Controllable fabrication of lightweight carbon with hierarchically hollow structure for enhanced microwave absorption

Herein, lightweight amorphous carbon blocks with hierarchically hollow structure are fabricated through a facile thermal treatment of furfuryl alcohol with silica nano/microparticles as template. The walls formed the spherical voids are also porous structure, which generates a heterogeneously porous structure. This unique structure can effectively reduce the densities of the carbon blocks (≤87 ± 2.1 mg/cm3). The thermal treatment temperature has a great effect on the porosity and graphitization of the final samples, and a lowest density of 59 ± 1.4 mg/cm3 is obtained from the sample prepared under the carbonization temperature of 950 °C. More importantly, the as-obtained lightweight amorphous carbon shows excellent microwave absorption (MA) properties, and a minimum reflection loss value of −57.2 dB and absorption bandwidth of 4.4 GHz are gained for the absorber with a thin thickness of 1.7 mm possessing the lowest density with a low filling rate of 7.5 wt%. The excellent MA properties combining with the lightweight density and low loading rate make the heterogeneously porous carbon materials be promising candidates for practical application in MA absorption field.