Co含量对轻质微波吸收剂C/Co纳米纤维吸波性能的影响

doi:10.15541/jim20170065

摘要/Abstract

摘要：

采用静电纺丝法结合热处理制备了一种可应用于2~18 GHz频段的高性能轻质微波吸收剂C/Co纳米纤维, 详细研究了金属Co含量对纳米纤维的电磁特性及微波吸收性能的影响。相对于纯碳纳米纤维, C/Co纳米纤维的微波吸收性能得到显著加强, 其主要吸波机制仍是介电损耗。随着Co含量的增加, C/Co纳米纤维的电磁衰减能力逐渐下降, 而微波吸收却先增强后减弱, 含37.8wt% Co的C/Co-5纳米纤维因金属Co粒子和纳米碳纤维的良好结合与协同效应, 以及纤维中特殊的Co粒子@石墨核壳结构所带来的良好阻抗匹配与足够高的电磁衰减能力而表现出最好的吸波性能。模拟计算结果表明, 涂层厚度在1.1~5.0 mm间变化时, 填充5wt% C/Co-5纳米纤维的硅胶吸波涂层的反射损耗(RL)值超过-20 dB的频率范围在3.2~18 GHz, 最小RL值达到-78.8 dB, 其中当涂层厚度仅为1.5 mm时, RL值低于-20 dB的吸收带宽可达6.0 GHz (12~18 GHz)。C/Co纳米纤维优异的微波吸收性能表明, 这些磁性碳杂化纳米纤维有望成为一种极具应用前景的新型吸波材料。

关键词: C/Co纳米纤维, 微波吸收, 轻质, 静电纺丝

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

中图分类号:

TM25

张雪珂, 向军, 吴志鹏, 刘敏, 沈湘黔. Co含量对轻质微波吸收剂C/Co纳米纤维吸波性能的影响[J]. 无机材料学报, 2017, 32(12): 1299-1307.

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.

图/表 10

图1 CNFs和C/Co纳米纤维的XRD图谱

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

图2 Co/C纳米纤维的Raman光谱图

Fig. 2 Raman spectra of Co/C NFs

图3 纳米纤维的SEM、TEM及高分辨TEM照片

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

图4 C/Co纳米纤维的室温磁滞回线

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

图5 C/Co纳米纤维-硅胶复合体电磁参数对频率的依赖关系

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

图6 C/Co纳米纤维-硅胶复合体的μ″(μ′)-2f -1值(a)、磁损耗正切和介电损耗正切(b)随频率的变化

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

图7 纳米纤维-硅胶复合体的衰减常数

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

图8 不同涂层厚度各纳米纤维-硅胶复合体的反射损耗曲线

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

表1 本工作与近期报道的一些Co/C纳米复合材料的微波吸收性能

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

图9 各纳米纤维-硅胶复合体的delta值分布图

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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