Preparation And Properties Of MoSi₂/Cu/Al₂O₃ Microwave Absorbing Coating By Plasma Spraying

With the rapid development of radar detection technology,the battlefield survival of military equipment stealth defense system is seriously threatened.In order to reduce the detectability of targets and improve the penetration ability,the development of stealth technology is of great significance.In radar stealth technology,coated absorbing materials have attracted much attention due to their excellent absorbing properties and simple and convenient preparation process.Excellent absorbing materials must have the characteristics of light weight,low density,thin coating,strong absorption,wide effective absorption band,high temperature resistance and oxidation resistance.It is a great challenge for researchers to integrate these excellent properties into the absorbing coating.At present,the research and development of electromagnetic wave absorbing materials and preparation technology with excellent performance has become the focus.This project mainly studies the preparation process and performance of MoSi₂/Cu/Al₂O₃ microwave absorbing coating,which is realized by the combination of experiment and electromagnetic simulation.Firstly,taking full advantage of MoSi₂'s excellent high temperature oxidation resistance and conductivity,nine groups of MoSi₂/Cu/Al₂O₃microwave absorbing coatings were prepared by atmospheric plasma spraying under different process parameters;The effects of process parameters on porosity,microhardness and thickness of the coating were analyzed.Secondly,the influence of the temperature change of 30??700?on the electromagnetic parameters and absorbing properties of the absorbing coating in the frequency range of 8.2?12.4GHz was studied.Finally,FEKO simulation software was used to establish the coating model,and the effects of temperature,incident angle of electromagnetic wave and coating thickness on the microwave absorption performance of the coating were studied.The main research contents and results are as follows(1)Micro characterization:the micro surface layer of MoSi₂/Cu/Al₂O₃microwave absorbing coating is composed of completely melted and incompletely melted regions,and the surface is rough and uneven;The crystal phase composition of the coating is Cu,?Cu₂O?-Al₂O₃??-Al₂O₃?MoSi₂,?Mo₅Si₃ and h-MoSi₂.(2)The surface porosity of MoSi₂/Cu/Al₂O₃microwave absorbing coatings of 9groups ranged from 6.21%to 9.34%.The order of the effect of process parameters on the porosity of coating is:argon flow rate>spraying distance>spraying voltage>spraying current.(3)The microhardness of nine groups of MoSi₂/Cu/Al₂O₃ absorbing coatings is above630 kgf·mm^-2,and the highest is 770.21 kgf·mm^-2.The order of influence of process parameters on microhardness is argon flow rate>voltage>spraying distance>current;The increase of porosity on the surface of the coating will lead to the decrease of microhardness.(4)The thickness of MoSi₂/Cu/Al₂O₃absorbing coatings of 9 groups ranged from36.59 to 53.67?M.The order of influence level of process parameters on coating thickness is:spraying distance>spraying current>spraying voltage>argon flow rate.(5)For MoSi₂/Cu/Al₂O₃ microwave absorbing coating,the curves of real part(?')and imaginary part(?')of complex permittivity with frequency increase with the increase of temperature between 30?and 700?;At the same temperature,it decreases with the increase of frequency,showing dispersion characteristics,but increases with the increase of frequency.At the same time,with the increase of temperature,the reflectivity of the nine groups of coatings decreased,the absorption peak moved to the low frequency direction,and the absorption bandwidth increased gradually.(6)The simulation model of coating was established by FEKO.When the thickness of MoSi₂/Cu/Al₂O₃ coating is 1 mm,the reflection intensity of the coating first increases or decreases,and the absorption bandwidth first widens and then narrows with the increase of temperature from 30?to 700?;It has the best absorbing capacity at 500?.At 500?,at0°?80°With the angle of incidence of electromagnetic wave(?)The reflection intensity and absorption bandwidth of the coating decrease with the increase of the temperature;stay??40°In the range of 1 mm thickness,the coating can still maintain more than 90%absorption.The results show that:at the two temperatures,with the increase of thickness,the absorption peak gradually moves to the low frequency direction,the absorption intensity first increases and then decreases,and the absorption bandwidth first widens and then narrows.At 500?,at 2.0 mm and 9.964 GHz,the absorption peak is the lowest,the peak is-35.08 d B,and the effective absorption bandwidth(<-20 d B)is 0.945 GHz;At 1.6 mm,10.489 GHz,it has the widest absorption bandwidth(<-20 d B)of 1.155 GHz.At 700?,it has the lowest absorption peak and the widest absorption band at 2.0 mm and 9.649 GHz,which are-31.68 d B and 0.945 GHz,respectively.