CN114956192A - Lanthanum-cobalt co-doped barium ferrite dual-waveband wave-absorbing powder material and preparation method thereof - Google Patents

Abstract

The invention discloses a lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material and a preparation method thereof. The wave-absorbing powder material is Ba _1-x La _x Co _x Fe _12-x O ₁₉ , Wherein x=0.1～0.4. The preparation method is as follows, the rare earth element lanthanum and the metal element cobalt are co-doped into the barium ferrite to replace Ba ²⁺ and Fe ³⁺ in the barium ferrite respectively, so as to realize the simultaneous substitution of different element sites, The lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material is obtained. The lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material of the invention is low in price, simple in production process, and can be used for wave-absorbing coatings, and can be used in decimeter wavebands (300MHz-3GHz) and centimeter wavebands (3GHz-30GHz) And millimeter wave band (30GHz ~ 300GHz) can have certain applications.

Description

Lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material and preparation method thereof

technical field

The invention relates to the technical field of wave-absorbing materials, in particular to a lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material and a preparation method thereof.

Background technique

With the continuous advancement of science and technology, electromagnetic waves are more and more widely used in human life, such as radio waves for communications, microwaves for microwave ovens and satellite communications, and so on. However, electromagnetic waves inevitably cause problems such as electromagnetic radiation and electromagnetic wave interference, which have certain harm to the human body. At the same time, the military stealth aircraft technology also puts forward higher requirements for absorbing materials. The research of new multifunctional wave absorbing materials with wide absorption frequency band and strong absorption capacity is imminent.

As an important resource, rare earth is a kind of element with similar electronic structure and chemical properties. Due to its unique electronic layer structure, the outermost 4f electron orbital is not filled, so it exhibits distinctive optical, electrical, magnetic and The chemical properties make rare earth elements have a wide range of applications in various fields. In recent years, many researchers have also applied rare earths to absorbing materials, using the unique properties of rare earth elements to obtain relatively ideal absorbing effects.

Due to its high uniaxial magnetocrystalline anisotropy, high coercivity, low price and high stability, M-type ferrite has become a widely used permanent magnet material. It is found that the magnetic properties of ferrite can be improved to a certain extent by simply improving the preparation process conditions of ferrite.

Ion doping in barium ferrite is an effective method to tune the properties, usually using non/weak magnetic ions or ion combinations such as Al ³⁺ , Cr ³⁺ , Co ²⁺ -Ti ⁴⁺ , Co ²⁺ -Ru ⁴⁺ and so on replace Fe ³⁺ ions in doped barium ferrite to improve the dielectric constant of barium ferrite, or use rare earth ions to replace Ba ²⁺ ions in barium ferrite, by controlling doping The content of impurity ions can effectively adjust the magnetic properties of barium ferrite. However, there are few reports on the absorbing performance of lanthanum-cobalt co-doped barium ferrite in the dual frequency bands of 1-18GHz and 26.5-40GHz. The preparation of materials with dual-band wave absorption properties requires that the resonant frequency of the material itself is close to a certain frequency band. Secondly, the interaction between the elements of the material should cause multiple resonance peaks to be generated under the joint action of multiple resonances, thereby broadening the absorption frequency band.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material and a preparation method thereof, which can improve the electromagnetic constant of the barium ferrite, and obtain an efficient and effective dual-band wave absorbing powder material. Absorber.

In one aspect of the present invention, the present invention provides a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material. According to an embodiment of the present invention, the wave absorbing powder material is Ba _1-x La _x Co _x Fe _12-x O ₁₉ , where x=0.1-0.4.

In another aspect of the present invention, the present invention provides a preparation method of a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material. According to the embodiment of the present invention, the rare earth element lanthanum and the metal element cobalt are co-doped into the barium ferrite, respectively replacing Ba ²⁺ and Fe ³⁺ in the barium ferrite, thereby realizing the simultaneous substitution of different element sites , to obtain lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material.

In addition, according to the preparation method of a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material according to the above-mentioned embodiment of the present invention, it can also have the following additional technical features:

In some embodiments of the present invention, the method includes the steps of:

(1) mixing barium nitrate, lanthanum nitrate, cobalt nitrate, iron nitrate and citric acid monohydrate, adding deionized water and stirring for 30-60min to dissolve to obtain a sol;

(2) adding an appropriate amount of ammonia water to the sol obtained in step (1) to adjust the pH to 7, and then placing the sol in an oil bath at 120° C. for continuous stirring and heating for 3 to 5 hours to obtain a tan wet gel;

(3) drying the wet gel obtained in step (2) to form a dry gel;

(4) grinding the xerogel obtained in step (3) to obtain a tan precursor powder;

(5) The precursor powder obtained in step (4) is calcined, cooled to room temperature, and then ground to finally obtain a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material.

In some embodiments of the present invention, in the step (1), the molar ratio of barium nitrate, lanthanum nitrate, cobalt nitrate, iron nitrate and citric acid monohydrate is 0.6-0.9:0.1-0.4:0.1-0.4:11.6 ~11.9:13.

In some embodiments of the present invention, in the step (3), the drying temperature is 150° C. and the drying time is 12 h.

In some embodiments of the present invention, in the step (5), the calcination process is as follows: firstly the temperature is raised to 250°C for 1.5h, then the temperature is raised to 450°C for 2h, and finally the temperature is raised to 1100-1400°C for 3h.

Compared with the prior art, the beneficial effects of the present invention are:

1) The present invention uses the sol-gel method to co-dope the rare earth element lanthanum and the metal element cobalt into the barium ferrite, the rare earth ion La ³⁺ replaces the Ba ²⁺ in the barium ferrite, and Co ²⁺ replaces the Ba 2+ in the barium ferrite. Fe ³⁺ in barium ferrite realizes the simultaneous substitution of different element sites of barium ferrite. The introduction of rare earth elements can improve the activity of the grain boundary magnetic domain, increase the domain wall resonance and natural resonance, and the natural resonance is the main mechanism of the magnetic loss of barium ferrite as a wave absorbing material at 26.5-40 GHz. Substituting Co ²⁺ for Fe ³⁺ reduces the magnetocrystalline anisotropy, thereby improving the dielectric constant of barium ferrite. In addition, the interaction between the rare earth element lanthanum and the transition group metal element cobalt makes the material more conducive to broadening the effective absorption frequency band under the action of natural resonance and exchange resonance, so that the material has both 1-18GHz and 26.5-40GHz frequency bands. It has a certain loss ability to electromagnetic waves, so the material can be applied in the three frequency bands of decimeter wave (300MHz~3GHz), centimeter wave (3GHz~30GHz) and millimeter wave (30GHz~300GHz) at the same time.

2) Adjusting the amount of lanthanum ions and cobalt ions doped into the barium ferrite can reduce the thickness of the material and change the absorbing frequency band of the barium ferrite, so as to obtain a lighter and more efficient absorbing material. When x≤0.4, the higher the doping content, the lower the matching thickness of the material. When the doping amount x = 0.1, 0.2, the increase of the doping content brings about a decrease in the matching thickness, and at the same time the maximum reflection loss value also decreases, that is, the absorbing performance is improved; when x = 0.3, 0.4, with the doping As the content increases, the matching thickness decreases, and the maximum reflection loss value increases to about -19dB, which still has good absorbing performance (the reflection loss <-10dB can attenuate 90% of the electromagnetic waves, and the reflection loss <-20dB can attenuate the loss 99% % of electromagnetic waves). When X=0.1, 0.2, 0.3, the absorbing frequency band of maximum reflection loss decreases from 40GHz to around 27GHz; when x=0.4, the absorbing frequency band of maximum reflection loss increases to around 38GHz.

3) The wave absorbing material of the present invention has the characteristics of strong reflection loss. Samples doped with a certain amount have good reflection loss in both frequency bands. When the doping amount x is 0.2, the optimal reflection loss value at a specific frequency can reach -52.69dB.

4) The preparation method of the present invention is simple and easy to operate, safe and pollution-free, and low in cost, which provides a possibility for industrial production, and provides a new way for the research of wave absorbing materials and magnetic materials.

Description of drawings

Fig. 1 is a graph showing the change of the absorbing performance of the absorbing material Ba _0.8 La _0.2 Co _0.2 Fe _11.8 O ₁₉ obtained in Example 1 of the present invention with frequency in the frequency range of 1-18 GHz;

FIG. 2 is a graph showing the variation relationship between the wave absorbing properties of the wave absorbing material Ba _0.8 La _0.2 Co _0.2 Fe _11.8 O ₁₉ obtained in Example 1 of the present invention in the frequency range of 26.5-40 GHz with frequency;

FIG. 3 is a graph showing the variation relationship between the wave absorbing properties of the wave absorbing material Ba _0.6 La _0.4 Co _0.4 Fe _11.6 O ₁₉ obtained in Example 2 of the present invention in the frequency range of 1-18 GHz with frequency;

FIG. 4 is a graph showing the change in the absorbing performance of the absorbing material Ba _0.6 La _0.4 Co _0.4 Fe _11.6 O ₁₉ obtained in Example 2 of the present invention with frequency in the frequency range of 26.5-40 GHz.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

A method for preparing a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material, comprising the following steps:

(1) mixing barium nitrate, lanthanum nitrate, cobalt nitrate, ferric nitrate and citric acid monohydrate in a molar ratio of 0.8:0.2:0.2:11.8:13, adding deionized water and stirring for 40min to dissolve to obtain a sol;

(2) adding an appropriate amount of ammonia water to the sol obtained in step (1) to adjust the pH to 7, and then placing the sol in an oil bath at 120°C for 4 hours with continuous stirring and heating to obtain a tan wet gel;

(3) putting the wet gel obtained in step (2) into a 150°C blast drying oven and drying for 12h to form a dry gel;

(4) the xerogel obtained in step (3) is ground in an agate mortar to obtain tan precursor powder;

(5) The precursor powder obtained in step (4) is placed in a muffle furnace, first heated to 250 °C for 1.5 hours, then heated to 450 °C for 2 hours, and finally heated to 1400 °C for 3 hours, and cooled to room temperature with the furnace , and then put it in a mortar and grind for 10 minutes, and finally obtain the lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material Ba _0.8 La _0.2 Co _0.2 Fe _11.8 O ₁₉ .

The wave-absorbing performance of the lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material prepared in this example was tested by a vector network analyzer. During the test, the absorbing material powder of the present invention is mixed with solid paraffin in a mass ratio of 8:2 to prepare a block paraffin sample for testing.

FIG. 1 and FIG. 2 are the curves of the change of the absorbing performance of the absorbing material Ba _0.8 La _0.2 Co _0.2 Fe _11.8 O ₁₉ obtained in Example 1 with frequency in 1-18 GHz and 26.5-40 GHz, respectively. Figure 1 is the data obtained when the matching thickness is 5.4mm. It can be seen from the figure that there is an absorption peak at the frequency of 5.04GHz and 16.26GHz, forming a double resonance loss mechanism. The effective absorption bandwidth in this band is It is 4.38GHz (that is, the frequency range of RL<-10dB), and the reflection loss is the strongest at 16.26GHz, reaching -18.36dB. Figure 2 is the data obtained when the matching thickness is 3.2mm. It can be seen from the figure that the reflection loss is the strongest at 27.72GHz, reaching -52.69dB, and the effective bandwidth in this band is 3.17GHz.

Example 2

A method for preparing a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material, comprising the following steps:

(1) mixing barium nitrate, lanthanum nitrate, cobalt nitrate, ferric nitrate and citric acid monohydrate in a molar ratio of 0.6:0.4:0.4:11.6:13, adding deionized water and stirring for 40min to dissolve to obtain a sol;

(2) adding an appropriate amount of ammonia water to the sol obtained in step (1) to adjust the pH to 7, and then placing the sol in an oil bath of 120 degrees for continuous stirring and heating for 4h to obtain a tan wet gel;

(3) put the wet gel obtained in step (2) into a 150 degree blast drying oven and dry for 12h to form a dry gel;

(4) the xerogel obtained in step (3) is ground in an agate mortar to obtain tan precursor powder;

(5) The precursor powder obtained in step (4) is placed in a muffle furnace, first heated to 250 °C for 1.5 hours, then heated to 450 °C for 2 hours, and finally heated to 1400 °C for 3 hours, and cooled to room temperature with the furnace , and then put it into a mortar for grinding for 10 minutes, and finally obtain the lanthanum-cobalt co-doped barium ferrite wave absorbing powder material Ba _0.6 La _0.4 Co _0.4 Fe _11.6 O ₁₉ .

The wave-absorbing properties of the lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material prepared in this example were tested by a vector network analyzer. During the test, the absorbing material powder of the present invention is mixed with solid paraffin in a mass ratio of 8:2 to prepare a block paraffin sample for testing.

FIG. 3 and FIG. 4 are the curves of the absorbing properties of the absorbing material Ba _0.6 La _0.4 Co _0.4 Fe _11.6 O ₁₉ obtained in Example 1 as a function of frequency in 1-18 GHz and 26.5-40 GHz, respectively. Figure 3 is the data obtained when the matching thickness is 5.2mm. It can be seen from the figure that there is an absorption peak at the frequency of 5.25GHz and 16.47GHz, forming a double resonance loss mechanism. The effective absorption bandwidth in this band is It is 3.44GHz, and the reflection loss is the strongest at 16.47GHz, reaching -23.38dB. Figure 4 is the data obtained when the matching thickness is 2.4mm. It can be seen from the figure that the reflection loss is the strongest at 37.27GHz, reaching -19.55dB, and the effective bandwidth in this band is 5.84GHz.

The above embodiments are all typical embodiments of the present invention, and do not limit the present invention. For example, the stirring time, oil bath temperature, drying temperature, etc. can be further adjusted. Therefore, according to the general idea of the present invention, any adjustments and modifications to the process parameters described by those skilled in the art shall belong to the present invention as long as they do not deviate from the concept of the invention or go beyond the scope defined by the claims. protected range.

The above contents are only examples and descriptions of the structure of the present invention. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the structure of the present invention. Or beyond the scope defined by the claims, all belong to the protection scope of the present invention.

Claims (6)

1. a lanthanum-cobalt co-doped barium ferrite dual-band wave-absorbing powder material is characterized in that: the wave-absorbing powder material is Ba _1-x La _x Co _x Fe _12-x O ₁₉ , wherein x = 0.1 to 0.4. 2. a preparation method of lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material according to claim 1, is characterized in that: rare earth element lanthanum and metal element cobalt are co-doped into barium ferrite body, respectively replacing the barium ferrite in

and

The simultaneous substitution of different element sites is realized, and the lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material is obtained. 3. The preparation method of a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material according to claim 2, wherein the method comprises the following steps: (1) mixing barium nitrate, lanthanum nitrate, cobalt nitrate, iron nitrate and citric acid monohydrate, adding deionized water and stirring for 30-60min to dissolve to obtain a sol; (2) adding an appropriate amount of ammonia water to the sol obtained in step (1) to adjust the pH to 7, and then placing the sol in an oil bath at 120° C. for continuous stirring and heating for 3 to 5 hours to obtain a tan wet gel; (3) drying the wet gel obtained in step (2) to form a dry gel; (4) grinding the xerogel obtained in step (3) to obtain a tan precursor powder; (5) The precursor powder obtained in step (4) is calcined, cooled to room temperature, and then ground to finally obtain a lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material. 4. A kind of lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material and preparation method thereof according to claim 3, characterized in that: in the step (1), barium nitrate, lanthanum nitrate, The molar ratio of cobalt nitrate, iron nitrate and citric acid monohydrate is 0.6-0.9:0.1-0.4:0.1-0.4:11.6-11.9:13. 5 . The lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material according to claim 3 and a preparation method thereof, characterized in that: in the step (3), the drying temperature is 150° C., Drying time is 12h. 6. a kind of lanthanum-cobalt co-doped barium ferrite dual-band wave absorbing powder material and preparation method thereof according to claim 3, it is characterized in that: in the described step (5), the calcination process is as follows, the temperature is raised first Heat to 250°C for 1.5h, then heat to 450°C for 2h, and finally heat up to 1100-1400°C for 3h.

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