Fabrication of Magnetic Cobalt and Electrically Conductive Polyaniline‐Filled Three‐Phase Nanocomposite for Microwave Absorption

Abstract

Magnetic cobalt (Co) and electrically conductive polyaniline (PANI)‐filled polyurethane (PU) composite (Co@PANI@PU) film is proposed for microwave absorption. This three‐phase Co@PANI@PU composite is fabricated through mechanical ball milling of Co microspheres and PANI particles, followed by their casting forming with PU. Prior to that, Co microspheres and conductive PANI are synthesized by ultrasonic‐assisted solution reduction and simple oxidation polymerization, respectively. Field‐emission scanning electron microscopy and X‐ray diffraction characterizations indicate that the Co microparticles have sufficient incorporation into PANI and PU matrices. Electrical conductivity measurement shows that the PANI composition improved the conductivity of Co@PANI@PU film, whereas the Co composition suppressed it. The microwave absorption property of these Co@PANI@PU composite films under low filling contents of Co and PANI, and with small thickness (1 mm), is investigated in the 0.1–18 GHz range. The results indicate that the reflection loss increased with increasing Co and PANI compositions. 16:8:100 w/w/w Co@PANI@PU shows the highest absorption within 0.1–8.8 GHz, whereas 16:16:100 Co@PANI@PU absorbed most at 10.2–18 GHz. This is attributed to different contributions of permittivity and permeability of the Co and PANI compositions to energy loss in the two frequency bands. Therefore, appropriate ratio and content of the Co and PANI compositions play significant roles for frequency‐adjustable microwave absorption.