Graphene/Fe 3 O Quaternary Nanocomposites: Synthesis and Excellent Electromagnetic Absorption Properties

Transcription

1 Graphene/Fe 3 O Quaternary Nanocomposites: Synthesis and Excellent Electromagnetic Absorption Properties Yu Lan Ren, Hong Yu Wu, Ming Ming Lu, Yu Jin Chen, *, Chun Ling Zhu, # Peng Gao *, # Mao Sheng Cao, Chun Yan Li, and Qiu Yun Ouyang, College of Science, Harbin Engineering University, Harbin , China School of Materials Science and Engineering, Beijing Institute of Technology, Beijing , China College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin , China * To whom correspondence should be addressed. chenyujin@hrbeu.edu.cn, and gaopeng@hrbeu.edu.cn College of Science, Harbin Engineering University School of Materials Science and Engineering, Beijing Institute of Technology, Beijing , China # College of Material Science and Chemical Engineering, Harbin Engineering University.

2 SI 1 Experimental details Materials. Graphene used in this work were purchased from Nanijng XFNano Material Tech Co., Ltd, and its thickness is about 0.8 nm. All of other reagents were analytically pure, and purchased from Tianjin Kermel Chemical Reagent Co. Ltd. (Tianjin, China), and used without further purification. Growth of β FeOOH Nanocrystals on Graphene g of the graphene was dispersed into 300 ml water, and then 3.0 g of Fe(NO 3 ) 3 9H 2 O was added. The mixture above was kept at 50 for 2 h under stirring. The precipitates were separated by centrifugation, washed with distilled water and absolute ethanol, dried under vacuum. The process above was repeatedly carried out for more β-feooh nanocrystals grown on the graphene. G/Fe 3 O Ternary Nanocomposites. The G/Fe 3 O Ternary Nanocomposites were obtained after G/β-FeOOH nanohybrids were thermally treated at 420 for 5 h under an Ar/H 2 flow. The products were preserved under vacuum before measurements. Fabrication of G/Fe 3 O Quaternary Nanocomposites g of G/β-FeOOH nanohybrids was dispersed in 300 ml aqueous solution containing 0.4g of LiOH H 2 O and 1.4 g of Zn(Ac) 2 2H 2 O. The mixture was then stirred at room temperature for 2 h. The precipitates were separated by centrifugation, washed with distilled water and absolute ethanol for several times, dried under vacuum. Finally the dried powder was thermally treated at 420 for 5 h under an Ar/H 2 flow. Fabrication of G/ZnO Nanocomposites g of graphene was dispersed in 300 ml aqueous solution containing 0.4g of LiOH H 2 O and 1.4 g of Zn(Ac) 2 2H 2 O. The mixture was then stirred at room temperature for 2 h. The precipitates were separated by centrifugation, washed with distilled water and absolute ethanol for several times, 2

3 dried under vacuum. Finally the dried powder was thermally treated at 420 for 5 h under an Ar/H 2 flow. Characterizations. The morphology and size of the synthesized smaples were characterized by scanning electron microscope (SEM) [HITACHI S 5200] and an FEI Tecnai-F20 transmission electron microscope (TEM) equipped with a Gatan imaging filter (GIF). The operating voltages of SEM and TEM are 5 and 200 kv, respectively. The crystal structure of the sample was determined by X-ray diffraction (XRD) [D/max 2550 V, Cu KR radiation]. X ray photoelectron spectroscopy (XPS) measurements were carried out using a spectrometer with Mg Ka radiation (ESCALAB 250, Thermofisher Co.). EM parameters measurements. The EM parameters of samples were measured by using the transmission/refection coaxial line method. The measurement setup consisted of in an ANRITSU 37269D vector network analyzer with a synthesized sweep oscillator source and an S parameter test set. The measured samples were prepared by uniformly mixing 20 wt% of the sample with a paraffin matrix. The mixture was then pressed into toroidal shaped samples (φ out : 7.00 mm; φ in : 3.04 mm). The input power of the EM wave is about 5 dbm. 3

4 SI 2 Structural characterizations of G/β-FeOOH nanohybrids Figure S1 (a) TEM image, (b) HRTEM image and (c) SAED pattern of G/β-FeOOH nanohybrids 4

5 SI 3 XRD patterns of the G/Fe 3 O ternary nanocomposites and the graphene. (a) Fe 3 O 4 Fe Intensity (a.u.) (b) Theta (degree) Figure S2 XRD patterns of the G/Fe 3 O ternary nanocomposites (a) and the graphene (b). SI 4 XPS spectra of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites Fe 2p 3/2 Fe 2p 12 Intensity (a.u.) (b) (a) G/Fe 3 O G/Fe 3 O Binding energy (ev) Figure S3 The Fe 2p core level XPS spectra of the G/Fe 3 O ternary nanocomposites (a) and the G/Fe 3 O quaternary nanocomposites (b). 5

6 SI 5 SEM image and EDS pattern of the G/Fe 3 O quaternary nanocomposites Figure S4 (a) SEM image and (b) EDS analysis of the G/Fe 3 O quaternary nanocomposites. SI 6 Angular dark-field (ADF) STEM and energy dispersive X ray (EDX) element mapping analyses of G/Fe 3 O quaternary nanocomposites. Figure S5 Angular dark-field (ADF) STEM and energy dispersive X ray (EDX) element mapping analyses of G/Fe 3 O quaternary nanocomposites. (a) STEM image, (b) C mapping, (c) Fe mapping, (d) O mapping and (e) Zn mapping. 6

7 SI 7 The EM parameters of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites Figure S6a shows the relative complex permittivity ( ε r = ε jε ) of the G/Fe 3 O ternary nanocomposites in the frequency range of 2 18 GHz. The values of the real part (ε ) are in the range of over 2 18 GHz, while the values of imaginary part (ε ) values gradually decrease from 5.6 to 2.7 with the increase of the frequency. Figure S6b shows the relative complex permeability ( µ = µ jµ ) of the quaternary nanocomposites. The values of µ are in the range of whereas the values of µ increase firstly, then decrease gradually and exhibit a very weak resonance peak at about 2.2 GHz. Figure S7a shows the relative complex permittivity ( ε r = ε jε ) of the quaternary nanocomposites in the frequency range of 2 18 GHz. The values of the real part (ε ) are in the range of over 2 18 GHz, while the values of imaginary part (ε ) values first decrease at low frequency region and then increase slightly at high frequency region, and are in the range of over 2 18 GHz. Figure S7b shows the relative complex permeability ( µ = µ jµ ) of the quaternary nanocomposites. The values of µ are in the r range of whereas the values of µ increase firstly, then decrease gradually and exhibit a very weak resonance peak at about 2.2 GHz. The results above show that the dielectric losses of the nanocomposites are relatively larger than those of other magnetic materials. S1 S3 In addition, a natural resonance peak is presented in these nanocomposites. Thus, they should have good EM absorption properties. It should be noted that the natural natural-resonance peaks are observed in both nanocomposites. According to the natural-resonance equations, S4 r 7

8 π = (1) 2 fr rh a H = 4 K / 3µ M (2) a 1 0 where is the gyromagnetic ratio, is the anisotropy energy, and K 1 is the anisotropy coefficient. The resonance frequency is around 1.5 GHz for bulk Fe 3 O 4 around several tens of megahertz for bulk α-fe. S5 S6 It demonstrates that the resonance frequency of the magnetic materials shifts to higher frequency, which is attributed to the small size effect. S7, S8 It is believed that the anisotropy energy of small size materials, especially on nanometer scale, would be remarkably increased due to the increased surface S7, S8 anisotropic field induced by the small size effect. S Figure S6 (a) The relative complex permittivity and (b) the relative complex permeability of the G/Fe 3 O ternary nanocomposites. Figure S7 (a) The relative complex permittivity and (b) the relative complex permeability of the G/Fe 3 O quaternary nanocomposites. 8

9 SI-8 The reflection losses of the G/ZnO nanocomposites 0-10 R L (db) mm 2.5 mm mm 3.5 mm mm 4.5 mm 5 mm Frequency (GHz) Figure S8 The reflection losses of the G/ZnO nanocomposites with thickness 2-5 mm. SI 9 The Cole Cole semicircles of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites Imaginary part of permittivity 6 G/Fe 3 O G/Fe 3 O Real part of permittivity Figure S9 The Cole Cole semicircles of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites 9

10 SI 10 The tangent losses of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites Tangent losses tanδ e tanδ m ternary nanocomposites quaternary nanocomposites Frequency (GHz) Figure S10 The tangent losses of the G/Fe 3 O ternary nanocomposites and the G/Fe 3 O quaternary nanocomposites References (S1) Chen, Y. J.; Gao, P.; Wang, R. X.; Zhu, C. L.; Wang, L. J.; Cao, M. S.; Jin, H. B. J. Phys. Chem. C 2009, 113, (S2) Zhu, C. L.; Zhang, M. L.; Qiao, Y. J.; Xiao, G.; Zhang, F.; Chen, Y. J. J. Phys. Chem. C 2010, 114, (S3) 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. J. Phys. Chem. C 2011, 115, (S4) Kittel, C. Phys. Rev. 1948, 73, (S5) Liu, X. G.; Geng, D. Y.; Meng, H.; Shang, P. J.; Zhang, Z. D. Appl. Phys. Lett. 2008, 92,

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