Heat shielding structure

Abstract

To provide a heat shielding structure having more excellent heat shielding properties than conventional ones.SOLUTION: A heat shielding structure includes a base material and a heat shielding layer formed on one main surface of the base material, wherein: the base material comprises a porous ceramic; the heat shielding layer has a bulk density of 2 g / cm3 or less; a ratio of pores having a pore diameter of 0.5 μm or more but less than 10 μm in a total pore volume of the heat shielding layer is 40 vol% or more; a ratio of pores having a pore diameter of 1 μm or more but less than 5 μm in the pore volume of 0.5 μm or more but less than 10 μm is 50 vol% or more; and a ratio of pores having a pore diameter of greater than 5.5 μm in the total pore volume of the heat shielding layer is 55 vol% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat shield structure, and more particularly to a heat shield structure made of ceramics and having an excellent heat shielding effect in a high temperature range. [Background technology]

[0002] 2. Description of the Related Art Heat-shielding structures include those made of a single material and those made of a material on the surface of which another material is formed.

[0003] However, when constructed from a single material, it is difficult for that single material to satisfy all of the properties required for a structural material, such as heat resistance, heat insulation, and impact resistance, so it is usually used in a form in which other materials are combined with the surface of a component made of one material.

[0004] Known examples of components made of one material on which another heat-insulating material is formed include a configuration in which the surface (high-temperature side) is made of an absorption layer that converts radiant light into heat using a highly absorptive material such as SiC or C, and the back (low-temperature side) is made of a heat-insulating layer made of a material with low thermal conductivity, or a configuration in which the component is made of a single material and uses a metal with a high melting point and low emissivity to form a layer that reflects linearly polarized radiant light.

[0005] One aspect of a heat shield structure with particularly high heat resistance is a technique for forming a coating made of a heat-resistant material on the surface of a member made of an aggregate of various heat-resistant fibers.

[0006] On the other hand, the mainstream heat-shielding structure for building materials is a structure that uses a low-emissivity material with low radiation absorption rate on the surface and a heat-insulating layer on the back. In this way, materials with different properties are combined depending on the application.

[0007] Incidentally, a material made of a magnesia spinel porous body and having a characteristic pore size distribution is known as a material that has excellent heat resistance and heat insulation properties, particularly in the temperature range of 1000°C or higher.

[0008] For example, Patent Document 1 describes a composite refractory insulating material that is composed of a heat insulating material made of porous ceramics and a refractory material that has a higher compressive strength than the porous ceramics, wherein the porous ceramics have a porosity of 65 vol% to 90 vol% and are a spinel material expressed by the chemical formula MgAl2O4, in which coarse pores with a pore size larger than 1000 μm account for 25 vol% or less of the total pore volume, and micropores with a pore size of 0.45 μm or less account for 5 vol% to 40 vol% of the volume of pores with a pore size of 1000 μm or less, and which has at least one pore size distribution peak within the pore size range of 0.14 μm to 10 μm, and is composed of ceramic particles with a calculated average particle size of 0.04 μm to 1 μm. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5877821 Summary of the Invention [Problem to be solved by the invention]

[0010] In recent years, there has been a need for heat-shielding structures that can provide excellent heat-shielding effects at high temperatures, particularly in environments of 1000°C or higher, and that are lightweight, small in volume, and highly durable.

[0011] In order to obtain a heat-shielding structure that meets these needs, for example, in a heat-resistant heat-shielding structure according to a conventional technique, the surface temperature rises in order to convert radiant light into heat, and the heat insulating layer on the back surface needs to be sufficiently thick and insulating, which is disadvantageous for applications that require a lightweight and low-volume structure.

[0012] Furthermore, in one embodiment of a thermal barrier structure in which a high-melting-point metal is used for the thermal barrier layer, an oxide film is formed on the surface of the metal in an oxygen-containing atmosphere, and the formation of this oxide film increases the emissivity, so the structure can only be used in a high vacuum, and its applications are limited, particularly in environments exposed to the atmosphere or combustion gases.

[0013] Alternatively, low-emissivity materials used in heat-shielding structures in building materials include those that combine a heat-shielding layer with a heat-insulating layer, but the low-emissivity materials used in heat-shielding layers have low heat resistance, and none of them can be used at high temperatures, especially above 1000°C.

[0014] Here, since the magnesia-spinel porous ceramics described in Patent Document 1 have excellent heat insulating properties in the temperature range exceeding 1000°C, it is easy to imagine applying them to heat shield structures.

[0015] However, although the porous ceramics described in Patent Document 1 suppresses the increase in thermal conductivity in the temperature range exceeding 1000°C, there are many unknown aspects regarding its heat-shielding properties, and simply applying this material to obtain a heat-shielding structure that is lightweight, small in volume, and highly durable is not enough to easily obtain the expected properties.

[0016] The present invention has been made in view of the above, and aims to provide a heat shielding structure that, compared to conventional techniques, has excellent radiant heat insulation performance, particularly in environments exceeding 1000°C, and is lightweight, small in volume, yet highly durable. [Means for solving the problem]

[0017] A thermal barrier structure according to one aspect of the present invention comprises a substrate and a thermal barrier layer formed on one main surface of the substrate, the substrate being made of porous ceramics, and the thermal barrier layer MgAlO 4 Includes , bulk density is 1g / cm 3 More than 1.7g / cm 3 belowand the ratio of pores having a pore diameter of 0.5 μm or more and less than 10 μm to the total pore volume of the thermal barrier layer is 50vol% or more and 77vol% or less The ratio of pores with a diameter of 1 μm or more and less than 5 μm to the pore volume with a diameter of 0.5 μm or more and less than 10 μm is 61vol% or more and 84vol% or less, The ratio of pores with a diameter of 5.5 μm or larger to the total pore volume of the thermal barrier layer is 3 vol% or more and 21vol% or less, is.

[0018] By having such a configuration, it is possible to provide a thermal barrier structure that can provide superior thermal barrier performance, particularly in environments exceeding 1000°C, compared to conventional techniques.

[0019] A thermal barrier structure according to another aspect of the present invention comprises a substrate and a thermal barrier layer formed on one main surface of the substrate, the substrate being made of a ceramic material having an emissivity of 0.75 or more, and the thermal barrier layer MgAlO 4 Includes , bulk density is 1g / cm 3 More than 1.7g / cm 3 below and the ratio of pores having a pore diameter of 0.5 μm or more and less than 10 μm to the total pore volume of the thermal barrier layer is 50vol% or more and 77vol% or less The ratio of pores with a diameter of 1 μm or more and less than 5 μm to the pore volume with a diameter of 0.5 μm or more and less than 10 μm is 61vol% or more and 84vol% or less, The ratio of pores with a diameter of 5.5 μm or larger to the total pore volume of the thermal barrier layer is 3 vol% or more and 21vol% or less, In a specific embodiment, the substrate is made of ceramic fiber cloth.

[0020] In this case, the total thickness of the substrate and the heat shield layer can be set to 2 mm or less, and the heat shield structure can be used as a lightweight, low-volume heat shield structure. [Effects of the Invention]

[0021] According to the present invention, by coating conventional materials that can be used at high temperatures with a highly reflective heat-shielding layer that is optimized to provide an appropriate heat-shielding effect, it is possible to obtain a heat-shielding structure that can be used at high temperatures and has an excellent heat-shielding effect. Furthermore, by coating such a highly reflective heat-shielding layer on a heat-shielding layer made of a highly absorptive material in order to suppress the transmission of radiant light, it is possible to obtain a heat-shielding effect equal to or greater than that of conventional products with a thickness that is about one-third of the conventional thickness, and it is also possible to obtain a heat-shielding structure that is lightweight and has a small volume. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing a method for evaluating a heat flux ratio and a temperature ratio used in verifying the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below. One aspect of the present invention is a thermal barrier structure comprising a substrate and a thermal barrier layer formed on one main surface of the substrate, wherein the substrate is made of porous ceramics, and the thermal barrier layer has a bulk density of 2 g / cm. 3 or less, the proportion of pores having a pore diameter of 0.5 μm or more and less than 10 μm in the total pore volume of the thermal barrier layer is 40 vol% or more, the proportion of pores having a pore diameter of 1 μm or more and less than 5 μm in the pore volume of pores having a diameter of 0.5 μm or more and less than 10 μm is 50 vol% or more, and the proportion of pores having a pore diameter of more than 5.5 μm in the total pore volume of the thermal barrier layer is 55 vol% or less.

[0024] In one embodiment of the present invention, the substrate is a porous material. Such porous materials can be widely used depending on the intended use of the heat shield structure, as long as they function as a heat insulating layer. Examples include heat-resistant ceramic materials such as alumina and silicon carbide, and foam ceramics. Ceramics containing added fibers may also be used.

[0025] A heat shielding layer according to one embodiment of the present invention is, in a broad sense, composed of diffuse reflection components with particles having a diameter of 1 to 5 μm and pores having a diameter of 1 to 5 μm as scatterers. It can be said that the heat shielding layer achieves its heat shielding effect through diffuse reflection based on the Mie theory, i.e., Mie scattering. Here, Mie scattering is scattering that occurs when the wavelength of radiant light and the size of the scatterers are approximately the same.

[0026] In addition, since other materials within the scope of conventional technology can provide sufficient heat-shielding effects in the temperature range below 1000°C, in order to differentiate this invention from conventional technology, it is assumed that this invention will be used in the temperature range of 1000°C or higher.

[0027] That is, in the present invention, since the dominant wavelength of radiant light at 1000°C to 2000°C is 1 to 5 μm, Mie scattering is caused by making the pores and particles approximately the same size as this. Note that Mie scattering does not occur at exactly the same size as the wavelength, but at a size close to it (approximately 1 / 10 to 10 times larger).

[0028] However, in order to use particles as scatterers, it is important that they have a certain degree of refractive index difference, and therefore it is necessary for the particles to contain many pores as well as particles. After considering these conditions, we decided that the bulk density of the thermal barrier layer should be 2 g / cm 3 It was found that optimally, the proportion of pores having a pore diameter of 0.5 μm or more and less than 10 μm to the total pore volume of the heat shield layer is 40 vol% or more, the proportion of pores having a pore diameter of 1 μm or more and less than 5 μm to the pore volume of pores having a diameter of 0.5 μm or more and less than 10 μm is 50 vol% or more, and the proportion of pores having a pore diameter of more than 5.5 μm to the total pore volume of the heat shield layer is 55 vol% or less.

[0029] First, the thermal barrier layer according to the present invention has a bulk density of 2 g / cm 3By making the bulk density 0.3 g / cm or less, the porosity can be increased and solid-state heat transfer can also be suppressed. Here, suppression of solid-state heat transfer includes not only the heat transfer in the thermal barrier layer but also the effect of increasing the contact resistance at the interface between the thermal barrier layer and the substrate, which is the heat insulating layer. However, if the bulk density is too low, the strength decreases and the layer becomes brittle, it becomes difficult to obtain the pore distribution of the present invention described below, sufficient diffuse reflection does not occur, and there is a concern that the manufacturing cost will increase. Therefore, in the present invention, the bulk density is set to 0.3 g / cm 3 is preferably set as the lower limit.

[0030] Next, in the thermal barrier layer according to the present invention, the proportion of pores with a pore diameter of 0.5 μm or more and less than 10 μm relative to the total pore volume of the thermal barrier layer is 40 vol% or more. If this proportion is less than 40 vol%, the radiant light falls outside the wavelength range assumed in the present invention, which is undesirable as it reduces the Mie scattering effect. Note that the closer this proportion is to 100 vol%, the more scatterers there are, so it can be said that this is theoretically effective.

[0031] In the thermal barrier layer according to the present invention, the proportion of pores with a pore diameter of 1 μm or more and less than 5 μm in the pore volume having a pore diameter of 0.5 μm or more and less than 10 μm is 50 vol % or more. If this proportion is 50 vol % or more, Mie scattering can occur efficiently.

[0032] In the thermal barrier layer according to the present invention, the proportion of pores having a pore diameter of greater than 5.5 μm relative to the total pore volume of the thermal barrier layer is 55 vol % or less. By keeping this proportion at 55 vol % or less, it is possible to suppress the transmission of radiant light.

[0033] The heat shield structure of the present invention having the above configuration can easily and significantly improve the radiant heat insulating performance by simply coating the surface layer of the substrate, compared to a structure consisting only of a heat insulating layer of the substrate. For coating, conventionally known methods such as spray coating, screen printing, brush coating, electrodeposition coating, coating with a bar coater, coating with a doctor blade, spin coating, etc. can be used.

[0034] The heat shield structure can be produced, for example, by applying a coating material, which is a mixture of spinel porous powder, a ceramic adhesive, and water, to a substrate by the above-mentioned method, and then firing the coating at approximately 1000°C.

[0035] Here, considering that the material for the thermal barrier layer is used at 1000°C or higher and that the above-mentioned pore size distribution can be obtained relatively easily, a porous body made of a high melting point composition, i.e., ceramics, is preferred. Furthermore, oxide ceramics have oxidation resistance. By using ceramics with a high melting point, heat resistance can be obtained, and since they can contain grain boundaries, the effect of suppressing solid heat transfer can also be obtained. Specific examples of high melting point ceramics are MgAl2O4 or LaAl 11 O 18 And so on.

[0036] It is preferable that the thermal barrier layer of the present invention not be made of a simple high-melting-point ceramic, but contain as an additive a reactive component such as Si or Ca in a range that ensures the pore size distribution of the present invention. This is because the inclusion of a reactive component promotes sintering between particles and prevents the thermal barrier layer from detaching from the base material, the thermal insulating layer or the high absorption thermal barrier layer. Specifically, the content of the additive is preferably 0.05 to 20 wt%.

[0037] Furthermore, the thermal barrier layer of the present invention may contain aggregate components such as particles or hollow particles made of a ceramic material (alumina, silicon carbide, etc.) and fibers, to the extent that the above-mentioned pore size distribution can be ensured. Note that those containing fibers are more preferable because they have the effect of suppressing the amount of shrinkage during production of the thermal barrier layer.

[0038] To summarize what we have discussed so far, the heat shield layer has the effect of effectively reflecting radiant light onto the surface of the heat shield structure, the substrate has the effect of suppressing solid-state heat transfer and gas-phase heat transfer, and interfacial thermal resistance occurs at the interface between the heat shield layer and the substrate. Interfacial thermal resistance suppresses solid-state heat transfer because the heat shield layer is a porous body, and if the substrate is made of fiber, the contact area between the fiber and the heat shield layer is reduced, improving interfacial thermal resistance. Furthermore, because the heat shield layer has low emissivity, radiant light is suppressed not only from the surface but also from the heat shield layer to the insulating layer.

[0039] As described above, the thermal barrier structure according to one embodiment of the present invention can easily impart good thermal barrier properties to conventional thermal insulation materials by providing a thermal barrier layer having oxidation resistance and heat resistance on its surface. Conventional thermal insulation materials have a problem with radiant light transmission due to their high porosity, but this problem can be solved by combining them with the present heat shielding material.

[0040] Next, another embodiment of the present invention will be described. Another embodiment of the present invention is a thermal barrier structure comprising a substrate and a thermal barrier layer formed on one main surface of the substrate, wherein the substrate is made of a ceramic material having an emissivity of 0.75 or more, and the thermal barrier layer has a bulk density of 2 g / cm 3 or less, and the proportion of pores having a pore diameter of 0.5 μm or more and less than 10 μm in the total pore volume of the thermal barrier layer is 40 vol% or more, the proportion of pores having a pore diameter of 1 μm or more and less than 5 μm in the pore volume of pores having a diameter of 0.5 μm or more and less than 10 μm is 50 vol% or more, and the proportion of pores having a pore diameter of more than 5.5 μm in the total pore volume of the thermal barrier layer is 55 vol% or less.

[0041] That is, the substrate in one embodiment of the present invention is porous ceramic, while the substrate in another embodiment is made of a ceramic material with an emissivity of 0.75 or more. On the other hand, the configuration of the heat shield layer in both embodiments is the same.

[0042] In another embodiment of the present invention, by using a ceramic material with an emissivity of 0.75 or more for the substrate, the thickness of the entire heat shielding structure can be made even thinner while obtaining equivalent heat shielding properties.

[0043] Specific examples of the substrate include heat-resistant, highly absorbent materials such as SiC, C, and Si3N4. Furthermore, by using a fiber fabric structure for the substrate, it is possible to increase the thermal interface resistance between the heat shield layer and the substrate, improving radiant insulation performance and offering the advantage of greater freedom in shape, making it advantageous for on-site construction and heat shielding of special shapes.

[0044] Furthermore, when using a combination of SiC fiber cloth for the substrate and MgAl2O4 for the thermal barrier layer, the total thickness of the thermal barrier structure can be kept to 2 mm or less, even when used in an oxidizing atmosphere at 1000°C or higher. In conventional structures, to achieve the same level of thermal insulation, the thickness of the substrate and the thermal barrier layer had to be increased. In contrast, in a more preferred embodiment of the present invention, a sufficient thermal insulation effect can be achieved even with a thickness of 1 mm.

[0045] In another aspect of the present invention, a heat shield structure can be manufactured by applying a coating material, which is a mixture of spinel porous powder, a ceramic adhesive, and water, to a substrate, and firing the coating material, as in the heat shield structure described above.

[0046] In particular, in the above-mentioned embodiment, the heat shield layer has the effect of effectively reflecting radiant light toward the surface of the heat shield structure, and because there are gaps between the fibers at the interface between the heat shield layer and the substrate, the contact area with the heat shield layer is small, suppressing heat transfer between solids and improving the heat shielding properties at the interface. Furthermore, because the substrate is made of SiC fiber cloth, the temperature distribution within the substrate is small, thereby reducing heat re-distribution. The heat shield structure of the present invention, which combines all of these factors, can achieve approximately the same heat shielding effect in a lighter form compared to conventional thermal insulation materials alone or thermal insulation materials with a heat shield layer formed on them. The present invention does not particularly limit the form of the SiC fiber cloth (such as the diameter, density, and folded shape of the fiber bundles, or the ratio of short fibers to long fibers), and it can be widely applied.

[0047] In another embodiment of the present invention, the substrate may be made of a conductive material that transmits little radiant light, such as a metal material (e.g., an alloy such as platinum or stainless steel).

[0048] Conductive materials that transmit little radiant light are opaque bodies similar to heat-resistant, highly absorptive materials such as SiC, Si3N4, and C, and can be used as the substrate of the present invention as long as heat resistance is ensured, thereby achieving a heat-shielding effect similar to that of SiC or C. However, they are somewhat disadvantageous compared to ceramic materials in terms of weight reduction and corrosion resistance.

[0049] Furthermore, Mie scattering is caused by diffuse reflection with little directionality. For this reason, applying this coating to the innermost layer of a heat treatment furnace is expected to not only provide a heat barrier effect, but also reduce temperature distribution within the furnace. [Example]

[0050] The present invention will be specifically described below based on examples, but the present invention is not limited to the examples shown below.

[0051] [Examples 1 to 8] 11 mol of hydraulic alumina powder (BK-112, manufactured by Sumitomo Chemical Co., Ltd.) and 9 mol of magnesium oxide powder (MGO11PB, manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed and purified water was added to form a slurry. The mixture was then hydraulically formed into a 60 mm x 70 mm x 20 mm compact. This compact was then fired in an oxygen atmosphere at 1500 °C for 3 hours to produce a porous spinel. This porous spinel was then crushed using an alumina mortar and pestle and sieved through a 1 mm mesh to obtain a porous spinel powder. The porous spinel powder was mixed with a commercially available ceramic adhesive (FF adhesive, manufactured by Nichias Corporation) in a weight ratio of 3:2 or 4:1, and alumina (Al2O3) fiber (Denka Arsen B100, manufactured by Denka Co., Ltd.) was added at 0 wt% or 10 wt%. A coating material was then prepared by adding purified water in an amount sufficient to achieve fluidity. The obtained coating material was applied to a thickness of 1 to 2 mm on the surface of a substrate (diameter 50 mm, thickness 0.3 to 4 mm) processed into a disk shape, and then fired at 1000°C for 3 hours to produce the heat shielding structures of Examples 1 to 7, and fired at 1500°C for 3 hours to produce the heat shielding structure of Example 8. In Examples 1 to 6 and 8, a porous ceramic fiber insulation material (Fibermax 1600P board: manufactured by Isolite Kogyo Co., Ltd.) was used as the substrate, and in Example 7, a silicon carbide continuous fiber cloth (Hi-Nicalon Type S: manufactured by Nippon Carbon Co., Ltd.) made of silicon carbide ceramic material with an emissivity of 0.86 was used. The mixing ratio of the spinel porous powder to the ceramic adhesive, the heat shield layer that forms the obtained heat shield structure, the substrate layer, and the overall thickness are shown in Table 1. In Table 1, the substrates of Examples 1 to 6 and Example 8 are described as heat insulating layers, and the substrate of Example 7 is described as a high absorptivity material.

[0052] [Example 9] 11 mol of hydraulic alumina and 11 mol of lanthanum oxide were mixed and added with pure water to form a slurry. This slurry was cast to obtain a 60 mm × 70 mm × 20 mm green body. This green body was fired at 1700°C for 3 hours to obtain lanthanum hexaaluminate ceramics. This lanthanum hexaaluminate was crushed using an alumina mortar and pestle and sieved with 1 mm mesh to obtain lanthanum hexaaluminate powder. The resulting lanthanum hexaaluminate powder was mixed with a commercially available ceramic adhesive (FF adhesive: manufactured by Nichias Corporation) in a weight ratio of 4:1, and pure water was added in an amount sufficient to achieve fluidity to prepare a coating material. The obtained coating material was applied to a fiber-based insulation material in a thickness of 1 mm and baked at 1500°C for 3 hours in a 100% oxygen atmosphere to form LaAl 11 O 18 A heat shield structure having a coating layer made of lanthanum hexaaluminate was obtained.

[0053] [Comparative Examples 1 to 4] Comparative Example 1 uses only a substrate (heat insulating layer) without a thermal barrier layer. In Comparative Examples 2 to 4, the type and amount of ceramic adhesive were appropriately changed from the manufacturing conditions of each example to obtain structures outside the scope of the present invention.

[0054] Table 1 shows the production conditions for Examples 1 to 9, and Table 2 shows the structures and heat-shielding effects (temperature ratio and heat flux ratio) of Examples 1 to 9 and Comparative Examples 1 to 4. Conditions 1 to 4 shown in Table 2 are as follows. That is, Condition 1 is the proportion of pore volume with a pore diameter of 0.5 μm or more and less than 10 μm to the total pore volume. Condition 2 is the proportion of pore volume with a pore diameter of 1 μm or more and less than 5 μm to the total pore volume of pores of 0.5 μm or more and less than 10 μm. Condition 3 is the proportion of pores larger than 5.5 μm to the total pore volume. Condition 4 is bulk density.

[0055] [evaluation] For the structure of the heat shield layer in Table 2, the pore size distribution in the heat shield layer was measured using JIS R1655:2003 "Test method for pore size distribution in molded fine ceramics by mercury intrusion porosimetry," which is a method for measuring pore size distribution using mercury intrusion porosimetry. The heat-shielding effect of the sample was measured using a tungsten lamp surface-irradiation type infrared vacuum furnace (IVF29VS, manufactured by Thermo Riko Co., Ltd.). Specifically, a disk-shaped sample with a diameter of 50 mm and a thickness of 1.6 to 5 mm was prepared. The sample was then placed on a 50 mm diameter, 1 mm thick SiC disk. The sample surface was irradiated with a tungsten lamp. The heat flux was measured 2 mm from the rear surface of the SiC disk, and the temperature was measured using a K-type thermocouple sandwiched between the sample and the sample. The heat flux ratio and temperature ratio were calculated with and without the sample. A small heat flux ratio and temperature ratio indicate a high heat-shielding effect. The tungsten lamp output was adjusted to two levels: 50% (equivalent to a wavelength temperature of 1965 K) and 80% (equivalent to a wavelength temperature of 2318 K). Figure 1 is a schematic diagram illustrating the evaluation method for the heat flux ratio and temperature ratio.

[0056] [Table 1]

[0057] [Table 2]

[0058] From Tables 1 and 2, it can be seen that by combining a heat shielding layer and a base material (thermal insulating layer), Examples 1 to 9 have lower temperatures and heat fluxes than the insulating material without a heat shielding layer of Comparison Example 1, and therefore achieve a heat shielding effect.

[0059] Here, the combination of Example 1 and Example 2, and the combination of Example 3 and Example 4 are both combinations of materials containing 10 wt% Al2O3 fibers and not containing them, but it can be seen from Table 2 that there is no significant difference in the heat-shielding effect as long as the pore diameter structure is within the range.

[0060] Furthermore, Example 7 is composed of a heat-shielding layer and a base material (high-absorption material), which is a structure according to another aspect of the present invention, and even though its thickness is about one-third of the overall thickness of Examples 1 to 6, it achieves a heat-shielding effect that is not significantly inferior to Examples 1 to 6.

[0061] The waveform of the radiated light differs between 50% and 80% lamp output. The higher the output, the more light there is on the short wavelength side, and the higher the energy. Therefore, the heat flux and temperature are higher at 80% lamp output than at 50%. The reason why the temperature ratio does not change significantly between 50% and 80% in Examples 8 and 9 is thought to be because the proportion of pore volume with pore diameters of 0.5 μm or more and less than 10 μm was 77% or more, which is the highest among the examples.

[0062] In Comparative Examples 2 to 4, the heat shield layers were prepared by adjusting the pore size structure and bulk density to include those outside the ranges. All of these examples include examples where the temperature ratio exceeded 0.50 or the heat flux ratio exceeded 0.16, and it can be seen that the temperature ratio and heat flux ratio were larger than those of Examples 1 to 9, i.e., the heat shield properties were inferior.

Claims

1. A thermal barrier structure comprising a substrate and a thermal barrier layer formed on one main surface of the substrate, the substrate is made of porous ceramics, the thermal barrier layer contains MgAlO 4 and has a bulk density of 1 g / cm 3 or more and 1.7 g / cm 3 or less; a proportion of pores having a pore diameter of 0.5 μm or more and less than 10 μm in the total pore volume of the thermal barrier layer that is between 50 vol% and 77 vol%; a proportion of pores having a pore diameter of 1 μm or more and less than 5 μm in the pore volume of pores having a diameter of 0.5 μm or more and less than 10 μm that is between 61 vol% and 84 vol%; and a proportion of pores having a pore diameter larger than 5.5 μm in the total pore volume of the thermal barrier layer that is between 3 vol% and 21 vol%.

2. A thermal barrier structure comprising a substrate and a thermal barrier layer formed on one main surface of the substrate, the substrate is made of a ceramic material having an emissivity of 0.75 or more, the thermal barrier layer contains MgAlO 4 and has a bulk density of 1 g / cm 3 or more and 1.7 g / cm 3 or less; a proportion of pores having a pore diameter of 0.5 μm or more and less than 10 μm in the total pore volume of the thermal barrier layer that is between 50 vol% and 77 vol%; a proportion of pores having a pore diameter of 1 μm or more and less than 5 μm in the pore volume of pores having a diameter of 0.5 μm or more and less than 10 μm that is between 61 vol% and 84 vol%; and a proportion of pores having a pore diameter larger than 5.5 μm in the total pore volume of the thermal barrier layer that is between 3 vol% and 21 vol%.

3. 3. The heat shield structure according to claim 2, wherein the substrate is made of ceramic fiber cloth.

4. 3. The thermal barrier structure according to claim 2, wherein the total thickness of the substrate and the thermal barrier layer is 2 mm or less.

5. 4. The thermal barrier structure according to claim 3, wherein the total thickness of the substrate and the thermal barrier layer is 2 mm or less.

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