Glazed ceramic structure

Abstract

This ceramic structure (1) with a glazing layer comprises a base (2) constituted of a ceramic and the glazing layer (3) lying on the base (2). The base (2) includes a first region (R1), which includes the surface in contact with the glazing layer (3), and a second region (R2), which lies farther from the glazing layer (3) than the first region (R1). The first region (R1) has a smaller crystal grain diameter than the second region (R2).

Description

[Technical Field]

[0001] The present disclosure relates to a glazed ceramic structure. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a technique for providing a glaze layer on a ceramic structure has been known from the viewpoint of ensuring airtightness, insulation, and the like.

[0003] Patent Document 1 discloses a method for producing a ceramic structure with a glaze layer by producing a ceramic sintered body, applying a glaze paste to the produced ceramic sintered body, and then heat-treating the ceramic structure to which the glaze paste has been applied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-252524 Summary of the Invention

[0005] A ceramic structure with a glaze layer according to one embodiment of the present disclosure includes a ceramic substrate and a glaze layer disposed on the substrate. The substrate includes a first region including an interface with the glaze layer and a second region farther from the glaze layer than the first region. The crystal grain size in the first region is smaller than the crystal grain size in the second region. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic perspective view of a ceramic structure with a glaze layer according to an embodiment. [Figure 2] FIG. 2 is a schematic vertical cross-sectional view of a ceramic structure with a glaze layer according to an embodiment. [Figure 3] FIG. 3 is a schematic enlarged view of part III shown in FIG. [Figure 4]FIG. 4 shows SEM images of the ceramic structure according to the example and the ceramic structure according to the comparative example. [Figure 5] FIG. 5 is a table showing the measurement results of the average crystal grain size of the substrate in the ceramic structures according to the examples and the ceramic structures according to the comparative examples. [Figure 6] FIG. 6 is a table showing the measurement results of the void ratio of the substrate in the ceramic structures according to the examples and the ceramic structures according to the comparative examples. [Figure 7] FIG. 7 is an explanatory diagram of the bending strength measurement. [Figure 8] FIG. 8 is a table showing the results of measuring the bending strength of the ceramic structures according to the examples and the ceramic structures according to the comparative examples. [Figure 9] FIG. 9 is a graph showing the measurement results of the Si concentration in the glaze layer of the ceramic structure according to the example. [Figure 10] FIG. 10 is a graph showing the measurement results of the Si concentration in the glaze layer of the ceramic structure according to the example. [Figure 11] FIG. 11 is a graph showing the measurement results of the Ca concentration in the glaze layer of the ceramic structure according to the example. [Figure 12] FIG. 12 is a graph showing the measurement results of the Ca concentration in the glaze layer of the ceramic structure according to the example. [Figure 13] FIG. 13 is a graph showing the measurement results of the Si concentration in the substrate of the ceramic structure according to the example. [Figure 14] FIG. 14 is a graph showing the measurement results of the Al concentration in the substrate of the ceramic structure according to the example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a form for carrying out a ceramic structure with a glaze layer according to the present disclosure (hereinafter referred to as an "embodiment") will be described in detail with reference to the drawings. Note that the ceramic structure with a glaze layer according to the present disclosure is not limited to this embodiment. Furthermore, each embodiment can be appropriately combined within a range that does not cause contradiction in processing content. Furthermore, the same parts in each of the following embodiments will be given the same reference numerals, and duplicated explanations will be omitted.

[0008] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision, installation precision, etc.

[0009] Conventional ceramic structures with a glaze layer have room for further improvement in terms of improving mechanical strength. The present disclosure provides a ceramic structure with a glaze layer that can improve mechanical strength.

[0010] Fig. 1 is a schematic perspective view of a ceramic structure with a glaze layer according to an embodiment. Fig. 2 is a schematic longitudinal sectional view of the ceramic structure with a glaze layer according to an embodiment. Specifically, Fig. 2 shows a cross section of the ceramic structure 1 that is perpendicular to the first wall portion 21 and the second wall portion 22. The substrate 2 in the ceramic structure 1 with a glaze layer may be plate-shaped. An opening may be located in the second wall portion 22 in Fig. 2.

[0011] As shown in FIGS. 1 and 2, a ceramic structure 1 with a glaze layer according to an embodiment (hereinafter simply referred to as “ceramic structure 1 ”) has a substrate 2 and a glaze layer 3 .

[0012] The substrate 2 may have a container shape. The container shape may have, for example, a plate-like portion having one main surface and the other main surface, and a sidewall portion integrally connected to the end of the plate-like portion and extending in a direction from the one main surface toward the other main surface, with the end of the sidewall portion opposite the plate-like portion being open. As an example, as shown in FIGS. 1 and 2, the substrate 2 may have, for example, four first walls 21 (corresponding to the sidewall portions) and one second wall portion 22 (corresponding to the plate-like portion) continuous with the four first walls 21. The side of the ceramic structure 1 opposite the second wall portion 22 may be open. Note that the first wall portion 21 or the second wall portion 22 may have a recessed or protruding portion.

[0013] Here, the second wall portion 22 forms the lower wall of the ceramic structure 1, but is not limited thereto, and the second wall portion 22 may form the upper wall of the ceramic structure 1. That is, the ceramic structure 1 may be upside down from the state shown in Fig. 1. Also, here, an example is shown in which the outline shape of the base 2 is quadrangular in plan view, but the outline shape of the base 2 may be a polygonal shape other than a quadrangle, or may be circular.

[0014] The ceramic structure 1 according to the embodiment may be used as a heat-resistant container. For example, the ceramic structure 1 may be used as a container for storing a high-temperature substance (e.g., molten metal). The high-temperature substance is not limited to a liquid, but may also be a solid. When the high-temperature substance is a solid, the ceramic structure 1 serving as a heat-resistant container may have an opening located on the bottom or wall. The ceramic structure 1 may also be used as a container in which at least a portion of the inner wall surface is exposed to plasma. In this case, the ceramic structure 1 may have an opening located on the bottom or wall. Furthermore, the opening may be closed by a member other than the ceramic structure 1 (e.g., a heat-resistant metal member).

[0015] The ceramic structure 1 according to the embodiment is made of ceramics. Examples of the ceramic that can be used to form the ceramic structure 1 include aluminum oxide ceramics, silicon nitride ceramics, aluminum nitride ceramics, and silicon carbide ceramics.

[0016] When the ceramic structure 1 is made of aluminum oxide ceramics, it has excellent mechanical properties while being relatively inexpensive, including the cost of raw materials and manufacturing costs, among ceramics. Furthermore, disposal of the ceramic structure 1 with a glaze layer causes little environmental pollution.

[0017] Aluminum oxide ceramics may contain 85 mass% or more of alumina (Al2O3) out of 100 mass% of all components constituting the ceramic. In other words, ceramics containing alumina as the main component are called aluminum oxide ceramics. In this embodiment, the base 2 may be made of aluminum oxide ceramics (i.e., containing alumina as the main component). The base 2 according to this embodiment may contain 90 mass% or more of alumina. Furthermore, the alumina content of the base 2 according to this embodiment may be 96 mass% or less.

[0018] The material of the base 2 can be confirmed, for example, by the following method. First, the base 2 is measured using an X-ray diffractometer (XRD), and the obtained 2θ (2θ is the diffraction angle) value is compared with the JCPDS card. Next, quantitative analysis of aluminum (Al) is performed using an inductively coupled plasma (ICP) emission spectrometer or an X-ray fluorescence analyzer (XRF). If the Al content measured by ICP or XRF is converted to aluminum oxide (Al2O3) and the content is 85 mass% or more, the material of the base 2 is aluminum oxide ceramics.

[0019] The base 2 may also contain a component used as a sintering aid. Specifically, the base 2 may contain Si (silicon). In addition to Si, the sintering aid may also contain, for example, Ca (calcium), Mg (magnesium), etc.

[0020] The substrate 2 has a density of 3.5 g / cm 3 The substrate 2 may have an area ratio of pores of 0.5% or less as measured on a cross section. Such a dense substrate has particularly high strength.

[0021] The glaze layer 3 may be located on the inner surface of the substrate 2. The glaze layer 3 may be provided on the inner surface of the substrate 2, for example, to ensure the airtightness and insulating properties of the ceramic structure 1.

[0022] In this way, by providing a glaze layer 3 on the inner surface of the container-shaped base 2, stress remains in the direction in which the opening of the container closes (toward the center of the opening), thereby improving the mechanical strength of the ceramic structure 1.

[0023] 1 and 2 show an example in which the glaze layer 3 is located only on the inner surface of the base 2, but the glaze layer 3 may also be located on the outer surface of the base 2. The base 2 may be entirely covered with the glaze layer 3.

[0024] The glaze layer 3 may contain at least Si (silicon) as a metal element. As an example, the glaze layer 3 may contain Al (aluminum), Ca (calcium), K (potassium), Na (sodium), etc. as a metal element in addition to Si.

[0025] In this way, by including Si in both the base 2 and the glaze layer 3, the chemical bonding between the base 2 and the glaze layer 3 is improved, thereby improving the mechanical strength of the ceramic structure 1.

[0026] Fig. 3 is a schematic enlarged view of part III shown in Fig. 2. As shown in Fig. 3, a region of the base 2 including the interface with the glaze layer 3 is defined as a first region R1.

[0027] As will be described later, the main component of the glaze layer 3 penetrates into the interior of the base 2 from the interface between the base 2 and the glaze layer 3. The concentration of the main component of the glaze layer 3 gradually decreases from the interface between the base 2 and the glaze layer 3 toward the center in the depth direction of the base 2. Therefore, the range in which the concentration of the main component (for example, Si) of the glaze layer 3 slopes (decreases) along the depth direction of the base 2 may be specified as the first region R1. Specifically, if the Si concentration at the center in the depth direction of the base 2 is defined as the "center concentration" and the interface between the base 2 and the glaze layer 3 is defined as "one end" of the first region R1, the "other end" of the first region R1 may be a position in the depth direction of the base 2 where the Si concentration matches the center concentration.

[0028] As an example, the first region R1 may be a region extending to a depth of 70 μm from the interface with the glaze layer 3. Furthermore, a region of the base 2 that is farther from the glaze layer 3 than the first region R1, in other words, a region located further inside the base 2 (deeper when viewed from the glaze layer 3 side) than the first region R1, is defined as the second region R2.

[0029] For example, one end of the second region R2 (the end on the glaze layer 3 side) may be at least 150 μm or more away from the other end of the first region R1. As an example, the second region R2 is a region extending from a depth of 1000 μm (1 mm) to a depth of 1020 μm from the interface with the glaze layer 3.

[0030] In the ceramic structure 1 according to the embodiment, the crystal grain size in the first region R1 may be smaller than the crystal grain size in the second region R2.

[0031] In this way, by making the crystal grain size in the first region R1 smaller than the crystal grain size in the second region R2, the mechanical strength of the base 2 is improved.

[0032] Furthermore, by making the crystal grain size of the second region R2 larger than that of the first region R1, the following effect is obtained. Specifically, the Young's modulus of the second region R2, which has a larger crystal grain size, is larger than that of the first region R1, which has a smaller crystal grain size. Therefore, when repeated stress (tensile stress or compressive stress) is applied to the first region R1 and the second region R2 simultaneously, the generation of microcracks in the second region R2 is suppressed, thereby suppressing the occurrence of fatigue fracture in the second region R2. This is because the larger the Young's modulus, the more the elastic deformation when stress is applied is suppressed. Here, fatigue fracture refers to the occurrence of microcracks in the base 2 when stress smaller than the fracture strength is applied multiple times, and these microcracks eventually grow, reducing the mechanical strength or leading to fracture (crack). On the other hand, because the crystal grain size of the first region R1 is smaller than that of the second region R2, even though the Young's modulus is smaller than that of the second region R2, the first region R1 has a high bending strength and can suppress the occurrence of microcracks when repeated stress is applied. As a result, the ceramic structure 1 according to the embodiment maintains a high mechanical bending strength and is resistant to fatigue fracture even when subjected to repeated stress.

[0033] Furthermore, by making the crystal grain size in the second region R2 larger than that in the first region R1, the following effect can be obtained. That is, by making the crystal grain size in the second region R2 larger, the thermal conductivity of the second region R2 can be made larger than that of the first region R1. Therefore, when heat is transferred from the glaze layer 3 to the base 2, the heat can be transferred efficiently from the first region R1 to the second region R2. This suppresses the generation of thermal stress between the first region R1 and the second region R2. Therefore, even if thermal stress is applied to the base 2 due to a sudden temperature change, the base 2 is prevented from cracking or being destroyed.

[0034] In the ceramic structure 1 according to the embodiment, the void fraction in the first region R1 may be lower than the void fraction in the second region R2.

[0035] In this way, by reducing the void fraction in the first region R1 in contact with the glaze layer 3, it is possible to suppress the occurrence of cracks in the base 2 from the interface between the base 2 and the glaze layer 3. Therefore, the ceramic structure 1 according to the embodiment has high mechanical strength.

[0036] The ceramic structure 1 according to the embodiment may have a region between the first region R1 and the second region R2 in which the average crystal grain size is smaller than that of the second region R2. In other words, the ceramic structure 1 may have a region between the first region R1 and the second region R2 in which the average crystal grain size is equivalent to that of the first region R1.

[0037] The glaze layer 3 according to the embodiment may contain Si as a metal element as described above. The Si concentration of the glaze layer 3 may be lower in a region closer to the base 2 than in a central portion in the thickness direction of the glaze layer 3.

[0038] In this way, by reducing the amount of Si contained in the glaze layer 3 on the substrate 2 side, the residual stress acting on the substrate 2 is reduced, and the mechanical strength of the ceramic structure 1 is improved.

[0039] As described above, the glaze layer 3 according to the embodiment may contain Ca as a metal element. The Ca concentration of the glaze layer 3 is higher in the region closer to the base 2 than in the central portion in the thickness direction of the glaze layer 3.

[0040] In this way, the glaze layer 3 Ca By increasing the amount of the SiO 2 on the substrate 2 side, the residual stress acting on the substrate 2 is reduced, and the mechanical strength of the ceramic structure 1 is improved.

[0041] As shown in FIG. 3, the glaze layer 3 may have a Si concentration increasing region Rx in which the Si concentration increases with increasing distance from the interface with the base 2.

[0042] In this way, by increasing the Si content in the region of the glaze layer 3 farther from the base 2, compressive stress can be generated in the base 2. This improves the mechanical strength of the ceramic structure 1. From another perspective, by decreasing the Si content in the glaze layer 3 closer to the base 2, the thermal expansion coefficient of the glaze layer 3 in contact with the base 2 can be made closer to the thermal expansion coefficient of the base 2. This reduces the difference in the thermal expansion coefficients of the base 2 and the glaze layer 3, thereby reducing the residual stress between the base 2 and the glaze layer 3. As a result, the mechanical strength of the ceramic structure 1 is improved.

[0043] The Si concentration increasing region Rx may include a third region R3 including the interface with the base 2, and a fourth region R4 that is continuous with the third region R3 and is farther from the base 2 than the third region R3. In this case, the rate of increase in the Si concentration in the third region R3 may be greater than the rate of increase in the Si concentration in the fourth region R4.

[0044] According to this configuration, residual stress acting on the outer surface of the glaze layer 3 is reduced, and the mechanical strength of the ceramic structure 1 is improved.

[0045] The glaze layer 3 may also include a fifth region R5 that is farther from the base 2 than the fourth region R4 in the Si concentration increasing region Rx. In this case, the rate of change in the Si concentration in the fifth region R5 may be smaller than the rate of change in the Si concentration in the fourth region R4. Specifically, the Si concentration in the fifth region R5 may be approximately constant.

[0046] With this configuration, if a crack occurs on the surface of the base 2, the crack is prevented from progressing to the glaze layer 3, and therefore the mechanical strength of the ceramic structure 1 is improved.

[0047] As described above, the Si concentration in the first region R1 is higher than the Si concentration in the center of the base 2 in the depth direction, for example, the Si concentration in the second region R2.

[0048] Increasing the amount of Si in the portion of the base 2 close to the glaze layer 3 in this way suppresses a sudden change in the thermal expansion coefficient in the region near the interface between the glaze layer 3 and the base 2. This reduces the residual stress between the base 2 and the glaze layer 3 after the glaze layer 3 has solidified, thereby improving the mechanical strength of the ceramic structure 1.

[0049] Furthermore, the base 2 according to the embodiment may contain Al as described above. In such a base 2, the Al concentration in the first region R1 may be lower than the Al concentration in the center of the base 2 in the depth direction, for example, the Al concentration in the second region R2.

[0050] In this way, when the amount of Al is reduced in the portion of the base 2 close to the glaze layer 3, a rapid change in the thermal expansion coefficient is suppressed in the region near the interface between the glaze layer 3 and the base 2. This reduces the residual stress between the base 2 and the glaze layer 3 after the glaze layer 3 has solidified, thereby improving the mechanical strength of the ceramic structure 1.

[0051] In the ceramic structure 1 according to the embodiment, the thickness of the glaze layer 33 located on the ridge (the edge of the inner bottom surface of the container) between the first wall portion 21 and the second wall portion 22 may be thicker than the thickness of the glaze layer 31 located on the first wall portion 21 and the thickness of the glaze layer 32 located on the second wall portion 22.

[0052] Thermal shock tends to concentrate on the ridges between the first wall portion 21 and the second wall portion 22. In response to this, the strength of the ridges is increased by making the thickness of the glaze layer 31 at the ridges relatively thick, which effectively prevents cracks and breakage due to thermal shock from occurring at the ridges.

[0053] Furthermore, the thickness of the glaze layer 3 located on the ridges between adjacent first wall portions 21 may be thicker than the thickness of the glaze layer 31 located on the first wall portion 21 and the thickness of the glaze layer 32 located on the second wall portion 22. With this configuration, cracks and breakage due to thermal shock are more effectively prevented from occurring on the ridges.

[0054] <Method of manufacturing ceramic structure 1> Next, an example of a method for manufacturing the ceramic structure 1 will be described. First, a bisque ceramic body is prepared. Here, the bisque body is obtained by heat-treating the raw shaped body of the base 2 at a temperature 200 to 800°C lower than the sintering temperature (the sintering temperature in the absence of glaze). For example, the bisque body is obtained by heat-treating the raw shaped body of the base 2 at 1000°C for 30 minutes.

[0055] The procedure for producing the green shaped body of the base 2 is as follows. First, aluminum oxide (Al2O3) powder, the main raw material of the base 2, is mixed with silicon oxide (SiO2) powder, calcium carbonate (CaCO3) powder, magnesium carbonate (MgCO3) powder, etc. as sintering aids in a specified ratio, and then wet-pulverized to produce a primary slurry. Next, a binder is added to the primary slurry and mixed to produce a secondary slurry. Next, the secondary slurry is spray-dried to produce granules. The granules are then uniaxially pressed to form them into the shape of a container, producing a green shaped body.

[0056] Next, a glaze-containing paste is prepared, for example, by mixing and kneading a known glaze raw material powder with a liquid and a binder to form a paste or low-viscosity liquid. The glaze paste is then applied to a biscuit body having a porosity (void fraction) of approximately 30 to 50% by volume. The application method is not particularly limited, and may be, for example, spraying, atomization, or impregnation. For example, the glaze paste can be stored in a tank and the biscuit body can be impregnated with the glaze paste by immersing it in the tank. The biscuit body is then removed from the tank, and the glaze paste accumulated inside the container is drained. At this time, a relatively large amount of glaze paste remains on the four sides of the bottom of the container, resulting in a relatively thick glaze layer on the four sides of the bottom of the container.

[0057] Next, the glazed bisque body is heat-treated to simultaneously sinter the bisque body and densify (solidify) the glaze. For example, the glazed bisque body is heat-treated at 1350°C to 1450°C for 2 hours. This produces the ceramic structure 1 according to the embodiment.

[0058] A portion of the glaze paste penetrates the open pores and interconnected pores of the bisque body, leaving a portion of the glaze on the surface. When the bisque body is sintered in this state, the sintering process proceeds with the glaze permeating the open pores and interconnected pores of the bisque body. Note that open pores refer to pores that open to the glaze-coated surface. Interconnected pores refer to pores that connect the coated surface to the interior of the bisque body. The glaze is initially paste-like, but when melted by heat treatment, it becomes a low-viscosity molten material. After the temperature is lowered during the sintering process, it remains solidified within the open pores and interconnected pores. This results in a smaller crystal grain size in the portion of the base 2 where the glaze has penetrated than in the other portions. Similarly, the portion of the base 2 where the glaze has penetrated has a lower void fraction than the other portions. Specifically, the void fraction in the first region R1 of the base 2 is less than one-third of the void fraction in the second region R2 of the base 2. More specifically, the void ratio in the first region R1 of the base 2 is 2% or less.

[0059] As mentioned above, a portion of the glaze near the interface with the bisque body penetrates into the open pores and interconnected pores of the bisque body. The sintering of the bisque body then proceeds in this state. As this occurs, the Si contained in the glaze migrates to the areas that were previously the open pores and interconnected pores of the bisque body, resulting in a relatively low Si content in the area of ​​the glaze layer 3 closest to the base 2.

[0060] The method for forming the increased Si concentration region Rx in the glaze layer 3 is the same as described above. Alternatively, for example, multiple layers of glaze may be applied. In this case, the increased Si concentration region Rx can be suitably formed by adjusting the Si concentration in the first glaze layer to be lower than that in the second glaze layer. The biscuit body may be subjected to a drying process after the first glaze layer is applied, or the second glaze layer may be applied directly without drying. [Example]

[0061] Next, examples of ceramic structures according to the present disclosure will be described. The inventors of the present application measured the crystal grain size and void ratio of the substrate, the bending strength, the Si concentration and Ca concentration of the glaze layer, and the Si concentration and Al concentration of the substrate for the ceramic structures produced by the above-mentioned manufacturing method.

[0062] The composition of the ceramic structure used in the measurement is as follows: (Glaze layer) SiO280 mass% Al2O3 12.5% ​​by mass K2O 5% by mass CaO 1% by mass Na2O 1% by mass Others 0.5% by mass The others are trace impurities such as Fe2O3, TiO2, and MgO. (Base) Al2O386 mass% SiO29 mass% MgO 2.3% by mass CaO 1.4% by mass TiO21 mass% Others 0.3% by mass The others are trace impurities such as Fe2O3, Na2O, and K2O.

[0063] <Grain size of the substrate> The inventors of the present application measured the crystal grain size of the substrate for the ceramic structures according to the examples and the ceramic structures according to the comparative examples. Here, for the ceramic structures according to the comparative examples, the substrate was sintered, and then a glaze was applied to the sintered substrate and heat-treated to densify the glaze layer. The cut surface of each ceramic structure was mirror-polished, and the measurement points on the resulting mirror surface were observed using a scanning electron microscope (SEM) at a magnification of approximately 3000x. The average crystal grain size was then calculated from the resulting SEM image using the code method. Specifically, three line segments (two diagonal lines and one horizontal line) were drawn on the resulting SEM image (a rectangular framed image), and the average crystal grain size was calculated from the length of the line segments and the number of crystals (particles) intersecting the line segments. Crystals located at the edge of the SEM image that overlap the line segments were included in the number of crystals used to calculate the crystal grain size.

[0064] The average crystal grain size may be calculated using a BEM image (backscattered electron image) instead of an SEM image (secondary electron image).

[0065] The measurement locations were three: a region from the interface between the base and the glaze layer to a depth of 20 μm inside the base (corresponding to part of the first region R1 described above; hereinafter referred to as the interface region); a region from a depth of 100 μm to a depth of 120 μm from the interface between the base and the glaze layer (hereinafter referred to as the intermediate region); and a region from a depth of 1000 μm (1 mm) to a depth of 1020 μm from the interface between the base and the glaze layer (corresponding to the second region R2 described above; hereinafter referred to as the deep region).

[0066] Figure 4 shows SEM images of a ceramic structure according to an example and a ceramic structure according to a comparative example. Figures 4(a) to 4(c) are SEM images of a ceramic structure according to a comparative example, and Figures 4(d) to 4(f) are SEM images of a ceramic structure according to an example. Figures 4(a) and 4(d) are SEM images of the interface region, Figures 4(b) and 4(e) are SEM images of the intermediate region, and Figures 4(c) and 4(f) are SEM images of the deep region.

[0067] FIG. 5 is a table showing the measurement results of the average crystal grain size of the substrate in the ceramic structures according to the examples and the ceramic structures according to the comparative examples.

[0068] As shown in Figures 4(a) to 4(c), the crystal grain size of the substrate in the ceramic structure according to the comparative example is roughly the same in the interface region, intermediate region, and deep region. In contrast, as shown in Figures 4(d) to 4(f), the crystal grain size of the substrate in the ceramic structure according to the example is smaller in the interface region than in the deep region. Specifically, the crystal grain size in the interface region is about 80% of the crystal grain size in the deep region.

[0069] Specifically, as shown in Fig. 5, the crystal grain size of the substrate in the ceramic structure according to the comparative example was 1.8 µm in the interface region, 1.7 µm in the intermediate region, and 1.7 µm in the deep region. In contrast, the crystal grain size of the substrate in the ceramic structure according to the example was 1.4 µm in the interface region, 1.4 µm in the intermediate region, and 1.8 µm in the deep region.

[0070] Thus, in the ceramic structure according to the embodiment, the crystal grain size in the first region of the base, which includes the interface with the glaze layer, is smaller than the crystal grain size in the second region of the base, which is farther from the glaze layer than the first region.

[0071] <Void ratio of the substrate> The inventors of the present application measured the void fraction of the substrate for the ceramic structures according to the examples and the comparative examples. First, the mirror surface was observed at a magnification of approximately 200x using a metallurgical microscope, and the obtained image was binarized using image analysis software "A-zo-kun" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.; hereinafter, the image analysis software "A-zo-kun" refers to the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.). The binarized image was then analyzed to calculate the void fraction. The measurement locations were the three aforementioned regions: the interface region, the intermediate region, and the deep region. Note that the binarization of the image may be performed using image analysis software other than "A-zo-kun." Examples of image analysis software other than "A-zo-kun" that may be used include digital microscopes manufactured by Keyence Corporation (e.g., VHX-5000, VHX-7000, and VHX-8000).

[0072] Fig. 6 is a table showing the measurement results of the void fraction of the substrate in the ceramic structure according to the example and the ceramic structure according to the comparative example. As shown in Fig. 6, the void fraction of the substrate in the ceramic structure according to the comparative example was 2.5% in the interface region, 7.0% in the middle region, and 7.2% in the deep region. In contrast, the void fraction of the substrate in the ceramic structure according to the example was 0.8% in the interface region, 6.0% in the middle region, and 5.9% in the deep region.

[0073] As described above, in the ceramic structure according to the example, the void fraction in the first region of the base, which includes the interface with the glaze layer, is lower than the void fraction in the second region of the base, which is farther from the glaze layer than the first region. Specifically, in the ceramic structure according to the example, the void fraction in the first region is 1 / 6 or less of the void fraction in the second region.

[0074] <Bending strength of ceramic structures> The inventors of the present application measured the bending strength of the ceramic structures according to the examples and the ceramic structures according to the comparative examples using a plurality of measurement samples with different glaze layer thicknesses, which were five patterns: 50 μm, 65 μm, 75 μm, 100 μm, and 180 μm.

[0075] Figure 7 is an explanatory diagram of bending strength measurement. As shown in Figure 7, first, a plate-shaped test sample is prepared. The dimensions of the test sample are 30 mm in length, 15 mm in width, and 2 mm in thickness. Next, the test sample is placed on the ridges of two triangular prism-shaped support members with the glaze layer facing downward. The distance between the two support members is 25 mm. Next, a terminal is used to press the test sample from above at the midpoint between the two support members. The terminal presses the test sample in a linear fashion parallel to the ridges of the support members. The pressure that the test sample received from the terminal when it broke was calculated as the bending strength.

[0076] Fig. 8 is a table showing the results of measuring the bending strength of the ceramic structures according to the examples and the comparative examples. As shown in Fig. 8, the bending strength of the ceramic structures according to the comparative examples was 307 MPa when the thickness of the glaze layer was 50 µm, 280 MPa when it was 65 µm, 373 MPa when it was 75 µm, 378 MPa when it was 100 µm, and 334 MPa when it was 180 µm. Example The bending strength of the ceramic structure according to the present invention was 349 MPa when the thickness of the glaze layer was 50 μm, 398 MPa when it was 65 μm, 463 MPa when it was 75 μm, 441 MPa when it was 100 μm, and 489 MPa when it was 180 μm.

[0077] As described above, it is clear that the ceramic structures according to the examples have higher mechanical strength than the ceramic structures according to the comparative examples. It is also clear that the mechanical strength of the ceramic structures according to the examples increases as the thickness of the glaze layer increases.

[0078] <Si and Ca concentrations in the glaze layer> The inventors of the present application measured the Si concentration and Ca concentration in the glaze layer of the ceramic structure according to the example using a wavelength dispersive X-ray analyzer (WDS).

[0079] 9 and 10 are graphs showing the results of measuring the Si concentration in the glaze layer of the ceramic structure according to the example. Fig. 9 shows the results of measuring the Si concentration in a measurement range of 30 μm in the depth direction, including the outer surface of the glaze layer (the surface opposite the interface with the substrate). Fig. 10 shows the results of measuring the Si concentration in a measurement range of 30 μm in the depth direction, including the interface with the substrate.

[0080] In Fig. 9, the position of the outer surface of the glaze layer is around 30 µm. In Fig. 10, the position of the interface between the glaze layer and the substrate is around 5 µm. In the graphs shown in Figs. 9 and 10, the behavior of the graphs at the measurement start and end points (0 µm and 30 µm in Figs. 9 and 10) is due to the specifications of the measuring device and will be ignored. This also applies to Figs. 11 to 14 described below.

[0081] As shown in Fig. 10, the glaze layer according to the example has a Si concentration increasing region in which the Si concentration increases with increasing distance from the interface with the substrate. The Si concentration increasing region is, for example, a region extending from the interface with the substrate (position 5 µm away in Fig. 10) to a depth of 20 µm (position 25 µm away in Fig. 10).

[0082] Furthermore, it can be seen that the Si concentration increase rate in the region including the interface with the substrate (corresponding to the third region R3) of the Si concentration increase region according to the example is greater than the Si concentration increase rate in a region farther from the substrate than the third region (corresponding to the fourth region R4). The third region here is, for example, a region extending from the interface with the substrate to a depth of 2 μm. The fourth region here is the region of the Si concentration increase region other than the third region.

[0083] 9, it can be seen that in the glaze layer according to the example, the rate of change in the Si concentration in a region (corresponding to the fifth region R5) farther from the base than the fourth region is even smaller than the rate of change in the Si concentration in the fourth region. The fifth region here is, for example, the region of 0 to 10 μm shown in FIG. 9. The Si concentration in this fifth region is approximately constant.

[0084] 11 and 12 are graphs showing the results of measuring the Ca concentration in the glaze layer of the ceramic structure according to the example. Fig. 11 shows the results of measuring the Ca concentration in a measurement range of 30 μm in the depth direction, including the outer surface of the glaze layer. Fig. 12 shows the results of measuring the Ca concentration in a measurement range of 30 μm in the depth direction, including the interface with the substrate.

[0085] As shown in Fig. 12, the glaze layer according to the example has a Ca concentration increased region where the Ca concentration increases with increasing distance from the interface with the substrate. The Ca concentration increased region is, for example, a region extending from the interface with the substrate (position 5 μm from the interface with the substrate) to a depth of 7.5 μm (position 12.5 μm from the interface with the substrate) (position 12.5 μm from the interface with the substrate).

[0086] Furthermore, it can be seen that the Ca concentration increasing region according to the example has a higher Ca concentration increasing rate in a region including the interface with the substrate (referred to as the eighth region) than in a region farther from the substrate than the eighth region (referred to as the ninth region). The eighth region is, for example, a region extending from the interface with the substrate to a depth of 2 μm. The ninth region is, Ca This is the area other than the eighth area among the density increasing areas.

[0087] <Si concentration and Al concentration of the substrate> The inventors of the present application measured the Si concentration and Al concentration of the substrate of the ceramic structure according to the example. The method for measuring the Si concentration and Al concentration in the substrate was the same as the method for measuring the Si concentration and Ca concentration in the glaze layer described above.

[0088] Fig. 13 is a graph showing the measurement results of the Si concentration in the substrate of the ceramic structure according to the example. Fig. 14 is a graph showing the measurement results of the Al concentration in the substrate of the ceramic structure according to the example. Figs. 13 and 14 show the Si concentration and the Al concentration in a measurement range of 90 µm in the depth direction, including the interface between the substrate and the glaze layer. Al 13 and 14, the interface between the glaze layer and the substrate is located at about 40 μm, the range of 0 to 40 μm is the substrate, and the range of 40 to 90 μm is the glaze layer.

[0089] As shown in Fig. 13, the Si concentration in the region of the base including the interface with the glaze layer (corresponding to the interface region) is higher than the Si concentration in the region of the base farther from the glaze layer than the interface region. The interface region here is, for example, the region from the interface between the base and the glaze layer (position 40 μm in Fig. 13) to a depth of 20 μm (position 20 μm in Fig. 13). Furthermore, the region of the base farther from the glaze layer than the interface region is, for example, the region from a position 20 μm deeper than the interface region (position 0 μm in Fig. 13) to the bottom end of the interface region (20 μm in Fig. 13).

[0090] 14, the Al concentration in the region of the base including the interface with the glaze layer (corresponding to the interface region) is lower than the Al concentration in the region of the base that is farther from the glaze layer than the interface region. The interface region here is, for example, the region from the interface between the base and the glaze layer (position 40 μm in FIG. 14) to a depth of 20 μm (position 20 μm in FIG. 14). The region of the base that is farther from the glaze layer than the interface region is, for example, the region from a position 20 μm deeper than the interface region (position 0 μm in FIG. 14) to the bottom end of the interface region (20 μm in FIG. 14).

[0091] <Glaze layer thickness measurement> The ceramic structure according to the example was cut along a plane perpendicular to the first and second wall portions, and the thickness of the glaze layer located on the cut surface was measured. The measurement positions were the same as the three locations indicated by the reference numerals 31 to 33 in FIG. 2. As a result, the thickness of the glaze layer located on the first wall portion was 260 μm, the thickness of the glaze layer located on the second wall portion was 295 μm, and the thickness of the glaze layer located on the ridge between the first and second wall portions was 596 μm. This result shows that the thickness of the glaze layer is relatively thick at the ridge between the first and second wall portions.

[0092] The thickness of the glaze layer at the ridge between two adjacent first wall portions was also measured. Specifically, the ceramic structure according to the example was cut along a plane perpendicular to the first wall portion and parallel to the second wall portion, and the thickness of the glaze layer located on the cut surface was measured. As a result, the thickness of the glaze layer located on the ridge between two adjacent first wall portions was 360 μm.

[0093] The thickness of the glaze layer at the four corners inside the base was also measured. Specifically, the ceramic structure according to the example was cut along a plane passing through both the outer and inner ridges of two adjacent first wall portions, and the thickness of the glaze layer located on the cut surface was measured. As a result, the thickness of the glaze layer located at the four corners inside the base was 851 μm.

[0094] In this way, Example In the ceramic structure according to the above, the thickness of the glaze layer is large at the ridges between the first wall portion and the second wall portion (including the four corners inside the base).

[0095] As described above, the ceramic structure with a glaze layer according to the embodiment (for example, ceramic structure 1) includes a ceramic substrate (for example, substrate 2) and a glaze layer (for example, glaze layer 3) located on the substrate. The crystal grain size in a first region (for example, first region R1) of the substrate including the interface with the glaze layer is smaller than the crystal grain size in a second region (for example, second region R2) of the substrate that is farther from the glaze layer than the first region.

[0096] Furthermore, a ceramic structure with a glaze layer according to an embodiment (for example, ceramic structure 1) has a base (for example, base 2) made of ceramic and a glaze layer (for example, glaze layer 3) located on the base. The void fraction in a first region (for example, first region R1) of the base including the interface with the glaze layer is lower than the void fraction in a second region (for example, second region R2) of the base that is farther from the glaze layer than the first region.

[0097] Therefore, the ceramic structure with a glaze layer according to the embodiment can improve mechanical strength.

[0098] In the above-described embodiment, an example in which the base 2 is made of aluminum oxide ceramics has been described. However, the base 2 may be made of a material other than aluminum oxide ceramics. Examples of materials other than aluminum oxide ceramics include cordierite, forsterite, and zirconia.

[0099] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0100] 1: Ceramic structure with glaze layer 2: Base 3: Glaze layer 21: 1st wall part 22:Second wall part R1: 1st area R2: 2nd area R3: 3rd area R4: 4th area R5: 5th area Rx: Si concentration increasing region

Claims

1. a substrate made of ceramic containing 85 mass % or more of alumina; a glaze layer having a thickness of 50 μm or more and containing Si as a metal element, which is located on the substrate; and the substrate includes a first region that is a region having a depth of up to 20 μm from the interface with the glaze layer, and a second region that is farther from the glaze layer than the first region and has a depth of 1000 μm to 1200 μm from the interface; A ceramic structure with a glaze layer, wherein the crystal grain size in the first region is smaller than the crystal grain size in the second region.

2. 2. The ceramic structure with a glaze layer according to claim 1, wherein the Si concentration of the glaze layer is lower in a region that is closer to the substrate than the central portion and is up to 2 μm from the interface, compared to a central portion that is located half the thickness of the glaze layer away from the interface toward the surface of the glaze layer.

3. 3. The ceramic structure with a glaze layer according to claim 2, wherein the glaze layer has, in a region up to 20 μm from the interface, a Si concentration increasing region in which the Si concentration increases with increasing distance from the interface.

4. 4. The ceramic structure with a glaze layer according to claim 3, wherein the region of increased Si concentration includes an interface with the substrate, a third region located up to 2 μm from the interface, and a fourth region located farther from the substrate than the third region, and a rate of increase in Si concentration in the third region is greater than a rate of increase in Si concentration in the fourth region.

5. the glaze layer includes a fifth region that is farther from the substrate than the fourth region and is 20 μm to 30 μm from the outer surface of the glaze layer; The ceramic structure with a glaze layer according to claim 4 , wherein a rate of change in the Si concentration in the fifth region is smaller than a rate of change in the Si concentration in the fourth region.

6. the substrate contains Si, 6. The ceramic structure with a glaze layer according to claim 1, wherein the Si concentration in the first region is higher than the Si concentration in the second region.

7. The ceramic structure with a glaze layer according to claim 6 , wherein the Al concentration in the first region is lower than the Al concentration in the second region.

8. the substrate has the shape of a container; 8. The ceramic structure with a glaze layer according to claim 1, wherein the glaze layer is located on the inner surface of the container.

9. the base body has a plate-like portion having one main surface and another main surface, and a sidewall portion integrally connected to the plate-like portion and extending in a direction from the one main surface toward the other main surface, 9. The ceramic structure with a glaze layer according to claim 8, wherein a thickness of the glaze layer at a ridge portion between the plate-like portion and the side wall portion is greater than a thickness of the glaze layer at the plate-like portion and the side wall portion.

10. The ceramic structure with a glaze layer according to any one of claims 1 to 9, which is used as a heat-resistant container.

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