Dendritic silica spheres, composite phase change energy storage material and preparation method and application thereof

Abstract

The application discloses dendritic silica spheres, a composite phase change energy storage material and a preparation method and application thereof; the preparation method of the dendritic silica spheres comprises the following steps: dispersing a block type polyurethane surfactant and a cationic surfactant in a solvent to prepare a dispersion liquid, stirring to form an emulsion after adding cyclohexane oil phase, adding tetraethoxysilane and ammonia water to react, and washing, drying and calcining the separated solid product to obtain the dendritic silica spheres. The prepared silica nanospheres and a phase change material are prepared into the dendritic silica composite phase change energy storage material through a vacuum impregnation method. The new method for synthesizing the dendritic silica spheres is simple and controllable, the particle size and pore structure of the silica spheres can be controlled, and the synthesized composite phase change energy storage material exhibits good thermal energy storage capacity and shape stability. The application has great application potential in the fields of building energy saving, electronic equipment and battery heat management.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of porous materials and phase change materials, and particularly relates to a dendritic silica sphere, a composite phase change energy storage material and a preparation method and application thereof. TECHNICAL BACKGROUND

[0002] With the development of industrialized society, the demand for traditional fossil energy has been increasing in the past few decades, which has caused energy shortage and greenhouse gas emission problems increasingly prominent in today's society. As the largest developing country, China is in the stage of overall rapid economic development, and the demand for energy is gradually increasing, so the use of energy has become a major national strategy. Renewable energy has received more and more attention in recent years due to its great application potential. However, renewable energy has problems such as time and space mismatch in the use process, which will limit the application of renewable energy in the energy consumption structure. Energy storage technology can well improve the imbalance between supply and demand of renewable energy in time and space, and thus increase the efficiency of energy application process. Developing new energy storage technology is considered to be one of the most effective renewable energy utilization methods to reduce traditional energy consumption and protect the environment.

[0003] At present, energy storage technology mainly includes mechanical energy, electrical energy, chemical energy and thermal energy storage. Among them, thermal energy storage is an important storage and release form in the energy storage process, which is achieved by changing the internal energy of the material. Among various renewable energies, thermal energy is increasingly concerned and widely studied due to its multiple application occasions and simple heat storage and release process. There are three main ways of thermal energy storage: sensible heat storage, thermo-chemical heat storage and latent heat storage. Among them, phase change heat storage is to store a large amount of latent heat by phase change of phase change materials. In the phase change process, the phase change material absorbs heat from the environment or releases heat to the environment to achieve the purpose of energy storage and release. Among them, solid-liquid organic phase change materials are widely studied due to their small phase change volume, high thermal energy storage density, no phase separation, non-toxicity and other advantages (Renew. Sust. Energ. Rev., 2018, 82: 281-323). Polyethylene glycol is a commonly used solid-liquid organic phase change energy storage material, which has the advantages of wide range of phase change temperature selection and good compatibility in addition to the above advantages. The phase change temperature of polyethylene glycol phase change material can be simply adjusted by changing the molecular weight, and the melting temperature and latent heat increase with the increase of the molecular weight when the molecular weight changes from 200 to 20000. Although polyethylene glycol is a good solid-liquid organic phase change candidate material, it also has the disadvantage of easy leakage of phase change.

[0004] Currently, researchers generally use microcapsulation, porous carrier adsorption and high polymer polymerization porous material composite shaping technology to improve the leakage problem of solid-liquid phase change materials. The porous carrier adsorption method is an effective method for preparing composite shaped phase change materials by limiting phase change materials in the pores of the porous carrier. The porous carrier includes inorganic materials with porous or layered structure and polymers with three-dimensional network structure. The present application adopts a surfactant compound system to prepare dendritic silica spheres as the porous carrier by a soft template method. The synthesis process is simple, and the silica spheres have a unique dendritic morphology, a larger specific surface area and relatively more adsorption sites. The new method for synthesizing the dendritic silica spheres has adjustable particle size and pore size, and provides feasibility for the subsequent composite with phase change materials.

[0005] Therefore, the dendritic silica sphere composite phase change material with high heat storage capacity and stable shape is prepared by a simple synthesis method, and has great application value in the fields of building energy saving, electronic equipment and battery heat management. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a dendritic silica sphere, a composite phase change energy storage material and a preparation method and application thereof.

[0007] The purpose of the present application is achieved by the following technical solutions.

[0008] A preparation method of a dendritic silica sphere, comprising the following steps:

[0009] The block type polyurethane surfactant and the cationic surfactant are dispersed in a solvent to form a dispersion liquid, and then cyclohexane oil phase is added to form an emulsion after stirring, and then tetraethoxysilane and ammonia water are added to react, and then the separated solid product is washed, dried and calcined to obtain the dendritic silica sphere.

[0010] Preferably, the mass ratio of the block type polyurethane surfactant, the cationic surfactant, the cyclohexane and the tetraethoxysilane is 1:0.2-0.7:2.0-4.5:2.0-4.0;

[0011] Preferably, the solvent is composed of ethanol and water in a mass ratio of 1:2-4; and the mass ratio of the solvent to the total mass of the block type polyurethane surfactant and the cationic surfactant is 1:0.04-0.07;

[0012] Preferably, the volume ratio of the ammonia water to the mass of the solvent is 1ml:30-100g; and the mass concentration of the ammonia water is 25%-50%;

[0013] Preferably, the cationic surfactant is at least one of cetyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and cetyltrimethylammonium chloride.

[0014] Preferably, the stirring is mechanical stirring; the stirring speed is 500-600 rpm, and the stirring time is 3-6 h.

[0015] Preferably, the reaction temperature is 15-50℃, and the reaction time is 12-24 h; the reaction is carried out under stirring, and the stirring speed is 500-600 rpm.

[0016] Preferably, homogenization is carried out before the reaction; the homogenization speed is 1000-2000 rpm, and the homogenization time is 5-10 min.

[0017] Preferably, the calcination is carried out in a muffle furnace; the calcination temperature is 500-600℃, the heating rate is 2-5℃ / min, and the calcination time is 3-4 h.

[0018] Preferably, the block type polyurethane surfactant is prepared by the following method: heating isocyanate to 70-90℃, then adding organic tin catalyst and hydrophilic chain extender solution, reacting for 1-3 h, then adding the mixed system to polyethylene glycol at 60-100℃, reacting for 1-3 h, and removing the solvent under vacuum to obtain the block type polyurethane surfactant.

[0019] Further preferably, the molar ratio of the isocyanate, the hydrophilic chain extender and the polyethylene glycol is 1:0.05-1.5:0.1-1.0.

[0020] Further preferably, the isocyanate is at least one of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, xylylene diisocyanate and methylcyclohexyl diisocyanate.

[0021] Further preferably, the hydrophilic chain extender is at least one of dimethylol propanoic acid (DMPA), dimethylol butanoic acid (DMBA), 1,2-propanediol-3-sodium sulfonate, 1,4-butanediol-2-sodium sulfonate, diethylene triamine and methyldiethanolamine.

[0022] Further preferably, the number average molecular weight of the polyethylene glycol is 600-3500 g / mol.

[0023] Further preferably, the mass ratio of the isocyanate and the organic tin catalyst is 1:0.0005-0.005.

[0024] Further preferably, the organic tin catalyst is at least one of dibutyltin dilaurate, stannous octoate, bis(dodecylthio)dibutyltin, and dibutyltin diacetate.

[0025] A dendritic silica sphere is prepared by the above preparation method.

[0026] A preparation method of a dendritic silica sphere composite phase change energy storage material, comprising the following steps:

[0027] The dendritic silica sphere is dispersed in the polyethylene glycol phase change material, vacuum impregnation, and separation of the polyethylene glycol phase change material not deposited on the dendritic silica sphere, to obtain the dendritic silica sphere composite phase change energy storage material.

[0028] Preferably, the polyethylene glycol phase change material is at least one of polyethylene glycol 4000-8000; further preferably, the polyethylene glycol phase change material is at least one of polyethylene glycol 6000, polyethylene glycol 8000, and polyethylene glycol 4000.

[0029] Preferably, the vacuum impregnation time is 6-18 hours; the vacuum impregnation temperature is 70-90℃; the vacuum impregnation is carried out in a vacuum drying oven; further preferably, the vacuum impregnation time is 12 hours.

[0030] Preferably, the separation of the polyethylene glycol phase change material not deposited on the dendritic silica sphere is carried out in a blast drying oven; the separation temperature is 70-90℃.

[0031] Preferably, the mass ratio of the dendritic silica sphere to the polyethylene glycol phase change material is 1:10-15.

[0032] A dendritic silica sphere composite phase change energy storage material is prepared by the above preparation method.

[0033] The dendritic silica sphere composite phase change energy storage material is applied to thermal energy storage, including building energy saving, electronic device and battery heat management fields.

[0034] The present application has the following advantages:

[0035] (1) The present application adopts a block type polyurethane anion and a traditional cationic surfactant to prepare a dendritic silica sphere with a high specific surface area by a soft template method, and the preparation method is simple and controllable, the particle size and pore structure of the silica sphere can be controlled, the process conditions are mild, the cost is low, and the method is suitable for large-scale production and application.

[0036] (2) The present application provides a dendritic silica sphere for shaping phase change materials to solve the problem of easy leakage of solid-liquid phase change materials, and the prepared composite material not only has good heat energy storage and heat management capacity, high thermal stability and shape stability, but also has good phase change reliability and durability in actual use. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 SEM images of the dendritic silica spheres in Example 1 (a) and SEM images of the dendritic silica sphere composite phase change material in Example 1 (b).

[0038] Figure 2 Nitrogen adsorption-desorption curves (a) and pore size distribution diagrams (b) of the dendritic silica spheres in Example 1.

[0039] Figure 3 Thermal performance curves of the dendritic silica sphere composite phase change materials in Example 1-Example 5 and pure polyethylene glycol.

[0040] Figure 4 SEM images of the dendritic silica spheres in Example 2 (a) and SEM images of the dendritic silica sphere composite phase change material in Example 2 (b).

[0041] Figure 5 Nitrogen adsorption-desorption curves (a) and pore size distribution diagrams (b) of the dendritic silica spheres in Example 2.

[0042] Figure 6 SEM images of the dendritic silica spheres in Example 3 (a) and SEM images of the dendritic silica sphere composite phase change material in Example 3 (b).

[0043] Figure 7 Nitrogen adsorption-desorption curves (a) and pore size distribution diagrams (b) of the dendritic silica spheres in Example 3.

[0044] Figure 8 SEM images of the dendritic silica spheres in Example 4 (a) and SEM images of the dendritic silica sphere composite phase change material in Example 4 (b).

[0045] Figure 9 Nitrogen adsorption-desorption curves (a) and pore size distribution diagrams (b) of the dendritic silica spheres in Example 4.

[0046] Figure 10 SEM images of the dendritic silica spheres in Example 5 (a) and SEM images of the dendritic silica sphere composite phase change material in Example 5 (b).

[0047] Figure 11Nitrogen adsorption-desorption curve (a) and pore size distribution graph (b) of the dendritic silica sphere of Example 5.

[0048] Figure 12 SEM graph of the silica sphere of Comparative Example 1.

[0049] Figure 13 Digital image of the dendritic silica sphere composite phase change material of Example 4 and pure polyethylene glycol at 80℃. DETAILED DESCRIPTION

[0050] The examples of the present application are described in detail below in conjunction with specific experimental processes. The examples described herein are merely used to explain the present application and are not intended to limit the present application. It is hereby stated.

[0051] A preparation method of a dendritic silica sphere composite phase change energy storage material, comprising the following steps:

[0052] The block type polyurethane surfactant and the cationic surfactant are dispersed in a solvent at 15-50℃ for 0.5-1h to form a dispersion liquid, and then the cyclohexane oil phase is added to form an emulsion at 15-50℃ by mechanical stirring. The ammonia water and the tetraethoxysilane are homogenized by a high-speed homogenizer at 15-50℃, and then the stirring reaction is carried out at 15-50℃ for 12-24h. The solid product is separated, washed and dried, and then placed in a muffle furnace for calcination to obtain the dendritic silica sphere. The dendritic silica sphere is dispersed in the polyethylene glycol phase change material, vacuum impregnation is carried out in a vacuum drying oven, and then the phase change material not fixed on the dendritic silica sphere is separated in a blast drying oven, to obtain the dendritic silica sphere composite phase change energy storage material.

[0053] The molar ratio of the block type polyurethane surfactant, the cationic surfactant, the cyclohexane and the tetraethoxysilane is 1:2-5:85-100:20-45;

[0054] The solvent is composed of ethanol and water in a molar ratio of 1:5-8;

[0055] The volume ratio of the ammonia water to the solvent is 1:30-100;

[0056] The cationic surfactant is at least one of cetyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and cetyltrimethylammonium chloride;

[0057] The mechanical stirring speed is 500-600rpm, and the stirring time is 3-6h.

[0058] The high-speed homogenizer homogenization speed is 1500rpm, and the homogenization time is 5min.

[0059] The muffle calcination temperature is 500-600℃, the muffle temperature rising rate is 2-5℃ / min, and the calcination time is 3-4 hours.

[0060] Preferably, the phase change material is at least one of polyethylene glycol 6000, polyethylene glycol 8000 and polyethylene glycol 4000.

[0061] Preferably, the impregnation time is 12 hours.

[0062] Preferably, the impregnation temperature and the separation temperature are both 80℃.

[0063] Preferably, the mass ratio of the dendritic silica to the polyethylene glycol phase change material is 1:10-15.

[0064] The preparation method of the block type polyurethane surfactant used in the following examples is as follows:

[0065] The block type polyurethane surfactant is prepared by the following method: 44.5g of isophorone diisocyanate is heated to 80℃, then 0.1g of dibutyltin dilaurate is added, then 13.4g of a DMF (N,N-dimethylformamide) solution (16.67wt%) of 2,2-dimethylol propionic acid is slowly added, the reaction is carried out for 2h after the addition is completed, then the reacted mixture is added to 150g of polyethylene glycol (number average molecular weight 1000g / mol) heated to 80℃, the reaction is carried out for 2h, and the solvent is removed by vacuum extraction, thereby obtaining the block type polyurethane surfactant (number average molecular weight about 2200g / mol).

[0066] Example 1

[0067] A preparation method of a dendritic silica sphere composite phase change energy storage material, specifically comprising the following steps:

[0068] A dispersion liquid is prepared by stirring 1.38g of block type polyurethane surfactant and 0.4g of cetyltrimethylammonium bromide in 26g of deionized water and 11.85g of anhydrous ethanol solvent at room temperature for 0.5h, an emulsion is formed by mechanical stirring for 3h after adding 4g of cyclohexane oil phase at room temperature, 1ml of 28% ammonia water and 4g of tetraethoxysilane are added and homogenized at 1500rpm for 5min by using a high-speed homogenizer at room temperature, and then the reaction is carried out at room temperature by stirring at 500rpm for 24h, a white solid product is obtained by centrifugation and washing the sample with water and ethanol, drying in a 80℃ air-drying oven for 24h, and then calcining in a muffle furnace at 500℃ for 3h (temperature rising rate 5℃ / min) to obtain dendritic silica spheres.

[0069] 0.3 g dendritic silica spheres were dispersed in 3 g polyethylene glycol phase change material (number average molecular weight of 6000 g / mol), vacuum impregnated in a vacuum drying oven at 80 ℃ for 12 h, and then separated from the phase change material not shaped on the dendritic silica spheres with filter paper in a 80 ℃ air drying oven, to obtain dendritic silica sphere composite phase change energy storage material.

[0070] The dendritic silica spheres and the dendritic silica sphere composite phase change energy storage material prepared in Example 1 were subjected to scanning electron microscopy, and the results are shown in Figs. (a) and (b), respectively. Figure 1 As can be seen from Fig. (a), the dendritic silica spheres have a dendritic morphology and a uniform particle size distribution, and the pores are obvious. The average particle size of the dendritic silica spheres is 260 nm. Figure 1 As can be seen from Fig. (b), after being combined with the polyethylene glycol phase change material, the pores of the dendritic silica spheres are filled with the phase change material, and the polyethylene glycol is uniformly adsorbed in the pores due to capillary force and surface tension.

[0071] The specific surface area and pore size distribution of the dendritic silica spheres prepared in Example 1 were characterized by BET, as shown in Fig. Figure 2 . Figure 2 Fig. (a) is a nitrogen adsorption-desorption curve, Figure 2 Fig. (b) is a pore size distribution graph of the dendritic silica spheres. According to the BET characterization, the average pore size of Example 1 is 4.6 nm, which is the smallest dendritic silica of all examples. The specific surface area is 469.84 m 2 / g.

[0072] The dendritic silica sphere composite phase change energy storage material prepared in Example 1 was subjected to differential scanning calorimetry characterization (DSC), as shown in Fig. Figure 3 .

[0073] Example 2

[0074] A preparation method of a dendritic silica sphere composite phase change energy storage material, specifically comprising the following steps:

[0075] 1.38 g of block polyurethane surfactant and 0.6 g of cetyltrimethylammonium bromide were dispersed in 26 g of deionized water and 11.85 g of anhydrous ethanol solvent at room temperature for 0.5 h to form a dispersion liquid. After adding 4 g of cyclohexane oil phase at room temperature, an emulsion was formed by mechanical stirring for 3 h. 1 ml of 28% ammonia water and 4 g of tetraethoxysilane were added at room temperature and homogenized at 1500 rpm for 5 min using a high-speed homogenizer. Then, the mixture was stirred at 500 rpm for 24 h at room temperature. The white solid product was separated by centrifugation and washed with water and ethanol. The product was dried in a 80 ℃ air drying oven for 24 h, and then calcined in a muffle furnace at 500 ℃ for 3 h (the heating rate was 5 ℃ / min) to obtain dendritic silica spheres.

[0076] 0.3 g dendritic silica spheres were dispersed in 3 g polyethylene glycol phase change material (number average molecular weight of 6000 g / mol), vacuum impregnated in a vacuum drying oven at 80℃ for 12 h, and then the phase change material not shaped on the dendritic silica spheres was separated with filter paper in a 80℃ air drying oven to obtain dendritic silica sphere composite phase change energy storage material.

[0077] The dendritic silica spheres and dendritic silica sphere composite phase change energy storage material prepared in Example 2 were subjected to scanning electron microscopy, and the results are shown in Figs. Figure 4 (a) and (b) of the drawings, respectively. Figure 4 As can be seen from Fig. a of the drawings, compared with the pore size of the dendritic silica in Example 1, the dendritic silica spheres in Example 2 have a larger pore size in terms of morphology. Compared with the other examples, the particle size of the dendritic silica spheres in Example 2 is 420 nm on average, which is larger, indicating that the method realizes the particle size control of the dendritic silica spheres.

[0078] The specific surface area and pore size distribution of the dendritic silica spheres prepared in Example 2 were characterized by BET as shown in Fig. Figure 5 . Figure 5 Fig. (a) is a nitrogen adsorption-desorption curve, Figure 5 Fig. (b) is a pore size distribution graph of the dendritic silica spheres. The average pore size is 6.5 nm, and the specific surface area is 562.61 m 2 / g.

[0079] The dendritic silica sphere composite phase change energy storage material prepared in Example 2 was subjected to differential scanning calorimetry (DSC) characterization as shown in Fig. Figure 3 .

[0080] Example 3

[0081] A preparation method of dendritic silica sphere composite phase change energy storage material, specifically comprising the following steps:

[0082] 1.38 g of block polyurethane surfactant and 0.8 g of cetyltrimethylammonium bromide were dispersed in 26 g of deionized water and 11.85 g of anhydrous ethanol solvent at room temperature for 0.5 h to form a dispersion liquid. After adding 4 g of cyclohexane oil phase at room temperature, an emulsion was formed by mechanical stirring for 3 h. 1 ml of 28% ammonia water and 4 g of tetraethoxysilane were added at room temperature and homogenized by a high-speed homogenizer at 1500 rpm for 5 min. Then, the mixture was stirred at room temperature at 500 rpm for 24 h. The white solid product was separated by centrifugation and washed with water and ethanol. The product was dried in a 80℃ air drying oven for 24 h, and then calcined in a muffle furnace at 500℃ for 3 h (the heating rate was 5℃ / min) to obtain dendritic silica spheres.

[0083] 0.3g of dendritic silica spheres were dispersed in 3g of polyethylene glycol phase change material (number average molecular weight of 6000g / mol), and vacuum impregnated in a vacuum drying oven at 80℃ for 12h. Then, the phase change material that was not shaped on the dendritic silica spheres was separated by filter paper in a forced-air drying oven at 80℃, thus obtaining the dendritic silica sphere composite phase change energy storage material.

[0084] Scanning electron microscopy was performed on the dendritic silica spheres and the dendritic silica sphere composite phase change energy storage material prepared in Example 3. The results are as follows: Figure 6 As shown in (a) and (b), the average particle size of the dendritic silica spheres is 160 nm; from Figure 6 As can be seen from (a), the dendritic silica spheres have a more uniform distribution and more pores.

[0085] The dendritic silica spheres prepared in Example 3 were characterized by their specific surface area and pore size distribution (BET). Figure 7 As shown. Figure 7 (a) is the nitrogen adsorption-desorption curve. Figure 7 (b) shows the pore size distribution of the dendritic silica spheres. BET characterization revealed that Example 3 had a specific surface area as high as 777.69 m². 2 / g, with an average pore size of 11.58nm.

[0086] Differential scanning calorimetry (DSC) was used to characterize the dendritic silica sphere composite phase change energy storage material prepared in Example 3. Figure 3 As shown.

[0087] Example 4

[0088] A method for preparing a dendritic silica sphere composite phase change energy storage material specifically includes the following steps:

[0089] 1.38 g of block polyurethane surfactant and 0.8 g of hexadecyltrimethylammonium bromide were dispersed in 26 g of deionized water and 11.85 g of anhydrous ethanol solvent at room temperature for 0.5 h to form a dispersion. At room temperature, 4 g of cyclohexane oil phase was added and mechanically stirred for 4 h to form an emulsion. 1 ml of 28% ammonia and 4 g of tetraethoxysilane were added, and the mixture was homogenized at 1500 rpm for 5 min at room temperature, followed by stirring at 500 rpm for 24 h at room temperature. The mixture was then centrifuged, and the sample was washed with water and ethanol to obtain a white solid product. This solid was dried in an 80℃ oven for 24 h, and then calcined in a muffle furnace at 500℃ for 3 h (heating rate 5℃ / min) to obtain dendritic silica spheres.

[0090] 0.3g of dendritic silica spheres were dispersed in 3g of polyethylene glycol phase change material (number average molecular weight of 6000g / mol), and vacuum impregnated in a vacuum drying oven at 80℃ for 12h. Then, the phase change material that was not shaped on the dendritic silica spheres was separated by filter paper in a forced-air drying oven at 80℃, thus obtaining the dendritic silica sphere composite phase change energy storage material.

[0091] Scanning electron microscopy was performed on the dendritic silica spheres and the dendritic silica sphere composite phase change energy storage material prepared in Example 4. The results are as follows: Figure 8 As shown in (a) and (b), the average particle size of the dendritic silica spheres is 230 nm; from Figure 8 As can be seen in Figure (a), compared with the other embodiments, the dendritic silica spheres in Example 4 have larger pore structures and the most uniform distribution, indicating that the method of the present invention has controllable adjustment of the dendritic silica pore structure.

[0092] The dendritic silica spheres prepared in Example 4 were characterized by their specific surface area and pore size distribution (BET). Figure 9 As shown. Figure 9 (a) is the nitrogen adsorption-desorption curve. Figure 9 (b) shows the pore size distribution of the dendritic silica spheres. BET characterization revealed that Example 4 had a specific surface area as high as 879.40 m². 2 / g, with an average pore size of 16.85nm.

[0093] Differential scanning calorimetry (DSC) was used to characterize the dendritic silica sphere composite phase change energy storage material prepared in Example 4. Figure 3 As shown.

[0094] Example 5

[0095] A method for preparing a dendritic silica sphere composite phase change energy storage material specifically includes the following steps:

[0096] 1.38 g of block polyurethane surfactant and 0.8 g of hexadecyltrimethylammonium bromide were dispersed in 26 g of deionized water and 11.85 g of anhydrous ethanol solvent at room temperature for 0.5 h to form a dispersion. At room temperature, 4 g of cyclohexane oil phase was added and mechanically stirred for 6 h to form an emulsion. 1 ml of 28% ammonia and 4 g of tetraethoxysilane were added, and the mixture was homogenized at 1500 rpm for 5 min at room temperature, followed by stirring at 500 rpm for 24 h at room temperature. The mixture was then centrifuged, and the sample was washed with water and ethanol to obtain a white solid product. This solid was dried in an 80℃ oven for 24 h, and then calcined in a muffle furnace at 500℃ for 3 h (heating rate 5℃ / min) to obtain dendritic silica spheres.

[0097] 0.3g of dendritic silica spheres were dispersed in 3g of polyethylene glycol phase change material (number average molecular weight of 6000g / mol), and vacuum impregnated in a vacuum drying oven at 80℃ for 12h. Then, the phase change material that was not shaped on the dendritic silica spheres was separated by filter paper in a forced-air drying oven at 80℃, thus obtaining the dendritic silica sphere composite phase change energy storage material.

[0098] Scanning electron microscopy was performed on the dendritic silica spheres and the dendritic silica sphere composite phase change energy storage material prepared in Example 5. The results are as follows: Figure 10 As shown in (a) and (b), the average particle size of the dendritic silica spheres is 300 nm.

[0099] The dendritic silica spheres prepared in Example 5 were characterized by their specific surface area and pore size distribution (BET). Figure 11 As shown. Figure 11 (a) is the nitrogen adsorption-desorption curve. Figure 11 (b) shows the pore size distribution of the dendritic silica spheres. The average pore size is 12.64 nm, and the specific surface area is 772.75 m². 2 / g.

[0100] Differential scanning calorimetry (DSC) was used to characterize the dendritic silica sphere composite phase change energy storage material prepared in Example 5. Figure 3 As shown.

[0101] Comparative Example 1

[0102] 0.8 g of hexadecyltrimethylammonium bromide was dispersed in 26 g of deionized water and 11.85 g of anhydrous ethanol at room temperature for 0.5 h to form a dispersion. At room temperature, 4 g of cyclohexane oil phase was added and mechanically stirred for 4 h to form an emulsion. 1 ml of 28% ammonia and 4 g of tetraethoxysilane were added, and the mixture was homogenized at 1500 rpm for 5 min at room temperature. The mixture was then stirred at 500 rpm for 24 h at room temperature. The sample was centrifuged and washed with water and ethanol to obtain a white solid product. This solid was dried in an 80℃ oven for 24 h and then calcined in a muffle furnace at 500℃ for 3 h (heating rate 5℃ / min) to obtain dendritic silica spheres. No self-made block polyurethane surfactant was used in this process.

[0103] Scanning electron microscopy was performed on the silica spheres prepared in Comparative Example 1, and the results are as follows: Figure 12 As shown, compared with Example 4, the silica spheres have significantly smaller and denser pores, and the particle size distribution is uneven, which cannot provide strong support for combining with phase change materials and solving the leakage problem of phase change materials.

[0104] The phase change temperature and latent heat value of the dendritic silica sphere composite phase change energy storage material of examples 1-5 are shown in table 1. As shown in the table, compared with the pure polyethylene glycol phase change material, the phase change enthalpy of the composite phase change material will be reduced, which is related to the addition of the dendritic silica sphere. Because the phase change material is shaped and compounded, the composite phase change material has shape stability and will not produce leakage of the phase change material in the phase change process. Figure 13 As shown in the table, the composite phase change material has shape stability and will not produce leakage of the phase change material in the phase change process. Thus, it can be concluded that the present application solves the shortcomings of easy leakage of solid-liquid phase change material and prepares a composite phase change material with shape stability. As shown in table 1, the dendritic silica sphere composite phase change material prepared in example 4 has the best thermal performance, the phase change enthalpy value is 151.54 J / g, and the encapsulation rate of the dendritic silica sphere to the solid-liquid phase change material is >70%.

[0105] Table 1: phase change temperature and latent heat value of examples 1-5

[0106]

[0107] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples. Any simple change, replacement, combination, simplification made by a person skilled in the art according to the technical content disclosed by the present application should be regarded as equivalent replacement, and all of them are included in or belong to the protection scope of the present application.

Claims

1. A method for preparing dendritic silica spheres, characterized in that, The process includes the following steps: dispersing a block polyurethane surfactant and a cationic surfactant in a solvent to form a dispersion; adding a cyclohexane oil phase and stirring to form an emulsion; adding tetraethoxysilane and ammonia to react; washing, drying, and calcining the separated solid product to obtain dendritic silica spheres; wherein the mass ratio of the block polyurethane surfactant, cationic surfactant, cyclohexane, and tetraethoxysilane is 1:0.2-0.7:2.0-4.5:2.0-4.0; the solvent is composed of ethanol and water in a mass ratio of 1:2-4; the mass ratio of the solvent to the total mass of the block polyurethane surfactant and cationic surfactant is 1:0.04-0.07; the volume ratio of ammonia to the mass of the solvent is 1 ml:30-100 g; the mass concentration of ammonia is 25%-50%; the cationic surfactant is at least one of hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride; the stirring is mechanical stirring at a speed of 500-600 rpm for 3-6 minutes. h; the reaction temperature is 15-50 °C, and the time is 12-24 h; the calcination is carried out in a muffle furnace at a calcination temperature of 500-600 °C, a heating rate of 2-5 °C / min, and a calcination time of 3-4 h; the block polyurethane surfactant is prepared by the following method: isocyanate is heated to 70-90 °C, then an organotin catalyst and a hydrophilic chain extender solution are added, and the reaction is carried out for 1-3 h; then the mixture is added to polyethylene glycol at 60-100 °C, and the reaction is carried out for 1-3 h; the solvent is removed by vacuum to obtain the block polyurethane surfactant; the molar ratio of isocyanate, hydrophilic chain extender, and polyethylene glycol is 1:0.05-1.5:0.1-1.0; the isocyanate, hydrophilic chain extender, and polyethylene glycol are ... The cyanate is at least one selected from dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, phenylenediamine diisocyanate, and methylcyclohexyl diisocyanate; the hydrophilic chain extender is at least one selected from dimethylolpropionic acid, dimethylolbutyric acid, sodium 1,2-propanediol-3-sulfonate, sodium 1,4-butanediol-2-sulfonate, diethylenetriamine, and methyldiethanolamine; the number average molecular weight of the polyethylene glycol is 600 g / mol to 3500 g / mol; the mass ratio of the isocyanate to the organotin catalyst is 1:0.0005 to 0.005; the organotin catalyst is at least one selected from dibutyltin dilaurate, stannous octanoate, di(dodecyl sulfide)dibutyltin, and dibutyltin diacetate.

2. A dendritic silica sphere, characterized in that, It is prepared by the method described in claim 1.

3. A method for preparing a dendritic silica sphere composite phase change energy storage material, characterized in that, Includes the following steps: The dendritic silica spheres described in claim 2 are dispersed in polyethylene glycol phase change material, vacuum impregnated, and the polyethylene glycol phase change material that is not amorphous on the dendritic silica spheres is separated to obtain the dendritic silica sphere composite phase change energy storage material.

4. The preparation method of the dendritic silica sphere composite phase change energy storage material according to claim 3, characterized in that: The polyethylene glycol phase change material is at least one of polyethylene glycol 4000-8000; The vacuum impregnation time is 6-18 hours; the vacuum impregnation temperature is 70-90℃; the vacuum impregnation is carried out in a vacuum drying oven; The separation of polyethylene glycol phase change material unformed on dendritic silica spheres is carried out in a forced-air drying oven; the separation temperature is 70-90℃.

5. The preparation method of the dendritic silica sphere composite phase change energy storage material according to claim 3, characterized in that, The mass ratio of the dendritic silica spheres to the polyethylene glycol phase change material is 1:10~15.

6. A dendritic silica sphere composite phase change energy storage material, characterized in that, It is prepared by the method described in any one of claims 3-5.

7. The application of the dendritic silica sphere composite phase change energy storage material according to claim 6 in thermal energy storage.

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