Preparation method and application of radar antenna housing or antenna window compressive stress coating
Technical Field
The invention belongs to the field of high-technology coating preparation, and particularly relates to a radar antenna housing or antenna window compressive stress coating and a preparation method thereof.
Background
Quartz fiber reinforced quartz-based composite material (SiO)2/SiO2) Due to good mechanical property and dielectric property, the material has a huge application prospect in the field of radar antenna housing/antenna window, and has been successfully applied to American trident buried missiles. However, due to SiO2Porous structure of itself and hydrophilic groups on the surface, SiO2/SiO2The radome/antenna window is very easy to absorb moisture in the air, and the mechanical property and the wave transmission performance of the material are influenced. The preparation of the coating on the surface of the radar antenna housing/antenna window is a common means for improving the moisture resistance of the radar antenna housing/antenna window. Coatings can generally be divided into organic coatings and inorganic coatings. The organic coating has the characteristics of simple process and excellent waterproof performance, but is slow in curing, easy to thermally decompose at high temperature, high in carbon residue rate and capable of influencing wave-transmitting performance; the inorganic coating has good high temperature resistance, does not contain impurity carbon, but is complex in process and difficult to form.
Wherein the influence of the additive on the sintering and crystallization of the quartz ceramic [ J]Refractory material, 1994(4) 201-.。。。Chao C H,Lu H Y.Crystallization of Na2O-doped colloidal gel-derived silica[J].Materials Science&The paper of Engineering A (Structural Materials, Properties, MicroStructure and Processing),2000,282(1-2): 123-. The organic-inorganic hybrid coating can exert the mechanical property and the heat resistance of the inorganic material, can exert the forming property and the waterproof property of the organic material, and can further improve the mechanical property of the material on the premise of reducing the moisture absorption rate of the material through special process treatment.
Disclosure of Invention
In order to obtain a coating structure with good mechanical properties for the field of radar radomes or antenna windows, SiCl is utilized in the invention4Hydrolyzing under the catalytic action of a surfactant to generate SiO with uniform fineness2Powder, adding proper auxiliary agent, mixing with organic silicon resin as coating material to coat on SiO2/SiO2A layer of compressive stress coating is formed on the surface of the radome/antenna window, and the radome/antenna window has good mechanical property and moisture-proof effect. The method comprises the following specific steps: the method comprises the following specific steps:
(one) preparation of Mixed solution 1
Adding (2-5) wt.% polyvinyl alcohol PVA and (1-10) wt.% boron carbide B into deionized water4C, heating the powder C and (1-2) wt.% of surfactant to 92-96 ℃, and stirring until the PVA is completely dissolved to obtain a mixed solution 1;
(II) preparation of Mixed solution 2
Taking a proper amount of the mixed solution 1, and dropwise adding tetrachlorosilane SiCl into the mixed solution4Keeping the temperature of 45-50 ℃ in a water bath and stirring for 1-2 hours to obtain a mixed solution 2;
(III) preparation of Mixed solution 3
Adding (10-50) wt.% of organic solvent and (0.5-2) wt.% of antioxidant into the silicone resin, and stirring until the silicone resin is completely dissolved in the organic solvent to obtain a mixed solution 3;
(IV) preparation of mixture 4
Mixing the solutionDropwise adding the solution 3 into the mixed solution 2, keeping the temperature of 45-50 ℃ in a water bath, stirring until most of the water and the organic solvent are volatilized, and then drying the mixture in a muffle furnace at 45-50 ℃ for 24-48 hours to obtain a mixture 4; wherein, the organic silicon resin and SiCl4The mass ratio is (1-2): 1;
(V) obtaining a coating
Taking out the mixture 4 and uniformly coating the mixture on SiO2/SiO2Controlling the thickness (400-: heating to 400-460 ℃ for 1-2 hours and preserving the heat for 1-2 hours; cooling to room temperature for 1-2 hours to obtain a coating; wherein the flow rate of nitrogen or argon is 50-100 ml/min.
As a modification, the surfactant in the step (one) includes, but is not limited to, Tween 80, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.
As an improvement, SiCl is adopted in the step (two)4And B4The mass ratio of C is 100: (3-10).
As a modification, the organic silicon resin in the step (III) comprises but is not limited to monosilane, disilane and tetraethoxysilane, and the organic solvent comprises but is not limited to acetone and xylene.
As an improvement, the organic silicon resin and SiCl are adopted in the step (IV)4The mass ratio is (1-2): 1.
meanwhile, the radar antenna housing/antenna window prepared by the method is also provided.
Has the advantages that: the compressive stress coating provided by the invention can greatly reduce the moisture absorption performance of the radome/antenna window, improve the mechanical property and the heat resistance of the radome/antenna window and has good dielectric property. Meanwhile, the strength of the coating prepared by the method is improved by 20% or more when the coating is coated on the surface of a radome/antenna window; standing at 60 deg.C under 95% high temperature and high humidity for 28 days with weight increasing rate of less than or equal to 1%; the strength retention rate of the alloy reaches 80 percent or more after working for 8-10 hours at the temperature of 400-; the dielectric constant and the variation of dielectric loss are less than or equal to 8 percent, and the use requirement of the radome/antenna window under the harsh environment is met.
Drawings
FIG. 1 shows the strength of the radome of the invention as B4Schematic diagram of change rule of C content increase.
FIG. 2 shows the retention rate of the high-temperature strength of the radome according to the invention along with B4Schematic diagram of change rule of C content increase.
Detailed Description
The preparation of the compressive stress coating specifically comprises the following steps: using PVA water solution as adhesive material, heating and physically stirring to obtain B4The C particles and the surfactant are uniformly dispersed, so that SiCl is ensured4The hydrolysis is more sufficient and uniform; by using SiCl4The hydrolysis and the high-temperature sintering of the organic silicon resin form a pressure stress layer on the surface of the antenna housing/antenna window on the premise of not influencing the base material, so that the local tensile stress on the surface of the antenna housing/antenna window material in the stress process is relieved.
During the preparation, a small amount of B is added into the system4And C, an antioxidant, wherein on one hand, the antioxidant can slow down the high-temperature oxidation of the organic silicon resin in the air service environment. On the other hand, B4C is oxidized at high temperature to form B2O3The volume expansion is about 250 percent, and the shrinkage thermal stress of the organic silicon resin can be relieved; at the same time, B2O3The melting point is low, the fluidity is high, microcracks on the surface of the material can be healed, and the quartz devitrification can be inhibited.
The invention provides a change rule about strength and high temperature resistance of a radome, which is shown in figures 1-2, wherein the change rule of figures 1 and 2 is obtained based on B4C variable, obtained with other parameters unchanged: with B4The increase of C content, the strength of the radome and the change rule of high temperature resistance.
As can be seen from FIG. 1, with B4The increase of the content of C increases the strength of the radome first and then keeps unchanged basically. Overall modification effect and cost reasons, B4C and SiCl4The preferable range of the mass ratio is 0.03 to 0.15. As can be seen from FIG. 2, the retention of high temperature strength with B4The increase in C content is such that it increases, then remains substantially constant, and then decreasesTrend. B is4C and SiCl4The preferable range of the mass ratio is 0.03 to 0.10. In summary, SiCl is used in the present invention4And B4The mass ratio of C is 100: (3-10).
The present invention is further illustrated below with reference to examples.
Wherein, the surfactant includes, but is not limited to, tween 80, sodium dodecyl benzene sulfonate and sodium dodecyl sulfate. The organic silicon resin includes but is not limited to monosilane, disilane and tetraethoxysilane, and the organic solvent includes but is not limited to acetone and xylene.
The first embodiment is as follows:
1. adding 2 wt.% polyvinyl alcohol (PVA), 2 wt.% boron carbide (B) to deionized water4C) Powder and 1 wt.% sodium dodecylbenzene sulfonate, heated to 96 ℃ and stirred until PVA is completely dissolved, which is designated as mixed solution 1.
2. Taking a proper amount of the mixed solution 1, and dropwise adding tetrachlorosilane (SiCl) into the mixed solution4) And the temperature was kept at 50 ℃ in a water bath and stirred for 1 hour to obtain a mixed solution 2. Wherein, SiCl4And B4The mass ratio of C is 20: 1.
3. 20 wt.% of xylene and 2 wt.% of antioxidant are added to the monosilane, and the mixture is stirred until the silicone resin is completely dissolved in the organic solvent, so that a mixed solution 3 is obtained.
4. And dropwise adding the mixed solution 3 into the mixed solution 2, keeping the temperature of the water bath at 50 ℃, stirring until most of the water and the organic solvent are volatilized, and drying the mixture in a muffle furnace at 50 ℃ for 48 hours to obtain a mixture 4. Wherein, the organic silicon resin and SiCl4The mass ratio is 1: 1.
5. taking out the mixture 4 and uniformly coating the mixture on SiO2/SiO2The thickness of the surface of the radome is controlled to be 400 μm. Then, the mixture was placed in a high temperature furnace, and nitrogen gas was introduced at a flow rate of 50 ml/min. The temperature-raising program is controlled as follows: heating to 460 ℃ for 2 hours and preserving the temperature for 2 hours; the temperature is reduced to room temperature for 2 hours.
The coating prepared by the embodiment is coated on the surface of the radome, so that the strength is improved by 30%; standing at 60 deg.C under 95% high temperature and high humidity for 28d with weight increasing rate of 0.93%; the strength retention rate of the high-temperature-resistant high-strength steel reaches 87 percent after working for 10 hours at the high temperature of 400 ℃; the dielectric constant is improved by 5.4 percent and is 3.64; the dielectric loss is improved by 2.3 percent and is 0.014, and the use requirement of the radar antenna housing under the harsh environment is met.
The second embodiment is as follows:
1. to deionized water was added 5 wt.% polyvinyl alcohol (PVA), 5 wt.% boron carbide (B)4C) Powder and 1 wt.% tween 80, heated to 92 ℃ and stirred until PVA was completely dissolved, denoted as mixed solution 1.
2. Taking a proper amount of the mixed solution 1, and dropwise adding tetrachlorosilane (SiCl) into the mixed solution4) And the temperature was kept at 50 ℃ in a water bath and stirred for 2 hours to obtain a mixed solution 2. Wherein, SiCl4And B4The mass ratio of C is 10: 1.
3. adding 50 wt.% of acetone and 1 wt.% of antioxidant into the tetraethoxysilane organic silicon resin, and stirring until the organic silicon resin is completely dissolved in the organic solvent to obtain a mixed solution 3.
4. And dropwise adding the mixed solution 3 into the mixed solution 2, keeping the temperature of the water bath at 50 ℃, stirring until most of the water and the organic solvent are volatilized, and drying the mixture in a muffle furnace at 50 ℃ for 24 hours to obtain a mixture 4. Wherein, the organic silicon resin and SiCl4The mass ratio is 2: 1.
5. taking out the mixture 4 and uniformly coating the mixture on SiO2/SiO2The thickness of the surface of the radar antenna window is controlled to be 800 mu m. Then the mixture is put into a high temperature furnace, argon is introduced, and the flow rate is 100 ml/min. The temperature-raising program is controlled as follows: heating to 400 ℃ for 2 hours and preserving the temperature for 2 hours; the temperature is reduced to room temperature for 1 hour.
When the coating prepared by the embodiment is coated on the surface of the radar antenna window, the strength is improved by 27%; standing at 60 deg.C under 95% high temperature and high humidity for 28d with weight increasing rate of 0.65%; the strength retention rate of the high-temperature-resistant high-strength steel reaches 82 percent after working for 10 hours at the high temperature of 600 ℃; the dielectric constant is improved by 8.7 percent and is 3.75; the dielectric loss is improved by 7.1 percent and is 0.015 percent, and the use requirement of the radar antenna window under the harsh environment is met.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.