Synthesis of Electromagnetic Functionalized Nickel/Polypyrrole Core/Shell Composites

Abstract

Microstructured Ni/PPy (PPy: polypyrrole) core/shell composites were prepared from an in situ chemical oxidative polymerization of pyrrole (Py) monomer in the presence of Ni powder, with ammonium persulfate (APS) as oxidant and citric acid (C6H8O7) as dopant. X-ray diffraction and Fourier transform infrared analyses indicate that there is no chemical interaction between Ni powder and protonated PPy. The mass percentages of PPy, calculated from the remanent weight percentages of Ni/PPy composites after thermogravimetric analysis, are in consistent with those as designed. The prepared Ni/PPy composites are soft and ferromagnetic materials, where a linear increase of saturation magnetization (MS) and remanent magnetization (MR) as a function of Ni powder content is proposed. The permeability of Ni/PPy composites presents a natural magnetic resonance at 6.0 GHz, and Cole-Cole semicircle was applied to explain the permittivity. Electromagnetic absorption less than -10 dB is found for Ni/Py=4:1 (11-15.4 GHz) and Ni/Py=2:1 (12-17.5 GHz). The ternary Debye relaxations for enhanced dielectric loss induced by PPy coatings and proper electromagnetic impedance matching due to the synergetic consequence of the Ni cores and PPy shells contribute to the improvement of the electromagnetic absorption of the Ni/PPy core/shell composites. It is important to notice that dielectric loss and electrical conductivity should be considered simultaneously in designing dielectric-type electromagnetic absorbing materials.

One-step synthesis, electromagnetic and microwave absorbing properties of α-FeOOH/polypyrrole nanocomposites

“…8 shows the results for the reflection loss of the specimens as a function of frequency, in which the thickness for the specimens is 2 mm. The microwave absorbing parameter for the specimens is listed in [13] observed that a relatively low electrical resistivity (namely a relatively high conductivity) is not definitely beneficial to enhancing microwave absorption in nickel/PPy composites. Wan et al [31] proposed that the absorbing parameter of the conducting polymers was not directly proportional to the conductivity.…”

“…Han et al synthesized barium ferrite/PPy nanocomposites [12] and nickel/PPy core-shell nanocomposites [13] and found that the nanocomposites have better reflection loss properties than barium ferrite and nickel alone. Liu et al [14] reported the ZnFe 2 O 4 / PPy core-shell nanocomposites exhibit better microwave absorption performance than ZnFe 2 O 4 alone.…”

“…Thus, it is clear that usage of PPy to make nanocomposites can substantially reinforce the reflection loss of magnetic nanoparticles. However, the synthesis of these PPy nanocomposites is somewhat complex because it needs first synthesis of the magnetic materials and then introduction of nanoparticles into PPy matrix [12][13][14]. Thus, it is desirable to develop a facile one-step synthetic method to produce the electromagnetic PPy nanocomposites.…”

High porosity scaffold composites of graphene and carbon nanotubes as microwave absorbing materials

“…35 In the case of e 0 this is a direct consequence of a higher number of interfaces prompting polarization (Maxwell-Wagner-Sillars effect) associated with the migration and accumulation of charges at the conductive filler/ polymer interfaces. 34 For e 00 , it is due to the reduction of the average distance between adjacent CNTs which, in turn, implies higher dielectric and ohmic losses.…”

Ag3PO4 nanoparticle-decorated Ni/C nanocapsules with tunable electromagnetic absorption properties

“…[2][3][4] Core/shell-structured nanocapsules, comprising a magnetic nanoparticle core and a dielectric shell of nanometer size, have attracted considerable attention because of their synergetic effects between dielectric and magnetic losses for absorbing EM waves. [1][2][3][4][5][6][7] Among various types of core/shell-structured nanocapsules, nickel/carbon (Ni/C) nanocapsules are regarded as a highpotential candidate due to their simple material type, simple preparation process, interesting dielectric and magnetic properties, good EM impedance match, and high EM absorption properties, etc. 1,2,6 For instance, a Ni/C nanocapsule absorber with 2.0 mm thickness exhibits a large reflection loss (RL) of ∼-32 dB at ∼13 GHz and a wide effective absorption bandwidth (for RL<-10 dB) of ∼4.3 GHz (i.e.,11.2-15.5 GHz).…”