Preparation of NiFe2O4 nanorod–graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties

Abstract

Novel NiFe 2 O 4 nanorod-graphene composites were synthesized by a facile one-step hydrothermal process in the presence of 1-propyl-3-hexadecylimidazolium bromide ([PHeIm][Br]). The structure and morphology of as-prepared hybrid materials were characterized by FESEM, TEM, HRTEM, AFM, XRD, FTIR, XPS and Raman spectroscopy. The results showed that uniform NiFe 2 O 4 nanorods with a typical length of about 400 nm and a diameter of about 50 nm were well distributed on graphene sheets. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained composites exhibited a saturation magnetization of 22.5 emu g À1 and a coercivity of 48.67 Oe at room temperature. A minimum reflection loss of À29.2 dB was observed at 16.1 GHz with a thickness of 2.0 mm, and the effective absorption frequency (RL < À10 dB) ranged from 13.6 to 18 GHz, indicating the excellent microwave absorption performance of the novel composites in the range of 13.6-18 GHz. The absorbing performance of the NiFe 2 O 4 nanorodgraphene composites was better than that of the NiFe 2 O 4 nanoparticle-graphene composites.

Graphene nanosheet- and flake carbonyl iron particle-filled epoxy–silicone composites as thin–thickness and wide-bandwidth microwave absorber

“…For example, the RL values of Sample 3 below À5 dB were obtained in the frequency range of 6.9-18 GHz with a thickness of 0.7 mm, and the RL values of Sample 1 below À10 dB were obtained in the frequency range of 10.5-18 GHz with a thickness of 1.0 mm. Detailed EM properties and RL of GN/FCI particle/ epoxy-silicone composites and a comparison of other representative GP/magnetic particle composites [28][29][30][31][32][33][34][35][36][37][38][39][40]42,51] are summarized in Tables 1 and 2. These results indicate that GN/FCI particle-filled composites with wider microwave absorption bandwidth and/or thinner thicknesses can be obtained simply by using GNs and FCI particles as the absorber and then optimizing the filler content and properties.…”

“…In order to effectively improve their absorptions, attention has been directed toward adding magnetic materials to GP-filled composites to enhance their complex permeability. Therefore, GP/magnetic particle-filled composites as MAMs, such as GP/ Fe, GP/Fe 3 O 4 , GP/MnFe 2 O 4 , GP/CoFe 2 O 4 , GP@Fe 3 O 4 @SiO 2 @NiO, and GP/NiFe 2 O 4 , have been intensively investigated to improve the microwave absorption of GP-filled composites [28][29][30][31][32][33][34][35][36][37][38][39][40]. For example, GP/Fe-filled composites with ferromagnetic properties were fabricated and such composites exhibited enhanced EM absorption properties.…”

Broadening Electromagnetic Absorption Bandwidth: Design from Microscopic Dielectric‐Magnetic Coupled Absorbers to Macroscopic Patterns

“…In particular, carbon materials including carbon fibers, carbon nanotubes, and graphene have been widely explored for fabricating lightweight fillers that are effective in microwave absorption composites, with receiving the greatest attention among recent electromagnetic sensitive materials. [13][14][15][16][17][18][19] In the recent study on the carbonbased hybrid fillers, carbon nanotube and graphene nanostructures, mostly reduced graphene oxide (RGO), are more attractive because the sp2 hybridized carbon structure not only provides effective pathways for electromagnetic energy loss, but offers the active site for chemically bonding heterostructures or hetero-atoms in tuning electromagnetic parameters. [20][21][22] In typical examples, Bai and co-workers used polyethylene oxide as the both dispersion agents and matrices in the fabrication of polymeric RGO composites, which show a strong absorption peak around À38.8 dB and an effective absorption bandwidth (the bandwidth with absorption intensity <À10 dB) from 14 to 18 GHz in the investigation range.…”

Enhanced microwave absorption capabilities of Ni microspheres after coating with SnO2 nanoparticles

“…However, too high permittivity of absorber was not beneficial for the impedance match and could result in strong reflection and weak absorption [28,29]. On the other hand, according to free-electron theory [30], e 00 % 1=pe 0 qf , where q is the resistivity, the higher e 00 of Ni microspheres implies the lower resistivity.…”