Low-temperature synthesis of medium-entropy spinel oxide powders with electromagnetic wave-absorbing and anti-corrosion properties

To meet the requirements for electromagnetic wave (EMW) absorbing materials in corrosive environments such as the ocean, (NiZnCuMn)Co2O4 medium-entropy oxides (MEOs) with anticorrosion properties have been developed as novel EMW absorbing materials. The (NiZnCuMn)Co2O4 MEOs, which are synthesized via a hydrothermal reaction followed by calcination, exhibit robust EMW absorption performance with a minimum reflection loss of −64.05 dB and an ultrabroad effective absorption bandwidth that can reach 7.35 GHz by adjusting the hydrothermal reaction time. This high performance is attributed to the synergistic effect of dielectric loss, magnetic loss, and the unique structure of the MEOs. (NiZnCuMn)Co2O4 can be doped into epoxy resin, endowing it with excellent anti-corrosion properties. After being soaked in 3.5 wt.% NaCl for 14 days, (NiZnCuMn)Co2O4 prepared with a hydrothermal time of 12 h, shows a minimum corrosion current of 6.61 × 10−6 A cm−2. When the hydrothermal time is 18 h, the corrosion current is 6.66 × 10−6 A cm−2 and the corrosion potential reaches −0.712 V. This study provides new insights into the design of EMW absorbing materials with anticorrosion properties.