Development of a hollow carbon sphere absorber displaying the multiple-reflection effect to attenuate electromagnetic waves

Abstract

The development and use of hollow amorphous carbon spheres has been considered to be an efficient strategy to combat severe electromagnetic interference. In the current work, hollow carbon spheres were treated at various high temperatures to improve their graphitization levels and conductivity loss abilities in an attempt to best eliminate the unwanted electromagnetic wave. Of the various samples tested, the hollow carbon spheres obtained at 900 °C showed the best and excellent electromagnetic absorption, with a reflection loss value (RLmin) of up to -23.0 dB and the ability to effectively absorb frequencies spanning a range of 4.4 GHz, when using a sample layer with a thickness of only 1.5 mm. A mechanism for the electromagnetic absorption was proposed. Besides the strong conductivity, the occurrence of multiple reflections of electromagnetic waves in the interior void was indicated to strengthen the attenuation of the electromagnetic wave.