Multiwalled carbon nanotubes-BaTiO₃/silica composites with high complex permittivity and improved electromagnetic interference shielding at elevated temperature

Composites with silica matrix and mixed filler of multiwalled carbon nanotubes (MWCNTs) and BaTiO₃ powder were fabricated. Excellent uniform dispersion of MWCNTs can be obtained using a two-step mixing method. Both of the real and imaginary parts of complex permittivity increased with increasing MWCNT content and measured temperature. The electromagnetic interference (EMI) shielding results showed that the absorption mechanism is the main contribution to the total EMI shielding effectiveness (SE). Compared with the EMI SE resulting from reflection, the absorption showed more dependence on the MWCNT content, measured temperature and frequency. The total EMI SE is greater than 20dB at 25°C and 50dB at 600°C in the whole frequency range of 12.4-18GHz with a 1.5mm composite thickness, which suggests that the MWCNT-BaTiO₃/silica composites could be good candidates for the EMI shielding materials in the measured frequency and temperature region.