Effect of Carbon Nanotubes' Dimension on Microwave Absorption Property of Polyaniline Nanocomposites

Abstract

Hexanoic acid (HA) doped PAni nanocomposites which containing aniline (Ani) as monomer was synthesized via template free method. Dielectric (titanium dioxide, TiO2) and magnetic (different dimension of multiwall carbon nanotubes (MWNT)) materials have been added to improve the dielectric and magnetic behavior of the PAni nanocomposites. Fourier transform infrared (FTIR) spectrometer, ultraviolet-visible (UV-Vis) spectrometer and X-ray diffractometer (XRD) analysis confirmed the chemical structure of doped-PAni. Morphology study and thermal behavior of the PAni nanocomposites have been investigated by field emission scanning electron microscope (FESEM) and thermal gravimetric analyzer (TGA), respectively. PAni nanocomposites with longer length and bigger diameter of MWNT possess the highest conductivity (1.51 × 10−2 S/cm) compared with those shorter length and smaller diameter PAni nanocomposites. Microwave absorption study was investigated by microwave vector network analyzer (MVNA) from 0.5 to 18 GHz. Among all the PAni nanocomposites, PAni nanocomposites with MWNT (φ = 10–20 nm, l = 5–15 μm) possess a sharp and narrow peak with high absorption (RL = −58 dB) at 7 GHz. In this study, it is observed that PAni nanocomposites with longer length and smaller diameter exhibit the largest amount of entangled nanorods/nanotubes that will eventually enhance the heterogeneity of the nanocomposites. Thus, it significantly induces the space charge polarization along the PAni backbone and indicates the strongest microwave absorption.