Preparation and Microwave Absorption Properties of Cenospheres-Barium Ferrite Composites

Abstract

The magnetic composites with low density of cenospheres-barium ferrite were prepared by a sol-gel self-propagating combustion technology. The morphology, structure, electromagnetic properties and microwave absorption properties of the composite powders were characterized by the scanning electron microscope, thermogravimetry-differential scanning calorimetry, X-ray diffraction, vibrating sample magnetometer and vector network analyzer. The results show that cenospheres were covered with barium ferrite coating of ca 5 nm to 15 nm in thickness. The size of barium ferrite coated particles is less than 60 nm. In addition, it is found that the composites are composed of barium ferrite, hematite, minor mullite and quartz, and the magnetic properties of the composite material could be enhanced with the increasing mass ratio of barium ferrite to cenospheres. Furthermore, the samples exhibit better dielectric loss and magnetic loss properties within a frequency range from 2 GHz to 18 GHz. The maximum reflection loss of the composite material of 1.5 mm in thickness reaches -29.2 dB at 14.2 GHz and the bandwidth for reflection loss of -10 dB is 4.5 GHz.