Silicate radiation heat dissipation coating and preparation method thereof

Abstract

The application discloses a silicate radiation heat dissipation coating and a preparation method thereof, and belongs to the technical field of heat dissipation coating. First, silicic acid is used as a silicon source, and calcium chloride is used as a calcium source, which are respectively dissolved in an alkaline aqueous solution, the solid-liquid ratio and the pH value of a reaction system are controlled, then a dispersing agent is added, the dispersed solution is placed in a reaction kettle, and after being fully reacted under high-temperature conditions, the solution is naturally cooled to obtain a nano calcium silicate whisker slurry, then a high modulus alkali metal silicate solution is used as a film forming material, a certain proportion of the nano calcium silicate whisker slurry and the wollastonite are uniformly added to obtain a coating slurry, the coating slurry is coated on a metal substrate through a brushing method, and the silicate radiation heat dissipation coating is obtained through room temperature solidification. The silicate radiation heat dissipation coating solves the problems of high cost, complex process and environmental pollution of the existing radiation heat dissipation coating.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat dissipation coatings, and particularly relates to a preparation method of a silicate radiation heat dissipation coating. BACKGROUND

[0002] When electronic devices such as computers and mobile phones work, a large amount of heat will be generated, and if the heat cannot be dissipated in time, the device will overheat and affect its performance and service life; in the aerospace industry, the external temperature rise will cause the spacecraft to overheat, affecting the normal and safe operation of the spacecraft; the temperature of buildings rises under the sunlight, and air conditioners need to be used for refrigeration, consuming a large amount of electric power resources and aggravating the greenhouse effect. Therefore, in the fields of electronics, construction, aerospace, etc., the problem of how to efficiently and quickly dissipate heat is faced. Materials with high infrared emissivity can spontaneously emit the absorbed heat from the sun or surrounding high-temperature objects in the form of infrared rays to outer space or the surrounding low-temperature environment, which is an effective heat dissipation method.

[0003] The existing heat dissipation coating mainly uses graphite, graphene or rare earth-based radiation heat dissipation materials as the main filler, supplemented by high thermal conductivity fillers such as silicon nitride and silicon carbide and organic high molecular resins such as acrylic resin and fluorocarbon resin dispersed in organic solvents to prepare a heat dissipation coating, thereby achieving the heat dissipation effect. However, the price of pure graphene powder on the market is high, which increases the cost of the heat dissipation coating, the preparation process of the rare earth-based material is relatively complex, and the organic resin used has poor high-temperature resistance, and the volatile products are harmful to the human body and pollute the environment. Therefore, it is necessary to develop an inorganic radiation heat dissipation coating with low cost and no pollution, which can realize radiation heat dissipation while having excellent high-temperature resistance and aging resistance. SUMMARY

[0004] In view of the deficiencies in the prior art, the application aims to provide a preparation method of a silicate radiation heat dissipation coating with micron size and high purity. The method uses high modulus potassium silicate as a film forming material, uniformly adds nano calcium silicate whiskers and micron-sized wollastonite according to a certain proportion, and then prepares a micro-nano structure coating, thereby solving the problems of high cost, complex process and environmental pollution of the existing radiation heat dissipation coating.

[0005] To achieve the above-mentioned purpose, the application realizes the technical scheme as follows.

[0006] A preparation method of a silicate radiation heat dissipation coating, comprising the following steps:

[0007] S1, dissolving silicon acid as a silicon source and calcium chloride as a calcium source in an alkaline aqueous solution respectively, controlling the water-solid ratio and the pH value of the reaction system, then adding a dispersant, and placing the dispersed solution in a reaction kettle to fully react under high temperature conditions and then naturally cooling to obtain a nano calcium silicate whisker slurry;

[0008] S2, centrifuging the calcium silicate nanowhisker slurry and mixing with the high modulus alkali metal silicate solution in a designed ratio, and stirring to disperse uniformly;

[0009] S3, adding wollastonite powder and dispersing uniformly to obtain a coating slurry;

[0010] S4, cleaning and polishing the surface of the substrate to obtain a non-polluted rough substrate;

[0011] S5, coating the coating slurry prepared in S3 on the surface of the substrate, and curing at room temperature to obtain a silicate radiation heat dissipation coating.

[0012] The silicon-oxygen bond in the nanometer calcium silicate whisker, wollastonite and film-forming material in the high modulus alkali metal silicate solution in the coating has a resonance absorption at 10 μm, so that the coating has a high emissivity at the atmospheric window of 8-10 μm. In addition, the combined water in the coating has multiple absorptions at 2.5-8 μm, which helps the coating to achieve high emissivity in a wide spectrum range greater than 2.5 μm, thereby enhancing the radiation heat dissipation effect of the coating, and thus the coating can be used as a radiation heat dissipation coating for buildings or spacecraft.

[0013] Preferably, in S1, the molar ratio of silicic acid to calcium chloride is 1:1.

[0014] Preferably, in S1, the alkaline aqueous solution is a potassium hydroxide solution, the dispersing agent is sodium dodecyl sulfate, the water-solid ratio is 40:1-60:1, and the pH value of the system is greater than 12.6. Controlling the water-solid ratio and the pH value of the system is conducive to the formation of whiskers and increases the yield of nanometer calcium silicate whiskers.

[0015] Preferably, in S1, the specific parameters for the reaction under high temperature conditions are as follows: increasing the temperature from room temperature to 225-230 °C at a rate of 15 °C / min, maintaining the temperature for 16 h, and then naturally cooling. The high temperature conditions increase the crystallinity of the product and promote the growth of nanometer calcium silicate whiskers.

[0016] Preferably, in S2, the solid content of the nanometer calcium silicate whisker slurry after centrifugation is 3%-5%.

[0017] Preferably, in S2, the alkali metal silicate solution is a potassium silicate solution, a sodium silicate solution or a lithium silicate solution, and the modulus of the high modulus alkali metal silicate is 5.3-5.5, and the solid content is 22%-28%. Within this modulus and solid content range, the film-forming effect of the high modulus alkali metal silicate solution is best.

[0018] Preferably, in S2, the mass ratio of the nanometer calcium silicate whisker slurry after centrifugation to the high modulus alkali metal silicate solution is 1:2-1:1.

[0019] Preferably, in S3, the mass ratio of the wollastonite powder to the high modulus alkali metal silicate solution is 1:5-1:3, and the mesh number of the wollastonite powder is greater than 1250 mesh.

[0020] Preferably, in S5, the coating thickness is 150-200 microns.

[0021] A silicate radiation heat dissipation coating prepared by the preparation method of the silicate radiation heat dissipation coating as described above.

[0022] The technical solution provided by the present application has the following advantages and beneficial effects:

[0023] 1. The silicate radiation heat dissipation coating prepared by the present application has good radiation performance, and the emissivity in the atmospheric window band reaches 90%, which can effectively achieve the radiation heat dissipation effect.

[0024] 2. The silicate radiation heat dissipation coating of the present application breaks through the limitation that most traditional radiation heat dissipation coatings use organic resins, and solves the problems of environmental pollution, harm to human body, high cost, and poor weather resistance.

[0025] 3. The preparation method of the present application is simple, low in cost, easy to scale up, and suitable for large-area use, and the coating formed after the coating is brushed has excellent high-temperature resistance and aging resistance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a preparation method flow chart of a silicate radiation heat dissipation coating of the present application.

[0027] Figure 2 is a mid-infrared emissivity spectrum diagram of the coating prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions of the present application, the preferred embodiments of the present application are described below in combination with specific examples, but it should not be understood as a limitation on the present application, which is only for illustration.

[0029] The test methods or test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are all obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0030] Example 1

[0031] As shown in Figure 1 , the present embodiment provides a preparation method of a silicate radiation heat dissipation coating, which comprises the following steps:

[0032] Step 1, preparation of nano calcium silicate whiskers

[0033] Silicic acid and calcium chloride were dissolved in potassium hydroxide solution respectively with a molar ratio of 1:1, water-solid ratio of 50:1, and pH value of the system of 12.7, and 1.0% of sodium dodecyl sulfate was added as a dispersant. The reaction kettle was heated from room temperature to 226°C at a heating rate of 15°C / min, and kept for 16 h, and then naturally cooled to obtain a uniformly dispersed nano calcium silicate whisker slurry.

[0034] Step 2, preparation of silicate radiation heat dissipation coating slurry

[0035] The nano calcium silicate whisker slurry obtained in step 1 was centrifuged, and the solid content of the slurry after centrifugation was 3%. A high modulus potassium silicate solution with a mass fraction of 28% and a modulus of 5.3 was used as a film forming material, and the centrifuged nano calcium silicate whisker slurry was added. The mass ratio of the centrifuged nano calcium silicate whisker slurry to the high modulus potassium silicate solution was 1:2, and after uniform dispersion by magnetic stirring, 1250 mesh wollastonite was added in a mass ratio of 1:4 of wollastonite to high modulus potassium silicate solution. After ball milling for 1 h, a uniformly dispersed coating slurry was obtained.

[0036] Step 3, preparation of silicate radiation heat dissipation coating

[0037] The coating prepared in step 1 can be uniformly brushed on a cleaned and polished circular iron base plate, and cured at room temperature to obtain a 200 μm thick inorganic radiation heat dissipation coating. The coating has good dispersibility and a smooth surface.

[0038] Figure 2 The prepared coating has an emissivity spectrum in the 2.5-25 μm mid-infrared waveband, and the emissivity of the coating in the mid-infrared waveband is 0.90.

[0039] Example 2

[0040] As shown in the Figure 1 embodiment, a preparation method of a silicate radiation heat dissipation coating is provided, comprising the following steps:

[0041] Step 1, preparation of nano calcium silicate whisker

[0042] Silicic acid and calcium chloride were dissolved in potassium hydroxide solution respectively with a molar ratio of 1:1, water-solid ratio of 40:1, and pH value of the system of 12.8, and 1.0% of sodium dodecyl sulfate was added as a dispersant. The reaction kettle was heated from room temperature to 228°C at a heating rate of 15°C / min, and kept for 16 h, and then naturally cooled to obtain a uniformly dispersed nano calcium silicate whisker slurry.

[0043] Step 2, preparation of silicate radiation heat dissipation coating slurry

[0044] The nanometer calcium silicate whisker slurry obtained in step 1 is centrifuged, and the solid content of the slurry after centrifugation is 4%. A high modulus potassium silicate solution with a mass fraction of 26% and a modulus of 5.4 is used as a film forming material, and the nanometer calcium silicate whisker slurry after centrifugation is added. The mass ratio of the nanometer calcium silicate whisker slurry after centrifugation to the high modulus potassium silicate solution is 1:1. After uniform dispersion by magnetic stirring, 1250 mesh wollastonite is added according to the mass ratio of wollastonite to high modulus potassium silicate solution of 1:5. After ball milling for 1 h, a uniformly dispersed coating slurry is obtained.

[0045] Step 3, preparation of silicate radiation heat dissipation coating

[0046] The coating prepared in step 1 can be uniformly brushed on a 10 cm*10 cm square iron substrate after cleaning and polishing, and a 150 μm thick silicate radiation heat dissipation coating is prepared by curing at room temperature.

[0047] The prepared coating and the blank iron plate without any coating are irradiated under the strong irradiation lamp of the simulated sunlight for 50 min. After the temperature of the coating and the blank iron plate stabilizes, the temperature of the coating is 5℃ lower than that of the blank iron plate, and the radiation heat dissipation effect can be achieved.

[0048] Example 3

[0049] As shown in Figure 1 , the present embodiment provides a preparation method of a silicate radiation heat dissipation coating, comprising the following steps:

[0050] Step 1, preparation of nanometer calcium silicate whisker

[0051] Silicic acid and calcium chloride are dissolved in potassium hydroxide solution respectively according to a molar ratio of 1:1, the water solid ratio is 60:1, the pH value of the system is 12.9, and 1.0% of sodium dodecyl sulfate is added as a dispersant. In the reaction kettle, the temperature is raised from room temperature to 230℃ at a rate of 15℃ / min, and the temperature is kept for 16 h, and then the uniformly dispersed nanometer calcium silicate whisker slurry is obtained by natural cooling.

[0052] Step 2, preparation of silicate radiation heat dissipation coating slurry

[0053] The nanometer calcium silicate whisker slurry obtained in step 1 is centrifuged, and the solid content of the slurry after centrifugation is 5%. A high modulus potassium silicate solution with a mass fraction of 27% and a modulus of 5.5 is used as a film forming material, and the nanometer calcium silicate whisker slurry after centrifugation is added. The mass ratio of the nanometer calcium silicate whisker slurry after centrifugation to the high modulus potassium silicate solution is 1:1.5. After uniform dispersion by magnetic stirring, 1250 mesh wollastonite is added according to the mass ratio of wollastonite to high modulus potassium silicate solution of 1:3. After ball milling for 1 h, a uniformly dispersed coating slurry is obtained.

[0054] Step 3, preparation of silicate radiation heat dissipation coating

[0055] The prepared paint in step 1 can be uniformly brushed on a 10cm*10cm square iron substrate after cleaning and polishing, and the paint is cured at room temperature to prepare a 200μm thick silicate radiation heat dissipation coating.

[0056] The prepared coating and the blank iron plate without any coating are irradiated under the strong irradiation light of the simulated sunlight for 50min, and after the temperature of the coating and the blank iron plate is stabilized, the temperature of the coating is 7℃ lower than that of the blank iron plate, and the radiation heat dissipation effect can be realized.

[0057] The above is only the preferred embodiment of the present application, and it should be pointed out that the above preferred embodiment should not be regarded as a limitation of the present application, and the protection scope of the present application should be limited by the scope defined by the claims. For ordinary skilled in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for preparing a silicate radiation heat dissipation coating, characterized in that, Includes the following steps: S1. Using silicic acid as the silicon source and calcium chloride as the calcium source, they are dissolved in alkaline aqueous solutions, controlling the water-to-solid ratio at 40:1-60:1 and the pH of the reaction system to be greater than 12.

6. Then, a dispersant is added, and the dispersed solution is placed in a reaction vessel. After fully reacting under high temperature conditions, it is naturally cooled to obtain nano-calcium silicate whisker slurry. The specific parameters for the reaction under high temperature conditions are: heating from room temperature to 225-230℃ at a heating rate of 15℃ / min, holding at this temperature for 16 hours, and then naturally cooling. S2. After centrifuging the nano-calcium silicate whisker slurry, mix it with a high-modulus alkali metal silicate solution according to the designed ratio, and disperse it evenly after stirring; the high-modulus alkali metal silicate solution is a potassium silicate solution, sodium silicate solution, or lithium silicate solution, with a modulus of 5.3-5.5; the mass ratio of the centrifuged nano-calcium silicate whisker slurry to the high-modulus alkali metal silicate solution is 1:2-1:1; S3. Add wollastonite powder with a mesh size greater than 1250 and disperse it evenly to obtain a coating slurry; the mass ratio of wollastonite powder to high modulus alkali metal silicate solution is 1:5-1:

3. S4. After cleaning and polishing the substrate surface, a pollution-free rough substrate is obtained; S5. The coating slurry prepared in S3 is coated onto the substrate surface and cured at room temperature to obtain a silicate radiation heat dissipation coating.

2. The method for preparing the silicate radiation heat dissipation coating according to claim 1, characterized in that, In S1, the molar ratio of silicic acid to calcium chloride is 1:

1.

3. The method for preparing the silicate radiation heat dissipation coating according to claim 1, characterized in that, In S1, the alkaline aqueous solution is potassium hydroxide solution, and the dispersant is sodium dodecyl sulfate.

4. The method for preparing the silicate radiation heat dissipation coating according to claim 1, characterized in that, In S2, the solid content of the nano-calcium silicate whisker slurry obtained after centrifugation is 3%-5%.

5. The method for preparing the silicate radiation heat dissipation coating according to claim 1, characterized in that, In S2, the solid content of the high-modulus alkali metal silicate solution is 22%-28%.

6. The method for preparing the silicate radiation heat dissipation coating according to claim 1, characterized in that, In S5, the coating thickness is 150-200μm.

7. A silicate radiation heat dissipation coating, characterized in that, It is prepared by the method for preparing silicate radiation heat dissipation coating according to any one of claims 1-6.

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