Composite phase change material and preparation method thereof

Abstract

The invention belongs to the technical field of phase change materials, and relates to a composite phase change material and a preparation method thereof.The composite phase change material comprises a porous material and a solid-liquid phase change material located in pore channels of the porous material, and at least one part of pore openings of the porous material are closed and / or semi-closed; the preparation method comprises the following steps: filling the solid-liquid phase change material in the pore channels of the porous material, and then closing and / or semi-closing at least one part of the pore openings of the porous material to obtain the composite phase change material. The preparation method is simple and low in cost, and the leakage risk of the prepared composite phase change material in the using process is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of phase change materials and relates to a composite phase change material and a preparation method thereof. Background Art

[0002] Thermal energy, as the most common form of energy in life, is widely present in solar radiation, flue gas waste heat and other places. However, there are problems of mismatch in time and space distribution in the process of energy utilization and conversion. In order to effectively cope with these challenges, the development of thermal storage technology has been given extremely important significance. Solid-liquid phase change materials have been widely used in the fields of solar energy utilization, waste heat recovery, etc. due to their advantages such as high thermal storage density, wide phase change temperature range, abundant phase change materials and low price. However, solid-liquid phase change materials will turn into liquid at high temperature, and there is a risk of liquid leakage; in addition, during the phase change process, the volume of solid-liquid phase change materials may change, resulting in unstable shape. Therefore, the requirements for solid-liquid phase change material packaging technology are becoming more and more stringent, and are also facing greater challenges.

[0003] At present, there are two main methods for encapsulating solid-liquid phase change materials. The first is to encapsulate solid-liquid phase change materials using the capillary effect of porous media such as porous carbon, mesoporous silica, copper foam, expanded graphite, and graphene aerogel. Through the capillary effect of porous media, solid-liquid phase change materials can be wrapped therein to achieve the effect of encapsulation. For example, patent application CN117866597A discloses a magnetic carbon aerogel-based phase change material with photothermal-electrical thermal properties and a preparation method thereof. The prepared magnetic carbon aerogel-based phase change material is a flexible carbon aerogel interwoven and assembled with long-chain carboxylated cellulose (CNF) and graphene oxide (GO), and then eicosane is encapsulated into the aerogel by vacuum impregnation. The composite phase change material prepared finally has good thermal conductivity and a high enthalpy value. However, carbon aerogel still has an open pore structure, which will cause the phase change energy storage unit to leak, especially in the process of repeated phase change cycles, the phase change energy storage unit will gradually precipitate from the porous medium, resulting in a gradual reduction in the encapsulation effect.

[0004] The second encapsulation method is to use organic or inorganic materials to form a shell layer on the surface of the solid-liquid phase change material, thereby forming a microcapsule structure. The materials of the organic shell layer mainly include high polymers such as polypropylene and polyurethane, and the materials of the inorganic shell layer include silicon dioxide, titanium dioxide, calcium carbonate, etc. By forming a shell layer on the surface of the solid-liquid phase change material, the solid-liquid phase change material can be effectively encapsulated to form a microcapsule structure, thereby improving its stability and application performance. For example, patent application CN117801790A discloses a rapid synthesis method of nano phase change microcapsules encapsulated by silicon dioxide, and its synthesis method is to prepare phase change microcapsules by wrapping paraffin with styrene-butadiene-styrene copolymer as the capsule wall. Although the coverage rate and enthalpy value of the microcapsule are high, its preparation process is complicated and the production cost is high. The microcapsule is prone to cracking during repeated solid-liquid phase change cycles, and because the capsule wall is a high polymer, its thermal conductivity and mechanical strength are also low.

[0005] Therefore, it is of great significance to develop a composite phase change material and a preparation method thereof to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art and to provide a composite phase change material and a preparation method thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A composite phase change material comprises a porous material and a solid-liquid phase change material located in the pores of the porous material, wherein at least a part of the pores of the porous material are closed and / or semi-closed.

[0009] As the preferred technical solution:

[0010] A composite phase change material as described above, wherein the porous material is porous carbon, mesoporous silica, porous MOF, copper foam, expanded graphite or graphene aerogel, and the porous material is preferably in powder form. If it is in block form, it is difficult to close all pores; the porosity of the porous material is 60-95%.

[0011] In the composite phase change material as described above, the solid-liquid phase change material is an alkane solid-liquid phase change material (eg eicosane).

[0012] A composite phase change material as described above, after being placed on filter paper, heated to a certain temperature and kept warm for 3 days, no trace of leakage of the solid-liquid phase change material was found on the filter paper, wherein the certain temperature is 20-80°C higher than the phase change temperature of the solid-liquid phase change material, and at the same time 20-80°C lower than the thermal decomposition temperature of the solid-liquid phase change material.

[0013] The present invention also provides a method for preparing a composite phase change material as described in any of the preceding items, the specific steps of which are as follows:

[0014] (1) Filling the pores of the porous material with a solid-liquid phase change material;

[0015] (2) At least a portion of the pores of the porous material are closed and / or semi-closed to obtain a composite phase change material.

[0016] As the preferred technical solution:

[0017] In the method for a composite phase change material as described above, the specific process of step (1) is: after mixing the porous material and the solid-liquid phase change material in a mass ratio of 5-10:1, keeping the mixture at a certain temperature for 2-4 hours and then cooling it to a phase change temperature lower than the solid-liquid phase change material, wherein the certain temperature is 45-73°C higher than the phase change temperature of the solid-liquid phase change material and 70-80°C lower than the thermal decomposition temperature of the solid-liquid phase change material.

[0018] In the method for preparing a composite phase change material as described above, in step (2), closing and / or semi-closing at least a portion of the pores of the porous material is achieved by forming a carbon shell on the surface of the porous material.

[0019] In the above-mentioned method for composite phase change material, the carbon shell is formed by a dehydration condensation reaction of carbohydrates on the outer surface of the porous material.

[0020] In the above-mentioned method for preparing a composite phase change material, step (2) is specifically as follows:

[0021] (2.1) The aqueous solution containing carbohydrate and X is first heated to T1 and kept at temperature t1, then heated to T2 and kept at temperature t2, and a pretreatment solution is obtained by solid-liquid separation, wherein X is APS, hydrogen peroxide or potassium permanganate;

[0022] (2.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, first heat it to T3 and keep it at t3, then heat it to T4 and keep it at t4, and perform post-treatment (cooling, centrifugal collection of the precipitate, washing with deionized water for multiple times, and drying in a vacuum oven at 80°C), wherein T4 is higher than T3 to promote the staged formation of the carbon shell, T3 is higher than the phase change temperature of the solid-liquid phase change material, and T4 is lower than the thermal decomposition temperature of the solid-liquid phase change material;

[0023] Carbohydrate is glucose, T1 is 60-80℃, t1 is 1-4h, T2 is 150-190℃, t2 is 1-2h, T3 is 100-130℃, t3 is 2-6h, T4 is 150-180℃, t4 is 1-3h;

[0024] At temperature T1, the hydroxyl radicals generated by X oxidize glucose to generate a series of oxygen-containing compounds such as aldehydes and acids (such as acetic acid, oxalic acid, lactic acid, tartaric acid, erythritol, etc.); at temperature T2, X accelerates the oxidation of more glucose, and the generated oxygen-containing compounds undergo esterification condensation reaction, aldol condensation reaction and aromatization reaction, etc., to generate a large number of polymer particles, which are removed by solid-liquid separation;

[0025] At temperature T3, the oxygen-containing small molecules remaining in the pretreatment liquid will continue to undergo condensation and cyclization reactions, thereby forming more fulvic acid carbon structures. At the same time, the surface of the porous material provides a preferential site for the growth and deposition of these small molecules. The fulvic acid substances deposited on the surface of the carbon particles can maintain a relatively uniform, dense and non-porous outer coating structure; as the temperature rises to T4, the growth rate of the carbon shell is further accelerated. At this time, the small amount of precursor remaining in the pretreatment liquid can also be quickly converted and continue to be deposited on the outside of the existing carbon shell, promoting the further growth and cross-linking of the carbon shell. The higher temperature also helps the carbon skeleton inside the carbon shell to graphitize, thereby increasing the number and crystallinity of the carbon-containing layer, forming a more dense and graphitized carbon shell structure;

[0026] The carbohydrate is soluble starch, T1 is 100-150℃, t1 is 1-4h, T2 is 160-220℃, t2 is 1-2h, T3 is 100-130℃, t3 is 2-6h, T4 is 150-180℃, t4 is 1-3h;

[0027] At temperature T1, starch undergoes accelerated hydrolysis through thermal decomposition and X catalysis; a large number of monosaccharide and oligosaccharide units such as glucose and maltose are released; the hydroxyl radicals produced by X oxidize some monosaccharides to generate small molecular aldehyde acid substances; these small molecules begin to undergo condensation and cyclization reactions to form a preliminary fulvic acid carbonaceous structure; at temperature T2, in the presence of X, the monosaccharides in the solution are rapidly oxidized to generate more small molecules such as aldehyde acid; the small molecules undergo a series of fulvic acid reactions such as condensation, esterification, aromatization, and a large number of polymer particles are generated; after solid-liquid separation, the polymer particles are removed; at temperature T3, the oxygen-containing small molecules remaining in the pretreatment solution will Condensation and cyclization reactions continue to occur, thereby forming more fulvic acid carbon structures. At the same time, the surface of the porous material provides a preferential site for the growth and deposition of these small molecules. The fulvic acid substances deposited on the surface of the carbon particles can maintain a relatively uniform, dense and non-porous outer coating structure; as the temperature rises to T4, the growth rate of the carbon shell is further accelerated. At this time, the small amount of precursor remaining in the pretreatment liquid can also be quickly converted and continue to be deposited on the outside of the existing carbon shell, promoting the further growth and cross-linking of the carbon shell. The higher temperature also helps the carbon skeleton inside the carbon shell to graphitize, thereby increasing the number and crystallinity of the carbon-containing layer, forming a more dense and graphitized carbon shell structure;

[0028] The carbohydrate is chitosan, T1 is 100-150℃, t1 is 1-4h, T2 is 160-220℃, t2 is 1-2h, T3 is 100-130℃, t3 is 2-6h, T4 is 150-180℃, t4 is 1-3h;

[0029] At temperature T1, chitosan undergoes accelerated hydrolysis through thermal decomposition and X catalysis; a large number of monosaccharide and oligosaccharide units such as glucose and maltose are released; the hydroxyl radicals produced by X oxidize some monosaccharides to generate small molecular aldehyde acid substances; these small molecules begin to undergo condensation and cyclization reactions to form a preliminary fulvic acid carbonaceous structure; at temperature T2, in the presence of X, the monosaccharides in the solution are rapidly oxidized to generate more small molecules such as aldehyde acid; the small molecules undergo a series of fulvic acid reactions such as condensation, esterification, aromatization, and a large number of polymer particles are generated; after solid-liquid separation, the polymer particles are removed; at temperature T3, the oxygen-containing small molecules remaining in the pretreatment solution will Condensation and cyclization reactions continue to occur, thereby forming more fulvic acid carbon structures. At the same time, the surface of the porous material provides a preferential site for the growth and deposition of these small molecules. The fulvic acid substances deposited on the surface of the carbon particles can maintain a relatively uniform, dense and non-porous outer coating structure; as the temperature rises to T4, the growth rate of the carbon shell is further accelerated. At this time, the small amount of precursor remaining in the pretreatment liquid can also be quickly converted and continue to be deposited on the outside of the existing carbon shell, promoting further growth and cross-linking of the carbon shell. Higher temperatures also help the carbon skeleton inside the carbon shell to graphitize, thereby increasing the number and crystallinity of the carbon-containing layer, forming a denser and graphitized carbon shell structure.

[0030] In the method for preparing a composite phase change material as described above, in step (2.1), in the aqueous solution containing both carbohydrate and X, the concentration of carbohydrate is 0.1-0.3 g / mL, and the concentration of X is 0.1-0.3 g / mL;

[0031] In step (2.2), the concentration of the porous material dispersion is 0.1-0.3 g / mL, the dispersion medium is propylene glycol, polyethylene glycol or DMF; the volume ratio of the porous material dispersion to the pretreatment liquid is 2-10:10-30.

[0032] Beneficial effects:

[0033] (1) The present invention fills the pores of the porous material with a solid-liquid phase change material, and then forms a carbon shell by causing a dehydration condensation reaction of carbohydrates on the outer surface of the porous material to close and / or semi-close at least a portion of the pores of the porous material, thereby encapsulating the solid-liquid phase change material in the pores of the porous material; in addition, as the temperature increases, the carbon skeleton inside the carbon shell is also helped to graphitize, thereby increasing the number and crystallinity of the carbon-containing layers, forming a more dense and graphitized carbon shell structure, thereby greatly reducing the risk of leakage of the composite phase change material during use.

[0034] (2) The preparation method of the present invention is simple and low in cost, and the prepared composite phase change material has a higher enthalpy value and better thermal stability. Most importantly, its energy storage unit is completely isolated from the outside world, which significantly increases its durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The DCS curves of the composite phase change material (GSME) prepared in Example 1 of the present invention and the porous material (ME) filled with solid-liquid phase change material;

[0036] Figure 2 The temperature-time curve of the composite phase change material (GSME) prepared in Example 1 of the present invention and the porous material (ME) filled with solid-liquid phase change material after being heated and placed in a room temperature environment;

[0037] Figure 3 This is a transmission electron microscope image of the composite phase change material prepared in Example 1 of the present invention;

[0038] Figure 4 This is a scanning electron microscope image of the composite phase change material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0040] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0041] Enthalpy value: The enthalpy value of the composite phase change material prepared in each example was measured using a differential scanning calorimeter (DSC).

[0042] Example 1

[0043] A method for preparing a composite phase change material, the specific steps are as follows:

[0044] (1) Preparation of raw materials;

[0045] Porous material: porous carbon, with a porosity of 85-95%;

[0046] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0047] Dispersion medium: propylene glycol;

[0048] X: APS (ammonium persulfate);

[0049] Carbohydrate: Glucose, CAS number is 50-99-7;

[0050] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.1 g / mL, the concentration of X is 0.1 g / mL;

[0051] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0052] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 9:1, the mixture was kept at 80°C for 4 hours and then cooled to 25°C;

[0053] (3) preparing a dispersion of porous material;

[0054] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.1 g / mL;

[0055] (4) preparing composite phase change materials;

[0056] (4.1) The aqueous solution containing carbohydrate and X is first heated to 80°C and kept warm for 3 h, then heated to 190°C and kept warm for 1 h, and a pre-treatment solution is obtained by solid-liquid separation;

[0057] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 110°C and keep it for 2 hours, then heat it to 180°C and keep it for 3 hours, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 2:10.

[0058] The final composite phase change material is composed of a porous material, a solid-liquid phase change material in the pores of the porous material, and a carbon shell on the surface of the porous material. At least a portion of the pores of the porous material are closed and / or semi-closed by the carbon shell. The transmission electron microscope image and the scanning electron microscope image of the composite phase change material are shown in FIG. Figure 3 , Figure 4 As shown, the enthalpy value of the composite phase change material is 127.9 J / g; after the composite phase change material is placed on the filter paper, it is heated to 80°C and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper;

[0059] In order to verify whether the composite phase change material prepared in this embodiment forms a shell layer, 50 mL of sodium dodecylbenzene sulfonate aqueous solution (concentration of 2 wt%) is first prepared, and then 0.1 g of the composite phase change material prepared in this embodiment is added thereto and mixed evenly to obtain a mixture, and then the mixture is placed in a water bath and heated to 80 ° C and vigorously stirred for 20 minutes. After the stirring is completed, the solid-liquid phase change material in the upper layer of the solution is absorbed with filter paper, and then it is dried. Finally, the enthalpy of the product after drying is tested to be 109 J / g; by comparing the enthalpy values ​​of the composite phase change materials before and after verification, it can be seen that the composite phase change material prepared in this embodiment forms a shell layer, and the shell layer closes and / or semi-closes the pores of the porous material, and the solid-liquid phase change material can be encapsulated in the pores of the porous material. Under extreme conditions of high temperature and vigorous stirring, the risk of successfully throwing the liquid solid-liquid phase change material out of the pores is greatly reduced, ensuring that the material can remain stably in the pores.

[0060] Comparative Example 1

[0061] A method for preparing a composite phase change material is basically the same as that of Example 1, except that steps (3) and (4) are not performed.

[0062] In order to verify whether the composite phase change material prepared in this comparative example forms a shell layer, 50 mL of sodium dodecylbenzene sulfonate aqueous solution (concentration of 2 wt%) is first prepared, and then 0.1 g of the composite phase change material prepared in this comparative example is added thereto, mixed evenly to obtain a mixture, and then the mixture is placed in a water bath and heated to 80° C. and vigorously stirred for 20 minutes. After the stirring is completed, the solid-liquid phase change material present in the upper layer of the solution is absorbed with filter paper, and then it is dried. Finally, the enthalpy value of the dried product is tested to be 0 J / g; the enthalpy value of the composite phase change material can prove that the prepared composite phase change material does not form a shell layer, and under the conditions of high temperature and vigorous stirring, the liquid solid-liquid phase change material is thrown out of the pores.

[0063] By comparing Comparative Example 1 with Example 1, it can be seen that the enthalpy value of the composite phase change material prepared in Comparative Example 1 is 0 J / g. This is because the composite phase change material prepared in Comparative Example 1 does not form a shell layer on the outside, and thus cannot have an encapsulation effect on the solid-liquid phase change material. Under high temperature conditions, the solid-liquid phase change material in the pores will change from solid to liquid, and then transfer from the pores to the solution under vigorous stirring and the action of surfactants. Since there is a lack of solid-liquid phase change material in the pores, the enthalpy value of the composite phase change material measured is 0 J / g.

[0064] The composite phase change material of Example 1 and the composite phase change material of Comparative Example 1 were tested using a differential scanning calorimeter, and their DCS curves are shown as follows: Figure 1As shown in the figure, it can be seen that there are differences in the DSC curve characteristics of the composite phase change material (GSME) prepared in Example 1 and the porous material (ME) filled with solid-liquid phase change material. Both ME and GSME begin to show melting endothermicity at 32°C, the phase change point of GSME is 38°C, and the phase change point of ME is 41°C. The phase change points of the two are not much different, but the peak area of ​​ME is significantly larger than that of GSME. This is because a shell layer without phase change function is formed in the composite phase change material, which weakens the enthalpy value of the overall composite phase change material, thereby making the peak area of ​​GSME smaller.

[0065] In order to test the thermal insulation performance of the composite phase change material of Example 1 and the composite phase change material of Comparative Example 1, the two were heated to 70°C on a constant temperature heating table, and then cooled down in a room temperature environment. They were observed with an infrared thermal imager and a temperature-time curve was drawn. The results are shown in FIG. Figure 2 As shown in the figure, it can be seen that the time taken for the composite phase change material and the porous material filled with solid-liquid phase change material to be heated to 70°C is not much different, but the ability of the composite phase change material to maintain a constant temperature is greatly enhanced. This is because the composite phase change material forms a shell structure, which makes at least a part of the pores of the porous material closed and / or semi-closed, thereby playing a role in heat preservation. After the heating source disappears, the heat will also be lost more slowly.

[0066] Example 2

[0067] A method for preparing a composite phase change material, the specific steps are as follows:

[0068] (1) Preparation of raw materials;

[0069] Porous material: mesoporous silica, with a porosity of 80-95%;

[0070] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0071] Dispersion medium: propylene glycol;

[0072] X: Hydrogen peroxide;

[0073] Carbohydrate: Glucose, CAS number is 50-99-7;

[0074] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.2 g / mL, and the concentration of X is 0.1 g / mL;

[0075] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0076] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 10:1, the mixture was kept at 80°C for 2 hours and then cooled to 25°C;

[0077] (3) preparing a dispersion of porous material;

[0078] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.3 g / mL;

[0079] (4) preparing composite phase change materials;

[0080] (4.1) The aqueous solution containing carbohydrate and X is first heated to 70°C and kept warm for 1 hour, then heated to 180°C and kept warm for 1 hour, and a pre-treatment solution is obtained by solid-liquid separation;

[0081] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 130°C and keep it for 6 hours, then heat it to 150°C and keep it for 1 hour, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 2:30.

[0082] The enthalpy value of the final composite phase change material is 105 J / g; after the composite phase change material is placed on filter paper, it is heated to 90°C and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0083] Example 3

[0084] A method for preparing a composite phase change material, the specific steps are as follows:

[0085] (1) Preparation of raw materials;

[0086] Porous materials: porous MOFs with a porosity of 70-95%;

[0087] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0088] Dispersion medium: polyethylene glycol, number average molecular weight 400;

[0089] X: Potassium permanganate;

[0090] Carbohydrate: Glucose, CAS number is 50-99-7;

[0091] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.1 g / mL, and the concentration of X is 0.15 g / mL;

[0092] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0093] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 9:1, the mixture was kept at 80°C for 3 hours and then cooled to 25°C;

[0094] (3) preparing a dispersion of porous material;

[0095] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.15 g / mL;

[0096] (4) preparing composite phase change materials;

[0097] (4.1) The aqueous solution containing carbohydrate and X is first heated to 60°C and kept warm for 4 h, then heated to 150°C and kept warm for 2 h, and a pre-treatment solution is obtained by solid-liquid separation;

[0098] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 100°C and keep it for 4 hours, then heat it to 160°C and keep it for 2 hours, and perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 10:10.

[0099] The enthalpy value of the final composite phase change material is 98 J / g. After the composite phase change material is placed on filter paper, it is heated to 70°C and kept warm for 3 days. No trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0100] Example 4

[0101] A method for preparing a composite phase change material, the specific steps are as follows:

[0102] (1) Preparation of raw materials;

[0103] Porous material: copper foam, porosity 60-95%;

[0104] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0105] Dispersion medium: DMF (N,N-dimethylformamide);

[0106] X: APS;

[0107] Carbohydrate: soluble starch, manufacturer is Yonghua Chemical Co., Ltd., CAS number is 9005-84-9;

[0108] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.15 g / mL, and the concentration of X is 0.2 g / mL;

[0109] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0110] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 5:1, the mixture was kept at 80°C for 4 hours and then cooled to 25°C;

[0111] (3) preparing a dispersion of porous material;

[0112] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.1 g / mL;

[0113] (4) preparing composite phase change materials;

[0114] (4.1) The aqueous solution containing carbohydrate and X is first heated to 100°C and kept at this temperature for 4 hours, then heated to 220°C and kept at this temperature for 1 hour, and a pre-treatment solution is obtained by solid-liquid separation;

[0115] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 130°C and keep it for 6 hours, then heat it to 180°C and keep it for 1 hour, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 10:30.

[0116] The enthalpy value of the final composite phase change material is 76 J / g. After the composite phase change material is placed on filter paper, it is heated to 85° C. and kept warm for 3 days. No trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0117] Example 5

[0118] A method for preparing a composite phase change material, the specific steps are as follows:

[0119] (1) Preparation of raw materials;

[0120] Porous material: expanded graphite, porosity 80-95%;

[0121] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0122] Dispersion medium: DMF (N,N-dimethylformamide);

[0123] X: Hydrogen peroxide;

[0124] Carbohydrate: Chitosan, manufacturer is Sinopharm Chemical Reagent Co., Ltd., brand number 69047438;

[0125] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.2 g / mL, the concentration of X is 0.2 g / mL;

[0126] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0127] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 7.5:1, the mixture was kept at 80°C for 4 hours and then cooled to 25°C;

[0128] (3) preparing a dispersion of porous material;

[0129] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.1 g / mL;

[0130] (4) preparing composite phase change materials;

[0131] (4.1) The aqueous solution containing carbohydrate and X is first heated to 150°C and kept at this temperature for 1 hour, and then heated to 220°C and kept at this temperature for 1 hour, and a pre-treatment solution is obtained by solid-liquid separation;

[0132] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 130°C and keep it for 6 hours, then heat it to 180°C and keep it for 1 hour, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 5:10.

[0133] The enthalpy value of the final composite phase change material is 110 J / g. After the composite phase change material is placed on filter paper, it is heated to 95° C. and kept warm for 3 days. No trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0134] Example 6

[0135] A method for preparing a composite phase change material, the specific steps are as follows:

[0136] (1) Preparation of raw materials;

[0137] Porous materials: graphene aerogel, with a porosity of 70-95%;

[0138] Solid-liquid phase change material: eicosane, phase change temperature is 35°C, thermal decomposition temperature is 150°C;

[0139] Dispersion medium: polyethylene glycol, number average molecular weight 400;

[0140] X: APS;

[0141] Carbohydrate: Chitosan, manufacturer is Sinopharm Chemical Reagent Co., Ltd., brand number 69047438;

[0142] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.3 g / mL, the concentration of X is 0.3 g / mL;

[0143] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0144] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 5:1, the mixture was kept at 80°C for 4 hours and then cooled to 25°C;

[0145] (3) preparing a dispersion of porous material;

[0146] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.1 g / mL;

[0147] (4) preparing composite phase change materials;

[0148] (4.1) The aqueous solution containing carbohydrate and X is first heated to 100°C and kept for 4 h, then heated to 160°C and kept for 2 h, and a pre-treatment solution is obtained by solid-liquid separation;

[0149] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 100°C and keep it for 2 hours, then heat it to 150°C and keep it for 3 hours, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 5:15.

[0150] The enthalpy value of the final composite phase change material is 90 J / g. After the composite phase change material is placed on filter paper, it is heated to 80° C. and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0151] Example 7

[0152] A method for preparing a composite phase change material, the specific steps are as follows:

[0153] (1) Preparation of raw materials;

[0154] Porous material: porous carbon, with a porosity of 85-95%;

[0155] Solid-liquid phase change material: paraffin, phase change temperature is 57°C, thermal decomposition temperature is 200°C;

[0156] Dispersion medium: DMF;

[0157] X: APS;

[0158] Carbohydrate: soluble starch, manufacturer is Yonghua Chemical Co., Ltd., CAS number is 9005-84-9;

[0159] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.1 g / mL, the concentration of X is 0.1 g / mL;

[0160] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0161] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 9:1, the mixture was kept at 130°C for 4 hours and then cooled to 25°C;

[0162] (3) preparing a dispersion of porous material;

[0163] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.15 g / mL;

[0164] (4) preparing composite phase change materials;

[0165] (4.1) The aqueous solution containing carbohydrate and X is first heated to 150°C and kept for 1 hour, then heated to 160°C and kept for 2 hours, and a pre-treatment solution is obtained by solid-liquid separation;

[0166] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 100°C and keep it for 2 hours, then heat it to 150°C and keep it for 3 hours, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 2:30.

[0167] The enthalpy value of the composite phase change material finally obtained is 95 J / g; after the composite phase change material is placed on the filter paper, it is heated to 120° C. and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0168] Example 8

[0169] A method for preparing a composite phase change material, the specific steps are as follows:

[0170] (1) Preparation of raw materials;

[0171] Porous material: porous carbon, with a porosity of 85-95%;

[0172] Solid-liquid phase change material: paraffin, phase change temperature is 57°C, thermal decomposition temperature is 200°C;

[0173] Dispersion medium: DMF;

[0174] X: APS;

[0175] Carbohydrate: soluble starch, manufacturer is Yonghua Chemical Co., Ltd., CAS number is 9005-84-9;

[0176] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.1 g / mL, the concentration of X is 0.1 g / mL;

[0177] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0178] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 9:1, the mixture was kept at 130°C for 4 hours and then cooled to 25°C;

[0179] (3) preparing a dispersion of porous material;

[0180] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.15 g / mL;

[0181] (4) preparing composite phase change materials;

[0182] (4.1) The aqueous solution containing carbohydrate and X is first heated to 125°C and kept warm for 2.5 hours, then heated to 190°C and kept warm for 1.5 hours, and a pre-treatment solution is obtained by solid-liquid separation;

[0183] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 115°C and keep it for 4 hours, then heat it to 180°C and keep it for 1.5 hours, and perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 5:10.

[0184] The enthalpy value of the composite phase change material finally obtained is 94.1 J / g; after the composite phase change material is placed on the filter paper, it is heated to 120°C and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper.

[0185] Example 9

[0186] A method for preparing a composite phase change material, the specific steps are as follows:

[0187] (1) Preparation of raw materials;

[0188] Porous material: porous carbon, with a porosity of 85-95%;

[0189] Solid-liquid phase change material: paraffin, phase change temperature is 57°C, thermal decomposition temperature is 200°C;

[0190] Dispersion medium: polyethylene glycol, number average molecular weight 400;

[0191] X: APS;

[0192] Carbohydrate: Chitosan, manufacturer is Sinopharm Chemical Reagent Co., Ltd., brand number 69047438;

[0193] An aqueous solution containing both carbohydrate and X: the concentration of carbohydrate is 0.1 g / mL, the concentration of X is 0.1 g / mL;

[0194] (2) Filling the pores of the porous material with a solid-liquid phase change material;

[0195] After mixing the porous material and the solid-liquid phase change material in a mass ratio of 9:1, the mixture was kept at 130°C for 4 hours and then cooled to 25°C;

[0196] (3) preparing a dispersion of porous material;

[0197] The porous material filled with the solid-liquid phase change material in step (2) is mixed evenly with the dispersion medium to obtain a dispersion of the porous material with a concentration of 0.15 g / mL;

[0198] (4) preparing composite phase change materials;

[0199] (4.1) The aqueous solution containing carbohydrate and X is first heated to 125°C and kept warm for 2.5 hours, then heated to 190°C and kept warm for 1.5 hours, and a pre-treatment solution is obtained by solid-liquid separation;

[0200] (4.2) After adding the pretreatment liquid to the dispersion of the porous material, stir evenly, heat it to 115°C and keep it for 4 hours, then heat it to 165°C and keep it for 1.5 hours, and then perform post-treatment to obtain a composite phase change material; wherein the volume ratio of the dispersion of the porous material to the pretreatment liquid is 5:15.

[0201] The enthalpy value of the final composite phase change material is 85 J / g. After the composite phase change material is placed on filter paper, it is heated to 130° C. and kept warm for 3 days, and no trace of leakage of the solid-liquid phase change material is found on the filter paper.

Claims

1. A composite phase change material, comprising a porous material and a solid-liquid phase change material located in the pores of the porous material, characterized in that: At least a portion of the pores of the porous material are closed and / or semi-closed.

2. A composite phase change material according to claim 1, characterized in that: The porous material is porous carbon, mesoporous silica, porous MOF, copper foam, expanded graphite or graphene aerogel; the porosity of the porous material is 60-95%.

3. A composite phase change material according to claim 1, characterized in that: The solid-liquid phase change material is an alkane solid-liquid phase change material.

4. A composite phase change material according to claim 1, characterized in that: After placing the composite phase change material on the filter paper, it was heated to a certain temperature and kept warm for 3 days. No trace of leakage of the solid-liquid phase change material was found on the filter paper. The certain temperature was 20-80°C higher than the phase change temperature of the solid-liquid phase change material, and 20-80°C lower than the thermal decomposition temperature of the solid-liquid phase change material.

5. A method for preparing a composite phase change material as claimed in any one of claims 1 to 4, characterized in that: The specific steps are as follows: (1) Filling the pores of the porous material with a solid-liquid phase change material; (2) At least a portion of the pores of the porous material are closed and / or semi-closed to obtain a composite phase change material.

6. The method of composite phase change material according to claim 5, characterized in that: The specific process of step (1) is: after mixing the porous material and the solid-liquid phase change material in a mass ratio of 5-10:1, keeping the mixture at a certain temperature for 2-4 hours and then cooling it to a temperature lower than the phase change temperature of the solid-liquid phase change material, wherein the certain temperature is 45-73°C higher than the phase change temperature of the solid-liquid phase change material and 70-80°C lower than the thermal decomposition temperature of the solid-liquid phase change material.

7. The method of composite phase change material according to claim 5, characterized in that: In step (2), at least a portion of the pores of the porous material are closed and / or semi-closed by forming a carbon shell on the surface of the porous material.

8. The method of composite phase change material according to claim 7, characterized in that: The carbon shell is formed by the dehydration condensation reaction of carbohydrates on the outer surface of the porous material.

9. The method of composite phase change material according to claim 8, characterized in that: Step (2) is as follows: (2.1) The aqueous solution containing carbohydrate and X is first heated to T1 and kept at temperature t1, then heated to T2 and kept at temperature t2, and a pretreatment solution is obtained by solid-liquid separation, wherein X is APS, hydrogen peroxide or potassium permanganate; (2.2) After adding the pretreatment liquid to the dispersion of the porous material, the mixture is stirred evenly, and the temperature is first raised to T3 and maintained at t3, and then raised to T4 and maintained at t4 for post-treatment, wherein T3 is higher than the phase change temperature of the solid-liquid phase change material, and T4 is lower than the thermal decomposition temperature of the solid-liquid phase change material; Carbohydrate is glucose, T1 is 60-80℃, t1 is 1-4h, T2 is 150-190℃, t2 is 1-2h, T3 is 100-130℃, t3 is 2-6h, T4 is 150-180℃, t4 is 1-3h; Carbohydrate is soluble starch, T1 is 100-150℃, t1 is 1-4h, T2 is 160-220℃, t2 is 1- 2h, T3 is 100-130℃, t3 is 2-6h, T4 is 150-180℃, t4 is 1-3h; The carbohydrate is chitosan, T1 is 100-150°C, t1 is 1-4h, T2 is 160-220°C, t2 is 1-2h, T3 is 100-130°C, t3 is 2-6h, T4 is 150-180°C, t4 is 1-3h.

10. The method of composite phase change material according to claim 9, characterized in that: In step (2.1), in the aqueous solution containing both carbohydrate and X, the concentration of carbohydrate is 0.1-0.3 g / mL, and the concentration of X is 0.1-0.3 g / mL; In step (2.2), the concentration of the porous material dispersion is 0.1-0.3 g / mL, the dispersion medium is propylene glycol, polyethylene glycol or DMF; the volume ratio of the porous material dispersion to the pretreatment liquid is 2-10:10-30.

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