Influence of silica fume additions on electromagnetic interference shielding effectiveness of multi-walled carbon nanotube/cement composites

Dispersion of carbon nanotubes (CNTs) in cement matrix has been a stumbling block to take advantage of their outstanding physical properties. Silica fume (SF), which was often used to disperse fibers in cement matrix materials, was selected in an effort to disperse CNTs. The present study aimed to test electromagnetic interference shielding effectiveness (EMI SE) of cement matrix materials that incorporated both SF and multi-walled carbon nanotube (MWNT) with varying weights and to investigate the influence of SF addition on EMI SE of MWNT/cement composites. The EMI SE of each specimen was determined using a network analyzer with a coaxial transmission line. The results were observed to compare EMI SE of each case with respect to variation of SF addition (or MWNT addition) in a frequency range of 45 MHz–18 GHz. When 0.6 wt.% of MWNT and 20 wt.% of SF were added in a cement–matrix material, the greatest EMI SE was obtained at 0.94 GHz, 1.56 GHz, and 2.46 GHz. The reflection loss in EMI SE was superior to the absorption loss for all kinds of specimens at 0.94 GHz, 1.56 GHz, and 2.46 GHz, but was reversed at 10 GHz.