The impact of carbonization temperature on the microwave-absorbing properties of hollow porous carbon spheres

The increasing problem of electromagnetic pollution has significant drawbacks on both the accurate functioning of electronic facilities and the welfare of humans. To combat and eliminate the impact of electromagnetic radiation, it is crucial to design microwave-absorbing materials that possess both strong absorption strength and a broad frequency range. This study employed a straightforward sol–gel technique to regulate the hydrolysis reaction of tetraethyl orthosilicate (TEOS) and the synthesis reaction of phenolic resin. The objective was to fabricate a core–shell precursor consisting of silica coated with phenolic resin/silica spheres. Hollow carbon spheres with a porous structure were created using a process including high-temperature calcination with argon gas atmosphere and pickling etching. The manipulation of calcination temperature allows for the convenient adjustment of both the degree of graphitization and dielectric characteristics of hollow porous carbon spheres. The micromorphology, phase composition, graphitization degree, specific surface area, pore size, dielectric properties, and absorption properties were investigated through scanning electron microscopy (SEM), X-ray diffractometry (XRD), Raman spectroscopy, specific surface and porosity analyzer, and vector network analysis, respectively. The result indicates a positive correlation between the graphitization degree and the calcination temperature. With an ultralow filling ratio of 3.6 wt