scholarly journals Investigation of Microwave Absorption Performance of CoFe2O4/NiFe2O4/Carbon Fiber Composite Coated with Polypyrrole in X-Band Frequency

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 809
Author(s):  
Rozhin Sadeghi ◽  
Abbas Sharifi ◽  
Marta Orlowska ◽  
Isabelle Huynen

The current research reports the preparation of a microwave absorber containing CoFe2O4/NiFe2O4/Carbon fiber (H/S/CF) coated with polypyrrole polymer (PPy@H/S/CF) through sol-gel and in-situ polymerization processes. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and a vector network analyzer (VNA) are utilized to evaluate the features of the prepared composite. The microstructure analysis results revealed carbon fibers well decorated with submicron-size particles having hard/soft magnetic phases and thoroughly coated with polymer. The paraffin-based microwave absorber sample filled with 45 wt.% of PPy@H/S/CF has simultaneously both magnetic and dielectric losses in the 8.2–12.4  GHz frequency range. The absorber is used in a Salisbury screen configuration aiming at reducing the radar cross-section of objects. A minimum reflection loss of −55  dB at 10.6 GHz frequency with 5 GHz bandwidth is obtained for the sample with a 2  mm thickness. Different mechanisms, such as interfacial polarization, ferromagnetic resonance, and electron hopping, are the main factors for achieving such an appropriate microwave absorption. These results suggest that the PPy@H/S/CF composite is an ideal candidate for microwave absorption applications requiring high performance and low thickness.

2020 ◽  
Vol 858 ◽  
pp. 140-145
Author(s):  
Sung Soo Kim

The microwave absorbing properties of multi-layer carbon/carbon fiber composites, designed to function as radar absorbing structures (RAS), were studied over the X-band frequency range (8.0-12.4 GHz). High-frequency electromagnetic properties of various fibers (glass, carbon) and particulate filler (carbon black) are investigated as the major constituent materials of the RAS. Free space measurement depicts the perfect reflecting properties of carbon fiber composites (S11 = 0 dB, S21 = −40 dB). In the two-layered composite laminate (impedance transformer/reflecting substrate), the use of carbon black is necessary in the impedance transforming layer to obtain the high level of microwave absorbance and frequency tuning. Through the layer combination of the glass-fiber composite (thickness = 2.45 mm) containing carbon black (3% in weight) and carbon fiber composite as reflecting substrate, S11 can be reduced to as low as −40 dB at the frequency of 11.7 GHz, maintaining a low level of S21. The results demonstrate that RAS can be efficiently designed with the laminates of fiber reinforced composites with impedance transforming layer (glass fiber with suitable amount of carbon black) and perfectly reflecting substrate (carbon fiber).


2008 ◽  
Author(s):  
Andrew Littlefield ◽  
Edward Hyland ◽  
Jack Keating

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