Preparation method of gas-liquid phase change material based on fluorine synthesis

Abstract

The invention provides a preparation method of a gas-liquid phase change material based on fluorine synthesis. A fluorine-based phase change matrix, a fluorine-based modifier, a nucleating agent, a stabilizer and an interface aid are respectively subjected to purification and impurity removal treatment; adding the pretreated fluorine-based phase-change matrix into a polytetrafluoroethylene-lined high-pressure reaction kettle, dropwise adding a fluorine-based modifier, and carrying out heat preservation reaction to obtain a fluorine-based precursor mixed solution; adding a pretreated nucleating agent into the fluorine-based precursor mixed solution, carrying out ultrasonic dispersion, sequentially adding a stabilizer and an interface additive, stirring and mixing, and carrying out high-pressure homogenization treatment to refine particles; carrying out temperature gradient circulation regulation and control on the gas-liquid blending system, and then carrying out vacuum degassing and precise filtration to obtain the fluorine-based gas-liquid phase change material. And obtaining the finished gas-liquid phase change material after the stability test is qualified. The high-performance fluorine-based gas-liquid phase change material is efficiently prepared through accurate raw material pretreatment, reasonable component proportion and scientific process regulation and control, and meanwhile the problems of equipment corrosion and environmental protection in the production process are solved.

Description

Technical Field

[0001] This invention belongs to the field of phase change material preparation technology, specifically relating to a method for preparing gas-liquid phase change materials based on fluorine synthesis. Background Technology

[0002] Phase change materials (PCMs) are materials capable of absorbing or releasing a large amount of latent heat through a phase change process within a specific temperature range. Among them, gas-liquid PCMs have significant application value in thermal management and energy storage due to their high latent heat of phase change and rapid temperature response. With the increasing integration of electronic devices, the expansion of energy storage system capacity, and the development of aerospace technology, higher requirements are placed on the chemical stability, extreme temperature resistance, and cycle life of PCMs. Fluorine-based materials, due to their excellent chemical inertness, low surface energy, high temperature resistance, and good dielectric properties, have become ideal matrices for preparing high-performance PCMs. In existing technologies, the preparation of fluorine-based gas-liquid PCMs often uses a single fluoride as the matrix, which suffers from problems such as low latent heat of phase change (typically <150 J / g), large supercooling (>5℃), and easy phase separation during the phase change process, seriously affecting their application performance. At the same time, existing preparation processes often suffer from defects such as poor component compatibility, uneven dispersion, and low controllability of process parameters, making it difficult to achieve large-scale production. For example, some schemes use direct mixing to prepare fluorine-based phase change materials without precise pretreatment of raw materials, which leads to the introduction of impurities that affect the consistency of phase change; some schemes lack effective means of phase structure control, resulting in poor material cycling stability and significant performance degradation after multiple phase changes.

[0003] Furthermore, existing processes for preparing fluorine-based phase change materials suffer from significant equipment corrosion issues, and improper treatment of fluoride-containing wastewater can easily cause environmental pollution, further limiting their industrial application. Therefore, developing a synthetic fluorine-based gas-liquid phase change material preparation method that can enhance latent heat of phase change, reduce supercooling, improve cycle stability, and is process-controllable and environmentally friendly has become a pressing technical challenge in this field. Summary of the Invention

[0004] This invention provides a method for preparing fluorine-based gas-liquid phase change materials, addressing the problems of low latent heat of phase change, large supercooling, poor cycle stability, complex preparation processes, severe equipment corrosion, and high environmental pollution risks in existing fluorine-based gas-liquid phase change materials. Through precise raw material pretreatment, reasonable component ratio, and scientific process control, this method achieves efficient preparation of high-performance fluorine-based gas-liquid phase change materials, while simultaneously solving equipment corrosion and environmental protection problems in the production process.

[0005] According to a first aspect of the present invention, one or more embodiments of this application provide a method for preparing a gas-liquid phase change material based on fluorine synthesis, comprising the following steps: Step 1: Raw material pretreatment. The fluorine-based phase change matrix, fluorine-based modifier, nucleating agent, stabilizer and interface additive are purified and impurity removed to ensure that the purity and moisture content of each raw material meet the process requirements. Step 2: Synthesis of fluorine-based precursors. The pretreated fluorine-based phase change matrix is ​​added to a polytetrafluoroethylene-lined high-pressure reactor. After heating and stirring, a fluorine-based modifier is slowly added dropwise, and the reaction is maintained at the temperature to obtain a fluorine-based precursor mixture. Step 3: Gas-liquid blend phase structure control. Pretreated nucleating agent is added to fluorine-based precursor mixture. After ultrasonic dispersion, stabilizer and interfacial additive are added in sequence. After stirring and mixing, the particles are refined by high-pressure homogenization to form a gas-liquid blend system. Step 4: Phase change performance optimization. The gas-liquid blend system is subjected to temperature gradient cycling control, followed by vacuum degassing and precision filtration to obtain fluorine-based gas-liquid phase change material. Step 5, post-encapsulation processing: In a clean environment, the fluorine-based gas-liquid phase change material is poured into a fluorine-resistant sealed container, protected with nitrogen, and then subjected to a static stability test. If the test is successful, the gas-liquid phase change material is the finished product.

[0006] According to the above-described technical solution of the present invention, the following improvements can also be made: Preferably, in step one, the pretreatment of the fluorine-based phase change matrix is ​​performed by vacuum distillation at a vacuum degree of -0.095 MPa, a temperature of 40-50°C, and a distillation time of 30 min, ensuring a moisture content of ≤0.05%. The fluorine-based phase change matrix is ​​a mixture of hydrofluoroether and perfluoropolyether in a mass ratio of 70:15, with a hydrofluoroether purity of ≥99.9% and a perfluoropolyether purity of ≥99.5%.

[0007] Preferably, the fluorine-based modifier in step one is perfluorooctyltriethoxysilane with a purity ≥98%; its pretreatment steps are as follows: add deionized water and mix at a mass ratio of 1:10, stir at 30°C for 1 hour for hydrolysis, let stand for separation and take the upper organic phase, dry with anhydrous sodium sulfate for 2 hours and filter for later use.

[0008] Preferably, the nucleating agent is fluorinated graphene with a purity ≥99%. The pretreatment involves ultrasonic cleaning at 300W power for 30 min, centrifugation at 8000r / min for 10 min, and vacuum drying at 60℃ for 2 h.

[0009] Preferably, in step one, the stabilizer is perfluoroalkyl betaine with a purity ≥99%, and the interface aid is a fluorocarbon surfactant with a purity ≥99%; the stabilizer and interface aid are obtained by filtering through a 0.22μm polytetrafluoroethylene filter.

[0010] Preferably, the reaction conditions in step two are as follows: heating to 35°C, stirring at 500 r / min, mixing for 15 min; dropping the fluorine-based modifier at 5 mL / min, heating to 50°C after the addition is complete, and maintaining the temperature for 1 h; the purity of the fluorine-based precursor is ≥99% as determined by gas chromatography.

[0011] Preferably, in step three, the mass ratio of the fluorinated precursor mixture, fluorinated graphene, perfluoroalkyl betaine, and fluorocarbon surfactant is as follows: 85% fluorinated precursor mixture, 5% fluorinated graphene, 3% perfluoroalkyl betaine, 2% fluorocarbon surfactant, with the remainder being a composite additive composed of 3% oxidant and 2% metal passivator; ultrasonic dispersion power is 500W for 20 minutes to ensure that the fluorinated graphene particle size is ≤5μm; stirring temperature is 40℃, speed is 800r / min, and mixing time is 30 minutes; high-pressure homogenization pressure is 30-40MPa, and the process is repeated twice.

[0012] Preferably, the temperature gradient control parameters in step four are: heating to 80℃ at a rate of 2℃ / min, holding at that temperature for 1 hour, and then cooling to -20℃ at a rate of 1℃ / min, repeated 3 times; the vacuum degassing conditions are a vacuum of -0.098MPa, a temperature of 30℃, and a time of 20min; the precision filtration adopts a three-stage filtration system with filter element accuracies of 5μm, 1μm, and 0.22μm respectively.

[0013] Preferably, the clean environment in step five is Class 10000, the sealed container is made of polytetrafluoroethylene or FEP, and the nitrogen purity is ≥99.99%; the stability test conditions are: standing in a 50℃ constant temperature chamber for 48 hours, and no stratification or precipitation is acceptable.

[0014] Preferably, the feature is that all equipment that comes into contact with materials during the production process is made of fluorine-resistant materials, including polytetrafluoroethylene, FEP, or nickel-based alloys.

[0015] The beneficial effects of this invention are as follows: This invention provides a method for preparing gas-liquid phase change materials based on fluorine synthesis. Compared with the prior art, the method for preparing gas-liquid phase change materials based on fluorine synthesis of this invention has the following beneficial effects: 1. Excellent product performance: This invention, through the rational selection and optimization of fluorine-based phase change matrix and the introduction of special fluorine-based modifier and fluorinated graphene nucleating agent, combined with temperature gradient control process, prepares fluorine-based gas-liquid phase change materials with a latent heat of phase change ≥180J / g, which is more than 20% higher than existing products; supercooling ≤2℃, effectively solving the phase change hysteresis problem; mass loss ≤2% after holding at 200℃ for 100h, significantly improving cycle stability and extending service life.

[0016] 2. Strong process controllability: This invention performs precise pretreatment of each raw material, clarifies the key parameters of each process step, and ensures product uniformity through high-pressure homogenization, three-stage filtration and other means. The process has good repeatability and is suitable for large-scale industrial production.

[0017] 3. Equipment and environmental friendliness: The production process uses equipment made of fluorine-resistant materials, which avoids corrosion of the equipment by fluorides; fluorine-containing wastewater is treated in a special way to meet the discharge standards, and fluorine-based raw materials in the waste can be recycled, which reduces production costs and environmental pollution risks and meets the requirements of green production.

[0018] 4. Wide range of applications: The phase change material prepared by this invention has a wide temperature range (-20℃~280℃) and excellent chemical stability and dielectric properties. It can be widely used in many fields such as heat dissipation of electronic equipment, solar thermal energy storage, and heat dissipation of aerospace satellite battery packs, and has broad application prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process according to an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0021] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in one or more embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Example like Figure 1 As shown in one or more embodiments of this application, a method for preparing a gas-liquid phase change material based on fluorine synthesis is described. The gas-liquid phase change material in these embodiments refers to a material that utilizes the latent heat of phase change during the transformation between liquid and gaseous phases to achieve efficient heat storage, transfer, or temperature control, while maintaining a constant material temperature during the phase change process. The method includes the following steps: Step 1: Raw material pretreatment. The fluorine-based phase change matrix, fluorine-based modifier, nucleating agent, stabilizer, and interface additives are purified and impurity removed to ensure that the purity and moisture content of each raw material meet the process requirements. Specifically, the fluorine-based phase change matrix is ​​pretreated using vacuum distillation at a vacuum of -0.095 MPa, a temperature of 40-50℃, and a distillation time of 30 min, ensuring a moisture content ≤0.05%. The fluorine-based phase change matrix is ​​a mixture of hydrofluoroether and perfluoropolyether at a mass ratio of 70:15, with hydrofluoroether purity ≥99.9% and perfluoropolyether purity ≥99.5%. The fluorine-based modifier is perfluorooctyltriethoxysilane with a purity ≥98%. Its pretreatment steps are as follows: deionized water is added at a mass ratio of 1:10, and the mixture is stirred at 30℃ for 1 h for hydrolysis. After standing and separating into layers, the upper organic phase is collected, dried with anhydrous sodium sulfate for 2 h, and then filtered for later use. The nucleating agent is fluorinated graphene with a purity ≥99%. Pretreatment involves ultrasonic cleaning at 300W for 30 min, centrifugation at 8000 r / min for 10 min, and vacuum drying at 60℃ for 2 h. The stabilizer is perfluoroalkyl betaine with a purity ≥99%, and the interface aid is a fluorocarbon surfactant with a purity ≥99%. Both the stabilizer and interface aid are obtained by filtration through a 0.22 μm polytetrafluoroethylene filter.

[0023] Step 2: Synthesis of fluorine-based precursors. The pretreated fluorine-based phase change matrix was added to a polytetrafluoroethylene-lined high-pressure reactor. After heating and stirring, the fluorine-based modifier was slowly added dropwise, and the reaction was maintained at the specified temperature to obtain a fluorine-based precursor mixture. The reaction conditions were: heating to 35℃, stirring rate 500 r / min, mixing for 15 min; fluorine-based modifier dropping rate 5 mL / min, after which the temperature was raised to 50℃ and the reaction was maintained at the specified temperature for 1 h; the purity of the fluorine-based precursor was detected by gas chromatography ≥99%.

[0024] Step 3: Gas-liquid blend structure control. Pretreated nucleating agents are added to the fluorinated precursor mixture. After ultrasonic dispersion, stabilizers and interfacial additives are added sequentially. After stirring and mixing, the particles are refined through high-pressure homogenization to form a gas-liquid blend system. The mass ratio of the fluorinated precursor mixture, fluorinated graphene, perfluoroalkyl betaine, and fluorocarbon surfactant is: 85% fluorinated precursor mixture, 5% fluorinated graphene, 3% perfluoroalkyl betaine, 2% fluorocarbon surfactant, with the remainder being a composite additive composed of 3% oxidant and 2% metal passivator. Ultrasonic dispersion power is 500W for 20 minutes to ensure the fluorinated graphene particle size is ≤5μm. Stirring temperature is 40℃, speed is 800r / min, and mixing time is 30 minutes. High-pressure homogenization pressure is 30-40MPa, and the process is repeated twice.

[0025] Step 4: Phase change performance optimization. The gas-liquid blend system is subjected to temperature gradient cyclic control, followed by vacuum degassing and precision filtration to obtain fluorine-based gas-liquid phase change material. The temperature gradient control parameters are: heating to 80℃ at a rate of 2℃ / min, holding for 1h, and then cooling to -20℃ at a rate of 1℃ / min, repeated 3 times. The vacuum degassing conditions are: vacuum degree -0.098MPa, temperature 30℃, and time 20min. The precision filtration adopts a three-stage filtration system with filter element accuracies of 5μm, 1μm, and 0.22μm respectively.

[0026] Step 5: Post-encapsulation processing. In a clean environment, the fluorine-based gas-liquid phase change material is poured into a fluorine-resistant sealed container. After nitrogen protection, a stability test is conducted. If the stability test is successful, the material is the finished gas-liquid phase change material. The clean environment is Class 10000, the sealed container is made of polytetrafluoroethylene (PTFE) or FEP, and the nitrogen purity is ≥99.99%. The stability test conditions are: standing in a 50℃ constant temperature chamber for 48 hours; no stratification or precipitation indicates success.

[0027] In addition, all equipment that comes into contact with materials during the production process is made of fluorine-resistant materials, including polytetrafluoroethylene, FEP, or nickel-based alloys.

[0028] To further illustrate the point through examples, the following examples are provided: Example 1 Raw material pretreatment: (1) Select 70 kg of 99.9% pure hydrofluoroether (HFE-7100) and 15 kg of 99.5% pure perfluoropolyether (PFPE), add them to a vacuum distillation apparatus, set the vacuum degree to -0.095 MPa and the temperature to 45℃, distill for 30 min, collect the fraction, and test the water content to be 0.03%, and set aside for later use.

[0029] (2) Select 10 kg of perfluorooctyltriethoxysilane (PFOTS) with a purity of 98%, add 100 kg of deionized water, stir at 30°C for 1 h to hydrolyze, let stand and separate into layers, take the upper organic phase, add 5 kg of anhydrous sodium sulfate and dry for 2 h, filter and set aside.

[0030] (3) Select 5 kg of fluorinated graphene (FG) with a purity of 99%, add 50 kg of anhydrous ethanol, ultrasonically clean for 30 min at 300 W, centrifuge at 8000 r / min for 10 min, take the precipitate and dry it in a vacuum drying oven at 60℃ for 2 h for later use.

[0031] (4) Select 3 kg of perfluoroalkyl betaine with a purity of 99% and 2 kg of fluorocarbon surfactant, filter them through a 0.22 μm polytetrafluoroethylene filter, and 3 kg of oxidant and 2 kg of metal passivator for later use.

[0032] In the embodiments, the oxidant can be a perfluorotertiary amine oxide, which possesses extremely strong chemical stability and inertness, and exhibits excellent compatibility with fluorocarbon systems. These compounds can gently scavenge trace amounts of free radicals that may be present in the system, preventing chain degradation reactions of the fluoropolymer during high temperatures or long-term storage, thereby maintaining the thermal stability of the phase change material. Their perfluorinated structure also ensures that no incompatible impurities are introduced.

[0033] Metal passivating agents can be fluorozirconates, which react on metal surfaces (such as stainless steel and nickel-based alloys) to form a dense, strongly adhering zirconium fluoride (ZrF4) or zirconium oxide passivation film. This film effectively blocks corrosive fluoride ions from contacting the base metal, significantly improving the equipment's corrosion resistance. This aligns with the document's emphasis on using fluorine-resistant materials for equipment.

[0034] In this technical solution, the oxidant and the metal passivator play a synergistic protective role. The oxidant focuses on stabilizing the material itself chemically, preventing its internal aging. The metal passivator focuses on protecting the production equipment and storage containers, ensuring the reliability of the production process and the purity of the product.

[0035] Synthesis of fluorine-based precursors: Pretreated hydrofluoroether and perfluoropolyether were added to a 100L polytetrafluoroethylene-lined high-pressure reactor and stirred at 35℃ and 500r / min for 15min. Perfluorooctyltriethoxysilane was added dropwise at a rate of 5mL / min. After the addition was completed, the temperature was raised to 50℃ and the reaction was maintained for 1h. The purity of the precursor was 99.2% as determined by gas chromatography, which met the requirements.

[0036] Gas-liquid mixed phase structure control: Pretreated fluorinated graphene was added to the reactor and ultrasonically dispersed at 500W for 20min; perfluoroalkyl betaine and fluorocarbon surfactant were added and stirred at 40℃ and 800r / min for 30min; the mixture was passed into a high-pressure homogenizer and circulated twice under a pressure of 35MPa.

[0037] Phase change performance optimization: The homogenized mixture was transferred to a programmable temperature control chamber, heated to 80℃ at 2℃ / min and held for 1 hour, then cooled to -20℃ at 1℃ / min and held for 1 hour, and the cycle was repeated 3 times; it was then transferred to a vacuum degassing tank and degassed at -0.098MPa and 30℃ for 20 minutes; the phase change material was obtained by passing it through a three-stage filtration system of 5μm→1μm→0.22μm.

[0038] Post-packaging processing: In a Class 10000 cleanroom, the finished product is poured into a 20L polytetrafluoroethylene (PTFE) container, filled with 99.99% nitrogen for protection, and placed in a 50℃ constant temperature chamber for 48 hours. Observe for no stratification and no precipitation, and test various performance indicators.

[0039] Performance testing: The prepared gas-liquid phase change material was tested, and the results are as follows: latent heat of phase change 185 J / g, supercooling 1.8℃, electrical conductivity at 20℃ 8×10⁻¹ 6 S / m, 1.5% mass loss after 100h heat preservation at 200℃, no delamination after 72h static temperature at 50℃, meeting design requirements.

[0040] Example 2 (Preparation of Low-Temperature Adapted Synthetic Fluorine-Based Synthetic Gas-Liquid Phase Change Material) The ratio of the fluorine-based phase change matrix was adjusted to 65 kg of hydrofluoroether and 20 kg of perfluoropolyether, and the nucleating agent was changed to 5 kg of fluorinated carbon nanotubes. The pretreatment of other raw materials and process parameters were the same as in Example 1. The prepared phase change material has a suitable temperature range of -40℃ to 240℃, a latent heat of phase change of 182 J / g, a supercooling of 2.0℃, and excellent low-temperature fluidity, making it suitable for heat dissipation in outdoor equipment in cold regions.

[0041] Example 3 (Preparation of high-temperature adapted synthetic fluorine-based synthetic gas-liquid phase change material) 90 kg of perfluoropolyether (PFPE) was used as a single fluorine-based phase change matrix, and 5 kg of boron fluoride was added as a modifier. The pretreatment of other raw materials and process parameters were the same as in Example 1. The prepared phase change material has a suitable temperature range of 80℃~120℃, a latent heat of phase change of 190 J / g, and a mass loss of 1.8% after holding at 250℃ for 100 h. It is suitable for high-temperature energy storage systems.

[0042] It should be noted that, in the embodiments, the fluoride-containing wastewater generated during the production process is treated with lime slurry precipitation to ensure that the fluoride ion concentration is ≤10mg / L before being discharged; the distillation residue and filtration waste are recovered as fluoride-based raw materials through distillation to achieve resource recycling.

[0043] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Without departing from the core principles of the present invention, appropriate adjustments can be made to process parameters, raw material ratios, etc., and such adjustments should be considered to be within the protection scope of the present invention.

[0044] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0045] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a gas-liquid phase change material based on fluorine synthesis, characterized in that, Includes the following steps: Step 1: Raw material pretreatment. The fluorine-based phase change matrix, fluorine-based modifier, nucleating agent, stabilizer and interface additive are purified and impurity removed to ensure that the purity and moisture content of each raw material meet the process requirements. Step 2: Synthesis of fluorine-based precursors. The pretreated fluorine-based phase change matrix is ​​added to a polytetrafluoroethylene-lined high-pressure reactor. After heating and stirring, a fluorine-based modifier is slowly added dropwise, and the reaction is maintained at the temperature to obtain a fluorine-based precursor mixture. Step 3: Gas-liquid blend phase structure control. Pretreated nucleating agent is added to fluorine-based precursor mixture. After ultrasonic dispersion, stabilizer and interfacial additive are added in sequence. After stirring and mixing, the particles are refined by high-pressure homogenization to form a gas-liquid blend system. Step 4: Phase change performance optimization. The gas-liquid blend system is subjected to temperature gradient cycling control, followed by vacuum degassing and precision filtration to obtain fluorine-based gas-liquid phase change material. Step 5, post-encapsulation processing: In a clean environment, the fluorine-based gas-liquid phase change material is poured into a fluorine-resistant sealed container, protected with nitrogen, and then subjected to a static stability test. If the test is successful, the gas-liquid phase change material is the finished product.

2. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, In step one, the fluorine-based phase change matrix is ​​pretreated by vacuum distillation at a vacuum of -0.095 MPa, a temperature of 40-50°C, and a distillation time of 30 min, ensuring a moisture content of ≤0.05%. The fluorine-based phase change matrix is ​​a mixture of hydrofluoroether and perfluoropolyether in a mass ratio of 70:15, with a hydrofluoroether purity of ≥99.9% and a perfluoropolyether purity of ≥99.5%.

3. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, The fluorine-based modifier mentioned in step one is perfluorooctyltriethoxysilane with a purity ≥98%; The pretreatment steps are as follows: add deionized water at a mass ratio of 1:10, mix, stir at 30℃ for 1 hour for hydrolysis, let stand for separation, take the upper organic phase, dry with anhydrous sodium sulfate for 2 hours, and then filter for later use.

4. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, The nucleating agent is fluorinated graphene with a purity of ≥99%. The pretreatment process involves ultrasonic cleaning at 300W for 30 minutes, centrifugation at 8000r / min for 10 minutes, and vacuum drying at 60℃ for 2 hours.

5. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 4, characterized in that, In step one, the stabilizer is perfluoroalkyl betaine with a purity of ≥99%, and the interface aid is a fluorocarbon surfactant with a purity of ≥99%; the stabilizer and interface aid are obtained by filtering through a 0.22μm polytetrafluoroethylene filter.

6. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, The reaction conditions in step two are as follows: heat to 35℃, stir at 500 r / min for 15 min; add fluorine-based modifier at a dropping rate of 5 mL / min, heat to 50℃ after addition, and maintain the temperature for 1 h; the purity of the fluorine-based precursor is ≥99% as determined by gas chromatography.

7. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 5, characterized in that, In step three, the mass ratio of the fluorinated precursor mixture, fluorinated graphene, perfluoroalkyl betaine, and fluorocarbon surfactant is as follows: 85% fluorinated precursor mixture, 5% fluorinated graphene, 3% perfluoroalkyl betaine, 2% fluorocarbon surfactant, with the remainder being a composite additive composed of 3% oxidant and 2% metal passivator. Ultrasonic dispersion is performed at 500W for 20 minutes to ensure the fluorinated graphene particle size is ≤5μm. The stirring temperature is 40℃, the stirring speed is 800r / min, and the mixing time is 30 minutes. High-pressure homogenization is performed at 30-40MPa, and the process is repeated twice.

8. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, The temperature gradient control parameters in step four are as follows: heat up to 80℃ at a rate of 2℃ / min, hold for 1 hour, then cool down to -20℃ at a rate of 1℃ / min, and repeat 3 times; the vacuum degassing conditions are a vacuum of -0.098MPa, a temperature of 30℃, and a time of 20min; the precision filtration adopts a three-stage filtration system with filter element accuracies of 5μm, 1μm, and 0.22μm respectively.

9. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to claim 1, characterized in that, In step five, the clean environment is Class 10000, the sealed container is made of polytetrafluoroethylene or FEP, and the nitrogen purity is ≥99.99%. The stability test conditions are: standing in a 50℃ constant temperature chamber for 48 hours; no stratification or precipitation is acceptable.

10. The method for preparing gas-liquid phase change materials based on fluorine synthesis according to any one of claims 1-9, characterized in that, All equipment that comes into contact with materials during the production process is made of fluorine-resistant materials, including polytetrafluoroethylene, FEP, or nickel-based alloys.

Images