Preparation of carbon-based microwave absorbing materials by hybrid activation pyrolysis of lignin and coal

Abstract

• Preparation of carbon materials by potassium hydroxide activation. • Lignin and coal synergistically improved the microwave absorption performance. • The best reflection loss of the prepared carbon-based material was -61.02 dB. In this work, the cheap and eco-friendly microwave absorber materials were prepared by the activation pyrolysis of lignin and coal blends. The microwave absorption performance of the carbon materials prepared by mixing and activation of lignin and coal is more than twice as high as that of pure coal and lignin carbon-based materials. The optimum reflection loss of -61.02 dB at 6.16 GHz and less than -10 dB in the frequency range of 4.72 GHz to 7.6 GHz, with an effective absorption bandwidth of 2.88 GHz. The results indicate that the lignin and coal mixture have a synergistic effect during pyrolysis, which can effectively improve the pore structure and graphitization degree of the carbon material, thus improving the microwave absorption performance of the material. This study provides a low-cost and effective way to produce lightweight and efficient microwave absorbing materials.