Synthesis of Electromagnetic Functionalized Fe₃O₄ Microspheres/Polyaniline Composites by Two-Step Oxidative Polymerization

Abstract

Composites consisting of Fe(3)O(4) microspheres (FMS) and polyaniline (PANI), FMS/PANI, have been successfully prepared through a two-step oxidative polymerization of aniline monomers in the presence of Fe(3)O(4) microspheres. In our two-step polymerization technique, Fe(3+) and ammonium persulfate (APS) are used as the oxidants in each step. It is discovered that the two-step oxidative process plays a dominant role in the morphology of these composites: aniline oligomers oxidized by Fe(3+) are mainly produced in the first stage, and "egg-like" PANI aggregates are obtained in the second stage. It can be found that embedding Fe(3)O(4) microspheres in the polymer matrixes will not only modulate the complex permittivity but also produce magnetic resonance and loss in the composites. Therefore, the characteristic impedance and reflection loss of these composites are greatly improved. Especially, the composite with equal amount of FMS and PANI, FMS/PANI(50), displays very strong reflection loss over a wide frequency range that can be manipulated by the absorber thickness. More importantly, the composites prepared from the two-step chemical oxidative polymerization using hierarchical magnetic materials have better microwave absorption and environmental stability as compared with those composites from Fe(3)O(4) nanoparticles, one-step oxidative polymerization, and physical mixture. We believe the two-step oxidative polymerization technique can be a novel route for the design and preparation of lightweight and highly effective microwave absorbers in the future.

Polyaniline containing W-type hexaferrite composites for microwave absorption in high-frequency applications

“…whereas the imaginary part (μ″) of the permeability remains constant with a little fluctuation in the measured frequency range. The increase results of the μ′ of the composites with the increasing PANI ratio were consistent with that of polymer-ferrite composites reported in the papers [25,26], although some of the opposite results were reported in the previous papers [27,28]. With the increasing frequency, the magnetic dipole tries to rotate with the frequency, but at a higher frequency due to the strong anisotropy, the induced magnetization (B) lags behind the applied field (H), which results in magnetic losses.…”

Interfacially Engineered Sandwich‐Like rGO/Carbon Microspheres/rGO Composite as an Efficient and Durable Microwave Absorber

“…However, the high complex permittivity and preferable tan δ e of rGO (Figure 3 a-c) also fail to endow excellent microwave absorption, because there is another important parameter relating to the refl ection loss properties of microwave absorbers, the concept of matched characteristic impedance, where the characteristic impedance of the absorbing materials should be equal/close to that of the free space (377 Ω sq −1 ) to achieve zero refl ection at the front surface of the materials. [ 3,59 ] In general, an overly large difference between complex permittivity and complex permeability is not favorable for the matching of characteristic impedance and always results in strong refl ection of the incident EM wave at the surface of absorbers. [ 9,33 ] In our case, the rather limited complex permeability from these carbon materials means that their complex permittivity should be controlled within a rational range.…”

“…[1][2][3] Microwave absorbers with low refl ection and high absorption have received extensive attention in recent years due to their promising functions for regulating the multi-interfaces and triple junctions were considered to be greatly helpful to the attenuation of incident EM waves. [ 24 ] Although these graphene-based composites make signifi cant achievements, it has to point out that these improvements on microwave absorption are at the expense of the low density of graphene, which will hinder their practical application; meanwhile, poor chemical stability of magnetic metals/metal oxides cannot guarantee their durable performance.…”

Porous Flower-like α-Fe2O3 Nanostructure: A High Performance Anode Material for Lithium-ion Batteries

“…Among the transition metal oxides, hematite (α-Fe 2 O 3 ) has attracted great interest due to its favorable properties, such as low cost, good stability, nontoxicity, and environmental friendly properties. It has been studied for applications in Li-ion batteries [7][8][9][10], supercapacitors [11][12][13], magnetic materials [14,15], catalytic agents [16], gas sensors and so on [17,18].…”