New energy-storage 18 DEG C phase change material and preparation method thereof

Abstract

The invention discloses a novel energy-storage 18-DEG C phase change material and a preparation method thereof, and belongs to the technical field of novel phase change materials. The material is prepared from a modified anhydrous calcium chloride-magnesium nitrate hexahydrate compound, a phase change temperature micro-adjusting agent, nano modified ammonium carbonate, a sodium silicate reinforcing agent, a polymer network structure thickening agent, graphene oxide nanosheets, a low-temperature stabilizer and the like. Stable phase change and high latent heat energy storage capacity near-18 DEG C are achieved, meanwhile, the material has excellent stability and durability and is suitable for various low-temperature energy storage applications, the preparation method is simple and efficient, the steps of ultrasonic dispersion, high-speed shearing, microwave treatment, secondary ultrasonic treatment and the like are adopted, and uniform dispersion and rapid curing of the material are achieved; the material also has good environmental protection performance and sustainability, and is widely applied to a freezer, a freezer car and other places needing cold storage.

Description

Technical Field

[0001] The present invention relates to the technical field of new phase change materials, and more specifically, to a new phase change material for energy storage at -18°C and a preparation method thereof. Background Art

[0002] With the continuous growth of energy demand and the increasing awareness of environmental protection, finding efficient and environmentally friendly energy storage technologies has become a hot topic in current scientific and technological research. As a new type of energy storage technology, phase change energy storage materials have attracted much attention due to their high energy storage density, good stability, and reusability. However, traditional phase change energy storage materials often have problems such as a single phase change temperature, low energy storage efficiency, and poor stability, making it difficult to meet the requirements of practical applications.

[0003] In response to the above problems, researchers have begun to explore and develop new phase change energy storage materials. Among them, phase change energy storage materials based on inorganic salts have gradually become the focus of research due to their abundant raw materials, low cost, and environmental friendliness. However, there are still some problems in the preparation and application of inorganic salt-based phase change energy storage materials, such as difficult regulation of the phase change temperature, low energy storage efficiency, and easy decomposition of the materials. Summary of the Invention

[0004] 1. Technical Problems to be Solved

[0005] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a new phase change material for energy storage at -18°C and a preparation method thereof.

[0006] 2. Technical Solutions

[0007] To solve the above problems, the present invention adopts the following technical solutions.

[0008] The new phase change material for energy storage at -18°C comprises the following components in weight percentages:

[0009] Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 60 - 70%;

[0010] Phase change temperature regulator: 10 - 20%;

[0011] Nano-modified ammonium carbonate: 8 - 15%;

[0012] Sodium silicate enhancer: 2 - 5%;

[0013] Polymer network structure thickener: 3 - 6%;

[0014] Graphene oxide nanosheets: 0.2 - 1%;

[0015] Low-temperature stabilizer: 1 - 3%;

[0016] Environmentally friendly solvent system: the balance.

[0017] As a further improvement of the present invention, the modified anhydrous calcium chloride - magnesium nitrate hexahydrate complex is prepared by mixing anhydrous calcium chloride and magnesium nitrate hexahydrate in a ratio of 1:1 - 1.5 and reacting them by heating to 100°C - 200°C in an inert atmosphere.

[0018] As a further improvement of the present invention, the phase change temperature regulator is a binary or ternary eutectic mixture of sodium chloride, potassium chloride, and barium nitrate.

[0019] As a further improvement of the present invention, the nano - modified ammonium carbonate is double - coated with polyethylene glycol and nano - titanium dioxide.

[0020] As a further improvement of the present invention, the polymer network structure thickener is cross - linked by polyacrylamide, sodium alginate, and nano - cellulose. Polyacrylamide accounts for 30% - 70% of the total amount, sodium alginate accounts for 10% - 40% of the total amount, and nano - cellulose accounts for 5% - 20% of the total amount.

[0021] As a further improvement of the present invention, the low - temperature stabilizer is a complex of polyvinyl alcohol and nano - aluminum oxide, and this complex can effectively inhibit the crystallization behavior of the material at low temperatures and improve the low - temperature stability of the material.

[0022] As a further improvement of the present invention, the environment - friendly solvent system is a mixture of ethanol and ethylene glycol, and its ratio is 7:3 to 9:1.

[0023] A preparation method of the energy - storage phase - change new material at - 18 degrees includes the following steps:

[0024] a. Mix the modified anhydrous calcium chloride - magnesium nitrate hexahydrate complex, the phase change temperature regulator, the nano - modified ammonium carbonate, the sodium silicate enhancer, the polymer network structure thickener, the graphene oxide nanosheets, and the low - temperature stabilizer evenly to form a premix;

[0025] b. Under the protection of an inert gas, slowly add the premix into the environment - friendly solvent system, and at the same time, use ultrasonic dispersion and high - speed shear technology to ensure the uniform dispersion of the components;

[0026] c. Place the dispersion liquid in a microwave - assisted heating reaction kettle for microwave treatment to promote the interaction between components and the evaporation of the solvent;

[0027] d. Slowly cool the treated dispersion liquid to room temperature under vacuum conditions, and then cool it to around - 18°C through a precise temperature control system, and perform secondary ultrasonic treatment to eliminate internal stress, obtaining the energy - storage phase - change material at - 18°C.

[0028] As a further improvement of the present invention, in step b, the frequency of ultrasonic dispersion is 20 - 40 kHz, and the rotational speed of the high-speed shearing machine is 3000 - 5000 rpm;

[0029] In step c, the power of microwave treatment is 400 - 600 W, and the treatment time is 15 - 25 minutes;

[0030] In step d, the frequency of secondary ultrasonic treatment is 25 - 35 kHz, and the treatment time is 5 - 10 minutes to ensure the uniformity and stability of the internal structure of the material.

[0031] As a further improvement of the present invention, the low-temperature stabilizer is modified before being added. The specific steps include:

[0032] S1. Dissolve PVA in deionized water and heat it until completely dissolved to form a uniform PVA solution. The dissolution temperature is usually between 80°C and 90°C to ensure the complete dissolution of PVA;

[0033] S2. Disperse nano-aluminum oxide in the PVA solution and make it uniformly dispersed by ultrasonic or stirring. The content of nano-aluminum oxide is between 5% and 20% of the mass of PVA;

[0034] S3. Add the modifier ethylene glycol and the catalyst p-toluenesulfonic acid to the PVA solution and stir evenly. The dosage of the modifier is between 5% and 15% of the mass of PVA, and the dosage of the catalyst is between 0.1% and 1% of the mass of PVA;

[0035] S4. Heat the mixed solution to the reaction temperature, usually between 90 and 120°C, to accelerate the esterification reaction. The reaction time is 2 - 6 hours. During the reaction process, continuously stir the solution to ensure the uniform progress of the reaction;

[0036] S5. After the reaction is completed, cool the solution to room temperature. Then, remove the unreacted catalyst and by-products through methods such as neutralization, filtration or centrifugation. Dry the obtained modified PVA and nano-aluminum oxide composite, such as vacuum drying or oven drying, to remove the solvent and moisture.

[0037] 3. Beneficial effects

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] (1) The energy storage new phase change material at -18°C provided by the present invention realizes stable phase change near -18°C through the carefully designed component ratio and preparation process, has high latent heat energy storage capacity, can effectively store and release energy, and is applicable to various low-temperature energy storage applications.

[0040] (2) By introducing phase change temperature regulators, such as binary or ternary eutectic mixtures of sodium chloride, potassium chloride, and barium nitrate, the phase change temperature of the material can be adjusted according to specific requirements, making it more flexible to adapt to different application scenarios.

[0041] (3) The addition of nano-modified ammonium carbonate, sodium silicate enhancer, and polymer network structure thickener significantly improves the stability and durability of the material, enabling it to maintain excellent performance after multiple phase change cycles.

[0042] (4) Using the composite of polyvinyl alcohol and nano-aluminum oxide as a low-temperature stabilizer effectively inhibits the crystallization behavior of the material at low temperatures, improves the low-temperature stability of the material, and ensures its reliability in extremely low-temperature environments. Description of the Drawings

[0043] Figure 1 It is the preparation flow chart of the new energy storage -18 °C phase change material of the present invention;

[0044] Figure 2 It is the performance characterization diagram of Examples 1-5 of the present invention. Detailed Embodiments

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] Example 1

[0047] Component ratio:

[0048] Modified anhydrous calcium chloride - magnesium nitrate hexahydrate composite: 65%

[0049] Phase change temperature regulator (binary eutectic mixture of sodium chloride and potassium chloride): 15%

[0050] Nano-modified ammonium carbonate (double-coated with polyethylene glycol and nano-titanium dioxide): 12%

[0051] Sodium silicate enhancer: 3%

[0052] Polymer network structure thickener (polyacrylamide: sodium alginate: nano-cellulose = 50%: 25%: 25%): 4%

[0053] Graphene oxide nanosheets: 0.5%

[0054] Low-temperature stabilizer (composite of modified polyvinyl alcohol and nano-aluminum oxide): 2%

[0055] Environmentally friendly solvent system (ethanol: ethylene glycol = 8:2): the balance

[0056] Preparation method:

[0057] Mix each component according to the above ratio to form a premix.

[0058] Under nitrogen protection, slowly add the premix to the environmentally friendly solvent system. The ultrasonic dispersion frequency is 30 kHz, and the high-speed shearer speed is 4000 rpm.

[0059] The microwave treatment power is 500 W, and the treatment time is 20 minutes.

[0060] Slowly cool to room temperature under vacuum conditions, and then cool to -18 °C through a precision temperature control system for secondary ultrasonic treatment. The frequency is 30 kHz, and the treatment time is 7 minutes.

[0061] Low-temperature stabilizer modification:

[0062] PVA dissolution temperature: 85 °C

[0063] Content of nano-aluminum oxide: 10% of the mass of PVA

[0064] Dosage of ethylene glycol: 10% of the mass of PVA

[0065] Dosage of toluenesulfonic acid: 0.5% of the mass of PVA

[0066] Reaction temperature: 100 °C

[0067] Reaction time: 4 hours

[0068] Example 2

[0069] Component ratio:

[0070] Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 70%

[0071] Phase change temperature regulator (binary eutectic mixture of potassium chloride and barium nitrate): 10%

[0072] Nano-modified ammonium carbonate: 8%

[0073] Sodium silicate enhancer: 4%

[0074] Polymer network structure thickener (polyacrylamide: sodium alginate: nano-cellulose = 70%: 15%: 15%): 3%

[0075] Graphene oxide nanosheets: 0.2%

[0076] Low-temperature stabilizer: 1%

[0077] Environmentally friendly solvent system (ethanol: ethylene glycol = 7:3): the balance

[0078] The preparation method is similar to that of Example 1, but the ultrasonic dispersion frequency is adjusted to 25 kHz, the rotational speed of the high-speed shearing machine is 3500 rpm, the microwave treatment time is 25 minutes, and the secondary ultrasonic treatment time is 5 minutes.

[0079] Low-temperature stabilizer modification:

[0080] PVA dissolution temperature: 90 °C

[0081] Content of nano-aluminum oxide: 5% of the mass of PVA

[0082] Dosage of ethylene glycol: 5% of the mass of PVA

[0083] Dosage of toluenesulfonic acid: 0.1% of the mass of PVA

[0084] Reaction temperature: 120 °C

[0085] Reaction time: 2 hours

[0086] Example 3

[0087] Component ratio:

[0088] Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 60%

[0089] Phase change temperature regulator (ternary eutectic mixture of sodium chloride, potassium chloride and barium nitrate): 20%

[0090] Nano-modified ammonium carbonate: 15%

[0091] Sodium silicate enhancer: 2%

[0092] Polymer network structure thickener (polyacrylamide: sodium alginate: nano-cellulose = 30%: 40%: 30%): 5%

[0093] Graphene oxide nanosheets: 1%

[0094] Low-temperature stabilizer: 3%

[0095] Environmentally friendly solvent system (ethanol: ethylene glycol = 9:1): the balance

[0096] The preparation method is similar to that of Example 1, but the ultrasonic dispersion frequency is adjusted to 40 kHz, the rotational speed of the high-speed shearing machine is 5000 rpm, the microwave treatment power is 400 W, the treatment time is 15 minutes, and the secondary ultrasonic treatment time is 10 minutes.

[0097] Low-temperature stabilizer modification:

[0098] PVA dissolution temperature: 80 °C

[0099] Content of nano-aluminum oxide: 20% of the mass of PVA

[0100] Dosage of ethylene glycol: 15% of the mass of PVA

[0101] Dosage of p-toluenesulfonic acid: 1% of the mass of PVA

[0102] Reaction temperature: 95 °C

[0103] Reaction time: 6 hours

[0104] Example 4

[0105] Component ratio is similar to that of Example 1, but adjusted as follows:

[0106] Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 63%

[0107] Phase change temperature regulator (only sodium chloride): 18%

[0108] Nano-modified ammonium carbonate: 14%

[0109] Polymer network structure thickener (polyacrylamide:sodium alginate = 60%:40%): 5% (without nano-cellulose)

[0110] Graphene oxide nanosheets: 0.7%

[0111] Preparation method is similar to that of Example 1, but adjust the microwave treatment power to 600 W and the treatment time to 18 minutes.

[0112] Low-temperature stabilizer modification:

[0113] The same as Example 1.

[0114] Example 5

[0115] Component ratio:

[0116] Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 68%

[0117] Phase change temperature regulator (binary eutectic mixture of potassium chloride and barium nitrate, but the ratio is 1:1): 12%

[0118] Nano-modified ammonium carbonate: 10%

[0119] Sodium silicate enhancer: 3.5%

[0120] Polymer network structure thickener (polyacrylamide:sodium alginate:nano-cellulose = 40%:30%:30%): 4.5%

[0121] Graphene oxide nanosheets: 0.5%

[0122] Low-temperature stabilizer: 2.5%

[0123] Environmentally friendly solvent system (ethanol: ethylene glycol = 8.5:1.5): the balance

[0124] The preparation method is similar to that of Example 1, but the ultrasonic dispersion frequency is adjusted to 28 kHz, the rotation speed of the high-speed shearer is 4500 rpm, the microwave treatment time is 22 minutes, and the secondary ultrasonic treatment time is 8 minutes.

[0125] Modification of low-temperature stabilizer:

[0126] Similar to Example 2, but the dosage of ethylene glycol is adjusted to 12% of the mass of PVA, and the reaction time is 3 hours.

[0127] Please refer to Figure 2 , performance characterization description:

[0128] Phase change temperature (°C):

[0129] The phase change temperatures of all examples are controlled near -18°C, meeting the design requirements of the energy storage -18°C phase change material.

[0130] The fluctuation range of the phase change temperature is small (within ±0.3°C), indicating that the phase change behavior of the material is stable.

[0131] Latent heat (J / g):

[0132] The latent heat values are between 110 and 130 J / g, indicating that the material can store and release more heat during the phase change process.

[0133] The level of the latent heat value is related to the content of the phase change substances in the material and their interactions.

[0134] Thermal conductivity (W / m·K):

[0135] The thermal conductivity is between 0.48 and 0.60 W / m·K. Although relatively low, it is suitable for certain specific energy storage applications.

[0136] The addition of the polymer network structure thickener and graphene oxide nanosheets helps to improve the thermal conductivity of the material.

[0137] Cycle stability (times):

[0138] The cycle stabilities all exceed 400 times, indicating that the material can still maintain good performance after multiple phase change cycles.

[0139] The polymer network structure thickener and sodium silicate enhancer help to enhance the cycle stability of the material.

[0140] Supercooling degree (°C):

[0141] The degree of supercooling is relatively low, between 1.2 and 2.5 °C, which helps the material to quickly enter the phase change state when needed.

[0142] The addition of a phase change temperature regulator and a low-temperature stabilizer helps to reduce the degree of supercooling.

[0143] Low-temperature stability (°C):

[0144] The low-temperature stability test shows that the material has no crystallization behavior in the range of -25 °C to room temperature, meeting the requirements of low-temperature applications.

[0145] The addition of a low-temperature stabilizer (a composite of modified polyvinyl alcohol and nano-aluminum oxide) significantly improves the low-temperature stability of the material.

[0146] Summary

[0147] The above data show that the prepared energy storage phase change material at -18 °C has a stable phase change temperature, a high latent heat value, good cycle stability and low-temperature stability, and a moderate thermal conductivity. These performance characteristics make the material have potential application value in the field of low-temperature energy storage.

[0148] The above is only a preferred specific embodiment of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its improved concept, makes an equivalent substitution or change, and should be covered by the protection scope of the present invention.

Claims

1. Energy storage -18 degree phase change new material, characterized by: Contains the following components in weight percentage: Modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex: 60-70%; Phase change temperature fine-tuning agent: 10-20%; Nano-modified ammonium carbonate: 8-15%; Sodium silicate enhancer: 2-5%; Polymer network structure thickener: 3-6%; Graphene oxide nanosheets: 0.2-1%; Low temperature stabilizer: 1-3%; Environmentally friendly solvent system: balance.

2. The new energy storage -18 degree phase change material according to claim 1 is characterized in that: The modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex is prepared by mixing anhydrous calcium chloride and magnesium nitrate hexahydrate in a ratio of 1:1-1.5, and heating the mixture to 100°C-200°C in an inert atmosphere for reaction.

3. The new energy storage -18 degree phase change material and preparation method according to claim 1 are characterized in that: The phase change temperature fine-tuning agent is a binary or ternary eutectic mixture of sodium chloride, potassium chloride and barium nitrate.

4. The new energy storage -18 degree phase change material according to claim 1 is characterized in that: The nano modified ammonium carbonate is double coated with polyethylene glycol and nano titanium dioxide.

5. The new energy storage -18 degree phase change material according to claim 1 is characterized in that: The polymer network structure thickener is formed by cross-linking polyacrylamide, sodium alginate and nanocellulose, wherein the polyacrylamide accounts for 30%-70% of the total amount, the sodium alginate accounts for 10%-40% of the total amount, and the nanocellulose accounts for 5%-20% of the total amount.

6. The new energy storage -18 degree phase change material according to claim 1 is characterized in that: The low-temperature stabilizer is a composite of polyvinyl alcohol and nano-alumina, which can effectively inhibit the crystallization behavior of the material at low temperatures and improve the low-temperature stability of the material.

7. The new energy storage -18 degree phase change material according to claim 1 is characterized in that: The environmentally friendly solvent system is a mixture of ethanol and ethylene glycol, with a ratio of 7:3 to 9:

1.

8. The method for preparing the new energy storage -18 degree phase change material as claimed in claim 1, characterized in that: The following steps are involved: a. The modified anhydrous calcium chloride-magnesium nitrate hexahydrate complex, the phase change temperature fine-tuning agent, the nano-modified ammonium carbonate, the sodium silicate enhancer, the polymer network structure thickener, the graphene oxide nanosheets and the low-temperature stabilizer are mixed uniformly to form a premix; b. Under the protection of inert gas, slowly add the premix into the environmentally friendly solvent system, and use ultrasonic dispersion and high-speed shearing technology to ensure uniform dispersion of the components; c. placing the dispersion in a microwave-assisted heating reactor and subjecting it to microwave treatment to promote interaction between components and evaporation of the solvent; d. The treated dispersion is slowly cooled to room temperature under vacuum conditions, and then cooled to around -18°C through a precision temperature control system, and subjected to secondary ultrasonic treatment to eliminate internal stress to obtain an energy storage -18°C phase change material.

9. The preparation method according to claim 8, characterized in that: In step b, the frequency of ultrasonic dispersion is 20-40kHz, and the speed of the high-speed shearing machine is 3000-5000rpm; In step c, the power of the microwave treatment is 400-600 W, and the treatment time is 15-25 minutes; In step d, the frequency of the secondary ultrasonic treatment is 25-35 kHz and the treatment time is 5-10 minutes to ensure the uniformity and stability of the internal structure of the material.

10. The preparation method according to claim 8, characterized in that: The low temperature stabilizer is modified before being added, and the specific steps include: S1. Dissolve PVA in deionized water and heat until completely dissolved to form a uniform PVA solution. The dissolution temperature is usually between 80°C and 90°C to ensure complete dissolution of PVA. S2. Dispersing the nano-alumina in the PVA solution, uniformly dispersing the nano-alumina by ultrasound or stirring, wherein the content of the nano-alumina is between 5% and 20% of the mass of the PVA; S3. The modifier ethylene glycol and the catalyst toluenesulfonic acid are added to the PVA solution and stirred evenly. The amount of the modifier is between 5% and 15% by mass of the PVA, and the amount of the catalyst is between 0.1% and 1% by mass of the PVA; S4. The mixed solution is heated to a reaction temperature, usually between 90-120° C., to accelerate the esterification reaction. The reaction time is 2-6 hours. During the reaction, the solution is continuously stirred to ensure uniform reaction. S5. After the reaction is completed, the solution is cooled to room temperature, and then the unreacted catalyst and by-products are removed by neutralization, filtration or centrifugation, and the obtained modified PVA and nano-alumina composite is dried, such as vacuum drying or oven drying, to remove the solvent and moisture.

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