Composition for preparing high-thermal-conductivity composite phase change material, high-thermal-conductivity composite phase change material, and preparation method and application thereof

Abstract

The application relates to the technical field of phase change materials, and discloses a composition for preparing a high-thermal-conductivity composite phase change material, the high-thermal-conductivity composite phase change material, a preparation method of the high-thermal-conductivity composite phase change material and application of the high-thermal-conductivity composite phase change material, the composition contains the following components which are independently stored or stored in mixture: the content of the modified thermal-conductivity fiber is 3wt%-15wt% based on the total mass of the modified thermal-conductivity filler, the modified thermal-conductivity fiber, and the base phase change material; the content of the modified thermal-conductivity filler is 4wt%-20wt%; and the content of the base phase change material is 65wt%-93wt%. The high-thermal-conductivity composite phase change material prepared by the application can make the thermal-conductivity fiber / nano material stably disperse in the base phase change material, and has good stability.

Description

Technical Field

[0001] This invention relates to the field of phase change materials technology, specifically to a composition for preparing high thermal conductivity composite phase change materials, the high thermal conductivity composite phase change materials, their preparation methods, and applications. Background Technology

[0002] Phase change materials (PCMs) are substances that can provide a large amount of latent heat while maintaining a constant temperature during a phase transition. PCMs can be divided into inorganic and organic PCMs. Regardless of whether they are inorganic or organic, their thermal conductivity is relatively low, leading to a long time required for an external temperature source to reach the center of the PCM and a long time required for internal heat to transfer to the outside. This necessitates the use of complex heat exchangers to improve heat transfer efficiency. Furthermore, inorganic hydrated salt PCMs are often highly corrosive, requiring an additional protective coating on the heat exchanger, resulting in very high overall costs and limiting their practical application.

[0003] Microencapsulated phase change materials (PCCs) are composite PCCs formed by encapsulating PCC materials within microcapsule shells made of highly thermally conductive materials using microencapsulation technology. This effectively increases the heat exchange area and enhances the thermal conductivity of the PCC. Furthermore, the small size of the microcapsules can hinder phase separation, suppress supercooling effects, and improve the overall performance of the PCC. However, these microcapsules are prone to leakage, expensive, and involve complex manufacturing processes.

[0004] To overcome the complexity of the microcapsule phase change material (PCM) fabrication process, a method using thermally conductive fillers can be employed. This involves uniformly mixing the PCM with one or more thermally conductive fillers (expanded graphite, carbon nanotubes, graphene, copper nanoparticles, etc.), followed by pressing using a molding machine. The thermally conductive fillers form a thermally conductive network within the PCM system, which conducts heat and accelerates internal heat exchange. However, this method can only produce PCMs of specific shapes and is prone to open circuits. Furthermore, constructing the thermally conductive network requires a large amount of thermally conductive filler (greater than 10%) to be effective, which occupies significant volume of the PCM, ultimately resulting in a low enthalpy per unit volume.

[0005] To avoid the thermal conductivity network breakage caused by insufficient compaction in the thermally conductive filler mixing and pressing method, a thermally conductive framework (graphene aerogel) can be pre-formed, and then the phase change material (PCM) can be infused into the framework. This method effectively improves the thermal conductivity of the PCM, and the micropores in the aerogel have a capillary effect, which firmly locks in the PCM and effectively inhibits phase separation. However, the construction cost of the thermally conductive framework is expensive, and the filling process of the PCM is slow and difficult.

[0006] Therefore, there is an urgent need for a high thermal conductivity composite phase change material with a simple preparation method and a uniform and stable thermally conductive network framework. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects in the prior art, such as uneven distribution of the thermally conductive network framework and easy agglomeration of nanofillers inside the phase change material.

[0008] To achieve the above objectives, a first aspect of the present invention provides a high thermal conductivity composite phase change material having an enthalpy of 140-230 kJ / kg and a thermal conductivity of 4.0-6.9 W / (m*K).

[0009] A second aspect of the present invention provides a composition for preparing a high thermal conductivity composite phase change material, the composition comprising the following components, which are stored individually or in combination:

[0010] Based on the total mass of the modified thermally conductive filler, modified thermally conductive fiber, and matrix phase change material,

[0011] Modified thermally conductive fiber: 3wt%-15wt%,

[0012] Modified thermally conductive filler: 4wt%-20wt%,

[0013] Matrix phase change material: 65wt%-93wt%;

[0014] The modified thermally conductive fiber is prepared from raw thermally conductive fiber by any one of the following methods: chemical oxidation, electrochemical method, and electron beam surface modification.

[0015] The modified thermally conductive filler is obtained from the raw thermally conductive filler by chemical oxidation and / or chemical grafting.

[0016] Furthermore, in the high thermal conductivity composite phase change material, the modified thermally conductive filler and the modified thermally conductive fiber are grafted together by chemical covalent bonds to obtain thermally conductive fibers grafted with thermally conductive filler, and the thermally conductive fibers grafted with thermally conductive filler are combined with the matrix phase change material to obtain the high thermal conductivity composite phase change material.

[0017] A third aspect of the present invention provides a method for preparing a high thermal conductivity composite phase change material, the method comprising subjecting the composition for preparing a high thermal conductivity composite phase change material according to the second aspect to a contact reaction, wherein the contact reaction includes:

[0018] S1: Modified thermally conductive fibers and modified thermally conductive fillers are connected by chemical covalent bonds to obtain thermally conductive fibers grafted with thermally conductive fillers, and the obtained thermally conductive fibers grafted with thermally conductive fillers are graphitized to obtain intermediate 1.

[0019] S2: The molten material containing the matrix phase change material is first mixed with the intermediate 1 described in step S1 to obtain mixture I.

[0020] The fourth aspect of the present invention provides a high thermal conductivity composite phase change material prepared by the method described in the third aspect.

[0021] The fifth aspect of the present invention provides the application of the high thermal conductivity composite phase change material described in the first or fourth aspect in energy storage materials.

[0022] The high thermal conductivity composite phase change material provided by this invention enables the fiber / nanomaterial to be stably and uniformly dispersed in the phase change material matrix, exhibiting good stability. Meanwhile, the composite phase change material provided by this invention has an enthalpy of 140-230 kJ / kg and a thermal conductivity of 4.0-6.9 W / (m*K). Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the high thermal conductivity composite phase change material of the present invention;

[0024] Figure 2 This is a SEM image of the high thermal conductivity composite phase change material obtained in Example 1 of this invention;

[0025] Figure 3 This is a SEM image of a high thermal conductivity composite phase change material made from carbon fiber and a matrix phase change material. Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] It should be noted that, in all aspects of the present invention, the same components in each aspect are described only once in one aspect and not repeatedly, and those skilled in the art should not understand this as a limitation of the present invention.

[0028] It should be noted that, in this invention, all raw materials not specified can be obtained through commercial purchases through general channels. Those skilled in the art can purchase them as needed, and they will not be described in detail in this invention.

[0029] As previously stated, the first aspect of the present invention provides a high thermal conductivity composite phase change material having an enthalpy of 140-230 kJ / kg and a thermal conductivity of 4.0-6.9 W / (m*K).

[0030] To construct a uniform and stable thermally conductive network structure, this invention bridges the nanofillers and thermally conductive fibers with chemical covalent bonds to form a stable thermally conductive network framework. Then, a phase change material is introduced to prepare a high thermal conductivity composite phase change material. For example... Figure 1 As shown, two-dimensional nano-thermal conductive fillers are connected to thermally conductive fibers via chemical covalent bonds, increasing the specific surface area of ​​the thermally conductive fibers, and then phase change materials are added ( Figure 1 The PCM in the phase change material allows heat to be transferred from the interior of the phase change material to the skeleton of the thermally conductive fiber through two-dimensional nano-thermal conductive filler, resulting in a composite phase change material with good thermal conductivity.

[0031] As previously described, a second aspect of the present invention provides a composition for preparing a high thermal conductivity composite phase change material, the composition containing the following components, which may be stored individually or in combination:

[0032] Based on the total mass of the modified thermally conductive filler, modified thermally conductive fiber, and matrix phase change material,

[0033] Modified thermally conductive fiber: 3wt%-15wt%,

[0034] Modified thermally conductive filler: 4wt%-20wt%,

[0035] Matrix phase change material: 65wt%-93wt%;

[0036] The modified thermally conductive fiber is prepared from raw thermally conductive fiber by any one of the following methods: chemical oxidation, electrochemical method, and electron beam surface modification.

[0037] The modified thermally conductive filler is obtained from the raw thermally conductive filler by chemical oxidation and / or chemical grafting.

[0038] Furthermore, in the high thermal conductivity composite phase change material, the modified thermally conductive filler and the modified thermally conductive fiber are grafted together by chemical covalent bonds to obtain thermally conductive fibers grafted with thermally conductive filler, and the thermally conductive fibers grafted with thermally conductive filler are combined with the matrix phase change material to obtain the high thermal conductivity composite phase change material.

[0039] Preferably, the composition contains the following components, which are stored independently or in combination: based on the total mass of the modified thermally conductive filler, modified thermally conductive fiber, and matrix phase change material,

[0040] Modified thermally conductive fiber: 3wt%-11wt%,

[0041] Modified thermally conductive filler: 7wt%-12wt%,

[0042] Matrix phase change material: 75wt%-90wt%.

[0043] In a preferred embodiment, the matrix phase change material is an organic phase change material and / or an inorganic phase change material.

[0044] More preferably, the organic phase change material is selected from at least one of paraffin, stearic acid, dodecanoic acid, docosane, and xylitol.

[0045] More preferably, the inorganic phase change material is selected from at least one of sodium acetate trihydrate, calcium chloride hexahydrate, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, and barium hydroxide octahydrate.

[0046] Preferably, the matrix phase change material has an enthalpy greater than 140 kJ / kg and a thermal conductivity greater than 2.2 W / (m*K).

[0047] According to a preferred embodiment, the matrix phase change material is an inorganic phase change material, and the composition further contains a nucleating agent and a thickener.

[0048] Preferably, based on the total mass of the modified thermally conductive filler, modified thermally conductive fiber, matrix phase change material, nucleating agent and thickener, the content of the nucleating agent is 0.1wt%-10wt%, and the content of the thickener is 0.1wt%-10wt%.

[0049] More preferably, based on the total mass of the modified thermally conductive filler, modified thermally conductive fiber, matrix phase change material, nucleating agent and thickener, the content of the nucleating agent is 1wt%-5wt% and the content of the thickener is 1wt%-5wt%.

[0050] More preferably, the nucleating agent is selected from at least one of disodium hydrogen phosphate dodecahydrate, sodium pyrophosphate decahydrate, sodium metasilicate nonahydrate, sodium borate decahydrate, sodium carbonate decahydrate, sodium phosphate hexahydrate, and borax pentahydrate.

[0051] Preferably, the nucleating agent reduces the supercooling of the matrix phase change material to below 5°C.

[0052] Preferably, the thickener is selected from at least one of starch, gelatin, xanthan gum, sodium carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, polyacrylamide, polyethylene glycol, sodium polyacrylate, and clay.

[0053] In a preferred embodiment, the thermally conductive fiber is carbon fiber; the carbon fiber is selected from at least one of T800, T1000, T1100, M40, M55J, M60J, T300, T700, M35 and M45J.

[0054] In a preferred embodiment, the thermal conductivity of the thermally conductive filler material is greater than 50 W / (m*K).

[0055] Preferably, the thermally conductive filler material is selected from at least one of carbon nanotubes, graphene, graphene oxide, expanded graphite, hexagonal boron nitride, MXene, and silicon carbide.

[0056] More preferably, the carbon nanotubes are selected from at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, hydroxylated carbon nanotubes, and carboxylated carbon nanotubes.

[0057] The MXene described in this invention is a two-dimensional material composed of one or two or more atomic layers of transition metal carbides, nitrides or carbonitrides.

[0058] As previously described, a third aspect of the present invention provides a method for preparing a high thermal conductivity composite phase change material, the method comprising subjecting the composition for preparing a high thermal conductivity composite phase change material described in the second aspect to a contact reaction, wherein the contact reaction includes:

[0059] S1: Modified thermally conductive fibers and modified thermally conductive fillers are connected by chemical covalent bonds to obtain thermally conductive fibers grafted with thermally conductive fillers, and the obtained thermally conductive fibers grafted with thermally conductive fillers are graphitized to obtain intermediate 1.

[0060] S2: The molten material containing the matrix phase change material is first mixed with the intermediate 1 described in step S1 to obtain mixture I.

[0061] In order to make the thermally conductive fibers / nanomaterials more stably dispersed in the matrix phase change material, preferably, the chemical covalent bonds are at least one of amide bonds, ester bonds, ether bonds and imide bonds.

[0062] Preferably, in step S1, the reaction conditions for graphitizing the thermally conductive fibers grafted with thermally conductive fillers are at least: the reaction temperature is 800-2300℃ and the reaction time is 2-12h.

[0063] In a preferred embodiment, in step S2, the conditions for the first mixing are at least: a time of 1-4 hours and a stirring speed of 200-600 r / min.

[0064] In this invention, intermediate 1 refers to graphitized thermally conductive fibers grafted with thermally conductive fillers.

[0065] According to a preferred embodiment, in step S1, the step of linking the modified thermally conductive fiber and the modified thermally conductive filler by chemical covalent bonds includes:

[0066] S11: Surface carboxylation is performed on either the raw material thermally conductive fiber or the raw material thermally conductive filler, and amination is performed on the other to obtain modified thermally conductive fiber and modified thermally conductive filler, respectively.

[0067] S12: In the presence of a solvent, the modified thermally conductive fiber, the modified thermally conductive filler, and a condensing agent are subjected to a condensation reaction to obtain the thermally conductive fiber grafted with the thermally conductive filler.

[0068] More preferably, in step S11, the raw material thermally conductive fiber is surface carboxylated, and the raw material thermally conductive filler is aminated to obtain modified thermally conductive fiber and modified thermally conductive filler, respectively.

[0069] Preferably, the method for surface carboxylation of the raw material thermally conductive fiber is any one of chemical oxidation, electrochemical method, and electron beam surface modification.

[0070] For example, the raw material thermally conductive fiber is carboxylated by chemical oxidation, the steps of which include:

[0071] (1) The purchased short carbon fiber (raw thermal conductive fiber) is refluxed in acetone solution at 75°C for 12-48 hours to remove the sizing agent on the surface of the short carbon fiber, so that its surface or functional groups are directly exposed. The short carbon fiber is then taken out, ultrasonically cleaned with deionized water for 1-4 hours, and dried to obtain short carbon fiber with the sizing agent removed.

[0072] (2) The surface of the short-cut carbon fiber after removing the sizing agent was oxidized with 68% concentrated nitric acid for 24-48 hours; the pH value was adjusted to 7 by adding 0.5 mol / L sodium hydroxide aqueous solution, and then 30% hydrogen peroxide and deionized water were added to convert the nitrite generated by oxidizing the carbon fiber into nitrate. The carbon fiber was then placed in a dialysis bag, deionized water was added, and dialysis was performed for 12-36 hours. After cleaning, carboxylated short-cut carbon fiber was obtained.

[0073] In a preferred embodiment, the carboxylated thermally conductive fiber can also be obtained by direct purchase.

[0074] According to another preferred embodiment, the method for amifying the thermally conductive filler material is a chemical oxidation method combined with chemical grafting. Exemplarily, a graphene oxide dispersion is prepared using the HUMMERS method, and then the graphene oxide dispersion is freeze-dried to obtain graphene oxide powder. The graphene oxide powder is added to an excess of DMF, along with an amine substance in an amount equal to that of the graphene oxide. The mixture is stirred, refluxed, and cooled at 65-85°C for 12-24 hours to obtain aminated graphene oxide. The aminated graphene oxide is washed multiple times with deionized water and a centrifuge, and then freeze-dried to obtain aminated graphene oxide powder. The amine substance is at least one selected from triethylenetetramine, diethylenetriamine, p-phenylenediamine, and 2,4-diaminotoluene.

[0075] In a preferred embodiment, the amination thermally conductive filler can also be obtained directly by purchasing. It should be noted that, in the preparation process of this invention, directly purchased amination thermally conductive fillers are used to prepare the high thermal conductivity composite phase change material.

[0076] Preferably, in step S12, the solvent is selected from at least one of ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), acetone, and chloroform.

[0077] In a preferred embodiment, in step S12, the amount of the condensing agent used in step S12 is 0.007wt%-0.7wt%, based on the total mass of the modified thermally conductive fiber, the modified thermally conductive filler, and the matrix phase change material.

[0078] More preferably, in step S12, the amount of the condensing agent used in step S12 is 0.1wt%-0.3wt%, based on the total mass of the modified thermally conductive fiber, the modified thermally conductive filler and the matrix phase change material.

[0079] Preferably, the condensing agent in step S12 is selected from at least one of dicyclohexylcarbodiimide (DCC), carbodiimide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC), 1-ethyl-(3-dimethylaminopropyl)carbodiimide (BOP), 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate (HATU), and O-benzotriazole-tetramethylurea hexafluorophosphate (HBTU).

[0080] In a preferred embodiment, in step S12, the condensation reaction conditions must at least satisfy the following: reaction temperature of 65-150°C and time of 6-36 hours.

[0081] According to a preferred embodiment, in a third aspect, the method further includes: before performing step S2, first melting the matrix phase change material to obtain the molten material, and then performing the first mixing on the molten material; the conditions for the melting treatment are at least: the reaction temperature is 40-90℃, and the stirring speed is 200-600r / min.

[0082] More preferably, the molten material further contains a nucleating agent.

[0083] The present invention does not have a particular requirement for the reaction time of the melt treatment, as long as the matrix phase change material and the nucleating agent are completely melted. For example, the reaction time of the melt treatment is 2 hours.

[0084] According to another preferred embodiment, the method further includes: mixing the mixture I described in step S2 with a thickener in a second mixing; controlling the amount of thickener added so that the viscosity of the material system participating in the second mixing is 20,000-50,000 mp*s.

[0085] This invention does not impose particular limitations on the reaction temperature, reaction time, and rotation speed of the second mixture, and can be carried out using known techniques in the art. For example, mixture I is stirred with a thickener at 500 r / min for 30 min.

[0086] The method for preparing composite phase change materials provided by this invention can achieve a uniform distribution of the thermally conductive network framework and prevent the agglomeration of nanofillers inside the phase change material.

[0087] As previously described, the fourth aspect of the present invention provides a high thermal conductivity composite phase change material prepared by the method described in the second aspect.

[0088] The present invention does not impose any special requirements on the amount of the composite phase change material used in energy storage materials, and those skilled in the art can adjust it as needed.

[0089] As previously stated, the fifth aspect of the present invention provides the application of the high thermal conductivity composite phase change material described in the first or fourth aspect in energy storage materials.

[0090] The invention will be described in detail below through examples. All materials used in the following examples are commercially available, as detailed in Table 1 below:

[0091] Table 1

[0092]

[0093] The total mass of the composite phase change material prepared in the following examples and comparative examples is 200g. Based on the total mass of the composite phase change material, the amount of each component is calculated as a percentage by mass.

[0094] In this invention, the concentrated nitric acid has a mass fraction of 68%.

[0095] The specific method for carboxylating the raw material thermally conductive fiber in this example is as follows:

[0096] (1) Place the purchased short-cut carbon fiber M55J into a round-bottom flask, add 350mL of acetone to completely submerge 100g of carbon fiber, reflux at 75℃ for 48h, and then ultrasonically clean with deionized water for 3h to obtain short-cut carbon fiber with the sizing agent removed.

[0097] (2) Use 200 mL of concentrated nitric acid to oxidize the surface of 10 g of chopped carbon fibers (with the sizing agent removed) in step (1) for 24 h; add 0.5 mol / L sodium hydroxide aqueous solution to adjust the pH value to 7, then add 1500 mL of 30% H2O2 and 500 mL of deionized water, then put it into a dialysis bag, add deionized water, dialyze for 24 h, and wash it clean with deionized water to obtain carboxylated chopped carbon fibers M55J (which is a type of "modified thermal conductive fiber" described in this invention).

[0098] In both the examples and comparative examples, the modified thermally conductive fillers were purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.

[0099] Example 1

[0100] The formulation for this embodiment is shown in Table 2.

[0101] Table 2

[0102] type Dosage Modified thermally conductive fibers Carboxylated short-cut carbon fiber M55J (self-made) 4wt% Modified thermally conductive filler Aminated multi-walled carbon nanotubes 11wt% matrix phase change materials Sodium acetate trihydrate 80wt% nucleating agent Sodium pyrophosphate decahydrate 3wt% Thickener Xanthan Gum 2wt%

[0103] Preparation method:

[0104] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.3 wt% HATU were added to 500 mL of DMSO for a condensation reaction. After cleaning, thermally conductive fibers grafted with thermally conductive fillers were obtained; among which,

[0105] The conditions for the condensation reaction were: temperature 65℃ and time 36 hours.

[0106] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain intermediate 1; wherein...

[0107] The graphitization conditions are: temperature 2100℃, time 2 hours.

[0108] S2: The matrix phase change material and nucleating agent are melt-treated to obtain a molten material containing the matrix phase change material and nucleating agent; intermediate 1 is mixed with the molten material to obtain mixture I; wherein,

[0109] The melting conditions were: temperature 75℃, stirring speed 250 r / min, and time 2 h.

[0110] The conditions for the first mixing were: stirring speed of 550 r / min and time of 4 h.

[0111] S3: Mixture I is mixed with a thickener for a second time to adjust its viscosity to 30000 mp*s. After cooling, a high thermal conductivity composite phase change material sample S1 is obtained; whereby...

[0112] The conditions for the second mixing were: stirring speed of 500 r / min and time of 30 min.

[0113] Example 2

[0114] The formulation of this embodiment is shown in Table 3.

[0115] Table 3

[0116] type Dosage Modified thermally conductive fibers Carboxylated short-cut carbon fiber M55J (self-made) 3wt% Modified thermally conductive filler Aminographene 10wt% matrix phase change materials n-Docosane 87wt%

[0117] Preparation method:

[0118] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.15 wt% DCC were added to 500 mL of DMF for a condensation reaction. After cleaning, thermally conductive fibers grafted with thermally conductive fillers were obtained; wherein,

[0119] The conditions for the condensation reaction were: temperature 80℃ and time 24 hours.

[0120] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain intermediate 1; wherein...

[0121] The graphitization conditions were: temperature 2100℃, time 4 hours.

[0122] S2: The matrix phase change material is melted to obtain a molten material containing the matrix phase change material. Intermediate 1 is then mixed with the molten material to obtain a high thermal conductivity composite phase change material sample S2; wherein...

[0123] The melting conditions were: temperature 75℃, stirring speed 400 r / min, and time 2 h.

[0124] The conditions for the first mixing were: stirring speed of 500 r / min and time of 4 h.

[0125] Example 3

[0126] The formulation for this embodiment is shown in Table 4.

[0127] Table 4

[0128] type Dosage Modified thermally conductive fibers Carboxylated short-cut carbon fiber T1100 (self-made) 3wt% Modified thermally conductive filler Aminographene 12wt% matrix phase change materials paraffin 85wt%

[0129] Preparation method:

[0130] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.3 wt% HBTU were added to 500 mL of DMF for a condensation reaction, followed by cleaning to obtain thermally conductive fibers grafted with thermally conductive fillers; wherein,

[0131] The conditions for the condensation reaction were: temperature 75℃ and time 6.5h.

[0132] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain intermediate 1; wherein...

[0133] The graphitization conditions were: temperature 850℃, time 12h.

[0134] S2: The matrix phase change material is melted to obtain a molten material containing the matrix phase change material. Intermediate 1 is mixed with the molten material to obtain a high thermal conductivity composite phase change material sample S3.

[0135] The melting conditions were: temperature 65℃, stirring speed 500 r / min, and time 2 h.

[0136] The conditions for the first mixing were: stirring speed of 500 r / min and time of 4 h.

[0137] Example 4

[0138] The formulation for this embodiment is shown in Table 5.

[0139] Table 5

[0140]

[0141]

[0142] Preparation method:

[0143] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.3 wt% HATU were added to 500 mL of DMSO for a condensation reaction. After cleaning, thermally conductive fibers grafted with thermally conductive fillers were obtained; wherein,

[0144] The conditions for the condensation reaction were: temperature 65℃ and time 36 hours.

[0145] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain intermediate 1; wherein...

[0146] The graphitization conditions were: temperature 2000℃, time 2 hours.

[0147] S2: The matrix phase change material and nucleating agent are melt-treated to obtain a molten material containing the matrix phase change material and nucleating agent; intermediate 1 is mixed with the molten material to obtain mixture I; wherein,

[0148] The melting conditions were: temperature 85℃, stirring speed 250 r / min, and time 2 h.

[0149] The conditions for the first mixing were: stirring speed of 550 r / min and time of 4 h.

[0150] S3: Mixture I is mixed with a thickener for a second time to adjust its viscosity to 20000 mp*s. After cooling, a high thermal conductivity composite phase change material sample S4 is obtained; wherein...

[0151] The conditions for the second mixing were: stirring speed of 500 r / min and time of 30 min.

[0152] Example 5

[0153] The formulation for this embodiment is shown in Table 6.

[0154] Table 6

[0155]

[0156]

[0157] Preparation method:

[0158] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.3 wt% DCC were added to 500 mL of DMSO for a condensation reaction. After cleaning, thermally conductive fibers grafted with thermally conductive fillers were obtained; wherein,

[0159] The conditions for the condensation reaction were: temperature 125℃ and time 9 hours.

[0160] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain graphitized intermediate 1; wherein...

[0161] The graphitization conditions were: temperature 850℃, time 12h.

[0162] S2: The matrix phase change material and nucleating agent are melt-treated to obtain a molten material containing the matrix phase change material and nucleating agent; intermediate 1 is mixed with the molten material to obtain mixture I; wherein,

[0163] The melting conditions were: temperature 65℃, stirring speed 300 r / min, and time 2 h.

[0164] The conditions for the first mixing were: stirring speed of 600 r / min and time of 2.5 h.

[0165] S3: Mixture I is mixed with a thickener for a second time to adjust its viscosity to 50,000 mp*s. After cooling, a high thermal conductivity composite phase change material sample S5 is obtained; wherein...

[0166] The conditions for the second mixing were: stirring speed of 500 r / min and time of 30 min.

[0167] Example 6

[0168] The formulation for this embodiment is shown in Table 7.

[0169] Table 7

[0170]

[0171]

[0172] Preparation method:

[0173] S12: Modified thermally conductive fibers, modified thermally conductive fillers, and 0.12 wt% HATU were added to 500 mL of DMSO for a condensation reaction. After cleaning, thermally conductive fibers grafted with thermally conductive fillers were obtained; wherein,

[0174] The conditions for the condensation reaction were: temperature 65℃ and time 36 hours.

[0175] S1: Thermally conductive fibers grafted with thermally conductive fillers are placed in a muffle furnace for graphitization to obtain intermediate 1; wherein...

[0176] The graphitization conditions are: temperature 2100℃, time 2 hours.

[0177] S2: The matrix phase change material is melted to obtain a molten material containing the matrix phase change material; intermediate 1 is mixed with the molten material to obtain a high thermal conductivity composite phase change material sample S6; wherein...

[0178] The melting conditions were: temperature 75℃, stirring speed 250 r / min, and time 2 h.

[0179] The conditions for the first mixing were: stirring speed of 550 r / min and time of 4 h.

[0180] Comparative Example 1

[0181] This comparative example uses a similar formulation and method to Example 1 to prepare a high thermal conductivity composite phase change material. The difference is that the modified thermally conductive fiber in Example 1 is replaced with an equal amount of raw thermally conductive fiber, that is, an equal amount of carboxylated short-cut carbon fiber M55J is replaced with an equal amount of short-cut carbon fiber M55J; a high thermal conductivity composite phase change material sample D1 is obtained.

[0182] Comparative Example 2

[0183] This comparative example uses a similar formulation and method to Example 1 to prepare a high thermal conductivity composite phase change material. The difference is that the modified thermally conductive filler in Example 1 is replaced with an equal amount of raw thermally conductive filler, that is, an equal amount of aminated multi-walled carbon nanotubes is replaced with an equal amount of multi-walled carbon nanotubes; a high thermal conductivity composite phase change material sample D2 is obtained.

[0184] Comparative Example 3

[0185] This comparative example uses a similar formulation and method to Example 1 to prepare composite phase change materials, except that: an equal amount of carboxylated short-cut carbon fiber M55J was replaced with an equal amount of short-cut carbon fiber M55J, and an equal amount of aminated multi-walled carbon nanotubes were replaced with an equal amount of multi-walled carbon nanotubes; thus, composite phase change material sample D3 was prepared.

[0186] Test case

[0187] The performance testing and instruments used for the composite phase change materials in the above embodiments and comparative examples are shown in Table 8.

[0188] Table 8

[0189] Serial Number Test Project Test instrument model Manufacturer 1 enthalpy value DSC Q2000 TA Company, USA 2 thermal conductivity LFA427 Laser Thermal Conductor Netzsch, Germany

[0190] Enthalpy measurement: Take 10mg of composite phase change material and add it into the DSC test crucible. The test program is set as follows: temperature range of 25℃ to 90℃, heating rate of 5℃ / min, and nitrogen atmosphere.

[0191] Thermal conductivity test: The composite phase change material is prepared into a 10mm*10mm sample, compacted and placed on the sample stage. The test temperature is 25℃, and the static test is performed to obtain the test results.

[0192] The performance of the composite phase change material samples from the examples and comparative examples was tested, and the results are shown in Table 9.

[0193] Table 9

[0194]

[0195]

[0196] The results in Table 9 show that the thermal conductivity of the high thermal conductivity composite phase change materials prepared in Examples 1-6 ranges from 4.2 to 6.6 W / (m*K), while the thermal conductivity of the comparative examples ranges from 2 to 4 W / (m*K). This indicates that by linking the modified thermally conductive fibers and modified thermally conductive fillers through chemical covalent bonds and working together with the matrix phase change material, the resulting composite phase change material exhibits even higher thermal conductivity.

[0197] The present invention provides, by way of example, SEM images of the high thermal conductivity composite phase change material S1 prepared in Embodiment 1 of the present invention. Figure 2 Specifically, from Figure 2 It can be seen that a large number of carbon nanotubes are grafted onto the surface of the carbon fiber, which increases the specific surface area of ​​the short-cut carbon fiber. The carbon fiber / nanomaterial is stably and uniformly dispersed in the matrix phase change material.

[0198] A composite phase change material prepared using carbon fiber and a matrix phase change material was used as a control. The SEM test results of this composite phase change material are as follows: Figure 3 As shown, from Figure 3 As can be seen, the unmodified grafted carbon fibers have a smooth surface and are dispersed in the matrix phase change material, with the two being independent of each other.

[0199] pass Figure 2 and Figure 3 The comparison shows that in Example 1, carbon nanotubes were successfully grafted onto the surface of carbon fibers, and the carbon fibers / nanomaterials were stably and uniformly dispersed in the matrix phase change material. This indicates that in the composite phase change material, the thermally conductive fibers can maintain a good thermally conductive network framework, and the nano-thermally conductive fillers can be uniformly dispersed inside the phase change material.

[0200] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity composite phase change material, characterized in that, The method includes: S1: The raw thermally conductive fiber is surface carboxylated, and the raw thermally conductive filler is aminated to obtain modified thermally conductive fiber and modified thermally conductive filler, respectively; the modified thermally conductive fiber and the modified thermally conductive filler are connected by chemical covalent bonds to obtain thermally conductive fiber grafted with thermally conductive filler, and the obtained thermally conductive fiber grafted with thermally conductive filler is graphitized to obtain intermediate 1; S2: The molten material containing the matrix phase change material is first mixed with the intermediate 1 described in step S1 to obtain mixture I; The thermally conductive fiber used as the raw material is carbon fiber; the carbon fiber is selected from at least one of T800, T1000, T1100, M55J, M60J and M45J; The thermally conductive filler material is selected from at least one of carbon nanotubes, graphene, graphene oxide, expanded graphite, hexagonal boron nitride, MXene, and silicon carbide. Based on the total mass of the modified thermally conductive filler, the modified thermally conductive fiber, and the matrix phase change material, the amount of the modified thermally conductive fiber is 3wt%-15wt%, the amount of the modified thermally conductive filler is 4wt%-20wt%, and the amount of the matrix phase change material is 65wt%-93wt%.

2. The method according to claim 1, wherein, The matrix phase change material is an organic phase change material and / or an inorganic phase change material; the organic phase change material is selected from at least one of paraffin, stearic acid, dodecanoic acid, docosane, and xylitol; the inorganic phase change material is selected from at least one of sodium acetate trihydrate, calcium chloride hexahydrate, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, and barium hydroxide octahydrate.

3. The method according to claim 1, wherein, The thermal conductivity of the raw material thermally conductive filler is greater than 50 W / (m*K).

4. The method according to claim 1, wherein, In step S1, the step of connecting the modified thermally conductive fiber and the modified thermally conductive filler by chemical covalent bonds includes: In the presence of a solvent, the modified thermally conductive fiber, the modified thermally conductive filler, and a condensing agent are subjected to a condensation reaction to obtain the thermally conductive fiber grafted with the thermally conductive filler.

5. The method according to claim 4, wherein, Based on the total mass of the modified thermally conductive fiber, the modified thermally conductive filler, and the matrix phase change material, the amount of the condensing agent is 0.007wt%-0.7wt%.

6. The method according to claim 4 or 5, wherein, The condensing agent is selected from at least one of dicyclohexylcarbodiimide, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate and O-benzotriazole-tetramethylurea hexafluorophosphate.

7. The method according to claim 4 or 5, wherein, The condensation reaction conditions must at least meet the following: reaction temperature of 65-150℃ and time of 6-36h.

8. The method according to claim 1, wherein, In step S2, the conditions for the first mixing must at least satisfy: time of 1-4 hours and stirring speed of 200-600 r / min.

9. The method according to claim 1, wherein, The method further includes: before performing step S2, first melting the matrix phase change material to obtain the molten material, and then performing the first mixing on the molten material; the conditions for the melting treatment are at least: the reaction temperature is 40-90℃ and the stirring speed is 200-600r / min.

10. The method according to claim 9, wherein, The matrix phase change material is an inorganic phase change material, and the molten material also contains a nucleating agent.

11. The method according to claim 10, wherein, The method further includes: mixing the mixture I described in step S2 with a thickener for a second time; controlling the amount of thickener added so that the viscosity of the material system participating in the second mixing is 20,000-50,000 mp*s.

12. The method according to claim 11, wherein, Based on the total mass of the modified thermally conductive filler, the modified thermally conductive fiber, the matrix phase change material, the nucleating agent, and the thickener, the amount of the nucleating agent is 0.1wt%-10wt%, and the amount of the thickener is 0.1wt%-10wt%.

13. The method according to claim 10, wherein, The nucleating agent is selected from at least one of disodium hydrogen phosphate dodecahydrate, sodium pyrophosphate decahydrate, sodium metasilicate nonahydrate, sodium borate decahydrate, sodium carbonate decahydrate, sodium phosphate hexahydrate, and borax pentahydrate.

14. The method according to claim 11, wherein, The thickener is selected from at least one of starch, gelatin, xanthan gum, sodium carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, polyacrylamide, polyethylene glycol, sodium polyacrylate, and clay.

15. A high thermal conductivity composite phase change material prepared by the method according to any one of claims 1-14.

16. The application of the high thermal conductivity composite phase change material according to claim 15 in energy storage materials.

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