Iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material, preparation method and application thereof

Abstract

This invention discloses an iron-nitride-based amorphous and nanocrystalline electromagnetic wave absorbing material, its preparation method, and its applications. The material comprises an in-situ generated Fe4N phase, which forms a composite structure with an iron-based amorphous and / or nanocrystalline matrix. The material possesses a composite phase structure of the amorphous phase and Fe4N phase, or an amorphous phase, α-Fe(Si) phase, and Fe4N phase. The preparation method involves a three-step nitriding treatment of iron-based amorphous and / or nanocrystalline powder: first, stress-relief heat treatment in a nitrogen atmosphere; second, reduction heat treatment in a mixed atmosphere of nitrogen and hydrogen; and third, nitriding heat treatment in a mixed atmosphere of hydrogen and ammonia, resulting in the in-situ generation of the Fe4N phase. This invention can improve the dielectric loss of the material, optimize impedance matching, and enhance electromagnetic wave absorption performance. This material has a minimum reflection loss of -73.28dB in the 1-18GHz frequency band, a -10dB bandwidth of up to 1.99GHz, and a matching thickness as low as 3.85mm. It can be applied to electromagnetic wave absorbing devices in fields such as high-frequency communication, radar detection, and remote sensing navigation.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material, its preparation method, and its application. Background Technology

[0002] The rapid development of electromagnetic wave technology in fields such as high-frequency communication, radar detection, and remote sensing navigation has led to increased electromagnetic radiation and interference in the GHz band, which can also affect human health. Therefore, the demand for electromagnetic wave absorbing materials (wave-absorbing materials) is increasing, and they need to be applied in complex environments. Iron-based amorphous / nanocrystalline materials possess characteristics such as high magnetic permeability, high saturation magnetization, and relatively high electromagnetic loss. Research on novel amorphous / nanocrystalline materials holds promise for developing excellent wave-absorbing materials.

[0003] To optimize the microwave absorption performance of iron-based amorphous / nanocrystalline absorbing materials, methods such as powder morphology, composition, and composite material modification can be employed. For example, regarding powder morphology, patent CN115537684B discloses a method for preparing flake-like powder through ball milling, followed by crystallization heat treatment to form an amorphous phase and an α-Fe(Si) nanocrystalline composite dual-phase structure. The absorbing material prepared by this method exhibits excellent microwave absorption performance in the 8–12 GHz frequency band. In terms of composition design, patent CN116345183A designs a FeSiBPCu system amorphous / nanocrystalline alloy absorbing composition, with the general chemical formula Fe... x Si y B z P m Cu n The formula 70 < x < 90, 3 < y < 8, 5 < z < 14, 1 < m < 6, 0.1 < n < 2 exhibits excellent wave absorption characteristics in the 2–18 GHz frequency band. Regarding composite material modification, patent CN113333743B discloses a core-shell structured carbon-coated iron-based nanocrystalline alloy composite wave-absorbing material prepared by ball milling, achieving a reflection loss of less than -10 dB in the 8–18 GHz band, with a minimum reflection loss of -54 dB.

[0004] However, existing technologies still lack a technical solution to generate the Fe4N phase in situ by controlling the nitrogen content of amorphous / nanocrystalline microwave absorbing materials, which makes it difficult to further improve the impedance matching performance and electromagnetic wave absorption capability of amorphous / nanocrystalline microwave absorbing materials. Summary of the Invention

[0005] The purpose of this invention is to solve the aforementioned technical problems existing in the prior art, and to provide an iron-nitride-based amorphous / nanocrystalline electromagnetic wave absorbing material, its preparation method, and its application. By increasing the nitrogen content within the iron-based amorphous / nanocrystalline material through nitriding heat treatment, a composite material with an in-situ Fe4N phase is generated, improving the material's dielectric loss capability, optimizing the impedance matching of the iron-based amorphous / nanocrystalline material, and enhancing its electromagnetic wave absorption capability.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention provides an iron nitride-based amorphous and nanocrystalline electromagnetic wave absorbing material, which includes an in-situ generated Fe4N phase, forming a composite structure with an iron-based amorphous and / or nanocrystalline matrix. By generating the Fe4N phase in situ, the dielectric loss of the material can be significantly improved while maintaining good magnetic loss, thereby optimizing impedance matching and enhancing electromagnetic wave absorption capability.

[0008] Furthermore, the composite phase structure of the material is either an amorphous phase and a Fe4N phase, or an amorphous phase, an α-Fe(Si) phase, and a Fe4N phase. Both of these composite phase structures can form multiphase interfaces, which is beneficial for improving the dielectric constant and dielectric loss.

[0009] This invention also provides a method for preparing the above-mentioned iron-nitride-based amorphous and / or nanocrystalline electromagnetic wave absorbing material. The method includes a step of nitriding iron-based amorphous and / or nanocrystalline powders, wherein the iron-based amorphous and / or nanocrystalline powders are used to form the iron-based amorphous and / or nanocrystalline matrix in the material. The nitriding process includes three steps:

[0010] (a) Stress relief heat treatment was performed in a nitrogen atmosphere to eliminate the internal stress generated in the powder during ball milling;

[0011] (b) A reduction heat treatment is performed in a mixed atmosphere of nitrogen and hydrogen to improve the surface activity of the powder and create conditions for subsequent nitriding reaction.

[0012] (c) Nitriding heat treatment is performed in a mixed atmosphere of hydrogen and ammonia to generate the Fe4N phase in situ. The content and distribution of the Fe4N phase can be controlled by adjusting the nitriding temperature and time.

[0013] Furthermore, the preparation method also includes the step of preparing iron-based amorphous and / or nanocrystalline powders prior to nitriding treatment:

[0014] S1: Preparation of iron-based master alloys by induction melting;

[0015] S2: Amorphous alloy strips are prepared from iron-based master alloys by melt quenching.

[0016] S3: The amorphous alloy strip is subjected to embrittlement heat treatment to make it embrittled in order to facilitate subsequent ball milling;

[0017] S4: The embrittled amorphous alloy strip is ball-milled to obtain iron-based amorphous and / or nanocrystalline powder.

[0018] In the above preparation method, the process parameters of each step can be adjusted according to actual needs. Specifically:

[0019] In step S1, the general chemical formula of the iron-based master alloy is Fe. (100-a-b-c-d-e) Si a B b P c Nb d Cu e The atomic percentages are as follows: 2.0≤a≤13.5; 6.0≤b≤9.0; 0.0≤c≤6.0; 0≤d≤3.0; 0.0≤e≤1.5. Alloys within this composition range exhibit good amorphous forming ability and thermal stability.

[0020] In step S2, the melt quenching method is either single-roll rapid quenching or double-roll rapid quenching; the thickness of the resulting amorphous alloy strip is 15.0–30.0 μm, and the width is 1.0–30.0 mm.

[0021] In step S3, the embrittlement heat treatment temperature is 50.0–200.0℃ below the crystallization temperature of the amorphous alloy strip, the heating rate is 0.5–20.0℃ / min, and the holding time is 30.0–240.0min.

[0022] In step S4, the ball milling speed is 50.0–1000.0 r / min, the ball-to-material ratio is 20.0–50.0:1, and the ball milling time is 30.0–1440.0 min; the thickness of the obtained iron-based amorphous and / or nanocrystalline powder is 1.0–25.0 μm, the particle size is 50.0–100.0 μm, and the aspect ratio is 2.0–100.0.

[0023] The preferred ranges for the three-step nitriding process parameters are as follows:

[0024] In step (a), the stress-relieving heat treatment temperature is 200.0–400.0℃, and the holding time is 30.0–600.0 min;

[0025] In step (b), the temperature of the reduction heat treatment is 400.0~480.0℃, the holding time is 30.0~120.0min, and the volume ratio of hydrogen to nitrogen in the mixed atmosphere is 1.0:1.0~10.0;

[0026] In step (c), the nitriding heat treatment temperature is 480.0~620.0℃, the holding time is 30.0~300.0min, and the volume ratio of hydrogen to ammonia in the mixed atmosphere is 1.0:1.0~10.0.

[0027] Furthermore, the nitriding heat treatment temperature is 500.0–600.0℃, the holding time is 60.0–180.0 min, and the volume ratio of hydrogen to ammonia in the mixed atmosphere is 1:2.5–3.5. Within this preferred parameter range, the Fe4N phase is formed most fully, and the material exhibits the best microwave absorption performance.

[0028] This invention also provides the application of the above-mentioned iron nitride-based amorphous and nanocrystalline electromagnetic wave absorbing material in the fabrication of electromagnetic wave absorbing devices. This material can be applied to electromagnetic wave absorbing devices in fields such as high-frequency communication, radar detection, and remote sensing navigation.

[0029] The present invention, by adopting the above-described technical solution, has the following beneficial effects:

[0030] 1. This invention employs a three-step nitriding process, comprising stress-relief heat treatment, reduction heat treatment, and nitriding heat treatment, to generate an in-situ Fe4N phase within an iron-based amorphous / nanocrystalline matrix. Unlike existing technologies that modify the matrix through powder morphology optimization, composition design, or carbon coating, this invention enhances microwave absorption performance by controlling the nitrogen content to form a composite phase structure of amorphous phase and Fe4N phase, or amorphous phase, α-Fe(Si) phase, and Fe4N phase.

[0031] 2. In the three-step nitriding process of this invention, the stress relief, reduction, and nitriding steps are synergistic and indispensable. Comparative Example 2 omitted the reduction step, resulting in a significant reduction in nitrogen content (from 7.32 × 10⁻⁶ in Example 1). 4 ppm decreased to 1.72 × 10 4 (ppm), demonstrating the crucial role of reduction treatment in improving powder surface activity and promoting nitriding reactions. Simultaneously, this invention experimentally determined the critical parameter ranges for nitriding treatment: below 480℃, Fe4N phase cannot be generated; above 620℃, the Fe4N phase decomposes; below 30 min, Fe4N phase formation is incomplete; above 300 min, grain coarsening leads to performance degradation. By controlling the key parameters of nitriding temperature, holding time, and hydrogen / ammonia ratio, the content and distribution of the Fe4N phase can be precisely controlled, thereby obtaining microwave absorbing materials with different performance requirements.

[0032] 3. This invention promotes the formation of multiphase interfaces by constructing a multiphase structure containing the Fe4N phase. For example... Figure 2As shown, the sample containing the Fe4N phase exhibits a significant increase in the real part of the dielectric constant, improved dielectric constant stability, a distinct resonance peak in the imaginary part of the dielectric constant, and an increased dielectric loss tangent. Simultaneously, the Fe4N phase can suppress the decay of the real part of the permeability, maintaining good magnetic loss capability. This synergistic effect of magnetic and dielectric loss achieves good impedance matching between permeability and dielectric constant. Experimental results show that the minimum reflection loss of Example 2 reaches -69.19 dB, and the minimum reflection loss of Example 7 reaches -73.28 dB, which is superior to existing technologies (the minimum reflection loss of CN113333743B is -54 dB). Furthermore, the -10 dB bandwidth can reach 1.99 GHz, and the matching thickness can be as low as 3.85 mm, achieving excellent comprehensive performance with thinness, wide bandwidth, and strong absorption.

[0033] 4. The three-step nitriding process of this invention is simple to operate, and the parameters such as temperature, time, and atmosphere ratio in each step can be adjusted according to actual needs. Examples 1-8 use different component systems (Fe... 73.5 Si 13.5 B9Nb3Cu1 and Fe 80 Materials with excellent microwave absorption properties were successfully prepared using Si5B9P5Cu1, different nitriding temperatures (550℃, 600℃, 650℃), different holding times (30min, 60min, 180min, 300min), and different hydrogen / ammonia ratios (1:1, 1:3, 1:10). This demonstrates that the preparation method is applicable to iron-based amorphous / nanocrystalline alloys with different composition systems and has good process versatility.

[0034] 5. The absorbing material prepared by this invention has excellent absorbing performance in the 1-18 GHz frequency band, which can meet the high performance requirements of electromagnetic wave absorbing materials in fields such as high-frequency communication, radar detection, and remote sensing navigation, and has broad application prospects. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 The XRD patterns are those of Examples 1-3 and Comparative Examples 1-2.

[0037] Figure 2 The electromagnetic parameters of Examples 1-3 and Comparative Examples 1-2 are shown in the 1-18 GHz frequency band.

[0038] Figure 3 The XRD patterns are for Examples 4 and 5. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0040] Example 1,

[0041] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0042] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0043] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0044] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0045] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was heated at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was subjected to reduction treatment at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was subjected to nitriding treatment at 550℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0046] Example 2,

[0047] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5Si 13.5 B9Nb3Cu1 master alloy;

[0048] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0049] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0050] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0051] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding. First, it was held at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was subjected to reduction treatment at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was subjected to nitriding treatment at 600℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0052] Example 3,

[0053] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0054] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0055] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0056] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0057] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was held at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was subjected to reduction treatment at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was subjected to nitriding treatment at 650℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0058] Comparative Example 1,

[0059] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0060] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0061] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0062] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0063] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was held at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress, and then it was held at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 for reduction treatment.

[0064] Comparative Example 2,

[0065] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0066] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0067] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0068] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0069] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was held at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress, and then nitrided at 550℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0070] Example 4,

[0071] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0072] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0073] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0074] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0075] Step 5: Add Fe 73.5 Si 13.5 The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was heated at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was reduced by heating at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was nitrided by heating at 600℃ for 30.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0076] Example 5,

[0077] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 73.5 Si 13.5 B9Nb3Cu1 master alloy;

[0078] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0079] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 73.5 Si 13.5 The B9Nb3Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment at a temperature of 400.0℃, a heating rate of 10.0℃ / min, and a holding time of 60.0min.

[0080] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 73.5 Si 13.5 B9Nb3Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 73.5 Si 13.5 The thickness of the non-crystalline B9Nb3Cu1 powder is 4μm, the particle size of the flakes is 100μm, and the aspect ratio is 25.

[0081] Step 5: Add Fe 73.5 Si 13.5The non-crystalline B9Nb3Cu1 powder was placed in an atmosphere heat treatment furnace for nitriding. First, it was held at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was subjected to reduction treatment at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was subjected to nitriding treatment at 600℃ for 300.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0082] Example 6,

[0083] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 80 Si5B9P5Cu1 master alloy;

[0084] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0085] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 80 The Si5B9P5Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment. The heat treatment temperature was 400.0℃, the heating rate was 10.0℃ / min, and the holding time was 60.0min.

[0086] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 80 Si5B9P5Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 80 The thickness of the non-crystalline Si5B9P5Cu1 powder is 2μm, the particle size of the flakes is 80μm, and the aspect ratio is 40.

[0087] Step 5: Add Fe 80 Si5B9P5Cu1 non-crystalline powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was heated at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was reduced by heating at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was nitrided by heating at 600℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:1.

[0088] Example 7

[0089] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 80 Si5B9P5Cu1 master alloy;

[0090] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0091] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 80 The Si5B9P5Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment. The heat treatment temperature was 400.0℃, the heating rate was 10.0℃ / min, and the holding time was 60.0min.

[0092] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 80 Si5B9P5Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 80 The thickness of the non-crystalline Si5B9P5Cu1 powder is 2μm, the particle size of the flakes is 80μm, and the aspect ratio is 40.

[0093] Step 5: Add Fe 80 Si5B9P5Cu1 non-crystalline powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was heated at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was reduced by heating at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was nitrided by heating at 600℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:3.

[0094] Example 8

[0095] Step 1: Prepare 50.0g of Fe by vacuum induction melting. 80 Si5B9P5Cu1 master alloy;

[0096] Step 2: Under the protection of high-purity argon gas (purity better than 99.9%), the master alloy is prepared into amorphous alloy strip by single-roll rapid cooling. The linear speed of the copper roller is 40.0 m / s, the thickness of the amorphous alloy strip is 20.0 μm, the width is 5.0 mm, and the length exceeds 50.0 mm.

[0097] Step 3: Under the protection of high-purity argon gas (purity better than 99.9%), Fe... 80 The Si5B9P5Cu1 amorphous alloy strip was placed in a heat treatment furnace for embrittlement heat treatment. The heat treatment temperature was 400.0℃, the heating rate was 10.0℃ / min, and the holding time was 60.0min.

[0098] Step 4: Place the embrittled amorphous alloy strip in a ball mill. The ball milling speed is 500.0 r / min, the ball-to-material ratio is 20.0:1, the ball milling media is anhydrous ethanol, and the ball milling time is 960.0 min. The ball milling yields Fe. 80 Si5B9P5Cu1 non-crystalline powder, after ball milling, the crystalline powder was cleaned and dried in a forced-air drying oven, Fe 80 The thickness of the non-crystalline Si5B9P5Cu1 powder is 2μm, the particle size of the flakes is 80μm, and the aspect ratio is 40.

[0099] Step 5: Add Fe 80 Si5B9P5Cu1 non-crystalline powder was placed in an atmosphere heat treatment furnace for nitriding treatment. First, it was heated at 300℃ for 60.0 min in a nitrogen atmosphere to eliminate internal stress. Then, it was reduced by heating at 450℃ for 60.0 min in a hydrogen-nitrogen mixed atmosphere with a hydrogen-nitrogen volume ratio of 1:3 to improve the surface activity of the powder. Finally, it was nitrided by heating at 600℃ for 180.0 min in a hydrogen-ammonia mixed atmosphere with a hydrogen-ammonia volume ratio of 1:10.

[0100] Performance Testing and Result Analysis

[0101] 1. XRD phase analysis

[0102] Figure 1 XRD patterns of Examples 1-3 and Comparative Examples 1-2 are shown. The results show that the unnitrided sample exhibits an amorphous phase (Comparative Example 1); the unreduced powder has low surface activity, and the Fe4N phase content is low after nitriding (Comparative Example 2); when the nitriding temperature is below 480℃, the nitrogen atom diffusion rate is low, requiring a long holding time to generate the Fe4N phase; increasing the nitriding temperature to 550℃ yields both an amorphous phase and the Fe4N phase (Example 1); when the temperature is between 480 and 620℃, the Fe4N phase diffraction peaks are obvious, and the peak intensity increases with increasing temperature (Example 2); when the temperature exceeds 620℃, the Fe4N phase diffraction peaks disappear, indicating that the Fe4N phase decomposes (Example 3). Therefore, the suitable nitriding temperature range is 480–620℃, preferably 500–600℃.

[0103] Figure 3XRD patterns of Examples 4 and 5 are shown. The results indicate that during nitriding at 600℃, when the holding time is less than 30 min, the Fe4N phase is incompletely formed, exhibiting a weak (111) diffraction peak; while when the holding time exceeds 300 min, the Fe4N content is too high, exhibiting excessively strong (111) and (200) diffraction peaks, which is not conducive to obtaining excellent microwave absorption performance. Therefore, the suitable holding time is 30–300 min, preferably 60–180 min.

[0104] 2. Nitrogen content analysis

[0105] Table 1 shows the nitrogen content and phase composition of different embodiments.

[0106] Table 1:

[0107] Sample Name <![CDATA[Nitrogen content (10 4 ppm)]]> Phase composition Comparative Example 1 0.18 amorphous Comparative Example 2 1.72 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 1 7.32 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 2 12.80 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 3 0.76 <![CDATA[Amorphous + Fe4N]]>

[0108] The results showed that the unnitrided sample had a low nitrogen content (Comparative Example 1); the unreduced powder had low surface activity, and the nitrogen content of the nitrided sample was not high (Comparative Example 2); when the temperature was between 480 and 620 °C, increasing the nitriding temperature could increase the nitrogen content inside the amorphous nanocrystals (Examples 1 and 2); when the temperature exceeded 620 °C, the nitrogen content inside the sample decreased significantly, indicating that the Fe4N phase decomposed (Example 3).

[0109] Table 2 shows the nitrogen content and phase composition of Examples 4 and 5.

[0110] Table 2:

[0111] Sample Name <![CDATA[Nitrogen content (10 4 ppm)]]> Phase composition Example 4 7.58 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 5 14.3 <![CDATA[Amorphous + α-Fe + Fe4N]]>

[0112] The results showed that during nitriding treatment at 600℃, extending the holding time from 30 min to 300 min reduced the nitrogen content from 7.58 × 10⁻⁶. 4 ppm increased to 14.3 × 10 4 The ppm indicates that extending the heat preservation time is beneficial to improving the degree of nitriding.

[0113] Table 3 shows the nitrogen content and phase composition of Examples 6-8.

[0114] Table 3:

[0115] Sample Name <![CDATA[Nitrogen content (10 4 ppm)]]> Phase composition Example 6 4.31 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 7 12.3 <![CDATA[Amorphous + α-Fe + Fe4N]]> Example 8 30.5 <![CDATA[Amorphous + α-Fe + Fe4N]]>

[0116] The results show that the nitrogen content in the sample increases with the increase of the ammonia gas integral. When the ammonia-nitrogen volume ratio is 1:3, the nitrogen content in the nitrided sample is moderate, which is beneficial for obtaining excellent microwave absorption performance. Therefore, the suitable hydrogen:ammonia volume ratio is 1:2.5–3.5.

[0117] 3. Electromagnetic parameter analysis

[0118] Figure 2 The electromagnetic parameters (complex permittivity, dielectric loss tangent, complex permeability, and magnetic loss tangent) of Examples 1-3 and Comparative Examples 1-2 in the 1–18 GHz frequency band are shown. Figure 2 It can be seen that, for magnetic permeability, increasing the Fe4N content (Examples 1 and 2) can suppress the decay of the real part of the magnetic permeability, and the imaginary part of the magnetic permeability exhibits a significant resonance peak. However, the permeability tangent shows a decreasing trend, indicating a slight decrease in magnetic loss capability. For dielectric constant, constructing the Fe4N phase structure and promoting the formation of multiphase interfaces can significantly increase the real part of the dielectric constant, improve the stability of the dielectric constant, and make the imaginary part of the dielectric constant exhibit a significant resonance peak. At the same time, the dielectric loss tangent increases, which is beneficial to improving the dielectric loss of the sample. However, excessively high nitriding temperatures lead to the decomposition of Fe4N (Example 3), which causes a deterioration in dielectric parameters.

[0119] 4. Wave absorption performance analysis

[0120] Table 4 shows the minimum reflection loss of Examples 1-3 and Comparative Examples 1-2, along with their corresponding frequencies, thicknesses, and -10dB bandwidth.

[0121] Table 4:

[0122] Sample Name Minimum reflection loss (dB) Minimum reflection loss corresponding frequency and thickness -10dB bandwidth (GHz) Comparative Example 1 -48.37 11.4GHz / 2.37mm 1.21 Comparative Example 2 -55.52 4.72GHz / 4.23mm 1.16 Example 1 -60.17 5.85GHz / 4.20mm 1.26 Example 2 -69.19 5.84GHz / 4.03mm 1.54 Example 3 -25.13 4.46GHz / 4.99mm 0.91

[0123] The results show that the Fe4N phase generated after nitriding can reduce the minimum reflection loss and its corresponding frequency and thickness, and increase the bandwidth with a reflection loss of less than -10dB.

[0124] Table 5 shows the minimum reflection loss of Examples 4 and 5, along with their corresponding frequencies, thicknesses, and -10dB bandwidths.

[0125] Table 5:

[0126] Sample Name Minimum reflection loss (dB) Minimum reflection loss corresponding frequency and thickness -10dB bandwidth (GHz) Example 4 -53.16 6.31GHz / 4.27mm 1.24 Example 5 -58.24 6.04GHz / 4.54mm 1.20

[0127] The results show that when nitriding at 600℃, the minimum reflection loss is -53.16dB when the holding time is 30min (Example 4) and the minimum reflection loss is -58.24dB when the holding time is 300min (Example 5). This indicates that appropriately extending the holding time is beneficial to improving the absorption performance, but the performance improvement slows down after exceeding a certain range.

[0128] Table 6 shows the minimum reflection loss of Examples 6-8 and their corresponding frequencies, thicknesses, and -10dB bandwidths.

[0129] Table 6:

[0130] Sample Name Minimum reflection loss (dB) Minimum reflection loss corresponding frequency and thickness -10dB bandwidth (GHz) Example 6 -67.12 4.98GHz / 4.11mm 1.73 Example 7 -73.28 4.15GHz / 3.85mm 1.99 Example 8 -63.42 5.76GHz / 4.58mm 1.23

[0131] The results show that the absorption performance changes regularly with the change of the hydrogen to ammonia volume ratio. When the hydrogen to ammonia volume ratio is 1:3 (Example 7), the minimum reflection loss reaches -73.28dB and the -10dB bandwidth reaches 1.99GHz, both of which are better than other ratios, indicating that the suitable hydrogen to ammonia volume ratio is 1:2.5 to 3.5.

[0132] This invention provides an iron nitride-based amorphous / nanocrystalline electromagnetic wave absorbing material and its preparation method. Through a three-step nitriding process, an Fe4N phase is generated in situ within an iron-based amorphous / nanocrystalline matrix, forming a composite phase structure of the amorphous phase and Fe4N phase, or the amorphous phase, α-Fe(Si) phase, and Fe4N phase. This material exhibits strong electromagnetic wave absorption capability in the 1–18 GHz frequency range, with a minimum reflection loss of -73.28 dB, a -10 dB bandwidth of 1.99 GHz, and a matching thickness as low as 3.85 mm. The preparation method is simple, with controllable parameters and strong applicability, and can be widely applied to electromagnetic wave absorbing devices in high-frequency communications, radar detection, remote sensing navigation, and other fields, demonstrating significant industrial practical value.

[0133] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. An iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material, characterized in that: The material contains an in-situ generated Fe4N phase, which forms a composite structure with an iron-based amorphous and / or nanocrystalline matrix.

2. The iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 1, characterized in that: The composite phase structure of the material is an amorphous phase and Fe4N phase, or an amorphous phase, α-Fe(Si) phase and Fe4N phase.

3. A method for preparing the iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material as described in claim 1 or 2, characterized in that: The step includes nitriding iron-based amorphous and / or nanocrystalline powders, wherein the iron-based amorphous and / or nanocrystalline powders are used to form the iron-based amorphous and / or nanocrystalline matrix in the material as described in claim 1 or 2; the nitriding process includes, in sequence: (a) Stress-relief heat treatment in a nitrogen atmosphere; (b) Reduction heat treatment is carried out in a mixed atmosphere of nitrogen and hydrogen; (c) Nitriding heat treatment is carried out in a mixed atmosphere of hydrogen and ammonia to generate the Fe4N phase in situ.

4. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 3, characterized in that: The process also includes the step of preparing the iron-based amorphous and / or nanocrystalline powder prior to the nitriding treatment: S1: Preparation of iron-based master alloys by induction melting; S2: The iron-based master alloy is prepared into an amorphous alloy strip by melt quenching. S3: Perform embrittlement heat treatment on the amorphous alloy strip; S4: The embrittled amorphous alloy strip is ball-milled to obtain the iron-based amorphous and / or nanocrystalline powder.

5. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 4, characterized in that: In step S1, the general chemical formula of the iron-based master alloy is: Fe (100-a-b-c-d-e) Si a B b P c Nb d Cu e The atomic percentages are as follows: 2.0≤a≤13.5; 6.0≤b≤9.0; 0.0≤c≤6.0; 0≤d≤3.0; 0.0≤e≤1.

5.

6. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 4, characterized in that: In step S2, the melt quenching method is a single-roll rapid quenching or a double-roll rapid quenching; the thickness of the resulting amorphous alloy strip is 15.0 to 30.0 μm and the width is 1.0 to 30.0 mm.

7. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 4, characterized in that: In step S3, the embrittlement heat treatment temperature is 50.0 to 200.0°C below the crystallization temperature of the amorphous alloy strip, the heating rate is 0.5 to 20.0°C / min, and the holding time is 30.0 to 240.0min.

8. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 4, characterized in that: In step S4, the ball milling speed is 50.0–1000.0 r / min, the ball-to-material ratio is 20.0–50.0:1, and the ball milling time is 30.0–1440.0 min; the thickness of the obtained iron-based amorphous and / or nanocrystalline powder is 1.0–25.0 μm, the particle size is 50.0–100.0 μm, and the aspect ratio is 2.0–100.

0.

9. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 3, characterized in that: In step (a), the temperature of the stress-relieving heat treatment is 200.0 to 400.0 °C, and the holding time is 30.0 to 600.0 min.

10. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 3, characterized in that: In step (b), the temperature of the reduction heat treatment is 400.0 to 480.0 °C, the holding time is 30.0 to 120.0 min, and the volume ratio of hydrogen to nitrogen in the mixed atmosphere is 1.0:1.0 to 10.

0.

11. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 3, characterized in that: In step (c), the nitriding heat treatment temperature is 480.0~620.0℃, the holding time is 30.0~300.0min, and the volume ratio of hydrogen to ammonia in the mixed atmosphere is 1.0:1.0~10.

0.

12. The method for preparing an iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 11, characterized in that: The nitriding heat treatment temperature is 500.0–600.0℃, the holding time is 60.0–180.0 min, and the volume ratio of hydrogen to ammonia in the mixed atmosphere is 1:2.5–3.

5.

13. The application of the iron nitride-based amorphous nanocrystalline electromagnetic wave absorbing material according to claim 1 or 2 in the preparation of electromagnetic wave absorbing devices.

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