A silicon-aluminum-coated high-temperature-resistant iron-cobalt wave-absorbing agent and its preparation method

Abstract

The present invention provides a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate and a preparation method thereof. The prepared iron-cobalt wave-absorbing agent has a core-shell microstructure, with the core being iron-cobalt alloy particles and the outside being a shell layer composed of aluminum silicate. The preparation method includes: pouring iron-cobalt alloy powder into a phosphoric acid solution for passivation; washing the passivated iron-cobalt alloy powder and then pouring it into a sodium silicate solution for pretreatment; pouring the pretreated iron-cobalt alloy powder into an aluminum sulfate solution, adjusting the pH value and continuously stirring; washing and calcining the reacted solid to obtain an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer. The raw materials of the present invention are easy to obtain, the process is simple, and the cost is relatively low. It can efficiently and batch-prepare iron-cobalt wave-absorbing agents with high Curie temperature and high-temperature oxidation resistance characteristics, and can meet the requirements of equipment for wave-absorbing performance in harsh high-temperature environments.

Description

Technical Field:

[0001] The present invention belongs to the technical field of microwave absorbing materials, and particularly relates to a high-temperature resistant iron cobalt microwave absorbing agent coated with aluminum silicate and a preparation method thereof. Background Art:

[0002] With the rapid progress of radar detection technology, it is of increasing importance to achieve multi-angle and all-round stealth of weapons and equipment. Microwave absorbing materials are one of the key elements of stealth technology. However, the high temperature generated by the friction between high-speed aircraft and air and the operation of engines will cause the performance of a large number of microwave absorbing materials to deteriorate rapidly, unable to meet the stealth requirements of high-temperature parts of various equipment, and severely restricting the development of stealth technology.

[0003] Magnetic materials play an irreplaceable role in microwave absorbing agents, especially in low-frequency microwave absorption. Compared with ferrites, iron cobalt-based magnetic metal materials have higher Snoek limit values, saturation magnetization intensities, and magnetic permeabilities. Their good microwave absorbing ability has been widely applied in military and civilian fields. In addition, the Curie temperature of iron cobalt alloys is much higher than that of ferrites, making their microwave absorbing performance not easily attenuated at high temperatures and more stable. However, iron cobalt microwave absorbing agents have the problem of being easily oxidized at high temperatures. Oxides that no longer have microwave absorbing ability will greatly reduce the performance of microwave absorbing agents, restricting their application in high-temperature environments. Therefore, it is very necessary to develop high-temperature resistant and antioxidant iron cobalt microwave absorbing agents.

[0004] Patent CN112744870 discloses a method for coating carbonyl iron with aluminum oxide. The performance of the coated microwave absorbing agent can be maintained after being treated at 450 °C, but the surface treatment process of carbonyl iron by this method is complex and has high requirements for process parameters. Patent CN 112692276 discloses a method for coating an iron-based microwave absorbing agent with titanium dioxide. This technology raises the complete oxidation temperature of the iron-based microwave absorbing agent to 700 °C and has the characteristics of simple process. However, the dielectric constant of titanium dioxide is relatively high, which is not conducive to impedance matching and will have a negative impact on the absorption performance. Patent CN 110586933 discloses a high-temperature resistant modification method for coating FeCo absorbent with zirconium dioxide. The reflection loss attenuation of the modified FeCo absorbent is only 1.2 dB after sintering at 500 °C, effectively improving the antioxidant property. However, the raw material zirconium butoxide used is costly, which is not conducive to large-scale production. Therefore, the present invention provides a high-temperature resistant iron cobalt microwave absorbing agent coated with aluminum silicate and a preparation method thereof to solve the above problems. Summary of the Invention:

[0005] The purpose of the present invention is to provide a high-temperature resistant iron cobalt microwave absorbing agent coated with aluminum silicate and a preparation method thereof in view of the deficiencies of the prior art, so that the iron cobalt microwave absorbing agent can have better antioxidant performance in a high-temperature environment, reduce the performance degradation caused by oxidation, and improve the service life.

[0006] The present invention adopts the following technical solutions:

[0007] (1) The present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, comprising the following steps:

[0008] S1. Pour the iron-cobalt alloy powder into a phosphoric acid solution for passivation;

[0009] S2. After cleaning the passivated iron-cobalt alloy powder, pour it into a sodium silicate solution for pretreatment;

[0010] S3. Pour the pretreated iron-cobalt alloy powder into an aluminum sulfate solution, adjust the pH value and continuously stir;

[0011] S4. Wash and calcine the reacted solid to obtain an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer.

[0012] Furthermore, the present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may also have the following characteristics: In S1, the concentration of the phosphoric acid solution is 0.1%-5%, preferably 1-3%; the passivation temperature is 40-70°C, preferably 50-65°C, and the passivation time is 10-60 min.

[0013] Furthermore, the present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may also have the following characteristics: In S2, in sodium silicate Na2O·nSiO2, the value of n ranges from 1 to 4, preferably the range of 3 to 3.5; the concentration of SiO2 in the sodium silicate solution is 1 wt%-10 wt%, preferably 2 wt%-8 wt%.

[0014] Furthermore, the present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may also have the following characteristics: In S2, the pretreatment temperature is 20-80°C, preferably 40-50°C, the pretreatment time is 1-30 min, preferably 10-30 min.

[0015] Furthermore, the present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may also have the following characteristics: In S3, the concentration of the aluminum sulfate solution is 1%-15%, preferably 5%-10%, the pH value of the reaction system is 8-10, preferably 9; the stirring reaction time is 30-120 min, preferably 60-120 min.

[0016] Furthermore, the present invention provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may also have the following characteristics: In S4, the calcination atmosphere is nitrogen or argon, the calcination temperature is 200-500°C, preferably 300°C; the calcination time is 60-240 min, preferably 90-180 min.

[0017] Further, the present invention provides a method for preparing a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may further have the following characteristics: In S1, the mass-volume ratio of the iron-cobalt alloy powder to the phosphoric acid solution is 100 g: 1000 ml; in S2, the mass-volume ratio of the passivated iron-cobalt alloy powder to the sodium silicate solution is 100 g: 500 ml; in S3, the mass-volume ratio of the pretreated iron-cobalt alloy powder to the aluminum sulfate solution is 100 g: 500 ml.

[0018] Further, the present invention provides a method for preparing a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may further have the following characteristics: The iron-cobalt alloy is Fe x Co 100 -x, where x ranges from 20 to 80.

[0019] Further, the present invention provides a method for preparing a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, which may further have the following characteristics: In the prepared iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer, the aluminum silicate shell layer accounts for 1% - 30% of the total mass.

[0020] (II) The present invention also provides an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer prepared by the above preparation method. The beneficial effects of the present invention:

[0021] The raw materials used in the present invention are easy to obtain, the process is simple, and the cost is low, which is conducive to the efficient and batch production of wave-absorbing agents. In the process of the present invention, the passivation process enables the iron-cobalt wave-absorbing agent to have a phosphated inner layer with preliminary protection performance, and at the same time, this passivation layer can strengthen the interfacial bonding property, making the high-oxidation-resistant aluminum silicate outer layer more tightly coated on the surface, ultimately effectively improving the high-temperature resistance of the iron-cobalt wave-absorbing agent. Description of the drawings:

[0022] Figure 1 It is the reflectivity curve graph of Examples 1 - 3 of the present invention;

[0023] Figure 2 It is the reflectivity curve graph of Example 3 of the present invention before and after heating in an air atmosphere at 600 °C for 60 min. Detailed implementation manners:

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, comprising the following steps:

[0027] (1) Pour 100 g of Fe 60 Co 40 powder into a 1% phosphoric acid solution and passivate it at 50 °C for 20 min;

[0028] (2) After washing the passivated iron-cobalt alloy powder, pour it into a sodium silicate solution, where n in Na2O·nSiO2 is 3, the SiO2 concentration in the solution is 2 wt%, and pre-treat it at 40 °C for 10 min;

[0029] (3) Pour the pre-treated iron-cobalt alloy powder into a 5% aluminum sulfate solution, adjust the pH value of the system to 9 and continuously stir for 60 min;

[0030] (4) After the reaction is completed, wash the above product and transfer it to an atmosphere furnace, and calcine it at 300 °C for 90 min in nitrogen or argon to obtain an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer.

[0031] Example 2

[0032] This embodiment provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, comprising the following steps:

[0033] (1) Pour 100 g of Fe 60 Co 40 powder into a 2% phosphoric acid solution and passivate it at 60 °C for 20 min;

[0034] (2) After washing the passivated iron-cobalt alloy powder, pour it into a sodium silicate solution, where n in Na2O·nSiO2 is 3.5, the SiO2 concentration in the solution is 8 wt%, and pre-treat it at 50 °C for 10 min;

[0035] (3) Pour the pre-treated iron-cobalt alloy powder into a 10% aluminum sulfate solution, adjust the pH value of the system to 9 and continuously stir for 120 min;

[0036] (4) After the reaction is completed, wash the above product and transfer it to an atmosphere furnace, and calcine it at 300 °C for 180 min in nitrogen or argon to obtain an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer.

[0037] Example 3

[0038] This embodiment provides a preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, comprising the following steps:

[0039] (1) Pour 100 g of Fe 60 Co40 The powder is poured into a 3% phosphoric acid solution and passivated at 65 °C for 15 min;

[0040] (2) After washing the passivated iron-cobalt alloy powder, it is poured into a sodium silicate solution. The value of n in Na2O·nSiO2 is 3.5, and the SiO2 concentration in the solution is 6 wt%. It is pretreated at 50 °C for 20 min.

[0041] (3) The pretreated iron-cobalt alloy powder is poured into a 7% aluminum sulfate solution, and the pH value of the system is adjusted to 9 and continuously stirred for 90 min;

[0042] (4) After the reaction is completed, the above product is washed and transferred to an atmosphere furnace. It is calcined at 300 °C for 120 min in nitrogen or argon to obtain an iron-cobalt wave-absorbing agent coated with an aluminum silicate shell layer.

[0043] The iron-cobalt wave-absorbing agents prepared in Examples 1-3 are made into an alumina composite wave-absorbing coating with a mass ratio of 50% and a thickness of 2 mm by plasma spraying and the reflectivity is tested. The obtained reflectivity curve is as Figure 1 shown. The test results show that the coating amount of aluminum silicate can be effectively controlled through different process routes, thereby affecting the electromagnetic parameters of the iron-cobalt wave-absorbing agent and regulating the absorption frequency points at a fixed thickness.

[0044] Figure 2 This is the reflectivity curve of Example 3 of the present invention before and after heating in an air atmosphere at 600 °C for 60 min. The test results show that the high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate has only slight attenuation and shift in absorption rate and absorption frequency points after undergoing high-temperature treatment, maintaining good absorption performance and effectively improving the high-temperature resistance of the iron-cobalt wave-absorbing agent.

[0045] The raw materials used in the present invention are easy to obtain, the process is simple, and the cost is low, which is beneficial to the preparation and production of wave-absorbing agents in an efficient and batch manner. In the process of the present invention, the passivation process enables the iron-cobalt wave-absorbing agent to have a phosphated inner layer with preliminary protection performance. At the same time, this passivation layer can strengthen the interfacial bonding, making the aluminum silicate outer layer with high antioxidant property more tightly coated on the surface, ultimately effectively improving the high-temperature resistance of the iron-cobalt wave-absorbing agent.

[0046] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A preparation method of a high-temperature resistant iron-cobalt wave-absorbing agent coated with aluminum silicate, characterized in that, It includes the following steps: S1. Pour the iron-cobalt alloy powder into the phosphoric acid solution for passivation; S2. After washing the passivated iron-cobalt alloy powder, pour it into the sodium silicate solution for pretreatment; S3. Pour the pretreated iron-cobalt alloy powder into the aluminum sulfate solution, adjust the pH value and continuously stir; S4. Wash and calcine the reacted solid to obtain an iron-cobalt wave absorber coated with a aluminum silicate shell layer.

2. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S1, the concentration of the phosphoric acid solution is 0.1%-5%, the passivation temperature is 40-70 °C, and the passivation time is 10-60 min.

3. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S2, in sodium silicate Na2O·nSiO2, the value range of n is 1-4; the concentration of SiO2 in the sodium silicate solution is 1 wt%-10 wt%.

4. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S2, the pretreatment temperature is 20-80 °C, and the pretreatment time is 1-30 min.

5. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S3, the concentration of the aluminum sulfate solution is 1%-15%, the pH value of the reaction system is 8-10, and the stirring reaction time is 30-120 min.

6. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S4, the calcination atmosphere is nitrogen or argon, the calcination temperature is 200-500 °C, and the calcination time is 60-240 min.

7. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In S1, the mass-volume ratio of the iron-cobalt alloy powder to the phosphoric acid solution is 100 g: 1000 ml; In S2, the mass-volume ratio of the passivated iron-cobalt alloy powder to the sodium silicate solution is 100 g: 500 ml; In S3, the mass-volume ratio of the pretreated iron-cobalt alloy powder to the aluminum sulfate solution is 100 g: 500 ml.

8. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, The iron-cobalt alloy is Fe x Co 100-x , where the value range of x is 20 - 80.

9. The preparation method of the aluminum silicate-coated high-temperature resistant iron-cobalt wave absorber according to claim 1, characterized in that, In the prepared iron-cobalt wave absorber coated with an aluminum silicate shell layer, the aluminum silicate shell layer accounts for 1%-30% of the total mass.

10. The iron-cobalt wave absorber coated with an aluminum silicate shell layer prepared by the preparation method according to any one of claims 1-9.

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