Xian Wang

Preparation and microwave absorption properties of metal magnetic micropowder-coated honeycomb sandwich structures

Radar absorbing materials with metal magnetic micropowder-coated honeycomb sandwich structures are prepared by a spray process. Metal magnetic micropowder is applied as an absorber which maintains a high absorption, and a honeycomb sandwich structure as a supporter enhancing mechanical strength. The microwave absorption properties are measured by a network analyzer system in the frequency range of 2.6–18 GHz. The concentration of the MMP and the coating thickness of the absorber affect the attenuation properties, a suitable value of them contributing to a broad bandwidth and high loss. A matching layer is introduced to the honeycomb sandwich structure on top, which allows the incident electromagnetic wave to enter and largely get attenuated through the absorbing system, increasing the microwave absorption.

Electromagnetic Properties and Impedance Matching Effect of Flaky Fe–Si–Al/Co2Z Ferrite Composite

Fe–Si–Al/Co2Z ferrite composites were prepared by ball-milling. The microstructure, microwave electromagnetic properties, and impedance-matching performance of a series of composites were determined and the results are discussed. Experimental results indicated that, in frequency range 1–18xa0GHz, the permittivity and permeability of the complexes can be adjusted by changing the Fe–Si–Al-to-Co2Z weight ratio. Calculated reflection losses indicate that the absorption performance of Fe–Si–Al/Co2Z ferrite composites is superior to that of the pure Fe–Si–Al and Co2Z ferrites. It was found that the impedance-matching performance of the materials, which contributes to perfect absorption, can be improved by use of an appropriate weight ratio for the Fe–Si–Al/Co2Z ferrite composite.

Influence of Zinc-Zirconium Substitution on Magnetic Properties of Ba(ZnZr)xFe12-2xO19 Hexaferrite Prepared by the Molten Salt Method

M-type hexaferrites Ba(ZnZr)xFe12-2xO19 (x=0, 0.5, 1.0, 1.5) powders, have been synthesized by molten salt method, where x varies from 0 to 1.5 in steps of 0.5. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer(VSM) were used to analyze the structures and magnetic properties. The results showed that, the magnetoplumbite structures for all samples calcining at 1100°C have been formed. The magnetic hysteresis loop measurements of the hexagonal ferrites powders showed that the saturation magnetization (Ms), the remanent magnetization (Mr), and the coercitivity (Hc) of ferrites depend strongly on the chemical compositions of materials. The data showed that the max Hc was obtained when substitution of x=1.0 (Hc=63.9 Oe), while the best Ms was obtained when substitution of x=0.5 (Ms=54.02 emu/g). Zn and Zr substitutions greatly modified the magnetic properties of BaM hexaferrite.

Design, fabrication and characteristic of two-layer microwave absorbers composed of magnetic micropowder-rubber composites in X-band frequency range

Both experimentally and theoretically, a two-layer microwave absorber exhibits the possibility of meeting the demand for effective radar absorbing materials. The design methodology is based on the modulus of permittivity (permeability) which obeys a logarithmic law of mixtures, and the loss tangent is related through a linear law of mixtures. A linear regression analysis performed on the data points provides constants that can be used to predict the effective parameters at different frequencies, and a program is presented that computes the optimum amount of magnetic micropowder and the required thickness for each layer. A two-step sulfur treatment is then applied to preparation of the two-layer absorber, vulcanized firstly by heating at 165 °C for 15 min and then at 150 °C for 4 h. Finally, tensile strength is experimentally investigated as well as power reflection coefficient. Test results indicate the two-layer absorber has excellent mechanical and microwave attenuation properties for X-band frequency.

Electromagnetic Noise Suppression Characteristics of FeCoBM-Al2O3 Amorphous Soft Magnetic Films

The electromagnetic noise suppression characteristics of a series of FeCoBM -Al2O3 amorphous soft magnetic films were reported in the frequency range from 0.5GHz to 6 GHz. Effect of dopants on the reflection coefficient (S11), transmission coefficient (S21) and power loss (PLOSS/PIN) of as-deposited FeCoBM(M=Nb, Zr, Hf, Ta, Mo, Ti)-Al2O3 films were studied. The (Fe40Co40B20)89Mo8–(Al2O3)3 film had the highest power loss with the value of 0.85 at 6GHz. The transmission properties of the FeCoBNi-Al2O3 also studied in the paper. The power loss of the (Fe40Co40B20)68.36Ni28.64–(Al2O3)3 film was more than 0.6 from 3.0-6.0GHz, which had the best electromagnetic noise suppression characteristics. These results show that the presented films possesses potential in noise suppressor applied in electronic devices .

Effect of Dopants on the Microwave Magnetic Characteristics of FeCoBM-Al2O3 Soft Magnetic Thin Films

A series of FeCoBM (M=Nb, Zr, Hf, Mo ,Ta, Ti)–Al2O3 films were prepared on glass and polymer substrates by means of RF magnetron co-sputtering. Effect of dopants on the soft magnetic properties and microwave magnetic characteristics of FeCoBM-Al2O3 Thin Films were studied. To further tailor the magnetic characteristics of the films, the (Fe40Co40B20)94.5Hf2.5–(Al2O3)3 film was annealed at 200 to 400°C for 60 min. As a consequence, the (Fe40Co40B20)94.5Hf2.5–(Al2O3)3 film annealed at 350°C exhibit excellent properties with high saturation magnetization of 1197 kA/m, high resonant frequency of 1.76 GHz, and the real part of permeability is about 600, which is maintained up to 1.5GHz. These results show that the presented films possesses potential in designing micro-magnetic devices for Monolithic Microwave Integrated Circuit (MMIC) and surface mount technology (SMT)industry.