Investigation of different graphite morphologies for microwave absorption at X and Ku-band frequency range

• Published in: Journal of materials science. Materials in electronics Vol. 31; no. 21; pp. 19064 - 19073
• Main Authors: Batista, A. F., de Oliveira, A. P. S., Rodrigues, A. C., do Amaral Junior, M. A., Mineiro, S. L., Baldan, M. R.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2020; Springer Nature B.V
• Subjects: Broadband; Characterization and Evaluation of Materials; Chemistry and Materials Science; Electromagnetic properties; Frequency ranges; Graphite; Heat treatment; Intercalation compounds; Investigations; Materials Science; Microwave absorbers; Microwave absorption; Microwave attenuation; Morphology; Network analysers; Optical and Electronic Materials; Raman spectroscopy; Rectangular waveguides; Structural analysis; Superhigh frequencies; Surface chemistry; Thickness; Ultrasonic agitation
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-04443-y

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).