Ferrite-grafted polyaniline nanofibers as electromagnetic shielding materials

Abstract

A functional structure of Mn 0.5 Zn 0.5 Fe 2 O 4 -on-polyaniline nanocomposites with high dielectric absorbing properties and electromagnetic shielding effectiveness at low frequencies was successfully fabricated through a facile in situ emulsion polymerization. Polyaniline (PANI) was doped with hydrochloric acid to improve its electrical properties and interactions with ferrite nanoparticles. The electrostatic force, paramagnetic force and hydrogen bonding strongly bonded or assembled ferrite nanoparticles on the polyaniline surface and improved the thermal stability of the polyaniline nanostructure. Polyaniline nanofibers were found to have an average diameter of 100 nm and length of 500 nm, consisting of a bundle of smaller individual units, whereas ferrite nanoparticles were of spherical shape with an average diameter 30 nm. The research findings show that ferrite particles overcome the common problem of aggregation and evenly dispersed on the surface of polyaniline. The ferrite-grafted polyaniline nanostructures were demonstrated as a promising functional material for the absorbing of electromagnetic microwaves because of a large amount of dipole polarizations in the polymer backbone and at the interfaces of the ferrite nanoparticles and polyaniline nanofibers. Both the complex permittivity and shielding effectiveness of the ferrite-grafted polyaniline nanocomposites increased with the increasing weight percentage of PANI. There is also a good match of real and imaginary parts of the complex permittivity, giving rise to almost an equal dielectric loss angle tangent in the measured frequency (30 MHz to 1 GHz). This superior property allows the nanocomposites to function within an extended absorbing band.

Optimization of multiroute synthesis for polyaniline-barium ferrite composites

“…These results reveal that composites obtained by solid-based polymerization exhibit higher thermal stability than that of composites obtained by aqueous-based polymerization. It can be attributed to their lower oxidation level and doping degree, as confirmed FTIR analysis [43]. This latter may be calculated [49] using the obtained results from Fig.…”

“…In fact, unlike solventless medium, in aqueous medium, there is more contact between the monomer, oxidant and ferrite particles [42]. In HCl solution, aniline monomer can form easily anilinium ions, while, chloride ions can compensate the positive charges on BaFe 12 O 19 surface, as a result electrostatic forces are created between anions adsorbed at ferrite surface and anilinium ions [43]. These electrostatic interactions favour the aggregation of PaniBaFe 12 O 19 nanocomposites [44].…”

Synthesis and excellent electromagnetic absorbing properties of copolymer (N-methylpyrrole-co-pyrrole) and Ba–Nd–Cr ferrite

“…However, their applications in the military industry especially as the EMW absorbents are limited by the higher http applying frequency and their relatively narrow absorption bandwidth. In order to obtain the ideal EMW absorption materials featuring thin thickness, lower density, wider bandwidth, better flexibility and so on, the absorbing properties of binary composites formed by the conductive polymers and ferrites have aroused researchers' attention [24][25][26]. For example, the Mn 0.5 Zn 0.5 Fe 2 O 4 -grafted polyaniline nanocomposites possess the shielding effectiveness ($6 to 20 dB) in the low frequency range of MHz when the weight percent of polyaniline is above 60% [24].…”

“…In order to obtain the ideal EMW absorption materials featuring thin thickness, lower density, wider bandwidth, better flexibility and so on, the absorbing properties of binary composites formed by the conductive polymers and ferrites have aroused researchers' attention [24][25][26]. For example, the Mn 0.5 Zn 0.5 Fe 2 O 4 -grafted polyaniline nanocomposites possess the shielding effectiveness ($6 to 20 dB) in the low frequency range of MHz when the weight percent of polyaniline is above 60% [24]. The hard-soft BaFe 12 O 19 /polypyrrole nanocomposites show the minimum reflection losses of À25 dB at the frequency of 11.5 GHz [19].…”

Nanoferrites as Catalysts and Fillers for Polyaniline/Nanoparticle Composites Preparation

“…Among them, intrinsically conducting polymers (ICPs) containing magnetic nanoparticles (NPs) exhibit many potential applications in electromagnetic interference shielding, [2] electrochromic devices [3] and non-linear optical systems [4]. Polyaniline (PANI) is one of the most investigated ICPs thanks to its extraordinary electrical properties, reversibly switching from an insulator to a conducting material by deprotonation/protonation processes [5,6]. It can exist in different forms: leucoemeraldine (totally reduced form, x = 1 in Figure 1), emeraldine (half-oxidized form, x = 0.5 in Figure 1), pernigraniline (totally oxidized form, x = 0 in Figure 1) and many other intermediate structures (Figure 1).…”