Composite phase change material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of phase change energy storage, and discloses a composite phase change material and a preparation method and application thereof. The composite phase change material comprises an organic modified vermiculite carrier and hydrated salt adsorbed on the carrier, wherein the organic modified vermiculite is expanded vermiculite intercalated and modified by long-chain alkane quaternary ammonium salt. Mixing a long-chain alkane quaternary ammonium salt solution with the expanded vermiculite suspension, and reacting under a heating condition to obtain organic modified vermiculite; mixing the organic modified vermiculite and the hydrated salt, and performing vacuum impregnation to obtain the composite phase change material. Based on the adjustable characteristic of the interlayer structure of vermiculite, the long-chain alkane quaternary ammonium salt is adjusted by introducing the special structure of the long-chain alkane quaternary ammonium salt, and the organic modified vermiculite with the large interlayer spacing is successfully prepared; the organic modified vermiculite is used as a carrier of the phase-change material, and the composite phase-change material with high phase-change latent heat is prepared by adopting a vacuum impregnation method, so that the performance and the application value of the material are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change energy storage, and in particular to a composite phase change material and a preparation method and application thereof. Background Art

[0002] With the development of society, energy shortages have become increasingly prominent, hindering the rapid development of modern industry. Against this backdrop, energy storage technology has attracted considerable attention. Thermal energy storage technology can effectively alleviate the temporal and spatial mismatch between energy supply and actual demand, thereby improving energy efficiency and reducing greenhouse gas emissions. Consequently, it has attracted considerable attention from both the scientific research and industrial communities. Phase change energy storage technology is a mainstream, highly energy-efficient renewable energy storage method in the thermal energy storage field, offering broad application prospects.

[0003] Phase change materials (PCMs) are highly promising energy storage materials that can utilize their phase changes to store and release latent heat, offering advantages such as low cost and high efficiency. Because PCMs can absorb and store heat, they transform from solid to liquid when the temperature rises. The temperature remains constant during the phase change, and they subsequently release energy and transform from liquid to solid, thus achieving a cycle of heat absorption and release. Compared to other thermal storage materials, PCMs offer advantages such as high reliability, high energy storage density, and low power consumption. Inorganic hydrated salts are a common type of phase change material, composed of inorganic salts and water molecules and represented by the general formula AB·nH2O. In hydrated salts, crystalline water combines with ions in the inorganic salt to form chemical bonds. This crystalline water is detached at a fixed temperature, requiring more energy. However, their widespread application still faces many challenges, such as phase separation, supercooling, corrosion to metal containers, and slightly low thermal conductivity, which limit their long-term stability and heat storage capacity.

[0004] Wang et al. (Wang T, Zhao S, Liu S, et al.. Journal of Energy Storage, 2022, 54: 717-723.) used a 30% potato starch solution as a porous carbon source and obtained a binary pore structure of expanded vermiculite "sandwich" and three-dimensional network porous carbon by high-temperature carbonization. The enthalpy value of the composite phase change material increased from 200.5 J / g to 208 J / g. Sari et al. (Sari A, Bicer A, G.Journal of Composite Materials,2019,53(21):2967-2980.) used a melt blending method to impregnate a sunflower acid-stearic acid eutectic mixture into expanded vermiculite and doped with carbon nanotubes to obtain a stable composite phase change material. Zhang et al. (Zhang J, Wang Z, Li X, et al. Solar Energy, 2020, 196:419-426.) obtained expanded vermiculite (EVT) intercalated with TiO2-TiC-C by hydrothermal method and reduction roasting, and then obtained EVTa by acid treatment. A lauric acid-myristic acid-stearic acid eutectic mixture was used as a phase change material, and the eutectic mixture was impregnated into two carriers to obtain a new composite phase change material.

[0005] Previous studies have shown that expanded vermiculite as a carrier of phase change materials exhibits excellent performance. However, in most of the literature, expanded vermiculite after high temperature expansion is directly used as a carrier, which to some extent does not fully play the unique advantage of the layered structure of vermiculite. In addition, some studies modify and modify vermiculite by high-temperature carbonization and other methods, which have achieved certain results in improving the performance of the material, but such methods usually involve multi-step complex processes such as hydrothermal method, reduction roasting and acid treatment, which are difficult to operate, have high preparation cost and high energy consumption, and are difficult to meet the requirements of green and sustainable development. SUMMARY

[0006] The purpose of the present application is to overcome the problems existing in the prior art and provide a composite phase change material, a preparation method and application thereof. Specifically, the composite phase change material is a high latent heat composite phase change material prepared by compounding hydrated salt with organic modified vermiculite as a carrier and nucleating agent.

[0007] The present application uses long-chain alkyl quaternary ammonium salt as an interlayer modifier, and through the regulation of the alkyl chain length and the insertion amount, the expanded vermiculite is organically modified, and is used as a carrier to compound with hydrated salt to prepare a composite phase change material with high latent heat performance. The present application breaks through the application limitation of interlayer modified expanded vermiculite in the preparation of high latent heat composite phase change material, and further expands the application prospect of vermiculite as a two-dimensional material in the field of energy storage.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a composite phase change material, wherein the composite phase change material comprises an organic modified vermiculite carrier and a hydrated salt adsorbed on the carrier; wherein the organic modified vermiculite is an expanded vermiculite intercalated and modified by long-chain alkyl quaternary ammonium salt.

[0009] The second aspect of the present application provides a preparation method of the composite phase change material according to the first aspect, wherein the method comprises the following steps:

[0010] (1) mixing long-chain alkane quaternary ammonium salt solution with expanded vermiculite suspension, and obtaining organic modified vermiculite after reaction under heating condition;

[0011] (2) mixing the organic modified vermiculite obtained in step (1) with hydrated salt, and obtaining the composite phase change material by vacuum impregnation.

[0012] The third aspect of the present application provides a composite phase change material prepared by the preparation method according to the second aspect.

[0013] The fourth aspect of the present application provides an application of the composite phase change material according to the first aspect or the third aspect in building insulation materials, electric appliance heat dissipation systems and building constant temperature systems.

[0014] Through the above technical solution, the present application has the following beneficial technical effects:

[0015] (1) The composite phase change material provided by the present application effectively solves the problems of small phase change latent heat, phase separation and high supercooling degree of traditional phase change materials, reduces the supercooling degree of the obtained composite material and significantly weakens the phase separation phenomenon;

[0016] (2) Based on the controllable characteristics of the interlayer structure of vermiculite, the present application successfully prepares organic modified vermiculite with large interlayer spacing by introducing the special structure of long-chain alkane quaternary ammonium salt to regulate it; and the present application prepares a composite phase change material with high phase change latent heat by using the organic modified vermiculite as a carrier of the phase change material and adopting a vacuum impregnation method, which significantly improves the performance and application value of the material. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The XRD spectra of the organic modified vermiculite (CVM) and the expanded vermiculite (VM) prepared in Example 1 of the present application.

[0018] Figure 2 The infrared spectra of the organic modified vermiculite (CVM), the expanded vermiculite (VM) and the quaternary ammonium salt (CTAB) prepared in Example 1 of the present application.

[0019] Figure 3 The SEM photos of the organic modified vermiculite (CVM) and the expanded vermiculite (VM) prepared in Example 1 of the present application and the Mapping graph of the organic modified vermiculite (CVM); wherein a and b are the SEM photos of the VM; c and d are the SEM photos of the CVM; and e is the Mapping graph of the CVM.

[0020] Figure 4 The TG and DTG curves of the composite phase change material (FCVM), the expanded vermiculite (VM) and the organic modified vermiculite (CVM) prepared in Example 1 of the present application; wherein a is the TG curve; and b is the DTG curve.

[0021] Figure 5 SEM photos of the composite phase change material (FCVM) prepared in Example 1 of the present application and sodium sulfate decahydrate and Mapping diagram of the composite phase change material (FCVM); wherein a and b are SEM photos of sodium sulfate decahydrate; c and d are SEM photos of the FCVM; e is a Mapping diagram of the FCVM.

[0022] Figure 6 DSC curves of the composite phase change material (FCVM) prepared in Example 1 of the present application, the composite phase change material (FVM) prepared in Comparative Example 1, and sodium sulfate decahydrate.

[0023] Figure 7 Step cooling curves of sodium sulfate decahydrate, the composite phase change material (FVM) prepared in Comparative Example 1, and the composite phase change material (FCVM) prepared in Example 1.

[0024] Figure 8 Phase separation diagrams of sodium sulfate decahydrate, the composite phase change material (FVM) prepared in Comparative Example 1, and the composite phase change material (FCVM) prepared in Example 1. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and any values are understood to be approximations. The endpoints of the ranges and any values should be rounded to the nearest significant figure. The exact numerical values of the endpoints of the ranges and any values are understood to be approximations. The exact numerical values of the endpoints of the ranges and any values should be rounded to the nearest significant figure.

[0026] In a first aspect, the present application provides a composite phase change material, wherein the composite phase change material comprises an organic modified vermiculite carrier and a hydrated salt adsorbed on the carrier.

[0027] The organic modified vermiculite is an expanded vermiculite modified by intercalation of a long-chain alkyl quaternary ammonium salt.

[0028] The present application is based on the controllability of vermiculite lamella and interlamellar guest, uses a special composition of quaternary ammonium salt as a pillar supporting agent for constructing vermiculite lamella, and replaces the octahedron composed of cations and water molecules as an interlamellar guest, to prepare an organic modified vermiculite by in-situ composite reaction in one step, thereby overcoming the shortcomings of small interlamellar spacing and low adsorption capacity of vermiculite, and effectively compounding the hydrated salt by using the electronegativity of vermiculite lamella, to prepare a composite phase change material with high phase change latent heat, which can be widely applied to environments with heat storage needs.

[0029] In some embodiments of the present application, the number of carbon atoms in the carbon chain of the long-chain alkyl quaternary ammonium salt is 12-18.

[0030] In some embodiments of the present application, the anion in the long-chain alkane quaternary ammonium salt is a halide anion.

[0031] In some embodiments of the present application, the long-chain alkane quaternary ammonium salt is selected from at least one of dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (OTAB).

[0032] In some embodiments of the present application, the hydrated salt is selected from at least one of sodium sulfate decahydrate and calcium chloride hexahydrate, preferably sodium sulfate decahydrate or a composite salt of sodium sulfate decahydrate and calcium chloride hexahydrate.

[0033] In some embodiments of the present application, in the composite salt of sodium sulfate decahydrate and calcium chloride hexahydrate, the mass ratio of sodium sulfate decahydrate to calcium chloride hexahydrate is 1:0.05-2, such as 1:0.05, 1:0.2, 1:0.5, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, etc., and any value within the range between any two of the above values, preferably 1:1.2-2. The composite salt can be prepared by mixing sodium sulfate decahydrate and calcium chloride hexahydrate in a mass ratio, melting (e.g. for 1 h) under water bath conditions (e.g. 70°C), and then cooling and grinding.

[0034] In some embodiments of the present application, the mass ratio of the hydrated salt to the organically modified vermiculite is 1:0.1-1, such as 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, etc., and any value within the range between any two of the above values, preferably 1:0.1-0.2.

[0035] The second aspect of the present application provides a method for preparing the composite phase change material according to the first aspect, wherein the method comprises the following steps:

[0036] (1) mixing a long-chain alkane quaternary ammonium salt solution with an expanded vermiculite suspension, and obtaining organically modified vermiculite after reaction under heating conditions;

[0037] (2) mixing the organically modified vermiculite obtained in step (1) with a hydrated salt, and obtaining the composite phase change material by vacuum impregnation.

[0038] In some embodiments of the present application, the concentration of the long-chain alkane quaternary ammonium salt solution in step (1) is 5-11 g / L.

[0039] In some embodiments of the present application, in step (1), the molar amount of the long-chain alkane quaternary ammonium salt in the long-chain alkane quaternary ammonium salt solution is 1-10 times, for example 1, 2, 4, 8, 10, and any value within the range between any two of the above values, of the ion exchange capacity of the expanded vermiculite in the expanded vermiculite suspension. For example, taking the expanded vermiculite with an ion exchange capacity (CEC) of 76.86 mmol / 100 g as an example, if the expanded vermiculite in the expanded vermiculite suspension is 2 g, the ion exchange capacity is 2 g*76.86 mmol / 100 g = 1.5372 mmol, and the molar amount of the long-chain alkane quaternary ammonium salt in the long-chain alkane quaternary ammonium salt solution is (1-10 times)*1.5372 mmol.

[0040] In some embodiments of the present application, in step (1), the temperature of the reaction is 50-110℃, for example 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, and any value within the range between any two of the above values, preferably 80-100℃.

[0041] In some embodiments of the present application, the time of the reaction is 0.5-6h, for example 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, and any value within the range between any two of the above values, preferably 4h.

[0042] In some embodiments of the present application, in step (2), the mass ratio of the hydrated salt to the organically modified vermiculite is 1:0.1-1, for example 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, and any value within the range between any two of the above values, preferably 1:0.1-0.2.

[0043] In some embodiments of the present application, the temperature of the vacuum impregnation is 40-80℃, preferably 50℃.

[0044] In some embodiments of the present application, the time of the vacuum impregnation is 1-5h, preferably 2h.

[0045] The third aspect of the present application provides a composite phase change material prepared by the method according to the second aspect.

[0046] The fourth aspect of the present application provides the use of the composite phase change material according to the first aspect or the third aspect in building insulation materials, electric appliance heat dissipation systems, and building thermostatic systems.

[0047] The present application will be described in detail below through examples.

[0048] The following examples and comparative examples are carried out under conventional conditions or the conditions recommended by the manufacturer unless otherwise specified. The reagents or instruments used are conventional products available on the market unless otherwise specified.

[0049] The chemicals used in the following examples and comparative examples are all of analytical purity.

[0050] Expanded vermiculite: CEC is 76.86 mmol / 100g.

[0051] Comparative Example 1

[0052] 10g of sodium sulfate decahydrate and expanded vermiculite are mixed in a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material (FVM).

[0053] Example 1

[0054] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0055] (1) 2g of expanded vermiculite (VM) is weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0056] (2) CTAB (molar mass is 2 times the ion exchange capacity of expanded vermiculite) is weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0057] (3) The quaternary ammonium salt solution is added to the expanded vermiculite suspension under water bath and uniform stirring; after the dropwise addition is completed, the slurry is reacted at 80°C for 4h, and the reaction product is centrifuged and washed 5 times, and then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0058] (4) 10g of sodium sulfate decahydrate and the above prepared organic modified vermiculite are mixed in a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as a carrier (FCVM).

[0059] Figure 1 The XRD spectrum of the organic modified vermiculite (CVM) prepared in Example 1. The characteristic peaks of vermiculite appear in the spectrum, indicating that CVM has a complete layered crystal structure, and from the spectrum it can be seen that the characteristic peaks of organic modified vermiculite (CVM) are shifted to the left compared with expanded vermiculite (VM), indicating that the organic modified vermiculite has a larger interlayer spacing.

[0060] Figure 2 The infrared spectrum of the organic modified vermiculite (CVM) prepared in Example 1. Through the analysis of the characteristic absorption peaks, VM is 3432cm -1A broad and strong absorption peak at 3432 cm"1corresponds to the stretching vibration of -OH in the interlayer of the vermiculite. In addition, a strong absorption peak at 1000-1100 cm -1 corresponds to the Si-O-Si vibration peak, which is a typical feature of the layered silicate tetrahedral structure of vermiculite. In contrast, the intensity of the -OH stretching vibration peak at 3432 cm -1 in the CVM sample is reduced, indicating that the intercalation of the quaternary ammonium salt has changed the interlayer environment of the vermiculite to some extent, possibly affecting the vibration mode of the hydroxyl group through hydrogen bonding. At the same time, new absorption peaks appear at 2900-3000 cm -1 corresponding to the stretching vibration of C-H (-CH2 and -CH3) of the quaternary ammonium salt, further proving the successful intercalation of the quaternary ammonium salt. In addition, C-N or N-H vibration absorption peaks can also be observed near 1500 cm -1 This result is consistent with the increase in interlayer spacing in the XRD test, further verifying the organic modification effect of the quaternary ammonium salt on the vermiculite.

[0061] Figure 3 Scanning electron microscope images of expanded vermiculite (VM) and organic modified vermiculite (CVM) prepared in Example 1 and Mapping image of CVM. The layered structure of the expanded vermiculite is obvious, and the layers are tightly connected. After local magnification, the interlayer space is smaller and the surface is smooth. After modification with quaternary ammonium salt, the layered structure of the vermiculite is still obvious, indicating that the quaternary ammonium salt does not destroy the layered structure of the vermiculite, and there is a waxy quaternary ammonium salt between the layers. The layered surface is no longer smooth and has more quaternary ammonium salt attached. This is because quaternary ammonium salt is a cationic intercalating agent, and the surface of the vermiculite is electronegative due to the presence of hydroxyl groups, which has strong adsorption to cations. It can be clearly seen that the interlayer spacing of the vermiculite after intercalation with quaternary ammonium salt is larger, but the layered structure of the vermiculite is not destroyed. According to the Mapping image, the presence of Br and N elements indicates the presence of quaternary ammonium salt, and the Br and N elements are uniformly distributed on the vermiculite layers, further confirming that the quaternary ammonium salt modified vermiculite is successfully intercalated.

[0062] Figure 4The TG and DTG curves of the composite phase change material (FCVM) prepared in Example 1 show that expanded vermiculite (VM) loses a small amount of mass at around 80°C. This is because vermiculite contains a small amount of crystal water, which is rapidly lost at this temperature. Subsequently, as the temperature rises, the vermiculite's mass remains unchanged. This is because vermiculite is composed of silica sheets and some metal ligand salts, which have good thermal stability. Organically modified vermiculite (CVM) exhibits two significant weight losses. The first, similar to vermiculite, is due to the loss of crystal water. The second weight loss is caused by the carbonization of the quaternary ammonium salt, and its mass no longer changes as the temperature rises. The composite phase change material (FCVM) begins to lose weight at around 50°C and quickly loses most of its mass. This is because sodium sulfate decahydrate begins to melt and evaporates rapidly at this temperature. As the temperature rises, the mass of the composite phase change material changes little. At around 250°C, there is a small decrease in mass, which is caused by the carbonization and loss of quaternary ammonium salt in the modified vermiculite. There is no obvious change in the mass of the material when the temperature continues to rise, indicating that after the sodium sulfate decahydrate and quaternary ammonium salt are lost, the remaining vermiculite is difficult to decompose at this temperature, accounting for about 60% of the total weight.

[0063] Depend on Figure 5 It can be seen that the sodium sulfate decahydrate crystals are obviously rod-shaped and clustered. The sodium sulfate decahydrate crystals in the composite phase change material (FCVM) are attached to the surface of the organic modified vermiculite and appear thorn-like. The enlarged image shows that the sodium sulfate decahydrate crystals exist in the vermiculite layer. The mapping shows that the S and Na elements are evenly distributed, indicating that sodium sulfate is evenly adsorbed on the vermiculite surface and between the layers. At the same time, Figure 5 d clearly shows the presence of vermiculite nanosheets within the sodium sulfate crystal clusters. This is likely due to the vermiculite flakes acting as crystal nuclei, providing heterogeneous nucleation for the sodium sulfate decahydrate, promoting its rapid crystallization and reducing its supercooling and phase separation. This is likely due to the large spacing between the underlying layers of the CVM, which is corroborated by XRD results.

[0064] Figure 6DSC curves of sodium sulfate decahydrate, the composite phase change material (FVM) prepared in Comparative Example 1, and the composite phase change material (FCVM) prepared in Example 1. The results show that the phase change material has a very obvious melting peak and has an obvious phase change process; compared with sodium sulfate decahydrate, the melting enthalpy of FCVM is reduced, which is because the organic modified vermiculite acts as a carrier and nucleating agent and does not provide a phase change function; the FCVM has a higher melting enthalpy, which is possibly because the CVM enhances the adsorption energy of the matrix; the organic matter has a porous structure between and inside the expanded vermiculite layers / gaps, has a high specific surface area and abundant micron-sized pores, and can better adsorb sodium sulfate crystals. The porous vermiculite can better adsorb sodium sulfate in a basic structural unit and form a "net" between the expanded vermiculite layers / gaps, and the sodium sulfate has a double isolation function in the binary pore structure between the vermiculite layers / gaps. At the same time, the nano vermiculite acts as a nucleating agent and has a heterogeneous nucleation function, and the FCVM has a more ideal phase change behavior.

[0065] Figure 7 Cooling curves of sodium sulfate decahydrate, the composite phase change material (FVM) prepared in Comparative Example 1, and the composite phase change material (FCVM) prepared in Example 1. As can be seen from the figure, the sodium sulfate decahydrate reaches the minimum value at 28℃, and then the phase change temperature rises to 32.1℃, and the supercooling degree is 4.1℃; with the addition of the organic modified vermiculite, the phase change temperature is reduced to about 12℃, and the supercooling degree is reduced to 0.5℃, which has an ultra-low supercooling degree, which is consistent with the DSC test.

[0066] Figure 8 Phase separation diagrams of sodium sulfate decahydrate, the composite phase change material (FVM) prepared in Comparative Example 1, and the composite phase change material (FCVM) prepared in Example 1. As can be seen from the figure, the sodium sulfate decahydrate and the FVM have obvious phase separation phenomena, but the phase separation phenomenon of the FVM is inhibited to a certain extent due to the addition of the vermiculite, and the phase separation phenomenon of the FCVM does not occur, which indicates that the FCVM has a good inhibitory effect on the phase separation performance.

[0067] The following examples are analyzed by using the same test method as in Example 1.

[0068] Example 2

[0069] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0070] (1) 2g of expanded vermiculite (VM) is weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0071] (2) DTAB (the molar weight is twice the ion exchange capacity of the expanded vermiculite) is weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0072] (3) Under the water bath and uniform stirring, the quaternary ammonium salt solution was added to the expanded vermiculite suspension; after the dropwise addition was completed, the slurry was reacted at 80°C for 4h, the reaction product was placed in a 60°C oven after 5 times of centrifugation and washing, and dried for 24h to obtain the organic modified vermiculite (CVM);

[0073] (4) 10g of sodium sulfate decahydrate was mixed with the organic modified vermiculite prepared above according to a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material (FCVM) with the organic modified vermiculite as the carrier.

[0074] It was tested that the interlayer spacing of the organic modified vermiculite (CVM) was larger than that of the expanded vermiculite, and the characteristic peak was shifted to the left by 2.4°; at the same time, the TG test showed that the mass of the sample decreased less at the decomposition temperature, so it can be known that the insertion amount of DTAB is less.

[0075] Example 3

[0076] This example is used to illustrate the preparation of a composite phase change material with the organic modified vermiculite as the carrier.

[0077] (1) 2g of expanded vermiculite (VM) was weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0078] (2) OTAB (molar mass is 2 times the ion exchange capacity of the expanded vermiculite) was weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0079] (3) Under the water bath and uniform stirring, the quaternary ammonium salt solution was added to the expanded vermiculite suspension; after the dropwise addition was completed, the slurry was reacted at 80°C for 4h, the reaction product was placed in a 60°C oven after 5 times of centrifugation and washing, and dried for 24h to obtain the organic modified vermiculite (CVM);

[0080] (4) 10g of sodium sulfate decahydrate was mixed with the organic modified vermiculite prepared above according to a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material (FCVM) with the organic modified vermiculite as the carrier.

[0081] It was tested that the interlayer spacing of the organic modified vermiculite (CVM) was larger than that of the expanded vermiculite, and the characteristic peak was shifted to the left by 2.8°; at the same time, the TG test showed that the mass of the sample decreased more at the decomposition temperature, so it can be known that the insertion amount of OTAB is larger.

[0082] Example 4

[0083] This example is used to illustrate the preparation of a composite phase change material with the organic modified vermiculite as the carrier.

[0084] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0085] (2) Take CTAB (molar mass is 4 times the ion exchange capacity of expanded vermiculite), dissolve in 50mL deionized water to obtain a quaternary ammonium salt solution;

[0086] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80°C for 4h, and the reaction product is centrifuged and washed 5 times, then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0087] (4) Mix 10g of sodium sulfate decahydrate with the above prepared organic modified vermiculite according to a mass ratio of 1:0.1, then vacuum impregnate at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0088] Test results show that the interlayer spacing of the organic modified vermiculite (CVM) is larger than that of the expanded vermiculite, and the characteristic peak is shifted to the left by 2.25°; at the same time, TG test shows that the sample mass decreases more at the decomposition temperature, indicating that the amount of CTAB inserted has increased.

[0089] Example 5

[0090] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as the carrier.

[0091] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0092] (2) Take CTAB (molar mass is 8 times the ion exchange capacity of expanded vermiculite), dissolve in 50mL deionized water to obtain a quaternary ammonium salt solution;

[0093] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80°C for 4h, and the reaction product is centrifuged and washed 5 times, then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0094] (4) Mix 10g of sodium sulfate decahydrate with the above prepared organic modified vermiculite according to a mass ratio of 1:0.1, then vacuum impregnate at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0095] Test results show that the interlayer spacing of the organic modified vermiculite (CVM) is larger than that of the expanded vermiculite, and the characteristic peak is shifted to the left by 1.4°; at the same time, TG test shows that the sample mass decreases more at the decomposition temperature, indicating that the amount of CTAB inserted has increased.

[0096] Example 6

[0097] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0098] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0099] (2) Take CTAB (molar mass is twice the ion exchange capacity of expanded vermiculite), dissolve in 50mL deionized water to obtain a quaternary ammonium salt solution;

[0100] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is complete, the slurry is reacted at 90°C for 4h, and the reaction product is centrifuged and washed 5 times and then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0101] (4) Mix 10g of sodium sulfate decahydrate with the above prepared organic modified vermiculite according to a mass ratio of 1:0.1, and then vacuum impregnate at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as a carrier (FCVM).

[0102] The test shows that the interlayer spacing of the organic modified vermiculite (CVM) is larger than that of the expanded vermiculite, and the characteristic peak is shifted to the left by 2.2°; at the same time, the TG test shows that the mass of the sample decreases more at the decomposition temperature, so it can be known that the increase of temperature increases the amount of CTAB insertion.

[0103] Example 7

[0104] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0105] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0106] (2) Take CTAB (molar mass is twice the ion exchange capacity of expanded vermiculite), dissolve in 50mL deionized water to obtain a quaternary ammonium salt solution;

[0107] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is complete, the slurry is reacted at 100°C for 4h, and the reaction product is centrifuged and washed 5 times and then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0108] (4) Mix 10g of sodium sulfate decahydrate with the above prepared organic modified vermiculite according to a mass ratio of 1:0.1, and then vacuum impregnate at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as a carrier (FCVM).

[0109] The interlayer spacing of the organic modified vermiculite (CVM) is larger than that of the expanded vermiculite, and the characteristic peak is shifted to the left by 2.3°. The TG test shows that the mass of the sample decreases more at the decomposition temperature, and thus it can be known that the amount of CTAB inserted is increased.

[0110] Example 8

[0111] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0112] (1) 2g of expanded vermiculite (VM) was weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0113] (2) CTAB (molar weight is 2 times the ion exchange capacity of the expanded vermiculite) was weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0114] (3) The quaternary ammonium salt solution was added to the expanded vermiculite suspension under water bath and uniform stirring; after the dropwise addition was completed, the slurry was reacted at 110°C for 4h, and the reaction product was centrifuged and washed 5 times and then dried in a 60°C oven for 24h to obtain organic modified vermiculite (CVM);

[0115] (4) 10g of sodium sulfate decahydrate was mixed with the above prepared organic modified vermiculite according to a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material with organic modified vermiculite as a carrier (FCVM).

[0116] The interlayer spacing of the organic modified vermiculite (CVM) is larger than that of the expanded vermiculite, and the characteristic peak is shifted to the left by 2.3°, and thus it can be seen that the continued increase in temperature has less effect on the interlayer spacing; at the same time, the TG test shows that the mass of the sample decreases less at the decomposition temperature, and thus it can be known that the amount of CTAB inserted changes little.

[0117] Example 9

[0118] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as a carrier.

[0119] (1) 2g of expanded vermiculite (VM) was weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0120] (2) CTAB (molar weight is 2 times the ion exchange capacity of the expanded vermiculite) was weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0121] (3) Under the water bath and uniform stirring, the quaternary ammonium salt solution was added to the expanded vermiculite suspension; after the dropwise addition was completed, the slurry was reacted at 80°C for 5h, and the reaction product was placed in a 60°C oven for drying for 24h after being centrifuged and washed for 5 times, to obtain the organic modified vermiculite (CVM);

[0122] (4) 10g of sodium sulfate decahydrate was mixed with the organic modified vermiculite prepared above according to a mass ratio of 1:0.1, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material (FCVM) with the organic modified vermiculite as the carrier.

[0123] It was tested that the interlayer spacing of the organic modified vermiculite (CVM) was increased compared with the expanded vermiculite, and the characteristic peak was shifted to the left by 2.05°, from which it could be seen that the influence of the reaction time was smaller; meanwhile, the TG test showed that the mass reduction of the sample was smaller at the decomposition temperature, from which it could be known that the insertion amount of CTAB changed little.

[0124] Example 10

[0125] This example is used to illustrate the preparation of a composite phase change material with the organic modified vermiculite as the carrier.

[0126] (1) 2g of expanded vermiculite (VM) was weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0127] (2) CTAB (the molar weight was 2 times of the ion exchange capacity of the expanded vermiculite) was weighed and dissolved in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0128] (3) Under the water bath and uniform stirring, the quaternary ammonium salt solution was added to the expanded vermiculite suspension; after the dropwise addition was completed, the slurry was reacted at 80°C for 4h, and the reaction product was placed in a 60°C oven for drying for 24h after being centrifuged and washed for 5 times, to obtain the organic modified vermiculite (CVM);

[0129] (4) The sodium sulfate decahydrate and the calcium chloride hexahydrate mixed according to a mass ratio of 1:1.2 were melted at 70°C under water bath stirring for 1h, cooled to room temperature and ground to obtain a composite salt for standby use;

[0130] (5) The composite salt was mixed with the organic modified vermiculite prepared above according to a mass ratio of 1:0.2, and then vacuum impregnated at 50°C for 2h to obtain a composite phase change material (FCVM) with the organic modified vermiculite as the carrier.

[0131] Example 11

[0132] This example is used to illustrate the preparation of a composite phase change material with the organic modified vermiculite as the carrier.

[0133] (1) 2g of expanded vermiculite (VM) was weighed and added to water to prepare a 50mL expanded vermiculite suspension;

[0134] (2) Take CTAB (molar mass is 2 times the ion exchange capacity of expanded vermiculite), dissolved in 50 mL of deionized water to obtain a quaternary ammonium salt solution;

[0135] (3) Under the water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80℃ for 4h, and the reaction product is centrifuged, washed 5 times, and then dried in a 60℃ oven for 24h to obtain organic modified vermiculite (CVM);

[0136] (4) Mix sodium sulfate decahydrate and calcium chloride hexahydrate with a mass ratio of 1:1.4, melt at 70℃ water bath for 1h, cool to room temperature and grind to obtain a composite salt for standby;

[0137] (5) Mix the composite salt with the organic modified vermiculite prepared above according to a mass ratio of 1:0.2, and then vacuum impregnate at 50℃ for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0138] Example 12

[0139] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as the carrier.

[0140] (1) Take 2g of expanded vermiculite (VM), add water to prepare 50mL of expanded vermiculite suspension;

[0141] (2) Take CTAB (molar mass is 2 times the ion exchange capacity of expanded vermiculite), dissolved in 50 mL of deionized water to obtain a quaternary ammonium salt solution;

[0142] (3) Under the water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80℃ for 4h, and the reaction product is centrifuged, washed 5 times, and then dried in a 60℃ oven for 24h to obtain organic modified vermiculite (CVM);

[0143] (4) Mix sodium sulfate decahydrate and calcium chloride hexahydrate with a mass ratio of 1:1.6, melt at 70℃ water bath for 1h, cool to room temperature and grind to obtain a composite salt for standby;

[0144] (5) Mix the composite salt with the organic modified vermiculite prepared above according to a mass ratio of 1:0.2, and then vacuum impregnate at 50℃ for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0145] Example 13

[0146] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as the carrier.

[0147] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0148] (2) Take CTAB (molar mass is twice the ion exchange capacity of expanded vermiculite) and dissolve it in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0149] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80℃ for 4h, and the reaction product is centrifuged and washed 5 times and then dried in a 60℃ oven for 24h to obtain organic modified vermiculite (CVM);

[0150] (4) Mix sodium sulfate decahydrate and calcium chloride hexahydrate with a mass ratio of 1:1.8, melt at 70℃ water bath for 1h, cool to room temperature and grind to obtain a composite salt for standby;

[0151] (5) Mix the composite salt and the organic modified vermiculite prepared above according to a mass ratio of 1:0.2, and then vacuum impregnate at 50℃ for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0152] Example 14

[0153] This example is used to illustrate the preparation of a composite phase change material with organic modified vermiculite as the carrier.

[0154] (1) Take 2g of expanded vermiculite (VM) and add water to prepare a 50mL expanded vermiculite suspension;

[0155] (2) Take CTAB (molar mass is twice the ion exchange capacity of expanded vermiculite) and dissolve it in 50mL of deionized water to obtain a quaternary ammonium salt solution;

[0156] (3) Under water bath and uniform stirring, add the quaternary ammonium salt solution to the expanded vermiculite suspension; after the dropwise addition is completed, the slurry is reacted at 80℃ for 4h, and the reaction product is centrifuged and washed 5 times and then dried in a 60℃ oven for 24h to obtain organic modified vermiculite (CVM);

[0157] (4) Mix sodium sulfate decahydrate and calcium chloride hexahydrate with a mass ratio of 1:2, melt at 70℃ water bath for 1h, cool to room temperature and grind to obtain a composite salt for standby;

[0158] (5) Mix the composite salt and the organic modified vermiculite prepared above according to a mass ratio of 1:0.2, and then vacuum impregnate at 50℃ for 2h to obtain a composite phase change material with organic modified vermiculite as the carrier (FCVM).

[0159] Test Example

[0160] The DSC curves and step cooling curves of the composite phase change materials prepared in Comparative Example 1 and Examples 1-14 were tested respectively to obtain the latent heat values and supercooling degree values of the samples.

[0161] The results are shown in Table 1.

[0162] Table 1

[0163]

[0164]

[0165] As can be seen from the results in Table 1, the organic modified vermiculite has a higher capacity of accommodating hydrated salts due to its excellent narrow space accommodation and heterogeneous nucleation effect of matrix breaking to form micro-nano particles, so that a higher phase change enthalpy value is obtained, and the presence of heterogeneous nucleation makes the supercooling degree of the phase change material have a higher degree of reduction.

[0166] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A composite phase change material, characterized in that: The composite phase change material includes an organic modified vermiculite carrier and a hydrated salt adsorbed on the carrier; Wherein, the organic modified vermiculite is expanded vermiculite modified by intercalation of long-chain alkane quaternary ammonium salt.

2. The composite phase change material according to claim 1, wherein: The number of carbon atoms in the carbon chain of the long-chain alkane quaternary ammonium salt is 12-18; Preferably, the anion in the long-chain alkane quaternary ammonium salt is a halogen anion; Preferably, the long-chain alkane quaternary ammonium salt is at least one selected from the group consisting of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide.

3. The composite phase change material according to claim 1 or 2, wherein: The hydrated salt is selected from at least one of sodium sulfate decahydrate and calcium chloride hexahydrate, preferably sodium sulfate decahydrate or a composite salt of sodium sulfate decahydrate and calcium chloride hexahydrate; Preferably, in the composite salt of sodium sulfate decahydrate and calcium chloride hexahydrate, the mass ratio of sodium sulfate decahydrate to calcium chloride hexahydrate is 1:0.05-2, preferably 1:1.2-2; Preferably, the mass ratio of the hydrated salt to the organically modified vermiculite is 1:0.1-1, preferably 1:0.1-0.

2.

4. A method for preparing a composite phase change material according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) mixing a long-chain alkane quaternary ammonium salt solution with an expanded vermiculite suspension, and reacting the mixture under heating conditions to obtain an organically modified vermiculite; (2) The organic modified vermiculite obtained in step (1) is mixed with hydrated salt and then vacuum impregnated to obtain the composite phase change material.

5. The preparation method according to claim 4, wherein In step (1), the molar amount of the long-chain alkane quaternary ammonium salt in the long-chain alkane quaternary ammonium salt solution is 1-10 times the ion exchange capacity of the expanded vermiculite in the expanded vermiculite suspension.

6. The preparation method according to claim 4 or 5, wherein In step (1), the reaction temperature is 50-110°C, preferably 80-100°C; Preferably, the reaction time is 0.5-6 h, preferably 4 h.

7. The preparation method according to any one of claims 4 to 6, wherein In step (2), the mass ratio of the hydrated salt to the organically modified vermiculite is 1:0.1-1, preferably 1:0.1-0.

2.

8. The preparation method according to any one of claims 4 to 6, wherein The vacuum impregnation temperature is 40-80°C, preferably 50°C; Preferably, the vacuum impregnation time is 1-5 hours, preferably 2 hours.

9. The composite phase change material obtained by the preparation method according to any one of claims 4 to 8.

10. Use of the composite phase change material according to any one of claims 1 to 3 and 9 in building thermal insulation materials, electrical heat dissipation systems and building constant temperature systems.

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