To improve electromagnetic (EM) wave attenuation and its absorption properties, herein, for the first time, we grow needle-like magnetic NiCo2O4 nanoparticles in situ on lightweight open cell reticulated vitreous carbon (RVC) foam by the hydrothermal method, leading to hierarchically nanostructured foam. The foam was synthesized by the carbonization of flexible polyurethane foam followed by acid treatment. The coating structure, stability, and performance were systematically investigated by various complementary techniques using XRD, XPS, Raman, and FTIR spectroscopies, compression test, and ultrasonication. The foam coated for 12 h exhibited considerably improved shielding effectiveness (SE), i.e., ∼36 dB from ∼23 dB for the bare RVC foam in the X-band, leading to ∼99.97% shielding efficiency. Although the foams mainly showed reflection-dominated properties regardless of the coating, the EM absorption improved with coating. The shielding mechanism is explained by means of reflection and absorption coefficients and dielectric and magnetic losses manifested by NiCo2O4 coating and interfacial polarization.

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A one-dimensional (1D) nanoneedles of nickel cobaltite have been developed and applied to treat nitroaromatics-bearing wastewater. A significant change in the magnetic and photocatalytic properties of NCO has been observed at different annealing temperatures and is correlated to the morphology and phase structure. The sample annealed at 550 °C displayed the sharpest 1D nanoneedle-like structure with an optimum surface area (44 m 2 g −1 ), pore size (11 nm), band gap energies (1.87 and 2.52 eV), and saturation magnetizations (5.09 emu g −1 ) at a 5 T magnetic field. The complete photodegradation of 2,4,6-trinitrotoluene (50 mg L −1 ) occurred within 3 h by using NCO-550 (300 mg L −1 ) under UV−vis light. The degradation rate showed first-order kinetics with a rate constant of 1.6 h −1 . The magnetic behavior of the catalyst showed negligible wastage even after repeated cycles. The degradation mechanism, as elucidated by gas chromatography−mass spectroscopy (GCMS), indicated complete mineralization of the nitroaromatics into CO 2 and H 2 O.