Porous boron nitride antenna window and hole sealing coating method thereof

Abstract

The invention discloses a porous boron nitride antenna window and a hole sealing coating method thereof, and belongs to the field of aerospace materials. In order to solve the problem that an existing antenna window cannot give consideration to both low water absorption and high wave permeability, the invention provides a hole sealing coating method of a porous boron nitride antenna window, and before a hole sealing material is sprayed on the surface of the porous boron nitride antenna window, hole pre-sealing operation is carried out on the porous boron nitride antenna window, the hole pre-sealing operation comprises the steps of sequentially carrying out organic silicon resin impregnation, curing and sintering on the porous boron nitride antenna window; the hole sealing material is a mixture of organic silicon resin and a silane coupling agent. Before the hole sealing material is sprayed on the surface of the porous boron nitride antenna window, hole pre-sealing operation is carried out, the water absorption rate of the porous boron nitride antenna window is preliminarily reduced, then the low water absorption rate characteristic of the porous boron nitride antenna window is further consolidated through the hole sealing material, the low water absorption rate is considered, and meanwhile reduction of other performance is not affected; the method is simple in steps, easy to operate and high in applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of aerospace material preparation, and more specifically, relates to a porous boron nitride antenna window and a sealing coating method thereof. Background Art

[0002] Antenna window is an important part of aircraft. It is a multifunctional part integrating wave transmission and heat protection. Boron nitride has the characteristics of high temperature resistance, chemical corrosion resistance, good processability, self-lubrication, and non-wetting with various metals. These characteristics enable high-quality boron nitride to be used for a long time in oxidizing atmospheres below 900°C and inert atmospheres below 2800°C. At the same time, boron nitride has a large wave transmittance, i.e., power transmittance coefficient, low reflectivity and loss, and has little effect on the antenna directional performance of the radar, meeting the requirements of radar search and target accuracy. The main application material of boron nitride antenna window is high-temperature wave-transmitting material, which plays an important role in protecting the normal operation of aircraft communication, telemetry, guidance, detonation and other systems in harsh use environments. Due to its excellent physical and chemical properties, boron nitride antenna windows are widely used in key parts of re-entry vehicles such as launch vehicles, spacecraft, missiles and recoverable satellites. However, in order to ensure its high wave transmission and low loss performance, the boron nitride antenna window has a certain porosity. The porosity causes the boron nitride antenna window to absorb water under natural conditions. After the boron nitride antenna window is washed with water, the wave transmittance, reflectivity and wave transmission loss will be greatly affected.

[0003] Corresponding improvements have also been made to address the above problems, such as Chinese patent application number CN201610537283.2, published on January 16, 2018, which discloses a method for sealing the surface of porous ceramic materials. The method comprises the following steps: step one, drying the porous ceramic material; step two, vacuuming the porous ceramic material; step three, sealing the surface by evaporation coating, sputtering coating or ion coating. The disadvantage of this patent is that the quality of evaporation coating, sputtering coating or ion coating is affected by many factors, such as the performance of the coating equipment, the selection of coating parameters and the purity of the coating material, which can easily lead to poor sealing effect and increase production costs.

[0004] Another example is Chinese patent application number CN201110423290.7, published on April 15, 2015. The patent discloses a method for sealing a ceramic layer, comprising the following steps: providing a metal substrate; using a flame spraying method to form a ceramic layer on the surface of the metal substrate, wherein the ceramic layer is formed with a plurality of ceramic pores; using an electrostatic powder spraying method to spray a sealing layer on the surface of the ceramic layer, wherein the sealing layer comprises a plurality of filling parts, wherein the plurality of filling parts are respectively formed in the ceramic pores, and are used to seal the ceramic pores, wherein the main component of the sealing powder for the sealing treatment is a thermosetting resin powder with corrosion resistance. The disadvantage of the patent is that the electrostatic powder spraying method may have problems such as uneven spraying or difficulty in complete filling, resulting in poor sealing effect of the sealing layer. Summary of the invention

[0005] 1. Problems to be solved In view of the problem that the existing antenna window cannot take into account both low water absorption and high wave transmittance, the present invention provides a porous boron nitride antenna window and a sealing coating method thereof. The present invention pre-seales the porous boron nitride antenna window before spraying the sealing material on its surface, thereby preliminarily reducing the water absorption of the porous boron nitride antenna window, and then further consolidates the low water absorption property of the porous boron nitride antenna window through the sealing material, so that the low water absorption is taken into account without affecting the decline of other performances; the steps are simple, the operation is easy, and the applicability is strong.

[0006] 2. Technical solution To solve the above problems, the present invention adopts the following technical solutions.

[0007] A sealing coating method for a porous boron nitride antenna window, which includes pre-sealing the porous boron nitride antenna window before spraying a sealing material on the surface of the porous boron nitride antenna window, wherein the pre-sealing operation includes sequentially impregnating, curing and sintering the porous boron nitride antenna window with a silicone resin; and the sealing material is a mixture of a silicone resin and a silane coupling agent.

[0008] By adopting the above technical scheme, before spraying the sealing material on the porous boron nitride antenna window, the porous boron nitride antenna window is impregnated with silicone resin, and the silicone resin enters the pores inside the porous boron nitride to fill the pores; and a dense waterproof layer is formed on the surface of the porous boron nitride, thereby blocking moisture from entering the internal structure of the porous boron nitride and reducing the water absorption rate; and through curing and sintering operations, the inside and surface of the antenna window substrate are covered with silicone hydroxyl groups, and then the surface silicone hydroxyl groups are treated with a hydrophobic agent to enhance the surface hydrophobicity and enhance the adhesion of the subsequent coating to the surface of the antenna window, so that the silicone resin can be closely combined with the porous boron nitride, thereby further reducing its water absorption rate; and then by spraying the sealing coating on the surface of the porous boron nitride antenna window, the low water absorption rate characteristics of the porous boron nitride antenna window are further consolidated, so that it can take into account the low water absorption rate without affecting the decline of other performances; the whole operation method is simple in steps, easy to operate, and has strong applicability.

[0009] Furthermore, in the pre-sealing operation, the silicone resin impregnation time is 1 to 2 hours, and the concentration of the silicone resin is 70% to 90%; during curing, the temperature is kept at 100°C for 60 minutes to 90 minutes; the sintering temperature is 600°C to 750°C; and the sintering time is 2 hours to 3 hours.

[0010] By adopting the above technical scheme, the impregnation time and concentration of the silicone resin are strictly controlled so that the silicone resin can completely and evenly penetrate into the pores inside the porous boron nitride, so that a uniform coating can be formed on the surface of the porous boron nitride, thereby ensuring better waterproof performance; the curing insulation time and the sintering temperature and time are strictly controlled so that the coating formed by the silicone resin is denser and more stable, further consolidating the waterproof performance, thereby achieving a lower water absorption rate.

[0011] Furthermore, before the pre-sealing operation is performed on the porous boron nitride antenna window, a surface cleaning operation is also performed on the porous boron nitride antenna window: the surface of the porous boron nitride antenna window is blown with compressed air and then the surface of the porous boron nitride antenna window is wiped.

[0012] By adopting the above technical scheme, two methods are used to remove impurities from the surface of the porous boron nitride antenna window, which can ensure the thorough cleaning of the surface of the porous boron nitride antenna window and provide a good foundation for subsequent sealing operations; and firstly, compressed air is used to blow away larger granular impurities, which has fast impurity removal efficiency and short time; and then tiny and strongly adhesive granular impurities are removed by wiping, avoiding the occurrence of local impurity accumulation and ensuring the thoroughness of cleaning. Furthermore, the porous boron nitride antenna window is sprayed with a sealing material on the surface and then dried. After drying, it is heated to 110° C. and kept at 110° C. for 60 min±10 min.

[0013] By adopting the above technical scheme, after the sealing material is sprayed on the surface of the porous boron nitride antenna window, the sealing material forms a sealing coating on the surface of the porous boron nitride antenna window. The drying operation can remove moisture from the surface and pores of the porous boron nitride antenna window, and enable the sealing coating to adhere more tightly to the surface and internal pores of the porous boron nitride antenna window, thereby increasing the adhesion of the coating and making the porous boron nitride antenna window have a lower water absorption rate. The heat preservation operation after drying can ensure that the coating is fully cured at a suitable temperature to form a dense waterproof layer, effectively blocking external moisture from entering the interior of the porous boron nitride antenna window, thereby reducing its water absorption rate.

[0014] Furthermore, in the sealing material, the organic silicone resin is transparent methyl silicone resin, and the silane coupling agent is γ-aminopropyltriethoxysilane; and the mass ratio of the transparent methyl silicone resin to γ-aminopropyltriethoxysilane is 100:(1~2).

[0015] By adopting the above technical scheme, the transparent property of the transparent methyl silicone resin enables it to maintain the original appearance of the porous boron nitride antenna window without having a negative impact on its visual effect; and the combination with γ-aminopropyltriethoxysilane can significantly improve the adhesion between the transparent methyl silicone resin and the porous boron nitride antenna window, ensuring that the sealing material can be firmly attached to the surface of the porous boron nitride antenna window, thereby reducing the water absorption rate of the porous boron nitride antenna window; and the mass ratio of the two is strictly controlled to avoid waste of raw materials and increase costs while ensuring the water resistance and adhesion of the sealing material.

[0016] Furthermore, the spraying amount of the sealing material , where y is the spraying amount of the sealing material and the unit of the spraying amount is g, n is the number of porous boron nitride antenna windows, x is a fixed value, and the value range of x is 5~10; and when the formula is used to calculate the spraying amount of the sealing material, the physical quantities in the formula are dimensionless during the calculation.

[0017] By adopting the above technical scheme, the spraying amount is associated with the number of porous boron nitride antenna windows, which not only avoids the waste or shortage of sealing materials, reduces costs and improves the utilization rate of resources; but also enables each porous boron nitride antenna window to be sprayed with sufficient and appropriate amount of sealing material, which helps to form a uniform and dense sealing layer, thereby reducing its water absorption rate.

[0018] Furthermore, the method of spraying the sealing material on the surface of the porous boron nitride antenna window comprises the following steps: placing the porous boron nitride antenna window on a rotating platform through a carrying device; The spray gun starts to spray the sealing material: the first corner of the porous boron nitride antenna window is used as the spraying starting point, and the spraying is performed in a "Z"-shaped direction, and the second corner of the porous boron nitride antenna window is used as the spraying end point; wherein the first corner and the second corner of the porous boron nitride antenna window are set diagonally; after the first spraying is completed, the rotating platform is rotated 180°, and the second spraying is performed according to the spray gun spraying operation to complete the spraying of one side of the porous boron nitride antenna window; The porous boron nitride antenna window is turned over so that the other side which is not sprayed is placed on a rotating platform through a carrying device, and the operation of spraying the sealing material with a spray gun is repeated to complete the spraying of the other side of the porous boron nitride antenna window.

[0019] The above technical solution is adopted, and a "Z"-shaped spraying direction is adopted to ensure that the sealing material can evenly cover every corner of the porous boron nitride antenna window during the spraying process, avoid the accumulation of sealing material in a certain place, reduce the dead corners of spraying, improve the uniformity of spraying, effectively ensure the quality of spraying, and reduce the complexity and time consumption of manual operation, saving labor costs.

[0020] Furthermore, the gas source pressure of the spray gun is 0.25 MPa±0.05 MPa; the spray width is 100 mm±10 mm; and the distance between the muzzle of the spray gun and the porous boron nitride antenna window is 20 cm±5 cm.

[0021] The above technical solution ensures that the sealing material sprayed out from the spray gun is uniform and fine, which helps to better form a dense and uniform sealing layer on the surface of the porous boron nitride antenna window; and ensures work efficiency.

[0022] Furthermore, the method further includes performing a hydrophobic treatment on the porous boron nitride antenna window after the pre-sealing operation, wherein the hydrophobic treatment includes placing the porous boron nitride antenna window after the pre-sealing operation into a container, sealing and evacuating the container, inputting a hydrophobic agent into the container to immerse the porous boron nitride antenna window, and then heating and drying the porous boron nitride antenna window.

[0023] By adopting the above technical scheme, the hydrophobic treatment further improves the hydrophobic properties of the entire porous boron nitride antenna window, thereby ensuring that the porous boron nitride antenna window can still maintain stable dielectric properties in a humid environment, avoiding signal attenuation or distortion caused by moisture, and ensuring the stability of the dielectric properties; and the hydrophobic treatment also enhances the heat resistance, corrosion resistance and wear resistance of the porous boron nitride antenna window to a certain extent, so that it can maintain stable performance in various harsh environments.

[0024] A porous boron nitride antenna window is prepared by the sealing coating method of the porous boron nitride antenna window as described in any one of the above items. The porous boron nitride antenna window prepared by the sealing coating method can significantly reduce the water absorption rate of the porous boron nitride antenna window, and other properties do not show a significant decrease, so that it has both low water absorption rate and high wave transmittance, so that it can stably realize its function. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall process of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments and drawings.

[0027] like Figure 1 As shown, a sealing coating method for a porous boron nitride antenna window also includes a pre-sealing operation on the porous boron nitride antenna window before spraying the sealing material on the surface of the porous boron nitride antenna window, wherein the pre-sealing operation includes sequentially impregnating, curing and sintering the porous boron nitride antenna window with silicone resin; and the sealing material is a mixture of silicone resin and silane coupling agent.

[0028] By adopting the above technical scheme, a pre-sealing operation is performed on the porous boron nitride antenna window before spraying the sealing material. The purpose of the pre-sealing operation is to reduce the porosity of the boron nitride antenna window; through the curing and sintering operations, the interior and surface of the antenna window substrate are covered with silicone hydroxyl groups, and the surface silicone hydroxyl groups are subsequently treated with a hydrophobic agent to enhance the surface hydrophobicity and enhance the adhesion of the subsequent coating to the surface of the antenna window, so that the silicone resin can be tightly combined with the porous boron nitride, thereby further reducing its water absorption rate, and finally ensuring that the porous boron nitride antenna window has low water absorption while ensuring its wave transmittance. Specifically, the pre-sealing operation firstly impregnates the porous boron nitride antenna window with silicone resin, and the silicone resin penetrates into the boron nitride pores inside the porous boron nitride antenna window to achieve a certain sealing effect, thereby reducing the water absorption of the boron nitride antenna window. Then, through curing and sintering operations, the inside and surface of the porous boron nitride antenna window matrix are distributed with silicon hydroxyl groups, thereby strengthening the close bonding between the silicone resin and the porous boron nitride, and making the silicone resin more tightly filled in the pores of the boron nitride, thereby achieving the effect of enhancing waterproofing.

[0029] It is worth mentioning that the current mainstream method for improving the water absorption rate of porous boron nitride antenna windows is to prepare a coating on the surface of the antenna window or to improve the raw materials of the antenna window. Although preparing a waterproof coating on the surface of the antenna window can reduce the water absorption rate of the antenna window to a certain extent, the effect of reducing the water absorption rate is not ideal and cannot meet the application of some specific fields such as aerospace and other high-end fields. Improving the raw materials of the antenna window will increase the cost, because high-quality boron nitride raw materials are usually expensive, and some high-quality boron nitride raw materials may be scarce and difficult to obtain. In addition, the impurity content in the raw materials has an important influence on the performance of boron nitride. The need to control the purity of the raw materials means that the complexity and cost of raw material processing will increase. Secondly, the improvement of the water absorption rate of boron nitride through the synergistic effect between the raw materials is limited, and the effect is not very obvious. In addition, when the boron nitride raw material is not processed into a boron nitride antenna window, the block is thicker, and it is difficult to achieve the expected effect of impregnation. The overall impermeability will affect the impregnation effect. After being processed into an antenna window, the overall wall thickness becomes thinner, which is conducive to overall penetration to ensure the impregnation sealing effect.

[0030] In summary, the current mainstream methods all have a common drawback that the water absorption effect is not significantly improved and the cost will increase accordingly. Therefore, the present application pre-seales the porous boron nitride antenna window before spraying the sealing material on the antenna window, laying a good waterproof foundation for the subsequent spraying of the sealing material. The double waterproof operation greatly reduces the water absorption of the porous boron nitride antenna window, so that it has a lower water absorption rate and can meet the application of some specific fields.

[0031] In one embodiment, in the pre-sealing operation, the silicone resin is impregnated for 1 to 2 hours, and the concentration of the silicone resin is 70% to 90%; during curing, the temperature is kept at 100°C for 60 to 90 minutes; the sintering temperature is 600 to 750°C; and the sintering time is 2 to 3 hours.

[0032] Specifically, in this embodiment, the purpose of pre-sealing the holes is to reduce the water absorption rate of the porous boron nitride antenna window. Therefore, the silicone resin is infiltrated into the pores inside the boron nitride to fill the pores and form a dense waterproof layer on its surface to achieve a waterproof effect. The waterproof layer is then consolidated by curing and sintering to tightly combine the silicone resin and the boron nitride. Therefore, the immersion time and concentration of the silicone resin are limited, because the length of the immersion time will directly affect the penetration depth and uniformity of the silicone resin in the pores, so as to avoid the situation that the silicone resin cannot completely penetrate into the pores for filling due to too short immersion time, and the silicone resin is excessively accumulated in the pores due to too long time, which may cause material deformation, etc. The concentration of the silicone resin directly affects whether the silicone resin can fill the pores smoothly and effectively, so as to avoid the situation that the concentration is too low, resulting in a coating that is too thin and cannot completely cover the pores, thereby reducing the waterproof effect; the concentration is too high, and the silicone resin is excessively accumulated in the pores, which may cause material deformation, etc. By limiting the curing insulation time as well as the sintering temperature and time, the waterproof layer formed by the silicone resin can be fully cured, thereby ensuring that the structure of the waterproof layer is more dense and stable, thereby improving its waterproof performance and overall performance.

[0033] In one embodiment, before the pre-sealing operation is performed on the porous boron nitride antenna window, a surface cleaning operation is also performed on the porous boron nitride antenna window: the surface of the porous boron nitride antenna window is blown with compressed air and then the surface of the porous boron nitride antenna window is wiped.

[0034] Specifically, in this embodiment, the combination of the two methods is used to remove impurities from the surface of the porous boron nitride antenna window, which can ensure that the surface of the porous boron nitride antenna window is thoroughly cleaned, providing a good foundation for the subsequent sealing operation. First, compressed air is used to blow and wipe to remove larger granular impurities, which has a fast impurity removal efficiency and a short time; then, tiny and strongly adherent granular impurities are removed by wiping to avoid the accumulation of local impurities, ensuring the thoroughness of cleaning, and providing a good foundation for the subsequent sealing operation. It is explained here that if only wiping is used to remove impurities, the impurities on the surface of the boron nitride antenna window may be pushed into the pores, causing secondary pollution; if only compressed air is used to blow and wipe to remove impurities, it may not be possible to remove fine impurities on the surface and contact the surface of the porous boron nitride antenna window for a long time, which is easy to damage it and increase the cost. Therefore, compressed air is first used to blow and wipe for a short time to blow away the impurities from the surface and the edge of the pores; then the stubborn tiny impurities on the surface are removed by wiping to ensure that the surface of the porous boron nitride antenna window is completely and thoroughly cleaned.

[0035] In one embodiment, the porous boron nitride antenna window is dried after the sealing material is sprayed on the surface, and then heated to 110° C. after drying, and kept at 110° C. for 60 min±10 min. The drying, heating and heat preservation operations solidify the coating formed by the sealing material, further effectively filling the pores in the porous boron nitride antenna window, thereby achieving the effect of reducing its water absorption rate.

[0036] In one embodiment, in the sealing material, the silicone resin is transparent methyl silicone resin-5, and the silane coupling agent is γ-aminopropyltriethoxysilane; and the mass ratio of the transparent methyl silicone resin to the γ-aminopropyltriethoxysilane is 100:(1~2).

[0037] Specifically, the transparent methyl silicone resin is selected because of its inherent transparency, which enables it to maintain the original appearance of the porous boron nitride antenna window without having a negative impact on its appearance; the combination of transparent methyl silicone resin and γ-aminopropyltriethoxysilane can significantly improve the adhesion between the transparent methyl silicone resin and the porous boron nitride antenna window, ensuring that the sealing material can be firmly attached to the surface of the antenna window and is not easy to fall off, thereby ensuring its stable waterproof performance; and the content between the two is limited to avoid the cost increase caused by the waste of raw materials, while ensuring that the two give full play to their respective characteristics, while ensuring their basic excellent performance while enhancing their adhesion and water resistance, so that they have lower water absorption.

[0038] In one embodiment, the amount of the sealing material sprayed is , where y is the spraying amount of the sealing material and the unit of the spraying amount is g, n is the number of porous boron nitride antenna windows, x is a fixed value, and the value range of x is 5~10; and when the formula is used to calculate the spraying amount of the sealing material, the physical quantities in the formula are dimensionless during the calculation.

[0039] In this embodiment, the spraying amount of the sealing material is correlated with the number of porous boron nitride antenna windows. Firstly, it is ensured that each porous boron nitride antenna window has a precise spraying amount, so that a uniform and dense sealing layer can be formed on the surface of the porous boron nitride antenna window to achieve a good waterproof effect; avoid waste or shortage of sealing materials, reduce costs and improve resource utilization; secondly, quantitative configuration avoids the errors caused by manual configuration, helps to realize the automation and standardization of the production process, and improves production efficiency.

[0040] In one embodiment, the step of spraying a sealing material on the surface of the porous boron nitride antenna window comprises the following steps: The porous boron nitride antenna window is placed on a rotating platform through a carrying device, and the carrying device can be a tray; and the porous boron nitride antenna window in the present application is usually in the shape of a flat plate or a plate with a curved surface, or a rectangular shape; The spray gun starts to spray the sealing material: the first corner of the porous boron nitride antenna window is used as the spraying starting point, and the spraying is carried out in a "Z"-shaped direction, and the second corner of the porous boron nitride antenna window is used as the spraying end point, and the spraying is completed by moving back and forth between the spraying starting point and the spraying end point; generally speaking; the gun is moved in a "Z" shape, and the second corner is used as the spraying end point after 2.5 back and forth; wherein the first corner and the second corner of the porous boron nitride antenna window are set diagonally; after completing the first spraying, the rotating platform is rotated 180°, and the second spraying is carried out according to the spray gun spraying operation to complete the spraying of one side of the porous boron nitride antenna window; and then it is dried and cured; The porous boron nitride antenna window is turned over so that the other side that is not sprayed is placed on a rotating platform through a carrying device, and the operation of spraying the sealing material with a spray gun is repeated to complete the spraying of the other side of the porous boron nitride antenna window, followed by drying and curing.

[0041] In this embodiment, when spraying the porous boron nitride antenna window, the spray gun follows a "Z" shape to ensure that the paint can evenly cover every part of the porous boron nitride antenna window, especially the corners, during the spraying process, reducing dead angles for spraying. At the same time, it can also avoid excessive accumulation of sealing materials in a certain area, thereby reducing problems such as uneven coating thickness and uneven drying caused by paint accumulation, effectively improving the uniformity of spraying, so that the thickness of the sealing coating can be kept consistent; and the setting of the rotating platform eliminates the need to move the position of the porous boron nitride antenna window multiple times for spraying, thereby improving spraying efficiency and saving manual operation and time costs.

[0042] In one embodiment, the air source pressure of the spray gun is 0.25MPa±0.05MPa; the spray width is 100mm±10mm; the distance between the muzzle of the spray gun and the porous boron nitride antenna window is 20cm±5cm. The various parameters of the spray gun are limited so that the sealing coating can be evenly sprayed on the surface of the porous boron nitride antenna window and can reasonably cover the set spraying area, avoiding waste of sealing materials or insufficient spraying, so as to achieve both effect and efficiency.

[0043] In one embodiment, the method further includes performing a hydrophobic treatment on the porous boron nitride antenna window after the pre-sealing operation, wherein the hydrophobic treatment includes placing the porous boron nitride antenna window after the pre-sealing operation into a container, sealing and evacuating the container, inputting a hydrophobic agent into the container to immerse the porous boron nitride antenna window, and after the immersion is completed, placing the porous boron nitride antenna window together with the container in an electric closed drying oven for heat preservation, taking the porous boron nitride antenna window out of the container and draining it, and then heating and drying the porous boron nitride antenna window.

[0044] Specifically, the hydrophobic treatment is performed by using a hydrophobic agent to treat the silicon hydroxyl groups in the porous boron nitride antenna window to enhance the overall hydrophobicity, while also enhancing the adhesion of subsequent sealing materials to the surface of the porous boron nitride antenna window, thereby further enhancing the overall waterproof performance of the porous boron nitride antenna window. The hydrophobic treatment also enhances the heat resistance, corrosion resistance and wear resistance of the porous boron nitride antenna window to a certain extent, enabling it to maintain stable performance in various harsh environments.

[0045] Preferably, in the hydrophobic treatment, the specific parameters for heating and drying the porous boron nitride antenna window are: setting the room temperature in an electrically heated closed drying oven to rise to 60°C in 20 minutes, and keeping at 60°C for 24 hours; and drying is setting the room temperature to rise to 150°C in 45 minutes, and keeping at 150°C for 2 hours.

[0046] A porous boron nitride antenna window is prepared by the above-mentioned sealing coating method for a porous boron nitride antenna window. The porous boron nitride antenna window prepared by the above-mentioned sealing coating method can significantly reduce the water absorption rate of the porous boron nitride antenna window, and other properties do not show a significant decrease, so that it has both low water absorption rate and high wave transmittance, so that it can stably realize its function.

[0047] In order to further facilitate the understanding of this application, the following examples are given: Example 1 A sealing coating method for a porous boron nitride antenna window comprises the following steps: S1: Cleaning the surface of the porous nitride shed antenna window: Use 0.25MPa compressed air to blow the uncoated surface of the porous nitride shed antenna window, and then use a dust-removing cloth to wipe the surface of the porous nitride shed antenna window to ensure that there is no dust or other excess residue on the surface of the porous nitride shed antenna window; S2: Silicone resin impregnation: Place the clean porous nitride shed antenna window in an enamel tray, with 8 antenna windows in total, and pour 70% silicone resin-2 (i.e., SAR-2) until the porous nitride shed antenna window is completely immersed in the silicone resin. After leaving it for 2 h, take it out with tweezers and wipe the silicone resin on the surface of the porous nitride shed antenna window with a clean non-woven cloth; S3: Curing: The porous boron nitride antenna window that is initially cured on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 100°C in 30 minutes, and the temperature is kept at 100°C for 60 minutes. After the insulation is completed, the door of the electric heating sealed drying oven is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C. S4: Sintering: The porous boron nitride antenna window is placed in a sintering furnace for sintering. The sintering furnace is set at 650°C for 3 hours. After the sintering is completed, it is naturally cooled with the furnace, and then the furnace door is opened to take out the porous boron nitride antenna window; S5: Hydrophobic treatment: Place the porous boron nitride antenna window in the hydrophobic treatment tooling, cover it with a lid, seal the hydrophobic treatment tooling and evacuate it until the vacuum degree is less than -0.09MPa, maintain this vacuum degree for 10 minutes, and inject hexamethyldisilazane (hydrophobic agent) into the hydrophobic treatment tooling through the feed pipe so that the porous boron nitride antenna window is completely immersed under the liquid surface. Turn off the vacuum pump, open the vent valve, remove the air pipe connected to the hydrophobic treatment tooling, and place the porous boron nitride antenna window in the hydrophobic treatment tooling. Put it in an electric heating sealed drying oven with the hydrophobic treatment tooling, set the room temperature to 60°C for 20 minutes, keep it at 60°C for 24 hours, take out the porous boron nitride antenna window from the hydrophobic treatment tooling after the insulation is completed, place it on a clean tray, drain it, put the drained porous boron nitride antenna window into an electric heating sealed drying oven for drying, set the room temperature to 150°C for 45 minutes, keep it at 150°C for 2 hours, cool it to room temperature after the drying is completed, and take out the porous boron nitride antenna window; S6: Surface coating spraying: Prepare a material with a mass ratio of 200:3 of silicone resin-5 (SAR-5): KH-550 silane coupling agent (γ-aminopropyltriethoxysilane). Specifically, 200g of silicone resin-5 (SAR-5) and 3g of KH-550 silane coupling agent (γ-aminopropyltriethoxysilane) are used to form 203g of sealing material. The 203g of sealing material is used to spray 8 porous boron nitride antenna windows. The specific spraying effect is as follows: Place the porous boron nitride antenna window with a clean surface on a plastic tray, place one porous boron nitride antenna window on each plastic tray, place the plastic tray with the porous boron nitride antenna window on the rotating platform of the spraying workbench in the clean room, filter the paint through filter paper and pour it into a special spray pot for topcoat, install the spray gun, turn on the air compressor, set the spray gun air source pressure to 0.25MPa, adjust the spray gun spray width to 100mm, and spray the porous boron nitride antenna window with the upper left corner as the starting point and "Z" shape in the spray gun. After 2.5 round trips, the lower right corner is used as the spraying end point, and then the rotating platform is rotated 180°, and the second spraying is performed according to the above spraying operation to complete the single-sided spraying of the porous boron nitride antenna window; S7: Drying: The porous boron nitride antenna window with single-sided spraying is transferred together with the plastic tray to the product temporary table in the clean room and placed for 30 minutes to wait for the initial curing of the coating surface; S8: Coating curing: The porous boron nitride antenna window with the preliminary curing on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 110°C in 30 minutes, and the temperature is kept at 110°C for 60 minutes. After the insulation is completed, the door of the electric heating sealed drying oven is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C; S9: Turn the porous boron nitride antenna window over and place it on a plastic tray, repeat the above steps S6, S7 and S8, keep the parameters unchanged, complete the spraying of the other side of the porous boron nitride antenna window, and finally complete the sealing coating operation on both sides of the porous boron nitride antenna window.

[0048] Example 2 A sealing coating method for a porous boron nitride antenna window comprises the following steps: S1: Cleaning the surface of the porous nitride shed antenna window: Use 0.25MPa compressed air to blow the uncoated surface of the porous nitride shed antenna window, and then use a dust-removing cloth to wipe the surface of the porous nitride shed antenna window to ensure that there is no dust or other excess residue on the surface of the porous nitride shed antenna window; S2: Silicone resin impregnation: Place the clean porous nitride shed antenna window in an enamel tray, with 8 antenna windows in total, and pour 80% silicone resin-2 (SAR-2) until the porous nitride shed antenna window is completely immersed in the silicone resin. After 2 h, take it out with tweezers and wipe the silicone resin on the surface of the porous nitride shed antenna window with a clean non-woven cloth; S3: Curing: The porous boron nitride antenna window that has been initially cured on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 100°C in 30 minutes, and the temperature is kept at 100°C for 75 minutes. After the insulation is completed, the door of the electric heating sealed drying oven is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C. S4: Sintering: The porous boron nitride antenna window is placed in a sintering furnace for sintering. The sintering furnace is set at 680°C for 3 hours. After the sintering is completed, the porous boron nitride antenna window is naturally cooled with the furnace, and then the furnace door is opened to take out the porous boron nitride antenna window; S5: Hydrophobic treatment: Place the porous boron nitride antenna window in the hydrophobic treatment tooling, cover it with a lid, seal the hydrophobic treatment tooling and evacuate it until the vacuum degree is less than -0.09MPa, maintain this vacuum degree for 10 minutes, and inject hexamethyldisilazane (hydrophobic agent) into the hydrophobic treatment tooling through the feed pipe so that the porous boron nitride antenna window is completely immersed under the liquid surface. Turn off the vacuum pump, open the vent valve, remove the air pipe connected to the hydrophobic treatment tooling, and place the porous boron nitride antenna window in the hydrophobic treatment tooling. Put it in an electric heating sealed drying oven with the hydrophobic treatment tooling, set the room temperature to 60°C for 20 minutes, keep it at 60°C for 24 hours, take out the porous boron nitride antenna window from the hydrophobic treatment tooling after the insulation is completed, place it on a clean tray, drain it, put the drained porous boron nitride antenna window into an electric heating sealed drying oven for drying, set the room temperature to 150°C for 45 minutes, keep it at 150°C for 2 hours, cool it to room temperature after the drying is completed, and take out the porous boron nitride antenna window; S6: Surface coating spraying: Prepare a coating with a mass ratio of 200:3 of silicone resin-5 (SAR-5): KH-550 silane coupling agent (γ-aminopropyltriethoxysilane), that is, specifically, 200g of silicone resin-5 (SAR-5) and 3g of KH-550 silane coupling agent (γ-aminopropyltriethoxysilane) are used to form 203g of sealing material, and 203g of sealing material is used to spray 8 porous boron nitride antenna windows; the specific spraying effect is as follows: Place the porous boron nitride antenna window with a clean surface on a plastic tray, place one porous boron nitride antenna window on each plastic tray, place the plastic tray with the porous boron nitride antenna window on the rotating platform of the spraying workbench in the clean room, filter the paint through filter paper and pour it into a special spray pot for topcoat, install the spray gun, turn on the air compressor, set the spray gun air source pressure to 0.25MPa, adjust the spray gun spray width to 100mm, and spray the porous boron nitride antenna window with the upper left corner as the starting point and "Z" shape in the spray gun. After 2.5 round trips, the lower right corner is used as the spraying end point, and then the rotating platform is rotated 180°, and the second spraying is performed according to the above spraying operation to complete the single-sided spraying of the porous boron nitride antenna window; S7: Drying: The porous boron nitride antenna window with single-sided spraying is transferred together with the plastic tray to the product temporary table in the clean room and placed for 30 minutes to wait for the initial curing of the coating surface; S8: Coating curing: The porous boron nitride antenna window with the preliminary curing on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 110°C in 30 minutes, and the temperature is kept at 110°C for 60 minutes. After the insulation is completed, the door of the electric heating sealed drying oven is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C; S9: Turn the porous boron nitride antenna window over and place it on a plastic tray, repeat the above steps S6, S7 and S8, keep the parameters unchanged, complete the spraying of the other side of the porous boron nitride antenna window, and finally complete the sealing coating operation on both sides of the porous boron nitride antenna window.

[0049] Example 3 A sealing coating method for a porous boron nitride antenna window comprises the following steps: S1: Cleaning the surface of the porous nitride shed antenna window: Use 0.25MPa compressed air to blow the uncoated surface of the porous nitride shed antenna window, and then use a dust-removing cloth to wipe the surface of the porous nitride shed antenna window to ensure that there is no dust or other excess residue on the surface of the porous nitride shed antenna window; S2: Organic silicon resin impregnation: Place the porous nitride shed antenna window with a clean surface in an enamel tray, with a total of 8 antenna windows in one enamel tray, and pour 90% organic silicon resin (i.e., SAR-2) until the porous nitride shed antenna window is completely immersed in the organic silicon resin. After leaving it for 2 hours, take it out with tweezers, and wipe the organic silicon resin on the surface of the porous nitride shed antenna window with a clean non-woven cloth; S3: Curing: The porous boron nitride antenna window that is initially cured on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 100°C in 30 minutes, and the temperature is kept at 100°C for 90 minutes. After the insulation is completed, the electric heating sealed drying oven door is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C. S4: Sintering: The porous boron nitride antenna window is placed in a sintering furnace for sintering. The sintering furnace is set at 700°C for 3 hours. After the sintering is completed, the porous boron nitride antenna window is naturally cooled with the furnace, and then the furnace door is opened to take out the porous boron nitride antenna window; S5: Hydrophobic treatment: Place the porous boron nitride antenna window in the hydrophobic treatment tooling, cover it with a lid, seal the hydrophobic treatment tooling and evacuate it until the vacuum degree is less than -0.09MPa, maintain this vacuum degree for 10 minutes, and inject hexamethyldisilazane (hydrophobic agent) into the hydrophobic treatment tooling through the feed pipe so that the porous boron nitride antenna window is completely immersed under the liquid surface. Turn off the vacuum pump, open the vent valve, remove the air pipe connected to the hydrophobic treatment tooling, and place the porous boron nitride antenna window in the hydrophobic treatment tooling. Put it in an electric heating sealed drying oven with the hydrophobic treatment tooling, set the room temperature to 60°C for 20 minutes, keep it at 60°C for 24 hours, take out the porous boron nitride antenna window from the hydrophobic treatment tooling after the insulation is completed, place it on a clean tray, drain it, put the drained porous boron nitride antenna window into an electric heating sealed drying oven for drying, set the room temperature to 150°C for 45 minutes, keep it at 150°C for 2 hours, cool it to room temperature after the drying is completed, and take out the porous boron nitride antenna window; S6: Surface coating spraying: Prepare a coating with a mass ratio of 200:3 of silicone resin-5 (SAR-5): KH-550 silane coupling agent (γ-aminopropyltriethoxysilane), that is, specifically, 200g of silicone resin-5 (SAR-5) and 3g of KH-550 silane coupling agent (γ-aminopropyltriethoxysilane) are used to form 203g of sealing material, and 203g of sealing material is used to spray 8 porous boron nitride antenna windows; the specific spraying effect is as follows: Place the porous boron nitride antenna window with a clean surface on a plastic tray, place one porous boron nitride antenna window on each plastic tray, place the plastic tray with the porous boron nitride antenna window on the rotating platform of the spraying workbench in the clean room, filter the paint through filter paper and pour it into a special spray pot for topcoat, install the spray gun, turn on the air compressor, set the spray gun air source pressure to 0.25MPa, adjust the spray gun spray width to 100mm, and spray the porous boron nitride antenna window with the upper left corner as the starting point and "Z" shape in the spray gun. After 2.5 round trips, the lower right corner is used as the spraying end point, and then the rotating platform is rotated 180°, and the second spraying is performed according to the above spraying operation to complete the single-sided spraying of the porous boron nitride antenna window; S7: Drying: The porous boron nitride antenna window with single-sided spraying is transferred together with the plastic tray to the product temporary table in the clean room and placed for 30 minutes to wait for the initial curing of the coating surface; S8: Coating curing: The porous boron nitride antenna window with the preliminary curing on the coating surface is transferred to an electric heating sealed drying oven equipped with a PID system, and the room temperature is set to rise to 110°C in 30 minutes, and the temperature is kept at 110°C for 60 minutes. After the insulation is completed, the door of the electric heating sealed drying oven is opened and the porous boron nitride antenna window is taken out after naturally cooling to below 50°C; S9: Turn the porous boron nitride antenna window over and place it on a plastic tray, repeat the above steps S6, S7 and S8, keep the parameters unchanged, complete the spraying of the other side of the porous boron nitride antenna window, and finally complete the sealing coating operation on both sides of the porous boron nitride antenna window.

[0050] Comparative Example 1 The difference from the above-mentioned embodiment 1 is that the porous boron nitride antenna window does not go through steps S2, S3 and S4, and the remaining steps are the same as those in embodiment 1.

[0051] The performance comparison of the porous boron nitride antenna windows prepared in the above examples and comparative examples is shown in Table 1 below: Table 1 Performance comparison of porous boron nitride antenna windows

[0052] It can be seen from Table 1 above that the porous boron nitride antenna window prepared by the sealing coating method described in this application can significantly reduce the water absorption rate of the porous boron nitride antenna window, while the dielectric constant and dielectric loss are controlled within a certain range, and other properties do not show a significant decrease.

[0053] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A sealing coating method for a porous boron nitride antenna window, characterized in that: Before the porous boron nitride antenna window is surface-sprayed with sealing material, the porous boron nitride antenna window is pre-sealed, wherein the pre-sealing comprises sequentially impregnating, curing and sintering the porous boron nitride antenna window with silicone resin; and the sealing material is a mixture of silicone resin and silane coupling agent.

2. The sealing coating method for a porous boron nitride antenna window according to claim 1, characterized in that: In the pre-sealing operation, the silicone resin is impregnated for 1 to 2 hours, and the concentration of the silicone resin is 70% to 90%; during curing, the temperature is kept at 100° C. for 60 to 90 minutes; the sintering temperature is 600 to 750° C.; and the sintering time is 2 to 3 hours.

3. A sealing coating method for a porous boron nitride antenna window according to claim 1 or 2, characterized in that: Before the pre-sealing operation is performed on the porous boron nitride antenna window, a surface cleaning operation is also performed on the porous boron nitride antenna window: the surface of the porous boron nitride antenna window is blown with compressed air and then the surface of the porous boron nitride antenna window is wiped.

4. The sealing coating method for a porous boron nitride antenna window according to claim 1, characterized in that: The porous boron nitride antenna window is sprayed with a sealing material on the surface and then dried. After drying, it is heated to 110° C. and kept at 110° C. for 60 min±10 min.

5. The sealing coating method for a porous boron nitride antenna window according to claim 1, characterized in that: In the sealing material, the organic silicone resin is transparent methyl silicone resin, and the silane coupling agent is γ-aminopropyltriethoxysilane; and the mass ratio of the transparent methyl silicone resin to the γ-aminopropyltriethoxysilane is 100:(1-2).

6. The sealing coating method for a porous boron nitride antenna window according to claim 1, characterized in that: The spraying amount of the sealing material , where y is the spraying amount of the sealing material and the unit of the spraying amount is g, n is the number of porous boron nitride antenna windows, x is a fixed value, and the value range of x is 5~10; and when the formula is used to calculate the spraying amount of the sealing material, the physical quantities in the formula are dimensionless during the calculation.

7. A sealing coating method for a porous boron nitride antenna window according to claim 5 or 6, characterized in that: The method of spraying sealing material on the surface of the porous boron nitride antenna window comprises the following steps: placing the porous boron nitride antenna window on a rotating platform through a carrying device; The spray gun starts to spray the sealing material: the first corner of the porous boron nitride antenna window is used as the spraying starting point, and the spraying is performed in a "Z"-shaped direction, and the second corner of the porous boron nitride antenna window is used as the spraying end point; The first corner and the second corner of the porous boron nitride antenna window are arranged diagonally; after the first spraying is completed, the rotating platform is rotated 180 degrees, and the second spraying is performed according to the spraying operation of the spray gun to complete the spraying of one side of the porous boron nitride antenna window, and then dried and cured; The porous boron nitride antenna window is turned over so that the other side that is not sprayed is placed on a rotating platform through a carrying device, and the operation of spraying the sealing material with a spray gun is repeated to complete the spraying of the other side of the porous boron nitride antenna window, followed by drying and curing.

8. The sealing coating method for a porous boron nitride antenna window according to claim 7, characterized in that: The air source pressure of the spray gun is 0.25 MPa±0.05 MPa; the spray width is 100 mm±10 mm; and the distance between the muzzle of the spray gun and the porous boron nitride antenna window is 20 cm±5 cm.

9. The sealing coating method for a porous boron nitride antenna window according to claim 1, characterized in that: The method also includes performing a hydrophobic treatment on the porous boron nitride antenna window after the pre-sealing operation, wherein the hydrophobic treatment includes placing the porous boron nitride antenna window after the pre-sealing operation into a container, sealing and evacuating the container, inputting a hydrophobic agent into the container to immerse the porous boron nitride antenna window, and then heating and drying the porous boron nitride antenna window.

10. A porous boron nitride antenna window, characterized in that: The porous boron nitride antenna window is prepared by the sealing coating method of any one of claims 1 to 9.

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