Trimetallic\nFeCoNi@C Nanocomposite Hollow Spheres\nDerived from Metal–Organic Frameworks with Superior Electromagnetic\nWave Absorption Ability

Abstract

Organic\nligands and metal ions in the metal–organic frameworks\n(MOFs, a type of porous magnetic metal/carbon nanocomposites obtained\nthrough high-temperature carbonization) have caused widespread concerns\nin the field of microwave absorption because of the existence of various\nmicrowave loss mechanisms in these materials. However, MOF-driven\nmicrowave absorbing materials with high absorption intensity and wide\nabsorption band still require further research and development. In\nthis work, hollow sphere trimetallic FeCoNi@C microwave absorbing\nmaterials via high-temperature carbonization were obtained using FeCoNi-based\nMOF-74 (FeCoNi-MOF) as the precursor. The effects of different carbonization\nconditions on the microwave absorption properties of the materials\nwere studied. FeCoNi-MOF-74 annealed at 700 °C showed superior\nmicrowave absorption capacity, where the RL value reached −64.75\ndB at 15.44 GHz corresponding to the actual application thickness\nof the absorber (only 2.1 mm), and the minimum RL values reached −69.03\ndB at 5.52 GHz. Furthermore, the as-prepared sample can fully cover\nthe Ku band and X band at only 2.1 and 3.1 mm, respectively. The maximum\nEAB reached 8.08 GHz (9.92–18 GHz) when the thickness of the\nabsorber was 2.47 mm. Such remarkable absorption performance is attributed\nto the synergetic effects between the multiple loss mechanisms of\nthe FeCoNi@C, and the improved impedance matching characteristic came\nfrom the hollow sphere morphology.