Preparation of NiCo/NPC composites and study on their wave absorbing properties

With the rapid development of electronic communication equipment, the problem of electromagnetic pollution has become increasingly prominent. Metal–organic framework (MOF) materials have the advantages of simple synthesis process, low production cost, large specific surface area and high porosity, and the derived porous carbon/magnetic metal particle composites (NPC) overcome the characteristics of uneven dispersion of magnetic particles. In this study, bimetal NiCo-MOF-74 synthesized by solvothermal method was used as precursor, and then, NiCo/NPC composite was prepared by high temperature carbonization. The influences of Ni/Co molar ratio on the morphology, graphitization degree, magnetic properties and wave absorption properties of the composite were investigated. The results indicate that with the increase in Co content, the degree of graphitization of the carbon component in the composite material increases, leading to a gradual enhancement of its ferromagnetic properties. With the increase in Co content, the wave absorbing properties of NiCo/NPC composites first increased and then decreased. When the paraffin filling ratio was 50% (mass fraction) and the molar ratio of Ni/Co was 1:1, the NiCo/NPC composites had the best wave absorbing properties. The optimal reflection loss of Ni₁Co₁/NPC composite at 16.96 GHz with a thickness of 2 mm is − 50.8 dB, and the effective absorption bandwidth is 4.56 GHz (13.44–18 GHz).