CN115332819A - Aluminum silicate coated high-temperature-resistant iron-cobalt wave absorber and preparation method thereof - Google Patents

Abstract

The invention provides a high-temperature resistant iron cobalt wave absorbing agent coated by aluminum silicate and a preparation method thereof, the prepared iron cobalt wave absorbing agent has a core-shell microstructure, the core is iron cobalt alloy particles, and the outer part is a shell layer formed by aluminum silicate, and the preparation method comprises the following steps: pouring iron-cobalt alloy powder into a phosphoric acid solution for passivation; cleaning the passivated iron-cobalt alloy powder, and then pouring the cleaned iron-cobalt alloy powder 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; and cleaning and calcining the reacted solid to obtain the iron-cobalt wave absorbing agent coated with an aluminum silicate shell. The method has the advantages of easily obtained raw materials, simple process and lower cost, can efficiently prepare the iron-cobalt wave absorbing agent with high Curie temperature and high-temperature oxidation resistance in batches, and can meet the requirement of equipment on wave absorbing performance in a high-temperature harsh environment.

Description

A high temperature resistant iron-cobalt wave absorber coated with aluminum silicate and preparation method thereof

Technical field:

The invention belongs to the technical field of wave-absorbing materials, and in particular relates to a high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate and a preparation method thereof.

Background technique:

With the rapid progress of radar detection technology, it is more and more important to realize the multi-angle and all-round stealth of weapons and equipment, and the absorbing material is one of the key contents of stealth technology. However, the friction between high-speed aircraft and the air and the high temperature generated by the engine will cause the performance of a large number of absorbing materials to deteriorate sharply, which cannot meet the stealth requirements of high-temperature parts of various equipment, and severely limits the development of stealth technology.

Magnetic materials have an irreplaceable position in microwave absorbers, especially in low-frequency microwave absorption. Compared with ferrite, iron-cobalt-based magnetic metal materials have higher Snoek limit value, saturation magnetization and magnetic permeability, and their good wave-absorbing ability makes them widely used in military and civilian fields. In addition, the Curie temperature of iron-cobalt alloy is much higher than that of ferrite, so that its absorbing performance is not easy to decay at high temperature and is more stable. However, iron-cobalt wave absorbers have the problem of being easily oxidized at high temperatures, and oxides that no longer have wave-absorbing ability will greatly reduce the performance of wave absorbers, limiting their application in high-temperature environments. Therefore, it is necessary to develop iron-cobalt wave absorbers with high temperature resistance and oxidation resistance.

Patent CN112744870 discloses a method for coating carbonyl iron with aluminum oxide. The performance of the coated wave absorbing agent can be maintained after being treated at 450°C. However, the treatment process for the surface of carbonyl iron in this method is complicated and requires high process parameters. Patent CN 112692276 discloses a method for coating iron-based wave-absorbing agent with titanium dioxide. This technology raises the complete oxidation temperature of iron-based wave-absorbing agent to 700°C and has the characteristics of simple process, but the dielectric constant of titanium dioxide is high, so it is not It is good for impedance matching and will have a negative impact on absorption performance. Patent CN 110586933 discloses a high-temperature-resistant modification method of FeCo absorbent coated with zirconia. The reflection loss attenuation of the modified FeCo absorbent is only 1.2dB after sintering at 500°C, which effectively improves the oxidation resistance, but The raw material zirconium n-butoxide is expensive, which is not conducive to large-scale production. Therefore, the present invention provides a high-temperature-resistant iron-cobalt wave absorber coated with aluminum silicate and a preparation method thereof to solve the above problems.

Invention content:

The purpose of the present invention is to address the deficiencies of the prior art, to provide a high-temperature-resistant iron-cobalt wave absorber coated with aluminum silicate and its preparation method, so that the iron-cobalt wave absorber can have better oxidation resistance in high-temperature environments performance, reduce performance degradation due to oxidation, and increase service life.

The present invention adopts following technical scheme:

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

S1, pour the iron-cobalt alloy powder into the phosphoric acid solution for passivation;

S2, after cleaning the passivated iron-cobalt alloy powder, pour it into a sodium silicate solution for pretreatment;

S3. Pour the pretreated iron-cobalt alloy powder into the aluminum sulfate solution, adjust the pH value and keep stirring;

S4. Cleaning and calcining the reacted solid to obtain an iron-cobalt wave absorbing agent coated with an aluminum silicate shell.

Further, 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 10-60min.

Further, in S2, in sodium silicate Na2O _· nSiO2, n ranges from ₁ to 4, preferably from 3 to 3.5; the concentration of _SiO2 in the sodium silicate solution is 1wt%-10wt%, Preferably it is 2wt%-8wt%.

Further, in S2, the pretreatment temperature is 20-80°C, preferably 40-50°C, and the pretreatment time is 1-30min, preferably 10-30min.

Further, in S3, the concentration of 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 30-120min, preferably 60- 120min.

Further, in S4, the calcination atmosphere is nitrogen or argon, the calcination temperature is 200-500°C, preferably 300°C; the calcination time is 60-240min, preferably 90-180min.

Further, in S1, the mass volume ratio of iron-cobalt alloy powder to phosphoric acid solution is 100g:1000ml; in S2, the mass volume ratio of passivated iron-cobalt alloy powder to sodium silicate solution is 100g:500ml; in S3, The mass volume ratio of the pretreated iron-cobalt alloy powder to the aluminum sulfate solution is 100g:500ml.

Further, the iron-cobalt alloy is FexCo100 _{-x ,} where x ranges from 20-80.

Further, in the prepared iron-cobalt wave absorbing agent coated with an aluminum silicate shell, the aluminum silicate shell accounts for 1%-30% of the total mass.

(2) The present invention also provides the iron-cobalt wave absorbing agent coated with an aluminum silicate shell prepared by the above preparation method. Beneficial effects of the present invention:

The raw materials used in the invention are easy to obtain, the process is simple, and the cost is low, which is beneficial to the efficient and mass production of the wave absorbing agent. The passivation process in the process of the present invention enables the iron-cobalt wave absorber to have a phosphating inner layer with preliminary protective properties, and at the same time, the passivation layer can strengthen the interface bonding, making the outer layer of aluminum silicate with high oxidation resistance more compact Coated on the surface, finally realizes the effective improvement of the high temperature resistance of the iron-cobalt wave absorber.

Description of drawings:

Fig. 1 is the reflectance curve figure of embodiment 1-3 of the present invention;

Fig. 2 is a graph of reflectance before and after heating in an air atmosphere at 600° C. for 60 minutes in Example 3 of the present invention.

Detailed ways:

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are Some, but not all, embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

This embodiment provides a method for preparing a high-temperature-resistant iron-cobalt wave absorbing agent coated with aluminum silicate, which includes the following steps:

(1) Pour 100g of Fe ₆₀ Co ₄₀ powder into a phosphoric acid solution with a concentration of 1%, and passivate it at 50°C for 20 minutes;

(2) Pour the passivated iron-cobalt alloy powder into the sodium silicate solution after cleaning, the value of n in Na2O _· nSiO2 is 3, the concentration of _SiO2 in the solution is _2wt %, pretreatment at 40°C for 10min ;

(3) Pour the pretreated iron-cobalt alloy powder into 5% aluminum sulfate solution, adjust the pH value of the system to 9 and continue stirring for 60 minutes;

(4) After the reaction is completed, the above product is cleaned and transferred to an atmosphere furnace, and calcined at 300° C. for 90 minutes in nitrogen or argon to obtain an iron-cobalt wave absorber coated with an aluminum silicate shell.

Example 2

This embodiment provides a method for preparing a high-temperature-resistant iron-cobalt wave absorbing agent coated with aluminum silicate, which includes the following steps:

(1) Pour 100g of Fe ₆₀ Co ₄₀ powder into a phosphoric acid solution with a concentration of 2%, and passivate it at 60°C for 20 minutes;

(2) Pour the passivated iron-cobalt alloy powder into the sodium silicate solution after cleaning, the value of n in Na2O _· nSiO2 is 3.5, the concentration of _SiO2 in the solution is 8wt%, _pretreatment at 50°C for 10min ;

(3) Pour the pretreated iron-cobalt alloy powder into 10% aluminum sulfate solution, adjust the pH value of the system to 9 and continue stirring for 120 minutes;

(4) After the reaction is completed, the above product is cleaned and transferred to an atmosphere furnace, and calcined at 300° C. for 180 min in nitrogen or argon to obtain an iron-cobalt wave absorber coated with an aluminum silicate shell.

Example 3

This embodiment provides a method for preparing a high-temperature-resistant iron-cobalt wave absorbing agent coated with aluminum silicate, which includes the following steps:

(1) Pour 100g of Fe ₆₀ Co ₄₀ powder into a phosphoric acid solution with a concentration of 3%, and passivate it at 65°C for 15 minutes;

(2) Pour the passivated iron-cobalt alloy powder into the sodium silicate solution after cleaning, the value of n in Na2O _· nSiO2 is 3.5, the concentration of _SiO2 in the solution is 6wt%, _pretreatment at 50°C for 20min . ;

(3) Pour the pretreated iron-cobalt alloy powder into 7% aluminum sulfate solution, adjust the pH value of the system to 9 and continue stirring for 90 minutes;

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

The iron-cobalt wave-absorbing agent prepared in Examples 1-3 is made into an aluminum oxide composite wave-absorbing coating with a mass ratio of 50% and a thickness of 2mm by plasma spraying, and the reflectivity test is carried out. The reflectivity curve obtained by the test is as follows: Figure 1 shows. 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 absorber, and adjusting the absorption frequency point under a fixed thickness.

Figure 2 is the reflectance curve of Example 3 of the present invention before and after heating in an air atmosphere at 600°C for 60 minutes. The test results show that the absorptivity and absorption frequency point of the high-temperature-resistant iron-cobalt wave absorber coated with aluminum silicate are only There is slight attenuation and offset, maintaining good absorption performance, and effectively improving the high temperature resistance of iron-cobalt absorbers.

The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the thinking of the present invention all belong to the protection scope of the present invention. For personnel, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (10)

1. a preparation method of an aluminum silicate-coated high-temperature-resistant iron-cobalt wave absorbing agent, is characterized in that, comprises the following steps: S1, pour the iron-cobalt alloy powder into the phosphoric acid solution for passivation; S2, after cleaning the passivated iron-cobalt alloy powder, pour it into a sodium silicate solution for pretreatment; S3. Pour the pretreated iron-cobalt alloy powder into the aluminum sulfate solution, adjust the pH value and keep stirring; S4. Cleaning and calcining the reacted solid to obtain an iron-cobalt wave absorbing agent coated with an aluminum silicate shell. 2. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In S1, the concentration of phosphoric acid solution is 0.1%-5%, the passivation temperature is 40-70°C, and the passivation time is 10-60min. 3. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In S2, in sodium silicate Na ₂ O·nSiO ₂ , n ranges from 1 to 4; the concentration of SiO ₂ in the sodium silicate solution is 1 wt% to 10 wt%. 4. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In S2, the pretreatment temperature is 20-80°C, and the pretreatment time is 1-30min. 5. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is 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 30-120min. 6. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In S4, the calcination atmosphere is nitrogen or argon, the calcination temperature is 200-500°C, and the calcination time is 60-240min. 7. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In S1, the mass volume ratio of the iron-cobalt alloy powder to the phosphoric acid solution is 100g: 1000ml; In S2, the mass volume ratio of the passivated iron-cobalt alloy powder to the sodium silicate solution is 100g:500ml; In S3, the mass volume ratio of the pretreated iron-cobalt alloy powder to the aluminum sulfate solution is 100g:500ml. 8. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, The iron-cobalt alloy is FexCo100 _{-x ,} where x ranges from 20-80. 9. the preparation method of the high-temperature-resistant iron-cobalt wave-absorbing agent coated with aluminum silicate according to claim 1, is characterized in that, In the prepared iron-cobalt wave absorbing agent coated with aluminum silicate shell, the aluminum silicate shell accounts for 1%-30% of the total mass. 10. The iron-cobalt wave absorbing agent coated with an aluminum silicate shell prepared by the preparation method described in any one of claims 1-9.

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