Preparation And Detection Of Carbon Composite Cobalt And Its Oxide Absorbing Materials

Since the new century,electromagnetic pollution has become more and more serious.It is listed as the fourth largest source of pollution in the world after water,electricity and noise.The damage caused by electromagnetic pollution to some electronic instruments and equipment is more than billions of dollars every year,and the damage to human body is immeasurable.Therefore,the research and development of microwave absorbing materials has always been a hot issue.With the development of material science,new materials gradually replace traditional materials.Graphene,due to its high electron mobility and low density,is a good dielectric loss absorbing material.In this paper,in the presence of the large specific surface area of graphene,the nano cobalt hydroxide is distributed evenly on the substrate of graphene by the solvothermal process.The precursors were treated by high temperature calcination and hydrogen peroxide oxidation respectively,and then CoO/Co3O4/rGO and Co3O4/rGO absorbing materials were obtained.A concentric ring was made by mixing the absorbing material and paraffin in accordance with the mass ratio of 1:1 to detect the absorption effect.It is found that the magnetic particle size of CoO/Co3O4/rGO is mainly 40-55 nm.The reflection loss of the 1.82mm concentric concentric ring at 9.5-13 GHz is less than-10dB and the minimum reflection loss is-59 dB.With the increase of concentric ring thickness,the absorption peak gradually moves towards low frequency.As a contrast,the Co3O4/rGO absorbing material has the best absorption effect when the thickness of concentric ring is 2 mm.The effective frequency band of the reflection loss less than-10 dB is 8-9 GHz,and the minimum reflection loss is-15dB.With the increase of the thickness,the absorption peak moves left.In addition to graphene,the amorphous carbon structure formed by high temperature pyrolysis of organic compounds is another typical structure.In order to analyze the influence of the electromagnetic absorption properties of carbon coated structures,two typical preparation processes of organic high temperature pyrolysis and arc combustion were selected.It is found that KH-550 silane coupling agent is a carbon encapsulated cobalt structure formed by high temperature pyrolysis of organic carbon elements,presenting "ant hole" and porous structure.The concentric ring at the thickness of 3.03 mm has a minimum reflection loss of-48dB,and the absorption band of reflection loss less than-10 dB is 7-16.1 GHz.Compared with the pyrolysis of high temperature,the carbon coated cobalt nanostructure made by the arc combustion process is about 30 nm,and the concentric ring under the thickness of 2.46 mm has the minimum reflection loss-48 dB,and the reflection loss is less than-10 dB at 7.8-10.2 GHz.In this paper,composite preparation of carbon materials and cobalt and its oxides from different structures was carried out from two preparation processes of graphene cobalt oxide and carbon cobalt inclusion.Solvothermal method was used to obtain CoO/Co3O4/rGO from precursor calcined at high temperature,and its absorption property(intensity and bandwidth)was better than that of hydrogen peroxide oxidation product Co3O4/rGO.The high temperature pyrolysis of KH-550 silane coupling agent can reduce the electromagnetic wave attenuation of carbon coated cobalt structure,and its comprehensive performance is stronger than that of the arc combustion process.