Controllable synthesis of mesoporous carbon hollow microsphere twined by CNT for enhanced microwave absorption performance

The low dielectric loss of mesoporous carbon hollow microsphere (PCHM) requires high filler loading (higher than 20 wt%) when it is used as microwave absorbers. In order to decrease the filler loading of PCHM, a new strategy for synergistic increase of polarization and conductive loss was developed by twining PCHM with carbon nanotube (CNT) according to theoretic calculation. By the optimization of CNT content, the minimum reflection coefficient was -34.6 dB with a filler loading of only 10 wt%, which was much lower than -2.1 dB of PCHM. In addition, the effective absorption bandwidth was 3.6 GHz at X band with a thickness of 2.8 mm. The enhanced microwave absorption performance can be ascribed to the unique combination of hollow PCHM and one-dimensional CNT with higher graphitization degree, leading to increase of conductivity and heterogeneous interfaces. As a result, the conductive loss increased from 0.12 to 2.27 and polarization loss increased from 0.15 to 0.67, achieving the balance between attenuation ability and impedance match.