melamine derived carbon foam as a comprehensive microwave absorbing material

Accepted Manuscript 3D hierarchical Co3O4/Reduced graphene oxide/melamine derived carbon foam as a comprehensive microwave absorbing material Ye Li, Shuang Li, Tong Zhang, Luolin Shi, Shitai Liu, Yan Zhao PII:

S0925-8388(19)31203-4

DOI:

https://doi.org/10.1016/j.jallcom.2019.03.359

Reference:

JALCOM 50123

To appear in:

Journal of Alloys and Compounds

Received Date: 26 December 2018 Revised Date:

25 March 2019

Accepted Date: 26 March 2019

Please cite this article as: Y. Li, S. Li, T. Zhang, L. Shi, S. Liu, Y. Zhao, 3D hierarchical Co3O4/Reduced graphene oxide/melamine derived carbon foam as a comprehensive microwave absorbing material, Journal of Alloys and Compounds (2019), doi: https://doi.org/10.1016/j.jallcom.2019.03.359. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT 3D Hierarchical Co3O4/Reduced Graphene Oxide/Melamine Derived Carbon Foam as a Comprehensive Microwave Absorbing Material a Ye Li , Shuang Lia, Tong Zhanga,b, Luolin Shia, Shitai Liua, Yan Zhaoa,* a School of Materials and Engineering, Beihang University, Beijing 100191, China b Beijing Institute of Aeronautical Materials, Beijing 100095, China

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Abstract In this work, a simple and cost-effective method was developed to prepare a novel structure with Co3O4 nanoparticles dispersed on 3D graphene-wrapped carbon foam with melamine foam as initial skeleton. This Co3O4/ Reduced graphene oxide/ Melamine derived carbon foam (Co3O4/RGO/MDCF) hybrid with a continuous conductive network and low bulk density of 10.6 mg/cm3 exhibits high specific microwave absorption performance. The maximum Reflection Loss (RL) value of −31.88 dB at 11.54 GHz and a qualified bandwidth of 3.4GHz (RL≤-10dB) with the coating layer thickness of only 2.0 mm under 10 wt.% loading was achieved by Co3O4/RGO/MDCF composite. Notably our work provides a general and low-cost method to fabricate comprehensive microwave absorption materials with high RL value, low density, thin thickness and low loading content, which can be applied on scale and meet the requirement for the new type of electromagnetic wave absorptive material. Keywords: Microwave absorption performance; Co3O4; Reduced graphene oxide; Melamine Foam

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1 Introduction In the era of information explosion with extensive use of communication and electronic devices in various fields, electromagnetic wave pollution has become a severe problem, limiting the precision of the sophisticated electronic devices and causing harm in environment and human being [1-4]. In order to reduce electromagnetic contamination, Microwave absorption (MA) materials have received great attention. Conventional MA materials, such as magnetic metal oxides, magnetic metal powders can attenuate electromagnetic wave effectively, while their application is restrained by the drawbacks of large density and serious aggregation problem [5-7]. Therefore, the new comprehensive MA material with light weight and high efficiency electromagnetic interference shielding are urgently demanded [8]. Graphene, a novel two-dimensional carbon material with excellent electrical and mechanical properties [9,10], has attracted tremendous attention as its broad application in various fields, including energy, sensor, mechanics and environment [11-14]. Due to its low density, large specific surface area and high electron mobility, it’s a promising candidate for supporting and inducing growth of dielectric loss materials or magnetic loss materials to achieve better electromagnetic interference shielding effect through significant synergistic or complementary behavior between graphene and nanomaterials [15-19]. Co3O4 is one of the most intriguing magnetic p-type semiconductors, which has been widely used in various fields [20-22]. Many successful efforts have been devoted to synthesizing composites of Co3O4 with graphene to be used as MA materials [23-33]. However, according to literature survey, they still suffer from high thickness and loading content (usually more than 50 wt.%). To overcome this problem, one strategy is to construct 3D conductive network in the MA

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materials. Carbon foam was expected to be a promising candidate to build conductive network. Disappointedly, it owns superior electromagnetic interference shielding with high microwave reflection performance, but poor microwave absorption performance [34,35]. The emerging graphene foam has broken this paradoxical state of affairs [36-41]. Nevertheless, for practical application, the typical route to prepare graphene foam, chemical vapor deposition (CVD), is difficult to be scaled up due to the complex fabrication process and expensiveness of the raw material [42]. Thus, developing simple and cost-effective alternatives of graphene foam as substrate for 3D carbon-based microwave absorber with light weight and high MA performance is worth investigating. Zhang et al. prepared 3D and ternary rGO/MCNTs/Fe3O4 composite via hydrothermal process and achieved a maximum absorption value of -36 dB at 13.44 GHz with a coating layer thickness of only 2.0 mm [39]. Shi et al. synthesize 3D lightweight Fe3O4/MWCNT/GF hybrids with high performance microwave absorption by solvothermal reaction [43]. Here, we introduce a new route to prepare 3D structure with high microwave absorption in low content of graphene to further reduce the cost. In this paper, we fabricated 3D conductive network in the MA materials through carbonizing the reduced graphene oxide modified melamine foam. After carbonization, RGO/MDCF displayed of −21.54 dB at 11.20 GHz with the coating layer thickness of

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2.1 mm, which is even higher than some reported graphene foam [43,44]. With implantation of Co3O4, the obtained Co3O4/RGO/MDCF hybrids exhibit an excellent MA properties in the measured frequency range of 2–18 GHz, with minimum RL reaching −31.88 dB at 11.54 GHz with the coating layer thickness of only 2.0 mm under 10 wt.% loading, showing a promising future to be used in the application of aerospace, automobile etc. due to its high specific RL, low density, thin thickness and low loading content.

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2.1 Materials A commercially available melamine foam (MF) with flexible three-dimensional open hole structure and excellent hydrophilicity which was manufactured by Greencare Co., Ltd. was used as the raw template material. Flake graphene oxide (GO) powder used to synthesis reduced graphene oxide in this study was obtained from Shanghai Ashine Technology Development Co., Ltd. Cobalt chloride hexahydrate and urea were provided by Beijing Chemical Works. All the chemical reagents were utilized as acquired without any further purification or treatment. 2.2 Synthesis of Co3O4/RGO/MDCF composites First, a piece of melamine foam was washed with deionized water and ethanol for three times, followed by drying at room temperature for 32 hours. Graphene oxide was dispersed in deionized water by sonication at the concentration of 5 mg/mL. Vitamin C was mixed with the GO solution at mass ratio of 1: 2. Then melamine foam with the size of 5×4×3 cm3 was immersed into the mixture and stirred at 300 rpm for 5 min to achieve the self–assembled graphene on the melamine foam. After dialyzing for 48 hours with deionized water, the as-prepared samples (RGO/MF) was freeze dried for another 72 hours, keeping the original porous morphological structure away from collapsing. The obtained aerogel was annealed at 800 in a tubular furnace under nitrogen

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atmosphere for 1 hour to be carbonized and then the graphene coated three-dimensional carbon foam was formed (RGO/MDCF). In a typical procedure of Co3O4/RGO/MDCF, RGO/MDCF was immersed in the mixture of 2 mmol cobalt chloride hexahydrate and 2mmol urea in 40 mL deionized water, followed by stirring for 10 min. Next, the mixture and RGO/MDCF was sealed into 50 mL Teflon-lined autoclaves and hydrothermal treated at 120◦C for 16 h. After cooled to room temperature naturally, the as-prepared products were taken out with tweezer, washed with deionized water repeatedly and heated at 450◦C for 2h in air.

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2.3. Characterization The X-ray diffraction (XRD) was conducted with a Rigaku D/max-rB equipment. It took Cu Kα radiation as the X-ray source (λ= 1.5406 Å) and a self-calibration process carried out with a SiO2 internal standard sample prior to target measurement. The samples were scanned ranging from 5–80◦ with a step size of 0.02◦. Scanning electron microscopy (SEM) images were obtained via a JSM-7500 scanning electron microscope equipment with an accelerating voltage of 15 kV for further morphological analysis. X-ray photo-electron spectroscopy (XPS) was measured via a ESCALab 220i-XL spectrometer with Al K radiation (1486.6 eV) as the X-ray source for excitation. Thermogravimetric analysis (TGA) profile was obtained in air via NETZSCH STA409C/3/F instrument. Electromagnetic wave S parameters (S11, S12, S21, S22) were measured using an Agilent HP-8722ES vector network analyzer in the frequency ranging from 2 to 18 GHz. The measured sample was prepared by uniformly mixing with paraffin matrix, which contains a low ratio of 10 wt.% of as-prepared product. The mixture was crushed into a toroidal-shaped sample with outer diameter of 7.00 mm and inner diameter of 3.04 mm, respectively. Permittivity and permeability were calculated from the S parameters based on the open literature. RL and bandwidth, as intuitionistic characteristic parameters, were calculated from permittivity and permeability according to certain formula.

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3. Results and discussion The fabrication process of Co3O4/RGO/MDCF composites is schematically illustrated in Figure 1. Here melamine foam, a melamine-formaldehyde polymer, was utilized as skeleton because of its low density, high porosity and high adsorption capacity [42]. GO sheets were wrapped on the sponge skeleton due to electrostatic effect. During annealing process, the polymer foam formed a stable carbon structure with breakdown of the methylene bridge [45]. Meanwhile, reduced graphene oxide was self-assembled on melamine derived carbon foam (MDCF) via π − π stacking. The obtained RGO/ MDCF was utilized as substrate for dispersion and implantation of Co3O4 particles. Co2+ permeated into interior through pores and absorbed on the large surface of RGO. Co(OH)2 is formed in the alkaline environment during hydrothermal process, which changed into Co3O4 by subsequent annealing [46].

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Figure 1 Schematic of synthesis procedure for Co3O4/RGO/MDCF hybrids.

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Figure 2 XRD patterns for Co3O4/RGO/MDCF hybrids.

XRD patterns of the as-prepared samples are shown in Figure 2. The diffraction peak at 22 can be assigned to the (002) plane of graphitic carbon which is formed during carbonization [47]. With RGO deposition, a shoulder peak emerges at around 25 , which corresponds to the moderately aligned graphitic arrays along the (002) direction, indicating thorough reduction of GO after thermal annealing [48]. Compared with that of MDCF and RGO/MDCF, the new peaks indicated by circle pattern can be indexed to planes of Co3O4 according to JCPDS card No.43-1003.

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Figure 3 TGA curve of Co3O4/RGO/MDCF hybrids

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To evaluate the mass content of Co3O4 in Co3O4/RGO/MDCF composite, TG was conducted in air, which result is shown in Figure 3. The drastic decline of mass can be ascribed to the violent burning of carbon, beginning at around 400oC and ending at around 600oC, which is consistent with our previous research [43]. The residual quality should be attributed to Co3O4. Hence, the weight percentage of Co3O4 is around 25% and that for carbon is around 75%. The low loading of Co3O4 on RGO/MDCF ensures the low density of 10.6 mg/cm3 for Co3O4/RGO/MDCF composite.

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Figure 4 The SEM images of a) MDCF, b) RGO/MDCF, c) Co3O4/RGO/MDCF

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SEM was employed to study the morphology and internal structure of Co3O4/RGO/MDCF composite. As shown in Figure 4a, the morphology for MDCF is highly porous, with triangular branches forming three-dimensional interconnected network. It proves that the 3D porous structure remained after carbonization. The surface of MDCF is uneven, caused by the inorganic particles exuded during carbonization. From Figure 4b, it can be seen that graphene layer tightly wrapped on the surface of carbon foam with lamellar sheets outwardly extending, which can facilitate the rapid transmission of electrons and heat. Meanwhile, the deposition of graphene retards shrinkage of the carbon foam. Figure 4c clearly demonstrates that Co3O4 particles are uniformly distributed on the surface of RGO/MDCF.

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Figure 5 a) The XPS survey spectra of Co3O4/RGO/MDCF b) Co2p XPS spectrum of Co3O4/RGO/MDCF c) and d) N1s XPS spectra of Co3O4/RGO/MDCF and MDCF respectively

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The chemical states of elements in Co3O4/RGO/MDCF composite were investigated by XPS measurements, which result is presented in Figure 5. The survey spectrum clearly shows that Co, C, O and N elements coexist in the as-prepared samples. The strong peak of carbon signal also proves carbon is main component of the sample, which can ensure the low density characteristics. Figure 5b exhibits the Co 2p XPS spectrum with two major peaks locating at 780.8 and 796.2 eV, corresponding to the Co 2p3/2 and Co 2p1/2 spin-orbit peaks of Co3O4, respectively, and two shake-up satellite peaks locating at approximately 6 eV above the main peaks, which is characteristic of a Co3O4 phase and in good agreement with the open literature [23,25,26,28]. In Figure 5c, the N 1s spectrum could be deconvoluted into two peaks with binding energies located at 400.3 eV and 398.3 respectively, which is attributed to quaternary and pyridinic N respectively [45,49]. As comparison, the N 1s spectrum of MDCF is exhibited in Figure 5d. It is clearly exhibited that the relative pyridinic N content in Co3O4/RGO/MDCF is higher than that in MDCF. According to previous literature, the amount of peripheral pyridine nitrogen decreases, while the proportion of quaternary nitrogen increases with heat treatment temperature increasing [45]. It means that the introduction of graphene and Co3O4 on melamine will slow down the condensation reactions during carbonization. The pyridinic nitrogen at periphery of the graphene layers can provide a pair of electrons introducing electron donor properties to the layer [45]. Therefore, we can reasonably expect better electron transfer performance of Co3O4/RGO/MDCF than MDCF, which is beneficial to MA performance.

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Figure 6 Real part of permittivity (a), imaginary part of permittivity (b), real part of permeability (c), imaginary part of permeability (d), dielectric tangent loss (e), magnetic tangent loss (f) of MDCF,

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RGO/MDCF, Co3O4/ RGO/MDCF and Co3O4 respectively.

The electromagnetic parameters were measured through coaxial method to estimate the MA ability of the samples. According to the Debye theory, the real parts of complex permittivity ε′ and complex permeability µ′ stand for the storage ability of electric and magnetic energy, and imaginary parts (ε″ and µ″) represent the loss capability of electric and magnetic energy. From Figure 6a and 6b, it is clear to see that wrapping of graphene on the skeleton of MDCF can enhance ε′ and ε′’ significantly. Permittivity parameters can be clarified by the following equations [50]:  −     

1    −   " 



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 Where  represents static dielectric constant,  represents the relative dielectric constant at

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tangent (tan 

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high frequency limit, represents angular frequency, τ represents the polarization relaxation time and  represents the electrical conductivity. To study the effect of graphene on MA properties, electromagnetic parameters for MDCF with different graphene loading was tested and shown in Figure S1. With graphene content increment, permittivity of composite increases gradually until loading concentration of 5 mg/ml. At further higher loading content of graphene, permittivity declines. It proves that optimized content of graphene on MDCF is essential to construct 3D conductive network as microwave absorbers. Our previous study shows that RGO/MDCF prepared with 5 mg/ml graphene owns the highest electrical and thermal conductivity [51]. It suggests that the high permittivity of RGO/MDCF may be ascribed to its high conductivity, contributed from fast electron and thermal transfer between RGO. Due to the existence of 3D conductive network, slight addition of Co3O4 into RGO/MDCF composite has little influence on ε′ value, while it declines ε′′ value (Figure S2), which is beneficial to impendence match of the wave absorption, because too high permittivity will give rise to strong reflection, resulting in weak absorption [33,52]. Figure 6c and 6d show the real part (µ′) and imaginary part (µ″) of the relative complex permeability respectively. It reveals that the values of µ′ are in the range of 0.9–1.1 and the µ″ values are less than 0.28 over 2–18 GHz. Dielectric loss ) and magnetic loss tangent (tan 



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ranging from 2-18 GHz, which result is shown in Figure 6e and 6f. The higher values of dielectric loss tangent than the values of magnetic loss tangent indicate that the composites are mainly dependent on the dielectric loss. For Co3O4/RGO/MDCF, it can be observed that, its dielectric loss tangent is lower than that of RGO/MDCF while its magnetic loss tangent is higher, leading to the relatively complementarities between dielectric loss and magnetic loss, which can contribute to the MA performance.

Figure 7 3D RL plots of (a) MDCF, (b)RGO/MDCF, (c) Co3O4/ RGO/MDCF and (d) Co3O4 samples

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To further evaluate the MA properties, the reflection loss (RL) is calculated by the following formula: %&' − 1 RLdB  20log $ $ %&' + 1 ) ) %&' = ( *+* ,-.ℎ 01(22+3)( *+* 456

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Where %&' is the normalized input impedance, % is the impedance of free space, )* and * are complex permeability and permittivity of absorber respectively, c is the speed of light, d is the thickness of measured sample and f is the microwave frequency. The MA properties of the as-prepared samples under 10 wt.% loading in different thickness are illustrated in Figure 7. As expected from electromagnetic parameters, pure MDCF or Co3O4 shows poor MA, while the wrapping of graphene and growth of Co3O4 on graphene enhances the MA of composites significantly. With the thickness of samples increasing, RL peaks for RGO/MDCF and Co3O4/RGO/MDCF shift to lower frequency. RL peaks for RGO/MDCF with different graphene content shows the same trend with electromagnetic parameters, as shown in Figure S3. At graphene concentration of 5mg/mL, RGO/MDCF shows good MA properties that the maximum RL reaches −21.54 dB at 11.20 GHz with the coating layer thickness of 2.1 mm. As is known, carbon foam is a promising candidate for electromagnetic interference shielding owing to its open cell wall structure and large surface area. However, the ability to attenuate radiation is mainly contributed from reflecting microwave power which is detrimental to the penetration of electromagnetic waves and MA performance [34]. The great enhancement of MA performance after coating of graphene on carbon foam can be attributed to the following reasons: i) conductive 3D network constructed by shell-core carbon structure which can attenuate electromagnetic fields-induced currents and dissipate thermal energy rapidly, ) polarization relaxation of defects or π electron and interfacial polarization between graphene and MDCF [36], ) the pores in MDCF produce many times of reflections and refractions, resulting in the waves going through multi-absorptions [46]. The RGO/MDCF hybrids with only 0.88 wt.% graphene provides a cost-effective strategy to overcome drawbacks of carbon foam and graphene foam, which even shows better MA performance than some reported graphene foam [33,43]. Co3O4/RGO/MDCF exhibits a maximum absorption of −31.88 dB at 11.54 GHz and a qualified bandwidth of 3.4GHz (RL ≤ −10dB) with the coating layer thickness of only 2.0 mm under 10 wt.% loading. The enhancement of MA performance is mainly due to dipole polarization of Co3O4 nanoparticles and multiple interface polarization between Co3O4 particles and graphene sheets which can generate capacitor-like structures and bring strong relaxation loss. Furthermore, implantation of optimized amount of Co3O4 on 3D RGO/MDCF conductive network could achieve good impedance matching in absence of sacrificing conductivity (Figure 4S). As MA materials are widely used in aerospace, aviation and automobile, low loading and thin thickness should be considered as key elements in designing and evaluating MA performance [36]. Therefore, we compare the specific 89:&' which is defined as maximum RL per thickness (dB/mm) and load content of Co3O4/RGO/MDCF to the other cobalt oxide/graphene based composite, as shown in Figure 7. It’s clear to see that high loading content is essential for cobalt

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oxide/graphene based composite to achieve high specific reflection loss according to open literature survey [23-32]. In this work, Co3O4/RGO/MDCF shows a relatively high specific 89:&' of 15.94 dB/mm under only 10 wt.% load content. The high specific MA performance of Co3O4/RGO/MDCF is mainly contributed from its unique porous 3D structure due to the following reasons: i) it ensures light weight of the composite, ii) it plays the role as substrate to disperse Co3O4 and response to the incident microwave spontaneously and intensely as tremendous resistance–inductance–capacitance coupled circuits and time-varying electromagnetic fields-induced currents occur on cell walls and struts of the 3D structure [36]; iii) the heat energy transformed by the high dielectric loss generated from interfacial polarization and polarization relaxation can be dissipated by the 3D structure with high thermal conductivity rapidly [51].

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Figure 8 Direct comparison of the MA performance of the Co3O4/ RGO/MDCF in this work with those of the representative materials.

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4. Conclusion In this study, a 3D graphene coated porous structure with melamine foam as the supporting framework is presented, which exhibits much better MA performance than melamine derived carbon foam. Implantation of Co3O4 particles on the 3D carbon structure further enhanced electromagnetic wave absorption properties due to a synergistic e ect upon impendence match, interfacial polarization and polarization relaxation. The maximum RL of −31.88 dB at 11.54 GHz and a qualified bandwidth of 3.4GHz (RL ≤ −10dB) are achieved by Co3O4/RGO/MDCF with the coating layer thickness of only 2.0 mm. The distinguished MA properties combined with low density of 10.6 mg/cm3 give Co3O4/RGO/MDCF superior MA performance under 10 wt.% loading, overcoming the barriers of previously reported cobalt oxide/graphene based composite. Notably, the functional and cost-effective carbon substrate presented here can also exhibit great merits for other microwave absorbers and electro-magnetic interference shielding material. References [1] J. Liu, H.B. Zhang, R. Sun, Y. Liu, Z. Liu, A. Zhou, Z.Z. Yu, Hydrophobic, flexible and lightweight MXene foams for high-performance electromagnetic-interference shielding, Adv. Mater. 29 (2017).

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[2] Z. Liu, N. Zhao, C. Shi, F. He, E. Liu, & C. He, Synthesis of three-dimensional carbon networks decorated with Fe3O4 nanoparticles as lightweight and broadband electromagnetic wave absorber. Journal of Alloys and Compounds, 776, 691-701 (2019). [3] X. Qiu, L. Wang, H. Zhu, Y. Guan, Q. Zhang, Lightweight and efficient microwave absorbing materials based on walnut shell-derived nano-porous carbon, Nanoscale 9: 7408-7418(2017). [4] L. Wang, M. Liu, G. Wang, B. Dai, F. Yu, & J. Zhang. An ultralight nitrogen-doped carbon aerogel anchored by Ni-NiO nanoparticles for enhanced microwave adsorption performance. Journal of Alloys and Compounds, 776, 43-51(2019). [5] G. Sun, B. Dong, M. Cao, B. Wei, & C. Hu. Hierarchical dendrite-like magnetic materials of Fe3O4, γ-Fe2O3, and Fe with high performance of microwave absorption. Chemistry of Materials, 23(6), 1587-1593(2011). [6] C. L. Zhu, M. L. Zhang, Y. J. Qiao, G. Xiao, F. Zhang, & Y. J. Chen. Fe3O4/TiO2 core/shell nanotubes: synthesis and magnetic and electromagnetic wave absorption characteristics. The Journal of Physical Chemistry C, 114(39), 16229-16235 (2010). [7] R. C. Che, L. M. Peng, X. F. Duan, Q. Chen, & X. L. Liang. Microwave absorption enhancement and complex permittivity and permeability of Fe encapsulated within carbon nanotubes. Advanced Materials, 16(5), 401-405 (2004). [8] W. Xing, P. Li, H. Wang, Q. Lei, Y. Huang, J. Fan & G. Xu. The similar Cole-Cole semicircles and microwave absorption of Hexagonal Co/C composites. Journal of Alloys and Compounds, 750, 917-926 (2018). [9] X. Du, I. Skachko, A. Barker, E.Y. Andrei. Approaching ballistic transport in suspended graphene. Nat Nanotechnol 3(8), 491 (2008). [10] A.A. Balandin, S. Ghosh, W.Z. Bao, I. Calizo, D. Teweldebrhan, F. Miao, C.N. Lau. Superior thermal conductivity of single-layer graphene. Nano Lett 8:902-7(2008). [11] R. Raccichini, A. Varzi, S. Passerini & B. Scrosati. The role of graphene for electrochemical energy storage. Nature materials, 14(3), 271(2015). [12] W. Li, X. Geng, Y. Guo, J. Rong, Y. Gong, L. Wu, & M. Sun. Reduced graphene oxide electrically contacted graphene sensor for highly sensitive nitric oxide detection. ACS nano, 5(9), 6955-6961(2011). [13] C. Galiotis, O. Frank, E. N. Koukaras & D. Sfyris. Graphene mechanics: current status and perspectives. Annual review of chemical and biomolecular engineering, 6, 121-140 (2015). [14] V. Chabot, D. Higgins, A. Yu, X. Xiao, Z. Chen & J. Zhang. A review of graphene and graphene oxide sponge: material synthesis and applications to energy and the environment. Energy & Environmental Science, 7(5), 1564-1596 (2014). [15] C. Hu, Z. Mou, G. Lu, N. Chen, Z. Dong, M. Hu & L. Qu. 3D graphene–Fe3O4 nanocomposites with high-performance microwave absorption. Physical Chemistry Chemical Physics, 15(31), 13038-13043 (2013). [16] H.L. Xu, H. Bi, & R. B. Yang. Enhanced microwave absorption property of bowl-like Fe3O4 hollow spheres/reduced graphene oxide composites. Journal of Applied Physics, 111(7), 07A522 (2012). [17] X. Bai, Y. Zhai, & Y. Zhang. Green approach to prepare graphene-based composites with high microwave absorption capacity. The Journal of Physical Chemistry C, 115(23), 11673-11677 (2011). [18] Song, C., Yin, X., Han, M., Li, X., Hou, Z., Zhang, L., & Cheng, L. Three-dimensional

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EP

TE D

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reduced graphene oxide foam modified with ZnO nanowires for enhanced microwave absorption properties. Carbon, 116, 50-58 (2017). [19] H. Zhang, X. Tian, C. Wang, H. Luo, J. Hu, & Y. Shen, et al. Facile synthesis of RGO/NiO composites and their excellent electromagnetic wave absorption properties. Applied Surface Science, 314, 228-232(2014). [20] J. Fester, A. Makoveev, D. Grumelli, R. Gutzler, Z. Sun, J. Rodríguez Fernández & J. V. Lauritsen. The Structure of the Cobalt Oxide/Au Catalyst Interface in Electrochemical Water Splitting. Angewandte Chemie International Edition, 57(37), 11893-11897 (2018). [21] Y. Tong, P. Chen, T. Zhou, K. Xu, W. Chu, C. Wu & Y. Xie. A Bifunctional Hybrid Electrocatalyst for Oxygen Reduction and Evolution: Cobalt Oxide Nanoparticles Strongly Coupled to B, N Decorated Graphene. Angewandte Chemie, 129(25), 7227-7231 (2017). [22] L. Zhuang, L. Ge, Y. Yang, M. Li, Y. Jia, X. Yao & Z. Zhu. Ultrathin Iron Cobalt Oxide Nanosheets with Abundant Oxygen Vacancies for the Oxygen Evolution Reaction. Advanced Materials, 29(17), 1606793 (2017). [23] P. Liu, & Y. Huang. Synthesis of reduced graphene oxide-conducting polymers- Co3O4 composites and their excellent microwave absorption properties. RSC Advances, 3(41), 19033-19039 (2013). [24] X. Wang, J. Yu, H. Dong, M. Yu, B. Zhang, W. Wang & L. Dong. Synthesis of nanostructured MnO2, SnO2, and Co3O4: graphene composites with enhanced microwave absorption properties. Applied Physics A, 119(4), 1483-1490 (2015). [25] P. Liu, Y. Huang, L. Wang & W. Zhang. Preparation and excellent microwave absorption property of three component nanocomposites: polyaniline-reduced graphene oxide-Co3O4 nanoparticles. Synthetic Metals, 177, 89-93 (2013). [26] Z. Wang, H. Bi, P. Wang, M. Wang, Z. Liu & X. Liu. Magnetic and microwave absorption properties of self-assemblies composed of core–shell cobalt–cobalt oxide nanocrystals. Physical Chemistry Chemical Physics, 17(5), 3796-3801 (2015). [27] Y. Zheng, X. Wang, S. Wei, B. Zhang, M. Yu, W. Zhao, & J. Liu. Fabrication of porous graphene-Fe3O4 hybrid composites with outstanding microwave absorption performance. Composites Part A: Applied Science and Manufacturing, 95, 237-247 (2017). [28] J. Ma, X. Wang, W. Cao, Han, C., Yang, H., Yuan, J., & Cao, M. A facile fabrication and highly tunable microwave absorption of 3D flower-like Co3O4-rGO hybrid-architectures. Chemical Engineering Journal, 339, 487-498 (2018). [29] J. Li, X. Zhao, J. Liu, L. Zhang & C. Yang. Ultralight carbon-based Co(OH)2-Co3O4/nanocomposite with superior performance in wave absorption. Journal of Alloys and Compounds, 777, 954-962 (2019). [30] P. B. Liu, Y. Huang & X. Sun. Excellent electromagnetic absorption properties of poly (3, 4-ethylenedioxythiophene)-reduced graphene oxide–Co3O4 composites prepared by a hydrothermal method. ACS applied materials & interfaces, 5(23), 12355-12360 (2013). [31] X. Li, S. Yang, J. Sun, P. He, X. Pu & G. Ding. Enhanced electromagnetic wave absorption performances of Co3O4 nanocube/reduced graphene oxide composite. Synthetic Metals, 194, 52-58 (2014). [32] Y. Ding, Z. Zhang, B. Luo, Q. Liao, S. Liu, Y. Liu, & Y. Zhang. Investigation on the broadband electromagnetic wave absorption properties and mechanism of Co3O4-nanosheets/reduced-graphene-oxide composite. Nano Research, 10(3), 980-990 (2017).

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carbonaceous Co3O4/Co microframes anchored on RGO with enhanced electromagnetic wave absorption performances. Synthetic Metals, 228, 32-40 (2017). [34] R. Kumar, S. R. Dhakate, T. Gupta, P. Saini, B. P. Singh & R. B. Mathur. Effective improvement of the properties of light weight carbon foam by decoration with multi-wall carbon nanotubes. Journal of Materials Chemistry A, 1(18), 5727-5735 (2013). [35] Y. Yang, M. C. Gupta, K. L. Dudley & R. W. Lawrence. Novel carbon nanotube− polystyrene foam composites for electromagnetic interference shielding. Nano letters, 5(11), 2131-2134 (2005). [36] Y. Zhang, Y. Huang, T. Zhang, H. Chang, P. Xiao, H. Chen & Y. Chen. Broadband and tunable high performance microwave absorption of an ultralight and highly compressible graphene foam. Advanced Materials, 27(12), 2049-2053 (2015). [37] Y. Zhang, Y. Huang, H. Chen, Z. Huang, Y. Yang, P. Xiao & Y. Chen. Composition and structure control of ultralight graphene foam for high-performance microwave absorption. Carbon, 105, 438-447 (2016). [38] H. Zhang, A. Xie, C. Wang, H. Wang, Y. Shen, & X. Tian. Novel rGO/α-Fe 2 O 3 composite

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hydrogel: synthesis, characterization and high performance of electromagnetic wave absorption. Journal of Materials Chemistry A, 1(30), 8547-8552. (2013) [39] H. Zhang, M. Hong, P. Chen, A. Xie & Y. Shen. 3D and ternary rGO/MCNTs/Fe3O4 composite hydrogels: synthesis, characterization and their electromagnetic wave absorption properties. Journal of Alloys and Compounds, 665, 381-387. (2016)

[40] H. Zhang, A. Xie, C. Wang, H. Wang, Shen, Y., & X. Tian. Room temperature fabrication of an RGO–Fe 3 O 4 composite hydrogel and its excellent wave absorption properties. RSC

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Advances, 4(28), 14441-14446. (2014)

[41] H. Zhang, , Xie, A., Wang, C., Wang, H., Shen, Y., & Tian, X. Bifunctional reduced graphene oxide/V2O5 composite hydrogel: fabrication, high performance as electromagnetic wave absorbent and supercapacitor. ChemPhysChem, 15(2), 366-373. (2014).

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[42] H. Zhu, D. Chen, W. An, N. Li, Q. Xu, H. Li & J. Lu. A Robust and Cost Effective Superhydrophobic Graphene Foam for Efficient Oil and Organic Solvent Recovery. Small, 11(39), 5222-5229 (2015). [43] L. Shi, Y. Zhao, Y. Li, X. Han, & T. Zhang. Octahedron Fe3O4 particles supported on 3D MWCNT/graphene foam: In-situ method and application as a comprehensive microwave absorption material. Applied Surface Science, 416, 329-337 (2017). [44] C. Hu, Z. Mou, G. Lu, N. Chen, Z. Dong, M. Hu & L. Qu 3D graphene–Fe3O4 nanocomposites with high-performance microwave absorption. Physical Chemistry Chemical Physics, 15(31), 13038-13043 (2013). [45] D. Hulicova, J. Yamashita, Y. Soneda, H. Hatori & M. Kodama. Supercapacitors prepared from melamine-based carbon. Chemistry of materials, 17(5), 1241-1247 (2005). [46] Z. H. Ibupoto, S. Elhag, M. S. AlSalhi, O. Nur, & M. Willander. Effect of urea on the morphology of Co3O4 nanostructures and their application for potentiometric glucose biosensor. Electroanalysis, 26(8), 1773-1781 (2014). [47] P. Zhang, R. Wang, M. He, J. Lang, S. Xu & X. Yan. 3D Hierarchical Co/CoO Graphene Carbonized Melamine Foam as a Superior Cathode toward Long Life Lithium Oxygen Batteries. Advanced Functional Materials, 26(9), 1354-1364 (2016).

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[48] L. Stobinski, B. Lesiak, A. Malolepszy, M. Mazurkiewicz, B. Mierzwa, J. Zemek & I. Bieloshapka. Graphene oxide and reduced graphene oxide studied by the XRD, TEM and electron spectroscopy methods. Journal of Electron Spectroscopy and Related Phenomena, 195, 145-154 (2014). [49] Y. C. Zhao, D. L. Yu, H. W. Zhou, Y. J. Tian & O. Yanagisawa. Turbostratic carbon nitride prepared by pyrolysis of melamine. Journal of materials science, 40(9-10), 2645-2647 (2005). [50] J.Z. He, X.X. Wang, Y.L. Zhang, M.S. Cao, Small magnetic nanoparticles decorating reduced graphene oxides to tune the electromagnetic attenuation capacity, J. Mater. Chem. C 4 (2016) 7130–7140. [51] S. Li, Y. Li, X. Han, X.R. Zhao & Y. Zhao. High-Efficiency Enhancement on Thermal and Electrical

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Epoxy

Nanocomposites

with

Core-Shell

Carbon

Foam

Template-Coated Graphene. Composites Part A: Applied Science and Manufacturing (2019).

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[52] Z. Liu, N. Zhao, C. Shi, F. He, E. Liu & C. He. Synthesis of three-dimensional carbon networks decorated with Fe3O4 nanoparticles as lightweight and broadband electromagnetic wave absorber. Journal of Alloys and Compounds, 776, 691-701(2019).

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Highlights: （1）Graphene wrapped melamine derived carbon foam with Co3O4 particles was prepared. （2）The ultralow bulk density is 10.6 mg/cm3. （3）The maximum RL is −31.88 dB at 11.54 GHz with 2.0 mm thickness under 10% loading. （4）It provides a general method to fabricate comprehensive microwave absorber.