Latent heat storage material and method for producing the same

Abstract

To provide a latent heat storage material having a larger latent heat storage capacity, and a method for producing the latent heat storage material.SOLUTION: A latent heat storage material includes a ceramic part made of a polycrystalline body and having a closed space formed therein and a metal part provided in the closed space and containing 50 mass% or more of silicon.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a latent heat storage material and a method for manufacturing a latent heat storage material. [Background technology]

[0002] Conventionally, an Al-Si alloy or the like has been used as a phase change material (PCM), and a latent heat storage medium has been proposed in which the PCM is surrounded by a protective layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-031507 [Patent Document 2] JP 2015-048393 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for larger amounts of latent heat storage.

[0005] An object of the present disclosure is to provide a latent heat storage material capable of storing a larger amount of latent heat and a method for manufacturing a latent heat storage material. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, there is provided a latent heat storage body having a ceramic part made of a polycrystalline body in which a closed space is formed, and a metal part disposed within the closed space and containing 50% or more by mass of silicon. Effect of the Invention

[0007] According to the disclosed technology, it is possible to store a larger amount of latent heat. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating a latent heat storage material according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a method for manufacturing a latent heat storage material according to the first embodiment. [Diagram 3] FIG. 11 is a diagram illustrating a latent heat storage material according to a second embodiment. [Figure 4] FIG. 13 is a diagram illustrating a latent heat storage material according to a third embodiment. [Diagram 5] 11A to 11C are diagrams illustrating a method for manufacturing a latent heat storage material according to a third embodiment. [Figure 6] 6A to 6C are diagrams illustrating a method for manufacturing a latent heat storage material according to a second embodiment. [Figure 7] FIG. 11 is a perspective view illustrating a latent heat storage material according to a fourth embodiment. [Figure 8] 10A to 10C are cross-sectional views illustrating a method for manufacturing a latent heat storage material in an experiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description may be omitted.

[0010] (First embodiment) A first embodiment will be described. The first embodiment relates to a latent heat storage material. Fig. 1 is a diagram illustrating a latent heat storage material according to the first embodiment. Fig. 1(a) is a perspective view, and Fig. 1(b) is a cross-sectional view.

[0011] The latent heat storage material 1 according to the first embodiment has a ceramic part 110 made of a polycrystalline body, and a metal part 120, as shown in FIGS. 1(a) and 1(b).

[0012] A closed space 111 is formed in the ceramic part 110. The ceramic part 110 and the closed space 111 are shaped like a rectangular parallelepiped. The ceramic part 110 is, for example, formed as an integral part. For example, the ceramic part 110 does not have a joint portion connected to the closed space 111. The ceramic portion 110 may contain, for example, mullite (3Al2O3·2SiO2), aluminum oxide (Al2O3), cordierite (2MgO·2Al2O3·5SiO2), anorthite (CaAl2Si2O8), sillimanite (Al2SiO5), silicon nitride (Si3N4), boron nitride (BN), aluminum nitride (AlN), a composite material of aluminum nitride and boron nitride (composite ceramic), silicon carbide (SiC), tungsten carbide (WC), boron carbide (B4C), molybdenum disilicide (MoSi2), or tungsten disilicide (WSi2), or any combination thereof. The ceramic portion 110 may be composed of mullite, aluminum oxide, cordierite, anorthite, sillimanite, silicon nitride, boron nitride, aluminum nitride, a composite of aluminum nitride and boron nitride, silicon carbide, tungsten carbide, boron carbide, molybdenum disilicide, or tungsten disilicide, or any combination thereof.

[0013] The metal part 120 is provided in the closed space 111. In other words, the metal part 120 is sealed in the ceramic part 110. It can also be said that the metal part 120 is airtightly covered by the ceramic part 110, which is a continuous body. The metal part 120 contains silicon (Si). For example, the main component of the metal part 120 is silicon. The metal part 120 contains silicon at a ratio of, for example, 50% by mass or more. The metal part 120 may be made of silicon with a purity of 50% by mass or more. Preferably, the metal part 120 contains 99% by mass or more of silicon and is made of 99% by mass or more of silicon. Metal portion 120 may contain boron (B), aluminum (Al), bismuth (Bi), antimony (Sb), gallium (Ga), copper (Cu), iron (Fe), titanium (Ti), yttrium (Y), indium (In), zinc (Zn), or tin (Sn), or any combination thereof, in a total amount of less than 50 mass%.

[0014] For example, when the metal part 120 is composed of 92% by mass Si-8% by mass B, the phase change temperature of the metal part 120 is 1385°C. When the metal part 120 is composed of 85% by mass Si-15% by mass Ti, the phase change temperature of the metal part 120 is 1330°C. When the metal part 120 is composed of 88% by mass Si-12% by mass Y, the phase change temperature of the metal part 120 is 1200°C. When the metal part 120 is composed of 99% by mass Si-1% by mass Fe, the phase change temperature of the metal part 120 is about 1200°C. When the metal part 120 is composed of 80% by mass Si-20% by mass Al or 80% by mass Si-20% by mass Cu, the phase change temperature of the metal part 120 is about 1300°C.

[0015] The volume of the closed space 111 may be equal to the volume of the metal part 120 or may be larger than the volume of the metal part 120 .

[0016] The melting point of silicon is 1414°C. When the main component of the metal part 120 is silicon, a phase change between solid and liquid occurs at about 1414°C. At this temperature, the ceramic part 110 made of polycrystalline material is chemically stable. Therefore, whether the metal part 120 is solid or liquid, the ceramic part 110 can confine the metal part 120 in the closed space 111. Even when used at high temperatures, the ceramic part 110 is unlikely to undergo chemical changes such as oxidation. The melting point of the metal part 120 is, for example, 1100°C or higher. The melting point of the metal part 120 is preferably 1200°C or higher, more preferably 1300°C or higher, and even more preferably 1350°C or higher. When the metal part 120 contains boron or the like in addition to silicon, the melting point of the metal part 120 may be lower than 1414°C. The melting point of the metal portion 120 can be measured, for example, by differential thermal analysis (DTA) or differential scanning calorimetry (DSC).

[0017] In the latent heat storage material 1, the metal part 120 functions as a phase change material (PCM) and contains 50 mass % or more of silicon, so that the solid-liquid phase change temperature of the metal part 120 is high and a larger amount of latent heat can be stored. The latent heat stored in the latent heat storage material 1 can be used for direct power generation by thermophotovoltaic (TPV), for example.

[0018] In addition, even if the latent heat storage material 1 is used at high temperatures, the ceramic part 110 is unlikely to be altered, such as oxidized. This improves stability. Therefore, an oxidizing medium such as air can be used as the heat medium, and the range of heat medium options can be expanded.

[0019] Furthermore, the surface of the latent heat storage material 1 can be easily cleaned. For example, when the heat medium is exhaust gas from a combustion furnace containing unburned components, the heat medium may contain substances such as soot that tend to adhere to the latent heat storage material 1. The adhesion of such substances may lead to a decrease in thermal conductivity and an increase in flow resistance. In contrast, in the latent heat storage material 1, the adhered substances can be easily removed by high-temperature treatment in the atmosphere. When the adhered substances are non-organic, they can also be removed by acid washing or the like.

[0020] The density of solid silicon at room temperature is 2.3290 g / cm 3 and the density of liquid silicon near its melting point is 2.57 g / cm 3 Therefore, the volume change accompanying the phase change of silicon is small.

[0021] Next, a method for manufacturing the latent heat storage material 1 according to the first embodiment will be described. Fig. 2 is a diagram illustrating a method for manufacturing the latent heat storage material 1 according to the first embodiment. Fig. 2(a) is a perspective view, and Fig. 2(b) is a cross-sectional view.

[0022] First, as shown in Figures 2(a) and 2(b), a composite 1A is prepared that has an unsintered ceramic part 130 and a metal part 140. The metal part 140 is covered with the ceramic part 130. Later, the ceramic part 130 becomes the ceramic part 110, and the metal part 140 becomes the metal part 120.

[0023] The ceramic portion 130 is, for example, a green sheet laminate, a slip casting body, a gel casting body, or a cold isostatic pressing (CIP) compact formed after preforming granulated powder, containing the material of the ceramic portion 110. The ceramic portion 130 contains, for example, mullite, aluminum oxide, cordierite, anorthite, sillimanite, silicon nitride, boron nitride, aluminum nitride, a composite material of aluminum nitride and boron nitride, silicon carbide, tungsten carbide, boron carbide, molybdenum disilicide, tungsten disilicide, or any combination thereof. The ceramic portion 130 may further include a sintering aid, etc. Ceramic portion 130 preferably contains 99 mass % or more of mullite, aluminum oxide, cordierite, anorthite, sillimanite, silicon nitride, boron nitride, aluminum nitride, a composite material of aluminum nitride and boron nitride, silicon carbide, tungsten carbide, boron carbide, molybdenum disilicide, tungsten disilicide, or any combination thereof. The grain size of the ceramic grains contained in ceramic portion 130 is preferably 3 μm or less, and more preferably 1 μm or less.

[0024] The metal part 140 is, for example, a wire material, a column material, a paste, a slip casting body, a gel casting body, or a CIP molded body obtained by preforming granulated powder, each of which contains silicon. The metal part 140 contains silicon at a ratio of, for example, 99% by mass or more.

[0025] A closed space 131 is formed in the ceramic part 130, and the metal part 140 is provided in the closed space 131. The metal part 140 may be in either a lump or powder form. The bulk of the metal part 140 is preferably adjusted in consideration of the shrinkage of the ceramic part 130 during firing, so that the volume of the metal part 120 in the latent heat storage material 1 and the volume of the closed space 111 in the ceramic part 110 are approximately the same.

[0026] Next, the ceramic part 130 and the metal part 140 are fired simultaneously. As a result, the ceramic part 110 is formed from the ceramic part 130, and the metal part 120 is formed from the metal part 140 (see FIG. 1(a) and FIG. 1(b)). At this time, the ceramic part 130, which was a porous body, becomes dense, and the relative density of the ceramic part 110 made of a polycrystalline body becomes about 95% to 99%. On the other hand, when the metal part 140 is a wire or a columnar material, it hardly becomes dense, and the relative density of the metal part 120 becomes almost 100%. Therefore, it is preferable to determine the relative densities of the ceramic part 130 and the metal part 140 in consideration of the difference in the change in relative density due to firing. Note that in the present disclosure, even if the metal part does not undergo any change in components or properties other than the phase change during firing of the ceramic part, the metal part is fired, and these may be fired simultaneously. Also, the relative density refers to the density relative to the density in a solid bulk state. In other words, the relative density refers to the ratio of the density of a comparison object to the density in a state where there are no voids or defects.

[0027] The temperature of the co-firing is determined as a condition for the relative density of the ceramic part 110 to be obtained so that it does not contain continuous pores (voids connecting the inside to the surface), specifically, a temperature of about 90% or more. Although it depends on the type and composition of the ceramic, it is preferable to set the temperature to be 50°C or higher and 300°C or lower than the melting point of the metal part 140. The heating rate during the co-firing is adjusted according to the possible densification rate depending on the type and composition of the ceramic and the size (thickness, etc.) of the object to be fired determined by design, but it is preferable to set the heating rate as high as possible. The atmosphere for the co-firing is, for example, one of reducing atmospheres containing reducing gas such as hydrogen, non-oxidizing atmospheres containing non-oxidizing gas such as nitrogen, and oxidizing atmospheres containing oxidizing gas such as air, depending on the properties of the material of the ceramic part 130. Note that when the co-firing is performed in an oxidizing atmosphere, the oxide film that was present on the surface of the metal material that constitutes the metal part 140 may remain as it is in the metal part 120. Even in this case, the heat capacity associated with the phase change can be sufficiently obtained, so the oxide film may remain in the metal part 120.

[0028] In this manner, the latent heat storage material 1 according to the first embodiment can be manufactured.

[0029] According to this manufacturing method, the metal part 120 is sealed by the ceramic part 110. It can also be said that the metal part 120 is air-tightly covered by the ceramic part 110, which is a continuous body.

[0030] Here, the material of the ceramic portion 110 will be described in detail.

[0031] Mullite, an example of a material for the ceramic portion 110, can be sintered at around 1600°C and does not react with silicon in the air, in a neutral atmosphere, or in a reducing atmosphere. The material for the ceramic portion 110 may be pure mullite, but the densification temperature can be reduced by adding a sintering aid. As a sintering aid, oxides of Group 2 and Group 3 elements are effective, and the effectiveness of magnesium oxide (MgO), calcium oxide (CaO), yttrium oxide (Y2O3), and lanthanum oxide (La2O3) has been confirmed. Yttrium oxide is particularly preferable in terms of effectiveness and ease of handling of the raw material.

[0032] Aluminum oxide, which is an example of a material for the ceramic part 110, is a relatively inexpensive material. However, in an atmosphere containing oxygen, a composite oxide containing silicon is likely to be generated, and there is a risk that the silicon contained in the metal part 120 will be consumed. For this reason, it is preferable that the atmosphere during the co-firing is a non-oxidizing atmosphere. In addition, it is also preferable that the atmosphere during use of the latent heat storage material 1 is a non-oxidizing atmosphere.

[0033] An example of the material of the ceramic portion 110 is a nitride. The nitride includes silicon nitride, boron nitride, aluminum nitride, and a composite material of aluminum nitride and boron nitride. Hexagonal boron nitride and a composite material of aluminum nitride and boron nitride (composite ceramic) are easy to machine after sintering. A composite material of aluminum nitride and boron nitride can obtain a higher mechanical strength than hexagonal boron nitride. The ratio of aluminum nitride and boron nitride in the composite material of aluminum nitride and boron nitride is not limited, but each ratio is preferably 50 mass %. When the main component of the ceramic portion 110 is a composite material of aluminum nitride and boron nitride, yttrium oxide and calcium carbonate are preferable as sintering aids.

[0034] An example of the material of the ceramic part 110 is carbide. Carbide includes silicon carbide, tungsten carbide, and boron carbide. Silicon carbide, tungsten carbide, and boron carbide have electrical conductivity, depending on the carbon content. Silicon carbide, tungsten carbide, and boron carbide are materials that generate heat when electricity is applied, and silicon carbide, tungsten carbide, and boron carbide can be used as heaters. When the ceramic part 110 includes silicon carbide, tungsten carbide, or boron carbide, the ceramic part 110 has the protection function and heating function of the metal part 120, and it is easy to achieve a higher heat storage density. In addition, the ceramic part 110 including silicon carbide, tungsten carbide, or boron carbide can reduce the size of the equipment in a method of directly using surplus electricity to store heat (ETES). Although silicon carbide can be sintered under atmospheric pressure, sintering by hot pressing is preferred to obtain a denser and more thermally conductive ceramic part 110. When sintering by hot pressing, gaps are unlikely to form between the metal part 120 and the ceramic part 110, but since the metal part 120 is mainly composed of silicon and does not increase in volume due to liquefaction, no gaps are formed.

[0035] An example of the material of the ceramic part 110 is a silicide. The silicide includes molybdenum disilicide (MoSi2) and tungsten disilicide (WSi2). Molybdenum disilicide and tungsten disilicide are materials that generate heat when electricity is applied, and can be stably used as a heater in the atmosphere in a temperature range including the phase change temperature of silicon (1414°C). When the ceramic part 110 includes molybdenum disilicide or tungsten disilicide, the ceramic part 110 has a protection function and a heating function of the metal part 120, and it is easy to achieve a higher heat storage density. In addition, in the atmosphere, a dense oxide film of silicon dioxide (SiO2) is formed on the surface of the molybdenum disilicide and tungsten disilicide, and oxidation inside the molybdenum disilicide and tungsten disilicide is suppressed. Therefore, the ceramic portion 110 containing molybdenum disilicide or tungsten disilicide is chemically stable even in the atmosphere.

[0036] To obtain a sintered body of molybdenum disilicide, for example, kaolinite (Al4Si4O 10 (OH)8) based additives or montmorillonite ((Na,Ca) 0.33 (Al,Mg)2Si4O 10 Additives such as (OH)2)-based additives are added, and a water-based or (polar) solvent-based slurry is used. A green body is formed through this slurry, and then fired at about 1550°C in a non-oxidizing atmosphere such as a nitrogen atmosphere or a hydrogen-containing nitrogen atmosphere.

[0037] From the viewpoints of raw material costs, manufacturing equipment, manufacturing difficulty, and cost, mullite is the most preferable material for the ceramic portion 110 .

[0038] Second embodiment A second embodiment will be described. The second embodiment relates to a latent heat storage material. Fig. 3 is a diagram illustrating a latent heat storage material according to the second embodiment. Fig. 3(a) is a perspective view, and Fig. 3(b) is a cross-sectional view.

[0039] The latent heat storage material 2 according to the second embodiment has a ceramic part 210 made of a polycrystalline body and a metal part 220, as shown in FIGS. 3(a) and 3(b).

[0040] A closed space 211 is formed in the ceramic part 210. The ceramic part 210 and the closed space 211 are cylindrical in shape. The ceramic part 210 is, for example, formed integrally. For example, the ceramic part 210 does not have a joint portion connected to the closed space 211. The ceramic part 210 is formed from the same material as the ceramic part 110.

[0041] The metal part 220 is provided in the closed space 211. In other words, the metal part 220 is sealed in the ceramic part 210. It can also be said that the metal part 220 is air-tightly covered by the ceramic part 210, which is a continuous body. The metal part 220 is made of the same material as the metal part 120.

[0042] The volume of the closed space 211 may be equal to the volume of the metal part 220 or may be larger than the volume of the metal part 220 .

[0043] Other configurations are the same as those of the first embodiment. Moreover, the latent heat storage material 2 according to the second embodiment can be manufactured by the same method as that of the first embodiment, except for the shape.

[0044] The second embodiment can provide the same effects as the first embodiment. Moreover, since external stress to the ceramic portion 210 is easily dispersed, higher durability can be obtained.

[0045] The latent heat storage material may have a spherical or prismatic shape.

[0046] Third embodiment A third embodiment will be described. The third embodiment relates to a latent heat storage material. Fig. 4 is a diagram illustrating a latent heat storage material according to the third embodiment. Fig. 4(a) is a perspective view, and Fig. 4(b) is a cross-sectional view.

[0047] The latent heat storage material 3 according to the third embodiment has a ceramic portion 310 made of a polycrystalline body, and a plurality of metal portions 320, as shown in FIGS. 4(a) and 4(b).

[0048] A plurality of closed spaces 311 are formed in the ceramic part 310. The ceramic part 310 and the closed spaces 311 are shaped like a rectangular parallelepiped. The ceramic part 310 is, for example, integrally formed. For example, the ceramic part 310 does not have a joint portion connected to the closed spaces 311. The ceramic part 310 is made of the same material as the ceramic part 110. The closed spaces 311 are arranged at equal intervals in two directions perpendicular to each other within a plane parallel to a pair of parallel planes of the ceramic part 310.

[0049] The metal parts 320 are provided one by one in the closed space 311. In other words, the metal parts 320 are sealed in the ceramic part 310. It can also be said that the metal parts 320 are airtightly covered by the ceramic part 310, which is a continuous body. The metal parts 320 are made of the same material as the metal parts 120.

[0050] The volume of the closed space 311 may be equal to the volume of the metal part 320 or may be larger than the volume of the metal part 320 .

[0051] The other configuration is similar to that of the first embodiment.

[0052] Next, a method for manufacturing the latent heat storage material 3 according to the third embodiment will be described. Fig. 5 is a diagram illustrating a method for manufacturing the latent heat storage material 3 according to the third embodiment.

[0053] First, as shown in FIG. 5(a), an unfired ceramic part 350A is prepared in which a plurality of cavities 351 that become the closed spaces 311 are formed. The ceramic part 350A is, for example, a laminate of green sheets. The ceramic part 350A may be formed by injection molding or the like. Later, the ceramic part 350A becomes a part of the ceramic part 310.

[0054] Preparation of the unsintered ceramic part 350A includes, for example, the following processes. First, a ceramic slurry is prepared by a ball mill method or the like, and a plurality of green sheets are formed by a doctor blade method or the like. Next, through holes corresponding to the closed spaces 331 are formed in the green sheets by a punching method or the like. In addition, green sheets without through holes are also prepared. Then, the green sheets with through holes are stacked on top of the green sheets without through holes.

[0055] 5(b), a metal portion 360 is provided in each cavity 351. Later, the metal portion 360 becomes the metal portion 320. The metal portion 360 is, for example, a paste, a bead, a winding, or a sheet.

[0056] 5(c), a sheet-like ceramic part 350B is provided on the ceramic part 350A so as to close the open end of the cavity 351. Later, the ceramic part 350B becomes a part of the ceramic part 310. A green sheet without through holes can be used as the sheet-like ceramic part 350B.

[0057] In this manner, a composite body 3A having unsintered ceramic portions 350A and 350B and a metal portion 360 is obtained.

[0058] Next, ceramic portions 350A and 350B and metal portion 360 are simultaneously fired. As a result, ceramic portion 310 is formed from ceramic portions 350A and 350B, and metal portion 320 is formed from metal portion 360 (see FIGS. 4(a) and 4(b)).

[0059] In this manner, the latent heat storage material 3 according to the third embodiment can be manufactured.

[0060] The third embodiment can also provide the same effects as the first embodiment.

[0061] Before firing the complex 3A, the complex 3A may be divided into each metal portion 360. In this case, the latent heat storage material 1 according to the first embodiment can be obtained.

[0062] The latent heat storage material 2 according to the second embodiment can also be obtained by a similar method. Fig. 6 is a diagram showing a method for producing the latent heat storage material 2 according to the second embodiment.

[0063] First, as shown in FIG. 6(a), an unfired ceramic part 250A having a plurality of cavities 251 that become the closed spaces 211 is prepared.

[0064] Next, as shown in FIG. 6(b), a metal portion 260 is provided in each cavity 251.

[0065] Next, as shown in FIG. 6(c), a sheet-like ceramic part 250B is provided on the ceramic part 250A so as to close the open end of the cavity 251, thereby obtaining a composite body 2A.

[0066] Next, the composite body 2A is divided into each metal portion 260. Then, the ceramic portions 250A and 250B and the metal portion 260 are fired simultaneously.

[0067] By using such a method, the latent heat storage material 2 according to the second embodiment can also be manufactured.

[0068] The composite for producing the latent heat storage medium may be produced by a method such as dip coating of a ceramic slurry.

[0069] (Fourth embodiment) A fourth embodiment will be described. The fourth embodiment relates to a latent heat storage material. Fig. 7 is a perspective view illustrating a latent heat storage material according to the fourth embodiment.

[0070] As shown in FIG. 7, the latent heat storage body 4 according to the fourth embodiment has a ceramic part 210 made of a polycrystalline body, a metal part 220, and an electric heater 430 capable of heating the metal part 220. The electric heater 430 is provided in the ceramic part 210. The electric heater 430 is provided between the surface of the ceramic part 210 and the surface of the metal part 220. The electric heater 430 has an approximately cylindrical shape as a whole. When viewed from a direction parallel to the long axis of the columnar metal part 220, the electric heater 430 forms a spiral, for example, by repeating clockwise and counterclockwise alternately. The electric heater 430 contains, for example, tungsten or molybdenum, or both of these. The electric heater 430 may contain a mixture of tungsten and aluminum oxide, or a mixture of molybdenum and aluminum oxide. In this case, the electric heater 430 may further contain one or more of silicon oxide, magnesium oxide, calcium carbonate, and the like. Heating element 430 is an example of a heater.

[0071] Other configurations of the fourth embodiment are similar to those of the second embodiment.

[0072] In manufacturing the latent heat storage body 4 according to the fourth embodiment, for example, tungsten or molybdenum powder is mixed with aluminum oxide powder, and organic components such as a solvent and a binder are added to prepare a resistor paste. The portion (circumferential portion) perpendicular to the long axis of the metal part 220 of the electric heater 430 can be formed, for example, by the resistor paste printed on the surface of a ceramic green sheet. The portion extending parallel to the long axis of the metal part 220 of the electric heater 430 can be formed, for example, by the resistor paste filled in a through hole formed in a ceramic green sheet. The resistivity of the electric heater 430 can be adjusted according to the proportion of aluminum oxide. One or more of silicon oxide, magnesium oxide, calcium carbonate, etc. may be further added to the resistor paste. These inorganic components form a liquid phase or a complex oxide phase during firing, and can improve the adhesive strength of the electric heater 430 with the ceramic part 230 and improve the stability of the resistivity.

[0073] The fourth embodiment can also provide the same effects as the second embodiment. In addition, since the electric heater 430 can heat the metal part 220, it is possible to convert electric energy applied from the outside into heat and store it in the latent heat storage body 4. For example, by generating heat from the electric heater 430 using surplus power, it is possible to store the surplus power as heat. The energy stored in the latent heat storage body 4 can be supplied to factories, offices, commercial buildings, etc. as energy in the form of heat, steam (pressure), or electricity (such as turbine power generation using steam pressure).

[0074] In addition, since the latent heat storage body 4 includes the electric heating body 430, it is possible to reduce energy loss. For example, when the electric heating body and the latent heat storage body are separated, the heat generated from the electric heating body is transferred to the latent heat storage body as hot air or the like, which tends to result in energy loss, but in this embodiment, it is possible to suppress such energy loss.

[0075] (Experimental Example) Next, an experiment conducted by the inventor of the present application will be described. Fig. 8 is a cross-sectional view illustrating a method for manufacturing a latent heat storage material in the experiment.

[0076] In the first experiment, polyvinyl butyral binder, phthalic acid plasticizer, and alcohol solvent were added to mullite powder, and the mixture was ground and mixed using a ball mill to prepare a slurry. The slurry was then vacuum degassed and the viscosity was adjusted, and four green sheets with a thickness of approximately 0.5 mm were produced using the doctor blade method.

[0077] Next, as shown in FIG. 8(a), through holes 532A having an opening shape determined from the volume after shrinkage due to firing were formed in two green sheets 532, and the two green sheets 532 were laminated on top of a green sheet 531 in which no through holes were formed.

[0078] 8(b), silicon pieces 540 cut out from a silicon substrate were placed in through holes 532A, and green sheets 533 without through holes were laminated on the laminate of green sheets 532. The proportion of silicon in silicon pieces 540 was 99 mass % or more.

[0079] Next, the structure shown in Fig. 8(b) was fired in an air atmosphere at 1600°C for 2 hours. As a result, as shown in Fig. 8(c), a latent heat storage body 5 having a ceramic part 510 made of a polycrystalline body in which a closed space 511 was formed and a metal part 520 provided in the closed space 511 was obtained.

[0080] Then, the latent heat storage material 5 was cut so that the metal part 520 was cut, the cut surface was polished, and the cut surface was observed. As a result, the metal part 520 exhibited a metallic luster, and the boundary between the ceramic part 510 and the metal part 520 was clear.

[0081] Furthermore, when the resistance value of metal part 520 was measured using a two-terminal tester, the resistance value of metal part 520 was approximately 40 kΩ. Furthermore, a ceramic material that was separately fired under the same conditions as ceramic part 510 had a relative density of approximately 90%.

[0082] In the second experiment, a polyvinyl butyral binder, a phthalic acid plasticizer, and an alcohol solvent were added to a mixture of mullite powder containing 5% by mass of yttrium oxide powder and yttrium oxide powder, and the mixture was ground and mixed by a ball mill method to prepare a slurry. Next, the slurry was vacuum degassed and the viscosity was adjusted, and four green sheets with a thickness of about 0.5 mm were produced by a doctor blade method. Then, a latent heat storage material 5 was obtained in the same manner as in the first experiment. The yttrium oxide powder functions as a sintering aid.

[0083] Then, the latent heat storage material 5 was cut so that the metal part 520 was cut, the cut surface was polished, and the cut surface was observed. As a result, similar to the first experiment, the metal part 520 exhibited a metallic luster, and the boundary between the ceramic part 510 and the metal part 520 was clear.

[0084] In addition, the microstructure and distribution of components of the latent heat storage material 5 were confirmed using a scanning electron microscope (SEM). As a result, the metal part 520 and the ceramic part 510 were closely joined to each other. Furthermore, oxygen, aluminum, and yttrium were not detected in the metal part 520, and the metal part 520 was substantially composed of only silicon. Furthermore, silicon that is thought to be derived from the silicon slice 540 was not detected in the ceramic part 510, and aluminum, oxygen, and silicon with low relative intensity were detected in the ceramic part 510, and yttrium was hardly detected. In addition, the relative density of the ceramic material sintered under the same conditions as the ceramic part 510 (including yttrium oxide powder) was about 98%.

[0085] Although preferred embodiments have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0086] 1, 2, 3, 4, 5 Latent heat storage body 110, 130, 210, 230, 250A, 250B, 310, 350A, 350B, 510 Ceramic part 111, 131, 211, 311, 331, 511 Closed space 120, 140, 220, 260, 320, 360, 520 Metal parts 531, 532, 533 Green Sheets 540 Silicon slice

Claims

1. A ceramic part made of a polycrystalline material in which a closed space is formed, A metal part containing 50% by mass or more of silicon is provided within the aforementioned closed space, A latent heat storage body.

2. A ceramic part made of a polycrystalline material in which a closed space is formed, A metal part containing silicon is provided within the aforementioned closed space, It has, The latent heat storage body has a melting point of 1100°C or higher for the metal part.

3. The latent heat storage body according to claim 2, wherein the metal part contains silicon in a proportion of 50% by mass or more.

4. The latent heat storage body according to claim 1 or 2, wherein the metal part contains silicon in a proportion of 99% by mass or more.

5. The latent heat storage body according to any one of claims 1 to 3, wherein the ceramic portion contains mullite, aluminum oxide, cordierite, anorthite, sillimanite, silicon nitride, boron nitride, aluminum nitride, a composite material of aluminum nitride and boron nitride, silicon carbide, tungsten carbide, boron carbide, molybdenum disilicide, or tungsten disilicide, or any combination thereof.

6. The latent heat storage body according to claim 5, wherein the ceramic portion contains mullite.

7. The latent heat storage body according to any one of claims 1 to 3, wherein the ceramic portion contains a material that generates heat when an electric current is passed through it.

8. A latent heat storage body according to any one of claims 1 to 3, having a heater capable of heating the metal part.

9. The latent heat storage body according to claim 8, wherein the heater is provided within the ceramic portion.

10. The heater is a latent heat storage body according to claim 8, comprising tungsten, molybdenum, or both thereof.

11. The ceramic portion has a pair of main surfaces that are parallel to each other, Multiple of the closed spaces are formed in a plane parallel to the main surface, The latent heat storage body according to any one of claims 1 to 3, wherein each of the multiple metal parts is provided one by one in each of the multiple closed spaces.

12. A step of preparing a composite having a metal part containing 50% by mass or more of silicon and an unfired ceramic part containing the metal part, A step of firing the metal part and the ceramic part simultaneously, It has, The method for manufacturing a latent heat storage body, wherein the ceramic portion is composed of multiple green sheets stacked together.

13. A step of preparing a composite having a metal part containing silicon and an unfired ceramic part containing the metal part, A step of firing the metal part and the ceramic part simultaneously, It has, The aforementioned ceramic part is constructed by laminating multiple green sheets. A method for manufacturing a latent heat storage body, wherein the melting point of the metal part is 1100°C or higher.

14. The method for producing a latent heat storage body according to claim 13, wherein the metal part contains silicon in a proportion of 50% by mass or more.

15. The method for producing a latent heat storage body according to claim 12 or 13, wherein the metal part contains silicon in a proportion of 99% by mass or more.

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