Cooling liquid and preparation method thereof, immersed energy storage device, data center and electric equipment

Abstract

The invention relates to the technical field of industrial oil, in particular to cooling liquid and a preparation method thereof, an immersed energy storage device, a data center and electric equipment, and the cooling liquid comprises fluorinated liquid and nanoparticles modified by fluorine-containing alkyl acid; the fluorine-containing alkyl acid modified nano particles are obtained by the method comprising the following steps: carrying out alkali washing on nano particle raw materials; modifying the nano particles by using fluorine-containing alkyl acid; and ball milling. According to the cooling liquid, the problems that nanoparticles are poor in stability and prone to precipitation and agglomeration can be solved, and the long-term stability and dispersity of the nanoparticles in a fluorinated liquid are improved; meanwhile, the insulation performance and the heat dissipation performance of the fluorination liquid are effectively improved, and good application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial oil technology, specifically to a coolant and its preparation method, an immersion energy storage device, a data center, and electrical equipment. Background Technology

[0002] With the continuous increase in power density of electronic devices and the rapid development of high-energy-density systems, efficient heat dissipation has become a key bottleneck restricting their performance and reliability. Fluorinated fluids, with their excellent chemical stability, flame retardancy, and wide liquid temperature range, show significant application potential in immersion cooling and single-phase or two-phase heat transfer systems. However, the basic thermal conductivity of most existing fluorinated fluids is relatively limited, typically in the range of 0.05-0.10 W / (m·K). This is gradually becoming a limiting factor for improving heat transfer efficiency when facing rapidly increasing heat flux densities. Traditional methods for improving the thermal conductivity of fluids, such as optimizing molecular structure or blending with high thermal conductivity solvents, often struggle to balance the improvement in thermal conductivity with maintaining the inherent properties of fluorinated fluids (such as dielectric properties and compatibility), resulting in significant performance bottlenecks. Therefore, how to significantly improve the thermal conductivity of fluorinated fluids while maintaining their core physicochemical properties has become a pressing technical problem to be solved in fields such as electronic thermal management, special cooling, and advanced energy systems.

[0003] In recent years, the rise of nanotechnology has provided new ideas for enhancing the thermal conductivity of fluids. Dispersing highly thermally conductive nanoparticles (such as metals, metal oxides, and carbon materials) in a base fluid to prepare nanofluids has become one of the effective ways to improve the thermal properties of heat transfer fluids. However, applying this strategy to fluorinated fluid systems faces a series of unique technical challenges: First, most nanoparticles have poor interfacial compatibility with fluorinated fluids and are prone to aggregation and sedimentation due to van der Waals forces, leading to poor long-term stability and a decrease in the thermal conductivity enhancement effect. Second, common surface modifiers or dispersants may damage the chemical inertness and electrical insulation properties of fluorinated fluids. Furthermore, the introduction of nanoparticles may significantly change the viscosity of the fluid, leading to negative effects such as increased pumping power consumption. Currently, research on nano-modification of fluorinated fluids is insufficient, especially lacking a reliable method that can achieve high thermal conductivity enhancement while ensuring long-term stable dispersion of nanoparticles without compromising the original excellent comprehensive properties of the fluorinated fluid. In addition, although fluorinated fluids have excellent flame retardant properties and material compatibility, their insulation properties are relatively poor, posing a safety risk of leakage and short circuits during long-term operation. Therefore, developing a coolant that can balance high thermal conductivity, insulation performance, and long-term stability has significant theoretical value and practical application prospects. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to provide a coolant that can address the problems of poor stability, easy precipitation and aggregation of nanoparticles, and improve the long-term stability and dispersibility of nanoparticles in fluorinated liquids; simultaneously, it effectively improves the insulation and heat dissipation properties of fluorinated liquids, showing promising application prospects.

[0005] Specifically, the first aspect of the present invention provides a coolant comprising: a fluorinated liquid and nanoparticles modified with fluorinated alkyl acids; The fluorinated alkyl acid-modified nanoparticles are obtained by a method comprising the following steps: alkaline washing of the nanoparticle raw material; modification of the nanoparticles with fluorinated alkyl acid; and ball milling.

[0006] The modified nanoparticles prepared by this invention through alkaline washing, fluorinated alkyl acid modification, and ball milling exhibit good dispersibility and long-term stability, improving the electrical insulation and thermal conductivity of fluorinated liquids. Modification of the nanoparticles with fluorinated alkyl acids enhances their compatibility with the fluorinated liquid, preventing precipitation and aggregation, and improving their long-term stability and dispersibility. Furthermore, due to the excellent breakdown resistance and thermal conductivity of the nanoparticles, the introduction of modified nanoparticles improves the thermal conductivity and dielectric properties of the fluorinated liquid, resulting in superior heat dissipation and electrical insulation. This overcomes the poor thermal conductivity and susceptibility to breakdown inherent in fluorinated liquids, broadening their application prospects. The coolant of this invention combines high thermal conductivity, insulation performance, and long-term stability.

[0007] According to some embodiments of the present invention, the fluoroalkyl acid includes a perfluoroalkyl acid; the perfluoroalkyl acid has at least four carbon atoms.

[0008] According to some embodiments of the present invention, the perfluoroalkyl acid includes one or more of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentadecanic acid, perfluorohexadecanoic acid, perfluoroheptadecanoic acid, perfluorooctadecanic acid, and perfluoroeicosanoic acid.

[0009] According to some embodiments of the present invention, the fluorinated liquid is one or more of perfluorocarbon, hydrofluorocarbon, perfluoroether, hydrofluoroamine, and perfluorocarbon; the nanoparticle raw material includes at least one of metal compound nanoparticles and non-metal compound nanoparticles; and the particle size of the nanoparticles modified with fluorinated alkyl acid is less than 100 nm.

[0010] According to some embodiments of the present invention, the nanoparticle raw materials include one or more of SiO2, FeO, Fe2O3, Fe3O4, Al2O3, TiO2, ZnO, SiC, AlN, and BN nanoparticles.

[0011] According to some embodiments of the present invention, the content of the fluorinated liquid is 80-99.9 parts by weight; the content of the nanoparticles modified with fluorinated alkyl acids is 0.1-20 parts by weight.

[0012] A second aspect of the present invention provides a method for preparing the coolant of the first aspect of the present invention, comprising the following steps: After alkaline washing, the nanoparticle raw materials are modified with fluorinated alkyl acids, and ball milling is performed to obtain nanoparticles modified with fluorinated alkyl acids. The fluorinated liquid is mixed with the nanoparticles modified with fluorinated alkyl acids; The mixing is carried out under stirring conditions at a temperature of 25℃-70℃.

[0013] The preparation method of this invention is simple, operates under mild conditions, is low-cost, and highly reproducible, making it suitable for large-scale industrial application. The coolant prepared by the method of this invention exhibits high thermal conductivity, excellent insulation properties, and long-term stability.

[0014] According to some embodiments of the present invention, the preparation of the fluorinated alkyl acid-modified nanoparticles includes the following steps: Alkaline washing: The nanoparticle raw material is placed in an alkaline solution and ultrasonically cleaned for 4-12 hours. After centrifugation, it is collected, cleaned, and dried for later use. Modification: Add the washed and dried nanoparticles to a 1wt%-5wt% fluoroalkyl acid solution, stir for 18h-36h, collect by centrifugation, and dry for later use; Ball milling: The modified nanoparticles are ball-milled.

[0015] According to some embodiments of the present invention, the concentration of the fluoroalkyl acid solution is 2wt%-4wt%.

[0016] A third aspect of the present invention provides a submersible energy storage device, comprising the coolant of the first aspect of the present invention or the coolant obtained by the method of the second aspect of the present invention.

[0017] Because of the use of the aforementioned coolant, the immersion energy storage device of the present invention has all the advantages of the aforementioned coolant, which will not be repeated here.

[0018] A fourth aspect of the present invention provides a data center comprising the coolant of the first aspect of the present invention or the coolant obtained by the method of the second aspect of the present invention.

[0019] Because of the use of the aforementioned coolant, the data center of this invention possesses all the advantages of the aforementioned coolant, which will not be elaborated further here.

[0020] The fifth aspect of the present invention provides an electrical device, including the immersion energy storage device of the third aspect of the present invention or the data center of the fourth aspect of the present invention.

[0021] Because of the use of the aforementioned coolant, the electrical equipment of the present invention possesses all the advantages of the aforementioned coolant, which will not be elaborated further here.

[0022] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. "Multiple" means two or more. Throughout this document, the terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] In recent years, the rise of nanotechnology has provided new ideas for enhancing the thermal conductivity of fluids. Dispersing highly thermally conductive nanoparticles (such as metals, metal oxides, and carbon materials) in a base fluid to prepare nanofluids has become one of the effective ways to improve the thermal properties of heat transfer fluids. However, applying this strategy to fluorinated fluid systems faces a series of unique technical challenges: First, most nanoparticles have poor interfacial compatibility with fluorinated fluids and are prone to aggregation and sedimentation due to van der Waals forces, leading to poor long-term stability and a decrease in the thermal conductivity enhancement effect; second, common surface modifiers or dispersants may damage the chemical inertness and electrical insulation properties of fluorinated fluids; third, the introduction of nanoparticles may significantly change the viscosity of the fluid, leading to negative effects such as increased pumping power consumption. Currently, research on nano-modification of fluorinated fluids is insufficient, especially lacking a reliable method that can achieve high thermal conductivity enhancement while ensuring long-term stable dispersion of nanoparticles without compromising the original excellent comprehensive properties of the fluorinated fluid.

[0027] To address the above problems, this invention proposes a coolant comprising: a fluorinated liquid and nanoparticles modified with fluorinated alkyl acids; The fluorinated alkyl acid-modified nanoparticles are obtained by a method comprising the following steps: alkaline washing of the nanoparticle raw material; modification of the nanoparticles with fluorinated alkyl acid; and ball milling.

[0028] The modified nanoparticles prepared by this invention through alkaline washing, fluorinated alkyl acid modification, and ball milling exhibit good dispersibility and long-term stability, improving the electrical insulation and thermal conductivity of fluorinated liquids. Modification of the nanoparticles with fluorinated alkyl acids enhances their compatibility with the fluorinated liquid, preventing precipitation and aggregation, and improving their long-term stability and dispersibility. Furthermore, due to the excellent breakdown resistance and thermal conductivity of the nanoparticles, the introduction of modified nanoparticles improves the thermal conductivity and dielectric properties of the fluorinated liquid, resulting in superior heat dissipation and electrical insulation. This overcomes the poor thermal conductivity and susceptibility to breakdown inherent in fluorinated liquids, broadening their application prospects. The coolant of this invention combines high thermal conductivity, insulation performance, and long-term stability.

[0029] Furthermore, the ball milling process of this invention can improve the particle size uniformity of the modified nanoparticles. After the modified nanoparticles are dispersed in the fluorinated liquid, they form a nanoparticle thermally conductive network. The more uniform the particle size of the modified nanoparticles, the higher the thermal conductivity and the better the thermal conductivity efficiency. In addition, the more uniform the particle size of the modified nanoparticles, the lower the dielectric loss factor and the better the insulation performance of the coolant.

[0030] In some embodiments, the fluorinated alkyl acid includes perfluoroalkyl acids. The more fluorine atoms in the alkyl acid, the better the compatibility between the modified nanoparticles and the fluorinated liquid, which is more conducive to improving the long-term stability and dispersibility of the modified nanoparticles in the fluorinated liquid.

[0031] In some embodiments, the perfluoroalkyl acid has at least four carbon atoms. For example, the perfluoroalkyl acid may have 4, 6, 8, 10, 12, 14, 16, 18, or 20 carbon atoms. Optimizing the carbon chain length of the perfluoroalkyl acid is beneficial for improving the dispersibility of modified nanoparticles in fluorinated liquids and for improving the overall performance of the coolant. Alkyl acids with excessively short carbon chains are too acidic and can corrode nanoparticles, impairing their original excellent properties such as thermal conductivity. Furthermore, using alkyl acids with excessively short carbon chains to modify nanoparticles results in poor dispersibility of the modified nanoparticles in fluorinated liquids.

[0032] In some embodiments, the perfluoroalkyl acid includes one or more of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentadecanic acid, perfluorohexadecanoic acid, perfluoroheptadecanoic acid, perfluorooctadecanic acid, and perfluoroeicosanoic acid. This allows the coolant to achieve a balance of high thermal conductivity, insulating properties, and long-term stability.

[0033] In some embodiments, the fluorinated fluid is one or more selected from perfluorocarbon, hydrofluorocarbon, perfluoroether, hydrofluoroether, and perfluoroamine. The fluorinated fluid includes at least one selected from perfluorotriethylamine, perfluorotripropylamine, perfluorooctane, perfluoroheptane, methyl nonafluorobutyl ether, and ethyl nonafluorobutyl ether. This improves the flame retardancy and material compatibility of the coolant while maintaining high thermal conductivity, insulation properties, and long-term stability.

[0034] In some embodiments, the nanoparticle raw material includes at least one of metal compound nanoparticles and non-metal compound nanoparticles. This improves the thermal conductivity and insulation properties of the coolant.

[0035] In some specific embodiments, the nanoparticle raw materials include one or more of SiO2, FeO, Fe2O3, Fe3O4, Al2O3, TiO2, ZnO, SiC, AlN, and BN nanoparticles.

[0036] In some embodiments, the fluoroalkyl acid-modified nanoparticles have a particle size of less than 100 nm, such as 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, or 100 nm. When the particle size is greater than 100 nm, the Brownian motion of the particles in the oil phase is weakened, and the gravitational effect is significant, making them prone to sedimentation or agglomeration to form larger particles. This leads to uneven and unstable performance of the modified coolant, and may even clog or deposit in equipment gaps, endangering the safety of electrical equipment. Controlling the particle size to less than 100 nm, especially at the nanoscale (typically 1-100 nm), can greatly enhance the Brownian motion effect, effectively counteract gravitational sedimentation, and ensure that the nanoparticles are uniformly and stably dispersed in the coolant for a long period of time.

[0037] The particle size of the fluoroalkyl acid-modified nanoparticles can be tested using a transmission electron microscope.

[0038] In some embodiments, the content of the fluorinated liquid is 80-99.9 parts by weight. The content of the fluoroalkyl acid-modified nanoparticles is 0.1-20 parts by weight. If the amount of modified nanoparticles is too small, the improvement in the thermal conductivity and insulation properties of the fluorinated liquid is not significant. If the amount of modified nanoparticles is too large, the particle dispersibility deteriorates, leading to severe agglomeration and sedimentation in the fluorinated liquid, which in turn worsens its thermal conductivity and insulation properties and increases the risk of equipment blockage.

[0039] In some specific embodiments, the content of the fluorinated liquid may be 80 parts by weight, 85 parts by weight, 90 parts by weight, 95 parts by weight, or 99.9 parts by weight.

[0040] In some specific embodiments, the content of the fluoroalkyl acid modified nanoparticles may be 0.1 parts by weight, 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, or 20 parts by weight.

[0041] A second aspect of the present invention provides a method for preparing the coolant of the first aspect of the present invention, comprising the following steps: After alkaline washing, the nanoparticle raw materials are modified with fluorinated alkyl acids, and ball milling is performed to obtain nanoparticles modified with fluorinated alkyl acids. The fluorinated liquid is mixed with the nanoparticles modified with fluorinated alkyl acids; The mixing is carried out under stirring conditions at a temperature of 25℃-70℃.

[0042] The preparation method of this invention is simple, mild, low-cost, and highly reproducible, making it suitable for large-scale industrial application. The nanofluid products prepared by this method exhibit high thermal conductivity, excellent insulation properties, and long-term stability.

[0043] In some embodiments, the mixing temperature can be 25°C, 30°C, 40°C, 50°C, 60°C, or 70°C. The mixing time can be 2h-12h, for example, 2h, 4h, 6h, 8h, 10h, or 12h. This allows the fluoroalkyl acid-modified nanoparticles to be uniformly and stably dispersed in the fluorinated liquid, improving the overall performance of the coolant.

[0044] In some embodiments, the preparation of the fluoroalkyl acid-modified nanoparticles includes the following steps: Alkaline washing: The nanoparticle raw material is placed in an alkaline solution and ultrasonically cleaned for 4-12 hours. After centrifugation, it is collected, cleaned, and dried for later use. Modification: Add the washed and dried nanoparticles to a 1wt%-5wt% fluoroalkyl acid solution, stir for 18h-36h, collect by centrifugation, and dry for later use; Ball milling: The modified nanoparticles are ball-milled.

[0045] This allows for the preparation of nanoparticles with good dispersibility and long-term stability, further improving the electrical insulation and thermal conductivity of fluorinated liquids.

[0046] In some specific embodiments, the alkaline solution includes an ethanol solution of NaOH or an ethanol solution of KOH. The concentration of the alkaline solution can be 1wt%-3wt%, for example, 1wt%, 2wt%, or 3wt%. Alkaline washing can activate the hydroxyl groups on the surface of the nanoparticles, thereby modifying the nanoparticle surface with fluoroalkyl acids to achieve modification.

[0047] In some specific embodiments, the ultrasonic cleaning time can be 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours. This allows for the full activation of the hydroxyl groups on the surface of the nanoparticles. After ultrasonic cleaning, the activated nanoparticles can be collected by centrifugation and then cleaned. For example, anhydrous ethanol can be used for cleaning 2-3 times.

[0048] In some specific embodiments, the concentration of the fluoroalkyl acid solution can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%. Preferably, the concentration of the fluoroalkyl acid solution can be 2 wt%-4 wt%. If the concentration of the fluoroalkyl acid solution is too low (e.g., <1 wt%), an effective thermally conductive network or stable interface effect cannot be formed, resulting in insufficient performance improvement. Conversely, if the concentration of the fluoroalkyl acid solution is too high, the surface load of the nanoparticles becomes excessive, leading to overload, which also affects the thermal conductivity and makes it difficult to form a thermally conductive network. The solvent used for the fluoroalkyl acid solution is a strongly polar solvent, such as one or more of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, methanol, acetonitrile, and tetrahydrofuran. Therefore, the fluoroalkyl acid can be completely dissolved in the above solvent to form a fluoroalkyl acid solution.

[0049] In some specific embodiments, the stirring time in the modification step can be 18h, 20h, 24h, 28h, 32h, or 36h. Stirring can be carried out at room temperature. This allows the fluoroalkyl acid to fully react with the hydroxyl groups on the surface of the nanoparticles, thereby achieving modification of the nanoparticles.

[0050] A third aspect of the present invention provides a submersible energy storage device, comprising the coolant of the first aspect of the present invention or the coolant obtained by the method of the second aspect of the present invention.

[0051] Because of the use of the aforementioned coolant, the immersion energy storage device of the present invention has all the advantages of the aforementioned coolant, which will not be repeated here.

[0052] A fourth aspect of the present invention provides a data center comprising the coolant of the first aspect of the present invention or the coolant obtained by the method of the second aspect of the present invention.

[0053] Because of the use of the aforementioned coolant, the data center of this invention possesses all the advantages of the aforementioned coolant, which will not be elaborated further here.

[0054] The fifth aspect of the present invention provides an electrical device, including the immersion energy storage device of the third aspect of the present invention or the data center of the fourth aspect of the present invention.

[0055] Because of the use of the aforementioned coolant, the electrical equipment of the present invention possesses all the advantages of the aforementioned coolant, which will not be elaborated further here.

[0056] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0057] Example 1 The coolant in this embodiment is made from the following raw materials in parts by weight: 97 parts by weight of perfluorooctane and 3 parts by weight of modified nano-silica, and is mechanically stirred at 25°C for 4 hours to obtain a stable nano-modified fluorinated liquid.

[0058] The preparation method of modified nano-silica includes the following steps: (1) Alkali washing: Weigh 500g of nano silica and put it into a 2wt% NaOH ethanol solution. Ultrasonic cleaning for 6 hours. After cleaning, centrifuge and collect. Then wash with anhydrous ethanol 2-3 times and dry for later use.

[0059] (2) Modification: The washed and dried nano-silica was added to a methanol solution of perfluorobutyric acid with a concentration of 2wt%, and stirred slowly for 24 hours at room temperature. Then it was collected by centrifugation and dried for later use.

[0060] (3) Ball milling: The modified nano silica was ball milled in a ball mill to obtain modified nano silica with uniform particle size of 50 nm.

[0061] Example 2 The coolant in this embodiment is made from the following raw materials in parts by weight: 95 parts by weight of perfluorooctane and 5 parts by weight of modified nano boron nitride, and is mechanically stirred at 25°C for 6 hours to obtain a stable nano-modified fluorinated liquid.

[0062] The preparation method of modified boron nitride nanoparticles includes the following steps: (1) Alkali washing: Weigh 500g of nano boron nitride and put it into a 2wt% NaOH ethanol solution. Ultrasonic cleaning for 6 hours. After cleaning, centrifuge and collect. Then wash with anhydrous ethanol 2-3 times and dry for later use.

[0063] (2) Modification: The washed and dried nano boron nitride was added to a methanol solution of perfluorovalerate with a concentration of 3wt%, stirred slowly for 24 hours at room temperature, then collected by centrifugation and dried for later use.

[0064] (3) Ball milling: The modified boron nanonitride was ball milled in a ball mill to obtain modified boron nanonitride with uniform particle size of 40 nm.

[0065] Example 3 The coolant in this embodiment is made from the following raw materials in parts by weight: 99.5 parts by weight of perfluorotripropylamine and 0.5 parts by weight of modified nano-titanium dioxide, and is mechanically stirred at 25°C for 6 hours to obtain a stable nano-modified fluorinated liquid.

[0066] The preparation method of modified nano-titanium dioxide includes the following steps: (1) Alkali washing: Weigh 500g of nano titanium dioxide and put it into a 2wt% NaOH ethanol solution. Ultrasonic cleaning for 6 hours. After cleaning, centrifuge and collect. Then wash with anhydrous ethanol 2-3 times and dry for later use.

[0067] (2) Modification: The washed and dried nano-titanium dioxide was added to a methanol solution of perfluorohexanoic acid with a concentration of 2wt%, stirred slowly for 24 hours at room temperature, then collected by centrifugation and dried for later use.

[0068] (3) Ball milling: The modified nano titanium dioxide was ball milled in a ball mill to obtain modified nano titanium dioxide with uniform particle size of 60 nm.

[0069] Example 4 The coolant in this embodiment is made from the following raw materials in parts by weight: 90 parts by weight of methyl nonafluorobutyl ether and 10 parts by weight of modified nano zinc oxide, and is mechanically stirred at 50°C for 8 hours to obtain a stable nano-modified fluorinated liquid.

[0070] The preparation method of modified nano zinc oxide includes the following steps: (1) Alkali washing: Weigh 500g of nano zinc oxide and put it into a 2wt% NaOH ethanol solution. Ultrasonic cleaning for 6 hours. After cleaning, centrifuge and collect. Then wash with anhydrous ethanol 2-3 times and dry for later use.

[0071] (2) Modification: The washed and dried nano zinc oxide was added to a methanol solution of perfluorotetradecanoic acid with a concentration of 4wt%, and stirred slowly for 24 hours at room temperature. Then it was collected by centrifugation and dried for later use.

[0072] (3) Ball milling: The modified nano zinc oxide was ball milled in a ball mill to obtain modified nano zinc oxide with uniform particle size of 80 nm.

[0073] Example 5 The coolant was prepared according to the method described in Example 4, except that perfluoroeicosanoic acid was used instead of perfluorotetradecanoic acid in the modification step.

[0074] Example 6 The coolant was prepared according to the method described in Example 1, except that 4-fluorobutyric acid was used instead of perfluorobutyric acid in the modification step.

[0075] Example 7 The coolant was prepared according to the method described in Example 1, except that trifluoroacetic acid was used instead of perfluorobutyric acid in the modification step.

[0076] Example 8 The coolant was prepared according to the method described in Example 4, except that 80 parts by weight of methyl nonafluorobutyl ether and 20 parts by weight of modified nano zinc oxide were used.

[0077] Example 9 The coolant was prepared according to the method described in Example 4, except that 99.9 parts by weight of methyl nonafluorobutyl ether and 0.1 parts by weight of modified nano zinc oxide were used.

[0078] Example 10 The coolant was prepared according to the method described in Example 4, except that 75 parts by weight of methyl nonafluorobutyl ether and 25 parts by weight of modified nano zinc oxide were used.

[0079] Example 11 The coolant was prepared according to the method described in Example 4, except that the mechanical stirring temperature of methyl nonafluorobutyl ether and modified nano zinc oxide was 70°C; the ultrasonic cleaning time in the alkaline washing step was 12 h; and the stirring time in the modification step was 36 h.

[0080] Example 12 The coolant was prepared according to the method described in Example 4, except that a methanol solution of perfluorotetradecanoic acid with a concentration of 1 wt% was used in the modification step.

[0081] Example 13 The coolant was prepared according to the method described in Example 4, except that a methanol solution of perfluorotetradecanoic acid with a concentration of 5 wt% was used in the modification step.

[0082] Comparative Example 1 The coolant in this comparative example was made from the following raw materials in parts by weight: 97 parts perfluorooctane and 3 parts nano-silica, and was mechanically stirred at 25°C for 4 hours to obtain a modified fluorinated liquid.

[0083] Comparative Example 2 The coolant in this embodiment is made from the following raw materials in parts by weight: 97 parts perfluorooctane and 3 parts modified nano-silica, and mechanically stirred at 25°C for 4 hours to obtain a modified fluorinated liquid.

[0084] The preparation method of modified nano-silica includes the following steps: Modification: 500g of nano-silica, which was ultrasonically cleaned with ethanol, was added to a methanol solution of perfluorobutyric acid with a concentration of 2wt%. The solution was stirred slowly at room temperature for 24h, then collected by centrifugation, dried and used. The particle size was 150nm.

[0085] Comparative Example 3 The coolant in this embodiment is made from the following raw materials in parts by weight: 97 parts perfluorooctane and 3 parts modified nano-silica, and mechanically stirred at 25°C for 4 hours to obtain a modified fluorinated liquid.

[0086] The preparation method of modified nano-silica includes the following steps: (1) Alkali washing: Weigh 500g of nano silica and put it into a 2wt% NaOH ethanol solution. Ultrasonic cleaning for 6 hours. After cleaning, centrifuge and collect. Then wash with anhydrous ethanol 2-3 times and dry for later use.

[0087] (2) Modification: The washed and dried nano-silica was added to a methanol solution of vinyltriethoxysilane (silane coupling agent) with a concentration of 2wt%, and stirred slowly for 24 hours at room temperature. Then it was collected by centrifugation and dried for later use.

[0088] (3) Ball milling: The modified nano silica was ball milled in a ball mill to obtain modified nano silica with uniform particle size of 50 nm.

[0089] Coolant performance test (1) Breakdown voltage test of coolant The breakdown voltage of the coolant in the above examples and comparative examples was tested according to the GB / T 507 national standard.

[0090] (2) Test of dielectric constant of coolant The dielectric constant of the coolant in the above examples and comparative examples was tested according to the national standard GB / T 5654.

[0091] (3) Test of thermal conductivity of coolant The thermal conductivity of the coolants in the above examples and comparative examples was tested according to ASTM D7896 national standard.

[0092] The test results are shown in Table 1.

[0093] Table 1

[0094] Results and Discussion: By comparing the above embodiments and comparative examples, it can be seen that the thermal conductivity of the coolant prepared by the present invention is greatly improved, thus enhancing the thermal conductivity of the fluorinated liquid. Furthermore, the breakdown voltage and dielectric constant of the fluorinated liquid are also significantly improved, enhancing its insulation properties. In addition, no precipitation occurs after prolonged standing, demonstrating good stability.

[0095] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0096] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A coolant, characterized in that, include: Fluorinated liquids and nanoparticles modified with fluorinated alkyl acids; The fluorinated alkyl acid-modified nanoparticles are obtained by a method comprising the following steps: alkaline washing of the nanoparticle raw material; modification of the nanoparticles with fluorinated alkyl acid; and ball milling.

2. The coolant according to claim 1, characterized in that, The fluorinated alkyl acid includes a perfluoroalkyl acid; the perfluoroalkyl acid has at least 4 carbon atoms.

3. The coolant according to claim 2, characterized in that, The perfluoroalkyl acids include one or more of the following: perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, perfluoropentadecanic acid, perfluorohexadecanoic acid, perfluoroheptadecanoic acid, perfluoroheptadecanoic acid, perfluorooctadecanoic acid, and perfluoroeicosanoic acid.

4. The coolant according to claim 1, characterized in that, The fluorinated liquid is one or more of perfluorocarbon, hydrofluorocarbon, perfluoroether, hydrofluoroether, and perfluoroamine; The nanoparticle raw materials include at least one of metal compound nanoparticles and non-metal compound nanoparticles. The nanoparticles modified with fluoroalkyl acids have a particle size of less than 100 nm.

5. The coolant according to claim 1, characterized in that, The nanoparticle raw materials include one or more of the following: SiO2, FeO, Fe2O3, Fe3O4, Al2O3, TiO2, ZnO, SiC, AlN, and BN nanoparticles.

6. The coolant according to claim 1, characterized in that, The content of the fluorinated liquid is 80-99.9 parts by weight; the content of the nanoparticles modified with fluorinated alkyl acids is 0.1-20 parts by weight.

7. A method for preparing a coolant according to any one of claims 1-6, characterized in that, Includes the following steps: After alkaline washing, the nanoparticle raw materials are modified with fluorinated alkyl acids, and ball milling is performed to obtain nanoparticles modified with fluorinated alkyl acids. The fluorinated liquid is mixed with the nanoparticles modified with fluorinated alkyl acids; The mixing is carried out under stirring conditions at a temperature of 25℃-70℃.

8. The preparation method according to claim 7, characterized in that, The method for producing nanoparticles modified with fluoroalkyl acids includes the following steps: Alkaline washing: The nanoparticle raw material is placed in an alkaline solution and ultrasonically cleaned for 4-12 hours. After centrifugation, it is collected, cleaned, and dried for later use. Modification: Add the washed and dried nanoparticles to a 1wt%-5wt% fluoroalkyl acid solution, stir for 18h-36h, collect by centrifugation, and dry for later use; Ball milling: The modified nanoparticles are ball-milled.

9. The preparation method according to claim 8, characterized in that, The concentration of the fluoroalkyl acid solution is 2wt%-4wt%.

10. A submersible energy storage device, characterized in that, Includes the coolant according to any one of claims 1-6 or the coolant obtained by the method according to any one of claims 7-9.

11. A data center, characterized in that, Includes the coolant according to any one of claims 1-6 or the coolant obtained by the method according to any one of claims 7-9.

12. An electrical appliance, characterized in that, This includes the immersion energy storage device of claim 10 or the data center of claim 11.

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