Preparation And Electromagnetic Properties Of Heat Resistant Absorbent

Carbonyl iron powder,as an important magnetic metal material,is a commonly used electromagnetic absorber.However,carbonyl iron is active and easy to be oxidized at high temperature in atmospheric environment,which limits its application temperature range.Therefore,it is necessary to carry out coating modification to achieve better thermal stability.Aiming at the lack of temperature resistance of carbonyl iron powder,the most commonly used ferromagnetic metal absorbent,this thesis focus on the surface modification of spherical carbonyl iron powder to improve the oxidation resistance,and selects three types of different process routes.The influence trends of process parameters on the surface morphology and composition,thermal stability and electromagnetic properties of the modified powders were investigated.The modified carbonyl iron powder with both temperature resistance and electromagnetic properties was prepared,and the best oxidation resistance and reflection loss properties were found.The main research contents and innovations of this thesis can be summarized as follows:1.The artificial oxidation modified carbonyl iron powder was prepared.The iron oxide coating layer was successfully formed on the surface of iron powder by the bluing reaction method.The coating process was studied by means of SEM,XPS,thermogravimetric analysis and electromagnetic parameter testing.It was confirmed that the higher the reaction temperature and the longer the reaction time,the thicker the oxide layer can be obtained,and the greater the thermal stability of the iron powder was improved.And the best reflection loss was obtained at 70?and 60 minutes.2.Two kinds of coating modified carbonyl iron powders using silane coupling agent as single silicon source were prepared.Two single-layer SiO₂-coated modified layers,KH-550 and KH-560,were prepared respectively.By adjusting the process parameters,SiO₂-coated modified carbonyl iron powder with better thermal stability was obtained.The coating of KH-560 was used.The modified carbonyl iron powder has a better balance between temperature resistance and electromagnetic properties.3.Double-layer coating modified carbonyl iron powders of SiO₂/Al₂O₃ and SiO₂/TiO₂ were prepared,and the effects of coating process parameters on the modified properties were studied.Results The modified samples with SiO₂/Al₂O₃ double-layer coating had better temperature resistance and improved electromagnetic properties.When the amount of NaAlO₂ was 2g/100m L,the Al₂O₃ coating formed by the reaction was dense and had sufficient thickness,and the peak reflection loss peaked.It reaches-22d B at 10.3GHz.However,the SiO₂/TiO₂ coating modification formed a thick and loose TiO₂-coating layer,which did not improve the temperature resistance significantly but lost the absorbing performance to a large extent.