Preparation And Application Of Fe₃O₄ Nanocomposites

Due to its low cost,corrosion resistance and high conductivity,nano-Fe₃O₄ has been widely used in anti-corrosion paints and energy materials.However,single nano-Fe₃O₄ has some problems such as aggregation and poor structural stability in service.In this paper,graphene and polyaniline（PANI）were used to prepare Fe₃O₄ nanocomposites through the nanocomposite pathway.The main contents of this paper are as follows:1.Preparation of Fe₃O₄/PANI nanocomposite and its metal anticorrosive activitySpherical Fe₃O₄/polyaniline（PANI）nanocomposites with core-shell structure were prepared by oxidative polymerization of aniline on the Fe₃O₄^-/ANI⁺ nanocompositetemplate formed by the electrostatic interaction between nano-Fe₃O₄ and aniline salt.FI-IR and UV-Vis results indicate that there is coordination interaction between Fe₃O₄ and PANI interface.SEM and TEM results show that the thickness of PANI shell increases with the increase of ANI/Fe₃O₄ mass ratio.Preparation of Fe₃O₄/PANI nanocomposite coating and its metal corrosion resistance.CV results showed that compared with PANI,Fe₃O₄/PANI still showed obvious redox activity in neutral medium.Fe₃O₄/PANI organic composite coatings were prepared by filling Fe₃O₄/PANI nanocomposites in waterborne acrylic amino baking coatings.The results of salt spray,EIS and Tafel plot show that the anti-corrosion activity of Fe₃O₄/PANI is greatly affected by the composition ratio of ANI/Fe₃O₄.Fe₃O₄/ANI（1:2）has the best metal corrosion resistance,which is three times of that of the unfilled organic coating.The rheological property test showed that the dispersion of 1%Fe₃O₄/PANI nanocomposites in the coating was the best.Further investigation by XRD and XPS revealed that the metal anti-corrosion activity of Fe₃O₄/PANI was due to the nano barrier effect of Fe₃O₄/PANI and the passivation mechanism of metal surface.2.Preparation of rGO/Fe₃O₄/PANI nanocomposite and its metal anticorrosive activityGraphene oxide（GO）nanosheets loaded with Fe₃O₄ nanoparticles were directly reduced by aniline monomer without any toxic reducing reagent,then the graphene oxide loaded withnano-Fe₃O₄（aniline oxide/Fe₃O₄/rGO）reduced by aniline was obtained.After that,the oxidative polymerization of aniline was carried out on the surface of Fe₃O₄/rGO to prepare rGO/Fe₃O₄/PANI nanocomposites.Transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,ultraviolet visible spectroscopy（UV-VIS）and cyclic voltammetry（C-V）were used to characterize the morphology,structure and interface interaction of the nanocomposites.The results show that the nanocomposites are composed of layers of nanosheets,and the interfacial π-electron interactions and electron coordination interactions are formed,which make them redox in neutral environment.The rheological and anticorrosive properties of the nanocomposite coating were tested by rheological properties,Tafel plot,EIS,salt spray resistance,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.The results show that the filled 0.5%rGO/Fe₃O₄/PANI（1:1:4）nanocomposites show the best metal anti-corrosion performance in waterborne acrylic amino baking paint.The dispersion of rGO/Fe₃O₄/PANI（1:1:4）nanocomposites in the coating is stable and the coating density is the highest.rGO/Fe₃O₄/PANI（1:1:4）nanocomposites play an effective role in physical barrier and passivation of metal surface.3.Preparation and characterization ofnitrogen doped carbon coated Fe₃O₄ nanomaterials（Fe₃O₄@C-N）Based on the study of Fe₃O₄/PANI binary nanocomposites,when the mass ratio of PANI to Fe₃O₄ is 2:1,the composite with regular core-shell morphology is obtained.This provides a precursor for the preparation of nitrogen-doped carbon-coated nano-Fe₃O₄ as anode material for lithium-ion batteries.Fe₃O₄/PANI nanocomposites were decomposed at high temperature in nitrogen atmosphere,and nitrogen-doped carbon-coated Fe₃O₄ nanocomposites（Fe₃O₄@C-N）were prepared using PANI as carbon source.The results of SEM,TEM,FT-IR and TGA show that the carbonization rate of PANI on Fe₃O₄ surface is 50%.The mass ratio of medium carbon layer to Fe₃O₄ is close to 1:1 in Fe₃O₄@C-N;There is no obvious change in morphology compared with that before calcination,showing a core-shell structure.The results of XRD and XPS show that there is an doping form of electronic interaction between Fe₃O₄ lattice and carbon layer.The electrochemical test results show that the cycling performance and rate performance of Fe₃O₄@C-N are significantly improved compared with nano-Fe₃O₄.This is because doped nitrogen and carbon coating can effectively improve the stability of Fe₃O₄ nanostructure during charge discharge process.