Accepted Manuscript Full Length Article Microwave absorption properties of graphene oxide capsulated carbonyl iron particles Seunggeun Jeon, Jinu Kim, Ki Hyeon Kim PII: DOI: Reference:
S0169-4332(19)30020-0 https://doi.org/10.1016/j.apsusc.2019.01.017 APSUSC 41416
To appear in:
Applied Surface Science
Received Date: Revised Date: Accepted Date:
15 September 2018 28 December 2018 2 January 2019
Please cite this article as: S. Jeon, J. Kim, K. Hyeon Kim, Microwave absorption properties of graphene oxide capsulated carbonyl iron particles, Applied Surface Science (2019), doi: https://doi.org/10.1016/j.apsusc. 2019.01.017
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Microwave absorption properties of graphene oxide capsulated carbonyl iron particles Seunggeun Jeon, Jinu Kim, Ki Hyeon Kim* Department of Physics, Yeungnam University, Gyeongsan 38541, Korea
To evaluate the microwave absorption properties of the graphene oxide (GO) sheets capsulated on carbonyl iron particles (CIP), we synthesized the GO capsulated on carbonyl iron particles (GOCIPs) by a simple wet stirring process. Complex permittivity were increased with the increment of mass ratio of GO in GOCIPs from 0.5 to 2 wt.% while the complex permeability values were not changed. The maximum reflection loss (RLmax) and frequency bandwidth at -10 dB ([email protected]
) of the 1.9 mm thick-GOCIP composite with 2.0 wt% of GO in GOCIPs exhibited about -56.4 dB @10.8 GHz and 5.1 GHz. The RLmax frequency shifted to lower frequency with the increment of absorber thickness from 1 mm to 3 mm. [email protected]
decreased with the increment of absorber thickness.
Keywords: Reflection loss, Hybrid Graphene oxide-Carbonyl iron, Tuning complex permittivity, Microwave absorber
1. Introduction Electromagnetic (EM) wave absorbing materials have been very important issues for the civil, commercial and military applications in microwave frequency region , , ,  and . These kinds of EM absorbers demand a broadband absorbing frequency, high absorption ability, and low density, etc.. In general, the microwave absorbers such as functional composites have composed of the magnetic and dielectric materials in polymeric matrix. Most of the composites have been used the conventional magnetic spherical powder and flakes and dielectric fillers , ,  and . The reduction of the EM wave is mainly generated by the impedance matching layers with air due to the magnetic and dielectric values. Thus, the tunable magnetodielectric values for the impedance matching will improve the absorbing performance . The EM absorption properties can be evaluated using reflection loss (RL) by the perfect electric conductor (PEC) back-panel model. RL is the ratio of the total reflected EM power against the incident EM power. Especially, X-band (8.2− 12.4 GHz) is often used for civil and military applications, which are generally required to design an EM absorbing material exhibiting a RL lower than −30 dB at a sample thickness below about 2 - 3 mm. Recently, the carbon based materials such as carbon nanotube, carbon fiber, graphite and graphene have attracted for the enhancement of tunable absorption frequency and ability as dielectric filler with magnetic materials in polymeric composites , , , , , , and . Among many kinds of candidate magnetic fillers in composite, the spherical shaped carbonyl iron particles (CIP) have been employed for the good magnetic properties of such as high saturation magnetization, small coercivity, , , , , , ,  and . Luo Kong et. al.  have been reported a facile solvothermal route to synthesize reduced graphene oxide (RGO) nanosheets combined with surface-modified γ-Fe2O3 colloidal nanoparticle clusters. They evaluated the microwave absorption properties of the RGO and Fe2O3 composites with 2.5 mm , which the maximum reflection loss (RLmax) and effective absorption bandwidth at -10 dB ([email protected]
) were obtained -59.65dB @10 GHz and 3 GHz. Zetao Zhu et. al.  have studied the microwave absorption properties using relatively high mass ratios of RGO to CIP over 1:20 which synthesized by wet chemical process at room temperature. They obtained the -52.46 dB of RLmax @9.46 GHz and 4.19 GHz of [email protected]
dB for the composite thickness of 3.0 mm. Therefore, we employed the relatively low mass ratio of graphene oxide (GO) to CIP below 1:50 for tuning permittivity values and the stable magnetic properties. We synthesized the GO sheets capsulated CIP by a simple wet process at room temperature and evaluated the microwave absorption behaviors of GOCIP composites.
2. Experimental The GO capsulated CIP (GOCIPs) synthesized by simple wet process with the increment of GO ratios of 0.1, 0.2, 0.5 1.0 and 2.0 wt. % to CIP. The water soluble GO (TNWGO-50, Timesnano Inc.) was dissolved in deionized water and stirred with CIP (BASF, EW) for 30 min. The GOCIPs solution was dried at 80 oC for 12 hr in vacuum oven as shown in Fig. 1(a). And then the formation of GO-wrapped CIP could be expected by the hydrogen bond of metallic oxide –OH and –COOH of GO and ion bond between positive charged metallic + and negative charged GO -  as shown in Fig. 1(b). To evaluate the structural properties, as-synthesized samples were analyzed by powder X-ray diffraction (XRD, Diatome) with Cu-K ( = 0.1542 nm), X-ray photoelectron spectroscopy (XPS, K-Alpha, Thermo scientific), the Raman spectra were measured by Raman system (XploRA Plus, Horiba) with 532 nm laser wavelength grating at room temperature. The surface morphologies were observed by using a field emission scanning electron microscopy (SEM, S-4800, Hitachi) The magnetic properties were measured by using vibrating sample magnetometer (VSM, 7404-S, Lake Shore) in order to characterize the electromagnetic properties, we prepared the CIP and GOCIPs powders mixed with 30 wt.% of paraffin which were pressed into the toroidal shape (outer diameter of 7.0 mm, inner diameter of 3.04 mm) with the thickness of approximately 2 mm. The complex relative permeability and permittivity were measured by using vector network analyzer (VNA, N5222B, Keysight) with a coaxial waveguide (3.04 mm and 7 mm of inner and outer diameter) from 0.1 GHz to 18 GHz.
3. Results and Discussion To investigate the crystalline structure and morphology, GO, CIP and GOCIPs with the increment of GO mass ratios of 0.1, 0.2, 0.5, 1.0 and 2.0 wt.% were characterized by powder XRD, Raman spectra and SEM. The diffraction peaks of CIP and GOCIPs are correspond to the (110), (211) and (200) peaks of body centered cubic (bcc) -Fe (JCPDS card 87-0721) as shown in Fig. 2(a). It implies that the crystalline structure of CIP was not changed after GO capsulated on CIP. However, we could not find any peaks of GO in GOCIPs in XRD patterns. To confirm the GO contents in GOCIPs, the Raman spectra of GOCIPs were observed in comparison with those of CIP and GO as shown in Fig. 2(b). GO exhibited two strong signals centered at 1352 and 1607 cm-1, which correspond to the D and G bands of graphene oxide, respectively. CIP showed the typical Fe3O4 and Fe2O3 signals centered at 665 and 1328 cm-1 due to the surface oxidation of CIP. GOCIPs showed the GO bands and iron oxide signals of CIP, respectively. The value of ID/IG for GO sheets and GOCIPs are found to be from 0.99
to 1.1 with the increment of GO mass ratios in GOCIPs, respectively. The values of ID/IG for GOCIPs linearly increased in comparison with that of GO sheets, it indicates the increase in disorder of GO sheets resulting from the incorporation of CIP magnetic particles. In order to verify the surface capsulation of GO on CIP, the surface morphologies of the CIP and GOCIPs with the GO contents exhibited as shown in Fig. 3, respectively. The surface of GOCIPs would be shown more rugged surface by GO than that of CIP with the increase of GO contents. The magnetic properties of CIP and GOCIPs were measured by using VSM at room temperature as shown in Fig. 4. The saturation magnetization of CIP and GOCIPs were not so changed, which exhibited approximately 191 emu/g, respectively. The small difference of the magnetization reversal process would be caused by GO contents and surface oxidation during synthesis. Figure 5(a) and (b) show the complex relative permittivity and permeability from 0.1 GHz to 18 GHz, respectively. To measure the EM properties, sample powders were mixed with 30 wt.% paraffin. The real part of permittivity of GOCIP are linearly increased up to 9.2 at 10 GHz from 0.5 to 2.0 wt.% while the values of CIP and GOCIPs with GO of 0.1 and 0.2 wt.% kept approximately 5. The dielectric loss tangent (tanE = /) of CIP and GOCIPs with GO of 0.1 and 0.2 wt.% showed similar behaviors, which values are about 0.02 at all the frequency region as shown in Fig. 5(a) and (c). The tanE abruptly increased from 0.02 to 0.13 for 0.5 wt.% of GO in GOCIP, although the GO of 0.1 wt.% and 0.2 wt.% in GOCIPs showed the similar values with that of CIP of 0.02 at 10 GHz. The critical mass ratio of GO contributes to the increase of the dielectric loss due to the conductive interconnecting GO network, which induce strong electron polarization and space charge polarization . The real and imaginary part of permeability of CIP and GOCIPs drastically decreased and increased with increase of frequency, respectively. The magnetic loss tangent (tanM = /) slightly decreased with the increment of GO mass ratio from 0.39 to 0.34 at 10 GHz as shown in Fig. 5(b) and (d). These results imply that the dielectric behaviors of GOCIPs are deeply related with critical contents of GO although the magnetic behaviors of GOCIPs were not changed with the increase of GO contents. The reflection loss (RL) can be calculated using relative complex permittivity and permeability for the sample thickness according to the transmission line theory , which is backed by a perfect conductor for single absorbing layer. It can be calculated the following expression: (1) (2) (3)
Where Z0 is the characteristic impedance of free space, 0 and 0 are the permittivity and permeability of free space, respectively. Zin is the input impedance of the sample, c is the velocity of EM wave in free space, f is the frequency of EM waves, and d is the thickness of the sample. Figure 6 shows the calculated the reflection loss with the increment of thickness of CIP and GOCIPs composites, which values were calculated using the measured complex permittivity and permeability of the CIP and GOCIPs composites. The RL behaviors of GOCIPs exhibited over the mass ratios of 0.5 wt.% in comparison with that of CIP without GO because the RL behaviors of GOCIPs of 0.1 and 0.2 wt.% were similar with those of CIP. The central frequency of RLmax of CIP and GOCIPs shifted to lower frequency with the increment of sample thickness from 1 mm to 3 mm. The RLmax of CIP and GOCIPs with the mass ratios of 0.5, 1.0 and 2.0 wt.% exhibited -16.1 [email protected]
GHz (1.75 mm), -22.2 [email protected]
(1.75 mm), -38.7 [email protected]
15.6GHz (1.5 mm) and [email protected]
GHz (1.9 mm), respectively. Especially, the RLmax of 2.0 wt% of GO mass ratio in GOCIPs exhibited a critical value at the thickness of 1.9 mm unlike the other results. The RLmax and frequency bandwidth at -10 dB ([email protected]
) values exhibited the listed as shown in table 1. When the RL is −10 dB, 10% of the microwave energy is reflected. The corresponding frequency range over which the RL is smaller than −10 dB is defined as the effective absorption bandwidth . The [email protected]
decreased with the increment of absorber thickness. Especially, the RLmax and [email protected]
for 2.0 mm thick-absorber exhibited the -21.4 [email protected]
GHz, 7.72 GHz and -17.1 [email protected]
GHz, 5.48GHz, respectively. The RLmax and [email protected]
values of GO mass ratio of 2 wt.% in GOCIPs with the thickness of 1.9 mm and 2 mm composites are comparable to those of the other reported results [3, 21] in key factors such as a sample thickness and the controllable permittivity by GO mass ratios. These results are good for X-band (8.2-12.4 GHz) and Ku-band (12-18 GHz) EM absorber.
4. Conclusions The GO capsulated CIP were fabricated by a simple wet process for the application of EM absorption. The magnetic properties of GOCIPs were not changed with the increment of GO mass ratios in GOCIPs. The complex permittivity of GOCIPs were controlled by GO contents, which values changed over 0.5 wt.% of GO. The absorbers thickness with 1.9 mm and 2 mm of 2.0 wt.% of GO mass ratio in GOCIPs exhibited good absorption properties, which RLmax and [email protected]
values were obtained -56.4 [email protected]
GHz, 5.1GHz and 33.0 [email protected]
GHz, 4.8 GHz, respectively. These results should be applicable to X-band (8.0-12 GHz)
microwave absorber. For the 1.0 wt.% of GO mass ratio in GOCIPs with the thickness of 1.5 mm and 1.75 mm, RLmax and [email protected]
exhibited -38.7 [email protected]
GHz, > 6 GHz and -31.1 [email protected]
GHz, 7.4 GHz, respectively, which is one of good candidates Ku-band (12-18 GHz) EM absorber. As results, the reflection loss and frequency bandwidth can be designed and optimized by GO mass ratio with magnetic particles as a filler of EM absorbers.
Acknowledgments This research was supported by Nano·Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (No. 2016M3A7B4900044)
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Fig. 1. (a) A schematic of GOCIP synthesis process and (b) the possibility of GOCIP bonding mechanism.
Fig. 2. (a) XRD and (b) Raman spectra of CIP and GOCIPs with the increment of GO mass ratios in GOCIPs, respectively.
Fig. 3. FE-SEM images of (a) CIP and GOCIPs with the increment of GO mass ratios from (b) 0.1 wt.%, (c) 0.2 wt.%, (d) 0.5 wt.%, (e) 1.0 wt.%, (f) 2.0 wt.%, respectively.
Fig. 4 (a) Magnetization curves of GOCIPs with the increment of GO mass ratios in GOCIPs in comparison with that of CIP.
Fig. 5. (a) The measured complex permittivity, (b) permeability and (c) the real part of permittivity and dielectric loss (tanE), (d) the real part of permeability and magnetic loss (tanE) at 10 GHz of CIP and GOCIPs with the increment of GO mass ratios, respectively.
Fig. 6. The reflection loss behaviors of (a) CIP and (b) 0.5 wt.%, (c) 1.0 wt.%, (d) 2.0 wt.% of GO mass ratios in GOCIPs with the increment of sample thickness from 1 mm to 3 mm, respectively.
Table 1. The values of the absorber thickness, RLmax, [email protected]
, the central frequency at RLmax, and microwave band of CIP and GOCIPs with the increment of GO mass ratios, respectively.
(GHz) > 5.0
frequenc y (GHz) 16.7
GO 1.0 GOCI
GO 2.0 wt.%
microwav e band
X, Ku band X, Ku
This wor k
band X, Ku band
Highlights Hybrid GOCIPs synthesized with different amounts of a GO by a simple wet stirring method. The dielectric losses were controlled by GO mass ratio in GOCIPs. The RLmax and [email protected]
exhibited -56.4 [email protected]
GHz and 5.1 GHz for 2 mm thick-GOCIPs composite.