Electromagnetic interference shielding effectiveness of multiwalled carbon nanotube reinforced fused silica composites

Electromagnetic interference (EMI) shielding properties of multiwalled carbon nanotube (MWCNT) reinforced fused silica composites were investigated in the frequency region of 26.5–40 GHz (Ka band). The experimental results indicate that the EMI shielding effectiveness (SE) of MWCNT-fused silica composites is sensitive to the MWCNT volume fraction and increases with the increase of the MWCNT content. The average value of EMI SE reaches 68 dB for 10 vol.% MWCNT-fused silica composites at 36–37 GHz, indicating a possible use for commercial application at high frequency. At the same filler loading, MWCNT-fused silica composites show higher EMI SE compared to that of carbon black (CB)-fused silica composites. In particular, the EMI SE of the CB-fused silica composites is easy to be saturated in high frequency. Moreover, the experimental data reveal that the improvement of EMI SE of the MWCNT-fused silica composites is primarily ascribed to the enhancement of conductivity, which leads to dramatic increase of complex permittivity by adding conducting MWCNTs.