Three dimensional carbon aerogel for microwave absorption from chitosan

Abstract

3D carbon aerogel is widely used for the fabrication of microwave absorption materials as it is characterized by tunable dielectric properties, ultra-low density, high porosity, and ultra-large specific surface area. We synthesize phenolic aerogels using chitosan as a soft template, phenol and formaldehyde as carbon sources, and acetic acid as a catalyst. We explore the influence of the carbonization temperature on the materials' microstructure, chemical composition, and absorption performance. We also study the mechanism of microwave absorption. The results revealed that carbonized carbon aerogel is characterized by a typical porous structure and a large specific surface area. It was also observed that the degree of carbonization improved with an increase in the carbonization temperature. The minimum reflection loss for the carbon aerogel (carbonized at 700 °C) with a filler loading of 15 wt % is recorded to be −41 dB at 12.24 GHz. The effective absorption bandwidth can reach 5.24 GH at 2.5 mm. The minimum reflection loss for the carbon aerogel (carbonized at 750 °C) with a filler loading of 8 wt % was −36 dB at 13.12 GHz. Under these conditions, the effective absorption bandwidth can reach 4.88 GH. When the thickness is only 1.5 mm, the minimum reflection loss is −14 dB, and the effective bandwidth can reach 4.2 GHz. The fine absorption performance can be attributed to the excellent dielectric constant of the material and the property of impedance matching. The results indicate that the synthesized lightweight and efficient carbon can promote the development and application of microwave-absorbing materials.