Preparation method of SiC absorbing-transmissive laminated wave-absorbing coating

Abstract

The application relates to a preparation method of a SiC absorbing-transmitting laminated wave-absorbing coating and belongs to the technical field of electromagnetic wave absorbing materials. The application aims at solving the problems that the existing wave-absorbing materials cannot simultaneously satisfy impedance matching and rapid absorption and cannot satisfy low-frequency broadband absorption. The method comprises the following steps: 1, mixing cobalt oxide, silicon powder, silicon dioxide powder and carbon powder; 2, calcining and high-temperature carbon removal; 3, preparing coating I; 4, preparing coating II; and 5, coating. The application is used for the preparation of the SiC absorbing-transmitting laminated wave-absorbing coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electromagnetic wave absorbing materials. BACKGROUND

[0002] Wave-absorbing coating is a key material widely used in electromagnetic wave absorption and stealth technology, especially in the fields of military, aerospace, communication and electronic equipment, etc. With the rapid development of modern radar detection technology and electronic countermeasure technology, how to effectively reduce the radar cross section (RCS) of the target object and reduce the reflection of electromagnetic waves has become one of the core problems of stealth technology research. Wave-absorbing coating can convert incident electromagnetic waves into heat or other forms of energy, thereby achieving the absorption and attenuation of electromagnetic waves and achieving the purpose of stealth or electromagnetic compatibility. Wave-absorbing materials need to have two conditions: one is that the electromagnetic wave enters the material inside without being reflected on its surface, which has the impedance matching characteristic; the other condition is that the material can quickly absorb and attenuate the entering electromagnetic wave. However, for a single coating or a single component, it is often difficult to meet both the requirements of impedance matching and rapid absorption, and it is also difficult to meet the purpose of low-frequency broadband absorption. SUMMARY

[0003] The present application solves the problem that the existing wave-absorbing materials cannot simultaneously meet the requirements of impedance matching and rapid absorption, and cannot meet the purpose of low-frequency broadband absorption, and further provides a preparation method of SiC absorbing-transmitting laminated wave-absorbing coating.

[0004] A preparation method of SiC absorbing-transmitting laminated wave-absorbing coating, which is carried out according to the following steps:

[0005] I. Mix cobalt oxide, silicon powder, silicon dioxide powder and carbon powder to obtain a mixture;

[0006] II. Under an inert atmosphere, heat the mixture to 900-1100°C, and under the condition of a temperature of 900-1100°C, heat for 20-60 min, then under an inert atmosphere, heat to 1300-1600°C, and under the condition of a temperature of 1300-1600°C, heat for 0.5-2 h, then cool under an inert atmosphere, and finally high-temperature carbon removal to obtain modified silicon carbide powder;

[0007] III. Mix 25-35 parts by mass of modified silicon carbide powder, 40-80 parts by mass of inorganic adhesive and 0-30 parts by mass of sol to obtain coating I;

[0008] IV. Mix 5-20 parts by mass of modified silicon carbide powder, 55-90 parts by mass of inorganic adhesive and 0-40 parts by mass of sol to obtain coating II;

[0009] V. Coating paint I, paint II and secondary glue on the substrate in turn, to obtain SiC absorption-transmission multilayer wave-absorbing coating.

[0010] The beneficial effects of the present application are:

[0011] 1. The present application is simple to operate, only the prepared powder and inorganic glue are mixed and dispersed in a certain proportion to prepare.

[0012] 2. The present application uses inorganic glue with high temperature resistance, effectively overcoming the poor high temperature resistance of traditional organic glue and resin.

[0013] 3. The present application has a thin wave-absorbing agent coating, low dosage and low density, and the obtained coating is lighter than other coatings made of wave-absorbing agents.

[0014] 4. The wave-absorbing coating is an inorganic composite coating, the silicon carbide material has certain wave-absorbing performance, and the silicon carbide itself has excellent high temperature stability, can maintain performance in an environment above 1000℃, has extremely high oxidation resistance and mechanical strength. The silicon carbide is modified by cobalt oxide to increase the magnetic loss of silicon carbide and enhance the absorption effect of silicon carbide. The appropriate high-temperature-resistant inorganic glue is selected as the adhesive to prepare the silicon carbide absorption-transmission multilayer wave-absorbing coating, which not only meets the requirement of impedance matching, but also realizes high-efficiency absorption. The traditional single coating cannot meet the low-frequency broadband absorption, the present application utilizes the magnetic loss and dielectric loss of modified silicon carbide, and simultaneously performs the compounding of multilayer composite coating, to make up for the defects of single coating, meet the low-frequency broadband absorption, meet the impedance matching and rapid absorption, and can achieve better absorption effect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 SEM image of the SiC absorption-transmission multilayer wave-absorbing coating prepared in Example One;

[0016] Figure 2 Wave-absorbing performance graph of the SiC absorption-transmission multilayer wave-absorbing coating prepared in Example One;

[0017] Figure 3 Wave-absorbing performance graph of the SiC absorption-transmission multilayer wave-absorbing coating prepared in Example Two;

[0018] Figure 4 Wave-absorbing performance graph of the SiC absorption-transmission multilayer wave-absorbing coating prepared in Example Three;

[0019] Figure 5 Wave-absorbing performance graph of the coating I prepared in Example Step Five. DETAILED DESCRIPTION

[0020] Detailed implementation one: a preparation method of the SiC absorption-transmission multilayer wave-absorbing coating in the embodiment, which is carried out according to the following steps:

[0021] I. Mix cobalt oxide, silicon powder, silicon dioxide powder and carbon powder to obtain a mixture;

[0022] II. Under an inert atmosphere, heat the mixture to 900-1100°C, and keep the temperature at 900-1100°C for 20-60 minutes, then heat to 1300-1600°C under an inert atmosphere, and keep the temperature at 1300-1600°C for 0.5-2 hours, then cool under an inert atmosphere, and finally remove carbon at high temperature to obtain modified silicon carbide powder;

[0023] III. Mix 25-35 parts by mass of the modified silicon carbide powder, 40-80 parts by mass of the inorganic adhesive and 0-30 parts by mass of the sol to obtain coating I;

[0024] IV. Mix 5-20 parts by mass of the modified silicon carbide powder, 55-90 parts by mass of the inorganic adhesive and 0-40 parts by mass of the sol to obtain coating II;

[0025] V. Apply coating I, coating II and secondary glue to the substrate in sequence to obtain the SiC absorbing-transmitting multilayer wave-absorbing coating.

[0026] The embodiment has the following advantages:

[0027] 1. The embodiment is simple to operate, and only needs to mix and disperse the prepared powder and the inorganic glue in a certain proportion.

[0028] 2. The embodiment uses inorganic glue with high-temperature resistance, effectively overcoming the poor high-temperature resistance of traditional organic glue and resin.

[0029] 3. The wave-absorbing agent coating of the embodiment is thin in thickness, low in dosage and low in density, and the obtained coating is lighter in quality than other coatings made of wave-absorbing agents.

[0030] 4. The wave-absorbing coating of the embodiment is an inorganic composite coating, the silicon carbide material has certain wave-absorbing performance, and the silicon carbide itself has excellent high-temperature stability, can maintain performance in an environment above 1000°C, has extremely high oxidation resistance and mechanical strength. The use of cobalt oxide to modify silicon carbide increases the magnetic loss of silicon carbide and enhances the absorption effect of silicon carbide. The use of suitable high-temperature-resistant inorganic glue as adhesive to prepare the silicon carbide absorbing-transmitting multilayer wave-absorbing coating not only meets the requirement of impedance matching, but also achieves efficient absorption. Traditional single coating cannot meet low-frequency broadband absorption, the embodiment makes use of the magnetic loss and dielectric loss of modified silicon carbide, and simultaneously performs the compounding of multilayer composite coating, makes up for the defects of single coating, meets low-frequency broadband absorption, meets impedance matching and rapid absorption, and can achieve better absorption effect.

[0031] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the molar ratio of cobalt oxide to silicon powder in step one is (0.2-1):1; the molar ratio of silicon powder to silicon dioxide powder in step one is 1:(1-2); the molar ratio of silicon powder to carbon powder in step one is 1:(2-4). The rest is the same as specific embodiment one.

[0032] Specific embodiment three: the difference between this embodiment and either of specific embodiment one or two is that the cobalt oxide in step one is cobalt oxide or tricobalt tetraoxide. The rest is the same as specific embodiment one or two.

[0033] Specific embodiment four: the difference between this embodiment and any one of specific embodiments one to three is that in step two, first, the temperature is raised to 400-600°C within 80-120 min under inert atmosphere, then the temperature is raised to 700-800°C within 20-40 min, and then the temperature is raised to 900-1100°C within 30-50 min under inert atmosphere; in step two, the temperature is raised to 1300-1600°C within 200-400 min under inert atmosphere. The rest is the same as specific embodiment three.

[0034] Specific embodiment five: the difference between this embodiment and any one of specific embodiments one to four is that in step two, the cooling is specifically as follows: the temperature is lowered to 900-1100°C within 200-400 min under inert atmosphere, then the temperature is lowered to 700-800°C within 30-50 min, and then the temperature is lowered to 400-600°C within 20-40 min, and finally the temperature is lowered to room temperature within 80-120 min. The rest is the same as specific embodiments one to four.

[0035] Specific embodiment six: the difference between this embodiment and any one of specific embodiments one to five is that in step two, the high-temperature carbon removal is specifically performed as follows: first, the temperature is raised to 450-550°C within 30-60 min under air atmosphere, then the temperature is raised to 650-800°C within 30-60 min, and under the conditions of air atmosphere and a temperature of 650-800°C, the temperature is kept for 1.5-3 h, then the temperature is lowered to 450-550°C within 30-60 min under air atmosphere, and finally the temperature is lowered to room temperature within 30-60 min. The rest is the same as specific embodiments one to five.

[0036] Specific embodiment seven: different from one of the specific embodiments one to six is that: the inorganic adhesive in steps three and four is aluminum dihydrogen phosphate aqueous solution with mass percentage of 40% to 80% or sodium silicate aqueous solution with mass percentage of 40% to 80%; the sol in steps three and four is zirconium sol or silicon sol; the secondary glue in step five is aluminum dihydrogen phosphate aqueous solution with mass fraction of 60% to 90% or sodium silicate secondary glue; the sodium silicate secondary glue is mixed by 40 to 70 parts of sodium silicate, 10 to 50 parts of silicon sol and 1 to 20 parts of aluminum oxide in terms of mass fraction. The others are the same as the specific embodiments one to six.

[0037] Specific embodiment eight: different from one of the specific embodiments one to seven is that: the substrate in step five is glass sheet, titanium steel, indium steel or quartz piece. The others are the same as the specific embodiments one to seven.

[0038] Specific embodiment nine: different from one of the specific embodiments one to eight is that: the coating thickness of the coating I in step five is 0.5mm to 2mm; the coating thickness of the coating II in step five is 0.5mm to 2mm; the coating thickness of the secondary glue in step five is 0.2mm to 2mm. The others are the same as the specific embodiments one to eight.

[0039] Specific embodiment ten: different from one of the specific embodiments one to nine is that: the coating I is coated on the substrate in step five, dried for 5h to 12h under the condition that the temperature is 25℃ to 100℃, to obtain coating I, then the coating II is coated on the coating I, dried for 5h to 12h under the condition that the temperature is 25℃ to 100℃, to obtain coating II, finally the secondary glue is coated on the coating II, dried for 12h to 24h under the condition that the temperature is 25℃ to 100℃, to obtain coating III. The others are the same as the specific embodiments one to nine.

[0040] The beneficial effects of the present application are verified by the following examples:

[0041] Example one:

[0042] A preparation method of SiC absorbing-transmitting laminated wave-absorbing coating, which is carried out according to the following steps:

[0043] I. mixing cobalt oxide, silicon powder, silicon dioxide powder and carbon powder to obtain a mixture;

[0044] The molar ratio of the cobalt oxide to the silicon powder is 0.5:1; the molar ratio of the silicon powder to the silicon dioxide powder is 1:1; the molar ratio of the silicon powder to the carbon powder is 1:4; the cobalt oxide is cobalt oxide;

[0045] II. Under argon atmosphere, the mixture is first heated to 500℃ in 100 min, then heated to 800℃ in 30 min, and then heated to 1000℃ in 40 min, and under argon atmosphere and at 1000℃, the mixture is kept for 30 min, then heated to 1500℃ in 200 min, and under argon atmosphere and at 1500℃, the mixture is kept for 120 min, then cooled under inert atmosphere, and finally high-temperature carbon removal to obtain the modified silicon carbide powder;

[0046] III. 30 parts of the modified silicon carbide powder and 70 parts of the inorganic adhesive are weighed according to the mass fraction and mixed uniformly to obtain coating I;

[0047] IV. 15 parts of the modified silicon carbide powder and 85 parts of the inorganic adhesive are weighed according to the mass fraction and mixed uniformly to obtain coating II;

[0048] V. The coating I is coated on the substrate, dried at room temperature for 12 h to obtain coating I, then the coating II is coated on the coating I, dried at room temperature for 12 h to obtain coating II, and finally the secondary glue is coated on the coating II, dried at room temperature for 24 h to obtain coating III, i.e. the SiC absorption-transmission laminated wave-absorbing coating.

[0049] In step II, the cooling is specifically cooling under argon atmosphere, from 1000℃ to 800℃ in 200 min, then from 800℃ to 500℃ in 40 min, and then from 500℃ to room temperature in 100 min.

[0050] The high-temperature carbon removal in step II is specifically as follows: under air atmosphere, first heated to 500℃ in 50 min, then heated to 700℃ in 40 min, and kept at 700℃ for 2 h under air atmosphere, then cooled to 500℃ in 40 min, and finally cooled to room temperature in 50 min.

[0051] The inorganic adhesive in steps III and IV is an aluminum dihydrogen phosphate aqueous solution with a mass percentage of 75%; the secondary glue in step V is an aluminum dihydrogen phosphate aqueous solution with a mass percentage of 75%;

[0052] The substrate in step V is a glass sheet, which is treated by wiping with a wet cloth dipped in detergent powder to remove oil, and then put into water for ultrasonic treatment for 10 min to remove impurities.

[0053] The coating thickness of the coating I in step V is 1 mm; the coating thickness of the coating II in step V is 0.5 mm; and the coating thickness of the secondary glue in step V is 1 mm.

[0054] Example 2: The difference between this example and example 1 is that: in step 3, 30 parts by mass of modified silicon carbide powder, 60 parts by mass of inorganic adhesive and 10 parts by mass of sol are mixed to obtain coating I; in step 4, 15 parts by mass of modified silicon carbide powder, 70 parts by mass of inorganic adhesive and 15 parts by mass of sol are mixed to obtain coating II; the sol in steps 3 and 4 is zirconium sol, which is acidic, and the solid content of the sol is 10% to 15%. The rest is the same as example 1.

[0055] Example 3: The difference between this example and example 1 is that: in step 3, 30 parts by mass of modified silicon carbide powder, 50 parts by mass of inorganic adhesive and 20 parts by mass of sol are mixed at a temperature of 40°C to obtain coating I; in step 4, 15 parts by mass of modified silicon carbide powder, 55 parts by mass of inorganic adhesive and 30 parts by mass of sol are mixed at a temperature of 40°C to obtain coating II; the inorganic adhesive in steps 3 and 4 is a 70% by mass aqueous sodium silicate solution; the sol in steps 3 and 4 is silica sol, which is alkaline, and the solid content of the sol is about 30%; the substrate in step 5 is titanium steel, which is treated by wiping the surface of the titanium steel with a wet cloth dipped in detergent powder to remove oil, then placing it in water for 10 minutes of ultrasonic treatment to remove impurities, and then sanding the surface of the titanium steel and washing the surface impurities with deionized water; the secondary glue in step 5 is sodium silicate secondary glue, which is prepared by mixing 50 parts by mass of sodium silicate, 35 parts by mass of silica sol and 5 parts by mass of alumina. The rest is the same as example 1.

[0056] Figure 1 SEM image of the SiC absorbing-transmissive multilayer absorbing coating prepared in example 1; as can be seen from the figure, the surface morphology of the coating is complete and has no obvious defects.

[0057] Figure 2 The absorbing performance graph of the SiC absorbing-transmissive multilayer absorbing coating prepared in example 1; as can be seen from the figure, the effective absorption bandwidth of the coating is 4.9GB, from 5.10GB to 10.0GB, and the low frequency absorbing band is relatively wide.

[0058] Figure 3 The absorbing performance graph of the SiC absorbing-transmissive multilayer absorbing coating prepared in example 2; Figure 4 The absorbing performance graph of the SiC absorbing-transmissive multilayer absorbing coating prepared in example 3; the finite absorption of the two coatings is below -10dB, both meeting the requirement of wide frequency absorption of electromagnetic waves.

[0059] Figure 5The wave-absorbing performance chart of the coating I prepared in Example Step Five. The lowest wave-absorbing performance did not reach below -10 dB, indicating that the reflection of electromagnetic waves was strong. Through comparison with the single coating of the comparative example, it was shown that the multi-layer wave-absorbing design met the requirement of impedance matching, and at the same time, the reflection of electromagnetic waves was reduced, and fast absorption instead of reflection was achieved on the interface surface of the coating.

Claims

1. A method for preparing a SiC absorbing-transmissive multilayer wave-absorbing coating, characterized in that It is carried out according to the following steps: I. mixing cobalt oxide, silicon powder, silicon dioxide powder and carbon powder to obtain a mixture; The molar ratio of the cobalt oxide to the silicon powder is (0.2-1):1; the molar ratio of the silicon powder to the silicon dioxide powder is 1:(1-2); and the molar ratio of the silicon powder to the carbon powder is 1:(2-4); II. under an inert atmosphere, heating the mixture to 900-1100 DEG C, and keeping the temperature at 900-1100 DEG C for 20-60 min, then under the inert atmosphere, heating to 1300-1600 DEG C, and keeping the temperature at 1300-1600 DEG C for 0.5-2 h, then cooling under the inert atmosphere, and finally removing carbon at high temperature to obtain modified silicon carbide powder; III. taking 25-35 parts by mass of the modified silicon carbide powder, 40-80 parts by mass of an inorganic adhesive and 0-30 parts by mass of sol, and mixing them uniformly to obtain coating I; IV. taking 5-20 parts by mass of the modified silicon carbide powder, 55-90 parts by mass of the inorganic adhesive and 0-40 parts by mass of sol, and mixing them uniformly to obtain coating II; V. coating coating I, coating II and secondary glue on a substrate in sequence to obtain a SiC absorbing-transmitting laminated wave-absorbing coating; The inorganic adhesive in steps III and IV is an aluminum dihydrogen phosphate aqueous solution with a mass percentage of 40-80% or a sodium silicate aqueous solution with a mass percentage of 40-80%; the sol in steps III and IV is zirconium sol or silicon sol; the secondary glue in step V is an aluminum dihydrogen phosphate aqueous solution with a mass percentage of 60-90% or sodium silicate secondary glue; the sodium silicate secondary glue is prepared by mixing 40-70 parts by mass of sodium silicate, 10-50 parts by mass of silicon sol and 1-20 parts by mass of aluminum oxide.

2. The method for preparing SiC absorbing-transmissive multilayer wave-absorbing coating according to claim 1, characterized in that The cobalt oxide in step I is cobalt oxide or tricobalt tetraoxide.

3. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... In step II, under the inert atmosphere, the temperature is first raised to 400-600 DEG C within 80-120 min, then raised to 700-800 DEG C within 20-40 min, and then raised to 900-1100 DEG C within 30-50 min; in step II, under the inert atmosphere, the temperature is raised to 1300-1600 DEG C within 200-400 min.

4. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... In step II, the cooling is carried out under the inert atmosphere, the temperature is lowered to 900-1100 DEG C within 200-400 min, then lowered to 700-800 DEG C within 30-50 min, then lowered to 400-600 DEG C within 20-40 min, and finally lowered to room temperature within 80-120 min.

5. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... The high-temperature decarburization in step two is carried out by the following steps: first, heating to 450-550°C in 30-60 minutes under air atmosphere, then heating to 650-800°C in 30-60 minutes under air atmosphere, and keeping the temperature for 1.5-3 hours under air atmosphere and at 650-800°C, then cooling to 450-550°C in 30-60 minutes under air atmosphere, and finally cooling to room temperature in 30-60 minutes.

6. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... The substrate in step five is a glass sheet, titanium steel, indium steel or a quartz piece.

7. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... The coating thickness of the coating I in step five is 0.5-2 mm; the coating thickness of the coating II in step five is 0.5-2 mm; and the coating thickness of the secondary adhesive in step five is 0.2-2 mm.

8. The method for preparing a SiC absorbing-transmitting multilayer microwave absorbing coating according to claim 1, characterized in that... In step five, the coating I is coated on the substrate, dried at 25-100°C for 5-12 hours to obtain coating I, then the coating II is coated on the coating I, dried at 25-100°C for 5-12 hours to obtain coating II, and finally the secondary adhesive is coated on the coating II, dried at 25-100°C for 12-24 hours to obtain coating III.

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