Structure regulation in N-doping biconical carbon frame decorated with CoFe2O4 and (Fe,Ni) for broadband microwave absorption

•Novel absorber of unique biconical carbon frame decorated with CoFe2O4 and (Fe, Ni) was prepared.•The geometrical morphology and size of decorated NPs can be simply regulated by controlling the pyrolysis temperature.•The broadband effective absorption bandwidth of 6.55 GHz would be achieved for only 1.87 mm thickness. The typical environment pollution of superfluous microwave radiation has become an urgent problem to be solved at current stage. Herein, a new-style composite of unique biconical carbon framework decorated with CoFe2O4 and (Fe,Ni) nanoparticles was obtained by the co-hydrothermal and pyrolysis route. With the temperature-depended adjustability in microstructure, the composite calcined under 600℃ possesses the largest length–width ratio of amorphous carbon skeleton and the smallest median diameter of decorated NPs among all the samples. This could promote the interface polarization ability and geometrical anisotropy for conductivity, together with N-doping induced dipole polarization, the composite represents excellent dielectric loss capacity for microwave absorption. Moreover, the eddy current effect of magnetic alloy and natural resonance associated with ferrite also assist to this wastage. Under the optimal impedance matching, this composite owns maximal RL of −34.3 dB at 12.92 GHz for 2.0 mm with its broadest effective absorption bandwidth of 6.55 GHz at only 1.87 mm, covering the whole Ku and partial X bands. This work offers a novel microwave absorber with appropriate absorbing intensity and excellent bandwidth for practical usage.