or via a porous support; and a second mounting surface adjacent to the first mounting surface and for placing the metal in the form of granules, wherein the second mounting surface includes a slope that slopes downward toward the first mounting surface.

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Description
CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit of priority to Japanese Patent Application No. 2022-196609 filed on Dec. 8, 2022 with the Japanese Patent Office, the entire contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a firing jig. The present invention also relates to a method for manufacturing a metal-impregnated ceramic fired body.

BACKGROUND OF THE INVENTION

A method of manufacturing a metal-impregnated ceramic fired body by firing a ceramic formed body while impregnating it with a molten metal is known. Examples of metal-impregnated ceramic fired bodies include silicon-impregnated silicon carbide. Silicon impregnated silicon carbide is known as a material with high thermal conductivity, low thermal expansion, high strength, heat resistance, and oxidation resistance, and conventionally, it is used for applications such as heat exchangers, heat sinks, members for semiconductor devices, refractory materials, and filters for purifying exhaust gases.

Patent Literature 1 (International Publication No. 2011/145387) describes a method for manufacturing a Si—SiC composite material, characterized in that the method uses a body to be impregnated containing SiC and an impregnating metal supplying body containing Si, at least one of the body to be impregnated and the impregnating metal supplying body containing AI, and the method comprises an impregnation step of impregnating the body to be impregnated with a molten metal containing Si from the impregnating metal supplying body in an inert gas atmosphere at normal pressure and in a temperature range of 1200° C. or higher and 1600° C. or lower. Patent Literature 1 describes that, as a specific impregnation method, a press-molded impregnating metal supplying body is placed on a body to be impregnated, which is a formed body, and heat treatment is performed to melt the impregnating metal supplying body and impregnate the body to be impregnated.

Patent Literature 2 (International Publication No. 2021/171670) describes a method for manufacturing a honeycomb formed body containing Si-impregnated SiC composite material as a main component, and a method of arranging a lump containing metal Si and a honeycomb formed body so as to be in contact with each other and firing them is illustrated.

Patent Literature 3 (Japanese Patent Application Publication No. 2017-218342) describes a method for manufacturing a honeycomb structure, the method comprising a forming step for obtaining a formed body; a degreasing step of removing the organic binder contained in the formed body to obtain a degreased body; and an impregnation step of impregnating a peripheral wall and an interior of partition walls of the degreased body with metallic silicon. Patent Literature 3 describes that in the impregnation step, it is preferable to heat the degreased body in a state in which a lump of metallic silicon is in contact with the degreased body.

Patent Literature 4 (Japanese Patent Application Publication No. 2019-156683) describes the drawbacks of the manufacturing method described in Patent Literature 3 as follows. In the manufacturing method described in Patent Literature 3, the degreased body is impregnated due to the weight of the molten metallic silicon. Therefore, an amount of metallic silicon exceeding the pore volume of the degreased body may be impregnated, and the excessive metallic silicon may hang down from the outer periphery of the honeycomb structure or may bulge into the cells in the honeycomb structure. Therefore, it is difficult for this manufacturing method to ensure stable shape accuracy.

In order to overcome such drawbacks, Patent Literature 4 proposes a method for manufacturing a honeycomb structure, the method comprising an impregnation step of impregnating a honeycomb porous body with a molten metallic silicon through a porous support by heating the inside of a container to a temperature equal to or higher than a melting point of metallic silicon, in a state in which the honeycomb porous body is arranged via the porous support inside the container containing solid metallic silicon.

PRIOR ART Patent Literature

    • [Patent Literature 1] International Publication No. 2011/145387
    • [Patent Literature 2] International Publication No. 2021/171670
    • [Patent Literature 3] Japanese Patent Application Publication No. 2017-218342
    • [Patent Literature 4] Japanese Patent Application Publication No. 2019-156683

SUMMARY OF THE INVENTION

As described in Patent Literature 1 to 3, in conventional methods for manufacturing a metal-impregnated ceramic fired body, an impregnation step is carried out by heat-treating in a state in which a ceramic formed body to be impregnated and an impregnating metal supplying formed body are in contact, typically, a state in which the impregnating metal supplying formed body is placed on the ceramic formed body to be impregnated.

However, such an impregnation step requires the provision of an impregnating metal supplying formed body. For this reason, in order to adjust the impregnation amount according to the size and material of the fired body, it is necessary to change the size of the impregnating metal supplying formed body or scrape off unnecessary portions, resulting in an increase of the manufacturing cost.

On the other hand, Patent Literature 4 describes the following advantages. In the impregnation step, the honeycomb porous body is impregnated with metallic silicon based on the sucking power of the honeycomb porous body due to capillary action. Therefore, it is unlikely that metallic silicon is impregnated in an amount exceeding the pore volume of the honeycomb porous body. Accordingly, excess metallic silicon hanging down from the outer circumference and bulging into the cells in the honeycomb structure, which makes the cells narrower than the design value, are suppressed. As a result, the shape stability of the honeycomb structure is improved.

However, the bottom surface of the container illustrated in Patent Literature 4 is flat. For this reason, the solid metallic silicon in the form of powder, grains, lumps, or the like placed on the bottom surface of the container in the impregnation step is not necessarily sucked up entirely through the porous support, and it has been found that there is a problem that it remains on the bottom surface of the container after impregnation and the yield tends to decrease. Furthermore, there has also been a problem that the amount of impregnation is reduced and a metal-impregnated ceramic fired body having the desired quality cannot be stably obtained.

The present invention has been made in view of the above circumstances, and in one aspect, an object of the present invention is to provide a firing jig for impregnating a ceramic formed body with a metal, which can contribute to the reduction of manufacturing costs and contribute to the stabilization of product quality and the improvement of yield. Further, in another aspect, an object of the present invention is to provide a method for manufacturing a metal-impregnated ceramic fired body using such a firing jig.

As a result of intensive studies in order to solve the above problems, the inventors of the present invention have found that, it is advantageous to use a firing jig having a slope on a surface on which metal in the form of granules is placed such that the metal in the form of granules can easily flow toward the surface on which the ceramic formed body is placed. The present invention has been created based on this knowledge, and is exemplified as below.

Aspect 1

A firing jig for impregnating a metal into a ceramic formed body,

    • the firing jig comprising: a first mounting surface for mounting the ceramic formed body directly, or via the metal in a form of granules, or via a porous support; and a second mounting surface adjacent to the first mounting surface and for placing the metal in the form of granules,
    • wherein the second mounting surface comprises a slope that slopes downward toward the first mounting surface.

Aspect 2

The firing jig according to aspect 1, wherein the second mounting surface comprises the slope with an average gradient of 5° to 85°.

Aspect 3

The firing jig according to aspect 1 or 2, wherein the second mounting surface comprises a partition plate for controlling a direction of flow when the metal in the form of granules is melted and flows on the second mounting surface.

Aspect 4

The firing jig according to any one of aspects 1 to 3, wherein the ceramic formed body comprises a hollow portion extending from one end surface to another end surface,

    • wherein the firing jig comprises a protrusion for inserting into the hollow portion from a side of the one end surface or the other end surface, and
    • wherein the protrusion comprises the slope of the second mounting surface.

Aspect 5

The firing jig according to aspect 4, wherein the protrusion has a shape selected from any one of shapes of a cone, a deformed cone obtained by deforming part or all of a generatrix of a cone into a curve, a frustum, and a deformed frustum in which part or all of a generatrix of the frustum is deformed into a curve.

Aspect 6

The firing jig according to aspect 4 or 5, wherein a ratio of a height from a lowest point of the first mounting surface to a top of the protrusion to a height from the lowest point of the first mounting surface to a top of the ceramic formed body is 1% to 200%.

Aspect 7

The firing jig according to any one of aspects 1 to 6, comprising a wall surface erected so as to surround the first mounting surface.

Aspect 8

The firing jig according to aspect 7, comprising the second mounting surface between the wall surface and the first mounting surface.

Aspect 9

The firing jig according to aspect 7 or 8, wherein a ratio of a height from a lowest point of the first mounting surface to a top of the wall surface to a height from the lowest point of the first mounting surface to a top of the ceramic formed body is 1% to 200%.

Aspect 10

The firing jig according to any one of aspects 1 to 9, containing 80% by mass or more in total of one or more selected from carbon, silicon carbide, boron nitride, tantalum carbide, alumina, and platinum.

Aspect 11

The firing jig according to any one of aspects 1 to 10, wherein one or both of the first mounting surface and the second mounting surface comprises a coating layer containing a material that is inert to all of a material that constitutes the first mounting surface, a material that constitutes the second mounting surface, a material that constitutes the ceramic formed body, and the metal.

Aspect 12

The firing jig according to any one of aspects 1 to 11, wherein the ceramic formed body comprises a honeycomb structure portion having an outer peripheral wall and partition walls disposed on an inner peripheral side of the outer peripheral wall and partitioning a plurality of cells forming flow paths from one end surface to another end surface.

Aspect 13

The firing jig according to any one of aspects 1 to 12, wherein the ceramic formed body contains silicon carbide, and the metal in the form of granules contains metallic silicon.

Aspect 14

A method for manufacturing a metal-impregnated ceramic fired body, comprising:

    • preparing the firing jig according to any one of aspects 1 to 13;
    • placing the ceramic formed body on the first mounting surface of the firing jig directly, or via the metal in the form of granules, or via the porous support;
    • placing the metal in the form of granules on the second mounting surface of the firing jig; and
    • heating the metal at or above a melting point thereof in a state where the ceramic formed body is placed on the first mounting surface and the metal in the form of granules is placed on the second mounting surface, so that the ceramic formed body is fired while the metal is impregnated into the ceramic formed body, thereby obtaining a metal-impregnated ceramic fired body.

Aspect 15

The manufacturing method according to aspect 14, wherein the metal-impregnated ceramic fired body is a heat exchanger.

Aspect 16

The manufacturing method according to aspect 14 or 15, wherein the metal-impregnated ceramic fired body has a porosity of 30% or less.

According to an embodiment of the present invention, when a ceramic formed body is placed on the first mounting surface of a firing jig, and a metal in the form of granules as an impregnating metal supplying body is placed on the second mounting surface of the jig, the metal in the form of granules easily flows toward the first mounting surface on which the ceramic formed body is placed. For this reason, when a metal-impregnated ceramic fired body is manufactured using the firing jig, it is difficult for residues derived from the metal in the form of granules to remain on the bottom surface of the jig after the impregnation step, thereby improving the yield. Moreover, it can contribute to stably manufacturing a metal-impregnated ceramic fired body having a desired impregnation amount. Furthermore, as a result of the second mounting surface having the slope, the contact area between the ceramic formed body and the metal in the form of granules is increased in the height direction compared to a flat second mounting surface, which contributes to reducing impregnation non-uniformity. Thus, the firing jig according to one embodiment of the present invention contributes to the stabilization of product quality and the improvement of yield.

Further, when manufacturing a metal-impregnated ceramic fired body using the firing jig according to one embodiment of the present invention, metal in the form of granules is used as the impregnating metal supplying body. Therefore, not only can the work of forming the impregnating metal supplying body be omitted, but also the amount required for impregnation can be easily adjusted. In addition, since it is not necessary to stack the metal in the form of granules on the ceramic formed body to be impregnated, the height required when a large number of ceramic formed bodies are loaded on a kiln tool for firing can be reduced, and the loading efficiency is also improved. Therefore, by manufacturing a metal-impregnated ceramic fired body using the firing jig according to one embodiment of the present invention, the manufacturing cost of the metal-impregnated ceramic fired body can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic perspective view of an example of a ceramic formed body.

FIG. 2 shows a schematic perspective view of another example of a ceramic formed body.

FIG. 3 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body is placed on the first mounting surface of a firing jig according to a first embodiment of the present invention, and metal in the form of granules is placed on the second mounting surface.

FIG. 4 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body is placed on the first mounting surface of a firing jig according to a second embodiment of the present invention, and metal in the form of granules is placed on the second mounting surface.

FIG. 5A is a schematic plan view showing a state in which a ceramic formed body is placed on a first mounting surface of a firing jig according to a third embodiment of the present invention.

FIG. 5B is a schematic cross-sectional view taken along the line X-X of FIG. 5A.

FIG. 6 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body is placed on the first mounting surface of a firing jig according to a fourth embodiment of the present invention, and metal in the form of granules is placed on the second mounting surface.

FIG. 7 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body is placed on the first mounting surface of a firing jig according to a fifth embodiment of the present invention, and metal in the form of granules is placed on the second mounting surface.

FIG. 8 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body is placed on the first mounting surface of a firing jig according to a sixth embodiment of the present invention, and metal in the form of granules is placed on the second mounting surface.

FIG. 9 is a schematic side cross-sectional view of a firing jig used in Examples.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will now be described in detail with reference to the drawings. It should be understood that the present invention is not intended to be limited to the following embodiments, and any change, improvement or the like of the design may be appropriately added based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

(1. Firing Jig)

According to an embodiment of the present invention, a firing jig for impregnating a metal into a ceramic formed body comprises a first mounting surface for mounting the ceramic formed body directly, or via the metal in the form of granules, or via a porous support; and a second mounting surface adjacent to the first mounting surface and for placing the metal in the form of granules, wherein the second mounting surface comprises a slope S that slopes downward toward the first mounting surface. The slope S refers to an inclined plane with a slope of more than 0° and less than 90° with respect to a line parallel to the horizontal plane. When observing the firing jig in one side cross-section, only one slope S may be visually recognized, but it is preferable that a plurality of slopes S are visually recognized, and it is preferable to provide a plurality of them in line symmetry with the imaginary center line extending in the vertical direction as the center of symmetry.

The firing jig preferably has excellent heat resistance. Therefore, as the material of the firing jig, for example, one or more selected from carbon (graphite or the like), silicon carbide, boron nitride, tantalum carbide, alumina, and platinum is preferably contained in a total of 80% by mass or more, more preferably 90% or more, and even more preferably 95% or more.

Moreover, it is preferable that one or both of the first mounting surface and the second mounting surface is coated with coating layer containing a material that is inert to all of the material that constitutes the first mounting surface, the second mounting surface, the material that constitutes the ceramic formed body, and the metal, such as a coating layer containing, for example, boron nitride and/or tantalum carbide. Similarly, it is also preferable that the inner wall surface of the firing jig is coated with a coating layer containing a material that is inert to all of the material that constitutes the first mounting surface, the second mounting surface, the material that constitutes the ceramic formed body, and the metal, such as a coating layer containing, for example, boron nitride and/or tantalum carbide.

From the viewpoint of facilitating the flow of the metal in the form of granules toward the first mounting surface on which the ceramic formed body is placed, the average gradient θ of the slope S is preferably 5° or more, more preferably 15° or more, and even more preferably 30° or more. However, if the average gradient of the slope S is excessively increased, the space for placing the metal in the form of granules tends to become narrow, so it is desirable to adjust the gradient as appropriate within a range in which the target impregnation amount can be achieved. For example, the average gradient θ of the slope S is 85° or less, typically 45° or less. Therefore, the average gradient θ of the slope S is, for example, preferably 5° to 85°, more preferably 15° to 45°, even more preferably 30° to 45°.

The average gradient θ of one slope S visually recognized in the side cross-section of the jig as shown in FIGS. 3 to 8 refers to the angle of a line segment with respect to the line parallel to the horizontal plane when the top end and the bottom end of the slope S is connected with this line segment. Then, for example, when the average gradient θ of the slope S of the second mounting surface 210b is A° or more and B° or less, it means that the average gradient θ of any slope S measured in any side cross-section of the firing jig is A° or more and B° or less.

FIG. 1 shows a schematic perspective view of an example of a ceramic formed body 100. FIG. 2 shows a schematic perspective view of another example of the ceramic formed body 100. There are no particular restrictions on the shape of the ceramic formed body 100, but in one embodiment, the ceramic formed body 100 comprises a honeycomb structure portion 110 having an outer peripheral wall 112 and partition walls 113 disposed on the inner peripheral side of the outer peripheral wall 112 and partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116. The external shape of the ceramic formed body 100 is typically pillar-shaped.

The shape of the end surfaces of the ceramic formed body 100 is not limited, and for example, it may be a round shape such as a circular, elliptical, racetrack and elongated circular shape, a polygonal shape such as a triangular and quadrangle shape, and other irregular shapes. The ceramic formed body 100 shown in FIG. 1 has a circular end surface shape and has a cylindrical shape as a whole.

Further, as shown in FIG. 2, the ceramic formed body 100 may have a hollow portion 117 extending from one end surface 114 to the other end surface 116. The hollow portion 117 is preferably formed coaxially with the central axis in the direction in which cells 115 of honeycomb structure portion 110 extend. In this case, the ceramic formed body 100 comprises a honeycomb structure portion 110 having an outer peripheral wall 112, an inner peripheral wall 119, and partition walls 113 disposed between the outer peripheral wall 112 and the inner peripheral wall 119, the partition walls 113 partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116.

The height of the ceramic formed body 100 (the length from the one end surface to the other end surface) is not particularly limited and may be appropriately set according to the application and required performance. There is no particular limitation on the relationship between the height of the ceramic formed body 100 and the maximum diameter of each end surface (referring to the maximum length among the diameters passing through the center of gravity of each end surface of the ceramic formed body 100). Therefore, the height of the ceramic formed body 100 may be longer than the maximum diameter of each end surface, or the height of the ceramic formed body 100 may be shorter than the maximum diameter of each end surface.

The shape of the opening of the cells in the cross-section orthogonal to the direction in which the cells extend is not limited, and it is preferably quadrangle, hexagonal, octagonal, or a combination thereof. Among these, squares and hexagons are preferred. By making the shape of the opening of the cells as described above, the pressure loss when a fluid is allowed to flow through the cells 115 is reduced. In the honeycomb structure portion 110 of the ceramic formed body 100 shown in FIG. 1, most of the cell shapes in the cross-section perpendicular to the flow paths of the cells are square.

In a cross-section perpendicular to the direction in which the cells 115 extend, a plurality of cells 115 may be arranged radially. With such a configuration, the heat of the fluid flowing through the cells 115 can be efficiently transmitted to the outside of the honeycomb structure, which is advantageous when using the metal-impregnated ceramic fired body as a heat exchanger. In the honeycomb structure portion 110 of the ceramic formed body 100 shown in FIG. 2, a plurality of cells 115 are arranged radially. In a cross-section perpendicular to the direction in which the cells 115 extend, each of the plurality of cells 115 of the ceramic formed body 100 shown in FIG. 2 is partitioned by a pair of partition wall surfaces 113a extending from the center side of the honeycomb structure portion 110 toward the outer peripheral side, and the partition wall surfaces 113b on the center side and outer peripheral side connecting the pair of partition wall surfaces 113a. More specifically, each of the plurality of cells 115 of the ceramic formed body 100 shown in FIG. 2 is partitioned by a pair of linear partition wall surfaces 113a extending from the center side of the honeycomb structure portion 110 toward the outer peripheral side, and a pair of concentric arc partition wall surfaces 113b.

Cells 115 may extend through from one end surface 114 to the other end surface 116. Further, the cells 115 may be arranged such that first cells sealed on one end surface 114 and opening on the other end surface 116, and second cells opening on one end surface 114 and sealed on the other end surface 116, are alternately arranged adjacent to each other with the partition walls 113 interposed therebetween.

The material of the ceramic formed body 100 is not particularly limited as long as it is ceramics. However, when using the metal-impregnated ceramic fired body as a heat exchanger, filter or catalyst carrier, it preferably comprises at least one selected from carbides such as silicon carbide, tantalum carbide and tungsten carbide, and nitrides such as silicon nitride and boron nitride, and more preferably comprises silicon carbide. The ceramic formed body 100 may contain only one type of ceramic component, or may contain two or more types in combination. The ceramic formed body 100 preferably contains 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more of silicon carbide in the ceramic component.

A method of preparing the ceramic formed body 100 having the honeycomb structure portion 110 will be described. The ceramic formed body 100 having the honeycomb structure portion 110 can be manufactured according to a known honeycomb structure manufacturing method. For example, first, a binder, a surfactant, a pore-forming material, water, etc. are added to silicon carbide powder to prepare a forming raw material. Metallic silicon powder may be added to the forming raw material as required.

Next, after kneading the obtained forming raw material to form a green body, the green body is extrusion molded to prepare an undried ceramic formed body having the honeycomb structure portion. For extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

Next, by drying the obtained undried ceramic formed body, a dried ceramic formed body having the honeycomb structure portion 110 is obtained. In the drying step, conventionally known drying methods such as hot wind drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying can be used. When sealing portions are necessary, they can be formed by forming the sealing portions at predetermined positions on both end surfaces of the dried ceramic formed body and then drying the sealing portions.

First Embodiment, Second Embodiment

FIG. 3 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body 100 is placed on the first mounting surface 210a of a firing jig 200 according to a first embodiment of the present invention, and metal 300 in the form of granules is placed on the second mounting surface 210b.

FIG. 4 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body 100 is placed on the first mounting surface 210a of a firing jig 200 according to a second embodiment of the present invention, and metal 300 in the form of granules is placed on the second mounting surface 210b.

In the first embodiment and second embodiment, the ceramic formed body 100 comprises a honeycomb structure portion 110 having an outer peripheral wall 112, an inner peripheral wall 119, and partition walls 113 disposed between the outer peripheral wall 112 and the inner peripheral wall 119, the partition walls 113 partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116. In addition, the ceramic formed body 100 has a hollow portion 117 extending from one end surface 114 to the other end surface 116 on the inner peripheral side of the inner peripheral wall 119.

The second mounting surface 210b on which the metal 300 in the form of granules is placed has a slope S that slopes downward toward the first mounting surface 210a on which the ceramic formed body 100 is placed. Therefore, when the metal 300 in the form of granules is placed on the second mounting surface 210b, it becomes easier to flow toward the first mounting surface 210a on which the ceramic formed body 100 is placed. The gradient of the slope S may change on the way or may be constant. In the first embodiment and the second embodiment, the firing jig 200 has a protrusion 230 for inserting into the hollow portion from the side of the one end surface 114 or the other end surface 116, and the protrusion 230 has a slope S of the second mounting surface 210b.

Although the shape of the protrusion 230 is not limited, and for example, it may be a shape selected from any one of shapes of a cone such as a circular cone or a polygonal pyramid (for example, a triangular pyramid, a square pyramid, a hexagonal pyramid), a deformed cone obtained by deforming part or all of a generatrix of a cone (for example, a deformed cone obtained by bending part or all of the generatrix of the cone outward or inward), a frustum such as a truncated cone or a truncated pyramid (for example, a truncated triangular pyramid, a truncated square pyramid, a truncated hexagonal pyramid), and a deformed frustum in which part or all of a generatrix of the frustum is deformed (for example, a deformed frustum in which part or all of the generatrix of the frustum is curved outward or inward). The deformed generatrix can be configured with polygonal lines, curves, and a combination of both. In the first embodiment, the protrusion 230 has a circular cone shape. In the second embodiment, the protrusion 230 has a deformed circular cone shape in which all of the generatrix of the circular cone is curved inward.

In the first and second embodiments, the ceramic formed body 100 is placed directly on the first mounting surface 210a of the firing jig 200. However, a metal 300 in the form of granules may be interposed between the first mounting surface 210 a and the ceramic formed body 100. Further, although the first mounting surface 210a is flat in the first and second embodiments, it is not necessarily required to be flat.

The ratio (h1/h2), in which h1 is the height from the lowest point of the first mounting surface 210a to the top of the protrusion 230, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 100%, even more preferably 5 to 50%, from the consideration that the higher the ratio is, the easier it is to form a steep slope, while the lower the ratio is, the lower the manufacturing cost of the jig is and the higher the loading efficiency on the kiln tool is.

The firing jig 200 according to the first embodiment and the second embodiment preferably has a wall surface 220 erected so as to surround the first mounting surface 210a, because it prevents the metal 300 in the form of granules from spilling out of the jig and prevents the ceramic formed body 100 from slipping off the jig. The height h3 from the lowest point of the first mounting surface 210a to the top of the wall surface 220 may be set appropriately, and there is no particular limitation. However, in view of the fact that it is desirable to improve the loading efficiency of the ceramic formed body 100 on the kiln tool and not to hinder the gas flow in the furnace during firing, the ratio (h3/h2), in which h3 is the height from the lowest point of the first mounting surface 210a to the top of the wall surface 220, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 100%, even more preferably 5 to 50%.

Third Embodiment

FIG. 5A shows a schematic plan view showing a state in which the ceramic formed body 100 is placed on the first mounting surface 210a of the firing jig 200 according to the third embodiment of the present invention. FIG. 5B shows a schematic cross-sectional view taken along line X-X of FIG. 5A. The firing jig 200 according to the third embodiment differs from the firing jig 200 according to the first embodiment in that the second mounting surface 210b has the partition plate 118 for controlling the direction of flow when the metal 300 in the form of granules is melted and flows on the second mounting surface 210b.

By installing the partition plate 118 on the second mounting surface 210b, it is possible to control the direction of flow when the metal 300 in the form of granules is melted and flows on the second mounting surface 210b. For example, by arranging the partition plates 118 at uniform intervals radially around the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex), it is possible to suppress flow deviation (channeling). The partition plates 118 are preferably arranged in two or more directions, more preferably in three or more directions, and even more preferably in four or more directions radially around the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex). If the number of installation directions of the partition plates 118 is increased, the uniformity of the flow when the metal 300 in the form of granules is melted and flows on the second mounting surface 210b is improved. However, usually 6 directions or less is sufficient, and typically there are 5 directions or less. Therefore, the partition plates 118 are preferably arranged in two or more and six or less directions, more preferably in three or more and five or less directions, and even more preferably in four or more and five or less directions radially around the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex). In the third embodiment, the partition plates 118 are arranged radially in four directions around the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex) at uniform intervals.

One partition plate 118 preferably extends in a direction from the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex) toward the base of the protrusion 230. In addition, it is preferable that one partition plate 118 extends over ½ or more of the length, more preferably ¾ or more of the length, and even more preferably over the entire length of the slope S in the direction from the center of gravity of the protrusion 230 in plan view (in this embodiment, the vertex) toward the base of the protrusion 230.

FIG. 5B shows an imaginary line of the upper end 310 of the metal 300 in the form of granules placed on the second mounting surface 210b. In addition, the height of the upper end 310 of the metal 300 in the form of granules from the lowest point of the first mounting surface 210a is indicated by h5. It is preferable that is the top height h4 of the partition plate 118 is at a position higher than the height h5 of the upper end 310 of the metal in the form of granules placed on the second mounting surface 210b, because the effect of suppressing flow deviation (channeling) is greater.

In addition, the description of the components designated by the same reference numerals as in the firing jig 200 according to the first embodiment has already been made.

Fourth Embodiment

FIG. 6 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body 100 is placed on the first mounting surface 210a of the firing jig 200 according to the fourth embodiment of the present invention, and the metal 300 in the form of granules is placed on the second mounting surface 210b.

In the fourth embodiment, the ceramic formed body 100 comprises a honeycomb structure portion 110 having an outer peripheral wall 112, an inner peripheral wall 119, and partition walls 113 disposed between the outer peripheral wall 112 and the inner peripheral wall 119, the partition walls 113 partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116. In addition, the ceramic formed body 100 has a hollow portion 117 extending from one end surface 114 to the other end surface 116 on the inner peripheral side of the inner peripheral wall 119.

The second mounting surface 210b on which the metal 300 in the form of granules is placed has a slope S that slopes downward toward the first mounting surface 210a on which the ceramic formed body 100 is placed. Therefore, when the metal 300 in the form of granules is placed on the second mounting surface 210b, it becomes easier to flow toward the first mounting surface 210a on which the ceramic formed body 100 is placed. The gradient of the slope S may change on the way or may be constant. In the fourth embodiment, the firing jig 200 has a protrusion 230 for inserting into the hollow portion from the side of the one end surface 114 or the other end surface 116, and the protrusion 230 constitutes the slope S of the second mounting surface 210b.

The description of the shape of the protrusion 230 is as described in the first and second embodiments. In the fourth embodiment, the protrusion 230 has a deformed frustum shape composed of a line segment whose generatrix extends vertically downward from the top of the protrusion 230, and an inclined line segment connected to said line segment and extending to the base of the protrusion 230.

In the fourth embodiment, the metal 300 in the form of granules is interposed between the first mounting surface 210a of the firing jig 200 and the ceramic formed body 100. However, the ceramic formed body 100 also may be placed directly on the first mounting surface 210a. Also, although the first mounting surface 210a is flat in the fourth embodiment, it is not necessarily required to be flat.

The ratio (h1/h2), in which h1 is the height from the lowest point of the first mounting surface 210a to the top of the protrusion 230, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 100%, even more preferably 5 to 50%, from the consideration that the higher the ratio is, the easier it is to form a steep slope, while the lower the ratio is, the lower the manufacturing cost of the jig is and the higher the loading efficiency on the kiln tool is.

Further, the firing jig 200 according to the fourth embodiment preferably has a wall surface 220 erected so as to surround the first mounting surface 210a, because it prevents the metal 300 in the form of granules from spilling out of the jig and prevents the ceramic formed body 100 from slipping off the jig. The height h3 from the lowest point of the first mounting surface 210a to the top of the wall surface 220 may be set appropriately, and there is no particular limitation. However, in view of the fact that it is desirable to improve the loading efficiency of the ceramic formed body 100 on the kiln tool and not to hinder the gas flow in the furnace during firing, the ratio (h3/h2), in which h3 is the height from the lowest point of the first mounting surface 210a to the top of the wall surface 220, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 100%, even more preferably 5 to 50%.

The firing jig 200 according to the fourth embodiment has a second mounting surface 210b having a slope S also between the wall surface 220 and the first mounting surface 210a. As a result, in the fourth embodiment, it is characterized in that the second mounting surface 210b having the slope S is arranged both inside the inner peripheral wall 119 and outside the outer peripheral wall 112 of the ceramic formed body 100. By adopting such a configuration, it is possible to obtain the advantage that variation in the amount of impregnation in the radial direction of the ceramic formed body 100 can be suppressed while suppressing the residual of the molten metal at the corners where the molten metal is likely to accumulate.

In addition, the description of the components designated by the same reference numerals as in the firing jig 200 according to the first embodiment has already been made.

Fifth Embodiment

FIG. 7 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body 100 is placed on the first mounting surface 210a of the firing jig 200 according to the fifth embodiment of the present invention, and the metal 300 in the form of granules is placed on the second mounting surface 210b.

In the fifth embodiment, the ceramic formed body 100 has a cylindrical outer shape, and comprises a honeycomb structure portion 110 having an outer peripheral wall 112 and partition walls 113 disposed on the inner peripheral side of the outer peripheral wall 112 and partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116.

The firing jig 200 according to the fifth embodiment preferably has a wall surface 220 erected so as to surround the first mounting surface 210a, because it prevents the metal 300 in the form of granules from spilling out of the jig and prevents the ceramic formed body 100 from slipping off the jig. The height h3 from the lowest point of the first mounting surface 210a to the top of the wall surface 220 may be set appropriately, and there is no particular limitation. However, in view of the fact that it is desirable to improve the loading efficiency of the ceramic formed body 100 on the kiln tool and not to hinder the gas flow in the furnace during firing, the ratio (h3/h2), in which h3 is the height from the lowest point of the first mounting surface 210a to the top of the wall surface 220, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 100%, even more preferably 5 to 50%.

The firing jig 200 according to the fifth embodiment has a second mounting surface 210b between the wall surface 220 and the first mounting surface 210a. The second mounting surface 210b on which the metal 300 in the form of granules is placed has a slope S that slopes downward toward the first mounting surface 210a on which the ceramic formed body 100 is placed. Therefore, when the metal 300 in the form of granules is placed on the second mounting surface 210b, it becomes easier to flow toward the first mounting surface 210a on which the ceramic formed body 100 is placed. The gradient of the slope S may change on the way or may be constant.

In the fifth embodiments, the ceramic formed body 100 is placed directly on the first mounting surface 210a of the firing jig 200. However, the metal 300 in the form of granules may be interposed between the first mounting surface 210 a and the ceramic formed body 100. Further, although the first mounting surface 210a is flat in the fifth embodiments, it is not necessarily required to be flat.

In addition, the description of the components designated by the same reference numerals as in the firing jig 200 according to the first embodiment has already been made.

Sixth Embodiment

FIG. 8 is a schematic side cross-sectional view and a partially enlarged view thereof showing a state in which a ceramic formed body 100 is placed on the first mounting surface 210a of the firing jig 200 according to the sixth embodiment of the present invention, and the metal 300 in the form of granules is placed on the second mounting surface 210b.

In the sixth embodiment, the ceramic formed body 100 has a cylindrical outer shape, and comprises a honeycomb structure portion 110 having an outer peripheral wall 112 and partition walls 113 disposed on the inner peripheral side of the outer peripheral wall 112 and partitioning a plurality of cells 115 forming flow paths from one end surface 114 to the other end surface 116. In the sixth embodiment, the ceramic formed body 100 is placed on the first mounting surface 210a of the firing jig 200 with a porous support 240 interposed therebetween. Although the first mounting surface 210a is flat in the sixth embodiment, it is not necessarily required to be flat.

The firing jig 200 according to the sixth embodiment preferably has a wall surface 220 erected so as to surround the first mounting surface 210a, because it prevents the metal 300 in the form of granules from spilling out of the jig and prevents the ceramic formed body 100 from slipping off the jig. The height h3 from the lowest point of the first mounting surface 210a to the top of the wall surface 220 may be set appropriately, and there is no particular limitation. However, in view of the fact that it is desirable to improve the loading efficiency of the ceramic formed body 100 on the kiln tool and not to hinder the gas flow in the furnace during firing, the ratio (h3/h2), in which h3 is the height from the lowest point of the first mounting surface 210a to the top of the wall surface 220, and h2 is the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, is preferably 1% to 200%, more preferably 3 to 150%, even more preferably 5 to 100%.

The firing jig 200 according to the sixth embodiment has a second mounting surface 210b (second mounting surface 210b on the outer peripheral side) between the wall surface 220 and the first mounting surface 210a. Furthermore, the firing jig 200 according to the sixth embodiment may have a second mounting surface 210b (second mounting surface 210b on the inner peripheral side) surrounded by the first mounting surface 210a. The second mounting surface 210b on the inner peripheral side may have the same shape as the protrusion 230 described earlier. In the side cross-sectional view of the sixth embodiment shown in FIG. 8, it can be visually recognized that the second mounting surface 210b on the outer peripheral side has a slope S that slopes downward toward the first mounting surface 210a on the inner peripheral side, and the second mounting surface 210b on the inner peripheral side has a slope S that slopes downward toward the first mounting surface 210a on the outer peripheral side.

The second mounting surface 210b on the outer peripheral side and on the inner peripheral side on which the metal 300 in the form of granules is placed has a slope S that slopes downward toward the first mounting surface 210a on which the ceramic formed body 100 is placed via the porous support 240. Therefore, when the metal 300 in the form of granules is placed on the second mounting surface 210b, it becomes easier to flow toward the porous support 240 on which the ceramic formed body 100 is placed. The gradient of the slope S may change on the way or may be constant.

Incidentally, when the firing jig 200 according to the sixth embodiment is used, the height tends to be increased by the porous support 240 when the ceramic formed body 100 is placed thereon. Moreover, since the ceramic formed body 100 is placed on the porous support 240 and the molten metal is sucked up, the metal impregnated in the porous support 240 is wasted. Therefore, other embodiments that do not use the porous support 240 are preferable in consideration of the loading efficiency on the kiln tool and the yield.

(2. Method for Manufacturing Metal-Impregnated Ceramic Fired Body)

According to one embodiment of the present invention, a method for manufacturing a metal-impregnated ceramic fired body comprises:

    • a step 1 of preparing the firing jig 200 as described above;
    • a step 2 of placing the ceramic formed body 100 on the first mounting surface 210a of the firing jig 200 directly, or via the metal 300 in the form of granules, or via a porous support 240;
    • a step 3 of placing the metal 300 in the form of granules on the second mounting surface 210b of the firing jig 200; and
    • a step 4 of heating the metal 300 at or above a melting point thereof in a state where the ceramic formed body 100 is placed on the first mounting surface 210a and the metal 300 in the form of granules is placed on the second mounting surface 210b, so that the ceramic formed body 100 is fired while the metal 300 is impregnated into the ceramic formed body 100, thereby obtaining a metal-impregnated ceramic fired body.

<Step 1>

The firing jig 200 prepared in step 1 is as described above.

<Step 2>

The step 2 comprises placing the ceramic formed body 100 on the first mounting surface 210a of the firing jig 200 directly, or via the metal 300 in the form of granules, or via the porous support 240. This is for impregnating the ceramic formed body 100 in step 4. The ceramic formed body 100 subjected to step 2 may be the one before degreasing, the one after degreasing, or the one further fired after degreasing. However, from the viewpoint of production efficiency, energy cost, and the like, it is preferable to perform step 2 on a ceramic formed body 100 before degreasing.

Specific embodiments for placing the ceramic formed body 100 on the first mounting surface 210a of the firing jig 200 is as described in the description of the firing jig 200 with various examples illustrated. When the ceramic formed body 100 has the honeycomb structure portion 110, it is preferable to place the ceramic formed body 100 in a jig having a mounting surface so that the direction in which the cells 115 extend is parallel to the vertical direction. Further, regardless of whether or not the ceramic formed body 100 has the honeycomb structure portion 110, when it has a hollow portion 117 extending from one end surface to the other end surface, it is preferable to place the ceramic formed body 100 on the first mounting surface 210a in advance before performing step 3 so that the direction in which the hollow portion 117 extends is parallel to the vertical direction. In this state, if the metal in the form of granules is placed in the hollow portion 117, it is easy to prevent the metal in the form of granules from spilling or scattering outside the jig, so the ceramic formed body 100 can be efficiently impregnated.

<Step 3>

Step 3 comprises placing the metal 300 in the form of granules on the second mounting surface 210b of the firing jig 200. The order of steps 2 and 3 is not restricted. The step 3 may be performed after performing the step 2, or the step 3 may be performed first. The arrangement of the first mounting surface 210a and the second mounting surface 210b, the shape of the ceramic formed body 100, and the like may be taken into consideration when determining the order as appropriate.

As used herein, the term “granules” refers to powders, grains, or a mixture of both, and refers to an aggregate of particles having a volume-based median diameter (D50) of 5000 μm or less when the particle size distribution is measured by a laser diffraction method. The lower limit of the median diameter of the metal in the form of granules is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 800 μm or more. By increasing the median diameter of the metal in the form of granules, it becomes easier to suppress strong adhesion of deposit derived from the metal in the form of granules to the surface of the ceramic formed body during impregnation. Further, the upper limit of the median diameter of the metal in the form of granules is preferably 3000 μm or less, more preferably 2000 μm or less, and even more preferably 1000 μm or less. Therefore, the median diameter of the metal in the form of granules is, for example, preferably 100 to 3000 μm, more preferably 200 to 2000 μm, even more preferably 800 to 1000 μm.

In the partially enlarged view of FIG. 3, the contact point between the metal 300 in the form of granules and the inner peripheral wall 119 of the ceramic formed body 100 is schematically depicted. It can be understood that the larger the particle size of the metal 300 in the form of granules is, the greater the distance between the contact points is, and the more likely a gap is formed between the metal 300 in the form of granules and the inner peripheral wall 119 of the ceramic formed body 100. Therefore, it can be understood that by increasing the particle size of the metal 300 in the form of granules, the adhesion between the metal 300 in the form of granules and the inner peripheral wall 119 of the ceramic formed body 100 can be reduced. Therefore, by performing the step 4, which will be described later, even if excessive metal 300 in the form of granules adheres to the surface of the inner peripheral wall 119, the metal 300 in the form of granules can be easily removed. The specific particle size of the metal 300 in the form of granules is as described above.

There are no particular restrictions on the type of metal in the form of granules. However, it preferably comprises one or more selected from metallic silicon, molybdenum, tungsten, beryllium, chromium, iron, aluminum, nickel, manganese, silver, copper, vanadium, cobalt, tantalum, niobium, titanium, and magnesium, and more preferably comprises metallic silicon. The metal in the form of granules may contain only one type of metal, or may contain two or more types in combination. The metal in the form of granules may contain a single metal, or may contain an alloy. In addition, in order to increase the fluidity during weighing, prevent excessive contact between particles constituting the granules when placed, and improve removability, about 30% by mass or less of auxiliary agents may be contained in the metal in the form of granules. Desirable auxiliary agents include sugars having 20 or less carbon atoms, carbon, and the like. In particular, when the ceramic formed body contains silicon carbide, it is preferable that the metal in the form of granules contains metallic silicon. The metal in the form of granules preferably contains 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more of metallic silicon in the metal in the form of granules. Preferably, metallic silicon may be contained in an amount of 99% by mass or more.

<Step 4>

The step 4 comprises heating the metal 300 at or above a melting point thereof in a state where the ceramic formed body 100 is placed on the first mounting surface 210a and the metal 300 in the form of granules is placed on the second mounting surface 210b, so that the ceramic formed body 100 is fired while the metal 300 is impregnated into the ceramic formed body 100, thereby obtaining a metal-impregnated ceramic fired body. When the metal 300 in the form of granules is melted in the step 4, it permeates into the inside of the ceramic formed body due to capillary action. The amount of metal 300 in the form of granules may be appropriately set in consideration of the pore volume inside the ceramic formed body during firing, but it is preferably 50% or more, preferably 70% or more, and even more preferable 90% or more of the pore volume. As to the upper limit, when it is set to 120% or less, preferably 110% or less, and more preferably 105% or less, the formation of deposit after impregnation can be suppressed, and a situation in which the impregnation amount becomes excessive can be avoided.

When the ceramic formed body 100 has not been degreased, it is possible to efficiently manufacture a metal-impregnated ceramic fired body by continuously performing degreasing and firing. The firing furnace to be used is not particularly limited, but an electric furnace, a gas furnace, or the like can be used.

For the degreasing, for example, the atmosphere, temperature, and time may be appropriately set according to the type and amount of forming aids contained in the ceramic formed body, and the loading amount per kiln, but it must be at least the decomposition temperature of the forming aids. For the firing, for example, the atmosphere, temperature, and time may be appropriately set according to the type of ceramics contained in the ceramic formed body, but it must be at least the melting point of the metal in the form of granules. Assuming that the melting point of the metal for impregnation is M ° C., and the maximum temperature during heating in step 4 is T1° C., for example, it is preferable that M≤T1≤M+300, more preferably M+20≤T1≤M+200, and even more preferably M+40≤T1≤M+150. However, even within this range, the temperature should be lower than the firing temperature of the ceramics constituting the ceramic formed body. For example, when the ceramic formed body contains silicon carbide and metallic silicon is used as the metal for impregnation, the maximum temperature T1 is preferably 1420 to 1720° C., more preferably 1440 to 1620° C., and even more preferably 1460 to 1570° C. The metal in the form of granules heated to the melting point or higher melts and enters the pores in the ceramic formed body one after another due to capillary action, thereby realizing the impregnation. After heating, the metal-impregnated ceramic fired body is cooled to room temperature.

The porosity of the metal-impregnated ceramic fired body decreases as the impregnation amount increases. The porosity of the metal-impregnated ceramic fired body is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less, in order to ensure strength and thermal conductivity. The metal-impregnated ceramic fired body may have a porosity of 0%. The porosity is measured by the open porosity measurement method (Archimedes method) specified in JIS R1634:1998, but when the porosity exceeds 10%, it is measured by the mercury intrusion method in accordance with JIS R1655:2003.

When the metal-impregnated ceramic fired body has a honeycomb structure portion, the cell density (the number of cells per unit area) in the cross-section perpendicular to the direction in which the cells extend is not particularly limited, but is preferably 4 to 320 cells/cm2. By setting the cell density to 4 cells/cm2 or more, the strength of the partition walls 113, and the strength and effective GSA (geometric surface area) of the metal-impregnated ceramic fired body itself can be sufficiently ensured. Further, by setting the cell density to 320 cells/cm2 or less, it is possible to suppress an increase in pressure loss when a fluid flows through the cells. The cell density is calculated by dividing the number of cells in the honeycomb structure portion of the metal-impregnated ceramic fired body by the area of one end surface excluding the hollow portion, the outer peripheral wall and the inner peripheral wall.

The thickness of the partition walls 113 is not particularly limited, but it is preferably 0.1 to 1.0 mm, more preferably 0.2 to 0.6 mm, when the metal-impregnated ceramic fired body is used as a heat exchanger. By setting the thickness of the partition walls 113 to 0.1 mm or more, the mechanical strength of the metal-impregnated ceramic fired body can become sufficient. In addition, by setting the thickness of the partition walls 113 to 1.0 mm or less, it is possible to suppress problems such as an increase in pressure loss when a fluid is caused to flow through the cells 115 due to the decrease in the opening area, and a decrease in heat recovery efficiency due to the decrease in the contact area with the fluid.

The thicknesses of the outer peripheral wall 112 and the inner peripheral wall 119 are not particularly limited, but are preferably larger than the thickness of the partition walls 113. With such a configuration, it is possible to increase the strength of the outer peripheral wall 112 and the inner peripheral wall 119, which are likely to break (for example, cracks, fractures, or the like) due to thermal stress caused by the temperature difference between the fluids. The thicknesses of the outer peripheral wall 112 and the inner peripheral wall 119 are not particularly limited, and may be appropriately adjusted depending on the application. For example, the thickness of the outer peripheral wall 112 and the inner peripheral wall 119 is preferably 0.3 mm to 10 mm, more preferably 0.5 mm to 5 mm, and even more preferably 1 mm to 3 mm, when the metal-impregnated ceramic fired body is used for general heat exchange applications. Further, when the metal-impregnated ceramic fired body is used for heat storage applications, the outer peripheral wall 112 may have a thickness of 10 mm or more to increase the heat capacity of the outer peripheral wall 112.

Examples

The following examples are provided for a better understanding of the invention and its advantages, but are not intended to limit the scope of the invention.

(1. Preparation of Cylindrical Green Body)

Forming aids such as a binder and a pore-forming material were added to silicon carbide (SiC) powder, and water was added to obtain a forming raw material. Then, the forming raw material was kneaded by a vacuum kneader to prepare a cylindrical green body.

(2. Preparation of Ceramic Formed Body)

The obtained cylindrical green body was formed using an extruder having a predetermined die structure, and a hollow cylindrical undried ceramic formed body having a honeycomb structure portion was obtained, such that each cell shape in the cross-section perpendicular to the direction in which cells extended was partitioned by a pair of linear partition wall surfaces extending from the center side toward the outer periphery side, and a pair of concentric arc partition wall surfaces as shown in FIG. 2. This undried ceramic formed body was dried at 120° C. for 12 hours or more using a hot air dryer, and both end surfaces were cut in a predetermined amount. As a result, a required number of hollow cylindrical dried ceramic formed bodies of height 25 mm, inner diameter 66 mm, and outer diameter 86 mm were prepared for the following tests.

(3. Preparation of Firing Jig)

A carbon firing jig having the structure shown in FIG. 3 was prepared by cutting a CIP material. This firing jig had a circular shape in a plan view, and had a circular conical protrusion in the center. Further, a peripheral wall was erected on the outer peripheral portion of the firing jig. Specific dimensions are as shown in FIG. 9. Further, the mounting surface and the inner wall surface (the inner surface of the peripheral wall) of this firing jig were covered with a coating layer containing boron nitride.

The average gradient θ of the slope S was approximately 20°.

(4. Impregnation and Firing)

The dried hollow cylindrical ceramic fired body prepared above was placed concentrically on the mounting surface of the jig prepared in the above procedure so that the direction in which the hollow portion and the cells extended were parallel to the vertical direction.

The ratio (h1/h2), in which h1 was the height from the lowest point of the first mounting surface 210a to the top of the protrusion 230, and h2 was the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, was 10/25=40%.

The ratio (h3/h2), in which h3 was the height from the lowest point of the first mounting surface 210a to the top of the wall surface 220, and h2 was the height from the lowest point of the first mounting surface 210a to the top of the ceramic formed body 100, was 4/25=16%.

Next, metallic silicon powder having a median diameter (D50) of 200 μm was placed in the hollow portion of the hollow cylindrical ceramic formed body placed on the jig. The median diameter (D50) of the metallic silicon powder was measured with a laser diffraction particle size distribution analyzer (model LA960) manufactured by HORIBA. The mass of the metallic silicon powder placed was 50 parts by mass when the mass of the ceramic formed body was 100 parts by mass.

Next, the hollow cylindrical ceramic formed body placed on the jig was put into a firing furnace and degreased under the heating conditions of 600° ° C. for 24 hours in a nitrogen atmosphere. After degreasing, the temperature was raised without cooling, and impregnation and firing were performed under the heating conditions of 1500° C.×2 hours in an argon atmosphere. After firing, the Si-impregnated silicon carbide fired body was cooled to room temperature and taken out from the firing furnace.

The obtained Si-impregnated silicon carbide fired body had the following specifications.

    • Overall shape: hollow cylindrical shape with a height of 25 mm, an inner diameter of 66 mm, and an outer diameter of 86 mm
    • Peripheral wall thickness: 2 mm
    • Inner peripheral wall thickness: 2 mm
    • Cell density: 56 cells/cm2
    • Partition wall thickness: 0.3 mm
    • Porosity: 5%

The weight of the residue derived from metallic silicon remaining on the mounting surface of the jig after firing was investigated, and the weight ratio to the metallic silicon powder placed in the hollow portion before firing was calculated.

Furthermore, the above test was performed three times under the same conditions, and the weight ratio of the residue derived from the metallic silicon remaining on the mounting surface of the jig after firing to the metallic silicon powder arranged in the hollow portion before firing was calculated. When the average value of the weight ratios thus calculated was calculated, it was 0.3%. The minimum weight ratio was 0% and the maximum weight ratio was 1%.

Comparative Example

Using a firing jig having the same structure as in the above working example except that the circular conical protrusion was flattened, a test was conducted in which 10 hollow cylindrical ceramic formed bodies were fired under the same conditions as in the above working example. For each test, the weight ratio of the residue derived from metallic silicon remaining on the mounting surface of the jig after firing to the metallic silicon powder arranged in the hollow portion before firing was calculated. When the average value of the weight ratios thus calculated was calculated, it was 79%. The minimum weight ratio was 3% and the maximum weight ratio was 90%.

From the above results, it can be understood that, when a metal-impregnated ceramic fired body is manufactured using the firing jig according to the working example, the yield is improved because the residue derived from the metal in the form of granules is less likely to remain on the bottom surface of the jig after the impregnation step. Further, it can also be understood that metal-impregnated ceramic fired bodies having a desired impregnation amount can be stably manufactured.

DESCRIPTION OF REFERENCE NUMERALS

    • 100: Ceramic formed body
    • 110: Honeycomb structure portion
    • 112: Outer peripheral wall
    • 113: Partition wall
    • 113a: Partition wall surface
    • 113b: Partition wall surface
    • 114: End surface
    • 115: Cell
    • 116: End surface
    • 117: Hollow portion
    • 118: Partition plate
    • 119: Inner peripheral wall
    • 200: Firing jig
    • 210a: First mounting surface
    • 210b: Second mounting surface
    • 220: Wall surface
    • 230: Protrusion
    • 240: Porous support
    • 300: Metal
    • 310: Upper end

Claims

1. A firing jig for impregnating a metal into a ceramic formed body,

the firing jig comprising: a first mounting surface for mounting the ceramic formed body directly, or via the metal in a form of granules, or via a porous support; and a second mounting surface adjacent to the first mounting surface and for placing the metal in the form of granules,
wherein the second mounting surface comprises a slope that slopes downward toward the first mounting surface.

2. The firing jig according to claim 1, wherein the second mounting surface comprises the slope with an average gradient of 5° to 85°.

3. The firing jig according to claim 1, wherein the second mounting surface comprises a partition plate for controlling a direction of flow when the metal in the form of granules is melted and flows on the second mounting surface.

4. The firing jig according to claim 1, wherein the ceramic formed body comprises a hollow portion extending from one end surface to another end surface,

wherein the firing jig comprises a protrusion for inserting into the hollow portion from a side of the one end surface or the other end surface, and
wherein the protrusion comprises the slope of the second mounting surface.

5. The firing jig according to claim 4, wherein the protrusion has a shape selected from any one of shapes of a cone, a deformed cone obtained by deforming part or all of a generatrix of the cone into a curve, a frustum, and a deformed frustum in which part or all of a generatrix of the frustum is deformed into a curve.

6. The firing jig according to claim 4, wherein a ratio of a height from a lowest point of the first mounting surface to a top of the protrusion to a height from the lowest point of the first mounting surface to a top of the ceramic formed body is 1% to 200%.

7. The firing jig according to claim 1, comprising a wall surface erected so as to surround the first mounting surface.

8. The firing jig according to claim 7, comprising the second mounting surface between the wall surface and the first mounting surface.

9. The firing jig according to claim 7, wherein a ratio of a height from a lowest point of the first mounting surface to a top of the wall surface to a height from the lowest point of the first mounting surface to a top of the ceramic formed body is 1% to 200%.

10. The firing jig according to claim 1, containing 80% by mass or more in total of one or more selected from carbon, silicon carbide, boron nitride, tantalum carbide, alumina, and platinum.

11. The firing jig according to claim 1, wherein one or both of the first mounting surface and the second mounting surface comprises a coating layer containing a material that is inert to all of a material that constitutes the first mounting surface, a material that constitutes the second mounting surface, a material that constitutes the ceramic formed body, and the metal.

12. The firing jig according to claim 1, wherein the ceramic formed body comprises a honeycomb structure portion having an outer peripheral wall and partition walls disposed on an inner peripheral side of the outer peripheral wall and partitioning a plurality of cells forming flow paths from one end surface to another end surface.

13. The firing jig according to claim 1, wherein the ceramic formed body contains silicon carbide, and the metal in the form of granules contains metallic silicon.

14. A method for manufacturing a metal-impregnated ceramic fired body, comprising:

preparing the firing jig according to claim 1;
placing the ceramic formed body on the first mounting surface of the firing jig directly, or via the metal in the form of granules, or via the porous support;
placing the metal in the form of granules on the second mounting surface of the firing jig; and
heating the metal at or above a melting point thereof in a state where the ceramic formed body is placed on the first mounting surface and the metal in the form of granules is placed on the second mounting surface, so that the ceramic formed body is fired while the metal is impregnated into the ceramic formed body, thereby obtaining a metal-impregnated ceramic fired body.

15. The manufacturing method according to claim 14, wherein the metal-impregnated ceramic fired body is a heat exchanger.

16. The manufacturing method according to claim 14, wherein the metal-impregnated ceramic fired body has a porosity of 30% or less.

Patent History
Publication number: 20240189900
Type: Application
Filed: Nov 20, 2023
Publication Date: Jun 13, 2024
Applicants: NGK INSULATORS, LTD. (Nagoya-City), NGKADREC COMPANY (Mitake-Cho)
Inventors: Sora GOTO (Komaki-Shi), Shuhei KUNO (Komaki-Shi), Hiroomi MATSUBA (Mizunami-Shi)
Application Number: 18/514,031
Classifications
International Classification: B22F 3/00 (20060101); B22F 7/08 (20060101);