| Nowadays,due to the rapid development of information technology and high-power electronic equipment,various novel electronic products in modern society are playing an increasingly important role in people's lives.However,electromagnetic radiation has become a serious environmental pollution problem,which endangers human health.Electromagnetic wave absorbers can absorb and convert electromagnetic wave energy into thermal energy and other forms of energy,which has proven to be an effective method to solve the problem of electromagnetic radiation pollution.Therefore,it is of great significance to develop effective electromagnetic wave absorbing materials.Ferrite is the earliest and most widely used wave absorbing material.Due to its unique structure with high uniaxial magnetic crystal anisotropy,it is widely used in the field of wave absorbing materials.In this paper,the barium ferrite(BaFe12O19)prepared by a two-step molten salt method was used as the matrix,and the barium ferrite-based composites with core-shell structure were successfully prepared by hydrothermal method and in-situ polymerization method.The phase composition,morphology,and microwave absorption properties were analyzed and studied.The effects of different reaction parameters on the absorbing properties of composite materials were discussed.The results of research indicate:The core-shell BaFe12O19@MnO2 and BaFe12O19@MoS2 composites prepared by a simple one-step hydrothermal method exhibit good microwave absorption capabilities.Both MnO2 and MoS2 can be well coated on the surface of BaFe12O19,they can enhance the interfacial polarization and the dielectric loss ability of the composites and improve the impedance matching of the composites.When the hydrothermal temperature is 170?,the BaFe12O19@MnO2 composite exhibits the best absorption performance.The maximum reflection loss value is-54.39 dB at 11.26 GHz,and the effective absorption bandwidth is 3.25 GHz with the matching thickness of 2.60 mm.When the added amount of thiourea is 28 mmol,the reflection loss of BaFe12O19@MoS2 composite can reach-61.0 dB at 16.01 GHz with the matching thickness of 1.70 mm and the effective absorption bandwidth is 4.4 GHz.Using dopamine hydrochloride as raw material,BaFe12O19@PDA precursor was prepared by in-situ polymerization.Under the protection of Ar gas,a series of BaFe12O19@C composites were prepared at different calcination temperatures.The carbon can significantly improve the dielectric loss capability of the composites,while the calcination temperature has a greater impact on the microwave absorption properties of the composites.When the calcination temperature is 800?,the absorption performance of the composite is significantly improved,and its reflection loss value reaches-59.22 GHz corresponds to the effective absorption bandwidth of 4.48 GHz and the matching thickness is only 1.72 mm.Through the hydrothermal method,the Ni-Zn MOFs were supported on the BaFe12O19 matrix prepared by the molten salt method.Subsequently,under the protection of Ar gas,the pyrolysis reduction reaction was performed in a tube furnace at different temperatures to prepare BaFe12O19/ZnO/Ni/C composites.The experimental results showed that the pyrolysis temperature can significantly affect the absorbing properties of composites and BaFe12O19/ZnO/Ni/C composites obtained by pyrolysis reduction at 800? and 900? showed good absorbing properties.At 800?,the reflection loss value of the sample reaches-45.46 dB when the matching thickness was 1.56 mm corresponding to effective absorption bandwidth of 2.72 GHz.At 900?,the reflection loss value of the sample when the matching thickness was 2.20 mm up to-43.5 dB corresponding to effective absorption bandwidth of 4.88 GHz. |
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