Nano cooling liquid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of cooling liquid, and particularly relates to nano cooling liquid as well as a preparation method and application thereof. The preparation method of the nano cooling liquid comprises the following steps: providing a mixed solution containing a modified nano material and base oil, and carrying out ultrasonic treatment on the mixed solution to obtain the nano cooling liquid, wherein the modified nano material comprises at least two of oleic acid modified copper nanoparticles, silane coupling agent modified silicon dioxide nanoparticles, silane coupling agent modified boron nitride nanosheets and silicon dioxide coated boron nitride nanosheets; the ultrasonic treatment comprises the following steps: carrying out ultrasonic treatment for the first time at 35-45 kHz, and then carrying out ultrasonic treatment for the second time at 55-65 kHz. The nano-particles can be effectively utilized to improve the heat-conducting property of the cooling liquid, meanwhile, the dielectric loss factor is reduced, and the breakdown voltage is improved.

Description

Technical Field

[0001] This invention belongs to the field of coolant technology, specifically relating to a nano-coolant, its preparation method, and its application. Background Technology

[0002] Thermal conductivity is a crucial performance characteristic of coolants. To meet the increasingly demanding heat dissipation requirements of high-power devices, it is essential to improve the thermal conductivity of coolants. Adding nanoparticles to coolants is expected to create heat conduction paths, thereby enhancing thermal conductivity. However, in practical applications, it has been found that nanoparticles have a limited effect on improving the thermal conductivity of coolants. Moreover, the addition of nanoparticles can increase the dielectric loss factor and degrade the insulation properties of the coolant, thus affecting its application in the thermal management of high-frequency, high-power electronic devices. Summary of the Invention

[0003] The purpose of this invention is to solve the problems that adding nanoparticles to coolant has limited effect on improving thermal conductivity and can cause insulation degradation. The invention provides a nano-coolant, its preparation method, and its application, which can effectively utilize nanoparticles to improve the thermal conductivity of coolant, while reducing the dielectric loss factor and increasing the breakdown voltage.

[0004] To achieve the above objectives, the present invention adopts the following technical solution.

[0005] In a first aspect, the present invention provides a method for preparing a nano-cooling liquid, comprising:

[0006] A mixture containing modified nanomaterials and base oil is provided, and the mixture is ultrasonically treated to obtain a nano-coolant;

[0007] The modified nanomaterials include at least two of the following: oleic acid modified copper nanoparticles, silane coupling agent modified silica nanoparticles, silane coupling agent modified boron nitride nanosheets, and silica-coated boron nitride nanosheets.

[0008] The ultrasonic treatment includes a first ultrasonic treatment at 35–45 kHz, followed by a second ultrasonic treatment at 55–65 kHz.

[0009] This invention employs at least two modified nanomaterials blended with base oil. The modified layers within the nanomaterials enhance the compatibility between the nanomaterials and the base oil, and the two modified nanomaterials exhibit a synergistic effect, effectively improving the dispersion stability of the modified nanomaterials in the base oil. Simultaneously, a step-by-step ultrasonic treatment process is used in the preparation of the nano-coolant. A first ultrasonic treatment at low frequency removes agglomerates of the modified nanomaterials; a second ultrasonic treatment at high frequency achieves stable dispersion of the modified nanomaterials, forming a uniform nano-coolant. Therefore, the scheme of this invention effectively utilizes the modified nanomaterials to form heat conduction paths, improving the thermal conductivity of the nano-coolant. Furthermore, by increasing the solubility of various substances within the system, the dielectric loss factor of the nano-coolant can be reduced, insulation improved, and breakdown voltage increased.

[0010] In some embodiments, the power of the first ultrasonic treatment is 300-500W; the power of the second ultrasonic treatment is 1000-1500W.

[0011] In some embodiments, the duration of the first ultrasonic treatment is 55–65 min; the duration of the second ultrasonic treatment is 25–35 min.

[0012] In some embodiments, the average particle size of the modified nanomaterial is 30–50 nm.

[0013] In some embodiments, the oleic acid modified copper nanoparticles comprise copper nanoparticles and oleic acid coated on the surface of the copper nanoparticles, wherein the mass ratio of oleic acid to copper nanoparticles is 1:(8-12).

[0014] The silane coupling agent modified silica nanoparticles consist of silica nanoparticles and a silane coupling agent coated on the surface of the silica nanoparticles, with a mass ratio of silane coupling agent to silica nanoparticles of 1:(16-24).

[0015] The silane coupling agent modified boron nitride nanosheets contain boron nitride nanosheets and a silane coupling agent coated on the surface of the boron nitride nanosheets, with a mass ratio of silane coupling agent to boron nitride nanosheets of 1:(8-12).

[0016] Silica-coated boron nitride nanosheets consist of boron nitride nanosheets and silica coated on the surface of the boron nitride nanosheets, with a mass ratio of silica to boron nitride nanosheets of (0.4–0.8):1.

[0017] In some embodiments, oleic acid-modified copper nanoparticles can be prepared by thermal decomposition, which may specifically include the following steps:

[0018] S1-1. Mix copper precursor (such as copper acetylacetonate) with oleic acid and add a high-boiling-point solvent (such as octadecene).

[0019] S1-2. Under a protective atmosphere, heat the mixture obtained in step S1-1 to 180℃~300℃ and maintain it for 3.5~4.5h;

[0020] S1-3. After cooling the mixture obtained in step S1-2, wash it (for example, by centrifugation washing with ethanol or acetone), and then dry it.

[0021] In step S1-1, the mass ratio of copper precursor to oleic acid is 1:(8-12).

[0022] At high temperatures, copper precursors can decompose and reduce to generate copper nanoparticles. These copper nanoparticles then nucleate and grow, while oleic acid molecules coordinate to the surface of the copper nanoparticles, forming an oleic acid-coated copper nanoparticle structure. This method yields oleic acid-modified copper nanoparticles with good monodispersity, excellent oleic acid coating, and high stability.

[0023] In some embodiments, silane coupling agent modified silica nanoparticles can be prepared by a sol-gel in-situ modification method, which may specifically include the following steps:

[0024] S2-1. Add silane coupling agent and ethanol to sodium silicate aqueous solution to obtain precursor solution;

[0025] S2-2, Emulsify phase change material, emulsifier and dilute hydrochloric acid to form an emulsion;

[0026] S2-3. Add the precursor solution dropwise to the emulsion, adjust the pH to 2.5-4.5, heat to 60±5℃ and react for 3-5 hours, then wash and dry.

[0027] Understandably, steps S2-1 and S2-2 are not sequential.

[0028] This method can yield silane coupling agent modified silica nanoparticles with high coating rates (>80%).

[0029] In step S2-1, the mass ratio of sodium silicate to silane coupling agent is (3-5):1. The mass concentration of sodium silicate in the precursor solution is 10-50 g / L, and the mass concentration of silane coupling agent in the precursor solution is 2-20 g / L.

[0030] The silane coupling agent includes at least one of KH-560, KH-550, and A-151.

[0031] In step S2-2, the phase change material includes at least one of octadecane and a mixture of fatty acids;

[0032] Emulsifiers include at least one of CTAB (hexadecyltrimethylammonium bromide) and poloxamer;

[0033] The concentration of dilute hydrochloric acid is 0.08–0.12 mol / L. The mass ratio of phase change material to emulsifier and dilute hydrochloric acid is (3.5–4.5):0.1:(48–52).

[0034] In steps S2-3, the volume ratio of the precursor solution to the emulsion is 1:(2-3).

[0035] In some embodiments, silane coupling agent modified boron nitride nanosheets can be prepared by ball milling-assisted functionalization, which may specifically include the following steps:

[0036] S3-1. Add boron nitride nanosheets (BNNS) to an ethanol / water solution of silane coupling agent and disperse by ultrasonication to obtain a dispersion.

[0037] S3-2, Ball milling at 100-2000 rpm for 1-48 hours.

[0038] S3-3. Remove after ball milling is complete.

[0039] In step S3-1, the mass ratio of boron nitride nanosheets to silane coupling agent is 1:(9-11); the silane coupling agent includes at least one of KH-560, KH-550, and A-151.

[0040] In step S3-1, the pH of the dispersion is 0 to 6, and hydrochloric acid can be used to adjust the pH of the dispersion.

[0041] In some embodiments, silica-coated boron nitride nanosheets can be prepared by the following method:

[0042] S4-1, BNNS dispersion and pretreatment: 5.0g of BNNS was uniformly dispersed in a solvent (ethanol / water mixture, with a volume ratio of ethanol to water of 3 to 5:1) to obtain a BNNS dispersion.

[0043] S4-2, Sol preparation and deposition: Add 14-18g of catalyst (ammonia) to 50mL of BNNS dispersion, then slowly add 10-14g of silane precursor (TEOS) with stirring, and then react at 30-45℃ for 20-24h;

[0044] S4-3. Aging and Drying: After the reaction is complete, age at 80-100℃ for 2-3 hours, then centrifuge, collect the solid particles and wash with ethanol, then dry.

[0045] In some embodiments, the base oil includes at least one of naphthenic oil, PAO-based oil, GTL-based oil, synthetic ester, and silicone oil.

[0046] In some embodiments, the base oil is a synthetic ester, and the modified nanomaterials include silane coupling agent-modified boron nitride nanosheets and oleic acid-modified copper nanoparticles.

[0047] Synthetic esters are prone to acid value increases during application. Silane coupling agent-modified boron nitride nanosheets can directionally adsorb oxidation products, forming a passivation film and reducing the acid value of the nano-coolant. This not only reduces the corrosion caused by the high acid value of the synthetic ester-based nano-coolant but also extends the coolant's replacement cycle.

[0048] In some embodiments, the base oil is a PAO-based oil, and the modified nanomaterials include silica-coated boron nitride nanosheets and oleic acid-modified copper nanoparticles. Silica-coated boron nitride nanosheets can improve the breakdown voltage of the PAO-based oil. The two types of nanomaterials are uniformly dispersed in the oil, forming a multilayer insulating barrier that forces electron migration paths to become tortuous, thus prolonging the breakdown channel.

[0049] In some embodiments, the mass ratio of base oil to modified nanomaterial is 100:(0.1-5), and optionally 100:(0.1-0.3).

[0050] In some embodiments, the mixture further comprises a dispersant, which includes at least one selected from polyetheramine dispersants, silane coupling agents, and acrylate copolymers. The mass ratio of base oil to dispersant is 100:(0.5–3).

[0051] In some embodiments, the mixture is prepared by adding modified nanomaterials and dispersants to base oil and subjecting it to shearing and / or stirring treatment; the shearing and stirring rates are each independently 2000–5000 rpm, for example 3000 rpm; the shearing and stirring times are each independently 30–60 min, for example 40 min.

[0052] In a second aspect, the present invention provides a nano-coolant obtained by the preparation method described in the first aspect above.

[0053] The coolant of this invention has a high thermal conductivity and a low dielectric loss factor.

[0054] Thirdly, the present invention provides the application of the above-mentioned nano-cooling liquid in the immersion heat dissipation system of at least one of data centers and power electronic equipment.

[0055] The coolant of this invention has a high thermal conductivity and a low dielectric loss factor, which enables efficient heat transfer to data centers, power electronic equipment, etc., and it is highly safe during application, reducing electrical failures. Detailed Implementation

[0056] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0057] Unless otherwise specified, the reagents, methods, and equipment used in this invention are all conventional reagents, methods, and equipment in this technical field, which can be obtained commercially or prepared using known methods. Unless otherwise specified, "room temperature" or "room temperature" as used in this invention refers to 20–25°C.

[0058] The present invention provides five types of nano-coolants using different base oils: cycloalkyl oil-based nano-coolant, PAO-based nano-coolant, GTL-based nano-coolant, synthetic ester nano-coolant, and silicone oil nano-coolant.

[0059] The modified nanomaterials used in the cycloalkyl oil-based nanocooling fluid, PAO-based nanocooling fluid, GTL-based nanocooling fluid, and synthetic ester nanocooling fluid were prepared according to the following methods:

[0060] 1. Oleic acid modified copper nanoparticles

[0061] S1-1. Mix 0.26g of copper acetylacetonate with 1.66g of oleic acid and add 25mL of high-boiling-point solvent (octadecene).

[0062] S1-2. Under nitrogen protection, heat the mixture obtained in step (1) to 200°C and maintain it at that temperature for 12 min.

[0063] S1-3. After naturally cooling to room temperature, the copper nanoparticles are centrifuged and washed with ethanol to remove excess oleic acid and solvent, resulting in oleic acid-coated copper nanoparticles, i.e., oleic acid-modified copper nanoparticles with an average particle size of about 30 nm and a mass ratio of oleic acid to copper nanoparticles of 1:10.

[0064] 2. Silane coupling agent modified silica nanoparticles

[0065] S2-1. Prepare a sodium silicate aqueous solution with a concentration of 0.2 mol / L, add 2.5 g of silane coupling agent (KH550) and 50 mL of anhydrous ethanol and mix to obtain a precursor solution;

[0066] S2-2, Mix 4.0g of phase change material (n-octadecane), 0.1g of emulsifier (poloxam) with 50mL of dilute hydrochloric acid (concentration of 0.1mol / L) and emulsify to form an emulsion;

[0067] S2-3. The precursor solution obtained in step S2-1 is added dropwise to the emulsion in step S2-2. The pH is adjusted to 3 with hydrochloric acid, and the mixture is heated to 60°C for 4 hours. After the reaction is completed, the mixture is washed with ethanol and then dried to obtain silane coupling agent modified silica nanoparticles with an average particle size of about 50 nm. The mass ratio of silane coupling agent to silica nanoparticles is 1:18.

[0068] 3. Silane coupling agent modified boron nitride nanosheets

[0069] S3-1. Add 3.0g of boron nitride nanosheets with an average thickness of 6nm and an average lateral dimension of 350nm to 100mL of KH-560 in ethanol (pH=3, adjusted with hydrochloric acid; KH-560 concentration is 3wt%, and the volume ratio of ethanol to water is 4:1) and disperse by ultrasonication.

[0070] S3-2. Ball milling at 2000 rpm for 10 h yielded epoxy-functionalized boron nitride, namely silane coupling agent modified boron nitride nanosheets with an average particle size of about 50 nm. The mass ratio of silane coupling agent to boron nitride nanosheets was 1:10.

[0071] 4. Silica-coated boron nitride nanosheets

[0072] S4-1, BNNS dispersion and pretreatment: 5.0g of BNNS was uniformly dispersed in a solvent (ethanol / water mixture, with a volume ratio of ethanol to water of 4:1) to obtain a BNNS dispersion.

[0073] S4-2, Sol preparation and deposition: Add 16g of catalyst (ammonia) to 50mL of BNNS dispersion, then slowly add 12g of silane precursor (TEOS) dropwise under stirring, and then react at 30-45℃ for 20-24h;

[0074] S4-3. Aging and Drying: After the reaction is complete, age at 80-100℃ for 2-3 hours, then centrifuge, collect the solid particles and wash with ethanol, then dry to obtain silica-coated boron nitride nanosheets with an average particle size of 40 nm and a mass ratio of silica to boron nitride of 0.6:1.

[0075] 5. Phosphate-modified zinc oxide / titanium dioxide nanoparticles

[0076] S5-1 Pre-dispersion: Add 0.5 parts ZnO and 2 parts TiO2 to 100 parts deionized water and treat with ultrasound at 2000W for 45 minutes to adjust the initial particle size D of the slurry. 90 ≤300nm;

[0077] S5-2 Phosphate ester modification: Add phosphate ester dispersant (BYK-190) at a rate of 2% of the water mass (e.g., 2g dispersant for 100g water); then shear emulsify at 35℃ and 4000rpm for 2h.

[0078] S5-3 Nano Grinding: Grind four times with 0.1mm zirconium bead media, controlling the temperature to ≤45℃ during the grinding process (to prevent phosphate ester decomposition);

[0079] S5-4 Stabilization Treatment: After adjusting the pH to 8.5 (ammonia or citric acid), add 0.1% defoamer (sodium hexametaphosphate), store in a light-proof and sealed container to obtain phosphate ester modified zinc oxide / titanium dioxide nanoparticles with an average particle size of 50 nm.

[0080] The oleic acid-modified copper nanoparticles used in the silicone oil nano-coolant were prepared using the aforementioned method, with the difference being a change in the raw material ratio in step S1-1, resulting in a final oleic acid-modified copper nanoparticle composition where the mass ratio of oleic acid to copper nanoparticles was 1:8, and the average particle size of the oleic acid-modified copper nanoparticles was 30 nm. In the silane coupling agent-modified silica nanoparticles used in the silicone oil nano-coolant, the mass ratio of silane coupling agent to silica nanoparticles was 1:20, and the average particle size of the silane coupling agent-modified silica nanoparticles was 50 nm; in the silane coupling agent-modified boron nitride nanosheets, the mass ratio of silane coupling agent to boron nitride nanosheets was 1:12, and the average particle size of the silane coupling agent-modified boron nitride nanosheets was 50 nm.

[0081] The following are other raw material information related to the embodiments or comparative examples:

[0082] Naphthenic oil: 45# transformer oil, manufactured by Wuhan Jiyesheng Chemical Co., Ltd.;

[0083] Polyether amine dispersant: D-156 polyether active amine dispersant, manufactured by Houtch, Taiwan, China;

[0084] PAO base oil: PAO2, manufactured by Chevron, USA;

[0085] GTL base oil: GTL420, manufactured by Shell;

[0086] Synthetic ester: RM1190, manufactured by Zhongke Runmei (Qingdao) Materials Technology Co., Ltd.;

[0087] Dimethyl silicone oil: 5cSt dimethyl silicone oil, manufactured by Qingdao Zhongbao Silicon Materials Technology Co., Ltd.

[0088] I. Naphthenic oil-based nano-coolant

[0089] Example A1

[0090] Take 100g of naphthenic oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.2g of silane coupling agent-modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0091] Example A2

[0092] Take 100g of naphthenic oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0093] Example A3

[0094] Take 100g of naphthenic oil, add 0.05g of oleic acid-modified copper nanoparticles and 0.05g of silane coupling agent-modified silica nanoparticles; then add 0.5g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0095] Example A4

[0096] Take 100g of naphthenic oil, add 2g of oleic acid-modified copper nanoparticles, 2g of silane coupling agent-modified silica nanoparticles, and 1g of silane coupling agent-modified boron nitride nanosheets; then add 3g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0097] Comparative Example A1

[0098] The difference between this comparative example and Example A1 is that only one step of low-frequency ultrasonic processing was performed.

[0099] Specifically, 100g of naphthenic oil was taken, and 0.1g of oleic acid-modified copper nanoparticles and 0.2g of silane coupling agent-modified silica nanoparticles were added. Then, 2g of polyetheramine dispersant was added, and the mixture was sheared and dispersed at 3000rpm for 40min. The mixture was then ultrasonically treated for 1.5h (40kHz, 300W) to obtain a nano-cooling liquid.

[0100] Comparative Example A2

[0101] The difference between this comparative example and Example A2 is that only one step of low-frequency ultrasonic processing was performed.

[0102] Take 100g of naphthenic oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0103] Comparative Example A3

[0104] The difference between this comparative example and Example A2 is that only one high-frequency ultrasonic processing step was performed.

[0105] Take 100g of naphthenic oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear and disperse at 3000rpm for 40min; sonicate for 1.5h (60kHz, 1500W) to obtain nano-cooling liquid.

[0106] Comparative Example A4

[0107] The difference between this comparative example and Example A2 is that high-frequency ultrasonic processing is performed first, followed by low-frequency ultrasonic processing.

[0108] Take 100g of naphthenic oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at high frequency (60kHz, 1500W) for 30min, then sonicate at low frequency (40kHz, 300W) for 60min to obtain nano-cooling liquid.

[0109] Comparative Example A5

[0110] The difference between this comparative example and Example A2 is that the frequency of the low-frequency ultrasonic processing is reduced to 30kHz.

[0111] Comparative Example A6

[0112] The difference between this comparative example and Example A2 is that the frequency of the low-frequency ultrasonic processing is increased to 50kHz.

[0113] Comparative Example A7

[0114] The difference between this comparative example and Example A2 is that the frequency of the high-frequency ultrasonic processing is reduced to 50 kHz.

[0115] Comparative Example A8

[0116] The difference between this comparative example and Example A2 is that the frequency of the high-frequency ultrasonic processing is increased to 70kHz.

[0117] Comparative Example A9

[0118] The difference between this comparative example and Example A2 is that only one type of modified nanomaterial is added.

[0119] Take 100g of naphthenic oil, add 0.2g of oleic acid modified copper nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first treat with low frequency (40kHz, 300W) ultrasound for 60min, then treat with high frequency (60kHz, 1500W) ultrasound for 30min to obtain nano-cooling liquid.

[0120] Comparative Example A10

[0121] The difference between this comparative example and Example A1 is that the silane coupling agent modified silica nanoparticles are replaced with an equal mass of phosphate ester modified zinc oxide / titanium dioxide nanoparticles.

[0122] Comparative Example A11

[0123] This comparative example uses a separate naphthenic oil as the coolant.

[0124] The performance test results of the nano-coolant in Examples A1 to A4 and Comparative Examples A1 to A11 are shown in the table below.

[0125] The test method for thermal conductivity is based on ASTM D7896-19, "Standard Test Method for Determination of Thermal Conductivity, Thermal Diffusivity and Volumetric Heat Capacity of Engine Coolants and Related Fluids by Transient Hot-Wire Method"; the test method for viscosity is based on GB / T 265, "Determination of Kinematic Viscosity of Petroleum Products"; the test method for breakdown voltage is based on IEC 60156-2018, "Determination of Breakdown Voltage of Insulating Oils"; and the test method for dielectric loss is based on GB / T 5654-2007, "Measurement of Relative Permittivity, Dielectric Loss Factor and DC Resistivity of Liquid Insulating Materials".

[0126] [Table 1]

[0127]

[0128]

[0129] The test results reflect:

[0130] Compared to the naphthenic oil alone in Comparative Example A11, Examples A1-A4, by adding two or more modified nanomaterials from oleic acid-modified copper nanoparticles, silane coupling agent-modified silica nanoparticles, and silane coupling agent-modified boron nitride nanosheets to the naphthenic oil and combining it with a stepwise ultrasonic treatment process, can improve the thermal conductivity of the nano-coolant (if these nano-coolants are applied to an immersion cooling thermal management system, the maximum operating temperature of the battery can be reduced by 4°C, effectively increasing the battery life); at the same time, the dielectric loss factor is significantly reduced (for example, the dielectric loss factor of Example A2 can be reduced to 0.76%), and at a low dielectric loss factor, the risk of local overheating during long-term operation can be avoided.

[0131] Meanwhile, the nano-coolants of Examples A1-A4 exhibit relatively low viscosity (viscosity change <10% compared to the naphthenic oil alone in Comparative Example A11), maintaining good fluidity; they also have high breakdown voltage, demonstrating excellent insulation properties and meeting industrial standards. Furthermore, in Examples A1-A4, the modified nanomaterials showed dispersion stability in the nano-coolants >6 months. That is, even after being placed at room temperature for more than 6 months, no sedimentation occurred.

[0132] In contrast, Comparative Examples A1-A3 only underwent one ultrasonic treatment step, while Comparative Example A4 underwent high-frequency ultrasonic treatment followed by low-frequency ultrasonic treatment. The resulting nano-coolant showed little improvement in thermal conductivity and relatively high dielectric loss. Comparative Examples A5-A8, due to excessively high or low ultrasonic frequencies, failed to effectively reduce the dielectric loss factor of the nano-coolant. Comparative Example 9 used only one modified nanomaterial, resulting in a lower thermal conductivity and increased dielectric loss compared to Examples A1-A4, indicating that the combined use of two modified nanomaterials can better improve the thermal conductivity and insulation properties of the nano-coolant. Comparative Example A10 used phosphate-modified zinc oxide / titanium dioxide nanoparticles. However, due to the competitive adsorption between the phosphate-modified zinc oxide / titanium dioxide nanoparticles and the oleic acid-modified copper nanoparticles, it did not significantly improve the thermal conductivity of the coolant, while also significantly increasing the dielectric loss and viscosity.

[0133] II. PAO-based nano-cooling fluid

[0134] Example B1

[0135] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.2g of silane coupling agent-modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0136] Example B2

[0137] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0138] Example B3

[0139] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silica-coated boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0140] Comparative Example B1

[0141] The difference between this comparative example and Example B1 is that only one step of low-frequency ultrasonic processing was performed.

[0142] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.2g of silane coupling agent-modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; ultrasonically treat for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0143] Comparative Example B2

[0144] The difference between this comparative example and Example B2 is that only one step of low-frequency ultrasonic processing was performed.

[0145] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silane coupling agent-modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0146] Comparative Example B3

[0147] The difference between this comparative example and Example B3 is that only one step of low-frequency ultrasonic processing was performed.

[0148] Take 100g of PAO-based oil, add 0.1g of oleic acid-modified copper nanoparticles and 0.1g of silica-coated boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0149] Comparative Example B4

[0150] The difference between this comparative example and Example B2 is that only one type of modified nanomaterial is added.

[0151] Take 100g of PAO base oil, add 0.2g of oleic acid modified copper nanoparticles (30nm); add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first treat with low frequency (40kHz, 300W) sonication for 60min, then treat with high frequency (60kHz, 1500W) sonication for 30min to obtain nano-cooling liquid.

[0152] Comparative Example B5

[0153] This comparative example uses a single PAO-based oil as the coolant.

[0154] The performance test results of the nano-coolant in Examples B1-B3 and Comparative Examples B1-B5 are shown in the table below.

[0155] [Table 2]

[0156]

[0157]

[0158] The test results reflect:

[0159] Compared to Comparative Examples B1-B5, Examples B1-B3, by adding two modified nanomaterials from the following categories—oleic acid-modified copper nanoparticles, silane coupling agent-modified silica nanoparticles, silane coupling agent-modified boron nitride nanosheets, and silica-coated boron nitride nanosheets—to PAO-based oil, and combining this with a stepwise ultrasonic treatment process, can improve the thermal conductivity of the nano-coolant while significantly reducing the dielectric loss factor. Furthermore, the modified nanomaterials in Example B3 include silica-coated boron nitride nanosheets prepared using a double-layer insulating layer coating process, which can significantly increase the breakdown voltage of the nano-coolant (from 45kV to 55kV).

[0160] III. GTL-based Nanocoolant

[0161] Example C1

[0162] Take 100g of GTL base oil, add 0.1g of oleic acid modified copper nanoparticles and 0.2g of silane coupling agent modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0163] Example C2

[0164] Take 100g of GTL base oil, add 0.1g of oleic acid modified copper nanoparticles and 0.1g of silane coupling agent modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0165] Comparative Example C1

[0166] The difference between this comparative example and Example C1 is that only one step of low-frequency ultrasonic processing was performed.

[0167] Take 100g of GTL base oil, add 0.1g of oleic acid modified copper nanoparticles and 0.2g of silane coupling agent modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; ultrasonically treat for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0168] Comparative Example C2

[0169] The difference between this comparative example and Example C2 is that only one step of low-frequency ultrasonic processing was performed.

[0170] Take 100g of GTL base oil, add 0.1g of oleic acid modified copper nanoparticles and 0.1g of silane coupling agent modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0171] Comparative Example C3

[0172] The difference between this comparative example and Example C1 is that only one type of modified nanomaterial is added.

[0173] Take 100g of GTL base oil, add 0.2g of oleic acid modified copper nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0174] Comparative Example C4

[0175] This comparative example uses a separate GTL-based oil as the coolant.

[0176] The coolant performance test results of Examples C1-C2 and Comparative Examples C1-C4 are shown in the table below.

[0177] [Table 3]

[0178]

[0179] The test results reflect:

[0180] Compared with comparative examples C1 to C4, examples C1 to C2 improved the thermal conductivity of the nano-coolant and significantly reduced the dielectric loss factor by adding two modified nanomaterials to GTL base oil and combining them with a stepwise ultrasonic treatment process.

[0181] IV. Synthetic Ester Nanocooling

[0182] Example D1

[0183] Take 100g of synthetic ester, add 0.1g of oleic acid modified copper nanoparticles and 0.2g of silane coupling agent modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0184] Example D2

[0185] Take 100g of synthetic ester, add 0.1g of oleic acid modified copper nanoparticles and 0.1g of silane coupling agent modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0186] Comparative Example D1

[0187] The difference between this comparative example and Example D1 is that only one step of low-frequency ultrasonic processing was performed.

[0188] Take 100g of synthetic ester, add 0.1g of oleic acid modified copper nanoparticles and 0.2g of silane coupling agent modified silica nanoparticles; then add 2g of polyetheramine dispersant, and shear and disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0189] Comparative Example D2

[0190] The difference between this comparative example and Example D2 is that only one step of low-frequency ultrasonic processing was performed.

[0191] Take 100g of synthetic ester, add 0.1g of oleic acid modified copper nanoparticles and 0.1g of silane coupling agent modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0192] Comparative Example D3

[0193] This comparative example uses a separate synthetic ester as the coolant.

[0194] The coolant performance test results of Examples D1-D2 and Comparative Examples D1-D3 are shown in the table below.

[0195] The initial acid value in the table refers to the acid value (TAN) of the freshly prepared nano-cooling fluid. 初始 The acid value change was determined by placing the nano-cooling liquid in a 60℃ oven for 121 hours, followed by sampling and testing of the acid value (TAN). 121 h The difference between the acid value and the initial acid value (TAN) 121 h -TAN 初始 This refers to the change in acid value. The test method for acid value is GB / T 4945-2002 Determination of Acid and Base Value of Petroleum Products and Lubricants (Color Indicator Method).

[0196] [Table 4]

[0197]

[0198] The test results reflect:

[0199] Compared with comparative examples D1 to D3, examples D1 to D2 improved the thermal conductivity of the nano-coolant by adding two modified nanomaterials from oleic acid-modified copper nanoparticles, silane coupling agent-modified silica nanoparticles, and silane coupling agent-modified boron nitride nanosheets to the synthetic ester, and combined with a stepwise ultrasonic treatment process. At the same time, the dielectric loss factor was significantly reduced, and the acid value was effectively reduced.

[0200] Furthermore, the modified nanomaterials added to the synthetic ester in Example D2 include silane coupling agent modified boron nitride nanosheets, which can reduce the acid value of the nano-coolant by 0.3 mg KOH / g, that is, from 0.5 mg KOH / g to 0.2 mg KOH / g, and can extend the liquid replacement cycle by more than 50%.

[0201] V. Silicone Oil Nano Coolant

[0202] Example E1

[0203] Take 100g of 5cSt dimethyl silicone oil, add 0.1g of oleic acid modified copper nanoparticles and 0.2g of silane coupling agent modified silica nanoparticles; add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first treat with low frequency (40kHz, 300W) ultrasonic treatment for 60min, then treat with high frequency (60kHz, 1500W) ultrasonic treatment for 30min to obtain nano-cooling liquid.

[0204] Example E2

[0205] Take 100g of 5cSt dimethyl silicone oil, add 0.1g of oleic acid modified copper nanoparticles and 0.1g of silane coupling agent modified boron nitride nanosheets; then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; first, sonicate at low frequency (40kHz, 300W) for 60min, and then sonicate at high frequency (60kHz, 1500W) for 30min to obtain nano-cooling liquid.

[0206] Comparative Example E1

[0207] The difference between this comparative example and Example E1 is that only one step of low-frequency ultrasonic processing was performed.

[0208] Take 100g of 5cSt dimethyl silicone oil, add 0.1g of oleic acid modified copper nanoparticles (30nm) and 0.2g of silane coupling agent modified silica nanoparticles (50nm); then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0209] Comparative Example E2

[0210] The difference between this comparative example and Example E2 is that only one step of low-frequency ultrasonic processing was performed.

[0211] Take 100g of 5cSt dimethyl silicone oil, add 0.1g of oleic acid modified copper nanoparticles (30nm) and 0.1g of silane coupling agent modified boron nitride nanosheets (50nm); then add 2g of polyetheramine dispersant, and shear disperse at 3000rpm for 40min; sonicate for 1.5h (40kHz, 300W) to obtain nano-cooling liquid.

[0212] Comparative Example E3

[0213] This comparative example uses dimethyl silicone oil alone as the coolant.

[0214] The coolant performance test results of Examples E1-E2 and Comparative Examples E1-E3 are shown in the table below.

[0215] [Table 5]

[0216]

[0217]

[0218] Similarly, Examples E1-E2, by adding two modified nanomaterials from oleic acid-modified copper nanoparticles, silane coupling agent-modified silica nanoparticles, and silane coupling agent-modified boron nitride nanosheets to dimethyl silicone oil and combining them with a stepwise ultrasonic treatment process, can improve the thermal conductivity of the nano-coolant and significantly reduce the dielectric loss factor compared to Comparative Examples E1-E3.

[0219] Meanwhile, the nano-cooling fluids of Examples E1 to E2 have low viscosity, which can maintain good fluidity; and have high breakdown voltage, which has good insulation properties and meets industrial standards.

[0220] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a nano-cooling fluid, characterized in that, include: A mixture comprising modified nanomaterials and base oil is provided, and the mixture is subjected to ultrasonic treatment to obtain a nano-coolant; The modified nanomaterials include at least two of the following: oleic acid modified copper nanoparticles, silane coupling agent modified silica nanoparticles, silane coupling agent modified boron nitride nanosheets, and silica-coated boron nitride nanosheets. The ultrasonic treatment includes performing a first ultrasonic treatment at 35–45 kHz, followed by a second ultrasonic treatment at 55–65 kHz.

2. The method for preparing the nano-cooling liquid according to claim 1, characterized in that, The power of the first ultrasonic treatment is 300-500W; the power of the second ultrasonic treatment is 1000-1500W; And / or, the duration of the first ultrasonic treatment is 55–65 min; the duration of the second ultrasonic treatment is 25–35 min.

3. The method for preparing the nano-cooling liquid according to claim 1, characterized in that, The modified nanomaterial has an average particle size of 30–50 nm.

4. The method for preparing the nano-cooling liquid according to claim 3, characterized in that, The oleic acid modified copper nanoparticles comprise copper nanoparticles and oleic acid coated on the surface of the copper nanoparticles, wherein the mass ratio of oleic acid to copper nanoparticles is 1:(8-12). And / or, the silane coupling agent modified silica nanoparticles comprise silica nanoparticles and a silane coupling agent coated on the surface of the silica nanoparticles, wherein the mass ratio of the silane coupling agent to the silica nanoparticles is 1:(16-24). The silane coupling agent modified boron nitride nanosheets comprise boron nitride nanosheets and a silane coupling agent coated on the surface of the boron nitride nanosheets, wherein the mass ratio of the silane coupling agent to the boron nitride nanosheets is 1:(8-12). The silica-coated boron nitride nanosheets comprise boron nitride nanosheets and silica coated on the surface of the boron nitride nanosheets, wherein the mass ratio of silica to boron nitride nanosheets is (0.4–0.8):

1.

5. The method for preparing the nano-cooling liquid according to any one of claims 1 to 4, characterized in that, The base oil is a synthetic ester, and the modified nanomaterials include the silane coupling agent modified boron nitride nanosheets and the oleic acid modified copper nanoparticles. Alternatively, the base oil may be a PAO-based oil, and the modified nanomaterials may include the silica-coated boron nitride nanosheets and the oleic acid-modified copper nanoparticles.

6. The method for preparing the nano-cooling liquid according to any one of claims 1 to 4, characterized in that, The mass ratio of the base oil to the modified nanomaterial is 100:(0.1-5).

7. The method for preparing the nano-cooling liquid according to any one of claims 1 to 4, characterized in that, The mixture further comprises a dispersant, which includes at least one of a polyetheramine dispersant, a silane coupling agent, and an acrylate copolymer; the mass ratio of the base oil to the dispersant is 100:(0.5-3).

8. The method for preparing the nano-cooling liquid according to claim 7, characterized in that, The mixture is prepared by adding the modified nanomaterial and the dispersant to the base oil and subjecting it to shearing and / or stirring treatment; the shearing treatment and the stirring treatment are each independently 2000-5000 rpm, and the shearing treatment and the stirring treatment are each independently 30-60 min.

9. A nano-coolant, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the nano-cooling liquid of claim 9 in an immersion heat dissipation system of at least one of a data center or a power electronic device.

Images