JP6667597B1 - Method for producing coating agent and coating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a coating agent capable of increasing the emissivity of an inorganic sintered body based on a ceramics sintered body or a refractory brick, and a coating agent produced by the production method. SOLUTION: A slurry having a silicon dioxide content, which is converted into a silicic acid-based glass by heating, is made to have a high emissivity by containing the elemental silicon which remains only as a silicon-only substance when the silicic acid-based glass is heated. A coating agent is manufactured. The produced coating agent is a slurry that contains silicon dioxide and becomes a silicic acid glass by heating, and contains only elemental silicon that remains as elemental silicon when it becomes silicic acid glass by heating. . [Selection diagram] Fig. 1

Description

  The present invention relates to a method for producing a coating agent for an inorganic sintered body having a ceramic sintered body or a refractory brick as a base, and a coating agent produced by the production method.

  Examples of the heat storage element that is disposed in the fluid flow path and recovers heat from the fluid include a heat storage element that is disposed in a heat exchange unit of a regenerative burner (regenerative burner). A regenerative burner is a burner used in industrial furnaces such as forging furnaces, heat treatment furnaces, melting furnaces, and firing furnaces. The flowing direction of the gas is switched at predetermined time intervals so that the gas flows alternately through the heat exchange unit. The heat of the exhaust gas is recovered by the regenerator, and the recovered heat preheats a newly supplied gas. The present applicant has been studying and developing from the viewpoint of the specific surface area and the heat capacity in order to enhance the heat exchange characteristics of the heat storage body having a ceramic sintered body as a base (for example, see Patent Document 1). Although heat transfer includes conduction, convection, and radiation (radiation), it is considered that radiation contributes greatly to heat transfer by a heat storage body. Since the radiant energy increases in proportion to the fourth power of the absolute temperature, increasing the emissivity of a heat storage element used in a high-temperature environment such as an industrial furnace is highly significant.

  On the other hand, refractory bricks are sinters formed from raw materials common to ceramics.In steelmaking and steelmaking facilities, furnace walls, furnace bottoms, pipes for discharging molten metal outside the furnace, It is used as a structure that constitutes a furnace accessory such as a blown pipe. The environment in which refractory bricks are used is extremely high temperature, and it is required that the high temperature be maintained efficiently. Therefore, it is highly significant to increase the emissivity of refractory bricks as a structure.

  The inventors of the present invention will not simply improve the base of the inorganic sintered body itself, but simply increase the emissivity of the inorganic sintered body regardless of the type of the base if the emissivity can be increased by a coating layer covering the base. Thought it could be.

Japanese Patent No. 6194068

  In view of the above circumstances, the present invention provides a method for producing a coating agent capable of increasing the emissivity of a ceramic sintered body or an inorganic sintered body based on a refractory brick, and is produced by the production method. It is an object to provide a coating agent.

In order to solve the above problems, a method for producing a high emissivity coating agent according to the present invention,
"Slurry containing silicon dioxide, which becomes silicate glass by heating,
When the silicate glass is formed by heating, only the simple silicon which remains as the simple silicon is contained. "

On the other hand, the high emissivity coating agent according to the present invention (may be simply referred to as “coating agent”) is
`` It is a slurry that contains silicon dioxide and becomes a silicate glass by heating,
It contains simple silicon which remains only as simple silicon when it becomes a silicate glass by heating. " This is the configuration of the coating agent manufactured by the manufacturing method having the above configuration.

  Generally, emissivity of an object having a smooth and smooth surface or an object having a glossy surface is small. Despite the fact that coating the surface of an object with a layer of silicate glass results in a smooth, smooth and glossy surface, as a result of our studies, surprisingly, the It has been found that the emissivity of the inorganic sintered body can be increased by coating the surface of the inorganic sintered body with a glass layer (hereinafter, may be referred to as a “coating layer”). This was considered to be one of the reasons that the silicate glass exhibited a deep color (blackish dark blue to black) by containing elemental silicon.

  Even when simple silicon is contained in the coating agent, at least a part of the single silicon is oxidized to silicon dioxide during heating for vitrifying the coating agent. Therefore, the coating agent of the present invention needs to contain a sufficient amount of elemental silicon to remain as elementary silicon even after vitrification.

High emissivity coating agent according to the present invention, instead of the above configuration,
`` It is a slurry that contains silicon dioxide and becomes a silicate glass by heating,
The content of elemental silicon in the solid content composition is at least 22% by mass. "

  As will be described in detail later, by setting the content of simple silicon in the solid content composition of the coating agent to at least 22% by mass, the simple silicon can be left in the coating layer where the coating agent is vitrified.

The high emissivity coating agent according to the present invention, in addition to the above configuration,
"It does not contain a cobalt component, or the content of the cobalt component is 1.5 parts by weight or less of cobalt atoms per 100 parts by weight of silicon atoms."

  Conventionally, when coating the surface of an inorganic material such as a ceramic sintered body with a certain coating agent, a coating agent containing a cobalt component has been frequently used. This is because it has been considered that when the coating agent contains a cobalt component, the adhesiveness of the coating agent to the inorganic material is enhanced. However, as a result of the study of the present inventors, it has been found that when a cobalt component is contained, the effect of increasing the emissivity of the layer of silicate glass containing elemental silicon is reduced.

  As will be described in detail later, it is desirable that the coating layer does not contain a cobalt component, and for that purpose, the coating agent does not contain a cobalt component. Further, even if the coating layer contains a cobalt component, it is desirable to suppress the content to 2.2 parts by weight or less based on 100 parts by weight of silicon atoms in terms of cobalt (III) oxide. For that purpose, the content of the cobalt component in the coating agent is set to 1.5 parts by weight or less of cobalt atoms with respect to 100 parts by weight of silicon atoms.

In the method for producing a high emissivity coating agent according to the present invention, the composition described above "contains 12 to 13 parts by weight of aluminum atoms per 100 parts by weight of silicon atoms". The high emissivity coating agent according to the present invention, Oite the above configuration, "containing 12 parts by weight to 13 parts by weight of aluminum atoms with respect to 100 parts by weight of silicon atoms" Ru der ones.

  This is a configuration of a coating agent that is suitable when the substrate of the inorganic sintered body on which the coating layer is to be formed is an alumina ceramic sintered body or a zirconia ceramic sintered body. As will be described in detail later, when the substrate is an alumina ceramic sintered body or a zirconia ceramic sintered body, the content of aluminum oxide in the coating layer is at least 23 parts by weight based on at least 100 parts by weight of silicon atoms. It was confirmed that the effect of increasing the emissivity was exhibited within the range of 25 parts by weight. For this purpose, the content of the aluminum component in the coating agent is set to 12 to 13 parts by weight of aluminum atoms with respect to 100 parts by weight of silicon atoms.

  As described above, according to the present invention, a method for producing a coating agent capable of increasing the emissivity of an inorganic sintered body based on a ceramic sintered body or a refractory brick, and a coating produced by the production method An agent can be provided.

(A), (b), and (c) respectively show the integrated emissivity of a sample in which the surface of a substrate of alumina, zirconia, or silicon carbide ceramics was coated with a coating layer of a coating agent E1, and the coating layer having a coating layer. It is a graph compared with the sample which does not. (A), (b), and (c) respectively show a sample in which the surface of a substrate of alumina, zirconia, and silicon carbide ceramics was coated with a coating layer of a coating agent E2 and a coating layer of a coating agent E3. 5 is a graph comparing the integrated emissivity of a sample obtained with a sample coated with a coating layer with a coating agent E1. (A), (b), and (c) show the integrated emissivity of a sample in which the surface of a substrate of alumina, zirconia, and silicon carbide ceramics was coated with a coating layer of a coating agent E4, respectively. It is a graph in comparison with the sample coated with the coating layer. (A), (b), and (c) show the samples obtained by coating the surface of the silicon carbide ceramics sintered body with coating layers having different thicknesses (by the coating agent E1) at 400 ° C., 600 ° C., respectively. 3 is a graph showing the integrated emissivity measured at 800 ° C.

  Hereinafter, a method of manufacturing a coating agent according to a specific embodiment of the present invention, a coating agent manufactured by the method, an inorganic sintered body having a coating layer formed by the coating agent, and a method of manufacturing an inorganic sintered body Will be described.

  The method for producing a coating agent according to the present embodiment contains silicon dioxide, and a slurry that becomes a silicate glass by heating, a simple silicon that only remains as a simple silicon when it becomes a silicate glass by heating. It is to be contained.

  More specifically, the method for producing the coating agent will be described. First, the raw material of the coating agent is sufficiently mixed with a liquid medium such as water or an organic solvent, and a binder to obtain a slurry whose viscosity is adjusted.

  As a source of silicon dioxide, which is a main component of the silicate glass, silica powder, glass powder (glass frit), and clay can be used alone or in combination. The coating agent contains elemental silicon (metallic silicon) as an essential component. At least a part of the elemental silicon is oxidized into silicon dioxide in the step of vitrifying the coating agent by heating. Therefore, a sufficient amount of elemental silicon to remain as elementary silicon after vitrification is contained in the coating agent.

The raw material of the coating agent may contain other components in addition to the source of silicon dioxide and the elemental silicon. By adding boron oxide (B ₂ O ₃ ), the viscosity (fluidity) and durability of the glass can be adjusted. Alkali metal oxides (Na ₂ O, K ₂ O, Li ₂ O, etc.) lower the viscosity of the glass and lower the glass transition point. Alkaline earth metal oxides (CaO, MgO, BaO, SrO, etc.) increase the chemical durability of the glass and affect the non-crystallization / crystallization of the glass. Aluminum oxide has the effect of increasing the chemical durability of the glass, but affects the emissivity of the inorganic sintered body, as described later.

  According to the above production method, a slurry containing silicon dioxide, which is a slurry that becomes a silicate glass by heating, and a coating agent containing a simple silicon that only remains as a simple silicon when it becomes a silicate glass by heating, Manufactured.

  By using the coating agent having the above structure, the surface of the ceramic sintered body or the refractory brick substrate is coated with a high emissivity coating layer which is a layer of silicate glass containing elemental silicon. A sintered body can be manufactured.

  More specifically, the inorganic sintered body having the above-described structure has a coating step of coating the surface of a substrate with a coating agent, and heating the substrate coated with the coating agent to vitrify the coating agent to form a coating on the surface of the substrate. And a vitrification step of fixing.

  The coating step can be a step of applying and spraying a coating agent on the surface of the substrate, or a step of dipping the substrate in the coating agent. When the substrate is porous, a step of impregnating the substrate with a coating agent can be performed. In that case, by placing the porous substrate in a decompressed atmosphere, the coating agent enters into the open pores from which air has been removed. Thus, the surface of the substrate is covered with the coating agent, and the open pores are filled with the coating agent in a portion near the surface.

  Here, the “ceramic” of the ceramic sintered body as the base may be an oxide ceramic or a non-oxide ceramic, and examples of the oxide ceramic include alumina, zirconia, magnesia, mullite, and magnesium aluminum spinel. Examples of the non-oxide ceramic include silicon carbide, silicon nitride, aluminum nitride, and magnesium nitride. Examples of the refractory brick as the base include high alumina, alumina-magnesia, magnesia, zirconia, alumina-carbon, magnesia-carbon, alumina-magnesia-carbon, and alumina-spinel-carbon. , Alumina-zirconia-carbon refractory bricks.

  In the vitrification step, first, a drying treatment for removing a liquid medium in the coating agent is performed. This drying treatment can be performed by heating at a low temperature of 70 ° C to 100 ° C for 2 hours to 30 hours. Next, vitrification treatment for vitrifying the coating agent is performed. This vitrification treatment can be performed, for example, by heating the substrate coated with the coating agent at a temperature of 800 ° C. to 1200 ° C. for 1 hour to 30 hours in an air atmosphere. By this treatment, the coating agent becomes silicate glass containing elemental silicon, softens, and adheres to the surface of the substrate. After cooling, the glass solidifies to form a coating layer that is a dense and airtight glass phase.

  In the inorganic sintered body manufactured as described above, the presence of the coating layer covering the surface of the base causes the inorganic sintered body not having such a coating layer (the inorganic sintered body including only the base) to be present. E), the emissivity is increased.

  Further, the silicate glass is softened and extended under high temperature and plastically deforms. Therefore, even if a ceramic sintered body which is a brittle material or an inorganic sintered body based on a refractory brick is used in a high-temperature atmosphere, even if a crack is generated, the softened silicate-based glass causes the crack. The filling suppresses the extension of the crack and the destruction. Therefore, the inorganic sintered body having the coating layer formed by the coating agent of the present embodiment has an increased emissivity and an increased thermal shock resistance.

  In addition, when the substrate is porous, the open pores of the substrate are also filled with a layer of silicate glass. As a result, the layer of silicate glass in the open pores serves as a cushion, and the thermal shock received by the inorganic sintered body is absorbed and moderated, which also increases the thermal shock resistance of the inorganic sintered body. I have.

  Hereinafter, a coating agent of an example, a manufacturing method thereof, and an inorganic sintered body having a coating layer formed by the coating agent of the example will be described. First, a coating agent was manufactured. As a raw material of the coating agent, two kinds of glass powders having different compositions, clay, simple silicon, silicon carbide, and sodium nitrate were used. These raw materials were mixed with water and a binder to form a slurry, which was used as a coating agent E1. Table 1 shows the solid composition of the coating agent E1.

As shown in Table 1, in addition to silicon dioxide (SiO ₂ ) and simple silicon (simple Si), the coating agent E1 includes silicon carbide (SiC), boron oxide (B ₂ O ₃ ), and aluminum oxide (Al ₂ O). ₃ ) contains alkali metal oxides (Na ₂ O, K ₂ O) and alkaline earth metal oxides (CaO). Note that this coating agent E1 does not contain a cobalt component.

  The above-mentioned solid content composition was analyzed by fluorescent X-ray analysis and wet chemical analysis. In the fluorescent X-ray analysis, the total weight ratio of silicon dioxide, elemental silicon, and silicon carbide is determined in terms of oxide, but the weight ratio of silicon dioxide, elemental silicon, and silicon carbide determined by wet chemical analysis is The respective weight ratios were calculated.

A plurality of substrates having the same shape and the same size are prepared by using a sintered body of alumina (Al ₂ O ₃ ), zirconia (ZrO 2), and silicon carbide (SiC), respectively, as a ceramic sintered body, and a coating agent E1 Was applied to the surface. Thereafter, the substrate whose surface was coated with the coating agent E1 was heated to vitrify the coating agent E1 and firmly adhere to the substrate. The thickness of the coating layer formed by vitrification of the coating agent E1 was 100 μm.

  Table 1 shows the composition of the coating layer analyzed in the same manner as described above. When the composition of the coating agent E1 is compared with the composition of the coating layer formed by the coating agent E1, silicon dioxide is increased in the coating layer compared to the coating agent E1, while elementary silicon is decreased. From this, it can be seen that, during the heat treatment for vitrification, a part of the simple silicon is oxidized to silicon dioxide, but the simple silicon remains after the vitrification.

  The emissivity was measured for each sample in which the surface of the substrate, which is a sintered body of alumina, zirconia, and silicon carbide, was coated with the coating layer of the silicate glass containing elemental silicon. The emissivity was measured at a temperature of 100 ° C. to 800 ° C. according to JIS R1801, using a far-infrared emissivity measuring device (IRTracer-100, manufactured by Shimadzu Corporation). FIGS. 1A to 1C show the integrated emissivity calculated for each sample when the integrated wavelength range is 2.5 μm to 25 μm. FIG. 1A shows the case where the substrate is alumina, FIG. 1B shows the case where the substrate is zirconia, and FIG. 1C shows the case where the substrate is silicon carbide.

  For comparison, the integrated emissivity of a sample consisting of only the same substrate (substrate which is a sintered body of alumina, zirconia and silicon carbide) and having no coating layer is shown in FIG. a) to FIG. 1 (c).

  As is clear from FIGS. 1 (a) and 1 (b), when the substrate is a sintered body of alumina and zirconia, by forming a coating layer with the coating agent E1, radiation is obtained over the entire temperature range. The rate has increased significantly. This is probably because the sintered body of alumina and zirconia is white, and the effect of increasing the emissivity by coating with a dark coating layer has been remarkably exhibited.

  On the other hand, as shown in FIG. 1 (c), when the substrate is a sintered body of silicon carbide, the emissivity increases in the range of 100 ° C. to 400 ° C. Smaller than the case of alumina or zirconia. This is because the silicon carbide sintered body used in this example originally exhibited a deep color (dark green) and had a higher emissivity than alumina or zirconia without a coating layer. It was thought that the effect of increasing the emissivity by the color coating layer was unlikely to appear. Further, when the substrate is silicon carbide, the same emissivity is exhibited at 500 ° C. regardless of the presence or absence of the coating layer. At a higher temperature, the emissivity of the sample having the coating layer is higher than that of the sample having no coating layer. A slight decrease was observed. However, there are many sites where the silicon carbide ceramic sintered body is actually used as a heat storage body or the like, in which the temperature range of the atmosphere is about 100 ° C. to 400 ° C. Therefore, even in this temperature range, the silicon carbide ceramics is used. It is highly significant that the emissivity of the sintered body can be increased.

  When the composition change and the measurement result of the emissivity shown in Table 1 are considered, the simple silicon necessary for increasing the emissivity by containing at least 22% by mass of the simple silicon in the solid content composition of the coating agent. Can be left in the coating layer.

Next, the effect of the cobalt component on the action of the coating layer to increase the emissivity will be described. Coating (E) was added to the solid content composition of the above coating agent E1 at an outer rate of 1% to obtain coating agent E2. When silicon atoms (total of Si of SiO ₂ , Si of elemental Si, and Si of SiC) are selected as a standard that does not change between the coating agent (before heating) and the coating layer (after vitrification), the coating agent E2 The content of the cobalt component in the coating layer is 2.2 parts by weight based on 100 parts by weight of silicon atoms in terms of cobalt (III) oxide.

  On the other hand, the cobalt component added to the coating agent may be a cobalt compound other than cobalt (III) oxide. Therefore, when the content is represented by cobalt atoms, the content of the cobalt component in the coating agent E2 is 1.5 parts by weight of cobalt atoms with respect to 100 parts by weight of silicon atoms.

  Furthermore, 2% of cobalt (III) oxide was externally added to the solid composition of the coating agent E1 to obtain a coating agent E3. When calculated in the same manner as described above, the content of the cobalt component in the coating layer by the coating agent E3 is 4.4 parts by weight based on 100 parts by weight of silicon atoms in terms of cobalt (III) oxide. Further, the content of the cobalt component in the coating agent E3 was 3.1 parts by weight of cobalt atoms with respect to 100 parts by weight of silicon atoms.

  The same substrate (a substrate as a sintered body of alumina, zirconia, and silicon carbide) is coated with a coating agent E2 at the same thickness (100 μm) as described above, and is vitrified to form a coating layer. A coating agent E3 is applied to each of the same substrates at the same thickness (100 μm) as described above, and the sample is vitrified to form a coating layer. The rate was measured. The results are shown in FIGS. 2A to 2C together with the measurement results for the coating agent E1 containing no cobalt component. FIG. 2A shows the case where the substrate is alumina, FIG. 2B shows the case where the substrate is zirconia, and FIG. 2C shows the case where the substrate is silicon carbide.

  As is clear from FIGS. 2A and 2C, when the substrate is alumina and silicon carbide, the emissivity of the sample using the coating agent E2 having a small content of the cobalt component is cobalt It is almost equal to the emissivity of the sample using the coating agent E1 containing no component. On the other hand, the emissivity of the sample using the coating agent E3 having a high content of the cobalt component is greatly reduced, and the emissivity of the sample having no coating layer (see FIGS. 1 (a) and 1 (c)). It is about the same.

  On the other hand, as shown in FIG. 2B, when the substrate is zirconia, the emissivity of the sample using the coating agent E2 having a low content of the cobalt component is lower than that of the sample using the coating agent E1 containing no cobalt component. Although the emissivity is lower, the emissivity is higher than when the coating layer is not provided (see FIG. 1B). On the other hand, the emissivity of the sample using the coating agent E3 having a large content of the cobalt component is greatly reduced.

  From the above results, in order to increase the emissivity of the inorganic sintered body, it is desirable that the coating agent and the coating layer formed therefrom do not contain a cobalt component. Further, even when a cobalt component is contained, the content of the cobalt component in the coating agent is suppressed to 1.5 parts by weight or less of cobalt atoms per 100 parts by weight of silicon atoms, and the content of the cobalt component in the coating layer is suppressed. It is desirable that the content be suppressed to 2.2 parts by weight or less in terms of cobalt oxide (III) per 100 parts by weight of silicon atoms.

  Next, the effect of aluminum oxide on the function of the coating layer to increase the emissivity will be described. The coating agent E1 contains 10.5% by weight of aluminum oxide in a solid content composition. When this is converted into the content of aluminum oxide in the coating layer formed from the coating agent E1, it is 23 parts by weight based on 100 parts by weight of silicon atoms. The aluminum component contained in the coating agent is not limited to an oxide, but may be another aluminum compound. Therefore, when the content is represented by aluminum atoms, the content of the aluminum component in the coating agent E1 is 100 parts by weight of silicon atoms. On the other hand, it is 12 parts by weight of aluminum atoms.

  On the other hand, 1% of aluminum oxide was externally added to the solid composition of the coating agent E1 to obtain a coating agent E4. When calculated in the same manner as described above, the content of aluminum oxide in the coating layer formed from the coating agent E4 is 25 parts by weight based on 100 parts by weight of silicon atoms. The content of the aluminum component in the coating agent E4 is 13 parts by weight of aluminum atoms with respect to 100 parts by weight of silicon atoms.

  Coating agent E4 was applied to each of the same substrates (substrates that were sintered bodies of alumina, zirconia, and silicon carbide) at the same thickness (100 μm) as above, and the sample was formed into a coating layer by vitrification. The integrated emissivity was measured in the temperature range of 100 ° C. to 800 ° C. in the same manner as described above. The results are shown in FIGS. 3 (a) to 3 (c) together with the measurement results for the sample using the coating agent E1. FIG. 3A shows the case where the substrate is alumina, FIG. 3B shows the case where the substrate is zirconia, and FIG. 3C shows the case where the substrate is silicon carbide.

  As shown in FIG. 3 (c), when the substrate is silicon carbide, the emissivity decreases as the content of aluminum oxide in the coating layer increases, and the emissivity decreases when the coating layer is not provided. (See FIG. 1C). On the other hand, as shown in FIG. 3 (b), when the base material is zirconia, the emissivity decreases as the content of aluminum oxide in the coating layer increases, but the emissivity is lower than that of the coating layer. If not (see FIG. 1B). Further, as shown in FIG. 3A, when the substrate is alumina, the emissivity further increases as the content of aluminum oxide in the coating layer increases.

  From the above, when the substrate is a sintered body of alumina or zirconia, the content of aluminum oxide in the coating layer is at least 23 parts by weight to 25 parts by weight with respect to at least 100 parts by weight of silicon atoms. For example, it was confirmed that the effect of increasing the emissivity of the inorganic sintered body by the coating layer was obtained. Further, the content of the aluminum component in the coating agent for forming such a coating layer was in the range of 12 to 13 parts by weight of aluminum atoms with respect to 100 parts by weight of silicon atoms.

  Next, the effect of the thickness of the coating layer on the effect of increasing the emissivity will be described. A coating agent E1 was applied at different thicknesses to the same sintered body of silicon carbide as described above and vitrified to form a coating layer. For samples having different coating layer thicknesses of 10 μm, 30 μm, 100 μm, 300 μm, and 400 μm, the integrated emissivity was measured in a temperature range of 100 ° C. to 800 ° C. in the same manner as described above. Among the measurement results, FIG. 4A shows the case of 400 ° C., FIG. 4B shows the case of 600 ° C., and FIG. 4C shows the case of 800 ° C.

  As is clear from FIGS. 4A to 4C, the emissivity was almost constant when the thickness of the coating layer was in the range of 10 μm to 300 μm at any temperature. Greatly reduced. This tendency was the same at other temperatures not shown. From the above, it was considered that it is desirable that the thickness of the coating layer be at least 10 μm to 300 μm in order to obtain the effect of increasing the emissivity of the inorganic sintered body by the coating layer.

  Further, when the substrate is a sintered body of non-oxide ceramics such as silicon carbide, there is a problem that when used in a high-temperature atmosphere where oxygen is present, there is a problem that the substrate is oxidized. It is considered that oxidation is suppressed. This is because the layer of the silicate glass that hermetically covers the surface of the substrate with high adhesion prevents the contact between the substrate and oxygen.

  Therefore, an oxidation test was performed on the above-described sample in which the sintered body of silicon carbide was used as a base and the thickness of the coating layer was varied by the coating agent E1 to evaluate the degree of oxidation of the base with heating in an air atmosphere. Was. Since the molecular weight of silicon carbide is 40 and the molecular weight of silicon dioxide is 60, when 1 mole of silicon carbide is oxidized to 1 mole of silicon dioxide, the mass increases by 20 g. The oxidation test utilizes this fact to evaluate the degree of oxidation by a change in mass before and after a heat treatment in an air atmosphere.

  In the oxidation test, the operation of raising the temperature to a temperature of 1300 ° C. at a predetermined rate, maintaining the temperature at that temperature for 50 hours, and then lowering the temperature to room temperature was performed once. It was done by doing. Based on the mass (initial mass) before the start of the oxidation test, if the rate of increase in mass after the oxidation test was 1% or less, it was evaluated as having oxidation resistance, and the rate of increase in mass exceeded 1%. Was evaluated as poor in oxidation resistance. For comparison, a similar oxidation test was also performed on a sample having no coating layer (only the silicon carbide sintered body substrate).

  As a result, samples having a coating layer thickness of 30 μm to 400 μm had oxidation resistance, whereas samples having a coating layer thickness of 10 μm and samples having no coating layer had acid resistance. It was inferior to chemical conversion. From this result, it is possible to suppress the oxidation of silicon carbide of the substrate by the coating layer. However, if the thickness of the coating layer is 10 μm, the thickness of the coating layer is required to exhibit the effect of suppressing the oxidation. Was considered too small.

  From the above, in the case of an inorganic sintered body having a sintered body of silicon carbide as a base, in order to obtain an effect of increasing the emissivity by the coating layer and to obtain an effect of suppressing oxidation of the base by the coating layer. It was confirmed that it is desirable that the thickness of the coating layer be at least 30 μm to 300 μm.

  The coating layer contains elemental silicon for the purpose of increasing the emissivity.However, the coating layer containing elemental silicon is advantageous in that oxidation of silicon carbide of the substrate is suppressed. is there. In other words, when the inorganic sintered body having a sintered body of silicon carbide as a base contains elemental silicon in the coating layer, when the inorganic sintered body is used in a high-temperature atmosphere, the silicon carbide of the base becomes Prior to this, the elemental silicon present in the surface coating layer is oxidized. This consumes oxygen in an atmosphere near the surface of the inorganic sintered body, thereby suppressing oxidation of silicon carbide of the base.

  The coating agent of this example contains silicon carbide, and this silicon carbide remains as it is in the coating layer after vitrification. Silicon carbide contained in the coating layer is also oxidized prior to the silicon carbide of the base similarly to the above-described single silicon, so that oxidation of the silicon carbide of the base is also suppressed.

  As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above embodiments, and various improvements can be made without departing from the gist of the present invention as described below. And design changes are possible.

  For example, since the shape of the substrate of the inorganic sintered body on which the coating layer is formed with the coating agent of the present invention is not particularly limited, it may be a solid sphere or a row extending in a single direction. The honeycomb structure may be a honeycomb structure including a plurality of cells partitioned by divided partitions, or may have another three-dimensional shape. Regardless of the shape of the substrate, the emissivity can be increased by coating the surface with a high emissivity coating layer as compared to a case without such a coating layer.

  Further, in the above description, the embodiment in which the base body is a ceramic sintered body is described. However, the refractory brick, which is produced from the same material as the ceramic sintered body and is also a sintered body, is similarly coated with the coating agent of the present invention. By covering the surface with a coating layer, the emissivity can likewise be increased.

Claims (4)

A slurry containing silicon dioxide, which becomes a silicate glass by heating,
In addition to containing simple silicon that only remains as simple silicon when it becomes silicate glass by heating ,
A method for producing a high-emissivity coating agent, comprising 12 to 13 parts by weight of aluminum atoms per 100 parts by weight of silicon atoms . A slurry containing silicon dioxide, which becomes a silicate glass by heating,
In addition to containing simple silicon that only remains as simple silicon when it becomes silicate glass by heating ,
A high emissivity coating agent comprising 12 to 13 parts by weight of aluminum atoms per 100 parts by weight of silicon atoms . A slurry containing silicon dioxide, which becomes a silicate glass by heating,
The content of elemental silicon in the solid content composition is at least 22% by mass ,
A high emissivity coating agent comprising 12 to 13 parts by weight of aluminum atoms per 100 parts by weight of silicon atoms . The high emissivity according to claim 2 or 3, wherein the cobalt component is not contained, or the content of the cobalt component is 1.5 parts by weight or less of cobalt atoms with respect to 100 parts by weight of silicon atoms. Coating agent.

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