Synthesis, thermal stability, magnetic properties, and microwave absorption applications of CoNi-C core-shell nanoparticles with tunable Co/Ni molar ratio

Hou, Lei; Zhen, Xing; Liu, Linlin; Kuang, Daitao; Gao, Yangyang; Luo, Hang; Deng, Lianwen; Chen, Chuansheng; Wang, Shiliang

doi:10.1016/j.rinp.2021.103893

Cited by 14 publications

(8 citation statements)

References 47 publications

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“…Though the Ms increased with increasing the Co content, the Hc showed a decrease. Since the saturation magnetization values of the bulk Co and Ni are 163 and 59 emu/g, respectively, the saturation magnetization was approximately proportional to composition.…”

Section: Resultsmentioning

confidence: 99%

“…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 . Further, the wave absorption characteristics of Co–Ni nanoparticles fabricated by the MOCVD method have been reported to depend on the composition and surface morphology . The nanoparticles with Co/Ni molar ratios of 56:44, 39:61, and 23:77 exhibited RL values −12.3, −22.9, and −31.8 dB, respectively .…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, soft magnetic metals and alloys such as Fe-based alloys with higher saturation magnetization are being considered to absorb microwaves in the 2.4–17.1 GHz region . However, when exposed to a magnetic field, metals/alloys have low electrical resistance and generate eddy currents. ,,, Thus, two methods have been proposed to avoid eddy current loss. In the first method, a light element such as boron is added to increase electrical resistance of magnetic materials. , In the second method, the particle diameter is decreased below the skin-depth thickness .…”

Section: Introductionmentioning

confidence: 99%

“…Further, the wave absorption characteristics of Co–Ni nanoparticles fabricated by the MOCVD method have been reported to depend on the composition and surface morphology . The nanoparticles with Co/Ni molar ratios of 56:44, 39:61, and 23:77 exhibited RL values −12.3, −22.9, and −31.8 dB, respectively . However, it should be noted that the particles considered in most of these studies have been heterogeneous in size, shapes, and elemental distribution.…”

Section: Introductionmentioning

confidence: 99%

“…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 . Further, the wave absorption characteristics of Co–Ni nanoparticles fabricated by the MOCVD method have been reported to depend on the composition and surface morphology .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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Co–Ni alloy nanoparticles, a potential candidate for microwave absorption material, were successfully synthesized by tuning the reduction timing of Co and Ni ions by introducing oleylamine as a complexing agent and 1-heptanol as a reducing solvent. The formation mechanism elucidated using time-resolved sampling and in situ X-ray absorption spectroscopy (XAS) and ultraviolet-visible (UV-vis) spectrophotometry measurements suggested that the delay in the reduction of Co ions via complexation with oleylamine facilitated the co-reduction of Co with Ni ions and led to the formation of Co–Ni alloys. The successful synthesis of Co–Ni alloys experimentally confirmed the differences in magnetic properties between alloy and core–shell structured Co50Ni50 particles. Further, the syntheses of Co–Ni alloys with different compositions were also possible using the above technique. In addition, the microwave absorption properties were measured using the free-space method utilizing a vector network analyzer of Co50Ni50polyethylene composite with different sheet thicknesses. A reflection loss (RL) value of −25.7 dB at 13.6 GHz for the alloy structure was more significant than the core–shell counterpart. The above values are high compared to results reported in the past. The validity of the measurements was confirmed by utilizing the parameter retrieval method to extract permittivity and permeability from the scattering parameter (S) and recalculation of the RL as a function of frequency.

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Section: Resultsmentioning

confidence: 99%