Electromagnetic interference shielding properties of silicon nitride ceramics reinforced by in situ grown carbon nanotubes

Carbon nanotubes reinforced silicon nitride (CNTs/Si₃N₄) composite ceramics were fabricated. CNTs were introduced into ceramics by catalytic chemical vapor infiltration. Due to the formation of CNTs, the original isolated pores were connected, which lead to the improvement in the electrical conductivity. When CNT content increased from 0 to 2.7 wt%, total shielding effectiveness (SE_T) of ceramics increased from 6.0 to 30.4 dB. The values of complex permittivity that obtained from scattering parameters have been used to calculate electrical conductivity and absorbed shielding effectiveness (SE_A) of the ceramics. Results had shown that combining CNTs and porous Si₃N₄ ceramics can be considered as an effective route to design high performance electromagnetic shielding materials. Comparison of SE_A calculated from different ways indicated that the multi-reflection effect increased with a higher CNT content.