Latent heat storage composite, method for manufacturing same, and electric heating device comprising same

Abstract

The present invention relates to a latent heat storage composite, a method for manufacturing same, and an electric heating device comprising same and, more specifically, to a latent heat storage composite, a method for manufacturing method same, and an electric heating device comprising same, wherein the latent heat storage composite comprises: a phase transition composite filler including a phase change material and a surface adsorption material formed on the surface of the phase change material; and a liquid metal matrix, wherein the phase transition composite filler is suspended in the liquid metal matrix and has viscoelastic properties while having excellent latent heat storage capacity and high thermal and electrical conductivity.

Description

Latent heat storage composite, method for manufacturing same, and heating device including same

[0001] This invention claims the benefit of Korean Patent Application No. 10-2023-0084017 filed on June 29, 2023 with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a latent heat storage composite, a method for producing the same, and a heating device comprising the same, and more particularly, to a phase change composite filler comprising a phase change material and a surface adsorption material formed on the surface of the phase change material; and a liquid metal matrix; wherein the phase change composite filler is suspended in the liquid metal matrix and has viscoelastic properties while having excellent latent heat storage capacity and high thermal and electrical conductivity, a method for producing the same, and a heating device comprising the same.

[0003] With the global demand for energy rapidly increasing, securing a variety of high-efficiency energy utilization technologies is urgent. Thermal energy storage is one of the most important energy utilization technologies, and the use of phase change materials (PCMs) for the effective utilization of latent heat energy is considered a promising approach. PCMs can effectively store or release significant amounts of latent heat at the temperature at which their phase transition occurs, making them highly potential applications in diverse fields, including clothing, construction, manufacturing plants, solar cells, electrical components, and electric vehicle batteries.

[0004] However, the low thermal conductivity, electrical conductivity, and weak optical absorption of pure phase transition materials hinder their widespread application and development. To overcome these shortcomings and enhance thermal energy utilization, research is being conducted on composite phase transition materials, which disperse high thermal conductivity metal, ceramic, or carbon-based fillers within the phase transition material matrix. However, these materials suffer from poor processability and limited improvement in thermal conductivity.

[0005] Accordingly, there was a need to develop a composite material composed of a conductive matrix with high thermal conductivity into which a phase transition material can be impregnated, thereby improving processability and thermal conductivity.

[0006] The technical problem to be achieved by the present invention is to provide a latent heat storage composite having high processability, excellent latent heat storage capacity, and excellent thermal and electrical conductivity, a method for producing the same, and a heating device including the same.

[0007] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0008] One embodiment of the present invention provides a latent heat storage composite including a phase transfer composite filler including a phase transfer material and a surface adsorption material formed on the surface of the phase transfer material; and a liquid metal matrix; wherein the phase transfer composite filler is suspended in the liquid metal matrix.

[0009] According to one embodiment of the present invention, the phase transition material may be an organic phase transition material.

[0010] According to one embodiment of the present invention, the surface adsorption material may be a surfactant or an oxide mineral particle.

[0011] According to one embodiment of the present invention, the oxide mineral particles may include one or more of kaolinite, dickite, nacrite, halloysite, pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite, montmorillonite, illite, chlorite, silica (SiO2), aluminum oxide (Al2O3), iron oxide (Fe2O3 and Fe3O4), magnesium oxide (MgO), manganese oxide (MnO2), tin oxide (SnO2), titanium dioxide (TiO2), zinc oxide (ZnO), and zirconia (ZrO2).

[0012] According to one embodiment of the present invention, the oxide mineral particles may have a diameter of 10 nm to 10 μm.

[0013] According to one embodiment of the present invention, the phase transfer complex filler may have a diameter of 0.1 ㎛ to 100 ㎛.

[0014] According to one embodiment of the present invention, the liquid metal matrix may be one selected from the group consisting of mercury (Hg), cesium (Cs), francium (Fr), rubidium (Rb), gallium (Ga), and gallium-based liquid metals.

[0015] According to one embodiment of the present invention, the gallium-based liquid metal may include at least one selected from the group consisting of gallium-indium eutectic alloy (Ga / In, EGaIn), gallium-tin eutectic alloy (Ga / Sn), gallium-aluminum eutectic alloy (Ga / Al), gallium-zinc eutectic alloy (Ga / Zn), gallium-mercury eutectic alloy (Ga / Hg), gallium-silver eutectic alloy (Ga / Ag), gallium-indium-tin eutectic alloy (Ga / In / Sn, Galinstan), and combinations thereof.

[0016] According to one embodiment of the present invention, the content of the phase transfer complex filler may be 1 wt% to 12 wt%.

[0017] According to one embodiment of the present invention, the thermal conductivity (k) is 7 W m -1 K -1 It could be something like this.

[0018] According to one embodiment of the present invention, the yield stress (τ y ) may be greater than 900 Pa.

[0019] According to one embodiment of the present invention, it may further include a metal filler.

[0020] According to one embodiment of the present invention, the volume ratio of the phase transition complex filler and the metal filler may be 5:1 to 5:2.

[0021] According to one embodiment of the present invention, the thermal conductivity (k) is 13 W m -1 K -1 It could be something like this.

[0022] One embodiment of the present invention provides a method for manufacturing a latent heat storage composite, including a step of introducing and mixing a phase transfer composite filler including a phase transfer material and a surface adsorption material into a liquid metal matrix.

[0023] One embodiment of the present invention provides a heating device including the latent heat storage composite.

[0024] A latent heat storage composite according to one embodiment of the present invention includes a phase transfer composite filler including a phase transfer material and a surface adsorption material; and a liquid metal matrix; thereby improving processability and thermal conductivity.

[0025] A latent heat storage composite according to one embodiment of the present invention has excellent electrical conductivity and can be used in a heating device.

[0026] Figure 1a shows a phase-transfer complex filler (C) through probe ultrasonic treatment according to one embodiment of the present invention. 22 H 46 @TiO2) is a schematic diagram of the manufacturing process.

[0027] Figures 1b to 1d show a freeze-dried phase transfer complex filler (C) according to one embodiment of the present invention. 22 H 46 @TiO2) SEM images at various magnifications.

[0028] Figure 1e is a phase transition complex filler (C) according to one embodiment of the present invention. 22 H 46 This is a graph showing the size distribution of @TiO2.

[0029] Figure 1f is a phase transition complex filler (C) including the corresponding energy dispersive spectroscopy (EDS) element mapping according to one embodiment of the present invention. 22 H 46 @TiO2) This is an SEM image of the surface.

[0030] Figure 2a is a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) is schematically depicted.

[0031] Figure 2b is a latent heat storage composite (10.1 wt% C) according to one embodiment of the present invention. 22 H 46 This is a photo of @TiO2-in-EGaIn.

[0032] Figure 2c is an SEM photograph of pure EGaIn liquid metal according to one embodiment of the present invention.

[0033] Figure 2d is a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 This is an SEM image of @TiO2-in-EGaIn.

[0034] Figure 2e shows a separated phase transition composite filler (C) surrounded by liquid metal (EGaIn) before exposure to FIB according to one embodiment of the present invention. 22 H 46 @TiO2) is an SEM image.

[0035] Figure 2f shows a separated phase transition composite filler (C) surrounded by liquid metal (EGaIn) after exposure to FIB according to one embodiment of the present invention. 22 H 46 @TiO2) is an SEM image.

[0036] Figure 2g shows an XPS narrow scan spectrum of pure liquid metal (EGaIn) according to one embodiment of the present invention.

[0037] Figure 2h is a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) shows the XPS narrow scan spectrum.

[0038] Figure 2i shows the separated phase transition complex filler (C) with corresponding energy dispersive spectroscopy (EDS) elemental mapping after exposure to FIB according to one embodiment of the present invention. 22 H 46 @TiO2) This is an SEM image of the surface.

[0039] Figures 3a to 3d sequentially illustrate a phase transition composite filler (C) surrounded by liquid metal (EGaIn) according to one embodiment of the present invention. 22 H 46 This is an SEM photograph of the process of destroying @TiO2 using a focused ion beam (FIB).

[0040] Figure 4a shows different phase transition complex fillers (C) according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46@TiO2-in-EGaIn) shows the storage (G', solid line) and loss (G", dotted line) coefficients of the samples.

[0041] Figures 4b to 4f show a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 This photo shows various examples of applications utilizing the viscoelastic properties and shape retention of @TiO2-in-EGaIn.

[0042] Figure 5a shows different phase transition complex fillers (C) according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46 @TiO2-in-EGaIn) shows the heating and cooling DSC curves of the samples.

[0043] Figure 5b shows a 10.1 wt% phase transfer composite filler (C) exposed to 100 heating-cooling cycles according to one embodiment of the present invention. 22 H 46 Latent heat storage composites (C) containing @TiO2 22 H 46 @TiO2-in-EGaIn) shows the DSC curve of the sample.

[0044] FIG. 5c shows a DSC curve of a latent heat storage composite including a phase transfer composite filler containing another phase transfer material according to one embodiment of the present invention.

[0045] Figure 6 is a pure n-docosane (C) according to one embodiment of the present invention. 22 H 46 ), heating and cooling DSC curves of EGaI and TiO2 are shown.

[0046] Figure 7 is a latent heat storage composite (C) including a phase transfer composite filler according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) comprising @TiO2-in-EGaIn and phase transition complex filler and metal filler 22 H46 @TiO2&Cu-in-EGaIn) is shown by comparing the thermal conductivities.

[0047] Figure 8a shows the measured composite k(k) for the proposed latent heat storage composite (PCM-in-LM) according to one embodiment of the present invention. c ) shows the Agari model fitting of the values.

[0048] Figure 8b shows the measured composite k(k) for a virtual latent heat storage composite (LM-in-PCM) according to one embodiment of the present invention. c ) shows the Agari model fitting of the values.

[0049] Figures 9a to 9c illustrate a demonstration of thermal management and thermal energy utilization performance of a latent heat storage composite (PCM-in-LM) according to one embodiment of the present invention.

[0050] FIG. 10a is a schematic diagram of a customized Joule heating system according to one embodiment of the present invention.

[0051] FIG. 10b illustrates time-temperature curves of a customized Joule heating system at various applied voltages according to one embodiment of the present invention.

[0052] Figure 10c shows the latent heat storage composite (C) at the same applied power (8 W) according to one embodiment of the present invention. 22 H 46 Infrared images of the Joule heating system embedded with @TiO2-in-EGaIn and pure EGaIn.

[0053] Figure 10d shows the latent heat storage composite (C) at the same applied power (8 W) according to one embodiment of the present invention. 22 H 46 Time-temperature curves of the Joule heating system embedded with @TiO2-in-EGaIn and pure EGaIn are shown.

[0054] Figure 10e shows the latent heat storage composite (C) after 100 heating-cooling cycles according to one embodiment of the present invention. 22 H 46 The circulating water-temperature curve of the system containing @TiO2-in-EGaIn is shown.

[0055] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0056] In this specification, “A and / or B” means “A and B, or A or B.”

[0057] In this specification, “liquid metal” means a metal in a liquid state or a metal that is liquid at or near room temperature.

[0058] In this specification, “PCM” means phase transition material, and “LM” means liquid metal.

[0059] In this specification, 'suspension' means a state in which a solid phase transition complex filler is dispersed without being dissolved in a liquid metal matrix in a liquid phase.

[0060] Hereinafter, the present invention will be described in more detail.

[0061] One embodiment of the present invention provides a latent heat storage composite including a phase transfer composite filler including a phase transfer material and a surface adsorption material formed on the surface of the phase transfer material; and a liquid metal matrix; wherein the phase transfer composite filler is suspended in the liquid metal matrix.

[0062] A latent heat storage composite according to one embodiment of the present invention includes a surface adsorption material formed on the surface of a phase change material, thereby pulverizing the phase change material and promoting interfacial adhesion between the phase change material and a liquid metal matrix, thereby improving compatibility, and can realize excellent thermal conductivity and electrical conductivity despite including a phase change material having a low thermal conductivity value and insulating properties.

[0063] According to one embodiment of the present invention, the latent heat storage composite includes a phase change composite filler and a liquid metal matrix, and the phase change composite filler is suspended in the liquid metal matrix. As described above, the latent heat storage composite includes a phase change composite filler and a liquid metal matrix, and the phase change composite filler is suspended in the liquid metal matrix, thereby realizing excellent thermal conductivity and electrical conductivity.

[0064] According to one embodiment of the present invention, by controlling the diameter of the solid phase transition complex filler, it can be suspended without being dissolved in the liquid metal matrix, which is a liquid phase.

[0065] According to one embodiment of the present invention, the latent heat storage composite includes a phase-transfer composite filler. Specifically, the phase-transfer composite filler is uniformly dispersed and suspended in a liquid metal matrix, thereby forming a colloidal latent heat storage composite, thereby improving thermal conductivity and electrical conductivity.

[0066] According to one embodiment of the present invention, the phase transfer complex filler may have a diameter of 0.1 ㎛ to 100 ㎛. Specifically, in the case of a phase transfer complex filler having a diameter smaller than 0.1 ㎛, there may be a problem of inefficiency due to a large energy consumption required for the atomization process. In the case of a phase transfer complex filler having a diameter larger than 100 ㎛, it may be difficult to mix with the liquid metal matrix, and it may be difficult to stably suspend in the liquid metal matrix and maintain a colloidal state. In addition, there may be a processing problem when manufacturing the final latent heat storage composite into a desired shape through a process such as extrusion.

[0067] According to one embodiment of the present invention, the phase transfer complex filler may be an organic phase transfer material. Specifically, the phase transfer material may be any commonly used organic phase transfer material, and is not limited in type. By including the organic phase transfer material, the phase transfer complex filler can effectively store latent heat during the phase transfer process.

[0068] According to one embodiment of the present invention, the organic phase transfer material may be selected from organic compounds or mixtures thereof, such as aliphatic paraffins or higher fatty acids, for example, propionamide, naphthalene, acetamide, stearic acid, polyglycol, wax, palmitic acid, myristic acid, stearic acid, lignocerate, camphene, 3-heptanecanone, polyethylene glycol, tetradecane, cyanamide, lauric acid, carpolone, trimyristrin, hexadecanone, capric acid, caprylic acid, and polyglycol.

[0069] According to one embodiment of the present invention, the aliphatic paraffins may be alkanes having 8 to 50 carbon atoms. The alkanes are hydrophobic and do not dissolve in hydrophilic solvents even in liquid phases, so they can effectively store latent heat during the phase transition process. Preferably, the organic phase transition material is n-eicosane (C 20 H 42), n-docosane (C 22 H 46 ) and n-tetracosane (C 24 H 50 ) can be used.

[0070] According to one embodiment of the present invention, the phase change composite filler comprises a surface-adsorbing material. Specifically, the surface-adsorbing material adsorbs onto the surface of the phase change material, thereby pulverizing the phase change material, forming a phase change composite filler, and promoting interfacial adhesion between the phase change material and the liquid metal matrix, thereby improving compatibility.

[0071] According to one embodiment of the present invention, the surface adsorption material may be a surfactant or an oxide mineral particle.

[0072] According to one embodiment of the present invention, the surfactant may include a low-molecular-weight surfactant including sodium dodecyl sulfate (SDS), a SPAN-based surfactant, and a TWEEN-based surfactant, and a high-molecular-weight surfactant including polyvinyl alcohol (PVA), polystyrene sulfonate (PSS), and polyvinyl pyrrolidine (PVP). The surfactant may be adsorbed onto the surface of the phase change material to atomize the phase change material, form a phase change complex filler, promote interfacial adhesion between the phase change material and the liquid metal matrix, and improve compatibility.

[0073] According to one embodiment of the present invention, the oxide mineral particles may include one or more of kaolinite, dickite, nacrite, halloysite, pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite, montmorillonite, illite, chlorite, silica (SiO2), aluminum oxide (Al2O3), iron oxide (Fe2O3 and Fe3O4), magnesium oxide (MgO), manganese oxide (MnO2), tin oxide (SnO2), titanium dioxide (TiO2), zinc oxide (ZnO), and zirconia (ZrO2). The above-mentioned oxide mineral particles can be adsorbed on the surface of a phase change material to micronize the phase change material, form a phase change complex filler, promote interfacial adhesion between the phase change material and the liquid metal matrix, and improve compatibility.

[0074] According to one embodiment of the present invention, the oxide mineral particles may have a diameter of 10 nm to 10 μm. Specifically, when the diameter of the oxide mineral particles is smaller than 10 nm, the adsorption area and adsorption energy are weakened, so that the oxide mineral particles may not be sufficiently adsorbed on the surface of the phase change material, and when the diameter of the oxide mineral particles is larger than 10 μm, the influence of gravity becomes strong, making it difficult for the oxide mineral particles to maintain a colloidal state, and even if they are adsorbed with the phase change material, there may be a problem in that it is difficult to stably disperse the phase change material.

[0075] According to one embodiment of the present invention, the latent heat storage composite comprises a liquid metal matrix. Specifically, the liquid metal matrix is ​​composed of a metal that is liquid at room temperature with a melting point of 30°C or lower and has viscoelastic properties. In addition, since the phase transfer composite filler is suspended due to its high thermal conductivity (k), a latent heat storage composite with excellent thermal conductivity in a colloidal state can be manufactured.

[0076] According to one embodiment of the present invention, the liquid metal matrix may be one selected from the group consisting of mercury (Hg), cesium (Cs), francium (Fr), rubidium (Rb), gallium (Ga), and gallium-based liquid metals. As described above, the liquid metal matrix may include a metal that is in a liquid state at room temperature and has a melting point of 30°C or lower and has viscoelasticity.

[0077] According to one embodiment of the present invention, the gallium-based liquid metal may include at least one selected from the group consisting of a gallium-indium eutectic alloy (Ga / In, EGaIn), a gallium-tin eutectic alloy (Ga / Sn), a gallium-aluminum eutectic alloy (Ga / Al), a gallium-zinc eutectic alloy (Ga / Zn), a gallium-mercury eutectic alloy (Ga / Hg), a gallium-silver eutectic alloy (Ga / Ag), and a gallium-indium-tin eutectic alloy (Ga / In / Sn, Galinstan), and combinations thereof. As described above, the gallium-based liquid metal may be a eutectic alloy containing gallium (Ga), and may be a viscoelastic metal that is in a liquid state at room temperature with a melting point of 30°C or lower.

[0078] In this specification, 'viscoelasticity' means having elasticity, a characteristic of a solid, and viscosity, a characteristic of a liquid, at the same time.

[0079] According to one embodiment of the present invention, the content of the phase transfer complex filler may be 1 wt% to 12 wt%. Specifically, the content of the phase transfer complex filler may be 1.5 wt% to 11.5 wt% or 2 wt% to 11 wt%. Most preferably, the content of the phase transfer complex filler may be 2.5 wt% to 10.5 wt%. By controlling the content of the phase transfer complex filler within the above-described range, the yield stress (τ) of the latent heat storage composite y ), density (ρ), heating (ΔH m ) and cooling (ΔH c ) can control the phase transition enthalpy and thermal conductivity (k).

[0080] According to one embodiment of the present invention, the latent heat storage composite has a thermal conductivity (k) of 7 W m -1 K -1 It may be ideal. Specifically, the thermal conductivity (k) of the latent heat storage composite is 7 W m -1 K -1 More than 16 W m -1 K -1 Less than or equal to 7.5 W m -1 K -1 More than 15.5 W m -1 K -1 It may be less than 7 W m with a thermal conductivity (k). -1 K -1 If it is less than that, it is insufficient to utilize latent heat, so by controlling the thermal conductivity of the latent heat storage composite within the above-described range, it can be utilized in a system that enables utilization of latent heat.

[0081] According to one embodiment of the present invention, the latent heat storage composite has a yield stress (τ y ) may be greater than 900 Pa. Specifically, the yield stress (τ) of the latent heat storage composite y ) may be 900 Pa or more and 9000 Pa or less or 950 Pa or more and 8050 Pa or less. Yield stress (τ y) is less than 900 Pa, it is insufficient to be used as ink for 3D printing. Therefore, by controlling the yield stress of the latent heat storage composite within the above-described range, shape retention ability sufficient for 3D printing can be secured.

[0082] According to one embodiment of the present invention, the latent heat storage composite may further include a metal filler. The metal filler may be at least one of gold (Au), silver (Ag), copper (Cu), tungsten (W), and aluminum (Al) having high thermal conductivity. Preferably, it may be copper (Cu). In addition, the latent heat storage composite may further include a carbon filler. The carbon filler may be at least one of graphite, graphene, and diamond having high thermal conductivity. By further including the metal filler or carbon filler, the thermal conductivity of the latent heat storage composite can be improved.

[0083] According to one embodiment of the present invention, the volume ratio of the phase transition composite filler and the metal filler may be 5:1 to 5:2. Preferably, the volume ratio of the phase transition composite filler and the metal filler may be 10:3. By controlling the volume ratio of the phase transition composite filler and the metal filler within the above-described range, the yield stress (τ) of the latent heat storage composite y ), density (ρ), heating (ΔH m ) and cooling (ΔH c ) can control the phase transition enthalpy and thermal conductivity (k).

[0084] According to one embodiment of the present invention, the latent heat storage composite further comprising the metal filler has a thermal conductivity (k) of 13 W m -1 K -1 It may be ideal. Specifically, the thermal conductivity (k) of the latent heat storage composite is 13 W m -1 K -1 More than 15 W m -1 K -1or less than 13.5 W m -1 K -1 Above 14.5 W m -1 K -1 It may be less than . For example, when the content of the phase transition complex filler is maximum, the thermal conductivity (k) without metal filler is about 8 W m -1 K -1 However, the thermal conductivity (k) when including metal filler is about 14 W m -1 K -1 Thermal conductivity can be significantly improved to this extent.

[0085] According to one embodiment of the present invention, various thermal management devices utilizing the latent heat storage composite can be provided. Specifically, the thermal management devices may include devices requiring essential thermal management, such as electric vehicle batteries, passive cooling of solar panels, and active cooling devices. By using the latent heat storage composite in thermal management devices, the risk of explosion due to thermal runaway can be reduced.

[0086] One embodiment of the present invention provides a method for manufacturing a latent heat storage composite, including a step of introducing and mixing a phase transition composite filler including a phase transition material and oxide mineral particles into a liquid metal matrix.

[0087] A method for manufacturing a latent heat storage composite according to one embodiment of the present invention can manufacture the latent heat storage composite of the present invention by introducing a phase-transition composite filler including a phase-transition material and oxide mineral particles into a liquid metal matrix and performing simple vortex mixing.

[0088] One embodiment of the present invention provides a heating device comprising the latent heat storage composite. Specifically, the heating device is a device that converts electrical energy into thermal energy to transfer heat, and may include an electrothermal heating device or an electrothermal heating device, and based on the viscoelastic properties of the composite, it may also be utilized as a flexible and stretchable heating device.

[0089] According to one embodiment of the present invention, a heating device is manufactured by injecting the latent heat storage composite material into a circuit built into a 3D printed acrylic device, thereby reducing convective heat dissipation by a phase-transfer composite filler suspended inside as an internal heat storage having a high heat capacity, thereby manufacturing an heating device with excellent efficiency in converting electrical energy into heat energy.

[0090] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0091]

[0092] <Manufacturing Example: Manufacturing of Latent Heat Storage Composite>

[0093] Figure 1a shows a phase-transfer complex filler (C) through probe ultrasonic treatment according to one embodiment of the present invention. 22 H 46 @TiO2) is a schematic diagram of the manufacturing process. The phase transfer composite filler was manufactured by melting the phase transfer material, oxide mineral particles, and the base solvent in a base solvent at a high temperature (60 ℃) through probe ultrasonic treatment, and then freeze-drying.

[0094] Manufactured phase transition composite filler (C 22 H 46 @TiO2) was injected into a liquid metal matrix and dispersed through vortex mixing using a vortex mixer to manufacture a latent heat storage composite.

[0095]

[0096] <Comparative example: pure EGaIn>

[0097] A pure gallium-indium eutectic alloy (Ga / In, EGaIn), which is a liquid metal, was used.

[0098]

[0099] <Example: Latent heat storage composite>

[0100] Example 1

[0101] n-docosane (C) as a phase transition material 22 H 46 ), titanium dioxide (TiO2) as an oxide mineral particle, and water as a base solvent were used to prepare a phase transfer complex filler (C) according to the manufacturing example. 22 H 46 @TiO2) was manufactured. The manufactured phase transfer composite filler (C 22 H 46 @TiO2) 2.7 wt% was dispersed in a liquid metal gallium-indium eutectic alloy (Ga / In, EGaIn) to form a latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) was manufactured.

[0102]

[0103] Example 2

[0104] Phase transition complex filler (C 22 H 46 @TiO2) was prepared in the same manner as in Example 1, except that it contained 5.4 wt%.

[0105]

[0106] Example 3

[0107] Phase transition complex filler (C 22 H 46 @TiO2) was prepared in the same manner as in Example 1, except that it contained 10.1 wt%.

[0108]

[0109] Example 4

[0110] n-docosane (C) as a phase transition material 22 H 46 ), titanium dioxide (TiO2) as an oxide mineral particle, and water as a base solvent were used to prepare a phase transfer complex filler (C) according to the manufacturing example. 22 H 46 @TiO2) was manufactured. The manufactured phase transfer composite filler (C22 H 46 @TiO2) 40 vol% was added to the liquid metal gallium-indium eutectic alloy (Ga / In, EGaIn) and vortex-mixed for several minutes. Afterwards, 12 vol% of copper (Cu) was additionally added as a metal filler and vortex-mixed to form a latent heat storage composite (C 22 H 46 @TiO2&Cu-in-EGaIn) was manufactured.

[0111]

[0112] <Experimental Example 1-1: Morphology and Structure Analysis of Phase Transition Complex Filler>

[0113] Phase transfer complex filler (C) of Examples 1 to 3 22 H 46 Scanning electron microscope (SEM) analysis was performed to determine the morphology and structure of @TiO2.

[0114] Figures 1b to 1d show a freeze-dried phase transfer complex filler (C) according to one embodiment of the present invention. 22 H 46 @TiO2) are SEM images at various magnifications. Specifically, the scale bars in Figures 1b to 1d represent 100, 10, and 10 μm, respectively. As shown in Figures 1b to 1d, the phase transfer composite filler (C 22 H 46 @TiO2) is spherical and its surface is densely covered with adsorbed titanium dioxide (TiO2) nanoparticles. Phase transition material (C 22 H 46 ) The titanium dioxide (TiO2) layer adsorbed on the surface can promote interfacial adhesion between the phase transition material and the liquid metal matrix and improve compatibility.

[0115] Figure 1e is a phase transition complex filler (C) according to one embodiment of the present invention. 22 H 46 @TiO2) is a graph showing the size distribution. As shown in Fig. 1e, the phase transition complex filler (C22 H 46 @TiO2) can be seen to have an average size of 56.5 ± 14.1 μm.

[0116] Figure 1f is a phase transition complex filler (C) including the corresponding energy dispersive spectroscopy (EDS) element mapping according to one embodiment of the present invention. 22 H 46 @TiO2) is an SEM photograph of the surface. Specifically, the scale bar in Fig. 1f represents 1 μm, and the white scale bars each represent 3 μm. As shown in Fig. 1f, the phase transfer complex filler (C 22 H 46 @TiO2) It can be seen that the surface is densely dispersed and covered with adsorbed titanium dioxide (TiO2) nanoparticles.

[0117]

[0118] <Experimental Example 1-2: Morphology and Structure Analysis of Latent Heat Storage Composites>

[0119] Latent heat storage composites of Examples 1 to 3 (C 22 H 46 Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) analyses were performed to determine the morphology and structure of @TiO2-in-EGaIn.

[0120] Figure 2a is a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) is schematically illustrated. Specifically, the phase transition complex filler (C 22 H 46 @TiO2) is suspended in a liquid metal matrix (EgaIn) through vortex mixing using a vortex mixer to form a colloidal latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) was formed.

[0121] Figure 2b is a latent heat storage composite (10.1 wt% C) according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) is a photograph. Specifically, the scale bar in Fig. 2b represents 5 mm, and the latent heat storage composite containing 10.1 wt% of the phase transfer composite filler exhibits a paste-like form with high viscosity, unlike the pure EGaIn liquid metal, which is a low-viscosity fluid of about 2 mPa·s. Specifically, despite the simplicity of the mixing method and the short processing time, no macroscopic phase separation was observed between the dispersed phase of the phase transfer composite filler and the continuous phase of the liquid metal, and these phases were separated into 42.4 vol% (10.1 wt% phase transfer composite filler (C 22 H 46 @TiO2)) and 57.6 vol% (liquid metal (EGaIn)) have similar volume contents, indicating good compatibility between these phases.

[0122] Figure 2c is a SEM photograph of pure EGaIn liquid metal according to one embodiment of the present invention. Figure 2d is a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) is an SEM image. Specifically, the scale bar in Figs. 2c and 2d represents 100 μm. As shown in Fig. 2d, the phase transfer composite filler (C 22 H 46 @TiO2) can be seen to be surrounded by liquid metal (EGaIn), and most of the phase transition complex fillers (C 22 H 46 @TiO2) was confirmed to be surrounded by liquid metal (EGaIn).

[0123] Figure 2e shows a separated phase transition composite filler (C) surrounded by liquid metal (EGaIn) before exposure to FIB according to one embodiment of the present invention. 22 H 46@TiO2) is a SEM photograph. Figure 2f shows a separated phase transfer composite filler (C) surrounded by liquid metal (EGaIn) after exposure to FIB according to one embodiment of the present invention. 22 H 46 @TiO2) is an SEM photograph. Specifically, the scale bar in Figures 2e and 2f represents 10 μm.

[0124] Figure 2i shows the separated phase transition complex filler (C) with corresponding energy dispersive spectroscopy (EDS) elemental mapping after exposure to FIB according to one embodiment of the present invention. 22 H 46 @TiO2) is an SEM photograph of the surface. Specifically, the white scale bar in Fig. 2i represents 20 μm.

[0125] Specifically, Figures 2e, 2f and 2i show a separated phase transition composite filler (C) surrounded by liquid metal (EGaIn). 22 H 46 The separated phase transition complex filler (C) was observed by performing SEM with energy dispersive spectroscopy (EDS) mapping to observe the @TiO2 22 H 46 @TiO2) was irradiated with a 30kV focused ion beam (FIB).

[0126] Figures 3a to 3d sequentially illustrate a phase transition composite filler (C) surrounded by liquid metal (EGaIn) according to one embodiment of the present invention. 22 H 46@TiO2) is a SEM image of the process of being destroyed by a focused ion beam (FIB). Specifically, due to the high energy of the focused ion beam (FIB), the outermost liquid metal (EGaIn), which is mostly composed of Ga and In, was gradually destroyed as the exposure time increased. As a result, as shown in Fig. 2f and Figs. 3a to 3d, the TiO2 nanoparticles (corresponding to Ti and O in Fig. 2i) revealed a rough surface that was surrounded by the liquid metal (EGaIn). From this, the oxide mineral (TiO2) particles were transformed into a phase transition material (C 22 H 46 , corresponding to C in Fig. 2i) and the liquid metal (EGaIn), it can be inferred that it promoted oxide-mediated adhesion between the two phases.

[0127] Figure 2g shows an XPS narrow scan spectrum of a pure liquid metal (EGaIn) according to an embodiment of the present invention. Figure 2h shows a latent heat storage composite (C) according to an embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) shows the XPS narrow scan spectrum. Specifically, depth profiling analysis was performed using X-ray photoelectron spectroscopy (XPS).

[0128] As shown in Fig. 2g, in the spectrum of pure liquid metal (EGaIn), the peak at higher binding energy (BE) above 1118 eV attributed to Ga oxide appeared only at the outermost surface, i.e., at an Ar ion beam etching time of 0 s. At longer etching times, the lower binding energy (BE) peak (1116.7 eV) due to metallic Ga became dominant.

[0129] On the other hand, as shown in Fig. 2h, the latent heat storage composite (C 22 H46 In the spectra of @TiO2-in-EGaIn, the Ga oxide peak at higher binding energy (BE) was found to be identifiable during long etching times. This is consistent with the latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) indicates that the Ga beneath the outermost surface is highly oxidized, unlike the Ga beneath the outermost surface of the pure liquid metal (EGaIn).

[0130] Oxidation of pure liquid metal (EGaIn) was found to occur only on the surface, which was observed in the phase-transfer composite filler (C) with densely adsorbed TiO2 nanoparticles as described above. 22 H 46 @TiO2) can be the basis for supporting the inference that it promotes the oxidation of liquid metal (EGaIn).

[0131]

[0132] <Experimental Example 2: Shape Retention and Density Analysis of Latent Heat Storage Composites>

[0133] Latent heat storage composites of Examples 1 to 3 (C 22 H 46 To investigate the shape retention ability of @TiO2-in-EGaIn, shear-stress-controlled oscillatory rheological analysis was performed.

[0134] Figure 4a shows different phase transition complex fillers (C) according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46 @TiO2-in-EGaIn) samples are shown with storage (G', solid line) and loss (G", dotted line) coefficients. Specifically, from the left side of the graph, 2.7 wt%, 5.4 wt%, and 10.1 wt% of the phase transfer composite filler (C 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46@TiO2-in-EGaIn) represents the storage and loss moduli of the sample. The storage modulus (G') and loss modulus (G") quantitatively reflect the solid-like and liquid-like properties of the viscoelastic sample, respectively.

[0135] As shown in Fig. 4a, the storage modulus (G') curves of all three samples dominate the loss modulus (G") curves in the linear viscoelastic region, indicating that the latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) exhibits gel-like properties and high shape retention. In particular, phase transfer composite filler (C 22 H 46 As the @TiO2) content increases from 2.7 wt% to 10.1 wt%, the volume increases from 15.6 vol% to 42.4 vol%, and the initial storage modulus value (G'0) is 1.5 × 10 4 4.6 × 10 in Pa 5 Pa increased by about 105 times. From this, the suspended phase transition complex filler (C 22 H 46 @TiO2) higher packing of latent heat storage composites (C 22 H 46 It can be seen that the solid-like properties of @TiO2-in-EGaIn will be greatly improved. In particular, the storage modulus (G') and loss modulus (G") curves suddenly dropped at a certain stress value, and the loss modulus (G") dominated the storage modulus (G') at higher stresses. The intersection of the storage modulus (G') and loss modulus (G") curves is generally considered to be the yield point of the sample, and the shear stress at this point is called the yield stress (τ y ) is called the yield stress (τ y ) In this case, the sample starts to flow, and the initial yield of the solid-like sample is useful for easy molding into a desired shape. Therefore, the latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) can be applied to various types of systems.

[0136] Figures 4b to 4f show a latent heat storage composite (C) according to one embodiment of the present invention. 22 H 46 The following are photographs showing various applications utilizing the viscoelastic properties and shape retention of @TiO2-in-EGaIn. For example, as shown in FIGS. 4b and 4c, it can be dispersed on a flat or curved surface, as shown in FIG. 4d, it can be filled into a mold of any shape, and as shown in FIGS. 4e to 4g, it can be fabricated into 2D patterns or various 3D independent objects through screen printing or direct writing. The samples maintained their shapes even after processing unless further external force was applied, which is indicated by the initial storage modulus value (G'0) and yield stress (τ y ) is high. In order for the colloidal ink to have sufficient shape retention to enable 3D printing with high accuracy and reliability, the yield stress (τ) must be near or above 1000 Pa. y ) values ​​are often recommended. Three latent heat storage composites (C 22 H 46 @TiO2-in-EGaIn) samples were prepared with 2.7, 5.4 and 10.1 wt% of phase transfer composite filler (C 22 H 46 @TiO2) content sufficiently high yield stress (τ y ) values, i.e., 950.5, 2940.0, and 8004.0 Pa. Therefore, Examples 1 to 3 can be considered to have excellent shape retention.

[0137] Latent heat storage composites of Examples 1 to 3 (C 22 H 46 Density analysis of @TiO2-in-EGaIn was performed.

[0138] Latent heat storage composite (C 22 H 46 An interesting feature of @TiO2-in-EGaIn is the suspended phase transition composite filler (C 22H 46 As the content of @TiO2 increases, the rheological stiffness increases, while the overall density (ρ) decreases with increasing phase transition composite filler (C 22 H 46 @TiO2), especially phase transition materials (C 22 H 46 ) core (~0.8g cm -3 ) is greatly reduced due to its low density (ρ). As an example, in the case of pure liquid metal (EGaIn), it is 6.3 g cm -3 The largest phase transition complex filler investigated in (C 22 H 46 Latent heat storage composite (C) at a content (10.1 wt%) of @TiO2 22 H 46 @TiO2-in-EGaIn) is 4.0g cm -3 The trade-off between rheological stiffness and density (ρ) reported for phase transition material (PCM)-in-liquid metal (LM) can be considered unique because such a large density (ρ) mismatch is uncommon in colloidal systems consisting of dispersed and continuous phases with low and high densities (ρ), respectively.

[0139]

[0140] <Experimental Example 3: Analysis of Phase Transition Enthalpy of Latent Heat Storage Composites>

[0141] Latent heat storage composites of Examples 1 to 3 (C 22 H 46 Differential scanning calorimetry (DSC) was performed to determine the phase transition enthalpy of @TiO2-in-EGaIn.

[0142] Figure 5a shows different phase transition complex fillers (C) according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46@TiO2-in-EGaIn) samples are shown as heating and cooling DSC curves. Specifically, 2.7 wt%, 5.4 wt%, and 10.1 wt% of the phase transfer composite filler (C 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46 @TiO2-in-EGaIn) sample and the DSC curves are shown when heated and cooled between 20 ℃ and 80 ℃.

[0143] Figure 6 is a pure n-docosane (C) according to one embodiment of the present invention. 22 H 46 ), heating and cooling DSC curves of EGaIn and TiO2 are shown.

[0144] As shown in Fig. 6, upon heating, latent heat storage, which is an endothermic process, occurs in the suspended n-docosane (C 22 H 46 ) occurred at about 41 to 46 °C, with a maximum temperature of about 44 °C. Upon cooling, the suspended n-docosane (C 22 H 46 ) occurred at about 42 to 39°C, and then a slight heat release occurred as the temperature decreased to about 31°C. The occurrence of multiple phase transition peaks is known to be easily formed at interfaces with restricted geometric structures or other phases of n-docosane (C 22 H 46 ) is due to the rotor phase. Therefore, as shown in the above Fig. 5a, the finely divided n-docosane (C) floating in contact with a significant amount of interfacial oxide 22 H 46 ) can also confirm multiple phase transition peaks.

[0145] Table 1 below shows the different phase transition complex fillers (C 22 H 46 Latent heat storage composite (C) with @TiO2 content 22 H 46@TiO2-in-EGaIn) samples were heated at 20°C to 80°C (ΔH m ) and cooling (ΔH c ) shows the expected and measured enthalpies of the phase transition.

[0146]

[0147] Phase transition complex filler (C 22 H 46 @TiO2) Content (weight%) Latent heat stored or released during phase transition (J cm -3 )H m (expectation) a H m (measurement)H c (expectation) b H c (Measurement) 2.7 (Example 1) 29.9 3 4.0 ± 5.2 3 0.1 3 4.1 ± 5.1 5.4 (Example 2) 51.8 5 5.7 ± 8.0 5 2.0 5 5.7 ± 7.8 1 0.1 (Example 3) 8 1.3 8 8.3 ± 9.3 8 1.6 8 7.9 ± 9.7 a) C in bulk form 22 H 46 About H m = 251.0 J g -1 In C 22 H 46 Calculated based on content b) C in bulk form 22 H 46 About H c = 251.9 J g -1 In C 22 H 46 Calculated based on content

[0148] As shown in Table 1 above, heating (ΔH m ) and cooling (ΔH c ) The total enthalpies of the phase transition (m and c represent melting and crystallization, respectively) were similar, and the suspended n-docosane (C 22 H 46 ) increases as the amount of ΔH increases m and ΔH cIt can be confirmed that all of them systematically increase. This indicates that the latent heat stored or released during the phase transition of the sample can be easily controlled by simply dispersing various amounts of micronized phase transition materials in the liquid metal matrix. Furthermore, the measured latent heat was close to the expected value for a given n-docosane content per sample, indicating minimal loss of the phase transition material during mixing with the liquid metal and excellent compatibility between the two phases.

[0149] Figure 5b shows a 10.1 wt% phase transfer composite filler (C) exposed to 100 heating-cooling cycles according to one embodiment of the present invention. 22 H 46 Latent heat storage composites (C) containing @TiO2 22 H 46 @TiO2-in-EGaIn) sample. Specifically, the intermediate peak that first appeared after the main peak upon cooling showed continuous shift (to lower or higher temperature) with repeated heating-cooling cycles, and n-docosane (C 22 H 46 ) can reflect the intermediate phase change. In the DSC cooling curve of bulk EGaIn or TiO2 in the corresponding temperature range of Fig. 6, no exothermic peak was found, so n-docosane (C 22 H 46 ) can be seen as a change in the intermediate phase.

[0150] As described above, despite possible variations in the intermediate stages, the entire temperature range (approximately 42 to 31 °C) over which latent heat release occurred was maintained, and the total amount of heat released during cooling did not change during repeated cycles. In addition, as shown in the upper photo of the inset in Fig. 5b, the bulk form of 10.1 wt% phase transfer composite filler (C) was subjected to 100 heating-cooling cycles using a convection oven (100 °C). 22 H 46 Latent heat storage composites (C) containing @TiO2 22 H46 @TiO2-in-EGaIn) sample shows high stability as it does not show macroscopic phase separation. Additionally, the lower photo in the inset of Fig. 5b is an SEM image of the sample obtained after the cycling stability test, showing the suspended phase transfer composite filler (C 22 H 46 @TiO2) maintains its shape surrounded by liquid metal (EGaIn) during repeated melting-crystallization. It is internally formed in the liquid metal matrix and the phase transition complex filler (C 22 H 46 Gallium oxide surrounding the @TiO2 particles is molten n-docosane (C 22 H 46 ) can act as an encapsulating shell to minimize leakage.

[0151] Phase transition complex filler (C 22 H 46 Latent heat storage composites (C) containing @TiO2 22 H 46 A possible phase transition material for @TiO2-in-EGaIn is n-docosane (C 22 H 46 ) is not the only one.

[0152] Figure 5c shows a DSC curve of a latent heat storage composite including a phase transition composite filler containing another phase transition material according to an embodiment of the present invention. Specifically, another homologous paraffin phase transition material, i.e., n-eicosane (C) suspended in a liquid metal (EGaIn) matrix. 20 H 42 ) and n-tetracosane (C 24 H 50 ) are DSC curves of latent heat storage composites, and all phase transition materials are C 22 H 46 @TiO2 was micronized using the same method used for manufacturing TiO2.

[0153] As shown in Figure 5c, latent heat storage composites containing different phase transition materials stored and released latent heat at different temperatures, depending on the known phase transition temperatures of the respective phase transition materials. Based on this conceptual simplicity, various latent heat storage composites with different phase transition temperatures can be utilized for various purposes.

[0154]

[0155] <Experimental Example 4: Thermal Conductivity Analysis of Latent Heat Storage Composites>

[0156] Latent heat storage composites of Examples 1 to 3 (C 22 H 46 @TiO2-in-EGaIn) and latent heat storage composite of Example 4 (C 22 H 46 To determine the thermal conductivity (k) of @TiO2&Cu-in-EGaIn, the Hot-Disk method was performed.

[0157] Theoretically, k(k) of the composite c ) is the k value of the filler and matrix (k f and k m ) and volume fraction (Φ f and Φ m ) is a function of, where the subscripts c, f and m represent the composite, filler and matrix, respectively. Therefore, in Examples 1 to 3, fillers (C) having low k values 22 H 46 In case of k f ~0.2 W m -1 K -1 , ~7.4-10.4 W m for TiO2 -1 K -1 ) increases the content of pure EGaIn matrix (Φ f k of =0) c to k c =k m =26.4 W m -1 K -1 In C 22 H 46 @TiO2 content is 2.7(Φ f ~0.16), 5.4(Φf ~0.27) and 10.1(Φ f ~0.42) wt%, 15.0, 10.3 and 7.8 W m, respectively. -1 K -1 was systematically reduced. As the filler content increased, k c This decreasing trend is in contrast to the trend observed in conventional polymer or phase transition material composites where the filler and matrix typically have high and low k values, respectively. However, up to the maximum filler content (10.1 wt% C 22 H 46 Latent heat storage composite (C) with @TiO2 22 H 46 @TiO2-in-EGaIn) is also a phase transition material (C 22 H 46 ) high Φ f (~0.4) and low k f (~0.2 W m -1 K -1 ) despite 7.8 W m -1 K -1 High k of c It can be confirmed that it maintains (Φ of TiO2 f ~0.02 is considered insignificant).

[0158] Latent heat storage composite of Example 4 (C 22 H 46 @TiO2&Cu-in-EGaIn) is k due to the low k value of the phase transition composite filler in the latent heat storage composites of Examples 1 to 3. c To overcome the tendency of the decrease in k, a metal filler with a high k value was additionally added.

[0159] Figure 7 is a latent heat storage composite (C) including a phase transfer composite filler according to one embodiment of the present invention. 22 H 46 Latent heat storage composite (C) comprising @TiO2-in-EGaIn and phase transition complex filler and metal filler 22 H 46@TiO2&Cu-in-EGaIn) is shown as a comparison of thermal conductivities. As shown in Fig. 7, a latent heat storage composite (C) with a phase transition complex filler of about 40 vol% 22 H 46 Latent heat storage composite (C) with approximately 40 vol% of @TiO2-in-EGaIn and phase transfer complex filler 22 H 46 A latent heat storage composite (C) with an additional addition of about 12 vol% copper (Cu) filler to @TiO2-in-EGaIn 22 H 46 @TiO2&Cu-in-EGaIn) measured the thermal conductivity, the k(k) of the electron c ) is about 8 W m -1 K -1 , the latter k(k c ) is about 14 W m -1 K -1 It was confirmed that the thermal conductivity was significantly improved when copper (Cu) filler was additionally added.

[0160] In contrast, similar composition (Φ f Low k values ​​(k ~0.6 and Φm~0.4) with f ~0.2 W m -1 K -1 ) for "reverse" colloidal composites consisting of liquid metal fillers with high k values ​​dispersed in an organic matrix, resulting in significantly lower k c Value (approximately 1 W m -1 K -1 ) was reported. This may be attributed to the oxide film formed on the surface of the dispersed liquid metal particles and the organic matrix existing between the particles, which essentially prevents effective heat penetration through the insulating and conductive filler inter-network.

[0161] k measured for the latent heat storage composite of the present invention c The value is Φ f and Φ mThe values ​​observed for composites containing silicone oil in liquid metal are as high as those observed for composites containing silicone oil in liquid metal, which may be due to the continuity of the metal matrix with high k values, leading to efficient electron transport.

[0162] Figure 8a shows the measured composite k(k) for the proposed latent heat storage composite (PCM-in-LM) according to one embodiment of the present invention. c ) represents the Agari model fitting. Specifically, the Agari model is defined as in Equation 1 below.

[0163]

[0164] Here, C1 and C2 are semi-empirical parameters describing the effect of added filler on matrix crystallinity or crystal size and the ease of forming continuous filler chains, respectively. k f =0.2(If TiO2 microparticles are confined only to the interface, k of the microparticles is larger than bulk C 22 H 46 Assuming that C is dominated by the core 22 H 46 @Approximate values ​​for TiO2) and k m =26.4 W m -1 K -1 The fitting is C1=0.98 and C2=0. These values ​​indicate that the suspended filler is practically k c (C2=0) and had a negligible effect on the crystallinity of the bulk EGaIn matrix (C1=1). Therefore, as shown in the schematic diagram of Fig. 8a, the measured high k of the latent heat storage composite (PCM-in-LM) c The values ​​are most likely due to conduction through the liquid metal matrix, consistent with the proposed conceptual framework.

[0165] Figure 8b shows the measured composite k(k) for a virtual latent heat storage composite (LM-in-PCM) according to one embodiment of the present invention. c) values ​​are shown in the Agari model fitting. Specifically, the same fitting was performed for a hypothetical "inverse" colloid, i.e., a LM (filler)-in-PCM (matrix) composite. k f =26.4 and k m =0.2 W m -1 K -1 Same k for same configuration c Assuming that the values ​​can be achieved, C1 = 2.28 and C2 = 0.98 were obtained as a result. However, C1 = 2.28 is physically unrealistic because the suspended liquid metal filler is unlikely to significantly improve the crystallinity of the phase transition material matrix. In addition, C2 = 0.98 is lower than the measured k c This indicates that to achieve high conductivity values, a network formation between the fillers is required, which is technically more difficult than simple dispersion of the fillers. This simple model analysis shows that composites with high PCM content have high k content in the formulation framework of a typical PCM composite where high-k fillers are dispersed in a low-k PCM matrix due to the limitations of continuous conductive network formation. c It is generally shown that it is difficult to achieve the value. On the other hand, the latent heat storage composite (PCM-in-LM) of the present invention has a high k without intentionally controlling the structure formed by the fillers dispersed inside due to the extensive electron transport through the continuous liquid metal matrix. c can be achieved.

[0166] Table 2 below summarizes various characteristics of the latent heat storage composite of the present invention.

[0167]

[0168] Initial storage modulus (Pa) Yield stress (Pa) Density (g cm -3 ) Heating transition enthalpy (J cm) -3 ) Cooling phase transition enthalpy (J cm -3 )Thermal conductivity (W m -1 K -1)Comparative example--6.3--26.4 Example 11.7 × 10 4 950.55.4 ± 0.134.0 ± 5.234.1 ± 5.115.0Example 26.0 × 10 4 2940.04.5 ± 0.155.7 ± 8.055.7 ± 7.810.3Example 34.8 × 10 5 8004.04.0 ± 0.188.3 ± 9.387.9 ± 9.77.8

[0169]

[0170] <Experimental Example 5: Analysis of the Thermal Management Function of Latent Heat Storage Composites>

[0171] Latent heat storage composite of the embodiment (C 22 H 46 Several experiments were conducted to investigate the thermal management capabilities of @TiO2-in-EGaIn.

[0172] Figures 9a to 9c illustrate the thermal management and thermal energy utilization performance of a latent heat storage composite (PCM-in-LM) according to one embodiment of the present invention. Specifically, the superior thermal management capabilities of a high-k-based latent heat storage composite (PCM-in-LM) are demonstrated using a customized test setup.

[0173] As shown in Fig. 9a, a small borosilicate vessel filled with 1 mL of hot water (80°C) contains n-docosane (C) in bulk form at an initial temperature of about 16°C. 22 H 46 ) or latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) was immersed in a large borosilicate vessel filled with 5 mL of the solution. The large vessel was exposed to natural convection at ambient temperature of about 16 °C, and the temperature change over time was measured in the middle of the water in the small vessel immersed in the large vessel. The temperature drop in the water in the small vessel, which occurred through heat transfer to the surrounding medium, was determined by the fact that the vessel was in the form of bulk n-docosane (C 22 H 46 ) than when in contact with latent heat storage composites (C22 H 46 @TiO2-in-EGaIn) was faster when in contact with latent heat storage composite (C 22 H 46 @TiO2-in-EGaIn) is thought to be due to its high k.

[0174] The experiment in Fig. 9a shows rapid cooling of an initially hot object, whereas Fig. 9b shows a rapid exothermic gas-forming chemical reaction (Mg (s) + 2HCl (aq) ↔ Mg 2+ (aq) + 2Cl - (aq) + H 2(g) ) shows the temperature control in the case of thermal runaway. As shown in Fig. 9b, the latent heat storage composite (C ) reached within about 10 seconds. 22 H 46 The maximum temperature of the system surrounded by @TiO2-in-EGaIn was only about 46 ℃, which is higher than that of the bulk n-docosane (C 22 H 46 ) was more than 15 ℃ lower than the system surrounded by suspended n-docosane (C 22 H 46 ) is close to the solid-liquid phase transition temperature of the particle. When this temperature is reached, the latent heat storage composite (C 22 H 46 In a system surrounded by @TiO2-in-EGaIn, the temperature decrease rate within the next 20 seconds is comparable to that of bulk n-docosane (C 22 H 46 ) was significantly higher than that of the system surrounded by suspended n-docosane (C 22 H 46 ) due to the latent heat absorbed by the composite, the maximum temperature difference reaches 23.6 ℃. The temperature difference between the two systems was maintained at about 10 ℃ for up to 10 minutes, and the latent heat storage composite (C 22 H 46The system surrounded by @TiO2-in-EGaIn reached ambient temperature within 20 minutes, but the bulk form of n-docosane (C 22 H 46 ) the system was surrounded by took more than 30 minutes.

[0175] These results suggest that systems surrounded by the proposed latent heat storage composite (PCM-in-LM) due to its high k will be more effective and provide more efficient thermal management than systems surrounded by the phase change material (PCM) alone in preventing undesirable heat accumulation or thermal runaway in devices containing a heat source.

[0176] The fundamental advantage of a system containing a latent heat storage composite (PCM-in-LM) is that the latent heat stored during the phase transition can be released and utilized when needed. In the experiment shown in Fig. 9c, pure EGaIn or various phase transition composite fillers (C 22 H 46 Latent heat storage composites (C) with @TiO2 contents (2.7, 5.4, 10.1 wt%) 22 H 46 A series of 2 mL high-temperature samples of @TiO2-in-EGaIn with an initial temperature of 60 °C were used to heat a 20 mL water bath with an initial temperature of 24 °C. The top of the bath was exposed to air at about 24 °C under natural convection. From the beginning of the experiment, the temperature of the bath rapidly increased for 6 min due to heat transfer from the high-temperature samples and then gradually decreased due to natural convection. The maximum water temperature reached during the temperature-rising period was the phase transition composite filler (C 22 H 46 @TiO2) increased systematically as the content increased.

[0177] Specifically, 10.1 wt% phase transfer composite filler (C 22 H 46 Latent heat storage composite (C) with @TiO2 22 H 46The maximum temperature achieved in the system containing @TiO2-in-EGaIn (31.8 °C) was about 3 °C higher than that in the system containing pure EGaIn (28.8 °C), which can be attributed to the latent heat released by the suspended phase change material (PCM) particles. In the subsequent decreasing temperature range, the phase change composite filler (C 22 H 46 @TiO2) High latent heat storage composite (C 22 H 46 The effectiveness of the system including the latent heat storage composite (PCM-in-LM) as a heat reservoir enabling the utilization of latent heat by maintaining higher temperatures over longer periods of time (more than 1 hour) was demonstrated in the water bath contacting the system including the latent heat storage composite (PCM-in-LM).

[0178]

[0179] <Experimental Example 6: Electrical Conductivity Analysis of Latent Heat Storage Composites>

[0180] Latent heat storage composite of the embodiment (C 22 H 46 To investigate the electrical conductivity of @TiO2-in-EGaIn, a custom Joule heating device was fabricated and a system including it was designed and several experiments were performed.

[0181] Figure 10a is a schematic diagram of a customized Joule heating system according to one embodiment of the present invention. Specifically, the customized Joule heating device of the heating system comprises 10.1 wt% phase transfer composite filler (C 22 H 46 Latent heat storage composites (C) containing @TiO2 22 H 46The sample was fabricated by injecting the sample (TiO2-in-EGaIn) into a circuit (width: 1 mm, height: 0.5 mm, length: 90 cm) embedded in a 3D-printed acrylic device. The easy application of the sample to the narrow circuit pattern can be attributed to the high processability of the latent heat storage composite (PCM-in-LM) due to the fluidity of the liquid metal (LM) as described above. The latent heat storage composite (C 22 H 46 The circuit filled with @TiO2-in-EGaIn had a relatively higher electrical resistance (2.6Ω) than the circuit filled with pure EGaIn (0.8Ω) due to the suspended insulating particles, but still allowed good electrical conduction.

[0182] Figure 10b illustrates time-temperature curves of a customized Joule heating system at various applied voltages according to one embodiment of the present invention. Specifically, the temperature change over time of the customized Joule heating device was measured at various applied voltages, and the power supply was designed to be turned off after each system reached its maximum temperature. As shown in Figure 10b, it can be confirmed that the maximum temperatures of 34.1, 53.4, and 82.9°C were reached within 450 seconds at applied voltages of 2, 3, and 4 V, respectively.

[0183] Figure 10c shows the latent heat storage composite (C) at the same applied power (8 W) according to one embodiment of the present invention. 22 H 46 Infrared images of the Joule heating system embedded with @TiO2-in-EGaIn and pure EGaIn.

[0184] Figure 10d shows the latent heat storage composite (C) at the same applied power (8 W) according to one embodiment of the present invention. 22 H 46 Time-temperature curves of the Joule heating system embedded with @TiO2-in-EGaIn and pure EGaIn are shown.

[0185] As shown in Fig. 10d, pure EGaIn and latent heat storage composite (C 22 H 46 The heating devices filled with @TiO2-in-EGaIn required 432 and 311 s, respectively, to reach a temperature of 80 °C, indicating that the latter achieved faster heating than the former. After reaching 80 °C, the power supply was immediately turned off, and the time required for both systems to reach ambient temperature (21 °C) through natural convection was recorded. Pure EGaIn and latent heat storage composites (C 22 H 46 The heating devices using @TiO2-in-EGaIn required 561 and 586 s, respectively, to reach 25 °C, indicating delayed cooling in the latter.

[0186] Therefore, in both heating and cooling experiments, the latent heat storage composite (PCM-in-LM) was found to be more efficient in converting electrical energy into thermal energy than the pure liquid metal (LM) system, due to the phase change composite filler (C) suspended inside as an internal heat reservoir with high heat capacity. 22 H 46 @TiO2) This may be due to the alleviation of convective heat dissipation by microparticles.

[0187] Figure 10e shows the latent heat storage composite (C) after 100 heating-cooling cycles according to one embodiment of the present invention. 22 H 46 @TiO2-in-EGaIn) shows the circulating water-temperature curve of the system. Specifically, the latent heat storage composite (C 22 H 46The Joule heating device embedded in @TiO2-in-EGaIn was subjected to 100 heating-cooling cycles, and the temperature curves obtained during these cycles are shown for cycles 1-10 and 91-100. No noticeable element degradation was observed even after 100 heating-cooling cycles, confirming the high reliability of the proposed device.

[0188] Therefore, the latent heat storage composite according to one embodiment of the present invention has high thermal conductivity, high electrical conductivity, and unique viscoelastic properties, and thus can be utilized as a new latent heat storage system having various potential formulations.

Claims

1. A phase transfer complex filler comprising a phase transfer material and a surface adsorption material formed on the surface of the phase transfer material; and Containing a liquid metal matrix; A latent heat storage composite, wherein the above-mentioned phase transition composite filler is suspended in the above-mentioned liquid metal matrix.

2. In paragraph 1, The above-mentioned phase transition material is, A latent heat storage composite material which is an organic phase transition material.

3. In paragraph 1, The above surface adsorption material is, A latent heat storage composite material comprising a surfactant or an oxide mineral particle.

4. In paragraph 3, The above oxide mineral particles are, A latent heat storage composite comprising at least one of kaolinite, dickite, nacrite, halloysite, pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite, montmorillonite, illite, chlorite, silica (SiO2), aluminum oxide (Al2O3), iron oxides (Fe2O3 and Fe3O4), magnesium oxide (MgO), manganese oxide (MnO2), tin oxide (SnO2), titanium dioxide (TiO2), zinc oxide (ZnO), and zirconia (ZrO2).

5. In paragraph 3, A latent heat storage composite, wherein the above-mentioned oxide mineral particles have a diameter of 10 nm to 10 μm.

6. In paragraph 1, A latent heat storage composite, wherein the above-mentioned phase transfer composite filler has a diameter of 0.1 ㎛ to 100 ㎛.

7. In paragraph 1, The above liquid metal matrix is, A latent heat storage composite material, wherein the latent heat storage composite material is one selected from the group consisting of mercury (Hg), cesium (Cs), francium (Fr), rubidium (Rb), gallium (Ga), and gallium-based liquid metals.

8. In paragraph 7, The above gallium-based liquid metal is, A latent heat storage composite comprising at least one selected from the group consisting of gallium-indium eutectic alloy (Ga / In, EGaIn), gallium-tin eutectic alloy (Ga / Sn), gallium-aluminum eutectic alloy (Ga / Al), gallium-zinc eutectic alloy (Ga / Zn), gallium-mercury eutectic alloy (Ga / Hg), gallium-silver eutectic alloy (Ga / Ag), gallium-indium-tin eutectic alloy (Ga / In / Sn, Galinstan), and combinations thereof.

9. In paragraph 1, A latent heat storage composite, wherein the content of the above-mentioned phase transfer complex filler is 1 wt% to 12 wt%.

10. In paragraph 1, Thermal conductivity (k) is 7 W m -1 K -1 A latent heat storage composite material.

11. In paragraph 1, Yield stress (τ y ) is a latent heat storage composite having a viscosity of 900 Pa or more.

12. In paragraph 1, A latent heat storage composite further comprising a metal filler.

13. In paragraph 12, A latent heat storage composite, wherein the volume ratio of the above-mentioned phase transition complex filler and the above-mentioned metal filler is 5:1 to 5:

2.

14. In paragraph 12, Thermal conductivity (k) is 13 W m -1 K -1 A latent heat storage composite material.

15. A method for manufacturing a latent heat storage composite, comprising the step of introducing a phase transfer composite filler including a phase transfer material and a surface adsorption material into a liquid metal matrix and mixing them.

16. A heating device comprising the latent heat storage composite of claim 1.

Images