CN102030544B - Preparation method of high temperature-resistant, radiation-insulated, heat-conducting and microwave-permeable inorganic coating - Google Patents

Abstract

The invention discloses a preparation method for forming an inorganic coating with high temperature resistance, radiation heat transfer and microwave transmission compatibility. Ester, isopropanol, deionized water, and ammonia water synthesize silica microspheres with a diameter of 0.3-3 μm, and then grow a 30-500 nm thick titanium oxide shell with a high refractive index on the silica microspheres to obtain a core-shell structure filler. The prepared core-shell particles are dispersed into the sol as a filler, and a dense and uniform inorganic coating can be obtained after heat treatment. The core-shell structure pigment added in the present invention has a high reflection ability to 1-10 μm infrared heat radiation, and the addition amount of the filler is very small, and the dielectric constant of the coating does not increase much, so that the coating has a higher thermal conductivity. At the same time, the reflectivity does not affect the ability of microwave transmission, which can be used for high temperature protection of 1200 ℃.

Description

A preparation method for forming an inorganic coating compatible with high temperature resistance, radiation heat transfer and microwave transmission

technical field

The invention relates to a method for preparing a high-temperature-resistant, radiation-insulated, heat-transfer and microwave-permeable coating material, specifically, an inorganic coating matrix material is prepared by a sol-gel method, and a synthesized functional filler with a core-shell structure is added to obtain Realize the compatibility of radiation heat transfer and microwave transmission.

Background technique

There are three basic ways of heat transfer: heat conduction, heat convection and heat radiation. Thermal radiation is one of the three basic ways of heat transfer. As the temperature increases, the proportion of radiation heat transfer gradually increases. Therefore, the development of high-temperature-resistant insulation materials needs to effectively suppress radiative heat transfer. Materials emit a large number of heat rays at high temperatures, and these heat rays are concentrated in the infrared region of the 0.76-10 μm band. Shielding the infrared heat radiation of 0.76-10 μm can effectively block radiation heat transfer and increase the use temperature and time of high-temperature insulation materials.

Ceramic materials such as quartz and silicon nitride, as high-temperature structural materials, can withstand high temperatures, are not afraid of oxidation, and are resistant to acid and alkali corrosion, and have been widely used in construction, automotive, aerospace and other fields. However, these materials have a transparent section in the infrared band, so the high-temperature radiation heat transfer is very obvious. It not only makes ceramic materials such as quartz and silicon nitride heat up rapidly at high temperature, shortening the service time, but also emits a large amount of heat rays inward, which will cause the internal equipment to fail. Therefore, the effective shielding of radiation heat transfer of such materials at high temperatures can prolong the service life of materials and protect internal equipment. In addition, the dielectric constant of ceramic materials such as quartz and silicon nitride is very low, and they are excellent high-temperature-resistant and microwave-transparent materials. When thermal and electrical properties are required at the same time, it is necessary to effectively shield radiation heat transfer without affecting its electrical properties. , that is, the coating is required to be compatible with radiation heat transfer and microwave transmission.

There is no relevant literature on the preparation of high temperature resistant radiation heat transfer and microwave transparent coatings.

Contents of the invention

A preparation method of the present invention to form an inorganic coating with high temperature resistance, radiation heat transfer and microwave transmission compatibility. In the preparation process, silicon oxide or aluminum oxide is used as the substrate, and a core-shell structure with anti-infrared heat radiation performance is added. The particles are fillers, which make it have excellent radiation and heat transfer capabilities without affecting its microwave transmission performance. The inorganic coating prepared by the method of the invention can be used as a high-temperature, heat-insulating, and microwave-transmitting coating material in a working environment of 1200°C. High temperature resistant heat insulation microwave transparent coating material is a brand new high temperature resistant heat insulation material, which has the functions of heat insulation and microwave transmission. The mechanism of heat insulation is to shield the infrared heat radiation at high temperature to achieve the purpose of high temperature heat insulation.

High temperature resistant radiation heat transfer and microwave transparent coating, the raw material components mainly include inorganic sol and core-shell structure particle filler. In the present invention, inorganic sol is selected as the high-temperature-resistant film-forming material, specifically selected from one or more of silica sol, titania sol, alumina sol or zirconia sol. The core-shell structure filler particles are spherical, with a radius of 0.3-3 μm and a shell thickness of 30-500 nm.

The above raw material inorganic sol and core-shell structure particles are all self-made.

A preparation method of the present invention to form an inorganic coating with high temperature resistance, radiation heat transfer and microwave transmission compatibility, the preparation of the inorganic coating is achieved by the following steps:

Step 1: Preparation of Inorganic Sol

(A) Add 5 to 10 g of precursor to 10 ml of the first solvent, and stir evenly to obtain a precursor solution;

(B) Add 20 to 50 ml of the second solvent and 5 to 6 drops of hydrochloric acid (HCl) (molar concentration is 1 mol/L) in 10 ml of deionized water, and stir evenly to obtain a sol reactant solution;

(C) Add the sol reactant solution prepared in step (B) to the precursor solution prepared in step (A), and react for 1 to 12 hours at a stirring speed of 400 to 800 r/min. After the reaction, prepare Inorganic sol;

The precursor is orthohexyl silicate (TEOS) or aluminum isopropoxide (C ₉ H ₂₁ AlO ₃ ).

The first solvent is one of ethanol (C ₂ H ₅ OH), acetone (C ₃ H ₆ O) and ether (C ₄ H ₁₀ O).

The second solvent is one of ethanol (C ₂ H ₅ OH), acetone (C ₃ H ₆ O) and ether (C ₄ H ₁₀ O).

In the present invention, in the preparation process, the first solvent and the second solvent should use the same materials.

Step 2: Preparation of core-shell structure packing

(A) Add 0.2-2 ml of inorganic salt and 2-10 g of silicon oxide powder (0.3-5 μm in particle size) to 50 ml of ethanol (C ₂ H ₅ OH), and stir evenly to obtain a filler precursor solution;

The inorganic salt is tetrabutyl titanate (TBOT) or zirconium oxychloride (ZrOCl ₂ );

(B) Add 25 to 50 ml of ethanol (C ₂ H ₅ OH) and 1 to 10 drops of concentrated nitric acid (HNO ₃ ) with a percentage concentration of 99% in 10 ml of deionized water, and stir evenly to obtain a filler reactant solution ;

(C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), under the condition that the reaction temperature is 25-100°C and the stirring speed is 400-800r/min React for 2 to 5 hours, and prepare a filler solution after the reaction;

(D) ultrasonically treat the filler solution obtained in step (C) for 3 to 10 minutes under the condition of ultrasonic power of 1000 W, and heat it for 2 to 24 hours in a hydrothermal kettle at a temperature of 140 to 180 ° C; then perform centrifugal drying to obtain the filler ;

The conditions of centrifugal drying are: rotating speed 400~800r/min, drying temperature 70~90℃, drying time 2~6h;

(E) keeping the filler prepared in step (D) in a muffle furnace at a temperature of 300-700°C for 2-10 hours to obtain a core-shell structure filler;

Step 3: Preparation of Coating Material

adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material;

Dosage: Add 2-10g of core-shell structure filler to 50ml of inorganic sol.

The excellent effects of the present invention are as follows:

1. The high-temperature-resistant radiation heat-transfer and microwave-transparent coating material of the present invention has good film-forming properties, no cracking, no falling off, and a simple preparation process.

2. In the present invention, the radiation and heat-transfer material is prepared by adding core-shell structure filler particles. Compared with the single-component spherical filler, it has a high effect of radiation and heat-transfer, and has little influence on the dielectric properties.

3. The coating material of the present invention is a multifunctional coating material, which can meet the requirements of radiation heat transfer at high temperature on the one hand, and meet the requirements of microwave transmission at the same time.

4. The high-temperature-resistant radiation heat-transfer and microwave-transparent coating of the present invention can be used for high temperature protection at 1200°C.

Description of drawings

Fig. 1 is a scanning electron microscope picture of a core-shell structure filler according to Example 1 of the present invention.

FIG. 1A is a transmission electron microscope image of a core-shell structure filler according to Example 1 of the present invention.

Fig. 2 is an SEM image of the surface of the 1100 μm thick coating in Example 1 of the present invention.

Fig. 2A is a cross-sectional SEM image of the 1100 μm thick coating in Example 1 of the present invention.

Fig. 3 is the infrared transmittance spectrum of the coating in Example 1 of the present invention at a wave number of 1000-4000 cm ⁻¹ .

Fig. 4 is a graph showing the variation of dielectric constant with frequency of the 100 μm thick coating prepared in Example 1 of the present invention.

Fig. 5 is a diagram showing the variation of dielectric loss with frequency of the coating according to Example 1 of the present invention.

Detailed ways

A preparation method of the present invention to form an inorganic coating with high temperature resistance, radiation heat transfer and microwave transmission compatibility, the preparation of the inorganic coating is achieved by the following steps:

Step 1: Preparation of Inorganic Sol

(A) Add 5 to 10 g of precursor to 10 ml of the first solvent, and stir evenly to obtain a precursor solution;

(B) Add 20 to 50 ml of the second solvent and 5 to 6 drops of hydrochloric acid (HCl) (molar concentration is 1 mol/L) in 10 ml of deionized water, and stir evenly to obtain a sol reactant solution;

(C) Add the sol reactant solution prepared in step (B) to the precursor solution prepared in step (A), and react for 1 to 12 hours at a stirring speed of 400 to 800 r/min. After the reaction, prepare Inorganic sol;

The precursor is orthohexyl silicate (TEOS) or aluminum isopropoxide (C ₉ H ₂₁ AlO ₃ ).

The first solvent is one of ethanol (C ₂ H ₅ OH), acetone (C ₃ H ₆ O) and ether (C ₄ H ₁₀ O).

The second solvent is one of ethanol (C ₂ H ₅ OH), acetone (C ₃ H ₆ O) and ether (C ₄ H ₁₀ O).

In the present invention, in the preparation process, the first solvent and the second solvent should use the same materials.

Step 2: Preparation of core-shell structure packing

(A) Add 0.2-2 ml of inorganic salt and 2-10 g of silicon oxide powder (0.3-5 μm in particle size) to 50 ml of ethanol (C ₂ H ₅ OH), and stir evenly to obtain a filler precursor solution;

The inorganic salt is tetrabutyl titanate (TBOT) or zirconium oxychloride (ZrOCl ₂ );

(B) Add 25 to 50 ml of ethanol (C ₂ H ₅ OH) and 1 to 10 drops of concentrated nitric acid (HNO ₃ ) with a percentage concentration of 99% in 10 ml of deionized water, and stir evenly to obtain a filler reactant solution ;

(C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), under the condition that the reaction temperature is 25-100°C and the stirring speed is 400-800r/min React for 2 to 5 hours, and prepare a filler solution after the reaction;

(D) ultrasonically treat the filler solution obtained in step (C) for 3 to 10 minutes under the condition of ultrasonic power of 1000 W, and heat it for 2 to 24 hours in a hydrothermal kettle at a temperature of 140 to 180 ° C; then perform centrifugal drying to obtain the filler ;

The conditions of centrifugal drying are: rotating speed 400~800r/min, drying temperature 70~90℃, drying time 2~6h;

(E) keeping the filler prepared in step (D) in a muffle furnace at a temperature of 300-700°C for 2-10 hours to obtain a core-shell structure filler;

Step 3: Preparation of Coating Material

adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material;

Dosage: Add 2-10g of core-shell structure filler to 50ml of inorganic sol.

Example 1:

Step 1: Preparation of Inorganic Sol

(A) Add 5.7 g of hexyl orthosilicate in 10 ml of ethanol, and stir evenly to obtain a precursor solution;

(B) Add 20 ml of ethanol and 5 drops of 1mol/L hydrochloric acid solution (HCl) in 10 ml of deionized water, and stir evenly to obtain a sol reactant solution;

(C) adding the reactant solution prepared in step (B) to the precursor solution prepared in step (A), reacting for 12 hours at a stirring speed of 600 r/min, and preparing an inorganic sol after the reaction;

Step 2: Preparation of core-shell structure packing

(A) Add 0.4 ml of tetrabutyl titanate and 2 g of silicon oxide powder (0.3 to 5 μm in particle size) in 50 ml of ethanol, and stir evenly to obtain a filler precursor solution;

(B) Add 25ml of ethanol and 4 drops of concentrated nitric acid (HNO ₃ ) with a percentage concentration of 99% in 10ml of deionized water, and stir evenly to obtain a filler reactant solution;

(C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), and react for 2 hours at a reaction temperature of 25°C and a stirring speed of 800r/min. Make filler solution after finishing;

(D) ultrasonically treat the filler solution obtained in step (C) for 5 minutes under the condition of an ultrasonic power of 1000 W, and heat it in water for 20 hours at a temperature of 180° C. in a hydrothermal kettle; then perform centrifugal drying to obtain the filler;

The conditions of centrifugal drying are: rotating speed 400r/min, drying temperature 90°C, drying time 3h;

(E) keeping the filler prepared in step (D) in a muffle furnace at 700° C. for 2 hours to obtain a core-shell structure filler;

The morphology of the core-shell filler was observed by scanning electron microscopy and transmission electron microscopy. The particle size of the core-shell filler was 0.3-5 μm, and the thickness of the shell was between 100-300 nm, as shown in Figure 1 and Figure 1A.

Step 3: Preparation of Coating Material

adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material;

Dosage: Add 8g of core-shell structure filler to 50ml of inorganic sol.

A film with a thickness of 80 μm was prepared on a glass substrate by a brushing process, and the morphology of the coating was observed with a scanning electron microscope (model Apollo 300 from CamScan Company). The morphology of the coating is shown in Figure 2 and Figure 2A. Figure 2 is the surface morphology, and Figure 2A is the cross-sectional morphology of the coating. From the surface scanning electron microscope photos, it can be seen that the surface of the inorganic coating is uniform and dense without cracks, and the thickness of the coating can be seen to be about 80 μm in the cross section.

The infrared microwave transmission and dielectric properties of the coating are shown in Figure 3, Figure 4 and Figure 5. It can be seen from Figure 3 that the coating with core-shell structure filler has obvious shielding effect on thermal radiation, and has little effect on dielectric properties. Since the melting point of _SiO2 is around 1400°C, this coating can be used for a long time at 1200°C.

The radiation heat transfer performance of the coating can be characterized by its infrared transmittance, which is produced by Nicolet Company, model NEXUS-470, and the infrared transmittance of the coating measured by an intelligent Fourier infrared spectrometer (FTIR) is shown in Figure 3. It can be seen from Figure 3 that the transmittance decreases to about 30% after the quartz plate is coated with an inorganic coating after 80 μm. That is to say, the inorganic coating can shield most of the infrared heat radiation and has good radiation insulation and heat transfer performance.

After adding core-shell fillers, the dielectric properties of inorganic coatings will change. A vector network analyzer (model 8722ES) produced by Agilent (USA) was used to analyze the changes in dielectric properties. The test results are shown in Figures 4 and 5. It can be seen from the figure that the dielectric constant and dielectric loss of the inorganic coating do not change much after adding the core-shell structure filler, which will not affect its microwave transmission performance.

Example 2:

Step 1: Preparation of Inorganic Sol

(A) Add 10 g of aluminum isopropoxide to 10 ml of acetone, and stir evenly to obtain a precursor solution;

(B) Add 50ml of acetone and 6 drops of hydrochloric acid (1mol/L) to 10ml of deionized water, and stir evenly to obtain a sol reactant solution;

(C) adding the reactant solution prepared in step (B) to the precursor solution prepared in step (A), reacting for 2 hours at a stirring speed of 800r/min, and preparing an inorganic sol after the reaction;

Step 2: Preparation of core-shell structure packing

(A) Add 2ml of zirconium oxychloride and 10g of silicon oxide powder (0.3-5 μm in particle size) in 50ml of ethanol, and stir evenly to obtain a filler precursor solution;

(B) Add 35ml of ethanol and 10 drops of concentrated nitric acid (HNO ₃ ) with a percentage concentration of 99% in 10ml of deionized water, and stir evenly to obtain a filler reactant solution;

(C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), and react for 3 hours at a reaction temperature of 60°C and a stirring speed of 700r/min. Make filler solution after finishing;

(D) Ultrasonic treatment of the filler solution obtained in step (C) for 8 minutes under the condition of ultrasonic power of 1000 W, and hydrothermal heating at a temperature of 150° C. for 10 hours in a hydrothermal kettle; and then centrifugally drying to obtain the filler;

The conditions of centrifugal drying are: rotating speed 800r/min, drying temperature 70°C, drying time 2h;

(E) keeping the filler prepared in step (D) in a muffle furnace at 300° C. for 10 hours to obtain a core-shell structure filler;

The morphology of the core-shell structure filler was observed by scanning electron microscope and transmission electron microscope. The particle size of the core-shell structure was 0.3-5 μm, and the thickness of the shell was between 300-500 nm.

Step 3: Preparation of Coating Material

adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material;

Dosage: Add 2-10g of core-shell structure filler to 50ml of inorganic sol.

The radiation and heat transfer performance of the coating prepared according to the method in Example 2 can be characterized by its infrared transmittance, and the transmittance is reduced to about 30% after the 80 μm coating is coated on the quartz plate. That is, the coating can shield most of the infrared heat radiation and has good radiation insulation and heat transfer performance.

The dielectric constant and dielectric loss of the coating do not change much after adding the core-shell structure filler, which will not affect its microwave transmission performance.

Example 3:

Step 1: Preparation of Inorganic Sol

(A) Add 8g of hexyl orthosilicate in 10ml of diethyl ether, and stir evenly to obtain a precursor solution;

(B) Add 30 ml of ether and 5 drops of 1mol/L hydrochloric acid solution (HCl) in 10 ml of deionized water, and stir evenly to obtain a sol reactant solution;

(C) adding the reactant solution prepared in step (B) to the precursor solution prepared in step (A), reacting for 6 hours at a stirring speed of 500 r/min, and preparing an inorganic sol after the reaction;

Step 2: Preparation of core-shell structure packing

(A) Add 1 ml of tetrabutyl titanate and 5 g of silicon oxide powder (0.3-5 μm in particle size) into 50 ml of ethanol, and stir evenly to obtain a filler precursor solution;

(B) Add 35ml of ethanol and 7 drops of concentrated nitric acid (HNO ₃ ) with a percentage concentration of 99% in 10ml of deionized water, and stir evenly to obtain a filler reactant solution;

(C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), and react for 5 hours at a reaction temperature of 60°C and a stirring speed of 500r/min. Make filler solution after finishing;

(D) ultrasonically treat the filler solution obtained in step (C) for 6 minutes under the condition of ultrasonic power of 1000 W, and heat it in water for 12 hours at a temperature of 160° C. in a hydrothermal kettle; then perform centrifugal drying to obtain the filler;

The conditions of centrifugal drying are: rotating speed 600r/min, drying temperature 80°C, drying time 4h;

(E) keeping the filler prepared in step (D) in a muffle furnace at 600° C. for 6 hours to obtain a core-shell structure filler;

The morphology of the core-shell structure filler was observed by scanning electron microscope and transmission electron microscope. The particle size of the core-shell structure was 0.3-5 μm, and the thickness of the shell was between 350-500 nm.

Step 3: Preparation of Coating Material

adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material;

Dosage: Add 2-10g of core-shell structure filler to 50ml of inorganic sol

The radiation and heat transfer performance of the coating prepared according to the method of Example 3 can be characterized by its infrared transmittance, and the transmittance is reduced to about 30% after the 80 μm coating is coated on the quartz plate. That is, the coating can shield most of the infrared heat radiation and has good radiation insulation and heat transfer performance.

The dielectric constant and dielectric loss of the coating do not change much after adding the core-shell structure filler, which will not affect its microwave transmission performance.

Claims (6)

1. A preparation method for forming an inorganic coating with high temperature resistance, radiation heat transfer and microwave penetration compatibility, characterized in that the preparation of the inorganic coating is achieved through the following steps: Step 1: Preparation of Inorganic Sol (A) Add 5 to 10 g of precursor to 10 ml of the first solvent, and stir evenly to obtain a precursor solution; (B) adding 20 to 50 ml of the second solvent and 5 to 6 drops of hydrochloric acid with a molar concentration of 1 mol/L in 10 ml of deionized water, and stirring evenly to obtain a sol reactant solution; (C) Add the sol reactant solution prepared in step (B) to the precursor solution prepared in step (A), and react for 1 to 12 hours at a stirring speed of 400 to 800 r/min. After the reaction, prepare Inorganic sol; The precursor is ethyl orthosilicate TEOS or aluminum isopropoxide C ₉ H ₂₁ AlO ₃ ; The first solvent is one of ethanol C ₂ H ₅ OH, acetone C ₃ H ₆ O and ether C ₄ H ₁₀ O; The second solvent is one of ethanol C ₂ H ₅ OH, acetone C ₃ H ₆ O and ether C ₄ H ₁₀ O; Step 2: Preparation of core-shell structure packing (A) Add 0.2-2ml of inorganic salt and 2-10g of silicon oxide powder with a particle size of 0.3-5μm to 50ml of ethanol C ₂ H ₅ OH, and stir evenly to obtain a filler precursor solution; The inorganic salt is tetrabutyl titanate TBOT or zirconium oxychloride ZrOCl ₂ ; (B) Add 25-50 ml of ethanol C ₂ H ₅ OH and 1-10 drops of concentrated nitric acid HNO ₃ with a percentage concentration of 99% in 10 ml of deionized water, and stir evenly to obtain a filler reactant solution; (C) Add the filler reactant solution prepared in step (B) to the filler precursor solution prepared in step (A), and react at a reaction temperature of 25-100°C and a stirring speed of 400800r/min. ~5h, the filler solution was prepared after the reaction; (D) ultrasonically treat the filler solution obtained in step (C) for 3 to 10 minutes under the condition of ultrasonic power of 1000 W, and heat it for 2 to 24 hours in a hydrothermal kettle at a temperature of 140 to 180 ° C; then perform centrifugal drying to obtain the filler ; The conditions of centrifugal drying are: rotating speed 400~800r/min, drying temperature 70~90℃, drying time 2~6h; (E) keeping the filler prepared in step (D) in a muffle furnace at a temperature of 300 to 700°C for 2 to 10 hours to obtain a core-shell structure filler; Step 3: Preparation of Coating Material adding the core-shell structure filler prepared in step 2 to the inorganic sol prepared in step 1, and stirring evenly to obtain an inorganic coating material; Dosage: Add 2-10g of core-shell structure filler to 50ml of inorganic sol. 2. A preparation method for forming an inorganic coating compatible with high temperature resistance, radiation heat transfer and microwave transmission according to claim 1, characterized in that: the particle size of the core-shell structure filler prepared in step 2 is between 0.3 ~5μm, the thickness of the shell is between 30~500nm. 3. A preparation method for forming an inorganic coating compatible with high temperature resistance, radiation heat transfer and microwave transmission according to claim 1, characterized in that: in the preparation process of step 1, the first solvent and the second solvent must be Use the same materials. 4. A preparation method for forming an inorganic coating with high temperature resistance, radiation heat insulation and microwave transmission compatibility according to claim 1, characterized in that: the surface of the prepared inorganic coating is uniform and dense without cracks. 5. A preparation method for forming an inorganic coating with high temperature resistance, radiation heat transfer and microwave penetration compatibility according to claim 1, characterized in that: a 100 μm thick inorganic coating can shield 28 to 60% of the infrared spectrum , indicating that the inorganic coating has good radiation and heat transfer performance. 6. A preparation method for forming an inorganic coating with high temperature resistance, radiation heat transfer and microwave penetration compatibility according to claim 1, characterized in that: the dielectric constant of the prepared inorganic coating on the dielectric property If the increase is less than 2% and the dielectric loss increases within 5%, it will not affect its microwave transmission performance. the

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