Simple Fabrication of Porous Nanocomposites with Gradient Composition for High‐Performance Terahertz Absorbers

Electromagnetic (EM) absorbing materials are highly demanding for higher frequency band since the carrier wave for many next generation information technologies is moving from microwave to millimeter (mm) and terahertz (THz) wave band. To achieve satisfied absorption of mm/THz wave, herein, a simple method is developed to fabricate large‐scale porous nanocomposite sponges using eco‐friendly sugar as sacrifice template, which are consisted of multi‐walled carbon nanotube (MWCNT) filled polydimethylsiloxane (PDMS). Simulated and measured results show that the MWCNT filled PDMS sponge with thickness of 2 mm can achieve average absorption of 99.95% from 0.2 to 1.2 THz. Further, to improve surface impedance matching and reduce reflectivity of THz wave, the MWCNT is grafted to magnetic Fe 3 O 4 nanoparticles and then treated by external magnetic field to achieve out‐of‐plane gradient distribution of the MWCNTs during solidification of the PDMS. Excellent absorption of ≈99.99% and reduced reflection are achieved by the synergic effects of the unique electronic properties of the MWCNT, its gradient‐distribution, and the porous structure of the nanocomposites. The easy preparation method also exerts great compatibility in 2D patterning and structural molding fabrication with magnetically induced gradience to suppress EM wave reflection for next generation information technologies.