Study On The Preparation And Properties Of Cobalt Ferrite/Reduced Graphene Oxide Nanocomposites

Spinel ferrite has excellent physical and chemical property which becomes a research hotspot in recent years,and graphene is often used as substrate of nanomaterials due to special structure,and it is considered that it will obtain functional materials of excellent properties to composite the materials with different advantages.So the preparation and characterization of cobalt ferrite（CoFe₂O₄）nanomaterials and cobalt ferrite/reduced graphene oxide（CoFe₂O₄/r GO）nanocomposites had been researched.The photocatalytic performance and microwave absorbing performance of materials had also been investigated.In this dissertation,single solvothermal method was used to synthesize CoFe₂O₄ nanomaterials.The effects of the ratio of ethylene glycol to water,cobalt source,solvothermal reaction temperature,time,surfactant and structure directing agent on the product were investigated.The optimum preparation conditions were as follows: the ratio of ethylene glycol to water was 3:1,the cobalt source was cobalt sulfate,the materials were prepared by solvothermal method at 120℃ for 24 h.On the basis of single solvothermal method,CoFe₂O₄ nanomaterials were prepared by membrane-solvothermal method.The reaction parameters of double membrane method were as follows: the mechanical stirring speed was 900 r/min and the average flow rate of solution was 120 mL/h.The effects of reaction temperature,time and calcination temperature on the product were further investigated and the best preparation conditions were as follows: the materials were prepared by membrane-solvothermal method at 120℃ for 18 h,the calcination temperature was 550℃.CoFe₂O₄/r GO nanocomposites were fabricated via ultrasonic method with different weight ratio of graphene oxide（GO）on the basis of CoFe₂O₄ nanomaterials.The morphology and crystal type of them were characterized by SEM and XRD,and it could clearly be seen that the rod-shaped CoFe₂O₄ materials prepared by single solvothermal method possessed the length of 20μm and the diameter of 1.5μm,and the rod-shaped CoFe₂O₄ materials which were self-assembled by nanoparticles with the diameter of about 20 nm prepared by membrane-solvothermal method possessed the length of 30μm and the diameter of 800 nm.The nanorods were loaded well on the graphene sheets.The results showed that the membrane-solvothermal method which had broad application prospect could not only shorten the reaction time,but also improved the morphology of the product.The photocatalytic degradation of malachite green（MG）dye wastewater was studied by using CoFe₂O₄ nanomaterials and CoFe₂O₄/r GO nanocomposites as photocatalysts.Ac-cording to the experimental results,all the graphene-based nanocomposites showed more outstanding photocatalytic performance than pure CoFe₂O₄.And the larger amount of r GO one photocatalyst contained,the higher adsorption efficiency it possessed.Among all the graphene-based nanocomposites,CoFe₂O₄/r GO-5 exhibited the optimal photocatalytic performance,which was able to eliminate about 93.48% of MG within 90 min,utilizing both UV and visible light.After five cycles,the photocatalytic degradation rate of MG remained above 88%,indicating that CoFe₂O₄/r GO-5 had good cycle stability.In this paper,the CoFe₂O₄ nanomaterials and CoFe₂O₄/r GO nanocomposites were used as microwave absorbers.The electromagnetic parameters were measured by the vector network analyzer and the microwave attenuation characteristics of the different thickness of the absorbing layer were simulated by computer.The microwave absorbing properties of them were analyzed and the results showed that: the maximum reflection loss of pure CoFe₂O₄ nanomaterial was only-5.8d B.The electromagnetic wave reflection loss of CoFe₂O₄/r GO nanocomposites were below that of pure CoFe₂O₄ nanomaterial,which indicated that the introduction of GO enhanced the absorbing property of materials.The maximum reflection loss of CoFe₂O₄/r GO-4 nanocomposites could reach-11.1d B and the bandwidth under-10 d B was 2.3GHz which proved that the material could absorb electromagnetic wave effectively.It was convinced that this material would have a great potential in the application of microwave absorber.