A method for preparing a bamboo-like NiFe2O4 / Fe3O4 heterostructure and its application

Abstract

This invention relates to a method for preparing a bamboo-like NiFe2O4 / Fe3O4 heterostructure and its application, belonging to the field of electromagnetic wave absorbing materials. Addressing the limitations of existing absorbing materials, such as single absorption frequency band, narrow effective absorption bandwidth, insufficient electromagnetic loss capability, and poor controllability of structural morphology, this invention struggles to simultaneously meet the practical application requirements of efficient cross-frequency absorption of radar waves and terahertz waves. The invention constructs a heterostructure by combining NiFe2O4 and Fe3O4, utilizing defects and charge enrichment at the heterostructure interface to enhance interfacial polarization and improve electromagnetic loss capability. Furthermore, the interface promotes electron transfer and optimizes conductivity, ultimately developing a multi-band absorbing material with both efficient radar wave and terahertz wave absorption characteristics. This overcomes the shortcomings of single-material absorption, achieves effective integration of multi-band absorption, provides reliable material support for radar stealth technology, and meets the urgent research needs of the field for novel absorbing materials.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, and relates to a method for preparing a bamboo-like NiFe2O4 / Fe3O4 heterostructure and its electromagnetic wave absorption characteristics. Background Technology

[0002] Electromagnetic waves play a crucial role in information transmission fields such as radar systems and satellite communications. In the military field, with the continuous upgrading of precision-guided weapons and breakthroughs in advanced detection technologies, national security is facing increasingly severe challenges. Against this backdrop, radar stealth technology, with its unique value in enhancing equipment survivability and operational concealment, has become an important research direction in the military technology field. At the same time, modern reconnaissance and detection technologies are becoming increasingly complex, placing higher and more stringent performance requirements on the effective absorption frequency band of radar-absorbing materials. Therefore, the development of new radar-absorbing materials with broadband absorption and strong electromagnetic attenuation characteristics has become an extremely urgent research need in this field. Due to the electronic structure characteristics of nickel and iron ions, NiFe2O4 can generate magnetic moments through electron spin and orbital motion under alternating magnetic fields. Through various magnetic loss mechanisms such as hysteresis loss, eddy current loss, natural resonance, and exchange resonance, it can efficiently convert the magnetic field energy of electromagnetic waves into heat energy. When NiFe2O4 is combined with Fe3O4 to construct a heterostructure, numerous defects are generated at the heterostructure interface, leading to local charge accumulation and inducing a strong interface polarization effect, effectively enhancing the electromagnetic wave attenuation performance of the composite material. Heterogeneous interfaces can promote electron transfer, forming conductive channels and further improving the conductivity of composite materials. This invention develops a multi-band absorbing material that combines efficient radar wave and terahertz wave absorption characteristics, achieving effective integration of multi-band absorption. Summary of the Invention

[0003] Existing absorbing materials generally suffer from limitations such as single absorption frequency band, narrow effective absorption bandwidth, insufficient electromagnetic loss capability, and poor controllability of structural morphology, making it difficult to simultaneously meet the practical application requirements of efficient absorption of radar waves and terahertz waves across frequency bands. This invention proposes a method for preparing a bamboo-like NiFe2O4 / Fe3O4 heterostructure and conducts in-depth research on its absorption characteristics. By constructing a heterostructure by combining NiFe2O4 and Fe3O4, the defects and charge enrichment generated at the heterostructure interface enhance the interface polarization effect, improving electromagnetic loss capability. Furthermore, the interface promotes electron transfer and optimizes conductivity, ultimately developing a multi-band absorbing material with efficient radar wave and terahertz wave absorption characteristics. This addresses the shortcomings of single-material absorption, achieves effective integration of multi-band absorption, provides reliable material support for radar stealth technology, and meets the current urgent research needs for novel absorbing materials in the field.

[0004] Ferric chloride hexahydrate, nickel nitrate hexahydrate, and terephthalic acid were added to N,N-dimethylformamide in a 2:1:2 molar ratio. After magnetic stirring, the mixture was placed in a high-pressure reactor. The magnetic stirring time was controlled at 10-30 minutes, and the stirring speed was 200-1000 rpm. A hydrothermal reaction was then carried out to form uniformly sized rod-shaped nickel-iron precursors. The hydrothermal reaction temperature was controlled at 100-120℃, and the reaction time was controlled at 10-18 hours. The obtained one-dimensional rod-shaped nickel-iron precursors were then centrifuged and dried. The centrifugation speed was controlled at 5000-9000 rpm, and the centrifugation time was controlled at 5-15 minutes. Finally, high-temperature heat treatment was performed to obtain the bamboo-like NiFe2O4 / Fe3O4 composite material. The heating rate was controlled at 2-10℃ / min, the holding temperature was controlled at 400-600℃, and the holding time was controlled at 2-8 hours. Scanning electron microscopy (SEM) characterization results showed that the NiFe2O4 / Fe3O4 composite material exhibited a regular morphology and uniform overall size. To evaluate the electromagnetic wave absorption performance of the material, the obtained NiFe2O4 / Fe3O4 composite material was mixed with paraffin wax at different proportions. The results showed that when the filling ratio was 70 wt%, the maximum effective absorption bandwidth was 4.8 GHz, with a matching thickness of 1.6 mm, covering the 9.8-14.6 GHz radar frequency band. Furthermore, Measurement NiFe2O4 / Fe3O4 Composite materials in 0.2-2 Absorption of 0.0 THz terahertz waves was demonstrated, with an average absorption rate greater than 97% in the 0.2–2.0 THz range, achieving absorption across the entire frequency band and further verifying the excellent cross-frequency absorption performance. The lattice mismatch at the heterojunction forms numerous defects and interfacial dipoles, which generate differentiated polarization effects under excitation by different electromagnetic wave frequencies. This enables the bamboo-like NiFe2O4 / Fe3O4 composite material to maintain excellent high absorption performance across the frequency band from radar waves to terahertz waves.

[0005] This invention breaks through the technical bottleneck of traditional material research and development being limited to single-band wave absorption. It proposes a method for preparing bamboo-like NiFe2O4 / Fe3O4 heterostructures. Unlike the conventional approach of simply mixing materials, this method constructs a heterostructure interface between NiFe2O4 and Fe3O4. The lattice mismatch and charge migration at the interface not only stimulate a multi-polarization loss mechanism, but also achieve absorption of high-frequency radar waves and 0.2-2.0 THz terahertz waves, opening up a new path for the development of multi-band electromagnetic wave stealth material systems. Attached Figure Description

[0006] Figure 1 XRD patterns of NiFe2O4 / Fe3O4 composite materials

[0007] Figure 2 (a) SEM images of one-dimensional rod-shaped nickel-iron precursor and (b) NiFe2O4 / Fe3O4 composite material.

[0008] Figure 3 Microwave absorption properties of NiFe2O4 / Fe3O4 composites with different filling ratios

[0009] Figure 4 Terahertz wave absorption performance of NiFe2O4 / Fe3O4 composite materials Detailed Implementation

[0010] Example 1: 2.6 mmol FeCl3·6H2O, 1.3 mmol Ni(NO3)2·6H2O, and 2.6 mmol terephthalic acid were dissolved in 40 ml N,N-dimethylformamide. The mixture was magnetically stirred for 10 min at a stirring speed of 500 rpm until all particles were completely dissolved. The solution was then transferred to a 100 ml stainless steel autoclave and reacted for 15 hours at 100 °C. After hydrothermal treatment, the mixture was allowed to stand at room temperature to obtain a one-dimensional rod-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then centrifuged at 7000 rpm using N,N-dimethylformamide and anhydrous ethanol, six times in total. The drying temperature was 80 °C, and the drying time was 8 hours to obtain a bamboo-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then placed in a muffle furnace and heated at a rate of 5°C. By heating at ℃ / minute, holding at 450 ℃ for 6 hours, a bamboo-like NiFe2O4 / Fe3O4 can be obtained. Figure 1 The XRD pattern of the NiFe2O4 / Fe3O4 composite material indicates that the NiFe2O4 / Fe3O4 composite material was successfully prepared. Figure 2 The SEM image of the NiFe2O4 / Fe3O4 composite material clearly shows that the bamboo-like structure of the NiFe2O4 / Fe3O4 composite material has an average diameter of approximately 82 nm and an average length of approximately 463 nm. To evaluate the electromagnetic wave absorption performance of the material, Figure 3 The radar wave absorption performance of NiFe2O4 / Fe3O4 composites with different filling ratios is described. When the doping content of this bamboo-shaped NiFe2O4 / Fe3O4 composite material is 70wt%, the reflection loss can reach -39.2 dB, meaning that it can absorb more than 99.99% of the incident electromagnetic waves. With a matching thickness of only 1.8 mm, its effective absorption bandwidth is 4.8 GHz, covering a frequency range of 9.8-14.6 GHz, successfully achieving the absorption of high-frequency radar electromagnetic waves. Figure 4The description focuses on the terahertz wave absorption performance of NiFe2O4 / Fe3O4 composite materials. The prepared NiFe2O4 / Fe3O4 exhibits terahertz absorption performance in the 0.2-2.0 THz range, with an average absorption rate of 97%, an average reflection loss of 18.89 dB, and an average shielding effectiveness of 31.22 dB, achieving absorption across the entire frequency range.

[0011] Example 2: 2.6 mmol FeCl3·6H2O, 1.3 mmol Ni(NO3)2·6H2O, and 2.6 mmol terephthalic acid were dissolved in 40 ml N,N-dimethylformamide. The mixture was magnetically stirred for 10 min at a stirring speed of 500 rpm until all particles were completely dissolved. The solution was then transferred to a 100 ml stainless steel autoclave and reacted for 15 hours at 100 °C. After hydrothermal treatment, the mixture was allowed to stand at room temperature to obtain a one-dimensional rod-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then centrifuged at 7000 rpm using N,N-dimethylformamide and anhydrous ethanol, six times in total. The drying temperature was 80 °C, and the drying time was 8 hours to obtain a bamboo-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then placed in a muffle furnace and heated at a rate of 5°C. A NiFe2O4 / Fe3O4 composite material was obtained by heating at ℃ / min, holding at 550 ℃ for 6 hours. To evaluate the electromagnetic wave absorption performance of the material, the obtained NiFe2O4 / Fe3O4 composite material was mixed with paraffin wax in different proportions. When the filling ratio was 80 wt% and the matching thickness was only 1.65 mm, the effective absorption bandwidth was 3.9 GHz, covering the 12.7-16.6 GHz radar band. The NiFe2O4 / Fe3O4 composite material was then pressed into thin sheets of 2cm*2cm*1mm using a mold. Measurement NiFe2O4 / Fe3O4 Composite materials in 0.2-2 The absorption of 0 THz terahertz waves was demonstrated, with an average absorption rate of 94%, an average reflection loss of 15.25 dB, and an average shielding effectiveness of 30.2 dB in the 0.2–2.0 THz range, achieving absorption across the entire frequency band.

[0012] Example 3: 2.6 mmol FeCl3·6H2O, 1.3 mmol Ni(NO3)2·6H2O, and 2.6 mmol terephthalic acid were dissolved in 40 ml N,N-dimethylformamide. The mixture was magnetically stirred for 10 min at a stirring speed of 500 rpm until all particles were completely dissolved. The solution was then transferred to a 100 ml stainless steel autoclave and reacted for 18 hours at 100 °C. After hydrothermal treatment, the mixture was allowed to stand at room temperature to obtain a one-dimensional rod-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then centrifuged at 7000 rpm using N,N-dimethylformamide and anhydrous ethanol, six times in total. The drying temperature was 80 °C, and the drying time was 8 hours to obtain a bamboo-shaped nickel-iron precursor. The one-dimensional rod-shaped nickel-iron precursor was then placed in a muffle furnace and heated at a rate of 5°C. A NiFe2O4 / Fe3O4 composite material was obtained by heating at ℃ / min, holding at 450 ℃ for 6 hours. To evaluate the electromagnetic wave absorption performance of the material, the obtained NiFe2O4 / Fe3O4 composite material was mixed with paraffin wax in different proportions. When the filling ratio was 80 wt% and the matching thickness was only 1.2 mm, the effective absorption bandwidth was 2.35 GHz, covering the 12.45-14.8 GHz radar band. The NiFe2O4 / Fe3O4 composite material was then pressed into thin sheets of 2cm*2cm*1mm using a mold. Measurement NiFe2O4 / Fe3O4 Composite materials in 0.2-2 The absorption of 0 THz terahertz waves was demonstrated, with an average absorption rate of 92%, an average reflection loss of 13.2 dB, and an average shielding effectiveness of 26.8 dB in the 0.2–2.0 THz range, achieving absorption across the entire frequency band.

Claims

1. A method for preparing a bamboo-like NiFe2O4 / Fe3O4 heterostructure, characterized in that: Ferric chloride hexahydrate, nickel nitrate hexahydrate, and terephthalic acid were added to N,N-dimethylformamide in a 2:1:2 molar ratio. After magnetic stirring, the mixture was placed in a high-pressure reactor and subjected to hydrothermal reaction to form uniform rod-shaped nickel-iron precursors. The hydrothermal reaction temperature was controlled at 100-120℃, and the reaction time was 10-18 hours. The obtained one-dimensional rod-shaped nickel-iron precursors were then centrifuged and dried, followed by heat treatment to obtain bamboo-like NiFe2O4 / Fe3O4 composite materials. The heating rate was controlled at 2-10℃ / min, the holding temperature was controlled at 400-600℃, and the holding time was controlled at 2-8 hours.

2. The method according to claim 1, characterized in that, The magnetic stirring time should be controlled at 10-30 minutes, and the magnetic stirring speed should be 200-1000 rpm.

3. The method according to claim 1, characterized in that, Control the centrifugation speed to 5000-9000 rpm and the centrifugation time to 5-15 minutes.

4. The application of the material obtained according to claim 1, characterized in that, The resulting material was used as a terahertz wave absorbing material.

5. The application of the material obtained according to claim 1, characterized in that, The obtained NiFe2O4 / Fe3O4 was mixed with paraffin in different proportions, with a filling ratio of 20-80 wt%.

6. The material obtained according to claim 5 is used as a microwave absorbing material.

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