Ceramic members and ceramic-metal composites

Abstract

To provide a ceramic member that suppresses cracks and fractures on a ceramic body, prevents detachment of a metal body, prevents sliding marks with the metal body from being generated on the ceramic body, and has a small thickness change and small warpage.SOLUTION: The ceramic member has a ceramic body. The ceramic body has a first surface and a second surface facing the first surface. The ceramic body also has a groove extending from the first surface to the second surface for storing a band-shaped metal body inside. The groove is spiral-shaped and is wound a plurality of times when the first surface is plan viewed. The average value of the groove width of an end portion of the first surface side is larger than the average value of the groove width of an end portion of the second surface side. In a portion of the groove, there is a narrow portion where the groove width of the end portion of the first surface side is smaller than the groove width of the end portion of the second surface side.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure relates to a ceramic member and a ceramic-metal composite used, for example, in a heating element or the like.

Background Art

[0002] Conventionally, a metal that is a heating element is often used as a composite with ceramics. Patent Document 1 describes a spiral ceramic heating element obtained by winding a resistance film such as a metal between ceramic sheets in a spiral shape and firing the same. Patent Document 2 describes that a rod-shaped ceramic heater can be obtained by forming a resistance heating element such as a metal and an external connection terminal on an insulating composition sheet having a predetermined shape, then winding the insulating composition sheet into a rod shape and performing firing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the ceramic heating elements described in Patent Document 1 and Patent Document 2, since the ceramic sheets are fired in a state of being in contact with the resistance film, the surface of the ceramic sheet in contact with the resistance film is likely to have crystals detached during firing, resulting in a decrease in insulation characteristics or the possibility of cracks occurring from the portion where the crystals have detached.

[0005] Furthermore, differences in firing shrinkage between the ceramic sheet and the resistive coating can easily cause cracks and fractures in the ceramics, peeling of the resistive coating, and the retention of friction marks (irregularities) on the ceramics. In addition, the thickness changes and warping of the ceramic sheet become larger, and the concentricity in the spiral shape deteriorates. In particular, the above problems became more pronounced when attempting to increase the thickness of the resistive coating, making it difficult to increase the thickness of the resistive coating.

[0006] The object of this disclosure is to provide a ceramic component that suppresses the occurrence of cracks and fractures in the ceramic body, prevents the metal body from detaching, prevents friction marks from forming on the ceramic body with the metal body, and exhibits minimal thickness changes and warping, as well as a ceramic-metal composite using the same. [Means for solving the problem]

[0007] To solve the above problems, the ceramic member of this disclosure has a first surface and a second surface facing the first surface, and has a ceramic body having a groove extending from the first surface toward the second surface for housing a strip-shaped metal body inside, wherein the groove is spiral-shaped when viewed from above on the first surface, winding over multiple turns, the average value of the groove width on the first surface side is greater than the average value of the groove width on the second surface side, and in a part of the groove there is a narrow portion where the groove width at the end on the first surface side is smaller than the groove width at the end on the second surface side.

[0008] The ceramic-metal composite of the present disclosure comprises the ceramic member and a metal body housed in a groove of the ceramic member. [Effects of the Invention]

[0009] According to this disclosure, the spiral grooves in the ceramic body have an average groove width on the first surface that is greater than the average groove width on the second surface. Therefore, when a strip-shaped (sheet-shaped) metal body is placed in the grooves or after it has been placed, the contact area between the side surface of the groove and the main surface of the strip-shaped metal body is reduced, thereby reducing the stress applied from the metal body to the ceramic body and reducing cracks and fractures in the ceramic body. In addition, no sliding marks are generated on the ceramic body with the metal body, and thickness changes and warping are also reduced. Furthermore, the narrow section restrains the metal body to the ceramic body, making it less likely to come loose. In this case, if the narrow section is curved, it can reduce the concentration of stress in the narrow section, which can lead to cracking or other damage. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a plan view showing the first surface of a ceramic member according to one embodiment of the present disclosure. [Figure 1B] This is a rear view showing the second surface of the ceramic member shown in Figure 1A. [Figure 2A] This is a partial cross-sectional view showing an example of a groove in a ceramic component. [Figure 2B] This is a partial cross-sectional view showing another example of a groove. [Figure 3A] This is an enlarged partial plan view showing the narrow portion of the groove in the ceramic component. [Figure 3B] This is a cross-sectional view along line XX in Figure 3A. [Figure 4A] This is an explanatory diagram showing the procedure for creating grooves in the method for manufacturing ceramic members according to the present disclosure. [Figure 4B] This is an explanatory diagram showing the procedure for creating grooves in the method for manufacturing ceramic members according to the present disclosure. [Figure 4C] This is an explanatory diagram showing the procedure for creating grooves in the method for manufacturing ceramic members according to the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, a ceramic member and a ceramic-metal composite according to one embodiment of the present disclosure will be described based on the drawings.

[0012] The ceramic member 100 of this embodiment has a ceramic body 1 having a first surface 11 (upper surface or front surface) shown in FIG. 1A and a second surface 12 (lower surface or back surface) facing the first surface shown in FIG. 1B. A spiral groove 2 extending from the first surface toward the second surface is formed in the ceramic body 1. As will be described later, a strip-shaped metal body 4 is housed in this groove 2.

[0013] Examples of the ceramics constituting the ceramic body 1 include sintered bodies of alumina, zirconia, silicon carbide, silicon nitride, aluminum nitride, mullite, steatite, cordierite, and the like. Further, as the metal body 4, for example, when used as a heating element, Ni—Cr-based, Cu—Ni-based, Fe—Cr—Al-based, MoSi2, Mo(Si,Al)2, C, SiC, W, Mo, Pt, etc. are used, and it is particularly preferable to use a metal heating element.

[0014] The groove 2 is spiral and wound over a plurality of turns when the first surface 11 is viewed in plan. The shape of the spiral may be a polygon such as an ellipse or a hexagon in addition to a circle as shown in the figure. Also, the number of turns of the spiral is not particularly limited, but it may be two or more turns, preferably four or more turns, and preferably eight or less turns. Both circumferential ends of the groove 2 may be open or closed as shown in FIGS. 1A and 1B.

[0015] Further, the ceramic body 1 preferably has a through hole 3 penetrating the central portion. This through hole 3 can be used to hold and fix the ceramic member 1 by inserting a cylinder or a cylindrical body (not shown) into the through hole. Also, a fluid can flow through the through hole 3. That is, if the metal body 4 is a heating element, the fluid can be efficiently heated.

[0016] FIG. 2A is a partial cross-sectional view showing an example of the groove 2. As shown in FIG. 2A, the groove 2 is formed such that the average value of the groove width w1 at the end on the first surface 11 side (hereinafter sometimes abbreviated as the groove width w1 on the first surface 11 side) is larger than the average value of the groove width w2 at the end on the second surface 12 side (hereinafter sometimes abbreviated as the groove width w2 on the second surface 12 side). Specifically, the groove width w1 on the first surface 11 side is preferably 1.03 times or more, more preferably 1.07 times or more, and further preferably 1.20 times or less, more preferably 1.10 times or less, in terms of the average value, with respect to the groove width w2 on the second surface 12 side. Here, the average value is obtained by measuring at least four groove widths (excluding the groove width of the narrow portion 5 described later) for each circumference of the groove 2 and summing them up.

[0017] Thus, since the groove width w1 on the first surface 11 side is larger than the groove width w2 on the second surface 12 side, when the strip-shaped (sheet-shaped) metal body 4 is stored in the groove 2 or after it is stored, the contact area between the inner wall surface 21 of the groove 2 and the main surface of the metal body 4 becomes smaller. Therefore, stress applied from the metal body 4 to the ceramic body 1 can be reduced during high-temperature atmosphere or cooling in normal-temperature atmosphere, etc., and cracks and fractures in the ceramic body 1 can be reduced. In addition, in order to reduce the contact area between the inner wall surface 21 of the groove 2 and the main surface of the metal body 4, the thickness of the metal body 4 is preferably substantially equal to the groove width w2 on the second surface 12 side.

[0018] The groove 2 shown in FIG. 2A penetrates the ceramic body 1 and opens on the second surface 12 side. However, as shown in FIG. 2B, the groove 2' may be a bottomed groove that does not penetrate the ceramic body 1. Even such a bottomed groove 2' has the same effect as the penetrating groove 2.

[0019] The inner wall surface 21 of the groove 2 is preferably a fired surface. This means that after groove processing is performed on the molded body, it is fired, as described in the manufacturing method described later. Since there are no microcracks on the fired surface, cracks and fractures are less likely to occur even if stress concentrates.

[0020] On the first surface 11, the groove width w1 of the groove 2 is preferably larger than the width w3 of the ceramic body 1 located between adjacent grooves 2, 2. This allows for a larger number of turns (windings) of the spiral groove 2, even if the ceramic body 1 is small, and increases the length of the groove 2, thereby increasing the volume ratio of the metal body 4 that can be housed within the groove 2.

[0021] Furthermore, the depth D from the end of groove 2 on the first surface 11 side to the end of groove 2 on the second surface 12 side is preferably greater than the groove width w1 on the first surface 11 side. This allows the occupancy rate of groove 2 when viewed from above to be reduced while maintaining the volume of groove 2, so that the width w1 of groove 2 can be reduced and more grooves 2 for housing the metal body 4 can be provided. Also, if the depth D of groove 2 is large, the volume ratio of the metal body 4 that is housed can be increased. The depth D, and therefore the thickness of the ceramic body 1, is not particularly limited. The ceramic body 1 may be in the form of a sheet (for example, with a thickness of 300 μm or more and 2000 μm or less), or it may be in the form of a cylinder or column.

[0022] The average value of the groove width w4 at the center of the depth D in the ceramic body 1 should be greater than the average value of the groove width w2 on the second surface 12 side and smaller than the average value of the groove width w1 on the first surface 11 side. This reduces the contact area between the inner wall surface of the groove 2 and the main surface of the strip-shaped metal body 4, thereby reducing the stress applied from the metal body 4 to the ceramic body 1 and reducing the occurrence of cracks and fractures in the ceramic body 1.

[0023] In this embodiment, as shown in Figures 3A and 3B, the ceramic member 100 has a narrow section 5 in a part of the groove 2 where the groove width w11 on the first surface 11 side is smaller than the groove width w22 on the second surface 12 side. That is, in the narrow section 5, the groove width w11 is preferably 0.7 or more and less than 1 compared to w22. Here, the groove width w11 refers to the minimum width in the narrow section 5. In this way, the presence of the narrow section 5 restrains the metal body 4 to the ceramic body 1 by the narrow section 5, making it difficult for the metal body 4 to come out of the groove 2. The part of the groove 2 in which the narrow portion 5 exists means that it exists at least one location in the circumferential direction of the spiral groove 2, preferably at least one location at each of the circumferential ends of the groove 2, and more preferably at least one location on each circumference of the groove 2.

[0024] Furthermore, the narrow section 5 should have a curved surface that follows the circumferential direction of the spiral groove 2. In other words, the narrow section 5 has a smooth curved surface. A smooth curved surface means that it is not protruding, which reduces the concentration of stress that can cause cracks and other damage.

[0025] Next, a method for manufacturing the ceramic member will be described. The method for manufacturing the ceramic member 100 in this embodiment may include the following steps (1) to (4).

[0026] (1) A molded body is obtained by kneading a ceramic material and a binder to obtain a molded body having a first surface and a second surface facing the first surface. Examples of ceramic materials include alumina, zirconia, silicon carbide, silicon nitride, aluminum nitride, mullite, steatite, and cordierite. A slurry is prepared by adding conventionally known sintering aids, dispersants, solvents (such as water), etc., to the ceramic material powder and kneading the mixture. For example, if the ceramic body 1 is a ceramic mainly composed of alumina (aluminum oxide), a slurry is prepared by mixing alumina powder with a purity of 99.6% by mass or higher and an average particle size (D50) of 1 μm to 3 μm, a binder, a lubricant, and a solvent (ion-exchanged water). The average particle size (D50) can be determined by laser diffraction particle size distribution analysis. In addition to alumina powder, at least one titanium compound, such as titanium carbide, titanium carbonitride, and titanium boride, may be included as a minor component. If the ceramic body 1 is a ceramic mainly composed of silicon carbide, a solvent (ion-exchanged water) and a dispersant are added to the silicon carbide powder, and the mixture is ground and mixed for 40 to 60 hours using a ball mill or bead mill to form a slurry. Then, to the obtained slurry, a sintering aid consisting of, for example, boron carbide powder and amorphous carbon powder or phenolic resin, and a binder are added and mixed.

[0027] Examples of binders include methylcellulose (MC), carboxymethylcellulose (CMC), hydroxypropylcellulose (HPC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB). The total amount of binder should be between 2 and 8 parts by mass of solids per 100 parts by mass of ceramic material powder.

[0028] Using the slurry described above, a molded body having a first surface and a second surface facing the first surface is formed, for example, by a casting method. Another method for forming a molded body is to produce granules by spray-drying the slurry using a spray-drying granulation method, and then mold the resulting granules using a roll compaction method. Alternatively, the granules may be used to form the molded body using a mechanical press method, a cold isostatic pressing (CIP) method, or by preparing a clay base instead of slurry.

[0029] (2) The obtained molded body is cut with a machining drill from the first surface 11 toward the second surface 12 to form spiral grooves. In this case, it is preferable to cut the groove 2 in multiple steps so that the cutting depth from the first surface 11 increases sequentially. Figures 4A to 4C show the process of forming spiral grooves 2 and 2' by cutting the molded body 6 with a machining drill 7. First, as shown in Figure 4A, the first pass is made in a spiral pattern to a depth a from the first surface 11, and the machining drill 7 is removed. Next, in the second pass, as shown in Figure 4B, the same route as the first pass is used to make a spiral cut to a depth b from the first surface, and the machining drill 7 is removed in the same manner as above. Furthermore, in the third pass, as shown in Figure 4C, the same route as the first and second passes is used to make a spiral cut to a depth c from the first surface (i.e., the thickness of the molded body 6), and the machining drill 7 is removed in the same manner as above. The same machining drill 7 is used for the first to third passes, but for the second and third passes, other drills with the same outer diameter as the drill 7 used in the first pass may be used. As machining drills, for example, micro drills made of synthetic diamond, cemented carbide, or hardened steel, or milling inserts made of the same materials can be used.

[0030] In this way, by cutting in multiple steps so that the cutting depth from the first surface 11 increases sequentially, the groove width at the end on the first surface 11 side, which the machining drill 7 passes through multiple times, becomes larger than the groove width at the end on the second surface 12 side, which the machining drill 7 passes through fewer times. In Figures 4A to 4C, reference numeral 8 denotes a sacrificial plate (raw horse chestnut portion), which is formed in the same manner as the molded body 6 using the same material, and is removed by cutting or other means after firing. Furthermore, although the groove machining was performed in three separate steps in Figures 4A to 4C, it is not limited to this, and the groove machining may be performed in two to five separate steps, taking into consideration the thickness of the ceramic body 1, etc.

[0031] To form a narrow section 5 in a part of the groove formed as described above, for example, a part of the groove 2 may be left uncut, the remaining part may be cut to form the groove, then a drill with a smaller outer diameter than the cutting drill 7 used (not shown) may be used for cutting, and then the part on the second surface 12 side may be cut with a drill with a thicker tip.

[0032] (3) After groove processing, the molded body 6 is heated to vaporize and decompose the organic binder. For example, the molded body 6 is held in a nitrogen atmosphere at a temperature of 450°C to 650°C for 2 to 10 hours to allow the organic binder to vaporize and decompose.

[0033] (4) The molded body 6 is fired at a high temperature to obtain a ceramic member 100 having spiral grooves 2. For example, if the main component of the molded body 6 is alumina, it is preferable to sinter the molded body 6 in a reduced-pressure atmosphere of an inert gas such as argon at a temperature of 1800°C to 2200°C for 0.5 hours to 5 hours. On the other hand, if the main component of the molded body 6 is silicon carbide, it is preferable to fire the molded body 6 in a reduced-pressure atmosphere of an inert gas such as argon at a temperature of 1800°C to 2200°C for 0.5 hours to 5 hours.

[0034] In the example above, machining was performed on the molded body 6, but the same machining process may be performed on the fired body in multiple steps, with the cutting depth from the first surface gradually increasing.

[0035] The ceramic-metal composite of this disclosure comprises a ceramic member 100 and a metal body 4 housed in a groove 2 of the ceramic member 100. The metal body 4 can be used, for example, as a heating element, particularly a resistance heating element, but can also be used as an induction heating coil or a medical coil. An example of an induction heating coil is described in Japanese Patent Application Publication No. 2010-20963. An example of a medical coil is described in Japanese Patent Application Publication No. 2014-83384. The metal body 4 is strip-shaped, and to house the metal body 4 in the groove 2, for example, the strip-shaped metal body 4 can be inserted sequentially from the end of the groove 2, or the strip-shaped metal body 4 can be inserted by fitting it in from the first surface 11 side. The length of the metal body 4 is preferably equal to or greater than the length of the spiral groove 2, but multiple shorter metal bodies 4 may be arranged in the circumferential direction of the groove 2. In this case, it is preferable that adjacent metal bodies 4 are arranged so that both ends are in contact.

[0036] In the above explanation, we have mainly described a ceramic member 100 having a through groove 2 as shown in Figure 2A, but the same can be applied to a ceramic member 100' having a bottomed groove 2' as shown in Figure 2B.

[0037] Although embodiments of the present disclosure have been described above, the ceramic members of the present disclosure are not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the present disclosure. [Explanation of symbols]

[0038] 1. Ceramic body 11 Page 1 12 Side 2 2, 2´ groove 3 Through hole 4 Metal body 5 Narrow part 6. Molded body 7. Drills for machining 8 Disposable boards 100 Ceramic components

Claims

1. It has a ceramic body having a first surface and a second surface opposite to the first surface, and a groove extending from the first surface toward the second surface for housing a strip-shaped metal body inside, The groove, when viewed from above, is spiral-shaped, winding around multiple turns. The average value of the groove width at the end of the first surface is greater than the average value of the groove width at the end of the second surface. In a portion of the groove, there is a narrow section where the groove width at the end on the first surface side is smaller than the groove width at the end on the second surface side. The narrow portion of the ceramic member is curved along the circumferential direction of the spiral groove.

2. The ceramic member according to claim 1, wherein the inner wall surface of the groove is a fired surface.

3. The ceramic member according to claim 1 or 2, wherein, on the first surface, the width of the groove is greater than the width of the ceramic body located between adjacent grooves.

4. The ceramic member according to any one of claims 1 to 3, wherein the depth from the groove end on the first surface to the groove end on the second surface is greater than the width of the end on the first surface.

5. The ceramic member according to claim 4, wherein the average value of the groove width at the center of the depth is greater than the average value of the groove width at the end on the second surface side and less than the average value of the groove width at the end on the first surface side.

6. The ceramic member according to any one of claims 1 to 5, wherein the ceramic body has a through hole penetrating its center.

7. A ceramic member according to any one of claims 1 to 6, A ceramic-metal composite comprising a metal body housed in the groove of the ceramic member.

8. The ceramic-metal composite according to claim 7, wherein the metal body is a heating element.

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