Preparation method of carbonyl iron composite material with low-frequency efficient wave-absorbing characteristic

Abstract

The invention discloses a preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave-absorbing characteristics. The preparation method comprises the following steps: step 1, putting a certain mass of spherical carbonyl iron powder into a vacuum tube furnace, and carrying out pre-oxidation reaction at 200 DEG C for a period of time in an air atmosphere; and 2, placing the sample prepared in the step 1 at the tail gas end of a vacuum tube furnace, uniformly mixing sodium hypophosphite and selenium powder according to a certain mass ratio, placing the mixture at the gas inlet end of the vacuum tube furnace, and reacting for a period of time at the reaction temperature of 400 DEG C in an Ar atmosphere to obtain a final product, namely the carbonyl iron / iron selenide / iron phosphide composite material. The carbonyl iron composite material with the phosphorus / selenium heterogeneous interface prepared by the invention has the characteristic of efficient low-frequency wave-absorbing performance, is beneficial to breaking through the Snoek limit of a carbonyl iron wave-absorbing material, and has extremely high engineering application value.

Description

Technical Field

[0001] The present invention belongs to the field of ferromagnetic wave-absorbing materials, and particularly relates to a preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave-absorbing characteristics. Background Art

[0002] With the booming development of modern communication technologies carried by gigahertz electromagnetic waves (EMWs), in today's intelligent 5G and 6G eras, the electromagnetic radiation and interference suffered by biological organisms and sensitive electronic devices are increasing. Research and development of advanced EMW absorbing materials with wide bandwidth, strong absorption, light weight, and thin thickness are necessary conditions for alleviating electromagnetic pollution. However, the complexity and severity of the electromagnetic environment in practical applications pose more challenges to wave-absorbing materials. Especially for the S-band (2 - 4 GHz) of remote airborne warning radars and the C-band (4 - 8 GHz) widely used in 5G communications and lower frequencies, the development of high-performance low-frequency wave-absorbing materials suitable for the S and C bands is particularly crucial. Carbonyl iron wave-absorbing materials (CI) have prominent advantages in regulating low-frequency wave-absorbing performance due to their high saturation magnetization intensity, good dispersion characteristics, low coercivity, and high low-frequency magnetic permeability.

[0003] Currently, for the low-frequency wave-absorbing regulation technology of carbonyl iron wave-absorbing materials, the modification mainly focuses on the following two aspects. On the one hand, through ball milling, spherical carbonyl iron is processed into flakes to enhance its shape anisotropy and improve its magnetic permeability in the low-frequency band, such as the patent application with the patent publication number CN114684863A. However, although this method is simple and direct, it often causes the activity and aspect ratio of carbonyl iron to increase after ball milling, which in turn leads to problems such as spontaneous combustion, agglomeration, and impedance mismatch, and has high requirements for the material synthesis process. On the other hand, other dielectric materials are often introduced to prepare various composite materials to regulate their impedance matching characteristics with free space and increase the dielectric loss ability, such as the patent application with the patent publication number CN117750751A. However, due to the use of a large amount of dielectric materials, the effective volume fraction of carbonyl iron wave-absorbing materials will be significantly reduced, greatly weakening its magnetic loss ability, and the attenuation of low-frequency band electromagnetic waves often depends more on the magnetic loss ability of ferromagnetic wave-absorbing materials. Summary of the Invention

[0004] Aiming at the above existing problems or deficiencies, in order to solve the negative impact of the existing technical solutions on the low-frequency wave-absorbing performance regulation of carbonyl iron wave-absorbing materials, the present invention proposes a preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave-absorbing characteristics.

[0005] Carbonyl iron composite material with low-frequency high-efficiency wave absorption characteristics and its preparation method. First, the spherical carbonyl iron is pre-oxidized to synthesize a layer of iron-containing oxide on its surface. Then, the phosphorus / selenium heterointerface is in-situ constructed by means of gas-phase induction to optimize the impedance matching characteristics of the composite material and maintain a high electromagnetic wave attenuation loss ability, and finally the purpose of optimizing the low-frequency wave absorption performance of the carbonyl iron wave absorption material in the S and C bands is achieved.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A preparation method of a carbonyl iron composite material with low-frequency high-efficiency wave absorption characteristics, comprising the following steps: Step 1: Place a certain mass of spherical carbonyl iron powder in a vacuum tube furnace, and carry out a pre-oxidation reaction at 200 °C for a period of time in an air atmosphere; Step 2: Place the sample prepared in Step 1 at the tail gas end of the vacuum tube furnace, mix a certain mass ratio of sodium hypophosphite and selenium powder evenly and place it at the inlet end of the vacuum tube furnace, and react at a certain reaction temperature for a period of time in an Ar atmosphere to obtain the final product as a carbonyl iron / iron selenide / iron phosphide composite material.

[0007] Specifically, in Step 2, the mass of the pre-oxidized carbonyl iron sample is fixed, and the mass ratio of sodium hypophosphite to selenium powder is 1.0.

[0008] As a preference, in Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to the same mass of sodium hypophosphite.

[0009] As another preference, in Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to the same mass of selenium powder.

[0010] As a preference, the reaction temperature in Step 2 is 350 °C.

[0011] As another preference, the reaction temperature in Step 2 is 400 °C.

[0012] As another preference, the reaction temperature described in Step 2 is adjusted to 450 °C.

[0013] The application of the carbonyl iron composite material is used to prepare a wave absorption material. This is a low-frequency wave absorption application, showing high-efficiency low-frequency wave absorption performance in the S and C bands.

[0014] The principle of the preparation method of the present invention is as follows: Using the reaction mechanism of chemical vapor induction, first pre-oxidize the carbonyl iron powder to lay a structural foundation for the construction of the phosphorus / selenium heterointerface; then the pre-oxidized sample undergoes a chemical reaction with the vaporized sodium hypophosphite and selenium powder precursors at high temperature to convert the surface iron-containing oxide into iron selenide and iron phosphide, and construct a heterointerface, and finally prepare a carbonyl iron-based composite material with high-efficiency low-frequency wave absorption performance.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The carbonyl iron composite material prepared by the present invention utilizes the oxidation and gas-phase induced synthesis mechanism of carbonyl iron, sodium hypophosphite, and selenium powder. By controlling parameters such as the mass ratio of different reactants, reaction time, temperature, and Ar atmosphere, a phosphorus / selenium heterojunction interface is in-situ constructed on the surface of carbonyl iron, realizing the optimization of the microwave absorption performance of spherical carbonyl iron.

[0016] 2. The carbonyl iron composite material prepared by the present invention has excellent low-frequency microwave absorption properties, good impedance matching characteristics and extremely high electromagnetic wave attenuation ability in the S and C bands. The design of the phosphorus / selenium heterojunction interface provides a new idea for the regulation of the low-frequency microwave absorption performance of carbonyl iron materials.

[0017] 3. The preparation process conditions of the present invention are mild, the structure is stable and controllable, the cost is low, the yield is high, it is green and environmentally friendly, and has extremely high commercial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD patterns of the original carbonyl iron (CI) of the present invention, and the samples prepared in Example 1, Example 2, and Example 3; Figure 2 SEM images of the original carbonyl iron of the present invention and the sample prepared in Example 1; among them, a is the SEM image of the original carbonyl iron (CI) (scale bar is 10 μm), b is the SEM image of the original carbonyl iron (CI) (scale bar is 1 μm), c is the SEM image of Example 1 (scale bar is 10 μm), d is the SEM image of Example 1 (scale bar is 1 μm); Figure 3 XPS analysis results of the sample prepared in Example 1 of the present invention; among them, a is the XPS analysis result of Fe element; b is the XPS analysis result of O element; c is the XPS analysis result of phosphorus element; d is the XPS analysis result of selenium element; Figure 4 RL diagrams of the original carbonyl iron (CI) of the present invention, and the samples prepared in Example 1, Example 2, and Example 3; among them, a is the RL diagram of the sample prepared from the original carbonyl iron (CI), b is the RL diagram of the sample prepared in Example 2, c is the RL diagram of the sample prepared in Example 3, d is the RL diagram of the sample prepared in Example 1; Figure 5 Impedance matching diagrams of the original carbonyl iron (CI) of the present invention, and the samples prepared in Example 1, Example 2, and Example 3; among them, a is the impedance matching diagram of the sample prepared from the original carbonyl iron (CI), b is the impedance matching diagram of the sample prepared in Example 2, c is the impedance matching diagram of the sample prepared in Example 3, d is the impedance matching diagram of the sample prepared in Example 1; Figure 6Attenuation constant curves of the original carbonyl iron (CI) of the present invention, and the samples prepared in Example 1, Example 2, and Example 3 Figure 7 RL diagrams of the samples prepared in Example 4 and Example 5 of the present invention; where a is the RL diagram of the sample prepared in Example 4, and b is the RL diagram of the sample prepared in Example 5. Detailed implementation manners

[0019] The technical solution of the present invention will be further described in detail below with reference to the drawings and examples.

[0020] A preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics includes the following steps: Step 1: Place a certain mass of spherical carbonyl iron powder in a vacuum tube furnace, and perform a pre-oxidation reaction at 200 °C for a certain period of time in an air atmosphere. Step 2: Place the sample prepared in Step 1 at the tail gas end of the vacuum tube furnace, mix a certain mass ratio of sodium hypophosphite and selenium powder evenly and place it at the inlet end of the vacuum tube furnace, and react at a certain reaction temperature in an Ar atmosphere for a certain period of time to obtain the final product as a carbonyl iron / iron selenide / iron phosphide composite material.

[0021] Specifically, in Step 2, the mass of the pre-oxidized carbonyl iron sample is fixed, and the mass ratio of sodium hypophosphite to selenium powder is 1.0.

[0022] As a preference, in Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to the same mass of sodium hypophosphite.

[0023] As another preference, in Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to the same mass of selenium powder.

[0024] As a preference, the reaction temperature in Step 2 is 350 °C.

[0025] As another preference, the reaction temperature in Step 2 is 400 °C.

[0026] As another preference, the reaction temperature described in Step 2 is adjusted to 450 °C.

[0027] Application of the carbonyl iron composite material for preparing a wave-absorbing material. This is a low-frequency wave-absorbing application, showing high-efficiency low-frequency wave-absorbing performance in the S and C bands.

[0028] Example 1 A carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics and its preparation method include the following steps: Step 1: Place 10 g of spherical carbonyl iron powder in a vacuum tube furnace, and perform a pre-oxidation reaction at 200 °C for 5 hours in an air atmosphere.

[0029] Step 2: Weigh 2 g of the sample prepared in Step 1 and place it at the tail gas end of the vacuum tube furnace. Mix 2 g of sodium hypophosphite and selenium powder materials with a mass ratio of 1:1 evenly and place them at the inlet end of the vacuum tube furnace. Under an Ar atmosphere, the gas flow rate is 40 ml / min, the heating rate is 5 °C / min, the reaction temperature is 400 °C, and the final product obtained after reacting for 2 h is the sample of Example 1, named CIPSe.

[0030] Example 2 Compared with Example 1, the difference in this example is that in Step 2, the sodium hypophosphite and selenium powder materials with a mass ratio of 1:1 are adjusted to 2 g of sodium hypophosphite; the remaining steps are the same as those in Example 1, and the prepared sample is named CIP.

[0031] Example 3 Compared with Example 1, the difference in this example is that in Step 2, the sodium hypophosphite and selenium powder materials with a mass ratio of 1:1 are adjusted to 2 g of selenium powder; the remaining steps are the same as those in Example 1, and the prepared sample is named CISe.

[0032] Example 4 Compared with Example 1, the difference in this example is that in Step 2, the reaction temperature is adjusted to 350 °C, and the remaining steps are the same as those in Example 1. The prepared sample is named CIPSe-350.

[0033] Example 5 Compared with Example 1, the difference in this example is that in Step 1, the reaction temperature is adjusted to 450 °C, and the remaining steps are the same as those in Example 1. The prepared sample is named CIPSe-450.

[0034] Figure 1 are the XRD patterns of the original carbonyl iron (CI) of the present invention, and the samples prepared in Example 1, Example 2, and Example 3; from Figure 1 it can be seen that the original carbonyl iron used in this invention shows three main characteristic peaks, indicating that the sample has a high purity and no obvious impurities are found; in addition to the characteristic peaks of carbonyl iron, the CIP sample shows Fe3O4 and Fe3P; the CISe sample shows new substances such as Fe3O4, Fe2O3, and FeSe2; the XRD pattern results of the CIP and CISe samples show that the purity of these two samples is not high and there are obvious impurity phases; while the CIPSe sample is mainly composed of carbonyl iron materials, supplemented by FeSe, Fe3O4, and Fe3P, indicating that Fe3O4 generated on the surface after the pre-oxidation treatment of carbonyl iron successfully undergoes a gas-phase reaction with sodium hypophosphite and selenium powder, generating a certain amount of iron selenide and iron phosphide substances.

[0035] Figure 2SEM images of the original carbonyl iron and CIPSe sample of the present invention; It can be seen from Figure 2 that the microscopic morphology of the original carbonyl iron of this invention as a whole presents a regular spherical structure. However, after pre-oxidation and phosphorus / selenization treatment, the surface structure has changed to some extent, presenting a structure similar to egg yolk - eggshell, and the surface substances of some particles have fallen off.

[0036] Figure 3 XPS analysis results of Example 1 of the present invention; Figure 3 The results of the fine spectra of Fe 2p, O 1s, P 2P and Se 3d in

[0037] Figure 4 show that the surface substances of this sample are mainly composed of FeSe, Fe3O4 and Fe3P. This result is basically consistent with the XRD analysis result, proving that this scheme can successfully construct a phosphorus / selenium heterojunction interface. Figure 4 min show that when the thickness is 2.5 mm, the original carbonyl iron can obtain the lowest reflection loss value (RL min ) of about -44.0 dB at 6.5 GHz, and the effective absorption bandwidth (EAB, RL < -10 dB) is about 3.2 GHz, effectively covering the frequency band of 4.8 - 8.0 GHz. However, its wave absorption performance is poor at other thicknesses; The samples prepared by phosphidation and selenization have RL min values that can be lower than -10 dB within the thickness range of 2.5 - 5.0 mm, but none of them can reach below -15 dB, showing poor wave absorption performance; While the sample CIPSe prepared by phosphorus / selenization has RL min values all below -15 dB within the range of 2.0 - 8.0 GHz and 2.5 - 5.0 mm thickness. In particular, when the thickness is 3.5 mm, it obtains an RL

[0038] Figure 5 value of about -35.2 dB at 4.4 GHz, and the EAB is about 2.0 GHz, effectively covering the frequency band of 3.6 - 5.6 GHz. In addition, when the thickness is within the range of 2.5 - 5.0 mm, it can achieve broadband absorption in the range of 2.6 - 8.0 GHz, indicating that the phosphorus / selenium heterojunction interface can significantly improve the wave absorption performance of carbonyl iron magnetic wave absorption materials in the low-frequency band and has extremely high application value. Impedance matching diagrams of the samples prepared from the original carbonyl iron (CI), Example 1, Example 2 and Example 3 of the present invention; Figure 5The results show that the area of the impedance matching value |Δ| < 0.4 of the original carbonyl iron in the range of 2 - 8 GHz is significantly lower than that of the other three samples, which means that a large amount of electromagnetic waves are difficult to effectively enter the absorber, explaining to some extent the poor microwave absorption performance in the low - frequency band. After comparative analysis of the other three samples, it is found that the impedance matching of the sample prepared by selenization is better than that of the phosphorus / selenium - doped sample, which is better than that of the phosphorus - doped sample, indicating that the selenization scheme can effectively improve the impedance matching characteristics of the carbonyl iron composite, promoting a large amount of electromagnetic waves to enter its interior and laying a foundation for the rapid attenuation of electromagnetic waves.

[0039] Figure 6 This is the attenuation constant curve of the original carbonyl iron (CI) of the present invention and the samples prepared in Example 1, Example 2 and Example 3. Figure 6 The results show that in the frequency band of 2.0 - 8.0 GHz, the attenuation constant of the phosphorus - doped sample is the largest, indicating that the composite material constructed by the phosphorus - doping scheme can achieve rapid attenuation of the electromagnetic waves entering its interior. The attenuation constant of the selenized sample is close to that of the original carbonyl iron in the frequency band of 2.0 - 4.0 GHz, but as the frequency continues to increase, its attenuation constant is significantly lower than that of the original carbonyl iron, which explains the poor low - frequency microwave absorption performance. The attenuation constant of the phosphorus / selenium - doped sample is close to that of the original carbonyl iron in the frequency band of 2.0 - 6.0 GHz and shows a slight decrease after further increase. Combining the analysis results of impedance matching, it can be seen that the excellent impedance matching characteristics and strong electromagnetic wave attenuation ability in the low - frequency band ensure the high - efficiency low - frequency microwave absorption performance of the phosphorus / selenium - doped sample.

[0040] Figure 7 This is the RL diagram of the samples prepared in Example 4 and Example 5 of the present invention. Figure 7 The results show that after phosphorus / selenium doping treatment at different temperatures of 350 °C and 450 °C, it still exhibits excellent microwave absorption performance in the frequency band of 2.0 - 8.0 GHz. However, the frequency at which its RL min is located is slightly higher than that of the sample at 400 °C, indicating that the low - frequency microwave absorption performance of the phosphorus / selenium - doped sample can be effectively regulated by temperature control.

Claims

1. A preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics, characterized in that, It includes the following steps: Step 1: Place spherical iron carbonyl powder of a certain mass in a vacuum tube furnace and carry out a pre-oxidation reaction at 200 °C for a certain period of time in an air atmosphere; Step 2: Place the sample prepared in Step 1 at the tail gas end of the vacuum tube furnace. After uniformly mixing sodium hypophosphite and selenium powder in a certain mass ratio, place them at the inlet end of the vacuum tube furnace. Under an Ar atmosphere and at a certain reaction temperature, react for a certain period of time to obtain a final product of iron carbonyl / iron selenide / iron phosphide composite material.

2. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, characterized in that, In Step 2, the mass of the pre-oxidized iron carbonyl sample is fixed, and the mass ratio of sodium hypophosphite to selenium powder is 1.

0.

3. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, characterized in that, In Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to sodium hypophosphite of the same mass.

4. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, characterized in that, In Step 2, the sodium hypophosphite and selenium powder precursors are adjusted to selenium powder of the same mass.

5. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, wherein In Step 2, the reaction temperature is 350 °C.

6. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, wherein In Step 2, the reaction temperature is 400 °C.

7. The preparation method of a carbonyl iron composite material with low-frequency and high-efficiency wave absorption characteristics according to claim 1, characterized in that, The reaction temperature described in Step 2 is adjusted to 450 °C.

8. Use of the carbonyl iron composite material prepared by the method according to any one of claims 1 to 7, characterized in that, It is used for preparing wave-absorbing materials.

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