JP7016109B2 - Composite structure, method for manufacturing composite structure, and method for heat storage - Google Patents

Description

The present invention relates to a composite structure useful as a heat storage body and the like, a method for producing the same, and a heat storage method using the composite structure as a heat storage body.

As one of the heat storage methods, latent heat storage using latent heat accompanying a phase change is known. As a heat storage body using such latent heat storage, a capsule-shaped heat storage body having a latent heat storage substance inside thereof has been proposed.

For example, Patent Document 1 proposes a latent heat storage capsule in which one or more metal coatings are formed on the surface of a latent heat storage material by an electrolytic plating method. Further, in Patent Document 2, a water-soluble latent heat storage substance that stores heat or dissipates heat due to a phase change is used as a core substance, and this core substance is covered with a composite capsule wall formed by combining an inorganic compound and an organic polymer compound. The heat storage microcapsules have been proposed.

Further, in Patent Document 3, a core substance made of a water-soluble heat storage material such as a saccharide, a first capsule wall made of a composite material of an inorganic compound and an organic polymer compound covering the core substance, and the first capsule wall. A heat storage microcapsule having a second capsule wall made of a polymer material covering the above has been proposed.

However, since the metal film of the latent heat storage capsule proposed in Patent Document 1 has low heat resistance, there is a problem that the metal film is torn when used in a high temperature state and the internal heat storage substance easily leaks out. Further, since the capsule wall of the heat storage microcapsules proposed in Patent Documents 2 and 3 has a low density, the strength is low. Therefore, it has been difficult to use it under high temperature conditions or in a harsh environment where corrosion is likely to occur. Furthermore, the above-mentioned conventional heat storage capsules and the like have a low energy density and the heat resistance of the outer shell portion is not sufficient, so that the sensible heat utilizing the temperature difference cannot be sufficiently utilized and the energy density is low. There was also a problem.

In order to solve such a problem, for example, Patent Document 4 proposes a heat storage body in which an internal heat storage body such as a metal is contained in an outer shell formed by fitting a pair of hollow hemispheres made of ceramics on a split surface. Has been done.

Japanese Unexamined Patent Publication No. 11-23172 JP-A-2007-238912 Japanese Unexamined Patent Publication No. 2009-108167 Japanese Unexamined Patent Publication No. 2012-11182

The heat storage body proposed in Patent Document 4 has a high energy density and is useful to some extent. However, at the time of use, air may enter the inside from the fitting portion of the pair of hollow hemispheres forming the outer shell. For this reason, there are problems that the internal heat storage body such as metal is easily deteriorated by oxidation and the mechanical strength is insufficient due to the existence of the fitting portion. Further, since there is a slight void between the outer shell and the internal heat storage body, this void may become a thermal resistance and the rate of temperature rise may decrease. Further, in the manufacturing method disclosed in Patent Document 4, as shown in FIG. 5, it is necessary to individually prepare the internal heat storage body 80 and the outer shells 92 and 94, and then combine them to form the heat storage body 100. For this reason, the manufacturing process becomes complicated and the cost is high, and it is difficult to constantly manufacture a heat storage body having stable performance.

The present invention has been made in view of the problems of the prior art, and the problems thereof are excellent temperature rise characteristics, high mechanical strength, and stable heat storage performance. It is an object of the present invention to provide a composite structure useful as a heat storage body or the like that can be effectively exhibited. Further, an object of the present invention is to provide a simple method for producing the above-mentioned composite structure and a heat storage method using the above-mentioned composite structure.

That is, according to the present invention, the following composite structure is provided.
[1] The metal includes an internal structural portion made of a metal material and a seamless outer shell portion made of ceramics containing 90% by volume or more of silicon carbide formed by reaction sintering and containing the internal structural portion. A composite structure in which the melting point of the material is 1,500 ° C. or lower .
[2] The composite structure according to the above [1], further comprising a buffer layer arranged between the internal structure portion and the outer shell portion.
[3] The composite structure according to the above [2], wherein the buffer layer is made of at least one of boron nitride and carbon.
[ 4 ] The composite material according to any one of the above [ 1 ] to [3], wherein the metal material is at least one metal selected from the group consisting of copper, aluminum, nickel, and iron.
[ 5 ] The composite structure according to any one of the above [1] to [ 4 ], wherein the metal material contains silicon.
[6] The composite structure according to any one of the above [1] to [3], wherein the metal material is copper or a copper-silicon alloy containing 35% by mass or less of silicon.
[7] The composite structure according to any one of the above [1] to [6], which is used as a heat storage body.

Further, according to the present invention, there is provided a method for producing a composite structure shown below.
[8] The method for producing a composite structure according to any one of the above [1] to [7], wherein the outer peripheral surface of the molded body made of the metal material is coated with a coating layer containing silicon carbide and carbon. A composite structure having a step of obtaining a body to be fired and a step of heating at least the coating layer of the obtained body to be fired in contact with silicon and forming the outer shell portion by reaction sintering. Manufacturing method.

Further, according to the present invention, the following heat storage method is provided.
[9] A heat storage method comprising a step of heating the composite structure according to the above [7] to a temperature equal to or higher than the melting point of the internal structure portion to store heat in the composite structure.

According to the present invention, it is possible to provide a composite structure useful as a heat storage body or the like, which is excellent in temperature rise characteristics, has high mechanical strength, and can stably exhibit heat storage performance. Further, according to the present invention, it is possible to provide a simple method for producing the above-mentioned composite structure and a heat storage method using the above-mentioned composite structure.

It is sectional drawing which shows typically one Embodiment of the composite structure of this invention. It is sectional drawing which shows typically the other embodiment of the composite structure of this invention. It is a schematic diagram which shows one Embodiment of the manufacturing method of the composite structure of this invention. It is a schematic diagram which shows the other embodiment of the manufacturing method of the composite structure of this invention. It is a schematic diagram which shows an example of the manufacturing method of the conventional heat storage body. It is a graph which shows the influence which each factor has on the temperature rise characteristic of a composite structure. It is a graph which shows the influence which each factor has on the mechanical strength of a composite structure.

<Composite structure>
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. The composite structure of the present invention includes an internal structure portion made of a metal material and a seamless outer shell portion made of ceramics containing silicon carbide as a main component, which is formed by reaction sintering and contains the internal structure portion. .. Hereinafter, the details of the composite structure of the present invention will be described.

FIG. 1 is a cross-sectional view schematically showing an embodiment of the composite structure of the present invention. As shown in FIG. 1, the composite structure 10 of the present embodiment includes an internal structure portion 2 and a seamless outer shell portion 4 including the internal structure portion 2.

(Internal structure)
The internal structure portion 2 constituting the composite structure 10 is formed of a metal material and is a portion that mainly functions as an internal heat storage body. Considering the case where the composite structure 10 is used as a heat storage body for recovering and reusing waste heat in a temperature range of 1,000 to 1,500 ° C., the melting point of the metal material constituting the internal structure portion 2 is 1,500. The temperature is preferably 1 ° C. or lower, and more preferably 1,000 to 1,400 ° C. Examples of such metal materials include copper, aluminum, nickel, iron and the like. These metallic materials can be used alone or in combination of two or more.

The metal material constituting the internal structure portion 2 preferably contains silicon. In the method for manufacturing a composite structure described later, a body to be fired in which the outer peripheral surface of a molded body made of a metal material is covered with a coating layer is heated to a predetermined temperature. Therefore, by including silicon that shrinks during the phase transformation from a solid to a liquid in the metal material, it is possible to suppress excessive expansion of the molten metal material due to heating. As a result, the obtained composite structure is less likely to be damaged, and the properties such as thermal conductivity of the obtained composite structure can be further improved.

When the metal material constituting the internal structure portion 2 contains silicon, the content of silicon in the metal material is preferably 2 to 35% by mass, more preferably 5 to 30% by mass. It is particularly preferably 10 to 25% by mass. If the content of silicon in the metallic material is less than 2% by mass, the effect obtained by containing silicon becomes insufficient. On the other hand, if the content of silicon in the metal material is more than 35% by mass, the characteristics of silicon are likely to be manifested, and the thermal characteristics of the metal material itself may be insufficient.

(Outer shell)
The outer shell portion 4 constituting the composite structure 10 is formed of ceramics. Further, this ceramic contains silicon carbide formed by reaction sintering as a main component. Since the composite structure 10 of the present embodiment has the internal structure portion 2 covered with the outer shell portion 4 formed of such ceramics, it has good temperature rising characteristics and excellent mechanical strength. show. The amount of silicon carbide contained in the ceramics forming the outer shell portion 4 is not particularly limited, but is preferably 50% by volume or more, and more preferably 90% by volume or more.

Further, the outer shell portion 4 is a so-called seamless portion in which a fitting portion, a joint portion, a gap, or the like is substantially not present. Therefore, it is difficult for air to enter from the outside through the outer shell portion 4, and the internal structure portion 2 is less likely to deteriorate. Further, since there is substantially no fitting portion or gap in the outer shell portion 4, excellent mechanical strength is exhibited.

(Cushioning layer)
FIG. 2 is a cross-sectional view schematically showing another embodiment of the composite structure of the present invention. As shown in FIG. 2, it is preferable that the composite structure 20 of the present embodiment further includes a buffer layer 6 arranged between the internal structure portion 2 and the outer shell portion 4. In the method for manufacturing a composite structure described later, a body to be fired in which the outer peripheral surface of a molded body made of a metal material is covered with a coating layer is heated to a predetermined temperature. Therefore, by arranging the buffer layer at a predetermined position, the stress generated by the expansion of the molten metal material due to heating can be buffered. It is also expected that by arranging the buffer layer, it is possible to prevent the molten metal material from easily flowing out due to heating. That is, it is preferable that the buffer layer also has a function as a shielding layer. By arranging the buffer layer, the obtained composite structure is less likely to be damaged, and the properties such as thermal conductivity of the obtained composite structure can be further improved.

The thickness of the buffer layer 6 is not particularly limited, but is preferably 3 mm or less, and more preferably 1 mm or less. If the thickness of the buffer layer 6 is more than 3 mm, heat conduction from the outside to the internal structure portion 2 may be easily hindered.

Examples of the material constituting the buffer layer 6 include boron nitride and carbon. These materials can be used alone or in combination of two.

The composite structure of the present invention is physically and chemically remarkable, such as (i) a robust and seamless outer shell portion, and (ii) an internal structural portion made of a metallic material contained in the outer shell portion. It has two structural parts that differ from each other. Therefore, the composite structure of the present invention makes use of its characteristics, for example, a heat storage element for recovering waste heat in a harsh environment such as a steel converter at a high temperature of 1,000 ° C. or higher and easily corroded; radiation. It is useful as a heating element or the like using the above. In addition, if the composite structure of the present invention has excellent corrosion resistance and high thermal conductivity, it is expected to be applied to a catalyst base material, a heat radiating substrate, and a heat exchanger.

<Manufacturing method of composite structure>
Next, a method for producing the composite structure of the present invention will be described. The method for producing a composite structure of the present invention is the method for producing the above-mentioned composite structure, and the outer peripheral surface of a molded body made of a metal material is coated with a coating layer containing silicon carbide and carbon to obtain a fired body. It has a step (step (1)) and a step (step (2)) of heating at least the coating layer of the obtained body to be fired in contact with silicon and forming an outer shell portion by reaction sintering. .. Hereinafter, the details of the method for producing the composite structure of the present invention will be described.

(Step (1))
In the step (1), the outer peripheral surface of the molded body made of a metal material is coated with a coating layer containing silicon carbide and carbon to obtain a body to be fired. Examples of the metal material constituting the molded body include the same metal materials as those described above for forming the internal structural portion. The above-mentioned cushioning layer may be formed on the outer peripheral surface of the molded body made of a metal material. In order to form the buffer layer, for example, a slurry obtained by dispersing boron nitride or carbon powder in an appropriate dispersion medium (water, ethanol, etc.) may be applied onto the outer peripheral surface of the molded body.

FIG. 3 is a schematic view showing an embodiment of the method for manufacturing a composite structure of the present invention. In order to obtain a body to be fired, first, a powder layer 14 containing silicon carbide and carbon is formed on the outer peripheral surface of a molded body 12 made of a metal material to obtain a powder coating 16 (FIG. 3 (A). ), (B)). The powder layer 14 is formed by, for example, applying a slurry obtained by dispersing silicon carbide powder and carbon powder in an appropriate dispersion medium (water, ethanol, etc.) on the outer peripheral surface of the molded body 12. be able to. The obtained powder coating material 16 is placed in the chamber 18 of the rotary mixer 20, and the chamber 18 is rotated to roll the powder coating material 16 (FIG. 3 (C)). As a result, it is possible to obtain the fired body 30 in which the outer peripheral surface of the molded body 12 made of a metal material is covered with the coating layer 22 which is denser than the powder layer (FIG. 3 (D)).

In addition, the fired body can also be obtained by the following method. FIG. 4 is a schematic view showing another embodiment of the method for producing a composite structure of the present invention. First, outer shell molded bodies 32a and 32b containing silicon carbide and carbon corresponding to the shape of the molded body 12 made of a metal material are manufactured (FIG. 4A). Then, if the molded body 12 is housed inside the manufactured outer shell molded bodies 32a and 32b, it is possible to obtain the fired body 40 in which the outer peripheral surface of the molded body 12 made of a metal material is covered with the coating layer 34 ( Figure (B)). The outer shell molded bodies 32a and 32b can be produced, for example, by mixing silicon carbide powder and carbon powder with an appropriate binder, and then molding and degreasing. When two or more outer shell molded bodies 32a and 32b as shown in FIGS. 4A and 4B are manufactured, for example, a screw for forming a fitting portion 42 is attached to these abutting portions. It is preferable to form a portion.

In the step (2), at least the coating layer of the object to be fired obtained in the step (1) is heated in a state of being in contact with silicon. Specifically, as shown in FIGS. 3 (E) and 4 (C), the objects to be fired 30 and 40 are placed in a container containing silicon and heated to a predetermined temperature. Since the melting point of silicon is about 1,400 ° C., the silicon is melted to become molten silicon 50 by heating to around 1,500 ° C. As a result, the coating layers 22 and 34 of the objects to be fired 30 and 40 can be heated in contact with silicon. The molten silicon (molten silicon 50) permeates the coating layers 22 and 34 and reacts with carbon to form silicon carbide. As a result, an outer shell portion 4 made of ceramics containing silicon carbide as a main component is formed, and a composite structure 10 having an internal structure portion 2 and a seamless outer shell portion 4 including the internal structure portion 2 is obtained. Can be done (FIGS. 3 (F) and 4 (D)).

As shown in FIGS. 4C and 4D, since the molten silicon is also impregnated in the gap between the fitting portions 42, the impregnated silicon reacts with carbon to form silicon carbide. As a result, the gap between the fitting portions 42 is substantially eliminated, and the seamless outer shell portion 4 can be formed.

<Heat storage method>
Next, the heat storage method of the present invention will be described. The heat storage method of the present invention is a method of using the above-mentioned composite structure as a heat storage body. That is, the heat storage method of the present invention includes a step (heat storage step) of heating the above-mentioned composite structure (heat storage body) to a temperature equal to or higher than the melting point of the internal structure portion to store heat in the composite structure.

In the heat storage step, for example, the total heat amount of the sensible heat of the internal structure part before melting, the latent heat of the internal structure part before melting, the sensible heat of the internal structure part in the molten state, and the sensible heat of the outer shell part (of the heat storage body). It is preferable to heat the composite structure to store heat so that the amount of sensible heat stored in the outer shell portion is 20% or more with respect to the total amount of heat). According to such a heat storage method, all of the sensible heat of the internal structure part before melting, the latent heat of the internal structure part before melting, the sensible heat of the internal structure part in the molten state, and the sensible heat of the outer shell part are utilized. It is possible to realize heat storage with high energy density. These sensible heat and latent heat can be calculated using the following formula (1). Then, the temperature for heating the composite structure can be determined based on the calculated sensible heat and latent heat.

In the above formula (1), Ti is the initial temperature, Te is the final temperature, m is the mass, Cps is the specific heat in the fixed state, Cpl is the specific heat in the liquid state, and L is the latent heat.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, "part" and "%" in Examples and Comparative Examples are based on mass unless otherwise specified.

<Manufacturing of composite structure>
(Examples 1-1 to 1-12)
[Manufacturing of molded body (core molded body) made of metal material]
Three types of spherical core molded bodies composed of (1) Cu, (2) Cu-10% Si, and (3) Cu-25% Si were produced by a casting method. The diameter of each of the produced core molded bodies was about 18.5 mm.

[Formation of outer shell (manufacturing method 1)]
Silicon carbide (SiC) powder (average particle size: about 1 μm) and carbon (C) powder (average particle size: about 2 μm) are weighed and mixed so as to have a mass ratio of SiC: C = 90:10. To obtain a mixed powder. Ethanol was added as a dispersion medium to the obtained mixed powder to prepare a slurry. The prepared slurry was applied to the surface of the core molded product. A core molded product having a slurry coated on its surface was placed in a chamber of a rotary mixer in which a predetermined amount of mixed powder having the same components was charged. The chamber of the rotary mixer was rotated for 20 minutes to roll the core molded body, and a coated body containing silicon carbide and carbon was formed on the outer peripheral surface of the core molded body to obtain a fired body. The obtained body to be fired was a sphere having a diameter of about 22 mm.

The calcined body was placed in a graphite container lined with coarse silicon particles having a particle size of several mm, and heated to 1,500 ° C. in argon gas. The melting point of silicon is about 1,400 ° C. Therefore, the molten silicon permeates into the gaps between the silicon carbide powders constituting the coating layer and reacts with carbon to form silicon carbide (reaction sintering). As a result, a composite structure including an internal structure and an outer shell portion containing silicon carbide as a main component containing the internal structure portion was obtained. The core molded body inside was also temporarily melted by heating, but the shape was not lost due to outflow to the outside. The obtained composite structure was a sphere having a diameter of about 22 mm. That is, no substantial dimensional shrinkage occurred due to reaction sintering.

(Examples 2-1 to 2-12)
[Manufacturing of molded body (core molded body) made of metal material]
Boron nitride (BN) in the form of a slurry was applied to the surfaces of the three types of core molded bodies produced in Examples 1 to 12 to form a buffer layer having a thickness of about 1 mm. The one having the buffer layer formed in this way was used as the core molded body.

[Formation of outer shell (manufacturing method 2)]
Silicon carbide (SiC) powder (average particle size: about 1 μm) and carbon (C) powder (average particle size: about 2 μm) are weighed so as to have a mass ratio of SiC: C = 90: 10 and mechanically. Mixing gave about 3,000 g of mixed powder. The obtained mixed powder and an organic binder containing polyethylene, wax, and stearic acid are put into a pressurized kneader, sufficiently kneaded while heating to a temperature equal to or higher than the melting point of the binder, and then cooled and solidified. I let you. The specific gravity of silicon carbide was 3.22, the specific gravity of carbon was 2.26, and the blending amount of the binder was about 50% by volume. The solidified product obtained by cooling was crushed to obtain pellets. The obtained pellets are put into an injection molding machine for injection molding, and then heated to 600 ° C. in argon gas for degreasing treatment to form an outer shell molded body (diameter::) which is a hollow hemisphere as shown in FIG. About 22 mm) was obtained. The core molded body was placed inside the pair of outer shell molded bodies, and the outer shell molded body was fitted with a screw portion. As a result, a fired body in which a coating layer (outer shell molded body) containing silicon carbide and carbon was formed on the outer peripheral surface of the core molded body was obtained. A slight gap remains in the fitting portion of the coating layer.

The calcined body was placed in a graphite container lined with coarse silicon particles having a particle size of several mm, and heated to 1,500 ° C. in argon gas. The melting point of silicon is about 1,400 ° C. Therefore, the molten silicon permeates into the gaps between the silicon carbide powders constituting the coating layer and reacts with carbon to form silicon carbide (reaction sintering). As a result, a composite structure including an internal structure portion and an outer shell portion containing silicon carbide as a main component containing the internal structure portion was obtained. The core molded body inside was also temporarily melted by heating, but the shape was not lost due to outflow to the outside. The obtained composite structure was a sphere having a diameter of about 22 mm. That is, no substantial dimensional shrinkage occurred due to reaction sintering. Further, the gaps in the fitting portion were also impregnated with silicon and reacted with carbon to form silicon carbide, so that the gaps in the fitting portion disappeared.

(Comparative Examples 1-1 to 1-12)
[Formation of outer shell (manufacturing method 3)]
Alumina (Al ₂ O ₃ ) (manufactured by Showa Denko Co., Ltd.) 3% and boron carbide (B ₄ ) per 100 g of silicon carbide (α-SiC) powder (manufactured by Yakushima Denko Co., Ltd., average particle size: 0.72 mm). C) 1 to 5% of the powder was added and placed in a container made of polyethylene. After mixing in ethanol with a wet ball mill using nylon balls for 20 hours, the mixture was dried to obtain a mixed powder. 55 parts by volume of the obtained mixed powder and 45 parts by volume of a binder containing an acrylic resin and wax were mixed to obtain a mixture of about 3,000 g. The obtained mixture was placed in a pressurized kneader, sufficiently kneaded while heating to a temperature equal to or higher than the melting point of the binder, and then cooled and solidified. The solidified product obtained by cooling was crushed to obtain pellets. The obtained pellets were put into an injection molding machine and injection molded to obtain a molded body (diameter: about 25 mm) which was a hollow hemisphere. The obtained molded product was heated to 600 ° C. in argon gas for degreasing treatment, and then heated to 2,100 ° C. for sintering. As a result, an outer shell portion having a diameter of about 22 mm, a wall thickness of 1 mm, and a relative density of 99%, which was a hollow hemisphere as shown in FIG. 5, was obtained.

[Integration]
A core molded body is placed inside the pair of outer shells, and a heat-resistant inorganic adhesive (trade name "Aron Ceramic", registered trademark, manufactured by Toagosei Co., Ltd.) is applied to the joint surface (fitting part) of the outer shells. It was applied thinly. After fitting the outer shell portion with the screw portion, the outer shell portion was heated at about 150 ° C. and adhered. As a result, a composite structure including an internal structure portion and an outer shell portion containing silicon carbide as a main component containing the internal structure portion was obtained. It should be noted that the gap in the fitting portion could not be completely filled, and a slight gap existed.

<Evaluation>
(Heating characteristics)
A hole with a diameter of 0.5 mm was drilled in the center of the manufactured composite structure. A thermocouple was inserted through the drilled hole so that its tip was located in the center of the internal structure. The composite structure with the thermocouple inserted was put into the furnace heated to about 1,150 ° C. The time until the temperature in the central part became almost constant (arrival time) was measured and used as an index of the temperature rise characteristic. Table 1 shows the measurement results of the arrival time. Table 2 shows the results of the analysis of variance of the measured arrival time. Further, FIG. 6 shows a graph showing the influence of each factor on the temperature rise characteristics of the composite structure. The analysis of variance was formulated using the L36 orthogonal array based on the Taguchi method. In addition, the SN ratio was adopted as an index for evaluating the presence or absence of statistical effects while separating the errors and effects of each data.

(Mechanical strength)
A compressive load was applied to the manufactured composite structure using a strength tester. The load at the time when the composite structure broke (crushing load) was measured and used as an index of mechanical strength. Table 1 shows the measurement results of the crushing load. Table 3 shows the results of the analysis of variance of the measured crushing load. Further, FIG. 7 shows a graph showing the influence of each factor on the mechanical strength of the composite structure. The analysis of variance was formulated using the L36 orthogonal array based on the Taguchi method. In addition, the SN ratio was adopted as an index for evaluating the presence or absence of statistical effects while separating the errors and effects of each data.

As shown in Table 1, it can be seen that the composite structure of the example has a shorter time to reach a predetermined temperature than the composite structure of the comparative example, and is excellent in temperature rising characteristics. Further, it can be seen that the composite structure of the example has a large crushing load and is excellent in mechanical strength as compared with the composite structure of the comparative example.

Further, as shown in Table 2 and FIG. 6 (graph), it can be seen from the test results based on the P value that the structure of the outer shell portion is significant with respect to the temperature rise characteristic of the composite structure. Further, regarding the SN ratio, it can be seen that the outer shell portion of the structure produced by the production method 1 is the largest and the effect is high. It can be seen that the outer shell portion of the structure produced by the production method 2 is slightly inferior to the outer shell portion produced by the production method 1, but has a larger SN ratio than the outer shell portion produced by the production method 3. In addition, it can be seen that the performance was slightly improved by containing silicon in the internal structure. It is considered that this is because the dimensional change due to the solid-liquid phase transformation was suppressed by containing silicon in the core molded body, and the gap between the internal structure portion and the outer shell portion became smaller.

Furthermore, as shown in Table 3 and FIG. 7 (graph), it can be seen that the structure of the outer shell portion is significant with respect to the mechanical strength of the composite structure. An unavoidable gap remains in the outer shell portion having the conventional fitting structure manufactured by the manufacturing method 3. For this reason, in the composite structure of the comparative example, the gap remaining in the outer shell portion is likely to be a defect that causes fracture, whereas in the outer shell portion of the composite structure of the example, the gap is substantially present. However, it is considered that this is because there are almost no defects that cause destruction. In the composite structure of the comparative example, a gap is created between the outer shell portion and the internal structure portion by design. On the other hand, in the composite structure of the embodiment, there is substantially no gap between the outer shell portion and the internal structure portion, and the outer shell portion and the internal structure portion are in close contact with each other, so that the thermal resistance is reduced. It is considered that the thermal conductivity was improved. Further, it is considered that since the surface of the internal structure portion is in contact with the inner surface of the outer shell portion, the tensile stress generated in the outer shell portion is reduced and the mechanical strength is improved.

The composite structure of the present invention is useful as a heat storage body for recovering waste heat in a harsh environment such as a steel converter, which has a high temperature of 1,000 ° C. or higher and is easily corroded.

2: Internal structure part 4: Outer shell part 6: Buffer layer 10, 20: Composite structure 12: Molded body (made of metal material) 14: Powder layer 16: Powder coating 18: Chamber 20: Rotating mixer 22, 34: Coating layer 30, 40: Fired body 50: Molten silicon 32a, 32b: Outer shell molded body 42: Fitting portion 80: Internal heat storage body 92, 94: Outer shell 100: Heat storage body

Claims (9)

Internal structure made of metal material and
A seamless outer shell portion made of ceramics containing 90% by volume or more of silicon carbide formed by reaction sintering, which encloses the internal structure portion, is provided .
A composite structure in which the melting point of the metal material is 1,500 ° C. or lower . The composite structure according to claim 1, further comprising a buffer layer arranged between the internal structure portion and the outer shell portion. The composite structure according to claim 2, wherein the buffer layer is made of at least one of boron nitride and carbon. The composite material according to any one of claims 1 to 3, wherein the metal material is at least one metal selected from the group consisting of copper, aluminum, nickel, and iron. The composite structure according to any one of claims 1 to 4 , wherein the metal material contains silicon. The composite structure according to any one of claims 1 to 3, wherein the metal material is copper or a copper-silicon alloy containing 35% by mass or less of silicon. The composite structure according to any one of claims 1 to 6, which is used as a heat storage body. The method for producing a composite structure according to any one of claims 1 to 7.
A step of coating the outer peripheral surface of the molded body made of the metal material with a coating layer containing silicon carbide and carbon to obtain a fired body.
A step of heating the obtained body to be fired in a state where at least the coating layer is in contact with silicon and forming the outer shell portion by reaction sintering.
A method for manufacturing a composite structure having the above. A heat storage method comprising a step of heating the composite structure according to claim 7 to a temperature equal to or higher than the melting point of the internal structure portion to store heat in the composite structure.

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