WO2019127991A1

WO2019127991A1 - Wave-absorbing agent and preparation method therefor

Info

Publication number: WO2019127991A1
Application number: PCT/CN2018/083696
Authority: WO
Inventors: 刘若鹏; 赵治亚; 林白阁
Original assignee: 洛阳尖端技术研究院; 洛阳尖端装备技术有限公司
Priority date: 2017-12-26
Filing date: 2018-04-19
Publication date: 2019-07-04
Also published as: CN109957376A

Abstract

Provided are a method for preparing a wave-absorbing agent and a wave-absorbing agent obtained thereby. The method comprises: adding butyl titanate to ethanol, followed by addition of acetic acid so as to obtain a mixed liquid of butyl titanate and acetic acid; adding barium acetate to first deionized water, heating same to a temperature T so as to obtain a barium acetate aqueous solution; and adding the barium acetate aqueous solution to the mixed liquid of butyl titanate and acetic acid to form a sol, the pH value of which is adjusted, and adding a pretreated carbonyl iron powder, stirring, centrifuging, drying and calcining same so as to obtain the wave-absorbing agent. The wave-absorbing agent prepared by the method significantly enhances the low frequency absorbing performance, with the wave-absorbing performance in the range 2-5 GHz being better.

Description

Absorbing agent and preparation method thereof

Technical field

The invention relates to an absorbing material, and more particularly to a Fe/BaTiO ₃ core-shell material absorbing agent and a preparation method thereof.

Background technique

With the development of electronic science and technology, electronic information equipment has been widely used in various industries. The effects of electromagnetic waves on humans have also penetrated into every corner. It is irreplaceable in the fields of machinery, electronics and biology. Electromagnetic technology has brought great convenience to people, and it has also caused serious electromagnetic radiation pollution. Electromagnetic radiation not only interferes with electronic instruments and equipment, causing it to malfunction, but also affects human health, interferes with normal physiological functions of the human body, and may even cause diseases. Therefore, absorbing materials for electromagnetic pollution have emerged.

As a typical magnetic loss absorbing material, carbonyl iron powder has the advantages of thin matching thickness, good absorption effect in intermediate frequency band and excellent thermal stability, but also low frequency (less than or equal to 5 GHz) absorption effect, easy to be oxidized and loss mechanism. A single disadvantage.

Summary of the invention

In order to further improve the low-frequency absorbing properties of carbonyl iron powder, the present invention has surface-modified carbonyl iron powder by BaTiO ₃ and prepared a composite absorbing wave of BaTiO ₃ surface-modified carbonyl iron powder by sol-gel method. Agent.

The present invention provides a method of preparing a absorbing agent, the method comprising:

Adding butyl titanate to ethanol to obtain a solution of butyl titanate in ethanol, and then adding acetic acid to obtain a mixture of butyl titanate acetate; adding cerium acetate in the first deionized water and heating to temperature T to obtain an aqueous solution of cerium acetate; And adding the cerium acetate aqueous solution to the butyl titanate acetic acid mixture to form a sol, adjusting the pH, adding the pretreated carbonyl iron powder, stirring, centrifuging, drying, and calcining to obtain the absorbing agent.

In the above method, the pretreated carbonyl iron powder is prepared by the following method:

Polyvinylpyrrolidone and carbonyl iron powder were added to the second deionized water, stirred, and separated to obtain a pretreated carbonyl iron powder.

In the above method, the mass ratio of the second deionized water, the polyvinylpyrrolidone and the carbonyl iron powder is from 450 to 550:5 to 15:3 to 8.

In the above method, the mass ratio of the ethanol, the butyl titanate, and the acetic acid is 4 to 6:3 to 5:6 to 8.

In the above method, the mass ratio of the first deionized water to the cerium acetate is from 5 to 9:2 to 3.

In the above method, the mass ratio of the aqueous solution of cerium acetate, the mixed solution of butyl titanate acetate, and the pretreated carbonyl iron powder is from 10 to 15:6 to 10:0.5 to 25.

In the above method, the pH adjustment is adjusted to a pH of 3 to 5, and the acetic acid is added at a temperature of 50 to 70 ° C, and the temperature T is 60 to 80 °C.

In the above method, the stirring speed is 600 to 800 r/min; and the stirring time is 10 to 30 minutes.

In the above method, the calcination temperature is 800 to 900 ° C, and the calcination time is 1 to 3 h.

The present invention also provides a wave absorbing agent prepared according to the above method.

The invention forms a composite material by introducing BaTiO ₃ into a carbonyl iron powder absorbing agent by surface modification, wherein the surface modification method can effectively improve the physical and chemical properties of the surface of the material, improve the surface activity and stability, and impart new electromagnetic to the particles. The characteristics, thus significantly improving the low-frequency absorbing properties of the absorbing agent, and making the prepared absorbing agent have better absorbing properties in the range of 2 to 5 GHz.

DRAWINGS

Figure 1 is a flow chart for preparing a Fe/BaTiO ₃ core-shell material absorbing agent.

Detailed ways

The following examples are intended to provide a more complete understanding of the invention, and are not intended to limit the invention in any way.

In recent years, in the field of absorbing materials, the effective absorption of low frequencies (less than or equal to 5 GHz) has been the focus and difficulty of research. BaTiO ₃ is a perovskite type ferroelectric with high dielectric constant and excellent piezoelectricity. Under the action of electromagnetic field, it mainly depends on the orientation polarization of the electric dipole and the electromagnetic wave of the interface polarization loss. It is good. Dielectric loss type absorbing material. The invention synthesizes BaTiO ₃ by the sol-gel method and coats it onto the surface of the carbonyl iron powder, thereby effectively improving the electromagnetic characteristics and the absorbing properties of the composite absorbing agent.

The invention provides a method for preparing a Fe/BaTiO ₃ core-shell material absorbing agent, the method comprising the following steps:

In a container (such as a beaker), 450-550 parts of deionized water, 5-15 parts of polyvinylpyrrolidone and 3-8 parts of carbonyl iron powder are sequentially added, and the mixture is electrically stirred at 600-800 r/min for 7-9 hours, 300~ 600 W of power magnetic separation to obtain pretreated carbonyl iron powder;

Add 3 to 5 parts of butyl titanate to 4-6 parts of ethanol, magnetically stir at 600-800r/min until the liquid is evenly mixed, heat to 50-70 ° C, reach the optimal hydrolysis temperature, and then drop into the solution. Add 6-8 parts of glacial acetic acid, stir at 600-800r/min for 30-60min to obtain a mixture of butyl titanate acetate;

Adding 2 to 3 parts of cerium acetate in 5 to 9 parts of deionized water, heating to 60 to 80 ° C, and fully dissolving cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 10 to 15 parts of an aqueous solution of cerium acetate is added dropwise to a mixture of 6 to 10 parts of butyl titanate acetic acid at a constant temperature of 30 to 50 ° C until the addition is complete, and magnetic stirring is performed at a rotational speed of 600 to 800 r/min. After 1~2h, the sol is formed, the ammonia is added dropwise to adjust the pH to 3~5, and 0.5~25 parts of the pretreated carbonyl iron powder is added. In the acidic environment with pH of 3-5, the pretreated carbonyl iron powder can be easily Adsorbing the sol; then stirring at a speed of 600-800 r/min for 10-30 min, centrifuging at 800-1000 r/min, washing the carbonyl iron powder adsorbing the sol with ethanol, and placing the carbonyl iron powder adsorbing the sol on the surface at 50 ～90°C drying oven for 2～5h, finally placed in a vacuum tube furnace and calcined at 800～900°C for 1-3h. After cooling, Fe/BaTiO ₃ core shell material absorbing agent is obtained.

In the above method, the carbonyl iron powder is effectively compounded with BaTiO ₃ by calcining at a temperature of 800 to 900 ° C for 1 to 3 hours.

In the above method, the effect of the ratio of BaTiO ₃ and carbonyl iron powder on the absorbing properties of the core-shell material:

The Fe/BaTiO ₃ core-shell absorbing material can be efficiently prepared by adding pretreated carbonyl iron powder to the sol system. As a typical magnetic loss absorbing material, carbonyl iron powder has the advantages of thin matching thickness, good absorption effect in the intermediate frequency band and excellent thermal stability. BaTiO ₃ is a perovskite type ferroelectric with high dielectric constant and excellent piezoelectricity. Under the action of electromagnetic field, it mainly depends on the orientation polarization of the electric dipole and the electromagnetic wave of the interface polarization loss. It is good. The dielectric loss type absorbing material, therefore, the present invention can obtain a material having good low frequency absorbing properties by adjusting the ratio of the two components. On the one hand, the Fe/BaTiO ₃ core-shell material after the composite dielectric loss material BaTiO ₃ can enhance the dielectric loss of the carbonyl iron powder, so that the imaginary part of the dielectric constant of the carbonyl iron powder is significantly increased. On the other hand, the magnetic permeability of the composite Fe/BaTiO ₃ core-shell material decreases to lower the magnetic loss, thus improving the impedance matching performance of the composite. The better the impedance matching of the material, that is, the closer to the impedance value of the free space, the electromagnetic wave can enter the inside of the material more effectively without being reflected, thereby improving the absorbing properties of the material, when the ratio of BaTiO ₃ or carbonyl iron powder Too high or too low will affect the impedance matching of the prepared composite material, which in turn affects the absorbing properties of the material.

In the above method, the influence of the stirring speed and time of the carbonyl iron powder added into the sol on the electromagnetic properties of the core-shell material powder can obtain a material with excellent electromagnetic properties by adjusting the mixing time of the two components at a certain stirring rate. . The sufficient stirring time can form a large number of interaction interfaces between the flaky carbonyl iron powder and BaTiO ₃ , enhance the interfacial polarization of different dielectric particles, and promote the different degrees of improvement of the real and imaginary parts of the dielectric constant. Therefore, different mixing times can make the coating amount of the core-shell structure different. When the stirring time is too short, the coating amount is small, so that the BaTiO ₃ particles are small, and the surface is easy to adsorb a large amount of paraffin, thereby causing iron powder between Leakage phenomenon occurs, and the dielectric constant increases remarkably; when the stirring time increases, the coating amount increases, and the agglomeration of BaTiO ₃ particles reduces the adsorption with paraffin, and the dielectric constant is low; When it is long, it will affect the mutual agglomeration of BaTiO ₃ particles, so that the surface of BaTiO ₃ particles can easily adsorb a large amount of paraffin, which causes leakage between the iron powders. Therefore, the stirring time is at 600-800 r/min. Should be controlled at 10 to 30 minutes.

Example 1

500 parts of deionized water, 10 parts of polyvinylpyrrolidone and 5 parts of carbonyl iron powder were sequentially added to the beaker, and the pretreated carbonyl iron powder was obtained by electric stirring and magnetic separation;

4 parts of butyl titanate was added to 5 parts of ethanol, magnetically stirred until the liquid was uniformly mixed, heated to 60 ° C, and then 7 parts of glacial acetic acid was added dropwise to the solution, and stirred to obtain a mixture of butyl titanate acetate;

Adding 2 parts of cerium acetate to 7 parts of deionized water, heating to 70 ° C, and fully dissolving cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 12 parts of an aqueous solution of cerium acetate was added dropwise to a mixture of 8 parts of butyl titanate acetic acid under a constant temperature of 40 ° C until the addition was complete, magnetic stirring was performed for 1 hour to form a sol, and ammonia was added dropwise to adjust the pH to 4, and then added. 25 pretreated carbonyl iron powder, stirred for 10 min, centrifuged and washed with ethanol to wash the carbonyl iron powder on the surface of the sol, and then the carbonyl iron powder adsorbing the sol on the surface was placed in a drying oven at 70 ° C for 4 h, and finally placed in a vacuum tube furnace. It was calcined at a temperature of 850 ° C for 2 h, and after cooling, a Fe/BaTiO ₃ core-shell material absorbing agent was obtained.

Example 2

520 parts of deionized water, 12 parts of polyvinylpyrrolidone and 4 parts of carbonyl iron powder were sequentially added to the beaker, and the pretreated carbonyl iron powder was obtained by electric stirring and magnetic separation;

4 parts of butyl titanate was added to 5 parts of ethanol, magnetically stirred until the liquid was uniformly mixed, heated to 55 ° C, and then 6 parts of glacial acetic acid was added dropwise to the solution, and stirred to obtain a mixture of butyl titanate acetic acid;

Adding 3 parts of cerium acetate to 5 to 9 parts of deionized water, heating to 70 ° C, and fully dissolving cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 12 parts of an aqueous solution of cerium acetate was added dropwise to 8 parts of a mixture of butyl titanate acetate at a constant temperature of 45 ° C until the addition was complete, magnetic stirring was carried out for 1.5 hours to form a sol, and aqueous ammonia was added dropwise to adjust the pH to 3. Add 15 parts of pretreated carbonyl iron powder, stir for 20min, centrifuge and wash the carbonyl iron powder adsorbing sol on the surface with ethanol, then place the carbonyl iron powder adsorbing the sol on the surface in a drying oven at 70 °C for 2 to 5 hours, and finally put it into the vacuum tube. The furnace was calcined at a temperature of 820 ° C for 2 h, and cooled to obtain a Fe/BaTiO ₃ core-shell material absorbing agent.

Example 3

520 parts of deionized water, 8 parts of polyvinylpyrrolidone and 4 parts of carbonyl iron powder were sequentially added to the beaker, and the pretreated carbonyl iron powder was obtained by electric stirring and magnetic separation;

5 parts of butyl titanate was added to 5 parts of ethanol, magnetically stirred until the liquid was uniformly mixed, heated to 60 ° C, and then 7 parts of glacial acetic acid was added dropwise to the solution, and stirred to obtain a mixture of butyl titanate acetate;

Add 3 parts of cerium acetate to 8 parts of deionized water, heat to 75 ° C, and fully dissolve the cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 11 parts of an aqueous solution of cerium acetate was added dropwise to 8 parts of a mixture of butyl titanate acetate at a constant temperature of 45 ° C until the addition was complete, magnetic stirring for 2 hours to form a sol, and ammonia was added dropwise to adjust the pH to 5, and added. 10 pretreated carbonyl iron powder, stirred for 30min, centrifuged and washed with ethanol to wash the carbonyl iron powder on the surface, then the carbonyl iron powder adsorbing the sol on the surface was placed in a drying oven at 70 ° C for 4 h, and finally placed in a vacuum tube furnace. It was calcined at a temperature of 810 ° C for 2 h, and after cooling, a Fe/BaTiO ₃ core-shell material absorbing agent was obtained.

Example 4

450 parts of deionized water, 5 parts of polyvinylpyrrolidone and 3 parts of carbonyl iron powder were sequentially added to the beaker, and the pretreated carbonyl iron powder was obtained by electric stirring and magnetic separation;

3 parts of butyl titanate was added to 4 parts of ethanol, magnetically stirred until the liquid was uniformly mixed, heated to 50 ° C, and then 6 parts of glacial acetic acid was added dropwise to the solution, and stirred to obtain a mixture of butyl titanate acetic acid;

Adding 2 parts of cerium acetate to 5 parts of deionized water, heating to 60 ° C, and fully dissolving cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 10 parts of an aqueous solution of cerium acetate was added dropwise to 6 parts of a mixture of butyl titanate acetate at a constant temperature of 30 ° C until the addition was complete, magnetic stirring for 1 h, a sol was formed, and ammonia was added dropwise to adjust the pH to 4, and added. 0.5 parts of pretreated carbonyl iron powder, stirred for 10 min, centrifuged and washed with carbonyl iron powder on the surface adsorption sol, and then placed the carbonyl iron powder adsorbed on the surface in a drying oven at 50 ° C for 2 h, and finally placed in a vacuum tube furnace. After calcination at 800 ° C for 1 h, the Fe/BaTiO ₃ core-shell material absorbing agent was obtained after cooling.

Example 5

550 parts of deionized water, 15 parts of polyvinylpyrrolidone and 8 parts of carbonyl iron powder were sequentially added to the beaker, and the pretreated carbonyl iron powder was obtained by electric stirring and magnetic separation;

5 parts of butyl titanate was added to 6 parts of ethanol, magnetically stirred until the liquid was uniformly mixed, heated to 70 ° C, and then 8 parts of glacial acetic acid was added dropwise to the solution, and stirred to obtain a mixture of butyl titanate acetate;

Adding 3 parts of cerium acetate to 9 parts of deionized water, heating to 80 ° C, and fully dissolving cerium acetate to obtain an aqueous solution of cerium acetate;

Thereafter, 15 parts of an aqueous solution of cerium acetate was added dropwise to 10 parts of a mixture of butyl titanate acetate at a constant temperature of 50 ° C until the addition was complete, magnetic stirring was carried out for 3 hours to form a sol, and ammonia was added dropwise to adjust the pH to 4, and added. 5 pretreated carbonyl iron powder, stirred for 30min, centrifuged and washed with ethanol to wash the carbonyl iron powder on the surface, then the carbonyl iron powder adsorbing the sol on the surface was placed in a 90 ° C drying oven for 5 h, and finally placed in a vacuum tube furnace. After calcination at 900 ° C for 3 h, the Fe/BaTiO ₃ core-shell material absorbing agent was prepared after cooling.

Example 6

Thereafter, 10 parts of an aqueous solution of cerium acetate was added dropwise to 6 parts of a mixture of butyl titanate acetate at a constant temperature of 30 ° C until the addition was complete, magnetic stirring for 1 h, a sol was formed, and ammonia was added dropwise to adjust the pH to 4, and added. 1 part of pretreated carbonyl iron powder, stirred for 10min, centrifuged and washed with carbon to wash the surface of the sol-coated carbonyl iron powder, and then the surface of the sol-coated carbonyl iron powder was placed in a 90 ° C drying oven for 2 h, and finally placed in a vacuum tube furnace After calcination at 800 ° C for 3 h, the Fe/BaTiO ₃ core-shell material absorbing agent was prepared after cooling.

The above parts are all parts by mass.

The absorbing properties of the Fe/BaTiO ₃ core-shell absorbing agent prepared in Examples 1 to 6 in the frequency range of 2 to 6 GHz were tested by methods commonly used in the art.

The test results are shown in Table 1 below:

实施例Example	峰值所在频率Peak frequency	最大反射损耗Maximum reflection loss	≤-10dB的频宽≤-10dB bandwidth
11	4GHz4GHz	-14.68dB-14.68dB	2.75GHz2.75GHz
22	3.5GHz3.5GHz	-13.26dB-13.26dB	2.31GHz2.31GHz
33	3.1GHz3.1GHz	-12.68dB-12.68dB	1.92GHz1.92GHz
44	3.7GHz3.7GHz	-13.65dB-13.65dB	2.02GHz2.02GHz
55	3.2GHz3.2GHz	-14.21dB-14.21dB	1.96GHz1.96GHz
66	3.6GHz3.6GHz	-12.95dB-12.95dB	2.26GHz2.26GHz

It can be seen from the above Table 1 that the Fe/BaTiO ₃ core-shell material absorbing agent prepared by the method of the invention effectively increases the absorbing property of the carbonyl iron powder, so that the maximum reflection loss at low frequency (less than or equal to 5 GHz) is as low as - 14.68dB, because BaTiO ₃ is a perovskite type ferroelectric with high dielectric constant and excellent piezoelectricity. Under the action of electromagnetic field, it mainly depends on the orientation polarization and interfacial polarization of electric dipole. The lossy electromagnetic wave is a good dielectric loss type absorbing material. The sol-gel method combines the magnetic loss type material carbonyl iron powder with the dielectric loss material BaTiO ₃ to effectively improve the impedance matching performance of the material and improve the low frequency band. Absorbing performance.

In addition, BaTiO ₃ is a dielectric material, which can significantly increase the dielectric constant of the composite when combined with carbonyl iron powder.

In summary, the absorbing agent prepared by the invention can be applied to the technical fields of mobile phone, electronic equipment, high-frequency equipment, microwave active device, clutter suppression and anti-electromagnetic interference of radar and microwave communication systems; Stealth, ship stealth, flight missile stealth, and tank stealth.

Those skilled in the art will appreciate that the above-described embodiments are merely exemplary embodiments, and various changes, substitutions and changes may be made without departing from the spirit and scope of the invention.

Claims

A method of preparing a absorbing agent, the method comprising:

Adding butyl titanate to ethanol to obtain a solution of butyl titanate in ethanol, and then adding acetic acid to obtain a mixture of butyl titanate acetate;

Adding cerium acetate to the first deionized water and heating to a temperature T to obtain an aqueous solution of cerium acetate;

The aqueous solution of cerium acetate is added to the mixed solution of butyl titanate acetic acid to form a sol, and the pH is adjusted, and the pretreated carbonyl iron powder is added, stirred, centrifuged, dried, and calcined to obtain the absorbing agent.
The method of claim 1 wherein said pretreated carbonyl iron powder is prepared by the following method:

Polyvinylpyrrolidone and carbonyl iron powder were added to the second deionized water, stirred, and separated to obtain a pretreated carbonyl iron powder.
The method according to claim 2, wherein the mass ratio of the second deionized water, the polyvinylpyrrolidone and the carbonyl iron powder is from 450 to 550:5 to 15:3 to 8.
The method according to claim 1, wherein the mass ratio of the ethanol, the butyl titanate and the acetic acid is from 4 to 6:3 to 5:6 to 8.
The method according to claim 1, wherein the mass ratio of the first deionized water to the cerium acetate is from 5 to 9:2 to 3.
The method according to claim 1, wherein the mass ratio of the aqueous solution of cerium acetate, the mixed solution of butyl titanate acetate and the pretreated carbonyl iron powder is from 10 to 15:6 to 10:0.5. ~25.
The method according to claim 1, wherein said adjusting the pH adjusts the pH to 3 to 5, and said acetic acid is added at a temperature of 50 to 70 ° C, said temperature T being 60 to 80 °C.
The method according to claim 1, wherein the stirring speed is 600 to 800 r/min; and the stirring time is 10 to 30 minutes.
The method according to claim 1, wherein the calcination temperature is 800 to 900 ° C, and the calcination time is 1 to 3 h.
A absorbing agent prepared by the method of any one of claims 1-9.