Study On The Electromagnetic Performance Of Flaky FeSiAl/polyurethane Microwave Absorption Composite Coatings

On the basis of meeting the request of thin in thickness,light in weight,wide absorption bandwidth and strong absorption performance,fabricating absorption coatings with stronger absorption performance is the research emphasis.In this dissertation,the absorption coatings are fabricated using flaky FeSiAl as the main absorber.And using the methods of adding composite absorber and structure design to improve the absorption performance of coatings.In this dissertation,the morphology of flaky FeSiAl（FFSA）,carbon black（CB）and silicon dioxide（SiO₂）are tested by scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.The electromagnetic characteristics are tested by vector network analyzer（VNA）.The electromagnetic wave absorption mechanisms of these absorbers are studied by analyzing the results above.Absorption coatings are using flaky FeSiAl as the main absorber,CB or SiO₂ as composite absorber to investigate the impact of composite absorber on absorption performance.Discrete structure is applied on FFSA and FFSA/CB coatings to study the effect of structure design on absorption performance.Moreover,FFSA/carbon fiber（CF）coatings with sandwich structure are fabricate to investigate the impact of carbon fiber on improving the absorption performance.Discrete structure are also applied on this kind absorption coatings to better the absorption performance.The results show that:FFSA,CB and SiO₂ are three different types of absorbers.FFSA is a magnetic loss type absorber and its loss mechanism can be attributed to the natural resonance in high frequency.CB as a resistive-type absorber,is easy to aggregated to form conductivity networks because of the small particle size.Damped vibration,multiple reflection and eddy current loss are the main methods it consumes electromagnetic wave.SiO₂ is a type of wave-transmitting material without strong ability of consuming electromagnetic wave.In the FFSA/CB composite coatings,the addition of CB can reduce the absorption peak values and broaden the absorption bandwidths（RL<-8d B）.The improvement of absorption performance is very obvious.In the FFSA/ SiO₂ composite coatings,although the absorption bandwidths（RL<-8dB）doesn’t broaden obviously,the absorption peak values reduce remarkably.All these manifest that adding composite absorber is an effective method to improve the absorption performance of FFSA coatings.Discrete structure are applied on the FFSA coatings and FFSA/CB composite coatings and the absorption performance comparison is made between two type structures.Results show that the absorption coatings with discrete structure possess better absorption performance.They have lower absorption peak values and wider absorption bandwidths（RL<-8d B）.And the absorption performance improve greater with the reduction of discrete unit sizes.Compared with FFSA coatings,FFSA/CF coatings in sandwich structure possess better absorption performance.Especially when the length direction of CF is parallel to the electric field direction of the incident wave,the absorption peak shift toward higher frequency range,the lower absorption peak values and the wider absorption bandwidths were obtained.Further cutting these coatings into discrete structure,the absorption performance improve as experiments show before.