| Single absorbent is difficult to meet the requirements of thin, light, wide bandwidth and strong absorption for modern absorbing materials. Compounding different types of absorbents for developing high performance microwave absorbing materials has attracted a lot of attention recently. In this paper, new types of barium titanate (BaTiO3) composite absorbents have been synthesized. The phase structure, morphology, chemical composition, magnetic properties and electromagnetic characteristies in the frequeney range of 2-18 GHz were studied by means of X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS), Vibrating sample magnetometer (VSM), Vector network analyzer. And, the microwave absorption properties were evaluated by calculating the reflection loss.BaTiO3/Ni composite powders were prepared by an electroless plating technique using hydrazine hydrate as a reducing agent. It is found that Ni coating layer possesses a crystalline structure. Ni particles vary from sphere to needle and flake with the increase of plating bath temperature. The shape of the Ni particles is insensitive of the loadage. The complex permittivity and permeability are influenced by the shape and content of the Ni particles. A minimum reflection loss of-50.3 dB is reached for BaTiO3/Ni-paraffin complex containing needle-like and flake-like Ni particles with a matching thickness of 1.7 mm. The microwave absorption capability of the needle-like and flake-like particles is significantly better than that of the spheric particles. The absorption efficiency of the composite powders does not increase monotonically with an increase in the Ni content, and there is an optimal Ni content.BaTiO3/Co and BaTiO3/Co-Ni composite powders were prepared via electroless plating approach by using hydrazine hydrate as reducing agent. The results show that the deposited Co coating is of crystalline structure. Both the complex permittivity and permeability of the BaTiO3/Co composite powders increase with the increasing amount of Co. The absorption frequency band can be tuned through changing loadage. The deposited Co-Ni coating is crystalline. The microstructure of the Co-Ni coating is independent of the composition of the coating. The ratio of metal in the deposited coating is consistent with the ratio of metal ions in the plating bath. The complex permittivity and permeability of the BaTiO3/Co-Ni composite powders are dependent on the compision of the deposited coating. When the ratio of Co to Ni is 3:1 and 1:3, the corresponding BaTiO3/Co-Ni composite powders-paraffin complexs present good microwave absorption performances with thinner thickness. Particularly when the ratio of Co to Ni is 3:1, the corresponding paraffin matrix complex of only 1mm thickness can absorb more than 90% of incident electromagnetic wave over the frequency range of 9.8-18GHz.Cobalt ferrite (CoFe2O4) powders were synthesized through a copreeipitation method. It is found that pH value of 12, stirring speed of 1000 rpm and adding dropwise NaOH solution in mixed salt solution, are optimal to achieve CoFe2O4 powders with relatively high saruration magnetization. BaTiO3/CoFe2O4 composite powders were fabricated by a sol-gel method, using CoFe2O4 powders prepared under optimal conditions as core material. The experimental results indicate that, with increasing BaTiO3 content, the uniformity of BaTiO3 coating layer is reduced and the defects are increased. The variation in the components of the composie powders has significant effect on the complex permittivity, but it has relatively small effect on the complex permeability. The paraffin matrix complex containing BaTiO3/CoFe2O4 composite powders with BaTiO3 content of 70% shows best microwave absorption properties with a minimum reflection loss of-41 dB on an absorber with thickenss of 1.2 mm.
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