Preparation And Properties Of Magnetic Graphene Hollow Microspheres/Epoxy Foam

As a new type of two-dimensional atomic crystal,graphene has large specific surface area,light weight and unique force,thermal,optical properties.Compared with the traditional magnetic metal nano-absorbers,graphene-loaded magnetic nano-absorbers exhibit more excellent absorbing properties,therefore it becomes a hot spot in the research field of absorbing materials in recent years.In this paper,water-in-oil and high-temperature calcination are used to prepare the reduced graphene oxide(rGO)hollow microsphere-loaded magnetic nanoparticles which include cobalt(Co),nickel(Ni)and cobalt-nickel alloy(CoNi).And the magnetic graphene hollow microsphere/epoxy absorbing foam composite was prepared through epoxy resin foam.X-ray diffractometry(XRD),scanning electron microscopy(SEM)and infrared spectroscopy(FTIR)were used to test the phase structure,chemical composition and morphology of magnetic graphene hollow microspheres and their epoxy resin foam composites.The electromagnetic parameters of coaxial samples were tested by vector network analyzer.The electromagnetic reflection loss of absorbing foam in the range of 1~18GHz was simulated by Matlab,and the electromagnetic loss mechanism was analyzed.At the same time,the true reflectivity of the magnetic graphene hollow microsphere/epoxy absorbing foam flat composite was tested by the bow method.The results show that the absorbing foam composites have excellent electromagnetic wave absorption performance.Among them,CoNi/rGO hollow microspheres/epoxy absorbing foam has the best absorption performance.When the thickness and frequency of the foam coaxial sample were 2.3mm and 12.82 GHz,the minimum reflectivity is-58.6dB,the reflectances of 10.6~16.9GHz and 17.74~18GHz frequency bands were less than-10 dB,and the frequency width was 6.56 GHz.When the thickness and frequency of Ni/rGO hollow microspheres/epoxy absorbing foam are 2.5mm and 8.39 GHz,the minimum reflectivity is-58.23 dB,the reflectivity in the frequency band of 7.46~9.67 GHz is less than-10 dB,and the effective bandwidth is 2.21 GHz.When the thickness of Co/rGO hollow microspheres/epoxy absorbing foam is 2.1mm and the frequency is 12.22 GHz,the reflectivity reaches-50.79 dB,the reflectivity in the frequency band of 10.69~14.43 GHz is less than-10 dB,and the effective bandwidth is 3.74 GHz.Three composite epoxy absorbing foam plates with different particles have multi-bands absorption which cover high,medium and low frequencies.