Preparation of porous magnetic nanocomposites using corncob powders as template and their applications for electromagnetic wave absorption

Strong absorption, low density, and thin matching thickness are important parameters for electromagnetic (EM) wave absorbers. In this study, we prepared novel porous magnetic nanocomposites using corncob powders as template. The presence of corncob will significantly decrease the bulk density of samples from more than 4.0 to about 0.55 g cm−3. The porous structures remarkably decreased the permittivity (ε) and permeability (μ) and enhanced the impendence matching between the absorber and air. The porous magnetic nanocomposites exhibit enhanced absorption for EM waves at thin matching thickness. The optimum thickness is only 1.0–1.4 mm, with bandwidth of RL < −5 dB of about 8 GHz, covering the half X-band and the whole Ku-band. The areal density of magnetic absorbers at this study is only about 0.7–1.0 kg m−2 at thickness of 1.0–1.4 mm, much lower than the reported values of other magnetic absorbers. Due to the strong absorption at low density and thin matching thickness, the porous magnetic nanocomposites prepared using corncob powders as template are promising light-weight EM wave absorbers.