Radar wave absorbing paint with hollow microsphere as filling material and preparation method thereof

Example 1:

Radar wave absorbing coatings are mixed according to the following mass percentages:

Epoxy silicone resin 40%;

The leveling agent is CAB-551-0.010.2%;

Thickener is 0.2% sodium polyacrylate;

40% of hollow microspheres covered with metal coating;

The solvent is the balance of xylene (C8H10).

In this example, the method of preparing the radar wave absorbing coating with hollow microspheres as the filler is to put (A) epoxy silicone resin and the hollow microspheres coated with a metal coating in a high-speed mixer at 1000r/min Under the conditions, stir for 15 minutes and take it out to obtain the first mixture; (B) Grind the first mixture in a three-roll mill for 15 minutes to obtain a second mixture with a particle size of 30 μm; (C) the second mixture, flow The leveling agent, thickening agent and solvent are put into a high-speed mixer, stirred for 15 minutes at 1000r/min, and then allowed to stand for 3 minutes to obtain radar wave absorbing paint. The radar wave absorbing paint prepared by the above method has a coating thickness of 2mm and a maximum absorption rate of 20dB in the electromagnetic wave frequency band of 2-18GHz, and the frequency bandwidth greater than 10dB is 5GHz.

The hollow microspheres coated with a metal coating in this example are hollow microspheres with a particle size of 5-10μm (the KW-10 hollow microspheres produced by Qinhuangdao Glass Microsphere Co., Ltd., whose main components are SiO2 and Al2O3), and a metal nickel plating layer Composition: the nickel-plated metal layer covers the surface of the hollow microspheres, and the thickness of the nickel-plated metal layer is 250 nm.

The preparation steps of using an electroless plating process to coat the metal nickel-plated layer on the hollow microspheres are as follows:

Step 1: Selection of base material

The matrix material is KW-10 hollow microspheres with a particle size of 5-10μm;

Step 2: Pre-treatment of the substrate

(A) Preparation of alkaline washing treatment solution

The alkaline washing treatment liquid is composed of sodium hydroxide (NaOH) and deionized water;

Dosage: Add 10g of sodium hydroxide (NaOH) to 500ml of deionized water;

(B) Alkaline washing process

Add the hollow microspheres selected in the first step to the alkaline washing treatment solution;

Alkaline washing conditions: Under the conditions of 80℃ alkaline washing temperature and 500W power, the first reaction solution was prepared after 90 minutes of reaction with magnetic stirring dispersion (88-1 high-power magnetic stirrer, produced by Changzhou Guohua Electric Co., Ltd.);

Washing the first reaction liquid with water to obtain a first product;

Water washing conditions: at 25°C, add 800ml of deionized water to 100ml of the first reaction solution and stir to evenly dilute. After settling for 60 minutes, the supernatant is removed, and the first product is obtained after repeating twice;

In the present invention, water washing is used to remove Na+ and OH- in the first reaction solution and impurities in the raw materials on the basis of not affecting the dispersibility of the hollow microspheres, thereby obtaining the first product.

(C) Preparation of coupling treatment solution

The coupling treatment liquid is composed of Y-aminopropyltriethoxysilane (KH550) and ethanol (C2H5OH);

Dosage: Add 0.5g of Y-aminopropyltriethoxysilane to 500ml of ethanol (C2H5OH);

(D) Coupling process

Adding the first product to the coupling treatment solution;

Coupling conditions: Under the conditions of coupling temperature of 50°C and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacted for 8 hours, then stood still for 3 minutes to prepare the second reaction solution ;

Suction filtration of the second reaction liquid to obtain a second product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at 25°C, and obtain the second product after 5 minutes of suction filtration;

In the present invention, suction filtration is used to remove 40% of the amount of coupling agent added in the second reaction solution and 95% of the amount of ethanol (C2H5OH) added to obtain the second product.

(E) Preparation of activation treatment liquid

The activation treatment solution is composed of stannous chloride (SnCl2·2H2O), sodium stannate (Na2SnO3), palladium chloride (PdCl2), hydrochloric acid (HCl) and deionized water;

Dosage: Add 1g of stannous chloride (SnCl2·2H2O) and 0.2g of palladium chloride (PdCl2) to 100ml of hydrochloric acid (HCl), add 12.5g of stannous chloride (SnCl2·2H2O) and 2g of tin after reacting for 20 minutes Sodium (Na2SnO3) and 400ml of deionized water;

(F) Activation process

Adding the second product to the activation treatment solution;

Activation conditions: Under the conditions of activation temperature of 70°C and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacted for 60 minutes, and then stood still for 3 minutes to prepare the third reaction solution;

Suction filtration of the third reaction liquid to obtain a third product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at 25°C, and obtain the third product after 5 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Sn4+, Pd2+, Cl- and H+ in the third reaction solution, where Sn4+ is obtained by chemical reaction between Sn2+ and palladium chloride (PdCl2).

(G) Preparation of gel treatment solution

The gel solution is composed of hydrochloric acid (HCl) and deionized water;

Dosage: Add 50ml of hydrochloric acid (HCl) to 500ml of deionized water;

(H) Degumming process

Adding the third reaction product to the degumming treatment solution;

Degelling conditions: Under the conditions of 35℃ degelling temperature and 500W power, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 3 minutes and then stands for 3 minutes to prepare the fourth reaction solution ;

Suction filtration of the fourth reaction liquid to obtain a fourth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the fourth product after 5 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Cl- and H+ in the fourth reaction liquid, thereby obtaining the fourth product. Among them, Sn2+ is attached to the hollow microspheres of the fourth product;

Put the fourth product in a drying box and dry it at 90°C for 4 hours to obtain the fifth product;

The third step: electroless plating treatment

(A) Prepare chemical plating solution

The electroless plating solution is composed of nickel sulfate (NiSO4·6H2O), sodium hypophosphite (NaH2PO2), trisodium citrate (Na3C6H5O7) and deionized water;

Dosage: Add 20g of trisodium citrate (Na3C6H5O7), 8g of nickel sulfate (NiSO4·6H2O) and 8.5g of sodium hypophosphite (NaH2PO2) to 500ml of deionized water;

Adding ammonia water (NH3·H2O) to the electroless plating solution to adjust the pH of the electroless plating solution=8.5 to obtain an electroless plating solution;

(B) Electroless plating process

Put the prepared fifth product into an electroless plating solution;

Electroless plating conditions: Under the conditions of chemical plating temperature of 70℃, power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.), react for 60 minutes, and then stand for 3 minutes to obtain the product. Five reaction liquid;

Suction filtration of the fifth reaction liquid to obtain a fifth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the fifth product after 5 minutes of suction filtration;

In the present invention, suction filtration is used to remove C6H5O7 3-, H2PO3-, Na+, and Ni2+ in the fifth reaction solution to obtain the fifth product.

The fifth product was put into a drying box, and dried at 90° C. for 4 hours to obtain the sixth product, that is, the hollow microspheres were coated with a metal nickel plating layer.

The hollow microspheres (KW-10 hollow microspheres + metal nickel layer) prepared by the above process with a metal coating on the surface have a relative permittivity of 50 and a relative permeability of 1.5 when the coating thickness is 250nm. The density of the hollow microspheres coated with the metal plating layer is 3.5 g/cm3. The relative permittivity of KW-10 hollow microspheres is 4, and the relative permeability is 1. The maximum absorption rate of KW-10 hollow microspheres + metal nickel layer coated with metal coating in the electromagnetic wave frequency band of 2-18GHz is 20dB, and the frequency bandwidth greater than 10dB is 5GHz.

Using the same process as described above, the metal cobalt (Co) layer is electrolessly plated on the KW-10 hollow microspheres. When the coating thickness is 250nm, the relative permittivity is 40, the relative permeability is 1.4, and the hollow microspheres coated with the metal coating The density of the ball is 3.5 g/cm3. The maximum absorption rate of KW-10 hollow microspheres + metal cobalt layer covered with metal coating in the electromagnetic wave frequency band of 2-18GHz is 20dB, and the bandwidth greater than 10dB is 5GHz.

Using the same process as above, the metal iron (Fe) layer is electrolessly plated on the KW-10 hollow microspheres. The relative permittivity is 60 and the relative permeability is 2.0 when the coating thickness is 250nm. The density of the ball is 3.4 g/cm3. The maximum absorption rate of KW-10 hollow microspheres + metal iron layer coated with metal coating in the electromagnetic wave frequency band of 2-18GHz is 20dB, and the bandwidth greater than 10dB is 6GHz.

Example 2:

Radar wave absorbing coatings are mixed according to the following mass percentages:

30% epoxy silicone resin;

The leveling agent is CAB-551-0.20.3%;

Thickener is 0.3% polyurethane;

50% of hollow microspheres covered with metal coating;

The solvent is a mixture of xylene and n-butanol with the remainder of the mixture.

Medium xylene is 60wt%, n-butanol is 40wt%

The method of preparing radar wave absorbing coating with hollow microspheres as filler is to put (A) epoxy silicone resin and hollow microspheres coated with metal coating in a high-speed mixer, and stir for 20min under 800r/min Then take it out to obtain a first mixture; (B) Grind the first mixture in a three-roll mill for 15 minutes to obtain a second mixture with a particle size of 40 μm; (C) second mixture, leveling agent, thickening The agent and solvent are put into a high-speed mixer, stirred for 20 minutes at 800r/min, and then stand for 5 minutes to obtain radar wave absorbing coatings. The radar wave absorbing paint prepared by the above method has a coating thickness of 2mm and a maximum absorption rate of 20dB in the electromagnetic wave frequency band of 2-18GHz, and the frequency bandwidth greater than 10dB is 8GHz.

The hollow microspheres coated with a metal plating layer in this example are KW-10 hollow microspheres with a particle size of 10-20μm, composed of a metal plating nickel + iron + cobalt layer, and the metal plating nickel + iron + cobalt layer is coated on the hollow microspheres The thickness of the metal nickel plating layer is 150nm. The mass percentage of iron in the metal nickel+iron+cobalt layer is 15, the mass percentage of cobalt is 40, and the balance is nickel.

Using the electroless plating process, the surface of KW-10 hollow microspheres with a particle size of 10-20μm is coated with a 150nm thick metal plating nickel+iron+cobalt layer. The preparation steps are as follows:

Step 1: Selection of base material

The matrix material is KW-10 hollow microspheres with a particle size of 10-20μm;

Step 2: Pre-treatment of the substrate

(A) Preparation of alkaline washing treatment solution

The alkaline washing treatment liquid is composed of sodium hydroxide (NaOH) and deionized water;

Dosage: Add 15g of sodium hydroxide (NaOH) to 500ml of deionized water;

(B) Alkaline washing process

Add the hollow microspheres selected in the first step to the alkaline washing treatment solution;

Alkaline washing conditions: at 70℃ alkaline washing temperature, power 500W, magnetic stirring dispersion (88-1 high-power magnetic stirrer, produced by Changzhou Guohua Electric Co., Ltd.) for 75 minutes to prepare the first reaction solution;

Washing the first reaction solution with water for multiple times to obtain the first product;

Water washing conditions: at 25°C, add 1000ml of deionized water to 100ml of the first reaction solution and stir to evenly dilute, remove the supernatant liquid after settling for 75min, repeat 3 times to obtain the first product;

In the present invention, water washing is used to remove Na+ and OH- in the first reaction solution and impurities in the raw material without affecting the dispersibility of the hollow microspheres, thereby obtaining the first product.

(C) Preparation of coupling treatment solution

The coupling treatment liquid is composed of Y-aminopropyltriethoxysilane (KH550) and ethanol (C2H5OH);

Dosage: Add 1g of KH550 to 500ml of ethanol (C2H5OH);

(D) Coupling process

Adding the first product to the coupling treatment solution;

Coupling conditions: Under the conditions of coupling temperature of 40℃ and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 7 hours, then stands for 4 minutes to prepare the second reaction solution ;

Suction filtration of the second reaction liquid to obtain a second product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at 25°C, and obtain the second product after 8 minutes of suction filtration;

In the present invention, suction filtration is used to remove 45% of the amount of coupling agent added in the second reaction solution and 98% of the amount of ethanol (C2H5OH) added to obtain the second product.

(E) Preparation of activation treatment solution

The activation treatment solution is composed of stannous chloride (SnCl2·2H2O), sodium stannate (Na2SnO3), palladium chloride (PdCl2), hydrochloric acid (HCl) and deionized water;

Dosage: Add 1.5g of stannous chloride (SnCl2·2H2O) and 0.4g of palladium chloride (PdCl2) to 100ml of hydrochloric acid (HCl), and add 37.5g of stannous chloride (SnCl2·2H2O), 3g of Sodium stannate (Na2SnO3) and 400ml deionized water;

(F) Activation process

Add the second product to the activation treatment solution;

Activation conditions: Under the conditions of activation temperature of 60°C and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 45 minutes and then stands for 4 minutes to prepare the third reaction solution;

Suction filtration of the third reaction liquid to obtain a third product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at 25°C, and obtain the third product after 8 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Sn4+, Pd2+, Cl- and H+ in the third reaction solution, where Sn4+ is obtained by chemical reaction between Sn2+ and palladium chloride (PdCl2).

(G) Preparation of gel treatment solution

The gel solution is composed of hydrochloric acid (HCl) and deionized water;

Dosage: Add 75ml of hydrochloric acid (HCl) to 500ml of deionized water;

(H) Degumming process

Adding the third reaction product to the degumming treatment solution;

Degelling conditions: Under the conditions of sensitization temperature of 40℃ and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 2 minutes and then stands for 4 minutes to prepare the fourth reaction solution ;

Suction filtration of the fourth reaction liquid to obtain a fourth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at 25°C, and obtain the fourth product after 8 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Cl- and H+ in the fourth reaction liquid, thereby obtaining the fourth product. Among them, Sn2+ is attached to the hollow microspheres of the fourth product;

Put the fourth product in a drying box and dry it at 100°C for 3.5 hours to obtain the fifth product;

The third step: electroless plating treatment

(A) Prepare chemical plating solution

The electroless plating solution is composed of nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4·7H2O), ferrous sulfate (FeSO4·7H2O), sodium hypophosphite (NaH2PO2), trisodium citrate (Na3C6H5O7) and deionized water;

Dosage: Add 51.5g of trisodium citrate (Na3C6H5O7), 8g of nickel sulfate (NiSO4·6H2O), 8g of cobalt sulfate (CoSO4·7H2O), 16g of ferrous sulfate (FeSO4·7H2O) and 21.5g of sodium hypophosphite (NaH2PO2);

Adding ammonia (NH3·H2O) to the electroless plating solution to adjust the pH=9 of the electroless plating solution to obtain an electroless plating solution;

(B) Electroless plating process

Put the prepared fifth product into an electroless plating solution;

Electroless plating conditions: Under the conditions of electroless plating temperature of 80℃, power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.), react for 90 minutes, then stand for 4 minutes. Five reaction liquid;

Suction filtration of the fifth reaction liquid to obtain a fifth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the fifth product after 8 minutes of suction filtration;

In the present invention, suction filtration is used to remove C6H5O7 3-, H2PO3 -, Na+ and Ni2+ in the fifth reaction solution to obtain the fifth product.

Put the fifth product in a drying oven and dry it at 100° C. for 3.5 hours to obtain the sixth product, that is, the hollow microspheres are coated with a metal coating.

The hollow microspheres (KW-10 hollow microspheres + metal nickel + cobalt + iron layer) prepared by the above process are coated with a metal coating, and the relative dielectric constant is 70 when the coating thickness is 150nm, and the relative permeability The density of the hollow microspheres coated with the metal plating layer is 3.0 g/cm3. The relative permittivity of KW-10 hollow microspheres is 4, and the relative permeability is 1. The maximum absorption rate of KW-10 hollow microspheres + metal nickel + cobalt + iron layer coated with metal coating is 15dB in the electromagnetic wave frequency band of 2-18GHz, and the frequency bandwidth greater than 10dB is 3GHz.

Example 3:

Radar wave absorbing coatings are mixed according to the following mass percentages:

Epoxy silicone resin 35%;

Leveling agent is BYK3330.2%;

Thickener is RM-8W0.2%;

45% of hollow microspheres covered with metal coating;

The solvent is the balance of n-butanol.

The method of preparing the radar wave absorbing coating with hollow microspheres as filler is to put (A) epoxy silicone resin and hollow microspheres coated with metal coating in a high-speed mixer, and stir for 30min under the condition of 600r/min. Then take it out to obtain a first mixture; (B) Grind the first mixture in a three-roll mill for 20 minutes to obtain a second mixture with a particle size of 40 μm; (C) second mixture, leveling agent, thickening The agent and solvent are put into a high-speed mixer, stirred for 30 minutes at 600r/min, and then allowed to stand for 3 minutes to obtain radar wave absorbing paint. The radar wave absorbing paint prepared by the above method has a coating thickness of 2mm and a maximum absorption rate of 22dB in the electromagnetic wave frequency band of 2-18GHz, and the bandwidth greater than 10dB is 5GHz.

The hollow microspheres covered with a metal coating in this example are composed of KW-10 hollow microspheres with a particle size of 1-20 μm, and a metal coating of cobalt + iron layer. The metal coating of cobalt + iron coats the surface of the hollow microspheres, and The thickness of the metal nickel plating layer is 50nm.

The surface of the hollow microspheres is coated with a metal-plated cobalt + iron layer by an electroless plating process, and the preparation steps are as follows:

Step 1: Selection of base material

The matrix material is KW-10 hollow microspheres with a particle size of 1-20μm;

Step 2: Pre-treatment of the substrate

(A) Preparation of alkaline washing treatment solution

The alkaline washing treatment liquid is composed of sodium hydroxide (NaOH) and deionized water;

Dosage: Add 20g of sodium hydroxide (NaOH) to 500ml of deionized water;

(B) Alkaline washing process

Add the hollow microspheres selected in the first step to the alkaline washing treatment solution;

Alkaline washing conditions: at a temperature of 60°C and a power of 500W, the first reaction solution was prepared after 60 minutes of reaction with a magnetic stirring dispersion (88-1 high-power magnetic stirrer, produced by Changzhou Guohua Electric Co., Ltd.); The first reaction liquid is washed with water multiple times to obtain the first product;

Water washing conditions: at 25°C, add 900ml of deionized water to 100ml of the first reaction solution and stir to evenly dilute. After settling for 60 minutes, the supernatant is removed, and the first product is obtained after repeating 3 times;

In the present invention, water washing is used to remove Na+, OH- in the first reaction solution and impurities in the raw materials on the basis of not affecting the dispersibility of the hollow microspheres, thereby obtaining the first product.

(C) Preparation of coupling treatment solution

The coupling treatment liquid is composed of Y-aminopropyltriethoxysilane (KH550) and ethanol (C2H5OH);

Dosage: Add 2g of KH550 to 500ml of ethanol (C2H5OH);

(D) Coupling process

Adding the first product to the coupling treatment solution;

Coupling conditions: Under the conditions of coupling temperature of 35℃ and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacted for 6 hours, then stood for 5 minutes to prepare the second reaction solution ;

Suction filtration of the second reaction liquid to obtain a second product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the second product after 10 minutes of suction filtration;

In the present invention, suction filtration is used to remove 50% of the amount of coupling agent added in the second reaction solution and 95% of the amount of ethanol (C2H5OH) added to obtain the second product.

(E) Preparation of activation treatment liquid

The activation treatment solution is composed of stannous chloride (SnCl2·2H2O), sodium stannate (Na2SnO3), palladium chloride (PdCl2), hydrochloric acid (HCl) and deionized water;

Dosage: Add 2g of stannous chloride (SnCl2·2H2O) and 0.5g of palladium chloride (PdCl2) to 100ml of hydrochloric acid (HCl), add 50g of stannous chloride (SnCl2·2H2O) and 4g of stannic acid after reacting for 10 minutes Sodium (Na2SnO3) and 400ml deionized water;

(F) Activation process

Adding the second product to the activation treatment solution;

Activation conditions: Under the conditions of activation temperature of 50°C and power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 30 minutes, and then stands for 5 minutes to prepare the third reaction solution;

Suction filtration of the third reaction liquid to obtain a third product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa at room temperature (25°C), and obtain the third product after 10 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Sn4+, Pd2+, Cl- and H+ in the third reaction solution, where Sn4+ is obtained by chemical reaction between Sn2+ and palladium chloride (PdCl2).

(G) Preparation of gel treatment solution

The gel solution is composed of hydrochloric acid (HCl) and deionized water;

Dosage: Add 100ml of hydrochloric acid (HCl) to 500ml of deionized water;

(H) Degumming process

Adding the third reaction product to the degumming treatment solution;

Dissolution conditions: Under the conditions of 50℃ dissolution temperature and 500W power, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.) reacts for 1 min, and then stands for 5 min to prepare the fourth reaction solution ;

Suction filtration of the fourth reaction liquid to obtain a fourth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the fourth product after 10 minutes of suction filtration;

In the present invention, suction filtration is used to remove Sn2+, Cl- and H+ in the fourth reaction liquid, thereby obtaining the fourth product. Among them, Sn2+ is attached to the hollow microspheres of the fourth product;

Put the fourth product in a drying box and dry it at 110°C for 3 hours to obtain the fifth product;

The third step: electroless plating treatment

(A) Prepare chemical plating solution

The electroless plating solution is composed of cobalt sulfate (CoSO4·7H2O), ferrous sulfate (FeSO4·7H2O), sodium hypophosphite (NaH2PO2), trisodium citrate (Na3C6H5O7) and deionized water;

Dosage: Add 110g of trisodium citrate (Na3C6H5O7), 20g of nickel sulfate (CoSO4·7H2O), 20g of ferrous sulfate (FeSO4·7H2O) and 42.5g of sodium hypophosphite (NaH2PO2) into 500ml of deionized water;

Adding ammonia (NH3·H2O) to the electroless plating solution to adjust the pH of the electroless plating solution=10 to obtain the electroless plating solution;

(B) Electroless plating process

Put the prepared fifth product into an electroless plating solution;

Electroless plating conditions: Under the conditions of chemical plating temperature of 90℃, power of 500W, ultrasonic dispersion (KQ-500B ultrasonic cleaner, produced by Kunshan Ultrasonic Instrument Co., Ltd.), react for 120 minutes, and then stand for 5 minutes to obtain the product. Five reaction liquid;

Suction filtration of the fifth reaction liquid to obtain a fifth product;

Suction filtration conditions: adjust the vacuum degree of the suction filtration vacuum instrument (SHZ-III type circulating water vacuum pump) to -0.1MPa under the condition of 25°C, and obtain the fifth product after 10 minutes of suction filtration;

In the present invention, suction filtration is used to remove C6H5O7 3-, H2PO3 -, Na+, Co2 + and Fe2+ in the fifth reaction solution, thereby obtaining the fifth product.

Put the fifth product in a drying box and dry it at 110° C. for 4 hours to obtain the sixth product, that is, the hollow microspheres are coated with a metal coating.

The hollow microspheres (KW-10 hollow microspheres + metal cobalt + iron layer) prepared by the above process with a metal coating on the surface have a relative permittivity of 60 and a relative permeability of 1.4 when the coating thickness is 50nm , The density of the hollow microspheres covered with metal plating is 2.65g/cm3. The relative permittivity of KW-10 hollow microspheres is 4, and the relative permeability is 1. The maximum absorption rate of KW-10 hollow microspheres + metal cobalt + iron layer coated with metal coating in the electromagnetic wave frequency band of 2-18GHz is 10dB, and the frequency bandwidth greater than 8dB is 3GHz.

Electroless plating of metal cobalt + nickel layer on KW-10 hollow microspheres using the same process mentioned above, the relative permittivity is 50 when the coating thickness is 50nm, the relative permeability is 1.5, and the surface is covered with metal coating. The density is 2.60g/cm3. The maximum absorption rate of KW-10 hollow microspheres + metal nickel + cobalt layer covered with metal coating in the electromagnetic wave frequency band of 2-18GHz is 10dB, and the frequency bandwidth greater than 8dB is 3GHz.

Electroless plating of metal iron + nickel layer on KW-10 hollow microspheres using the same process described above, the relative permittivity is 70 when the coating thickness is 50nm, the relative permeability is 1.8, and the surface is covered with metal coating. The density is 2.71g/cm3. The maximum absorption rate of KW-10 hollow microspheres + metal nickel + iron layer coated with metal coating in the electromagnetic wave frequency band of 2-18GHz is 10dB, and the frequency bandwidth greater than 8dB is 4GHz.