Study On Preparation And Properties Of Iron Aluminum Spinel Based Composite Coating

Since the 20 th century,with the continuous development of science and technology,the demand for resources is also increasing.At the same time,more and more resource consumption leads to the demand on land is no longer satisfied,and development of the ocean economy is also increasing in importance.Countries around the world have successively launched deep-sea research and development programs.In the "National Medium and Long Term Science and Technology Development Plan",China has clearly put forward the strategic goal of "building a strong ocean country" and "going to the deep sea." The ocean environment is very complex and harsh.In addition to corrosive media,the adhesion of marine organisms induces accelerated corrosion,resulting in degradation of material structure performance,reduced bearing capacity and shortened life.In the military field,the electromagnetic waves radiated by various military electronic equipment,such as aircraft,ships and ground military equipment,will leak military secrets if they are collected by the enemy.Therefore,it is of great research value and significance to develop a composite material with corrosion resistance and good electromagnetic wave absorption performance on marine equipment.In this dissertation,a ceramic-based composite coating with corrosion resistance and electromagnetic wave absorption properties was prepared by adding nickel powder and graphene oxide.Two kinds of ceramic matrix composites with different components of Ni / RGO composite powder and iron-aluminum spinel mechanical mixing were prepared by mechanical mixing of iron-aluminum spinel and nickel powder,centrifugal spray granulation and thermal reduction.X-ray diffractometer,scanning electron microscope,electrochemical workstation,and sagittal network analyzer were used to discuss the corrosion resistance and electromagnetic wave absorption characteristics,and to examine whether the inclusion of nickel powder and graphene had an effect on the corrosion resistance and electromagnetic wave absorption regime of the ceramic-based coating.A series of iron-aluminum spinel composite micro-nickel composite coatings were prepared by thermal spraying method,and the corrosion resistance was tested and evaluated by artificial simulated seawater and sulfate reducing bacteria(SRB)solution.Both in man-made seawater and in sulphate-reducing bacteria,the composite coating after adding nickel powder is more resistant to corrosion than a single pure aluminospinel,and the 15 wt.% Ni/aluminospinel composition has the optimal corrosion resistance.The test analysis by electrochemical impedance chromatography showed that the composite coating will produce certain physical protection in the corrosion resistance,which can enhance its physical shielding effect.The arguments in the impedance profile were analyzed and the equivalent circuit was tailored to the actual situation.The corrosion mechanism of the coating was investigated and analyzed by the results of microstructure and phase analysis explained.In addition,nickel powder and graphene oxide were converted into powder by centrifugal granulation spray,and then Ni / RGO composite powder was obtained by thermal reduction in an argon-protected 600-degree atmosphere.After mixing,the coating was also prepared by plasma spraying.The 15 wt.% coating was tested in artificial simulated seawater and sulfate-reducing bacteria.The performance showed that the corrosion resistance of the coating was enhanced further by the doping of graphene.Spinel is widely used as an electromagnetic wave absorbing material,but a single spinel also has a series of disadvantages such as poor reflection loss and poor impedance matching.In this dissertation,firstly,nickel powder is added to spinel to improve its performance.The mass ratio of the powder to be tested and paraffin is 1 : 1.The dielectric constant and magnetic loss parameters are tested by vector network analyzer to analyze its storage capacity and attenuation ability for electromagnetic waves,and verified by dielectric loss tangent and magnetic loss tangent.By optimizing the electromagnetic parameters,the reflection loss of the material under different thicknesses is found to be improved,but it is not obvious.Then,the loss mechanism is analyzed by Cole-Cole curve and eddy current loss,and the thickness and proportion are selected by impedance matching and attenuation constant.On this basis,the Ni /RGO and hercynite prepared by spray granulation technology were mixed.By comparing the reflection loss of the combinations,it was found that the composite with15 wt.% Ni/RGO composite particles had the best reflection loss.Compared with other composite powders,It has superior dielectric and magnetic losses and better impedance matching.When the thickness is 2 mm,the composite has a broad bandwidth of 6 GHz and a reflection loss of-18 GHz at 15 GHz.