JP7339645B2 - Latent heat storage material, method for producing latent heat storage material, and heat exchange material - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a latent heat storage medium, a method for manufacturing a latent heat storage medium, and a heat exchange material.

Examples of techniques for storing heat include sensible heat storage and latent heat storage. Sensible heat storage utilizes the temperature change of a heat storage medium. On the other hand, in latent heat storage, for example, a phase change of a heat storage medium from a solid phase to a liquid phase is used.

Patent Literature 1 discloses a latent heat storage body composed of a core portion and a shell covering the core portion. Regarding the shell, it is disclosed that the core particles are subjected to a chemical conversion coating treatment and then a thermal oxidation treatment to form an oxide coating. Patent Document 2 discloses the use of sodium dodecyl sulfate as a nucleation accelerator, and further discloses that the addition of a nucleation accelerator enables the formation of a thick coating.

U.S. Patent Application Publication 2017/044415 (WO2015/162929) WO2017/200021

In the core-shell type latent heat storage device described above, it is important to prevent the melted core material from leaking out.

Although Patent Literature 1 and the like disclose a manufacturing method that enables the thickness of the shell to be increased, there is room for improvement from the viewpoint of the strength of the latent heat storage medium. That is, when a physical force (for example, a force due to repeated expansion and contraction of internal particles due to repeated heat exchange) is applied to the film, there is still a possibility of breakage and/or leakage.

In view of the above, it is an object of the present disclosure to provide a latent heat storage body with reduced leakage of molten core material.

As a result of intensive studies by the present inventors, it was found that the thickness of the coating layer can be increased by improving the conventional manufacturing method for the latent heat storage element. Further, the inventors have found that the specific surface area of the latent heat storage material can be significantly improved by improving the conventional manufacturing method for the latent heat storage material. More specifically, the present inventors have found that by blending an amine compound during chemical conversion coating treatment, it is possible to form a coating layer that is different from conventional coating layers. The present invention has been completed based on the above findings, and includes the following inventions in one aspect.

(Invention 1)
A latent heat storage material comprising a core portion and a coating layer, the latent heat storage material having a BET specific surface area of 10 m ² /g or more.
(Invention 2)
The latent heat store of invention 1, further comprising a porous structure in said coating layer.
(Invention 3)
The latent heat storage material according to invention 1 or 2, wherein the ratio of the area of the coating layer to the total area of the core portion and the coating layer is 15% or more when a cross section is observed.
(Invention 4)
The latent heat storage material according to any one of Inventions 1 to 3, wherein the latent heat storage material has a strength of 30 MPa or more at which 10% displacement occurs.
(Invention 5)
The latent heat storage material according to any one of Inventions 1 to 4, wherein the core component is an alloy selected from Group A and Group B below:
Group A: Ca, Si, Bi, Mg, Sb, In, Sn, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, Au, Pb, Ge, and combinations thereof B: Al, Cr, Mn, Si, Mg, Co, Ni, and combinations thereof.
(Invention 6)
The latent heat storage material according to any one of Inventions 1 to 4, wherein the component of the core portion is either Al or an Al alloy.
(Invention 7)
The latent heat storage medium according to invention 6, wherein the component of the core portion is an Al--Si alloy.
(Invention 8)
A method for manufacturing a latent heat storage material, the method comprising:
providing a core particle;
a step of subjecting the core particles to chemical conversion coating;
a step of thermally oxidizing the core particles;
wherein said conversion coating treatment is carried out in the presence of an amine compound.
(Invention 9)
The method of invention 8, wherein said amine compound is one or more selected from the group consisting of: monoalkylamines, dialkylamines, and trialkylamines.
(Invention 10)
The method of invention 8, wherein the amine compound is one or more selected from the group consisting of: ethylamine and diethylamine.
(Invention 11)
A heat exchange material comprising the latent heat storage element according to any one of inventions 1 to 7.
(Invention 12)
The latent heat storage material according to any one of inventions 1 to 7, further comprising a catalyst on the surface.

In one aspect, the latent heat storage medium of the present disclosure has a specific specific surface area. As a result, the material of the core portion can be easily captured, and leakage of the core portion can be reduced.

4 is a SEM photograph of a latent heat storage medium (showing cases of processing in the presence of monoethylamine, processing in the presence of diethylamine, and processing in the presence of triethanolamine (TEA)). 10 is a photograph of a cross section of a sample of Comparative Example 2. FIG. The photograph was subjected to image processing, and the core portion, the coating layer (shell), and the combined portion (whole) were colored, and the area and perimeter length of each were calculated. 1 is a photograph of a cross section of a sample of Example 1; The photograph was subjected to image processing, and the core portion, the coating layer (shell), and the combined portion (whole) were colored, and the area and perimeter length of each were calculated. 1 is a photograph of a cross section of a sample of Example 1; The surface of a certain particle was magnified and observed.

Specific embodiments for carrying out the present invention will be described below. The following description is intended to facilitate understanding of the invention. it is not intended to limit the scope of the invention.

1. Latent Heat Store One embodiment of the present disclosure includes a latent heat store. The latent heat storage medium can include a core and a coating layer covering the core.

1-1. Core part
1-1-1. Ingredients In one embodiment of the present disclosure, the core constituents of the present disclosure include at least two alloying ingredients (ie, at least including alloying ingredient A and alloying ingredient B).

The alloy component can function as a heat storage material. Said alloy component B can function mainly to form an oxide phase.
Alloy component A: Ca, Si, Bi, Mg, Sb, In, Sn, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, Au, Pb, Ge, and combinations thereof Alloy component B: Al, Cr, Mn, Si, Mg, Co, Ni, and combinations thereof

The above alloy components are not limited to binary alloys. That is, the above alloy components also include ternary or higher alloys (alloys formed by combining three or more elements).

In another embodiment of the present disclosure, the core component may be Al (ie, pure Al, not an alloy), or an Al alloy.

In a more preferred embodiment, the combination of alloys includes a combination of a component with a positive coefficient of volume expansion when melted and a component with a negative coefficient of volume expansion when melted. Al is an example of a component having a positive coefficient of volume expansion when melted. On the other hand, examples of components having a negative coefficient of volume expansion when melted include Si and Bi.

When the component of the core portion is an Al alloy, the total content ratio of elements other than Al (for example, Si, Bi, and combinations thereof) is preferably 25 wt% or less, more preferably 12 wt%. above and 25 wt % or less. In particular, when the Si content ratio of the Al—Si alloy is 25 wt %, the volume expansion coefficient of the Al—Si alloy can be controlled to 0% when melted.

1-1-2. Size and shape of latent heat storage body In one embodiment of the present disclosure, the shape of the latent heat storage body is not particularly limited. For example, the shape of the latent heat storage medium may be spherical or cubic. The average particle size of the latent heat storage medium may be 10 to 150 μm, but is not limited to this size. A preferred average particle size is 20 μm or more and/or 45 μm or less.

The average particle size described in this specification (for example, the average particle size of the core particles and the average particle size of the latent heat storage medium) is the value measured by a laser diffraction particle size distribution analyzer (eg, HORIBA LA-920). be. More specifically, the volume distribution of the particles is measured with a laser diffraction particle size distribution meter, and the cumulative 50 volume % diameter value (D50) is regarded as the average particle size.

1-2. covering layer
1-2-1. The coating layer covering the component core portion is not particularly limited, but may be a single layer or may be provided with a plurality of layers. For example, but not limited to, the coating layer may contain Al ₂ O ₃ as a component, preferably α-Al ₂ O ₃ as a component. Components constituting the coating layer are not limited to Al ₂ O ₃ alone, and may contain other elements and/or unavoidable impurities. Further, in one embodiment of the present disclosure, the latent heat storage body includes a core portion, a coating layer covering the core portion, and projections on the coating layer. The formation of the protrusions becomes noticeable when the core particles are treated with an amine compound as described later. In another embodiment of the present disclosure, the latent heat store comprises a porous structure inside said protrusions and/or said coating layer. The presence of this porous structure increases the specific surface area of the latent heat storage medium. By increasing the number of porous structures (porous structure), the specific surface area of the latent heat storage medium can achieve the value described later.

1-2-2. thickness

In one embodiment of the present disclosure, the thickness of the coating layer of the latent heat storage body may be 2 μm or more. In addition, since the larger the thickness, the more preferable, the upper limit is not particularly limited, but is typically 15 μm or less, more typically 10 μm or less, still more typically 5 μm or less, and 3 μm. It is also possible to: More preferably, the thickness of the coating layer is defined by two numbers selected from 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15. (unit: μm) (for example, 8 μm to 12 μm).

In another embodiment of the present disclosure, the thickness of the coating layer of the latent heat storage material is 5% or more with respect to the average particle size of the latent heat storage material (for example, when the average particle size of the latent heat storage material is 100 μm, The thickness of the coating layer may be 5 μm or more). Moreover, since the larger the thickness, the better, the upper limit is not particularly limited, but is typically 21% or less. If the upper limit is exceeded, the volume occupied by the core portion of the latent heat storage body decreases (for example, the volume of the coating layer exceeds the volume of the core portion), thereby resulting in insufficient heat storage density and/or heat transfer performance. may become. More preferably, the thickness of the coating layer with respect to the average particle size of the latent heat storage medium is , and 21 (unit: %).

In another embodiment of the present disclosure, the ratio of the area of the coating layer to the area of the core portion+the area of the coating layer when observing the cross section of the latent heat storage body may be 15% or more. Although the upper limit is not particularly limited, it is preferably 37% or less. If it exceeds 37%, the area ratio of the coating layer portion becomes too large, and the area of the core portion becomes too small. This means that the volume of the core becomes too small (for example, the volume of the coating layer exceeds the volume of the core). If the volume of the core portion becomes too small, the heat storage density and/or heat transfer performance may become insufficient. More preferably, the ratio of the area of the coating layer to the area of the core + the area of the coating layer when observing the cross section of the latent heat storage element is selected from 15, 20, 25, 30, 35, and 37. It may be within a range defined by two numerical values (unit: %).

1-3. Properties (strength)
In one embodiment of the present disclosure, the latent heat store has higher strength than conventional. The strength described here refers to the strength that can prevent the coating layer from breaking and the internal core portion from leaking out when a physical force is applied from the outside.

More specifically, the strength of the latent heat storage medium can be evaluated by the following method. First, pick up one particle. Next, pressure is applied to the particles using a microcompression tester (eg, Shimadzu MCT-210). The pressure at which 10% displacement occurs is regarded as the strength of the latent heat storage medium. Intensity measurements are made on multiple particle samples and the average value is calculated. However, particle samples in which 10% displacement occurs at low pressure (eg, less than 10 MPa) are excluded from statistical processing (eg, calculation of average value, deviation, etc.).

In one embodiment of the present disclosure, the strength of the latent heat storage medium measured by the above method may be 30 MPa or higher, preferably 35 MPa or higher, and more preferably 38 MPa or higher.

The upper limit of strength is not particularly limited, but is typically 100 MPa or less, more typically 75 MPa or less, still more typically 50 MPa or less, and even more typically 45 MPa or less. is.

1-4. Surface Area In one embodiment of the present disclosure, the latent heat store has a characteristic surface area. The characteristic surface area can be represented by the BET specific surface area. More specifically, the BET specific surface area of the latent heat storage medium is 10 or more, preferably 10 to 100, more preferably 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100. It may be within a range defined by two selected numerical values (unit: m ² /g). The lower limit is more preferably 30 or higher, even more preferably 40 or higher, and most preferably 50 or higher. The upper limit is usually 90 or less, typically 80 or less, more typically 70 or less, still more typically 60 or less. Also, when the specific surface area is large, the physical force is easily dispersed. Therefore, the latent heat storage material is less likely to be destroyed, and the strength is improved.

In one embodiment of the present disclosure, the latent heat store comprises protrusions on the coating layer. As a result, the specific surface area is improved as compared with the conventional one. In a preferred embodiment of the present disclosure, the coating layer of the latent heat store (optionally also within the protrusion structure) is provided with numerous pores (porous structure), which further increases the specific surface area. By providing a large number of pores, even if cracks occur from the inside, the material of the core portion can be captured. In this regard, in the coating layer of the latent heat storage element according to the prior art, if cracks occur from the inside, the material of the core portion tends to leak out. Therefore, in this respect, the latent heat storage medium of the preferred embodiment of the present disclosure is advantageous.

1-5. Crystal Structure In one embodiment of the present disclosure, the coating layer of the latent heat store has a phase of α-Al ₂ O ₃ . The coating layer of the latent heat store may also have a θ-Al ₂ O ₃ phase, albeit to a lesser extent. The presence or absence of these phases can be determined by whether or not specific peaks can be detected under the following XRD conditions.
Measurement conditions X-ray diffraction device: X-ray diffraction device XRD Rigaku MiniFlex600 X-ray source: Cu line Detector: High-speed one-dimensional detector D/teX Ultra2
・Tube voltage: 40 kV,
・Tube current: 15mA,
・Scan speed: 1.0°/min,
・Step: 0.01°

2. Method of Manufacturing a Latent Heat Store In one embodiment of the present disclosure, a method of manufacturing a latent heat store is provided. The method includes at least the following steps.
providing a core particle;
a step of subjecting the core particles to chemical conversion coating;
a step of thermally oxidizing the core particles;
A specific example of each step will be described below.

2-1. Provision of Core Particles In the method for manufacturing a latent heat storage material according to an embodiment of the present disclosure, the components of the coating layer covering the core particles are mainly supplied from the components of the core particles. The components of the core particles are not particularly limited, but the core particles preferably have the components described above. Al or Al alloys are more preferred, and Al—Si alloys are most preferred.

The average particle size of the core particles is not particularly limited, but is 10 to 150 μm (preferably 20 μm or more and/or 45 μm or less).

2-2. Chemical Conversion Coating Treatment The core particles may be subjected to a chemical conversion coating treatment to form a coating. As chemical coating treatment, chemical coating treatment includes boehmite treatment, sol-gel method, anodizing treatment, alkali-chromic acid method, chromic acid method, phosphoric acid-chromic acid method, zinc phosphate method, non-chromate chemical conversion coating method. method. Preferably, boehmite treatment can be performed. Boehmite treatment is a treatment defined in "JIS H 0201:1998 Aluminum Surface Treatment Terms", and is a method of forming a film on the surface of aluminum in high-temperature pure water. In some cases, a small amount of ammonia or the like is added to this for treatment. Also, in the present disclosure, the coating target is not limited to Al and Al alloys. That is, it is possible to coat core particles of any of the components described above.

It was confirmed that the higher the pH value of the boehmite treatment solution, the better the quality of the Al oxide film obtained. .5 is more preferred and 8 is most preferred.

As conditions for the boehmite treatment, the core particles can be treated at a temperature of 80° C. to 100° C. for 0.25 to 3 hours (preferably while stirring). As a result, a primary coating having a composition of Al ₂ O ₃ .H ₂ O is formed on the surface of the core particles.

The boehmite-treated solution may then be allowed to cool down to room temperature. Then, the particles after the boehmite treatment may be recovered, and the particles may be subjected to a thermal oxidation treatment, which will be described later.

In another embodiment, the solution after boehmite treatment may be cooled and held for a period of time to further promote film formation. The temperature after cooling is less than 80° C., depending on the Al concentration of the solution. Although the lower limit is not particularly limited, it is typically room temperature (eg, 25°C). The holding time after supercooling may be 10 hours to 25 hours, preferably 15 hours or longer.

In embodiments of the present disclosure, a conversion coating treatment solution, such as a boehmite treatment, may further include an amine compound. By containing the amine compound, the formation of the secondary coating is significantly promoted, and the thickness of the secondary coating can be increased. In some cases, the specific surface area and/or the uniformity of the film can also be increased. And the strength of the particles can be improved by increasing the thickness. In addition, by containing the amine compound, the frequency of particle damage (cracks, holes, leakage) can be reduced.

Amine compounds include, but are not limited to, monoalkylamines, dialkylamines, and trialkylamines, and combinations thereof. Monoalkylamines and dialkylamines are preferred, and monoalkylamines are more preferred. In addition, the "amine compound" described in this specification does not include triethanolamine. In more preferred embodiments, the "amine compounds" referred to herein do not include alcohol amines.

Monoalkylamines include monoalkylamines having a C1-C10 (preferably C1-C5) alkyl group. More specific examples include monomethylamine, monoethylamine, monopropylamine, monobutylamine and the like. Monoethylamine is preferred.

Dialkylamines include dialkylamines each independently having a C1 to C10 (preferably C1 to C5) alkyl group. More specific examples include dimethylamine, diethylamine, dipropylamine, dibutylamine, ethylpropylamine and the like. Diethylamine is preferred.

The concentration of the amine compound may be 0.001 to 2 mol/L (more preferably 0.005 mol/L or more and/or 2 mol/L or less). If it is less than 0.001 mol/L, supersaturated precipitation will be insufficient, making it difficult to obtain a good film. If it exceeds 2 mol/L, it is uneconomical because a film thickness greater than this cannot be obtained.

Alcohol amine (eg, triethanolamine) is sometimes used as a treatment component in the boehmite treatment, but its chelate effect suppresses precipitation, so its film-forming effect is inferior to that of the alkylamine described above.

On the other hand, the chemical conversion coating solution may not contain Al(OH) ₃ . Patent _Document 2 discloses a chemical conversion coating treatment solution containing Al(OH) ₃ in order to improve the film thickness. is not required.

2-3. After the thermal oxidation treatment and then the boehmite treatment, the particles can be subjected to a high temperature treatment in an oxidizing atmosphere. As a result, the primary coating and secondary coating described above are oxidized to form an Al oxide coating.

The temperature of the thermal oxidation treatment is preferably higher than the melting point of the metal (including the alloy) that constitutes the core portion. For example, when the component of the core portion is an Al--Si alloy, particularly in the case of an Al--25 wt % Si alloy, the melting point is 580.degree. _Al (OH) ₃ contained in the secondary coating becomes a crystalline _Al2O3 coating according to the reaction formula _of Al(OH) ₃ → _0.5Al2O3 + _1.5H2O . Also, Al ₂ O ₃ ·H ₂ O contained in the primary coating or secondary coating becomes crystalline Al ₂ O ₃ due to dissociation of water.

In a more preferred embodiment, the heat treatment can be performed at temperatures of 880° C. or higher. The reason for this is that the aluminum oxide film formed by the treatment assumes the crystalline form of γ-Al ₂ O ₃ at a relatively low temperature of 800° C. or lower, and the crystalline α-Al ₂ O ₃ is chemically stable. This is because a shaped secondary coating can be obtained at a relatively high temperature of 880° C. or higher. Although the upper limit is not particularly limited, it is preferably 1230° C. or less. The heat treatment time may be 1 to 5 hours, preferably 3 hours or more.

2-4. Formation of Additional Coating A further coating may be formed on the Al oxide coating obtained in the above steps to enhance the strength. For example, chemical or physical treatments may be performed to form metallic and/or ceramic coatings. For example, chemical methods include sol-gel method, CVD, electroplating, electroless plating and the like, and physical methods include PVD and the like. The mechanical strength of the capsule can be enhanced by applying a metal coating and/or a ceramic coating over it.

3. Use of latent heat storage medium
3-1. Heat Exchange Material One embodiment of the present disclosure includes a heat exchange material. The heat exchange material comprises the latent heat store described above. For example, the latent heat accumulator may be contained in a thermal base material or carried in a porous material. More preferably, the latent heat accumulator may be contained in the thermal base material or carried in the porous material in a dispersed state. Examples of heat exchange materials include, but are not limited to, heat storage bricks, heat storage ceramic balls, porous ceramic filters, and the like.

3-2. Catalytic Latent Heat Store One embodiment of the present disclosure includes a catalytic latent heat store. Various catalyst particles can be supported or deposited on the surface of the latent heat storage medium. This makes it possible to provide a material having both a function as a catalyst and a function as a heat storage medium.

4-1. Production of latent heat storage medium First, core particles made of an Al-Si alloy (Al-25 wt% Si) containing 75% by weight of Al and 25% by weight of Si were prepared. The average particle diameter of the core particles was measured using a laser diffraction particle size distribution analyzer (HORIBA LA-920) and found to be 20 to 38 μm.

Next, a chemical conversion coating solution was prepared. More specifically, the following various compounds were added to pure water to prepare a chemical conversion coating solution. Specifically, monoethylamine (Example 1, final concentration 0.15M) or diethylamine (Example 2, final concentration 0.15M) was added. Also, as Comparative Example 1, triethanolamine was added (final concentration 0.15 M). As Comparative Example 2, a chemical conversion coating solution was prepared by adding ammonia to adjust the pH to about 8 without adding an amine compound or triethanolamine. Also, in Comparative Example 2, Al(OH) ₃ was added (1.152 g/L in terms of Al amount).

For Examples 1 and 2 and Comparative Examples 1 and 2, 3.33 g of Al—Si alloy core particles were added to 100 mL of the chemical conversion coating solution. Then, the core particles were treated at 100° C. for 3 hours while being stirred at a rotational speed of 450 rpm using a hot stirrer. Thereafter, for Examples 1 and 2 and Comparative Example 1, the chemical conversion coating solution was allowed to cool to room temperature. However, for the chemical conversion coating solution of Comparative Example 2, the temperature was once lowered to 75° C. and maintained for 16 hours to form a coating. For Examples 1-2 and Comparative Examples 1-2, after the conversion coating treatment, the particles were taken out, and a 150 μL Al ₂ O ₃ pan was filled with the core particles after the conversion coating treatment. After that, heat treatment was performed at 930° C. for 3 hours in an oxygen atmosphere using a thermogravimeter (Mettler Toledo TGA-DSC-3).

4-2. Analysis of Latent Heat Storage Material The characteristics of the latent heat storage material having the core portion and the coating layer according to the examples and comparative examples obtained by the above steps were analyzed.

4-2-1. Strength of latent heat storage material For the samples of Example 1 and Comparative Example 1, the strength of the latent heat storage material was measured using a microcompression tester (eg, Shimadzu MCT-210). More specifically, the strength was measured by the method described in “1-3. Characteristics (strength)”. For Example 1, the average value was calculated from 43 samples. For Comparative Example 1, the average value was calculated from 37 samples. As a result, the average strength of Example 1 was 39.7 MPa, and the average strength of Comparative Example 1 was 28.8 MPa.

4-2-2. Surface shape of the latent heat storage body The state of the surface of the latent heat storage body was observed with an SEM (JEOL, JSM-7001FA). The results are shown in FIG. As is clear from FIG. 1, in Example 1 (monoethylamine) and Example 2 (diethylamine), it was found that unevenness was formed on the surface of the particles. On the other hand, such unevenness was not formed in Comparative Example 1 (triethanolamine). The presence of irregularities on the surface of the particles suggests that a thicker coating layer was formed than conventionally. Then, it is considered that the strength of the sample of Example 1 was higher than the strength of the sample of Comparative Example 1 for this reason. Also, in the sample of Example 2, it is considered that the strength is improved as in Example 1, considering that the surface of the particles is uneven. Although not shown in the photograph of FIG. 1, in Comparative Examples 1 and 2, damage was observed in some particles (cracks, holes, leakage). Further, when the sample of Example 1 was further enlarged and the particle surface was observed, the presence of a porous structure was confirmed (see FIG. 4 and the arrows in the figure).

4-2-3. Area Ratio and Thickness of Coating Layer of Latent Heat Storage Material The latent heat storage material was cut and its cross section was photographed with a microscope. The cross-sectional photograph was image-analyzed by a computer, and the area and peripheral length of the latent heat storage element, the area and peripheral length of the core portion, and the area and peripheral length of the coating layer (shell) were measured. More specifically, image processing software "NIS-Element D" (Nikon Corporation) was used for image analysis. The contours of the core portion, the coating layer (shell), and the combined portion were drawn using the contrast of the core portion, the coating layer, and the projections, and the area and perimeter length of each were calculated using image processing software.

A cross-sectional photograph of the latent heat storage material of Comparative Example 2 is shown in FIG. 2, and a cross-sectional photograph of the latent heat storage material of Example 1 is shown in FIG. The area of the coating layer in the total area of the core portion and the coating layer (shell) was 14.3% (147.5/1030×100) in Comparative Example 2 and 22.8% (218. 5÷957.4×100).
Further, when the area of the core portion is S ₁ , the area of the coating layer portion is S ₂ , the particle size of the core portion is r, and the thickness of the coating layer is x, the following relationship is established.
(r+x) ² π: {(r+x) ² −r ² }π= (S ₁ +S ₂ ):S ₂
Note that r can be calculated from the area S ₁ of the core portion.
Solving this relational expression yields the following equation.
S ₁ x ² +2S ₁ rx−S ₂ r ² =0
Based on this, the thicknesses of the coating layers of Example 1 and Comparative Example 2 were calculated to be 2.12 μm and 1.35 μm, respectively.

4-2-4. Specific Surface Area of Latent Heat Storage Material Next, the specific surface areas of the latent heat storage materials of Example 1 and Comparative Example 2 were measured by the BET method. More specifically, it was calculated by the multi-point BET method using measurement points in the range of 0.05<(p/p0)<0.30. As a result, the specific surface area of the sample of Example 1 was 52.36 (m ² /g). On the other hand, the specific surface area of the sample of Comparative Example 2 was 7.7 (m ² /g).

It should be noted that the large specific surface area achieved in Example 1 cannot be explained only by the formation of protrusions on the surface (shown in FIG. 1). That is, it is considered to suggest that pores are formed in the coating layer. Therefore, it is considered that the existence of the pores makes the structure difficult for the material of the core portion to leak out.

As described above, it was shown that the strength of the latent heat storage material can be improved and the thickness of the coating layer can be increased by blending a specific amine compound.

In this specification, the descriptions of “or” and “or” include cases where only one option is satisfied, cases where several options are satisfied, and cases where all options are satisfied. For example, in the case of the description "A, B or C" and "A, B or C", there are cases where only A is satisfied, cases where only B is satisfied, cases where only C is satisfied, and cases where only A and B are satisfied. , cases where only B and C are satisfied, cases where only A and C are satisfied, cases where all of A to C are satisfied, etc. are intended to be included.

Specific embodiments of the present disclosure have been described above. The above embodiments are only specific examples, and the present invention is not limited to the above embodiments. For example, technical features disclosed in one of the above embodiments can be provided in other embodiments. Also, for a particular method, some steps may be interchanged with other steps, and additional steps may be added between two particular steps. The scope of the invention is defined by the claims.

Claims (12)

A latent heat storage body comprising a core portion and a coating layer, wherein the latent heat storage body has a BET specific surface area of 30 m ² /g or more , wherein the component of the core portion is either Al or an Al alloy. and wherein the coating layer contains Al ₂ O ₃ as a component . 2. The latent heat store of claim 1, further comprising a porous structure in said coating layer. 3. The latent heat storage body according to claim 1, wherein the ratio of the area of said coating layer to the total area of said core portion and said coating layer is 15% or more when a cross section is observed. 4. The latent heat storage material according to any one of claims 1 to 3, wherein the latent heat storage material has a strength of 30 MPa or more at which a 10% displacement occurs. The latent heat storage medium according to any one of claims 1 to 4, wherein the component of the core portion is an alloy containing Al and Si . 6. The latent heat storage medium according to claim 5 , wherein said core is made of Al alloy, and the total content of elements other than Al is 25 wt % or less . 7. The latent heat storage material according to claim 6, wherein said latent heat storage material has an average particle diameter of 20 μm or more and/or 45 μm or less . A method for manufacturing a latent heat storage material according to any one of claims 1 to 7 , wherein the method comprises
providing a core particle , wherein the composition of the core particle is one of Al and an Al alloy ;
a step of subjecting the core particles to chemical conversion coating;
a step of thermally oxidizing the core particles;
wherein the conversion coating treatment is carried out in the presence of an amine compound ,
The method, wherein the amine compound is one or more selected from the group consisting of: monoalkylamines, dialkylamines, and trialkylamines . 9. The method of claim 8, wherein the amine compound is one or more selected from the group consisting of: C1-C5 monoalkylamines and C1-C5 dialkylamines . 9. The method of claim 8, wherein said amine compound is one or more selected from the group consisting of: ethylamine, and diethylamine. A heat exchange material comprising the latent heat storage medium according to any one of claims 1 to 7. The latent heat storage material according to any one of claims 1 to 7, further comprising a catalyst on its surface.