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Electrospinning of Fe/SiC Hybrid Fibers for Highly Efficient Microwave Absorption Yi Hou,† Laifei Cheng,† Yani Zhang,*,† Yong Yang,*,‡ Chaoran Deng,‡ Zhihong Yang,§ Qi Chen,† Peng Wang,† and Lianxi Zheng⊥ †
Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, 710072 Xi’an, China ‡ Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, 117411 Singapore § College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing, China ⊥ Department of Mechanical Engineering, Khalifa University, 127788 Abu Dhabi, United Arab Emirates ABSTRACT: Fe/SiC hybrid fibers have been fabricated by electrospinning and subsequent high-temperature (1300 °C) pyrolysis in Ar atmosphere using polycarbosilane (PCS) and Fe3O4 precursors. It is found that the introduction of Fe has had a dramatic impact on the morphology, crystallization temperature, and microwave electromagnetic properties of the hybrid fibers. In addition, the Fe particles have acted as catalyst sites to facilitate the growth of SiCO nanowires on the surface of the hybrid fibers. As a result, the permittivity and permeability have been enhanced effectively, and the high reflection loss (RL) has been achieved at a low frequency band with a thin absorber thickness. At an optimal PCS/Fe ratio of 3:0.5, the hybrid fiber/silicone resin composite (35 wt %) with a 2.25 mm absorber thickness exhibits a minimal RL of about −46.3 dB at 6.4 GHz. The wide frequency band (4−9.6 GHz) and thin absorber thickness (1.5−3.5 mm) for effective absorption ( −10 dB) (Figure 6c1). Such remarkable drop of microwave absorption property should be attributed to the dramatic decrease of ε″ due to the absent of free carbon at high Fe loading ratio (Figure 5b). Moreover, it is worth noting that the fibers with PCS/Fer ratio of 3:0.5 exhibit the thinnest absorber thickness at the same frequency compared with other two samples. To better understand this, the frequency dependence of quarter-wavelength (λ/4) of the samples was investigated. The λ/4 cancellation was widely accepted to explain the relationship between RL peak frequency and the absorber thickness.41 In the λ/4 model, the relationship between the absorber thickness (tm) and the peak frequency ( f) can be given by42−45 tm = nc /[(4f )(|εr || μr |)1/2 ]
(n = 1, 3, 5...)
(4)
Parts a2−c2 Figure 6 show the frequency-dependent λ/4 and 3λ/4 of the hybrid fibers. Apparently, all of the samples obey the λ/4 model. The λ/4 line of the 3:0.5 (PCS/Fer) ratio sample lied obviously below the λ/4 lines of the other two samples, indicating that the sample with 3:0.5 (PCS/Fer) ratio offered the thinnest absorber thickness. To date, various 1D SiC hybrid materials, including SiC nanowire,18,46 Fe/SiC whisker,20 and Fe3O4- or Co-doped SiC nanowires,21,22 have been reported as promising microwave absorbers. Table 2 compares the microwave absorption performance of these reported 1D SiC hybrids with our Fe/ SiC hybrid fibers (last line in Table 2). It clearly suggests that the Fe/SiC hybrid fibers exhibit outstanding performance especially in the low frequency C band (4−8 GHz), which is not discovered in other SiC hybrids. In addition, the Fe/SiC hybrid fibers also show the thinnest absorber thickness and relatively low weight fraction. All these advantages enable Fe/ SiC hybrid fibers to be an ideal lightweight microwave absorber.
where Zin is the impedance of the composite backed by the ground plane, Z0 is the intrinsic impedance of free space, d is the thickness of absorber, f is the frequency of incident EM waves, and c is the speed of light. Parts a1−c1 Figure 6 provide the calculated RL curves of SiC fibers and Fe/SiC hybrid fibers. As shown in Figure 6a1, the SiC fibers could achieve effective absorption (RL < −20 dB) above 6 GHz in the investigated frequency band, and a minimum RL of −41.1 was observed at around 12.7 GHz when the thickness was 2.5 mm. In comparison, the Fe/SiC hybrid fibers (PCS: Fer = 3:0.5) exhibited effective absorption in the frequency range of 4−9.6 GHz (Figure 6b1), which covered the entire C band (4−8 GHz), and the minimum RL value of −46.3 dB was reached at 7269
DOI: 10.1021/acsami.6b15721 ACS Appl. Mater. Interfaces 2017, 9, 7265−7271
Research Article
ACS Applied Materials & Interfaces
(5) Wang, L.; Wei, G.; Gao, F.; Li, C.; Yang, W. High-Temperature Stable Field Emission of B-Doped SiC Nanoneedle Arrays. Nanoscale 2015, 7 (17), 7585−7592. (6) Wang, B.; Wang, Y.; Lei, Y.; Wu, N.; Gou, Y.; Han, C.; Fang, D. Hierarchically Porous SiC Ultrathin Fibers Mat with Enhanced Mass Transport, Amphipathic Property and High-Temperature Erosion Resistance. J. Mater. Chem. A 2014, 2 (48), 20873−20881. (7) Ogihara, H.; Sadakane, M.; Nodasaka, Y.; Ueda, W. ShapeControlled Synthesis of ZrO2, Al2O3, and SiO2 Nanotubes Using Carbon Nanofibers as Templates. Chem. Mater. 2006, 18 (21), 4981− 4983. (8) Wan, C.; Guo, G.; Zhang, Q. SiOC Ceramic Nanotubes of Ultrahigh Surface Area. Mater. Lett. 2008, 62 (17), 2776−2778. (9) Guo, A.; Roso, M.; Modesti, M.; Maire, E.; Adrien, J.; Colombo, P. Characterization of Porosity, Structure, and Mechanical Properties of Electrospun SiOC Fiber Mats. J. Mater. Sci. 2015, 50 (12), 4221− 4231. (10) Li, Y.; Gong, J.; Deng, Y. Hierarchical Structured ZnO Nanorods on ZnO Nanofibers and Their Photoresponse to UV and Visible Lights. Sens. Actuators, A 2010, 158 (2), 176−182. (11) Siddheswaran, R.; Sankar, R.; Ramesh Babu, M.; Rathnakumari, M.; Jayavel, R.; Murugakoothan, P.; Sureshkumar, P. Preparation and Characterization of ZnO Nanofibers by Electrospinning. Cryst. Res. Technol. 2006, 41 (5), 446−449. (12) Wu, R.; Zhou, K.; Yue, C. Y.; Wei, J.; Pan, Y. Recent Progress in Synthesis, Properties and Potential Applications of SiC Nanomaterials. Prog. Mater. Sci. 2015, 72, 1−60. (13) LaChapelle, D.; Noe, M.; Edmondson, W.; Stegemiller, H.; Steibel, J.; Chang, D. CMC Materials Applications to Gas Turbine Hot Section Components. American Institute of Aeronautics and Astronautics. AIAA 1998, 98, 3266. (14) Cheng, L.; Xu, Y.; Zhang, L.; Yin, X. Oxidation Behavior of Three-Dimensional SiC/SiC Composites in Air and Combustion Environment. Composites, Part A 2000, 31 (9), 1015−1020. (15) Naslain, R. Design, Preparation and Properties of Non-Oxide CMCs for Application in Engines and Nuclear Reactors: An Overview. Compos. Sci. Technol. 2004, 64 (2), 155−170. (16) Wang, L.; Li, C.; Yang, Y.; Chen, S.; Gao, F.; Wei, G.; Yang, W. Large-Scale Growth of Well-Aligned SiC Tower-Like Nanowire Arrays and Their Field Emission Properties. ACS Appl. Mater. Interfaces 2015, 7 (1), 526−533. (17) Chang, C.-H.; Hsia, B.; Alper, J. P.; Wang, S.; Luna, L. E.; Carraro, C.; Lu, S.-Y.; Maboudian, R. High-Temperature All SolidState Microsupercapacitors Based on SiC Nanowire Electrode and YSZ Electrolyte. ACS Appl. Mater. Interfaces 2015, 7 (48), 26658− 26665. (18) Chiu, S.-C.; Yu, H.-C.; Li, Y.-Y. High Electromagnetic Wave Absorption Performance of Silicon Carbide Nanowires in the Gigahertz Range. J. Phys. Chem. C 2010, 114 (4), 1947−1952. (19) Kuang, J.; Cao, W. Stacking Faults Induced High Dielectric Permittivity of SiC Wires. Appl. Phys. Lett. 2013, 103 (11), 112906. (20) Kuang, J.; Jiang, P.; Liu, W.; Cao, W. Synergistic Effect of Fedoping and Stacking Faults on the Dielectric Permittivity and Microwave Absorption Properties of SiC Whiskers. Appl. Phys. Lett. 2015, 106 (21), 212903. (21) Liang, C.; Liu, C.; Wang, H.; Wu, L.; Jiang, Z.; Xu, Y.; Shen, B.; Wang, Z. SiC−Fe3O4 Dielectric−Magnetic Hybrid Nanowires: Controllable Fabrication, Characterization and Electromagnetic Wave Absorption. J. Mater. Chem. A 2014, 2 (39), 16397−16402. (22) Wang, H.; Wu, L.; Jiao, J.; Zhou, J.; Xu, Y.; Zhang, H.; Jiang, Z.; Shen, B.; Wang, Z. Covalent Interaction Enhanced Electromagnetic Wave Absorption in SiC/Co Hybrid Nanowires. J. Mater. Chem. A 2015, 3 (12), 6517−6525. (23) Wang, X.; Ding, B.; Sun, G.; Wang, M.; Yu, J. Electro-Spinning/ Netting: A Strategy for the Fabrication of Three-Dimensional Polymer Nano-Fiber/Nets. Prog. Mater. Sci. 2013, 58 (8), 1173−1243. (24) Lu, X.; Wang, C.; Wei, Y. One-Dimensional Composite Nanomaterials: Synthesis by Electrospinning and Their Applications. Small 2009, 5 (21), 2349−70.
Table 2. Microwave Absorption Properties of Some 1D Magnetic/Ceramic Materials samples Fe/ SiCwhisker Fe3O4/ SiCnanowire Co/ SiCnanowire SiCnanowire SiCnanowire Fe/SiCfiber
minimal RL (dB)
dm (mm) (RL< −20 dB)
freq band (GHz) (RL < −20 dB)
wt fraction (%)
ref
−21
2
11.2
20
20
−51
2−5
6−18
50
21
−25
2−4.5
6−18
50
22
−31 −30 −42
1−3 4−5 1.5−3.5
8−8.8 6.5−9 4−9.6
35 50 35
18 46
■
CONCLUSIONS In conclusion, Fe/SiC hybrid fibers were successfully fabricated via electrospinning and heat treatment afterward. It was found that introducing Fe into SiC not only facilitated the growth of amorphous nanowires on the surface of the SiC fibers but also increased the permittivity and permeability, resulting in a shift of RL peak to lower frequency band. At the optimal PCS/Fe ratio of 3:0.5, the hybrid fiber composite (35 wt % fiber) with a 2.25 mm absorber thickness exhibited a minimal reflection loss of −46.3 dB at 6.4 GHz. Compared with other reported 1D SiC hybrid materials, the Fe/SiC hybrid fibers could achieve effective absorption (
