Carbon Nanospheres for Electromagnetic Wave Absorption and Shielding

Here, composites filled with carbon nanospheres of different morphologies exhibit the same electromagnetic wave (EMW) absorption and loss mechanisms when they possess the same carbon content. Conductive loss is their primary EMW absorbing mechanism, while the effect of polarization loss can be ignored entirely. Composites with a filling amount lower than the percolation threshold of the carbon nanospheres and certain conductivity possess excellent EMW absorbing behavior, while composites with a filling amount close to or higher than the percolation threshold reveal outstanding EM interference (EMI) shielding. The minimum reflection loss (RLmin) and maximum effective absorption bandwidth (EABmax) of mesoporous carbon hollow nanospheres (MCHS) reach −50.52 dB and 5.90 GHz at an ultralow filling amount of 3 wt %. The EMI shielding effectiveness (SE) of the MCHS is as high as 118.23 dB at a fill level of 12 wt %, with an average SE of 84.50 dB. Among them, conductive loss has a more significant contribution to low-frequency EMW absorption. Frequency-selective EMW absorbing performance can be obtained by simply adjusting the material conductivity. Compared with the currently reported carbon nanomaterials, the carbon nanospheres in this study reveal significant advantages in EM-resisting performances and unique low-filling characteristics.