Modulation of impedance matching of hollow cubic carbon with semi-closed structure for effective microwave absorption

Abstract

In this paper, a certain degree of semi-closed structure was successfully introduced in hollow cubic carbons (HCCs) by selective dissolution of phenolic resin (PR)/NaCl precursor by acetone. The impedance matching of the HCCs absorber was improved, which in turn lead to the enhancement of the electromagnetic wave absorption capacity. By controlling the selective dissolution time of acetone, HCCs with different degrees of integrity were formed, and the degree and mechanism of the influence of the semi-closed structure of HCCs on the wave absorbing properties were investigated by analyzing the microstructure and physical phase composition of HCCs. From the scanning electron microscope photographs, it can be seen that with the increase of the acetone treatment time of HCCs, the samples gradually appeared a certain degree of semi-closed structure. With the extension of the acetone treatment time to 60 min, the structure of the HCCs was seriously damaged, at which time the impedance matching of the wave-absorbing materials was seriously deteriorated, and the electromagnetic wave absorption performance was also decreased. Among them, the electromagnetic wave absorption performance of HCCs30min is the most outstanding, specifically, when the loading rate is 10 wt%, the maximum absorption peak value of HCCs30min with a thickness of 2.7 mm reaches −41.1 dB, and the corresponding absorption bandwidth is 3.8 GHz (8.9 GHz–12.7 GHz). The experiment confirms that the existence of the degree of structural integrity can affect the impedance matching and wave absorption performance of HCCs.