Preparation of Multiwalled Carbon Nanotube/Si3N4/Polyaniline Ternary Composites and Their Microwave Absorption Properties

Herein, multiwalled carbon nanotube (MWCNT)/silicon nitride (Si3N4)/polyaniline (PANI) ternary composites are prepared. The preparation method involves attaching carboxyl groups to acid-modified MWCNT surfaces and amino groups to Si3N4 surfaces modified using a silane-coupling agent. Then they are combined to binary composites using the solvent-thermal method. Finally, the ternary composites are prepared by coating PANI on the surface of MWCNT/Si3N4 composites in situ polymerization. The morphology and structure of these composites are characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Results show that the reflection loss at 8.8 GHz reaches -42.57 dB when the feeding ratio of MWCNT:Si3N4:PANI is 3:20:40 and the corresponding effective absorption bandwidth reaches 4.06 GHz when the thickness is 3.5 mm. A conductive network with effective electron leaps is formed among MWCNT, Si3N4, and PANI, which increases the conductive loss of the composites. An abundant number of interfaces have formed in the composite materials and promoted dielectric loss. Multiple loss mechanisms and good impedance matching performance endow MWCNT/Si3N4/PANI with excellent microwave absorption performance, and the incorporation of Si3N4 enables the composites to exhibit satisfactory high-temperature resistance. Thus, these performances render the composites promising materials to address increasing electromagnetic pollution, particularly at high temperatures.