Ferromagnetic and excellent microwave absorbing properties of CoNi microspheres and heterogeneous Co/Ni nanocrystallines

Abstract

CoNi microspheres with different diameters and heterogeneous Co/Ni nanocrystallines were synthesized via changing hydrothermal reaction parameters.

Synthesis of Electromagnetic Wave-Absorbing Co–Ni Alloys and Co–Ni Core–Shell Structured Nanoparticles

“…The preferred RL value is −20 dB, with a microwave absorption efficiency of about 99% . In almost all cases, ,, the absorption properties have been investigated by controlling the sheet thickness of the composite, and the investigation related to Co–Ni alloy nanoparticles is hardly reported. In this study, as in the above reports, the microwave absorption properties are evaluated by varying the thickness of Co–Ni core–shell and Co–Ni alloy–polyethylene composite sheets.…”

“…Considering the difficulty in large-scale synthesis of either FeCo or FeNi, Co–Ni nanocrystals that also possess high saturation magnetization and high magnetic permeability have attracted considerable attention as microwave absorbers. ,,, The microwave absorption properties of Co–Ni alloys attributed to ferromagnetic, dielectric, and eddy current losses are influenced by the particles’ morphology, size, and structure. Composites of Co 50 Ni 50 , or Co 20 Ni 80 , particles with varying sheet thicknesses have been studied in frequencies between 2 and 18 GHz, , and a maximum RL value of −34 dB at 3 GHz has been reported .…”

Extending effective microwave absorbing bandwidth of CoNi bimetallic alloy derived from binary hydroxides

“… Sample Filling ratio (wt %) Minimum RL value RL ≤ − 10 dB References d m (mm) RL min (dB) d m (mm) f e (GHz) CoNi microspheres 60 2.5 − 41 1.5 4.16 Ref. 41 CoNi microflowers 20 2 − 28.5 2 6.5 Ref. 42 Co 67 Ni 33 /Ni 0.6 Zn 0.4 Fe 2 O 4 60 2.1 − 43.8 2.1 5 Ref.…”

Synthesis of Ni0.5Zn0.5Fe2O4-reinforced E-glass/epoxy nanocomposites for radar-absorbing structures

“…Microwave absorption corresponding to a reflection loss of −10 dB, which is considered suitable for a microwave absorber, was observed in RAS 5 and RAS 6, with a thickness of 4 mm. In a recent study [36], a 3-GHz bandwidth and an RL of −33 dB at 17.6 GHz were achieved; however, a high weight percentage (60%) of magnetic filler was required. In this work, RAS 5 exhibited a maximum RL of −33 dB at a frequency of 9.6 GHz while only requiring 10 and 25 wt-% of NZF in the first and second layers, respectively.…”

“…The combination of polyaniline (PANI) coated MWCNTs with manganese zinc ferrite exhibited a maximum RL of −32.5 dB at 10.8 GHz [33]. The drawback of the magnetic materials that have been used as radar-absorbing materials in the literature is that they are effective only when used in high weight percentages [8, 20, 26, 29, 34-37]; this leads to an increase in the overall weight of the structure. Additionally, no significant research has been found with regard to their utilisation in RASs, especially those of NZF; this is true even though their chemical synthesis methods are relatively simple when compared to the RASs of dielectric materials [9, 21-25, 27].…”