Controllable N-Doped Carbonaceous Composites with Highly

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Controllable N-Doped Carbonaceous Composites with Highly dispersed Ni Nanoparticles for Excellent Microwave Absorption Shengshuai Gao, Qingda An, ZuoYi Xiao, Shang-Ru Zhai, and Dongjiang Yang ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.8b01556 • Publication Date (Web): 27 Sep 2018 Downloaded from http://pubs.acs.org on October 2, 2018

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ACS Applied Nano Materials

Controllable N-Doped Carbonaceous Composites with Highly dispersed Ni Nanoparticles for Excellent Microwave Absorption Shengshuai Gao †, Qingda An *†, Zuoyi Xiao †, Shangru Zhai *†, Dongjiang Yang *‡ † Faculty of Light Industry and Chemical Engineering, Dalian Polytechnic University, Dalian 116034, China ‡ Collaborative Innovation Center for Marine Biomass Fibers Materials and Textiles of Shandong Province, School of Environmental Science and Engineering, Qingdao University, Qingdao 266071, P. R. China

*Corresponding authors. E-mail: [email protected] (Q.-D. An); [email protected] (S.-R. Zhai)

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ABSTRACT Microwave absorption materials with great reflection loss and wide absorption band that can provide electromagnetic waves (EMWs) absorption with minimal thickness are highly desirable, particularly when they could be controllably fabricated through a facile process. Herein, N-doped three-dimensional (3D) carbonaceous composites with highly dispersed nickel nanoparticles (N-SA/Ni-X, X = 3%, 6%, 9%) were successfully prepared by a facile one-step encapsulation process and carbonization. The performance of absorber has a significant enhancement due to the introduction of nitrogen elements into carbon network for controlling the dispersion and size distribution of Ni nanoparticles. When a 6% Ni2+ mass percentage was used, the maximum reflection loss (RL) could reach −42.2 dB at 9.8 GHz. Moreover, the effective absorption (below -10 dB) bandwidth can reach 2.3 GHz from 8.5 to 10.8 GHz with the absorber thickness of only 2 mm and it can be tuned between 2.8 to 14.4 GHz by adjusting the thickness from 1.5 mm to 5 mm. The excellent electromagnetic wave absorbing performance could be assigned to the combinatorial advantages of the light-weight conductive porous network with favorable dielectric loss and magnetic loss features induced by highly dispersed Ni nanoparticles. These newly fabricated N-SA/Ni-X composites could be regarded as promising candidates for lightweight and high-performance microwave absorption materials. KEYWORDS: Controllable nanostructures, Seaweed, Nickel nanoparticles, N-doped, Electromagnetic wave absorption

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INTRODUCTION Nowadays, electromagnetic wave technology is experiencing rapid advancement in civil fields and military application. People are enjoying benefits from these advanced technologies, at the same time, however, they are also inevitably disturbed by electromagnetic interference (EMI). The EMI pollution can cause terrible influence on human biological systems.1,2 Therefore, the high-performance electromagnetic wave (EMW) absorption materials have evoked significant attention to solve these problems.3,4 As an ideal electromagnetic wave absorber, it is proposed to have wide absorption bandwidth, strong absorption performance, light weight and stable chemical composition and physical performance.5,6 From the physical point of view, the performance of absorbing material can be mainly determined by the electromagnetic parameters, both complex permeability (μr=μ'-jμ'') and complex permittivity (εr=ε'-jε''). Therefore, conventional EMW absorber can normally be classified into two categories by the two complex parameters, namely magnetic loss materials such as Ni, Co, Fe and alloys,7-10 dielectric loss materials such as TiO2, SiC, CuS and conductive polymers.11-14 Taking into account of the reported cases for microwave absorption materials, there are two unavoidable shortcomings for reported absorbers. The first one is the imbalance of physical properties which might lead to a weak absorption, the second one is the high density, which practically limits their potential applications, whereas they could have hold excellent absorbing properties.15 To address these problematic issues required for practical applications of microwave absorption materials, currently, those alternative carbonaceous materials, for which have light-weight and favorable mechanical properties, have been considered as next generation of electromagnetic wave absorbers, including carbon nanotubes, carbon fibers, carbon-nanotube films and 3



graphene foam, etc.16-19 However, those one-dimensional (1D) and two-dimensional (2D) absorbing materials still have many disadvantages when compared to the three-dimensional ones, and the most considerable drawback is that they would have a tendency to aggregate and restack in preparation or applied processes, which would possibly lead to an unavoidable compromise to the absorption performance of this kind of 1D and 2D absorbers. More importantly, in most studies for carbon nanotubes, carbon fibers and graphene-based adsorption composites, the synthesis processes are relatively complicated and the cost of total production is somewhat high, which further restricts their potential applications widely.20 Currently, three-dimensional porous carbonaceous composites have received particularly high attention in electromagnetic waves absorption.21,22 As was demonstrated, the synergetic behaviors between the electromagnetic parameters (complex permeability and permittivity) are one of the essential issues for designing high-performance microwave absorbers. The 3D porous composites can be regarded as ideal adsorbing platforms, due to the fact that they would typically provide new interfacial effect to achieve mutual cooperation of host and guest species. At this regard, the electromagnetic parameters of microwave absorbing materials would be facilely tunable by adjusting the components and nanostructures of resultant composites. Furthermore, the increment of the heterogeneous interfaces that induced by hetero-junction of host network and guest species would also generate favorable reactive space to improve the EMW absorption performance by the reflection and scattering of electromagnetic waves. Consequently, those 3D porous carbonaceous composites would potentially make some significant breakthroughs in the field of EMW absorption. As is reported, Zhai et al. prepared 3D cabbage-like Fe/CCMs-X (X represents temperature) composites and investigated its electromagnetic wave 4


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absorption properties.21 The maximum reflection loss (RL) of -22.9 dB can be achieved at a frequency of 4.32 GHz with a thickness of 2.5 mm. In addition, Chen and co-workers synthesized 3D Fe3O4-MWCNTs composites, and the materials exhibited a greater reflection loss and a wider absorption band.22 Nevertheless, even though these kinds of 3D EMW absorbing material have been reported in previous works, in which superior EMW absorbing capability was achieved, there remains a great challenge to controllably fabricate a potential 3D carbonaceous porous network with high dispersion of magnetic species and much reduced production cost, namely using renewable, available seaweed as starting materials. In view of aforementioned issues for traditional EMW absorbing materials, we have turned to another sustainable strategy to design 3D EMW absorbing composites using seaweed biomass which is abundant in ocean plants as renewable and low-cost carbon precursors. As is known, sodium alginate (SA), a linear polysaccharide copolymer derived from seaweed, has been extensively researched and widely applied to fabricate supercapacitor electrodes, pollutants adsorbents and battery anodes materials, due to its unique characteristics.23-25 However, such materials are rarely reported for exploring their electromagnetic wave absorption materials, even though SA can favorably cross-link with metal ions to form hydrogels, which can be potentially employed to design 3D EMW absorbing materials with enhanced absorption performance. Moreover, it should be noted that the uncontrollable dispersion and size distribution of magnetic metal particles in the carbon network would potentially compromise the microwave absorption properties. As an example, our previous work on preparing the heterostructured EMW absorber SA-Fe-X (X means Fe content) using SA has clearly verified this important issue.26 Herein, in continuation of our research interest on designing high-performance 5



microwave absorbers,27,28 a novel 3D, N-doped carbon composites loaded with highly dispersed Ni nanoparticles for microwave absorption was prepared by a controllable fabrication method of one-step encapsulation, after which was the carbonization at 600 oC in N2 atmosphere. This N-doped carbon composites solve the problem of uncontrollable dispersion and size distribution of magnetic metal particles in the carbon network. With introducing N element from polyethylenimine (PEI), a biocompatible polymer with primary, secondary and ternary amine groups, its effect on binding ability towards targeted metal ions to tackle the problem of the dispersion and size distribution of magnetic nanoparticles was correlated to the EMW absorption of resultant composites. The controllable dispersion and size distribution of magnetic metal particles in the carbon network would be effective to enhance the absorbing property of absorber. A synergistic utilization of PEI and SA for improving the dispersion of metal particles and controlling the 3D network to optimize the absorber performance was firstly demonstrated in designing high-performance microwave absorbers using seaweed-derived by-products.

EXPERIMENTAL SECTION Materials. PEI (Mw = 600, 99%) was supplied by Aladdin Company. Glutaraldehyde solution (50%) was obtained from Guangfu Fine Chemical Industry Research Institute, Tianjin, China.

Sodium alginate (SA) and NiCl2 were supplied by Beijing Chemical Factory,

China. Nitrogen gases were obtained from cylinders by Heli factory with 99.999% purity.

All chemicals were of analytical grade and used without further purification.

Ultra-pure water with resistivity = 18 MΩ·cm-1 was used. Synthesis. 6


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Briefly, PEI (1 g) and Glutaraldehyde (2 mL) were added into 100 mL water and stirred for 2 h at 50 oC, the solution turned yellow and then red gradually. Sodium alginate (2 g) was dispersed in the red solution and stirred for 12 h. The mixture was then dropped to a 3 wt% aqueous solution containing NiCl2 using peristaltic pump with 3.5 rotating speed and stirred to form Ni(II) cross-linked hydrogels. After 6 h, the as-prepared hydrogels were separated from the solution and washed with distilled water and ethanol to remove residul Ni2+ and Cl-. After that, the prepared hydrogels beads suffered in -50

C for 12 h at a refrigerator. The three dimensional

o

Ni(II)-alginate aerogels were obtained via a freeze-drying process in vacuum freeze dryer for 12 h. The as-prepared aerogels were placed in a tube furnace and heated from 20 oC to 600 oC at a heating rate of 5 oC and kept for another 2 h in N2 atmosphere. When cooled down to room temperature, the obtained composite was named as N-SA/Ni-3%. The products were called N-SA/Ni-6% and N-SA/Ni-9% when the aqueous solution containing NiCl2 were 6 wt% and 9 wt%, respectively. Additionally, the composite material without PEI was named as SA/Ni-6%. Materials Characterization. The crystal structures were investigated by X-ray diffraction (XRD, ESCALAB210) operating at Cu Kα radiation (λ = 1.5406 Å) at 40 kV and an applied current of 40 mA, the scan rate (2θ) is 8°/min and the ranges is 10°-70°. Raman spectra were characterized with a RM 2000 Microscopic Confocal Raman Spectrometer (Renishaw PLC) under Ar ion laser with an excitation wavelength of 514.5 nm. The structure and morphology of the samples were measured by scanning electron microscopy (SEM, JEM JEOL 2100) with energy dispersive spectroscopy (EDS) and high-resolution transmission electron microcopy (HRTEM, Hitachi H9000NAR) images, respectively. In addition, chemical states of the N-SA/Ni-X(X=3%, 6%, 9%) were analyzed by 7



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X-ray photoelectron spectroscopy (XPS) using a PHI 5000 (Versa Prob II, FEI Inc.) spectrometer with Al Kα (1486.6 eV) monochromatic source. The vibration sample magnetometry (VSM) was employed to study magnetic properties of the all samples at room temperature. Electromagnetic Measurements. The N-SA/Ni-X(X=3%, 6%, 9%) mixing paraffin with 50 wt % were pressed into toroidal shape (ψout: 7.00 mm, ψin: 3.04 mm) and measured by the vector network analyzer (VNA) in the frequency of 2−18 GHz. The complex permeability and permittivity computed from the electromagnetic parameters were used to calculate the microwave reflection loss (RL) by following equations:6,9,17 Zin = Zo (μ r/εr)1/2 tanh[j(2πƒd)/c(μr εr)1/2]

(1)

RL=20log| (Zin-Zo)/ (Zin+Zo) |

(2)

where Zin represents the input characteristic impedance, Zo represents the impedance of free space, c represents the velocity of light, f represents the frequency and d represents the thickness of the composites. RESULTS AND DISCUSSION The manufacturing course of N-SA/Ni-X(X=3%, 6%, 9%) is illustrated in Scheme 1. Briefly, PEI, Glutaraldehyde and Sodium alginate were added into water and stirred for 2 h. The mixture was then dropped to a 6 wt% aqueous solution containing NiCl2 stirred to form Ni(II) cross-linked hydrogels. Then, the obtained hydrogels beads were freezed at -50 oC for 12 h in a refrigerator. The three dimensional Ni(II)-alginate aerogels were obtained via a freeze-drying process in vacuum freeze dryer for 12 h. The as-prepared aerogels were placed in a tube furnace and heated from 20 oC to 600 oC at a heating rate of 5 oC and kept for another 2 h in N2 atmosphere. The products of N-SA/Ni-6% were obtained. If there was no PEI, all 8


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the SA which cross-linked with Ni2+ would connected together by chemical bonds, causing a lot of accumulation. The introduction of PEI which having a good space structure into SA could change the cross-linked spatial structure about SA and Ni2+ to improve the dispersion of Ni. The changing would bring a difference in size and dispersion of Ni nano-particles in carbonaceous composites. The structures and morphologies of the SA/Ni-6% and N-SA/Ni-X(X=3%, 6%, 9%) composites were characterized by SEM, and the details are shown in Figure 1. After calcination in N2, the appearance of SA/Ni-6% (Figure 1a1) presented irregular structure while other three samples possessed regular spherical structure (Figure 1b1, c1, d1). Figure 1a2 shows that the irregular crystalline particles were accumulated on the SA with uneven size. When PEI was introduced in SA (Figure 1(b2 and c2)), the Ni nanoparticles were evenly distributed in the profile with average particle size after all the samples were cut into a profile. Thereby, the introduction of PEI could really improve the Ni dispersion in host. The high dispersion guest in host hybrids structure would be good for improving microwave absorption benefiting from many structural defects and strong interface polarization. And defect sites could generate an additional energy state originating from the terraced and uneven fields near the Fermi level.21 Then, the N-SA/Ni-3% (Figure 1b1) and N-SA/Ni-6% (Figure 1c1) show a hollow structure, while the N-SA/Ni-9% (Figure 1d1) was broken in interior. For N-SA/Ni-9% (Figure 1d2), except many Ni nanoparticles in the profile, there are some big size crystals on the surface of N-SA. These big size crystals were from Ni2+ adsorbed on the surface of N-SA rather than chelation with it. The heavy mass was the mainly reason for the broken of the N-SA/Ni-9%, and it would have bad influences in microwave absorption. The elemental mapping by EDS of N-SA/Ni-6% is shown in Figure 1e. Obviously, the hybrids character is confirmed by distribution of element, that is, Ni 9



element was scattered in C element region homogeneously. Besides, TEM was employed to reveal further microstructures of the SA/Ni-6% and N-SA/Ni-6% (Figure 2). As shown in Figure 2(a1 and a2), the crystalline particles of SA/Ni-6% has an obvious aggregation with uniformly size. For N-SA/Ni-6%, the images confirm that tiny spherical Ni nanoparticles were uniformly decorated on the transparent N-SA structure without remarkable aggregation (Figure 2(b1 and b2)). Especially, single Ni nanoparticle with diameters about 30 nm was clearly shown in Figure 2b2. The size distribution of Ni nanoparticles in N-SA/Ni-6% (Figure 2d) is accord with Gaussian distribution and the standard deviations σ is less than 6%, displaying that the Ni nanoparticles have a uniform diameter located in narrow size distribution. Furthermore, from Figure 2c, the C layer covers Ni nanoparticles, even the interface between Ni and N-SA can be seen clearly. Moreover, the HRTEM also shows a lattice image of Ni crystal with an interplanar spacing of 0.25 nm, coinciding with the (111) surface of Ni lattice. Notably, the degree of crystallinity of the N-SA/Ni-6% was demonstrated by bright and distinguishable diffraction rings of the SAED patterns (inset of Figure 2c). The diffraction rings could be indexed to the (111) and (200) planes, proving the formation of highly crystalline Ni crystal. The crystal structure of SA/Ni-6% and N-SA/Ni-X(X=3%, 6%, 9%) composites were investigated by XRD technique and shown in (Figure S1a) (ESI†)). And it can be seen that the peaks located at 44.5o and 51.8o correspond to the (111) and (200) crystal face of spinel structured Ni (JCPDS: 65-0380), respectively. The result is consistent with the TEM results. The sharp peaks show that all the samples of N-SA/Ni-X are highly crystalline and no other impurity characteristic peaks were discovered, indicating the phase purity of all samples. Moreover, no characteristic peaks of NiO peaks in 36.4o, 43.6o and 67.7o (JCPDS: 65-2901) were observed, 10


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meaning that the complexed Ni2+ were reduction to Ni crystalline after calcination in N2. By contrast, the NiO was appeared in SA/Ni-6% when there is no PEI in SA, demonstrating that PEI could also change the crystal structure in calcination process. Meanwhile, the characteristic broad peaks at about 26.1o were unobserved, indicating that the loading Ni nano-particles could destroy the graphitization degree of N-SA and make it more disordered in the N-SA/Ni-X composites. For more information about the graphitization degree of the SA/Ni-6% and N-SA/Ni-X(X=3%, 6%, 9%) composites, Raman spectra were acquired. For all composites, two broad bands located at 1330 cm−1 and 1604 cm−1 can be clearly seen in (Figure S1b)(ESI†), corresponding to the D and G band which represent amorphous carbon and graphitic carbon, respectively.29,30 The D band is a characteristic out-plane vibration of sp3 carbon atoms of disordered or defective carbon, while the G band is attributed to in-plane vibration of sp2 hybridized carbon atoms structure.31 For N-SA/Ni-3%, N-SA/Ni-6% and N-SA/Ni-9%, the calculated ID/IG is 1.70, 1.86 and 2.42, respectively. The intensity ratio of ID/IG is related to the degree of carbon. The N-SA/Ni-9% has the highest value of ID/IG in all samples, implying that the structure became more disorder after modified with Ni nano-particles that accompanied with more defects, which also agrees with the XRD result. Compared to N-SA/Ni-6%, the ID/IG values of SA/Ni-6% is 1.60, meaning that the doped N could make the carbonaceous composites structure more disorder. The elemental character of N-SA/Ni-X(X=3%, 6%, 9%) were analyzed by XPS measurements (Figure 3), which can further obtain the information about the atomic compositions and identify the type of bonds between atoms. In survey of wide scan spectra (Figure 3a), it is clearly shown that N-SA/Ni-X(X=3%, 6%, 9%) contains all expected C, Ni, O and N elements (The N was not shown in SA/Ni-6% (Figure 11



S2)(ESI†), which located at 284.7, 858.6, 529.3 and 398.6 eV, respectively. High accurate XPS results were used to evaluate the elements states. The magnifying C 1s spectrum of N-SA/Ni-6% was shown in Figure 3b. There are three fitted peaks with binding energies located at 282.7, 283.9 and 284.3 eV corresponding to the C-C, C-N and C-O groups, respectively. As shown in the high resolution Ni 2p spectrum (Figure 3c), the Ni 2p3/2 peak located at 853.2 eV could be assigned to the Ni-Ni bond, while the Ni 2p1/2 peak located at 871.8 eV could be attributed to Ni2+, which may stem from the NiO.32 On the other hand, in O 1s spectrum (Figure 3d), the fitting peak at 531.2 was attributed to Ni-O. Interestingly, there are no characteristic peaks belong to NiO in XRD results and no obviously NiO particles in SEM images. It is meaning that NiO was existed in composites, but the amount is so little that it can be ignored in influencing the performance of microwave absorption. The high resolution N 1s was shown in Figure 3e, the curve can be well fitted by two deconvoluted peaks with the binding energies at 397.4eV and 398.4eV, coinciding with the pyridinic N bonding and pyrrolic N bonding. It is suggested that the doped nitrogen atoms can form a six-membered heterocyclic ring due to two neighbored sp2 hybridized C atoms bonded with non-equivalent sp2 hybridized N atoms. Addtionally, pyrrolic N bonding formed in a five-membered heterocyclic ring is related to one H atom and two neighbored sp2 hybridized C atoms bonded with equivalent sp2 hybridized N atoms.33 Favorably, this form of doped nitrogen atoms can provide a large amount of space on the surface of the N-SA, which could produce electronic dipole polarization relaxation and polarization relaxation to improve the performance of microwave absorption. Based on foregoing characterization results, a type of Ni-encaspulaing composites were fabricated successfully by an encapsulation process combined with heating treatment. Then, the magnetic properties of bare all samples were researched 12


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at room temperature by the vibrating sample magnetometer (VSM). As shown in (Figure S3)(ESI†)), four samples present typical ferromagnetic hysteresis loops (S-like shape) originated from Ni particles, indicating a superparamagnetic characteristic of composites. The saturation magnetization (MS) and coercivity (HC) of N-SA/Ni-X are shown in Table 1. The value MS of SA/Ni-6% was much lower than that of N-SA/Ni-X, this would has a severe restriction in performance of EMW absorption. It can be clearly seen that N-SA/Ni-9% has higher MS values than N-SA/Ni-6% and N-SA/Ni-3%, which possibly resulted from that more magnetic Ni increases the corresponding data. Meanwhile, the coercivity also increases with the increasing of Ni amount in the composites. The higher magneto-crystalline anisotropy energy would induced by larger Hc value, which would enhance the microwave absorption properties.34 Table 1. Saturation magnetization (MS) and Coercivity (HC) of all samples. samples

saturation magnetization(MS)(emu/g)

coercivity (HC)(Oe)

SA/Ni-6%

2.9

73.7

N-SA/Ni-3%

6.2

94.3

N-SA/Ni-6%

9.4

100.6

N-SA/Ni-9%

15.3

121.4

According to the electromagnetic energy conversion theory, complex permeability (μr=μ'-jμ'') and permittivity (εr=ε'-jε'') play a key role in determining the microwave absorption performance of samples. The real permeability (μ') and imaginary permeability (μ'') represent the storage and dissipation ability of magnetic energy, while the real permittivity (ε') and imaginary permittivity (ε'') are connected with the capability of electric energy, respectively.3,4,16,20 Figure 4(a, b) shows that the values of μ' and μ'' for the N-SA/Ni-X are obviously improved in comparison with that of SA/Ni-6% from 2 to 18 GHz, and the values enhanced when enlarge the content of Ni 13



nanocrystals. The lifted complex permeability for N-SA/Ni-X hybrids is mainly due to introduction of N into SA for improving the dispersion of metal particles. The real part (μ') of complex permeability for the N-SA/Ni-3% has a slight fluctuation in 2-5.3 GHz, and then slowly reduced from 1.2 to 0.7 by the frequency increasing from 5.4 to 14.4 GHz, with a negligible increasing tendency from 14.5 to 18 GHz. Then, the μ' value of N-SA/Ni-6% and N-SA/Ni-9% composites were obviously increased when they were added with more content of Ni nanocrystals. The improved complex permeability for N-SA/Ni-X hybrids is mainly due to magnetic property of Ni nanocrystals.

It is worth noting that the values of μ'' and μ' show similar tendency,

and the broad resonance band of μ'' about 6 GHz could be attributed to natural resonance.35-40 All the broad resonance peaks are beneficial to enhance electromagnetic wave absorption because they are believed to induce strong magnetic loss.41 The values of ε' and ε'' for the samples are shown in Figure 4c and d. It is clearly seen that the variation tendency of ε' and ε'' are same with μ' and μ'', the values of ε' and ε'' are also higher than SA/Ni-6% owing to the introduction of N into SA. According to the free electron theory,7 the enhanced complex permittivity for N-SA/Ni-X hybrids is related to polarization and the relaxation by the functional groups and residual defects in N-SA. The values of ε' and ε'' for N-SA/Ni-X hybrids are slightly decreased in the whole frequency band when increased the content of Ni nanocrystals.42 The real permittivity(ε') of N-SA/Ni-9% ranging from 11.3 to 7.2 was lower than that of another two samples in 2-18 GHz. In comparison, the ε' of N-SA/Ni-6% are relatively stable with frequency increasing from 2 to 18 GHz, with the values between 15.7 and 13.6. The N-SA/Ni-3% have the highest real permittivity (ε') than other samples in 2-18 GHz, ranging from 21.3 to 16.2. The result indicates 14


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that N-SA/Ni-3% has better energy storage and polarization capability. Nevertheless, too high permittivity (ε') may results in poor impedance match. The impedance match requires that the values of permeability and permittivity should be close as much as possible to achieve zero-reflection at the surface of absorbing materials.43 Hence, higher permittivity of N-SA/Ni-3% might have weak microwave absorption performance. From Figure 4d, the ε'' values of N-SA/Ni-6% and N-SA/Ni-9% are lower than N-SA/Ni-3% and relatively stable over the whole frequency. One can also observe that there exists multi-peaks for N-SA/Ni-3% on the ε'' curve, this behaviors are the typical properties of nonlinear resonant phenomena. According to previous reports,44 dielectric resonances at 5.8 GHz were resulted from Ni particles. Furthermore, heterojunction capacitance originated from the interface of Ni nanocrystals and N-SA induced the other resonant peaks. Magnetic loss and dielectric loss are two possible factors contributing to performance of electromagnetic wave absorption.45 The frequency dependence of two loss parameters (dielectric loss tangent (tanδε = ε /ε ) and magnetic loss tangent (tanδµ =µ /µ )) for all the samples were calculated and shown in Figure S4. The variation tendencies of tanδµ (Figure S4a) for all samples are nearly the same, which maintains nearly constant from 2 to 7 GHz and then slightly decreases in the frequency range of 7-18 GHz. In contrast, the values of magnetic loss tangent show distinct difference between SA/Ni-6% and N-SA/Ni-X(X=3%, 6%, 9%) hybrids, suggesting that the introduction of PEI could affect the magnetic loss of samples. And the more contents of Ni nanocrystals, the higher magnetic loss tangent. The magnetic loss mainly results from the domain-wall displacement, magnetic hysteresis, eddy current effect, and natural resonance exchange resonance.46 The domain wall resonance could be neglected in this work, because of which is usually existed in a 15



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lower frequency range (1-100 MHz) in absorbing materials. The magnetic hysteresis loss could be also excluded, since it is caused by irreversible magnetization, while all samples possess the characteristic of superparamagnetic in this work. Hence, it might be eddy current and natural resonance influencing the magnetic loss of samples. The eddy current loss can be evaluated by the following equation:47 Co=μ''(μ')-2ƒ-1 = 2πσd2μo

(3)

where Co is the eddy current coefficient. When the eddy current coefficient changes with an increase in frequency, the magnetic loss is not caused by the eddy current effect. If magnetic loss only originates from eddy current effects, the values of Co should be constant when the frequency changes. Figure S5 shows the frequency dependence of Co for three samples. It can be found that the values of three samples have an obvious decrease in the low frequency range of 2-7 GHz, then maintain constant in a relatively wide frequency range of 7-18 GHz. These results indicate that the magnetic loss in the N-SA/Ni-X hybrids mainly came from natural resonance in low frequency of 2-7 GHz range and the eddy current effect in high frequency of 7-18 GHz range. The dielectric loss of the N-SA/Ni-X(X=3%, 6%, 9%) and SA/Ni-6% were shown in Figure S4b. The value of tanδε improved with the decreasing of Ni contents in the whole frequency range. Besides, the appearance of PEI in N-SA/Ni-6% is greatly significant for the dielectric loss tangent, which is of great enhancement for the performance of microwave absorption. This results from that in the absorbing samples (N-SA/Ni-X), the N-SA is uniformly decorated by Ni particles, which could introduce more interfaces followed by dipole polarization, interfacial polarization and stronger contacted relaxation at the interfaces to significant promote the absorbing performance.48,49 These polarization are known as Maxwell-Wagner polarization,50 16


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which originated from virtual charges accumulated on the interface of two media with different dielectric constants and conductivities. According to transmission line theory, effective microwave absorption performance is dominated by two key factors. One is the electromagnetic absorption attenuation in the interior absorber, and another is impedance match, which requires the complex permeability and permittivity to be equal. The electromagnetic absorption attenuation was determined by the attenuation constant α, which can be calculated as:51 α = (√2πƒ/c) x √[(μ'' ε'' - μ' ε')+√[(μ'' ε'' - μ' ε')2 +(μ'' ε'' + μ' ε')2]]

(4)

where c represents the velocity of electromagnetic waves in free space and f is the frequency of the electromagnetic waves. Figure 5a shows the frequency dependence of α values for all absorbing samples. It can be seen clearly that the N-SA/Ni-X composites show relatively higher attenuation constant than SA/Ni-6% in the whole frequency range, meaning that highly dispersed Ni in N-SA could attenuate the EMW effectively. In addition, the N-SA/Ni-3% composites show the biggest value of attenuation constant α in the frequency from 2-18 GHz. Theoretically, the higher attenuation constant means a stronger microwave attenuation ability. In view of above discussion and the attenuation constant α, it could be speculated that the absorption properties of all the samples should match the following order: N-SA/Ni-3% composites > N-SA/Ni-6% composites > N-SA/Ni-9% > SA/Ni-6% composites. However, this speculation is inconsistent with another key factor: impedance matching performance. As shown in Figure 5b, the values of N-SA/Ni-6% were higher than N-SA/Ni-3%, N-SA/Ni-9% and SA/Ni-6%. Impedance matching that means the synergistic effect between dielectric loss and magnetic loss could assure the microwave entering into the absorber efficiently. The “perfect impedance matching” 17



will appeare when the value of microwave absorbing impedance matching ratio is equal to 1, and then the absorber should have the best microwave absorption performance. The impedance matching ratio of N-SA/Ni-6% reached 1 at 9.8 GHz with a thickness of 2.0 mm, and other three samples are far from 1 in the whole frequency range. The results suggest that N-SA/Ni-6% may have the best microwave absorption performances at 9.8 GHz, N-SA/Ni-3%, N-SA/Ni-9% and SA/Ni-6% have relatively weak microwave absorption performances because the microwave can hardly come into the absorber. For further electromagnetic wave absorption properties, the three-dimensional diagrams for the SA/Ni-6% and N-SA/Ni-X(X=3%, 6%, 9%) are shown in Figure 6. The SA/Ni-6% (Figure 6a) has poor electromagnetic absorption performance and its maximum RL is −7.0 dB at 8.8 GHz with a thickness of 4.5 mm. While the N-SA/Ni-6% (Figure 6c) composite exhibits the best microwave absorption properties, of which the maximum reflection loss (RL) reached −42.2 dB at 9.8 GHz. Moreover, the effective absorption (below -10 dB) bandwidth can reach 2.3 GHz from 8.5 to 10.8 GHz with absorbing thickness of 2 mm and it can be tuned between 2.8 to 14.4 GHz by tuning the thickness of 1.5-5 mm. It verified that introduction of N into SA for improving the dispersion of metal particles could obviously enhancement the performance of absorber. Moreover, the maximum RL of N-SA/Ni-3% (Figure 6b) was -33.7 dB at 11.4 GHz with the absorber thickness is only 2 mm and the maximum RL of N-SA/Ni-9% (Figure 6d) was -26.8 dB at 12.9 GHz with absorbing thickness of 2 mm, respectively. The results answer that the impedance matching was the mainly factor for N-SA/Ni-6% to possess best microwave absorption performance, meaning that the improved microwave absorption performance mainly came from the synergistic effect between magnetic loss of Ni nanocrystals and dielectric loss of 18


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N-SA. All the results showing that the N-SA/Ni-X hybrids present efficient microwave absorption performance in a wide frequency range, especially for N-SA/Ni-6%, completely cover the whole C (4-8 GHz) band and X (8-12 GHz) bands. These properties are greatly important for satellite communications, military radar systems, direct broadcast satellite and weather radar due to the precision object identification and high resolution imaging capacities. Simultaneously, a same method was also carried out for another two samples N-SA/Ni-12% and N-SA/Ni-15%, respectively. From Figure 2c1, the N-SA/Ni-9% already has some collapse in materials. So, the production of N-SA/Ni-12% and N-SA/Ni-15% were broken in the post processing due to the nature of the material itself. As a result, it can be concluded that a ratio of more than 9% could not exhibit well microwave absorption performance. Table. 2 shows the microwave absorption properties of typical absorbing composites in the frequency range of 2-18 GHz. It can be deduced that this newly synthesized N-SA/Ni-6% composite is better than most of related carbonaceous absorbers.

Table 2. Microwave absorption properties of typical absorbing composites in the frequency range of 2−18 GHz

absorber

content

RL(min)

thickness

effective bandwidth

ref

SA-Ni-(Fe3O4/CNTs)-X

15

-32

3.9

9.3-12.5

27

CuS

50

-17.5

1.1

14.5-17.5

53

Fe3O4/Fe@C

40

-28.18

1.5

3.2-9.5

54

carbon@Fe3O4

50

-10.8

4.0

1.1-2.6

55

N-SA/Ni-6%

50

-42.2

2.0

8.5-10.8

This work work

Taking into comprehensive analysis of the loss factors, microwave attenuation ability, impedance matching properties and microwave absorption results, the possible 19



Page 20 of 40

microwave absorbing mechanism of the N-SA/Ni-X(X=3%, 6%, 9%) composites is shown in Scheme 2. Firstly, when the incident wave reaches surface of absorber, improved impedance matching condition ensures that microwave can efficiently enter into the materials and partially dissipated by the form of heat due to electrons and charged particles.56 Secondly, the microwave attenuation ability could consume the incident microwave as much as possible by intrinsic magnetic loss of Ni particles and dielectric loss of N-SA. Simultaneously, the defects and residual groups formed in N-SA/Ni structure could lead to reflections and multiple scattering, which would further enhance the electromagnetic wave absorption capacity.57-60 Thirdly, the Ni particles, N element and oxygen functional groups in SA can act as a polarization centers, inducing interfacial polarization and related relaxation at the interfaces between Ni particles and N-SA, which can also contribute to the electromagnetic wave absorption properties.61-62 Commonly, the excellent electromagnetic wave absorption performance of the absorbing material is related to the synergistic effect between the components of N-SA/Ni-X(X=3%, 6%, 9%). CONCLUSIONS A new type of N-doped, three-dimensional carbonaceous composites decorated with highly dispersed Ni nanoparticles (N-SA/Ni-X) have been fabricated via a facile one-step encapsulation process and then carbonization at 600

o

C in nitrogen

atmosphere. The N-SA/Ni-6% composite exhibits the best microwave absorption properties, the maximum reflection loss (RL) reached −42.2 dB at 9.8 GHz. Besides, the effective absorption (below -10 dB) bandwidth can reach 2.3 GHz from 8.5 to 10.8 GHz with the absorber thickness of 2 mm and it can be tuned between 2.8 to 14.4 GHz by tuning the thickness of 1.5-5 mm. It was demonstrated that the introduction of N into SA for improving the dispersion of metal particles could obviously enhance the 20


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performance of absorber. Taking combinatorial advantages of the light-weight conductive N-SA porous framework with favorable dielectric loss and Ni particles with magnetic loss features, the absorber possessed superior electromagnetic wave absorbing performance. As a result, these newly synthesized N-SA/Ni-X composites could be regarded as promising candidates for lightweight and high-performance microwave absorption materials. ACKNOWLEDGMENTS Financial support from the National Natural Science Foundation of China (21676039), State Key Laboratory of Bio-Fibers and Eco-Textiles (2017kfkt12) and Innovative Talents in Liaoning Universities and Colleges (LR2017045) are highly appreciated. REFERENCES 1. Shahzad, F.; Alhabeb M.; Hatter, C. B.; Anasori, B.; Hong, S. M.; Koo, C. M.; Gogotsi, Y. Electromagnetic Interference Shielding With 2D Transition Metal Carbides (MXenes). Science. 2016, 353,1137-1140. 2. Liu, P.; Huang, Y.; Sun, X. Excellent Electromagnetic Absorption Properties of Poly(3,4--ethylenedioxythiophene)-Reduced Graphene Oxide-Co3O4 Composites Prepared by a Hydrothermal Method. ACS Appl. Mater. Interfaces. 2013, 5, 12355-12360. 3. Hanzo, L.; Haas, H.; Imre, S.; O’Brien, D.; Rupp, M.; Gyongyosi, L. Wireless Myths, Realities, and Futures: From 3G/4G to Optical and Quantum Wireless. PIEEE 2012, 100, 1853-1888. 4. Yan, D. X.; Pang H.; Li, B.; Vajtai, R.; Xu, L.; Ren, P. G. , Wang, J. H.; Li, Z. M.; Structured Reduced Graphene Oxide/Polymer Composites for Ultra-Efficient Electromagnetic Interference Shielding. Adv. Funct. Mater, 2015, 25, 559-566. 21



5. Wang, L. N.; Jia, X. L.; Li, Y. F.; Yang, F.; Zhang, L. Q.; Liu, L. P.; Ren, X and Yang, H. T. Synthesis and Microwave Absorption Property of Flexible Magnetic Film Based on Graphene Oxide/Carbon Nanotubes and Fe3O4 Nanoparticles. J. Mater. Chem. A, 2014, 2, 14940-14947. 6. Zheng, X. L.; Feng, J.; Zong, Y.; Miao, H.; Hu, X. Y.; Bai, J. T. and Li, X. H. Hydrophobic Graphene Nanosheets Decorated by Monodispersed Superparamagnetic Fe3O4 Nanocrystals as Synergistic Electromagnetic Wave Absorbers. J. Mater. Chem. C, 2015, 3, 4452-4464. 7. Liu, J.; Cao, M. S.; Luo, Q.; Shi, H. L.; Wang, W. Z.; Yuan, J. Electromagnetic Property and Tunable Microwave Absorption of 3D Nets From Nickel Chains at Elevated Temperature. Acs Appl. Mater. Interfaces 2016, 8, 22615-22622. 8. Liu, T.; Xie, X.; Pang, Y.; Kobayashi, S. Co/C Nanoparticles with Low Graphitization Degree: A High Performance Microwave-absorbing Material. J. Mater. Chem. C 2016, 4, 1727-1735. 9. Qu, B.; Zhu, C.-L.; Li, C.-Y.; Zhang, X. -T.; Chen, Y.-J. Coupling Hollow Fe3O4-Fe Nanoparticles with Graphene Sheets for High-Performance Electromagnetic Wave Absorbing Material. ACS Appl. Mater. Interfaces 2016, 8, 3730-3735. 10. Feng, J.; Pu, F.; Li, Z.; Li, X.; Hu, X and Bai, J. Interfacial Interactions and Synergistic Effect of CoNi Nanocrystals and Nitrogen-doped Graphene in a Composite Microwave Absorber. Carbon 2016, 104, 214-225. 11. Xia, T.; Zhang, C.; Oyler, N.; Chen, X. Hydrogenated TiO2 Nanocrystals: A Novel Microwave Absorbing Material. Adv. Mater. 2013, 25, 6905-6910. 12. Han, M. K.; Yin, X. W.; Hou, Z. X.; Song, C. Q.; Li, X. L.; Zhang, L. T. and Cheng, L. F. Flexible and Thermostable Graphene/SiC Nanowires Foam Composites with Tunable Electromagnetic Wave Absorption Properties. ACS Appl. Mater. 22


Page 22 of 40

Page 23 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Interfaces 2017, 9, 11803-11810 13. Liu, P.; Huang, Y.; Yan, J.; Yang, Y.; Zhao, Y. Construction of CuS Nanoflakes Vertically Aligned on Magnetically Decorated Graphene and their Enhanced Microwave Absorption Properties. ACS Appl. Mater. Interfaces 2016, 8, 5536-5546. 14. Cao, M. S.; Yang, J.; Song, W. L.; Zhang, D. Q.; Wen, B.; Jin, H. B.; Hou, Z. L.; Yuan, J. Ferroferric Oxide/Multiwalled Carbon Nanotube vs Polyaniline/Ferroferric Oxide/Multiwalled Carbon Nanotube Multiheterostructures for Highly Effective Microwave Absorption. ACS Appl. Mater. Interfaces 2012, 4, 6949−6956. 15. Liu, P. J.; Ng, V. M. H.; Yao, Z. J.; Zhou, J. T.; Kong, L. B. Ultrasmall Fe3O4 Nanoparticles on MXenes with High Microwave Absorption Performance. Materials Letters 2018, 229, 286-289. 16. Zhu, Y. F.; Ni, Q. Q. and Fu, Y. Q. One-Dimensional Barium Titanate Coated Multi-Walled Carbon Nanotube Heterostructures: Synthesis and Electromagnetic Absorption Properties. RSC Adv. 2015, 5, 3748-3756 17. Zhi, C. X.; Chen,Y. J.; Li, W.; Li, J. B; Yu, H.; Liu, L. Y.; Wu, G. L.; Yang, T. and Luo, L. J. Preparation of Boron Nitride Nanosheet-Coated Carbon Fibres and Their Enhanced Antioxidant and Microwave-Absorbing Properties. RSC Adv. 2018, 8, 17944-17949. 18. Sun, H.; Che, R. C.; You, X.; Jiang, Y. S.; Yang, Z. B.; Deng, J.; Qiu, L. B.; Peng, H. S. Cross-Stacking Aligned Carbon-Nanotube Films to Tune Microwave Absorption Frequencies and Increase Absorption Intensities. Adv. Mater. 2014, 26, 8120−8125. 19. Zhang, Y.; Huang, Y.; Zhang, T.; Chang, H.; Xiao, P.; Chen, H.; Huang, Z.; Chen, Y. Broadband and Tunable High-performance Microwave Absorption of an Ultralight and Highly Compressible Graphene Foam. Adv. Mater. 2015, 27, 2049–2053. 20. Liu, X. G.; Ou, Z. Q.; Geng, D. Y.; Han, Z. J.; Jiang, J.; Liu, W.; Zhang, Z. D. 23



Influence of a Graphite Shell on the Thermal and Electromagnetic Characteristics of FeNi Nanoparticles. Carbon 2010, 48, 891−897. 21. Lv, J. L.; Zhai, S. R.; Gao, C.; Zhou, N.; An, Q. D.; Zhai, B. Synthesis of Lightweight, Hierarchical Cabbage-Like Composites as Superior Electromagnetic Wave Absorbent. Chem. Eng. J. 2016, 289, 261−269. 22. Chen,Y. H.; Huang, Z. H.; Lu, M. M.; Cao, W. Q.; Yuan, J.; Zhang, D. Q. and Cao, M. S. 3D Fe3O4 Nanocrystals Decorating Carbon Nanotubes to Tune Electromagnetic Properties and Enhance Microwave Absorption Capacity. J.Mater. Chem. A 2015, 3, 12621. 23. Sun, J.; Lv, C. X.; Lv, F.; Chen, S.; Li, D. H.; Guo, Z. Q.; Han, W.; Yang D. J. and Guo, S. J.

Tuning the Shell Number of Multishelled Metal Oxide Hollow Fibers for

Optimized Lithium-Ion Storage, ACS Nano 2017, 11, 6186−6193. 24. Yan, Y. Z.; An, Q. D.; Xiao, Z. Y.; Zheng, W.; Zhai, S. R. Flexible Core-Shell/Bead-like Alginate@PEI with Exceptional Adsorption Capacity, Recycling Performance toward Batch and Column Sorption of Cr(VI). Chem. Eng. J. 2017, 313, 475−486. 25. Zou, Y. H.; Yang, X. F.; Lv, C. X.; Liu, T. C.; Xia, Y. Z.; Shang, L.; Yang, D. J.; Zhang, T. R. Multi-Shelled Ni-rich Li(NixCoyMnz)O2 Hollow Fibers with Low Cation Mixing as High-Performance Cathode Materials for Li-ion Batteries. Adv. Sci. 2016, 9, 1−8. 26. Zhou, N.; An, Q.-D.; Zheng, W.; Xiao, Z. Y.; Zhai, S. R. High-Performance Electromagnetic Wave Absorbing Composites Prepared by One-Step Transformation of Fe3+ Mediated Egg-Box Structure of Seaweed. RSC Adv. 2016, 6, 98128−98140. 27. Zhou, N.; An, Q. D.; Xiao, Z. Y.; Zhai, S. R. Rational Design of Superior Microwave Shielding Composites Employing Synergy of Encapsulating Character of 24


Page 24 of 40

Page 25 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Alginate Hydrogels and Task-Specific Components (Ni NPs, Fe3O4/CNTs) ACS Sustainable Chem. Eng. 2017, 5, 5394−5407. 28. Yan, Y. Z.; An, Q. D.; Xiao, Z. Y.; Zhai, S. R.; Zhai, B.; Shi, Z. Multi-Cavities/Surface Exceptionally

Engineering

Efficient

Aqueous Systems

of

Chromium

Alginate Removal

Hydrogels with in

Interior PEI

for

Batch and Continuous

J. Mater. Chem. A 2017, 5, 17073-17087.

29. Lu, M. M.; Cao, M. S.; Chen, Y. H.; Cao, W. Q.; Liu, J.; Shi, H. L.; Zhang, D. Q.; Wang, W. Z.; Yuan, J. Multiscale Assembly of Grape-Like Ferroferric Oxide and Carbon Nanotube: A Smart Absorber Prototype Varying Temperature to Tune Intensities. ACS Appl. Mater. Interfaces 2015, 7, 19408-19415. 30. Chen, Y. J.; Xiao, G.; Wang, T. S.; Ouyang, Q. Y.; Qi, L. H.; Ma, Y.; Gao, P.; Zhu, C. L.; Cao, M. S.; Jin, H. B. Porous Fe3O4/Carbon Core/Shell Nanorods: Synthesis and Electromagn Properties. J. Phys. Chem. C 2011, 115, 13603-13608. 31. Wang, G. S.; Wu, Y. Y.; Zhang, X. J.; Li, Y.; Guo, L.; Cao, M. S.; Controllable Synthesis of Uniform ZnO Nanorods and Their Enhanced Dielectric and Absorption properties. J. Mater. Chem. A 2014, 2, 8644-8651. 32. Belavin, V. V.; Okotrub, A. V.; Bulusheva, L. G. A Study of the Influence of Structural Imperfection on the Electronic Structure of Carbon Nanotubes by X-ray Spectroscopy and Quantum-Chemical Methods. Phys. Solid State 2002, 44, 663−665. 33. Li, Z. X.; Li, X. H. ; Zong, Y.; Z. Y.; Zheng, X. L.

Tan, G. G.; Yong, S.;

Lan, Y. Y.; He, Mi.; Ren,

Solvothermal Synthesis of Nitrogen-Doped Graphene Decorated

by Superparamagnetic Fe3O4 Nanoparticles and Their Applications as Enhanced Synergistic Microwave Absorbers. Carbon 2017, 115, 493-502. 34. Wang, C.; Han, X.; Zhang, X.; Hu, S.; Zhang, T.; Wang, J.; Du, Y.; Wang, X.; Xu, P. Controlled Synthesis of Hierarchical Nickel and Morphology-Dependent 25



Electromagnetic Properties. J. Phys. Chem. C 2010, 114, 14826−14830. 35. Zhao, B.; Shao, G.; Fan, B. B.; Zhao, W. Y. and Zhang, R. Facile Synthesis and Enhanced Microwave Absorption Properties of Novel Hierarchical Heterostructures Based on a Ni Microsphere-CuO Nano-Rice Core-Shell Composite. Phys. Chem. Chem. Phys.2015, 17, 6044. 36.Zhao, B.; Liu, J. W.; Guo, X. Q.; Zhao, W. Y.; Liang, L. Y.; Ma, C. and Zhang, R. Hierarchical Porous Ni@Boehmite/Nickel Aluminum Oxide Flakes with Enhanced Microwave Absorption Ability. Phys. Chem. Chem. Phys. 2017, 19, 9128-9136 37. Zhao, B.; Guo, X. Q.; Zhao, W. Y.; Deng, J. S.; Fan, B. B.; Shao, G.; Bai, Z. Y. and Zhang, R. Facile Synthesis of Yolk-Shell Ni@Void@SnO2(Ni3Sn2) Ternary Composites via Galvanic Replacement/Kirkendall Effect and Their Enhanced Microwave Absorption Properties. Nano Research 2017, 10, 331-343 38.Zhao, B.; Guo, X. Q.; Zhao, W. Y.; Deng, J. S.; Shao, G.; Fan, B. B.; Bai, Z. Y. and Zhang, R. Yolk-Shell Ni@SnO2 Composites with a Designable Interspace To Improve the Electromagnetic Wave Absorption Properties. ACS Appl. Mater. Interfaces 2016, 8, 28917-28925. 39. Zhao, B.; Zhao, W. Y.; Shao, G.; Fan, B. B.; and Zhang, R. Morphology-Control Synthesis of a Core-Shell Structured NiCu Alloy with Tunable Electromagnetic-Wave Absorption Capabilities. ACS Appl. Mater. Interfaces 2015, 23, 12951-12960 40. Zhao, B.; Fan, B. B.; Shao, G.; Zhao, W. Y.; and Zhang, R. Facile Synthesis of Novel Heterostructure Based on SnO2 Nanorods Grown on Submicron Ni Walnut with Tunable Electromagnetic Wave Absorption Capabilities. ACS Appl. Mater. Interfaces 2015, 33, 18815-18823 41. Zheng, X. L.; Feng, J.; Zong,Y.; Miao, H.; Hu, X. Y.; Bai, J. T. and Li, X. H. Hydrophobic Graphene Nanosheets Decorated by Monodispersed Superparamagnetic 26


Page 26 of 40

Page 27 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fe3O4 Nanocrystals as Synergistic Electromagnetic Wave Absorbers. J. Mater. Chem. C 2015, 3, 4452. 42. Du, Y. C.; Liu, T.; Yu, B.; Gao, H. B.; Xu, P.; Wang, J. Y.; Wang, X. H.; Han, X. J. The Electromagnetic Properties and Microwave Absorption of Mesoporous Carbon Mater. Chem. Phys. 2012, 135, 884-891. 43. Tong, G.; Hu, Q.; Wu, W.; Li, W.; Qian, H.; Liang, Y. Submicrometer-Sized NiO Octahedra: Facile One-Pot Solid Synthesis, Formation Mechanism, and Chemical Conversion into Ni Octahedra with Excellent Microwave-Absorbing Properties. J. Mater. Chem. 2012, 22, 17494-17504. 44. Zheng, X. L.; Feng, J.; Zong, Y.; Miao, H.; Hu, X.Y.; Bai, J. T. Hydrophobic Graphene Nanosheets Decorated by Monodispersed Superparamagnetic Fe3O4 Nanocrystals as Synergistic electromagnetic wave absorbers, J. Mater. Chem. C 2015, 3, 4452-4463. 45. Li, X.; Du, D.; Wang, C.; Wang, H.; Xu, Z. In Situ Synthesis of Hierarchical Rose-like Porous Fe@C with Enhanced Electromagnetic Wave Absorption. J. Mater. Chem. C 2018, 6, 558-567. 46. Du, Y. C.; Liu,W. W.; Qiang, R.; Wang, Y.; Han, X. J.; Ma, J. and Xu, P. Shell Thickness-Dependent Microwave Absorption of Core–Shell Fe3O4@C Composites ACS Appl. Mater. Interfaces

2016, 15, 12997-13006.

47. Wang, G. Z.; Peng, X. G.; Yu, L.; Wan, G. P.; Lin, S. W.; Qin, Y. Enhanced Microwave Absorption of ZnO Coated with Ni Nanoparticles Produced by Atomic Layer Deposition. J. Mater. Chem. A 2015, 3, 2734−2740. 48. He, J. Z.; Wang, X. X.; Zhang, Y. L.; Cao, M. S.

Small Magnetic Nanoparticles

Decorating Reduced Graphene Oxides to Tune the Electromagnetic Attenuation Capacity, J. Mater. Chem. C 2016, 4, 7130-7140. 27



49. Hu, C. G.;

Page 28 of 40

Mou, Z. Y.; Lu G.W.; Chen, N.; Dong, Z. L.; Hu, M. J. and Qu, L. T.

3D Graphene–Fe3O4 Nanocomposites

with

High-Performance

Microwave

Absorption. Phys. Chem. Chem. Phys. 2013, 15, 13038-13043. 50. Zong, M.; Huang, Y.; Zhao, Y.; Sun, X.; Qu, C.; Luo, D.; Zheng, J. Facile Preparation, High Microwave Absorption and Microwave Absorbing Mechanism of RGO-Fe3O4 Composites. RSC Adv. 2013, 3, 23638-23648. 51. Wang, Y. F.;

Chen, D. L.;

Yin, X.; Xu, P.;

Wu, F. and He, M. Hybrid of

MoS2 and Reduced Graphene Oxide: A Lightweight and Broadband Electromagnetic Wave Absorber. ACS Appl. Mater. Interfaces 2015, 7, 26226-26234. 52. Zhang, X. M.; Ji, G. B.; Liu, W.; Quan, B.; Liang, X. H.; Shang, C. M.; Cheng, Y.; Du, Y. W. Thermal Conversion of an Fe3O4@Metalorganic Framework: A New Method for an Efficient Fe-Co/nanoporous Carbon Microwave Absorbing Material. Nanoscale 2015, 7, 12932-12942. 53. Zhao, B.; Guo, X. Q.; Zhou, Y. Y.; Su, T. T.; Ma, C. and Zhang, R. Constructing Hierarchical Hollow CuS Microspheres Via a Galvanic Replacement Reaction and Their Use as Wide-band Microwave Absorbers. CrystEngComm 2017, 19, 2178. 54. Liu, Y.; Li, Y. N.; Jiang, K. D.; Tong, G. X.; Lv, T. X. and Wu, W. H.

Controllable

Synthesis of Elliptical Fe3O4@C and Fe3O4/Fe@C Nanorings for Plasmon Resonance Enhanced Microwave Absorption. J. Mater. Chem. C 2016, 4, 7316. 55. Yin, P. F.; Deng, Y.; Zhang, L. M.; Li, N.; Feng, X.; Wang, J. and Zhang, Y.

Facile

Synthesis and Microwave Absorption Investigation of Activated Carbon@Fe3O4 Composites in the Low Frequency Band. RSC Adv. 2018, 8, 23048. 56. Xing, H. L.; Liu, Z. F.; Lin, L.; Wang, L.; Tan, D. X.; Gan, Y.; Ji, X. L.; Xu, G. C. Excellent Microwave Absorption Properties of Fe Ion-doped SnO2/Multi-Walled Carbon Nanotube Composites. RSC Adv. 2016, 6, 41656−41664. 28


Page 29 of 40 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


57. Lu, M. M.; Cao, W. Q.; Shi, H. L.; Fang, X. Y.; Yang, J.; Hou, Z. L.; Jin, H. B.; Wang, W. Z.; Yuan, J.; Cao, M. S. Multi-Wall Carbon Nanotubes Decorated with ZnO Nanocrystals: Mild Solution-Process Synthesis and Highly Efficient Microwave Absorption Properties at Elevated Temperature. J. Mater. Chem. A 2014, 2, 10540 − 10547. 58. Yan, J.; Huang, Y.; Wei, C.; Zhang, N.; Liu, P. B.; Covalently Bonded Polyaniline/Graphene Composites as High-Performance Electromagnetic (EM) Wave Absorption Materials. Composites Part A: Applied Science & Manufacturing 2017, 99, 121-128. 59. Zhang, N.; Huang, Y.;

Zong, M.; Ding, X.; Li, S. P.; Wang, M. Y.;

Synthesis of

ZnS Quantum Dots and CoFe2O4 Nanoparticles Co-Loaded with Graphene Nanosheets as An Efficient Broad Band EM Wave Absorber. Chemical Engineering Journal 2017, 308, 214-221. 60. Liu, P. B.; Yan, J.; Gao, X. G.; Huang, Y.; Zhang, Y. Q. Construction of Layer-by-Layer

Sandwiched

Graphene/Polyaniline

Nanorods/Carbon

Heterostructures for High Performance Supercapacitors.

Nanotubes

Electrochimica Acta 2018,

272, 77-87. 61. Liu, P. J.; Ng, V. M. H.; Yao, Z. J.; Zhou, J. T.; Lei, Y. M.; Yang, Z. H.; Lv, H. L. and Kong, L. B. Facile Synthesis and Hierarchical Assembly of Flowerlike NiO Structures with Enhanced Dielectric and Microwave Absorption Properties. ACS Appl. Mater. Interfaces 2017, 9, 16404-16416. 62. Liu, P. J.; Yao, Z. J.; Zhou, J. T.; Yang, Z. H.; and Kong, L. B. Small Magnetic Co-doped NiZn Ferrite/Graphene Nanocomposites and Their Dual-Region Microwave Absorption Performance. J. Mater. Chem. C 2016, 4, 9738.

29


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Figure 1. SEM images of SA/Ni-6% (a1, a2), N-SA/Ni-3% (b1, b2), N-SA/Ni-6% (c1, c2) and N-SA/Ni-9% (d1, d2); the EDS elemental mapping images of N-SA/Ni-6% (e).

31


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Figure 2. TEM images of SA/Ni-6% (a1, a2), N-SA/Ni-6% (b1, b2) composites, HRTEM image of Ni lattice area of SA-Ni (c), inset is the SAED pattern of N-SA/Ni-6% hybrids; Size distributions of Ni nanocrystals for N-SA/Ni-6% (d).

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Figure 3. XPS spectra: (a) wide scan of N-SA/Ni-X (X=3%, 6%, 9%); (b) C 1s, (c) Ni 2p, (d) O 1s and (e) N 1s spectra of N-SA/Ni-6%.

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Figure 4. Frequency dependence of (a) real and (b) imaginary parts of complex permeability, (c) real parts and (d) imaginary parts of complex permittivity for the SA/Ni-6% and N-SA/Ni-X (X=3%, 6%, 9%).

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Figure 5. (a) The attenuation constant of SA/Ni-6% and N-SA/Ni-X (X=3%, 6%, 9%), (b) the modulus of normalized input impedance of the products at a thickness of 2.0mm.

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Figure 6. Three-dimension images of calculated RL values of (a) SA/Ni-6%, (b) N-SA/Ni-3%, (c) N-SA/Ni-6% and (d) N-SA/Ni-9% composites.

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Scheme 1. Controllable fabrication process of N-SA/Ni-X (X = 3%, 6%, 9%) composites that prepared through encapsulation and carbonization processes.

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Scheme 2. Plausible mechanism for the microwave absorption over fabricated N-SA/Ni-6% composites.

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Controllable N-Doped Carbonaceous Composites with Highly

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