Investigation of different graphite morphologies for microwave absorption at X and Ku-band frequency range
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Investigation of different graphite morphologies for microwave absorption at X and Ku-band frequency range A. F. Batista1, A. P. S. de Oliveira1, A. C. Rodrigues1,* S. L. Mineiro1, and M. R. Baldan1 1
, M. A. do Amaral Junior1,
Laboratório Associado de Materiais e Sensores, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP 12227-010, Brazil
Received: 6 July 2020
ABSTRACT
Accepted: 5 September 2020
The different graphite morphologies, like graphite intercalation compound (GIC), expanded graphite (EG), and exfoliated graphite (ExfG), were investigated as microwave absorbing materials (MAMs). The modification of the GIC was carried out in two independent parts, consisting of heat treatment and subsequent ultrasound agitation, forming the EG and ExfG, respectively. The surface morphology and structural characterization were investigated using the scanning electron microscope and Raman spectroscopy. Electromagnetic characterization was performed with a vector network analyzer and rectangular waveguide in the frequency range from 8.2 to 12.4 GHz (X-band) and from 12.4 to 18 GHz (Ku-band). The effects of different graphite morphologies and thickness of the composite were analyzed on the electromagnetic properties. The results of the reflection loss show that the samples affect the performance of the MAMs. The EG sample presents an excellent attenuation of around - 22.5 dB (& 99 microwave attenuation) for 2 mm thickness samples within the X-band frequency range. This behavior can be attributed to the expanded and interconnected structure of the EG, which has a large surface area and connectivity between the structures within the composite. Thus, it was found that EG is the best graphite structure for application in microwave absorber of broadband. The GIC and ExfG exhibited poor performance of microwave absorption (above - 10 dB).
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10854-020-04443-y
J Mater Sci: Mater Electron
1 Introduction Radiation-absorbing material (RAM) is a material specially designed and shaped to absorb incident radiation. It allows aircraft, tanks, or ships to stay stealth in some frequencies range [1–3]. However, they also have used in civilian applications, such as standards of compatibility and interference electromagnetic in the area of the industry, telecommunication, and medical [4]. There are several materials technologies to absorb electromagnetic radiation, like how by depositing metal films [5], particulate form [6], frequency selective surfaces (FSS) [7], pyramid surfaces [8], and metamaterial [9]. Basically, the enhanced microwave absorption properties can be attributed to a good impedance match, multiple reflections, and an effective balance of dielectric loss and magnetic loss [10]. These absorption properties depend directly on the sample thickness, complex permittivity ðe ¼ e0 þ ie00 Þ, complex permeabilityðl ¼ l0 þ il00 Þ, and desired work frequency [
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