Co Content on Absorption Property of C/Co Nanofibers as a Lightweight Microwave Absorber

doi:10.15541/jim20170065

Abstract

Abstract:

C/Co nanofibers (NFs) as a high-performance lightweight microwave absorber in the 2-18 GHz band were fabricated by a facile electrospinning process combined with subsequent heat treatment. The effects of Co content on the electromagnetic characteristics and microwave absorption properties of C/Co NFs were investigated. The microwave absorption performance of C/Co NFs is significantly enhanced as compared to that of pure carbon nanofibers (CNFs) and the primary microwave absorption mechanism is ascribed to the dielectric loss. With increase of Co content, the electromagnetic attenuation capability of C/Co NFs monotonically decreases, while their microwave absorbing ability firstly rises and then drops. The C/Co-5 NFs sample with 37.8wt% Co exhibits the best performance for microwave absorption due to a good impedance matching and sufficiently high electromagnetic attenuation capability, which result from proper combination and synergistic effect between Co particles and CNFs, as well as the particular Co particle@graphite core-shell structure in the NFs. The simulation results show that a reflection loss (RL) exceeding -20 dB is obtained in a wide frequency range of 3.2-18 GHz for the silicone composite contained only 5wt% C/Co-5 NFs by choosing an appropriate layer thickness between 1.1 mm and 5.0 mm, and an optimal RL value of -78.8 dB is obtained at a layer thickness of 2.5 mm. More importantly, when the absorber thickness is as thin as 1.5 mm, the absorption bandwidth (RL≤-20 dB) is up to about 6 GHz ranging from 12 GHz to 18 GHz, which covers the whole Ku-band. The excellent microwave absorption property together with lightweight and ultrathin thickness of C/Co NFs indicate that these magnetic carbon hybrid nanofibers can be used as a novel and promising microwave absorbing material.

Key words: C/Co nanofiber, microwave absorption, lightweight, electrospinning

CLC Number:

TM25

ZHANG Xue-Ke, XIANG Jun, WU Zhi-Peng, LIU Min, SHEN Xiang-Qian. Co Content on Absorption Property of C/Co Nanofibers as a Lightweight Microwave Absorber[J]. Journal of Inorganic Materials, 2017, 32(12): 1299-1307.

Figures/Tables 10

Fig. 1 XRD patterns of CNFs and C/Co NFs

Fig. 2 Raman spectra of Co/C NFs

Fig. 3 SEM, TEM and HRTEM images of NFs(a) CNFs; (b) C/Co-2; (c) C/Co-5; (d) C/Co-8; (e) TEM image of single C/Co-5 NFs; (f) HRTEM image of a Co particle embedded into the surface of C/Co-5 NFs

Fig. 4 Room-temperature hysteresis loops of C/Co NFs

Fig. 5 Frequency dependences of the electromagnetic parameters for the C/Co NFs-silicone composite Insets in (a) and (b) are the relative complex permittivity of the CNFs-silicone composite

Fig. 6 Frequency dependences of the μ″(μ′)-2f -1 values (a) and the magnetic loss tangent and dielectric loss tangent (b) for C/Co NFs-silicone composites

Fig. 7 Attenuation constants of the NFs-silicone composites versus frequency

Fig. 8 Reflection loss curves of the NFs-silicone composites with different coating thicknesses(a) CNFs; (b) C/Co-2; (c) C/Co-5; (d) C/Co-8

Table 1 Microwave absorption properties of some Co/C nanocomposites reported in recent researches and this work

Sample	Loading /wt%	Min RL values/dB	Frequency range (RL≤-20 dB, GHz) (Bandwidth, thickness)		Ref.
Co/CNTs	20	-60.4	4.6-18.0 (13.2 GHz, 1.0-5.0 mm)	14.1-15.9 (1.8 GHz, 1.81 mm)	[1]
Co@C Microspheres	70	-68.7	5.5-18.0 (12.5 GHz, 1.0-5.0 mm)	10.0-11.2 (1.1 GHz, 1.65 mm)	[4]
Co/C Nanoparticles	50	-43.4	6.0-18.0 (12.0 GHz, 1.0-4.0 mm)	10.8-18.0 (7.2 GHz, 2.3 mm)	[5]
Co/C Nanocomposites	60	-35.3	4.3-15.8 (11.5 GHz, 1.0-5.0 mm)	14.4-15.8 (1.4 GHz, 2.0 mm)	[8]
Co/CNT-Graphene	30	-65.6	4.2-18.0 (13.8 GHz, 1.0-5.0 mm)	13.4-15.9 (2.5 GHz, 1.9 mm)	[10]
Co/Porous carbon	30	-40.0	4.0-9.6 (5.6 GHz, 2.5-5.0 mm)	8.8-9.6 (0.8 GHz, 2.5 mm)	[25]
Co/Graphene	60	-47.5	3.3-12.4 (9.1 GHz, 2.0-5.0 mm)	10.9-12.4 (1.5 GHz, 2.0 mm)	[26]
Co@C Nanoparticles	40	-42.0	4.6-18.0 (13.4 GHz, 1.0-5.0 mm)	8.2-13.8 (5.6 GHz, 3.0 mm)	[27]
C/Co-5 NFs	5	-78.8	3.2-18.0 (14.8 GHz, 1.1-5.0 mm)	12.0-18.0 (6.0 GHz, 1.5 mm)	This work

Fig. 9 Calculated delta value maps of the NFs-silicone composites(a) CNFs; (b) C/Co-2; (c) C/Co-5; (d) C/Co-8

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