Fig. 1. EM response capability for the magnetic, spatially symmetric structure: (a-b) schematic illustration of the multiple dispersion method to measure the EM parameters; (c-d) representative transmission electron microscopy (TEM) images of magntic carbonyl iron microspheres; (e-f) EM wave frequency-dependent magnetic loss and dielectric loss of EM absorbers prepared using the multiple dispersion method.

Fig. 2. EM response for the non-symmetrical and spatially symmetrical structures: (a-b) representative field emission scanning electron microscopy (FE-SEM) images of carbonyl iron flakes after ball-milling the carbonyl iron microspheres; (c-d) dielectric loss and magntic loss curves of the carbon iron flake-based EM absorbers preprared using multiple dispersion; (e-f) FE-SEM image and the magnetic loss curve of magnetic cobalt nanospheres.

Fig. 3. Effect of the magnetic loss on the EM absorption performance: (a) schematic illustration of the spatially symmetric (spherical) structure; (b) schematic illustration of the magnetic domains of a magnetic nanosphere; (c-e) two-dimensional (2D) color mapping of the reflection loss curve of three different batches of cobalt nanosphere-based EM absorbers prepared using multiple dispersion methods; (f) the effective absorption region of cobalt nanosphere-based EM absorbers with a thickness of 1.4 mm.

Fig. 4. Analysis of structutral sensitivity of the dielectric structure: (a) representative TEM images of carbon nanospheres prepared via hydrothermal processing; (b) dielectric loss curves of the carbon nanosphere-based EM absorbers prepared using multiple dispersion methods; (c-e) representative FE-SEM images of the hierarchical polygon CuS structure; (f-g) dielectric loss and Cole-Cole curves of CuS prepared using the multiple dispersion method; (h-i) dielectric loss curves of the carbon nanotubes.

Fig. 5. EM absorption performance of EM incident angle-insensitive carbon nanospheres derived from bamboo: (a-b) representative FE-SEM images of the carbon nanospheres (The inset shows the bamboo); (c-e) 2D color mapping of the reflection loss curves of the cobalt nanosphere-based EM absorbers prepared using multiple dispersion methods; (f-h) the effective absorption region of different dispersion batches of the cobalt nanosphere-based EM absorbers with a thickness < 2.0 mm. Inset in (a) shows the bamboo.