阅读说明：本技术 一种三氧化二铝-羰基铁微球吸波剂及其制备方法 (Aluminum oxide-carbonyl iron microsphere wave absorbing agent and preparation method thereof ) 是由 刘若鹏 赵治亚 刘志礼 于 2019-10-30 设计创作，主要内容包括：本发明提供了一种Al-2O-3-羰基铁微球吸波剂,由羰基铁微球和包覆于所述羰基铁微球表面的Al-2O-3组成,所述羰基铁微球表面具有多孔结构。本申请还提供了一种Al-2O-3-羰基铁微球吸波剂的制备方法。在制备Al-2O-3-羰基铁微球吸波剂的过程中,本申请首先将羰基铁微球进行多孔化处理,然后进行Al-2O-3纳米层表面包覆,制备了一种新型的Al-2O-3-羰基铁微球吸波剂。本申请提供的Al-2O-3-多孔羰基铁微球吸波剂独特的多孔及核壳结构极大降低了羰基铁微球的密度,该吸波剂耐高温和抗氧化特性优异,在保持磁导率基本不变的前提下可降低介电常数、提高阻抗匹配、改善吸波效能,还可改善与基体的相容性,提高界面结合力。(The invention provides Al 2 O 3 The carbonyl iron microsphere wave absorbing agent consists of carbonyl iron microspheres and Al coated on the surfaces of the carbonyl iron microspheres 2 O 3 The carbonyl iron microsphere has a porous structure on the surface. The application also provides Al 2 O 3 A preparation method of the carbonyl iron microsphere wave absorbing agent. In the preparation of Al 2 O 3 In the process of the wave absorbing agent of the carbonyl iron microsphere, the carbonyl iron microsphere is firstly subjected to porosification treatment and then Al 2 O 3 The surface of the nano layer is coated to prepare novel Al 2 O 3 -carbonyl iron microsphere wave absorbers. Al provided by the present application 2 O 3 The unique porous and core-shell structure of the porous carbonyl iron microsphere wave absorber greatly reduces the carbonyl iron microsphereThe wave absorbing agent has excellent high temperature resistance and oxidation resistance, can reduce dielectric constant, improve impedance matching and wave absorbing efficiency on the premise of keeping magnetic conductivity unchanged basically, and can also improve compatibility with a matrix and interface binding force.)

1. Al (aluminum)₂O₃The carbonyl iron microsphere wave absorbing agent consists of carbonyl iron microspheres and Al coated on the surfaces of the carbonyl iron microspheres₂O₃The carbonyl iron microsphere has a porous structure on the surface.

2. Al according to claim 1₂O₃The carbonyl iron microsphere wave absorbing agent is characterized in that the particle size of the carbonyl iron microsphere is 2-20 microns; the Al is₂O₃The tap density of the-carbonyl iron microsphere wave absorbing agent is 2.5-4.05g/cm³。

3. The Al of claim 1₂O₃The preparation method of the carbonyl iron microsphere wave absorbing agent comprises the following steps:

A) pretreating carbonyl iron microspheres in acid liquor, and drying in vacuum to obtain carbonyl iron microspheres with passivation films on the surfaces;

B) reacting the carbonyl iron microspheres obtained in the step A) with a ferric trichloride solution to obtain porous carbonyl iron microspheres;

C) pickling the porous carbonyl iron microspheres, and drying in vacuum to obtain carbonyl iron microspheres without passivation films on the surfaces;

D) reacting the carbonyl iron microspheres obtained in the step C) with an aluminum source, and then drying in vacuum to obtain Al₂O₃-carbonyl iron microsphere wave absorbers.

4. The preparation method according to claim 3, wherein the acid solution in step A) and step C) is dilute hydrochloric acid with pH of 1-4.

5. The preparation method according to claim 4, wherein in the step A), the carbonyl iron microspheres are 1-4 parts by weight, and the diluted hydrochloric acid is 20-50 parts by weight.

6. The preparation method of claim 3, wherein in the step B), the carbonyl iron microspheres obtained in the step A) are 1-4 parts by weight, the ferric trichloride solution is 60-140 parts by weight, and the concentration of the ferric trichloride solution is 0.1-0.3 mol/L.

7. The method according to claim 3, wherein step D) is in particular:

mixing the carbonyl iron microspheres obtained in the step C) with deionized water, adding an aluminum source, adjusting the pH value to 6-9 with acid liquor, and carrying out vacuum drying after reaction.

8. The method according to claim 7, wherein the carbonyl iron microspheres obtained in step C) are 1 to 8 parts by weight, the deionized water is 30 to 80 parts by weight, the aluminum source is 5 to 30 parts by weight, the concentration of the aluminum source is 1.0 to 3.0mol/L, and the concentration of the acid solution is 0.1 to 0.4 mol/L.

9. The method according to claim 7, wherein the acid solution is hydrochloric acid or citric acid, and the aluminum source is sodium metaaluminate.

10. The preparation method according to claim 3, wherein in the step A), the temperature of the vacuum drying is 30-60 ℃ and the time is 20-50 min; in the step C), the temperature of the vacuum drying is 40-80 ℃, and the time is 20-50 min; in the step D), the temperature of vacuum drying is 60-80 ℃, and the time is 12-24 hours.

Technical Field

The invention relates to the technical field of wave absorbing agents, in particular to Al₂O₃-carbonyl iron microsphere wave absorbing agent and preparation method thereof.

Background

With the rapid development of electronic information and military strength, the flying speed of weaponry is faster and faster in the use process, a large amount of heat is generated by the friction between special parts such as skin and the like and air, and in order to achieve the stealth effect, the wave-absorbing material is required to have high temperature resistance and oxidation resistance, but most of the wave-absorbing materials researched at home at present are normal-temperature wave-absorbing materials. In order to realize the high temperature resistance and oxidation resistance of the wave absorbing material, the preparation of the wave absorbing agent is very important.

The carbonyl iron microsphere is the most important electromagnetic wave absorbent material, has the advantages of low price, easy preparation, large industrial yield, stable quality, high magnetic saturation intensity, higher magnetic permeability, high real part of the magnetic permeability, good imaginary part frequency dispersion characteristic, high wave absorbing performance under low matching thickness and the like, and has the Curie temperature of 770 ℃, which indicates that the carbonyl iron microsphere is possibly applied to high temperature. However, the carbonyl iron microspheres have high density, poor oxidation resistance and corrosion resistance, high dielectric constant, poor impedance matching property and other factors, so that the application of the carbonyl iron microspheres in wider fields is limited.

Disclosure of Invention

The invention aims to provide Al with low density₂O₃The wave absorbing agent has excellent high temperature resistance and oxidation resistance, can reduce dielectric constant, improve impedance matching and wave absorbing efficiency on the premise of keeping magnetic conductivity unchanged basically, and can also improve compatibility with a matrix and interface binding force.

In view of the above, the present application provides an Al₂O₃The carbonyl iron microsphere wave absorbing agent consists of carbonyl iron microspheres and Al coated on the surfaces of the carbonyl iron microspheres₂O₃The carbonyl iron microsphere has a porous structure on the surface.

Preferably, the particle size of the carbonyl iron microsphere is 2-20 μm; the Al is₂O₃Tap density of iron carbonyl microsphere wave absorber2.5 to 4.05g/cm³。

The application also provides the Al₂O₃The preparation method of the carbonyl iron microsphere wave absorbing agent comprises the following steps:

A) pretreating carbonyl iron microspheres in acid liquor, and drying in vacuum to obtain carbonyl iron microspheres with passivation films on the surfaces;

B) reacting the carbonyl iron microspheres obtained in the step A) with a ferric trichloride solution to obtain porous carbonyl iron microspheres;

C) pickling the porous carbonyl iron microspheres, and drying in vacuum to obtain carbonyl iron microspheres without passivation films on the surfaces;

D) reacting the carbonyl iron microspheres obtained in the step C) with an aluminum source, and then drying in vacuum to obtain Al₂O₃-carbonyl iron microsphere wave absorbers.

Preferably, the acid solution in the step A) and the acid solution in the step C) are both diluted hydrochloric acid with the pH value of 1-4.

Preferably, in the step A), the carbonyl iron microspheres are 1-4 parts by weight, and the diluted hydrochloric acid is 20-50 parts by weight.

Preferably, in the step B), the carbonyl iron microspheres obtained in the step A) account for 1-4 parts by weight, the ferric trichloride solution accounts for 60-140 parts by weight, and the concentration of the ferric trichloride solution is 0.1-0.3 mol/L.

Preferably, the step D) is specifically:

mixing the carbonyl iron microspheres obtained in the step C) with deionized water, adding an aluminum source, adjusting the pH value to 6-9 with acid liquor, and carrying out vacuum drying after reaction.

Preferably, the carbonyl iron microspheres obtained in the step C) are 1-8 parts by weight, the deionized water is 30-80 parts by weight, the aluminum source is 5-30 parts by weight, the concentration of the aluminum source is 1.0-3.0 mol/L, and the concentration of the acid solution is 0.1-0.4 mol/L.

Preferably, the acid solution is hydrochloric acid or citric acid, and the aluminum source is sodium metaaluminate.

Preferably, in the step A), the vacuum drying temperature is 30-60 ℃ and the time is 20-50 min; in the step C), the temperature of the vacuum drying is 40-80 ℃, and the time is 20-50 min; in the step D), the temperature of vacuum drying is 60-80 ℃, and the time is 12-24 hours.

The present application provides an Al₂O₃The carbonyl iron microsphere wave absorbing agent consists of carbonyl iron microspheres and Al coated on the surfaces of the carbonyl iron microspheres₂O₃The carbonyl iron microsphere has a porous structure on the surface. Al provided by the present application₂O₃The carbonyl iron microsphere wave absorber fundamentally solves the problem of high density of carbonyl iron microspheres, the porous core-shell structure of the carbonyl iron microsphere wave absorber can improve multiple reflection loss of electromagnetic waves in multiple pores of particles and between core shells, the magnetic conductivity and the dielectric constant of the particles are improved, and the absorption efficiency of the wave absorber is obviously improved; by reaction with Al₂O₃The cladding matching effectively reduces the dielectric constant, improves the impedance matching and obviously improves the bandwidth on the premise of keeping the magnetic conductivity unchanged basically; al with compact wave absorber surface₂O₃The nano shell layer has the characteristics of small density, high melting point, good oxidation resistance, high hardness, high strength, excellent wear resistance, excellent insulativity and the like, can obviously improve the oxidation resistance of the carbonyl iron microsphere, improve the thermal stability and the processing stability, and improve the dispersibility and the uniformity of the wave absorbing agent in a matrix.

Drawings

FIG. 1 shows the preparation of Al according to the invention₂O₃-a reaction scheme of a carbonyl iron microsphere wave absorber;

fig. 2 is an SEM photograph of the porous carbonyl iron powder micropowder prepared in step 1 of example 1 of the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

In view of the influence of the high density of carbonyl iron microspheres on the application of carbonyl iron microspheres as a wave absorbing agent, the application provides Al₂O₃The surface of the porous carbonyl iron microsphere is coated with a layer of Al₂O₃The nanometer antioxidant film aims at solving a series of problems of poor antioxidant capacity, high density, high dielectric constant, poor frequency dispersion characteristic and the like of carbonyl iron microspheres.

Al provided by the present application₂O₃The unique porous and core-shell structure of the carbonyl iron microsphere wave absorbing agent greatly reduces the density of the carbonyl iron microsphere, improves the multiple reflection loss of electromagnetic waves in particles and improves the wave absorbing performance; al (Al)₂O₃The alloy has the characteristics of low density, high melting point, good oxidation resistance, high hardness, high strength, excellent wear resistance, excellent insulativity and the like, and can be used for preventing core particles from being further oxidized and reducing eddy current loss; compact Al formed on the surface of carbonyl iron microsphere₂O₃The nano shell layer can obviously improve the oxidation resistance of the carbonyl iron microsphere, improve the thermal stability, reduce the dielectric constant on the premise of keeping the magnetic conductivity unchanged basically and improve the impedance matching of the carbonyl iron microsphere; al (Al)₂O₃The coating layer can be embedded into the pores of the porous carbonyl iron microsphere, so that the reflection area and loss can be further increased, and Al can be improved₂O₃Interfacial bonding force between coating layer and carbonyl iron microsphere, and Al₂O₃The surface of the special nano shell contains a large amount of hydroxyl, which is beneficial to the infiltration of a macromolecular chain of the adhesive, can improve the compatibility of the absorbent and a matrix and improve the interface bonding force with the resin matrix.

Specifically, first, the present application provides an Al₂O₃The carbonyl iron microsphere wave absorbing agent consists of carbonyl iron microspheres and Al coated on the surfaces of the carbonyl iron microspheres₂O₃The carbonyl iron microsphere has a porous structure on the surface.

Al according to the invention₂O₃The core carbonyl iron microspheres in the carbonyl iron microsphere wave absorber are carbonyl iron microspheres well known to those skilled in the art, and the preparation method of the carbonyl iron microspheres is not particularly limited in the present application; the grain size of the carbonyl iron microsphere is 2-20 mu m, the surface of the carbonyl iron microsphere has a porous structure, and the porous structure can reduce Al₂O₃-density of carbonyl iron microsphere wave absorber. The Al is₂O₃Al in carbonyl iron microsphere wave absorber₂O₃And the thickness of the coating layer is different from nanometer to micron. Al (Al)₂O₃The coating layer is thin, the dielectric constant is not obviously reduced, and the impedance matching effect is poor; al (Al)₂O₃The coating layer is too thick, so that the magnetic conductivity can be greatly reduced, and the powder absorption efficiency is reduced; with Al₂O₃The coating layer is thickened, and the oxidation resistance of the powder is obviously improved. Verification shows that when the thickness of the coating layer is about 1um, the dielectric constant is obviously reduced under the condition that the magnetic permeability is kept unchanged, and the impedance matching and absorption efficiency of the coating layer can be obviously improved.

The application also provides the Al₂O₃The preparation method of the carbonyl iron microsphere wave absorbing agent comprises the following steps:

A) pretreating carbonyl iron microspheres in acid liquor, and drying in vacuum to obtain carbonyl iron microspheres with passivation films on the surfaces;

B) reacting the carbonyl iron microspheres obtained in the step A) with a ferric trichloride solution to obtain porous carbonyl iron microspheres;

C) pickling the porous carbonyl iron microspheres, and drying in vacuum to obtain carbonyl iron microspheres without passivation films on the surfaces;

D) reacting the carbonyl iron microspheres obtained in the step C) with an aluminum source, and then drying in vacuum to obtain Al₂O₃-carbonyl iron microsphere wave absorbers.

In the above-mentioned preparation of Al₂O₃In the process of the carbonyl iron microsphere wave absorbing agent, the carbonyl iron microsphere is pretreated in acid liquor, and the carbonyl iron microsphere with a passivation film on the surface is obtained after vacuum drying; in order to reduce the introduction of impurities, dilute hydrochloric acid with the pH value of 1-4 is preferably adopted for pretreatment of the carbonyl iron microspheres, so that a layer of passivation film appears on the surfaces of the carbonyl iron microspheres, and a small amount of pit-shaped structures appear on the surface parts. The content of the carbonyl iron microspheres is 1-4 parts by weight, and the dosage of the dilute hydrochloric acid is 20-50 parts by weight; the dilute hydrochloric acid is too little to form a complete passive film, is not beneficial to the formation of subsequent reaction and is not easy to form a pit; the excessive dilute hydrochloric acid and the too thick passive film lead the subsequent reaction time to be too long, the excessive and overlarge pits are formed, and the powder is damagedThe magnetic permeability of the body. The surface pretreatment process of the carbonyl iron microsphere specifically comprises the following steps:

carrying out ultrasonic treatment on the carbonyl iron microspheres and dilute hydrochloric acid for 3-8 min, separating the carbonyl iron microspheres and the dilute hydrochloric acid by using a magnet, cleaning twice by using deionized water and absolute ethyl alcohol respectively, and carrying out vacuum drying for 20-50 min at the temperature of 30-60 ℃.

And (3) after the carbonyl iron microspheres are pretreated, carrying out porous treatment on the carbonyl iron microspheres, namely reacting the obtained carbonyl iron microspheres with a ferric trichloride solution to obtain the porous carbonyl iron microspheres. Mixing the carbonyl iron microsphere with the surface pretreatment with ferric trichloride, and then adding into Cl^-The passivation film is destroyed under the auxiliary action of the magnetic microsphere, naked carbonyl iron is formed on the surface of the magnetic microsphere as a reaction nucleus, the nucleated carbonyl iron is used as a negative electrode, and the passivation layer outside the nucleus is used as a positive electrode to form a primary battery to react to generate Fe²⁺And gradually forming a porous structure; fe in pores²⁺The concentration increases as the reaction continues, and Cl in the solution is maintained in order to maintain charge balance^-Migration into the pores, high concentration of Fe in the pores²⁺With Cl^-Making FeCl₂Hydrolysis is carried out, pH is reduced, and solution reaction is facilitated; after reacting for a period of time, the porous surface is covered with a membrane with a porous structure, and the structure is convenient for anions and cations to enter and exit, so that porous carbonyl iron with a small amount of corrosive substances and a passivation layer on the surface is formed. In the process, the content of the carbonyl iron microspheres subjected to surface pretreatment is 1-4 parts by weight, the content of the ferric trichloride solution is 60-140 parts by weight, and the concentration is 0.1-0.3 mol/L; the concentration of the ferric trichloride is too small, a passivation film is not easy to damage, subsequent reaction is slow, and finally pits are not easy to form; if the concentration is too high, the reaction speed is accelerated, and the formed pits are too much and too large, so that the magnetic conductivity is seriously reduced. The process for obtaining the porous carbonyl iron microspheres specifically comprises the following steps: and mixing the pretreated carbonyl iron microspheres with a ferric trichloride solution, and ultrasonically stirring for 8-25 min.

The porous carbonyl iron microspheres obtained by the method are subjected to acid washing and vacuum drying to obtain the carbonyl iron microspheres without passivation films on the surfaces. The carbonyl iron microsphere porous structure greatly reduces the density of the carbonyl iron microsphere, improves the multiple reflection loss of electromagnetic waves in particles and improves the wave absorbing performance. In order not to introduce impurities, the acid solution for acid washing is selected from dilute hydrochloric acid in the embodiment, and after the acid washing by the dilute hydrochloric acid, a small amount of corrosion substances and passivation films attached to the surfaces of the porous carbonyl iron microspheres are cleaned, so that the carbonyl iron microspheres without passivation films on the surfaces can be obtained. The pickling process specifically comprises the following steps: adding dilute hydrochloric acid with the pH value of 1-4 into the porous carbonyl iron microsphere precipitate for acid washing, pouring out the mixed liquid, adding distilled water, carrying out ultrasonic cleaning, and repeating the operation for three times; adding absolute ethyl alcohol, and repeating the above operations for three times; and finally, putting the residual porous carbonyl iron microspheres into vacuum drying equipment, and carrying out vacuum drying for 20-50 min at the temperature of 40-80 ℃.

Finally coating Al on the surface of the carbonyl iron microsphere₂O₃Reacting the porous carbonyl iron microspheres obtained by the treatment with an aluminum source, and then drying in vacuum to obtain Al₂O₃-carbonyl iron microsphere wave absorbers. The carbonyl iron microspheres without the passivation films on the surfaces in the steps have rough surfaces and micropores, so that the surface activity of the carbonyl iron microspheres is increased, and the carbonyl iron microspheres are more favorable for adsorbing an aluminum source. The aluminum source is selected from sodium metaaluminate in specific embodiments. The process comprises the following steps: mixing the porous carbonyl iron microspheres with deionized water, adding an aluminum source, adjusting the pH value to 6-9 with acid liquor, and performing vacuum drying after reaction. The using amount of the porous carbonyl iron microspheres is 1-8 parts by weight, the using amount of the deionized water is 30-80 parts by weight, the using amount of the sodium metaaluminate solution is 5-30 parts by weight, and the concentration of the sodium metaaluminate solution is 1.0-3.0 mol/L; the concentration of the sodium metaaluminate is too small, the supply of an aluminum source is insufficient, and Al is formed₂O₃The particles are small, the coating layer is thin and incomplete, the dielectric constant is not obviously reduced, and the impedance matching effect is poor; the concentration of the sodium metaaluminate is too large, and Al is formed₂O₃The particles are large, the coating layer is thick, the magnetic conductivity can be greatly reduced, and the powder absorption efficiency is reduced. The temperature of the vacuum drying is 60-80 ℃, and the time is 12-24 hours. FIG. 1 shows the preparation of Al according to the present application, as shown in FIG. 1₂O₃Reaction scheme of iron carbonyl microsphere wave-absorbing agent.

In the preparation of Al₂O₃In the process of the wave absorbing agent of the carbonyl iron microspheres, the carbonyl iron microspheres are firstly subjected to porosification treatment and then Al is carried out₂O₃The surface of the nano layer is coated to prepare novel Al₂O₃-carbonyl iron microsphere wave absorbers. Al (Al)₂O₃The unique porous and core-shell structure of the porous carbonyl iron microsphere wave absorber greatly reduces the density of carbonyl iron microspheres, improves multiple reflection loss of electromagnetic waves in particles, and improves wave absorbing performance; surface-coated compact Al₂O₃The nano shell layer can obviously improve the oxidation resistance of the carbonyl iron microsphere, reduce the dielectric constant and improve the impedance matching of the carbonyl iron microsphere on the premise of keeping the magnetic conductivity unchanged basically; al (Al)₂O₃The coating layer can be embedded into the pores of the porous carbonyl iron microsphere, so that the reflection area and loss can be further increased, and Al can be improved₂O₃Interfacial bonding force between coating layer and carbonyl iron microsphere, and Al₂O₃The surface of the special nano shell contains a large amount of hydroxyl, which is beneficial to the infiltration of a macromolecular chain of the adhesive, can improve the compatibility of the absorbent and a matrix and improve the interface bonding force with the resin matrix.

Finally ensures the Al prepared by the method₂O₃The carbonyl iron microsphere wave absorber has the effects of small density, strong oxidation resistance, low dielectric constant, high frequency dispersion characteristic, and strong impedance matching and absorbing capacity; in addition, the process method and equipment are simple, the reaction period is short, no pollution is caused, and the structure and the performance of the catalyst are easy to control.

For further understanding of the present invention, the following examples are given to provide Al₂O₃The carbonyl iron microsphere wave absorber and the preparation method thereof are illustrated in detail, and the protection scope of the present invention is not limited by the following examples.

Example 1

Novel Al₂O₃The preparation method of the porous carbonyl iron microsphere wave absorbing agent comprises the following two steps:

1. preparation of porous carbonyl iron microspheres

1.1 pretreatment of the surface of carbonyl iron

Weighing 4 parts of carbonyl iron microspheres with the particle size of 2-20 microns, placing the carbonyl iron microspheres in a beaker, adding 20 parts of dilute hydrochloric acid with the pH value of 4, carrying out ultrasonic treatment on the beaker for 3min, separating the carbonyl iron microspheres and the dilute acid by using a magnet, then respectively washing the carbonyl iron microspheres and the dilute acid twice by using deionized water and absolute ethyl alcohol, and placing the mixture in a vacuum drying device for vacuum drying at 40 ℃ for 30 min;

1.2 porosification of carbonyl iron microspheres

Weighing 4 parts of carbonyl iron microspheres subjected to surface pretreatment, placing the carbonyl iron microspheres in a beaker, adding 60 parts of ferric trichloride solution with the concentration of 0.1mol/L, and carrying out ultrasonic treatment for 8min to ensure that the carbonyl iron microspheres and the solution fully react;

1.3 treatment and cleaning of porous carbonyl iron microspheres

Attaching a magnet to the bottom of a beaker from the outside to enable carbonyl iron microspheres to be adsorbed to the bottom of the beaker to obtain precipitated powder and transparent solution, adding dilute hydrochloric acid with the pH value of 4 into the precipitate for pickling, pouring out the mixed liquid, adding distilled water into the beaker, carrying out ultrasonic cleaning, and repeating the operation for three times. Adding absolute ethyl alcohol, and repeating the above operations for three times; finally, putting the rest porous carbonyl iron microspheres into vacuum drying equipment, and carrying out vacuum drying for 40min at 60 ℃ to obtain porous carbonyl iron microspheres; FIG. 2 is an SEM photograph of the porous carbonyl iron powder micropowder prepared in step 1 of this example;

2、Al₂O₃preparation of porous carbonyl iron powder

Uniformly stirring 8 parts of porous carbonyl iron microspheres and 80 parts of deionized water in a dispersion machine for 30min, dripping 5 parts of sodium metaaluminate solution with the concentration of 1.0mol/L into the dispersion liquid in a beaker, slowly adjusting the pH value of the solution to 6 by using 0.1mol/L hydrochloric acid (citric acid), continuously stirring for 10h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃The coated porous carbonyl iron microsphere core-shell wave absorber.

Example 2

Novel Al₂O₃The preparation method of the porous carbonyl iron microsphere wave absorbing agent comprises the following two steps:

1. preparation of porous carbonyl iron microspheres

1.1 pretreatment of the surface of carbonyl iron

Weighing 2 parts of carbonyl iron microspheres with the particle size of 2-20 microns, placing the carbonyl iron microspheres in a beaker, adding 30 parts of dilute hydrochloric acid with the pH value of 2, carrying out ultrasonic treatment on the beaker for 5min, separating the carbonyl iron microspheres and the dilute acid by using a magnet, then respectively cleaning the carbonyl iron microspheres and the dilute acid twice by using deionized water and absolute ethyl alcohol, and placing the mixture in a vacuum drying device for vacuum drying at 40 ℃ for 30 min;

1.2 porosification of carbonyl iron microspheres

Weighing 2 parts of carbonyl iron microspheres subjected to surface pretreatment, placing the carbonyl iron microspheres in a beaker, adding 80 parts of ferric trichloride solution with the concentration of 0.1mol/L, and carrying out ultrasonic treatment for 10min to ensure that the carbonyl iron microspheres and the solution fully react;

1.3 treatment and cleaning of porous carbonyl iron microspheres

Attaching a magnet to the bottom of a beaker from the outside to enable carbonyl iron microspheres to be adsorbed to the bottom of the beaker to obtain a precipitated powder and a transparent solution, adding dilute hydrochloric acid with the pH value of 2 into the precipitate for pickling, pouring out the mixed liquid, adding distilled water into the beaker, carrying out ultrasonic cleaning, repeating the operation for three times, adding absolute ethyl alcohol, and repeating the operation for three times; finally, putting the rest porous carbonyl iron microspheres into vacuum drying equipment, and carrying out vacuum drying for 40min at 60 ℃ to obtain porous carbonyl iron microspheres;

2、Al₂O₃preparation of porous carbonyl iron microspheres

Uniformly stirring 6 parts of porous carbonyl iron microspheres and 60 parts of deionized water in a dispersion machine for 40min, dripping 10 parts of sodium metaaluminate solution with the concentration of 1.0mol/L into the dispersion liquid in a beaker, slowly adjusting the pH value of the solution to 7 by using 0.1mol/L hydrochloric acid (citric acid), continuously stirring for 15h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃The coated porous carbonyl iron microsphere core-shell wave absorber.

Example 3

Novel Al₂O₃The preparation method of the porous carbonyl iron microsphere wave absorbing agent comprises the following two steps:

1. preparation of porous carbonyl iron microspheres

1.1 pretreatment of the surface of carbonyl iron

Weighing 1 part of carbonyl iron microspheres with the particle size of 2-20 microns, placing the carbonyl iron microspheres in a beaker, adding 30 parts of dilute hydrochloric acid with the pH value of 1.5, carrying out ultrasonic treatment on the beaker for 5min, separating the carbonyl iron microspheres and the dilute acid by using a magnet, respectively washing the carbonyl iron microspheres and the dilute acid twice by using deionized water and absolute ethyl alcohol, and then placing the mixture in a vacuum drying device to carry out vacuum drying at 40 ℃ for 30 min;

1.2 porosification of carbonyl iron microspheres

Weighing 1 part of carbonyl iron microspheres subjected to surface pretreatment, placing the carbonyl iron microspheres in a beaker, adding 100 parts of ferric trichloride solution with the concentration of 0.18mol/L, and carrying out ultrasonic treatment for 12min to ensure that the carbonyl iron microspheres and the solution are fully reacted;

1.3 treatment and cleaning of porous carbonyl iron microspheres

Attaching a magnet to the bottom of a beaker from the outside to enable carbonyl iron microspheres to be adsorbed to the bottom of the beaker to obtain a precipitated powder and a transparent solution, adding dilute hydrochloric acid with the pH value of 2 into the precipitate for pickling, pouring out the mixed liquid, adding distilled water into the beaker, carrying out ultrasonic cleaning, and repeating the operation for three times; adding absolute ethyl alcohol, and repeating the above operations for three times; finally, putting the rest porous carbonyl iron microspheres into vacuum drying equipment, and carrying out vacuum drying for 40min at 60 ℃ to obtain porous carbonyl iron microspheres;

2、Al₂O₃preparation of porous carbonyl iron microspheres

Uniformly stirring 4 parts of porous carbonyl iron microspheres and 50 parts of deionized water in a dispersion machine for 40min, dripping 15 parts of sodium metaaluminate solution with the concentration of 1.0mol/L into the beaker dispersion liquid, slowly adjusting the pH value of the solution to 8 by using 0.1mol/L hydrochloric acid (citric acid), continuously stirring for 18h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃The coated porous carbonyl iron microsphere core-shell wave absorber.

Example 4

Novel Al₂O₃The preparation method of the porous carbonyl iron microsphere wave absorbing agent comprises the following two steps:

1. preparation of porous carbonyl iron microspheres

1.1 pretreatment of the surface of carbonyl iron

Weighing 1 part of carbonyl iron microspheres with the particle size of 2-20 microns, placing the carbonyl iron microspheres in a beaker, adding 40 parts of dilute hydrochloric acid with the pH value of 1.5, carrying out ultrasonic treatment on the beaker for 8min, separating the carbonyl iron microspheres and the dilute acid by using a magnet, then respectively cleaning the carbonyl iron microspheres and the dilute acid twice by using deionized water and absolute ethyl alcohol, and placing the mixture in a vacuum drying device for vacuum drying at 40 ℃ for 30 min;

1.2 porosification of carbonyl iron microspheres

Weighing 1 part of carbonyl iron microspheres subjected to surface pretreatment, placing the carbonyl iron microspheres in a beaker, adding 120 parts of ferric trichloride solution with the concentration of 0.3mol/L, and carrying out ultrasonic treatment for 20min to ensure that the carbonyl iron microspheres and the solution are fully reacted;

1.3 treatment and cleaning of porous carbonyl iron microspheres

Attaching a magnet to the bottom of a beaker from the outside to enable carbonyl iron microspheres to be adsorbed to the bottom of the beaker to obtain precipitated powder and a transparent solution, adding dilute hydrochloric acid with the pH value of 2 into the precipitate for pickling, pouring out the mixed liquid, adding distilled water into the beaker, carrying out ultrasonic cleaning, repeating the operation for three times, adding absolute ethyl alcohol, repeating the operation for three times for alcohol cleaning, and finally putting the residual porous carbonyl iron microspheres into vacuum drying equipment for vacuum drying at the temperature of 60 ℃ for 40min to obtain the porous carbonyl iron microspheres.

2、Al₂O₃Preparation of porous carbonyl iron microspheres

Uniformly stirring 2 parts of porous carbonyl iron microspheres and 50 parts of deionized water in a dispersion machine for 60min, dripping 20 parts of sodium metaaluminate solution with the concentration of 2mol/L into the dispersion liquid in a beaker, slowly adjusting the pH value of the solution to 8 by using 0.2mol/L hydrochloric acid (citric acid), continuously stirring for 20h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃The coated porous carbonyl iron microsphere core-shell wave absorber.

Example 5

Novel Al₂O₃The preparation method of the porous carbonyl iron microsphere wave absorbing agent comprises the following two steps:

1. preparation of porous carbonyl iron microspheres

1.1 pretreatment of the surface of carbonyl iron

Weighing 1 part of carbonyl iron microspheres with the particle size of 2-20 microns, placing the carbonyl iron microspheres in a beaker, adding 50 parts of dilute hydrochloric acid with the pH value of 1, carrying out ultrasonic treatment on the beaker for 8min, separating the carbonyl iron microspheres and the dilute acid by using a magnet, then respectively cleaning the carbonyl iron microspheres and the dilute acid twice by using deionized water and absolute ethyl alcohol, and placing the mixture in a vacuum drying device for vacuum drying at 40 ℃ for 30 min;

1.2 porosification of carbonyl iron microspheres

Weighing 1 part of carbonyl iron microspheres subjected to surface pretreatment, placing the carbonyl iron microspheres in a beaker, adding 140 parts of ferric trichloride solution with the concentration of 0.3mol/L, and carrying out ultrasonic treatment for 25min to ensure that the carbonyl iron microspheres and the solution fully react;

1.3 treatment and cleaning of porous carbonyl iron microspheres

Attaching a magnet to the bottom of a beaker from the outside to enable carbonyl iron microspheres to be adsorbed to the bottom of the beaker to obtain a precipitated powder and a transparent solution, adding dilute hydrochloric acid with the pH value of 1 into the precipitate for pickling, pouring out the mixed liquid, adding distilled water into the beaker, carrying out ultrasonic cleaning, repeating the operation for three times, adding absolute ethyl alcohol, and repeating the operation for three times; finally, putting the rest porous carbonyl iron microspheres into vacuum drying equipment, and carrying out vacuum drying for 40min at 60 ℃ to obtain porous carbonyl iron microspheres;

2、Al₂O₃preparation of porous carbonyl iron microspheres

Uniformly stirring 1 part of porous carbonyl iron microspheres and 30 parts of deionized water in a dispersion machine for 80min, dripping 30 parts of sodium metaaluminate solution with the concentration of 3.0mol/L into the dispersion liquid in a beaker, slowly adjusting the pH value of the solution to 9 by using 0.4mol/L hydrochloric acid (citric acid), continuously stirring for 24h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃The coated porous carbonyl iron microsphere core-shell wave absorber.

Al prepared in the above examples₂O₃Al of coated porous carbonyl iron microsphere core-shell wave absorber₂O₃The thickness of the coating layer has great relation with the stirring speed, the concentration of sodium metaaluminate and the pH value; the higher the stirring speed, the higher the sodium metaaluminate concentration and the higher the pH value, the Al is formed₂O₃The larger the particle, the thicker the coating formed; that is, the thickness of the coating layer in examples 1 to 5 is varied from nanometer to micrometer, and the thickness is gradually increased, and the thickness of the coating layer in example 3 is set to beThe magnetic conductivity of the material is basically kept unchanged when the thickness is 0.5-1 mu m, the dielectric constant is obviously reduced, and the impedance matching and absorption efficiency of the material can be obviously improved.

Comparative example 1

The comparative example is carbonyl iron microsphere with particle size of 2-20 μm.

Comparative example 2

Al (aluminum)₂O₃The preparation method of the carbonyl iron microsphere wave absorbing agent comprises the following two steps:

Al₂O₃preparation of carbonyl iron microspheres

Uniformly stirring 4 parts of carbonyl iron microspheres with the particle size of 2-20 microns and 50 parts of deionized water in a dispersion machine for 40min, dripping 15 parts of sodium metaaluminate solution with the concentration of 1.0mol/L into the beaker dispersion liquid, slowly adjusting the pH value of the solution to 8 by using 0.1mol/L hydrochloric acid (citric acid), continuously stirring for 18h, filtering and washing, collecting solids, and performing vacuum drying at 80 ℃ for 18h to obtain Al₂O₃A coated carbonyl iron microsphere core-shell wave absorber.

Respectively preparing 80% of coaxial samples of the wave absorbing agent prepared in the embodiment and the comparative example and the original carbonyl iron microspheres with the particle size of 2-20 mu m and testing, wherein the main steps are as follows: the method comprises the steps of firstly, mixing powder with paraffin according to the ratio of 8:2, placing the mixture into a high-temperature oven at 65 ℃ for heating for 10min, then, taking out the mixture quickly, mixing and stirring the mixture evenly, preparing a viscous solid, filling the viscous solid into a coaxial circular ring mold (the outer diameter of the mold is 7mm, and the inner diameter of the mold is 3.04mm), preparing samples with the thickness of 1-2 mm respectively, then, measuring a complex dielectric constant and a complex permeability respectively by using a network vector analyzer, and then calculating a reflection loss curve of the test sample along with the frequency when the thickness of the test sample is 2.5mm by matlab simulation according to an electromagnetic field transmission line theory. Measuring the tap densities of the powder and the original carbonyl iron microspheres prepared in the examples and the comparative examples by using a densitometer; the powder prepared in the examples and the comparative examples and the original carbonyl iron microspheres are respectively placed at 450 ℃ for observing the powder condition, then 80% of coaxial samples are prepared and tested, the reflection results are simulated, and the test results are shown in table 1.

TABLE 1 table of performance data of carbonyl iron microspheres prepared in examples and comparative examples

Through the examples, the comparative examples and the original powder test, it is found that: the porous carbonyl iron microspheres can obviously reduce the powder density; and with Al₂O₃Increased thickness of the coating layer, Al₂O₃The dielectric constant and the magnetic conductivity of the carbonyl iron microsphere wave absorbing agent are correspondingly reduced, the magnetic conductivity can be ensured to be unchanged while the dielectric constant is obviously reduced in example 3, and the absorption performance is greatly improved under the condition, and the absorption performance is improved along with Al₂O₃The thickness of the coating layer is increased, and the magnetic conductivity is obviously reduced, so that the absorption performance and the bandwidth are obviously reduced; al (Al)₂O₃When the coating is less, the powder is easy to oxidize and even burn, and along with Al₂O₃The coating layer is thickened, the oxidation resistance of the powder is obviously improved, the wave absorbing performance of the wave absorbing agent powder prepared by the scheme is greatly reduced compared with the density of the original carbonyl iron microspheres, the dielectric constant is reduced, and the magnetic conductivity, the wave peak intensity and the frequency width are obviously improved. After the treatment at 450 ℃, the surface and the absorption performance of the original carbonyl iron microspheres and the powder in the examples and the comparative examples are respectively changed to different degrees, and the Al coated on the surface is effectively verified₂O₃Can obviously improve the oxidation resistance of the surface of the powder, and the Al prepared in the embodiment 3₂O₃The electromagnetic parameters and the absorption performance of the porous carbonyl iron microsphere wave absorbing agent processed at 450 ℃ are not greatly changed.

Al prepared in the examples of the invention₂O₃Porous carbonyl iron microsphere performance, carbonyl iron powder micropore size and Al₂O₃The coating layer has great relation; the concentrations of dilute hydrochloric acid and ferric trichloride in examples 1 to 5 are gradually increased, and if the concentrations are too low, the micropores of the formed carbonyl iron powder are too small, the density is not obviously reduced, and electromagnetism is realizedMultiple reflections of waves between holes are not obvious, and the absorption efficiency is not ideal; the magnetic permeability of the iron powder can be seriously influenced by too large micropores of the carbonyl iron powder with too large concentration. In addition, the thickness of the coating layer in the embodiment 3 is 0.5-1 μm, the coating layer is moderate, and the dielectric constant is obviously reduced; the concentration, pH value and stirring time of the sodium metaaluminate can influence the thickness of the coating layer, and if the thickness of the coating layer is too small and discontinuous, the prepared Al₂O₃The dielectric constant of the porous carbonyl iron microsphere is not obviously reduced, the impedance matching effect is poor, and if the coating layer is too thick, the magnetic conductivity is seriously influenced, and the absorption efficiency and the bandwidth are reduced.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.