A thermal safety management coating with thermal rectification function and its preparation method and application

Abstract

The present invention relates to the field of thermal management technology, and in particular to a thermal safety management coating with a thermal rectification function, a preparation method thereof, and an application thereof, wherein the thermal safety management coating comprises a heat-conducting layer and a radiation cooling layer connected in series, wherein the heat-conducting layer is a coating comprising an inorganic non-metal, and the radiation cooling layer is a coating comprising a high-refractive-index medium scatterer. The thermal safety management coating prepared by the present invention has the advantages of directional heat conduction, radiation cooling, thermal safety management, etc., and can be applied to the fields of high-temperature equipment, heat dissipation of electronic devices, and building energy conservation.

Description

Technical Field

[0001] The present invention relates to the field of thermal management technology, and in particular to a thermal safety management coating with a thermal rectification function, a preparation method and an application thereof. Background Art

[0002] With the global promotion and application of high-tech technologies such as 5G, the demand for heat dissipation of power equipment has exploded. At present, the heat generated by these devices is usually dissipated by active cooling methods that consume huge amounts of energy. Taking power equipment as an example, the internal heat is first transferred to the outer casing and then dissipated through convection and thermal radiation. However, active heat dissipation methods require the consumption of a large amount of fossil energy, which has a negative impact on global climate change.

[0003] Therefore, using radiative cooling coatings to cover the housing of power equipment has become a feasible passive energy-free heat dissipation method. This coating mainly improves heat dissipation efficiency by reducing the absorption of solar heat and enhancing infrared heat radiation. However, conventional radiative cooling coatings achieve high reflection of sunlight by constructing a porous structure. The thermal conductivity of this porous coating is extremely low (<0.1), which will seriously reduce the heat dissipation efficiency of the housing.

[0004] The core function of the thermal rectification effect is to achieve unidirectional conduction of heat flow, that is, good thermal conductivity in one direction and poor thermal conductivity in the opposite direction. Based on the principle of thermal rectification, the present invention has developed a thermal safety management coating that takes into account both thermal conductivity and radiative cooling. Summary of the invention

[0005] The purpose of the present invention is to provide a thermal safety management coating with a thermal rectification function, and a preparation method and application thereof. The prepared thermal safety management coating has the advantages of directional heat conduction, radiation cooling, thermal safety management, etc., and can be applied to high-temperature equipment, electronic device heat dissipation, building energy conservation and other fields.

[0006] To achieve the above objectives, the present invention provides a thermal safety management coating with a thermal rectification function, wherein the thermal safety management coating comprises a heat conductive layer and a radiation cooling layer connected in series, wherein the heat conductive layer is a coating comprising an inorganic non-metal, and the radiation cooling layer is a coating comprising a high refractive index medium scatterer.

[0007] Preferably, the inorganic non-metal includes one or more of silicon carbide, silicon nitride, boron nitride, silicon dioxide, titanium dioxide, zinc oxide, aluminum oxide, aluminum nitride, magnesium oxide, cerium dioxide, and beryllium oxide.

[0008] Preferably, the high refractive index medium scatterer is one of hollow silica spheres, hollow titanium dioxide spheres, glass microspheres and hollow polyphosphazene spheres.

[0009] Preferably, the size of the high refractive index medium scatterer is 0.5-1 μm, and the shell thickness of the high refractive index medium scatterer accounts for 10%-60% of the diameter of the sphere.

[0010] The method for preparing the thermal safety management coating having a thermal rectification function comprises the following steps:

[0011] S1. After modifying the inorganic non-metal, add it to the base resin, stir it in vacuum, coat it on the surface of the base material by an automatic coating machine, and cure it at a constant temperature to obtain a thermal conductive layer;

[0012] S2. Add a high refractive index medium scatterer to the polyurea matrix, and after vacuum stirring, coat it on the surface of the thermal conductive layer by an automatic coating machine to form a radiation cooling layer, and cure it at a constant temperature to obtain a composite thermal safety management coating.

[0013] Preferably, in S1, the modification is surface modification using a modifier, and the modifier includes one of dopamine, tannic acid, and a silane coupling agent.

[0014] Preferably, in S1, the inorganic non-metallic material accounts for 30 wt% of the matrix resin, and the thickness of the thermal conductive layer is 50-450 μm.

[0015] Preferably, the high refractive index medium scatterer in S2 accounts for 10-30wt% of the polyurea matrix, and the thickness of the radiation cooling layer is 50-450μm.

[0016] Preferably, the constant temperature curing temperature in S1 and S2 is 25° C., and the curing time is 24 hours.

[0017] The above-mentioned thermal safety management coating with thermal rectification function is applied in the heat dissipation coating of high-temperature power equipment and electronic devices.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention provides a thermal safety management coating with a thermal rectification function. Based on the principle of thermal rectification, a heat-conducting layer and a radiation cooling layer are connected in series, so that the heat-conducting layer can quickly transfer the heat generated by the equipment to the radiation cooling layer, and the radiation cooling layer then radiates the heat to the external environment, thereby achieving efficient heat dissipation and solving the problems of a single thermal regulation path and the risk of thermal runaway of the radiation cooling coating.

[0020] (2) The present invention provides a thermal safety management coating with a thermal rectification function. The high refractive index medium scatterer used has the characteristics of high scattering efficiency, high emissivity, flame retardancy, and adjustable particle size. The grafted modified non-metallic oxide used contains a flame retardant structure. The flame retardant properties of the high refractive index medium scatterer and the flame retardant structure in the grafted modified non-metallic oxide cooperate with each other, giving the coating excellent flame retardant properties. In addition, the characteristics of the high refractive index medium scatterer itself also enable the coating to have the ability of radiation cooling, so that the thermal safety management coating takes into account both radiation cooling and flame retardant properties.

[0021] (3) The present invention adopts a method for preparing a thermal safety management coating with a thermal rectification function, using a high refractive index medium scatterer and an inorganic non-metal as fillers and a common resin as a coating matrix, and prepares a double-layer thermal safety management coating through a simple spraying or coating process. The preparation method is simple and easy to operate, the material cost is low, and it is easy to control and adjust the quality, and it is easy to carry out large-scale industrial production and popularization and application.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Thermogravimetric curves of high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention;

[0024] Figure 2 The XPS graphs of the high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention;

[0025] Figure 3 The reflectivity curves of the high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention in the sunlight band are as follows;

[0026] Figure 4 This is a graph showing the emissivity of the thermal safety management coating in the infrared band of Example 1 of the present invention;

[0027] Figure 5 This is a thermal rectification combination diagram of the thermal safety management coating of Example 1 of the present invention; Figure 5 a in the figure is a schematic diagram when the thermal safety management coating is not heated; Figure 5 b is a schematic diagram of the thermal safety management coating being heated for 5 seconds; Figure 5 c in the figure is a schematic diagram of heating the thermal safety management coating for 10 seconds; Figure 5 d in the figure is a schematic diagram of the thermal safety management coating being heated for 20 seconds; Figure 5 e in the figure is a schematic diagram of heating the thermal safety management coating for 30 seconds; Figure 5 f in the figure is a schematic diagram of the thermal safety management coating being heated for 50 seconds; Figure 5g in the figure is a schematic diagram of the thermal safety management coating being heated for 100 seconds; Figure 5 h in it is a schematic diagram of the thermal safety management coating being heated for 180 seconds;

[0028] Figure 6 This is a heat dissipation performance diagram of the thermal safety management coating of Example 1 of the present invention;

[0029] Figure 7 It is a schematic diagram of the thermal conductivity and thermal rectification coefficient in the forward and reverse directions of the thermal safety management coating of Example 1, Example 4, Example 5, and Example 6 of the present invention;

[0030] Figure 8 It is a schematic diagram of the thermal conductivity and thermal rectification coefficient in the forward and reverse directions of the thermal safety management coating of Example 1, Example 7, and Example 8 of the present invention;

[0031] Fig. 9 Transmission electron microscopy images of hollow microspheres of different sizes and different shell thicknesses obtained in Example 1 of the present invention; Fig. 9 a in the equation is SiO 2 -NH 2 Morphology of hollow microspheres with a size of 1 μm obtained after 8 hours of polymerization. Fig. 9 b in the equation is SiO 2 -NH 2 Morphology of hollow microspheres with a size of 1 μm obtained after 24 hours of polymerization. Fig. 9 The c in the equation is SiO 2 -NH 2 Morphology of hollow microspheres with a size of 0.5 μm obtained after 24 hours of polymerization. Fig. 9 The d in the equation is SiO 2 -NH 2 Morphology of hollow microspheres with a size of 0.5 μm obtained after 24 h of polymerization;

[0032] Fig.10 The scattering intensity diagram of hollow microspheres of different sizes and different shell thicknesses in Example 1 is calculated based on the Mie scattering principle of the present invention. Fig.10 a in the figure is the scattering spectrum of hollow microspheres with a shell thickness of 10%. Fig.10 Figure b is the scattering spectrum of hollow microspheres with a shell thickness of 50%. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features of the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0034] Example 1

[0035] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0036] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0037] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0038] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0039] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0040] S1.4, by regulating SiO 2 -NH 2 High refractive index polyphosphazene hollow spheres with different particle size distributions and different shell thickness ratios were prepared by adjusting the size (0.5-1μm) and time (8-24 hours).

[0041] S2. Modified inorganic non-metal (modified boron nitride)

[0042] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0043] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0044] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0045] S3. Preparation of thermal conductive layer

[0046] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0047] S4. Coating radiation cooling layer

[0048] 30wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0049] Example 2

[0050] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0051] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0052] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of 4,4'-diaminodiphenyl ether and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0053] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C, reflux and continue stirring (magnetic stirring) the solution for 8 hours to obtain PZM@SiO 2 Nanoparticles, PZM@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0054] S1.3, 1g PZM@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed three times with water and dried to obtain polyphosphazene hollow spheres, which were recorded as PZM hollow spheres.

[0055] S2. Modified inorganic non-metal (modified boron nitride)

[0056] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0057] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the above dispersion (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0058] S2.3. Wash the product solution with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0059] S3. Preparation of thermal conductive layer

[0060] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0061] S4. Coating radiation cooling layer

[0062] 30wt% of PZM hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0063] Example 3

[0064] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0065] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0066] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol A and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0067] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZA@SiO 2 Nanoparticles, PZA@SiO 2The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0068] S1.3, 1g PZA@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed three times with water and dried to obtain polyphosphazene hollow spheres, which were recorded as PZA hollow spheres.

[0069] S2. Modified inorganic non-metal (modified boron nitride)

[0070] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0071] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the above dispersion (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0072] S2.3. Wash the product solution with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0073] S3. Preparation of thermal conductive layer

[0074] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0075] S4. Coating radiation cooling layer

[0076] 30 wt% of PZA hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 250 μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0077] Example 4

[0078] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0079] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0080] S1.1, 0.5g SiO 2 -NH 2(1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0081] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0082] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0083] S2. Modified inorganic non-metal (modified boron nitride)

[0084] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0085] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0086] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0087] S3. Preparation of thermal conductive layer

[0088] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0089] S4. Coating radiation cooling layer

[0090] 10wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0091] Example 5

[0092] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0093] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0094] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0095] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0096] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0097] S2. Modified inorganic non-metal (modified boron nitride)

[0098] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0099] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0100] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0101] S3. Preparation of thermal conductive layer

[0102] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0103] S4. Coating radiation cooling layer

[0104] 20wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0105] Example 6

[0106] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0107] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0108] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0109] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0110] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0111] S2. Modified inorganic non-metal (modified boron nitride)

[0112] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0113] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0114] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0115] S3. Preparation of thermal conductive layer

[0116] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0117] S4. Coating radiation cooling layer

[0118] 30 wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 100 μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0119] Example 7

[0120] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0121] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0122] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0123] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0124] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0125] S2. Modified inorganic non-metal (modified boron nitride)

[0126] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0127] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0128] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0129] S3. Preparation of thermal conductive layer

[0130] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 450 μm thick coating was coated on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0131] S4. Coating radiation cooling layer

[0132] 30 wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 50 μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0133] Example 8

[0134] The present invention provides a method for preparing a thermal safety management coating with a thermal rectification function, comprising the following steps:

[0135] S1. Preparation of high refractive index medium scatterers (polyphosphazene hollow spheres)

[0136] S1.1, 0.5g SiO 2 -NH 2 (1 μm) was added into 600 mL of acetonitrile and stirred for 2 h under ultrasonic conditions, and then (0.0096 mol, 2.4 g) of bisphenol S (4,4'-dihydroxydiphenyl sulfone) and 8 mL of triethylamine were quickly added to obtain a reaction system.

[0137] S1.2. Add (0.004 mol, 1.4 g) hexachlorocyclotriphosphazene in 50 mL acetonitrile to the reaction system of S1.1 (maintain magnetic stirring) within 30 minutes, then raise the reaction temperature to 80 ° C and reflux while continuously stirring (magnetic stirring) the solution for 8 hours to obtain PZS@SiO 2 Nanoparticles, PZS@SiO 2 The nanoparticles were washed with water and ethanol to obtain a white solid, which was dried under vacuum at 60 °C overnight.

[0138] S1.3, 1g of PZS@SiO 2 The nanoparticles were added into a 4 wt % hydrofluoric acid solution, stirred for 4 hours, washed with water three times and dried to obtain polyphosphazene hollow spheres, which were recorded as PZS hollow spheres.

[0139] S2. Modified inorganic non-metal (modified boron nitride)

[0140] S2.1. Place 3.0 g of BN in 500 mL of deionized water and perform ultrasonic treatment for 5 h to disperse it evenly to obtain a dispersion.

[0141] S2.2. Mix 0.6 g Tris (tris(hydroxymethyl)aminomethane) with the dispersion in S2.1 (PH=8.5-9.0), add 0.2 g tannic acid (TA), and stir magnetically at room temperature for 3 h to obtain a product solution.

[0142] S2.3. Wash the product solution in S2.2 with deionized water for multiple times until the product solution is neutral, and finally put it into an oven at 60°C for 24 hours to obtain modified boron nitride, recorded as TA-BN.

[0143] S3. Preparation of thermal conductive layer

[0144] 30 wt% TA-BN was added to the polyurea matrix. After 5 minutes of vacuum stirring, a 50 μm thick coating was applied on the surface of the substrate by an automatic coating machine, and the thermal conductive layer was obtained by curing at room temperature for 24 hours.

[0145] S4. Coating radiation cooling layer

[0146] 30wt% of PZS hollow spheres were added to the polyurea matrix. After 5 minutes of vacuum stirring, a 450μm thick coating was applied on the surface of the thermal conductive layer by an automatic coating machine to form a radiative cooling layer. The composite thermal safety management coating was obtained by curing at room temperature for 24 hours.

[0147] Performance Testing

[0148] Figure 1 The thermogravimetric curves of the high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention are as follows: Figure 1As shown in the figure, the initial pyrolysis temperatures of PZS hollow spheres, PZM hollow spheres and PZA hollow spheres are 340.9℃, 234.2℃ and 335.0℃, respectively, and the pyrolysis peak temperatures of PZS hollow spheres, PZM hollow spheres and PZA hollow spheres are 529.7℃, 460.8℃ and 466.8℃, respectively. Among them, PZS hollow spheres show excellent high-temperature thermal stability. Combined with the carbon residue analysis, it was found that the carbon residue of PZM hollow spheres was as high as 65.7%, showing excellent carbonization. The carbon residues of PZS hollow spheres and PZA hollow spheres were 47.7% and 41.5%, respectively. PZM hollow spheres have good carbonization performance, but the initial degradation temperature is too low. Overall, PZS hollow spheres have higher thermal stability. In short, polyphosphazene microspheres form efficient flame retardant structures, providing protection for the thermal safety of the coating.

[0149] Figure 2 The XPS graphs of the high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention are as follows: Figure 2 As shown in the figure, the distribution of P element was detected on the surface of three kinds of microspheres: PZS hollow sphere, PZM hollow sphere and PZA hollow sphere, which is closely related to the successful grafting of polyphosphazene. In addition, the distribution of S element was also detected on the surface of PZS hollow sphere, which further confirmed that the reaction between polyphosphazene and bisphenol S was successful.

[0150] Figure 3 The reflectivity curves of the high refractive index medium scatterers prepared in Examples 1 to 3 of the present invention in the sunlight band are as follows: Figure 3 As shown, due to the enhanced backscattering effect of the hollow structure, the average solar reflectivity of PZS hollow spheres, PZM hollow spheres and PZA hollow spheres reached 97.7%, 87.7% and 90.1%, respectively. High reflectivity means that less solar energy is absorbed, which can achieve efficient cooling.

[0151] Figure 4 This is a graph showing the emissivity of the thermal safety management coating obtained in Example 1 of the present invention in the infrared band. Figure 4 As shown in the figure, the abundant infrared groups inside the polyurea molecules and PZS molecules absorb external radiation energy, undergo strong stretching vibrations, and high-energy electrons transition to low energy levels, which in turn leads to photon emission. Therefore, the thermal safety management coating emits heat in the form of mid-infrared electromagnetic waves, with an emissivity of up to 95.0%, achieving radiative cooling.

[0152] Figure 5 This is a thermal rectification combination diagram of the thermal safety management coating obtained in Example 1 of the present invention, such as Figure 5As shown, in order to more intuitively evaluate the asymmetric thermal conductivity of the thermal safety management coating, the thermal safety management coating was placed on a hot table surface at 70°C, and an infrared camera was used to capture the surface temperature distribution of the two coatings placed forward and reversely. The sample on the left was placed forward and the sample on the right was placed reversely. After 100 seconds of heating, the surface temperatures of the forward and reverse coatings were 63.8°C and 60.9°C, respectively. The unique thermal rectification effect of the thermal safety management coating is beneficial to the heat dissipation of the substrate.

[0153] Figure 6 This is a heat dissipation performance diagram of the thermal safety management coating obtained in Example 1 of the present invention, such as Figure 6 As shown, the blank group is a model without thermal safety management coating, and the experimental group is a model coated with thermal safety management coating of Example 1. In a closed space, a 200°C heating plate is used to heat the environment. After heating for half an hour, the internal temperature of the experimental group is 6.7°C lower than that of the blank group, which indicates that the experimental group accelerates the heat loss inside the space. Correspondingly, the external temperature of the experimental group is also about 5.4°C lower than that of the blank group, which is due to the radiation cooling effect of the surface of the thermal safety management coating to scatter more heat.

[0154] Figure 7 Schematic diagram of thermal conductivity and thermal rectification coefficient in the positive and negative directions of the invention embodiments 1, 4, 5 and 6, Figure 7 TRC T-R It represents the thermal conductivity from the heat conduction layer to the radiation cooling layer. Figure 7 TRC R-T It represents the thermal conductivity from the radiation cooling layer to the heat conduction layer, such as Figure 7 As shown in the figure, as the addition amount of polyphosphazene hollow spheres increases (10-30 wt%), the forward thermal conductivity of the coating gradually increases, showing a higher thermal rectification coefficient (1.49). In addition, the thickness of the coating will also increase the thermal rectification coefficient. For example, the thermal rectification coefficient of the coating shown in Example 1 reaches 1.78.

[0155] Figure 8 Schematic diagram of thermal conductivity and thermal rectification coefficient in the positive and negative directions of the invention embodiments 1, 7 and 8, Figure 8 TRC T-R It represents the thermal conductivity from the heat conduction layer to the radiation cooling layer. Figure 8 TRC R-T It represents the thermal conductivity from the radiation cooling layer to the heat conduction layer, such as Figure 8As shown, the thermal rectification coefficient is affected by the ratio of the thickness of the double-layer coating. When the ratio of the heat-conducting layer (boron nitride layer) to the cooling layer (polyphosphazene hollow sphere layer) is 9:1 (Example 7), 5:5 (Example 1) and 1:9 (Example 8), the thermal rectification coefficients of the coating are 1.42, 1.78 and 0.14 respectively. Therefore, when the ratio of the double-layer thickness is 5:5, that is, the coating in Example 1 exhibits the best thermal rectification coefficient.

[0156] Fig. 9 TEM images of hollow microspheres of different sizes and different shell thicknesses obtained in Example 1 are shown in FIG. Fig. 9 As shown, SiO 2 -NH 2 The shell thickness of the hollow microspheres with a size of 1 μm obtained by polymerization for 8 h accounts for 10% of the diameter of the sphere. 2 -NH 2 The shell thickness of the hollow microspheres with a size of 1 μm obtained by polymerization for 24 h accounts for 57% of the sphere diameter. 2 -NH 2 The shell thickness of the hollow microspheres with a size of 0.5 μm obtained by polymerization for 24 h accounts for 16% of the sphere diameter. 2 -NH 2 The shell thickness of the hollow microspheres with a size of 0.5 μm obtained after 24 h of polymerization accounts for 40% of the sphere diameter.

[0157] In different sizes of SiO 2 -NH 2 The hollow microspheres prepared under different microsphere templates and polymerization reaction time conditions showed significant differences in size and shell thickness. Specifically, as the polymerization reaction time increased, the shell thickness of the hollow microspheres increased significantly; at the same time, the shell thickness of the hollow microspheres prepared by the template microspheres of smaller size (0.5μm) was relatively thin, while the shell thickness of the hollow microspheres prepared by the template microspheres of larger size (1μm) was relatively thick.

[0158] Fig.10 The scattering intensity diagram of hollow microspheres of different sizes and different shell thicknesses in Example 1 is calculated based on the Mie scattering principle of the present invention. As shown in the figure, the hollow microspheres with a shell thickness of 10% show a significant scattering effect in the 300-700nm visible light band, and their scattering efficiency can reach about 50% of the solar energy. The best scattering performance is shown in the solar radiation energy peak area near 500nm (corresponding to the AM1.5 spectrum standard), and the scattering efficiency is improved by about 12% relative to other wavelength areas. The hollow microspheres with a shell thickness of 50% show differentiated scattering characteristics. Although they achieve more than 90% of the solar light scattering efficiency in the wide spectrum range of 200-1000nm, the scattering efficiency at the characteristic wavelength of 500nm is about 15% lower than that of the thin shell structure.

[0159] In summary, there is a significant correlation between the shell thickness parameters of hollow microspheres and scattering performance: when the shell thickness increases from 10% to 50%, the scattering spectrum bandwidth expands by about 67%, but the characteristic wavelength scattering efficiency decreases by about 8.5%. This discovery provides a theoretical basis for the design of microsphere structures in different application scenarios, that is, thin shell structures are suitable for efficient scattering requirements of specific wavelengths, while thick shell structures are more suitable for wide-spectrum scattering applications.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A thermal safety management coating with thermal rectification function, characterized in that: Thermal safety management coatings are used in heat dissipation coatings for high-temperature power equipment and electronic devices; The thermal safety management coating comprises a heat conducting layer and a radiation cooling layer connected in series, wherein the heat conducting layer is a coating comprising an inorganic non-metal, and the radiation cooling layer is a coating comprising a high refractive index medium scatterer; The high refractive index medium scatterer is a polyphosphazene hollow sphere, which includes one of a PZS hollow sphere, a PZM hollow sphere and a PZA hollow sphere. The polyphosphazene hollow spheres are prepared by the following steps: S1.1, adding SiO2-NH2 to acetonitrile, stirring for 2 hours under ultrasonic conditions, and then quickly adding bisphenol S or 4,4'-diaminodiphenyl ether or bisphenol A and triethylamine to obtain a reaction system; S1.2, adding a mixed solution of hexachlorocyclotriphosphazene dissolved in acetonitrile dropwise to the reaction system of S1.1, then raising the reaction temperature to 80°C for reflux and continuously stirring the solution for 8 hours to obtain nanoparticles, washing the nanoparticles with water and ethanol to obtain a white solid, and vacuum drying at 60°C overnight; S1.

3. Add the nanoparticles in S1.2 into a hydrofluoric acid solution, stir for 4 hours, wash three times with water and dry to obtain polyphosphazene hollow spheres, which are PZS hollow spheres, PZM hollow spheres or PZA hollow spheres.

2. A thermal safety management coating with thermal rectification function according to claim 1, characterized in that: The inorganic non-metallic material includes one or more of silicon carbide, silicon nitride, boron nitride, silicon dioxide, titanium dioxide, zinc oxide, aluminum oxide, aluminum nitride, magnesium oxide, cerium dioxide, and beryllium oxide.

3. A thermal safety management coating with thermal rectification function according to claim 2, characterized in that: The size of the high refractive index medium scatterer is 0.5-1 μm, and the shell thickness of the high refractive index medium scatterer accounts for 10%-60% of the diameter of the sphere.

4. A method for preparing a thermal safety management coating with a thermal rectification function according to any one of claims 1 to 3, characterized in that: The following steps are included: S1. After modifying the inorganic non-metal, add it to the base resin, stir it in vacuum, coat it on the surface of the base material by an automatic coating machine, and cure it at a constant temperature to obtain a thermal conductive layer; S2. Add a high refractive index medium scatterer to the polyurea matrix, and after vacuum stirring, coat it on the surface of the thermal conductive layer by an automatic coating machine to form a radiation cooling layer, and cure it at a constant temperature to obtain a composite thermal safety management coating.

5. The method for preparing a thermal safety management coating with a thermal rectification function according to claim 4, characterized in that: In S1, the modification is to perform surface modification using a modifier, and the modifier includes one of dopamine, tannic acid, and a silane coupling agent.

6. The method for preparing a thermal safety management coating with a thermal rectification function according to claim 4, characterized in that: In S1, inorganic non-metallic materials account for 30wt% of the matrix resin, and the thickness of the thermal conductive layer is 50-450μm.

7. The method for preparing a thermal safety management coating with a thermal rectification function according to claim 4, characterized in that: In S2, the high refractive index medium scatterer accounts for 10-30wt% of the polyurea matrix, and the thickness of the radiation cooling layer is 50-450μm.

8. The method for preparing a thermal safety management coating with a thermal rectification function according to claim 4, characterized in that: The constant temperature curing temperature in S1 and S2 is 25°C, and the curing time is 24 hours.

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