Design Of Organic/Inorganic Composite And Study On Microwave Absorption And Corrosion Resistance Of FeSi-based Alloy

Although the development of electronic and communication technology has brought convenience to human beings,a large amount of electromagnetic pollution has also followed.When the electromagnetic waves enter into the microwave absorbing materials,electromagnetic energy converts to heat energy or dissipate it through interference,which is beneficial to solve these problems caused by electromagnetic radiation pollution.However,since microwave absorbers are mostly used in harsh environments,such as oceans and acid rain,corrosive particles with extremely strong penetrating power make traditional absorbers ineffective.FeSiAl has high saturation magnetization and excellent magnetic loss performance,and does not contain noble metals,which has the advantage of low cost.Therefore,in this thesis,an organic/inorganic bilayer is developed on the surface of FeSi-based alloy,so that the composite has efficient microwave absorption and anti-corrosion performance.Firstly,FeSiAl@SiO₂@PUA composite is prepared by combining Sol-Gel method and in-situ polymerization technology by selecting SiO₂ with wave-transmitting properties and acrylic polyurethane(PUA)with dielectric regulation.The process is systematically optimized.The microstructure of the multi-level interface is regulated,and the microwave absorbing performance of the composite is enhanced.It is found that the FeSiAl@SiO₂@PUA composite has a minimum reflection loss value(RL_min)of-49 d B and an effective absorption bandwidth of 3.5 GHz(4.3-7.8 GHz)at a thickness of 4.5 mm.Secondly,the order of cladding layers is optimized and plasma-induced technology(PECVD)is introduced to fabricate the FeSiAl@PUA@SiO₂ gradient organic/inorganic composite.The proces increases the interfacial bonding,improves the chemical stability,and overcomes the bad heat-resistance of the FeSiAl@SiO₂@PUA composite.Systematic studies on the microstructure and microwave absorbing properties of the material find that the organic/inorganic double-layer structure is not only beneficial to the interface polarization,but also effectively reduces the dielectric constant and optimizes impedance matching.When the thickness is 2.3 mm,the RL_min of the composite reaches-47 d B,and the effective bandwidth is 5.3 GHz,covering almost the entire Ku-band(12-18 GHz).Finally,the corrosion resistance of FeSi-based organic/inorganic composites in 5.0wt%Na Cl solution is evaluated by electrochemical corrosion analysis.Since the organic/inorganic bilayer effectively shields the corrosion particles,compared with FeSiAl,the corrosion potential of composite increases from-0.167 V to-0.047 V.The corrosion current decreases from 3.04×10^-6 A/cm~2 to 2.16×10^-6 A/cm~2.The annual corrosion rate decreases from 9.77×10^-13 m/s to 6.94×10^-13 m/s,and the polarization resistance increased from 8064?cm~2 to 16273?cm~2.In short,SiO₂ acts as a dense heat-resistant layer and a shielding layer for corrosion particles,and PUA has a dielectric adjustment effect and high adhesion.PECVD technology realizes the densification of PUA and enhances the interface bonding of the composite.The prepared FeSi-based organic/inorganic composite possesses both high-efficiency microwave absorbing and anti-corrosion properties.